Activation of the hypothalamic-pituitary-adrenal axis by exogenous and endogenous GDF15.

An acute increase in the circulating concentration of glucocorticoid hormones is essential for the survival of severe somatic stresses. Circulating concentrations of GDF15, a hormone that acts in the brain to reduce food intake, are frequently elevated in stressful states. We now report that GDF15 potently activates the hypothalamic-pituitary-adrenal (HPA) axis in mice and rats. A blocking antibody to the GDNF-family receptor α-like receptor completely prevented the corticosterone response to GDF15 administration. In wild-type mice exposed to a range of stressful stimuli, circulating levels of both corticosterone and GDF15 rose acutely. In the case of Escherichia coli or lipopolysaccharide injections, the vigorous proinflammatory cytokine response elicited was sufficient to produce a near-maximal HPA response, regardless of the presence or absence of GDF15. In contrast, the activation of the HPA axis seen in wild-type mice in response to the administration of genotoxic or endoplasmic reticulum toxins, which do not provoke a marked rise in cytokines, was absent in Gdf15-/- mice. In conclusion, consistent with its proposed role as a sentinel hormone, endogenous GDF15 is required for the activation of the protective HPA response to toxins that do not induce a substantial cytokine response. In the context of efforts to develop GDF15 as an antiobesity therapeutic, these findings identify a biomarker of target engagement and a previously unrecognized pharmacodynamic effect, which will require monitoring in human studies.

Resveratrol Inhibits Neointimal Growth after Arterial Injury in High-Fat-Fed Rodents: The Roles of SIRT1 and AMPK.

We have shown that both insulin and resveratrol (RSV) decrease neointimal hyperplasia in chow-fed rodents via mechanisms that are in part overlapping and involve the activation of endothelial nitric oxide synthase (eNOS). However, this vasculoprotective effect of insulin is abolished in high-fat-fed insulin-resistant rats. Since RSV, in addition to increasing insulin sensitivity, can activate eNOS via pathways that are independent of insulin signaling, such as the activation of sirtuin 1 (SIRT1) and AMP-activated kinase (AMPK), we speculated that unlike insulin, the vasculoprotective effect of RSV would be retained in high-fat-fed rats. We found that high-fat feeding decreased insulin sensitivity and increased neointimal area and that RSV improved insulin sensitivity (p < 0.05) and decreased neointimal area in high-fat-fed rats (p < 0.05). We investigated the role of SIRT1 in the effect of RSV using two genetic mouse models. We found that RSV decreased neointimal area in high-fat-fed wild-type mice (p < 0.05), an effect that was retained in mice with catalytically inactive SIRT1 (p < 0.05) and in heterozygous SIRT1-null mice. In contrast, the effect of RSV was abolished in AMKPα2-null mice. Thus, RSV decreased neointimal hyperplasia after arterial injury in both high-fat-fed rats and mice, an effect likely not mediated by SIRT1 but by AMPKα2.

Phase 2 study of the efficacy and safety of ponsegromab in patients with cancer cachexia: PROACC-1 study design.

BACKGROUND: Cancer cachexia is a multifactorial metabolic wasting syndrome characterized by anorexia, unintentional loss of weight involving both skeletal muscle and adipose tissues, progressive functional impairment and reduced survival. Therapeutic strategies for this serious condition are very limited. Growth differentiation factor 15 (GDF-15) is a cytokine that is implicated in cancer cachexia and may represent both a biomarker of cancer cachexia and a potential therapeutic target. Ponsegromab is a potent and selective humanized monoclonal antibody that inhibits GDF-15-mediated signalling. Preclinical and preliminary phase 1 data suggest that ponsegromab-mediated inactivation of circulating GDF-15 may lead to improvement in key characteristics of cachexia. The primary objective of this phase 2 study is to assess the effect of ponsegromab on body weight in patients with cancer, cachexia and elevated GDF-15 concentrations. Secondary objectives include assessing physical activity, physical function, actigraphy, appetite, nausea and vomiting, fatigue and safety. Exploratory objectives include evaluating pharmacokinetics, pharmacodynamics, immunogenicity, lumbar skeletal muscle index and Response Evaluation Criteria in Solid Tumors. METHODS: Approximately 168 adults with non-small-cell lung, pancreatic or colorectal cancers who have cachexia and elevated GDF-15 concentrations will be randomized in a double-blind, placebo-controlled study (NCT05546476). Participants meeting eligibility criteria will be randomized 1:1:1:1 to one of three dose groups of ponsegromab (100, 200 or 400 mg) or matching placebo administered subcutaneously every 4 weeks for an initial 12-week treatment period. This is followed by optional open-label treatment with ponsegromab of 400 mg administered every 4 weeks for up to 1 year. The primary endpoint is mean change from baseline in body weight at Week 12. A mixed model for repeated measures followed by a Bayesian Emax model will be used for the primary analysis. Secondary endpoints include physical activity, physical function and actigraphy measured by remote digital sensors; patient-reported appetite-related symptoms assessed by Functional Assessment of Anorexia-Cachexia Therapy subscale scores; anorexia/appetite, nausea and vomiting, and fatigue evaluated according to questions from the Cancer-Related Cachexia Symptom Diary; and incidence of adverse events, safety laboratory tests, vital signs and electrocardiogram abnormalities. PERSPECTIVE: Cancer-related cachexia is an area of significant unmet medical need. This study will support the clinical development of ponsegromab as a novel inhibitor of GDF-15, which may ameliorate key pathologies of cancer cachexia to improve patient symptoms, functionality and quality of life. TRIAL REGISTRATION: ClinicalTrials.gov ID: NCT05546476.

Duodenal activation of cAMP-dependent protein kinase induces vagal afferent firing and lowers glucose production in rats.

BACKGROUND & AIMS: The duodenum senses nutrients to maintain energy and glucose homeostasis, but little is known about the signaling and neuronal mechanisms involved. We tested whether duodenal activation of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase A (PKA) is sufficient and necessary for cholecystokinin (CCK) signaling to trigger vagal afferent firing and regulate glucose production. METHODS: In rats, we selectively activated duodenal PKA and evaluated changes in glucose kinetics during the pancreatic (basal insulin) pancreatic clamps and vagal afferent firing. The requirement of duodenal PKA signaling in glucose regulation was evaluated by inhibiting duodenal activation of PKA in the presence of infusion of the intraduodenal PKA agonist (Sp-cAMPS) or CCK1 receptor agonist (CCK-8). We also assessed the involvement of a neuronal network and the metabolic impact of duodenal PKA activation in rats placed on high-fat diets. RESULTS: Intraduodenal infusion of Sp-cAMPS activated duodenal PKA and lowered glucose production, in association with increased vagal afferent firing in control rats. The metabolic and neuronal effects of duodenal Sp-cAMPS were negated by coinfusion with either the PKA inhibitor H89 or Rp-CAMPS. The metabolic effect was also negated by coinfusion with tetracaine, molecular and pharmacologic inhibition of NR1-containing N-methyl-d-aspartate (NMDA) receptors within the dorsal vagal complex, or hepatic vagotomy in rats. Inhibition of duodenal PKA blocked the ability of duodenal CCK-8 to reduce glucose production in control rats, whereas duodenal Sp-cAMPS bypassed duodenal CCK resistance and activated duodenal PKA and lowered glucose production in rats on high-fat diets. CONCLUSIONS: We identified a neural glucoregulatory function of duodenal PKA signaling.

Local insulin application on the carotid artery inhibits neointima formation.

Anti-mitogenic agents currently used to prevent restenosis in drug-eluting stents delay re-endothelialization. Delayed re-endothelialization is now considered as the main cause of late stent thrombosis with drug-eluting stents, which emphasizes the need for new treatments. We have shown that systemic insulin treatment decreases neointimal growth and accelerates re-endothelialization after arterial injury in a rat model of restenosis. However, systemic insulin treatment cannot be given to non-diabetic individuals because of the risk of hypoglycemia. Thus, we investigated whether local insulin treatment is also effective in reducing neointimal growth after arterial injury. Rats were given local vehicle or local insulin delivered via Pluronic gel applied around the carotid artery immediately following balloon injury. Plasma glucose and systemic insulin levels were not affected by local insulin treatment. Insulin decreased intimal area at 28 days (P < 0.05) and also inhibited vascular smooth muscle cell migration by 60% at 4 days (P < 0.05). NPH (a longer-lasting insulin) also decreased neointimal area. These results indicate that local insulin treatment can lead to decreased restenosis, suggesting a protective vascular effect of insulin in vivo and that local insulin treatment, possibly via insulin-eluting stents, may be clinically relevant.

Body composition and lung cancer-associated cachexia in TRACERx.

Cancer-associated cachexia (CAC) is a major contributor to morbidity and mortality in individuals with non-small cell lung cancer. Key features of CAC include alterations in body composition and body weight. Here, we explore the association between body composition and body weight with survival and delineate potential biological processes and mediators that contribute to the development of CAC. Computed tomography-based body composition analysis of 651 individuals in the TRACERx (TRAcking non-small cell lung Cancer Evolution through therapy (Rx)) study suggested that individuals in the bottom 20th percentile of the distribution of skeletal muscle or adipose tissue area at the time of lung cancer diagnosis, had significantly shorter lung cancer-specific survival and overall survival. This finding was validated in 420 individuals in the independent Boston Lung Cancer Study. Individuals classified as having developed CAC according to one or more features at relapse encompassing loss of adipose or muscle tissue, or body mass index-adjusted weight loss were found to have distinct tumor genomic and transcriptomic profiles compared with individuals who did not develop such features. Primary non-small cell lung cancers from individuals who developed CAC were characterized by enrichment of inflammatory signaling and epithelial-mesenchymal transitional pathways, and differentially expressed genes upregulated in these tumors included cancer-testis antigen MAGEA6 and matrix metalloproteinases, such as ADAMTS3. In an exploratory proteomic analysis of circulating putative mediators of cachexia performed in a subset of 110 individuals from TRACERx, a significant association between circulating GDF15 and loss of body weight, skeletal muscle and adipose tissue was identified at relapse, supporting the potential therapeutic relevance of targeting GDF15 in the management of CAC.

Duodenal mucosal protein kinase C-δ regulates glucose production in rats.

BACKGROUND & AIMS: Activation of protein kinase C (PKC) enzymes in liver and brain alters hepatic glucose metabolism, but little is known about their role in glucose regulation in the gastrointestinal tract. We investigated whether activation of PKC-δ in the duodenum is sufficient and necessary for duodenal nutrient sensing and regulates hepatic glucose production through a neuronal network in rats. METHODS: In rats, we inhibited duodenal PKC and evaluated whether nutrient-sensing mechanisms, activated by refeeding, have disruptions in glucose regulation. We then performed gain- and loss-of-function pharmacologic and molecular experiments to target duodenal PKC-δ; we evaluated the impact on glucose production regulation during the pancreatic clamping, while basal levels of insulin were maintained. RESULTS: PKC-δ was detected in the mucosal layer of the duodenum; intraduodenal infusion of PKC inhibitors disrupted glucose homeostasis during refeeding, indicating that duodenal activation of PKC-δ is necessary and sufficient to regulate glucose homeostasis. Intraduodenal infusion of the PKC activator 1-oleoyl-2-acetyl-sn-glycerol (OAG) specifically activated duodenal mucosal PKC-δ and a gut-brain-liver neuronal pathway to reduce glucose production. Molecular and pharmacologic inhibition of duodenal mucosal PKC-δ negated the ability of duodenal OAG and lipids to reduce glucose production. CONCLUSIONS: In the duodenal mucosa, PKC-δ regulates glucose homeostasis.

Gut-brain signalling: how lipids can trigger the gut.

The gut plays a unique role in the metabolic defence against energy excess and glucose imbalance. Nutrients, such as lipids, enter the small intestine and activate sensing mechanisms to maintain energy and glucose homeostasis. It is clear that a lipid-induced gut-brain axis exists and that cholecystokinin and a neuronal network are involved, yet the underlying mechanisms in gut lipid sensing that regulate homeostasis remain largely unknown. In parallel, studies underscore the importance of enzymes involved in lipid metabolism within the brain, such as adenosine monophosphate -activated protein kinase, to maintain homeostasis. In this review, we will first examine what is known regarding the mechanisms involved in this lipid-induced gut-brain neuronal axis that regulate food intake and hepatic glucose production. We will also discuss how enzymes that govern brain lipid metabolism could potentially reveal how lipids trigger the gut, and that both the gut and brain may share common biochemical pathways to sense lipids.

Growth differentiation factor 15 neutralization does not impact anorexia or survival in lipopolysaccharide-induced inflammation.

Growth differentiation factor 15 (GDF15) causes anorexia and weight loss in animal models, and higher circulating levels are associated with cachexia and reduced survival in cancer and other chronic diseases such as sepsis. To investigate the role of sepsis-induced GDF15, we examined whether GDF15 neutralization via a validated and highly potent monoclonal antibody, mAB2, modulates lipopolysaccharide (LPS)-induced anorexia, weight loss, and mortality in rodents. LPS injection transiently increased circulating GDF15 in wild-type mice, decreased food intake and body weight, and increased illness behavior and mortality at a high dose. GDF15 neutralization with mAB2 did not prevent or exacerbate any of the effects of LPS. Similarly, in GDF15 knockout mice, the LPS effect on appetite and survival was comparable with that observed in wild-type controls. Therefore, effective inhibition of circulating active GDF15 via an antibody or via gene knockout demonstrated that survival in the LPS acute inflammation model was independent of GDF15.

Insulin inhibits and oral sucrose increases neointimal growth after arterial injury in rats.

BACKGROUND/AIMS: In our previous studies, rats on insulin treatment (5 U/day) and oral glucose to avoid hypoglycemia had reduced neointimal growth after arterial injury. However, plasma glucose in the insulin-treated rats was lower than normal and the effect of oral glucose remained undetermined. In this study, the effects of normoglycemic hyperinsulinemia and oral glucose or sucrose were investigated in the same model. METHODS: Rats were divided into 6 groups: (1) control implants and tap water; (2) insulin implants (5 U/day) and oral glucose + i.p. glucose to avoid any glucose lowering; (3) insulin implants (4 U/day) and oral glucose; (4) insulin implants (4 U/day) and oral sucrose; (5) control implants and oral glucose, and (6) control implants and oral sucrose. RESULTS: Insulin treatment at both doses reduced neointimal area (p < 0.001) 14 days after injury in rats receiving oral glucose but not in those receiving oral sucrose. Oral glucose, without insulin, had no effect on neointimal formation, whereas oral sucrose increased neointimal growth (p < 0.05). Oral sucrose (p < 0.05) but not oral glucose decreased insulin sensitivity measured with hyperinsulinemic clamps. CONCLUSIONS: (1) Insulin decreases neointimal growth after arterial injury independent of glucose-lowering or oral glucose administration and (2) oral sucrose per se affects neointimal growth.

Insulin increases reendothelialization and inhibits cell migration and neointimal growth after arterial injury.

OBJECTIVE: Insulin has both growth-promoting and protective vascular effects in vitro, however the predominant effect in vivo is unclear. We investigated the effects of insulin in vivo on neointimal growth after arterial injury. METHODS AND RESULTS: Rats were given subcutaneous control (C) or insulin implants (3U/d;I) 3 days before arterial (carotid or aortic) balloon catheter injury. Normoglycemia was maintained by oral glucose and, after surgery, by intraperitoneal glucose infusion (saline in C). Insulin decreased intimal area (P<0.01) but did not change intimal cell proliferation or apoptosis. However, insulin inhibited cell migration into the intima (P<0.01) and increased expression of smooth muscle cell (SMC) differentiation markers (P<0.05). Insulin also increased reendothelialization (P<0.01) and the number of circulating progenitor cells (P<0.05). CONCLUSIONS: These results are the first demonstration that insulin has a protective effect on both SMC and endothelium in vivo, resulting in inhibition of neointimal growth after vessel injury.

Characterization of cachexia in the human fibrosarcoma HT-1080 mouse tumour model.

BACKGROUND: Cancer cachexia is a complex metabolic disease with unmet medical need. Although many rodent models are available, none are identical to the human disease. Therefore, the development of new preclinical models that simulate some of the physiological, biochemical, and clinical characteristics of the human disease is valuable. The HT-1080 human fibrosarcoma tumour cell line was reported to induce cachexia in mice. Therefore, the purpose of this work was to determine how well the HT-1080 tumour model could recapitulate human cachexia and to examine its technical performance. Furthermore, the efficacy of ghrelin receptor activation via anamorelin treatment was evaluated, because it is one of few clinically validated mechanisms. METHODS: Female severe combined immunodeficient mice were implanted subcutaneously or heterotopically (renal capsule) with HT-1080 tumour cells. The cachectic phenotype was evaluated during tumour development, including body weight, body composition, food intake, muscle function (force and fatigue), grip strength, and physical activity measurements. Heterotopic and subcutaneous tumour histology was also compared. Energy balance was evaluated at standard and thermoneutral housing temperatures in the subcutaneous model. The effect of anamorelin (ghrelin analogue) treatment was also examined. RESULTS: The HT-1080 tumour model had excellent technical performance and was reproducible across multiple experimental conditions. Heterotopic and subcutaneous tumour cell implantation resulted in similar cachexia phenotypes independent of housing temperature. Tumour weight and histology was comparable between both routes of administration with minimal inflammation. Subcutaneous HT-1080 tumour-bearing mice presented with weight loss (decreased fat mass and skeletal muscle mass/fibre cross-sectional area), reduced food intake, impaired muscle function (reduced force and grip strength), and decreased spontaneous activity and voluntary wheel running. Key circulating inflammatory biomarkers were produced by the tumour, including growth differentiation factor 15, Activin A, interleukin 6, and TNF alpha. Anamorelin prevented but did not reverse anorexia and weight loss in the subcutaneous model. CONCLUSIONS: The subcutaneous HT-1080 tumour model displays many of the perturbations of energy balance and physical performance described in human cachexia, consistent with the production of key inflammatory factors. Anamorelin was most effective when administered early in disease progression. The HT-1080 tumour model is valuable for studying potential therapeutic targets for the treatment of cachexia.

GDF-15 Neutralization Alleviates Platinum-Based Chemotherapy-Induced Emesis, Anorexia, and Weight Loss in Mice and Nonhuman Primates.

Platinum-based cancer therapy is restricted by dose-limiting side effects and is associated with elevation of growth differentiation factor 15 (GDF-15). But whether this elevation contributes to such side effects has been unclear. Here, we explored the effects of GDF-15 blockade on platinum-based chemotherapy-induced emesis, anorexia, and weight loss in mice and/or nonhuman primate models. We found that circulating GDF-15 is higher in subjects with cancer receiving platinum-based chemotherapy and is positively associated with weight loss in colorectal cancer (NCT00609622). Further, chemotherapy agents associated with high clinical emetic score induce circulating GDF-15 and weight loss in mice. Platinum-based treatment-induced anorexia and weight loss are attenuated in GDF-15 knockout mice, while GDF-15 neutralization with the monoclonal antibody mAB1 improves survival. In nonhuman primates, mAB1 treatment attenuates anorexia and emesis. These results suggest that GDF-15 neutralization is a potential therapeutic approach to alleviate chemotherapy-induced side effects and improve the quality of life.

Pharmacologic or genetic activation of SIRT1 attenuates the fat-induced decrease in beta-cell function in vivo.

BACKGROUND: There is evidence that sirtuin 1 (SIRT1), a key regulator of nutrient metabolism, increases ß-cell secretory function. Excess circulating fat, as seen in obesity, has been shown to decrease ß-cell function, an effect that may involve decreased SIRT1 activity. Consequently, SIRT1 activation may increase ß-cell function in conditions of elevated plasma-free fatty acid levels. Here we attempted to attenuate the lipid-induced decrease in ß-cell function in vivo using pharmacological and genetic models of SIRT1 activation. METHODS: Our pharmacologic model involved 48 h intravenous infusion of Wistar rats with either saline or oleate with or without the SIRT1 activator resveratrol. Additionally, we used ß-cell-specific SIRT1 overexpressing (BESTO) mice and wild-type littermates infused for 48 h intravenously with either saline or oleate. In both models, the infusion period was followed by assessment of ß-cell function using the hyperglycemic clamp method. RESULTS: Lipid infusion resulted in a significant decrease in ß-cell function as expected in both rats (p < 0.05) and mice (p < 0.001). Both models of SIRT1 activation, which did not alter ß-cell function in the absence of fat, resulted in partial protection from the fat-induced decrease in ß-cell function (NS vs. control). CONCLUSION: These results suggest that SIRT1 is a therapeutic target in decreased ß-cell function specifically induced by fat.

Stimulation of muscle cell glucose uptake by resveratrol through sirtuins and AMPK.

Although recent studies in vitro and in vivo indicate that the polyphenol resveratrol (RSV) has anti-diabetic properties, the exact mechanisms involved are not known. In the present study, we examined the effects of RSV and the mechanism of regulation of glucose uptake in skeletal muscle cells. In L6 myotubes RSV (100 microM) induced maximum stimulation of glucose (2DG) uptake (201+/-8.90% of control, p<0.001), an effect that was similar to insulin action. RSV-stimulated glucose uptake was abolished by AMPK inhibition. In the presence of the sirtuin inhibitor nicotinamide, RSV-stimulated 2DG uptake and AMPK phosphorylation were abolished. RSV did not stimulate significant translocation of GLUT4 or GLUT1 transporters. However, treatment with indinavir, a GLUT4 specific inhibitor, blocked RSV-stimulated glucose uptake. We propose that RSV elevates glucose uptake in muscle cells through a mechanism that involves sirtuins and AMPK and possibly stimulation of GLUT4 transporter intrinsic activity.

High-dose metformin (420mg/kg daily p.o.) increases insulin sensitivity but does not affect neointimal thickness in the rat carotid balloon injury model of restenosis.

OBJECTIVE: Our laboratory has shown that insulin's effect to decrease neointimal thickness after arterial injury is greatly diminished in insulin resistant conditions. Thus, in these conditions, a better alternative to insulin could be to use an insulin sensitizing agent. Metformin, the most commonly prescribed insulin sensitizer, has a cardiovascular protective role. Therefore, the objective of this study was to investigate the potential benefit of metformin on neointimal area after arterial injury in a rat model of restenosis. METHODS: Rats fed with either normal or high fat diet and treated with or without oral metformin (420mg/kg daily) underwent carotid balloon injury. Effects of metformin on clamp-determined insulin sensitivity, vessel AMPK (AMP-activated protein kinase) phosphorylation (activation marker) and neointimal area were evaluated. RESULTS: Metformin increased insulin sensitivity, but did not affect neointimal thickness in either the normal fat or high fat diet-fed rats. Furthermore, metformin activated AMPK in uninjured but not in injured vessels. Similarly, 10mmol/L metformin inhibited proliferation and activated AMPK in smooth muscle cells of uninjured but not injured vessels, whereas 2mmol/L metformin did not have any effect. CONCLUSION: In rats, metformin does not decrease neointimal growth after arterial injury, despite increasing whole body insulin sensitivity.

Resveratrol prevents insulin resistance caused by short-term elevation of free fatty acids in vivo.

Elevated levels of plasma free fatty acids (FFA), which are commonly found in obesity, induce insulin resistance. FFA activate protein kinases including the proinflammatory IκBα kinase ß (IKKß), leading to serine phosphorylation of insulin receptor substrate 1 (IRS-1) and impaired insulin signaling. To test whether resveratrol, a polyphenol found in red wine, prevents FFA-induced insulin resistance, we used a hyperinsulinemic-euglycemic clamp with a tracer to assess hepatic and peripheral insulin sensitivity in overnight-fasted Wistar rats infused for 7 h with saline, Intralipid plus 20 U·mL(-1) heparin (IH; triglyceride emulsion that elevates FFA levels in vivo; 5.5 µL·min(-1)) with or without resveratrol (3 mg·kg(-1)·h(-1)), or resveratrol alone. Infusion of IH significantly decreased glucose infusion rate (GIR; P < 0.05) and peripheral glucose utilization (P < 0.05) and increased endogenous glucose production (EGP; P < 0.05) during the clamp compared with saline infusion. Resveratrol co-infusion, however, completely prevented the effects induced by IH infusion: it prevented the decreases in GIR (P < 0.05 vs. IH), peripheral glucose utilization (P < 0.05 vs. IH), and insulin-induced suppression of EGP (P < 0.05 vs. IH). Resveratrol alone had no effect. Furthermore, IH infusion increased serine (307) phosphorylation of IRS-1 in soleus muscle (∼30-fold, P < 0.001), decreased total IRS-1 levels, and decreased IκBα content, consistent with activation of IKKß. Importantly, all of these effects were abolished by resveratrol (P < 0.05 vs. IH). These results suggest that resveratrol prevents FFA-induced hepatic and peripheral insulin resistance and, therefore, may help mitigate the health consequences of obesity.

Latest approaches for the treatment of obesity.

INTRODUCTION: Obesity is a body weight disorder characterized by excess adiposity that increases the risk for developing co-morbidities such as type 2 diabetes. A large medical need exists for new anti-obesity treatments capable of promoting 10% or greater weight loss, with minimal side effects. AREAS COVERED: The authors describe the application of monogenic forms of rare obesity and genome-wide association studies in selecting critical pathways for drug discovery. Furthermore, they review in detail several pathways and pharmacological targets in the central nervous system (e.g., the leptin-melanocortin axis, the opioid system, GLP-1/GLP-1 system, and FGF21/FGFR1c/ß-Klotho axis) that play an important role in the regulation of feeding behavior and energy homeostasis. Special focus is given to new strategies that engage well-known targets via novel mechanisms in order to circumvent issues seen with previous drug candidates that failed in the clinic. Finally, the authors discuss the recent developments around fixed-dose combinations, targeted polypharmacology, and non-traditional combinations of drugs and devices. EXPERT OPINION: The future for new weight-loss approaches to treat obesity looks promising. Current therapies have shown modest effects on weight loss in the general obese population but will have greater impact in smaller homogeneous sub-populations of obese subjects using personalized medicine. Drug combinations that target multiple, complementary pathways have the potential to promote double-digit weight loss in a broader, heterogeneous patient population. Furthermore, the development of advanced subcutaneous delivery technologies has opened up opportunities to develop breakthrough peptide and biologic agents for the treatment of obesity.

In vivo effects of polyunsaturated, monounsaturated, and saturated fatty acids on hepatic and peripheral insulin sensitivity.

OBJECTIVE: Free fatty acids (FFAs) cause insulin resistance and are often elevated in obesity. Chronic ingestion of diets rich in saturated fat induces more insulin resistance than diets rich in unsaturated fat, however, it remains unclear whether different FFAs cause distinct levels of insulin resistance in the short-term, which is relevant to the feeding and fasting cycle. Protein kinase C (PKC)-δ is implicated in hepatic insulin resistance. Therefore, we investigated the effects of short-term elevation of fatty acids with different degrees of unsaturation on hepatic insulin action and liver PKC-δ membrane translocation, a marker of activation. MATERIALS/METHODS: Triglyceride emulsions of Soybean Oil+Heparin (polyunsaturated (POLY)), Olive Oil+Heparin (monounsaturated (MONO)), Lard Oil+Heparin (saturated (SATU)), or saline (SAL) were infused intravenously for 7h to elevate plasma FFA concentrations ~3-4 fold in rats. During the last 2h of infusion, a hyperinsulinemic-euglycemic clamp with tritiated glucose methodology was performed to examine hepatic and peripheral insulin sensitivity. RESULTS: Surprisingly, SATU, MONO, and POLY impaired peripheral insulin sensitivity (glucose utilization divided by insulin) to a similar extent. Furthermore, all lipids induced a similar degree of hepatic insulin resistance compared to SAL. Although there were changes in hepatic content of lipid metabolites, there were no significant differences in liver PKC-δ membrane translocation across fat groups. CONCLUSIONS: In summary, in the short-term, FFAs with different degrees of unsaturation impair peripheral insulin sensitivity and induce hepatic insulin resistance as well as hepatic PKC-δ translocation to the same extent.

Resveratrol activates duodenal Sirt1 to reverse insulin resistance in rats through a neuronal network.

Resveratrol improves insulin sensitivity and lowers hepatic glucose production (HGP) in rat models of obesity and diabetes, but the underlying mechanisms for these antidiabetic effects remain elusive. One process that is considered a key feature of resveratrol action is the activation of the nicotinamide adenine dinucleotide (NAD(+))-dependent deacetylase sirtuin 1 (SIRT1) in various tissues. However, the low bioavailability of resveratrol raises questions about whether the antidiabetic effects of oral resveratrol can act directly on these tissues. We show here that acute intraduodenal infusion of resveratrol reversed a 3 d high fat diet (HFD)-induced reduction in duodenal-mucosal Sirt1 protein levels while also enhancing insulin sensitivity and lowering HGP. Further, we found that duodenum-specific knockdown of Sirt1 expression for 14 d was sufficient to induce hepatic insulin resistance in rats fed normal chow. We also found that the glucoregulatory role of duodenally acting resveratrol required activation of Sirt1 and AMP-activated protein kinase (Ampk) in this tissue to initiate a gut-brain-liver neuronal axis that improved hypothalamic insulin sensitivity and in turn, reduced HGP. In addition to the effects of duodenally acting resveratrol in an acute 3 d HFD-fed model of insulin resistance, we also found that short-term infusion of resveratrol into the duodenum lowered HGP in two other rat models of insulin resistance--a 28 d HFD-induced model of obesity and a nicotinamide (NA)-streptozotocin (STZ)-HFD-induced model of mild type 2 diabetes. Together, these studies highlight the therapeutic relevance of targeting duodenal SIRT1 to reverse insulin resistance and improve glucose homeostasis in obesity and diabetes.