Orexin
- OMIM: 602358
- UniProt: O43612
Orexin A and B ( also Hypocretin-1/-2 ) are neuropeptide hormones in mammals, which are formed in the hypothalamus and influence on eating habits and sleeping patterns. Other effects are suspected in the autonomic nervous system, in fluid balance and energy metabolism. They are formed by enzymatic cleavage of a precursor or a precursor protein, the pre-pro orexin. Mutations in the HCRT gene can result in narcolepsy.
Function
Recent research shows that orexin has a strong influence on the sleep / wake behavior. Thus, the disease narcolepsy is associated with mutations in the gene of the orexin receptor -2 in experimental animal studies with dogs. In humans, it is considered a cell demise of the Hypothalamic cell groups ( Ncl. tuberomamillaris, TMN ).
In the lateral hypothalamus and the zona incerta nerve cells groupings that orexin and melanin - concentrating hormone ( MCH) are producing. The formation of the RNA for both hormones is activated by the transcription factor forkhead box protein A2 ( Foxa2 ).
In addition, it was recently shown that the distribution of orexin by leptin, the hormone - saturated the fat cells is inhibited. Becoming increasingly clear that the metabolism stimulating (catabolic ) function of orexin, namely, increase in body temperature, weight loss, increased attention and alertness, etc.
Pharmacology
A team led by Andrew Lawrence from the Howard Florey Institute in Melbourne has an active ingredient found that blocks the effect of orexins in the brain, which is to be causally responsible for euphoria after drinking alcohol. The research results showed that alcohol addiction and eating disorders are based on the same mechanisms as study leader Andrew Lawrence.
Name and Historical
The name of orexin (from Greek ὄρεξις " desire, appetite " ) comes from the scientists Masashi Yanagisawa, who found that an injection of orexin in the hypothalamus affects appetite- enhancing. The research group led by Luis DeLecea and Tom Kilduff found that orexin is produced in certain core areas ( groups of neurons ) in the hypothalamus and similarities with other hormones, the incretins, has (hence the name hypocretin: hypothalamic incretin ).