The effects of 3,5-diiodothyronine on energy balance

摘要: Thyroid hormones (THs) have been known to affect energy metabolism (calorigenic effect) for over a century (Magnus-Levy, 1895; Thompson et al., 1929). In 1985 Magnus-Levy observed that patients with mixedema exhibited an abnormal low oxygen consumption when compared normal individuals and unusually higher amount of was consumed by hyperthyroid patients. 3,3′,5-triiodo-L-thyronine (T3) is the active form THs it major regulator growth development cellular tissue (both intermediate metabolism) throughout body. Metabolic actions include regulation of: basal metabolic rate in homeotherms, synthesis mitochondrial respiratory enzymes membranes, oxidative phosphorylation transduction, movement water Na+ ions across cell membranes; calcium phosphorus metabolism, lipids storage, catabolism fatty acids, cholesterol, carbohydrate; nitrogen (urea, creatine) metabolism; developmental on: postnatal many mammalian avian tissue, maturation fetal brain bone, amphibian larval metamorphosis, molting birds. It now recognized T3 affects gene expression target tissues/cells binding its cognate nuclear receptors (TR) which are ligand-inducible transcription factors. Two TR genes α β encode four T3-binding receptor isoforms (α1, β1, β2, β3). The transcriptional activity TRs regulated at multiple levels. Besides being T3, also regulated: (i) type thyroid hormone response elements located on promoters genes, (ii) developmental- tissue-dependent isoforms, (iii) host coregulatory proteins (corepressors coactivators). These modulate T3-dependent manner. absence corepressors act repress activity, whereas presence coactivators activate transcription. activities via previous described mechanisms as “genomic actions.” However, between mid-1980's beginning 1990's became evident some TH effects non-genomic origin. Indeed, high-affinity sites years plasma membrane other such mitochondria cytoplasm (for review see Cheng 2010). Recently, structural protein membrane, integrin αvβ3, has shown contain domain iodothyronines initiation site hormone-directed complex events, division angiogenesis (Bergh 2005) this qualifies characterization receptor. Examples action activation Ca2-ATPase 2-Deoxyglucose transport, Na, K-ATPase current myocardiocytes, sensory neuron, Na+/H+ exchanger, cancer proliferation, addition this, or analogs/derivatives able exert relevant biological recent review, Moreno 2008; Senese 2014; Zucchi 2014). This article particularly intended describe 3,5 diiodo-L-thyronine (T2) balance (Moreno 1997; Goglia, 2005).