|Matteri, Robert - Bob|
Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/1996
Publication Date: N/A
Citation: Interpretive Summary: The hormone Leptin, also called the obesity gene product, is produced by fat cells and is thought to be a major stop-eating signal. This hormone acts in the brain by interacting with cell surface molecules which recognize and capture Leptin (Leptin receptors). An understanding of the biology of Leptin could lead to major advances in the control of food intake. While suppressing appetite is desirable in human obesity, stimulation of appetite would be beneficial in livestock production. Fast- growing, very lean genotype animals and animals treated with compounds that produce fast, lean growth have reduced appetites. Food intake can also be significantly suppressed during periods of stress in the production environment. Following the production of sheep Leptin receptor DNA clones, we localized production of the Leptin receptor in the brain, pituitary gland, and fat tissue. The receptor is localized in a portion of the brain n(ventromedial hypothalamus) which is known to be involved in appetite control. The level of receptor production also varies with different levels of food intake. These results point to a potentially major role of Leptin in livestock appetite control. An understanding of the function of Leptin in regulating feed intake may yield new approaches for improving the efficiency of meat production. This will contribute to cost-effectiveness for the producer and the maintenance of an affordable food supply for the consumer.
Technical Abstract: Leptin, produced by adipocytes, has receptors in the hypothalamus, but more precise locations of leptin receptor-expressing cell-bodies have not been reported. The leptin receptor transcript has several splice variants in the mouse and human, but only the "long form" is capable of signal transduction. A partial ovine long form leptin receptor (OBRL) cDNA was cloned and used to evaluate OBRL mRNA expression within hypothalamic, anterior pituitary and adipose tissues of ovariectomized adult ewes. Expression was detected in RT-PCR products of all tissues examined. OBRL mRNA was detected by in situ hybridization in the ventromedial hypothalamus and arcuate nucleus of the hypothalamus. In ewes that had been feed- restricted for three weeks prior to tissue collection, expression of OBRL mRNA in the ventromedial hypothalamus was greater (p<0.05) than that found in well-fed ewes. These findings provide evidence that the full length leptin receptor is expressed in hypothalamic, anterior pituitary, and adipose tissue (the latter proffering an autoregulatory mechanism for leptin), and that within the hypothalamus, this receptor form is differentially expressed in well-fed vs feed-restricted states.