Neither agouti-related protein nor neuropeptide Y is critically required for the regulation of energy homeostasis in mice.
Agouti-related protein (AgRP), a neuropeptide abundantly expressed in the arcuate nucleus of the hypothalamus, potently stimulates feeding and body weight gain in rodents. AgRP is believed to exert its effects through the blockade of signaling by alpha-melanocyte-stimulating hormone at central nervous system (CNS) melanocortin-3 receptor (Mc3r) and Mc4r. We generated AgRP-deficient (Agrp(-/-)) mice to examine the physiological role of AgRP. Agrp(-/-) mice are viable and exhibit normal locomotor activity, growth rates, body composition, and food intake. Additionally, Agrp(-/-) mice display normal responses to starvation, diet-induced obesity, and the administration of exogenous leptin or neuropeptide Y (NPY). In situ hybridization failed to detect altered CNS expression levels for proopiomelanocortin, Mc3r, Mc4r, or NPY mRNAs in Agrp(-/-) mice. As AgRP and the orexigenic peptide NPY are coexpressed in neurons of the arcuate nucleus, we generated AgRP and NPY double-knockout (Agrp(-/-);Npy(-/-)) mice to determine whether NPY or AgRP plays a compensatory role in Agrp(-/-) or NPY-deficient (Npy(-/-)) mice, respectively. Similarly to mice deficient in either AgRP or NPY, Agrp(-/-);Npy(-/-) mice suffer no obvious feeding or body weight deficits and maintain a normal response to starvation. Our results demonstrate that neither AgRP nor NPY is a critically required orexigenic factor, suggesting that other pathways capable of regulating energy homeostasis can compensate for the loss of both AgRP and NPY.
Qian
Su
S
Department of Obesity and Metabolic Research, Merck Research Laboratories, Rahway, NJ 07065, USA. su_qian@merck.com
Chen
Howard
H
Weingarth
Drew
D
Trumbauer
Myrna E
ME
Novi
Dawn E
DE
Guan
Xiaoming
X
Yu
Hong
H
Shen
Zhu
Z
Feng
Yue
Y
Frazier
Easter
E
Chen
Airu
A
Camacho
Ramon E
RE
Shearman
Lauren P
LP
Gopal-Truter
Shobhna
S
MacNeil
Douglas J
DJ
Van der Ploeg
Lex H T
LH
Marsh
Donald J
DJ
D054369:Agouti-Related Protein; D000818:Animals; D002490:Central Nervous System / Q000378:metabolism; D004734:Energy Metabolism; D006706:Homeostasis; D036341:Intercellular Signaling Peptides and Proteins; D051379:Mice; D018345:Mice, Knockout; D009478:Neuropeptide Y / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D011333:Pro-Opiomelanocortin / Q000235:genetics; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D044104:Receptor, Melanocortin, Type 3; D044105:Receptor, Melanocortin, Type 4; D018043:Receptors, Corticotropin / Q000235:genetics; D018000:Receptors, Peptide / Q000235:genetics; D015398:Signal Transduction
D054369:Agouti-Related Protein; C515199:Agrp protein, mouse; D036341:Intercellular Signaling Peptides and Proteins; D009478:Neuropeptide Y; D011506:Proteins; D012333:RNA, Messenger; D044104:Receptor, Melanocortin, Type 3; D044105:Receptor, Melanocortin, Type 4; D018043:Receptors, Corticotropin; D018000:Receptors, Peptide; D011333:Pro-Opiomelanocortin