Melatonin Inhibits the Regulation of Hypothalamo-Pituitary-adrenal Axis in Diabetic Rats

Objective:To study the effect of melatonin(Mel),a potent antioxidant,on the oxidative stress and the activity of hypothalamo-pituitary-adrenal axis in diabetic rats.Methods:Male SD rats were assigned to the following 4 groups:normal control(treated with 2% ethyl alcohol lavage\[NC,n=6\]),diabetes mellitus control(treated with 2% ethyl alcohol lavage \[DM,n=7\]),diabetes mellitus model group 1(treated with Mel lavage \[10 mg·kg-1·d-1,DM+Mel1,n=6\]),diabetes mellitus model group 2(treated with Mel lavage \[0.2 mg·kg-1·d-1,DM+Mel2,n=6\]).Diabetes in DM group,DM+Mel1 group and DM+Mel2 group was induced by intraperitoneal injection of streptozotacin(65 mg/kg).Blood glucose,body weight and adrenal gland weight/body weight(AW/BW)were determined in the 4 groups 12 weeks later;malondialdehyde(MDA)was examined with visible spectrophotometry;blood total cholesterol(TC)and triglyceride(TG)were examined with enzymology method;blood corticotrophin-releasing hormone(CRH),adreno-corticotrophic hormone(ACTH)and corticosterone(CORT)were examined with radioimmune method.Results:Blood glucose,MDA,TC,TG,CRH,ACTH,CORT and AW/BW in DM group were significantly higher than those in NC group(P0.01);and the body weight of rats in DM group were significantly lower those of NC group(P0.01).Compared with DM group,DM+Mel1 and DM+Mel2 group had a significantly lower blood glucose,MDA,TC,TG and AW/BW(P0.01 or P0.05)and higher body weight(P0.01).Blood CRH,ACTH and CORT were markedly decreased in DM+Mel1 group(P0.01);blood CORT were markedly decreased in DM+Mel2 group(P0.05);blood CRH and ACTH in DM+Mel2 group had no significant changes.Conclusion:Mel may lower the oxidase activity,improve metabolic disorder of glucose and fat,and inhibit the activity of hypothalamo-pituitary-adrenal axis in diabetic rats,exerting protective effect on diabetic rats.