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

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. We had screened 1021 relatives, of which 30 had shown ICA > or = 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. The 1.5, 3.0 and 5-year life-table estimates of keeping the FPIR > or = 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. Oral Nicotinamide protected beta-cell function and prevented clinical disease in ICA-positive first-degree relatives of type-1 diabetes.