Results from A Study of Cardiovascular Events in Diabetes (ASCEND): Taking a Closer Look at the Potential Benefit of Omega-3 Fatty Acids for Preventing Cardiac Death

Results from A Study of Cardiovascular Events in Diabetes (ASCEND): Taking a Closer Look at the Potential Benefit of Omega-3 Fatty Acids for Preventing Cardiac Death

By Kevin C Maki, PhD; Mary R Dicklin, PhD

 

Results from A Study of Cardiovascular Events in Diabetes (ASCEND) were recently presented at the European Society of Cardiology (ESC) Congress 2018 held in Munich, Germany, along with their simultaneous publication in the New England Journal of Medicine.1,2  ASCEND was designed to evaluate whether daily aspirin safely prevented cardiovascular disease (CVD) and cancer in patients with diabetes, but without known CVD.3  The study also assessed whether supplementation with 1 g/d omega-3 fatty acids prevented CVD.  Persons with diabetes (n = 15,480) were randomly assigned to receive 100 mg/d aspirin or placebo and, in a factorial design, 1 g/d omega-3 fatty acid capsules, containing 460 mg eicosapentaenoic acid (EPA) and 380 mg docosahexaenoic acid (DHA), or placebo (olive oil).  The primary outcome was a first serious vascular event, which was defined as a composite of nonfatal myocardial infarction or stroke (excluding confirmed intracranial hemorrhage), transient ischemic attack, or vascular death.  The secondary outcome was a composite of any serious vascular event or any arterial revascularization procedure. 

 

The results for the omega-3 fatty acid portion of the trial showed no benefit from omega-3 vs. placebo for the primary or secondary composite outcomes.  During a mean follow-up of 7.4 years, a serious vascular event occurred in 8.9% and 9.2% of patients in the omega-3 and placebo groups, respectively, with a rate ratio of 0.97, 95% confidence interval (CI) 0.87 to 1.08, p = 0.55.  The composite outcome of any serious vascular event or revascularization occurred in 11.4% and 11.5% of patients in the omega-3 and placebo groups, respectively, with a rate ratio of 1.00, 95% CI 0.91 to 1.09.  The lack of a significant benefit of omega-3 fatty acids on the pre-specified primary outcome in ASCEND was consistent with results from recent meta-analyses of randomized controlled trials (RCTs) of long-chain omega-3 polyunsaturated fatty acids (compared to control or no treatment) on coronary heart disease (CHD) events.4  In a meta-analysis of 10 RCTs (n = 77,917) Aung et al. reported a risk ratio (95% CI) for a CHD event of 0.96 (0.90 to 1.01).5  Similarly, in a meta-analysis of 18 RCTs (n = 93,633) Alexander et al. reported a risk ratio of 0.94 (0.85 to 1.06).6  Abdelhamid et al. reported a risk ratio of 0.93 (0.88 to 0.97) in a meta-analysis of 28 RCTs (n = 84,301).7

 

Although the balance of the evidence from the RCTs conducted to date is supportive of the conclusion that omega-3 long-chain polyunsaturated fatty acid supplementation does not reduce risk for CHD events, there is promising evidence to suggest that omega-3 fatty acids may be beneficial for preventing fatal CHD or cardiac death.4,8  A meta-analysis of the effects of omega-3 fatty acids on cardiac death (defined as deaths from CHD, cardiac arrhythmia or heart failure) in 14 RCTs (n = 71,899) showed a risk ratio of 0.92 (0.86 to 0.98), p = 0.015.8  Aung et al. also reported a marginally significant reduction in CHD death 0.93 (0.85-1.00).5  In ASCEND, there was a near-significant difference in coronary deaths (incidence rate ratio = 0.79, 95% CI 0.61 to 1.02).1  In addition, there were significantly fewer vascular deaths (which represented 28% of all deaths) in the fatty acid group than in the placebo group (incidence rate ratio = 0.82, 95% CI 0.68 to 0.98).  Vascular deaths included coronary, sudden, stroke, and pulmonary embolism mortality. 

 

The ASCEND investigators suggested the possibility that if their results were to be combined with the studies reported in the meta-analysis by Aung et al., that a small benefit for fatal CHD might be detected.1,5  To assess this possibility, we have added the events reported in ASCEND to the events reported by Aung et al., and there was, in fact, a significant reduction in CHD/coronary death.

 

CHD deaths were as follows:

  • Aung meta-analysis5: 1301 of 39017 participants for omega-3 and 1394 of 38900 participants for control
  • ASCEND1: 100 of 7740 participants for omega-3 and 127 of 7740 participants for control
  • When combined, this is 3.00% of 46757 participants for omega-3 and 3.26% of 46640 participants for control
  • The relative risk is 0.919 (95% CI 0.855 to 0.987, p = 0.021)

 

Commentary

Although it is important to not over-interpret findings from post-hoc subset analyses, these results show promise for the prevention of cardiac death with omega-3 fatty acid supplementation through mechanisms that we outlined in our recent editorial comment in Nutrients.4  Unfortunately, the dosages used in most RCTs of omega-3 fatty acids conducted to date have been small (most employed 1 g/d Omacor/Lovaza, which contains 840 mg of EPA + DHA).  Pooled results from observational studies with omega-3 biomarker measurements suggest that each 1-standard deviation (SD) increase in omega-3 status is associated with a 12-16% reduction in risk for CHD death.9  Based on the same observational study dataset, Harris et al. estimated that a 1-SD increase in omega-3 index (erythrocyte fatty acid EPA + DHA content), or 2.1% from the 10 cohorts included in the analysis, was associated with a 15% (95% CI 9% to 20%) reduction in risk for fatal CHD.10

 

A subset of 152 of the ASCEND participants had omega-3 index measurements completed.  There was no material change in the placebo group (6.6% at baseline and 6.5% at follow-up), whereas the index increased from 7.1% to 9.1% in the omega-3 fatty acid group, resulting in a net difference of 2.1% in the change from baseline, and a difference between groups of 2.6% at the end of the trial.  If the Harris et al. estimate of a 15% reduction in fatal CHD risk per 2.1% (1-SD) omega-3 index difference is applied to the ASCEND data, the predicted risk reduction would be 15%, or 18% if the difference between groups during follow-up of 2.6% (1.24-SDs) is used.10  These estimates are close to the observed difference of 21% in coronary death. 

 

At lower dosages, it is our opinion that there is no compelling evidence to suggest benefits regarding non-fatal myocardial infarction or stroke, but that there is promising evidence for prevention of cardiac death.  Of the three large-scale trials that have been recently completed or are underway, including the Vitamin D and Omega-3 Trial (VITAL),11 the Outcomes Study to Assess Statin Residual Risk Reduction with Epanova in High Cardiovascular Risk Patients with Hypertriglyceridemia (STRENGTH)12 and the Reduction of Cardiovascular Events with EPA – Intervention Trial (REDUCE-IT),13 only the latter two trials are using a higher EPA+DHA dosage (≥3000 mg/d).  Future investigation should focus on higher dosages than have generally been employed to date.

 

Our view is that the potential for omega-3 fatty acid supplementation to reduce cardiac death clearly deserves additional study.  Further details about why we hold this view may be found in our recent commentary in Nutrients.4  Also, we agree with the recent recommendation from the American Heart Association that it is reasonable to consider an omega-3 fatty acid supplement for patients with atherosclerotic CVD or heart failure.  The message to patients can be as follows:

  1. There is little or no risk associated with taking an omega-3 fatty acid (EPA + DHA) supplementation;
  2. The available evidence does not support a benefit of EPA + DHA supplements for reducing risk of heart attack or stroke;
  3. However, if a heart attack or heart failure should occur, those who take an omega-3 supplement might be less likely to die as a result.

 

References:

 

  1. The ASCEND Study Collaborative Group. Effects of n-3 fatty acid supplements in diabetes mellitus. N Engl J Med. 2018 [Epub ahead of print].

 

  1. The ASCEND Study Collaborative Group. Effects of aspirin for primary prevention in persons with diabetes mellitus. N Engl J Med. 2018 [Epub ahead of print].

 

  1. Bowman L, Mafham M, Stevens W, et al. ASCEND: A study of cardiovascular events in diabetes: characteristics of a randomized trial of aspirin and of omega-3 fatty acid supplementation in 15,480 people with diabetes. Am Heart J. 2018;198:135-144.

 

  1. Maki KC, Dicklin MR. Omega-3 fatty acid supplementation and cardiovascular disease risk: glass half full or time to nail the coffin shut? Nutrients. 2018;10:864.

 

  1. Aung T, Halsey J, Kromhout D, et al. Associations of omega-3 fatty acid supplement use with cardiovascular disease risks: Meta-analysis of 10 trials involving 77,917 individuals. JAMA Cardiol. 2018;3:224-234.

 

  1. Alexander DD, Miller PE, Van Elswyk ME, et al. A meta-analysis of randomized controlled trials and prospective cohort studies of eicosapentaenoic and docosahexaenoic long-chain omega-3 fatty acids and coronary heart disease risk. Mayo Clin Proc. 2017;29:15-29.

 

  1. Abdelhamid AS, Brown TJ, Brainard JS, et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2018;7:CD003177.

 

  1. Maki KC, Palacios OM, Bell M, Toth PP. Use of supplemental long-chain omega-3 fatty acids and risk for cardiac death: An updated meta-analysis and review of research gaps. J Clin Lipidol. 2017;11:1152-1160.

 

  1. Del Gobbo LC, Imamura F, Aslibekyan S, et al. n-3 polyunsaturated fatty acid biomarkers and coronary heart disease: pooling project of 19 cohort studies. JAMA Intern Med. 2016;176:1155-1166.

 

  1. Harris WS, Del Gobbo L, Tintle NL. The omega-3 index and relative risk for coronary heart disease mortality: estimation from 10 cohort studies. Atherosclerosis. 2017;262:51-54.

 

  1. Manson JE, Bassuk SS, Lee IM, et al. The Vitamin D and Omega-3 Trial (VITAL): rationale and design of a large randomized controlled trial of vitamin D and marine omega-3 fatty acid supplements for the primary prevention of cancer and cardiovascular disease. Contemp Clin Trials. 2012;33:159-171.

 

  1. NIH. U.S. National Library of Medicine. ClinicalTrials.gov. Outcomes study to assess statin residual risk reduction with Epanova in high CV risk patients with hypertriglyceridemia (STRENGTH). NCT02104817. https://clinicaltrials.gov.ct2/show/NCT02104817.

 

  1. Bhatt DL, Steg PG, Brinton EA, et al. Rationale and design of REDUCE-IT: Reduction of cardiovascular events with icosapent ethyl-intervention trial. Clin Cardiol. 2017;40:138-148.

 

Photo by Percy Pham

Participants with Elevated Lp (a) Had Greater than Average Benefit from Evolocumab in FOURIER

Participants with Elevated Lp (a) Had Greater than Average Benefit from Evolocumab in FOURIER

Kevin C Maki, PhD, CLS, FNLA and Mary R Dicklin, PhD

It has been known for decades that an elevated level of lipoprotein (a) or Lp (a) is associated with increased cardiovascular disease (CVD) risk.  The Lp (a) particle consists of a low-density lipoprotein (LDL) particle that has an apoprotein (a) glycoprotein linked to the apolipoprotein B via a single disulfide bond.

Lp (a) is mainly genetically determined and shows a right skewed distribution in most populations, with approximately 80% having values below 50 mg/dL, when measured by mass, and 100 nmol/L, when measured by particle concentration.1,2  Some individuals have extremely elevated levels, as high as 300 mg/dL in mass in some instances.  Lp (a) shares homology with the plasminogen molecule, and may interfere with fibrinolysis.  It can also enter the arterial endothelial space and participate, like other LDL particles, in initiation and promotion of atherosclerotic plaques.  In addition, oxidized phospholipids appear to bind to Lp (a); levels of Lp (a) and oxidized phospholipids are highly correlated.  Both elevated oxidized phospholipid and Lp (a) concentrations are associated with increased CVD risk.2,3

Mendelian randomization studies have shown that genetic variants associated with Lp (a) level are associated with CVD risk.  Smaller apolipoprotein (a) isoforms are associated with higher levels of Lp (a) in circulation, and both Lp (a) level (mass or particle concentration) and genetic variants associated with smaller isoforms have been associated with higher CVD risk in a dose-dependent manner (i.e., more alleles associated with higher CVD risk).  Thus, both traditional observational studies and studies of genetic variants that affect Lp (a) levels have been associated with CVD risk, which provides strong support for a causal relationship between Lp (a) level and CVD risk.

Statin therapy has little effect on the Lp (a) concentration.4  However, several interventions are known to affect the circulating Lp (a) concentration, but evidence has been lacking for a benefit of lowering Lp (a) level per se as an intervention to reduce CVD risk.  Among the interventions known to lower Lp (a) are niacin, estrogen, LDL apheresis, cholesterol ester transfer protein inhibition, and two drugs used to treat familial hypercholesterolemia (mipomersen and lomitapide).4  In addition, the proprotein convertase subtilisin kexin type 9 (PCKS9) inhibitor class of lipid-altering medications is known to lower Lp (a) by 25% or more.5-7

Because of the ability of PCSK9 inhibitors to lower Lp (a) mass and particle concentration, as well as LDL cholesterol and LDL particle concentration, it would be expected that if Lp (a) lowering produced CVD benefit, that the risk reduction associated with PCSK9 inhibitor therapy would be expected to be greater among those with elevated Lp (a) concentrations.

The Further Cardiovascular Outcomes Research with PCSK9 Inhibition in Subjects with Elevated Risk (FOURIER) was a CVD outcomes trial that tested the effects of treatment with maximally tolerated statin therapy plus the PCSK9 inhibitor evolocumab or placebo on CVD event risk in patients with stable atherosclerotic CVD at the time of randomization.  The main results showed a 15% reduction in the primary composite event outcome and a 20% reduction in a key secondary composite measure over a median treatment period of 22 months.8

A pre-planned subgroup analysis was presented at the 86th Annual Congress of the European Atherosclerosis Society in Lisbon, Spain in early May 2018.  At baseline, the median Lp (a) level was 37 nmol/L and the 25th and 75th percentiles were 13 and 165 nmol/L, respectively.  A higher baseline Lp (a) particle concentration was associated with greater risk for a CVD event in the placebo group, with the fourth quartile having 26% higher (95% confidence interval 2% to 56%) risk of coronary heart disease death or myocardial infarction compared with the first quartile.9

Evolocumab treatment lowered the Lp (a) concentration and the degree of lowering was related to the baseline level.  Median absolute (nmol/L) changes in Lp (a) were -1, -9, -24 and -36 nmol/L in the first through fourth quartiles, respectively.  An analysis of the results for those with baseline Lp (a) above and below the median baseline level showed a larger risk reduction in those with values above the median than below (24% vs. 15%) for the outcome of CV death, myocardial infarction or stroke.  The number needed to treat (NNT) to prevent one event was lower in those with Lp (a) above the median (NNT = 36) than those below the median (NNT = 79).  In addition, cumulative CVD event incidence was lowest in those who achieved both Lp (a) and LDL cholesterol levels at or below the median (6.57%), was intermediate in those who achieved only one value at or below the median (7.88-8.45%) and was highest in those who had both levels above the median value (9.43%).9,10

These findings add to the body of evidence supporting a causal role for Lp (a) in CVD risk.  They also provide support for the view that lowering Lp (a) reduces CVD event risk, and therefore is a promising therapeutic target.  Thus, PCSK9 inhibitor therapy may be a reasonable consideration for high risk patients who have elevated Lp (a).  These results also confer enhanced optimism regarding the potential efficacy of therapies in development that target Lp (a), such as monoclonal antibodies and an antisense oligonucleotide for apolipoprotein (a).11

References

  1. Nordestgaard BG, Chapman MJ, Ray K, et al. Lipoprotein (a) as a cardiovascular risk factor: current status. Eur Heart J. 2010;31:2844-2853.
  2. Kronenberg F. Human genetics and the causal role of lipoprotein(a) for various diseases. Cardiovasc Drugs Ther. 2016;30:87-100.
  3. Tsimikas S, Witztum JL. The role of oxidized phospholipids in mediating lipoprotein(a) atherogenicity. Curr Opin Lipidol. 2008;19:369-377.
  4. Van Capelleveen JC, van der Valk FM, Stroes ESG. Current therapies for lowering lipoprotein (a). J Lipid Res. 2016;57:1612-1618.
  5. Raal F, Giugliano RP, Sabatine MS, et al. Reduction in Lp(a) with PCSK9 monoclonal antibody evolocumab (AMG 145): a pooled analysis of more than 1,300 patients in 4 phase II trials. J Am Coll Cardiol. 2014;63:1278-1288.
  6. Raal FJ, Giugliano RP, Sabatine MS, et al. PCSK9 inhibition-mediated reduction in Lp(a) with evolocumab: an analysis of 10 clinical trials and the LDL receptor’s role. J Lipid Res. 2016;57:1086-1096.
  7. Gaudet D, Watts GF, Robinson JG, et al. Effect of alirocumab on lipoprotein(a) over ≥1.5 years (from the phase 3 ODYSSEY program). Am J Cardiol. 2017;119:40-46.
  8. Sabatine MS, Giugliano RP, Keech AC, et al. Evolocumab and clinical outcomes in patients with cardiovascular disease. N Engl J Med. 2017;376:1713-1722.
  9. Davenport L. Lp(a) levels may modulate CV benefits of evolocumab: FOURIER – Medscape – May 09, 2018. Accessed at file:///Users/Mary/Downloads/FOURIER%20Lp(a)%20Level%20Influences%20Benefit%20from%20Evolocumab%2010May18.pdf.
  10. Maxwell YL. Unlocking Lp(a): baseline levels matter, but so too does absolute reduction. tctMD/the heart beat. May 08, 2018. Accessed at https://www.tctmd.com/news/unlocking-lpa-baseline-levels-matter-so-too-does-absolute-reduction.

    11.  Vuorio A, Watts GF, Kovanen PT. Depicting new pharmacological strategies for familial hypercholesterolaemia involving lipoprotein(a). Eur

Photo by Joel Filipe

ODYSSEY Outcomes Trial: Topline Results and Clinical Implications

ODYSSEY Outcomes Trial: Topline Results and Clinical Implications

By Kevin C Maki, PhD, CLS, FNLA; Kristen N Smith, PhD, RD, LD; Mary R Dicklin, PhD

 Background:

Cardiovascular disease (CVD) event risk is high in those with recent acute coronary syndromes (ACS), despite treatment with evidence-based preventive therapies. Prior research has shown that CVD event risk is lowered when low-density lipoprotein cholesterol (LDL-C) is lowered through various means, such as:

  • Statin therapy (compared with placebo)2
  • High-intensity statin therapy (compared with moderate-intensity statin therapy)3
  • Ezetimibe added to statin therapy (compared with placebo)4
  • Anacetrapib added to statin therapy (compared with placebo)5
  • Evolocumab added to statin therapy (compared with placebo)6

Alirocumab is a fully human monoclonal antibody against proprotein convertase subtilisin kexin type 9 (PCSK9), a validated target for risk reduction in patients with stable atherosclerotic CVD.7-8. Research outcomes on alirocumab show that it reduces LDL-C (sustained reductions) and other atherogenic lipoproteins7 with documented safety and tolerability.8

The hypothesis of the Evaluation of Cardiovascular Outcomes after an Acute Coronary Syndrome During Treatment with Alirocumab (ODYSSEY Outcomes) trial was that alirocumab, versus placebo, reduces cardiovascular (CV) morbidity and mortality after recent ACS in patients with elevated levels of atherogenic lipoproteins despite intensive or maximum-tolerated statin therapy.9

 Methods:

This study was a randomized, double-blind, placebo-controlled, parallel group study of 18,924 patients randomized at 1315 sites in 57 countries between November 2, 2012 and November 11, 2017.1,9

Key inclusion criteria:

  • Age ≥40 years
  • ACS
    • 1 to 12 months prior to randomization [acute myocardial infarction (MI) or unstable angina]
  • High-intensity statin therapy
    • Atorvastatin 40 to 80 mg daily, or
    • Rosuvastatin 20 to 40 mg daily, or
    • Maximum tolerated dose of one of these agents for ≥2 weeks
    • Patients not taking statins were authorized to participate if tolerability issues were present and documented
  • Inadequate control of lipids
    • LDL-C ≥70 mg/dL (1.8 mmol/L), or
    • Non-high-density lipoprotein cholesterol (non-HDL-C) ≥100 mg/dL (2.6 mmol/L), or
    • Apolipoprotein B ≥80 mg/dL

 

Key exclusion criteria:

  • Uncontrolled hypertension
  • NYHA class III or IV heart failure; left ventricular ejection fraction <25% if measured
  • History of hemorrhagic stroke
  • Fasting triglycerides >400 mg/dL (4.52 mmol/L)
  • Use of fibrates, other than fenofibrate or fenofibric acid
  • Recurrent ACS within 2 weeks prior to randomization
  • Coronary revascularization performed within 2 weeks prior to or after randomization
  • Liver transaminases >3 x upper limit of normal; hepatitis B or C infection
  • Creatine kinase >3 x upper limit of normal
  • Estimated glomerular filtration rate <30 mL/min/1.73 m2
  • Positive pregnancy test

 

Primary Efficacy Outcome

Major Secondary Efficacy Endpoints

Other Secondary and Safety Endpoints

Time of first occurrence:

§  Coronary heart disease (CHD) death, or

§  Non-fatal MI, or

§  Fatal or non-fatal ischemic stroke, or

§  Unstable angina requiring hospitalization

Tested in the following hierarchical sequence:

§  CHD event: CHD death, non-fatal MI, unstable angina requiring hospitalization, or ischemia-driven coronary revascularization

§  Major CHD event: CHD death or non-fatal MI

§  CV event: CV death, non-fatal CHD event, or non-fatal ischemic stroke

§  All-cause death, non-fatal MI, non-fatal ischemic stroke

§  CHD death

§  CV death

§  All-cause death

Secondary endpoints:

§  Components of the primary endpoint considered individually:

·       CHD death

·       Non-fatal MI

·       Fatal and non-fatal ischemic stroke

·       Unstable angina requiring hospitalization

§  Ischemia-driven coronary revascularization

§  Congestive heart failure requiring hospitalization

 

Safety endpoints:

§  Adverse events

§  Laboratory assessments

Patients screened for this study completed a run-in period of 2 to 16 weeks on high-intensity or maximum-tolerated dose of atorvastatin or rosuvastatin. If at least one lipid entry criterion was met, then the subject was randomized to receive either subcutaneous alirocumab (75 or 150 mg) or placebo every 2 weeks. In order to maximize the number of patients in the target LDL-C range (25-50 mg/dL), alirocumab was blindly titrated or subjects were blindly switched to placebo if they were either substantially above or below (<15 mg/dL for LDL-C) the target range.

Results:

Of the 18,924 patients randomized for this study:

  • 9462 were assigned to alirocumab and 9462 received placebo
  • Median follow-up was 2.8 years (interquartile range limits 2.3-3.4 years)
  • 8242 (44%) patients with potential follow-up ≥3 years
  • 1955 patients experienced a primary endpoint; 726 patients died

Topline results showed that treatment with alirocumab was associated with significant reductions in LDL-C, and these reductions remained consistent over time.  Mean baseline and on-treatment LDL-C values are shown in the table below.

 

 

Placebo

(n = 9462)

Alirocumab

(n = 9462)

Baseline

  87.0 mg/dL

87.0 mg/dL

4 months

  93.3 mg/dL

39.8 mg/dL

12 months

  96.4 mg/dL

48.0 mg/dL

48 months

101.4 mg/dL

66.4 mg/dL

The “on-treatment” analysis showed that mean LDL-C was lowered by 55.7 mg/dL (-62.7%) in the alirocumab group vs. placebo at 4 months, 54.1 mg/dL (-61.0%) at 12 months and 48.1 mg/dL (-54.7%) at 48 months.

Several endpoints were significantly less frequent in the alirocumab group vs. placebo. Major adverse cardiac events (MACE; includes CHD death, non-fatal MI, ischemic stroke, or unstable angina requiring hospitalization) are shown in the table below, along with other endpoints.

 

Endpoint

Alirocumab

(n = 9462)

n (%)

Placebo

(n = 9462)

n (%)

Hazard Ratio (95% Confidence Interval)

Log-rank

P-value

MACE

903 (9.5)

1052 (11.1)

0.85 (0.78, 0.93)

0.0003

     CHD death

205 (2.2)

222 (2.3)

0.92 (0.76, 1.11)

0.38

     Non-fatal MI

626 (6.6)

722 (7.6)

0.86 (0.77, 0.96)

0.006

     Ischemic stroke

111 (1.2)

152 (1.6)

0.73 (0.57, 0.93)

0.01

     Unstable angina

37 (0.4)

60 (0.6)

0.61 (0.41, 0.92)

0.02

Secondary

       

     CHD event

1199 (12.7)

1349 (14.3)

0.88 (0.81, 0.95)

0.001

     Major CHD

     event

793 (8.4)

899 (9.5)

0.88 (0.80, 0.96)

0.006

     CV event

1301 (13.7)

1474 (15.6)

0.87 (0.81, 0.94)

0.0003

     Death, MI,

     ischemic stroke

973 (10.3)

1126 (11.9)

0.86 (0.79, 0.93)

0.0003

     CHD death

205 (2.2)

222 (2.3)

0.92 (0.76, 1.11)

0.38

     CV death

240 (2.5)

271 (2.9)

0.88 (0.74, 1.05)

0.25

     All-cause death

334 (3.5)

392 (4.1)

0.85 (0.73, 0.98)

0.026*

(nominal)

Several pre-specified subgroup analyses for the primary outcome variable were presented, including, notably, an analysis by baseline LDL-C categories of <80, 80-99, and ≥100 mg/dL.  Although the test for heterogeneity of response across subgroups was not statistically significant (p = 0.09), the hazard ratio (HR) for the comparison of alirocumab to placebo was numerically lower for the subgroup with baseline LDL-C ≥100 mg/dL [HR 0.76, 95% confidence interval (CI) 0.65 to 0.87] than for those with baseline LDL-C <80 mg/dL (HR 0.86, 95% CI 0.74 to 1.01) or 80-99 mg/dL (HR 0.96, 95% CI 0.92 to 1.14).

Comment by Kevin C Maki, PhD, CLS, FNLA:

When compared with placebo, the use of alirocumab 75 or 150 mg every two weeks, aiming for LDL-C levels of 25-50 mg/dL (and allowing levels as low as 15 mg/dL), led to reduced MACE, MI and ischemic stroke, and was associated with reduced all-cause death. Treatment was safe and well tolerated. CV and CHD death were not significantly reduced. Therefore, the results for total mortality should be viewed with caution, since roughly 70% of total mortality was attributable to CV causes. 

Subgroup analyses identified numerically larger benefits for the primary outcome in subjects with baseline levels of LDL-C ≥100 mg/dL (median LDL-C 118 mg/dL). However, the test for heterogeneity of effect across subgroups was not statistically significant (p = 0.09).  The proportional risk reductions for subjects with baseline LDL-C <80, 80-99 and ≥100 mg/dL were 14%, 4% and 24%, respectively. Only the subgroup with LDL-C ≥100 mg/dL showed a statistically significant reduction in the alirocumab group compared with placebo. That was also true for all-cause mortality, which was reduced by 29% in the alirocumab group vs. placebo in subjects with baseline LDL-C ≥100 mg/dL, but was not significantly reduced in the other subgroups. This finding should also be interpreted with caution because the test for heterogeneity was, again, not significant (p = 0.12). 

The US Institute for Clinical and Economic Review (ICER) provided new estimates of the price range that would be acceptable for the drug, based on the results of the ODYSSEY Outcomes trial.10 ICER calculated two updated value-based price benchmarks, net of rebates and discounts, for alirocumab in patients with a recent acute coronary event:  $2300-$3400 per year if used to treat all patients who meet trial eligibility criteria, and $4500-$8000 per year if used to treat higher-risk patients with LDL-C ≥100 mg/dL despite intensive statin therapy. The manufacturers of alirocumab (Sanofi and Regeneron Pharmaceuticals, Inc.) have announced plans for a reduced price for the drug that will be in the range of the $4500-$8000 identified by ICER, which is substantially below the “list price” of approximately $14,000 per year that had been charged initially.

A number of commentaries from experts in the field have suggested that this class of medications is appropriate for use mainly in patients in whom LDL-C is ≥100 mg/dL, based on the results from the analyses presented at the American College of Cardiology meeting (and not yet published in a peer reviewed journal), including the cost-effectiveness evaluation by ICER. For example, the highly respected cardiologist Milton Packer, MD wrote a piece in which he stated:11

“…the benefit in the entire trial was driven entirely by the effect seen in 5,629 patients who started with LDL cholesterol >100 mg/dL. There was no benefit in patients with lower values for baseline LDL cholesterol.”

With all due respect to Dr. Packer and others who hold this opinion, I view this conclusion as premature for several reasons. The test for heterogeneity (treatment by subgroup interaction) across baseline LDL-C categories was not significant at an alpha of 5%, showing a p-value of 0.09.  Moreover, the study was not designed with sufficient statistical power to reliably differentiate effects across baseline LDL-C categories. This lack of statistical power for tests of heterogeneity of treatment effects argues for caution in the clinical application of such findings, even when the test for heterogeneity is pre-specified and/or when it does reach statistical significance.

Sir Richard Peto, the eminent biostatistician and epidemiologist from the University of Oxford has quipped that only one thing is worse than doing subgroup analyses for a clinical trial, and that is believing the results! To demonstrate the potential unreliability, Peto reported on a set of subgroup analyses from the Second International Study of Infarct Survival (ISIS-2).12  In the trial overall, the survival advantage produced by aspirin for patients with suspected myocardial infarction was 23%, which was highly statistically significant (p < 0.000001).13 ISIS-2 patients were divided into 12 subgroups according to their astrological sign, and the treatment effect of aspirin compared with placebo was calculated in each subgroup. The results ranged from no apparent effect of aspirin in two subgroups (Libra and Gemini) to aspirin being associated with a halving of the mortality in another (Capricorn).

Results from subgroup analyses are useful for generating hypotheses to test prospectively, but should not, in most cases, be applied as the sole basis for clinical practice decisions without replication in other trials, and, ideally, prospective testing in one or more trials designed for the purpose of evaluating possible differences across subgroups in clinical response.  Regarding the results for the subgroup with baseline LDL-C <100 mg/dL in ODYSSEY Outcomes, it should be noted that the authors of the paper from the Further Cardiovascular Outcomes Research with PCSK9 Inhibition in Subjects with Elevated Risk (FOURIER) trial with the other approved PCSK9 inhibitor agent, evolocumab, report the following:6

“The benefits were also consistent across quartiles of baseline LDL cholesterol levels, from patients in the top quartile, who had a median LDL cholesterol level of 126 mg per deciliter (interquartile range, 116 to 143) (3.3 mmol per liter [interquartile range, 3.0 to 3.7]) at baseline, down to those in the lowest quartile, who had a median LDL cholesterol level of 74 mg per deciliter (interquartile range, 69 to 77) (1.9 mmol per liter [interquartile range, 1.8 to 2.0]) at baseline.”

Results from other trials such as the Improved Reduction of Outcomes: Vytorin Efficacy International Trial4 (IMPROVE-IT; statin plus ezetimibe) and the HPS3/TIMI55 Randomized Evaluation of the Effects of Anacetrapib through Lipid-modification5 (REVEAL; statin plus anacetrapib) have shown benefits with atherogenic cholesterol lowering that are generally consistent with the results observed in statin trials based on the Cholesterol Treatment Trialists’ (CTT) analyses,14 i.e., a HR of 0.78 (22% reduction) per mmol/L (38.7 mg/dL) reduction in LDL-C, despite average baseline LDL-C levels below 100 mg/dL (~94 mg/dL in IMPROVE-IT and 61 mg/dL in HPS2/TIMI55-REVEAL).  Notably, in both IMPROVE-IT and HPS3/TIMI55-REVEAL, the placebo and active treatment group Kaplan-Meier curves did not clearly separate for the first 2.0 to 2.5 years. In a prior study with evacetrapib [Assessment of Clinical Effects of Cholesteryl Ester Transfer Protein Inhibition with Evacetrapib in Patients at a High Risk for Vascular Outcomes (ACCELERATE)], no CVD event benefit (or harm) was observed over a median follow-up period of 2.2 years, despite modest lowering of LDL-C.15  The median follow-up period for both of the PCSK9 inhibitor trials (FOURIER, 2.2 years and ODYSSEY Outcomes, 2.8 years) was short compared with those from most trials of statins, which had median follow-up periods that averaged roughly 5 years.14 In fact, the FOURIER investigators reported that:

“… in FOURIER, the magnitude of the risk reduction with regard to the key secondary end point appeared to grow over time, from 16% during the first year to 25% beyond 12 months, which suggests that the translation of reductions in LDL cholesterol levels into cardiovascular clinical benefit requires time.”

Findings from studies of genetic variants that alter atherogenic cholesterol levels suggest that the benefits of maintaining lower levels may not be fully apparent after only a few years of intervention. The prototypical example of this is one of the findings that led to the development of the PCSK9 inhibitor class of lipid-altering agents. Cohen et al.16 reported that a nonsense loss-of-function mutation in the PCSK9 gene was associated with a 38 mg/dL (0.98 mmol/L) lower average level of LDL-C, and a missense mutation was associated with a 21 mg/dL (0.54 mmol/L) reduction in LDL-C. Based on the CTT relationship, the predicted reductions in CVD event risk would have been roughly 22% and 13%, respectively. However, the observed reductions in CVD (CHD and stroke) incidence were approximately 50% and 37%, respectively (estimated from data presented in the paper). The reductions in risk were most evident for CHD, where HRs were 0.11 (89% reduction) and 0.50 (50% reduction) for those with the nonsense and missense mutations, respectively. These results, and those from many other studies of lipid-altering genetic variants, suggest a greater CVD event risk reduction than would be predicted from the effects of statin and other lipid-altering therapies on risk.17 A likely explanation is that genetic variants produce differences that are maintained over decades, rather just a few years duration, as is the case in randomized, controlled intervention trials. 

Thus, there are reasons to believe that “lower is probably better” for atherogenic cholesterol levels with regard to CVD event reduction in high-risk patients, even if the baseline level of LDL-C is less than 100 mg/dL. Atherosclerosis is a disease that develops and progresses over decades. Thus, it seems possible, and indeed, likely, that benefits will be observed with therapy to further reduce atherogenic cholesterol among those with LDL-C less than 100 mg/dL over follow-up periods longer than the 2- to 3-year median durations in the ODYSSEY Outcomes and FOURIER trials. At present, this is a hypothesis that remains to be verified with additional clinical research. Given that the subgroup with baseline LDL-C <100 mg/dL who received placebo in the ODYSSEY Outcomes trial experienced an event rate above 3% per year, substantial residual risk is present in such patients. Dr. Packer ended his commentary by saying “The ODYSSEY trial shows that we may have reached the limits of what we can achieve by lowering lipids.” My view is that the potential for aggressive atherogenic cholesterol reduction to lower CVD event risk in those with recent ACS (and other high-risk patients) has not been fully evaluated. Accordingly, efforts to understand the effects of atherogenic cholesterol lowering in high-risk patients with LDL-C levels <100 mg/dL should remain an important priority.

References:

  1. Schwartz GG, Szarek M, Bhatt DL, et al. The ODYSSEY OUTCOMES trial: topline results. Alirocumab in patients after acute coronary syndrome. Presented at ACC.18 67th Annual Scientific Session & Expo. Acc.18 Joint ACC/JACC Late-breaking clinical trials. Accessed at https://accscientificsession.acc.org/features/2018/03/video-sanofi-regeneron on March 15, 2018.
  2. Schwartz GG, Olsson AG, Ezekowitz MD, et al. Effects of atorvastatin on early recurrent ischemic events in acute coronary syndromes: the MIRACL study: a randomized controlled trial. JAMA. 2001;285(13):1711-1718.
  3. Cannon CP, Braunwald E, McCabe CH, et al. Intensive versus moderate lipid lowering with statins after acute coronary syndromes. N Engl J Med. 2004;350(15):1495-1504.
  4. Cannon CP, Blazing MA, Giugliano RP, et al. Ezetimibe added to statin therapy after acute coronary syndromes. N Engl J Med. 2015;372(25):2387-2397.
  5. HPS3/TIMI55-REVEAL Collaborative Group, Bowman L, Hopewell JC, et al. Effects of anacetrapib in patients with atherosclerotic vascular disease. N Engl J Med. 2017;377(13):1217-1227.
  6. Sabatine MS, Giugliano RP, Keech AC, et al. Evolocumab and clinical outcomes in patients with cardiovascular disease. N Engl J Med. 2017;376(18):1713-1722.
  7. Robinson JG, Farnier M, Krempf M, et al. Efficacy and safety of alirocumab in reducing lipids and cardiovascular events. N Engl J Med. 2015;372(16):1489-1499.
  8. Robinson JG, Rosenson RS, Farnier M, et al. Safety of very low low-density lipoprotein cholesterol levels with alirocumab: pooled data from randomized trials. J Am Coll Cardiol. 2017;69(5):471-482.
  9. Schwartz GG, Bessac L, Berdan LG, et al. Effect of alirocumab, a monoclonal antibody to PCSK9, on long-term cardiovascular outcomes following acute coronary syndromes: rationale and design of the ODYSSEY outcomes trial. Am Heart J. 2014;168(5):682-689.
  10. Institute for Clinical and Economic Review, 2018. Alirocumab for treatment of high cholesterol: effectiveness and value. Preliminary New Evidence Update. March 10, 2018. Accessed at https://icer-review.org/wp-content/uploads/2018/03/Alirocumab-Preliminary-New-Evidence-Update_03102018.pdf on March 23, 2018.
  11. Packer, M. Confessions and omens from the ODYSSEY Trial - Milton Packer assesses his predictions in the future of lipid research. MEDPAGE TODAY, March 14, 2018. Accessed at https://www.medpagetoday.com/blogs/revolutionandrevelation/71755 on March 23, 2018.
  12. Peto R. Current misconception 3: that subgroup-specific trial mortality results often provide a good basis for individualising patient care. Br J Cancer. 2011;104:1057-1058.
  13. ISIS-2 (Second International Study of Infarct Survival) Collaborative Group. Randomised trial of intravenous streptokinase, oral aspirin, both, or neither among 17,187 cases of suspected acute myocardial infarction: ISIS-2. Lancet. 1988;2(8607):349-360.
  14. Baigent C, Keech A, Kearney PM, et al. Efficacy and safety of cholesterol-lowering treatment: prospective meta-analysis of data from 90,056 participants in 14 randomised trials of statins. Lancet. 2005;366(9493):1267-1278.
  15. Lincoff AM, Nicholls SJ, Riesmeyer JS, et al. Evacetrapib and cardiovascular outcomes in high-risk vascular disease. N Engl J Med. 2017;376(20):1933-1942.
  16. Cohen JC, Boerwinkle E, Mosley TH, Jr., et al. Sequence variations in PCSK9, low LDL, and protection against coronary heart disease. N Engl J Med. 2006;354(12):1264-1272.

17.       Ference BA. Mendelian randomization studies: using naturally randomized genetic data to fill evidence gaps. Curr Opin

Use of Supplemental Long Chain Omega-3 Fatty Acids and Risk for Cardiac Death: An Updated Meta-Analysis and Review of Research Gaps

Use of Supplemental Long Chain Omega-3 Fatty Acids and Risk for Cardiac Death: An Updated Meta-Analysis and Review of Research Gaps

By Orsolya M. Palacios, RD, PhD and Kevin C. Maki, PhD

Randomized, controlled trials (RCTs) assessing the use of supplemental long chain omega-3 polyunsaturated fatty acids (LC-OM3), mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on risk for various types of cardiovascular disease events have yielded mixed results.  Some studies have suggested a beneficial effect, while others shown a neutral effect.  The outcome for which both the observational evidence on LC-OM3 intake or status and RCTs of supplementation appears to show the most consistent association is cardiac death.  Therefore, this meta-analysis and review of research gaps was conducted with two aims: 1) to update and further explore the available RCT data regarding LC-OM3 supplementation and risk for cardiac death; and 2) to briefly review the evidence regarding the effects of LC-OM3 intake on cardiac event risk, and to propose testable hypotheses for the mixed results obtained in RCTs regarding supplemental LC-OM3 use and cardiac event risk.

A literature search was conducted using PubMed and Ovid/Medline to identify RCTs examining supplemental LC-OM3 use (as dietary supplements or pharmaceutical LC-OM3 concentrates) and the outcome of cardiac death.  An intervention period of at least one year was required to be included in the primary analysis.  Studies that provided LC-OM3 in a food vehicle and studies in which the subjects had implanted cardiac defibrillators were excluded from the primary analysis but included in the secondary analysis.  Meta-analysis was employed to compare cumulative frequencies of cardiac death events between the LC-OM3 and control groups, including sensitivity and subset analyses.  Fourteen RCTs were identified for the primary analysis (71,899 subjects).  In the LC-OM3 arms, 1613 cardiac deaths were recorded (4.48% of subjects), compared to 1746 cardiac deaths in the control groups (4.87% of subjects). The pooled relative risk estimate showed an 8.0% (95% confidence interval 1.6%, 13.9%, p = 0.015) lower risk in the LC-OM3 arms vs. controls. Subset analyses showed numerically larger effects (12.9% to 29.1% lower risks, all p < 0.05) in RCTs with EPA+DHA dosages >1 g/d and with higher risk groups (secondary prevention, baseline mean or median triglycerides (TG) ≥150 mg/dL or low-density lipoprotein cholesterol (LDL-C) ≥130 mg/dL, statin use <40% of subjects). Heterogeneity was low (I2 ≤ 15.5%, p > 0.05) for the primary and subset analyses.

Comment:

The present meta-analysis of RCTs showed a modest, but statistically significant, benefit of LC-OM3 supplementation on risk for cardiac death (8.0% in the primary analysis). Subgroup analyses show numerically larger benefits (12.9% to 29.1%, all p < 0.05) in studies that used >1 g/d of EPA+DHA, and in higher risk groups, including those with greater mean or median levels of TGs (≥150 mg/dL) or LDL-C (≥130 mg/dL), secondary prevention study samples, and studies with lower baseline use of statins (which is also a proxy for use of other cardioprotective agents).  These results suggest that additional research is warranted to further evaluate the potential risk reduction with LC-OM3 supplementation at higher dosages, and in higher risk samples.  Future RCTs should include evaluation of biomarkers of omega-3 status at baseline and during treatment, and should be designed to test specific hypotheses about the mechanisms through which benefits might be produced.  Taken together, the results of this analysis support the recent Science Advisory from the American Heart Association that concluded LC-OM3 “treatment is reasonable” for: 1) secondary prevention of coronary heart disease (CHD) and sudden cardiac death among patients with prevalent CHD, and 2) secondary prevention of adverse outcomes in patients with heart failure.  Because of the low risk for adverse effects with LC-OM3 supplementation, even a modest benefit is clinically meaningful.

A podcast by the lead author discussing this study is posted at Consultant 360: http://www.consultant360.com/content/omega3s-improve-cardio-health

 

Photo by Caroline Attwood

Redefining a Healthful Diet: New Results from the Largest Observational Study Ever Conducted on Nutrition and Heart Health Challenge Current Advice

Redefining a Healthful Diet: New Results from the Largest Observational Study Ever Conducted on Nutrition and Heart Health Challenge Current Advice

By Orsolya M. Palacios, RD, PhD and Kevin C. Maki, PhD

Background
Cardiovascular disease is a major cause of morbidity and mortality worldwide.  Its relationship to healthful diet and lifestyle practices has been an area of active research for decades since these represent modifiable behaviors that have the potential to affect cardiovascular disease risk and overall health.  Within dietary recommendations, health authorities advise reducing total and saturated dietary fats while increasing carbohydrates from whole grains, as well as intakes of fruits, vegetables, nuts, seeds and legumes (DGA, 2015). These recommendations are based on studies that have been mostly observational in nature and conducted in high-income countries such as the U.S. and those in Western Europe.  The advice to lower saturated fat intake and replace it with unsaturated fat sources stems largely from the linear relationship between saturated fat intake and a low-density lipoprotein cholesterol (LDL-C) level.  LDL-C is a risk factor for cardiovascular disease, and thus, the working concept is that reducing saturated fat intake reduces LDL-C levels which, in turn, reduce cardiovascular disease risk.  In conjunction with lowering saturated fat intake, health authorities recommend reducing intakes of animal products such as meat and dairy products to accommodate higher intake of plant foods.  However, the advice to increase fruit, vegetable and legume intake also stems from observational studies conducted mainly in high-income nations.  Research on the associations of fruit, vegetable and legume intakes with health outcomes in other nations is sparse and inconclusive.

The dietary habits of populations within wealthy countries are generally one of excess, which significantly differs from the dietary habits of populations in low- and middle-income countries, where intake of certain nutrients, including adequate intake of complete proteins, may be sub-optimal.  Furthermore, dietary habits are strongly rooted in cultural practices, which can also vary greatly among countries, regardless of income status.  Since cardiovascular disease is a leading cause of morbidity and mortality in low- and middle-income countries as well, understanding the link between currently recommended dietary patterns, cardiovascular disease events and/or mortality in more globally-represented populations is crucial in providing accurate and meaningful guidelines for healthful food consumption.

 Methods
The Prospective Urban Rural Epidemiology (PURE) study was conducted to address this topic.  Researchers recruited individuals aged 35 to 70 years of age in 18 low-income, middle-income and high-income countries between January 1, 2003 and March 31, 2013 to participate in the PURE prospective cohort study to assess the association between total mortality and major cardiovascular events and diet choices.  Habitual dietary intake data was analyzed from 135,355 individuals using validated food frequency questionnaires, which documented energy intake from fat (including total, saturated, monounsaturated and polyunsaturated fat), carbohydrate and protein as well as daily intake of fruit, vegetable and legume servings.  Demographic information, socioeconomic status, lifestyle, physical activity, health history and medication use questionnaires were also distributed and assessed.  Trained physicians using standard definitions completed standardized case-report forms to report mortality and major cardiovascular events.  The primary outcomes in this study were total mortality and major cardiovascular events (fatal cardiovascular disease, non-fatal myocardial infarction, stroke and heart failure) and secondary outcomes were all myocardial infractions, stroke, cardiovascular disease mortality, and non-cardiovascular disease mortality.

To assess associations between macronutrient energy contribution and cardiovascular disease events and/or mortality, participants were categorized into quintiles based on the dietary percentage of energy from total fat, individual fats, carbohydrates and protein; hazard ratios (HRs) were calculated using a multivariable Cox frailty model.  To assess the associations between daily fruit, vegetable and legume servings and cardiovascular disease events and/or mortality, Cox frailty models with random effects were also employed and HRs calculated.

Results
Median follow up of participants was 7.4 years during which time 5796 deaths and 4784 major cardiovascular disease events were recorded.  Regarding macronutrient intake, higher carbohydrate intake was associated with a significantly higher total mortality risk for the highest quintile versus the lowest quintile, but there was no significant association between carbohydrate intake and cardiovascular disease, myocardial infarction, stroke or cardiovascular disease mortality.

Results from this study indicate that total fat, as well as saturated, monounsaturated and polyunsaturated fats all were significantly associated with a lower risk of mortality for the highest quintile versus the lowest quintile of total and individual fat intake.  Specifically, the HR for the highest versus the lowest quintile of fat intake was 0.77 (95% confidence interval [CI] 0.67-0.87) for total fat, 0.86 (95% CI 0.76-0.99) for saturated fat, 0.81 (95% CI 0.71-0.92) for monounsaturated fat, and 0.80 (95% CI 0.71-0.89) for polyunsaturated fat.  For cardiovascular disease events, the highest quintile of saturated fat intake was associated with a significantly lower risk of stroke (HR 0.79, 95% CI 0.64-0.98) compared to the lowest quintile of saturated fat intake.  Neither total fat nor any of the individual fats were associated with myocardial infarction risk or cardiovascular disease mortality.

Like total fat, the highest quintile versus the lowest quintile of total protein intake was significantly and inversely associated with total mortality risk (HR 0.88, 95% CI0.77-1.00) and non-cardiovascular disease mortality (HR 0.85, 95% CI 0.73-0.99).  Animal protein intake was associated with a significantly lower risk of total mortality whereas plant protein intake had no significant association with total mortality.

Total Fat HR (5th Quintile vs. 1st Quintile) 95% CI P-trend
Total Mortality 0.77 0·67–0·87 <0.0001
CVD Mortality 0.92 0·72–1·16         0.50
Non-CVD Mortality 0.70 0·60–0·82       <0.0001
Major CVD Events 0.95 0·83–1·08         0.33
Saturated Fat HR (1st Quintile vs. 5th Quintile) 95% CI P-trend
Total Mortality 0.86 0·76–0·99 0.0088
CVD Mortality 0.83 0·65–1·07         0.20
Non-CVD Mortality 0.86 0·73–1·01 0.0108
Major CVD Events 0.95 0·83–1·10         0.49
Fruits, Vegetables & Legumes HR (< 1 serving/day vs. 3-4 servings/day) 95% CI P-trend
Total Mortality 0.78 0.69–0.88 0.0001
CVD Mortality 0.81 0.65–1.02 0.0568
Non-CVD Mortality 0.77 0.66–0.89 0.0038
Major CVD Events 1.06 0.92–1.22 0.1301

Abbreviations: CVD, cardiovascular disease; HR, hazard ratio

Adapted from: Ramsden et al. Lancet (2017) S0140 (17)32241-9; Toledo et al.  Lancet (2017) S0140-6736(17)32251-1.

The mean fruit, vegetable and legume intake was 3.91 (standard deviation 2.77) daily servings.  When the researchers assessed the links between fruit, vegetable and legume intakes and outcomes, they found that higher fruit, vegetable and legume intake was significantly inversely associated with major cardiovascular disease, myocardial infarction, cardiovascular mortality, non-cardiovascular mortality and total mortality after adjustments for age, sex and random effects.  However, these effects were diminished after multivariable adjustments.  The HR for total mortality was lowest for those consuming three to four daily servings of fruit, vegetables and legumes (HR 0.78, 95% CI 0.69-0.88) compared to the reference group, who consumed less than one serving of these foods per day.  Higher intakes of fruits, vegetables and legumes were not associated with further lowering of risk.  When assessed independently, fruit intake was associated with lower mortality, including total mortality, cardiovascular mortality and non-cardiovascular mortality.  Raw vegetables were strongly linked to lower mortality risk whereas cooked vegetables had a modest association with lower risk.  Legume intake was inversely associated with non-cardiovascular death and total mortality.

Comment

To date, the PURE study is the largest observational study to assess the link between nutrient intakes, food group intakes, cardiovascular disease events (including death) and overall mortality.  It encompassed data from over 135,000 participants in 18 countries across five continents from low-, mid- and high-income nations.  The results of this study align with some general recommendations (e.g,. emphasize consumption of fruits, vegetables and legumes) but are in conflict with some others.  For example, health authorities recommend increasing intakes of fruits, vegetables and legumes at the expense of animal foods (DGA, 2015).  However, the results of this study suggest that the association between increased fruit, vegetable and legume intake plateaus after three to four daily servings, and the median fruit, vegetable and legume intake among participants was already 3.9 daily servings.  Thus, as a whole, participants were theoretically obtaining the maximal benefit from intake of these foods and the incremental benefit beyond the median level of intake in the populations studied is uncertain.  The study’s finding that higher energy intake from animal protein is linked to reduced total mortality, while plant proteins, such as those found in legumes, showed no significant association, does not align with the some aspects of the current Dietary Guidelines for Americans (DGA, 2015).  Although it recommends an increase in seafood, The Dietary Guidelines for Americans also recommends strategies such as using legumes, nuts and seeds in place of meat and poultry in mixed dishes to attain protein needs and to increase vegetable intake while cutting back on foods such as some meats, poultry and cheeses to help lower saturated fat intake (DGA, 2015).

However, the PURE study results challenge the emphasis on reducing intake of saturated fat.  Higher energy intake from fat and each individual type of fat, including saturated fat, was associated with lower total mortality, as well as lower risk for some cardiovascular disease events.  Carbohydrate energy intake either showed no association on assessed outcomes or was associated with an increased risk for mortality.  However, it should be emphasized that intakes of saturated fats were generally low, with mean values ranging from 5.7% in China to 10.9% in Europe and North America.  Across countries, total and saturated fat intakes are positively associated with socioeconomic status.  Thus, in countries with higher intakes of total and saturated fat, and thus lower intakes of carbohydrate, higher socioeconomic status, with resulting access to higher quality healthcare, is a potential confounder.

Taken together, the results from PURE raise questions about current dietary guidance, which is largely based on results from observational studies completed in the U.S. and Europe.  Unfortunately, very few randomized, controlled trials have been completed to assess the influence of dietary guidance on long-term health and disease incidence.  While difficult and expensive, these are essential for fully evaluating the potential benefits and risks of dietary recommendations (Maki, 2014).  The strongest recommendations should be limited to those instances where results from randomized, controlled trials align with findings from observational studies.  While the results from PURE are at odds with some current dietary recommendations, they are consistent with the age-old adage “everything in moderation.”

 PURE Study References

Dehghan M, Mente A, Zhang X, et al. Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study.  Lancet. 2017; S0140-6736(17)32252-3.

Miller V, Mente A, Dehghan M, et al. Fruit, vegetable, and legume intake, and cardiovascular disease and deaths in 18 countries (PURE): a prospective cohort study.  Lancet. 2017; S0140-6736(17)32253-5.

Ramsden CE, Domenichiello AF. PURE study challenges the definition of a healthy diet: but key questions remain.  Lancet. 2017; S0140-6736(17)32241-9.

Toledo E, Martinez-Gonzalez MA. Fruits, vegetables, and legumes: sound prevention tools.  Lancet. 2017; S0140-6736(17)32251-1.

Additional References

Maki KC, Slavin JL, Rains TM, Kris-Etherton PM.  Limitations of observational evidence: implications for evidence-based dietary recommendations.  Adv Nutr. 2014;5(1)7-14.

U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2015 – 2020 Dietary Guidelines for Americans. 8th Edition. December 2015. Available at https://health.gov/dietaryguidelines/2015/guidelines/.

Photo by Eaters Collective

CVD-REAL Results Suggest that Cardiovascular Benefits of Sodium-Glucose Cotransporter-2 (SGLT-2) Inhibitors are, Indeed, Real

CVD-REAL

CVD-REAL Results Suggest that Cardiovascular Benefits of Sodium-Glucose Cotransporter-2 (SGLT-2) Inhibitors are, Indeed, Real

By Kevin C Maki, PhD

 Background

In 2015, the release of the Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients (EMPA-REG OUTCOME) trial results generated significant surprise and controversy.1 The investigators randomly assigned 7,020 patients with type 2 diabetes mellitus (T2D) to receive 10 or 25 mg/d of empagliflozin or placebo.  Empagliflozin is a sodium-glucose cotransporter-2 inhibitor that reduces renal reabsorption of glucose and sodium, thus increasing urinary losses and reducing the plasma glucose concentration.  The primary composite outcome was death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke in the pooled empagliflozin group compared with the placebo group.

The EMPA-REG OUTCOME results showed a 14% reduction (p = 0.04) in the primary outcome in the empagliflozin group.  Despite significant reductions in blood pressure, glycated hemoglobin and body weight, there were no differences between the groups in myocardial infarction or stroke.  However, there were substantial reductions (p ≤ 0.002) in death from cardiovascular causes (38%) and hospitalization for heart failure (35%).

More recently, the results from the Canagliflozin Cardiovascular Assessment Study (CANVAS) program were released in which data were pooled from two placebo-controlled studies of another SGLT-2 inhibitor, canagliflozin, involving 10,142 patients with T2D at high cardiovascular risk.2  The outcome for the primary composite, which was the same as that in EMPA-REG OUTCOME, showed that canagliflozin treatment was associated with a significant 14% reduction, a result that was essentially identical to that in the EMPA-REG OUTCOME study overall.  However, there were some differences between the results for individual components of the composite.

 

Outcome EMPA-REG OUTCOME (empagliflozin) CANVAS

(canagliflozin)

Hazard Ratio (95% Confidence Interval)
Primary Composite 0.86 (0.74-0.99) 0.86 (0.75-0.97)
Death from Cardiovascular Causes 0.62 (0.49-0.77) 0.87 (0.72-1.06)
Non-fatal Myocardial Infarction 0.87 (0.70-1.09) 0.85 (0.69-1.05)
Non-fatal Stroke 1.24 (0.92-1.67) 0.90 (0.71-1.15)
Hospitalization for Heart Failure 0.65 (0.50-0.85) 0.67 (0.52-0.87)
Death from Any Cause 0.68 (0.57-0.82) 0.87 (0.74-1.01)

The notable differences are for death from cardiovascular causes (38% reduction vs. non-significant 13% reduction) and death from any cause (32% reduction vs. non-significant 13% reduction), for which the results with empagliflozin appeared more favorable, and non-fatal stroke (non-significant 24% increase vs. non-significant 10% reduction), for which the results appeared more favorable for canagliflozin. Or course, such differences could easily be due to random variation, so additional studies are needed with these and other agents in the SGLT-2 inhibitor class.  Large-scale randomized, controlled clinical trials are expensive and time consuming, so it is useful to look at results in the real world for patients prescribed these medications in clinical practice.  Results from such investigations need to be viewed with caution because they are more susceptible to various types of bias and confounding than results from randomized trials.  Nevertheless, they can be useful for evaluating risks and benefits of drug therapies and to further evaluate hypotheses generated from clinical trial data, such as whether there are differences in cardiovascular outcomes between agents in the SGLT-2 inhibitor class.

Comparative Effectiveness of Cardiovascular Outcomes in New Users of SGLT-2 Inhibitors (CVD-REAL) Methods and Results3

Data were collected from medical claims in the US and several countries in the EU.  A propensity score was used to adjust for SGLT-2 inhibitor initiation.  Hazard ratios were calculated for hospitalization for heart failure, all-cause mortality, and incidence of either outcome among those taking SGLT-2 inhibitors compared with other glucose-lowering drugs (GLD).

Data were included for more than 300,000 patients, half of whom took an SGLT-2 inhibitor and half of whom took other GLDs.  Canagliflozin was the most commonly used SGLT-2 inhibitor (53% of exposure), followed by dapagliflozin (42% of exposure) and empagliflozin (5% of exposure).  Canagliflozin was the most commonly used SGLT-2 inhibitor in the US (76%), whereas dapagliflozin was the most commonly used in Europe (92%); 87% of subjects had no known cardiovascular disease at baseline.

Over 190,164 person-years of follow-up, hazard ratios for hospitalization for heart failure (0.61, 95% CI 0.51-0.73), death (0.49, 0.41-0.57) and either outcome (0.54, 0.48-0.60) were all significantly below the null, indicating that incidence rates for these outcomes were 39-51% lower for SGLT-2 inhibitors compared with other GLDs.  Sensitivity analyses were consistent with the main results, with no evidence of significant heterogeneity across type of SGLT-2 inhibitor or country.

Comment

The results of the CVD-REAL investigation support the hypothesis that use of the SGLT-2 inhibitor class reduces risks for heart failure and death in patients with T2D.  The mechanisms responsible for these benefits, which are generally confirmatory (significant reductions or trends) for those observed in the EMPA-REG OUTCOME and CANVAS trials, are not well understood.  The SGLT-2 inhibitor class does not differ markedly from other GLD classes regarding effects on glycemic control.  Additional research will be needed to elucidate mechanisms responsible, which may have implications for the application of this drug class to other high-risk groups who do not have T2D.

References:

  1. Zinman B, Wanner C, Lachin JM, et al. Empagliflozin, cardiovascular outcomes, and mortality in type 2 diabetes. N Engl J Med. 2015;373:2117-2128.
  2. Neal B, Perkovic V, Mahaffey KW, et al. Canagliflozin and cardiovascular and renal events in type 2 diabetes. 2017; Jun 12. [Epub ahead of print].
  3. Kosiborod M, Cavendar MA, Fu AZ, et al. Lower risk of heart failure and death in patients initiated on sodium-glucose cotransporter-2 inhibitors versus other glucose-lowering drugs: the CVD-REAL study (Comparative Effectiveness of Cardiovascular Outcomes in New Users of Sodium-Glucose Cotransporter-2 Inhibitors). Circulation. 2017;136:249-259.

 

 

 

FOURIER

Putting the FOURIER Findings in Perspective

FOURIER

Putting the FOURIER Findings in Perspective

By Kevin C Maki, PhD

Background and Methods
Earlier this year the results from the Further Cardiovascular Outcomes Research with PCSK9 Inhibition in Subjects with Elevated Risk (FOURIER) trial were published in the New England Journal of Medicine1 in conjunction with their presentation at the American College of Cardiology Scientific Sessions.  For the trial, 27,564 patients with atherosclerotic cardiovascular disease (ASCVD) and low-density lipoprotein cholesterol (LDL-C) at least 70 mg/dL while on statin therapy were randomly assigned to receive 140 mg of evolocumab or placebo by subcutaneous injection every 2 weeks.  Evolocumab is a proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitor that lowers LDL-C and cholesterol carried by other apolipoprotein B-containing lipoproteins by reducing the rate at which hepatic LDL receptors are catabolized.

The primary and key secondary composite outcomes were:

  • Primary: cardiovascular (CV) death, myocardial infarction, stroke, hospitalization for unstable angina, coronary revascularization;
  • Key secondary: CV death, myocardial infarction, stroke.

 

Results
The median baseline LDL-C level was 92 mg/dL, which was reduced by an average of 59% compared to placebo at 48 weeks to a median value of 30 mg/dL. Levels of non-high-density lipoprotein cholesterol (non-HDL-C) and apolipoprotein B, were also reduced by 52% and 49%, respectively. 

The primary outcome was reduced by 15% (95% confidence interval [CI] 8 to 21%) and the key secondary endpoint was reduced by 20% (95% CI 12 to 27%) with evolocumab vs. placebo over an average follow-up period of 2.2 years.  In the placebo group, the primary and key secondary outcomes occurred in 11.3% and 7.4% of subjects, respectively.  Efficacy results were consistent across subgroups, including men and women and quartiles of baseline LDL-C.  The effect appeared to grow over time.  Beyond 12 months, the reduction in the key secondary outcome with evolocumab was 25%, compared to 16% during the first 12 months.  Other than injection site reactions (2.1% vs. 1.6%), no significant differences in adverse events were present between treatment groups.

 

Comment
The results from FOURIER bolster the case for the view that “lower is better” when it comes to LDL-C and related atherogenic lipoprotein variables such as non-HDL-C and apolipoprotein B.  The trial had a shorter follow-up time (2.2 years) than most statin trials, which have averaged roughly 5 years of treatment.  The event rate in FOURIER was relatively high (about 3-5% per year in the placebo group).

The reduction in LDL-C from a median baseline level of 92 to an on-treatment level of 30 mg/dL is a reduction of about 62 mg/dL (1.6 mmol/L). The results from the Cholesterol Treatment Trialists’ (CTT) analysis of data from statin trials2,3 would predict a reduction in risk of roughly 33% over five years for major vascular events [1 – (0.78^1.6) = 0.328], assuming a hazard ratio of 0.78 per 1.0 mmol/L reduction in LDL-C.  However, the follow-up period was shorter than 5 years, so we have to look at the CTT analysis for shorter timeframes for comparison.  The definition of major vascular event in the CTT analysis included the combined outcome of major coronary event, non-fatal or fatal stroke, or coronary revascularization.  This outcome has elements of both the primary and key secondary outcomes in FOURIER.  For simplicity, I will focus on the key secondary outcome in FOURIER of CV death, myocardial infarction or stroke for comparison to the CTT results with statin therapy.

During years 0-1, the hazard ratio in the CTT analysis was 0.90 per mmol/L of LDL-C reduction.2 The corresponding hazard ratios for years 1-2 and 2-3 were 0.78 and 0.74, respectively.2  I will use 0.78 in my calculations for simplicity, since this corresponds to the overall result from the CTT analysis.  For the first year, the predicted risk reduction in FOURIER based on the CTT values would be 15.5% [1 – (0.90^1.6) = 0.155].  This corresponds very closely to the 16% reduction in the key secondary outcome during the first 12 months.  Beyond 12 months, the effect in FOURIER was a 25% reduction in risk.  This is slightly below the predicted 32.8% reduction predicted by the CTT relationship, but certainly not far enough below the predicted value to conclude that the relationship is not similar.

In his presentation at the American College of Cardiology meeting, the Principal Investigator, Dr. Marc Sabatine, compared the results from year 2 of follow-up in FOURIER and the CTT analysis for the outcomes of major coronary events and stroke.3 They were very similar, as you can see by examining the hazard ratios and 95% CIs, which are shown below:

  • Major coronary events
    • CTT: 0.78 (0.70 to 0.86)
    • FOURIER: 0.80 (0.71 to 0.90)
  • Stroke
    • CTT: 0.77 (0.66 to 0.91)
    • FOURIER: 0.77 (0.63 to 0.94)

Thus, once the relatively short follow-up period is taken into account, the results from FOURIER are consistent with those from the CTT analysis, and are generally supportive of a linear relationship between LDL-C reduction and lower CV event risk, extending to lower levels than had previously been studied in large CV outcomes trials.

The findings from FOURIER are consistent with those from a pooled analysis of 10 trials in the development program for another PCSK9 inhibitor, alirocumab.4 In that analysis, a 39 mg/dL reduction in LDL-C (roughly 1 mmol/L) was associated with a hazard ratio of 0.76 (95% CI 0.63 to 0.91) compared with control for major adverse CV events.  Similar results were obtained for non-HDL-C and apolipoprotein B reductions.  When expressed per 50% reduction from baseline, the relative risk reductions for LDL-C, non-HDL-C and apolipoprotein B were 29%, 29% and 32%, respectively.

The results from FOURIER have generated confusion because the risk reduction reported was less than some had expected.  The CV benefits of LDL-C reduction take some time to become fully apparent.  Thus, after taking into account the comparatively short follow-up period of 2.2 years, it is clear that the FOURIER results are aligned with previous results from statin trials, as represented by the CTT analysis, as well as the findings from the Improved Reduction of Outcomes: Vytorin Efficacy International Trial (IMPROVE-IT), in which the small incremental reduction of about 0.4 mmol/L in LDL-C when ezetimibe was added to statin therapy translated into additional CV event risk reduction of 7-10%.5  Accordingly, the FOURIER results further strengthen the evidence that reducing LDL-C (and related variables such as non-HDL-C and apolipoprotein B) will reduce CV event risk in high-risk patients.

Additional evidence is expected to become available in 2018 from a trial with the other PCSK9 inhibitor currently cleared by the Food and Drug Administration, ODYSSEY Outcomes: Evaluation of Cardiovascular Outcomes After an Acute Coronary Syndrome During Treatment with Alirocumab.  Assuming that the results from that trial confirm those from FOURIER, the debate will continue to focus not on who might benefit from therapy, but rather for whom PCSK9 inhibitor therapy is justified, given the cost of approximately $14,000 per year.

References:
1.     Sabatine MS, Giugliano RP, Keech AC, et al. Evolocumab and clinical outcomes in patients with cardiovascular disease. N Engl J Med. 2017;376:1713-1722.

2.     The Cholesterol Treatment Trialists’ Collaboration. Efficacy and safety of cholesterol-lowering treatment: prospective meta-analysis of data from 90,056 participants in 14 randomised trials of statins. Lancet. 2005;366:1267-1278.

3.     The Cholesterol Treatment Trialists’ Collaboration. Efficacy and safety of more intensive lowering of LDL cholesterol: a meta-analysis of data from 170,000 participants in 26 randomised trials. Lancet. 2010;376:1670-1681.

4.     Ray KK, Ginsberg HN, Davidson MH, et al. Reductions in atherogenic lipids and major cardiovascular events: a pooled analysis of 10 ODYSSEY trials comparing alirocumab with control. 2016;134:1931-1943.

5.     Cannon CP, Blazing MA, Giugliano RP, et al. Ezetimibe added to statin therapy after acute coronary syndromes. N Engl J Med. 2015;372:2387-2397.

 

FOURIER

Changes in Diet Quality and Mortality

Changes in Diet Quality and Mortality

Changes in Diet Quality and Mortality

By Kevin C Maki, PhD

Background
Sotos-Prieto and colleagues from the Departments of Nutrition and Epidemiology at Harvard University published an analysis of the relationships between changes in diet quality scores and mortality [all-cause, cardiovascular (CV), and cancer] in a recent issue of the New England Journal of Medicine.1  These relationships were examined in two large cohorts of health professionals, the US Nurses’ Health Study (women) and the US Health Professionals Follow-up Study (men).

Previous studies have shown that higher diet quality scores are associated with lower mortality.  Of course, the potential problem with observational evidence is that it is difficult to know whether it is higher diet quality per se that is responsible for the relationship to lower mortality, or other differences between those with lower and higher diet quality scores.  People who consume diets that conform to recommendations from health authorities often have other characteristics that might contribute to better outcomes.  They tend to be more health conscious, have higher educational attainment, exercise more regularly, have lower body mass index, and be less likely to smoke, use illicit substances and consume alcohol to excess, just to name a few of the differences.

Epidemiologists attempt to adjust for these differences using statistical techniques to reduce the potential for bias and confounding by differences other than the exposure of interest; in this case diet quality score.  It is often impossible to identify and adjust for all of the variables that may be relevant.  The ultimate goal is to identify exposures that are causally related to disease status and modifiable, which can serve as the basis for public health actions, including recommendations for the characteristics of a healthy diet.

While far from perfect, it is useful to investigate the relationships between changes in exposure variables over time and disease risk.  For example, it bolstered the case for a causal relationship between cigarette smoking and risks for lung cancer and heart disease when it was shown that risks declined over time in those who quit smoking, but did not in those who continued to smoke.  Similarly, the Harvard group sought to assess whether changes in diet quality scores over time predicted risks for all-cause and cause-specific mortality.

Methods
In order to address this question, the researchers calculated changes over time in three scores:  the Alternative Healthy Eating Index (aHEI), the Alternative Mediterranean Diet (aMED) score, and the Dietary Approaches to Stop Hypertension (DASH) score.  Scores were calculated based on responses to the Willett Food Frequency Questionnaire that was administered every 4 years over long periods in both cohorts.  For the main analysis, changes in diet quality were calculated from 1986 to 1998 and follow-up was through 2010 (12 years).  The analysis included data from 73,739 participants (65% women).

The aHEI used scores from 0-10 for 11 food components selected on the basis of their relationships with chronic diseases.  Thus, the score could be from 0 to 110.  The aMED score included 9 components and were scored as 0 or 1 according to whether intake was above or below the cohort-specific median, allowing a score from 0 to 9.  The DASH score included 8 components, each scored 1-5, thus producing scores ranging from 8 to 40.  For all, a higher score indicated higher diet quality.

Results
Participants who increased their diet quality scores reported increased intakes of whole grains, vegetables and omega-3 fatty acids, as well as reduced intakes of sodium.  Compared to participants with relatively stable scores (middle quintile for change), those in the top 20% for increases (roughly 15-16 points for aHEI, 2-3 points for aMED, and 5-6 points for DASH), had 9-14% lower mortality risk, all p < 0.05 for the fifth vs. the third quintile in multivariable-adjusted models.  Similar results were obtained when a 20-percentile increase in score was modeled (8-17% lower risk for mortality).

Results were somewhat less consistent for deaths from CV causes and cancer.  A 20-percentile increase in aHEI was associated with 15% lower CV mortality (p < 0.05), while the same increase in aMED was associated with a 7% lower CV mortality (p < 0.05), and a 20-percentile increase in DASH score was associated with a non-significant 4% reduction in mortality.  For cancer mortality, a 20-percentile increase was associated with 6-9% lower mortality, which was only statistically significant (p < 0.05) for the DASH score (9%).

Having constant high diet quality score was associated with reductions of 9-14% in all-cause mortality over 12 years compared to those with constant low scores.  The investigators also looked at 8-year and 16-year changes.  In general, the effect became more pronounced with longer periods.  This was particularly evident for the aHEI, although that may be due to the greater range of values possible, which increases the variation in the populations studied.

Comment
This study adds support for the healthy eating patterns recommended in the Dietary Guidelines for Americans (2015-2020).2  Although confounding by unmeasured, or crudely measured, factors cannot be ruled out, the available data are consistent with a causal association between a healthy diet pattern and reduced risks for all-cause and CV mortality.  The evidence for a reduction in cancer mortality with a healthy dietary pattern is less convincing.  These results particularly support the recommendations for increased consumption of whole grains, fruits, vegetables, and fish/omega-3 fatty acids, compared with the average American diet, since these were the foods that were primarily responsible for changes in diet quality scores over time.

As I have stated repeatedly, public policy recommendations regarding diet often have to be based on evidence from observational studies assessing disease risk and intervention studies of biomarkers for disease risk, because few randomized, controlled dietary intervention studies have been completed to assess effects on disease incidence.  The strongest recommendations should be reserved for those areas where we have alignment between results from all three types of studies.

The results from the Prevención con Dieta Mediterránea (PREDIMED) study support health benefits, including reduced incidence of CV events (particularly stroke) and diabetes associated with advice to consume a Mediterranean diet pattern supplemented with nuts or olive oil, compared to low-fat diet advice.3 PREDIMED was not a perfect trial.  More randomized, controlled dietary intervention trials with outcomes of disease incidence are badly needed to answer questions about risks and benefits of various types of dietary advice.  PREDIMED demonstrates the feasibility of completing such studies.

For now, despite a number of caveats and uncertainties, the best available evidence suggests that the dietary patterns recommended in the Dietary Guidelines for Americans (healthy US diet, Mediterranean diet, DASH diet) are associated with a variety of favorable outcomes, including reduced total and CV mortality.

References:

  1. Sotos-Prieto M, Bhupathiraju SN, Mattei J, et al. Association of changes in diet quality with total and cause-specific mortality. N Engl J Med. 2017;377:143-153.
  2. US Department of Health and Human Services and US Department of Agriculture. Dietary Guidelines for Americans 2015-2020. 8th December 2016. Available at https://health.gov/dietaryguidelines/2015/resources/2015-2020_Dietary_Guidelines.pdf.
  3. Estruch R, Martínez-González MA, Corella D, et al.; PREDIMED Study Investigators. Effects of a Mediterranean-style diet on cardiovascular risk factors: a randomized trial. Ann Intern Med. 2006;145:1-11.

 

 

Changes in Diet Quality and Mortality

Another CETP Inhibitor Fails to Show Cardiovascular Benefit, Despite Reducing LDL Cholesterol and Raising HDL Cholesterol: Implications of the ACCELERATE Trial

CETP Inhibitor

Another CETP Inhibitor Fails to Show Cardiovascular Benefit, Despite Reducing LDL Cholesterol and Raising HDL Cholesterol: Implications of the ACCELERATE Trial

  By Kevin C Maki, PhD

Cholesteryl ester transfer protein (CETP) is an enzyme that modulates the transfer of cholesterol esters from high-density lipoprotein (HDL) particles to apolipoprotein (apo)-B containing particles, including very-low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) particles.  CETP inhibitor drugs, by blocking this action, raise the level of HDL cholesterol (HDL-C) and lower the level of LDL cholesterol (LDL-C).

Previous outcomes trials with two CETP inhibitors, torcetrapib and dalcetrapib, failed to show cardiovascular disease (CVD) event risk reduction.1 Torcetrapib use was associated with increased CVD event risk, which was believed to be secondary to off-target effects, including raising blood pressure and aldosterone levels and lowering serum potassium concentration.  Whereas torcetrapib raised HDL-C by 70% and lowered LDL-C by 25%, dalcetrapib was a weak CETP inhibitor and raised HDL-C by only 30%, while having no effect on LDL-C.  A CVD outcomes trial with dalcetrapib was stopped for futility, showing no evidence of benefit or harm regarding CVD event risk.

The ACCELERATE (Assessment of Clinical Effects of Cholesteryl Ester Transfer Protein Inhibition with Evacetrapib in Patients at a High Risk for Vascular Outcomes) trial evaluated the effects of evacetrapib 130 mg/d vs. placebo, when added to standard therapies in ~12,000 men and women with high CVD risk secondary to having clinical atherosclerotic CVD with a history of a recent acute coronary syndrome, cerebrovascular atherosclerosis, peripheral atherosclerosis, or diabetes mellitus with known coronary disease).2

After randomization, the effects of evacetrapib compared to placebo on mean or median changes from baseline to the 3-month timepoint in lipoprotein-related parameters were as follows (all p < 0.001):

  • HDL-C: +134.8%;
  • LDL-C: -37.1%;
  • Triglycerides (TG): -6.0%;
  • Apo B: -19.3%;
  • Lipoprotein (a): -22.3%.

There were also small changes (all p < 0.01), relative to placebo, in systolic/diastolic blood pressure (+1.2/+0.5 mm Hg) and C-reactive protein (8.6%).

Despite substantial changes in potentially favorable directions in lipoprotein-related variables, no difference was present for the primary efficacy outcome of the first occurrence of any component of the composite of death from cardiovascular causes, myocardial infarction, stroke, coronary revascularization, or hospitalization for unstable angina:  hazard ratio (HR) 1.01, 95% confidence interval (CI) 0.91 to 1.11, p = 0.91.  After an interim analysis with 82% of the final projected number of events, the trial was stopped early for futility.  No significant benefits were present for any of the individual components of the primary outcome, nor for a secondary composite that excluded hospitalization for unstable angina.

Comment.  The third failure of a CETP inhibitor to show CVD event risk reduction may sound the death knell for this class of lipid-altering agents.  The reasons for the lack of benefit in ACCELERATE are unclear.  Although HDL-C concentration is a strong inverse predictor for CVD event risk, the mechanisms responsible for this consistent finding are uncertain.   There are numerous ways that the HDL-C level can be raised, some of which could be beneficial, while others may be only cosmetic.

More disturbing than the lack of benefit associated with a rise in HDL-C, is the fact that LDL-C, TG, apo B and lipoprotein (a) were all lowered, yet this did not reduce CVD event risk.  Reduced CVD event risk has been observed with other agents that lower apo B-containing lipoproteins such statins, ezetimibe and proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitors, so why did changes in these values with evacetrapib fail to lower risk?

Niacin lowers apo B-containing lipoproteins and lipoprotein (a), while also raising HDL-C, and it failed to demonstrate CVD event risk reduction in both the HPS2-THRIVE (Heart Protection Study 2-Treatment of HDL to Reduce the Incidence of Vascular Events) study (co-administered with laropiprant) and in the AIM-HIGH (Atherothrombosis Intervention in Metabolic Syndrome with Low HDL/High Triglycerides: Impact on Global Health Outcomes) trial .3  However, there were issues in both trials regarding whether the subjects enrolled were appropriate candidates for niacin therapy.3  For example, more than two-thirds of the subjects in HPS2-THRIVE had baseline non-HDL-C of less than 100 mg/dL.  Such individuals would not be likely to have been prescribed niacin in clinical practice.

Interventions that lower LDL-C and apo B-containing lipoproteins through mechanisms that involve inducing an upregulation in hepatic LDL receptor activity, including statins, ezetimibe and PCSK9 inhibitors have all been shown to reduce CVD event risk.  Lowering LDL-C and apo B-containing lipoproteins with evacetrapib had no effect on risk.  Should we infer from these results that lowering LDL-C and apo B-containing lipoproteins through mechanisms that do not upregulate hepatic LDL receptor activity will not reduce CVD risk?  Alternatively, is it the case that evacetrapib had some off-target effect(s) that offset the benefits of LDL-C and apo B-containing lipoprotein reduction, as has been hypothesized for torcetrapib?  Evacetrapib did produce modest increases in blood pressure and C-reactive protein.  These changes were small enough that they are unlikely to have been sufficient to directly offset the expected CVD benefits from reductions in LDL-C and apo B-containing lipoproteins.  However, they could be indicators of other adverse neuroendocrine and/or inflammatory effects.  At present, it is not possible to determine whether the explanation for the lack of benefit with evacetrapib was attributable to one of these, or perhaps some other explanation.

References:

  1. Barter PJ, Rye KA. Targeting high-density lipoproteins to reduce cardiovascular risk: what is the evidence? Clin Ther. 2015;37:2716-2731.
  2. Lincoff AM, Nicholls SJ, Riesmeyer JS, et al.; ACCELERATE Investigators. Evacetrapib and cardiovascular outcomes in high-risk vascular disease. N Engl J Med. 2017;376:1933-1942.
  3. Mani P, Rohatgi A. Niacin therapy, HDL cholesterol, and cardiovascular disease: is the HDL hypothesis defunct? Curr Atheroscler Rep. 2015;17:521.

 

 

CETP Inhibitor

Debates Rage on About the Health Effects of Low-Calorie Sweeteners – Newly Published Study Shows No Effect of Sucralose on Carbohydrate Metabolism

Health Effects of Low-Calorie Sweeteners

Debates Rage on About the Health Effects of Low-Calorie Sweeteners – Newly Published Study Shows No Effect of Sucralose on Carbohydrate Metabolism

  By Kevin C Maki, PhD

A study published recently in the journal Regulatory Toxicology and Pharmacology by Grotz and colleagues investigated the effects of sucralose consumption on glucose homeostasis in healthy men and women.1  Sucralose is one of six high-intensity sweeteners approved by the United States’ Food and Drug Administration (FDA) as food additives.  The approved high-intensity (low-calorie) sweeteners include:  saccharinaspartame, acesulfame potassium (Ace-K), sucralose, neotame, and advantame.2  Sucralose is one of the largest selling of the high-intensity sweeteners on the market, although consumption in the US has declined in recent years along with sales of diet soda, which were more than 20% lower in 2016 than in 2009.

There has been significant controversy about effects of high-intensity sweeteners on health, which seems to have intensified lately.  One of the findings that has generated debate is the relatively recent discovery of gut receptors for sweet taste, which has triggered concern that high-intensity sweeteners might have previously unappreciated effects on metabolism through their interactions with these receptors.1,3  Researchers at Purdue University have also hypothesized that when people consume high-intensity sweeteners, the body produces physiologic responses in anticipation of the arrival of sugar and calories, which could increase appetite and partially or fully offset the reduction in energy consumption of substituting a high-intensity sweetener for calorie-containing sugars.4

The newly published study by Grotz et al.1 was conducted a number of years ago, and the data were submitted to the FDA as part of the food additive petition for sucralose in 1996, but had never appeared in the peer reviewed literature.  Given the recent concerns expressed regarding the potential for high-intensity sweeteners to influence glucose homeostasis through their effects on sweet taste receptors in the gut, the investigators felt it would be useful to publish the results to make them more readily available to the scientific community.

The study was a randomized, double-blind parallel trial in which 48 healthy, normoglycemic males were randomly assigned to receive capsules containing either a cellulose placebo or 333.3 mg of sucralose, three times daily with meals.  The intake of 1000 mg/d in the sucralose group (n = 25) far exceeds the expected consumption from foods and beverages.  For perspective, diet sodas sweetened with sucralose typically contain ≤40 mg per serving.  A packet of Splenda® contains 12 mg of sucralose, which is 300-1000 times as sweet as sucrose.

The subjects underwent assessments of serum chemistry, hematology and glycated hemoglobin (HbA1C) levels, as well as fasting and post-oral-glucose-load (75 g) concentrations of insulin, glucose and C-peptide at baseline (twice), weeks 7 and 12 during the treatment period, and again 4 weeks after the end of the 12-week treatment period.  There were no significant differences between the placebo and sucralose groups for changes from baseline in HbA1C, or in fasting and post-glucose-load levels of glucose, insulin or C-peptide.  No differences were observed in clinical chemistry or hematology values.

Comment.  Given the widespread consumption of high-intensity sweeteners by large segments of the United States’ population, it is important to understand their effects on physiologic processes with implications for human health.  The results from this study in healthy men suggest that even very large intakes have no influence on indicators of glucose homeostasis.  Similar results have been obtained in patients with obesity or type 2 diabetes mellitus.1  Furthermore, reviews of the effects of high-intensity sweeteners, including sucralose, on appetite, gut hormones and gut motility have concluded that there is no evidence for material effects in humans.3,5  It is important for research on the physiological and psychological effects of high-intensity sweeteners to continue.  However, the results of this study and others suggest that sucralose has no adverse effects on glucose homeostasis.  Given evidence that sugar-sweetened products appear to have adverse effects on glucose homeostasis,6 the use of products sweetened with sucralose (and other high-intensity sweeteners) may be an acceptable option for those who would like to limit their intakes of added sugars and calories.7

References:

 Grotz VL, Pi-Sunyer X, Porte, Jr. D, et al. A 12-week randomized clinical trial investigating the potential for sucralose to affect glucose homeostasis. Regul Toxicol Pharmacol. 2017;88:22-33.

  1. S. Department of Health and Human Services. U.S. Food & Drug Administration. High-Intensity Sweeteners. Accessed at https://www.fda.gov/food/ingredientspackaginglabeling/foodadditivesingredients/ucm397716.htm on 11 July 2017.
  2. Magnuson BA, Roberts A, Nestmann ER. Critical review of the current literature on the safety of sucralose. Food Chem Toxicol. 2017;106 (Part A):324-355.
  3. Swithers SE, Martin AA, Davidson TL. High-intensity sweeteners and energy balance. Physiol Behav. 2010;100:55-62.
  4. Bryant C, Mclaughlin J. Low calorie sweeteners: evidence remains lacking for effects on human gut function. Physiol Behav. 2016;164 (Pt B):482-485.
  5. Maki KC, Nieman KM, Schild AL, et al. Sugar-sweetened product consumption alters glucose homeostasis compared with dairy product consumption in men and women at risk of type 2 diabetes mellitus. J Nutr. 2015;145:1-8.
  6. Peters JC, Wyatt HR, Foster GD, et al. The effects of water and non-nutritive sweetened beverages on weight loss during a 12-week weight loss treatment program. Obesity. 2014;22:1415-1421.
Health Effects of Low-Calorie Sweeteners