EFFECTS OF COMBINATION OF HIGH-FAT DIET AND CHRONIC STRESS ON HYPOTHALAMO-PITUITARY-ADRENAL AXIS AND INSULIN RESISTANCE IN RATS

[Objective] To explore the effects of combination of high-fat Diet and chronic stress on hypothalamo-pituitary-adrenal axis (HPA axis) and insulin resistance (IR) in rats [Methods] 32 male Wistar rats were randomly divided into 4 groups, A group was fed standard rat chow diet, B group was fed high-fat diet, C group was fed with standard rat chow diet and took the electric footshock and noise stress, D group was fed with high-calorie diet and took the electric footshock and noise stress. After having been treated for 12 weeks, insulin sensitivity was estimated by hyperinsulinemic euglycemic clamp. Serum corticosterone, adrenocorticotropic hormone (ACTH), glucose and insulin were measured. [Results] After 12 weeks, compared with A group, the body weight was significantly decreased in C, D groups (P﹤0.05), while there was no significant difference in B group (P﹥0.05). Serum ACTH and corticosterone were increased significantly in B, C, D group compared with A group (P﹤0.05), meanwhile they were also elevated significantly in D group compared with B, C groups (P﹤0.05). Serum glucose in B, C groups was no significant difference compared with A group (P﹥0.05), but it was increased significantly in D group compared with A, B, C groups (P﹤0.05). Serum insulin in B, D groups was increased significantly compared with A group (P﹤0.05). The glucose infusion rates (GIR) in B, C, D groups as shown by hyperinsulinemic euglycemic clamp was decreased significantly compared with A group (P ﹤ 0.05) , especially it was decreased by 78.7% compared with A group. Meanwhile GIR in D group was decreased significantly compared with B, C groups (P﹤0.05). [Conclusion] High-fat diet and chronic stress could enhance the activity of HPA axis and lead to IR, meanwhile the combination of the two factors has a cooperation on enhancing the activity of HPA axis and leading to IR .