Neuropeptide Y hormone by Ray Sahelian, M.D. Fat cells make Neuropeptide Y hormone

The hypothalamus and other brain regions that control energy homeostasis contain neuronal populations that produce specific neuropeptides which have experimental effects on feeding behavior and body weight. Neuropeptides exert anabolic effects, notably stimulation of feeding and increased body weight. For more information on peptides. Neuropeptide Y is an appetite stimulant.

Neuropeptide Y (NPY)
Neuropeptide Y neurons in the hypothalamic arcuate nucleus are inhibited by leptin and insulin, and thus are stimulated in states of energy deficit and fat loss, e.g., underfeeding. Neuropeptide Y neuronal overactivity contributes to enhanced hunger and food-seeking activity under these conditions.

Fat cells in abdomen can make neuropeptide Y
A rodent study indicates that fat cells within the abdomen produce neuropeptide Y, an appetite stimulant that was previously thought to originate only in the brain. Rats that are bred to be heavy around the middle produce substantially more neuropeptide Y in their belly-fat cells than thin rats. This excess neuropeptide Y stimulates the production of fat-cell precursors, which mature into full-fledged fat, creating a vicious cycle by which excess belly fat leads to more belly fat. The FASEB Journal, online March 7, 2008.

Orexin
The lateral hypothalamic area contains specific neuronal populations that affect feeding in different ways. Neurons expressing the appetite-stimulating peptide orexin A are stimulated by starvation (but not food restriction) and by hypoglycemia, but only if food is withheld. Orexin neurons are apparently activated by low glucose but are promptly inhibited by visceral feeding signals, probably mediated via vagal sensory pathway and the nucleus of the solitary tract; a short-term role in initiating feeding seems most likely.

Melanin concentrating hormone
Other lateral hypothalamic area neurons express melanin-concentrating hormone, which transiently increases food intake when injected centrally. Melanin concentrating hormone neurons may be regulated by leptin, insulin and glucose. Glucose-sensing neurons in the hypothalamus and elsewhere are sensitive to other cues of nutritional state, including visceral satiety signals (transmitted via the vagus) and orexin.

Neuroeptides and Appetite
During the past decade, a detailed understanding has emerged of the aminergic and peptidergic neural pathways present within the brain that regulate appetite. Central among the peptide regulators is neuropeptide Y (NPY), a potent orexigenic agent that acts through five different receptor subtypes.
   A neuropeptide essential for wakefulness and appetite also appears to enhance the brain's appetite for cocaine. Drug addiction may be related to the neural circuits that control appetite. In studies with rats, orexin A, a neuro peptide produced in the lateral hypothalamus, strengthens the potential for addiction by enhancing synaptic connections between neurons in the lateral hypothalamus and dopaminergic neurons in the ventral tegmental area (VTA) of the brain. This connection helps provide the "synaptic plasticity" important for full-fledged addiction.