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Title: EFFECTS OF AN INTRAVENOUS INJECTION OF NPY ON LEPTIN AND NPY-Y1 RECEPTOR MRNA EXPRESSION IN OVINE ADIPOSE TISSUE

Author
item DYER, CHERYL - UNIVERSITY OF MISSOURI
item SIMMONS, J - UNIVERSITY OF MISSOURI
item Matteri, Robert
item KEISLER, D - UNIVERSITY OF MISSOURI

Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Neuropeptide Y (NPY) and leptin are two hormones involved in the control of appetite. NPY is mainly found in the brain, while leptin is produced only in fat tissue. The production of NPY, which is a stimulator of food intake, is high in undernourished animals. The production of leptin, a potent suppressor of appetite, is high in well-nourished animals. For food dintake to be properly regulated, the production of signals to eat and to stop eating must be coordinated. This study investigated the possibility that NPY could directly affect the production of leptin and the receptor for NPY. The NPY receptor is a molecule which recognizes NPY and must be present for the hormone to have a biological effect. NPY was injected into lambs 30 min prior to taking a fat tissue sample which was analyzed for the production of leptin and the NPY receptor. The animals injected with NPY had increased levels of leptin and of NPY receptor production. An improved dunderstanding of appetite control will be essential for controlling feed intake, which directly affects animal growth and reproduction.

Technical Abstract: Neuropeptide Y (NPY) is highly expressed in hypothalami of undernourished and genetically obese animals, and is a potent regulator of food intake and reproduction. Leptin, a protein expressed by adipocytes, has been reported to reduce hypothalamic NPY expression. We recently detected (by ribonuclease protection assay (RPA) expression of the NPY receptor subtype Y1 (but not Y2) mRNA in adipose tissue. Based on these observations we hypothesized that NPY-Y1 receptors in adipose may represent a peripheral mechanism by which NPY can regulate leptin expression in a direct and rapid manner. To test this hypothesis, adipose from the tailhead region of 48 +/- 3 kg wether lambs was sampled before and 30 min after a single intravenous injection of 50 ug porcine NPY ("treated" animals, n = 5), or vehicle ("control" animals, n = 4). Injection of NPY resulted in an increase in expression (P = 0.013; as measured by RPA) of both leptin and NPY-Y1 mRNA. In treated animals, negative correlations were found between response in leptin expression and body weight (r = -0.82, P = 0.092), and between leptin response and initial leptin mRNA levels (r = -0.81, P = 0.097). These data provide evidence of a peripheral mechanism by which NPY may regulate adipocyte expression of both leptin and NPY-Y1 receptor mRNA.