The aim was to determine the influence of melatonin on basal levels of glucose (BG), activities of glucose-6-phosphate dehydrogenase (G6PD), pyruvate kinase (PK),

The aim of this study was to determine the influence of melatonin on basal level of glucose in the blood (BG), glycogen content (GC), activities of glucose-6-phosphate dehydrogenase (G6PD), pyruvate kinase (PK) and lactate dehydrogenase (LDH) in muscles of alloxan diabetic rats under conditions of different photoperiod (artificial equinox, constant darkness and constant light). In the DM rats the LDH activity increased on average by 61%, whereas the GC and the activities of PK and G6PD decreased on average by 37, 53 and 40% respectively compared with control values. All of these changes were not dependent on the light conditions. The BG level of the IGT rats didn't reliably differ from the control, however, the LDH and the G6PD activities were respectively higher on average by 24 and 49%, except rats under the constant light conditions whose G6PD activity was lower by 48%. A melatonin administration (14 daily injections of 10 mg/kg) led to an improvement of the carbohydrate metabolism: the BG level, the GC, the activities of PK and LDH were normalized, while the G6PG activity was increased by an average of 32%. The influence of melatonin was more prominent in the IGT rats under the constant light conditions.

The aim was to determine the influence of melatonin on basal levels of glucose (BG), the levels of protein carbonyl content, HbA 1c and thiobarbituric acid reactive compounds (TBCRC), reduced glutathione (GSH), activities of glutathione reductase [EC 1.6.4.2] (GR), glutathione peroxidase [EC 1.11.1.9] (GPx), glucose-6-phosphate dehydrogenase [EC 1.1.1.49] (G-6-PhD) in the muscles of alloxan diabetic rats (DM1T). BG levels in blood of rats with DM1T increased on 139%, while in group of alloxan diabetic rats with impaired glucose tolerance (IGT)-were not differ from control. HbA 1c levels in the blood of animals with DM1T and IGT exceeded control by 219% and 123%, the level of protein carbonyl groups-by 76% and 36%, the level of TBCRC-by 58% and 36% respectively. Activities of GR, GPx, G-6-PhD and the level of GSH were decreased on 25%, 18%, 50% and 42% in rats with DM1T while in rats with IGT these indexes (besides GSH) were increased on 37%, 22%, 35% respectively than control. Melatonin lowered the BG level on 56% in DM1T rats in comparison to initial levels. It normalized activities of GR, GPx, G-6-PhD and lipid peroxidation, and protein carbonylation as well as hemoglobin glycosylation, so these indexes did not differ from control. Thus, melatonin has strong potential to regulate glucose homeostasis through enhanced glucose consumption, decreased oxidative stress by activation of the glutathione protection system.

No abstract