Effects of treatment with insulin and melatonin on body temperature and activity/rest rhythms in diabetic rats

Abstract

In mammals, the central endogenous clock located in the hypothalamic suprachiasmatic nuclei (SCN) coordinate the biologic rhythmicity, regulating circadian and seasonal rhythms as well as establishing an important influence over the peripherical clocks.Melatonin, a hormone produced by the pineal gland, is known for being an important regulator of the endogenous rhythms, including locomotor activity and body temperature. Type 1 diabetes mellitus is a metabolic disease spread worldwide and it is characterized by hyperglycemia, polyphagia, polydipsia and glycosuria. It is well documented that diabetes promotes a decrease in body temperature, daily average locomotor activity and melatonin secretion in rats. Data show that insulin treatment reverses the effect of diabetes on body temperature and melatonin secretion, but fails to do so in daily average locomotor activity. However, the effect of diabetes on the circadian profile and on the activity/rest rhythm remains unknown. In addition, the possible effects of insulin and melatonin over these parameters in diabetic rats are also unknown. Thus, the aim of this project is to study the potential effects of diabetes on homeostatic systems, especially chronobiological systems, and the action of insulin and melatonin treatment on them. Activity/rest and body temperature daily profiles (Mini-mitter system), as well as glycemia and the triglycerides and cholesterol plasmatic concentrations will be analyzed in diabetic male Wistar rats (streptozotocin), treated with insulin (6U daily) or supplemented with melatonin. (AU)