High-throughput mediation analysis of human proteome and metabolome identifies mediators of post-bariatric surgical diabetes control.

To improve the power of mediation in high-throughput studies, here we introduce High-throughput mediation analysis (Hitman), which accounts for direction of mediation and applies empirical Bayesian linear modeling. We apply Hitman in a retrospective, exploratory analysis of the SLIMM-T2D clinical trial in which participants with type 2 diabetes were randomized to Roux-en-Y gastric bypass (RYGB) or nonsurgical diabetes/weight management, and fasting plasma proteome and metabolome were assayed up to 3 years. RYGB caused greater improvement in HbA1c, which was mediated by growth hormone receptor (GHR). GHR's mediation is more significant than clinical mediators, including BMI. GHR decreases at 3 months postoperatively alongside increased insulin-like growth factor binding proteins IGFBP1/BP2; plasma GH increased at 1 year. Experimental validation indicates (1) hepatic GHR expression decreases in post-bariatric rats; (2) GHR knockdown in primary hepatocytes decreases gluconeogenic gene expression and glucose production. Thus, RYGB may induce resistance to diabetogenic effects of GH signaling.Trial Registration: Clinicaltrials.gov NCT01073020.

Resolution of NASH and hepatic fibrosis by the GLP-1R/GcgR dual-agonist Cotadutide via modulating mitochondrial function and lipogenesis.

Non-alcoholic fatty liver disease and steatohepatitis are highly associated with obesity and type 2 diabetes mellitus. Cotadutide, a GLP-1R/GcgR agonist, was shown to reduce blood glycemia, body weight and hepatic steatosis in patients with T2DM. Here, we demonstrate that the effects of Cotadutide to reduce body weight, food intake and improve glucose control are predominantly mediated through the GLP-1 signaling, while, its action on the liver to reduce lipid content, drive glycogen flux and improve mitochondrial turnover and function are directly mediated through Gcg signaling. This was confirmed by the identification of phosphorylation sites on key lipogenic and glucose metabolism enzymes in liver of mice treated with Cotadutide. Complementary metabolomic and transcriptomic analyses implicated lipogenic, fibrotic and inflammatory pathways, which are consistent with a unique therapeutic contribution of GcgR agonism by Cotadutide in vivo. Significantly, Cotadutide also alleviated fibrosis to a greater extent than Liraglutide or Obeticholic acid (OCA), despite adjusting dose to achieve similar weight loss in 2 preclinical mouse models of NASH. Thus Cotadutide, via direct hepatic (GcgR) and extra-hepatic (GLP-1R) effects, exerts multi-factorial improvement in liver function and is a promising therapeutic option for the treatment of steatohepatitis.

Pancreatic ß-Cell Rest Replenishes Insulin Secretory Capacity and Attenuates Diabetes in an Extreme Model of Obese Type 2 Diabetes.

The onset of common obesity-linked type 2 diabetes (T2D) is marked by exhaustive failure of pancreatic ß-cell functional mass to compensate for insulin resistance and increased metabolic demand, leading to uncontrolled hyperglycemia. Here, the ß-cell-deficient obese hyperglycemic/hyperinsulinemic KS db/db mouse model was used to assess consequential effects on ß-cell functional recovery by lowering glucose homeostasis and/or improving insulin sensitivity after treatment with thiazolidinedione therapy or glucagon-like peptide 1 receptor agonism alone or in combination with sodium/glucose cotransporter 2 inhibition (SGLT-2i). SGLT-2i combination therapies improved glucose homeostasis, independent of changes in body weight, resulting in a synergistic increase in pancreatic insulin content marked by significant recovery of the ß-cell mature insulin secretory population but with limited changes in ß-cell mass and no indication of ß-cell dedifferentiation. Restoration of ß-cell insulin secretory capacity also restored biphasic insulin secretion. These data emphasize that by therapeutically alleviating the demand for insulin in vivo, irrespective of weight loss, endogenous ß-cells recover significant function that can contribute to attenuating diabetes. Thus, this study provides evidence that alleviation of metabolic demand on the ß-cell, rather than targeting the ß-cell itself, could be effective in delaying the progression of T2D.

Engineering of a GLP-1 analogue peptide/anti-PCSK9 antibody fusion for type 2 diabetes treatment.

Type 2 diabetes (T2D) is a complex and progressive disease requiring polypharmacy to manage hyperglycaemia and cardiovascular risk factors. However, most patients do not achieve combined treatment goals. To address this therapeutic gap, we have developed MEDI4166, a novel glucagon-like peptide-1 (GLP-1) receptor agonist peptide fused to a proprotein convertase subtilisin/kexin type 9 (PCSK9) neutralising antibody that allows for glycaemic control and low-density lipoprotein cholesterol (LDL-C) lowering in a single molecule. The fusion has been engineered to deliver sustained peptide activity in vivo in combination with reduced potency, to manage GLP-1 driven adverse effects at high dose, and a favourable manufacturability profile. MEDI4166 showed robust and sustained LDL-C lowering in cynomolgus monkeys and exhibited the anticipated GLP-1 effects in T2D mouse models. We believe MEDI4166 is a novel molecule combining long acting agonist peptide and neutralising antibody activities to deliver a unique pharmacology profile for the management of T2D.

Differential Effects of a Glucagon-Like Peptide 1 Receptor Agonist in Non-Alcoholic Fatty Liver Disease and in Response to Hepatectomy.

Non-alcoholic fatty liver disease (NAFLD) is associated with post-operative liver failure (PLF) and impaired liver regeneration. We investigated the effects of a glucagon-like peptide-1 (GLP-1) receptor agonist on NAFLD, PLF and liver regeneration in mice fed chow diet or methionine/choline-deficient diet (MCD) or high fat diet (HFD). Fc-GLP-1 decreased transaminases, reduced intrahepatic triglycerides (TG) and improved MCD-induced liver dysfuction. Macrophage/Kupffer cell-related markers were also reduced although Fc-GLP-1 increased expression of genes related to natural killer (NK), cytotoxic T lymphocytes and hepatic stellate cell (HSC) activation. After partial hepatectomy (PH), survival rates increased in mice receiving Fc-GLP-1 on chow or MCD diet. However, the benefit of Fc-GLP-1 on NASH-like features was attenuated 2 weeks post-PH and liver mass restoration was not improved. At this time-period, markers of NK cells and cytotoxic T lymphocytes were further elevated in Fc-GLP-1 treated mice. Increased HSC related gene expression in livers was observed together with decreased retinyl ester content and increased retinal and retinoic acid, reflecting HSC activation. Similar effects were found in mice fed HFD receiving Fc-GLP-1. Our results shed light on the differential effects of a long-acting GLP-1R agonist in improving NAFLD and PLF, but not enhancing liver regeneration in mice.

MEDI0382, a GLP-1 and glucagon receptor dual agonist, in obese or overweight patients with type 2 diabetes: a randomised, controlled, double-blind, ascending dose and phase 2a study.

BACKGROUND: Weight loss is often key in the management of obese or overweight patients with type 2 diabetes, yet few treatments for diabetes achieve clinically meaningful weight loss. We aimed to assess the efficacy, tolerability, and safety of treatment with MEDI0382, a balanced glucagon-like peptide-1 and glucagon receptor dual agonist developed to provide glycaemic control and weight loss, in patients with type 2 diabetes. METHODS: This randomised, placebo-controlled, double-blind, combined multiple-ascending dose (MAD) and phase 2a study was done at 11 study sites (hospitals and contract research organisations) in Germany. We enrolled patients aged 18-65 years with controlled type 2 diabetes (glycated haemoglobin A1c [HbA1c] levels of 6·5-8·5% at screening) and a body-mass index between 27 kg/m2 and 40 kg/m2. An interactive web-response system was used to randomly assign patients to receive MEDI0382 or placebo. Patients were randomly assigned 2:1 in cohorts A-C and 3:1 in cohorts D and E in the MAD portion of the study, and 1:1 in the phase 2a portion. Randomisation was done by a contracted third-party operator who was not involved in the clinical operations of the study. The pharmacists, participants, and study site personnel involved in treating and assessing participants were masked to treatment allocation. Patients received once-daily subcutaneous injections of the study drug at doses of no more than 300 µg for 22 days or less in the MAD portion of the study, and a dose of no more than 200 µg for 41 days or less in the phase 2a portion. The two primary endpoints of the phase 2a portion were the change from baseline to day 41 in glucose area under the curve at 0-4 h (AUC0-4 h) after a mixed-meal tolerance test (MMTT), assessed in all participants who received at least one dose of study drug and whose measurements were taken at baseline and day 41, and change from baseline in bodyweight, assessed in the intention-to-treat (ITT) population. Safety analyses were done in all participants who received any study drug analysed according to the treatment they received. This study is registered with ClinicalTrials.gov, number NCT02548585. FINDINGS: Patients were recruited between Dec 9, 2015, and Feb 24, 2017. 61 patients were randomly assigned to the MAD part of the study (42 to MEDI0382 and 19 to placebo). 51 patients were randomly assigned to the phase 2a part, of whom 25 were randomly assigned to MEDI0382 and 26 to placebo. In the phase 2a study, three patients in the MEDI0382 group and one in the placebo group discontinued, all as a result of adverse events. 22 (88%) patients in the MEDI0382 group and 25 (96%) in the placebo group received at least one dose and had measurements taken at baseline and day 41. Glucose AUC0-4 h post MMTT decreased significantly with MEDI0382 versus placebo (least squares [LS] mean -32·78% [90% CI -36·98 to -28·57] vs -10·16% [-14·10 to -6·21], and the mean difference was -22·62% [-28·40 to -16·85]; p<0·0001). In the ITT population, reduction in bodyweight was significantly greater with MEDI0382 than with placebo (LS mean -3·84 kg [90% CI -4·55 to -3·12] vs -1·70 kg [-2·40 to -1·01] and mean difference of 2·14 kg [-3·13 to -1·31]; p=0·0008). The proportion of patients who had a treatment-emergent adverse event (TEAE) was similar between treatment groups (22 [88%] of 25 in the MEDI0382 group vs 23 [88%] of 26 in the placebo group); gastrointestinal disorders (18 [72%] vs 13 [40%]) and decreased appetite (five [20%] vs none) occurred more frequently with MEDI0382 than placebo. No participants in the MEDI0382 group had a grade 3 or worse TEAE (vs two [8%] in the placebo group). INTERPRETATION: MEDI0382 has the potential to deliver clinically meaningful reductions in blood glucose and bodyweight in obese or overweight individuals with type 2 diabetes. FUNDING: MedImmune.

MEDI0382, a GLP-1/glucagon receptor dual agonist, meets safety and tolerability endpoints in a single-dose, healthy-subject, randomized, Phase 1 study.

AIMS: MEDI0382 is a balanced glucagon-like peptide-1/glucagon receptor dual agonist under development for the treatment of type 2 diabetes mellitus and non-alcoholic steatohepatitis. The primary objective was to assess the safety of MEDI0382 in healthy subjects. METHODS: In this placebo-controlled, double-blind, Phase 1 study, healthy subjects (aged 18-45 years) were randomized (3:1) to receive a single subcutaneous dose of MEDI0382 or placebo after ≥8 h of fasting. The study consisted of six cohorts that received study drug at 5 µg, 10 µg, 30 µg, 100 µg, 150 µg or 300 µg. The primary objective was safety and tolerability. Secondary endpoints included assessments of pharmacokinetics and immunogenicity. All subjects were followed for up to 28 days. RESULTS: A total of 36 subjects received MEDI0382 (n = 6 per cohort) and 12 subjects received placebo (n = 2 per cohort). Treatment-emergent adverse events (TEAEs) occurred more frequently with MEDI0382 vs. placebo, which was mostly due to an increased occurrence at MEDI0382 doses ≥150 µg. All TEAEs were mild or moderate in severity. The most common TEAEs were vomiting, nausea and dizziness. There appeared to be a dose-dependent increase in heart rate with MEDI0382 treatment. MEDI0382 showed linear pharmacokinetic profile (time to maximum plasma concentration: 4.50-9.00 h; elimination half-life: 9.54-12.07 h). No immunogenicity was observed in the study. CONCLUSIONS: In this single-dose, Phase 1 study in healthy subjects, the safety and pharmacokinetic profiles of MEDI0382 support once-daily dosing and further clinical development of MEDI0382.

LEAP2 Is an Endogenous Antagonist of the Ghrelin Receptor.

Ghrelin, an appetite-stimulatory hormone secreted by the stomach, was discovered as a ligand for the growth hormone secretagogue receptor (GHSR). Through GHSR, ghrelin stimulates growth hormone (GH) secretion, a function that evolved to protect against starvation-induced hypoglycemia. Though the biology mediated by ghrelin has been described in great detail, regulation of ghrelin action is poorly understood. Here, we report the discovery of liver-expressed antimicrobial peptide 2 (LEAP2) as an endogenous antagonist of GHSR. LEAP2 is produced in the liver and small intestine, and its secretion is suppressed by fasting. LEAP2 fully inhibits GHSR activation by ghrelin and blocks the major effects of ghrelin in vivo, including food intake, GH release, and maintenance of viable glucose levels during chronic caloric restriction. In contrast, neutralizing antibodies that block endogenous LEAP2 function enhance ghrelin action in vivo. Our findings reveal a mechanism for fine-tuning ghrelin action in response to changing environmental conditions.

Neurturin and a GLP-1 Analogue Act Synergistically to Alleviate Diabetes in Zucker Diabetic Fatty Rats.

Neurturin (NRTN), a member of the glial-derived neurotrophic factor family, was identified from an embryonic chicken pancreatic cDNA library in a screen for secreted factors. In this study, we assessed the potential antidiabetic activities of NRTN relative to liraglutide, a glucagon-like peptide 1 receptor agonist, in Zucker diabetic fatty (ZDF) rats. Subcutaneous administration of NRTN to 8-week-old male ZDF rats prevented the development of hyperglycemia and improved metabolic parameters similar to liraglutide. NRTN treatment increased pancreatic insulin content and ß-cell mass and prevented deterioration of islet organization. However, unlike liraglutide-treated rats, NRTN-mediated improvements were not associated with reduced body weight or food intake. Acute NRTN treatment did not activate c-Fos expression in key feeding behavior and metabolic centers in ZDF rat brain or directly enhance glucose-stimulated insulin secretion from pancreatic ß-cells. Treating 10-week-old ZDF rats with sustained hyperglycemia with liraglutide resulted in some alleviation of hyperglycemia, whereas NRTN was not as effective despite improving plasma lipids and fasting glucose levels. Interestingly, coadministration of NRTN and liraglutide normalized hyperglycemia and other metabolic parameters, demonstrating that combining therapies with distinct mechanism(s) can alleviate advanced diabetes. This emphasizes that therapeutic combinations can be more effective to manage diabetes in individuals with uncontrolled hyperglycemia.

Apelin-36 Modulates Blood Glucose and Body Weight Independently of Canonical APJ Receptor Signaling.

Apelin-36 was discovered as the endogenous ligand for the previously orphan receptor APJ. Apelin-36 has been linked to two major types of biological activities: cardiovascular (stimulation of cardiac contractility and suppression of blood pressure) and metabolic (improving glucose homeostasis and lowering body weight). It has been assumed that both of these activities are modulated through APJ. Here, we demonstrate that the metabolic activity of apelin-36 can be separated from canonical APJ activation. We developed a series of apelin-36 variants in which evolutionarily conserved residues were mutated, and evaluated their ability to modulate glucose homeostasis and body weight in chronic mouse models. We found that apelin-36(L28A) retains full metabolic activity, but is 100-fold impaired in its ability to activate APJ. In contrast to its full metabolic activity, apelin-36(L28A) lost the ability to suppress blood pressure in spontaneously hypertensive rats (SHR). We took advantage of these findings to develop a longer-acting variant of apelin-36 that could modulate glucose homeostasis without impacting blood pressure (or activating APJ). Apelin-36-[L28C(30kDa-PEG)] is 10,000-fold less potent than apelin-36 at activating the APJ receptor but retains its ability to significantly lower blood glucose and improve glucose tolerance in diet-induced obese mice. Apelin-36-[L28C(30kDa-PEG)] provides a starting point for the development of diabetes therapeutics that are devoid of the blood pressure effects associated with canonical APJ activation.

A novel glucagon-like peptide 1/glucagon receptor dual agonist improves steatohepatitis and liver regeneration in mice.

Because nonalcoholic steatohepatitis (NASH) is associated with impaired liver regeneration, we investigated the effects of G49, a dual glucagon-like peptide-1/glucagon receptor agonist, on NASH and hepatic regeneration. C57Bl/6 mice fed chow or a methionine and choline-deficient (MCD) diet for 1 week were divided into 4 groups: control (chow diet), MCD diet, chow diet plus G49, and M+G49 (MCD diet plus G49). Mice fed a high-fat diet (HFD) for 10 weeks were divided into groups: HFD and H+G49 (HFD plus G49). Following 2 (MCD groups) or 3 (HFD groups) weeks of treatment with G49, partial hepatectomy (PH) was performed, and all mice were maintained on the same treatment schedule for 2 additional weeks. Analysis of liver function, hepatic regeneration, and comprehensive genomic and metabolic profiling were conducted. NASH was ameliorated in the M+G49 group, manifested by reduced inflammation, steatosis, oxidative stress, and apoptosis and increased mitochondrial biogenesis. G49 treatment was also associated with replenishment of intrahepatic glucose due to enhanced gluconeogenesis and reduced glucose use through the pentose phosphate cycle and oxidative metabolism. Following PH, G49 treatment increased survival, restored the cytokine-mediated priming phase, and enhanced the proliferative capacity and hepatic regeneration ratio in mice on the MCD diet. NASH markers remained decreased in M+G49 mice after PH, and glucose use was shifted to the pentose phosphate cycle and oxidative metabolism. G49 administered immediately after PH was also effective at alleviating the pathological changes induced by the MCD diet. Benefits in terms of liver regeneration were also found in mice fed HFD and treated with G49. CONCLUSION: Dual-acting glucagon-like peptide-1/glucagon receptor agonists such as G49 represent a novel therapeutic approach for patients with NASH and particularly those requiring PH. (Hepatology 2017;65:950-968).

Inhibition of T-cell activation by the CTLA4-Fc Abatacept is sufficient to ameliorate proteinuric kidney disease.

Diabetic nephropathy (DN) remains an unmet medical challenge as its prevalence is projected to continue to increase and specific medicines for treatment remain undeveloped. Activation of the immune system, in particular T-cells, is emerging as a possible mechanism underlying DN disease progression in humans and animal models. We hypothesized that inhibition of T-cell activation will ameliorate DN. Interaction of B7-1 (CD80) on the surface of antigen presenting cells with its binding partners, CTLA4 (CD152) and CD28 on T-cells, is essential for T-cell activation. In this study we used the soluble CTLA4-Fc fusion protein Abatacept to block cell surface B7-1, preventing the cellular interaction and inhibiting T-cell activation. When Abatacept was dosed in an animal model of diabetes-induced albuminuria, it reduced albuminuria in both prevention and intervention modes. The number of T-cells infiltrating the kidneys of DN animals correlated with the degree of albuminuria, and treatment with Abatacept reduced the number of renal T-cells. As B7-1 induction has been recently proposed to underlie podocyte damage in DN, Abatacept could be efficacious in DN by protecting podocytes. However, this does not appear to be the case as B7-1 was not expressed in 1) kidneys of DN animals; 2) stimulated human podocytes in culture; or 3) glomeruli of DN patients. We conclude that Abatacept ameliorates DN by blocking systemic T-cell activation and not by interacting with podocytes.

BMP4 and BMP Antagonists Regulate Human White and Beige Adipogenesis.

The limited expandability of subcutaneous adipose tissue, due to reduced ability to recruit and differentiate new adipocytes, prevents its buffering effect in obesity and is characterized by expanded adipocytes (hypertrophic obesity). Bone morphogenetic protein-4 (BMP4) plays a key role in regulating adipogenic precursor cell commitment and differentiation. We found BMP4 to be induced and secreted by differentiated (pre)adipocytes, and BMP4 was increased in large adipose cells. However, the precursor cells exhibited a resistance to BMP4 owing to increased secretion of the BMP inhibitor Gremlin-1 (GREM1). GREM1 is secreted by (pre)adipocytes and is an inhibitor of both BMP4 and BMP7. BMP4 alone, and/or silencing GREM1, increased transcriptional activation of peroxisome proliferator-activated receptor γ and promoted the preadipocytes to assume an oxidative beige/brown adipose phenotype including markers of increased mitochondria and PGC1α. Driving white adipose differentiation inhibited the beige/brown markers, suggesting the presence of multipotent adipogenic precursor cells. However, silencing GREM1 and/or adding BMP4 during white adipogenic differentiation reactivated beige/brown markers, suggesting that increased BMP4 preferentially regulates the beige/brown phenotype. Thus, BMP4, secreted by white adipose cells, is an integral feedback regulator of both white and beige adipogenic commitment and differentiation, and resistance to BMP4 by GREM1 characterizes hypertrophic obesity.

In vivo siRNA delivery of Keap1 modulates death and survival signaling pathways and attenuates concanavalin-A-induced acute liver injury in mice.

Oxidative stress contributes to the progression of acute liver failure (ALF). Transcription factor nuclear factor-erythroid 2-related factor (Nrf2) serves as an endogenous regulator by which cells combat oxidative stress. We have investigated liver damage and the balance between death and survival signaling pathways in concanavalin A (ConA)-mediated ALF using in vivo siRNA delivery targeting Keap1 in hepatocytes. For that goal, mice were injected with Keap1- or luciferase-siRNA-containing liposomes via the tail vein. After 48 hours, ALF was induced by ConA. Liver histology, pro-inflammatory mediators, antioxidant responses, cellular death, and stress and survival signaling were assessed. Keap1 mRNA and protein levels significantly decreased in livers of Keap1-siRNA-injected mice. In these animals, histological liver damage was less evident than in control mice when challenged with ConA. Likewise, markers of cellular death (FasL and caspases 8, 3 and 1) decreased at 4 and 8 hours post-injection. Nuclear Nrf2 and its target, hemoxygenase 1 (HO1), were elevated in Keap1-siRNA-injected mice compared with control animals, resulting in reduced oxidative stress in the liver. Similarly, mRNA levels of pro-inflammatory cytokines were reduced in livers from Keap1-siRNA-injected mice. At the molecular level, activation of c-jun (NH2) terminal kinase (JNK) was ameliorated, whereas the insulin-like growth factor I receptor (IGFIR) survival pathway was maintained upon ConA injection in Keap1-siRNA-treated mice. In conclusion, our results have revealed a potential therapeutic use of in vivo siRNA technology targeted to Keap1 to combat oxidative stress by modulating Nrf2-mediated antioxidant responses and IGFIR survival signaling during the progression of ALF.

Essential role of protein tyrosine phosphatase 1B in obesity-induced inflammation and peripheral insulin resistance during aging.

Protein tyrosine phosphatase 1B (PTP1B) is a negative regulator of insulin signaling and a therapeutic target for type 2 diabetes (T2DM). In this study, we have evaluated the role of PTP1B in the development of aging-associated obesity, inflammation, and peripheral insulin resistance by assessing metabolic parameters at 3 and 16 months in PTP1B(-/-) mice maintained on mixed genetic background (C57Bl/6J × 129Sv/J). Whereas fat mass and adipocyte size were increased in wild-type control mice at 16 months, these parameters did not change with aging in PTP1B(-/-) mice. Increased levels of pro-inflammatory cytokines, crown-like structures, and hypoxia-inducible factor (HIF)-1α were observed only in adipose tissue from 16-month-old wild-type mice. Similarly, islet hyperplasia and hyperinsulinemia were observed in wild-type mice with aging-associated obesity, but not in PTP1B(-/-) animals. Leanness in 16-month-old PTP1B(-/-) mice was associated with increased energy expenditure. Whole-body insulin sensitivity decreased in 16-month-old control mice; however, studies with the hyperinsulinemic-euglycemic clamp revealed that PTP1B deficiency prevented this obesity-related decreased peripheral insulin sensitivity. At a molecular level, PTP1B expression and enzymatic activity were up-regulated in liver and muscle of 16-month-old wild-type mice as were the activation of stress kinases and the expression of p53. Conversely, insulin receptor-mediated Akt/Foxo1 signaling was attenuated in these aged control mice. Collectively, these data implicate PTP1B in the development of inflammation and insulin resistance associated with obesity during aging and suggest that inhibition of this phosphatase by therapeutic strategies might protect against age-dependent T2DM.

The emerging role of the intestine in metabolic diseases.

The intestine is an important metabolic organ that has gained attention in recent years for the newly identified role that it plays in the pathophysiology of various metabolic diseases including obesity, insulin resistance and diabetes. Recent insights regarding the role of enteroendocrine hormones, such as GIP, GLP-1, and PYY in metabolic diseases, as well as the emerging role of the gut microbial community and gastric bypass bariatric surgeries in modulating metabolic function and dysfunction have sparked a wave of interest in understanding the mechanisms involved, in an effort to identify new therapeutics and novel regulators of metabolism. This review summarizes the current evidence that the gastrointestinal tract has a key role in the development of obesity, inflammation, insulin resistance and diabetes and discusses the possible players that can be targeted for therapeutic intervention.

Discovery of orally active carboxylic acid derivatives of 2-phenyl-5-trifluoromethyloxazole-4-carboxamide as potent diacylglycerol acyltransferase-1 inhibitors for the potential treatment of obesity and diabetes.

Diacylglycerol acyltransferase-1 (DGAT-1) is the enzyme that catalyzes the final and committed step of triglyceride formation, namely, the acylation of diacylglycerol with acyl coenzyme A. DGAT-1 deficient mice demonstrate resistance to weight gain on high fat diet, improved insulin sensitivity, and reduced liver triglyceride content. Inhibition of DGAT-1 thus represents a potential novel approach for the treatment of obesity, dyslipidemia, and metabolic syndrome. In this communication, we report the identification of the lead structure 6 and our lead optimization efforts culminating in the discovery of potent, selective, and orally efficacious carboxylic acid derivatives of 2-phenyl-5-trifluoromethyloxazole-4-carboxamides. In particular, compound 29 (DGAT-1 enzyme assay, IC(50) = 57 nM; CHO-K1 cell triglyceride formation assay, EC(50) = 0.5 µM) demonstrated dose dependent inhibition of weight gain in diet induced obese (DIO) rats (0.3, 1, and 3 mg/kg, p.o., qd) during a 21-day efficacy study. Furthermore, compound 29 demonstrated improved glucose tolerance determined by an oral glucose tolerance test (OGTT).

PTP1B deficiency enhances liver growth during suckling by increasing the expression of insulin-like growth factor-I.

Protein tyrosine phosphatase 1B (PTP1B) is a negative regulator of insulin and tyrosine kinase growth factor signaling. We have recently demonstrated that PTP1B deficiency increases GLUT2/insulin receptor (IR) A complexes and glucose uptake in suckling, but not adult, primary hepatocytes. Herein we have investigated intrahepatic glucose utilization in 3-5 days old wild-type and PTP1B(-/-) mice. PTP1B deficiency decreased glycogen, lactate, and pyruvate content in the livers from suckling mice. Conversely, the activity of glucose 6-phosphate dehydrogenase (G6PD), the rate limiting enzyme of the pentose phosphate cycle (PPC) which provides substrates for DNA synthesis, was enhanced in the liver of PTP1B(-/-) animals. Liver weight, liver-to-body mass ratio, DNA content, and PCNA expression were increased in PTP1B(-/-) suckling mice compared to the wild-type controls. At the molecular level, STAT 5B phosphorylation, IGF-I mRNA, and protein levels as well as IGF-IR tyrosine phosphorylation were increased in the livers of PTP1B-deficient neonates. Unexpectedly, hepatic and serum triglycerides (TG) were increased by PTP1B deficiency, although the expression of lipogenic enzymes remained as in the wild-type controls. However, the analysis of milk composition revealed higher TG content in lactating females lacking PTP1B. The effects of PTP1B deficiency on G6PD activity, STAT 5B/IGF-I/IGF-IR axis, PCNA expression and liver growth during suckling were maintained by transferring PTP1B(-/-) embryos (PTP1B(-/-T)) to a wild-type female. Conversely, PTP1B(-/-T) mice did not show hepatic fat accumulation. In conclusion, the present study suggests that PTP1B plays a unique role in the control of the physiological liver development after birth.

Beneficial effects of PTP1B deficiency on brown adipocyte differentiation and protection against apoptosis induced by pro- and anti-inflammatory stimuli.

Insulin is an inducer of brown fat adipogenesis through the activation of a signalling network that involves positive/negative modulators. Given the importance of brown adipose tissue (BAT) for basal thermogenic energy expenditure, we investigated the role of PTP1B in the acquisition of terminal differentiated phenotype and in the apoptotic responses of brown adipocytes. Immortalized brown preadipocytes lacking (PTP1B(-/-)) or expressing (PTP1B(+/+)) PTP1B have been generated. PTP1B deficiency accelerated a full program of brown adipogenesis including induction of transcription factors, coactivators, adipogenic markers and signalling molecules. Fully differentiated PTP1B(-/-) brown adipocytes were resistant to tumor necrosis factor (TNFalpha)-induced apoptosis as these cells were protected against caspase-8 activation, FLIP degradation, Bid cleavage and caspase-3 activation compared to wild-type controls. These events were recovered by PTP1B rescue. Survival signalling including phosphorylation of IRS-1 and Akt/PKB and BclxL expression were decreased in TNFalpha-treated PTP1B(-/-) cells but not in the wild-type. Similarly, PTP1B(-/-) brown adipocytes were protected against resveratrol-induced apoptosis. Phosphorylation of Akt/PKB and Foxo1 phosphorylation/acetylation decreased exclusively in resveratrol-treated wild-type cells, leading to nuclear localization of Foxo1 and up-regulation of Bim. Thus, PTP1B inhibition could be of benefit against obesity by counteracting TNFalpha-induced brown fat atrophy, and combined with resveratrol might improve low-grade inflammation.