Triiodothyronine improves age-induced glucose intolerance and increases the expression of sirtuin-1 and glucose transporter-4 in skeletal muscle of aged rats

Abstract

To evaluate the potential beneficial impact and to clarify the underlying mechanisms of triiodothyronine (T 3) on glucose intolerance in aged rats. Rats were divided into adult group, aged group, and T 3-treated aged group (T 3-aged). T 3 was administered at a dose of 8 µg/kg body weight for 2 weeks. In comparison to adult group, aged rats presented significant higher levels of fasting insulin and homeostatic model assessment of insulin resistance (HOMA-IR). Glucose area under the curve (AUC), and peak glycemia, estimated from oral glucose tolerance curve, were significantly increased along with decreased mRNA expression of skeletal muscle sirtuin-1, glucose transporter-4 (GLUT-4) and uncoupling protein-3 (UCP-3) in aged versus adult group. T 3 administration significantly decreased the serum levels of fasting insulin, HOMA-IR, glucose AUC, and peak glycemia in T 3-aged versus aged rats. Skeletal muscle mRNA expression of sirtuin-1 and GLUT-4 were increased, whereas UCP-3 was not changed by T 3 administration. T 3 administration improved glucose intolerance, and decreased insulin resistance in aged rats. This was associated with upregulation of skeletal muscle sirtuin-1 and GLUT-4 which could mediate such beneficial effect.

The role of the thyroid in polycystic ovary syndrome

“…Centrally, T3 regulates glucose synthesis in the liver through the sympathetic nervous system ( 87 ). Peripherally, T3 enhances skeletal muscle glucose transporter 4 (GLUT-4) expression and downstream signaling cascade proteins responsible for glucose transport, which increases the insulin-dependent transmembrane glucose transport ( 88 ). Mueller et al.…”

“…Centrally, T3 regulates glucose synthesis in the liver through the sympathetic nervous system (87). Peripherally, T3 enhances skeletal muscle glucose transporter 4 (GLUT-4) expression and downstream signaling cascade proteins responsible for glucose transport, which increases the insulin-dependent transmembrane glucose transport (88). Mueller et al discovered a significant correlation between TSH-the most sensitive indicator of thyroid functionand insulin resistance, but not between insulin resistance and the patient's age or BMI (89).…”