Modulation of age-related loss of glucagon-promoted lipolysis by food restriction.
Male Fischer 344 rats were fed ad libitum (Group A) or 60% of the ad libitum intake (Group R) starting at 6 weeks of age. The latter is a dietary manipulation that prolongs life. At 6, 10 and 15 weeks of age, rats were killed, free adipocytes prepared, and lipolytic, adenylate cyclase, and phosphodiesterase activities of adipocytes measured. The ability of glucagon to promote lipolysis markedly declined between 6 and 15 weeks of age in adipocytes from Group A rats but not in those from Group R rats. Glucagon-promoted adenylate cyclase activity paralleled lipolytic activity. Phosphosdiesterase activities increased with age, to a greater extent in adipocytes from Group A rats than in those from Group R rats. It is concluded that the loss in glucagon-promoted lipolysis with age in adipocytes from Group A rats is primarily the result of either a loss of or a change in the characteristics of the glucagon receptors or an alteration in the system coupling the receptors with adenylate cyclase and that food restriction prevents these changes. The relevance of these findings in analysis of the mode by which food restriction delays the aging process is discussed.
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism; D000273:Adipose Tissue / Q000378:metabolism*; D000375:Aging; D000818:Animals; D005508:Food Deprivation / Q000502:physiology*; D005934:Glucagon / Q000378:metabolism / Q000494:pharmacology*; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344
D005934:Glucagon; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D000262:Adenylyl Cyclases