Central control of food intake in aging.

Abstract

Energy homeostasis and fuel metabolism undergo significant modifications in the course of aging. This presents in elderly subjects either as increased body mass and glucose intolerance - which may lead to obesity and type 2 diabetes - or loss of appetite, which may also seriously compromise health. The hypothalamic expression of neuropeptide Y (NPY), the most potent orexigen, and its receptors, was highly suppressed in old rats. Moreover, induction of the NPY-dependent responses was severely blunted in old animals. Similar reductions, although of a lower magnitude, were reported for other hypothalamic orexigens, A and orexins. Orexigenic activity of ghrelin, the only peripheral orexigen, was clearly suppressed in old humans and rats. However, aging did not alter hypothalamic expression of key anorexigens, alpha-MSH and CART. Age-related decrease of central anorexigenic action of leptin was likely caused by the impaired leptin signal transduction. Thus, aging in rodents is associated with the general down-regulation of orexigenic hypothalamic pep-tides - and unchanged expression of anorexigenic hypothalamic peptides - which may lead to weight loss at the end of life. If similar changes at the level of CNS underlie the 'anorexia of aging' observed in some elderly, therapeutic interventions at this regulatory level may be possible in the future.