β1/β2/β3‐adrenoceptor knockout mice are obese and cold‐sensitive but have normal lipolytic responses to fasting

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Abstract
Catecholamines are viewed as major stimulants of diet- and cold-induced thermogenesis and of fasting-induced lipolysis, through the beta-adrenoceptors (beta(1)/beta(2)/beta(3)). To test this hypothesis, we generated beta(1)/beta(2)/beta(3)-adrenoceptor triple knockout (TKO) mice and compared them to wild type animals. TKO mice exhibited normophagic obesity and cold-intolerance. Their brown fat had impaired morphology and lacked responses to cold of uncoupling protein-1 expression. In contrast, TKO mice had higher circulating levels of free fatty acids and glycerol at basal and fasted states, suggesting enhanced lipolysis. Hence, beta-adrenergic signalling is essential for the resistance to obesity and cold, but not for the lipolytic response to fasting.