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

Toxicity assessment of di(2-ethylhexyl) phthalate using zebrafish embryos: Cardiotoxic potential

Plasticizers are considered as newly emerged contaminants. They are added to plastics to increase their flexibility and softness. Phthalate plasticizers including the Di-2-ethylhexyl phthalates (DEHP) are toxic and induce adverse effects on the different organization levels of the environment. In the current study, we investigated the potential toxicity of DEHP using Zebrafish as a biological model. Five ascending concentrations of DEHP were tested in embryos throughout 96 hpf: 0.0086, 0.086, 0.86, 8.6, and 86 mg/L. Embryotoxicity assessments revealed limited lethal effects on DEHP-exposed embryos, yet notable anticipation of the hatching process was observed at 48 hpf. Although DEHP showed negligible influence on the length and pericardial area of exposed embryos, it led to multiple bodily deformities. Gene expression analyses of key cardiogenic and inflammatory genes evidenced alterations in tbx20, bcl2, and il1b expression in Zebrafish embryos at 96 h post-fertilization. Results from the cardiac function analysis displayed that DEHP significantly affected the arterial pulse and linear velocity within the Posterior Cardinal Vein (PCV) of exposed fish. These findings strongly advance that even at low concentrations, DEHP can be considered as potential toxic agent, capable of inducing cardiotoxic effects.

PPARβ/δ as a promising molecular drug target for liver diseases: A focused review

Various liver diseases pose great threats to humans. Although the etiologies of these liver diseases are quite diverse, they share similar pathologic phenotypes and molecular mechanisms such as oxidative stress, lipid and glucose metabolism disturbance, hepatic Kupffer cell (KC) proinflammatory polarization and inflammation, insulin resistance, and hepatic stellate cell (HSC) activation and proliferation. Peroxisome proliferator-activated receptor β/δ (PPARβ/δ) is expressed in various types of liver cells with relatively higher expression in KCs and HSCs. Accumulating evidence has revealed the versatile functions of PPARβ/δ such as controlling lipid homeostasis, inhibiting inflammation, regulating glucose metabolism, and restoring insulin sensitivity, suggesting that PPARβ/δ may serve as a potential molecular drug target for various liver diseases. This article aims to provide a concise review of the structure, expression pattern and biological functions of PPARβ/δ in the liver and its roles in various liver diseases, and to discuss potential future research perspectives.

Peroxisome proliferator-activated receptors: A key link between lipid metabolism and cancer progression

Lipids represent the essential components of membranes, serve as fuels for high-energy processes, and play crucial roles in signaling and cellular function. One of the key hallmarks of cancer is the reprogramming of metabolic pathways, especially abnormal lipid metabolism. Alterations in lipid uptake, lipid desaturation, de novo lipogenesis, lipid droplets, and fatty acid oxidation in cancer cells all contribute to cell survival in a changing microenvironment by regulating feedforward oncogenic signals, key oncogenic functions, oxidative and other stresses, immune responses, or intercellular communication. Peroxisome proliferator-activated receptors (PPARs) are transcription factors activated by fatty acids and act as core lipid sensors involved in the regulation of lipid homeostasis and cell fate. In addition to regulating whole-body energy homeostasis in physiological states, PPARs play a key role in lipid metabolism in cancer, which is receiving increasing research attention, especially the fundamental molecular mechanisms and cancer therapies targeting PPARs. In this review, we discuss how cancer cells alter metabolic patterns and regulate lipid metabolism to promote their own survival and progression through PPARs. Finally, we discuss potential therapeutic strategies for targeting PPARs in cancer based on recent studies from the last five years.

pparβ regulates lipid catabolism by mediating acox and cpt-1 genes in Scophthalmus maximus under heat stress

Peroxisome proliferator-activated receptor β (pparβ) is a key gene-regulating lipid metabolism pathway, but its function in turbot remains unclear. In this study, the CDS of pparβ was cloned from kidney for the first time. The CDS sequence length was 1533 bp encoding 510 amino acids. Structural analysis showed that the pparβ protein contained a C4 zinc finger and HOLI domain, suggesting that the pparβ gene of turbot has high homology with the PPAR gene of other species. The high expression patterns of pparβ, acox, and cpt-1 at high temperatures, as shown through qPCR, indicated that high temperatures activated the transcriptional activity of pparβ and increased the activity of the acox and cpt-1 genes. The expression of acox and cpt-1 was significantly inhibited when pparβ was downregulated using RNAi technology and inhibitor treatments, suggesting that pparβ positively regulated acox and cpt-1 expression at high temperatures and, thus, modulates lipid catabolism activity. These results demonstrate that pparβ is involved in the regulation of lipid metabolism at high temperatures and expand a new perspective for studying the regulation of lipid metabolism in stress environments of teleost.

Semaphorin 3A Inhibits Endoplasmic Reticulum Stress Induced by High Glucose in Müller Cells

PURPOSE

This study aimed to explore the effect of the Semaphorin3A (Sema3A)/Neuropilin-1 (Nrp-1) pathway on Müller cell activities and endoplasmic reticulum (ER) stress induced by high glucose (HG) in vitro.

METHODS

The primary Müller cells of C57BL/6J mice were isolated and cultured in normal or high glucose medium. The expression of endogenous Sema3A and its coreceptor Nrp-1 was measured by Western blot. Müller cells were incubated with exogenous recombinant Sema3A protein or transfected with lentiviral vectors expressing small hairpin RNA (shRNA) to knock down the expression of endogenous Sema3A. The proliferation of Müller cells was detected by CCK-8 assay and EdU staining. The migratory ability was detected by the Transwell migration assay. The level of endoplasmic reticulum (ER) stress was analyzed through the detection of GRP78/BiP, IRE1α, phosphorylated IRE1αS724 (p-IRE1αS724), and the splicing rate of XBP1 (XBP1s/XBP1) by using immunofluorescence, Western blot or quantitative polymerase chain reaction (qPCR).

RESULTS

HG induced the upregulation of endogenous Sema3A and Nrp-1 receptors in Müller cells. The expression of GRP78/BiP and IRE1α was upregulated by HG, with an increased splicing rate of XBP1. Exogenous Sema3A inhibited HG-induced Müller cell proliferation, migration, and GRP78/BiP-IRE1α-XBP1 axis activation. Knockdown of Sema3A promoted proliferation, migration, and ER stress induced by high glucose in Müller cells.

CONCLUSION

Sema3A inhibited the increased proliferative and migratory activities induced by high glucose by attenuating ER stress in Müller cells.

Adverse cardiovascular effects and potential molecular mechanisms of DEHP and its metabolites-A review

Currently, cardiovascular disease (CVD) is a health hazard that is associated with progressive deterioration upon exposure to environmental pollutants. Di(2-ethylhexyl) phthalate (DEHP) has been one of the focuses of emerging concern due to its ubiquitous nature and its toxicity to the cardiovascular (CV) system. DEHP has been noted as a causative risk factor or a risk indicator for the initiation and augment of CVDs. DEHP represents a precursor that contributes to the pathogenesis of CVDs through its active metabolites, which mainly include mono (2-ethylhexyl) phthalate (MEHP). Herein, we systematically presented the association between DEHP and its metabolites and adverse CV outcomes and discussed the corresponding effects, underlying mechanisms and possibly interventions. Epidemiological and experimental evidence has suggested that DEHP and its metabolites have significant impacts on processes and factors involved in CVD, such as cardiac developmental toxicity, cardiac injury and apoptosis, cardiac arrhythmogenesis, cardiac metabolic disorders, vascular structural damage, atherogenesis, coronary heart disease and hypertension. DNA methylation, PPAR-related pathways, oxidative stress and inflammation, Ca²⁺ homeostasis disturbance may pinpoint the relevant mechanisms. The preventive and therapeutic measures are potentially related with P-glycoprotein, heat-shock proteins, some antioxidants, curcumin, apigenin, β-thujaplicin, glucagon-like peptide-1 receptor agonists and Ang-converting enzyme inhibitors and so on. Promisingly, future investigations should aid in thoroughly assessing the causal relationship and molecular interactions between CVD and DEHP and its metabolites and explore feasible prevention and treatment measures accordingly.

Knocking on GDF15's door for the treatment of type 2 diabetes mellitus

Although a large number of drugs are available for the treatment of type 2 diabetes mellitus (T2DM), many patients do not achieve adequate disease control despite adhering to medication. Recent findings indicate that the pharmacological modulation of the stress-induced cytokine growth differentiation factor 15 (GDF15) shows promise for the treatment of T2DM. GDF15 suppresses appetite and reduces inflammation, increases thermogenesis and lipid catabolism, sustains AMP-activated protein kinase (AMPK) activity, and ameliorates insulin resistance and hepatic steatosis. In addition, circulating GDF15 levels are elevated in response to several antidiabetic drugs, including metformin, with GDF15 mediating some of their effects. Here, we review the mechanistic insights into the beneficial effects of recently explored therapeutic approaches that target GDF15 for the treatment of T2DM.

Old and new classes of glucose-lowering agents as treatments for non-alcoholic fatty liver disease: A narrative review

Non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease with a global prevalence of about 55% in people with type 2 diabetes mellitus (T2DM). T2DM, obesity and NAFLD are three closely inter-related pathological conditions. In addition, T2DM is one of the strongest clinical risk factors for the faster progression of NAFLD to non-alcoholic steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma. Increasing evidence suggests that newer classes of glucose-lowering drugs, such as peroxisome proliferator-activated receptor agonists, glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase-4 inhibitors or sodium-glucose cotransporter-2 inhibitors, could reduce the rates of NAFLD progression. This narrative review aims to briefly summarize the recent results from randomized controlled trials testing the efficacy and safety of old and new glucose-lowering drugs for the treatment of NAFLD or NASH in adults both with and without coexisting T2DM.

The Impact of Dietary Fiber as a Prebiotic on Inflammation in Children with Obesity

Background: Obesity is associated with dysbiosis, contributing to inflammation and insulin resistance. Inulin might reduce inflammation by manipulating intestinal microbiota. Objective: We aimed to determine the effects of inulin supplementation on inflammation and assess the relationships of inflammatory cytokines with adiposity and insulin resistance in obese Thai children. Design: Obese Thai children ages 7−15 years were randomly assigned to inulin (intervention), maltodextrin (placebo), and dietary fiber advice groups. All participants received monthly follow-up and identical advice on lifestyle modification for six visits. Body composition was evaluated using bioelectrical impedance analysis. IL-1β, IL-6, TNF-α, and fecal calprotectin were analyzed by ELISA technique at baseline and the final visit. Spearman correlation was used to assess the associations between inflammation and other clinical outcome variables. Results: A total of 155 obese children completed the study (mean age: 10.4 ± 2.2 years, 59% male). All groups showed a significant decrease in BMI z-score, fat mass index (FMI), percent body fat, and trunk FMI. A generalized estimating equation (GEE) model showed significantly decreased IL-1β and TNF-α of 34.8% and 25.8%, (p < 0.0001) but increased IL-6 (21.5%, p = 0.006) in all groups. There were no significant differences in inflammatory cytokines and fecal calprotectin between groups. Mean IL-6 was higher in obese children with acanthosis nigricans (p = 0.048). Only IL-6 was positively correlated with body fat percentage and FMI (r = 0.29, p = 0.008 and r = 0.25, p = 0.049, respectively). Conclusions: Intensive behavioral modification and frequent follow-up visits were effective methods to reduce BMI and adiposity leading to decreased inflammatory cytokines. The additional benefits of inulin on inflammation could not be demonstrated due to the Hawthorne effect. Among the three cytokines, IL-6 was the most likely mediator relating FM and insulin resistance at baseline; therefore, it could be used as a surrogate marker of inflammation in obese children who are at risk for insulin resistance and metabolic syndrome.

Peroxisomal Proliferator-Activated Receptor β/δ Deficiency Induces Cognitive Alterations

Peroxisome proliferator-activated receptor β/δ (PPARβ/δ), the most PPAR abundant isotype in the central nervous system, is involved in microglial homeostasis and metabolism, whose disturbances have been demonstrated to play a key role in memory impairment. Although PPARβ/δ function is well-established in metabolism, its contribution to neuronal and specifically memory process is underexplored. Therefore, the aim of the study is to determine the role of PPARβ/δ in the neuropathological pathways involved in memory impairment and as to whether a risk factor implicated in memory loss such as obesity modulates neuropathological markers. To carry out this study, 6-month-old total knock-out for the Ppard gene male mice with C57BL/6X129/SV background (PPARβ/δ-/-) and wild-type (WT) littermates with the same genetic background were used. Animals were fed, after the weaning (at 21 days old), and throughout their growth, either conventional chow (CT) or a palmitic acid-enriched diet (HFD). Thus, four groups were defined: WT CT, WT HFD, PPARβ/δ-/- CT, and PPARβ/δ-/- HFD. Before sacrifice, novel object recognition test (NORT) and glucose and insulin tolerance tests were performed. After that, animals were sacrificed by intracardiac perfusion or cervical dislocation. Different techniques, such as GolgiStain kit or immunofluorescence, were used to evaluate the role of PPARβ/δ in memory dysfunction. Our results showed a decrease in dendritic spine density and synaptic markers in PPARβ/δ-/- mice, which were corroborated in the NORT. Likewise, our study demonstrated that the lack of PPARβ/δ receptor enhances gliosis in the hippocampus, contributing to astrocyte and microglial activation and to the increase in neuroinflammatory biomarkers. Additionally, alterations in the hippocampal insulin receptor pathway were found. Interestingly, while some of the disturbances caused by the lack of PPARβ/δ were not affected by feeding the HFD, others were exacerbated or required the combination of both factors. Taken together, the loss of PPARβ/δ-/- affects neuronal and synaptic structure, contributing to memory dysfunction, and they also present this receptor as a possible new target for the treatment of memory impairment.

Endothelium-targeted delivery of PPARδ by adeno-associated virus serotype 1 ameliorates vascular injury induced by hindlimb ischemia in obese mice

Diabetic vasculopathy is a major health problem worldwide. Peripheral arterial disease (PAD), and in its severe form, critical limb ischemia is a major form of diabetic vasculopathy with limited treatment options. Existing literature suggested an important role of PPARδ in vascular homeostasis. It remains elusive for using PPARδ as a potential therapeutic target due to mostly the side effects of PPARδ agonists. To explore the roles of PPARδ in endothelial homeostasis, endothelial cell (EC) selective Ppard knockout and controlled mice were subjected to hindlimb ischemia (HLI) injury. The muscle ECs were sorted for single-cell RNA sequencing (scRNA-seq) analysis. HLI was also performed in high fat diet (HFD)-induced obese mice to examine the function of PPARδ in obese mice with delayed vascular repair. Adeno-associated virus type 1 (AAV1) carrying ICAM2 promoter to target endothelium for overexpressing PPARδ was injected into the injured muscles of normal chow- and HFD-fed obese mice before HLI surgery was performed. scRNA-seq analysis of ECs in ischemic muscles revealed a pivotal role of PPARδ in endothelial homeostasis. PPARδ expression was diminished both after HLI injury, and also in obese mice, which showed further delayed vascular repair. Endothelium-targeted delivery of PPARδ by AAV1 improved perfusion recovery, increased capillary density, restored endothelial integrity, suppressed vascular inflammation, and promoted muscle regeneration in ischemic hindlimbs of both lean and obese mice. Our study indicated the effectiveness of endothelium-targeted PPARδ overexpression for restoring functional vasculature after ischemic injury, which might be a promising option of gene therapy to treat PAD and CLI.

The Structure Basis of Phytochemicals as Metabolic Signals for Combating Obesity

The consumption of phytochemicals, bioactive compounds in fruits and vegetables, has been demonstrated to ameliorate obesity and related metabolic symptoms by regulating specific metabolic pathways. This review summarizes the progress made in our understanding of the potential of phytochemicals as metabolic signals: we discuss herein selected molecular mechanisms which are involved in the occurrence of obesity that may be regulated by phytochemicals. The focus of our review highlights the regulation of transcription factors toll like receptor 4 (TLR4), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), the peroxisome proliferator-activated receptors (PPARs), fat mass and obesity-associated protein (FTO) and regulation of microRNAs (miRNA). In this review, the effect of phytochemicals on signaling pathways involved in obesity were discussed on the basis of their chemical structure, suggesting molecular mechanisms for how phytochemicals may impact these signaling pathways. For example, compounds with an isothiocyanate group or an α, β-unsaturated carbonyl group may interact with the TLR4 signaling pathway. Regarding Nrf2, we examine compounds possessing an α, β-unsaturated carbonyl group which binds covalently with the cysteine thiols of Keap1. Additionally, phytochemical activation of PPARs, FTO and miRNAs were summarized. This information may be of value to better understand how specific phytochemicals interact with specific signaling pathways and help guide the development of new drugs to combat obesity and related metabolic diseases.

Human Milk Lipids Induce Important Metabolic and Epigenetic Changes in Neonates

Lipids are a major source of energy during the fetal/neonatal period. Most are received from the mother, transplacentally during the intrauterine period or via maternal milk after birth. However, in addition to the known nutritional roles, lipids are now known to bind a variety of cellular receptors to regulate specific patterns in metabolism and gene expression. The expression of these receptors is regulated by various genetic and environmental stimuli, and ligation can activate positive-feedback loops in the expression and the activity of downstream signaling pathways. The authors summarize the role of lipid ligands, cognate receptors, epigenetic regulation, and downstream signaling.

A detailed review on the phytochemical profiles and anti-diabetic mechanisms of Momordica charantia

Diabetes mellitus is the most well-known endocrine dilemma suffered by hundreds of million people globally, with an annual mortality of more than one million people. This high mortality rate highlights the need for in-depth study of anti-diabetic agents. This review explores the phytochemical contents and anti-diabetic mechanisms of M. charantia (cucurbitaceae). Studies show that M. charantia contains several phytochemicals that have hypoglycemic effects, thus, the plant may be effective in the treatment/management of diabetes mellitus. Also, the biochemical and physiological basis of M. charantia anti-diabetic actions is explained. M. charantia exhibits its anti-diabetic effects via the suppression of MAPKs and NF-κβin pancreatic cells, promoting glucose and fatty acids catabolism, stimulating fatty acids absorption, inducing insulin production, ameliorating insulin resistance, activating AMPK pathway, and inhibiting glucose metabolism enzymes (fructose-1,6-bisphosphate and glucose-6-phosphatase). Reviewed literature was obtained from credible sources such as PubMed, Scopus, and Web of Science.

Effects of Four Lipid Metabolism-Related Polymorphisms on Body Composition Improvements After 12 Weeks of High-Intensity Interval Training and Dietary Energy Restriction in Overweight/Obese Adult Women: A Pilot Study

Background: Polymorphisms in lipid metabolism-related genes have been associated with obesity and body composition, but these have been scarcely described concerning the magnitude of the response to exercise interventions in the overweight/obese population.

Objective: To evaluate the association of perilipin 1 (PLIN1; rs1052700 and rs2304795), lipoprotein lipase (rs283), and adrenoceptor beta 3 (rs4994) polymorphisms with high and low responders (LoRes) to fat mass reduction after 12 weeks of high-intensity interval training (HIIT) and dietary energy restriction in overweight/obese adult women. In addition, we examined the effect of these genetic variants on body composition changes.

Methods: Forty-three unrelated overweight/obese adult women were incorporated and genotyped, of which 30 women (age = 27.4 ± 7.9 years; BMI = 29.9 ± 3.3 kg/m²) successfully completed the 12-week supervised HIIT program plus an individually prescribed home hypocaloric diet.

Results: An association was observed between the PLIN1 rs1052700 polymorphism with high and LoRes (χ² = 8.138; 2 df; p = 0.01). Moreover, after the intervention, the carriers of TT genotype of PLIN1 rs1052700 as compared to AA and AT showed a greater reduction in absolute fat mass (Δ: −5.1 ± 1.8 vs. − 1.8 ± 1.4 vs. − 2.1 ± 2.3 kg; p = 0.04). The effect size of this fat mass reduction between TT and AT genotypes was a mean difference of −3.01 kg [95%IC − 4.88– − 1.1], and between TT and AA genotypes was −3.29 kg [95%IC − 4.86– − 1.65]. No differences were observed for other polymorphisms investigated.

Conclusion: These results suggest that the rs1052700 (14995A>T) polymorphism of the PLIN1 gene is associated with a differential response to fat mass reduction after a 12-week intervention in overweight/obese adult women. In addition, women with the TT genotype of this genetic variant showed greater changes in fat mass than AA and AT genotypes. However, further studies are needed to confirm these findings.

Brazil Nut Supplementation Does Not Regulate PPARβ/δ Signaling Pathway in Peripheral Blood Mononuclear Cells from Coronary Artery Disease Patients

BACKGROUND

Peroxisome proliferator-activated receptor (PPAR)β/δ activation is a potential target for modulation of inflammation in cardiovascular disease. PPARβ/δ activation depends on the presence of a ligand, which may be pharmacological or natural, such as bioactive compounds and nutrients. Due to its composition, rich in selenium and unsaturated fatty acids, Brazil nuts have been related to reduced oxidative stress and inflammation in chronic non-communicable diseases and could regulate PPARβ/δ. This study aimed to evaluate the effects of Brazil nut supplementation on PPARβ/δ mRNA expression in patients with Coronary Artery Disease (CAD).

METHODS

A secondary analysis of a randomized controlled clinical trial was performed with 36 CAD patients. Patients were randomly assigned to either the Supplementation group or the control group and followed up for three months. The Supplementation group consumed 1 Brazil nut/day; the control group did not receive any intervention. At the baseline and after three months, analysis of gene expression and biochemical parameters linked to inflammatory biomarkers and oxidative stress was carried out.

RESULTS

In the supplementation group, no significant change was observed in PPARβ/δ (0.9 ± 0.5 vs 1.2 ± 0.6; p = 0.178) and NF-κB (1.6 ± 1.5 vs 0.8 ± 0.30, p = 0.554) mRNA expression. There were no significant changes in both groups concerning all the other biochemical parameters.

CONCLUSION

One Brazil nut per day for three months was not able to increase the PPARβ/δ expression in CAD patients.

GDF15 mediates the metabolic effects of PPARβ/δ by activating AMPK

Peroxisome proliferator-activated receptor β/δ (PPARβ/δ) activates AMP-activated protein kinase (AMPK) and plays a crucial role in glucose and lipid metabolism. Here, we examine whether PPARβ/δ activation effects depend on growth differentiation factor 15 (GDF15), a stress response cytokine that regulates energy metabolism. Pharmacological PPARβ/δ activation increases GDF15 levels and ameliorates glucose intolerance, fatty acid oxidation, endoplasmic reticulum stress, and inflammation, and activates AMPK in HFD-fed mice, whereas these effects are abrogated by the injection of a GDF15 neutralizing antibody and in Gdf15-/- mice. The AMPK-p53 pathway is involved in the PPARβ/δ-mediated increase in GDF15, which in turn activates again AMPK. Consistently, Gdf15-/- mice show reduced AMPK activation in skeletal muscle, whereas GDF15 administration results in AMPK activation in this organ. Collectively, these data reveal a mechanism by which PPARβ/δ activation increases GDF15 levels via AMPK and p53, which in turn mediates the metabolic effects of PPARβ/δ by sustaining AMPK activation.

The PPARβ/δ-AMPK Connection in the Treatment of Insulin Resistance

The current treatment options for type 2 diabetes mellitus do not adequately control the disease in many patients. Consequently, there is a need for new drugs to prevent and treat type 2 diabetes mellitus. Among the new potential pharmacological strategies, activators of peroxisome proliferator-activated receptor (PPAR)β/δ show promise. Remarkably, most of the antidiabetic effects of PPARβ/δ agonists involve AMP-activated protein kinase (AMPK) activation. This review summarizes the recent mechanistic insights into the antidiabetic effects of the PPARβ/δ-AMPK pathway, including the upregulation of glucose uptake, muscle remodeling, enhanced fatty acid oxidation, and autophagy, as well as the inhibition of endoplasmic reticulum stress and inflammation. A better understanding of the mechanisms underlying the effects resulting from the PPARβ/δ-AMPK pathway may provide the basis for the development of new therapies in the prevention and treatment of insulin resistance and type 2 diabetes mellitus.

Pterostilbene Improves Insulin Resistance Caused by Advanced Glycation End Products (AGEs) in Hepatocytes and Mice

SCOPE

Increased consumption of modern processed foods rich in AGEs is drawing worldwide concerns because they are related with rising diabetes prevalence. This study aimed to investigate if pterostilbene (PTE) regulates glucose metabolism and insulin signaling, as well as its potential mechanism in the context of AGEs exposure.

METHODS AND RESULTS

In vitro, Lo2 and HepG2 cells are treated with vehicle, AGEs with or without PTE. AGEs exposure directly impair insulin action as evidenced by assays of insulin-stimulated glucose uptake, consumption, and output. However, PTE efficiently rescue the AGE-induced phenotypes in both cell lines, and enhance IRS-1/PI3K/AKT insulin signaling in a dose-dependent manner. In vivo, C57BL6 mice are fed with regular, high AGEs diet and high AGEs plus PTE. PTE administration effectively improves hyperglycemia, glucose tolerance, and impaired hepatic insulin signaling induced by AGEs, consistent with the in vitro experiments. Moreover, PTE reduce AGEs accumulation in liver and serum. RNA-seq data indicate that PTE counteracts several AGEs-induced dysfunctions including diabetes related process, glucose metabolic process, immune response, and so on.

CONCLUSION

PTE treatment prominently reduced AGEs accumulation and alleviated AGEs-associated diabetes symptoms. PTE could be used as a promising glucose-sensitizing agent for nutritional intervention.

Physiological Effects and Inter-Individual Variability to 12 Weeks of High Intensity-Interval Training and Dietary Energy Restriction in Overweight/Obese Adult Women

Background: Human adaptive response to exercise interventions is often described as group average and SD to represent the typical response for most individuals, but studies reporting individual responses to exercise show a wide range of responses.

Objective: To characterize the physiological effects and inter-individual variability on fat mass and other health-related and physical performance outcomes after 12 weeks of high-intensity interval training (HIIT) and dietary energy restriction in overweight/obese adult women.

Methods: Thirty untrained adult overweight and obese women (age = 27.4 ± 7.9 years; BMI = 29.9 ± 3.3 kg/m²) successfully completed a 12-week supervised HIIT program and an individually prescribed home hypocaloric diet (75% of daily energy requirements) throughout the whole intervention. High and low responders to the intervention were those individuals who were able to lose ≥ 10 and < 10% of initial absolute fat mass (i.e., kilograms), respectively.

Results: The prevalence for high and low responders was 33% (n = 11) and 66% (n = 19), respectively. At the whole group level, the intervention was effective to reduce the absolute fat mass (30.9 ± 7.2 vs. 28.5 ± 7.2 kg; p < 0.0001), body fat percentage (39.8 ± 4.3 vs. 37.8 ± 4.9%; p < 0.0001), and total body mass (76.7 ± 10.1 vs. 74.4 ± 9.9 kg; p < 0.0001). In addition, there were improvements in systolic blood pressure (SBP; Δ% = −5.1%), diastolic blood pressure (DBP; Δ% = −6.4%), absolute VO₂peak (Δ% = +14.0%), relative VO₂peak (Δ% = +13.8%), peak power output (PPO; Δ% = +19.8%), anaerobic threshold (AT; Δ% = +16.7%), maximal ventilation (VE; Δ% = +14.1%), and peak oxygen pulse (O₂ pulse; Δ% = +10.4%). However, at the individual level, a wide range of effects were appreciated on all variables, and the magnitude of the fat mass changes did not correlate with baseline body mass or fat mass.

Conclusion: A 12-week supervised HIIT program added to a slight dietary energy restriction effectively improved fat mass, body mass, blood pressure, and cardiorespiratory fitness (CRF). However, a wide range of inter-individual variability was observed in the adaptative response to the intervention. Furthermore, subjects classified as low responders for fat mass reduction could be high responders (HiRes) in many other health-related and physical performance outcomes. Thus, the beneficial effects of exercise in obese and overweight women go further beyond the adaptive response to a single outcome variable such as fat mass or total body mass reduction.

From Food to Genes: Transcriptional Regulation of Metabolism by Lipids and Carbohydrates

Lipids and carbohydrates regulate gene expression by means of molecules that sense these macronutrients and act as transcription factors. The peroxisome proliferator-activated receptor (PPAR), activated by some fatty acids or their derivatives, and the carbohydrate response element binding protein (ChREBP), activated by glucose-derived metabolites, play a key role in metabolic homeostasis, especially in glucose and lipid metabolism. Furthermore, the action of both factors in obesity, diabetes and fatty liver, as well as the pharmacological development in the treatment of these pathologies are indeed of high relevance. In this review we present an overview of the discovery, mechanism of activation and metabolic functions of these nutrient-dependent transcription factors in different tissues contexts, from the nutritional genomics perspective. The possibility of targeting these factors in pharmacological approaches is also discussed. Lipid and carbohydrate-dependent transcription factors are key players in the complex metabolic homeostasis, but these factors also drive an adaptive response to non-physiological situations, such as overeating. Possibly the decisive role of ChREBP and PPAR in metabolic regulation points to them as ideal therapeutic targets, but their pleiotropic functions in different tissues makes it difficult to "hit the mark".

Valine Supplementation Does Not Reduce Lipid Accumulation and Improve Insulin Sensitivity in Mice Fed High-Fat Diet

Branched-chain amino acids (BCAAs), particularly leucine, were reported to decrease obesity and relevant metabolic syndrome. However, whether valine has a similar effect has rarely been investigated. In the present study, mice were assigned into four treatments (n = 10): chow diet supplemented with water (CW) or valine (CV) and high-fat diet supplemented with water (HW) or valine (HV). Valine (3%, w/v) was supplied in the drinking water. The results showed that valine treatment markedly increased serum triglyceride and insulin levels of chow diet-fed mice. The body weight, serum triglyceride level, white adipose tissue weight, and glucose and insulin intolerance were significantly elevated by valine supplementation in high-fat diet-fed mice. Metabolomics and transcriptomics showed that several genes related to fat oxidation were downregulated, and arachidonic acid and linoleic acid metabolism were altered in the HV group compared to the HW group. In conclusion, valine supplementation did not suppress lipid deposition and metabolic disorders in mice, which provides a new understanding for BCAAs in the modulation of lipid metabolism.

Protective Effects of (E)-β-Caryophyllene (BCP) in Chronic Inflammation

(E)-β-caryophyllene (BCP) is a bicyclic sesquiterpene widely distributed in the plant kingdom, where it contributes a unique aroma to essential oils and has a pivotal role in the survival and evolution of higher plants. Recent studies provided evidence for protective roles of BCP in animal cells, highlighting its possible use as a novel therapeutic tool. Experimental results show the ability of BCP to reduce pro-inflammatory mediators such as tumor necrosis factor-alfa (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), thus ameliorating chronic pathologies characterized by inflammation and oxidative stress, in particular metabolic and neurological diseases. Through the binding to CB2 cannabinoid receptors and the interaction with members of the family of peroxisome proliferator-activated receptors (PPARs), BCP shows beneficial effects on obesity, non-alcoholic fatty liver disease/nonalcoholic steatohepatitis (NAFLD/NASH) liver diseases, diabetes, cardiovascular diseases, pain and other nervous system disorders. This review describes the current knowledge on the biosynthesis and natural sources of BCP, and reviews its role and mechanisms of action in different inflammation-related metabolic and neurologic disorders.

Discovery and SAR of Natural-Product-Inspired RXR Agonists with Heterodimer Selectivity to PPARδ-RXR

A known natural product, magnaldehyde B, was identified as an agonist of retinoid X receptor (RXR) α. Magnaldehyde B was isolated from Magnolia obovata (Magnoliaceae) and synthesized along with more potent analogs for screening of their RXRα agonistic activities. Structural optimization of magnaldehyde B resulted in the development of a candidate molecule that displayed a 440-fold increase in potency. Receptor-ligand docking simulations indicated that this molecule has the highest affinity with the ligand binding domain of RXRα among the analogs synthesized in this study. Furthermore, the selective activation of the peroxisome proliferator-activated receptor (PPAR) δ-RXR heterodimer with a stronger efficacy compared to those of PPARα-RXR and PPARγ-RXR was achieved in luciferase reporter assays using the PPAR response element driven reporter (PPRE-Luc). The PPARδ activity of the molecule was significantly inhibited by the antagonists of both RXR and PPARδ, whereas the activity of GW501516 was not affected by the RXR antagonist. Furthermore, the molecule exhibited a particularly weak PPARδ agonistic activity in reporter gene assays using the Gal4 hybrid system. The obtained data therefore suggest that the weak PPARδ agonistic activity of the optimized molecule is synergistically enhanced by its own RXR agonistic activity, indicating the potent agonistic activity of the PPARδ-RXR heterodimer.

Liraglutide Up-regulation Thioredoxin Attenuated Müller Cells Apoptosis in High Glucose by Regulating Oxidative Stress and Endoplasmic Reticulum Stress

Purpose: Diabetic retinopathy (DR) has become one of the most important complications of diabetes which is the leading cause of vision impairment and blindness all over the world. Increasing evidence shows that reactive gliosis are basic pathological features of early DR. The study was aimed to explore the protective effect and mechanism of Liraglutide (LIRA) which has similar properties to Glucagon-like peptide-1 (GLP-1) on Müller cell damage induced by diabetes. Materials and methods: In vitro, the Müller cell was cultured in high glucose (HG) to establish the model of diabetic retinopathy. The apoptosis was detected using flow cytometry. Western blot and immunofluorescence were used to detect the expression of related proteins. DCFH-DA probe was used to detect the ROS generation. Results: The data showed that the apoptosis and the expression of GFAP were increased significantly with HG treatment. However, the apoptosis percentage and the expression of GFAP were decreased after LIRA treatment. Moreover, the expression of p-Erk/Nrf2/Trx-signaling pathway proteins was also up-regulated and the generation of ROS was decreased after LIRA treatment which was inhibited after treatment with U0126 (Erk inhibitor). Besides, endoplasmic reticulum stress (ER stress) related proteins were up-regulated after Trx down-regulation by transfection with sh-RNA. Conclusions: LIRA could protect Müller cells from HG-induced damage via activating p-Erk pathway through increasing Trx expression which attenuated oxidative stress and ER stress. Trx could play a key role in the process.

Nutritional strategies to modulate inflammation pathways via regulation of peroxisome proliferator-activated receptor β/δ

The peroxisome proliferator-activated receptor (PPAR) β/δ has an important role in multiple inflammatory conditions, including obesity, hypertension, cancer, cardiovascular disease, diabetes mellitus, and autoimmune diseases. PPARβ/δ forms a heterodimer with the retinoic acid receptor and binds to peroxisome proliferator response elements to initiate transcription of its target genes. PPARβ/δ is also able to suppress the activities of several transcription factors, including nuclear factor κB, and activator protein 1, thus regulating anti-inflammatory cellular responses and playing a protective role in several diseases. Recent studies have shown that nutritional compounds, including nutrients and bioactive compounds, can regulate PPARβ/δ expression. This review discusses key nutritional compounds that are known to modulate PPARβ/δ and are likely to affect human health.

Anti-aging Effects of Calorie Restriction (CR) and CR Mimetics based on the Senoinflammation Concept

Chronic inflammation, a pervasive feature of the aging process, is defined by a continuous, multifarious, low-grade inflammatory response. It is a sustained and systemic phenomenon that aggravates aging and can lead to age-related chronic diseases. In recent years, our understanding of age-related chronic inflammation has advanced through a large number of investigations on aging and calorie restriction (CR). A broader view of age-related inflammation is the concept of senoinflammation, which has an outlook beyond the traditional view, as proposed in our previous work. In this review, we discuss the effects of CR on multiple phases of proinflammatory networks and inflammatory signaling pathways to elucidate the basic mechanism underlying aging. Based on studies on senoinflammation and CR, we recognized that senescence-associated secretory phenotype (SASP), which mainly comprises cytokines and chemokines, was significantly increased during aging, whereas it was suppressed during CR. Further, we recognized that cellular metabolic pathways were also dysregulated in aging; however, CR mimetics reversed these effects. These results further support and enhance our understanding of the novel concept of senoinflammation, which is related to the metabolic changes that occur in the aging process. Furthermore, a thorough elucidation of the effect of CR on senoinflammation will reveal key insights and allow possible interventions in aging mechanisms, thus contributing to the development of new therapies focused on improving health and longevity.

GQ-130, a novel analogue of thiazolidinedione, improves obesity-induced metabolic alterations in rats: Evidence for the involvement of PPARβ/δ pathway

The present investigation aimed to characterize the effect of a short-time treatment with a new thiazolidinedione (TZD) derivative, GQ-130, on metabolic alterations in rats fed a high-fat diet (HFD). We investigated whether metabolic alterations induced by GQ-130 were mediated though a mechanism that involves PPARβ/δ transactivation. Potential binding and transactivation of PPARα, PPARβ/δ or PPARγ by GQ-130 were examined through cell transactivation, 8-anilino-1-naphthalenesulfonic acid (ANS) fluorescence quenching assays and thermal shift assay. For in vivo experiments, male 8-week-old Wistar rats were divided into three groups fed for 6 weeks with: (a) a standard rat chow (14% fat) (control group), (b) a HFD (57.8% fat) alone (HFD group), or (c) a HFD associated with an oral treatment with GQ-130 (10 mg/kg/d) during the last week (HFD-GQ group). In 293T cells, unlike rosiglitazone, GQ-130 did not cause significant transactivation of PPARγ but was able to activate PPARβ/δ by 153.9 folds in comparison with control values (DMSO). Surprisingly, ANS fluorescence quenching assay reveals that GQ-130 does not bind directly to PPARβ/δ binding site, a finding that was further corroborated by thermal shift assay which evaluates the thermal stability of PPARβ/δ in the presence of GQ-130. Compared to the control group, rats of the HFD group showed obesity, increased systolic blood pressure (SBP), insulin resistance, impaired glucose intolerance, hyperglycaemia, and dyslipidaemia. GQ-130 treatment abolished the increased SBP and improved all metabolic dysfunctions observed in the HFD group. Oral treatment with GQ-130 was effective in improving HFD-induced metabolic alterations probably through a mechanism that involves PPARβ/δ activation.

Lifestyle and Food Habits Impact on Chronic Diseases: Roles of PPARs

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that exert important functions in mediating the pleiotropic effects of diverse exogenous factors such as physical exercise and food components. Particularly, PPARs act as transcription factors that control the expression of genes implicated in lipid and glucose metabolism, and cellular proliferation and differentiation. In this review, we aim to summarize the recent advancements reported on the effects of lifestyle and food habits on PPAR transcriptional activity in chronic disease.

Efficacy of a Validated Yoga Protocol on Dyslipidemia in Diabetes Patients: NMB-2017 India Trial

Background: Dyslipidemia is considered a risk factor in Type 2 diabetes mellitus (T2DM) resulting in cardio-vascular complications. Yoga practices have shown promising results in alleviating Type 2 Diabetes pathology. Method: In this stratified trial on a Yoga based lifestyle program in cases with Type 2 diabetes, in the rural and urban population from all zones of India, a total of 17,012 adults (>20 years) of both genders were screened for lipid profile and sugar levels. Those who satisfied the selection criteria were taught the Diabetes Yoga Protocol (DYP) for three months and the data were analyzed. Results: Among those with Diabetes, 29.1% had elevated total cholesterol (TC > 200 mg/dL) levels that were higher in urban (69%) than rural (31%) Diabetes patients. There was a positive correlation (p = 0.048) between HbA1c and total cholesterol levels. DYP intervention helped in reducing TC from 232.34 ± 31.48 mg/dL to 189.38 ± 40.23 mg/dL with significant pre post difference (p < 0.001). Conversion rate from high TC (>200 mg/dL) to normal TC (<200 mg/dL) was observed in 60.3% of cases with Type 2 Diabetes Mellitus (T2DM); from high LDL (>130 mg/dL) to normal LDL (<130 mg/dL) in 73.7%; from high triglyceride (>200 mg/dL) to normal triglyceride level (<200 mg/dL) in 63%; from low HDL (<45 mg/dL) to normal HDL (>45 mg/dL) in 43.7% of T2DM patients after three months of DYP. Conclusions: A Yoga lifestyle program designed specifically to manage Diabetes helps in reducing the co-morbidity of dyslipidemia in cases of patients with T2DM.

Unraveling the role of peroxisome proliferator-activated receptor-β/δ (PPARβ/δ) expression in colon carcinogenesis

The peroxisome proliferator-activated-β/δ (PPARβ/δ) was identified in 1994, but not until 1999 was PPARβ/δ suggested to be involved in carcinogenesis. Initially, it was hypothesized that expression of PPARβ/δ was increased during colon cancer progression, which led to increased transcription of yet-to-be confirmed target genes that promote cell proliferation and tumorigenesis. It was also hypothesized at this time that lipid-metabolizing enzymes generated lipid metabolites that served as ligands for PPARβ/δ. These hypothetical mechanisms were attractive because they potentially explained how non-steroidal anti-inflammatory drugs inhibited tumorigenesis by potentially limiting the concentration of endogenous PPARβ/δ ligands that could activate this receptor that was increased in cancer cells. However, during the last 20 years, considerable research was undertaken describing expression of PPARβ/δ in normal and cancer cells that has led to a significant impact on the mechanisms by which PPARβ/δ functions in carcinogenesis. Whereas results from earlier studies led to much uncertainty about the role of PPARβ/δ in cancer, more recent analyses of large databases have revealed a more consistent understanding. The focus of this review is on the fundamental level of PPARβ/δ expression in normal tissues and cancerous tissue as described by studies during the past two decades and what has been delineated during this timeframe about how PPARβ/δ expression influences carcinogenesis, with an emphasis on colon cancer.

PPARs as Nuclear Receptors for Nutrient and Energy Metabolism

It has been more than 36 years since peroxisome proliferator-activated receptors (PPARs) were first recognized as enhancers of peroxisome proliferation. Consequently, many studies in different fields have illustrated that PPARs are nuclear receptors that participate in nutrient and energy metabolism and regulate cellular and whole-body energy homeostasis during lipid and carbohydrate metabolism, cell growth, cancer development, and so on. With increasing challenges to human health, PPARs have attracted much attention for their ability to ameliorate metabolic syndromes. In our previous studies, we found that the complex functions of PPARs may be used as future targets in obesity and atherosclerosis treatments. Here, we review three types of PPARs that play overlapping but distinct roles in nutrient and energy metabolism during different metabolic states and in different organs. Furthermore, research has emerged showing that PPARs also play many other roles in inflammation, central nervous system-related diseases, and cancer. Increasingly, drug development has been based on the use of several selective PPARs as modulators to diminish the adverse effects of the PPAR agonists previously used in clinical practice. In conclusion, the complex roles of PPARs in metabolic networks keep these factors in the forefront of research because it is hoped that they will have potential therapeutic effects in future applications.

Pharmacological PPARβ/δ activation upregulates VLDLR in hepatocytes

The very low-density lipoprotein receptor (VLDLR) plays an important function in the control of serum triglycerides and in the development of non-alcoholic fatty liver disease (NAFLD). In this study, we investigated the role of peroxisome proliferator-activated receptor (PPAR)β/δ activation in hepatic VLDLR regulation. Treatment of mice fed a high-fat diet with the PPARβ/δ agonist GW501516 increased the hepatic expression of Vldlr. Similarly, exposure of human Huh-7 hepatocytes to GW501516 increased the expression of VLDLR and triglyceride accumulation, the latter being prevented by VLDLR knockdown. Finally, treatment with another PPARβ/δ agonist increased VLDLR levels in the liver of wild-type mice, but not PPARβ/δ-deficient mice, confirming the regulation of hepatic VLDLR by this nuclear receptor. Our results suggest that upregulation of hepatic VLDLR by PPARβ/δ agonists might contribute to the hypolipidemic effect of these drugs by increasing lipoprotein delivery to the liver. Overall, these findings provide new effects by which PPARβ/δ regulate VLDLR levels and may influence serum triglyceride levels and NAFLD development.

PPARδ: A Potential Therapeutic Target for the Treatment of Metabolic Hypertension

High blood pressure and its associated cardiovascular diseases have been major risks for public health. Multiple metabolic risk factors can cause the vascular dysfunction and vascular lesion, and the hypertension due to metabolic disturbances was defined as metabolic hypertension. The members of a subfamily of the nuclear receptors, peroxisome proliferator-activated receptors (PPARs), were found to be key regulators of metabolism and vascular function. We provide up-to-date knowledge on the role of subtype PPARδ in the regulation of metabolism and vascular function and the effect of its intervention on the metabolic hypertension management. We hope to give some insights into the development of more effective treatments of metabolic hypertension and its main complications.

Gymnemic acid alleviates inflammation and insulin resistance via PPARδ- and NFκB-mediated pathways in db/db mice

GA ameliorates obesity-induced inflammation and IR via PPARδ- and NFκB-mediated signaling in the liver, skeletal muscle and adipose tissue of db/db mice.

Identification and Molecular Characterization of Peroxisome Proliferator-Activated Receptor δ as a Novel Target for Covalent Modification by 15-Deoxy-Δ12,14-prostaglandin J2

PPARδ belongs to the peroxisome proliferator-activated receptor (PPAR) family of nuclear receptors. Upon activation by an agonist, PPARδ controls a variety of physiological processes via regulation of its target genes. 15-Deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) is a cyclopentenone prostaglandin that features an electrophilic, α,β-unsaturated ketone (an enone) in the cyclopentenone ring. Many of 15d-PGJ2's biological effects result from covalent interaction between C9 and the thiol group of a catalytic cysteine (Cys) in target proteins. In this study, we investigated whether 15d-PGJ2 activates PPARδ by forming a covalent adduct. Our data show that 15d-PGJ2 activates PPARδ's transcriptional activity through formation of a covalent adduct between its endocyclic enone at C9 and Cys249 in the receptor's ligand-binding domain. As expected, no adduct formation was seen following a Cys-to-Ser mutation at residue 249 (C249S) of PPARδ or with a PGD2/PGJ2 analogue that lacks the electrophilic C9. Furthermore, the PPARδ C249S mutation weakened induction of the receptor's DNA binding activity by 15d-PGJ2, which highlights the biological significance of our findings. Calculated chemical properties as well as data from molecular orbital calculations, reactive molecular dynamics simulations, and intrinsic reaction coordinate modeling also supported the selectivity of 15d-PGJ2's C9 toward PPARδ's Cys thiol. In summary, our results provide the molecular, chemical, and structural basis of 15d-PGJ2-mediated PPARδ activation, designating 15d-PGJ2 as the first covalent PPARδ ligand to be identified.

Crosstalk between MicroRNAs and Peroxisome Proliferator-Activated Receptors and Their Emerging Regulatory Roles in Cardiovascular Pathophysiology

Peroxisome proliferator-activated receptors (PPARs) play vital roles in cardiovascular pathophysiology, such as energy balance, cell proliferation/apoptosis, inflammatory response, and adipocyte differentiation. These vital roles make PPARs potential targets for therapeutic prevention of cardiovascular diseases (CVDs). Emerging evidence indicates that the crosstalk of microRNAs (miRNAs) and PPARs contributes greatly to CVD pathogenesis. PPARs are inhibited by miRNAs at posttranscriptional mechanisms in the progress of pulmonary hypertension and vascular dysfunction involving cell proliferation/apoptosis, communication, and normal function of endothelial cells and vascular smooth muscle cells. In the development of atherosclerosis and stroke, the activation of PPARs could change the transcripts of target miRNA through miRNA signalling. Furthermore, the mutual regulation of PPARs and miRNAs involves cell proliferation/apoptosis, cardiac remodeling, and dysfunction in heart diseases. In addition, obesity, an important cardiovascular risk, is modulated by the regulatory axis of PPARs/miRNAs, including adipogenesis, adipocyte dysfunction, insulin resistance, and macrophage polarization in adipose tissue. In this review, the crosstalk of PPARs and miRNAs and their emerging regulatory roles are summarized in the context of CVDs and risks. This provides an understanding of the underlying mechanism of the biological process related to CVD pathophysiology involving the interaction of PPARs and miRNAs and will lead to the development of PPARs/miRNAs as effective anti-CVD medications.

PPARδ, a Potential Therapeutic Target for Heart Disease

The nuclear receptor peroxisome proliferator-activated receptor δ (PPARδ) can transcriptionally regulate target genes. PPARδ exerts essential regulatory functions in the heart, which requires constant energy supply. PPARδ plays a key role in energy metabolism, controlling not only fatty acid (FA) and glucose oxidation, but also redox homeostasis, mitochondrial biogenesis, inflammation, and cardiomyocyte proliferation. PPARδ signaling is impaired in the heart under various pathological conditions, such as pathological cardiac hypertrophy, myocardial ischemia/reperfusion, doxorubicin cardiotoxicity and diabetic cardiomyopathy. PPARδ deficiency in the heart leads to cardiac dysfunction, myocardial lipid accumulation, cardiac hypertrophy/remodeling and heart failure. This article provides an up-today overview of this research area and discusses the role of PPARδ in the heart in light of the complex mechanisms of its transcriptional regulation and its potential as a translatable therapeutic target for the treatment of cardiac disorders.

The Opportunities and Challenges of Peroxisome Proliferator-Activated Receptors Ligands in Clinical Drug Discovery and Development

Peroxisome proliferator-activated receptors (PPARs) are a well-known pharmacological target for the treatment of multiple diseases, including diabetes mellitus, dyslipidemia, cardiovascular diseases and even primary biliary cholangitis, gout, cancer, Alzheimer's disease and ulcerative colitis. The three PPAR isoforms (α, β/δ and γ) have emerged as integrators of glucose and lipid metabolic signaling networks. Typically, PPARα is activated by fibrates, which are commonly used therapeutic agents in the treatment of dyslipidemia. The pharmacological activators of PPARγ include thiazolidinediones (TZDs), which are insulin sensitizers used in the treatment of type 2 diabetes mellitus (T2DM), despite some drawbacks. In this review, we summarize 84 types of PPAR synthetic ligands introduced to date for the treatment of metabolic and other diseases and provide a comprehensive analysis of the current applications and problems of these ligands in clinical drug discovery and development.

PPARβ/δ: A Key Therapeutic Target in Metabolic Disorders

Research in recent years on peroxisome proliferator-activated receptor (PPAR)β/δ indicates that it plays a key role in the maintenance of energy homeostasis, both at the cellular level and within the organism as a whole. PPARβ/δ activation might help prevent the development of metabolic disorders, including obesity, dyslipidaemia, type 2 diabetes mellitus and non-alcoholic fatty liver disease. This review highlights research findings on the PPARβ/δ regulation of energy metabolism and the development of diseases related to altered cellular and body metabolism. It also describes the potential of the pharmacological activation of PPARβ/δ as a treatment for human metabolic disorders.

Hepatic regulation of VLDL receptor by PPARβ/δ and FGF21 modulates non-alcoholic fatty liver disease

Objective

The very low-density lipoprotein receptor (VLDLR) plays an important role in the development of hepatic steatosis. In this study, we investigated the role of Peroxisome Proliferator-Activated Receptor (PPAR)β/δ and fibroblast growth factor 21 (FGF21) in hepatic VLDLR regulation.

Methods

Studies were conducted in wild-type and Pparβ/δ-null mice, primary mouse hepatocytes, human Huh-7 hepatocytes, and liver biopsies from control subjects and patients with moderate and severe hepatic steatosis.

Results

Increased VLDLR levels were observed in liver of Pparβ/δ-null mice and in Pparβ/δ-knocked down mouse primary hepatocytes through mechanisms involving the heme-regulated eukaryotic translation initiation factor 2α (eIF2α) kinase (HRI), activating transcription factor (ATF) 4 and the oxidative stress-induced nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathways. Moreover, by using a neutralizing antibody against FGF21, Fgf21-null mice and by treating mice with recombinant FGF21, we show that FGF21 may protect against hepatic steatosis by attenuating endoplasmic reticulum (ER) stress-induced VLDLR upregulation. Finally, in liver biopsies from patients with moderate and severe hepatic steatosis, we observed an increase in VLDLR levels that was accompanied by a reduction in PPARβ/δ mRNA abundance and DNA-binding activity compared with control subjects.

Conclusions

Overall, these findings provide new mechanisms by which PPARβ/δ and FGF21 regulate VLDLR levels and influence hepatic steatosis development.

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PPARβ/δ deficiency leads to increased levels of hepatic VLDLR levels.

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FGF21 protects against hepatic steatosis by attenuating ER stress-induced VLDLR upregulation.

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Human hepatic steatosis is accompanied by increased levels of VLDLR and reduced expression of PPARβ/δ.

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PPARβ/δ and FGF21 may influence NAFLD development by regulating VLDLR levels.

PPARβ/δ selectively regulates phenotypic features of age-related macular degeneration

Peroxisome proliferator-activated receptor-β/δ (PPARβ/δ) is a nuclear receptor that regulates differentiation, inflammation, lipid metabolism, extracellular matrix remodeling, and angiogenesis in multiple tissues. These pathways are also central to the pathogenesis of age-related macular degeneration (AMD), the leading cause of vision loss globally. With the goal of identifying signaling pathways that may be important in the development of AMD, we investigated the impact of PPARβ/δ activation on ocular tissues affected in the disease. PPARβ/δ is expressed and can be activated in AMD vulnerable cells, including retinal pigment epithelial (RPE) and choroidal endothelial cells. Further, PPARβ/δ knockdown modulates AMD-related pathways selectively. Specifically, genetic ablation of Pparβ/δ in aged mice resulted in exacerbation of several phenotypic features of early dry AMD, but attenuation of experimentally induced choroidal neovascular (CNV) lesions. Antagonizing PPARβ/δ in both in vitro angiogenesis assays and in the in vivo experimentally induced CNV model, inhibited angiogenesis and angiogenic pathways, while ligand activation of PPARβ/δ, in vitro, decreased RPE lipid accumulation, characteristic of dry AMD. This study demonstrates for the first time, selective regulation of a nuclear receptor in the eye and establishes that selective targeting of PPARβ/δ may be a suitable strategy for treatment of different clinical sub-types of AMD.

The Roles of SUMO in Metabolic Regulation

Protein modification with the small ubiquitin-related modifier (SUMO) can affect protein function, enzyme activity, protein-protein interactions, protein stability, protein targeting and cellular localization. SUMO influences the function and regulation of metabolic enzymes within pathways, and in some cases targets entire metabolic pathways by affecting the activity of transcription factors or by facilitating the translocation of entire metabolic pathways to subcellular compartments. SUMO modification is also a key component of nutrient- and metabolic-sensing mechanisms that regulate cellular metabolism. In addition to its established roles in maintaining metabolic homeostasis, there is increasing evidence that SUMO is a key factor in facilitating cellular stress responses through the regulation and/or adaptation of the most fundamental metabolic processes, including energy and nucleotide metabolism. This review focuses on the role of SUMO in cellular metabolism and metabolic disease.

Hypolipidemic effect of XH601 on hamsters of Hyperlipidemia and its potential mechanism

BACKGROUND

The novel compound XH601 is a synthesized derivative of formononetin. The present study was to investigate the hypolipidemia effect and potential mechanism of XH601.

METHODS

Male Golden Syrian hamsters were induced by high-fat diet (HFD) for eight weeks and the hyperlipidemic model was established successfully. After XH601 treatment, serum and hepatic biochemistry parameters of hamsters were detected and the effect of XH601 on adipose tissue was also analyzed. Furthermore, 3 T3-L1 cell differentiation by Oil-Red-O staining was observed and the mRNA and protein expression of peroxisome proliferator-activated receptors (PPARs) were measured by qRT-PCR and Western-blot in mature adipocytes.

RESULTS

The in vivo results suggest that XH601 significantly decreased the adipose weight and levels of serum triglyceride (TG), total cholesterol (TC), low-density lipoprotein (LDL-C), apolipoprotein B (Apo-B), apolipoprotein E (Apo-E), while increased serum high-density lipoprotein (HDL-C). The in vitro results implied that XH601 up-regulated the mRNA and protein expression of both PPARα and PPARβ/δ in a dose-dependent manner.

CONCLUSIONS

The study suggests that XH601 exhibited strong ability to improve the dyslipidemia in hamsters fed with high-fat diet. The potential mechanism of XH601 was associated with the up-regulation of PPARα and PPARβ/δ mRNA and protein expression.

PPARs: regulators of metabolism and as therapeutic targets in cardiovascular disease. Part II: PPAR-β/δ and PPAR-γ

The PPARs are a subfamily of three ligand-inducible transcription factors, which belong to the superfamily of nuclear hormone receptors. In mammals, the PPAR subfamily consists of three members: PPAR-α, PPAR-β/δ and PPAR-γ. PPARs control the expression of a large number of genes involved in metabolic homeostasis, lipid, glucose and energy metabolism, adipogenesis and inflammation. PPARs regulate a large number of metabolic pathways that are implicated in the pathogenesis of metabolic diseases such as metabolic syndrome, Type 2 diabetes mellitus, nonalcoholic fatty liver disease and cardiovascular disease. The aim of this review is to provide up-to-date information about the biochemical and metabolic actions of PPAR-β/δ and PPAR-γ, the therapeutic potential of their agonists currently under clinical development and the cardiovascular disease outcome of clinical trials of PPAR-γ agonists, pioglitazone and rosiglitazone.

Intestinal PPARδ protects against diet-induced obesity, insulin resistance and dyslipidemia

Peroxisome proliferator-activated receptor δ (PPARδ) is a ligand-activated transcription factor that has an important role in lipid metabolism. Activation of PPARδ stimulates fatty acid oxidation in adipose tissue and skeletal muscle and improves dyslipidemia in mice and humans. PPARδ is highly expressed in the intestinal tract but its physiological function in this organ is not known. Using mice with an intestinal epithelial cell-specific deletion of PPARδ, we show that intestinal PPARδ protects against diet-induced obesity, insulin resistance and dyslipidemia. Furthermore, absence of intestinal PPARδ abolished the ability of PPARδ agonist GW501516 to increase plasma levels of HDL-cholesterol. Together, our findings show that intestinal PPARδ is important in maintaining metabolic homeostasis and suggest that intestinal-specific activation of PPARδ could be a therapeutic approach for treatment of the metabolic syndrome and dyslipidemia, while avoiding systemic toxicity.

Activation of Peroxisome Proliferator Activator Receptor β/δ Improves Endothelial Dysfunction and Protects Kidney in Murine Lupus

Women with systemic lupus erythematosus exhibit a high prevalence of hypertension, endothelial dysfunction, and renal injury. We tested whether GW0742, a peroxisome proliferator activator receptor β/δ (PPARβ/δ) agonist, ameliorates disease activity and cardiovascular complications in a female mouse model of lupus. Thirty-week-old NZBWF1 (lupus) and NZW/LacJ (control) mice were treated with GW0742 or with the PPARβ/δ antagonist GSK0660 plus GW0742 for 5 weeks. Blood pressure, plasma double-stranded DNA autoantibodies and cytokines, nephritis, hepatic opsonins, spleen lymphocyte populations, endothelial function, and vascular oxidative stress were compared in treated and untreated mice. GW0742 treatment reduced lupus disease activity, blood pressure, cardiac and renal hypertrophy, splenomegaly, albuminuria, and renal injury in lupus mice, but not in control. GW0742 increased hepatic opsonins mRNA levels in lupus mice and reduced the elevated T, B, Treg, and Th1 cells in spleens from lupus mice. GW0742 lowered the higher plasma concentration of proinflammatory cytokines observed in lupus mice. Aortae from lupus mice showed reduced endothelium-dependent vasodilator responses to acetylcholine and increased nicotinamide adenine dinucleotide phosphate oxidase-driven vascular reactive oxygen species production, which were normalized by GW0742 treatment. All these effects of GW0742 were inhibited by PPARβ/δ blockade with GSK0660. Pharmacological activation of PPARβ/δ reduced hypertension, endothelial dysfunction, and organ damage in severe lupus mice, which was associated with reduced plasma antidouble-stranded DNA autoantibodies and anti-inflammatory and antioxidant effects in target tissues. Our findings identify PPARβ/δ as a promising target for an alternative approach in the treatment of systemic lupus erythematosus and its associated vascular damage.