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Melanocortin receptor 4 deficiency affects body weight regulation, grooming behavior, and substrate preference in the rat.

Authors: Mul, JD  Van Boxtel, R  Bergen, DJ  Brans, MA  Brakkee, JH  Toonen, PW  Garner, KM  Adan, RA  Cuppen, E 
Citation: Mul JD, etal., Obesity (Silver Spring). 2012 Mar;20(3):612-21. doi: 10.1038/oby.2011.81. Epub 2011 Apr 28.
Pubmed: (View Article at PubMed) PMID:21527895
DOI: Full-text: DOI:10.1038/oby.2011.81

Obesity is caused by an imbalance between energy intake and expenditure and has become a major health-care problem in western society. The central melanocortin system plays a crucial role in the regulation of feeding and energy expenditure, and functional loss of melanocortin receptor 4 (MC4R) is the most common genetic cause of human obesity. In this study, we present the first functional Mc4r knockout model in the rat, resulting from an N-ethyl-N-nitrosourea mutagenesis-induced point mutation. In vitro observations revealed impaired membrane-binding and subsequent nonfunctionality of the receptor, whereas in vivo observations showed that functional loss of MC4R increased body weight, food intake, white adipose mass, and changed substrate preference. In addition, intracerebroventricular (ICV) administration of Agouti-Related Protein(79-129) (AgRP(79-129)), an MC4R inverse agonist, or Melanotan-II (MTII), an MC4R agonist, did affect feeding behavior in wild-type rats but not in homozygous mutant rats, confirming complete loss of MC4R function in vivo. Finally, ICV administration of MTII induced excessive grooming behavior in wild-type rats, whereas this effect was absent in homozygous mutant rats, indicating that MTII-induced grooming behavior is exclusively regulated via MC4R pathways. Taken together, we expect that the MC4R rat model described here will be a valuable tool for studying monogenic obesity in humans. More specifically, the relative big size and increased cognitive capacity of rats as compared to mice will facilitate complex behavioral studies and detailed mechanistic studies regarding central function of MC4R, both of which ultimately may help to further understand the specific mechanisms that induce obesity during loss of MC4R function.

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CRRD Object Information
CRRD ID: 6478803
Created: 2012-03-12
Species: All species
Last Modified: 2012-03-12
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.