Importance of leptin gene polymorphism in cattle

Abstract

Leptin is a protein hormone with a key role in feed intake regulation and energy expenditure. Leptin expression and secretion is highly correlated with body fat mass and adipocyte size. Leptin is thought to be a metabolic signal that regulates nutritional status effects on reproductive function. Leptin receptors are found in the ventromedial and arcuate regions of the hypothalamus and are thus positioned anatomically in regions associated with the control of appetite and reproductive neuroendocrine function. It is interesting that neuropeptid Y (NPY) is present in the hypothalamic regions involved in neuroendocrine control of feed intake. In contrast to leptin, NPY is a powerfull stimulator of feed intake and inhibitor of gonadotropin secretion. Leptin receptors have been localized on hypothalamic NPY neurons, and it has been revealed that leptin downregulates NPY expression. Investigations of leptin gene single nucleotide polymorphism (SNP) revealed that certain nucleotide supstitutions may lead to changes in leptin expression. Gene-specific single nucleotide polymorphisms in the regulatory region (promoter) of the bovine leptin gene were detected that show associations with serum leptin concentration, growth rate, body weight, feed intake, feeding behaviour, and measures of carcass merit. The polymorphisms may also be predictive of other important traits in cattle such as milk yield and composition. However, further efforts are required to validate these findings in other bovine populations before their application in marker-assisted selection.

Leptin je proteinski hormon koji ima ključne uloge u regulaciji unosa hrane i potrošnje energije. Ekspresija i sekrecija leptina su veoma povezani sa količinom masnog tkiva i veličinom adipocita. Smatra se da je leptin metabolički signal koji reguliše efekte nutritivnog statusa na reproduktivnu funkciju. Receptori za leptin pronađeni su u ventromedijalnom i arkuatnm regionu hipotalamusa, tako da su anatomski pozicionirani u regionima uključenim u kontrolu apetita i reproduktivne neuroendokrine funkcije. Interesanto je da se u hipotalamusu nalazi neuropeptid Y (NPY) u regionima uključenim u neuroendokrinu kontrolu unosa hrane. Nasuprot leptinu, NPY je moćan stimulator unosa hrane i inhibitor sekrecije gonadotropina. Receptori za leptin su lokalizovani na NPY neuronima hipotalamusa i pokazano je da leptin umanjuje eksperesiju NPY. Istraživanja polimorfizna pojedinačnih nukleotida (SNP) u okviru gena za leptin otkrila su da određene supstitucije nukleotida mogu voditi ka promenama u ekspresiji leptina. Detektovani su gen-specifični polimorfizmi pojedinačnih nukleotida u regulatornom regionu (promotoru) gena za leptin goveda koji su udruženi sa koncentracijama leptina u serumu, stopom rasta, telesnom težinom, unosom hrane, hranidbenim ponašanjem i karakteristikama trupa. Polimorfizmi bi mogli biti od značaja za predviđanje drugih važnih fenotipskih karakteristika kod goveda kao što je prinos i sastav mleka. Međutim, potrebni su dodatni napori da se dobijeni nalazi potvrde u drugim populacijama goveda pre njihove primene u selekciji na osnovu specifičnih genskih markera.