New peroxisome proliferator-activated receptor agonists: potential treatments for atherogenic dyslipidemia and non-alcoholic fatty liver disease

Physiological Suppression of Lipotoxic Liver Damage by Complementary Actions of HDAC3 and SCAP/SREBP

Liver fat accumulation precedes non-alcoholic steatohepatitis, an increasing cause of end-stage liver disease. Histone deacetylase 3 (HDAC3) is required for hepatic triglyceride homeostasis, and sterol regulatory element binding protein (SREBP) regulates the lipogenic response to feeding, but the crosstalk between these pathways is unknown. Here we show that inactivation of SREBP by hepatic deletion of SREBP cleavage activating protein (SCAP) abrogates the increase in lipogenesis caused by loss of HDAC3, but fatty acid oxidation remains defective. This combination leads to accumulation of lipid intermediates and to an energy drain that collectively cause oxidative stress, inflammation, liver damage, and, ultimately, synthetic lethality. Remarkably, this phenotype is prevented by ectopic expression of nuclear SREBP1c, revealing a surprising benefit of de novo lipogenesis and triglyceride synthesis in preventing lipotoxicity. These results demonstrate that HDAC3 and SCAP control symbiotic pathways of liver lipid metabolism that are critical for suppression of lipotoxicity.

The role of insulin resistance in nonalcoholic steatohepatitis and liver disease development--a potential therapeutic target?

Insulin resistance (IR) is defined by the inability of insulin to exert its metabolic actions, due to impaired activation of intracellular insulin signaling. This condition is caused by genetic defects or by environmental conditions, among which the most common is obesity. Systemic IR determines the development of hepatic fat accumulation, which can progress to nonalcoholic steatohepatitis, cirrhosis and hepatocellular carcinoma, and is a major determinant of liver disease independently of coexisting factors. Therefore, insulin-sensitizing drugs are currently under evaluation to improve steatohepatitis. Indeed, manipulation of nuclear hormone receptors is already under scrutiny for liver disease prevention by amelioration of IR, whereas NOTCH signaling inhibition represents a novel approach. Nevertheless, further research is warranted to better understand the mechanism linking IR to progressive fibrogenesis in the absence of inflammation and to identify novel drug targets.

Evaluation of Methionine Content in a High-Fat and Choline-Deficient Diet on Body Weight Gain and the Development of Non-Alcoholic Steatohepatitis in Mice

Aim

Non-alcoholic steatohepatitis (NASH) is a globally recognized liver disease. A methionine- and choline-deficient diet is used to induce NASH in mice; however, this diet also causes severe body weight loss. To resolve this issue, we examined the effects of methionine content in a high-fat and choline-deficient (HFCD) diet on body weight and the development of NASH in mice.

Methods

C57BL/6J mice (male, 10 weeks of age) were fed an L-amino acid rodent (control) diet, high-fat (HF) diet, or HFCD diet containing various amounts of methionine (0.1–0.6% (w/w)) for 12 weeks. Plasma lipid levels, hepatic lipid content and inflammatory marker gene expression were measured, and a pathological analysis was conducted to evaluate NASH.

Results

The 0.1% methionine in HFCD diet suppressed body weight gain, which was lower than that with control diet. On the other hand, the 0.2% methionine in HFCD diet yielded similar body weight gains as the control diet, while more than 0.4% methionine showed the same body weight gains as the HF diet. Liver weights and hepatic lipid contents were the greatest with 0.1% methionine and decreased in a methionine dose-dependent manner. Pathological analysis, NAFLD activity scores and gene expression levels in the liver revealed that 0.1% and 0.2% methionine for 12 weeks induced NASH, whereas 0.4% and 0.6% methionine attenuated the induction of NASH by HFCD diet. However, the 0.2% methionine in HFCD diet did not induce insulin resistance, despite the body weight gain.

Conclusions

The 0.2% methionine in HFCD diet for 12 weeks was able to induce NASH without weight loss.

Hypoxia-regulated mechanisms in the pathogenesis of obesity and non-alcoholic fatty liver disease

The pandemic rise in obesity has resulted in an increased incidence of metabolic complications. Non-alcoholic fatty liver disease is the hepatic manifestation of the metabolic syndrome and has become the most common chronic liver disease in large parts of the world. The adipose tissue expansion and hepatic fat accumulation characteristics of these disorders compromise local oxygen homeostasis. The resultant tissue hypoxia induces adaptive responses to restore oxygenation and tissue metabolism and cell survival. Hypoxia-inducible factors (HIFs) function as master regulators of this hypoxia adaptive response, and are in turn hydroxylated by prolyl hydroxylases (PHDs). PHDs are the main cellular oxygen sensors and regulate HIF proteasomal degradation in an oxygen-dependent manner. HIFs and PHDs are implicated in numerous physiological and pathological conditions. Extensive research using genetic models has revealed that hypoxia signaling is also a key mechanism in adipose tissue dysfunction, leading to adipose tissue fibrosis, inflammation and insulin resistance. Moreover, hypoxia affects liver lipid metabolism and deranges hepatic lipid accumulation. This review summarizes the molecular mechanisms through which the hypoxia adaptive response affects adipocyte and hepatic metabolism, and the therapeutic possibilities of modulating HIFs and PHDs in obesity and fatty liver disease.

Liver PPARα is crucial for whole-body fatty acid homeostasis and is protective against NAFLD

OBJECTIVE

Peroxisome proliferator-activated receptor α (PPARα) is a nuclear receptor expressed in tissues with high oxidative activity that plays a central role in metabolism. In this work, we investigated the effect of hepatocyte PPARα on non-alcoholic fatty liver disease (NAFLD).

DESIGN

We constructed a novel hepatocyte-specific PPARα knockout (Pparα(hep-/-)) mouse model. Using this novel model, we performed transcriptomic analysis following fenofibrate treatment. Next, we investigated which physiological challenges impact on PPARα. Moreover, we measured the contribution of hepatocytic PPARα activity to whole-body metabolism and fibroblast growth factor 21 production during fasting. Finally, we determined the influence of hepatocyte-specific PPARα deficiency in different models of steatosis and during ageing.

RESULTS

Hepatocyte PPARα deletion impaired fatty acid catabolism, resulting in hepatic lipid accumulation during fasting and in two preclinical models of steatosis. Fasting mice showed acute PPARα-dependent hepatocyte activity during early night, with correspondingly increased circulating free fatty acids, which could be further stimulated by adipocyte lipolysis. Fasting led to mild hypoglycaemia and hypothermia in Pparα(hep-/-) mice when compared with Pparα(-/-) mice implying a role of PPARα activity in non-hepatic tissues. In agreement with this observation, Pparα(-/-) mice became overweight during ageing while Pparα(hep-/-) remained lean. However, like Pparα(-/-) mice, Pparα(hep-/-) fed a standard diet developed hepatic steatosis in ageing.

CONCLUSIONS

Altogether, these findings underscore the potential of hepatocyte PPARα as a drug target for NAFLD.

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.

Unraveling the Effects of PPARβ/δ on Insulin Resistance and Cardiovascular Disease

Insulin resistance precedes dyslipidemia and type 2 diabetes mellitus (T2DM) development. Preclinical evidence suggests that peroxisome proliferator-activated receptor (PPAR) β/δ activators may prevent and treat obesity-induced insulin resistance and T2DM, while clinical trials highlight their potential utility in dyslipidemia. This review summarizes recent mechanistic insights into the antidiabetic effects of PPARβ/δ activators, including their anti-inflammatory actions, their ability to inhibit endoplasmic reticulum (ER) stress and hepatic lipogenesis, and to improve atherogenesis and insulin sensitivity, as well as their capacity to activate pathways that are also stimulated by exercise. Findings from clinical trials are also examined. Dissecting the effects of PPARβ/δ ligands on insulin sensitivity and atherogenesis may provide a basis for the development of therapies for the prevention and treatment of T2DM and cardiovascular disease (CVD).

Systematic review and meta-analysis deciphering the impact of fibrates on paraoxonase-1 status

OBJECTIVE

A significant residual cardiovascular risk is consistently observed in patients treated with statins. A combined treatment with fibrates reduces cardiovascular events in very high-risk patients. Because this is apparently unconnected to an improvement in lipid-related outcomes we hypothesized that the cardioprotective effects of fibrates might be associated with an improvement in paraoxonase-1 (PON1) status.

METHOD

The search for existing evidence, using the Medline, Scopus and Cochrane databases, was systematic and followed the PRISMA statement without restrictions on publication date. We excluded non-clinical and observational studies and we extracted data on baseline and post-treatment values of serum PON1 activity and other measurements of PON1 status.

RESULTS

Nine studies (including 12 treatment arms) in patients with hyperlipidemia, diabetes or metabolic syndrome treated with fibrates, alone or in combination with statins, were included to synthesize results. A meta-analysis of the data using a random-effects model revealed a significant increase in serum PON1 activity following fibrate therapy (WMD: 15.64U/L, 95% CI: 6.94, 24.34, p<0.001), an effect that was robust and not sensitive to any particular study. Subgroup analysis indicated differences in the effect size among types of fibrates and that PON1 alterations were associated with high-density lipoprotein cholesterol changes following fibrate therapy.

CONCLUSIONS

Results indicate a significant PON1-enhancing effect of fibrates. Whether this effect is associated with a clinical benefit, although likely, remains to be further investigated.

The role of PPARγ-mediated signalling in skin biology and pathology: new targets and opportunities for clinical dermatology

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that modulate the expression of multiple different genes involved in the regulation of lipid, glucose and amino acid metabolism. PPARs and cognate ligands also regulate important cellular functions, including cell proliferation and differentiation, as well as inflammatory responses. This includes a role in mediating skin and pilosebaceous unit homoeostasis: PPARs appear to be essential for maintaining skin barrier permeability, inhibit keratinocyte cell growth, promote keratinocyte terminal differentiation and regulate skin inflammation. They also may have protective effects on human hair follicle (HFs) epithelial stem cells, while defects in PPARγ-mediated signalling may promote the death of these stem cells and thus facilitate the development of cicatricial alopecia (lichen planopilaris). Overall, however, selected PPARγ modulators appear to act as hair growth inhibitors that reduce the proliferation and promote apoptosis of hair matrix keratinocytes. The fact that commonly prescribed PPARγ-modulatory drugs of the thiazolidine-2,4-dione class can exhibit a battery of adverse cutaneous effects underscores the importance of distinguishing beneficial from clinically undesired cutaneous activities of PPARγ ligands and to better understand on the molecular level how PPARγ-regulated cutaneous lipid metabolism and PPARγ-mediated signalling impact on human skin physiology and pathology. Surely, the therapeutic potential that endogenous and exogenous PPARγ modulators may possess in selected skin diseases, ranging from chronic inflammatory hyperproliferative dermatoses like psoriasis and atopic dermatitis, via scarring alopecia and acne can only be harnessed if the complexities of PPARγ signalling in human skin and its appendages are systematically dissected.

Future glucose-lowering drugs for type 2 diabetes

The multivariable and progressive natural history of type 2 diabetes limits the effectiveness of available glucose-lowering drugs. Constraints imposed by comorbidities (notably cardiovascular disease and renal impairment) and the need to avoid hypoglycaemia, weight gain, and drug interactions further complicate the treatment process. These challenges have prompted the development of new formulations and delivery methods for existing drugs alongside research into novel pharmacological entities. Advances in incretin-based therapies include a miniature implantable osmotic pump to give continuous delivery of a glucagon-like peptide-1 receptor agonist for 6-12 months and once-weekly tablets of dipeptidyl peptidase-4 inhibitors. Hybrid molecules that combine the properties of selected incretins and other peptides are at early stages of development, and proof of concept has been shown for small non-peptide molecules to activate glucagon-like peptide-1 receptors. Additional sodium-glucose co-transporter inhibitors are progressing in development as well as possible new insulin-releasing biological agents and small-molecule inhibitors of glucagon action. Adiponectin receptor agonists, selective peroxisome proliferator-activated receptor modulators, cellular glucocorticoid inhibitors, and analogues of fibroblast growth factor 21 are being considered as potential new approaches to glucose lowering. Compounds that can enhance insulin receptor and post-receptor signalling cascades or directly promote selected pathways of glucose metabolism have suggested opportunities for future treatments. However, pharmacological interventions that are able to restore normal β-cell function and β-cell mass, normalise insulin action, and fully correct glucose homoeostasis are a distant vision.

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.

Metabolic and Inflammatory Adaptation of Reactive Astrocytes: Role of PPARs

Astrocyte-mediated inflammation is associated with degenerative pathologies such as Alzheimer's and Parkinson's diseases and multiple sclerosis. The acute inflammation and morphological and metabolic changes that astrocytes develop after the insult are known as reactive astroglia or astrogliosis that is an important response to protect and repair the lesion. Astrocytes optimize their metabolism to produce lactate, glutamate, and ketone bodies in order to provide energy to the neurons that are deprived of nutrients upon insult. Firstly, we review the basis of inflammation and morphological changes of the different cell population implicated in reactive gliosis. Next, we discuss the more active metabolic pathways in healthy astrocytes and explain the metabolic response of astrocytes to the insult in different pathologies and which metabolic alterations generate complications in these diseases. We emphasize the role of peroxisome proliferator-activated receptors isotypes in the inflammatory and metabolic adaptation of astrogliosis developed in ischemia or neurodegenerative diseases. Based on results reported in astrocytes and other cells, we resume and hypothesize the effect of peroxisome proliferator-activated receptor (PPAR) activation with ligands on different metabolic pathways in order to supply energy to the neurons. The activation of selective PPAR isotype activity may serve as an input to better understand the role played by these receptors on the metabolic and inflammatory compensation of astrogliosis and might represent an opportunity to develop new therapeutic strategies against traumatic brain injuries and neurodegenerative diseases.

Improvement of plasma adiponectin, leptin and C-reactive protein concentrations by orlistat: a systematic review and meta-analysis

AIMS

To conduct a systematic review and meta-analysis of relevant randomized clinical trials (RCTs) to ascertain the effect size of orlistat in modulating plasma levels of adipokines, ghrelin and C-reactive protein (CRP).

METHODS

Medline, SCOPUS, Web of Science and Google Scholar databases were searched. A random-effects model and the generic inverse variance method were used for quantitative data synthesis. Heterogeneity was quantitatively assessed using I(2) index. Sensitivity analyses were conducted using the one-study remove approach. Random-effects meta-regression was performed using unrestricted maximum likelihood method to evaluate the impact of duration of treatment, percentage change in body mass index (BMI) and baseline BMI values as potential confounders of the estimated effect size.

RESULTS

Meta-analysis suggested a significant increase in plasma levels of adiponectin [weighted mean difference (WMD): 19.18%, 95% confidence interval (CI): 5.80, 32.57, p = 0.005] and significant reductions in plasma levels of leptin (WMD: -13.24%, 95% CI: -20.69, -5.78, p = 0.001) and CRP (WMD: -11.52%, 95% CI: -16.55, -6.49, p < 0.001) following treatment with orlistat. In meta-regression, changes in plasma concentrations of adiponectin, leptin and CRP were associated with duration of treatment, but not with either change in BMI or baseline BMI values.

CONCLUSION

Orlistat is effective in increasing plasma concentrations of adiponectin and decreasing those of leptin and CRP.

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.

Berberine prevents progression from hepatic steatosis to steatohepatitis and fibrosis by reducing endoplasmic reticulum stress

The histological spectrum of nonalcoholic fatty liver diseases (NAFLD) ranges from hepatic steatosis to steatohepatitis and fibrosis. Berberine (BBR) is known for its therapeutic effect on obesity, hyperglycaemia and dyslipidaemia; however, its effect on NAFLD has yet to be thoroughly explored. Db/db mice and methionine-choline-deficient diet-fed mice were administered BBR via gavage. We found that BBR-treated mice were more resistant to steatosis in the liver than vehicle-treated mice and that BBR significantly reduced hepatic inflammation, fibrosis and lipid peroxides. The beneficial effect of BBR was associated with suppressing endoplasmic reticulum (ER) stress. Additionally, BBR decreased the free fatty acid-induced lipid accumulation and tunicamycin-induced ER stress in primary hepatocytes and hepatocyte cell lines. We demonstrated that BBR exhibited chaperone activity, reduced protein aggregation in vitro and alleviated tunicamycin-induced triglyceride and collagen deposition in vivo. Finally, we showed that BBR could reverse ER stress-activated lipogenesis through the ATF6/SREBP-1c pathway in vitro. These results indicated that BBR may be a new therapeutic strategy against hepatic steatosis and non-alcoholic steatohepatitis.

Supplementation with coenzyme Q10 reduces plasma lipoprotein(a) concentrations but not other lipid indices: A systematic review and meta-analysis

Plasma lipoprotein(a) [Lp(a)] elevations are associated with increased cardiovascular risk. Coenzyme Q10 (CoQ10) is a member of the mitochondrial respiratory chain with a prominent role as a potent gene regulator. The Lp(a)-lowering efficacy of CoQ10 has been investigated in different clinical settings with contrasting results. A systematic literature search in Medline, SCOPUS, Web of Science and Google Scholar databases was conducted to identify controlled trials investigating the efficacy of CoQ10 supplementation on plasma Lp(a) levels. Inverse variance-weighted mean differences (WMDs) and 95% confidence intervals (CIs) were calculated for net changes in Lp(a) levels using a random-effects model. Random-effects meta-regression was performed to assess the effect of putative confounders on plasma Lp(a) levels. Seven randomized controlled trials with a total of 409 subjects (206 in the CoQ10 arm and 203 in the control arm) met the eligibility criteria. Overall, CoQ10 supplementation was paralleled by a slight but significant reduction of plasma Lp(a) levels (WMD: -3.54 mg/dL, 95% CI: -5.50, -1.58; p<0.001), this effect being more robust in those trials with higher baseline Lp(a) levels (slope: -0.44; 95% CI: -0.80, -0.08; p=0.018). Reduction of plasma Lp(a) levels was consistent across different CoQ10 doses, with an inverse association between administered CoQ10 dose and Lp(a) lowering (slope: 0.04; 95% CI: 0.01, 0.07; p=0.004). Neither total cholesterol and cholesterol subfractions, nor triglyceride levels were affected by CoQ10 supplementation. In conclusion, CoQ10 supplementation, in the tested range of doses, reduces plasma Lp(a) concentrations, particularly in patients with Lp(a)≥ 30 mg/dL. Other lipid indices were not altered by CoQ10 supplementation.

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.

Effects of combined PPAR-γ and PPAR-α agonist therapy on fructose induced NASH in rats: Modulation of gene expression

Peroxisome proliferator-activated receptors (PPARs) gamma and alpha have been shown to play key roles in maintaining glucose and lipid homeostasis by acting as insulin sensitizers and lipid-lowering agents respectively, which would make them potential candidates for the treatment of non-alcoholic steatohepatitis (NASH) characterized by insulin resistance, hyperglycemia, and hypertriglyceridemia. The effects of pioglitazone, a PPAR-γ agonist, and fenofibrate, a PPAR-α agonist, as monotherapy and in combination on the expressions of key genes linked to the development of NASH were studied in rats with fructose-induced NASH. Fructose-enriched diet was given to rats for 12 weeks. Fenofibrate (100mg/kg), pioglitazone (4 mg/kg) and combined treatment with both in half doses were given. Body weight, liver index, insulin resistance indices, triglycerides, oxidative stress markers, AST/ALT ratio and TNF-α were measured. Additionally, hepatic genes expressions of SOCS-3, sterol regulatory element binding protein-1c, fatty acid synthase, malonyl CoA decarboxylase, TGF-β1, and adipose tissue genes expressions of leptin and adiponectin were investigated. The combination of both drugs, in half doses, improved NASH-related disturbances similar to, or even better than, a full dose of fenofibrate alone possibly due to attenuating effects of pioglitazone on expression of genes responsible for insulin resistance, fatty acid synthesis and fibrosis in addition to correcting the balance between leptin and adiponectin. Histopathology confirmed the ability of this combination to decrease steatosis area and to normalize hepatic tissue structure. In Conclusion, dual activation of PPAR-γ and PPAR-α has remarkable effect in ameliorating NASH by modulation of some hepatic and adipose tissue genes expressions.

Does statin therapy reduce plasma VEGF levels in humans? A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

The effect of statins on plasma concentrations of vascular endothelial growth factor (VEGF), the main angiogenic growth factor with pro-inflammatory and atherogenic properties, is controversial. A systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to obtain a conclusive result in humans.

METHODS

PubMed-Medline, SCOPUS, Web of Science and Google Scholar databases were searched to identify RCTs investigating the impact of statins on plasma VEGF concentrations. A random-effects model and the generic inverse variance method were used for quantitative data synthesis. Meta-regression, sensitivity analysis and publication bias assessments were performed using standard methods.

RESULTS

Eight RCTs examining the effects of statins on plasma VEGF concentrations were included. Meta-analysis suggested a significant reduction of plasma VEGF levels following statin therapy (weighed mean difference: -19.88 pg/mL, 95% CI: -35.87, -3.89, p=0.015). VEGF reductions were observed in the subsets of trials with treatment durations ≥4 weeks (-19.54, -37.78, -1.30, p=0.036), LDL-C reductions ≥50 mg/dL (-28.59, -43.68, -13.50, p<0.001), lipophilic statins (-22.31, -40.65, -3.98, p=0.017), and diseased populations (-21.08, -39.97, -2.18, p=0.029), but not in the opposite subsets. Meta-regression also suggested a significant association between changes in plasma VEGF levels and LDL-C changes, treatment duration, but not molar dose of statins.

CONCLUSIONS

These results suggest a significant reduction in plasma VEGF concentrations following statin therapy. This effect depends on duration of treatment, LDL-lowering activity, lipophilicity of statins, and health status of studied individuals. Further RCTs are needed to explore if the VEGF reduction is implicated in the statin benefits on cardiovascular outcomes.

Utilizing small nutrient compounds as enhancers of exercise-induced mitochondrial biogenesis

Endurance exercise, when performed regularly as part of a training program, leads to increases in whole-body and skeletal muscle-specific oxidative capacity. At the cellular level, this adaptive response is manifested by an increased number of oxidative fibers (Type I and IIA myosin heavy chain), an increase in capillarity and an increase in mitochondrial biogenesis. The increase in mitochondrial biogenesis (increased volume and functional capacity) is fundamentally important as it leads to greater rates of oxidative phosphorylation and an improved capacity to utilize fatty acids during sub-maximal exercise. Given the importance of mitochondrial biogenesis for skeletal muscle performance, considerable attention has been given to understanding the molecular cues stimulated by endurance exercise that culminate in this adaptive response. In turn, this research has led to the identification of pharmaceutical compounds and small nutritional bioactive ingredients that appear able to amplify exercise-responsive signaling pathways in skeletal muscle. The aim of this review is to discuss these purported exercise mimetics and bioactive ingredients in the context of mitochondrial biogenesis in skeletal muscle. We will examine proposed modes of action, discuss evidence of application in skeletal muscle in vivo and finally comment on the feasibility of such approaches to support endurance-training applications in humans.

Apple Polyphenols Decrease Atherosclerosis and Hepatic Steatosis in ApoE-/- Mice through the ROS/MAPK/NF-κB Pathway

In this study, we examined the effects of apple polyphenols (APs) on hyperlipidemia, atherosclerosis, hepatic steatosis and endothelial function and investigated the potential mechanisms. ApoE^−/− mice were fed a western-type diet and orally treated with APs (100 mg/kg) or atorvastatin (10 mg/kg) for 12 weeks. Hyperlipidemia and atherosclerosis in the aortic sinuses and, and hepatic lipidosis were measured. The treatment with APs or atorvastatin induced a remarkable reduction in the atherosclerotic lesions and hepatic steatosis and decreased the levels of low-density lipoprotein, triglyceride, CCL-2 and VCAM-1 levels in the plasma. Conversely, the APs significantly increased the plasma levels of high-density lipoprotein (HDL) cholesterol and markedly up-regulated the glutathione peroxidase (GPx), catalase (CAT) and superoxide dismutase (SOD) levels in liver tissues. Moreover, the APs treatment modulated lipid metabolism by up-regulating the transcription of associated hepatic genes including PPARα, while down-regulating the transcription of SCAP and its downstream genes associated with lipid synthesis in the liver. Histological assessment showed that the APs treatment also reduced the macrophage infiltration in the aortic root plaque and the inflammatory cells infiltrations to the liver tissues. Moreover, we confirmed that the APs treatment greatly reduced the ox-LDL-induced endothelial dysfunction and monocyte adhesion to rat aortic endothelial cells (RAECs). Mechanistically, the APs treatment suppressed the ROS/MAPK/NF-κB signaling pathway, and consequently, reduced CCL-2, ICAM-1 and VCAM-1 expression. Our results suggest that the APs are a beneficial nutritional supplement for the attenuation of atherosclerosis.

Advances in the Study of the Antiatherogenic Function and Novel Therapies for HDL

The hypothesis that raising high-density lipoprotein cholesterol (HDL-C) levels could improve the risk for cardiovascular disease (CVD) is facing challenges. There is multitudinous clear clinical evidence that the latest failures of HDL-C-raising drugs show no clear association with risks for CVD. At the genetic level, recent research indicates that steady-state HDL-C concentrations may provide limited information regarding the potential antiatherogenic functions of HDL. It is evident that the newer strategies may replace therapeutic approaches to simply raise plasma HDL-C levels. There is an urgent need to identify an efficient biomarker that accurately predicts the increased risk of atherosclerosis (AS) in patients and that may be used for exploring newer therapeutic targets. Studies from recent decades show that the composition, structure and function of circulating HDL are closely associated with high cardiovascular risk. A vast amount of data demonstrates that the most important mechanism through which HDL antagonizes AS involves the reverse cholesterol transport (RCT) process. Clinical trials of drugs that specifically target HDL have so far proven disappointing, so it is necessary to carry out review on the HDL therapeutics.

The role of type 2 diabetes in neurodegeneration

A growing body of evidence links type-2 diabetes (T2D) with dementia and neurodegenerative diseases such as Alzheimer's disease (AD). AD is the most common form of dementia and is characterised neuropathologically by the accumulation of extracellular beta amyloid (Aβ) peptide aggregates and intracellular hyper-phosphorylated tau protein, which are thought to drive and/or accelerate inflammatory and oxidative stress processes leading to neurodegeneration. Although the precise mechanism remains unclear, T2D can exacerbate these neurodegenerative processes. Brain atrophy, reduced cerebral glucose metabolism and CNS insulin resistance are features of both AD and T2D. Cell culture and animal studies have indicated that the early accumulation of Aβ may play a role in CNS insulin resistance and impaired insulin signalling. From the viewpoint of insulin resistance and impaired insulin signalling in the brain, these are also believed to initiate other aspects of brain injury, including inflammatory and oxidative stress processes. Here we review the clinical and experimental pieces of evidence that link these two chronic diseases of ageing, and discuss underlying mechanisms. The evaluation of treatments for the management of diabetes in preclinical, and clinical studies and trials for AD will also be discussed.

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.

Nonalcoholic Fatty Liver Disease: Dyslipidemia, Risk for Cardiovascular Complications, and Treatment Strategy

Studies have shown that nonalcoholic fatty liver disease (NAFLD) is strongly associated with several metabolic disorders and diseases, such as obesity, type 2 diabetes mellitus, and dyslipidemia. In NAFLD, dyslipidemia is manifested as increased serum triglyceride and low-density lipoprotein cholesterol levels and decreased high-density lipoprotein cholesterol levels, all of which are key risk factors for cardiovascular disease (CVD). CVD is a leading cause of mortality in NAFLD patients. Thus, implementation of an aggressive therapeutic strategy for dyslipidemia with hypolipidemic agents may mitigate the risk for CVD among NAFLD patients. Here, we provide a current review of literature regarding NAFLD, with particular emphasis on dyslipidemia and available treatment options.

Early investigational drugs targeting PPAR-α for the treatment of metabolic disease

INTRODUCTION

The fibrates have been used for many years to treat dyslipidemias and have also recently been shown to have anti-inflammatory effects. They are relatively weak PPAR-α agonists and do have some adverse effects. Novel compounds are in development, which are selective PPAR modulators (SPPARMs) and have more potent PPAR-α agonist activity. These may prove to have advantages in the treatment of dyslipidemia, insulin resistance and non-alcoholic fatty liver disease (NAFLD).

AREAS COVERED

This review focuses on PPAR-α agonists or SPPARMs in development describing the preclinical and early clinical studies. The information was obtained by searching the published literature and abstracts from recent meetings. Ongoing clinical trials were identified using the Clinicaltrial.gov database.

EXPERT OPINION

There is still a need for new drugs to treat atherogenic dyslipidemia. The highly potent and selective PPAR-α agonist K-877 has shown beneficial effects on atherogenic dyslipidemia and absence of some adverse effects seen with fibrates. The dual PPAR-α/PPAR-δ agonist GFT-505 has shown favorable results in improving atherogenic dyslipidemia and insulin resistance and appears to be a potential candidate for the treatment of NAFLD. Long-term trials are needed to assess the safety and efficacy of these new agents for cardiovascular and liver outcomes.

Addressing unmet medical needs in type 2 diabetes: a narrative review of drugs under development

The global burden of type 2 diabetes is increasing worldwide, and successful treatment of this disease needs constant provision of new drugs. Twelve classes of antidiabetic drugs are currently available, and many new drugs are under clinical development. These include compounds with known mechanisms of action but unique properties, such as once-weekly DPP4 inhibitors or oral insulin. They also include drugs with new mechanisms of action, the focus of this review. Most of these compounds are in Phase 1 and 2, with only a small number having made it to Phase 3 at this time. The new drug classes described include PPAR agonists/modulators, glucokinase activators, glucagon receptor antagonists, anti-inflammatory compounds, G-protein coupled receptor agonists, gastrointestinal peptide agonists other than GLP-1, apical sodium-dependent bile acid transporter (ASBT) inhibitors, SGLT1 and dual SGLT1/SGLT2 inhibitors, and 11beta- HSD1 inhibitors.

High-density lipoprotein: structural and functional changes under uremic conditions and the therapeutic consequences

High-density lipoprotein (HDL) has attracted interest as a therapeutic target in cardiovascular diseases in recent years. Although many functional mechanisms of the vascular protective effects of HDL have been identified, increasing the HDL plasma level has not been successful in all patient cohorts with increased cardiovascular risk. The composition of the HDL particle is very complex and includes diverse lipids and proteins that can be modified in disease conditions. In patients with chronic kidney disease (CKD), the accumulation of uremic toxins, high oxidative stress, and chronic micro-inflammatory conditions contribute to changes in the HDL composition and may also account for protein/lipid modifications. These conditions are associated with a decreased protective function of HDL. Therefore, the HDL quantity and the functional quality of the particle must be considered. This review summarizes the current knowledge of dyslipidemia in CKD patients, the effects of lipid-modulating therapy, and the structural modifications of HDL that are associated with dysfunction.

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.

Supplementation with the extract of schisandrae fructus pulp, seed, or their combination influences the metabolism of lipids and glucose in mice fed with normal and hypercholesterolemic diet

SCHISANDRAE FRUCTUS (SF), WHICH POSSESSES FIVE TASTES

sweet (fruit skin), sour (pulp), bitter/pungent (seed core), and saltiness (all parts), can produce a wide spectrum of biological activities in the body. Here, we investigated the effects of the ethanolic extract of SF pulp, seed, or their combination (namely, EtSF-P, EtSF-S, or EtSF-P/S, resp.; collectively called EtSF) on the metabolism of lipids and glucose in normal diet- (ND-) and hypercholesterolemic diet- (HCLD-) fed mice. Supplementation with EtSF significantly reduced hepatic triglyceride and cholesterol levels by 18-47% in both ND- and HCLD-fed mice. EtSF supplementation reduced serum triglyceride levels (approximately 29%), whereas EtSF-P and EtSF-S/P elevated serum cholesterol (up to 26 and 44%, resp.) in HCLD-fed mice. Treatment with EtSF decreased hepatic glucose levels (by 9-44%) in both ND- and HCLD-fed mice. Supplementation with EtSF-S or EtSF-S/P (at 1 and 3%) increased biliary or fecal TC contents in HCLD-fed mice. However, supplementation with EtSF-S/P at 9% reduced biliary TC levels in HCLD-fed mice. EtSF-P or EtSF-S/P supplementation reduced serum alanine aminotransferase activity in HCLD-fed mice. The findings suggested that supplementation with EtSF lowered lipid and glucose accumulation in the liver and increased fecal cholesterol contents in mice. Dietary supplementation with EtSF-P or EtSF-S/P attenuated liver damage in HCLD-fed mice.