Treatment Of Diet-induced Obese Mice Research Articles

A small intestinal bile acid modulates the gut microbiome to improve host metabolic phenotypes following bariatric surgery

Bariatric surgical procedures such as sleeve gastrectomy (SG) provide effective type 2 diabetes (T2D) remission in human patients. Previous work demonstrated that gastrointestinal levels of the bacterial metabolite lithocholic acid (LCA) are decreased after SG in mice and humans. Here, we show that LCA worsens glucose tolerance and impairs whole-body metabolism. We also show that taurodeoxycholic acid (TDCA), which is the only bile acid whose concentration increases in the murine small intestine post-SG, suppresses the bacterial bile acid-inducible (bai) operon and production of LCA both invitro and invivo. Treatment of diet-induced obese mice with TDCA reduces LCA levels and leads to microbiome-dependent improvements in glucose handling. Moreover, TDCA abundance is decreased in small intestinal tissue from T2D patients. This work reveals that TDCA is an endogenous inhibitor of LCA production and suggests that TDCA may contribute to the glucoregulatory effects of bariatric surgery.

The novel adrenergic agonist ATR-127 targets skeletal muscle and brown adipose tissue to tackle diabesity and steatohepatitis

ObjectiveSimultaneous activation of β2- and β3-adrenoceptors (ARs) improves whole-body metabolism via beneficial effects in skeletal muscle and brown adipose tissue (BAT). Nevertheless, high-efficacy agonists simultaneously targeting these receptors whilst limiting activation of β1-ARs – and thus inducing cardiovascular complications – are currently non-existent. Therefore, we here developed and evaluated the therapeutic potential of a novel β2-and β3-AR, named ATR-127, for the treatment of obesity and its associated metabolic perturbations in preclinical models. MethodsIn the developmental phase, we assessed the impact of ATR-127's on cAMP accumulation in relation to the non-selective β-AR agonist isoprenaline across various rodent β-AR subtypes, including neonatal rat cardiomyocytes. Following these experiments, L6 muscle cells were stimulated with ATR-127 to assess the impact on GLUT4-mediated glucose uptake and intramyocellular cAMP accumulation. Additionally, in vitro, and in vivo assessments are conducted to measure ATR-127's effects on BAT glucose uptake and thermogenesis. Finally, diet-induced obese mice were treated with 5 mg/kg ATR-127 for 21 days to investigate the effects on glucose homeostasis, body weight, fat mass, skeletal muscle glucose uptake, BAT thermogenesis and hepatic steatosis. ResultsExposure of L6 muscle cells to ATR-127 robustly enhanced GLUT4-mediated glucose uptake despite low intramyocellular cAMP accumulation. Similarly, ATR-127 markedly increased BAT glucose uptake and thermogenesis both in vitro and in vivo. Prolonged treatment of diet-induced obese mice with ATR-127 dramatically improved glucose homeostasis, an effect accompanied by decreases in body weight and fat mass. These effects were paralleled by an enhanced skeletal muscle glucose uptake, BAT thermogenesis, and improvements in hepatic steatosis. ConclusionsOur results demonstrate that ATR-127 is a highly effective, novel β2- and β3-ARs agonist holding great therapeutic promise for the treatment of obesity and its comorbidities, whilst potentially limiting cardiovascular complications. As such, the therapeutic effects of ATR-127 should be investigated in more detail in clinical studies.

Central inhibition of HDAC6 re-sensitizes leptin signaling during obesity to induce profound weight loss

Leptin resistance during excess weight gain significantly contributes to the recidivism of obesity to leptin-based pharmacological therapies. The mechanisms underlying the inhibition of leptin receptor (LepR) signaling during obesity are still elusive. Here, we report that histone deacetylase 6 (HDAC6) interacts with LepR, reducing the latter's activity, and that pharmacological inhibition of HDAC6 activity disrupts this interaction and augments leptin signaling. Treatment of diet-induced obese mice with blood-brain barrier (BBB)-permeable HDAC6 inhibitors profoundly reduces food intake and leads to potent weight loss without affecting the muscle mass. Genetic depletion of Hdac6 in Agouti-related protein (AgRP)-expressing neurons or administration with BBB-impermeable HDAC6 inhibitors results in a lack of such anti-obesity effect. Together, these findings represent the first report describing a mechanistically validated and pharmaceutically tractable therapeutic approach to directly increase LepR activity as well as identifying centrally but not peripherally acting HDAC6 inhibitors as potent leptin sensitizers and anti-obesity agents.

Hepatic targeting of the centrally active cannabinoid 1 receptor (CB1R) blocker rimonabant via PLGA nanoparticles for treating fatty liver disease and diabetes.

Over-activation of the endocannabinoid/CB1R system is a hallmark feature of obesity and its related comorbidities, most notably type 2 diabetes (T2D), and non-alcoholic fatty liver disease (NAFLD). Although the use of drugs that widely block the CB1R was found to be highly effective in treating all metabolic abnormalities associated with obesity, they are no longer considered a valid therapeutic option due to their adverse neuropsychiatric side effects. Here, we describe a novel nanotechnology-based drug delivery system for repurposing the abandoned first-in-class global CB1R antagonist, rimonabant, by encapsulating it in polymeric nanoparticles (NPs) for effective hepatic targeting of CB1Rs, enabling effective treatment of NAFLD and T2D. Rimonabant-encapsulated NPs (Rimo-NPs) were mainly distributed in the liver, spleen, and kidney, and only negligible marginal levels of rimonabant were found in the brain of mice treated by iv/ip administration. In contrast to freely administered rimonabant treatment, no CNS-mediated behavioral activities were detected in animals treated with Rimo-NPs. Chronic treatment of diet-induced obese mice with Rimo-NPs resulted in reduced hepatic steatosis and liver injury as well as enhanced insulin sensitivity, which were associated with enhanced cellular uptake of the formulation into hepatocytes. Collectively, we successfully developed a method of encapsulating the centrally acting CB1R blocker in NPs with desired physicochemical properties. This novel drug delivery system allows hepatic targeting of rimonabant to restore the metabolic advantages of blocking CB1R in peripheral tissues, especially in the liver, without the negative CB1R-mediated neuropsychiatric side effects.

Using Target Engagement Biomarkers to Predict Clinical Efficacy of MetAP2 Inhibitors.

Target-engagement pharmacodynamic (PD) biomarkers are valuable tools in the prioritization of drug candidates, especially for novel, first-in-class mechanisms whose robustness to alter disease outcome is unknown. Methionine aminopeptidase 2 (MetAP2) is a cytosolic metalloenzyme that cleaves the N-terminal methionine from nascent proteins. Inhibition of MetAP2 leads to weight loss in obese rodents, dogs and humans. However, there is a need to develop efficacious compounds that specifically inhibit MetAP2 with an improved safety profile. The objective of this study was to identify a PD biomarker for selecting potent, efficacious compounds and for predicting clinical efficacy that would result from inhibition of MetAP2. Here we report the use of NMet14-3-3γ for this purpose. Treatment of primary human cells with MetAP2 inhibitors resulted in an approx. 10-fold increase in NMet14-3-3γ levels. Furthermore, treatment of diet-induced obese mice with these compounds reduced body weight (approx. 20%) and increased NMet14-3-3γ (approx. 15-fold) in adipose tissues. The effects on target engagement and body weight increased over time and were dependent on dose and administration frequency of compound. The relationship between compound concentration in plasma, NMet14-3-3γ in tissue, and reduction of body weight in obese mice was used to generate a pharmacokinetic-pharmacodynamic-efficacy model for predicting efficacy of MetAP2 inhibitors in mice. We also developed a model for predicting weight loss in humans using a target engagement PD assay that measures inhibitor-bound MetAP2 in blood. In summary, MetAP2 target engagement biomarkers can be used to select efficacious compounds and predict weight loss in humans. SIGNIFICANCE STATEMENT: The application of target engagement pharmacodynamic biomarkers during drug development provides a means to determine the dose required to fully engage the intended target and an approach to connect the drug target to physiological effects. This work exemplifies the process of using target engagement biomarkers during preclinical research to select new drug candidates and predict clinical efficacy. We determine concentration of MetAP2 antiobesity compounds needed to produce pharmacological activity in primary human cells and in target tissues from an appropriate animal model and establish key relationships between pharmacokinetics, pharmacodynamics, and efficacy, including the duration of effects after drug administration. The biomarkers described here can aid decision-making in early clinical trials of MetAP2 inhibitors for the treatment of obesity.

Long-Acting and Selective Oxytocin Peptide Analogs Show Antidiabetic and Antiobesity Effects in Male Mice.

Oxytocin (OXT) has been shown to suppress appetite, induce weight loss, and improve glycemic control and lipid metabolism in several species, including humans, monkeys, and rodents. However, OXT’s short half-life in circulation and lack of receptor selectivity limit its application and efficacy. In this study, we report an OXT peptide analog (OXTGly) that is potent and selective for the OXT receptor (OXTR). OXT, but not OXTGly, activated vasopressin receptors in vitro and acutely increased blood pressure in vivo when administered IP. OXT suppressed food intake in mice, whereas OXTGly had a moderate effect on food intake when administered IP or intracerebroventricularly. Both OXT (IP) and OXTGly (IP) improved glycemic control in glucose tolerance tests. Additionally, both OXT (IP) and OXTGly (IP) stimulated insulin, glucagon-like peptide 1, and glucagon secretion in mice. We generated lipid-conjugated OXT (acylated-OXT) and OXTGly (acylated-OXTGly) and demonstrated that these molecules have significantly extended half-lives in vivo. Compared with OXT, 2-week treatment of diet-induced obese mice with acylated-OXT [subcutaneous(ly) (SC)] resulted in enhanced body weight reduction, an improved lipid profile, and gene expression changes consistent with increased lipolysis and decreased gluconeogenesis. Treatment with acylated-OXTGly (SC) also resulted in a statistically significant weight loss, albeit to a lesser degree compared with acylated-OXT treatment. In conclusion, we demonstrate that selective activation of the OXTR pathway results in both acute and chronic metabolic benefits, whereas potential activation of vasopressin receptors by nonselective OXT analogs causes physiological stress that contributes to additional weight loss.

Role of microRNA in CB1 antagonist–mediated regulation of adipose tissue macrophage polarization and chemotaxis during diet-induced obesity

Although cannabinoid receptor 1 (CB1) antagonists have been shown to attenuate diet-induced obesity (DIO) and associated inflammation, the precise molecular mechanisms involved are not clear. In the current study, we investigated the role of microRNA (miR) in the regulation of adipose tissue macrophage (ATM) phenotype following treatment of DIO mice with the CB1 antagonist SR141716A. DIO mice were fed high-fat diet (HFD) for 12 weeks and then treated daily with SR141716A (10 mg/kg) for 4 weeks while continuing HFD. Treated mice experienced weight loss, persistent reduction in fat mass, improvements in metabolic profile, and decreased adipose inflammation. CB1 blockade resulted in down-regulation of several miRs in ATMs, including the miR-466 family and miR-762. Reduced expression of the miR-466 family led to induction of anti-inflammatory M2 transcription factors KLF4 and STAT6, whereas down-regulation of miR-762 promoted induction of AGAP-2, a negative regulator of the neuroimmune retention cues, Netrin-1 and its coreceptor UNC5B. Furthermore, treatment of primary macrophages with SR141716A up-regulated KLF4 and STAT6, reduced secretion of Netrin-1, and increased migration toward the lymph node chemoattractant CCL19. These studies demonstrate for the first time that CB1 receptor blockade attenuates DIO-associated inflammation through alterations in ATM miR expression that promote M2 ATM polarization and macrophage egress from adipose tissue. The current study also identifies additional novel therapeutic targets for diet-induced obesity and metabolic disorder.

Development of Oral Bioavailable Nicotinamide N-Methyltransferase Inhibitors to Reduce Adiposity, Insulin Resistance, and Hyperglycemia

There is a critical need for new mechanism-of-action drugs that reduce adiposity, a prime driver of type 2 diabetes. A novel target to treat adiposity and reverse type 2 diabetes is nicotinamide-N-methyltransferase (NNMT), a cytosolic enzyme with newly identified roles in regulating adipose tissue metabolism and energy homeostasis. We have recently developed first-in-class small molecule NNMT inhibitors and characterized physicochemical, pharmacological, pharmacokinetic (PK), and off-target safety profiles of these inhibitors to identify a drug-like efficacious, orally bioavailable, and safe lead candidate for IND-enabling studies. Our first generation of highly selective, stable, and soluble compounds demonstrated excellent PK properties, including high oral bioavailability (>90%) and half-life of 3 hours in rats. Finally, the efficacy of promising NNMT inhibitors at modulating adiposity and type 2 diabetes endpoints (e.g., fat mass, oral glucose tolerance, adipokine levels, circulating lipids) were assessed using diet-induced obese (DIO) mice maintained on a high-fat diet. Systemic treatment of DIO mice with a potent NNMT inhibitor significantly reduced body weight and white adipose tissue mass, decreased adipocyte cell size, and lowered plasma cholesterol levels (p<0.05). Notably, administration of NNMT inhibitors did not alter total food intake nor produce any observable adverse effects. These results support continued development of small molecule NNMT inhibitors as therapeutics to lessen adiposity and lower the burden of adiposity-associated type 2 diabetes. Disclosure H. Neelakantan: None. S. Watowich: None.

Selective and membrane-permeable small molecule inhibitors of nicotinamide N-methyltransferase reverse high fat diet-induced obesity in mice

There is a critical need for new mechanism-of-action drugs that reduce the burden of obesity and associated chronic metabolic comorbidities. A potentially novel target to treat obesity and type 2 diabetes is nicotinamide-N-methyltransferase (NNMT), a cytosolic enzyme with newly identified roles in cellular metabolism and energy homeostasis. To validate NNMT as an anti-obesity drug target, we investigated the permeability, selectivity, mechanistic, and physiological properties of a series of small molecule NNMT inhibitors. Membrane permeability of NNMT inhibitors was characterized using parallel artificial membrane permeability and Caco-2 cell assays. Selectivity was tested against structurally-related methyltransferases and nicotinamide adenine dinucleotide (NAD+) salvage pathway enzymes. Effects of NNMT inhibitors on lipogenesis and intracellular levels of metabolites, including NNMT reaction product 1-methylnicotianamide (1-MNA) were evaluated in cultured adipocytes. Effects of a potent NNMT inhibitor on obesity measures and plasma lipid were assessed in diet-induced obese mice fed a high-fat diet. Methylquinolinium scaffolds with primary amine substitutions displayed high permeability from passive and active transport across membranes. Importantly, methylquinolinium analogues displayed high selectivity, not inhibiting related SAM-dependent methyltransferases or enzymes in the NAD+ salvage pathway. NNMT inhibitors reduced intracellular 1-MNA, increased intracellular NAD+ and S-(5′-adenosyl)-l-methionine (SAM), and suppressed lipogenesis in adipocytes. Treatment of diet-induced obese mice systemically with a potent NNMT inhibitor significantly reduced body weight and white adipose mass, decreased adipocyte size, and lowered plasma total cholesterol levels. Notably, administration of NNMT inhibitors did not impact total food intake nor produce any observable adverse effects. These results support development of small molecule NNMT inhibitors as therapeutics to reverse diet-induced obesity and validate NNMT as a viable target to treat obesity and related metabolic conditions. Increased flux of key cellular energy regulators, including NAD+ and SAM, may potentially define the therapeutic mechanism-of-action of NNMT inhibitors.

Development of Dihydroxyphenyl Sulfonylisoindoline Derivatives as Liver-Targeting Pyruvate Dehydrogenase Kinase Inhibitors.

Pyruvate dehydrogenase kinases 1-4 (PDK1-4) negatively control activity of the pyruvate dehydrogenase complex (PDC) and are up-regulated in obesity, diabetes, heart failure, and cancer. We reported earlier two novel pan-PDK inhibitors PS8 [4-((5-hydroxyisoindolin-2-yl)sulfonyl)benzene-1,3-diol] (1) and PS10 [2-((2,4-dihydroxyphenyl)sulfonyl)isoindoline-4,6-diol] (2) that targeted the ATP-binding pocket in PDKs. Here, we developed a new generation of PDK inhibitors by extending the dihydroxyphenyl sulfonylisoindoline scaffold in 1 and 2 to the entrance region of the ATP-binding pocket in PDK2. The lead inhibitor (S)-3-amino-4-(4-((2-((2,4-dihydroxyphenyl)sulfonyl)isoindolin-5-yl)amino)piperidin-1-yl)-4-oxobutanamide (17) shows a ∼8-fold lower IC50 (58 nM) than 2 (456 nM). In the crystal structure, the asparagine moiety in 17 provides additional interactions with Glu-262 from PDK2. Treatment of diet-induced obese mice with 17 resulted in significant liver-specific augmentation of PDC activity, accompanied by improved glucose tolerance and drastically reduced hepatic steatosis. These findings support 17 as a potential glucose-lowering therapeutic targeting liver for obesity and type 2 diabetes.

Withaferin A is a leptin sensitizer with strong antidiabetic properties in mice.

The increasing global prevalence of obesity and its associated disorders point to an urgent need for the development of novel and effective therapeutic strategies that induce healthy weight loss. Obesity is characterized by hyperleptinemia and central leptin resistance. In an attempt to identify compounds that could reverse leptin resistance and thus promote weight loss, we analyzed a library of small molecules with mRNA expression profiles similar to that of celastrol, a naturally-occurring compound we previously identified as a leptin sensitizer. By this process we identified another natural compound, withaferin A, that also acts as a leptin sensitizer. We found that withaferin A treatment of diet-induced obese mice resulted in a 20-25% reduction of body weight, while also decreasing obesity-associated abnormalities including hepatic steatosis. Withaferin A marginally affects the body weight of ob/ob and db/db mice, which are both deficient in leptin signaling. In addition, withaferin A, unlike celastrol, has beneficial effects on glucose metabolism independently from its leptin-sensitizing effect. Our results show that the metabolic abnormalities of diet-induced obesity can be mitigated by sensitizing animals to endogenous leptin, and indicate that withaferin A is a potential leptin sensitizer with additional anti-diabetic actions.

Methylsulfonylmethane (MSM), an organosulfur compound, is effective against obesity-induced metabolic disorders in mice

Methylsulfonylmethane (MSM), an organosulfur compound, has been used as a dietary supplement that can improve various metabolic diseases. However, the effect of MSM on obesity-linked metabolic disorders remains unclear. The goal of the current study is to determine whether MSM has beneficial effects on glucose and lipid homeostasis in obesity-associated pathophysiologic states. High-fat diet-induced obese (DIO) and genetically obese diabetic db/db mice treated with MSM (1%–5% v/v, by drinking water) were studied. Metabolic parameters involved in glucose and lipid metabolism were determined. Treatment of DIO mice with MSM leads to a significant decrease in blood glucose levels. DIO mice treated with MSM are hypersensitive to insulin, as evidenced by decreased serum insulin and an increase in the area above the curve during an ITT. Concurrently, MSM reduces hepatic triglyceride and cholesterol contents in DIO mice. These effects are accompanied by reductions in gene expression of key molecules involved in lipogenesis and inflammation. FACS analysis reveals that MSM markedly increases the frequency of B cells and decreases the frequency of myeloid cells in peripheral blood and in bone marrow. Moreover, overnutrition-induced changes of femur microarchitecture are restored by MSM. In db/db mice, a marked impairment in glucose and lipid metabolic profiles is notably ameliorated when MSM is supplemented. These data suggest that MSM has beneficial effects on multiple metabolic dysfunctions, including hyperglycemia, hyperinsulinemia, insulin resistance, and inflammation. Thus, MSM could be the therapeutic option for the treatment of obesity-related metabolic disorders such as type 2 diabetes and fatty liver diseases.

Impaired compensation to femoral artery ligation in diet-induced obese mice is primarily mediated via suppression of collateral growth by Nox2 and p47phox.

The present study was undertaken to establish the role of NADPH oxidase (Nox) in impaired vascular compensation to arterial occlusion that occurs in the presence of risk factors associated with oxidative stress. Diet-induced obese (DIO) mice characterized by multiple comorbidities including diabetes and hyperlipidemia were used as a preclinical model. Arterial occlusion was induced by distal femoral artery ligation in lean and DIO mice. Proximal collateral arteries were identified as the site of major (∼70%) vascular resistance to calf perfusion by distal arterial pressures, which decreased from ∼80 to ∼30 mmHg with ligation in both lean and DIO mice. Two weeks after ligation, significant vascular compensation occurred in lean but not DIO mice as evidenced by increased perfusion (147 ± 48% vs. 49 ± 29%) and collateral diameter (151 ± 30% vs. 44 ± 17%). Vascular mRNA expression of p22(phox), Nox2, Nox4, and p47(phox) were all increased in DIO mice. Treatment of DIO mice with either apocynin or Nox2ds-tat or with whole body ablation of either Nox2 or p47(phox) ameliorated the impairment in both collateral growth and hindlimb perfusion. Multiparametric flow cytometry analysis demonstrated elevated levels of circulating monocytes in DIO mice without impaired mobilization and demargination after femoral artery ligation. These results establish collateral resistance as the major limitation to calf perfusion in this preclinical model, demonstrate than monocyte mobilization and demarginatin is not suppressed, implicate Nox2-p47(phox) interactions in the impairment of vascular compensation to arterial occlusion in DIO mice, and suggest that selective Nox component suppression/inhibition may be effective as either primary or adjuvant therapy for claudicants.

CD40-TRAF6 pathway as a therapeutic target in obesity-associated metabolic dysfunction

Objective: Inflammation contributes to the pathogenesis of obesity-associated metabolic dysregulation and co-stimulatory molecules, including CD40, are important mediators of this process. This study aimed to reveal the role of CD40 and its signaling intermediates, TNF-Receptor-Associated-Factors (TRAFs), in diet-induced obesity (DIO). Methods: The DIO model was performed in CD40-deficient or -sufficient mice as well as in mice with deficient CD40-TRAF2/3/5- or CD40-TRAF6-signaling in MHCII+ cells. Several metabolic parameters were measured and subcutaneous and gonadal adipose tissues (AT) and liver were isolated. FACS analysis of the stromal vascular fraction from AT as well as qPCR-analysis and histochemistry of the isolated tissues were performed. Virtual Ligand Screening, TRAF6 C-domain expression, purification and binding analyses were also performed to construct a CD40-TRAF6 signalling inhibitor that was used as therapy in DIO mice. Results: CD40ko mice were characterized by worsened insulin resistance linked to excessive AT inflammation, increased accumulation of CD8+ T-cells and M1 macrophages in AT, and enhanced hepatosteatosis. In contrast, mice with deficient CD40-TRAF6 signaling in MHCII+ cells displayed no insulin resistance and showed a reduction in both AT inflammation and hepatosteatosis in DIO, whereas the mice with deficient CD40-TRAF2/3/5 signaling excibited a phenotype similar to the CD40ko mice. Treatment of DIO mice with a small-compound that blocks CD40-TRAF6 interactions displayed improved insulin sensitivity, reduced AT inflammation and decreased hepatosteatosis. Conclusions: The CD40-TRAF6 pathway contributes whereas the CD40-TRAF2/3/5 pathway protects from obesity-associated metabolic dysfunction. Improvement of metabolic dysregulation by a newly-developed CD40-TRAF6-pathway inhibitor may represent a therapeutic innovation in the field of immunometabolism.

CCR2 antagonist CCX140-B provides renal and glycemic benefits in diabetic transgenic human CCR2 knockin mice

Chemokine (C-C motif) receptor 2 (CCR2) is central for the migration of monocytes into inflamed tissues. The novel CCR2 antagonist CCX140-B, which is currently in two separate phase 2 clinical trials in diabetic nephropathy, has recently been shown to reduce hemoglobin A1c and fasting blood glucose levels in type 2 diabetics. In this report, we describe the effects of this compound on glycemic and renal function parameters in diabetic mice. Since CCX140-B has a low affinity for mouse CCR2, transgenic human CCR2 knockin mice were generated and rendered diabetic with either a high-fat diet (diet-induced obesity) or by deletion of the leptin receptor gene (db/db). CCX140-B treatment in both models resulted in decreased albuminuria, which was associated with decreased glomerular hypertrophy and increased podocyte density. Moreover, treatment of diet-induced obese mice with CCX140-B resulted in decreased levels of fasting blood glucose and insulin, normalization of homeostatic model assessment of insulin resistance values, and decreased numbers of adipose tissue inflammatory macrophages. Unlike other CCR2 antagonists, CCX140-B had no effect on plasma levels of the CCR2 ligand CCL2 or on the numbers of blood monocytes. These results support the ongoing evaluation of this molecule in diabetic subjects with impaired renal function.

A Liver-Selective LXR Inverse Agonist That Suppresses Hepatic Steatosis

Fatty liver, which often accompanies obesity and type 2 diabetes, frequently leads to a much more debilitating hepatic disease including non-alcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma. Current pharmacological therapies lack conclusive efficacy and thus treatment options are limited. Novel therapeutics that suppress either hepatic lipogenesis and/or hepatic inflammation may be useful. Here, we describe the development of the first selective synthetic LXR inverse agonist (SR9238) and demonstrate that this compound effectively suppresses hepatic lipogenesis, inflammation, and hepatic lipid accumulation in a mouse model of non-alcoholic hepatosteatosis. SR9238 displays high potency for both LXRα and LXRβ (40-200 nM IC50) and was designed to display liver specificity so as to avoid potential side effects due to suppression of LXR in the periphery. Unexpectedly, treatment of diet-induced obese mice with SR9238 suppressed plasma cholesterol levels. These data indicate that liver-selective LXR inverse agonists may hold utility in the treatment of liver disease.

Inhibition of Serine Palmitoyl Transferase I Reduces Cardiac Ceramide Levels and Increases Glycolysis Rates following Diet-Induced Insulin Resistance

ObjectiveDiet-induced obesity (DIO) leads to an accumulation of intra-myocardial lipid metabolites implicated in causing cardiac insulin resistance and contractile dysfunction. One such metabolite is ceramide, and our aim was to determine the effects of inhibiting de novo ceramide synthesis on cardiac function and insulin stimulated glucose utilization in mice subjected to DIO.Materials and MethodsC57BL/6 mice were fed a low fat diet or subjected to DIO for 12 weeks, and then treated for 4 weeks with either vehicle control or the serine palmitoyl transferase I (SPT I) inhibitor, myriocin. In vivo cardiac function was assessed via ultrasound echocardiography, while glucose metabolism was assessed in isolated working hearts.ResultsDIO was not associated with an accumulation of intra-myocardial ceramide, but rather, an accumulation of intra-myocardial DAG (2.63±0.41 vs. 4.80±0.97 nmol/g dry weight). Nonetheless, treatment of DIO mice with myriocin decreased intra-myocardial ceramide levels (50.3±7.7 vs. 26.9±2.7 nmol/g dry weight) and prevented the DIO-associated increase in intra-myocardial DAG levels. Interestingly, although DIO impaired myocardial glycolysis rates (7789±1267 vs. 2671±326 nmol/min/g dry weight), hearts from myriocin treated DIO mice exhibited an increase in glycolysis rates.ConclusionsOur data reveal that although intra-myocardial ceramide does not accumulate following DIO, inhibition of de novo ceramide synthesis nonetheless reduces intra-myocardial ceramide levels and prevents the accumulation of intra-myocardial DAG. These effects improved the DIO-associated impairment of cardiac glycolysis rates, suggesting that SPT I inhibition increases cardiac glucose utilization.

Regulation of circadian behaviour and metabolism by synthetic REV-ERB agonists

Synchronizing rhythms of behavior and metabolic processes is important for cardiovascular health and preventing metabolic diseases. The nuclear receptors REV-ERBα and REV-ERBβ play an integral role in regulating the expression of core clock proteins driving rhythms in activity and metabolism. Here we describe the identification of potent synthetic REV-ERB agonists with in vivo activity. Administration of synthetic REV-ERB ligands alters circadian behavior and the circadian pattern of core clock gene expression in the hypothalami of mice. The circadian pattern of expression of an array of metabolic genes in the liver, skeletal muscle, and adipose tissue was also altered resulting in increased energy expenditure. Treatment of diet-induced obese mice with a REV-ERB agonist decreased obesity by reducing fat mass and markedly improving dyslipidemia and hyperglycemia. These results suggest that synthetic REV-ERB ligands that pharmacologically target the circadian rhythm may hold utility in the treatment of sleep disorders as well as metabolic diseases.

Bone morphogenetic protein 7 (BMP7) reverses obesity and regulates appetite through a central mTOR pathway

Body weight is regulated by coordinating energy intake and energy expenditure. Transforming growth factor β (TGFβ)/bone morphogenetic protein (BMP) signaling has been shown to regulate energy balance in lower organisms, but whether a similar pathway exists in mammals is unknown. We have previously demonstrated that BMP7 can regulate brown adipogenesis and energy expenditure. In the current study, we have uncovered a novel role for BMP7 in appetite regulation. Systemic treatment of diet-induced obese mice with BMP7 resulted in increased energy expenditure and decreased food intake, leading to a significant reduction in body weight and improvement of metabolic syndrome. Similar degrees of weight loss with reduced appetite were also observed in BMP7-treated ob/ob mice, suggesting a leptin-independent mechanism utilized by BMP7. Intracerebroventricular administration of BMP7 to mice led to an acute decrease in food intake, which was mediated, at least in part, by a central rapamycin-sensitive mTOR-p70S6 kinase pathway. Together, these results underscore the importance of BMP7 in regulating both food intake and energy expenditure, and suggest new therapeutic approaches for obesity and its comorbidities.

Vitamin D receptor agonist doxercalciferol modulates dietary fat-induced renal disease and renal lipid metabolism

Diet-induced obesity (DIO) and insulin resistance in mice are associated with proteinuria, renal mesangial expansion, accumulation of extracellular matrix proteins, and activation of oxidative stress, proinflammatory cytokines, profibrotic growth factors, and the sterol regulatory element binding proteins, SREBP-1 and SREBP-2, that mediate increases in fatty acid and cholesterol synthesis. The purpose of the present study was to determine whether treatment of DIO mice with the vitamin D receptor (VDR) agonist doxercalciferol (1α-hydroxyvitamin D2) prevents renal disease. Our results indicate that treatment of DIO mice with the VDR agonist decreases proteinuria, podocyte injury, mesangial expansion, and extracellular matrix protein accumulation. The VDR agonist also decreases macrophage infiltration, oxidative stress, proinflammatory cytokines, and profibrotic growth factors. Furthermore, the VDR agonist also prevents the activation of the renin-angiotensin-aldosterone system including the angiotensin II type 1 receptor and the mineralocorticoid receptor. An additional novel finding of our study is that activation of VDR results in decreased accumulation of neutral lipids (triglycerides and cholesterol) and expression of adipophilin in the kidney by decreasing SREBP-1 and SREBP-2 expression and target enzymes that mediate fatty acid and cholesterol synthesis and increasing expression of the farnesoid X receptor. This study therefore demonstrates multiple novel effects of VDR activation in the kidney which prevent renal manifestations of DIO in the kidney.