The effect of thyroid hormones on blood insulin level and metabolic parameters in diabetic rats

Abstract

The effect of exogenous thyroid hormones on blood insulin and metabolic parameters in diabetic rats was investigated. Three groups of rats were treated with streptozotocin (STZ; 50 mg/kg b.w., intravenously) and one group receiving only saline served as control. Beginning with the third day after STZ treatment, until the last day before decapitation, i.e. for 11 days, two groups of diabetic rats were treated with T3 (50 microg/kg b.w., i.p.) or T4 (250 microg/kg b.w., i.p.). After two weeks, STZ injected rats had lower body weight, hyperglycemia with a simultaneous drop in blood insulin and decrease of T3 and T4 concentrations in comparison to control animals. Liver glycogen content was also reduced, whereas serum lactate, free fatty acids, triglycerides and cholesterol were elevated. Exogenous thyroid hormones given to diabetic rats substantially attenuated hyperglycemia without any significant changes in blood insulin concentration. An additional reduction of body weight gain and depletion in liver glycogen stores were also observed. Thyroid hormones augmented serum lactate and cholesterol and had no beneficial effect on elevated free fatty acids and triglycerides. It can be concluded that in spite of partial restriction of hyperglycemia, thyroid hormones evoked several unfavourable changes strongly limiting their potential use in diabetes.

Hypothyroidism Affects Vascularization and Promotes Immune Cells Infiltration into Pancreatic Islets of Female Rabbits

“…In spite of the hypervascularization and immune cells infiltration in pancreas of female rabbits, we previously showed that neither insulin nor glucose levels are affected by hypothyroidism [ 3 ]. It is probable that a long time of treatment with methimazole may result in hyperglycemia and hyperinsulinemia because the treatment with thyroid hormones reduces the hyperglycemia of diabetic rats [ 48 ]. Thus, our present findings (inflammation, changes in vascularization, and immune cells infiltration into the islets) could appear before consolidating hyperinsulinemia and a hyperglycemic status.…”

Hyperinsulinemia and insulin resistance is associated with low T3/T4 ratio in pre diabetic euthyroid pakistani subjects

“…There is a recognized association between diabetes and thyroid disease (Dimitriadis et al, 1997;Szkudelski, Michalski, & Szkudelska, 2003;Jin et al, 2004;Akbar, Ahmed, & Al-Mughales, 2006;Fernandez-Real et al, 2006). These are common endocrine disorders in Pakistani population.…”

Thyroid hormone affects both endothelial and vascular smooth muscle cells in rat arteries

“…The diabetic rats were divided randomly into two groups, one receiving vehicle alone and the other a daily intraperitoneal injection of T3 (10μg/kg/day). T3 was selected over thyroxine, because it mediates the effects of the latter in vivo and is more widely used in experimental animals (Carrillo-Sepúlveda et al, 2010;Dillmann, 1982;Hiroi et al, 2006;Szkudelski et al, 2003). Doses of 3μg/kg (considered physiological) and 30 or 50μg/kg (considered pharmacological) of T3 have been administrated daily to diabetic rats by others investigators (Dillmann, 1982;Szkudelski et al, 2003).…”

“…T3 was selected over thyroxine, because it mediates the effects of the latter in vivo and is more widely used in experimental animals (Carrillo-Sepúlveda et al, 2010;Dillmann, 1982;Hiroi et al, 2006;Szkudelski et al, 2003). Doses of 3μg/kg (considered physiological) and 30 or 50μg/kg (considered pharmacological) of T3 have been administrated daily to diabetic rats by others investigators (Dillmann, 1982;Szkudelski et al, 2003). Since 3μg/kg has no obvious metabolic effect, preliminary experiments were performed using 10μg/kg, 50μg/kg and 100μg/kg of T3, however, the latter two doses were severely toxic in diabetic rats, prompting the use of 10μg/kg/day for further studies.…”