Background & Aims:
Diabetes mellitus is a self-management disease and depression is a common problem related to it. One of the causes of depression is serotonin depletion. The enzyme tryptophan hydroxylase is known as limiting enzyme in the production of serotonin in the brain. Aerobic exercise also has proven benefits in treating and reducing the incidence of chronic diseases such as diabetes. Thus in this study we examine the effect of aerobic training on serotonin and tryptophan hydroxylase of prefrontal cortex in type 2 diabetic rats.
Materials & Methods:
This study is experimental and post-test. 30 rats were randomly divided into 3 groups: 1- healthy control 2-diabetic control 3- exercise diabetic, were divided. 2 and 3 groups for diabetes by intraperitoneal injection two weeks after the high-fat diet, streptozotocin (37mg/kg) received. Groups of aerobic exercise 5 times in the week and 8 week ran that duration and intensity on a treadmill in the final weeks respectively 55min /d and 26m/min arrived. 24 hours after the last exercise the prefrontal cortex of mice tissue samples of all groups were extracted and serotonin (µg/g) and tryptophan hydroxylase concentration was measured respectively by Elisa and Western Blotting from prefrontal cortex tissue samples. To evaluate the differences between the group of design analysis of variance (ANOVA) and Tukey post hoc test at the significant level was less than 0.05 were used.
Statistical analysis showed that serotonin levels in the diabetic group was significantly lower than the healthy control group (P=0.001) and exercise diabetic (P=0.009) and average serotonin between control group and exercise diabetic has no significant difference. Tryptophan hydroxylase results show that the average diabetic groups was significantly lower than the healthy control group (P=0.000). The results showed that the amount of tryptophan hydroxylase in the exercise diabetic group was significantly higher than the diabetic control group (P=0.000).
In this study, diabetes reduces serotonin in the prefrontal cortex. Some studies have shown that inflammation in type 2 diabetes increases the cytokines IL-6 and TNF-α, and these cytokines by increasing the activity of indolamine 2, 3 dioxygenase in the brain alters the metabolism of tryptophan and reduce the production of 5-HT. Chronic activity reduces systemic and tissue inflammation thus increasing serotonin in the brain. The reduction of tryptophan hydroxylase due to diabetes can also be the factors that affect in the decrease of prefrontal serotonin.