White adipose tissue fatty acids of alpine marmots during their yearly cycle [Acides gras des tissus adipeux blancs des marmottes au cours de leur cycle annuel].

Résumé

Alpine marmots (Marmota marmota) were maintained on a laboratory diet, and the fatty acid composition of gonadal and subcutaneous white adipose tissues (WAT) was studied during a yearly cycle. Fatty acids (FA) released from isolated adipocytes were also identified after stimulation of in vitro lipolysis. Analysis of the FA composition of WAT depots showed that marmot WAT mainly contained monounsaturated FA (65 %, mostly oleic acid, 18:1n-9) altough laboratory food contained 45 % of linoleic cid (18:2n-6) and only 21 % of 18:1n-9. During stimulated lipolysis, saturated FA were preferentially released from isolated adipocytes wheras unsaturated FAs were retained. Despite this selective release of FA from isolated WAT cells in vitro , and despite the FA composition of the food, marmots maintained a constant FA composition in both WAT depots throughout the year. Six months of hibernation and fasting as well as an intense feeding period did not affect this composition. The potential adaptative benefit of such regulation of WAT composition, based on a high level of monounsaturated FA, might be to maintain fat with appropriate physical properties allowing animals to accomodate to and survive the wide range of body temperatures experienced during hibernation.