Here, we report the isolation and characterization of an endogenous peptide ligand of GPR103 from rat brains. The purified peptide was found to be the 43-residue RF-amide peptide QRFP. We also describe two mouse homologues of human GPR103, termed mouse GPR103A and GPR103B. QRFP binds and activates the human GPR103, as well as mouse GPR103A and GPR103B, with nanomolar affinities in transfected cells. Systematic in situ hybridization analysis in mouse brains showed that QRFP is expressed exclusively in the periventricular and lateral hypothalamus, whereas the two receptor mRNAs are distinctly localized in various brain areas without an overlap to each other. When administered centrally in mice, QRFP induced feeding behavior, accompanied by increased general locomotor activity and metabolic rate. QRFPinduced food intake was abolished by preadministration of BIBP3226, a specific antagonist for the Y1 neuropeptide Y receptor. Hypothalamic prepro-QRFP mRNA expression was up-regulated upon fasting and in genetically obese ob͞ob and db͞db mice. Central QRFP administration also evoked highly sustained elevation of blood pressure and heart rate. Our findings suggest that QRFP and GPR103A͞B may regulate diverse neuroendocrine and behavioral functions and implicate this neuropeptide system in metabolic syndrome.grooming ͉ hypothalamus ͉ QRFP ͉ wakefulness ͉ metabolic syndrome G protein-coupled receptors (GPCRs) are members of a large protein family that share common structural motifs, including seven transmembrane helices, and play pivotal roles in cell-to-cell communications and in the regulation of cell functions. A large number of GPCRs still remain as ''orphan receptors'' whose cognate ligands have yet to be identified. Identification of ligands for orphan GPCRs provides a basis for understanding the physiological roles of those GPCRs and their ligands, which can involve the central nervous, endocrine, reproductive, cardiovascular, immune, inflammatory, digestive, and metabolic systems.GPR103 (also referred to as SP9155 or AQ27) is an orphan GPCR that shows similarities with orexin, neuropeptide FF, and cholecystokinin receptors. Its mRNA has been detected predominantly in the brain including the cerebral cortex, pituitary, thalamus, hypothalamus, basal forebrain, midbrain, and pons in humans (1). Through bioinformatics approaches, two groups reported putative ligands for GPR103 as a part of a directed effort to identify the precursor genes for a novel RF-amide peptide and its receptor (2, 3). They identified a gene encoding a preproprotein that can be processed into several potential peptides, including a 26-aa (termed P518) and a 43-aa RF-amide peptide (termed QRFP) (2, 3). Both of these peptides activate GPR103, but the 43-aa QRFP exhibited more potent agonistic activity. When intravenously injected into rats, QRFP (43-aa) stimulates aldosterone release (3). The 26-aa RF-amide peptide (termed 26RFa) was independently purified from frog brain by monitoring NPFF-like immunoreactivity (4), and it exhibits orexigenic act...

Control of cell differentiation occurs through transcriptional mechanisms and through epigenetic modification. Using a chromatin immunoprecipitation-on-chip approach, we performed a genome-wide search for target genes of peroxisome proliferator-activated receptor ␥ (PPAR␥) and its partner protein retinoid X receptor ␣ during adipogenesis. We show that these two receptors target several genes that encode histone lysine methyltransferase SET domain proteins. The histone H4 Lys 20 (H4K20) monomethyltransferase PR-Set7/Setd8 gene is upregulated by PPAR␥ during adipogenesis, and the knockdown of PR-Set7/Setd8 suppressed adipogenesis. Intriguingly, monomethylated H4K20 (H4K20me1) levels are robustly increased toward the end of differentiation. PR-Set7/Setd8 positively regulates the expression of PPAR␥ and its targets through H4K20 monomethylation. Furthermore, the activation of PPAR␥ transcriptional activity leads to the induction of H4K20me1 modification of PPAR␥ and its targets and thereby promotes adipogenesis. We also show that PPAR␥ targets PPAR␥2 and promotes its gene expression through H4K20 monomethylation. Our results connect transcriptional regulation and epigenetic chromatin modulation through H4K20 monomethylation during adipogenesis through a feedback loop.Adipocytes play a central role in energy balance, both as reservoirs of fuel and as endocrine cells, secreting factors that regulate whole-body energy metabolism. Because of the rising incidence of obesity, understanding the adipocyte is increasingly important. The process of adipocyte differentiation represents the extraordinarily coordinated regulation of multiple transcriptional systems that direct multipotent stem-cell precursors to differentiate into fully mature, functionally distinct cell types.The 3T3-L1 preadipocyte cell line has been one of the most well-characterized and widely used models for studying adipocyte differentiation (7). C/EBP␤ and C/EBP␦ are induced very early during differentiation, and these in turn activate two critical proadipogenic transcription factors, peroxisome proliferator-activated receptor ␥ (PPAR␥) and C/EBP␣. PPAR␥ and C/EBP␣ mutually stimulate each other and mediate the transition to the adipocyte phenotype (6,15,32). Recently, a number of transcription factors have been identified as regulators of adipogenesis, including GATA2 (30, 31), the Krüp-pel-like factor (KLF) family (2, 20, 24), and Nr2f2 (35).PPAR␥, a prototypical member of the nuclear receptor superfamily, is activated by natural ligands, such as arachidonic acid metabolites and fatty acid-derived components, and by the insulin-sensitizing thiazolidinedione drugs. In white and brown preadipocyte cell lines, the activation of PPAR␥ by thiazolidinediones results in robust differentiation into adipocytes. The action of PPAR␥ is mediated by two protein isoforms: the widely expressed PPAR␥1 and PPAR␥2, which is restricted to adipose tissue. The expression of each isoform is driven by a specific promoter that confers the distinct tissue-specific expression and...

AMP-activated protein kinase (AMPK) is a sensor of cellular energy status that plays a central role in skeletal muscle metabolism. We used skeletal muscle-specific AMPKα1α2 double-knockout (mdKO) mice to provide direct genetic evidence of the physiological importance of AMPK in regulating muscle exercise capacity, mitochondrial function, and contraction-stimulated glucose uptake. Exercise performance was significantly reduced in the mdKO mice, with a reduction in maximal force production and fatigue resistance. An increase in the proportion of myofibers with centralized nuclei was noted, as well as an elevated expression of interleukin 6 (IL-6) mRNA, possibly consistent with mild skeletal muscle injury. Notably, we found that AMPKα1 and AMPKα2 isoforms are dispensable for contraction-induced skeletal muscle glucose transport, except for male soleus muscle. However, the lack of skeletal muscle AMPK diminished maximal ADP-stimulated mitochondrial respiration, showing an impairment at complex I. This effect was not accompanied by changes in mitochondrial number, indicating that AMPK regulates muscle metabolic adaptation through the regulation of muscle mitochondrial oxidative capacity and mitochondrial substrate utilization but not baseline mitochondrial muscle content. Together, these results demonstrate that skeletal muscle AMPK has an unexpected role in the regulation of mitochondrial oxidative phosphorylation that contributes to the energy demands of the exercising muscle.-Lantier, L., Fentz, J., Mounier, R., Leclerc, J., Treebak, J. T., Pehmøller, C., Sanz, N., Sakakibara, I., Saint-Amand, E., Rimbaud, S., Maire, P., Marette, A., Ventura-Clapier, R., Ferry, A., Wojtaszewski, J. F. P., Foretz, M., Viollet, B. AMPK controls exercise endurance, mitochondrial oxidative capacity, and skeletal muscle integrity.