White adipose tissue fatty acids of alpine marmots during their yearly cycle

Alpine marmots (Marmota marmota) were maintained on a laboratory diet, and the fatty acid composition of gonadal and subcutaneous white adipose tissue s (WAT) was studied during a yearly cycle. Fatty acids (FA) released from i solated adipocytes were also identified after stimulation of in vitro lipol ysis. Analysis of the FA composition of WAT depots showed that marmot WAT m ainly contained monounsaturated FA (65%, mostly oleic acid, 18:1n-9) althou gh laboratory food contained 45% of linoleic acid (18:2n-6) and only 21% of 18:1n-9. During stimulated lipolysis, saturated FA were preferentially rel eased from isolated adipocytes whereas unsaturated FAs were retained. Despi te this selective release of FA from isolated WAT cells in vitro, and despi te the FA composition of the food, marmots maintained a constant FA composi tion in both WAT depots throughout the year. Six months of hibernation and fasting as well as an intense feeding period did not affect this compositio n. The potential adaptive benefit of such regulation of WAT composition, ba sed on a high level of monounsaturated FA, might be to maintain fat with ap propriate physical properties allowing animals to accommodate to and surviv e the wide range of body temperatures experienced during hibernation.