Plasma and Dietary Linoleic Acid and 3-Year Risk of Type 2 Diabetes After Myocardial Infarction: A Prospective Analysis in the Alpha Omega Cohort

Abstract

Objective: To study plasma and dietary linoleic acid (LA) in relation to type 2 diabetes risk in post-myocardial infarction (MI) patients.

Research design and methods: We included 3,257 patients aged 60-80 years (80% male) with a median time since MI of 3.5 years from the Alpha Omega Cohort and who were initially free of type 2 diabetes. At baseline (2002-2006), plasma LA was measured in cholesteryl esters, and dietary LA was estimated with a 203-item food-frequency questionnaire. Incident type 2 diabetes was ascertained through self-reported physician diagnosis and medication use. Hazard ratios (with 95% CIs) were calculated by Cox regressions, in which dietary LA isocalorically replaced the sum of saturated (SFA) and trans fatty acids (TFA).

Results: Mean ± SD circulating and dietary LA was 50.1 ± 4.9% and 5.9 ± 2.1% energy, respectively. Plasma and dietary LA were weakly correlated (Spearman r = 0.13, P < 0.001). During a median follow-up of 41 months, 171 patients developed type 2 diabetes. Plasma LA was inversely associated with type 2 diabetes risk (quintile [Q]5 vs. Q1: 0.44 [0.26, 0.75]; per 5%: 0.73 [0.62, 0.86]). Substitution of dietary LA for SFA+TFA showed no association with type 2 diabetes risk (Q5 vs. Q1: 0.78 [0.36, 1.72]; per 5% energy: 1.18 [0.59, 2.35]). Adjustment for markers of de novo lipogenesis attenuated plasma LA associations.

Conclusions: In our cohort of post-MI patients, plasma LA was inversely related to type 2 diabetes risk, whereas dietary LA was not related. Further research is needed to assess whether plasma LA indicates metabolic state rather than dietary LA in these patients.

Trial registration: ClinicalTrials.gov NCT00127452.

© 2019 by the American Diabetes Association.

Figures

Figure 1

Associations of dietary LA (replacing SFA + TFA) (A) and plasma LA (B) with incident type 2 diabetes in 3,257 post-MI patients. Solid lines are risk estimates evaluated by restricted cubic splines from Cox models showing the shape of associations on a continuous scale with three knots located at the 5th, 50th, and 95th percentiles. The y-axis shows the multivariable HRs for type 2 diabetes incidence for any dietary or plasma LA value compared with the reference values set at the 5th percentile of dietary LA (3.0% energy) or 5th percentile of plasma LA (41.9%). Gray areas indicate 95% CIs. Results are presented for the fully adjusted models for dietary LA (model 3; adjusted for variables in model 2 [age, sex, Alpha Omega Trial treatment code, physical activity, smoking status, educational level, BMI, family history of type 2 diabetes, total energy intake excluding alcohol, alcohol consumption, dietary fiber, dietary cholesterol] plus dietary protein, carbohydrates, n-3 PUFA, and cis-MUFA) and plasma LA (model 2). Distribution of values of dietary or plasma LA are displayed in a histogram under each spline; % energy, percentage of total energy intake, excluding energy from alcohol.