Author
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Barb, Claude |
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Kraeling, Robert |
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Submitted to: Animal Reproduction Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/15/2004 Publication Date: 7/1/2004 Citation: Barb, C.R., Kraeling, R.R. 2004. Role of letptin in the regulation of gonadotrophin secretion in farm animals. Animal Reproduction Sciences. v.82-83. p.155-167. Interpretive Summary: Inadequate nutrition is characterized by low blood levels of pituitary hormones, such as luteinizing hormone (LH), that are necessary for stimulation of the reproductive system. A lack of these hormones results in delayed puberty, irregular heat cycles and failure of animals to breed. The recently discovered protein, leptin, secreted by fat cells in response to changes in body weight or energy, stimulates metabolism, LH secretion and in domestic farm animals. Leptin may serve as a signal linking the body's energy regulating system with the reproductive system. Literature is reviewed identifying specific action of leptin in regulating reproduction in domestic farm animals. Technical Abstract: The recently discovered protein, leptin, which is secreted by fat cells, has been implicated in regulation of feed intake or energy balance and the neuroendocrine axis in rodents, humans and large domestic animals. Leptin was first identified as the gene product found to be deficient in the obese (ob/ob) mouse. Administration of leptin to ob/ob mice restored reproduction as well as reducing feed intake and causing weight loss. The leptin receptor which has been cloned and is a member of the class 1 cytokine family of receptors, is found in the brain and pituitary of all species studied to date. Neuropeptide Y has been proposed as the primary mediator of leptin action in the hypothalamus to regulate luteinizing hormone (LH) and growth hormone (GH) secretion. In vitro studies using both hypothalamic explants and pituitary cell culture provided evidence that supports a direct action of leptin at the level of brain and pituitary gland in the pig, but only the pituitary in cattle. Central administration of leptin increased LH secretion in the fasted cow and ewe, but not in control fed animals, indicating that metabolic state is an important factor in modulating the hypothalamic-pituitary response to leptin. Changing serum leptin concentrations and leptin mRNA expression were associated with onset of puberty in heifers and gilts. Thus, leptin appears to be an important link between metabolic status and the neuroendocrine axis. |
