The endogenous lipid signaling agent oleoylethanolamide (OEA) has recently been described as a peripherally acting agent that reduces food intake and body weight gain in rat feeding models. This paper presents evidence that OEA is an endogenous ligand of the orphan receptor GPR119, a G protein-coupled receptor (GPCR) expressed predominantly in the human and rodent pancreas and gastrointestinal tract and also in rodent brain, suggesting that the reported effects of OEA on food intake may be mediated, at least in part, via the GPR119 receptor. Furthermore, we have used the recombinant receptor to discover novel selective small-molecule GPR119 agonists, typified by PSN632408, which suppress food intake in rats and reduce body weight gain and white adipose tissue deposition upon subchronic oral administration to high-fat-fed rats. GPR119 therefore represents a novel and attractive potential target for the therapy of obesity and related metabolic disorders.

To identify the gene or genes associated with insulin resistance in Type II (non-insulin-dependent) diabetes mellitus, subtraction libraries were prepared from skeletal muscle of normal and diabetic humans and screened with subtracted probes. Only one clone out of 4000 was selectively overexpressed in Type II diabetic muscle as compared to muscle of non-diabetic or Type I diabetic individuals. This clone encoded a new 29-kilodalton member of the Ras-guanosine triphosphatase superfamily and was termed Rad (Ras associated with diabetes). Messenger ribonucleic acid of Rad was expressed primarily in skeletal and cardiac muscle and was increased an average of 8.6-fold in the muscle of Type II diabetics as compared to normal individuals.

Background and purpose: Rimonabant (Acomplia TM , SR141716A), a cannabinoid CB 1 receptor inverse agonist, has recently been approved for the treatment of obesity. There are, however, concerns regarding its side effect profile. Developing a CB 1 antagonist with a different pharmacological mechanism may lead to a safer alternative. To this end we have screened a proprietary small molecule library and have discovered a novel class of allosteric antagonist at CB 1 receptors. Herein, we have characterized an optimized prototypical molecule, PSNCBAM-1, and its hypophagic effects in vivo. Experimental approach: A CB 1 yeast reporter assay was used as a primary screen. PSNCBAM-1 was additionally characterized in [ 35 S]-GTPgS, cAMP and radioligand binding assays. An acute rat feeding model was used to evaluate its effects on food intake and body weight in vivo. Key results: In CB 1 receptor yeast reporter assays, PSNCBAM-1 blocked the effects induced by agonists such as CP55,940, WIN55212-2, anandamide (AEA) or 2-arachidonoyl glycerol (2-AG). The antagonist characteristics of PSNCBAM-1 were confirmed in [ 35 S]-GTPgS binding and cAMP assays and was shown to be non-competitive by Schild analyses. PSNCBAM-1 did not affect CB 2 receptors. In radioligand binding assays, PSNCBAM-1 increased the binding of [ 3 H]CP55,940 despite its antagonist effects. In an acute rat feeding model, PSNCBAM-1 decreased food intake and body weight. Conclusions and implications: PSNCBAM-1 exerted its effects through selective allosteric modulation of the CB 1 receptor. The acute effects on food intake and body weight induced in rats provide a first report of in vivo activity for an allosteric CB 1 receptor antagonist.

Insulin resistance in skeletal muscle is a hallmark feature of type 2 diabetes. An increasing number of enzymes and metabolic pathways have been implicated in the development of insulin resistance. However, the primary cellular cause of insulin resistance remains uncertain. Proteome analysis can quantitate a large number of proteins and their post-translational modifications simultaneously and is a powerful tool to study polygenic diseases like type 2 diabetes. Using this approach on human skeletal muscle biopsies, we have identified eight potential protein markers for type 2 diabetes in the fasting state. The observed changes in protein expression indicate increased cellular stress, e.g. up-regulation of two heat shock proteins, and perturbations in ATP (re)synthesis and mitochondrial metabolism, e.g. down-regulation of ATP synthase ␤-subunit and creatine kinase B, in skeletal muscle of patients with type 2 diabetes. Phosphorylation appears to play a key, potentially coordinating role for most of the proteins identified in this study. In particular, we demonstrated that the catalytic ␤-subunit of ATP synthase is phosphorylated in vivo and that the levels of a down-regulated ATP synthase ␤-subunit phosphoisoform in diabetic muscle correlated inversely with fasting plasma glucose levels. These data suggest a role for phosphorylation of ATP synthase ␤-subunit in the regulation of ATP synthesis and that alterations in the regulation of ATP synthesis and cellular stress proteins may contribute to the pathogenesis of type 2 diabetes.Insulin resistance in skeletal muscle, defined as reduced insulin-stimulated glucose disposal, is a characteristic feature of type 2 diabetes mellitus (T2DM) 1 and is believed to be largely accounted for by reduced non-oxidative glucose metabolism (1-3). Furthermore, insulin stimulation of glucose oxidation and suppression of lipid oxidation is significantly impaired in patients with T2DM (2, 3). Conversely, in the basal, fasting state increased glucose oxidation and reduced lipid oxidation is seen in skeletal muscle of insulin resistant subjects, whether caused by T2DM or obesity alone (4). These defects suggest an impaired capacity to switch between carbohydrate and fat as oxidative energy sources in insulin-resistant subjects. Together with reports of reduced oxidative enzyme activity and dysfunction of mitochondria in skeletal muscle of patients with T2DM (4 -6) and the fact that mitochondrial DNA defects cause T2DM through impairment of oxidative phosphorylation (7, 8), these abnormalities in fuel metabolism have led to the hypotheses that perturbations in skeletal muscle mitochondrial metabolism (6, 9, 10) and defects in the signaling pathways of AMP-activated protein kinase (AMPK) are implicated in the pathogenesis of T2DM (11). That rates of fuel oxidation and mitochondrial function can affect glucose uptake and glycogen synthesis has been reported earlier (12, 13). In addition, both chronic activation of AMPK and induced expression of the transcriptional co-activator of peroxisom...

GPR119 is a G protein-coupled receptor expressed predominantly in the pancreas (b-cells) and gastrointestinal tract (enteroendocrine cells) in humans. De-orphanization of GPR119 has revealed two classes of possible endogenous ligands, viz., phospholipids and fatty acid amides. Of these, oleoylethanolamide (OEA) is one of the most active ligands tested so far. This fatty acid ethanolamide is of particular interest because of its known effects of reducing food intake and body weight gain when administered to rodents. Agonists at the GPR119 receptor cause an increase in intracellular cAMP levels via G as coupling to adenylate cyclase. In vitro studies have indicated a role for GPR119 in the modulation of insulin release by pancreatic b-cells and of GLP-1 secretion by gut enteroendocrine cells. The effects of GPR119 agonists in animal models of diabetes and obesity are reviewed, and the potential value of such compounds in future therapies for these conditions is discussed.

Screening subtraction libraries from normal and type II diabetic human skeletal muscle, we identified four different mitochondrially encoded genes which were increased in expression in diabetes. The genes were cytochrome oxidase I, cytochrome oxidase III, NADH dehydrogenase IV, and 12s rRNA, all of which are located on the heavy strand of the mitochondrial genome. There was a 1.5-to 2.2-fold increase in the expression of these mRNA molecules relative to total RNA in both type I and type II diabetes as assessed by Northern blot analyses. Since there was -50% decrease in mitochondrial DNA copy number as estimated by Southern blot analyses, mitochondrial gene expression increased -2.5-fold when expressed relative to mitochondrial DNA copy number. For cytochrome oxidase I similar changes in mitochondrial gene expression were observed in muscle of nonobese diabetic and ob/ob mice, models of type I and type II diabetes, respectively. By contrast there was no change or a slight decrease in expression of cytochrome oxidase 7a, a nuclear-encoded subunit of cytochrome oxidase, and the expression of mitochondrial transcription factor 1 in human skeletal muscle did not change with type I or type II diabetes. The increased mitochondrial gene expression may contribute to the increase in mitochondrial respiration observed in uncontrolled diabetes. (J. Clin. Invest. 1995. 95:1383-1388

Rad is a Ras-like GTPase that was isolated by subtraction cloning of human muscle and shown to have increased expression in some individuals with Type II diabetes. To ascertain the potential role of Rad in insulin-mediated signaling, we have overexpressed Rad in myocyte and adipocyte cell lines. Expression of Rad resulted in a 50-90% reduction in insulin-stimulated 2-deoxyglucose glucose uptake in C2C12 murine myotubes, L6 rat myotubes, and 3T3-L1 adipocytes and a 25% reduction in 3-O-methylglucose uptake in 3T3-L1 adipocytes. This occurred despite unaltered levels of glucose transporter expression, with no detectable change in Glut4 translocation and with no alteration in insulin receptor or substrate phosphorylation or phosphatidylinositol 3-kinase activity. These data indicate that Rad is a negative regulator of glucose uptake and that this effect may be due to a decrease in the intrinsic activity of the transporter molecules, rather than an effect on the translocation of Glut4.

The pyruvate dehydrogenase complex (PDC) oxidatively decarboxylates pyruvate to acetyl-CoA and CO 2 , coupled with the reduction of NAD + to NADH. In mammals, there is no pathway for the net conversion of acetyl-CoA to pyruvate and thus the catalytic activity of PDC represents the irreversible utilization of The pyruvate dehydrogenase complex occupies a central and strategic position in muscle intermediary metabolism and is primarily regulated by phosphorylation ⁄ dephosphorylation. The identification of multiple isoforms of pyruvate dehydrogenase kinase (PDK1-4) and pyruvate dehydrogenase phosphatase (PDP1-2) has raised intriguing new possibilities for chronic pyruvate dehydrogenase complex control. Experiments to date suggest that PDK4 is the major isoenzyme responsible for changes in pyruvate dehydrogenase complex activity in response to various different metabolic conditions. Using a cultured human skeletal muscle cell model system, we found that expression of both PDK2 and PDK4 mRNA is upregulated in response to glucose deprivation and fatty acid supplementation, the effects of which are reversed by insulin treatment. In addition, insulin directly downregulates PDK2 and PDK4 mRNA transcript abundance via a phosphatidylinositol 3-kinase-dependent pathway, which may involve glycogen synthase kinase-3 but does not utilize the mammalian target of rapamycin or mitogen-activated protein kinase signalling pathways. In order to further elucidate the regulation of PDK, the role of the peroxisome proliferatorsactivated receptors (PPAR) was investigated using highly potent subtype selective agonists. PPARa and PPARd agonists were found to specifically upregulate PDK4 mRNA expression, whereas PPARc activation selectively decreased PDK2 mRNA transcript abundance. PDP1 mRNA expression was unaffected by all conditions analysed. These results suggest that in human muscle, hormonal and nutritional conditions may control PDK2 and PDK4 mRNA expression via a common signalling mechanism. In addition, PPARs appear to independently regulate specific PDK isoform transcipt levels, which are likely to impart important metabolic mediation of fuel utilization by the muscle.