Caloric restriction leads to regional specialisation of adipocyte functionin the rat

The study analysed the responses of three metabolic parameters in five dist inct adipose tissue depots to caloric restriction (4 weeks) in the rat. The aims were to evaluate whether specific adipose tissue depots were recruite d for triacylglycerol (TAG) storage and/or mobilisation, and to determine t o what extent specific adipose tissue depots exhibited preferences for the source of fatty acid (FA) for TAG storage. Caloric restriction led to a gen eral enhancement of the response of lipoprotein lipase (LPL), FA synthesis and glucose utilisation to a meal. Effects were particularly marked in the parametrial, perirenal and interscapular depots compared with mesenteric an d subcutaneous depots. There was no evidence that individual depots selecti vely expressed a preference for the pathways concerned with the generation of FA for storage (the exogenous (LPL) and the endogenous (synthesis) pathw ay). However, the temporal sequence of activation of these pathways differe d in a manner consistent with a switch from preponderant use of FA produced via de novo synthesis during the very early phase of feeding towards later use of FA derived from circulating TAG. The overall excursions in insulin levels observed in the calorie-restricted rats were comparable to those fou nd in free-feeding rats, but the magnitude and the rapidity of the individu al metabolic responses of the adipocyte were augmented. The data are consis tent with a general enhancement of insulin sensitivity and responsiveness i n adipose tissue of calorie-restricted rats, together with adaptive regiona l specialisation of adipocyte function. These adaptations would be predicte d to facilitate the immediate conservation of dietary nutrients by promotin g their storage as the FA or glycerol moieties of adipose tissue TAG and th ereby to ensure the regulated release of FA and glycerol from adipose tissu e in accordance with the requirement for glucose conservation and/or produc tion. (C) 1999 Elsevier Science B.V. All rights reserved.