Morphological and functional characteristics of the thyroid gland in diet-induced obesity and its correction in male wistar rats

Abstract

Background. Obesity causes numerous endocrine and metabolic disorders. However, the issues of drug-free correction of obesity and thyroid dysfunction are insufficiently studied. The aim was to study the morpho-functional state of the thyroid gland in diet-induced obesity and possibilities of its drug-free correction in male Wistar rats. Methods. The experiments were performed in six groups of male Wistar rats: 1) Standard diet (StD) for 16 wks (Control group) 2) Нigh-calorie diet (HCD) for 16 wks (HCD group); 3) HCD for 8 wks with switching to StD (HCD/StD group) for 8 wks; 4) StD for 16 wks with treadmill running during the last 8 wks (StD+running group); 5) HCD for 16 wks with running during the last 8 wks (HCD+running group); 6) HCD for 8 wks followed by StD for 8 wks with running during the last 8 wks (HCD/StD+running group). Body weight, visceral fat, morphological characteristics of thyroid tissue (TG), thyroperoxidase (TPO) activity, triglyceride (TG) and interleukin 6 (IL-6) content in TG tissue, and serum levels of thyroxine (T4) and triiodothyronine (T3) were assessed. Results. HCD resulted in visceral obesity and thyroid histostructural abnormalities typical of hypofunction. Blood serum T4 increased, but, at the same time, TPO activity tended to decrease along with an increase in thyroid TG and a decrease in thyroid IL-6. After transition from HCD to StD, successful correction of obesity and normalization of thyroid function were achieved. The most complete recovery of TPO activity and other metabolic processes in the thyroid tissue was noted in the combined correction of obesity with treadmill running. Conclusion. Visceral diet-induced obesity is accompanied by an increase in blood T4. However, morphological and biochemical signs of reduced metabolic processes in thyroid tissue develop. Successful correction of visceral obesity restores thyroid structure and function.