GLUCOSE TOLERANCE AND INSULIN SECRETION IN MONOSODIUM GLUTAMATE (MSG) OBESE RATS

Abstract

Obesity is often associated with hyperinsulinemia and insulin resistance. Exercise training, in turn, can be used to trigger improvement in glucose homeostasis. The present study was designed to evaluate the effect of chronic aerobic exercise on glucose tolerance and insulin secretion of obese male wistar rats (MSG administration, 4mg/g body weight, each other day, from birth to 14 days old). After 14 weeks from drug administration, the rats were separated into two groups: MSG-S (sedentary) and MSG-T (T = swimming, 1h/day, 5 days/week, with an overload of 5% b/w for 10 weeks). Rats of the same age and strain, receiving saline at birth, were used as control (C), and subdivided into two groups: C-S and C-T. Insulin and glucose responses during an oral glucose tolerance test (GTT) were evaluated by the estimation of the total areas under the serum insulin (AI) and glucose (AG) by the trapezoidal method. A constant for serum glucose disappearance (Kitt) to exogenous insulin was calculated from the slope of the least square analysis of serum glucose 0–30 min after subcutaneous insulin administration. No differences were observed in AG among the 4 groups. MSG-S showed higher AI (418%) and lower Kitt (92.3%) than C-rats. Glucose-induced insulin secretion by isolated (collagenase method) pancreatic islets was also evaluated. Basal (2.8 mM glucose) insulin secretion was higher in MSG (60%) than C islets. No differences were observed between S and T islets. The increase in glucose concentration to 16.7 mM, elevated the insulin secretion by C-S (1.8 fold), C-T (1.6 fold), MSG-S (1.2 fold), but not by MSG-T islets in relation basal values. Aerobic training was able to counteract, in part, the effects of MSG-obesity on glucose tolerance by attenuating insulin hypersecretion and insulin resistance. Supported by CNPq, FAPESP, and FINEP-PRONEX.