Peroxisome Proliferator Activated Receptor-α Agonist Slows the Progression of Hypertension, Attenuates Plasma Interleukin-6 Levels and Renal Inflammatory Markers in Angiotensin II Infused Mice

Hepatic Vagotomy in Patients With Obesity Leads to Improvement of the Cholesterol to High-Density Lipoprotein Ratio

INTRODUCTION/PURPOSE

The obesity epidemic is rapidly growing, and visceral adiposity is associated with metabolic consequences secondary to peroxisome proliferator-activated receptor (PPAR)-induced inter-organ signaling pathways. PPARs are ligand-activated transcription factors that modulate vagal pathways which can improve blood pressure, arterial remodeling, cholesterol levels, and insulin sensitivity. However, an obesity-induced inflammatory milieu can interfere with the beneficial effects of PPAR activity, suggesting that a dysregulated PPAR-vagus pathway may play a role in the pathogenesis of obesity-related hypertension. Therefore, we hypothesized that hepatic vagotomy (HV) in patients with obesity would result in a significant reduction in blood pressure and/or the number of hypertension medications compared to control.

METHODS

We conducted a retrospective chart review of 160 patients undergoing laparoscopic sleeve gastrectomy. Patients were divided into HV and control groups, and information was collected at each clinic visit.

RESULTS

At six-months post-operation, the HV group was found to have significantly lower total cholesterol (TC)/high-density lipoprotein (HDL) ratios than the control group. The HV group also had a numerically better blood profile for TC, HDL, low-density lipoprotein (LDL), triglycerides, C-reactive protein, and LDL/HDL ratio. Hypertensive patients in the HV group showed numerically lower hypertension medication counts after six weeks when compared to control.

CONCLUSION

We present the first study to report clinically significant changes related to HV in human subjects. Our results did not support our initial hypothesis but did demonstrate an improvement of the TC/HDL ratio with HV in patients with obesity. Future studies should confirm these findings in a randomized control trial.

Peroxisome proliferator-activated receptors, farnesoid X receptor, and dual modulating drugs in hypertension

Hypertension characterized by an elevated blood pressure is a cardiovascular disease that afflicts greater than one in every three adults worldwide. Nuclear receptors are large superfamily of DNA-binding transcription factors that target genes to regulate metabolic and cardiovascular function. Drugs have been developed for nuclear receptors such as peroxisome proliferator-activated receptors (PPARα and PPARγ) and farnesoid X receptor (FXR). PPARα, PPARγ, and FXR agonists are used clinically to treat lipid disorders and metabolic diseases. Evidence from clinical studies and animal hypertension models have demonstrated that PPARα, PPARγ, and FXR agonism can lower blood pressure and decrease end organ damage which could be useful for the treatment of hypertension in patients with metabolic diseases. Unfortunately, PPAR and FXR agonists have unwanted clinical side effects. There have been recent developments to limit side effects for PPAR and FXR agonists. Combining PPAR and FXR agonism with soluble epoxide hydrolase (sEH) inhibition or Takeda G protein receptor 5 (TGR5) agonism has been demonstrated in preclinical studies to have actions that would decrease clinical side effects. In addition, these dual modulating drugs have been demonstrated in preclinical studies to have blood pressure lowering, anti-fibrotic, and anti-inflammatory actions. There is now an opportunity to thoroughly test these novel dual modulators in animal models of hypertension associated with metabolic diseases. In particular, these newly developed dual modulating PPAR and FXR drugs could be beneficial for the treatment of metabolic diseases, organ fibrosis, and hypertension.

Effects of angiotensin-II on brain endothelial cell permeability via PPARalpha regulation of para- and trans-cellular pathways

Angiotensin-II (Ang-II) is a key factor in hypertension, diabetes and aging, which are all primary risk factors for CNS disease. Furthermore, Ang-II may play under-appreciated roles in neurogenesis, angiogenesis and CNS remodeling. Therefore, any contemplated attempts for neurorestorative therapies in the CNS should consider the context of Ang-II signaling. Here, we investigate how Ang-II may regulate cerebral endothelial permeability, a key functional feature of the neurovascular unit. Exposure of human brain endothelial cell cultures to Ang-II increased its permeability to BSA-Alexa488 tracer. Immunocytochemistry and pulse-chase experiments suggested that both para-cellular as well as trans-cellular pathways were involved. Candesartan but not PD123319 blocked Ang-II permeability effects, suggesting that Ang-II effects may be mediated via type 1 receptor. Immunocytochemistry and western blots showed that Ang-II disrupted the membrane distributions of ZO-1 and VE-Cad, decreased total levels of JAM-A and Mfsd2a, and increased Cav1. These effects of Ang-II were accompanied by dephosphorylation of PPARalpha. Finally, Ang-II-induced increases in endothelial permeability were ameliorated by PPARalpha agonists. Taken together, these studies suggest that Ang-II may disrupt both para- and trans-cellular permeability in cerebral endothelium, and PPARalpha-related pathways may offer potential therapeutic targets for ameliorating these effects in cell-based regenerative medicine.

Genetic Variants Influencing Plasma Renin Activity in Hypertensive Patients From the PEAR Study (Pharmacogenomic Evaluation of Antihypertensive Responses)

BACKGROUND

Plasma renin is an important regulator of blood pressure (BP). Plasma renin activity (PRA) has been shown to correlate with variability in BP response to antihypertensive agents. We conducted a genome-wide association study to identify single-nucleotide polymorphisms (SNPs) associated with baseline PRA using data from the PEAR study (Pharmacogenomic Evaluation of Antihypertensive Responses).

METHODS

Multiple linear regression analysis was performed in 461 whites and 297 blacks using an additive model, adjusting for age, sex, and ancestry-specific principal components. Top SNPs were prioritized by testing the expected direction of association for BP response to atenolol and hydrochlorothiazide. Top regions from the BP response prioritization were tested for functional evidence through differences in gene expression by genotype using RNA sequencing data. Regions with functional evidence were assessed for replication with baseline PRA in an independent study (PEAR-2).

RESULTS

Our top SNP rs3784921 was in the SNN-TXNDC11 gene region. The G allele of rs3784921 was associated with higher baseline PRA (β=0.47; P=2.09×10^-6) and smaller systolic BP reduction in response to hydrochlorothiazide (β=2.97; 1-sided P=0.006). In addition, TXNDC11 expression differed by rs3784921 genotype (P=0.007), and rs1802409, a proxy SNP for rs3784921 (r²=0.98-1.00), replicated in PEAR-2 (β=0.15; 1-sided P=0.038). Additional SNPs associated with baseline PRA that passed BP response prioritization were in/near the genes CHD9, XIRP2, and GHR. CONCLUSIONS: We identified multiple regions associated with baseline PRA that were prioritized through BP response signals to 2 mechanistically different antihypertensive drugs.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT00246519.

Xenobiotic Metabolising Enzymes: Impact on Pathologic Conditions, Drug Interactions and Drug Design

Background:

The biotransformation of xenobiotics is a homeostatic defensive response of the body against bioactive invaders. Xenobiotic metabolizing enzymes, important for the metabolism, elimination and detoxification of exogenous agents, are found in most tissues and organs and are distinguished into phase I and phase II enzymes, as well as phase III transporters. The cytochrome P450 superfamily of enzymes plays a major role in the biotransformation of most xenobiotics as well as in the metabolism of important endogenous substrates such as steroids and fatty acids. The activity and the potential toxicity of numerous drugs are strongly influenced by their biotransformation, mainly accomplished by the cytochrome P450 enzymes, one of the most versatile enzyme systems.

Objective:

In this review, considering the importance of drug metabolising enzymes in health and disease, some of our previous research results are presented, which, combined with newer findings, may assist in the elucidation of xenobiotic metabolism and in the development of more efficient drugs.

Conclusion:

Study of drug metabolism is of major importance for the development of drugs and provides insight into the control of human health. This review is an effort towards this direction and may find useful applications in related medical interventions or help in the development of more efficient drugs.

Rosiglitazone, a Ligand to PPARγ, Improves Blood Pressure and Vascular Function through Renin-Angiotensin System Regulation

Rosiglitazone (RGZ), a peroxisome proliferator-activated receptor gamma (PPARγ) ligand, has been reported to act as insulin sensitizer and exert cardiovascular actions. In this work, we hypothesized that RGZ exerts a PPARγ–dependent regulation of blood pressure through modulation of angiotensin-converting enzyme (ACE)-type 2 (ACE2)/angiotensin-(1-7)/angiotensin II type-2 receptor (AT₂R) axis in an experimental model of high blood pressure. We carried on experiments in normotensive (Sham) and aortic coarctation (AoCo)-induced hypertensive male Wistar rats. Both sham and AoCo rats were treated 7 days with vehicle (V), RGZ (5 mg/kg/day), or RGZ+BADGE (120 mg/kg/day) post-coarctation. We measured blood pressure and vascular reactivity on aortic rings, as well as the expression of renin-angiotensin system (RAS) proteins. We found that RGZ treatment in AoCo group decreases blood pressure values and improves vascular response to acetylcholine, both parameters dependent on PPARγ-stimulation. RGZ lowered serum angiotensin II (AngII) but increased Ang-(1-7) levels. It also decreased 8-hydroxy-2′-deoxyguanosine (8-OH-2dG), malondialdehyde (MDA), and improved the antioxidant capacity. Regarding protein expression of RAS, RGZ decreases ACE and angiotensin II type 1 receptor (AT₁R) and improved ACE2, AT₂R, and Mas receptor in AoCo rats. Additionally, an in silico analysis revealed that 5′UTR regions of RAS and PPARγ share motifs with a transcriptional regulatory role. We conclude that RGZ lowers blood pressure values by increasing the expression of RAS axis proteins ACE2 and AT₂R, decreasing the levels of AngII and increasing levels of Ang-(1-7) in a PPARγ-dependent manner. The in silico analysis is a valuable tool to predict the interaction between PPARγ and RAS.

The endocannabinoid system in cardiovascular function: novel insights and clinical implications

RATIONALE

Cardiovascular disease is now recognized as the number one cause of death in the world, and the size of the population at risk continues to increase rapidly. The dysregulation of the endocannabinoid (eCB) system plays a central role in a wide variety of conditions including cardiovascular disorders. Cannabinoid receptors, their endogenous ligands, as well as enzymes conferring their synthesis and degradation, exhibit overlapping distributions in the cardiovascular system. Furthermore, the pharmacological manipulation of the eCB system has effects on blood pressure, cardiac contractility, and endothelial vasomotor control. Growing evidence from animal studies supports the significance of the eCB system in cardiovascular disorders.

OBJECTIVE

To summarize the literature surrounding the eCB system in cardiovascular function and disease and the new compounds that may potentially extend the range of available interventions.

RESULTS

Drugs targeting CB1R, CB2R, TRPV1 and PPARs are proven effective in animal models mimicking cardiovascular disorders such as hypertension, atherosclerosis and myocardial infarction. Despite the setback of two clinical trials that exhibited unexpected harmful side-effects, preclinical studies are accelerating the development of more selective drugs with promising results devoid of adverse effects.

CONCLUSION

Over the last years, increasing evidence from basic and clinical research supports the role of the eCB system in cardiovascular function. Whereas new discoveries are paving the way for the identification of novel drugs and therapeutic targets, the close cooperation of researchers, clinicians and pharmaceutical companies is needed to achieve successful outcomes.

Fenofibrate Therapy Restores Antioxidant Protection and Improves Myocardial Insulin Resistance in a Rat Model of Metabolic Syndrome and Myocardial Ischemia: The Role of Angiotensin II

Renin-angiotensin system (RAS) activation promotes oxidative stress which increases the risk of cardiac dysfunction in metabolic syndrome (MetS) and favors local insulin resistance. Fibrates regulate RAS improving MetS, type-2 diabetes and cardiovascular diseases. We studied the effect of fenofibrate treatment on the myocardic signaling pathway of Angiotensin II (Ang II)/Angiotensin II type 1 receptor (AT1) and its relationship with oxidative stress and myocardial insulin resistance in MetS rats under heart ischemia. Control and MetS rats were assigned to the following groups: (a) sham; (b) vehicle-treated myocardial infarction (MI) (MI-V); and (c) fenofibrate-treated myocardial infarction (MI-F). Treatment with fenofibrate significantly reduced triglycerides, non-high density lipoprotein cholesterol (non-HDL-C), insulin levels and insulin resistance index (HOMA-IR) in MetS animals. MetS and MI increased Ang II concentration and AT1 expression, favored myocardial oxidative stress (high levels of malondialdehyde, overexpression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4), decreased total antioxidant capacity and diminished expression of superoxide dismutase (SOD)1, SOD2 and catalase) and inhibited expression of the insulin signaling cascade: phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PkB, also known as Akt)/Glut-4/endothelial nitric oxide synthase (eNOS). In conclusion, fenofibrate treatment favors an antioxidant environment as a consequence of a reduction of the Ang II/AT1/NOX4 signaling pathway, reestablishing the cardiac insulin signaling pathway. This might optimize cardiac metabolism and improve the vasodilator function during myocardial ischemia.

Effect of DanQi Pill on PPARα, lipid disorders and arachidonic acid pathway in rat model of coronary heart disease

Background

Danqi pill (DQP) is one of the most widely prescribed formulas and has been shown to have remarkable protective effect on coronary heart disease (CHD). However, its regulatory effects on lipid metabolism disorders haven’t been comprehensively studied so far. We aimed to explore the effects of DQP on Peroxisome Proliferator activated receptors α (PPARα), lipid uptake-transportation-metabolism pathway and arachidonic acid (AA)-mediated inflammation pathway in rats with CHD.

Methods

80 Sprague-Dawley (SD) Rats were randomly divided into sham group, model group, positive control group and DQP group. Rat model of CHD was induced by ligation of left ventricle anterior descending artery and fed with high fat diet in all but the sham group. Rats in sham group only underwent thoracotomy. After surgery, rats in the positive control and DQP group received daily treatments of pravastatin and DQP respectively. At 28 days after surgery, rats were sacrificed and plasma lipids were evaluated by plasma biochemical detection. Western blot and PCR were applied to evaluate the expressions of PPARα, proteins involved in lipid metabolism and AA pathways.

Results

Twenty eight days after surgery, dyslipidemia developed in CHD model rats, as illustrated by elevated plasma lipid levels. Expressions of apolipoprotein A-I (ApoA-I), cluster of differentiation 36 (CD36) and fatty acid binding protein (FABP) in the heart tissues of model group were down-regulated compared with those in sham group. Expressions of carnitine palmitoyl transferase I (CPT-1A) and lipoproteinlipase (LPL) were also reduced significantly. In addition, levels of phospholipase A2 (PLA2) and cyclooxygenase 2 (COX-2) were up-regulated. Expressions of Nuclear factor-κB (NF- κB) and signal transducer and activator of transcription 3 (STAT3) also increased. Furthermore, Expression of PPARα decreased in the model group. DQP significantly up-regulated expressions of ApoA-I and FABP, as well as the expressions of CPT-1A and CD36. In addition, DQP down-regulated expressions of PLA2, COX-2 and NF-κB in inflammation pathway. Levels of STAT3 and LPL were not affected by DQP treatment. In particular, DQP up-regulated PPARα level significantly.

Conclusions

DQP could effectively regulate lipid uptake-transportation-metabolism process in CHD model rats, and the effect is achieved mainly by activating ApoA-I-CD36-CPT-1A molecules. Interestingly, DQP can up-regulate expression of PPARα significantly. The anti-inflammatory effect of DQP is partly exerted by inhibiting expressions of PLA2-COX2 -NF-κB pathway.

Restoration of Endothelial Function in Pparα (-/-) Mice by Tempol

Peroxisome proliferator activated receptor alpha (PPARα) is one of the PPAR isoforms belonging to the nuclear hormone receptor superfamily that regulates genes involved in lipid and lipoprotein metabolism. PPARα is present in the vascular wall and is thought to be involved in protection against vascular disease. To determine if PPARα contributes to endothelial function, conduit and cerebral resistance arteries were studied in Pparα^−/− mice using isometric and isobaric tension myography, respectively. Aortic contractions to PGF_2α and constriction of middle cerebral arteries to phenylephrine were not different between wild type (WT) and Pparα^−/−; however, relaxation/dilation to acetylcholine (ACh) was impaired. There was no difference in relaxation between WT and Pparα^−/− aorta to treatment with a nitric oxide (NO) surrogate indicating impairment in endothelial function. Endothelial NO levels as well as NO synthase expression were reduced in Pparα^−/− aortas, while superoxide levels were elevated. Two-week feeding with the reactive oxygen species (ROS) scavenger, tempol, normalized ROS levels and rescued the impaired endothelium-mediated relaxation in Pparα^−/− mice. These results suggest that Pparα^−/− mice have impaired endothelial function caused by decreased NO bioavailability. Therefore, activation of PPARα receptors may be a therapeutic target for maintaining endothelial function and protection against cardiovascular disease.

The SGLT2 inhibitor empagliflozin ameliorates early features of diabetic nephropathy in BTBR ob/ob type 2 diabetic mice with and without hypertension

Diabetic nephropathy is the leading cause of end-stage renal disease in humans in the Western world. The recent development of Na+-glucose cotransporter 2 (SGLT2) inhibitors offers a new antidiabetic therapy via enhanced glucose excretion. Whether this strategy exerts beneficial effects on the development of type 2 diabetic nephropathy is still largely unclear. We investigated the effects of the specific SGLT2 inhibitor empagliflozin in BTBR.Cg-Lep<ob>/WiscJ (BTBR ob/ob) mice, which spontaneously develop type 2 diabetic nephropathy. In the first experiment, BTBR ob/ob mice received either a diet containing 300 ppm empagliflozin or equicaloric placebo chow for 12 wk. In the second experiment, BTBR ob/ob mice received 1 μg·kg body wt(-1)·day(-1) ANG II to induce arterial hypertension and were separated into the same two diet groups for 6 wk. In both experiments, empagliflozin treatment enhanced glucosuria, thereby lowering blood glucose. Independently of hypertension, empagliflozin reduced albuminuria in diabetic mice. However, empagliflozin treatment affected diabetes-related glomerular hypertrophy, markers of renal inflammation, and mesangial matrix expansion only in BTBR ob/ob mice without hypertension. In summary, empagliflozin demonstrated significant antihyperglycemic effects, differentially ameliorating early features of diabetic nephropathy in BTBR ob/ob mice with and without hypertension.

PPARα ligand clofibrate ameliorates blood pressure and vascular reactivity in spontaneously hypertensive rats

AIM

Peroxisome proliferator activated receptors (PPARs) are nuclear transcription factors that regulate numerous genes influencing blood pressure. The aim of this study was to examine the effects of clofibrate, a PPARα ligand, on blood pressure in spontaneously hypertensive rats (SHR).

METHODS

Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR), 8-9 weeks old, were randomly allocated into groups treated with vehicle or clofibrate (250 mg·kg(-1)·d(-1), ip for 21 d). Systolic blood pressure (SBP) was measured before and after the study period using tail-cuff plethysmography. Rats were sacrificed under anesthesia and blood, urine and tissue samples were processed for subsequent analysis.

RESULTS

SHR rats showed significantly higher SBP compared with WKY rats (198±6 mmHg vs 93±7 mmHg), and a 3-fold increase in urinary protein excretion. Clofibrate treatment reduced SBP by 26%±2% and proteinuria by 43%±9% in SHR but not in WKY rats. The urinary nitrite/nitrate excretion in SHR rats was nearly 2-fold greater than that in WKY, and was further increased by 30%±4% and 48%±3%, respectively, following clofibrate treatment. In addition, PPARα protein expression and PPARα activity were significantly lower in SHR than that in WKY rats. Clofibrate treatment significantly increased PPARα protein expression and PPARα activity in SHR rats, but not in WKY rats. Moreover, the vasoconstrictor response of aortic ring was markedly increased in SHRs, which was blunted after clofibrate treatment.

CONCLUSION

PPARα contributes to regulation of blood pressure and vascular reactivity in SHR, and clofibrate-mediated reduction in blood pressure and proteinuria is probably through increased NO production.

Role of peroxisome proliferator-activated receptor α in atherosclerosis

Atherosclerosis is an inflammatory disease involving the immune response. In addition to lowering the cholesterol level, the peroxisome proliferator-activated receptor α (PPAR-α) can prevent atherosclerosis via its pleiotropic anti-inflammatory effects. However, the role of PPAR-α in modulating inflammatory progression of atherosclerosis has rarely been studied. Thus, we aimed to investigate the role of PPAR-α in atherosclerosis by evaluating the expression of inflammatory cytokines induced by PPAR-α in an in vivo rabbit model. New Zealand White rabbits were randomly divided into 5 groups: control, high-fat diet + balloon injury, high-fat diet + balloon injury + placebo, high-fat diet + balloon injury + fenofibrate, and high-fat diet + balloon injury + WY-14643. The femoral arteries of rabbits were balloon-injured after initiation of the high-fat diet and before administration of fenofibrate, WY-14643 or placebo solution. Atherosclerosis was induced by high-fat diet and balloon angioplasty, and the vessel wall lumen occlusion was determined by measuring the stenosis rate. PPAR-α gene expression was examined by quantitative polymerase chain reaction analysis. The cellular localization and distribution of PPAR-α was observed by immunohistochemistry, and its protein level was assessed by western blot analysis. The production of interleukin-10 (IL-10), tumor necrosis factor-α (TNF-α) and P-selectin, which are major inflammatory factors involved in atherosclerosis, was monitored by an enzyme-linked immunosorbent assay (ELISA). Treatment with PPAR-α agonists (fenofibrate or WY-14643) reduced the vascular occlusion rate, as compared to the high-fat diet + balloon injury and the placebo groups. Furthermore, the expression of PPAR-α at both the protein and the mRNA level was increased in the fenofibrate and WY-14643 groups. According to the results, the TNF-α and P-selectin levels were reduced in the fenofibrate and WY-14643 groups. These results suggest that PPAR-α activation can attenuate the effects of atherosclerosis by inhibiting the expression of major inflammatory factors in a rabbit atherosclerosis model.

Is there a role for the incretin system in blood pressure regulation?

Incretin-based therapies are now well established for diabetes management and are among the frontline agents for control of hyperglycemia. In addition to their antihyperglycemic effects, evidence is emerging on the role of these agents on blood pressure regulation, cardioprotective and renoprotective properties. Because of the pleiotropic nature of these affects, these agents could offer significant benefits with regards to the cardiorenal metabolic complications that are part of the diabetes and obesity epidemic in the United States and worldwide. We review the various known mechanisms or pathways by which incretin based therapy exerts its regulation of blood pressure with emphasis on novel mechanisms such as inflammation/immunomodulation and oxidative stress.

Fibrate treatment of eEOCs in murine AKI

BACKGROUND

Early endothelial outgrowth cells (eEOCs) protect mice from acute kidney injury (AKI). Peroxisome proliferator-activated receptor-alpha (PPAR-α) has been shown to mediate renoprotective effects under different experimental conditions. The aim of the study was to investigate consequences of fibrate treatment of murine eEOCs in a cell-based therapeutic approach to AKI.

METHODS

Male C57/Bl6N mice, subjected to unilateral renal ischemia (40 min) post-uninephrectomy, were systemically injected with 0.5 × 10(6) untreated or fenofibrate (FF 1, 5, 10 or 50 μm)/clofibrate (CF 1 mm) pretreated syngeneic murine eEOCs. Renal function and morphology were analyzed 48 h later. Cellular consequences of eEOC treatment with fibrates (FF 1, 5, 10, 50 μm, CF 1 mm) were evaluated using different in vitro assays (direct cell migration, apoptosis/necrosis, ELISA studies).

RESULTS

Administration of untreated eEOCs did not protect mice from AKI. Injection of eEOCs treated with CF (1 mm) or FF 50 μm did not result in any protection from ischemia-induced renal dysfunction. In vitro analysis showed reduced cellular secretion of vasoprotective vascular endothelial growth factor (VEGF), an effect that was more pronounced with CF; FF increased percentages of apoptotic/necrotic eEOCs, and both substances failed to stimulate migration of cultured cells. With lower FF concentrations (1, 5, 10 μm) cell survival was increased and 10 μm FF stimulated VEGF secretion. In vivo administration of FF-treated eEOCs (10 μm) also did not result in any renoprotective effect.

CONCLUSION

PPAR-α activation using fibrates does not stimulate renoprotective effects of syngeneic murine eEOCs in ischemic AKI, although lower fibrate concentrations significantly activate eEOCs in vitro.