Thyrotropin decreases leptin production in rat adipocytes

Leptin, which is secreted from adipocytes, has a role in the regulation of appetite and energy expenditure. The thyrotropin receptor (TSH-R) was recen tly found in adipocytes. We examined the effects of TSH on leptin productio n and lipolysis in rat epididymal adipocytes, TSH decreased the concentrati on of leptin in the medium time (similar to 24 hours)- and dose (similar to 10(-7) mol/L)-dependently (half-maximal inhibition [IC50] approximate to 1 0(-9) mol/L). TSH also decreased the ob mRNA level approximately 55% in adi pocytes. We confirmed the presence of TSH-R mRNA, in the adipocytes by reve rse transcription-polymerase chain reaction (RT-PCR). TSH stimulated glycer ol release dose-dependently (IC50 approximate to 10(-8) mol/L) in adipocyte s, This TSH-induced glycerol release was further enhanced by adenosine deam inase (ADA). In summary TSH reduced leptin production and stimulated lipoly sis in rat epididymal adipocytes. Although the pathophysiological relevance of the regulation of leptin production and lipolysis by TSH is unknown, we speculate that TSH may affect the regulation of appetite and energy expend iture in pathophysiological states. Copyright (C) 1999 by W.B. Saunders Com pany.