tailieunhanh - Chapter 041. Weight Loss

Because of the physiologic importance of maintaining energy stores, voluntary weight loss is difficult to achieve and and metabolism are regulated by an intricate network of neural and hormonal factors. The hypothalamic feeding and satiety centers play a central role in these processes (Chap. 74). Neuropeptides such as corticotropin-releasing hormone (CRH), α-melanocyte-stimulating hormone (α-MSH), and cocaine- and amphetamine-related transcript (CART) induce anorexia by acting centrally on satiety centers. The gastrointestinal peptides ghrelin, glucagon, somatostatin, and cholecystokinin signal satiety and thus decrease food intake. Hypoglycemia suppresses insulin, reducing glucose utilization and inhibiting the satiety center. . | Chapter 041. Weight Loss Because of the physiologic importance of maintaining energy stores voluntary weight loss is difficult to achieve and and metabolism are regulated by an intricate network of neural and hormonal factors. The hypothalamic feeding and satiety centers play a central role in these processes Chap. 74 . Neuropeptides such as corticotropin-releasing hormone CRH a-melanocyte-stimulating hormone a-MSH and cocaine- and amphetamine-related transcript CART induce anorexia by acting centrally on satiety centers. The gastrointestinal peptides ghrelin glucagon somatostatin and cholecystokinin signal satiety and thus decrease food intake. Hypoglycemia suppresses insulin reducing glucose utilization and inhibiting the satiety is produced by adipose tissue and it plays a central role in the long-term maintenance of weight homeostasis by acting on the hypothalamus to decrease food intake and increase energy expenditure Chap. 74 . Leptin suppresses expression of hypothalamic neuropeptide Y a potent appetite stimulatory peptide and it increases the expression of a-MSH which acts through the MC4R melanocortin receptor to decrease appetite. Thus leptin activates a series of downstream neural pathways that alter food-seeking behavior and metabolism. Leptin deficiency which occurs in conjunction with the loss of adipose tissue stimulates appetite and induces adaptive responses including inhibition of hypothalamic thyrotropin-releasing hormone TRH and gonadotropin-releasing hormone GnRH .A variety of cytokines including tumor necrosis factor a TNF-a interleukin IL 6 IL-6 IL-1 interferon Y IFN-y ciliary neurotrophic factor CNTF and leukemia inhibitory factor LIF can induce cachexia Chap. 17 . In addition to causing anorexia these factors may stimulate fever depress myocardial function modulate immune and inflammatory responses and induce a variety of specific metabolic alterations. TNF-a for example preferentially mobilizes fat but spares