The effect of nicotinamide on transplanted islet cells of Langerhans shortly after transplantation

We investigated whether the administration of nicotinamide (NA) shortly after transplantation could prevent the destruction of transplanted islets. Regarding islet transplantation, a large number of islets is required to cure diabetes as compared with the estimated number of islets existing in the pancreas. Furthermore, the insulin content or the graft decreases soon after transplantation, suggesting the destruction of the transplanted islets. In this study, 1,000 islets were transplanted under the renal capsule of streptozotocin (STZ)-induced diabetic rats. After transplantation, NA (0.5 g/kg) was administered for 7 days. Blood glucose levels at 0, 3, 7 and 14 days after transplantation were compared between the NA-treated group and the nontreated group. Oral glucose tolerance tests (OGTTs) were performed at day 14, and the grafts were removed for the measurements of insulin content and morphological examinations. Blood glucose levels of the rats treated with NA were significantly lower than those of nontreated rats. Insulin levels were significantly lower in the nontreated group than in the NA-administrated group, Histologically, vacuolated degeneration and fewer insulin-positive cells in the grafts was observed without NA. In conclusion, NA had beneficial effects on the survival of islets shortly after transplantation.