Effect of chronic psychological stress on carbohydrate metabolism in rat

Several studies have shown that stress has major effects on carbohydrate metabolism. There are some evidences suggesting that stress may induce type 1 and type 2 diabetes mellitus. The effects of psychological stress however need to be investigated. The present study has investigated the role of chronic psychological stress on carbohydrate metabolism in male rats.

Animals were assigned in two groups of control and stressed (n=8/group). The animals of the stressed group were exposed to different restraint stressors (1 hour twice daily) for 15 and 30 days. At the beginning and end of the experimental periods fasting blood samples were obtained by tail snipping and oral glucose tolerance test (OGTT) was carried out. Glucose was measured by glucose oxidase method. Insulin and corticosterone were assayed by their respective RIA kits.

Fasting plasma glucose level on the 15th day of the experiment showed significant increase in the stressed rats compared to the controls. The plasma levels of glucose at 15 and 60 min after performing OGTT were significantly increased on the 15th and 30th days of the experiment in the stressed group. Fasting plasma insulin showed significant decrease on the 15th and 30th days of the experiment in the stressed group compared to the controls. On the 15th day of the experiment, at 15 and 60 min after performing OGTT the plasma level of insulin showed significant decrease in the stressed group as compared to the control group. Fasting plasma corticosterone concentration was significantly increased on the 15th day of the experiment in the stressed rats compared with the control rats and the 1st day of the experiment. In the stressed group immediately after stress exposure plasma corticosterone was significantly higher than before stress exposure, only on the 1st day of the experiment.

Results have revealed that chronic psychological stress can impair glucose metabolism and this effect may be mediated by changes in insulin and corticosterone secretion. However the role of other stress hormones has to be investigated.