In this study, we defined the role of peroxisome proliferator-activated receptor ␤͞␦ (PPAR␦) in metabolic homeostasis by using subtype selective agonists. Analysis of rat L6 myotubes treated with the PPAR␦ subtype-selective agonist, GW501516, by the Affymetrix oligonucleotide microarrays revealed that PPAR␦ controls fatty acid oxidation by regulating genes involved in fatty acid transport, ␤-oxidation, and mitochondrial respiration. Similar PPAR␦-mediated gene activation was observed in the skeletal muscle of GW501516-treated mice. Accordingly, GW501516 treatment induced fatty acid ␤-oxidation in L6 myotubes as well as in mouse skeletal muscles. Administration of GW501516 to mice fed a high-fat diet ameliorated diet-induced obesity and insulin resistance, an effect accompanied by enhanced metabolic rate and fatty acid ␤-oxidation, proliferation of mitochondria, and a marked reduction of lipid droplets in skeletal muscles. Despite a modest body weight change relative to vehicle-treated mice, GW501516 treatment also markedly improved diabetes as revealed by the decrease in plasma glucose and blood insulin levels in genetically obese ob͞ob mice. These data suggest that PPAR␦ is pivotal to control the program for fatty acid oxidation in the skeletal muscle, thereby ameliorating obesity and insulin resistance through its activation in obese animals.obesity ͉ insulin resistance ͉ thermogenesis ͉ pancreatic ␤-cell ͉ PGC-1␣

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...

LDL receptor-related protein 5 (LRP5) plays multiple roles, including embryonic development and bone accrual development. Recently, we demonstrated that LRP5 is also required for normal cholesterol metabolism and glucose-induced insulin secretion. To further define the role of LRP5 in the lipoprotein metabolism, we compared plasma lipoproteins in mice lacking LRP5, apolipoprotein E (apoE), or both (apoE;LRP5 double knockout). On a normal chow diet, the apoE;LRP5 double knockout mice (older than 4 months of age) had ϳ60% higher plasma cholesterol levels compared with the agematched apoE knockout mice. In contrast, LRP5 deficiency alone had no significant effects on the plasma cholesterol levels. High performance liquid chromatography analysis of plasma lipoproteins revealed that cholesterol levels in the very low density lipoprotein and low density lipoprotein fractions were markedly increased in the apoE;LRP5 double knockout mice. There were no apparent differences in the pattern of apoproteins between the apoE knockout mice and the apoE; LRP5 double knockout mice. The plasma clearance of intragastrically loaded triglyceride was markedly impaired by LRP5 deficiency. The atherosclerotic lesions of the apoE;LRP5 double knockout mice aged 6 months were ϳ3-fold greater than those in the age-matched apoE-knockout mice. Furthermore, histological examination revealed highly advanced arthrosclerosis, with remarkable accumulation of foam cells and destruction of the internal elastic lamina in the apoE;LRP5 double knockout mice. These data suggest that LRP5 mediates both apoE-dependent and apoE-independent catabolism of plasma lipoproteins.Genetic defects in the catabolism of plasma lipoproteins are important causes of hypercholesterolemia and atherosclerosis in humans. The prototypic diseases are familial hypercholesterolemia, caused by a defect in the LDL 1 receptor (LDLR) (1), and familial type III hyperlipoproteinemia, caused by a defect in one of the ligands for LDLR, apolipoprotein E (apoE) (2).ApoE is hypothesized to mediate lipoprotein clearance by binding two receptors: (i) LDLR and (ii) a hepatic chylomicron remnant receptor. ApoE-deficient mice (3-5) and LDLR-deficient mice (6) exhibit hypercholesterolemia, but the severity and manifestations differ markedly. On a normal laboratory chow diet, the apoE knockout mice have much more profound hypercholesterolemia and develop spontaneous atherosclerosis (4).LDL receptor-related protein 5 (LRP5) is a member of the LDL receptor family that are characterized by the presence of cysteine-rich complement type ligand binding domains. LRP5 binds apoE-containing lipoproteins in vitro and is widely expressed in many tissues including hepatocytes, adrenal gland, and pancreas (7).LRP5 and its homologue, LRP6, are postulated to play as co-receptors for Wnt receptors, Frizzled (8 -13). The Wnt signaling pathway plays an essential role in embryonic development (14, 15) and oncogenesis (16) through various signaling molecules including Frizzled receptors (17), , and Dickkopf protei...

A wrist activity monitor is able to measure nocturnal scratching. However, further methods of analysis should be sought to select scratching activity exclusively.

In obesity-related insulin resistance, pancreatic islets compensate for insulin resistance by increasing secretory capacity. Here, we report the identification of sex-determining region Y-box 6 (SOX6), a member of the high mobility group box superfamily of transcription factors, as a co-repressor for pancreatic-duodenal homeobox factor-1 (PDX1). SOX6 mRNA levels were profoundly reduced by both a long term high fat feeding protocol in normal mice and in genetically obese ob/ob mice on a normal chow diet. Interestingly, we show that SOX6 is expressed in adult pancreatic insulin-producing ␤-cells and that overexpression of SOX6 decreased glucosestimulated insulin secretion, which was accompanied by decreased ATP/ADP ratio, Ca 2؉ mobilization, proinsulin content, and insulin gene expression. In a complementary fashion, depletion of SOX6 by small interfering RNAs augmented glucose-stimulated insulin secretion in insulinoma mouse MIN6 and rat INS-1E cells. These effects can be explained by our mechanistic studies that show SOX6 acts to suppress PDX1 stimulation of the insulin II promoter through a direct protein/protein interaction. Furthermore, SOX6 retroviral expression decreased acetylation of histones H3 and H4 in chromatin from the promoter for the insulin II gene, suggesting that SOX6 may decrease PDX1 stimulation through changes in chromatin structure at specific promoters. These results suggest that perturbations in transcriptional regulation that are coordinated through SOX6 and PDX1 in ␤-cells may contribute to the ␤-cell adaptation in obesity-related insulin resistance.

Acetate is activated to acetyl-CoA by acetyl-CoA synthetase 2 (AceCS2), a mitochondrial enzyme. Here, we report that the activation of acetate by AceCS2 has a specific and unique role in thermogenesis during fasting. In the skeletal muscle of fasted AceCS2(-/-) mice, ATP levels were reduced by 50% compared to AceCS2(+/+) mice. Fasted AceCS2(-/-) mice were significantly hypothermic and had reduced exercise capacity. Furthermore, when fed a low-carbohydrate diet, 4-week-old weaned AceCS2(-/-) mice also exhibited hypothermia accompanied by sustained hypoglycemia that led to a 50% mortality. Therefore, AceCS2 plays a significant role in acetate oxidation needed to generate ATP and heat. Furthermore, AceCS2(-/-) mice exhibited increased oxygen consumption and reduced weight gain on a low-carbohydrate diet. Our findings demonstrate that activation of acetate by AceCS2 plays a pivotal role in thermogenesis, especially under low-glucose or ketogenic conditions, and is crucially required for survival.

Acetyl-CoA synthetase 2 (AceCS2) produces acetylCoA for oxidation through the citric acid cycle in the mitochondrial matrix. AceCS2 is highly expressed in the skeletal muscle and is robustly induced by fasting. Quantification of AceCS2 transcripts both in C2C12 and human myotubes indicated that fasting-induced AceCS2 gene expression appears to be independent on insulin action. Characterization of 5 -flanking region of the mouse AceCS2 gene demonstrates that Krü ppel-like factor 15 (KLF15) plays a key role in the trans-activation of the AceCS2 gene. Deletion and mutation analyses of AceCS2 promoter region revealed that the most proximal KLF site is a curtail site for the trans-activation of the AceCS2 gene by KLF15. Using Sp-null Drosophila SL2 cells, we showed that the combination of KLF15 and Sp1 resulted in a synergistic activation of the AceCS2 promoter. Mutation analyses of three GC-boxes in the AceCS2 promoter indicated that the GC-box, located 8 bases downstream of the most proximal KLF15 site, is the most important GC-box in the synergistic trans-activation of the AceCS2 gene by KLF15 and Sp1. GST pull-down assays showed that KLF15 interacts with Sp1 in vitro. Quantification of various KLF transcripts revealed that 48 h fasting robustly induced the KLF15 transcripts in the skeletal muscle. Together with the trans-activation of the AceCS2 promoter, it is suggested that fasting-induced AceCS2 expression is largely contributed by KLF15. Furthermore, KLF15 overexpression induced the levels of AceCS2 transcripts both in myoblasts and in myotubes, indicating that AceCS2 gene expression in vivo is indeed induced by KLF15.Acetyl-CoA is an important intermediate in various metabolic pathways including fatty acid and cholesterol biosynthesis and the energy production by the citric acid cycle. There are several enzymes that generate acetyl-CoA in the mammals, including pyruvate dehydrogenase, which converts pyruvate to acetyl-CoA without generating free acetate. The degradation of fatty acid via ␤-oxidation system also produces acetyl-CoA as an end product. Although acetate is not an essential source of acetyl-CoA in animals, the enzymatic ligation for the production of acetyl-CoA from acetate and CoA is a key reaction in the catabolism of acetate formed by several conditions including bacterial fermentation in the colon, oxidation of ingested ethanol in the liver. Acetyl-CoA synthetase (AceCS, 1 EC 6.2.1.1) is an enzyme that catalyzes the production of acetyl-CoA from acetate and CoA. In particular, this enzyme plays a key role in the nervous system for recycling of acetate released by acetylcholine esterase for the formation and release of acetylcholine in cholinergic nerve terminals.There are two AceCSs with similar enzymatic properties in mammals: one designated AceCS1 is a cytosolic enzyme and the other, designated AceCS2, is a mitochondrial matrix enzyme (1). Localized in the cytoplasm, AceCS1 provides acetylCoA for the synthesis of fatty acids and cholesterol. In contrast, AceCS2 produces acetyl-CoA for oxida...

Background: Polycomb repressive complex PRC1 is an epigenetic regulator of cellular differentiation. However, its function during adipogenesis is unknown. Results: FBXL10/KDM2B recruited noncanonical PRC1 complex in F-box and LRR motifs dependent on cell cycle-related genes and Pparg genes and repressed 3T3-L1 adipogenesis. Conclusion: Noncanonical PRC1 complex containing FBXL10/KDM2B regulates adipogenesis. Significance: Our findings revealed a novel epigenetic mechanism of adipogenesis.