Changes in the hormonal status of cardiovascular and the thyroid systems in rats with 18-month type 2 diabetes mellitus

Abstract

Among the most common complications of type 2 diabetes mellitus (DM2) are disorders of the cardiovascular and the thyroid systems. The functions of these systems may be weakened with increasing age. However, the mechanisms of these disorders, including the role of alterations in the adenylyl cyclase signaling system (ACSS), are not fully elucidated. Objective was to study thyroid status and ACSS activity of the myocardium and the thyroid gland (TG) of rats with 8- and 18-month DM2 (DM-8 and DM-18) as compared to control animals of the same age (C-8 and C-18). In the myocardium of rats with DM2 an imbalance of β-adrenergic regulation of ACSS was detected, and these disturbances were amplified with increasing age. In the myocardium of rats of the C-18 group the disturbances of ACSS hormonal regulation were also identified, but they were less pronounced. In diabetic rats, the levels of free thyroxine and total triiodothyronine decreased, the level of thyroid stimulating hormone (TSH) increased, and the stimulatory effect of TSH on the ACSS in TG was attenuated, which indicates the hypothyroid state in long-term DM2. In the C-18 group, these changes were absent. Thus, in the myocardium and TG of rats with 18-month DM2 the hormonal regulation of ACSS was violated, which may be one of the causes of cardiovascular pathology and hypothyroid states in long-term DM2.