a1 Department of Physiology and Biochemistry, Szent Istvan University Faculty of Veterinary Sciences, 1078 Istvan u. 2, Budapest, Hungary
Controlling energy homeostasis involves modulating the desire to eat and regulating energy expenditure. The controlling machinery includes a complex interplay of hormones secreted at various peripheral endocrine endpoints, such as the gastrointestinal tract, the adipose tissue, thyroid gland and thyroid hormone-exporting organs, the ovary and the pancreas, and, last but not least, the brain itself. The peripheral hormones that are the focus of the present review (ghrelin, leptin, thyroid hormones, oestrogen and insulin) play integrated regulatory roles in and provide feedback information on the nutritional and energetic status of the body. As peripheral signals, these hormones modulate central pathways in the brain, including the hypothalamus, to influence food intake, energy expenditure and to maintain energy homeostasis. Since the growth of the literature on the role of various hormones in the regulation of energy homeostasis shows a remarkable and dynamic expansion, it is now becoming increasingly difficult to understand the individual and interactive roles of hormonal mechanisms in their true complexity. Therefore, our goal is to review, in the context of general physiology, the roles of the five best-known peripheral trophic hormones (ghrelin, leptin, thyroid hormones, oestrogen and insulin, respectively) and discuss their interactions in the hypothalamic regulation of food intake.
(Online publication March 22 2011)
Abbreviations: AgRP, agouti-related protein; D1, type I deiodinase; D2, type II deiodinase; D3, type III deiodinase; E2, 17β-oestradiol; ERα, oestrogen receptor α; ERβ, oestrogen receptor β; ERE, oestrogen response element; MSH, melanocyte-stimulating hormone; NPY, neuropeptide Y; POMC, pro-opiomelanocortin; STAT3, signal transducer and activator of transcription 3; T3, triiodothyronine; T4, thyroxine; TRα, thyroid hormone receptor α; TRβ, thyroid hormone receptor β; TSH, thyroid-stimulating hormone; UCP, uncoupling protein