Peroxisome proliferator-activated receptor-γ and the endothelium: implications in cardiovascular disease

PPARG, TMEM163, UBE2E2 and WFS1 Gene Polymorphisms Are Not Significant Risk Factors for Gestational Diabetes in the Polish Population

Gestational diabetes mellitus (GDM) is a common disorder that occurs in pregnant women, leading to many maternal and neonatal complications. The pathogenesis of GDM is complex and includes risk factors, such as: age, obesity, and family history of diabetes. Studies have shown that genetic factors also play a role in the pathogenesis of GDM. The present study investigated whether polymorphisms in the PPARG (rs1801282), TMEM163 (rs6723108 and rs998451), UBE2E2 (rs6780569), and WFS1 (rs4689388) genes are risk factors for the development of GDM and whether they affect selected clinical parameters in women with GDM. This study included 204 pregnant women with GDM and 207 pregnant women with normal glucose tolerance (NGT). The diagnosis of GDM was based on a 75 g oral glucose tolerance test (OGTT) at 24–28 weeks gestation, according to the International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria. There were no statistically significant differences in the distribution of polymorphisms studied between women with GDM and pregnant women with normal carbohydrate tolerance, which suggests that these polymorphisms are not risk factors for GDM. We also examined the associations between studied gene polymorphisms and clinical parameters: fasting glucose, daily insulin requirement, body mass before pregnancy, body mass at birth, body mass increase during pregnancy, BMI before pregnancy, BMI at birth, BMI increase during pregnancy, new-born body mass, and APGAR score in women with GDM. We observed lower BMI values before pregnancy and at birth in women with PPARG rs17036160 TT genotype. The results of this study suggest that the PPARG (rs1801282), TMEM163 (rs6723108 and rs998451), UBE2E2 (rs6780569), and WFS1 (rs4689388) gene polymorphisms are not significant risk factors for GDM development in the Polish population and do not affect the clinical parameters in women with GDM; only rs1801282 of the PPARG gene may influence BMI values in women with GDM.

Molecular updates on berberine in liver diseases: Bench to bedside

Liver diseases are life-threatening illnesses and are the major cause of mortality and morbidity worldwide. These may include liver fibrosis, liver cirrhosis, and drug-induced liver toxicity. Liver diseases have a wide prevalence globally and the fifth most common cause of death among all gastrointestinal disorders. Several novel therapeutic approaches have emerged for the therapy of liver diseases that may provide better clinical outcomes with improved safety. The use of phytochemicals for the amelioration of liver diseases has gained considerable popularity. Berberine (BBR), an isoquinoline alkaloid of the protoberberine type, has emerged as a promising molecule for the treatment of gastrointestinal disorders. Accumulating studies have proved the hepatoprotective effects of BBR. BBR has been shown to modulate multiple signaling pathways implicated in the pathogenesis of liver diseases including Akt/FoxO2, PPAR-γ, Nrf2, insulin, AMPK, mTOR, and epigenetic pathways. In the present review, we have emphasized the important pharmacological activities and mechanisms of BBR in liver diseases. Further, we have reviewed various pharmacokinetic and toxicological barriers of this promising phytoconstituent. Finally, formulation-based novel approaches are also summarized to overcome the clinical hurdles for BBR.

PPARγ and Its Agonists in Chronic Kidney Disease

Chronic kidney disease (CKD) has become a global healthcare issue. CKD can progress to irreversible end-stage renal diseases (ESRD) or renal failure. The major risk factors for CKD include obesity, diabetes, and cardiovascular diseases. Understanding the key process involved in the disease development may lead to novel interventive strategies, which is currently lagging behind. Peroxisome proliferator-activated receptor γ (PPARγ) is one of the ligand-activated transcription factor superfamily members and is globally expressed in human tissues. Its agonists such as thiazolidinediones (TZDs) have been applied as effective antidiabetic drugs as they control insulin sensitivity in multiple metabolic tissues. Besides, TZDs exert protective effects in multiple other CKD risk disease contexts. As PPARγ is abundantly expressed in major kidney cells, its physiological roles in those cells have been studied in both cell and animal models. The function of PPARγ in the kidney ranges from energy metabolism, cell proliferation to inflammatory suppression, although major renal side effects of existing agonists (including TZDs) have been reported, which limited their application in treating CKD. In the current review, we systemically assess the function of PPARγ in CKDs and the benefits and current limitations of its agonists in the clinical applications.

The Contribution of EDF1 to PPARγ Transcriptional Activation in VEGF-Treated Human Endothelial Cells

Vascular endothelial growth factor (VEGF) is important for maintaining healthy endothelium, which is crucial for vascular integrity. In this paper, we show that VEGF stimulates the nuclear translocation of endothelial differentiation-related factor 1 (EDF1), a highly conserved intracellular protein implicated in molecular events that are pivotal to endothelial function. In the nucleus, EDF1 serves as a transcriptional coactivator of peroxisome proliferator-activated receptor gamma (PPARγ), which has a protective role in the vasculature. Indeed, silencing EDF1 prevents VEGF induction of PPARγ activity as detected by gene reporter assay. Accordingly, silencing EDF1 markedly inhibits the stimulatory effect of VEGF on the expression of FABP4, a PPARγ-inducible gene. As nitric oxide is a marker of endothelial function, it is noteworthy that we report a link between EDF1 silencing, decreased levels of FABP4, and nitric oxide production. We conclude that EDF1 is required for VEGF-induced activation of the transcriptional activity of PPARγ.

Rosiglitazone attenuates indoxyl sulphate-induced endothelial dysfunction

Indoxyl sulphate is a protein-bound uraemic toxin that has deleterious effects on the cardiovascular system. Rosiglitazone (RGZ) is an insulin sensitizer used for glycaemic control in type 2 diabetes. Rosiglitazone has been shown to be beneficial for cardiovascular disease because of its pleiotropic effects. Whether RGZ can improve indoxyl sulphate-induced endothelial damage has not been investigated. In the present in vitro study, we examined the effects of RGZ on indoxyl sulphate-induced endothelial injury. Endothelial cells were exposed to RGZ (5 and 10 μmol/L) and then treated with indoxyl sulphate (100 and 1000 μmol/L) for 48 h. Indoxyl sulphate upregulated intracellular cell adhesion molecule-1, vascular cell adhesion molecule-1 and monocyte chemotactic protein-1 expression. Indoxyl sulphate also increased the abundance of NADPH oxidase 4 (NOX4) and nuclear factor (NF)-κB. Both extracellular signal-regulated kinase (ERK) 1/2 and p38 mitogen-activated protein kinase (MAPK) signalling pathways were activated after 48 h treatment with indoxyl sulphate. Pretreatment of cells with both concentrations of RGZ improved indices of endothelial injury. In addition, RGZ attenuated the increase in NOX4 and NF-κB and prevented the activation of the ERK1/2 and p38 MAPK signalling pathways. We conclude that RGZ ameliorates indoxyl sulphate-induced endothelial injury.

Pathophysiology of coronary vascular remodeling: relationship with traditional risk factors for coronary artery disease

The relationship between cardiovascular risk factors and vascular remodeling is a relatively new area of investigation. We discuss the various mechanisms by which cardiovascular risk factors cause vascular remodeling. Endothelial dysfunction, lipoprotein alterations, inflammation, and platelet activation are the mechanisms by which remodeling occurs. Plaque composition also plays an important role in directing remodeling. Plaque with extensive calcification is more likely to undergo constrictive remodeling. Positive and negative remodeling is based on how these factors coordinate and determine the direction of remodeling. Matrix metalloproteinases perform a crucial role in vascular remodeling. Advanced glycation end-products are key substances involved in the negative remodeling associated with diabetes. Remodeling in hypertension can be either eutrophic or hypertrophic. Endothelial dysfunction and low-grade inflammation lead to negative remodeling in hypertension. Dyslipidemia can be associated with either positive or negative remodeling. High high-density lipoprotein is associated with positive remodeling and high low-density lipoprotein with negative remodeling. Smoking causes endothelial dysfunction, increased oxidative stress, and decreased nitric oxide synthesis leading to inward remodeling. Aging also causes endothelial dysfunction and predisposes to negative remodeling. Knowledge of these associations can elucidate various clinical presentations and guide therapeutic choices in the future.

Osteoblast-targeted suppression of PPARγ increases osteogenesis through activation of mTOR signaling

Nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) is an essential transcription factor for adipocyte differentiation. In mesenchymal stem cells, PPARγ has been assumed to play a negative role in osteoblastic differentiation, by working in an adipogenesis dependent manner, due to the reciprocal relationship between osteoblast and adipocyte differentiation. However, the direct role of PPARγ in osteoblast function is not fully understood, due in part to inadequate model systems. Here, we describe an adenoviral-mediated PPARγ knockout system in which suppression of PPARγ in mesenchymal stem cells enhanced osteoblast differentiation and inhibited adipogenesis in vitro. Consistent with this in vitro observation, lipoatrophic A-ZIP/F1 mice, which do not form adipocytes, displayed a phenotype in which both cortical and trabecular bone was significantly increased compared with wild-type mice. We next developed an inducible osteoblast-targeted PPARγ knockout (Osx Cre/flox- PPARγ) mouse to determine the direct role of PPARγ in bone formation. Data from both in vitro cultures of mesenchymal stem cells and in vivo µCT analysis of bones suggest that suppression of PPARγ activity in osteoblasts significantly increased osteoblast differentiation and trabecular number. Endogenous PPARγ in mesenchymal stem cells and osteoblasts strongly inhibited Akt/mammalian target of rapamycin (mTOR)/p70S6k activity and led to decreased osteoblastic differentiation. Therefore, we conclude that PPARγ modulates osteoblast differentiation and bone formation through both direct and indirect mechanisms. The direct mode, as shown here, involves PPARγ regulation of the mTOR pathway, while the indirect pathway is dependent on the regulation of adipogenesis.

Estrogen sulfotransferase (SULT1E1) regulates inflammatory response and lipid metabolism of human endothelial cells via PPARγ

Estrogen sulfotransferase (SULT1E1) is a phase II drug-metabolizing enzyme known to catalyze sulfoconjugation of estrogens. 17β-estradiol (E2) plays a pivotal role in attenuating endothelial dysfunction. E2 can be further sulfated to estradiol sulfate (E2S) using SULT1E1. To date, there are no reports of expression and function of SULT1E1 in the endothelium. We identified that SULT1E1 is highly expressed in human umbilical vein endothelial cells (HUVECs) using immunofluorescence microscopy and Western immunoblot analyses. A synthesized siRNA targeting SULT1E1 was used to successfully suppress SULT1E1 expression and inhibit estrogen sulfation in HUVECs. This led to functional depletion, as confirmed by a SULT1E1 enzyme activity assay in vitro and by an in vivo estrogen sulfation assay. Knock-down of SULT1E1 in HUVECs resulted in regulation of genes involved in inflammation and lipid metabolism. Interestingly, this regulation was attenuated by PPARγ siRNA and by exposure to the PPARγ antagonist GW9662. Compared with cell response in the absence of estrogen, the effects of SULT1E1 interference on the inflammatory response and lipid metabolism related genes in the presence of 80nM estrogen were completely opposite. When exogenous estrogen was applied, cell responses depended on the ratio of E2 to E2S, due to the activity of SULT1E1, and the different regulation of these processes. It is suggested that E2 sulfation catalyzed by SULT1E1 plays an important role in modulating endothelial cell function.