Effect of a high-protein diet on insulin and glucagon secretion in ventromedial hypothalamic (VMH) lesioned rats

The effects of a high-protein diet on insulin and glucagon secretion in ventromedial hypothalamic (VMH) lesioned and sham-operated (sham) rats were studied in vivo as well as in perfusate from isolated pancreas. Two weeks after VMH destruction or sham operation, the rats were given either a balanced diet (protein 27%, carbohydrate 61%, fat 12%) or a high-protein diet (protein 55%, carbohydrate 30%, fat 15%) for the following 2 weeks. The calorie intake and body weight changes after the commencement of the diets were almost the same in the groups of VMH lesioned rats, but these were much greater than those in the two sham-operated groups. Fasting blood glucose, plasma insulin, and plasma glucagon concentrations were also similar between the two VMH groups, but in the sham-operated rats fasting blood glucose and plasma insulin concentrations of those rats on high-protein diet were significantly increased when compared to those on balanced diet. In the isolated, perfused pancreas, an arginine-induced excess insulin and glucagon secretion was not significantly different between the VMH lesioned rats. An arginine-induced rise in insulin concentration in the sham-operated rats on high-protein diet was significantly higher than for rats on balanced diet. We therefore suggest that hyperinsulinemia already produced in the VMH lesioned rats may not be influenced by the change in the composition of the dietary protein and carbohydrate.