Cross-sectional study of conjugated linoleic acid in adipose tissue and risk of diabetes.

BACKGROUND Some experimental studies on conjugated linoleic acid (CLA) and insulin regulation suggested that CLA could be associated with risk of diabetes, but epidemiologic studies are lacking. OBJECTIVE The aim of the study was to test whether the amount of CLA in adipose tissue is associated with risk of diabetes. DESIGN A cross-sectional design was used to test the study hypothesis in 232 adults with diabetes and 1512 adults without diabetes who lived in Costa Rica. The cis-9, trans-11 and trans-10, cis-12 CLA isomers in adipose tissue and 48 other fatty acids were assessed by using gas chromatography. Prevalence ratios (PRs) and 95% CIs were estimated by using Poisson regression adjusted for potential confounders. RESULTS The mean (±SD) percentage of total fatty acids of CLA for the cis-9, trans-11 isomer in adipose tissue was 0.57 ± 0.18% in adults without diabetes and 0.53 ± 0.17% in adults with diabetes (P = 0.0078). The trans-10, cis-12 CLA isomer was not detected in adipose tissue. The cis-9, trans-11 CLA isomer was associated with a lower risk of diabetes. In comparison with the first quintile, the PR (95% CI) for the fifth quintile was 0.48 (0.31, 0.76) (P-trend = 0.0005) in the basic and 0.46 (0.29, 0.72) (P-trend = 0.0002) in the multivariable model. Additional adjustment for other fatty acids in adipose tissue including trans-9 16:1, which is a fatty acid that was previously associated with diabetes, did not modify the results. CONCLUSION The observed inverse association between the cis-9, trans-11 CLA in adipose tissue and diabetes risk is consistent with the hypothesis that CLA may be involved in insulin regulation.