Adrenoceptors, uncoupling proteins, and energy expenditure.
Interest in the biology of adipose tissue has undergone a revival in recent years with the discovery of a host of genes that contribute to the regulation of satiety and metabolic rate. The catecholamines have long been known to be key modulators of adipose tissue lipolysis and the hydrolysis of triglyceride energy stores. However, more recent efforts to understand the role of individual adrenergic receptor subtypes expressed in adipocytes and their signal transduction pathways have revealed a complexity not previously appreciated. Combined with this interest in the modulation of adipocyte metabolism is a renewed focus upon brown adipose tissue and the mechanisms of whole body thermogenesis in general. The discovery of novel homologs of the brown fat uncoupling protein (UCP) such as UCP2 and UCP3 has provoked intensive study of these mitochondrial proteins and the role that they play in fuel metabolism. The story of the novel UCPs has proven to be intriguing and still incompletely understood. Here, we review the status of adipose tissue from inert storage depot to endocrine organ, interesting signal transduction pathways triggered by beta-adrenergic receptors in adipocytes, the potential of these receptors for discriminating and coordinated metabolic regulation, and current views on the role of UCP2 and UCP3 based on physiological studies and gene knockout models.
Collins
S
S
Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, North Carolina 27710, USA. colli008@mc.duke.edu
Cao
W
W
Daniel
K W
KW
Dixon
T M
TM
Medvedev
A V
AV
Onuma
H
H
Surwit
R
R
D017667:Adipocytes / Q000378:metabolism / Q000502:physiology; D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism* / Q000502:physiology*; D004734:Energy Metabolism; D006801:Humans; D007473:Ion Channels; D008565:Membrane Proteins / Q000378:metabolism* / Q000502:physiology*; D026901:Membrane Transport Proteins; D051379:Mice; D018345:Mice, Knockout; D008820:Mice, Obese; D024101:Mitochondrial Proteins; D008954:Models, Biological; D011506:Proteins / Q000378:metabolism; D011941:Receptors, Adrenergic / Q000502:physiology*; D015398:Signal Transduction; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3
D002352:Carrier Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D011506:Proteins; D011941:Receptors, Adrenergic; C000604389:UCP2 protein, human; C000604392:UCP3 protein, human; C000604390:Ucp2 protein, mouse; C000604393:Ucp3 protein, mouse; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3