Regulation of hypothalamic neuropeptide expression by peripheral metabolism

The mechanisms of appetite and body-weight regulation by peripheral signals are highly complex in vertebrates and remain poorly understood. It is intuitively apparent that such regulation must involve interactions between peripheral metabolic status and the brain, but what are the signals recognized by the brain to initiate feeding? The hypothalamus has long been recognized as central in "recognition" of peripheral nutrient and metabolic signals (and, perhaps, body weight status) and in "regulation" of hunger and satiety responses and, therefore, is a logical site on which to focus research aimed at understanding interactions between and regulation of the periphery and central nervous system. Recent studies demonstrating modulation of hypothalamic neurotransmitter expression by peripheral metabolic status may yield insights into regulation of appetite and metabolism in obesity and aberrant metabolic homeostasis. This review concentrates on summarizing data regarding regulation of expression of neuropeptide Y and growth hormone-releasing hormone as model peptide systems for addressing questions relating peripheral metabolism and hypothalamic neuropeptide expression.