Decreased incidence of diabetes mellitus by monosodium glutamate in the non-obese diabetic (NOD) mouse.

Subcutaneous administration of monosodium glutamate (MSG) to neonatal female non-obese diabetic (NOD) mice resulted in obesity associated with stunting and hyperinsulinemia. However, the cumulative incidence of diabetes mellitus at 25 weeks of age in the MSG group was significantly lower than in the control group (10.3% vs. 43.6%, P less than 0.005). The immunoreactive insulin content of the pancreas from the 13- to 20-week-old MSG-treated mice was higher than that of the control mice (P less than 0.005). Immunohistochemistry showed that the number of pancreatic B-cells was well preserved and insulitis was attenuated in the MSG-treated mice. Plasma corticosterone and 3, 5, 3'-triiodothyronine levels were elevated in the MSG group. These results suggested that, by the MSG treatment, the B-cell functions were maintained through the modification of the degenerative process of the islets in the NOD mouse.