Alterations of brown adipose tissue in genetically obese (ob/ob) mice. II. Studies of beta-adrenergic receptors and fatty acid degradation.
beta-Receptor number, norepinephrine-stimulated adenylate cyclase activity and lipolysis, octanoate-induced NAD(P) redox changes, and heat production were studied in brown adipose tissue (BAT) of lean and obese (ob/ob) mice. beta-Receptor number was increased 1.54-fold in purified brown adipocyte plasma membrane of ob/ob mice compared to that in lean controls. This increase was reversed by cold adaptation (5 C). Basal and norepinephrine-stimulated adenylate cyclase values were not different in the two groups. Norepinephrine stimulated lipolysis at 10 nM in BAT of lean mice, but only at 10 microM in BAT ob/ob mice. Octanoate produced an increase in the NAD(P) redox state in BAT of lean mice, but it did not modify the NAD(P) redox state in BAT of ob/ob mice. Concomitantly, octanoate increased heat production 3-fold in BAT of lean mice, but did not promote any significant increase in heat production in BAT of ob/ob mice. These two parameters were restored toward values observed in lean mice when the ob/ob mice were adapted to a cold environment. The data indicate that BAT of ob/ob mice exhibits three alterations; one at the level of the beta-receptor, one at the level of the lipolytic response to norepinephrine, and one at the level of fatty acid activation and/or beta-oxidation.
D000262:Adenylyl Cyclases / Q000032:analysis; D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000818:Animals; D002210:Caprylates / Q000378:metabolism; D003080:Cold Temperature; D004082:Dihydroalprenolol / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D066298:In Vitro Techniques; D008066:Lipolysis; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese / Q000378:metabolism*; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*
D002210:Caprylates; D005227:Fatty Acids; D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; D000262:Adenylyl Cyclases