Physiological characterization of a novel PPAR pan agonist, 2-(4-(5,6-methylenedioxybenzo[d]thiazol-2-yl)-2-methylphenoxy)-2-methylpropanoic acid (MHY2013).
ABSTRACT: Recently, agonists targeting multiple peroxisome proliferator-activated receptors (PPARs) have been developed to improve metabolic disorders and minimize the side effects of selective PPAR agonists such as weight gain and dyslipidemia. We newly synthesized six 2-methyl-2-(o-tolyloxy)propanoic acid derivatives based on the structure of a well-known PPAR pan agonist, bezafibrate. Of six compounds, MHY2013 was screened as the strongest activator of three PPAR subtypes based on protein docking simulation and luciferase assays. When treated orally in db/db mice, MHY2013 ameliorated obesity-induced insulin resistance, dyslipidemia, and hepatic steatosis without changes of the body weight and levels of liver and kidney injury markers. MHY2013 decreased the serum triglyceride and fatty acid levels, which is associated with an increase in fatty acid oxidation signaling in the liver and thermogenic signaling on white adipose tissue, respectively. Furthermore, MHY2013 markedly increased serum levels of insulin-sensitizing hormones including fibroblast growth factor 21 (FGF21) and adiponectin. In conclusion, this study suggests that, MHY2013 is a novel PPAR pan agonist that improves obesity-induced insulin resistance, dyslipidemia and hepatic steatosis and elevates insulin-sensitizing hormones in the blood.
Project description:The mechanisms underlying the enhancement of insulin sensitivity by selective peroxisome proliferator-activated receptor ? modulators (sPPAR?Ms) are still not completely known. Here, the representative sPPAR?M, INT131, was used as a probe to investigate the insulin-sensitizing mechanisms of sPPAR?M in the context of tissue selective compound distribution and PPAR? regulation. First, 30 mg kg<sup>-1</sup> INT131 was observed to produce an insulin-sensitizing effect comparable to that of 10 mg kg<sup>-1</sup> rosiglitazone (RSG) in both db/db and DIO mice using the oral glucose and insulin tolerance tests. Similar to RSG, INT131 significantly increased brown adipose tissue (BAT) mass and adipocyte size and up-regulated the expression of BAT-specific genes. Compared with RSG, INT131 exhibited greater potency in inducing white adipose tissue (WAT) browning, decreasing adipocyte size, and increasing BAT-specific and function-related gene expression in subcutaneous WAT (sWAT). However, it did not induce hepatomegaly or hepatic steatosis, which is associated with lower levels of lipogenic genes expression. Pharmacokinetic analysis reveals that in contrast with RSG, INT131 shows higher Cmax, and much longer residency time (AUC<sub>0-12h</sub>), as well relatively lower elimination rate in adipose tissues and skeletal muscle, this demonstrated INT131 distributed predominantly in adipose tissue. Whereas, INT131 was less abundant in the liver. These results thus suggest that the tissue-selective distribution underlies INT131's selective PPAR? modulation. Compounds favoring adipose tissue may aid in development of better, safer sPPAR?M to address the insulin resistance of diabetes.
Project description:The cJun N-terminal Kinases (JNK) emerged as a major link between obesity and insulin resistance, but their role in the loss of pancreatic ?-cell mass and function driving the progression from insulin resistance to type-2 diabetes and in the complications of diabetes was not investigated to the same extent. Furthermore, it was shown that pan-JNK inhibition exacerbates kidney damage in the db/db model of obesity-driven diabetes. Here we investigate the role of JNK1 in the db/db model of obesity-driven type-2 diabetes. Mice with systemic ablation of JNK1 (JNK1<sup>-/-</sup>) were backcrossed for more than 10 generations in db/+ C57BL/KS mice to generate db/db-JNK1<sup>-/-</sup> mice and db/db control mice. To define the role of JNK1 in the loss of ?-cell mass and function occurring during obesity-driven diabetes we performed comprehensive metabolic phenotyping, evaluated steatosis and metabolic inflammation, performed morphometric and cellular composition analysis of pancreatic islets, and evaluated kidney function in db/db-JNK1<sup>-/-</sup> mice and db/db controls. db/db-JNK1<sup>-/-</sup> mice and db/db control mice developed insulin resistance, fatty liver, and metabolic inflammation to a similar extent. However, db/db-JNK1<sup>-/-</sup> mice displayed better glucose tolerance and improved insulin levels during glucose tolerance test, higher pancreatic insulin content, and larger pancreatic islets with more ?-cells than db/db mice. Finally, albuminuria, kidney histopathology, kidney inflammation and oxidative stress in db/db-JNK1<sup>-/-</sup> mice and in db/db mice were similar. Our data indicate that selective JNK1 ablation improves glucose tolerance in db/db mice by reducing the loss of functional ?-cells occurring in the db/db mouse model of obesity-driven diabetes, without significantly affecting metabolic inflammation, steatosis, and insulin sensitivity. Furthermore, we have found that, differently from what previously reported for pan-JNK inhibitors, selective JNK1 ablation does not exacerbate kidney dysfunction in db/db mice. We conclude that selective JNK1 inactivation may have a superior therapeutic index than pan-JNK inhibition in obesity-driven diabetes.
Project description:The hepatic glucose fasting response is gaining traction as a therapeutic pathway to enhance hepatic and whole-host metabolism. However, the mechanisms underlying these metabolic effects remain unclear. Here, we demonstrate the epidermal-type lipoxygenase, eLOX3 (encoded by its gene, Aloxe3), is a potentially novel effector of the therapeutic fasting response. We show that Aloxe3 is activated during fasting, glucose withdrawal, or trehalose/trehalose analogue treatment. Hepatocyte-specific Aloxe3 expression reduced weight gain and hepatic steatosis in diet-induced and genetically obese (db/db) mouse models. Aloxe3 expression, moreover, enhanced basal thermogenesis and abrogated insulin resistance in db/db diabetic mice. Targeted metabolomics demonstrated accumulation of the PPAR? ligand 12-KETE in hepatocytes overexpressing Aloxe3. Strikingly, PPAR? inhibition reversed hepatic Aloxe3-mediated insulin sensitization, suppression of hepatocellular ATP production and oxygen consumption, and gene induction of PPAR? coactivator-1? (PGC1?) expression. Moreover, hepatocyte-specific PPAR? deletion reversed the therapeutic effect of hepatic Aloxe3 expression on diet-induced insulin intolerance. Aloxe3 is, therefore, a potentially novel effector of the hepatocellular fasting response that leverages both PPAR?-mediated and pleiotropic effects to augment hepatic and whole-host metabolism, and it is, thus, a promising target to ameliorate metabolic disease.
Project description:Peroxisome proliferator-activated receptor (PPAR) agonists are used for treating hyperglycemia and type 2 diabetes. However, the mechanism of action of these agonists is still under investigation. The lipid droplet-associated proteins FSP27/CIDEC and LSDP5, regulated directly by PPAR? and PPAR?, are associated with hepatic steatosis and insulin sensitivity. Here, we evaluated the expression levels of FSP27/CIDEC and LSDP5 and the regulation of these proteins by consumption of a high-fat diet (HFD) or administration of PPAR agonists. Mice with diet-induced obesity were treated with the PPAR? or PPAR? agonist, pioglitazone or fenofibrate, respectively. Liver tissues from db/db diabetic mice and human were also collected. Interestingly, FSP27/CIEDC was expressed in mouse and human livers and was upregulated in obese C57BL/6J mice. Fenofibrate treatment decreased hepatic triglyceride (TG) content and FSP27/CIDEC protein expression in mice fed an HFD diet. In mice, LSDP5 was not detected, even in the context of insulin resistance or treatment with PPAR agonists. However, LSDP5 was highly expressed in humans, with elevated expression observed in the fatty liver. We concluded that fenofibrate greatly decreased hepatic TG content and FSP27/CIDEC protein expression in mice fed an HFD, suggesting a potential regulatory role for fenofibrate in the amelioration of hepatic steatosis.
Project description:Type 2 diabetes mellitus (T2DM) is a pervasive metabolic syndrome that is characterized by insulin resistance, hyperglycemia and dyslipidemia. As full agonists of PPAR?, thiazolidinedione (TZD) drugs elicit antidiabetic effects by targeting PPAR? but is accompanied by weight gain, fluid retention and cardiovascular risk associated with their transcriptional agonism potency. We here identify a natural product chelerythrine as a unique selective PPAR modulator (SPPARM) with a potent PPAR? binding activity but much less classical receptor transcriptional agonism. Structural analysis reveals that chelerythrine exhibits unique binding in parallel with H3 of PPAR?. Unlike TZDs, chelerythrine destabilizes helix 12, especially residue tyrosine 473, resulting in a loose configuration of AF-2 and a selective cofactor profile distinct from TZDs, leading to a differential target gene profile in adipogenesis in db/db diabetic mice. Moreover, chelerythrine improved insulin sensitivity by more potently blocking the phosphorylation of PPAR? by CDK5 compared to TZDs. These data fundamentally elucidate the mechanism by which chelerythrine retains the benefits of improving insulin sensitivity while reducing the adverse effects of TZDs, suggesting that the natural product chelerythrine is a very promising pharmacological agent by selectively targeting PPAR? for further development in the clinical treatment of insulin resistance.
Project description:<h4>Background</h4>Protease-activated protein-2 (PAR2) has been reported to regulate hepatic insulin resistance condition in type 2 diabetes mice. However, the mechanism of lipid metabolism through PAR2 in obesity mice have not yet been examined. In liver, Forkhead box O1 (FoxO1) activity induces peroxisome proliferator-activated receptor ? (PPAR?), leading to accumulation of lipids and hyperlipidemia. Hyperlipidemia significantly influence hepatic steatoses, but the mechanisms underlying PAR2 signaling are complex and have not yet been elucidated.<h4>Methods</h4>To examine the modulatory action of FoxO1 and its altered interaction with PPAR?, we utilized db/db mice and PAR2-knockout (KO) mice administered with high-fat diet (HFD).<h4>Results</h4>Here, we demonstrated that PAR2 was overexpressed and regulated downstream gene expressions in db/db but not in db+ mice. The interaction between PAR2/?-arrestin and Akt was also greater in db/db mice. The Akt inhibition increased FoxO1 activity and subsequently PPAR? gene in the livers that led to hepatic lipid accumulation. Our data showed that FoxO1 was negatively controlled by Akt signaling and consequently, the activity of a major lipogenesis-associated transcription factors such as PPAR? increased, leading to hepatic lipid accumulation through the PAR2 pathway under hyperglycemic conditions in mice. Furthermore, the association between PPAR? and FoxO1 was increased in hepatic steatosis condition in db/db mice. However, HFD-fed PAR2-KO mice showed suppressed FoxO1-induced hepatic lipid accumulation compared with HFD-fed control groups.<h4>Conclusion</h4>Collectively, our results provide evidence that the interaction of FoxO1 with PPAR? promotes hepatic steatosis in mice. This might be due to defects in PAR2/?-arrestin-mediated Akt signaling in diabetic and HFD-fed mice.
Project description:Peroxisome proliferator-activated receptor (PPAR) ?/? dual agonists have been developed to alleviate metabolic disorders and have the potential to be used as therapeutic agents for the treatment of type 2 diabetes. In this study, we investigated the effects of a newly synthesized PPAR ?/? dual agonist, 2-[4-(5-chlorobenzo [d] thiazol-2-yl) phenoxy]-2-methylpropanoic acid (MHY908) on type 2 diabetes in vitro and in vivo. To obtain initial evidence that MHY908 acts as a PPAR ?/? dual agonist, ChIP and reporter gene assays were conducted in AC2F rat liver cells, and to investigate the anti-diabetic effects and molecular mechanisms, eight-week-old, male db/db mice were allowed to eat ad libitum, placed on calorie restriction, or administered MHY908 (1 mg or 3 mg/kg/day) mixed in food for 4 weeks. Age-matched male db/m lean mice served as non-diabetic controls. It was found that MHY908 enhanced the binding and transcriptional activity of PPAR ? and ? in AC2F cells, and it reduced serum glucose, triglyceride, and insulin levels, however increased adiponectin levels without body weight gain. In addition, MHY908 significantly improved hepatic steatosis by enhancing CPT-1 levels. Remarkably, MHY908 reduced endoplasmic reticulum (ER) stress and c-Jun N-terminal kinase (JNK) activation in the livers of db/db mice, and subsequently reduced insulin resistance. The study shows MHY908 has beneficial effects on type 2 diabetes by simultaneously activating PPAR ?/? and improving ER stress, and suggests that MHY908 could have a potent anti-diabetic effect as a PPAR ?/? dual agonist, and potential for the treatment of type 2 diabetes.
Project description:Creosote bush-derived nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, possesses antioxidant properties and functions as a potent antihyperlipidemic agent in rodent models. Here, we examined the effect of chronic NDGA treatment of ob/ob mice on plasma dyslipidemia, hepatic steatosis, and changes in hepatic gene expression. Feeding ob/ob mice a chow diet supplemented with either low (0.83 g/kg diet) or high-dose (2.5 g/kg diet) NDGA for 16 wk significantly improved plasma triglyceride (TG), inflammatory chemokine levels, hyperinsulinemia, insulin sensitivity, and glucose intolerance. NDGA treatment caused a marked reduction in liver weight and TG content, while enhancing rates of fatty acid oxidation. Microarray analysis of hepatic gene expression demonstrated that NDGA treatment altered genes for lipid metabolism, with genes involved in fatty acid catabolism most significantly increased. NDGA upregulated the mRNA and nuclear protein levels of peroxisome proliferator-activated receptor ? (PPAR?), and the activated (phosphorylated) form of AMP-activated kinase. NDGA increased PPAR? promoter activity in AML12 hepatocytes and also prevented the fatty acid suppression of PPAR? expression. In contrast, PPAR? siRNA abrogated the stimulatory effect of NDGA on fatty acid catabolism. Likewise, no stimulatory effect of NDGA on hepatic fatty acid oxidation was observed in the livers of PPAR?-deficient mice, but the ability of NDGA to reverse fatty liver conditions was unaffected. In conclusion, the beneficial actions of NDGA on dyslipidemia and hepatic steatosis in ob/ob mice are exerted primarily through enhanced fatty acid oxidation via PPAR?-dependent pathways. However, PPAR?-independent pathways also contribute to NDGA's action to ameliorate hepatic steatosis.
Project description:Type 2 diabetes mellitus is often treated with insulin-sensitizing drugs called thiazolidinediones (TZD), which improve insulin resistance and glycemic control. Despite their effectiveness in treating diabetes, these drugs provide little protection from eminent cardiovascular disease associated with diabetes. Here we demonstrate how chiglitazar, a configuration-restricted non-TZD peroxisome proliferator-activated receptor (PPAR) pan agonist with moderate transcription activity, preferentially regulates ANGPTL4 and PDK4, which are involved in glucose and lipid metabolism. CDK5-mediated phosphorylation at serine 273 (S273) is a unique regulatory mechanism reserved for PPAR?, and this event is linked to insulin resistance in type 2 diabetes mellitus. Our data demonstrates that chiglitazar modulates gene expression differently from two TZDs, rosiglitazone and pioglitazone, via its configuration-restricted binding and phosphorylation inhibition of PPAR?. Chiglitazar induced significantly greater expression of ANGPTL4 and PDK4 than rosiglitazone and pioglitazone in different cell models. These increased expressions were dependent on the phosphorylation status of PPAR? at S273. Furthermore, ChIP and AlphaScreen assays showed that phosphorylation at S273 inhibited promoter binding and cofactor recruitment by PPAR?. Based on these results, activities from pan agonist chiglitazar can be an effective part of a long-term therapeutic strategy for treating type 2 diabetes in a more balanced action among its targeted organs.
Project description:Hepatic steatosis is frequently observed in obese and aged individuals. Because hepatic steatosis is closely associated with metabolic syndromes, including insulin resistance, dyslipidemia, and inflammation, numerous efforts have been made to develop compounds that ameliorate it. Here, a novel peroxisome proliferator-activated receptor (PPAR) ? agonist, 4-(benzo[d]thiazol-2-yl)benzene-1,3-diol (MHY553) was developed, and investigated its beneficial effects on hepatic steatosis using young and old Sprague-Dawley rats and HepG2 cells.Docking simulation and Western blotting confirmed that the activity of PPAR?, but not that of the other PPAR subtypes, was increased by MHY553 treatment. When administered orally, MHY553 markedly ameliorated aging-induced hepatic steatosis without changes in body weight and serum levels of liver injury markers. Consistent with in vivo results, MHY553 inhibited triglyceride accumulation induced by a liver X receptor agonist in HepG2 cells. Regarding underlying mechanisms, MHY553 stimulated PPAR? translocation into the nucleus and increased mRNA levels of its downstream genes related to fatty acid oxidation, including CPT-1A and ACOX1, without apparent change in lipogenesis signaling. Furthermore, MHY553 significantly suppresses inflammatory mRNA expression in old rats. In conclusion, MHY553 is a novel PPAR? agonist that improved aged-induced hepatic steatosis, in part by increasing ?-oxidation signaling and decreasing inflammation in the liver. MHY553 is a potential pharmaceutical agent for treating hepatic steatosis in aging.