Rates of lipid metabolism in adipose tissue of pigs adapt to lactational state and dietary energy restriction

Abstract

To define better the role of metabolism in adipose tissue during gestation and lactation, adaptations to gestation, lactation and to decreased energy intakes were determined using pigs as a model. The effects of energy restriction and the interactions of restriction during both periods were tested by feeding one of two rations during gestation to provide either 19.3 or 25.1 MJ of metabolizable energy per day (ME/d) and adequate amino acids, vitamins and minerals. Pigs from each gestation treatment then consumed 27.7, 48.6, or 69.0 MJ of ME/d during lactation. Body weight and subcutaneous fat thickness were lower in the energy-restricted groups. Litter growth was slower only in the group receiving the lowest energy in gestation and lactation. During gestation, fatty acid synthesis, as measured in in vitro tissue incubations, was lower in subcutaneous adipose tissue of pigs consuming 19.3 compared with 25.1 MJ of ME/d. In pigs fed the highest energy, rates of lipogenesis and esterification were faster after parturition. Feeding 48.6 or 27.7 MJ of ME/d reduced lipogenesis during lactation by ~75 and 90% and rates of esterification by 35 and 60%, respectively, compared with controls fed 69.0 MJ of ME/d. Rates of lipid synthesis at d 7 of lactation were higher than at d 23. Lipolysis was ~twofold higher due to energy restriction. Lactation alone did not alter lipolysis compared with during gestation. The first-committed step of glucose conversion to fatty acids was decreased in a manner sensitive to energy restriction. Recycling of fatty acids was maintained at a significant rate regardless of energy intake. Lipid metabolism in adipose tissue of pigs during lactation is regulated in a manner similar to that observed in humans.