The Yin and Yang of the Ghrelin Gene Products

Obesity has increasingly become a major medical and public health burden in both developed and developing countries. Numerous hormones are involved in controlling appetite and food intake via the neuro-humoral gut-brain axis and several peptides that are synthesized and secreted from the gut have been recently investigated in order to determine their effects on food intake and satiety. Ghrelin is an appetite-stimulating peptide that rises in the fasted state causing increases in food intake. Obestatin is a newly discovered hormone encoded by the same gene as ghrelin, and its putative role in the regulation of appetite and metabolism is unclear. A number of studies using animal models have shown that obestatin opposes the effects of ghrelin on food intake whilst others found that obestatin has little if any affect on gastrointestinal motility, or on food intake. There are also controversies to the receptor mediating obestatin effects with the previously orphan G protein coupled receptor GPR39 suggested to be the main candidate. Investigating the molecular mechanism underlying obestatin and other gut hormones involved in appetite regulation may prove to be useful in finding new strategies to treat obesity.