Effects of a High Fat Diet and Electric Stress on Insulin Response to Hydrocortisone and Catecholamines in Isolated Pancreatic Islets

Rats divided into stress group (S) and non-stress group (NS) were fed either a control diet (C) or a high fat diet (F) for 12 weeks. Group S received electrical shocks (1 hr/day) for the last 3 weeks of the experimental period. The single or synergistic effects of hydrocortisone, epinephrine and dopamine on glucose-induced insulin release were examined in isolated pancreatic islets from rats fed for 24 hours after the end of electric stress. Glucose-induced insulin release was significantly reduced in F-S group. Hydrocortisone in the presence of 2.8 mM glucose significantly stimulated insulin release with a biphasic fashion which was not affected by both the high fat diet and stress. In the presence of 16.7 mM glucose, the stimulatory effect of hydrocortisone on insulin release was observed in C-S group, but not in C-NS group and F-S group. Conversely, in F-NS group hydrocortisone led to a significant decrease of glucose-induced insulin release. The inhibitory effects of epinephrine or dopamine on insulin response to glucose were completely abolished in F-S group. In the presence of 16.7 mM glucose plus 4 × 10 -6 M hydrocortisone, however, the inhibitory effects of epinephrine or dopamine on insulin release were restored in F-S group. These results indicate that a decrease of glucose-induced insulin release produced by the combined actions of a high fat diet and electric stress may be related to the inhibition of insulin release by glucocorticoids in the feeding of a high fat diet. Key-Words: Fat Diet - Stress - Hydrocortisone - Epinephrine - Dopamine - Insulin Release