Thermogenesis in Adipose Tissue Activated by Thyroid Hormone

Area of Science:

• Endocrinology
• Metabolism
• Thermogenesis

Background:

• Thermogenesis, the production of body heat, is crucial for warm-blooded animals, involving metabolic, shivering, and non-shivering mechanisms.
• White adipose tissue (WAT) can acquire thermogenic potential through browning, while brown adipose tissue (BAT) is a primary site for adaptive thermogenesis.
• Thyroid hormone (TH) significantly influences thermoregulation, with hypothyroidism and hyperthyroidism causing decreased and increased body temperatures, respectively.

Purpose of the Study:

• To review the thermogenic effects of thyroid hormone (TH) on adipose tissues.
• To elucidate the mechanisms by which TH influences heat production in brown and white adipose tissues.
• To summarize TH-mediated thermogenesis, including both UCP1-dependent and independent pathways.

Main Methods:

• Review of existing literature on thyroid hormone action and thermogenesis in adipose tissues.
• Analysis of studies investigating TH's central and peripheral effects on BAT and WAT.
• Examination of mechanisms involving uncoupling protein 1 (Ucp1) and autophagy.

Main Results:

• TH induces "activated" thermogenesis in adipose tissues under thermoneutral conditions.
• TH stimulates uncoupled respiration and heat generation in BAT and WAT, primarily through Ucp1 induction.
• TH acts centrally via the sympathetic nervous system and peripherally on BAT, utilizing both autophagy-dependent and Ucp1-independent pathways.

Conclusions:

• Thyroid hormone plays a critical role in regulating adipose tissue thermogenesis through multiple mechanisms.
• TH's effects on Ucp1 expression and Ucp1-independent pathways contribute to adaptive thermogenesis and overall thermoregulation.
• Understanding TH-mediated thermogenesis in adipose tissues offers insights into metabolic and endocrine regulation of body heat.