Effect of parthenolide, an NLRP3 inflammasome inhibitor, on insulin resistance in high-fat diet-obese mice

The activation of Nod-like receptor proteins (NLRP3) containing the pyrin domain inflammasome is a hallmark of the pathogenesis of metabolic disorders. Inhibition of the NLRP3 inflammasome by phytoconstituents has been attempted as a strategy to mitigate these disorders. Therefore, the present study aimed to evaluate the efficacy of an NLRP3 inflammasome inhibitor, parthenolide (PN; 5 mg/kg i.p.) against inflammation and insulin resistance in high-fat diet (HFD) - obese mice. Treatment with PN and pioglitazone (PIO; 30 mg/kg p.o.) attenuated lipopolysaccharide (LPS; 1 ng/ml) - induced elevation of tumor necrosis factor-α and interleukin-1β in mouse peritoneal macrophages in a dose-dependent manner. Sixty days of PN and PIO treatment marginally reduced obesity-induced insulin resistance in HFD-obese mice. PN treatment also decreased blood glucose from 14th to 60th day, supporting the hypothesis of simultaneous attenuation of inflammation and insulin resistance in obese mice. Thus, PN treatment was also evident with significant improvement in glucose tolerance and peripheral insulin resistance validated through the respective tolerance tests. Therefore, the present study suggests that PN, an NLRP3 inflammasome inhibitor, could be a possible therapeutic agent for attenuating obesity-induced insulin resistance.

Discovery and pharmacological evaluation of indole derivatives as potent and selective RORγt inverse agonist for multiple autoimmune conditions

Targeting nuclear receptor RORγ is recognized to be beneficial in multiple autoimmune disorders. We disclosed new indole analogues as potent RORγ inverse agonists. RO-2 as one of the potent and orally bioavailable compounds was evaluated in various models of autoimmune disorder. It showed potent suppression of downstream markers of RORγt activity in murine and human primary cells, ex vivo PD assay and in multiple animal models of autoimmune diseases. The results indicate the potential of these indole analogues as orally bioavailable small molecule inverse agonists of RORγt, efficacious in various Th17 driven models of autoimmune disorders.

Abstract 609: Pharmacological Inhibition of NLRP3 Inflammasome by Parthenolide Improves Obesity-Induced Insulin Resistance in Diet-Induced Obese Mice

Many landmark studies have reported the Nod-like receptor proteins containing Pyrin domain (NLRP3) inflammasome activation in metabolic diseases that include obesity, atherosclerosis and type 2 diabetes. Therefore, the present study was aimed: (i) to determine the role of NLRP3 in inflammation and insulin resistance in high fat diet-induced obesity (DIO) model of mice, and (ii) to determine whether parthenolide, a NLRP3 inhibitor, is able to protect mice against inflammation and insulin resistance in high fat DIO model.

METHODS: Lipopolysaccharide (1 ng/ml) primed mouse intraperitoneal macrophages were treated with Parthenolide (0.1 to 30 μM) to evaluate its effect on TNF-α and IL-1β. Parthenolide and Pioglitazone were administered to DIO mice (fed 60% high fat diet) at 5 and 30 mg/kg QD, PO, respectively for 60 days to evaluate their effect on insulin resistance.

RESULTS: Parthenolide (5 mg/kg) markedly attenuated inflammatory cytokines as evidenced by significant and dose dependant inhibition of both TNF-α and IL-1β in LPS primed macrophages. Treatment also lowered the fed blood glucose from day 14 to the entire course of study supporting the hypothesis that attenuating inflammation would be a possible intervention to insulin resistance. Parthenolide also improved peripheral insulin resistance, as demonstrated by insulin tolerance test and a significant improvement in the glucose intolerance as demonstrated by the oral glucose tolerance test. Moreover, treatment lowered plasma insulin levels indicating a trend in the improvement in insulin sensitivity.

CONCLUSIONS: Collectively, obtained results support our hypothesis that Parthenolide, an inflammasome inhibitor, could be a useful agent in antagonizing obesity-induced insulin resistance

Discovery of a potent and selective small molecule hGPR91 antagonist

GPR91, a 7TM G-Protein-Coupled Receptor, has been recently deorphanized with succinic acid as its endogenous ligand. Current literature indicates that GPR91 plays role in various pathophysiology including renal hypertension, autoimmune disease and retinal angiogenesis. Starting from a small molecule high-throughput screening hit 1 (hGPR91 IC(50): 0.8 μM)-originally synthesized in Merck for Bradykinin B(1) Receptor (BK(1)R) program, systematic structure-activity relationship study led us to discover potent and selective hGPR91 antagonists e.g. 2c, 4c, and 5 g (IC(50): 7-35 nM; >1000 fold selective against hGPR99, a closest related GPCR; >100 fold selective in Drug Matrix screening). This initial work also led to identification of two structurally distinct and orally bio-available lead compounds: 5g (%F: 26) and 7e (IC(50): 180 nM; >100 fold selective against hGPR99; %F: 87). A rat pharmacodynamic assay was developed to characterize the antagonists in vivo using succinate induced increase in blood pressure. Using two representative antagonists, 2c and 4c, the GPR91 target engagement was subsequently demonstrated using the designed pharmacodynamic assay.

Increased renal angiotensin II AT1 receptor function in obese Zucker rat

Angiotensin II (Ang II) via the activation of AT1 receptors and subsequent stimulation of the tubular sodium transporters increases sodium and water reabsorption in the proximal tubule. An enhanced tubular action of Ang II is implicated in obesity related hypertension; however, the mechanism of such a phenomenon is unknown. Present study was designed to determine the AT1 receptor numbers and function in the proximal tubule of obese and lean Zucker rats. Obese Zucker rats were hypertensive and hyperinsulinemic. The plasma renin activity was similar in the lean and obese rats. Angiotensin II stimulated the Na,H-exchanger (NHE) activity in the proximal tubule, but the stimulatory response was markedly greater in obese than in lean rats. Similarly, Ang II caused greater inhibition in cAMP accumulation in the proximal tubule of obese compared to lean rats. The (125I]sar-Ang II binding revealed a 100% increase in the AT1 receptor number in the brush border membrane (BBM) of obese compared to lean rats. The Western blot analysis revealed a 36-51% increase in the Gi(alpha)1 and Gi(alpha)3 in the BBM of obese compared to lean rats. We conclude that increases in the AT1 receptor number and abundance of the Gi(alpha) on BBM may be responsible for the enhanced signaling and subsequent greater stimulation of NHE by Ang II in proximal tubules of obese rats. The greater stimulation of NHE by Ang II may contribute to the increased tubular sodium reabsorption and to the hypertension in obese Zucker rats.