Yuan S, Larsson SC
Diabetologia 63 (1) 116-123 [2020-01-00; online 2019-11-05]
Epidemiological data on the associations of circulating fatty acid levels with type 2 diabetes are inconsistent. We conducted a two-sample Mendelian randomisation study to explore the causal associations of plasma levels of ten fatty acids with type 2 diabetes and glycaemic traits. Thirteen SNPs associated with circulating levels of ten individual fatty acids at the genome-wide significance level (p < 5 × 10-8) were selected as instrumental variables for the exposures. For the outcomes, summary-level data were obtained from the DIAbetes Genetics Replication And Meta-analysis (DIAGRAM) consortium for type 2 diabetes (898,130 individuals) and from the Meta-Analyses of Glucose and Insulin-related traits Consortium (MAGIC) for the glycaemic traits (up to 46,186 non-diabetic individuals). The inverse-variance weighted method was used for analyses. Genetic predisposition to higher plasma levels of eight of the ten fatty acids were statistically significantly associated with lower or higher odds of type 2 diabetes. The OR per one SD increment of each fatty acid was 0.93 (95% CI 0.90, 0.96; p = 2.21 × 10-5) for α-linolenic acid, 0.96 (95% CI 0.94, 0.98; p = 1.85 × 10-4) for linoleic acid, 0.86 (95% CI 0.81, 0.91; p = 6.68 × 10-7) for palmitoleic acid, 0.87 (95% CI 0.81, 0.93; p = 2.21 × 10-5) for oleic acid, 1.08 (95% CI 1.03, 1.12; p = 0.002) for eicosapentaenoic acid, 1.04 (95% CI 1.02, 1.07; p = 0.001) for docosapentaenoic acid, 1.03 (95% CI 1.02, 1.05; p = 2.51 × 10-5) for arachidonic acid and 1.09 (95% CI 1.03, 1.15; p = 0.003) for stearic acid. The same eight fatty acids were also associated with fasting glucose levels and HOMA-B. The associations, except that for palmitoleic acid, were driven by variants in FADS1/2. Genetic predisposition to higher circulating levels of eight out of ten fatty acids was associated with type 2 diabetes, fasting glucose and islet beta cell function. However, the associations, except that for palmitoleic acid, were driven by variants in FADS1/2, which encode enzymes with a key role in fatty acid metabolism.