Discovery and structure-activity relationship study of 2-piperazinyl-benzothiazole derivatives as potent and selective PPARδ agonists

Peroxisome proliferator-activated receptor δ (PPARδ) is considered to be a target for treating metabolic syndrome, whereas there is no PPARδ agonist in clinical use. Previously, we have reported the discovery of 2-(1-piperidinyl)-1,3-benzothiazole derivatives as a new series of PPARδ agonists using docking-based virtual screening techniques. In this study, we performed the further optimization study of the lead compound 1 focusing on improvement of hydrophobic interactions in the binding site to enhance agonist efficacy for PPARδ and subtype selectivity, thereby discovering a novel PPARδ agonist 5g which exhibited high in vitro agonist activity (hPPARδ, EC₅₀ = 4.1 nM) and sufficiently high selectivity ratio over PPARα and PPARγ. Moreover, 5g revealed a significant upregulation of high-density lipoprotein cholesterol level in vivo.

Target Deconvolution of Fenofibrate in Nonalcoholic Fatty Liver Disease Using Bioinformatics Analysis

Background

Nonalcoholic fatty liver disease (NAFLD) is a prevalent form of liver damage, affecting ~25% of the global population. NAFLD comprises a spectrum of liver pathologies, from hepatic steatosis to nonalcoholic steatohepatitis (NASH), and may progress to liver fibrosis and cirrhosis. The presence of NAFLD correlates with metabolic disorders such as hyperlipidemia, obesity, blood hypertension, cardiovascular, and insulin resistance. Fenofibrate is an agonist drug for peroxisome proliferator-activated receptor alpha (PPARα), used principally for treatment of hyperlipidemia. However, fenofibrate has recently been investigated in clinical trials for treatment of other metabolic disorders such as diabetes, cardiovascular disease, and NAFLD. The evidence to date indicates that fenofibrate could improve NAFLD. While PPARα is considered to be the main target of fenofibrate, fenofibrate may exert its effect through impact on other genes and pathways thereby alleviating, and possibly reversing, NAFLD. In this study, using bioinformatics tools and gene-drug, gene-diseases databases, we sought to explore possible targets, interactions, and pathways involved in fenofibrate and NAFLD.

Methods

We first determined significant protein interactions with fenofibrate in the STITCH database with high confidence (0.7). Next, we investigated the identified proteins on curated targets in two databases, including the DisGeNET and DISEASES databases, to determine their association with NAFLD. We finally constructed a Venn diagram for these two collections (curated genes-NAFLD and fenofibrate-STITCH) to uncover possible primary targets of fenofibrate. Then, Gene Ontology (GO) and KEGG were analyzed to detect the significantly involved targets in molecular function, biological process, cellular component, and biological pathways. A P value < 0.01 was considered the cut-off criterion. We also estimated the specificity of targets with NAFLD by investigating them in disease-gene associations (STRING) and EnrichR (DisGeNET). Finally, we verified our findings in the scientific literature.

Results

We constructed two collections, one with 80 protein-drug interactions and the other with 95 genes associated with NAFLD. Using the Venn diagram, we identified 11 significant targets including LEP, SIRT1, ADIPOQ, PPARA, SREBF1, LDLR, GSTP1, VLDLR, SCARB1, MMP1, and APOC3 and then evaluated their biological pathways. Based on Gene Ontology, most of the targets are involved in lipid metabolism, and KEGG enrichment pathways showed the PPAR signaling pathway, AMPK signaling pathway, and NAFLD as the most significant pathways. The interrogation of those targets on authentic disease databases showed they were more specific to both steatosis and steatohepatitis liver injury than to any other diseases in these databases. Finally, we identified three significant genes, APOC3, PPARA, and SREBF1, that showed robust drug interaction with fenofibrate.

Conclusion

Fenofibrate may exert its effect directly or indirectly, via modulation of several key targets and pathways, in the treatment of NAFLD.

Impact of fibrates on circulating cystatin C levels: a systematic review and meta-analysis of clinical trials

AIMS

To assess the effect of fibrates on circulating cystatin C levels.

MATERIAL AND METHODS

Clinical studies evaluating the effect of a fibrate on circulating cystatin C levels were searched in PubMed-Medline, SCOPUS, Web of Science, and Google Scholar databases. A random-effect model and generic inverse variance method were used for quantitative data synthesis, sensitivity analysis conducted using the leave-one-out method, and weighted random-effects meta-regression performed to evaluate potential confounders on cystatin C levels.

RESULTS

This meta-analysis of data from nine published studies (16 treatment arms) involved a total of 2195 subjects. In a single-arm analysis of clinical trials (without control group; eight studies comprising 14 treatment arms), fibrate therapy increased circulating cystatin C concentrations (WMD: 0.07 mg/dL, 95% CI: 0.04, 0.10, p < .001; I² = 82.66%). When the analysis was restricted to randomized controlled trials (four studies comprising six treatment arms), again elevation of circulating cystatin C levels was observed (WMD: 0.06 mg/L, 95% CI: 0.03, 0.09, p < .001; I² = 42.98%). Elevated cystatin C levels were only seen with fenofibrate and not with other fibrates.

CONCLUSIONS

The results suggest that fenofibrate treatment adversely affects cystatin C levels and might partially explain the limited efficacy of fenofibrate in reducing cardiovascular events. Key message Fenofibrate treatment adversely affects cystatin C levels and might partially explain the limited efficacy of fenofibrate in reducing cardiovascular events.

Fenofibrate improves renal function by amelioration of NOX-4, IL-18, and p53 expression in an experimental model of diabetic nephropathy

Among several pathological mechanisms involved in diabetic nephropathy, oxidative stress, inflammation, and apoptosis play a prominent role. Fenofibrate, a peroxisome proliferator-activated receptor-α (PPAR-α) agonist, has markedly improved oxidative stress and inflammatory responses, but there is no evidence about its effects on interleukin-18 (IL-18), NADPH oxidase type 4 (NOX-4), and p53 expression in diabetic kidneys. The aim of this study was to evaluate possible effects of fenofibrate on improving the underlying mechanisms of diabetic nephropathy. Male Wistar rats were randomly divided into four groups namely, normal, normal treated, diabetic and diabetic treated (N = 6). Diabetes was induced by a single dose of streptozotocin (40 mg/kg; IV). Treated animals received fenofibrate for 8 weeks daily (80 mg/kg; po). All groups were sacrificed on day 56 and blood, urine, and tissue samples were collected. Serum levels of urea, uric acid, creatinine, and glucose were assessed. Then, serum levels of malondialdehyde (MDA), nitrate, and glutathione (GLT), as well as the activities of catalase (CAT) and superoxide dismutase (SOD) enzymes were measured. The expression level of NOX-4, IL-18, and p53 proteins at both mRNA and protein levels were evaluated. Diabetes significantly increased albuminuria, free radicals production, inflammation, and apoptosis in non-treated rats while lowered antioxidant capacity. Moreover, diabetes caused histological damages leading to renal failure. Treatment with fenofibrate improved renal function by improving creatinine clearance (P = 0.01) and protein excretion (P = 0.001) and lowering plasma levels of blood urea nitrogen (P = 0.001), creatinine (P = 0.001), and uric acid (P = 0.01). Fenofibrate potentiated antioxidant defense systems by enhancing CAT (P = 0.01) and SOD (P = 0.01) enzymes activities and GLT content (P = 0.01), and reduced oxidative damage by lowering MDA generation (P = 0.02). Fenofibrate also attenuated the expression of NOX-4 (P = 0.05), IL-18 (P = 0.05), and p53 (P = 0.05) at both mRNA and protein levels. In conclusion, treatment with fenofibrate improved renal function by suppression of oxidative stress, attenuation of inflammation, and inhibition of apoptosis.

Effects of quercetin supplementation on lipid profile: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

In spite of promising experimental findings, randomized controlled trials (RCTs) have yielded mixed results on the impact of quercetin supplementation on plasma lipid levels.

AIM

The present study aimed to quantify the effects of quercetin on plasma lipids using a meta-analysis of RCTs.

METHODS

A systematic literature search of Medline was conducted for RCTs that investigated the efficacy of quercetin supplementation on plasma lipids comprising total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides. Weighted mean differences (WMDs) and 95% confidence intervals (CIs) were calculated for net changes in lipid concentrations using a random-effects model. Meta-regression analysis was conducted to assess the effect of quercetin dose and duration of supplementation as moderators on the calculated effect measures.

RESULTS

Five RCTs totaling 442 subjects (221 in the quercetin and 221 in the control group) fulfilled the eligibility criteria and selected for analyses. Combined estimate of effect size for the impact of quercetin on plasma LDL-C (WMD: 1.43 mg/dL, 95% CI: -0.92-3.78, p = 0.23), HDL-C (WMD: 0.26 mg/dL, 95% CI: -0.74-1.25, p = 0.61) and triglycerides (WMD: -9.42 mg/dL, 95% CI: -27.80-8.96, p = 0.32) was not statistically significant. However, a borderline significant but clinically non-relevant increase in total cholesterol was observed (WMD: 3.13 mg/dL, 95% CI: -0.01-6.27, p = 0.05). When the analysis was confined to the subgroups of studies with quercetin doses ≥500 mg/day and follow-up of ≥ 4 weeks, a significant increase in total cholesterol (WMD: 3.57 mg/dL, 95% CI: 0.21-6.92, p = 0.04) and a decline in triglycerides (WMD: -24.54 mg/dL, 95% CI: -33.09 to -15.99, p < 0.00001) was observed, but LDL-C and HDL-C concentrations remained unchanged (p > 0.05). Changes in plasma triglycerides, but not other indices of lipid profile, were significantly associated with quercetin dose (slope: -0.057; 95% CI: -0.103 to -0.010; p = 0.02) and duration of supplementation (slope: -5.314; 95% CI: -9.482 to -1.147; p = 0.01).

CONCLUSION

Available evidence from RCTs does not suggest any clinically relevant effect of quercetin supplementation on plasma lipids, apart from a significant reduction of triglycerides at doses above 50 mg/day.

Lipid-modifying effects of nutraceuticals: An evidence-based approach

The present review provides an up-to-date summary of the findings on the lipid-lowering effects of the most important nutraceuticals and functional foods. Based on current knowledge, nutraceuticals might exert significant lipid-lowering, and their use has several advantages: A number of important questions remain to be addressed, including whether longer durations of therapy would result in a better response and the exact safety profile of nutraceuticals, especially at doses higher than those consumed in an average diet. Additionally, data regarding the effects of nutraceutical supplementation on the incidence of cardiovascular outcomes are lacking, and it is not clear whether additional lipid lowering by nutraceuticals can modify the residual cardiovascular risk that remains after statin therapy.

Effects of statin therapy on augmentation index as a measure of arterial stiffness: A systematic review and meta-analysis

OBJECTIVE

To evaluate the effects of statin therapy on augmentation index (AIx) as a measure of arterial stiffness using a meta-analysis of clinical trials.

METHODS

The search included PubMed-Medline, Embase, SCOPUS, Web of Science and Google Scholar databases to identify randomized controlled trials investigating the effects of statin therapy on arterial stiffness measured as AIx. A random-effects model and generic inverse variance method were used for quantitative data synthesis. Sensitivity analysis was conducted using the leave-one-out method. Random-effects meta-regression was performed using unrestricted maximum likelihood method to evaluate the impact of potential confounders.

RESULTS

18 trials examining the effects of statin therapy on arterial stiffness were included. A significant reduction in aortic AIx following statin therapy was proven (WMD: -2.40%, 95% CI: -4.59, -0.21, p=0.032; I(2): 51.20%). HR-adjusted AIx 75% values also revealed a significant improvement by statin therapy (WMD: -5.04%, 95% CI: -7.81, -2.27, p<0.001; I(2): 0%), but not when analysis was restricted to unadjusted AIx values (WMD: -2.30%, 95% CI: -4.83, 0.23, p=0.075; I(2): 53.83%). There was no significant change in carotid (WMD: -2.75%, 95% CI: -8.06, 2.56, p=0.309; I(2): 26.86%) and peripheral (WMD: 0.25%, 95% CI: -3.31, 3.82, p=0.889; I(2): 72.19%) AIx due to statin treatment. There was also no difference in the effect size calculated for different statins subgroups. The impact of statins on AIx was independent of LDL-cholesterol level (slope: 0.05; 95% CI: -0.02, 0.13; p=0.181).

CONCLUSION

Statin therapy causes a significant reduction in aortic AIx which is independent of LDL-cholesterol changes.

Nigella sativa (black seed) effects on plasma lipid concentrations in humans: A systematic review and meta-analysis of randomized placebo-controlled trials

The effects of Nigella sativa (NS) on plasma lipid concentrations are controversial. A systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to obtain a conclusive result in humans. PubMed-Medline, SCOPUS, Web of Science, and Google Scholar databases were searched (up to August 2015) to identify RCTs investigating the impact of NS on total cholesterol, LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C), and triglycerides concentrations. A random-effects model and the generic inverse variance weighting method were used for quantitative data synthesis. Meta-regression, sensitivity analysis, and publication bias assessments were performed using standard methods. A total of 17 RCTs examining the effects of NS on plasma lipid concentrations were included. Meta-analysis suggested a significant association between NS supplementation and a reduction in total cholesterol (weighed-mean-difference [WMD]: -15.65mg/dL, 95% CI: -24.67, -6.63, p=0.001), LDL-C (WMD: -14.10mg/dL, 95% CI: -19.32, -8.88, p<0.001), and triglyceride levels (WMD: -20.64mg/dL, 95% CI: -30.29, -11.00, p<0.001). No significant effect on HDL-C concentrations (WMD: 0.28mg/dL, 95% CI: -1.96, 2.53, p=0.804) was found. A greater effect of NS seed oil versus seed powder was observed on serum total cholesterol and LDL-C levels, and an increase in HDL-C levels was found only after NS seed powder supplementation. NS has a significant impact on plasma lipid concentrations, leading to lower total cholesterol, LDL-C, and TG levels while increased HDL-C is associated with NS powder only. Further RCTs are needed to explore the NS benefits on cardiovascular outcomes.

Statin therapy and plasma free fatty acids: a systematic review and meta-analysis of controlled clinical trials

AIM

The aim of this meta-analysis was to evaluate the effect of statin therapy on plasma FFA concentrations in a systematic review and meta-analysis of controlled clinical trials.

METHODS

PubMed-Medline, SCOPUS, Web of Science and Google Scholar databases were searched (from inception to February 16 2015) to identify controlled trials evaluating the impact of statins on plasma FFA concentrations. A systematic assessment of bias in the included studies was performed using the Cochrane criteria. A random effects model and generic inverse variance method were used for quantitative data synthesis. Sensitivity analysis was conducted using the leave-one-out method. Random effects meta-regression was performed using unrestricted maximum likelihood method to evaluate the impact of potential moderators.

RESULTS

Meta-analysis of data from 14 treatment arms indicated a significant reduction in plasma FFA concentrations following treatment with statins (weighted mean difference (WMD) -19.42%, 95% CI -23.19, --15.64, P < 0.001). Subgroup analysis confirmed the significance of the effect with both atorvastatin (WMD -20.56%, 95% CI -24.51, -16.61, P < 0.01) and simvastatin (WMD -18.05%, 95% CI -28.12, -7.99, P < 0.001). Changes in plasma FFA concentrations were independent of treatment duration (slope -0.10, 95% CI -0.30, 0.11, P = 0.354) and magnitude of reduction in plasma low density lipoprotein cholesterol concentrations (slope 0.55, 95% CI -0.17, 1.27, P = 0.133) by statins.

CONCLUSIONS

The results of the present study suggest that statin therapy may lower plasma FFA concentrations. The cardiovascular and metabolic significance of this finding requires further investigation.

Impact of fibrate therapy on plasma plasminogen activator inhibitor-1: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

The aim of this systematic review was to perform a meta-analysis of randomized controlled trials (RCTs) examining the efficacy of fibrate therapy in reducing plasma concentration or activity of plasminogen activator inhibitor 1 (PAI-1).

METHODS

Scopus and MEDLINE databases were searched (up to October 15, 2014) to identify RCTs investigating whether fibrates lower plasma PAI-1 concentration or activity. A random-effects model and the generic inverse variance method were used for quantitative data synthesis. Sensitivity analyses were conducted using the one-study remove approach. Random-effects meta-regression was performed to assess the impact of potential moderators on the estimated effect sizes.

RESULTS

A total of 14 RCTs examining the effects of gemfibrozil (6 trials), bezafibrate (4 trials), and fenofibrate (5 trials) were included. Meta-analysis suggested that fibrate therapy did not significantly reduce plasma PAI-1 concentration (weighed mean difference [WMD]: -11.39 ng/mL, 95% CI: -26.64, 3.85, p=0.143) or activity (WMD: 2.02 U/mL, 95% CI: -0.87, 4.90, p=0.170). These results remained unchanged after subgroup analysis according to duration of treatment (<12 and ≥12 weeks) and type of fibrate administered (fenofibrate, bezafibrate or gemfibrozil). The estimated effects of fibrate therapy on plasma concentration and activity of PAI-1 were independent of treatment duration and changes in plasma triglyceride levels in the meta-regression analysis.

CONCLUSION

This meta-analysis of RCTs suggested that fibrate therapy does not reduce plasma concentration or activity of PAI-I. The putative benefits of fibrate therapy in patients with cardiovascular disease appear to be exerted via mechanisms independent of effects on PAI-1.

Recent advances in pharmacotherapy for hypertriglyceridemia

Elevated plasma triglyceride (TG) concentrations are associated with an increased risk of atherosclerotic cardiovascular disease (CVD), hepatic steatosis and pancreatitis. Existing pharmacotherapies, such as fibrates, n-3 polyunsaturated fatty acids (PUFAs) and niacin, are partially efficacious in correcting elevated plasma TG. However, several new TG-lowering agents are in development that can regulate the transport of triglyceride-rich lipoproteins (TRLs) by modulating key enzymes, receptors or ligands involved in their metabolism. Balanced dual peroxisome proliferator-activated receptor (PPAR) α/γ agonists, inhibitors of microsomal triglyceride transfer protein (MTTP) and acyl-CoA:diacylglycerol acyltransferase-1 (DGAT-1), incretin mimetics, and apolipoprotein (apo) B-targeted antisense oligonucleotides (ASOs) can all decrease the production and secretion of TRLs; inhibitors of cholesteryl ester transfer protein (CETP) and angiopoietin-like proteins (ANGPTLs) 3 and 4, monoclonal antibodies (Mabs) against proprotein convertase subtilisin/kexin type 9 (PCSK9), apoC-III-targeted ASOs, selective peroxisome proliferator-activated receptor modulators (SPPARMs), and lipoprotein lipase (LPL) gene replacement therapy (alipogene tiparvovec) enhance the catabolism and clearance of TRLs; dual PPAR-α/δ agonists and n-3 polyunsaturated fatty acids can lower plasma TG by regulating both TRL secretion and catabolism. Varying degrees of TG reduction have been reported with the use of these therapies, and for some agents such as CETP inhibitors and PCSK9 Mabs findings have not been consistent. Whether they reduce CVD events has not been established. Trials investigating the effect of CETP inhibitors (anacetrapib and evacetrapib) and PCSK9 Mabs (AMG-145 and REGN727/SAR236553) on CVD outcomes are currently in progress, although these agents also regulate LDL metabolism and, in the case of CETP inhibitors, HDL metabolism. Further to CVD risk reduction, these new treatments might also have a potential role in the management of diabetes and non-alcoholic fatty liver disease owing to their insulin-sensitizing action (PPAR-α/γ agonists) and potential capacity to decrease hepatic TG accumulation (PPAR-α/δ agonists and DGAT-1 inhibitors), but this needs to be tested in future trials. We summarize the clinical trial findings regarding the efficacy and safety of these novel therapies for hypertriglyceridemia.