Okinawa-Based Nordic Diet Decreases Plasma Levels of IAPP and IgA against IAPP Oligomers in Type 2 Diabetes Patients

Pancreas-derived islet amyloid polypeptide (IAPP) aggregates and deposits in the pancreas and periphery of Type 2 Diabetes (T2D) patients, contributing to diabetic complications. The excess IAPP can be removed by autoantibodies, and increased levels of immunoglobulin (Ig) G against IAPP have been reported in T2D patients. However, whether other Ig classes are also affected and if the levels can be managed is less known. This pre–post study examines IgA levels against IAPP oligomers (IAPP_O-IgA) in T2D patients and assesses the impact of the Okinawa-based Nordic (O-BN) diet—a low-carbohydrate, high-fiber diet—on these levels after following the diet for 3 months. IAPP, IAPP_O-IgA, and total IgA levels were measured in plasma and fecal samples from n = 30 T2D patients collected at baseline, after 3 months of diet, and after additional 4 months of unrestricted diets (a clinical follow-up). The IAPP and IAPP_O-IgA levels were significantly lower after 3 months, with the latter also being significantly reduced at the clinical follow-up. The reduction in plasma IAPP and IAPP_O-IgA levels correlated with reductions in plasma levels of metabolic and inflammatory markers. Hence, following the O-BN diet for at least 3 months is sufficient to reduce circulating IAPP and IAPP_O-IgA levels, which may be principal in managing T2D.