Preventive and Therapeutic Effects of Large-Dose Nicotinamide Injections on Diabetes Associated with Insulitis: An Observation in Nonobese Diabetic (NOD) Mice

This experiment was undertaken to explore a novel method of therapy for insulin-dependent diabetes mellitus (IDDM), using nonobese diabetic (NOD) mice that had symptoms and histologic changes similar to those of human IDDM patients. We examined preventive and therapeutic effects of large-dose nicotinamide administration on diabetes in NOD mice. Eighteen young female NOD mice without glycosuria were randomly divided into two groups; nine received subcutaneous nicotinamide (0.5 mg/g body wt) injections every day and the other nine were maintained as a control group and not injected. After 40 days, all of the mice given nicotinamide showed almost normal glucose tolerance and only mild insulitis on histologic study. On the other hand, marked glycosuria and severe insulitis were observed in six of the nine mice not injected. Four of six NOD mice given nicotinamide from the day of the first occurrence of marked glycosuria displayed a disappearance of glycosuria and an improvement in glucose tolerance during the therapy; however, urine sugar became negative in only one of six mice that received nicotinamide from 1 to 2 wk after the onset of marked glycosuria. These results indicate that nicotinamide has preventive and therapeutic effects on diabetes in NOD mice, and suggest the reversibility of B-cell damage, at least at a very early stage of IDDM.