The Effects of Thyroid Hormones on Glucokinase Enzyme Activity in diabetic Rat Liver Tissues

Objective: We aimed to investigate the effcts of insulin and various doses of thyroid hormones  with combine treatment on glucokinase (GK) enzyme activity, which is the one of the key  enzyme in carbohydrate metabolism, diabetes and hypothyroidism.  Material and methods: Rats were assigned to eight groups: Group 1: control, Group 2: diabetes  (DM), Group 3: DM + insulin, Group 4: thyroidectomized control, Group 5: thyroidectomized +  DM, Group 6: thyroidectomized + DM + insulin, Group 7: thyroidectomized + DM + insulin +  thyroid hormone (TH) (2.5μg/kg), Group 8: thyroidectomized + DM + insulin + TH (5 μg/kg).  Glucose concentration, HbA1c and thyroid hormone levels were measured in blood samples and  GK enzyme activities were determined in liver tissue samples. Results: Our results showed that the glucokinase enzyme activities were significantly decreased  in diabetic rat liver tissues compared to control group. Moreover it was observed that the enzyme  activities were slightly regulated by insulin. It is demonstrated that decreased GK enzyme  activity in thyroidectomized diabetic rat liver was regulated by insulin and various doses of  thyroid hormones. Conclusion: As a result the possible contribution of thyroid hormones to insulin effct to  normalize diabetic induced changes in liver tissue has been shown.