Interaction Between GAD65 Antibodies and Dietary Fish Intake or Plasma Phospholipid n-3 Polyunsaturated Fatty Acids on Incident Adult-Onset Diabetes: The EPIC-InterAct Study

<b><i>Objective:</i></b> Islet autoimmunity is associated with diabetes incidence. We investigated whether there was an interaction between dietary fish intake or plasma phospholipid polyunsaturated omega-3 fatty acid (n-3 PUFA) concentration with GAD65 antibody positivity on the risk of developing adult onset diabetes. <p><b><i>Research Design and Methods:</i></b> We used prospective data on 11,247 incident cases of adult onset diabetes and 14,288 non-cases from the EPIC-InterAct case-cohort study, conducted in eight European countries. Baseline plasma samples were analyzed for GAD65 antibodies and phospholipid n-3 PUFAs. Adjusted hazard ratios (HRs) for incident diabetes in relation to GAD65 antibody status and tertiles of plasma phospholipid n-3 PUFA or fish intake were estimated using Prentice-weighted Cox regression. Additive (proportion attributable to interaction; AP) and multiplicative interaction between GAD65 antibody positivity (≥65 U/ml) and low fish/n-3 PUFA were assessed.</p> <p><b><i>Results:</i></b> The hazard of diabetes in antibody positive individuals with low intake of total and fatty fish, respectively, was significantly elevated (HR 2.52, 95% CI 1.76-3.63; 2.48, 1.79-3.45) compared to people who were GAD65 antibody negative and had high fish intake, with evidence of additive (AP 0.44, 95% CI 0.16-0.72; 0.48, 0.24-0.72) and multiplicative (p=0.0465; 0.0103) interaction. Individuals with high GAD65 antibody levels (≥167.5 U/ml) and low total plasma phospholipid n-3 PUFA had more than 4-fold higher hazard of diabetes (HR 4.26, 2.70-6.72), AP 0.46 (0.12-0.80), compared to antibody negative individuals with high n-3 PUFA. </p> <b><i>Conclusions:</i></b> High fish intake or relative plasma phospholipid n-3 PUFA concentrations may partially counteract the increased diabetes risk conferred by GAD65 antibody positivity.