Dual Peroxisome Proliferator-Activated Receptor-alpha/gamma Agonists : In the Treatment of Type 2 Diabetes Mellitus and the Metabolic Syndrome

Parsing the Role of PPARs in Macrophage Processes

Cells are richly equipped with nuclear receptors, which act as ligand-regulated transcription factors. Peroxisome proliferator activated receptors (PPARs), members of the nuclear receptor family, have been extensively studied for their roles in development, differentiation, and homeostatic processes. In the recent past, there has been substantial interest in understanding and defining the functions of PPARs and their agonists in regulating innate and adaptive immune responses as well as their pharmacologic potential in combating acute and chronic inflammatory disease. In this review, we focus on emerging evidence of the potential roles of the PPAR subtypes in macrophage biology. We also discuss the roles of dual and pan PPAR agonists as modulators of immune cell function, microbial infection, and inflammatory diseases.

Recent Advances in Therapeutic Applications of Bisbenzimidazoles

Nitrogen-containing heterocycles are one of the most common structural motifs in approximately 80% of the marketed drugs. Of these, benzimidazoles analogues are known to elicit a wide spectrum of pharmaceutical activities such as anticancer, antibacterial, antiparasitic, antiviral, antifungal as well as chemosensor effect. Based on the benzimidazole core fused heterocyclic compounds, crescent-shaped bisbenzimidazoles were developed which provided an early breakthrough in the sequence-specific DNA recognition. Over the years, a number of functional variations in the bisbenzimidazole core have led to the emergence of their unique properties and established them as versatile ligands against several classes of pathogens. The present review provides an overview of diverse pharmacological activities of the bisbenzimidazole analogues in the past decade with a brief account of its development through the years.

Uncoupling Protein 2 and Peroxisome Proliferator-Activated Receptor γ Gene Polymorphisms in Association with Diabetes Susceptibility in Chinese Han Population with Variant Glucose Tolerance

OBJECTIVE

To investigate the association of polymorphisms in uncoupling protein 2 (UCP2) and peroxisome proliferator-activated receptor (PPARγ) with glucolipid metabolism in Chinese Han population.

METHODS

Five hundred eighty-nine subjects were divided into normal glucose tolerance (NGT) group (n = 198) and abnormal glucose tolerance group (n = 358). HbA1c, blood lipid profile, plasma glucose, and insulin were determined. Insulin sensitivity (HOMA-IR and Matsuda index (ISI_M)) and insulin secretion indexes (HOMA-β, early and total phase disposition index) were evaluated. Eight potential functional SNPs in UCP2 and 7 in PPARγ were selected. SNPs were genotyped on Sequenom MassARRAY platform.

RESULTS

The GG genotype of rs2920502 in PPARγ was associated with decreased risk of impaired glucose tolerance (G allele: OR: 0.818, 95%CI: 0.526-0.969, P = 0.042; GG: OR: 0.715, 95%CI: 0.527-0.97, P = 0.031). The TT genotype of rs3856806 in PPARγ was associated with increased risk of impaired glucose tolerance (T allele: OR: 1.46, 95%CI: 1.055-2.017, P = 0.022; TT: OR: 1.58, 95%CI: 1.104-2.761, P = 0.032). The GG genotype of rs2920502 in PPARγ had better blood glucose and increased insulin secretion and had lower HOMA-IR than GC/CC genotypes.

CONCLUSION

It probably could prevent insulin resistance in early stage by classifying the genotype of rs649446 and rs7109266 in UCP2. The GG genotype of rs2920502 in PPARγ had a decreased risk for diabetes. The TT genotype of rs3856806 in PPARγ had an increased risk for diabetes.

Hepatic structural enhancement and insulin resistance amelioration due to AT1 receptor blockade

Over the last decade, the role of renin-angiotensin system (RAS) on the development of obesity and its comorbidities has been extensively addressed. Both circulating and local RAS components are up-regulated in obesity and involved in non-alcoholic fatty liver disease onset. Pharmacological manipulations of RAS are viable strategies to tackle metabolic impairments caused by the excessive body fat mass. Renin inhibitors rescue insulin resistance, but do not have marked effects on hepatic steatosis. However, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers (ARB) yield beneficial hepatic remodeling. ARBs elicit body mass loss and normalize insulin levels, tackling insulin resistance. Also, this drug class increases adiponectin levels, besides countering interleukin-6, tumoral necrosis factor-alpha, and transforming growth factor-beta 1. The latter is essential to prevent from liver fibrosis. When conjugated with peroxisome proliferator-activated receptor (PPAR)-alpha activation, ARB fully rescues fatty liver. These effects might be orchestrated by an indirect up-regulation of MAS receptor due to angiotensin II receptor type 1 (AT1R) blockade. These associations of ARB with PPAR activation and ACE2-angiotensin (ANG) (1-7)-MAS receptor axis deserve a better understanding. This editorial provides a brief overview of the current knowledge regarding AT1R blockade effects on sensitivity to insulin and hepatic structural alterations as well as the intersections of AT1R blockade with peroxisome proliferator-activated receptor activation and ACE2-ANG (1-7) - MAS receptor axis.

Goodbye glitazars?

Glitazars are dual peroxisome proliferator-activated receptors (PPAR) alpha/gamma agonists that improve the lipid profile and exert an antidiabetic action — similar to a combination of a fibrate and a thiazolidinedione. In May 2006 the two glitazars most advanced in development, muraglitazar (Pargluva) and tesaglitazar (Galida) were discontinued. Muraglitazar was associated with an increased incidence of heart failure and tesaglitazar was associated with decreased glomerular filtration.

Expression profiling analysis: Uncoupling protein 2 deficiency improves hepatic glucose, lipid profiles and insulin sensitivity in high-fat diet-fed mice by modulating expression of genes in peroxisome proliferator-activated receptor signaling pathway

Aims/Introduction

Uncoupling protein 2 (UCP2), which was an important mitochondrial inner membrane protein associated with glucose and lipid metabolism, widely expresses in all kinds of tissues including hepatocytes. The present study aimed to explore the impact of UCP2 deficiency on glucose and lipid metabolism, insulin sensitivity and its effect on the liver‐associated signaling pathway by expression profiling analysis.

Materials and Methods

Four‐week‐old male UCP2−/− mice and UCP2+/+ mice were randomly assigned to four groups: UCP2−/− on a high‐fat diet, UCP2−/− on a normal chow diet, UCP2+/+ on a high‐fat diet and UCP2+/+ on a normal chow diet. The differentially expressed genes in the four groups on the 16th week were identified by Affymetrix gene array.

Results

The results of intraperitoneal glucose tolerance test and insulin tolerance showed that blood glucose and β‐cell function were improved in the UCP2−/− group on high‐fat diet. Enhanced insulin sensitivity was observed in the UCP2−/− group. The differentially expressed genes were mapped to 23 pathways (P < 0.05). We concentrated on the ‘peroxisome proliferator‐activated receptor (PPAR) signaling pathway’ (P = 3.19 × 10⁻¹¹), because it is closely associated with the regulation of glucose and lipid profiles. In the PPAR signaling pathway, seven genes (PPARγ, Dbi, Acsl3, Lpl, Me1, Scd1, Fads2) in the UCP2−/− mice were significantly upregulated.

Conclusions

The present study used gene arrays to show that activity of the PPAR signaling pathway involved in the improvement of glucose and lipid metabolism in the liver of UCP2‐deficient mice on a long‐term high‐fat diet. The upregulation of genes in the PPAR signaling pathway could explain our finding that UCP2 deficiency ameliorated insulin sensitivity. The manipulation of UCP2 protein expression could represent a new strategy for the prevention and treatment of diabetes.

Maternal high-fat diet modulates hepatic glucose, lipid homeostasis and gene expression in the PPAR pathway in the early life of offspring

Maternal dietary modifications determine the susceptibility to metabolic diseases in adult life. However, whether maternal high-fat feeding can modulate glucose and lipid metabolism in the early life of offspring is less understood. Furthermore, we explored the underlying mechanisms that influence the phenotype. Using C57BL/6J mice, we examined the effects on the offspring at weaning from dams fed with a high-fat diet or normal chow diet throughout pregnancy and lactation. Gene array experiments and quantitative real-time PCR were performed in the liver tissues of the offspring mice. The offspring of the dams fed the high-fat diet had a heavier body weight, impaired glucose tolerance, decreased insulin sensitivity, increased serum cholesterol and hepatic steatosis at weaning. Bioinformatic analyses indicated that all differentially expressed genes of the offspring between the two groups were mapped to nine pathways. Genes in the peroxisome proliferator-activated receptor (PPAR) signaling pathway were verified by quantitative real-time PCR and these genes were significantly up-regulated in the high-fat diet offspring. A maternal high-fat diet during pregnancy and lactation can modulate hepatic glucose, lipid homeostasis, and gene expression in the PPAR signaling in the early life of offspring, and our results suggested that potential mechanisms that influences this phenotype may be related partially to up-regulate some gene expression in the PPAR signalling pathway.

2-Azetidinone--a new profile of various pharmacological activities

2-azetidinone, a β-lactam four member heterocyclic compound involved in research aimed to evaluate new products that possess interesting biological activities. These compounds reported for their antimicrobial and antifungal activities. Successful introduction of aztreonam as a potent inhibitor of cephalosporinase and ezetimibe as a cholesterol absorption inhibitor proved potential of 2-azetidinone moiety. Subsequently 2-azetidinones were highlighted as a potent mechanism based inhibitor of several enzymes like human tryptase, chymase, thrombin, leukocyte elastase, human cytomegalovirus protease and serine protease enzyme. These derivatives also known to possess antitubercular, anti-inflammatory, antitumor, anti-HIV, antiparkinsonian, antidiabetic and vasopressin V1a antagonist activity. The present review article focuses on the pharmacological profile of 2-azetidinones with their potential activities.

PPARs as new therapeutic targets for the treatment of cerebral ischemia/reperfusion injury

Stroke is a leading cause of death and long-term disability in industrialized countries. Despite advances in understanding its pathophysiology, little progress has been made in the treatment of stroke. The currently available therapies have proven to be highly unsatisfactory (except thrombolysis) and attempts are being made to identify and characterize signaling proteins which could be exploited to design novel therapeutic modalities. The peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that control lipid and glucose metabolism. PPARs regulate gene expression by binding with the retinoid X receptor (RXR) as a heterodimeric partner to specific DNA sequences, termed PPAR response elements. In addition, PPARs may modulate gene transcription also by directly interfering with other transcription factor pathways in a DNA-binding independent manner. To date, three different PPAR isoforms, designated alpha, beta/delta, and gamma, have been identified. Recently, they have been found to play an important role for the pathogenesis of various disorders of the central nervous system and accumulating data suggest that PPARs may serve as potential targets for treating ischemic stroke. Activation of all PPAR isoforms, but especially of PPARgamma, was shown to prevent post-ischemic inflammation and neuronal damage in several in vitro and in vivo models, negatively regulating the expression of genes induced by ischemia/ reperfusion (I/R). This paper reviews the evidence and recent developments relating to the potential therapeutic effects of PPAR-agonists in the treatment of cerebral I/R injury.

Design, synthesis and structure-activity relationships of azole acids as novel, potent dual PPAR alpha/gamma agonists

The design, synthesis and structure-activity relationships of a novel series of N-phenyl-substituted pyrrole, 1,2-pyrazole and 1,2,3-triazole acid analogs as PPAR ligands are outlined. The triazole acid analogs 3f and 4f were identified as potent dual PPARalpha/gamma agonists both in binding and functional assays in vitro. The 3-oxybenzyl triazole acetic acid analog 3f showed excellent glucose and triglyceride lowering in diabetic db/db mice.

Review article: current management of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome.

AIM

To assess the epidemiological impact and the current management of patients with NAFLD.

METHODS

Published peer-reviewed literature and abstracts concerning NAFLD and non-alcoholic steatohepatitis (NASH) were reviewed. Articles specifically related to epidemiology, diagnosis and current treatment strategies for NAFLD and NASH are summarized.

RESULTS

NAFLD is strongly associated with the epidemic of obesity and type-2 diabetes mellitus, and is estimated to affect about 20-30% of the population in the US. From the spectrum of NAFLD, only patients with biopsy-proven NASH (estimated prevalence in the US population is about 3-5%) have been convincingly shown to progress to cirrhosis, liver failure and hepatocellular carcinoma. The clinical manifestation of NAFLD is usually absent or subtle, with abnormal aminotransferases or incidental radiographic findings of fatty liver. The pathogenesis of NAFLD is attributed to a multi-hit process involving insulin resistance, oxidative stress, apoptotic pathways, and adipocytokines. In 2008, there is no established treatment for NAFLD. Weight loss and treatment for each component of metabolic syndrome. Nevertheless, a large number of agents are being considered in clinical trials of patients with NASH.

CONCLUSIONS

Awareness of the tremendous impact of NAFLD as an important cause of chronic liver disease is increasing along with a great deal of information about its pathogenesis. Future, well-designed clinical trials that target specific pathways involved in the pathogenesis of NASH are urgently needed.

Differential effects of oral hypoglycemic agents on glucose control and cardiovascular risk

Cardiovascular disease (CVD) burden remains the predominant cause of mortality and morbidity in the United States and in most of the developed world. The ongoing twin epidemics of obesity and type 2 diabetes mellitus provide a groundswell source for sustaining this trend for the foreseeable future (increasing the prevalence of CVD by 2-4 times), unless radical changes are made in public health policy. Oral hypoglycemic agents (OHAs) remain a mainstay for management of type 2 diabetes in most practice settings. Although these agents are primarily prescribed to achieve better glycemic control, it is important to evaluate what effects they have on cardiovascular risk and whether there are significant differences in effects among the different OHAs. This review presents the available data on the effects of the various OHAs on cardiovascular risk surrogates and actual events in retrospective and prospective study design settings.

Medical treatment of non-alcoholic steatohepatitis

There is no proven medical treatment of non-alcoholic steatohepatitis (NASH). Most prior therapeutic trials have had methodologic limitations. Insulin sensitizers are the more promising therapeutic candidates among categories that include antioxidants, lipid-lowering agents, and antiobesity drugs. The future will see the evaluation of novel agents and a comprehensive treatment strategy that addresses the risk factors for the metabolic syndrome. This article reviews the current status of medical management options for NASH.

Assessment of dose proportionality of muraglitazar after repeated oral dosing in rats via a sparse sampling methodology

Muraglitazar is an alpha/gamma-dual peroxisome proliferator-activated receptor (PPAR) agonist. This study evaluated the single- and multiple-dose oral toxicokinetics of muraglitazar in rats at doses of 3, 30 and 300 mg/kg/day. In total, 15 rats/gender/dose group received muraglitazar every day for 1 month. On both day 1 and day 28, blood samples were obtained at 0.5, 2, 4, 6, 8 and 24 h post-dose, followed by LC/MS analysis. In order to minimize blood loss in the rats, a sparse sampling approach was used to delineate the toxicokinetics. The peak plasma concentration (C(max)) and area under the plasma concentration-time curve (TAUC(0-t)) values for muraglitazar increased in a proportion less than the increment in dose. As the dose increased in the ratio 1:10:100, the C(max) for muraglitazar in male and female rats increased in the ratio of 1:10.3:58.6 and 1:15.3:75.3 on day 1, and 1:5.9:28.1 and 1:13.3:37.3 on day 28, respectively. The corresponding TAUC(0-t) values for males and females were in the ratio of 1:10.2:131 and 1:12.4:131 on day 1, and 1:9.5:93.4 and 1:11.8:94.3 on day 28, respectively. The results indicate that muraglitazar exhibits a dose dependent toxicokinetics in rats and the systemic exposure of muraglitazar was decreased on day 28 compared with day 1.