Effects of the electric stress on insulin secretion and glucose metabolism in rats fed with a high fat diet.

The synergetic effects of dietary obesity and stress induced by electrical shocks on insulin secretion from the perfused pancreas, the action of insulin on adipose tissues and glucose tolerance were studied in rats. The rat was fed either a control (C) (50% starch) or a high fat diet (F) (40% butter) for a period of 12 weeks. Half of the rats on each diet received electrical shocks, one hour per day for the last three weeks of the experiment (group C-S, F-S). The remaining rats were not given any stress sessions (group C-N, F-N). The rats on the high fat diet gained a significant amount of weight at the 8th week, and as determined by the adipocytes, were obese at the end of 12 weeks. However, the high fat diet itself did not have any effect on plasma glucose, plasma insulin and insulin release from the perfused pancreas in response to glucose. It caused glucose intolerance and the insensitivity to insulin of adipose tissue. The rats which received electrical shocks stopped gaining weight when the shock sessions began. Moreover, the size of the adipocytes in F-S group was significantly smaller than that in F-N group, but the insensitivity to insulin of adipose tissue remained. In F-S group, glucose-induced insulin release from the perfused pancreas was signiffcantly diminished in the initial phase of release, and glucose tolerance was much impaired by stress, while in C-S group insulin release increased in the late phase of release, and glucose tolerance was unaffected by stress. These findings indicate that the ability of glucose to stimulate insulin secretion is decreased by the synergetic effects of a high fat diet and stress induced by electric shock. Thus, it may be concluded that the mechanism which mediates the effects of glucose upon insulin secretion, especially in the initial response phase, is modified by such synergetic effects.