Saroglitazar suppresses the hepatocellular carcinoma induced by intraperitoneal injection of diethylnitrosamine in C57BL/6 mice fed on choline deficient, l-amino acid- defined, high-fat diet.

BACKGROUND: Saroglitazar is a novel PPAR-α/γ agonist with predominant PPAR-α activity. In various preclinical models, saroglitazar has been shown to prevent & reverse symptoms of NASH. In view of these observations, and the fact that NASH is a progressive disease leading to HCC, we hypothesized that saroglitazar may prevent the development of HCC in rodents. METHODS: HCC was induced in C57BL/6 mice by a single intraperitoneal injection of 25 mg/kg diethylnitrosamine (DEN) at the age of 4 weeks and then feeding the animal a choline-deficient, L-amino acid- defined, high-fat diet (CDAHFD) for the entire study duration. Eight weeks after initiation of CDAHFD, saroglitazar (1 and 3 mg/kg) treatment was started and continued for another 27 weeks. RESULTS: Saroglitazar treatment significantly reduced the liver injury markers (serum ALT and AST), reversed hepatic steatosis and decreased the levels of pro-inflammatory cytokines like TNF-α in liver. It also resulted in a marked increase in serum adiponectin and osteopontin levels. All disease control animals showed hepatic tumors, which was absent in saroglitazar (3 mg/kg)- treatment group indicating 100% prevention of hepatic tumorigenesis. This is the first study demonstrating a potent PPARα agonist causing suppression of liver tumors in rodents, perhaps due to a strong anti-NASH activity of Saroglitazar that overrides its rodent-specific peroxisome proliferation activity. CONCLUSION: The data reveals potential of saroglitazar for chemoprevention of hepatocellular carcinoma in patients with NAFLD/NASH.

Dual PPARα/γ agonist saroglitazar improves liver histopathology and biochemistry in experimental NASH models.

BACKGROUND & AIMS: Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are common clinico-pathological conditions that affect millions of patients worldwide. In this study, the efficacy of saroglitazar, a novel PPARα/γ agonist, was assessed in models of NAFLD/NASH. METHODS & RESULTS: HepG2 cells treated with palmitic acid (PA;0.75 mM) showed decreased expression of various antioxidant biomarkers (SOD1, SOD2, glutathione peroxidase and catalase) and increased expression of inflammatory markers (TNFα, IL1ß and IL6). These effects were blocked by saroglitazar, pioglitazone and fenofibrate (all tested at 10µM concentration). Furthermore, these agents reversed PA-mediated changes in mitochondrial dysfunction, ATP production, NFkB phosphorylation and stellate cell activation in HepG2 and HepG2-LX2 Coculture studies. In mice with choline-deficient high-fat diet-induced NASH, saroglitazar reduced hepatic steatosis, inflammation, ballooning and prevented development of fibrosis. It also reduced serum alanine aminotransferase, aspartate aminotransferase and expression of inflammatory and fibrosis biomarkers. In this model, the reduction in the overall NAFLD activity score by saroglitazar (3 mg/kg) was significantly more prominent than pioglitazone (25 mg/kg) and fenofibrate (100 mg/kg). Pioglitazone and fenofibrate did not show any improvement in steatosis, but partially improved inflammation and liver function. Antifibrotic effect of saroglitazar (4 mg/kg) was also observed in carbon tetrachloride-induced fibrosis model. CONCLUSIONS: Saroglitazar, a dual PPARα/γ agonist with predominant PPARα activity, shows an overall improvement in NASH. The effects of saroglitazar appear better than pure PPARα agonist, fenofibrate and PPARγ agonist pioglitazone.

Hypothalamic leptin action is mediated by histone deacetylase 5.

Hypothalamic leptin signalling has a key role in food intake and energy-balance control and is often impaired in obese individuals. Here we identify histone deacetylase 5 (HDAC5) as a regulator of leptin signalling and organismal energy balance. Global HDAC5 KO mice have increased food intake and greater diet-induced obesity when fed high-fat diet. Pharmacological and genetic inhibition of HDAC5 activity in the mediobasal hypothalamus increases food intake and modulates pathways implicated in leptin signalling. We show HDAC5 directly regulates STAT3 localization and transcriptional activity via reciprocal STAT3 deacetylation at Lys685 and phosphorylation at Tyr705. In vivo, leptin sensitivity is substantially impaired in HDAC5 loss-of-function mice. Hypothalamic HDAC5 overexpression improves leptin action and partially protects against HFD-induced leptin resistance and obesity. Overall, our data suggest that hypothalamic HDAC5 activity is a regulator of leptin signalling that adapts food intake and body weight to our dietary environment.

Saroglitazar, a novel PPARα/γ agonist with predominant PPARα activity, shows lipid-lowering and insulin-sensitizing effects in preclinical models.

Saroglitazar is a novel nonthiazolidinediones (TZD) and nonfibric acid derivative designed to act as dual regulator of lipids and glucose metabolism by activating peroxisome proliferator-activated receptors (PPAR). These studies evaluate the efficacy and safety profile of Saroglitazar in preclinical in vitro and in vivo models. The EC50 values of Saroglitazar assessed in HepG2 cells using PPAR transactivation assay for hPPARα and hPPARγ were 0.65 pmol/L and 3 nmol/L, respectively. In db/db mice, 12-day treatment with Saroglitazar (0.01-3 mg/kg per day, orally) caused dose-dependent reductions in serum triglycerides (TG), free fatty acids (FFA), and glucose. The ED50 for these effects was found to be 0.05, 0.19, and 0.19 mg/kg, respectively with highly significant (91%) reduction in serum insulin and AUC-glucose following oral glucose administration (59%) at 1 mg/kg dose. Significant reduction in serum TG (upto 90%) was also observed in Zucker fa/fa rats, Swiss albino mice, and in high fat -high cholesterol (HF-HC)-fed Golden Syrian hamsters. LDL cholesterol was significantly lowered in hApoB100/hCETP double transgenic mice and HF-HC diet fed Golden Syrian Hamsters. Hyperinsulinemic-Euglycemic clamp study in Zucker fa/fa rats demonstrated potent insulin-sensitizing activity. Saroglitazar also showed a significant decrease in SBP (22 mmHg) and increase (62.1%) in serum adiponectin levels in Zucker fa/fa rats. A 90-day repeated dose comparative study in Wistar rats and marmosets confirmed efficacy (TG lowering) potential of Saroglitazar and has indicated low risk of PPAR-associated side effects in humans. Based on efficacy and safety profile, Saroglitazar appears to have good potential as novel therapeutic agent for treatment of dyslipidemia and diabetes.

Tachykinin-1 in the central nervous system regulates adiposity in rodents.

Ghrelin is a circulating hormone that targets the central nervous system to regulate feeding and adiposity. The best-characterized neural system that mediates the effects of ghrelin on energy balance involves the activation of neuropeptide Y/agouti-related peptide neurons, expressed exclusively in the arcuate nucleus of the hypothalamus. However, ghrelin receptors are expressed in other neuronal populations involved in the control of energy balance. We combined laser capture microdissection of several nuclei of the central nervous system expressing the ghrelin receptor (GH secretagoge receptor) with microarray gene expression analysis to identify additional neuronal systems involved in the control of central nervous system-ghrelin action. We identified tachykinin-1 (Tac1) as a gene negatively regulated by ghrelin in the hypothalamus. Furthermore, we identified neuropeptide k as the TAC1-derived peptide with more prominent activity, inducing negative energy balance when delivered directly into the brain. Conversely, loss of Tac1 expression enhances the effectiveness of ghrelin promoting fat mass gain both in male and in female mice and increases the susceptibility to diet-induced obesity in ovariectomized mice. Taken together, our data demonstrate a role TAC1 in the control energy balance by regulating the levels of adiposity in response to ghrelin administration and to changes in the status of the gonadal function.

High-density lipoprotein maintains skeletal muscle function by modulating cellular respiration in mice.

BACKGROUND: Abnormal glucose metabolism is a central feature of disorders with increased rates of cardiovascular disease. Low levels of high-density lipoprotein (HDL) are a key predictor for cardiovascular disease. We used genetic mouse models with increased HDL levels (apolipoprotein A-I transgenic [apoA-I tg]) and reduced HDL levels (apoA-I-deficient [apoA-I ko]) to investigate whether HDL modulates mitochondrial bioenergetics in skeletal muscle. METHODS AND RESULTS: ApoA-I ko mice exhibited fasting hyperglycemia and impaired glucose tolerance test compared with wild-type mice. Mitochondria isolated from gastrocnemius muscle of apoA-I ko mice displayed markedly blunted ATP synthesis. Endurance capacity during exercise exhaustion test was impaired in apoA-I ko mice. HDL directly enhanced glucose oxidation by increasing glycolysis and mitochondrial respiration rate in C2C12 muscle cells. ApoA-I tg mice exhibited lower fasting glucose levels, improved glucose tolerance test, increased lactate levels, reduced fat mass, associated with protection against age-induced decline of endurance capacity compared with wild-type mice. Circulating levels of fibroblast growth factor 21, a novel biomarker for mitochondrial respiratory chain deficiencies and inhibitor of white adipose lipolysis, were significantly reduced in apoA-I tg mice. Consistent with an increase in glucose utilization of skeletal muscle, genetically increased HDL and apoA-I levels in mice prevented high-fat diet-induced impairment of glucose homeostasis. CONCLUSIONS: In view of impaired mitochondrial function and decreased HDL levels in type 2 diabetes mellitus, our findings indicate that HDL-raising therapies may preserve muscle mitochondrial function and address key aspects of type 2 diabetes mellitus beyond cardiovascular disease.

The orphan receptor Gpr83 regulates systemic energy metabolism via ghrelin-dependent and ghrelin-independent mechanisms.

The G protein-coupled receptor 83 (Gpr83) is widely expressed in brain regions regulating energy metabolism. Here we report that hypothalamic expression of Gpr83 is regulated in response to nutrient availability and is decreased in obese mice compared with lean mice. In the arcuate nucleus, Gpr83 colocalizes with the ghrelin receptor (Ghsr1a) and the agouti-related protein. In vitro analyses show heterodimerization of Gpr83 with Ghsr1a diminishes activation of Ghsr1a by acyl-ghrelin. The orexigenic and adipogenic effect of ghrelin is accordingly potentiated in Gpr83-deficient mice. Interestingly, Gpr83 knock-out mice have normal body weight and glucose tolerance when fed a regular chow diet, but are protected from obesity and glucose intolerance when challenged with a high-fat diet, despite hyperphagia and increased hypothalamic expression of agouti-related protein, Npy, Hcrt and Ghsr1a. Together, our data suggest that Gpr83 modulates ghrelin action but also indicate that Gpr83 regulates systemic metabolism through other ghrelin-independent pathways.

Exercise protects against high-fat diet-induced hypothalamic inflammation.

Hypothalamic inflammation is a potentially important process in the pathogenesis of high-fat diet-induced metabolic disorders that has recently received significant attention. Microglia are macrophage-like cells of the central nervous system which are activated by pro-inflammatory signals causing local production of specific interleukins and cytokines, and these in turn may further promote systemic metabolic disease. Whether or how this microglial activation can be averted or reversed is unknown. Since running exercise improves systemic metabolic health and has been found to promote neuronal survival as well as the recovery of brain functions after injury, we hypothesized that regular treadmill running may blunt the effect of western diet on hypothalamic inflammation. Using low-density lipoprotein receptor deficient (l dlr-/-) mice to better reflect human lipid metabolism, we first confirmed that microglial activation in the hypothalamus is severely increased upon exposure to a high-fat, or "western", diet. Moderate, but regular, treadmill running exercise markedly decreased hypothalamic inflammation in these mice. Furthermore, the observed decline in microglial activation was associated with an improvement of glucose tolerance. Our findings support the hypothesis that hypothalamic inflammation can be reversed by exercise and suggest that interventions to avert or reverse neuronal damage may offer relevant potential in obesity treatment and prevention.

Effect of structurally constrained oxime-ether linker on PPAR subtype selectivity: Discovery of a novel and potent series of PPAR-pan agonists.

A novel series of thaizole and oxazole containing phenoxy acetic acid derivatives is reported as PPAR-pan agonists. Incorporation of structurally constrained oxime-ether based linker in the chemotype of a potent PPARδ selective agonist GW-501516 was adapted as designing strategy. In vitro, selected test compounds 12a, 12c, 17a and 18a showed PPAR-pan agonists activities and among these four compounds tested, 12a emerged as highly potent and efficacious compound, while 17a exhibited moderate and balanced PPAR-pan agonistic activity. In vivo, selected test compounds 12a and 17a exhibited significant anti-hyperglycemic and anti-hyperlipidemic activities in relevant animal models. These results support our hypothesis that the introduction of structurally constrained oxime-ether linker between lipophilic tail and acidic head plays an important role in modulating subtype selectivity and subsequently led to the discovery of potent PPAR-pan agonists.

Effect of atorvastatin treatment on isoproterenol-induced myocardial infarction in rats.

In the present study, chronic treatment of atorvastatin was evaluated on isoproterenol-induced myocardial infarction. Male Sprague-Dawley rats (200 +/- 25 g) were randomized into the following four groups: (1) control group, (2) isoproterenol-treated group, (3) atorvastatin-treated group, and (4) isoproterenol- and atorvastatin-treated group. Various serum and tissue parameters as well as histopathological studies were carried out in all groups. Isoproterenol administration produced severe myocardial damage and oxidative stress in rats. Atorvastatin treatment reduced myocardial infarction which has been reflected by improvement in serum parameters, ATPase activities and histopathological lesions. However, it could not reduce oxidative stress and hypertrophy induced by isoproterenol. Hence, it can be concluded that atorvastatin may protect myocardial infarction induced by isoproterenol independent of its antioxidant properties.

Effect of pioglitazone on L-NAME induced hypertension in diabetic rats.

The present study investigates the effect of pioglitazone treatment on blood pressure, vascular reactivity and antioxidant enzymes in L-NAME induced hypertension in normal and STZ-diabetic rats. Diabetes was induced in male Sprague Dawley rats (200+/-15 g) by single intravenous injection of 55 mg/kg of streptozotocin (STZ). Rats were randomized into diabetic and nondiabetic groups, Nomega-nitro-L-arginine-methyl ester (L-NAME, 50 mg/kg) was administered in drinking water for 4 weeks. They were treated with pioglitazone (10 mg/kg/day, p.o.) for 4 weeks and following protocol was carried out. Blood pressure, blood glucose levels and body weight were measured. Thoracic aorta was isolated and dose response curve of phenylephrine (PE) with intact and denuded endothelium was recorded. Dose response curve of acetylcholine (Ach) and sodium nitroprusside (SNP) was recorded in precontracted rings. Lipid peroxidation, superoxide dismutase, catalase, and reduced glutathione were estimated in liver, kidney, and aorta. Pioglitazone produced no significant effect on blood glucose levels, body weight and blood pressure of L-NAME administered nondiabetic and diabetic rats. Pioglitazone treatment had no significant effect on PE induced contraction and Ach induced relaxation in L-NAME diabetic and nondiabetic rats. SNP completely relaxed aortic rings of all the groups. Higher oxidative stress in case of diabetic rats was significantly (p<0.05) reduced by pioglitazone treatment. Although pioglitazone reduced oxidative stress in diabetic rats, there was no significant effect on blood pressure as there was complete absence of nitric oxide due to administration of L-NAME. Hence from the present study it can be concluded that reduction in blood pressure in case of STZ-diabetic rats is nitric oxide mediated.