ERK1/2 activated PHLPP1 induces skeletal muscle ER stress through the inhibition of a novel substrate AMPK.

Nutritional abundance associated with chronic inflammation and dyslipidemia impairs the functioning of endoplasmic reticulum (ER) thereby hampering cellular responses to insulin. PHLPP1 was identified as a phosphatase which inactivates Akt, the master regulator of insulin mediated glucose homeostasis. Given the suggestive role of PHLPP1 phosphatase in terminating insulin signalling pathways, deeper insights into its functional role in inducing insulin resistance are warranted. Here, we show that PHLPP1 expression is enhanced in skeletal muscle of insulin resistant rodents which also displayed ER stress, an important mediator of insulin resistance. Using cultured cells and PHLPP1 knockdown mice, we demonstrate that PHLPP1 facilitates the development of ER stress. Importantly, shRNA mediated ablation of PHLPP1 significantly improved glucose clearance from systemic circulation with enhanced expression of glucose transporter 4 (GLUT-4) in skeletal muscle. Mechanistically, we show that endogenous PHLPP1 but not PP2Cα interacts with and directly dephosphorylates AMPK Thr172 in myoblasts without influencing its upstream kinase, LKB1. While the association between endogenous PHLPP1 and AMPK was enhanced in ER stressed cultured cells and soleus muscle of high fat diet fed mice, the basal interaction between PP2Ac and AMPK was minimally altered. Further, we show that PHLPP1α is phosphorylated by ERK1/2 at Ser932 under ER stress which is required for its ability to interact with and dephosphorylate AMPK and thereby induce ER stress. Taken together, our data position PHLPP1 as a key regulator of ER stress.

Nephroprotective activity of Combretum micranthum G. Don in cisplatin induced nephrotoxicity in rats: In-vitro, in-vivo and in-silico experiments.

Nephrotoxicity is known to be a major complication during cisplatin chemotherapy in cancer patients. In the present study, the protective effect of a hydroalcoholic extract of Combretum micranthum (CM) against cisplatin (CP)-induced renal damage was evaluated using in-vitro human embryonic kidney (HEK)-293 cells and in-vivo experiments. Further, in-silico molecular docking and dynamic experiments were carried out with bioactive compounds of the title plant against nuclear factor kappa B (NF-κB) and soluble epoxide hydrolase (sEH). Incubation of HEK-293 cells with cisplatin resulted in a significant increase in cell death with changes in normal cellular morphology. Co-treatment of HEK-293 cells with CP and CM extract at varying concentrations resulted in significant enhancement of cell growth compared to CP treatment indicating the cytoprotective activity of CM with an EC50 8.136 µg/mL. In vivo nephroprotective activity was evaluated by administering CM (200 and 400 mg/kg, p.o) to rats for 10 days followed by single intraperitonial injection of CP (7.5 mg/kg) on the 5th day of the experiment. Nephrotoxicity induced by CP was apparent by elevated levels of serum and urine kidney function markers, transaminases, oxidative stress markers and histopathological alterations in kidney. Pre-treatment with CM normalized the renal function at both the doses by ameliorating the CP-induced renal damage markers, oxidative stress and histopathological variations. In-silico studies showed that, out of the thirty bioactive compounds, isovitexin and gallic acid exhibited a higher docking score of -22.467, -21.167 kcal/mol against NF-κB. Cianidanol and epicatechin exhibited a higher docking score of -14.234, -14.209 kcal/mol against sEH. The protective effect of CM extract in CP-induced nephrotoxicity might be attributed to its antioxidant, anti-inflammatory activity by inhibiting NF-κB and sEH upregulation.

Discovery of PAT-1102, a novel, potent and orally active histone deacetylase inhibitor with antitumor activity in cancer mouse models.

AIM: Histone deacetylase (HDAC) inhibitors are a class of drugs that modulate transcriptional activity in cells and are known to induce cell-cycle arrest and angiogenesis, the major components of tumor cell proliferation. The aim of the present study was to characterize a novel hydroxamic acid-based HDAC inhibitor, PAT-1102, and determine its efficacy and tolerability in pre-clinical models. MATERIALS AND METHODS: HDAC enzyme inhibition was measured using HeLa cell nuclear extracts, and recombinant HDAC enzymes. Antiproliferative activity was assessed in a panel of cancer cell lines. Histone hyper-acetylation status and p21 induction were assessed in HeLa cells by immunoblotting. The effect on apoptosis was tested by caspase-3 activation and detection of cleaved poly-ADP ribose polymerase (PARP). Single-dose pharmacokinetics of the compound were assessed in BALB/c mice following oral and intravenous administration. Antitumor efficacy was evaluated in tumor-bearing mice established from lung and colorectal cancer cells (A549 and HCT116, respectively). RESULTS: PAT-1102 demonstrated potent HDAC-inhibitory activity and growth-inhibitory properties against a panel of cancer cell lines. The optimized compound PAT-1102 exhibits good aqueous solubility, metabolic stability and a favorable pharmacokinetic profile. Once-daily oral administration of PAT-1102 resulted in significant antitumor activity and was well-tolerated in mice. CONCLUSION: Our results indicate that PAT-1102 is a novel, potent, orally available HDAC inhibitor with antiproliferative activity against several human cancer cell lines and antitumor activity in mouse xenograft models. Based on the pre-clinical efficacy and safety profile of PAT-1102, the compound demonstrates significant potential for evaluation as a novel drug candidate for cancer therapy.

Ragaglitazar: a novel PPAR alpha PPAR gamma agonist with potent lipid-lowering and insulin-sensitizing efficacy in animal models.

Ragaglitazar [(-) DRF 2725; NNC 61-0029] is a coligand of PPARalpha and PPARgamma. In ob/ob mice, ragaglitazar showed significant reduction in plasma glucose, triglyceride and insulin (ED50 values <0.03, 6.1 and <0.1 mg kg-1). These effects are three-fold better than rosiglitazone and KRP-297. In Zucker fa/fa rats, ragaglitazar showed dose-dependent reduction in triglyceride and insulin, hepatic triglyceride secretion and triglyceride clearance kinetics (maximum of 74, 53, 32 and 50% at 3 mg kg-1), which are better than rosiglitazone and KRP-297. In a high-fat-fed hyperlipidaemic rat model, the compound showed an ED50 of 3.95, 3.78 mg kg-1 for triglyceride and cholesterol lowering, and 0.29 mg kg-1 for HDL-C increase. It also showed improvement in clearance of plasma triglyceride and hepatic triglyceride secretion rate. All these effects are 3-10-fold better than fenofibrate and KRP-297. Ragaglitazar treatment showed significant reduction in plasma Apo B and Apo CIII levels, and increase in liver CPT1 and CAT activity and ACO mRNA. Significant increase of both liver and fat LPL activity and fat aP2 mRNA was also observed. In a high-fat-fed hamster model, ragaglitazar at 1 mg kg-1 showed 83 and 61% reduction in triglyceride and total cholesterol, and also 17% reduction in fat feed-induced body weight increase. In these hyperlipidaemic animal models, PPARgamma ligands failed to show any significant efficacy. Taken together, ragaglitazar shows better insulin-sensitizing and lipid-lowering potential, as compared to the standard compounds.

Antidiabetic and hypolipidemic potential of DRF 2519--a dual activator of PPAR-alpha and PPAR-gamma.

We investigated the biological activity of Dr. Reddy's Research Foundation (DRF) 2519, a benzoxazinone analogue of the thiazolidinedione class of compounds. In the in vitro transactivation assay, DRF 2519 showed interesting dual activation of Peroxisome Proliferator Activated Receptor (PPAR) alpha and gamma. In insulin-resistant ob/ob mouse model, DRF 2519 showed significant alleviation of insulin resistance and dyslipidemia, which is better than rosiglitazone. Fatty Zucker rats treated with DRF 2519 showed better reduction of plasma insulin, triglyceride and free fatty acid levels than those treated with rosiglitazone. In addition, these rats were able to clear plasma lipids better when challenged with exogenous lipid (i.v.). DRF 2519 treatment resulted in improved plasma lipid profiles in high-fat-fed Sprague-Dawley rats. Treated rats showed better plasma lipid clearance and hepatic triglyceride secretion. When compared to DRF 2519, fenofibrate was comparatively less efficacious while rosigltiazone showed no activity in these models. In ex vivo studies, DRF 2519 showed induction of liver acyl CoA oxidase mRNA and increase in lipoprotein lipase (LPL) protein expression and activity in adipose tissue. In the in vitro studies, DRF 2519 inhibited the lipid biosynthesis and secretion of apolipoprotein B from human hepatoma (Hep)G2 cells. It also enhanced insulin-induced relaxation of rat aortic smooth muscle. These results indicate that DRF 2519, a dual activator of PPAR-alpha and gamma, could be an interesting development candidate in the management of metabolic disorders and associated complications.

DRF 2655: a unique molecule that reduces body weight and ameliorates metabolic abnormalities.

OBJECTIVE: Preclinical evaluation of DRF 2655, a peroxisome proliferator-activated receptor alpha (PPARalpha) and PPARgamma agonist, as a body-weight lowering, hypolipidemic and euglycemic agent. RESEARCH METHODS AND PROCEDURES: DRF 2655 was studied in different genetic, normal, and hyperlipidemic animal models. HEK 293 cells were used to conduct the reporter-based transactivation of PPARalpha and PPARgamma. To understand the biochemical mechanism of lipid-, body-weight-, and glucose-lowering effects, activities of key beta-oxidation and lipid catabolism enzymes and gluconeogenic enzymes were studied in db/db mice treated with DRF 2655. 3T3L1 cells were used for adipogenesis study, and HepG2 cells were used to study the effect of DRF 2655 on total cholesterol and triglyceride synthesis using [(14)C]acetate and [(3)H]glycerol. RESULTS: DRF 2655 showed concentration-dependent transactivation of PPARalpha and PPARgamma. In the 3T3L1 cell-differentiation study, DRF 2655 and rosiglitazone showed 369% and 471% increases, respectively, in triglyceride accumulation. DRF 2655 showed body-weight lowering and euglycemic and hypolipidemic effects in various animal models. db/db mice treated with DRF 2655 showed 5- and 3.6-fold inhibition in phosphoenolpyruvate carboxykinase and glucose 6-phosphatase activity and 651% and 77% increases in the beta-oxidation enzymes carnitine palmitoyltransferase and carnitine acetyltransferase, respectively. HepG2 cells treated with DRF 2655 showed significant reduction in lipid synthesis. DISCUSSION: DRF 2655 showed excellent euglycemic and hypolipidemic activities in different animal models. An exciting finding is its body-weight lowering effect in these models, which might be mediated by the induction of target enzymes involved in hepatic lipid catabolism through PPARalpha activation.

PAT5A: a partial agonist of peroxisome proliferator-activated receptor gamma is a potent antidiabetic thiazolidinedione yet weakly adipogenic.

PAT5A [5-[4-[N-(2-pyridyl)-(2S)-pyrrolidine-2-methoxyl]phenylmethylene[thiazolidine-2,4-dione, malic acid salt]], a chemically distinct unsaturated thiazolidinedione, activates peroxisome proliferator-activated receptor gamma (PPARgamma) submaximally in vitro with the binding affinity approximately 10 times less than that of rosiglitazone, a highly potent thiazolidinedione. PAT5A reduces plasma glucose level and improves insulin sensitivity in insulin resistant db/db mice, similar to that of rosiglitazone, while exerting a relatively weak adipogenic effect. In contrast to rosiglitazone, PAT5A inhibits cholesterol and fatty acid biosynthesis suggesting that PAT5A possesses a unique receptor-independent non-PPAR related property. PAT5A induces qualitatively similar but quantitatively different protease digestion patterns and interacts with PPARgamma differently than rosiglitazone. PAT5A shows differential cofactor recruitment and gene activation than that of rosiglitazone. Thus, the partial agonism of PAT5A to PPARgamma together with its receptor independent effects may contribute to its antidiabetic potency similar to rosiglitazone in vivo despite reduced affinity for PPARgamma. These biological effects suggest that PAT5A is a PPARgamma modulator that activates some (insulin sensitization), but not all (adipogenesis), PPARgamma-signaling pathways.