Abstract
It is now commonly accepted that white adipocytes actively secrete a wide range of bioactive molecules including leptin, adiponectin, resistin and many other signals. These adipose-derived factors are mainly influenced by nutritional transitions. This review addresses essentially the differential regulation and role of animal adipose-secreted products in regulating metabolic, endocrine and behavioral responses during prolonged fasting. When reaching a low adiposity threshold, animals enter late fasting characterized by elevated rates of protein degradation while lipid utilization decreases. Low NEFA levels in late fasting could affect PPAR activation and the management of body reserves, thus promoting food seeking behavior. Low leptin levels are also likely involved in the efficient mobilization of energy stores and in the induction of strong rises in hypothalamic orexigenic neuropeptides in late fasting. This effect is prevented by leptin perfusion. During fasting, adiponectin reduced levels could be related to its ability to signal nutritional and/or metabolic changes, to promote energy preservation or to prepare the body to efficiently restore body weight in case of refeeding while resistin low levels could constitute an adipose status sensor and/or improve glucose homeostasis. The fasting-induced changes of other signals during the fed/fasted/refed transitions are also briefly discussed.
Keywords: Leptin, adiponectin, resistin, energy homeostasis, food intake, body reserves, long-term fasting paradigm
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