Cold exposure restores the decrease in leptin receptors (OB-Rb) caused by neonatal leptin treatment in 30-day-old...

Area of Science:

• Endocrinology
• Metabolism
• Developmental Biology

Background:

• Neonatal leptin treatment influences adult thyroid function.
• Both leptin and thyroid hormones (TH) are involved in thermogenesis.

Purpose of the Study:

• To investigate the effect of cold exposure on thyroid function in neonate rats previously treated with leptin.
• To evaluate the role of leptin receptors (OB-Rb) in mediating thyroid hormone responses to cold.

Main Methods:

• Neonatal rats received leptin or saline injections for 10 days.
• At 30 days old, rats were exposed to cold (8°C) or thermoneutrality (25°C).
• Serum leptin, TH, TSH, liver deiodinase (D1), and mitochondrial glycerol-3-phosphate dehydrogenase (mGPD) activities were measured. Hypothalamic and thyroidal OB-Rb levels were assessed via western blot.

Main Results:

• Leptin-treated rats exhibited hyperleptinemia and lower free tri-iodothyronine (FT3) levels.
• Cold exposure increased thyroid hormones (FT4, FT3) in both leptin-treated and control groups.
• Leptin treatment reduced D1 and mGPD activities, which were restored by cold exposure. OB-Rb levels were decreased by neonatal leptin but normalized with cold exposure.

Conclusions:

• Neonatal leptin programming alters thyroid hormone levels and responses to cold.
• Cold exposure normalizes OB-Rb levels and enhances thyroid hormone response in leptin-programmed rats.
• OB-Rb plays a role in the adaptive thyroid hormone response to cold stress.