title: Chronic ethanol feeding suppresses beta-adrenergic receptor-stimulated lipolysis in adipocytes isolated from epididymal fat.
abstract: Chronic ethanol consumption disrupts G protein-dependent signaling pathways in rat adipocytes. Because lipolysis in adipocytes is regulated by G protein-mediated cAMP signal transduction, we hypothesized that cAMP-regulated lipolysis may be vulnerable to long-term ethanol exposure. Male Wistar rats were fed a liquid diet containing ethanol as 35% of total calories or pair-fed a control diet that isocalorically substituted maltose dextrins for ethanol for 4 wk. Lipolysis was measured by glycerol release over 1 h with or without agonists in adipocytes isolated from epididymal fat. Chronic ethanol feeding decreased beta-adrenergic receptor-stimulated lipolysis, but had no effect on basal lipolysis. In response to beta-adrenergic activation, the early peak of cAMP accumulation was suppressed after ethanol feeding, although the basal cAMP concentration in adipocytes did not differ between pair- and ethanol-fed rats. The suppression in cAMP accumulation caused by ethanol feeding was associated with increased activity of phosphodiesterase 4. Chronic ethanol feeding also decreased beta-adrenergic receptor-stimulated protein kinase A activation and phosphorylation of its downstream proteins, perilipin A and hormone-sensitive lipase, the primary lipase-mediating lipolysis. In conclusion, these data suggest that chronic ethanol feeding increased phosphodiesterase 4 activity in adipocytes, resulting in decreased accumulation of cAMP in response to beta-adrenergic activation and a suppression of beta-adrenergic stimulation of lipolysis.
authors.affiliation: Department of Nutrition, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106-4906, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Kang
authors.forename: Laura E
authors.initials: LE
authors.lastname: Nagy
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000378:metabolism; D012368:4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone / Q000494:pharmacology; D017667:Adipocytes / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins; D000242:Cyclic AMP / Q000032:analysis / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D004032:Diet; D004822:Epididymis; D000431:Ethanol / Q000008:administration & dosage*; D005990:Glycerol / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D000070778:Perilipin-1; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D002787:Sterol Esterase / Q000378:metabolism
chemical_list: D000318:Adrenergic beta-Agonists; D002352:Carrier Proteins; D000070778:Perilipin-1; D010726:Phosphodiesterase Inhibitors; D010750:Phosphoproteins; D011943:Receptors, Adrenergic, beta; D012368:4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone; D000431:Ethanol; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D002787:Sterol Esterase; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D007545:Isoproterenol; D005990:Glycerol