Nicotinamide protected first-phase insulin response (FPIR) and prevented clinical disease in first-degree relatives of type-1 diabetics

Background: After a study of ICA prevalence among relatives of Type-1 diabetics (DM1) in Santiago, Chile, parents of those who tested positive asked us to go on forward with an intervention study. Methods: We had screened 1021 relatives, of which 30 had shown ICA ≥ 20 JDF units (2.9%). Among the 26/30 who participated in the intervention study, the baseline screening showed normal glucose tolerance in all, and the first-phase insulin response (FPIR) was normal in 24/26 individuals, which were randomized into Nicotinamide (n = 12; oral Nicotinamide, 1200 mg m^-2 day^-1) and Placebo (n = 12) groups. The FPIRs and ICAs were monitored yearly. Compliance was monitored by urine Nicotinamide. Results: The 1.5, 3.0 and 5-year life-table estimates of keeping the FPIR ≥ 10th centile were, for Nicotinamide group 100% in all time points, and for Placebo these were 90.0% (c.i. = 100-71.4), 72.0% (c.i. = 100-37.1) and 0.0% (c.i. = 0.0-0.0) (p = 0.0091). The 5-year life-table estimates of remaining diabetes-free were 100% for Nicotinamide and 62.5% for Placebo (p = 0.0483). No adverse effects were observed. Conclusions: Oral Nicotinamide protected beta-cell function and prevented clinical disease in ICA-positive first-degree relatives of type-1 diabetes.