Stimulation of cell replication in transplanted pancreatic islets by nicotinamide treatment

A major obstacle for islet transplantation in insulin-dependent diabetes mellitus is to obtain a sufficient amount of islet tissue. This may partly be overcome if the cell replication in the grafted islet preparation could be stimulated in the recipient. In the present study adult mice were treated for 14 days with daily injections of nicotinamide (500 mg/kg body weight) or saline. Subsequently, the autoradiographic labeling index in the cells of the pancreatic islets were calculated in normal mice and in syngeneic islets transplanted into alloxan-diabetic mice. Treatment with nicotinamide caused a more than three-fold increase in the islet cell labeling index in the endogenous pancreatic islets, and also a 50% increase in the cell replication rates of the transplanted islets. It thus appears that nicotinamide enhances islet cell replication, possibly through an inhibition of poly(ADP-ribose) synthetase activities.