Lupeol alleviates autoimmune myocarditis by suppressing macrophage pyroptosis and polarization via PPARα/LACC1/NF-κB signaling pathway.

BACKGROUND: Autoimmune myocarditis, with increasing incidence and limited therapeutic strategies, is in urgent need to explore its underlying mechanisms and effective drugs. Pyroptosis is a programmed cell death that may contribute to the pathogenesis of myocarditis. Nonetheless, no direct evidence validated the role of pyroptosis in autoimmune myocarditis. Lupeol (Lup), a pentacyclic triterpene, possesses various biological activities such as antidiabetic properties. However, the effects of Lup on autoimmune myocarditis and pyroptosis remain unelucidated. PURPOSE: This study aimed to reveal the role of pyroptosis in autoimmune myocarditis and explore the protective effects of Lup, and its engaged mechanisms. METHODS: The experimental autoimmune myocarditis (EAM) mouse model was established by immunization with a fragment of cardiac myosin in Balb/c mice. Lup and MCC950 were administered after EAM induction. The protective effects were assessed by inflammation score, cardiac injury, chronic fibrosis, and cardiac function. Mechanistically, the effects of Lup on the M1 polarization and pyroptosis of macrophages were evaluated. Transcriptome sequencing and molecular docking were subsequently employed, and the underlying mechanisms of Lup were further explored in vitro with small interfering RNA and adenovirus. RESULTS: Administration of Lup and MCC950 alleviated EAM progression. Western blotting and immunofluorescence staining identified macrophages as the primary cells undergoing pyroptosis. Lup inhibited the expression of pyroptosis-associated proteins in macrophages during EAM in a dose-dependent manner. Furthermore, Lup suppressed pyroptosis in both bone marrow-derived macrophages (BMDMs) and THP-1-derived macrophages in vitro. In addition, Lup inhibited the M1 polarization of macrophages both in vivo and in vitro. Mechanistically, the protective effects of Lup were demonstrated via the suppression of the nuclear factor-κΒ (NF-κB) signaling pathway. Transcriptome sequencing and molecular docking revealed the potential involvement of peroxisome proliferator-associated receptor α (PPARα). Subsequently, we demonstrated that Lup activated PPARα to reduce the expression level of LACC1, thereby inhibiting the NF-κB pathway and pyroptosis. CONCLUSION: Our findings indicated the crucial role of macrophage pyroptosis in the pathogenesis of EAM. Lup ameliorated EAM by inhibiting the M1 polarization and pyroptosis of macrophages through the PPARα/LACC1/NF-κB signaling pathway. Thus, our results provided a novel therapeutic target and agent for myocarditis.

Auraptene, a citrus peel-derived natural product, prevents myocardial infarction-induced heart failure by activating PPARα in rats.

BACKGROUND: Auraptene derived from the peel of Citrus hassaku possesses anti-tumor, anti-inflammatory, and neuroprotective activities. Thus, it could be a valuable pharmacological alternative to treat some diseases. However, the therapeutic value of auraptene for heart failure (HF) is unknown. STUDY DESIGN/METHODS: In cultured cardiomyocytes from neonatal rats, the effect of auraptene on phenylephrine-induced hypertrophic responses and peroxisome proliferator-activated receptor-alpha (PPARα)-dependent gene transcriptions. To investigate whether auraptene prevents the development of heart failure after myocardial infarction (MI) in vivo, Sprague-Dawley rats with moderate MI (fractional shortening < 40%) were randomly assigned for treatment with low- or high-dose auraptene (5 or 50 mg/kg/day, respectively) or vehicle for 6 weeks. The effects of auraptene were evaluated by echocardiography, histological analysis, and the measurement of mRNA levels of hypertrophy, fibrosis, and PPARα-associated genes. RESULTS: In cultured cardiomyocytes, auraptene repressed phenylephrine-induced hypertrophic responses, such as increases in cell size and activities of atrial natriuretic factor and endothelin-1 promoters. Auraptene induced PPARα-dependent gene activation by enhancing cardiomyocyte peroxisome proliferator-responsive element reporter activity. The inhibition of PPARα abrogated the protective effect of auraptene on phenylephrine-induced hypertrophic responses. In rats with MI, auraptene significantly improved MI-induced systolic dysfunction and increased posterior wall thickness compared to the vehicle. Auraptene treatment also suppressed MI-induced increases in myocardial cell diameter, perivascular fibrosis, and expression of hypertrophy and fibrosis response markers at the mRNA level compared with vehicle treatment. MI-induced decreases in the expression of PPARα-dependent genes were improved by auraptene treatment. CONCLUSIONS: Auraptene has beneficial effects on MI-induced cardiac hypertrophy and left ventricular systolic dysfunction in rats, at least partly due to PPARα activation. Further clinical studies are required to evaluate the efficacy of auraptene in patients with HF.

Brassica rapa L. (Tibetan turnip) prevents sleep-deprivation induced cognitive deficits via the inhibition of neuroinflammation and mitochondrial depolarization.

Brassica rapa L., an edible, feeding and medicinal plant cultivated on the Tibetan plateau with altitudes above 3800 m, has several pharmacological effects. However, its therapeutic effects against memory impairment and central fatigue have yet to be conclusively established. In this study, the Y-maze and Morris water maze tasks revealed that Brassica rapa L. aqueous extract (BE) significantly ameliorated cognitive deficits of sleep deprivation (SD)-treated mice. Moreover, BE treatment partially alleviated SD-induced reductions in the levels of peripheral energy metabolism, and significantly decreased inflammatory factor levels in serum and hippocampus. In addition, BE treatment significantly relieved central fatigue and stabilized the excitability as well as activities of neurons by regulating the levels of hypothalamus tryptophan metabolites and striatum neurotransmitters. The neuroprotective effects of BE were also confirmed using glutamate-treated HT22 cells, whereby BE pretreatment significantly attenuated intracellular ROS production and mitochondrial depolarization via adenosine 5'-monophosphate activated protein kinase/peroxisome proliferators-activated receptors (AMPK/PPAR-γ) signaling pathways. Thus, BE might probably prevent SD-induced learning and memory deficits by inhibiting neuroinflammation and restoring mitochondrial energy metabolism in the hippocampus. These findings imply that BE is a potential complementary therapy for those suffering from deficient sleep or neurometabolic disorders, although this needs verification by prospective clinical studies.

Synthetic PPAR Agonist DTMB Alleviates Alzheimer's Disease Pathology by Inhibition of Chronic Microglial Inflammation in 5xFAD Mice.

Abnormal productions of amyloid beta (Aß) plaque and chronic neuroinflammation are commonly observed in the brain of patients with Alzheimer's disease, and both of which induce neuronal cell death, loss of memory, and cognitive dysfunction. However, many of the drugs targeting the production of Aß peptides have been unsuccessful in treating Alzheimer's disease. In this study, we identified synthetic novel peroxisome proliferator-activating receptor (PPAR) agonist, DTMB, which can ameliorate the chronic inflammation and Aß pathological progression of Alzheimer's disease. We discovered that DTMB attenuated the proinflammatory cytokine production of microglia by reducing the protein level of NF-κB. DTMB also improved the learning and memory defects and reduced the amount of Aß plaque in the brain of 5xFAD mice. This reduction in Aß pathology was attributed to the changes in gliosis and chronic inflammation level. Additionally, bulk RNA-sequencing showed that genes related to inflammation and cognitive function were changed in the hippocampus and cortex of DTMB-treated mice. Our findings demonstrate that DTMB has the potential to be a novel therapeutic agent for Alzheimer's disease.

PPARα agonist WY-14,643 induces adipose atrophy and fails to blunt chronic ethanol-induced hepatic fat accumulation in mice lacking adipose FGFR1.

Fibroblast growth factor 21 (FGF21) is mainly regulated by peroxisome proliferator-activated receptor α (PPARα) in liver. The PPARα-FGF21 axis protects against alcohol-related liver disease (ALD). FGF21 exerts its effect via FGF receptor 1 (FGFR1). However, liver specific FGFR1 abrogation had no effect on ALD. Adipose tissues highly express FGFR1. When adipocyte specific FGFR1 knockout (fgfr1adipoQ-cre) mice and corresponding normal control (fgfr1fl/fl) mice were fed with Lieber-DeCarli ethanol liquid diet for 3 weeks, liver triglyceride (TG) accumulation was increased in the fgfr1fl/fl mice to a greater extent than in the fgfr1adipoQ-cre mice. When PPARα agonist WY-14,643 was added in the liquid ethanol diet at 10 mg/L, the ethanol-induced liver TG accumulation was blunted in the fgfr1fl/fl mice but not in the fgfr1adipoQ-cre mice. There was no significant difference in WY-14,643-induced fatty acid oxidation, ethanol metabolism, and oxidative stress between the fgfr1fl/fl and fgfr1adipoQ-cre mice. Interestingly, adipose atrophy was induced by WY-14,643 in the fgfr1adipoQ-cre mice but not in the fgfr1fl/fl mice. Serum free fatty acid was also decreased by WY-14,643 in the fgfr1adipoQ-cre mice but not in the fgfr1fl/fl mice. These results suggest that WY-14,643 inhibits alcoholic fatty liver and regulates adipose tissue mass and fat mobilization from adipose tissues to liver in an adipocyte FGFR1-dependent manner.

WY14643 produces anti-depressant-like effects in mice via the BDNF signaling pathway.

RATIONALE: Current anti-depressants are clinically effective only after several weeks of administration and always produce side effects. OBJECTIVES: WY14643 is a selective agonist of peroxisome proliferator-activated receptor-α with neuroprotective and neurotrophic effects. Here, we investigated the anti-depressant effects of WY14643 in mice models of depression. METHODS: We assessed the anti-depressant effects of WY14643 in the forced swim test (FST), tail suspension test (TST) and chronic social defeat stress (CSDS) model. Western blotting and immunohistochemistry studies were further performed to detect the effects of WY14643 on the brain-derived neurotrophic factor (BDNF) signaling pathway and hippocampal neurogenesis. The anti-BDNF antibody, BDNF signaling inhibitor, and tryptophan hydroxylase inhibitor were also used to explore the anti-depressant mechanisms of WY14643. RESULTS: WY14643 exhibited robust anti-depressant effects in the FST and TST and also protected against the CSDS stress in mice models. Moreover, WY14643 reversed the stress-induced elevation of corticosterone, deficiency of BDNF signaling pathway, and hippocampal neurogenesis. Blockade of BDNF signaling cascade, not the monoaminergic system, abolished all the anti-depressant effects of WY14643. CONCLUSIONS: These data provide the first evidence that WY14643 exerts anti-depressant-like activity through promoting the BDNF signaling pathway.

PPAR-alpha activation as a preconditioning-like intervention in rats in vivo confers myocardial protection against acute ischaemia-reperfusion injury: involvement of PI3K-Akt.

Peroxisome proliferator-activated receptors (PPAR) regulate the expression of genes involved in lipid metabolism, energy production, and inflammation. Their role in ischaemia-reperfusion (I/R) is less clear, although research indicates involvement of PPARs in some forms of preconditioning. This study aimed to explore the effects of PPAR-α activation on the I/R injury and potential cardioprotective downstream mechanisms involved. Langendorff-perfused hearts of rats pretreated with the selective PPAR-α agonist WY-14643 (WY, pirinixic acid; 3 mg·(kg body mass)·day(-1); 5 days) were subjected to 30 min ischaemia - 2 h reperfusion with or without the phosphatidylinositol 3-kinase (PI3K)-Akt inhibitor wortmannin for the evaluation of functional (left ventricular developed pressure, LVDP) recovery, infarct size (IS), and reperfusion-induced arrhythmias. A 2-fold increase in baseline PPAR-α mRNA levels (qPCR) in the WY-treated group and higher post-I/R PPAR-α levels compared with those in untreated controls were accompanied by similar changes in the expression of PPAR-α target genes PDK4 and mCPT-1, regulating glucose and fatty acid metabolism, and by enhanced Akt phosphorylation. Post-ischaemic LVDP restoration in WY-treated hearts reached 60% ± 9% of the pre-ischaemic values compared with 24% ± 3% in the control hearts (P < 0.05), coupled with reduced IS and incidence of ventricular fibrillation that was blunted by wortmannin. Results indicate that PPAR-α up-regulation may confer preconditioning-like protection via metabolic effects. Downstream mechanisms of PPAR-α-mediated cardioprotection may involve PI3K-Akt activation.

Plasma mannose-binding lectin is stimulated by PPARα in humans.

The peroxisome proliferator activated receptor-α (PPARα) is a major transcriptional regulator of lipid metabolism in liver and represents the molecular target for hypolipidemic fibrate drugs. Effects of PPARα on lipid metabolism are partially mediated by circulating proteins such as FGF21 and ANGPTL4. The present study was undertaken to screen for and identify circulating proteins produced by human liver that are under the control of PPARα. Toward that aim, primary human hepatocytes were treated with the synthetic PPARα agonist Wy-14643 and whole genome expression data selected for secreted proteins. Expression of FGF21, ANGPTL4, and mannose-binding lectin (MBL), a soluble mediator of innate immunity and primary component of the lectin branch of the complement system, was markedly upregulated by Wy-14643 in primary human hepatocytes. Mice express two MBL isomers, Mbl1 and Mbl2. Mbl1 mRNA was weakly induced by Wy-14643 in primary mouse hepatocytes and remained unaltered by Wy-14643 in mouse liver. Mbl2 mRNA was unchanged by Wy-14643 in primary mouse hepatocytes and was strongly reduced by Wy-14643 in mouse liver. Remarkably, plasma Mbl1 levels were increased by chronic PPARα activation in lean and obese mice. Importantly, in two independent clinical trials, treatment with the PPARα agonist fenofibrate at 200 mg/day for 6 wk and 3 mo increased plasma MBL levels by 73 (P = 0.0016) and 86% (P = 0.017), respectively. It is concluded that hepatocyte gene expression and plasma levels of MBL are stimulated by PPARα and fenofibrate in humans, linking PPARα to regulation of innate immunity and complement activation in humans and suggesting a possible role of MBL in lipid metabolism.

The effects of a PPARalpha agonist on myocardial damage in obese diabetic mice with heart failure.

Recent studies have confirmed that PPARalpha agonists have not brought the anticipated benefits to patients with type 2 diabetes and potentially fatal heart disease. We hypothesized that such agonists may have a cardio-suppressive effect in treating such disorders, therefore, we inoculated diabetic KKAy mice with encephalomyocarditis virus (EMCv) to induce a diabetic model with severe myocardial damage. WY14643, a potent PPARalpha agonist, was administered intraperitoneally either simultaneously (WY14643-late group) or 3 days before viral inoculation (WY14643-early group). WY14643-treated mice, especially those in the WY14643-early group, had higher mortality than those in the vehicle-treated group (vehicle) in the first 5 days after EMCv inoculation. However, the survival rate in the vehicle group decreased rapidly after day 4 and was the lowest of all 3 groups by day 9. The WY14643-treated mice showed reduced body weight and blood glucose, improved myocardial pathological changes, lower cardiac TNF-alpha expression, and significantly higher adiponectin expression, whereas the LW/LC ratio was lower and cardiac UCP3 mRNA expression higher in the WY14643 treatment groups than in the vehicle group on day 4. WY14643 therefore has cardioprotective and cardio-suppressive effects when used to treat EMCv-induced myocarditis in diabetic mice. The cardioprotective effect may be due to its anti-inflammatory properties and its ability to increase cardiac adiponectin expression, whereas the reduced cardiac efficiency may be due to its enhancement of cardiac UCP3 mRNA expression.

Short-term therapy with peroxisome proliferation-activator receptor-alpha agonist Wy-14,643 protects murine fatty liver against ischemia-reperfusion injury.

UNLABELLED: Steatosis increases operative morbidity/mortality from ischemia-reperfusion injury (IRI); few pharmacological approaches have been protective. Using novel genetic/dietary models of nonalcoholic steatohepatitis (NASH) and simple steatosis (SS) in Alms1 mutant (foz/foz) mice, we characterized severity of IRI in NASH versus SS and lean liver and tested our hypothesis that the lipid-lowering effects of the peroxisome proliferation-activator receptor (PPAR)-alpha agonist Wy-14,643 would be hepatoprotective. Mice were subjected to 60-minute partial hepatic IRI. Microvascular changes were assessed at 15-minute reperfusion by in vivo microscopy, injury at 24 hours by serum alanine aminotransferase (ALT), and hepatic necrosis area. Injury and inflammation mediators were determined by way of immunoblotting for intercellular cellular adhesion molecule, vascular cellular adhesion molecule, p38, c-jun N-terminal kinase, IkappaB-alpha, interleukin (IL)-1a, IL-12, tumor necrosis factor-alpha (TNF-alpha) and IL-6, cell cycle by cyclin D1 and proliferating cell nuclear antigen immunohistochemistry. In foz/foz mice fed a high-fat diet (HFD) to cause NASH or chow (SS), IRI was exacerbated compared with HFD-fed or chow-fed wild-type littermates by ALT release; corresponding necrotic areas were 60 +/- 22% NASH, 29 +/- 9% SS versus 7 +/- 1% lean. Microvasculature of NASH or SS livers was narrowed by enormous lipid-filled hepatocytes, significantly reducing numbers of perfused sinusoids, all exacerbated by IRI. Wy-14,643 reduced steatosis in NASH and SS livers, whereas PPAR-alpha stimulation conferred substantial hepatoprotection against IRI by ALT release, with reductions in vascular cellular adhesion molecule-1, IL-1a, TNF-alpha, IL-12, activated nuclear factor-kappaB (NF-kappaB), p38, IL-6 production and cell cycle entry. CONCLUSION: NASH and SS livers are both more susceptible to IRI. Mechanisms include possible distortion of the microvasculature by swollen fat-laden hepatocytes, and enhanced production of several cytokines. The beneficial effects of Wy-14,643 may be exerted by dampening adhesion molecule and cytokine responses, and activating NF-kappaB, IL-6 production, and p38 kinase to effect cell cycle entry.

WY14,643, a PPARalpha ligand, attenuates expression of anti-glomerular basement membrane disease.

Peroxisome proliferator-activated receptor alpha (PPARalpha) ligands are medications used to treat hyperlipidaemia and atherosclerosis. Increasing evidence suggests that these agents are immunosuppressive. In the following studies we demonstrate that WY14,643, a PPARalpha ligand, attenuates expression of anti-glomerular basement membrane disease (AGBMD). C57BL/6 mice were fed 0.05% WY14,643 or control food and immunized with the non-collagenous domain of the alpha3 chain of Type IV collagen [alpha3(IV) NC1] in complete Freund's adjuvant (CFA). WY14,643 reduced proteinuria and greatly improved glomerular and tubulo-interstitial lesions. However, the PPARalpha ligand did not alter the extent of IgG-binding to the GBM. Immunohistochemical studies revealed that the prominent tubulo-interstitial infiltrates in the control-fed mice consisted predominately of F4/80(+) macrophages and WY14,643-feeding decreased significantly the number of renal macrophages. The synthetic PPARalpha ligand also reduced significantly expression of the chemokine, monocyte chemoattractant protein (MCP)-1/CCL2. Sera from mice immunized with AGBMD were also evaluated for antigen-specific IgGs. There was a significant increase in the IgG1 : IgG2c ratio and a decline in the intrarenal and splenocyte interferon (IFN)-gamma mRNA expression in the WY14,643-fed mice, suggesting that the PPARalpha ligand could skew the immune response to a less inflammatory T helper 2-type of response. These studies suggest that PPARalpha ligands may be a novel treatment for inflammatory renal disease.

Ciprofibrate increases paraoxonase activity in patients with metabolic syndrome.

AIMS: Diabetic dyslipidaemia with decreased high-density lipoprotein-cholesterol (HDL-C) concentration plays a key role in enhanced atherosclerosis. The antioxidant effect of HDL is due to the influence of human paraoxonase 1 (PON1) and several authors have described decreased activity of this enzyme in Type 2 diabetics and subjects with metabolic syndrome. The goal of this study was to examine the effect of daily ciprofibrate on serum PON1 and lipoprotein concentrations in patients with metabolic syndrome. METHODS: Fifty-one patients with metabolic syndrome were enrolled into the study. We examined the effect of 100 mg day(-1) ciprofibrate treatment on lipid concentrations, oxidized low-density lipoprotein (LDL), PON1 concentrations and activity. We also investigated the calculated size of LDL-cholesterol (LDL-C). RESULTS: During the 3-month study, it was observed that following treatment with ciprofibrate, the serum triglyceride concentration decreased significantly (from 2.76 +/- 0.9 mmol l(-1) to 2.27 +/- 1.6 mmol l(-1); -18%; P < 0.001), while HDL-C increased significantly (from 0.95 +/- 0.2 mmol l(-1) to 1.2 +/- 0.3 mmol l(-1); 26%; P < 0.001). The oxidatively modified LDL-C concentration decreased significantly (from 137 +/- 19 U l(-1) to 117 +/- 20 U l(-1); P < 0.001), while HDL-associated apolipoprotein A1 significantly increased (from 1.35 +/- 0.2 g l(-1) to 1.75 +/- 0.3 g l(-1); P < 0.001). The LDL-C/LDL-apoB ratio, which reflects the size of LDL, increased significantly (from 0.96 +/- 0.05 to 1.05 +/- 0.06; P < 0.05). Serum PON1 activity was significantly elevated (from 108 +/- 34 U l(-1) to 129 +/- 31 U l(-1); P < 0.05), while standardized values for HDL-C remained significantly unchanged (PON1/HDL-C) (from 114 +/- 21 to 107 +/- 20; NS). CONCLUSION: Three months of treatment with ciprofibrate favourably affected the lipid profile, increased LDL resistance to oxidation and improved antioxidant status by increasing serum paraoxonase activity in these patients.

Peroxisome proliferator-activated receptors and atherogenesis: regulators of gene expression in vascular cells.

A large body of data gathered over the past couple of years has identified the peroxisome proliferator-activated receptors (PPAR) alpha, gamma, and beta/delta as transcription factors exerting modulatory actions in vascular cells. PPARs, which belong to the nuclear receptor family of ligand-activated transcription factors, were originally described as gene regulators of various metabolic pathways. Although the PPARalpha, gamma, and beta/delta subtypes are approximately 60% to 80% homologous in their ligand- and DNA-binding domains, significant differences in ligand and target gene specificities are observed. PPARalpha is activated by polyunsaturated fatty acids and oxidized derivatives and by lipid-modifying drugs of the fibrate family, including fenofibrate or gemfibrozil. PPARalpha controls expression of genes implicated in lipid metabolism. PPARgamma, in contrast, is a key regulator of glucose homeostasis and adipogenesis. Ligands of PPARgamma include naturally occurring FA derivatives, such as hydroxyoctadecadienoic acids (HODEs), prostaglandin derivatives such as 15-deoxyDelta12,14-prostaglandin J2, and glitazones, insulin-sensitizing drugs presently used to treat patients with type 2 diabetes. Ligands for PPARbeta/delta are polyunsaturated fatty acids, prostaglandins, and synthetic compounds, some of which are presently in clinical development. PPARbeta/delta stimulates fatty acid oxidation predominantly acting in muscle. All PPARs are expressed in vascular cells, where they exhibit antiinflammatory and antiatherogenic properties. In addition, studies in various animal models as well as clinical data suggest that PPARalpha and PPARgamma activators can modulate atherogenesis in vivo. At present, no data are available relating to possible effects of PPARbeta/delta agonists on atherogenesis. Given the widespread use of PPARalpha and PPARgamma agonists in patients at high risk for cardiovascular disease, the understanding of their function in the vasculature is not only of basic interest but also has important clinical implications. This review will focus on the role of PPARs in the vasculature and summarize the present understanding of their effects on atherogenesis and its cardiovascular complications.

Targeting peroxisome proliferator-activated receptors (PPARs) in kidney and urologic disease.

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors. Three PPAR isoforms, designated PPAR-alpha, beta/delta and -gamma, have been identified and were initially investigated in the tissues along urinary tract because of their known role in regulating lipid-activated gene transcription, lipid metabolism, inflammation and cell proliferation and differentiation. Gene distribution studies suggested that 3 PPAR isoforms are differentially expressed in the kidney. PPAR-alpha is predominantly expressed in renal proximal tubules and medullary thick ascending limbs. PPAR-gamma is mainly localized in renal medullary collecting duct with lower expression in renal glomeruli and renal microvasculature. Unlike PPAR-alpha and -gamma, PPAR-beta/delta is ubiquitously expressed in every segment along the nephron. In ureter and urinary bladder, all PPAR isoforms are mainly localized in urothelium of ureter and bladder. The emerging data have suggested physiological and pathophysiological roles of PPARs in tissues along urinary tract. PPAR-alpha plays a major role in triggering fatty acid utilization and the adaptive response to dietary lipids in the kidney. PPAR-beta/delta contributes to cell survival of renal interstitial cell in medullary hyperosmality. PPAR-gamma is involved in regulating renal hemodynamic and water and sodium transport. Furthermore, it also participates in the pathogenesis of glomerulopathy, antidiabetic thiazolidinedione-related water and sodium retention and renal, bladder and prostate carcinomas. PPARs may serve as potential therapeutic targets for certain diseases along urinary tract including glomerulosclerosis, diabetic nephropathy and kidney, prostate and bladder tumors.

Therapeutic treatment of DMBA-induced mammary tumors with PPAR ligands.

The objective of this study was to evaluate the ability of troglitazone (a thiazolidinedione) and Wy-14,643 (a clofibrate) to inhibit progression of non-detectable and detectable mammary tumors in rats induced by 7,12 dimethylbenz(a)anthracene (DMBA) when compared to those receiving no treatment or tamoxifen. Although not as effective as tamoxifen in decreasing overall tumor incidence, Wy-14,643 reduced the percentage and number of malignant tumors that developed when compared to both troglitazone and control. Treatment of detectable tumors with either Wy-14,643 or troglitazone induced regression or stasis of total tumor volume in 40-50% of the animals, compared to only 10% in control and 65% in tamoxifen treated animals. Moreover, each PPAR ligand was as effective as tamoxifen in preventing additional tumor development. In summary, both PPAR ligands were more effective than no treatment in preventing tumor progression once detected. However, only the PPAR-alpha activator, Wy-14,643 was able to reduce the development of malignant tumors when administered prior to detection.

The role of fibric acids in atherosclerosis.

The hypolipidemic fibric acid drugs are peroxisome proliferator-activated receptor a (PPAR alpha) ligands. PPAR alpha activated by fibric acids form heterodimers with the 9-cis retinoic acid receptor (RXR). The PPAR/RXR heterodimers bind to peroxisome proliferator response elements (PPRE), which are located in numerous gene promoters and increase the level of the expression of mRNAs encoded by PPAR alpha target genes. Fibric acids decrease triglyceride plasma levels through increases in the expression of genes involved in fatty acid-beta oxidation. Furthermore, they decrease triglycerides by increasing lipoprotein lipase gene expression and by decreasing apolipoprotein C-III gene expression. Fibric acids increase high-density lipoprotein (HDL) cholesterol partly by increasing apolipoprotein A-I and apolipoprotein A-II gene expression. Fibric acids also reduce vascular wall inflammation and the expression of genes involved in different vascular functions (ie, vasomotricity, thrombosis). Fibric acids are used to treat primary hypertriglyceridemia and mixed hyperlipidemia. Some fibric acid molecules are active in essential hypercholesterolemia. Clinical evidence shows that fibric acids reduce coronary atherosclerosis progression in dyslipidemic patients (eg, bezafibrate, gemfibrozil) and in type 2 diabetic patients (fenofibrate). Gemfibrozil decreases coronary morbidity and mortality in patients with low HDL cholesterol, normal triglycerides,and normal low-density lipoprotein (LDL) cholesterol plasma levels. Further clinical studies are necessary to investigate if fibric acids decrease cardiovascular mortality in type 2 diabetes and in primary prevention of hypertriglyceridemia and hypolipidemia.

Peroxisome proliferators as adjuvants for the reverse-electron-transport therapy of obesity: an explanation for the large increase in metabolic rate of MEDICA 16-treated rats.

The efficacy of reverse-electron-transport therapy of obesity should be promoted by agents which up-regulate hepatocyte enzymes that are potentially rate-limiting for mitochondrial fatty acid oxidation and electron shuttles. Peroxisome proliferator drugs, including the fibrates used to treat hyperlipidemia, may be useful in this regard, as they induce malic enzyme, the mitochondrial glycerol-3-phosphate dehydrogenase, and carnitine palmitoyl transferase I in rodent hepatocytes. An agent of this class, MEDICA 16, has the additional property of potently inhibiting both citrate lyase and acetyl-CoA carboxylase. As a result, methyl-substituted diacarboxylic acids (MEDICA) 16 can be expected to disinhibit hepatic fatty acid oxidation while up-regulating electron shuttle mechanisms, and thus should stimulate reverse electron transport. This may explain the remarkable 40% increase in basal metabolic rate observed in normal rats ingesting MEDICA 16--an effect not associated with any compensatory increase in food intake. Relative to controls, the MEDICA 16-treated rats achieved a 50% reduction in body fat and a modest increase in lean mass, such that weight and growth were not changed. In other rodent strains, MEDICA 16 has prevented obesity diabetes and atherogenesis. However, whether MEDICA 16 and other peroxisome proliferator drugs will have clinical utility in reverse-electron-transport therapy may hinge on their ability to induce key enzymes in human hepatocytes; cell culture studies to evaluate this are required.

[Current status of the treatment of type 2 diabetes mellitus. The revival of insulin-resistance drugs]. / Actualités dans les traitements du diabète de type 2. Renouveau des médications de l'insulinorésistance.

The relief of insulin resistance is one of the two therapeutic targets of the treatment of type 2 diabetes. Insulin-sensitizers are therefore complemental with other oral diabetic drugs. The treatment of insulin resistance was for a long time limited to dietary and exercise programmes, a biguanide, metformine, and benfluorex, a phenylethylamine derivative; the mechanisms of action of both drugs are now better understood and their indications more precisely targeted. A new therapeutic class, the thiazolidinediones (troglitazone, rosiglitazone, pioglitazone) has recently completed the family of insulin-sensitizing agents. These drugs, which should be soon available in France, act by a different way than metformin, which has been recently identified as the peroxisomes proliferator-activated receptor. The role of antilipolytic agents, which might increase glucose uptake by reducing free fatty acid production and oxidation is under evaluation, as well as the potential benefit of orlistat, an inhibitor of lipid digestion which has been proved effective, in addition to hypocaloric diet, in the management of obese patients.