Alterations of Brown Adipose Tissue in Genetically Obese (ob/ob) Mice, II. Studies of β-Adrenergic Receptors and Fatty Acid Degradation*

Publisher Website
Google Scholar
Abstract
β-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. β-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 (5C). 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 μM 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 β-receptor, one at the level of the lipolytic response to norepinephrine, and one at the level of fatty acid activation and/or β-oxidation.