PPARalpha: energy combustion, hypolipidemia, inflammation and cancer

Involvement of per- and polyfluoroalkyl compounds in tumor development

Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic persistent chemicals, which are used in many industrial and commercial applications. Hundreds of different PFAS have been identified in the environment and they are commonly found also in human blood. Due to the chemical stability and extensive use, PFAS pose a risk for human health and wildlife. Mounting evidence indicates that PFAS-exposure adversely affects many organs including liver, kidney, and reproductive tissues and induces tumors in laboratory rodents. Epidemiological studies show association between PFAS-exposure and some tumors also in humans. Effects of PFAS-exposure are complex and obviously do not depend only on the concentration and the structure of PFAS, but also on age and sex of the exposed individuals. It has been difficult to show a causal link between PFAS-exposure and tumors. Moreover, molecular mechanisms of the PFAS effects in different tissues are poorly understood. PFAS are not directly mutagenic and they do not induce formation of DNA binding metabolites, and thus are assumed to act more through non-genotoxic mechanisms. In this review, we discuss the involvement of PFAS-compounds in tumor development in tissues where PFAS exposure has been associated with cancer in epidemiological and animal studies (liver, kidney, testicle and breast). We will focus on molecular pathways and mechanisms related to tumor formation following PFAS-exposure.

Examining the Pathogenesis of MAFLD and the Medicinal Properties of Natural Products from a Metabolic Perspective

Metabolic-associated fatty liver disease (MAFLD), characterized primarily by hepatic steatosis, has become the most prevalent liver disease worldwide, affecting approximately two-fifths of the global population. The pathogenesis of MAFLD is extremely complex, and to date, there are no approved therapeutic drugs for clinical use. Considerable evidence indicates that various metabolic disorders play a pivotal role in the progression of MAFLD, including lipids, carbohydrates, amino acids, and micronutrients. In recent years, the medicinal properties of natural products have attracted widespread attention, and numerous studies have reported their efficacy in ameliorating metabolic disorders and subsequently alleviating MAFLD. This review aims to summarize the metabolic-associated pathological mechanisms of MAFLD, as well as the natural products that regulate metabolic pathways to alleviate MAFLD.

Identification and analysis of prognostic metabolic characteristics in colon adenocarcinoma

Colon adenocarcinoma (COAD) is a highly lethal gastrointestinal malignancy. The five-year survival rate of metastatic colorectal cancer remains low, at 14 percent. Numerous publications have suggested a role for peroxisome proliferator-activated receptors (PPARs) in malignancy. Recent studies have shown that PPARs, as nuclear transcription factors, may serve as potential targets for the treatment of metabolic syndrome tumors and their associated complications. However, the molecular mechanism has not been thoroughly investigated. Hence, in order to enhance the prediction of personalized medicine for PPAR-associated modulators in malignancy treatment, a timely review becomes essential. Utilizing TCGA-COAD expression profile data and patient overall survival (OS) information, this study systematically conducted investigations to identify and develop Hub stem cell-related diagnostic and prognostic identification models, aiming to enhance the multi-gene markers for COAD. Utilizing the differential expression profiles of stem cell-related genes, an 11-gene (SLC27A4, CPT1C, CPT1B, CPT2, CYP4A11, FABP3, FABP7, AQP7, MMP1, ACOX1, ANGPTL4) diagnostic and prognostic model was developed. This model demonstrated precise diagnostic and prognostic capabilities and holds the potential to characterize the clinicopathologic features of COAD. Univariate and multivariate Cox proportional hazards regression analyses were conducted to ascertain the independent factors influencing OS outcomes in COAD. The results revealed that CPT1B, SLC27A4, and FABP3 were identified as independent risk prognostic factors for OS in COAD, whereas ACOX1 and CPT2 served as independent protective prognostic factors. The hub genes associated with PPARs were identified through the differential expression of contrast agent COAD and normal tissues. Finally, the investigation of variations in immune infiltration and the analysis of relevant biological pathways validate the prognostic significance of the independent post-factors within this molecular model. This research aims to provide references for comprehending the mechanism of post-transcriptional regulation of COAD and molecular therapy.

Gentiopicroside improves non-alcoholic steatohepatitis by activating PPARα and suppressing HIF1

Gentiopicroside (GPS) is a highly water-soluble small-molecule drug and the main bioactive secoiridoid glycoside of Gentiana scabra that has been shown to have hepatoprotective effects against non-alcoholic steatohepatitis (NASH), a form of non-alcoholic fatty liver disease (NAFLD) that can progress to cirrhosis and hepatocellular carcinoma. However, the effects of GPS on NASH and the underlying mechanisms remain obscure. Firstly, a high-fat, high-cholesterol (HFHC) diet and a high-sugar solution containing d-fructose and d-glucose were used to establish a non-alcoholic steatohepatitis (NASH) mice model. Secondly, we confirmed GPS supplementation improve metabolic abnormalities and reduce inflammation in NASH mice induced by HFHC and high-sugar solution. Then we used metabolomics to investigate the mechanisms of GPS in NASH mice. Metabolomics analysis showed GPS may work through the Peroxisome Proliferator-Activated Receptor (PPAR) signaling pathway and glycine, serine, and threonine metabolism. Functional metabolites restored by GPS included serine, glycine, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Western blot and qRT-PCR analysis confirmed GPS improve NASH by regulating PPARα and Hypoxia-Inducible Factor-1α (HIF-1α) signaling pathways. In vitro, studies further demonstrated EPA and DHA enhance fatty acid oxidation through the PPARα pathway, while serine and glycine inhibit oxidative stress through the HIF-1α pathway in palmitic acid-stimulated HepG2 cells. Our results suggest GPS's anti-inflammatory and anti-steatosis effects in NASH progression are related to the suppression of HIF-1α through the restoration of L-serine and glycine and the activation of PPARα through increased EPA and DHA.

An insight to treat cardiovascular diseases through phytochemicals targeting PPAR-α

Peroxisome proliferator-activated receptor-α (PPAR-α) belonging to the nuclear hormone receptor superfamily is a promising target for CVDs which mechanistically improves the production of high-density lipid as well as inhibit vascular smooth muscle cell proliferation. PPAR-α mainly interferes with adenosine monophosphate-activated protein kinase, transforming growth factor-β-activated kinase, and nuclear factor-κB pathways to protect against cardiac complications. Natural products/extracts could serve as a potential therapeutic strategy in CVDs for targeting PPAR-α with broad safety margins. In recent years, the understanding of naturally derived PPAR-α agonists has considerably improved; however, the information is scattered. In vitro and in vivo studies on acacetin, apigenin, arjunolic acid, astaxanthin, berberine, resveratrol, vaticanol C, hispidulin, ginsenoside Rb3, and genistein showed significant effects in CVDs complications by targeting PPAR-α. With the aim of demonstrating the tremendous chemical variety of natural products targeting PPAR-α in CVDs, this review provides insight into various natural products that can work to prevent CVDs by targeting the PPAR-α receptor along with their detailed mechanism.

Recent advances in age-related metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) affects approximately 25% of the world's population and has become a leading cause of chronic liver disease. In recent years, an increasing amount of data suggests that MASLD is associated with aging. As the population ages, age-related MASLD will become a major global health problem. Targeting an aging will become a new approach to the treatment of MASLD. This paper reviews the current studies on the role of aging-related factors and therapeutic targets in MASLD, including: Oxidative stress, autophagy, mitochondrial homeostasis, bile acid metabolism homeostasis, and dysbiosis. The aim is to identify effective therapeutic targets for age-related MASLD and its progression.

Lipid Metabolism as a Potential Target of Liver Cancer

Hepatocellular carcinoma (HCC) stands as a severe malignant tumor with a profound impact on overall health, often accompanied by an unfavorable prognosis. Despite some advancements in the diagnosis and treatment of this disease, improving the prognosis of HCC remains a formidable challenge. It is noteworthy that lipid metabolism plays a pivotal role in the onset, development, and progression of tumor cells. Existing research indicates the potential application of targeting lipid metabolism in the treatment of HCC. This review aims to thoroughly explore the alterations in lipid metabolism in HCC, offering a detailed account of the potential advantages associated with innovative therapeutic strategies targeting lipid metabolism. Targeting lipid metabolism holds promise for potentially enhancing the prognosis of HCC.

Effects of an in vitro vitamin D treatment on the inflammatory responses in visceral adipose tissue from Ldlr-/- mice

BACKGROUND/OBJECTIVES

Atherosclerosis is associated with increased inflammation in the visceral adipose tissue (VAT). Vitamin D has been reported to modulate the inflammatory responses of stromal vascular cells (SVCs) and adipocytes in adipose tissue, but the role of vitamin D in atherosclerosis biology is unclear. This study examined the effects of in vitro 1,25-dihydroxyvitamin D3 (1,25[OH]2D3) treatment on the inflammatory responses of SVCs and adipocytes from atherosclerotic mice.

MATERIALS/METHODS

C57BL/6J (B6) mice were divided randomly into 2 groups and fed a 10% kcal fat control diet (control group, CON) or 41% kcal fat, 0.21% cholesterol (high fat + cholesterol, HFC) diet (obese group, OB), and B6.129S7-Ldlrtm1Her/J (Ldlr-/-) mice were fed a HFC diet (obese with atherosclerosis group, OBA) for 16 weeks. SVCs and adipocytes isolated from VAT were pre-incubated with 1,25(OH)2D3 for 24 h and stimulated with lipopolysaccarides for the next 24 h. Proinflammatory cytokine production by adipocytes and SVCs, the immune cell population in SVCs, and the expression of the genes involved in the inflammatory signaling pathway in SVCs were determined.

RESULTS

The numbers of total macrophages and SVCs per mouse were higher in OB and OBA groups than the CON group. The in vitro 1,25(OH)2D3 treatment significantly reduced macrophages/SVCs (%) in the OBA group. Consistent with this change, the production of interleukin-6 and monocyte chemoattractant protein 1 (MCP-1) by SVCs from the OBA group was decreased by 1,25(OH)2D3 treatment. The 1,25(OH)2D3 treatment significantly reduced the toll-like receptor 4 and dual-specificity protein phosphatase 1 (also known as mitogen-activated protein kinase phosphatase 1) mRNA levels in SVCs and MCP-1 production by adipocytes from all 3 groups.

CONCLUSIONS

These findings suggest that vitamin D can attribute to the inhibition of the inflammatory response in VAT from atherosclerotic mice by reducing proinflammatory cytokine production.

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.

Rescuing SERCA2 pump deficiency improves bone mechano-responsiveness in type 2 diabetes by shaping osteocyte calcium dynamics

Type 2 diabetes (T2D)-related fragility fractures represent an increasingly tough medical challenge, and the current treatment options are limited. Mechanical loading is essential for maintaining bone integrity, although bone mechano-responsiveness in T2D remains poorly characterized. Herein, we report that exogenous cyclic loading-induced improvements in bone architecture and strength are compromised in both genetically spontaneous and experimentally-induced T2D mice. T2D-induced reduction in bone mechano-responsiveness is directly associated with the weakened Ca2+ oscillatory dynamics of osteocytes, although not those of osteoblasts, which is dependent on PPARα-mediated specific reduction in osteocytic SERCA2 pump expression. Treatment with the SERCA2 agonist istaroxime was demonstrated to improve T2D bone mechano-responsiveness by rescuing osteocyte Ca2+ dynamics and the associated regulation of osteoblasts and osteoclasts. Moreover, T2D-induced deterioration of bone mechano-responsiveness is blunted in mice with osteocytic SERCA2 overexpression. Collectively, our study provides mechanistic insights into T2D-mediated deterioration of bone mechano-responsiveness and identifies a promising countermeasure against T2D-associated fragility fractures.

Mechanisms of weight-loss effect in obese mice by the endogenous cannabinoid receptor 2 agonist beta-caryophyllene

BACKGROUND AND AIMS

The endogenous cannabinoid system (ECS) is involved in the regulation of a variety of physiological activities in the body, such as metabolism and energy uptake, and cannabinoid receptor 2 (CNR2) is one of these receptors that is predominantly distributed in the periphery. β-caryophyllene (BCP) is an agonist of CNR2 which is known to possess pharmacological activities such as anti-inflammatory and antioxidant properties. In this study, we wanted to investigate whether BCP possesses pharmacological effects on obese mice and its mechanism.

METHODS

Reversed feeding rhythm, propylthiouracil was delivered intraperitoneally, and BCP was gavaged once daily for four weeks to establish a hyperlipidemic obese mouse model. A glucose tolerance test, lipid level measurements, liver, peritoneal, and subcutaneous fat removal, HE and Oil Red O staining of the liver, and immunohistochemistry (IHC) staining with an anti-CNR2 antibody were all carried out. The liver was examined using tools like GO and KEGG databases for differentially expressed genes and signaling pathways linked to medication effectiveness.

RESULTS

BCP had significant effects on weight reduction and improvement of dyslipidemia. What's more, it significantly reduced body fat percentage, improved steatosis and ballooning of liver cells, and reduced fat accumulation, while inhibiting the proliferation of peri-abdominal adipocytes. BCP exerted its effects to improve dyslipidemia and reduce body weight probably through circadian regulation and cholesterol metabolic pathways. Finally, and its efficacy in improving dyslipidemia and reducing body weight may be mainly through activating CNR2, activating SIRT1/PGC-1α/PPARγ and SIRT1/AMPK pathways.

CONCLUSION

BCP activates the CNR2, SIRT1/PGC-1α/PPARγ signaling pathway, and SIRT1/AMPK signaling pathway to exert dyslipidemia-improving and weight-loss effects.

Effects of Human Milk Fat Substitutes on Lipid Metabolism in First-Weaned Rats

Although numerous studies indicate that formula-fed infants are more prone to obesity than breastfed ones, the underlying reasons have not been fully elucidated. This study aimed to determine the impact of human milk fat substitutes (HMFS) on the lipid metabolism of first-weaned Sprague Dawley rats. The findings revealed that administering HMFS did not affect the body weight of the rats (control: 298.38 ± 26.73 g, OPO (1,3-dioleic acid-2-palmitoyl triglyceride): 287.82 ± 19.85 g and HMFS: 302.31 ± 19.21 g), but it significantly decreased their body fat content (control: 28.70 ± 1.17 cm3, OPO: 22.51 ± 1.10 cm3 and HMFS: 14.90 ± 0.95 cm3) (p < 0.05). Lipidome analysis revealed that glycerophospholipid was the primary differentiating lipid present in the liver of HMFS-fed rats. The abundance of Bacteroides significantly increased in the intestine of HMFS-fed rats (p < 0.05), and their short-chain fatty acid (SCFA) content significantly increased (p < 0.05). The multi-omics correlation analysis established the "Bacteroidetes-SCFAs-Glycerophospholipid pathway" as a potential mechanism by which administering HMFS affects body fat buildup in first-weaned rats. Additionally, it was found that HMFS administration significantly promoted lipid metabolism in the rat liver at both the gene and protein levels (p < 0.05). These findings serve to underscore the nutritional benefits of HMFS for infants.

Dietary n-3/n-6 polyunsaturated fatty acid ratio modulates growth performance in spotted seabass (Lateolabrax maculatus) through regulating lipid metabolism, hepatic antioxidant capacity and intestinal health

An 8-week feeding experiment was carried out to explore the effects of dietary n-3/n-6 polyunsaturated fatty acid (PUFA) ratio on growth performance, lipid metabolism, hepatic antioxidant status, and gut flora of spotted seabass (Lateolabrax maculatus). Six experimental diets were formulated to contain different levels of two purified oil sources including docosahexaenoic and eicosapentaenoic acids enriched oil (n-3) and linoleic acid-enriched oil (n-6) leading to n-3/n-6 PUFA ratios of 0.04, 0.35, 0.66, 1.35, 2.45 and 16.17. Each diet was fed to triplicate groups of juvenile L. maculatus (11.06 ± 0.20 g, 30 fish/tank). Final body weight (FBW), weight gain (WG), specific growth rates (SGR), protein efficiency ratio (PER) and feed utilization efficiency increased as n-3/n-6 PUFA ratio increased up to a certain level, and then decreased thereafter. Fish fed the diet with n-3/n-6 PUFA ratio of 0.66 exhibited the highest FBW, WG, SGR and PER and the lowest feed conversion ratio. Lower n-3/n-6 PUFA ratios induced up-regulated expression of lipid synthesis-related genes (fas, acc2 and srebp-1c) and down-regulated expression of lipolysis related genes (atgl, pparα, cpt-1 and aox). Higher expression of lipolysis-related genes (atgl, pparα and cpt-1) was recorded at moderate n-3/n-6 PUFA ratios (0.66 to 1.35). Moreover, inappropriate n-3/n-6 PUFA ratios triggered up-regulation of pro-inflammatory genes (il-6 and tnf-α) and down-regulation of anti-inflammatory genes (il-4 and il-10) in the intestine. The diet with n-3/n-6 PUFA ratio of 0.66 inhibited intestine inflammation, improved intestinal flora richness, increased the abundance of beneficial bacteria such as Lactobacillus, Alloprevotella and Ruminococcus, and reduced the abundance of harmful bacteria including Escherichia-Shigella and Enterococcus. In summary, it could be suggested that a dietary n-3/n-6 PUFA ratio of 0.66 can improve growth performance and feed utilization in L. maculatus, as is deemed to be mediated through regulation of lipid metabolism and intestinal flora.

Polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, pesticides, and diabetes in the Anniston Community Health Survey follow-up (ACHS II): single exposure and mixture analysis approaches

Dioxins and dioxin-like compounds measurements were added to polychlorinated biphenyls (PCBs) and organochlorine pesticides to expand the exposure profile in a follow-up to the Anniston Community Health Survey (ACHS II, 2014) and to study diabetes associations. Participants of ACHS I (2005-2007) still living within the study area were eligible to participate in ACHS II. Diabetes status (type-2) was determined by a doctor's diagnosis, fasting glucose ≥125 mg/dL, or being on any glycemic control medication. Incident diabetes cases were identified in ACHS II among those who did not have diabetes in ACHS I, using the same criteria. Thirty-five ortho-substituted PCBs, 6 pesticides, 7 polychlorinated dibenzo-p-dioxins (PCDD), 10 furans (PCDF), and 3 non-ortho PCBs were measured in 338 ACHS II participants. Dioxin toxic equivalents (TEQs) were calculated for all dioxin-like compounds. Main analyses used logistic regression models to calculate odds ratios (OR) and 95 % confidence intervals (CI). In models adjusted for age, race, sex, BMI, total lipids, family history of diabetes, and taking lipid lowering medication, the highest ORs for diabetes were observed for PCDD TEQ: 3.61 (95 % CI: 1.04, 12.46), dichloro-diphenyl dichloroethylene (p,p'-DDE): 2.07 (95 % CI 1.08, 3.97), and trans-Nonachlor: 2.55 (95 % CI 0.93, 7.02). The OR for sum 35 PCBs was 1.22 (95 % CI: 0.58-2.57). To complement the main analyses, we used BKMR and g-computation models to evaluate 12 mixture components including 4 TEQs, 2 PCB subsets and 6 pesticides; suggestive positive associations for the joint effect of the mixture analyses resulted in ORs of 1.40 (95% CI: -1.13, 3.93) for BKMR and 1.32 (95% CI: -1.12, 3.76) for g-computation. The mixture analyses provide further support to previously observed associations of trans-Nonachlor, p,p'- DDE, PCDD TEQ and some PCB groups with diabetes.

Emodin attenuates high lipid-induced liver metastasis through the AKT and ERK pathways in vitro in breast cancer cells and in a mouse xenograft model

Emodin, a natural anthraquinone derivative, can inhibit lipid synthesis and breast cancer cell proliferation. We previously found that emodin decreased breast cancer liver metastasis via epithelial-to-mesenchymal transition (EMT) inhibition. However, the mechanism through which emodin affects breast cancer liver metastasis in high-fat diet-induced obese and hyperlipidemic mice has not been elucidated. Bioinformatics analysis was used to reveal the potential targets and pathways of emodin. The mouse model of liver metastasis was established by injecting breast cancer cells into the left ventricle in high-fat diet-induced obese mice. The effect of emodin on inhibiting liver metastasis of breast cancer was evaluated by animal experiments. The mechanisms through which emodin inhibits liver metastasis of breast cancer were studied by cell and molecular biological methods. Emodin reduced lipid synthesis by inhibiting the expression of triglyceride (TG) synthesis-related genes, such as fatty acid synthase (Fasn), glycerol-3-phosphate acyltransferase 1 (Gpat1), and stearoyl-CoA desaturase (Scd1), and ultimately reduced liver metastasis in breast cancer. In addition, emodin inhibited breast cancer cell proliferation and invasion through the serine/threonine kinase (AKT) signaling and extracellular-regulated protein kinase (ERK) pathways by interacting with CSNK2A1, ESR1, ESR2, PIM1 and PTP4A3. Our results indicate that emodin may have therapeutic potential in the prevention or treatment of breast cancer liver metastasis.

Roles of the peroxisome proliferator-activated receptors (PPARs) in the pathogenesis of nonalcoholic fatty liver disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of disease phenotypes which start with simple steatosis and lipid accumulation in the hepatocytes - a typical histological lesions characteristic. It may progress to non-alcoholic steatohepatitis (NASH) that is characterized by hepatic inflammation and/or fibrosis and subsequent onset of NAFLD-related cirrhosis and hepatocellular carcinoma (HCC). Due to the central role of the liver in metabolism, NAFLD is regarded as a result of and contribution to the metabolic abnormalities seen in the metabolic syndrome. Peroxisome proliferator-activated receptors (PPARs) has three subtypes, which govern the expression of genes responsible for energy metabolism, cellular development, inflammation, and differentiation. The agonists of PPARα, such as fenofibrate and clofibrate, have been used as lipid-lowering drugs in clinical practice. Thiazolidinediones (TZDs) - ligands of PPARγ, such as rosiglitazone and pioglitazone, are also used in the treatment of type 2 diabetes (T2D) with insulin resistance (IR). Increasing evidence suggests that PPARβ/δ agonists have potential therapeutic effects in improving insulin sensitivity and lipid metabolism disorders. In addition, PPARs ligands have been considered as potential therapeutic drugs for hypertension, atherosclerosis (AS) or diabetic nephropathy. Their crucial biological roles dictate the significance of PPARs-targeting in medical research and drug discovery. Here, it reviews the biological activities, ligand selectivity and biological functions of the PPARs family, and discusses the relationship between PPARs and the pathogenesis of NAFLD and metabolic syndrome. This will open new possibilities for PPARs application in medicine, and provide a new idea for the treatment of fatty liver and related diseases.

Fibrates Affect Levels of Phosphorylated p38 in Intestinal Cells in a Differentiation-Dependent Manner

Fibrates are widely used hypolipidaemic agents that act as ligands of the peroxisome proliferator-activated receptor α (PPARα). p38 is a protein kinase that is mainly activated by environmental and genotoxic stress. We investigated the effect of the PPARα activators fenofibrate and WY-14643 and the PPARα inhibitor GW6471 on the levels of activated p38 (p-p38) in the colorectal cancer cell lines HT-29 and Caco2 in relation to their differentiation status. Fibrates increased p-p38 in undifferentiated HT-29 cells, whereas in other cases p-p38 expression was decreased. HT-29 cells showed p-p38 predominantly in the cytoplasm, whereas Caco2 cells showed higher nuclear positivity. The effect of fibrates may depend on the differentiation status of the cell, as differentiated HT-29 and undifferentiated Caco2 cells share similar characteristics in terms of villin, CYP2J2, and soluble epoxide hydrolase (sEH) expression. In human colorectal carcinoma, higher levels of p-p38 were detected in the cytoplasm, whereas in normal colonic surface epithelium, p-p38 showed nuclear positivity. The decrease in p-p38 positivity was associated with a decrease in sEH, consistent with in vitro results. In conclusion, fibrates affect the level of p-p38, but its exact role in the process of carcinogenesis remains unclear and further research is needed in this area.

Epigenetic Mechanisms of Aging and Aging-Associated Diseases

Aging is an inevitable outcome of life, characterized by a progressive decline in tissue and organ function. At a molecular level, it is marked by the gradual alterations of biomolecules. Indeed, important changes are observed on the DNA, as well as at a protein level, that are influenced by both genetic and environmental parameters. These molecular changes directly contribute to the development or progression of several human pathologies, including cancer, diabetes, osteoporosis, neurodegenerative disorders and others aging-related diseases. Additionally, they increase the risk of mortality. Therefore, deciphering the hallmarks of aging represents a possibility for identifying potential druggable targets to attenuate the aging process, and then the age-related comorbidities. Given the link between aging, genetic, and epigenetic alterations, and given the reversible nature of epigenetic mechanisms, the precisely understanding of these factors may provide a potential therapeutic approach for age-related decline and disease. In this review, we center on epigenetic regulatory mechanisms and their aging-associated changes, highlighting their inferences in age-associated diseases.

C Allele of the PPARδ+294T>C Polymorphism Confers a Higher Risk of Hypercholesterolemia, but not Obesity and Insulin Resistance: A Systematic Review and Meta-Analysis

The relationships of the PPARα Leu162Val and PPARδ+294 T>C polymorphisms with metabolic indexes have been reported to be inconsistent and even contradictory. The meta-analysis was conducted to clarify the relationships between the two variants and the indexes of obesity, insulin resistance, and blood lipids. PubMed, Google Scholar, Embase, and Cochrane Library were searched for eligible studies. Standardized mean difference with 95% confidence interval was calculated to estimate the differences in the metabolic indexes between the genotypes of the Leu162Val and+294 T>C polymorphisms. Heterogeneity among studies was assessed by Cochran's x2-based Q-statistic test. Publication bias was identified by using Begg's test. Forty-one studies (44 585 subjects) and 33 studies (23 018 subjects) were identified in the analyses for the Leu162Val and+294 T>C polymorphisms, respectively. C allele carriers of the+294 T>C polymorphism had significantly higher levels of total cholesterol and low-density lipoprotein cholesterol than TT homozygotes in the whole population. Notably, C allele carriers of the+294 T>C polymorphism had significantly higher levels of triglycerides and total cholesterol in East Asians, but lower levels of triglycerides in West Asians than TT homozygotes. Regarding the Leu162Val polymorphism, it was found that Val allele carriers had significantly higher levels of blood glucose than Leu/Leu homozygotes only in European Caucasians. The meta-analysis demonstrates that C allele of the+294 T>C polymorphism in PPARδ gene confers a higher risk of hypercholesterolemia, which may partly explain the relationship between this variant and coronary artery disease.

Peroxisome Proliferator-Activated Receptor α and γ Gene Polymorphisms among South Indian Patients with Diabetic Dyslipidaemia

Background

Peroxisome proliferator-activated receptors (PPAR) α and γ genes play an important role in dyslipidaemia of T2DM.

Aims

To estimate the frequency distribution of PPAR α and γ gene polymorphisms in South Indian T2DM patients with dyslipidaemia compared to healthy controls. Normative frequencies of SNPs were established and compared with data for 1000 genome populations.

Methods

Eligible 382 cases and 336 age and sex-matched controls were enrolled. Six SNPs in PPARα [rs1800206 C>G (Leu162Val), rs4253778 G>C, rs135542 T>C] and PPARγ [rs3856806 (C>T), rs10865710 (C>G), rs1805192 C>G (Pro12Ala)] genes were selected for genotyping.

Results

The allele and gene frequencies did not significantly differ between the diabetic dyslipidaemia cases and healthy controls. However, they were significantly different from that of 1000 genome populations except for rs1800206 C>G (Leu162Val) and rs1805192 C>G (Pro12Ala).

Conclusion

The studied polymorphisms in PPARα and PPARγ genes are not associated with diabetic dyslipidaemia among South Indian patients.

Ketogenic Diet Combined with Moderate Aerobic Exercise Training Ameliorates White Adipose Tissue Mass, Serum Biomarkers, and Hepatic Lipid Metabolism in High-Fat Diet-Induced Obese Mice

Obesity is a serious public health issue worldwide. Growing evidence demonstrates the efficacy of the ketogenic diet (KD) for weight loss, but there may be some adverse side effects such as dyslipidemia and hepatic steatosis. Aerobic exercise is a widely recognized approach for improving these metabolic markers. Here we explored the combined impacts of KD and moderate aerobic exercise for an 8-week intervention on body weight and fat loss, serum biomarkers, and hepatic lipid metabolism in a mouse model of high-fat diet-induced obesity. Both KD and KD combined with exercise significantly reduced body weight and fat mass. No significant adverse effects of KD were observed in serum biomarkers or hepatic lipid storage, except for an increase in circulating triglyceride level. However, aerobic exercise lowered serum triglyceride levels, and further ameliorated serum parameters, and hepatic steatosis in KD-fed mice. Moreover, gene and protein expression analysis indicated that KD combined with exercise was associated with increased expression of lipolysis-related genes and protein levels, and reduced expression of lipogenic genes relative to KD without exercise. Overall, our findings for mice indicate that further work on humans might reveal that KD combined with moderate aerobic exercise could be a promising therapeutic strategy for obesity.

The Role of PPARs in Breast Cancer

Breast cancer is a malignant tumor with high morbidity and lethality. Its pathogenesis is related to the abnormal expression of many genes. The peroxisome proliferator-activated receptors (PPARs) are a class of ligand-dependent transcription factors in the nuclear receptor superfamily. They can regulate the transcription of a large number of target genes, which are involved in life activities such as cell proliferation, differentiation, metabolism, and apoptosis, and regulate physiological processes such as glucose metabolism, lipid metabolism, inflammation, and wound healing. Further, the changes in its expression are associated with various diseases, including breast cancer. The experimental reports related to "PPAR" and "breast cancer" were retrieved from PubMed since the discovery of PPARs and summarized in this paper. This review (1) analyzed the roles and potential molecular mechanisms of non-coordinated and ligand-activated subtypes of PPARs in breast cancer progression; (2) discussed the correlations between PPARs and estrogen receptors (ERs) as the nuclear receptor superfamily; and (3) investigated the interaction between PPARs and key regulators in several signaling pathways. As a result, this paper identifies PPARs as targets for breast cancer prevention and treatment in order to provide more evidence for the synthesis of new drugs targeting PPARs or the search for new drug combination treatments.

Therapeutic potential of paeoniflorin in atherosclerosis: A cellular action and mechanism-based perspective

Epidemiological studies have shown that the incidence, prevalence and mortality of atherosclerotic cardiovascular disease (ASCVD) are increasing globally. Atherosclerosis is characterized as a chronic inflammatory disease which involves inflammation and immune dysfunction. P. lactiflora Pall. is a plant origin traditional medicine that has been widely used for the treatment of various diseases for more than a millennium in China, Japan and Korean. Paeoniflorin is a bioactive monomer extracted from P. lactiflora Pall. with anti-atherosclerosis effects. In this article, we comprehensively reviewed the potential therapeutic effects and molecular mechanism whereby paeoniflorin protects against atherosclerosis from the unique angle of inflammation and immune-related pathway dysfunction in vascular endothelial cells, smooth muscle cells, monocytes, macrophages, platelets and mast cells. Paeoniflorin, with multiple protective effects in atherosclerosis, has the potential to be used as a promising therapeutic agent for the treatment of atherosclerosis and its complications. We conclude with a detailed discussion of the challenges and future perspective of paeoniflorin in translational cardiovascular medicine.

Non-Alcoholic Fatty Liver Disease (NAFLD) Pathogenesis and Natural Products for Prevention and Treatment

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease, affecting approximately one-quarter of the global population, and has become a world public health issue. NAFLD is a clinicopathological syndrome characterized by hepatic steatosis, excluding ethanol and other definite liver damage factors. Recent studies have shown that the development of NAFLD is associated with lipid accumulation, oxidative stress, endoplasmic reticulum stress, and lipotoxicity. A range of natural products have been reported as regulators of NAFLD in vivo and in vitro. This paper reviews the pathogenesis of NAFLD and some natural products that have been shown to have therapeutic effects on NAFLD. Our work shows that natural products can be a potential therapeutic option for NAFLD.

First Evidence of Anti-Steatotic Action of Macrotympanain A1, an Amphibian Skin Peptide from Odorrana macrotympana

Many different amphibian skin peptides have been characterized and proven to exert various biological actions, such as wound-healing, immunomodulatory, anti-oxidant, anti-inflammatory and anti-diabetic effects. In this work, the possible anti-steatotic effect of macrotympanain A1 (MA1) (FLPGLECVW), a skin peptide isolated from the Chinese odorous frog Odorrana macrotympana, was investigated. We used a well-established in vitro model of hepatic steatosis, consisting of lipid-loaded rat hepatoma FaO cells. In this model, a 24 h treatment with 10 µg/mL MA1 exerted a significant anti-steatotic action, being able to reduce intracellular triglyceride content. Accordingly, the number and diameter of cytosolic lipid droplets (LDs) were reduced by peptide treatment. The expression of key genes of hepatic lipid metabolism, such as PPARs and PLINs, was measured by real-time qPCR. MA1 counteracted the fatty acid-induced upregulation of PPARγ expression and increased PLIN3 expression, suggesting a role in promoting lipophagy. The present data demonstrate for the first time a direct anti-steatotic effect of a peptide from amphibian skin secretion and pave the way to further studies on the use of amphibian peptides for beneficial actions against metabolic diseases.

Demystifying the Functional Role of Nuclear Receptors in Esophageal Cancer

Esophageal cancer (EC), an aggressive and poorly understood disease, is one of the top causes of cancer-related fatalities. GLOBOCAN 2020 reports that there are 544,076 deaths and 604,100 new cases expected worldwide. Even though there are various advancements in treatment procedures, this cancer has been reported as one of the most difficult cancers to cure, and to increase patient survival; treatment targets still need to be established. Nuclear receptors (NRs) are a type of transcription factor, which has a key role in several biological processes such as reproduction, development, cellular differentiation, stress response, immunity, metabolism, lipids, and drugs, and are essential regulators of several diseases, including cancer. Numerous studies have demonstrated the importance of NRs in tumor immunology and proved the well-known roles of multiple NRs in modulating proliferation, differentiation, and apoptosis. There are surplus of studies conducted on NRs and their implications in EC, but only a few studies have demonstrated the diagnostic and prognostic potential of NRs. Therefore, there is still a paucity of the role of NRs and different ways to target them in EC cells to stop them from spreading malignancy. This review emphasizes the significance of NRs in EC by discussing their diverse agonists as well as antagonists and their response to tumor progression. Additionally, we emphasize NRs’ potential to serve as a novel therapeutic target and their capacity to treat and prevent EC.

RAID: Regression Analysis–Based Inductive DNA Microarray for Precise Read-Across

Chemical structure-based read-across represents a promising method for chemical toxicity evaluation without the need for animal testing; however, a chemical structure is not necessarily related to toxicity. Therefore, in vitro studies were often used for read-across reliability refinement; however, their external validity has been hindered by the gap between in vitro and in vivo conditions. Thus, we developed a virtual DNA microarray, regression analysis–based inductive DNA microarray (RAID), which quantitatively predicts in vivo gene expression profiles based on the chemical structure and/or in vitro transcriptome data. For each gene, elastic-net models were constructed using chemical descriptors and in vitro transcriptome data to predict in vivo data from in vitro data (in vitro to in vivo extrapolation; IVIVE). In feature selection, useful genes for assessing the quantitative structure–activity relationship (QSAR) and IVIVE were identified. Predicted transcriptome data derived from the RAID system reflected the in vivo gene expression profiles of characteristic hepatotoxic substances. Moreover, gene ontology and pathway analysis indicated that nuclear receptor-mediated xenobiotic response and metabolic activation are related to these gene expressions. The identified IVIVE-related genes were associated with fatty acid, xenobiotic, and drug metabolisms, indicating that in vitro studies were effective in evaluating these key events. Furthermore, validation studies revealed that chemical substances associated with these key events could be detected as hepatotoxic biosimilar substances. These results indicated that the RAID system could represent an alternative screening test for a repeated-dose toxicity test and toxicogenomics analyses. Our technology provides a critical solution for IVIVE-based read-across by considering the mode of action and chemical structures.

Lipid Messenger Phosphatidylinositol-4,5-Bisphosphate Is Increased by Both PPARα Activators and Inhibitors: Relevance for Intestinal Cell Differentiation

Simple Summary

Fibrates, such as fenofibrate, are widely used drugs for dyslipidaemia treatment. It is known that they activate peroxisome proliferator-activated receptor α (PPARα) which serves as a lipid sensor in the organism. This article addresses how activators and inhibitor of the PPARα could affect differentiation of intestinal cells. Carcinogenesis is a disruption of normal differentiation process and colorectal carcinoma is the third most common cancer in terms of incidence, but the secondp in terms of mortality. One of the important signalling pathways in intestinal cell differentiation as well as carcinogenesis is PI3K/Akt/PTEN. We showed that PPARα activators as well as inhibitor affected the levels of one member of this pathway called phosphatidylinositol-4,5-bisphosphate. This molecule is important for formation of microvilli, the essential structures of fully differentiated intestinal cells.

Abstract

We investigated the effects of PPARα activators fenofibrate and WY-14643 as well as the PPARα inhibitor GW6471 on the PI3K/Akt/PTEN pathway of intestinal cell differentiation. Our previous study showed that all these compounds increased the expression of villin, a specific marker of intestinal cell differentiation in HT-29 and Caco2 cells. Our current results confirmed the central role of lipid messenger phosphatidylinositol-4,5-bisphosphate (PIP2), a known player in brush border formation, in mediating the effects of tested PPARα ligands. Although all tested compounds increased its levels, surprisingly, each of them affected different PIP2-metabolizing enzymes, especially the levels of PIP5K1C and PTEN. Moreover, we found a positive relationship between the expression of PPARα itself and PIP2 as well as PIP5K1C. By contrast, PPARα was negatively correlated with PTEN. However, the expression of antigens of interest was independent of PPARα subcellular localization, suggesting that it is not directly involved in their regulation. In colorectal carcinoma tissues we found a decrease in PTEN expression, which was accompanied by a change in its subcellular localization. This change was also observed for the regulatory subunit of PI3K. Taken together, our data revealed that fenofibrate, WY-14643, and GW6471 affected different members of the PI3K/Akt/PTEN pathway. However, these effects were PPARα-independent.

Accumulation of Lipid Droplets in a Novel Bietti Crystalline Dystrophy Zebrafish Model With Impaired PPARα Pathway

Purpose

Bietti crystalline dystrophy (BCD) is a progressive retinal degenerative disease primarily characterized by numerous crystal-like deposits and degeneration of retinal pigment epithelium (RPE) and photoreceptor cells. CYP4V2 (cytochrome P450 family 4 subfamily V member 2) is currently the only disease-causing gene for BCD. We aimed to generate a zebrafish model to explore the functional role of CYP4V2 in the development of BCD and identify potential therapeutic targets for future studies.

Methods

The cyp4v7 and cyp4v8 (homologous genes of CYP4V2) knockout zebrafish lines were generated by CRISPR/Cas9 technology. The morphology of photoreceptor and RPE cells and the accumulation of lipid droplets in RPE cells were investigated at a series of different developmental stages through histological analysis, immunofluorescence, and lipid staining. Transcriptome analysis was performed to investigate the changes in gene expression of RPE cells during the progression of BCD.

Results

Progressive retinal degeneration including RPE atrophy and photoreceptor loss was observed in the mutant zebrafish as early as seven months after fertilization. We also observed the excessive accumulation of lipid droplets in RPE cells from three months after fertilization, which preceded the retinal degeneration by several months. Transcriptome analysis suggested that multiple metabolism pathways, especially the lipid metabolism pathways, were significantly changed in RPE cells. The down-regulation of the peroxisome proliferator-activated receptor α (PPARα) pathway was further confirmed in the mutant zebrafish and CYP4V2-knockdown human RPE-1 cells.

Conclusions

Our work established an animal model that recapitulates the symptoms of BCD patients and revealed that abnormal lipid metabolism in RPE cells, probably caused by dysregulation of the PPARα pathway, might be the main and direct consequence of CYP4V2 deficiency. These findings will deepen our understanding of the pathogenesis of BCD and provide potential therapeutic approaches.

Cancer-Related Cachexia: The Vicious Circle between Inflammatory Cytokines, Skeletal Muscle, Lipid Metabolism and the Possible Role of Physical Training

Cachexia is a multifactorial and multi-organ syndrome that is a major cause of morbidity and mortality in late-stage chronic diseases. The main clinical features of cancer-related cachexia are chronic inflammation, wasting of skeletal muscle and adipose tissue, insulin resistance, anorexia, and impaired myogenesis. A multimodal treatment has been suggested to approach the multifactorial genesis of cachexia. In this context, physical exercise has been found to have a general effect on maintaining homeostasis in a healthy life, involving multiple organs and their metabolism. The purpose of this review is to present the evidence for the relationship between inflammatory cytokines, skeletal muscle, and fat metabolism and the potential role of exercise training in breaking the vicious circle of this impaired tissue cross-talk. Due to the wide-ranging effects of exercise training, from the body to the behavior and cognition of the individual, it seems to be able to improve the quality of life in this syndrome. Therefore, studying the molecular effects of physical exercise could provide important information about the interactions between organs and the systemic mediators involved in the overall homeostasis of the body.

Bio-Waste Products of Mangifera indica L. Reduce Adipogenesis and Exert Antioxidant Effects on 3T3-L1 Cells

Several studies highlighted the beneficial value of natural compounds in the prevention and treatment of obesity. Here, we investigated the anti-obesity effects of extracts of peel and seed of mango (Mangifera indica L.) cultivated in Sicily (Italy) in 3T3-L1 cells. Mango Peel (MPE) and Mango Seed (MSE) extracts at a 100 µg/mL concentration significantly reduced lipid accumulation and triacylglycerol contents during 3T3-L1 adipocyte differentiation without toxicity. HPLC-ESI-MS analysis showed that both the extracts contain some polyphenolic compounds that can account for the observed biological effects. The anti-adipogenic effect of MPE and MSE was the result of down-regulation of the key adipogenic transcription factor PPARγ and its downstream targets FABP4/aP2, GLUT4 and Adipsin, as well SREBP-1c, a transcription factor which promotes lipogenesis. In addition, both MPE and MSE significantly activated AMPK with the consequent inhibition of Acetyl-CoA-carboxylase (ACC) and up-regulated PPARα. The addition of compound C, a specific AMPK inhibitor, reduced the effects of MPE and MSE on AMPK and ACC phosphorylation, suggesting a role of AMPK in mediating MPE and MSE anti-lipogenic effects. Notably, MPE and MSE possess an elevated radical scavenging activity, as demonstrated by DPPH radical scavenging assay, and reduced ROS content produced during adipocyte differentiation. This last effect could be a consequence of the increase in the antioxidant factors Nrf2, MnSOD and HO-1. In conclusion, MPE and MSE possesses both anti-adipogenic and antioxidant potential, thus suggesting that the bio-waste products of mango are promising anti-obesity natural compounds.

Environmental adaptation in fish induced changes in the regulatory region of fatty acid elongase gene, elovl5, involved in long-chain polyunsaturated fatty acid biosynthesis

Fish are the main source of long-chain polyunsaturated fatty acids (LC-PUFA) for human consumption. In the process of evolution via natural selection, adaptation to distinct environments has likely driven changes in the endogenous capacity for LC-PUFA biosynthesis between marine and freshwater fishes. However, the molecular mechanisms underlying adaptive changes in this metabolic pathway are poorly understood. Here, we compared the transcriptional regulation of elongation of very long chain fatty acids protein 5 (Elovl5), which is one of the critical enzymes in LC-PUFA biosynthesis pathway, in marine large yellow croaker (Larimichthys crocea) and freshwater rainbow trout (Oncorhynchus mykiss). Comparative transcriptomic and absolute mRNA quantification analyses revealed that the expression of elovl5 in rainbow trout was markedly higher than that in large yellow croaker. Correspondingly, the number of chromatin accessible areas in the regulatory region of elovl5 in rainbow trout was higher than in large yellow croaker, which revealed that chromatin accessibility in the regulatory region of elovl5 in rainbow trout was higher. Furthermore, the differences in sequence and activity of the elovl5 promoter were observed between rainbow trout and large yellow croaker, and transcription factors including CCAAT/enhancer-binding protein β (CEBPβ), GATA binding protein 3 (GATA3) and upstream stimulatory factor 2 (USF2) displayed different regulatory roles on elovl5 expression between the two species. We propose that changes in the gene regulatory region driven by natural selection likely play a key role in differences in elovl5 expression and the activity of Elovl5, which may influence the LC-PUFA biosynthesis capacities of rainbow trout and large yellow croaker. These findings may also provide opportunities to improve the quality of aquatic products and, consequently, human health.

Review of in silico studies dedicated to the nuclear receptor family: Therapeutic prospects and toxicological concerns

Being in the center of both therapeutic and toxicological concerns, NRs are widely studied for drug discovery application but also to unravel the potential toxicity of environmental compounds such as pesticides, cosmetics or additives. High throughput screening campaigns (HTS) are largely used to detect compounds able to interact with this protein family for both therapeutic and toxicological purposes. These methods lead to a large amount of data requiring the use of computational approaches for a robust and correct analysis and interpretation. The output data can be used to build predictive models to forecast the behavior of new chemicals based on their in vitro activities. This atrticle is a review of the studies published in the last decade and dedicated to NR ligands in silico prediction for both therapeutic and toxicological purposes. Over 100 articles concerning 14 NR subfamilies were carefully read and analyzed in order to retrieve the most commonly used computational methods to develop predictive models, to retrieve the databases deployed in the model building process and to pinpoint some of the limitations they faced.

Mechanistic insights into the peroxisome proliferator-activated receptor alpha as a transcriptional suppressor

Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent hepatic disorders that 20-30% of the world population suffers from. The feature of NAFLD is excess lipid accumulation in the liver, exacerbating multiple metabolic syndromes such as hyperlipidemia, hypercholesterolemia, hypertension, and type 2 diabetes. Approximately 20-30% of NAFLD cases progress to more severe chronic hepatitis, known as non-alcoholic steatohepatitis (NASH), showing deterioration of hepatic functions and liver fibrosis followed by cirrhosis and cancer. Previous studies uncovered that several metabolic regulators had roles in disease progression as key factors. Peroxisome proliferator-activated receptor alpha (PPARα) has been identified as one of the main players in hepatic lipid homeostasis. PPARα is abundantly expressed in hepatocytes, and is a ligand-dependent nuclear receptor belonging to the NR1C nuclear receptor subfamily, orchestrating lipid/glucose metabolism, inflammation, cell proliferation, and carcinogenesis. PPARα agonists are expected to be novel prescription drugs for NASH treatment, and some of them (e.g., Lanifibranor) are currently under clinical trials. These potential novel drugs are developed based on the knowledge of PPARα-activating target genes related to NAFLD and NASH. Intriguingly, PPARα is known to suppress the expression of subsets of target genes under agonist treatment; however, the mechanisms of PPARα-mediated gene suppression and functions of these genes are not well understood. In this review, we summarize and discuss the mechanisms of target gene repression by PPARα and the roles of repressed target genes on hepatic lipid metabolism, fibrosis and carcinogenesis related to NALFD and NASH, and provide future perspectives for PPARα pharmaceutical potentials.

Exposure of male mice to perfluorooctanoic acid induces anxiety-like behaviors by increasing corticotropin-releasing factor in the basolateral amygdala complex

Perfluorooctanoic acid (PFOA), a hazardous environmental pollutant, has been found to enhance hepatic synthesis of fibroblast growth factor 21 (FGF21). FGF21 can enter the brain and increase the expression of corticotropin-releasing factor (CRF) in the paraventricular nucleus (PVN). In this study, adult male mice were orally administered PFOA to evaluate how it regulates emotion. Exposure of mice to PFOA (1 mg kg-1 bw) for 10 consecutive days (PFOA-mice) caused anxiety-like behaviors and a peroxisome proliferator-activated receptor α (PPARα)-dependent increase in hepatic FGF21 synthesis. The levels of CRF expression in not only PVN but also basolateral amygdala complex (BLA) neurons of PFOA-mice were increased via FGF receptor 1 (FGF-R1) activation. However, the microinjection of FGF-R1 or CRF 1 receptor (CRF-R1) antagonist in the BLA rather than the PVN of PFOA-mice could relieve their anxiety-like behaviors. In addition, external capsule-BLA synaptic transmission in PFOA-mice was enhanced by increasing CRF-R1-mediated presynaptic glutamate release, which was corrected by the blockade of PPARα, FGF-R1 and CRF-R1 or the inhibition of PKA. Furthermore, the threshold of frequency-dependent long-term potentiation (LTP) induction was decreased in the BLA of PFOA-mice, which depended on the activation of PPARα, FGF-R1, CRF-R1, PKA and NMDA receptor (NMDAR), whereas long-term depression (LTD) induction was unchanged. Thus, the results indicate that the exposure of male mice to PFOA (1 mg kg-1 bw) enhances CRF expression in BLA neurons by increasing hepatic FGF21 synthesis, which then enhances CRF-R1-mediated presynaptic glutamate release to facilitate NMDAR-dependent BLA-LTP induction, leading to the production of anxiety-like behaviors.

Activation of PPARα by Fenofibrate Attenuates the Effect of Local Heart High Dose Irradiation on the Mouse Cardiac Proteome

Radiation-induced cardiovascular disease is associated with metabolic remodeling in the heart, mainly due to the inactivation of the transcription factor peroxisome proliferator-activated receptor alpha (PPARα), thereby inhibiting lipid metabolic enzymes. The objective of the present study was to investigate the potential protective effect of fenofibrate, a known agonist of PPARα on radiation-induced cardiac toxicity. To this end, we compared, for the first time, the cardiac proteome of fenofibrate- and placebo-treated mice 20 weeks after local heart irradiation (16 Gy) using label-free proteomics. The observations were further validated using immunoblotting, enzyme activity assays, and ELISA. The analysis showed that fenofibrate restored signalling pathways that were negatively affected by irradiation, including lipid metabolism, mitochondrial respiratory chain, redox response, tissue homeostasis, endothelial NO signalling and the inflammatory status. The results presented here indicate that PPARα activation by fenofibrate attenuates the cardiac proteome alterations induced by irradiation. These findings suggest a potential benefit of fenofibrate administration in the prevention of cardiovascular diseases, following radiation exposure.

Role of Peroxisome Proliferator-Activated Receptors (PPARs) in Energy Homeostasis of Dairy Animals: Exploiting Their Modulation through Nutrigenomic Interventions

Peroxisome proliferator-activated receptors (PPARs) are the nuclear receptors that could mediate the nutrient-dependent transcriptional activation and regulate metabolic networks through energy homeostasis. However, these receptors cannot work properly under metabolic stress. PPARs and their subtypes can be modulated by nutrigenomic interventions, particularly under stress conditions to restore cellular homeostasis. Many nutrients such as polyunsaturated fatty acids, vitamins, dietary amino acids and phytochemicals have shown their ability for potential activation or inhibition of PPARs. Thus, through different mechanisms, all these nutrients can modulate PPARs and are ultimately helpful to prevent various metabolic disorders, particularly in transition dairy cows. This review aims to provide insights into the crucial role of PPARs in energy metabolism and their potential modulation through nutrigenomic interventions to improve energy homeostasis in dairy animals.

Targeting Peroxisome Proliferator-Activated Receptor-β/δ (PPARβ/δ) for the Treatment or Prevention of Alcoholic Liver Disease

Excessive, chronic alcohol consumption can lead to alcoholic liver disease. The etiology of alcoholic liver disease is multifactorial and is influenced by alterations in gene expression and changes in fatty acid metabolism, oxidative stress, and insulin resistance. These events can lead to steatosis, fibrosis, and eventually to cirrhosis and liver cancer. Many of these functions are regulated by peroxisome proliferator-activated receptors (PPARs). Thus, it is not surprising that PPARs can modulate the mechanisms that cause alcoholic liver disease. While the roles of PPARα and PPARγ are clearer, the role of PPARβ/δ in alcoholic liver disease requires further clarification. This review summarizes the current understanding based on recent studies that indicate that PPARβ/δ can likely be targeted for the treatment and/or the prevention of alcoholic liver disease.

Targeting immunometabolism by active ingredients derived from traditional Chinese medicines for treatment of rheumatoid arthritis

Rheumatoid arthritis (RA), the most common inflammatory arthropathy word wild, is a systemic autoimmune disease that mainly affects the synovium of joints with a high disability rate. Metabolic mis-regulation has emerged as a fundamental pathogenesis of RA linked to immune cell dysfunction, while targeting immunometabolism provides a new and effective approach to regulate the immune responses and thus alleviate the symptom of RA. Recently, natural active compounds from traditional Chinese medicines (TCMs) have potential therapeutic effects on RA and regulating immunometabolism. In this review, in addition to updating the connection between cellular metabolism and cell function in immune cells of RA, we summarized that the anti-inflammatory mechanisms of the potential natural compounds from TCM by targeting metabolic reprogramming of immune cells, and discusses them as a rich resource for providing the new potential paradigm for the treatment of RA.

Endoplasmic reticulum stress induces hepatic steatosis by transcriptional upregulating lipid droplet protein perilipin2

Previous studies have shown that endoplasmic reticulum (ER) stress contributes to hepatic steatosis in several manners. However, how lipid droplet (LD) proteins participate in this process has rarely been reported. In the present study, ER stress was induced at both in vitro and in vivo levels with tunicamycin in large yellow croaker (Larimichthys crocea). Effects of LD protein perilipin2 (PLIN2) on hepatic lipid accumulation and lipoprotein transport under normal physiological condition and ER stress were then explored using dsRNA mediated knockdown. Subsequently, the transcriptional regulation of plin2 expression by transcription factors generated in the unfolded protein response (UPR) was determined by dual-luciferase reporter assays, chromatin immunoprecipitation and electrophoretic mobility-shift assay. We demonstrated that ER stress could promote LDs accumulation and inhibit lipoprotein transport by transcriptionally upregulating PLIN2 in liver. Among the transcription factors generated by UPR, spliced X-box binding protein1 can directly upregulated the expression of plin2, whereas C/EBP homologous protein can upregulate the expression of plin2 through peroxisome proliferator activated-receptor α. These results revealed that the LD protein PLIN2 played an important role in ER stress-induced hepatic steatosis, which might be a novel mechanism explaining hepatic steatosis triggered by ER stress.

When Activator and Inhibitor of PPARα Do the Same: Consequence for Differentiation of Human Intestinal Cells

Peroxisome proliferator-activated receptor α (PPARα) is a ligand-dependent transcription factor that plays a role in various processes including differentiation of several cell types. We investigated the role of PPARα in the differentiation of intestinal cells using HT-29 and Caco2 cell lines as a model as well as human normal colon and colorectal carcinoma tissues. We detected a significant increase in PPARα expression in differentiated HT-29 cells as well as in normal surface colon epithelium where differentiated cells are localised. Thus, it seems that PPARα may play a role in differentiation of intestinal cells. Interestingly, we found that both PPARα activators (fenofibrate and WY-14643) as well as its inhibitor (GW6471) regulated proliferation and differentiation of HT-29 cells in vitro in the same way. Both compounds led to a decrease in proliferation accompanied by a significant increase in expression of villin, intestinal alkaline phosphatase (differentiation markers). Moreover, the same trend in villin expression was observed in Caco2 cells. Furthermore, villin expression was independent of subcellular localisation of PPARα. In addition, we found similar levels of PPARα expression in colorectal carcinomas in comparison to adjacent normal epithelium. All these findings support the hypothesis that differentiation of intestinal epithelium is PPARα-independent.

Dietary Protein From Different Sources Exerted a Great Impact on Lipid Metabolism and Mitochondrial Oxidative Phosphorylation in Rat Liver

Associations between meat diets and human health have been widely considered. In this study, we focused on long-term effects of different sources of meat protein on liver metabolic enzymes. For 90 days, rats were fed with semisynthetic diets that differed only with protein source. Casein was used as a reference and isolated soybean, fish, chicken, pork, and beef proteins were compared. Changes in liver proteome were determined by isobaric tag for relative and absolute quantitation (iTRAQ) labeling and liquid chromatography electrospray ionization tandem mass spectrometry/mass spectrometry (LC–ESI–MS/MS). Fish and pork protein diets upregulated the gene expression involved in cholesterol synthesis and esterification, and pork protein diet also upregulated the gene expression of high-density lipoprotein receptor and low-density lipoprotein receptor. Chicken, pork, and beef protein diets upregulated the gene expression involved in cholesterol reverse transport and bile acid production, which increased the total cholesterol level in the fish protein diet group. Total cholesterol levels in liver were lower in the pork and beef protein diet groups. Triglyceride levels in liver were lower in chicken, pork, and beef protein diet groups. Peroxisomal proliferator-activated receptor-gamma coactivator-1 was upregulated by chicken, pork and beef protein diets, and promoted the degradation and metabolism of triglyceride, resulting in lower triglyceride in the three diet groups. Meat proteins at a recommended level could be more conducive to cholesterol degradation, triglyceride decomposition, and energy balance maintenance at a healthy level. The findings give a new insight into the associations between meat diet intake and human health.

Appropriate leucine supplementation promotes glucose metabolism and enhances energy homeostasis in juvenile crucian carp (Carassius auratus gibelio var. CAS III)

In order to characterize the molecular mechanisms by which leucine regulates carbohydrate metabolism and energy homeostasis, juvenile crucian carps (Carassius auratus gibelio var. CAS III) fed with a high carbohydrate diet were supplemented with different levels of dietary leucine: 0% (Leu0), 0.4% (Leu4), 0.8% (Leu8), 1.2% (Leu12), 1.6% (Leu16), 2.0% (Leu20), and 5.0% (Leu50). After 8 weeks, RNA sequencing was performed on samples collected from the Leu0, Leu8, Leu12 and Leu50 groups. Differentially expressed genes were then detected and analyzed. The results showed a total of 91.6 Gb of clean bases were generated. Moreover, a total of 1131, 5254, and 1539 DEGs were detected in Leu8, Leu12, and Leu50 compared with Leu0, respectively, encompassing 161 common DEGs. STEM analysis elucidated four significant clusters of DEGs that were associated with "glycerophospholipid metabolism," "glycerolipid metabolism," "PPAR signaling pathway," and "adipocytokine signaling pathway." Moreover, the mRNA expression levels of acyl-CoA synthetase long chain family member 5 (ACSL5), choline kinase beta (CHKB), cryptochrome-1 (CRY1), lon protease homolog 2, peroxisomal isoform X2 (LONP2), lipin 1 (LPIN1), membrane bound O-acyltransferase domain containing 2 (MBOAT2), phosphoenolpyruvate carboxykinase 1 (PEPCK), and uridine-cytidine kinase 2b (UCK2b) were then further investigated in all leucine treatment groups at starvation times of 0 h, 24 h, and 48 h. The results revealed that the expression levels of UCK2b and MBOAT2 were negatively correlated with the addition of leucine, whereas CHKB, LONP2, CRY1, PEPCK, and LPIN1 were positively correlated. In conclusion, dietary leucine supplementation below 1.2% enhanced carbohydrate metabolism in juvenile crucian carp fed with a high-carbohydrate diet, whereas concentrations above 2.0% is a better choice for energy homeostasis under starvation.

A focused review on CB2 receptor-selective pharmacological properties and therapeutic potential of β-caryophyllene, a dietary cannabinoid

The endocannabinoid system (ECS), a conserved physiological system emerged as a novel pharmacological target for its significant role and potential therapeutic benefits ranging from neurological diseases to cancer. Among both, CB1 and CB2R types, CB2R have received attention for its pharmacological effects as antioxidant, anti-inflammatory, immunomodulatory and antiapoptotic that can be achieved without causing psychotropic adverse effects through CB1R. The ligands activate CB2R are of endogenous, synthetic and plant origin. In recent years, β-caryophyllene (BCP), a natural bicyclic sesquiterpene in cannabis as well as non-cannabis plants, has received attention due to its selective agonist property on CB2R. BCP has been well studied in a variety of pathological conditions mediating CB2R selective agonist property. The focus of the present manuscript is to represent the CB2R selective agonist mediated pharmacological mechanisms and therapeutic potential of BCP. The present narrative review summarizes insights into the CB2R-selective pharmacological properties and therapeutic potential of BCP such as cardioprotective, hepatoprotective, neuroprotective, nephroprotective, gastroprotective, chemopreventive, antioxidant, anti-inflammatory, and immunomodulator. The available evidences suggest that BCP, can be an important candidate of plant origin endowed with CB2R selective properties that may provide a pharmacological rationale for its pharmacotherapeutic application and pharmaceutical development like a drug. Additionally, given the wide availability in edible plants and dietary use, with safety, and no toxicity, BCP can be promoted as a nutraceutical and functional food for general health and well-being. Further, studies are needed to explore pharmacological and pharmaceutical opportunities for therapeutic and preventive applications of use of BCP in human diseases.

Methanolic Extract of Lysimachia Candida Lindl. Prevents High-Fat High-Fructose-Induced Fatty Liver in Rats: Understanding the Molecular Mechanism Through Untargeted Metabolomics Study

Fatty liver is one of the most common metabolic syndrome affecting the global population. Presently, limited treatment modalities with symptomatic approach are available for alleviating fatty liver. Traditional and herbal treatment modalities have shown evidence to improve the disease pathology. In the present research work, evaluation of a selected medicinal plant Lysimachia candida Lindl. was carried out to investigate its beneficial effects on fatty liver disease in rats. Male Sprague Dawley (SD) rats were fed with high-fat high-fructose diet to induce fatty liver phenotypes. After induction for 15 weeks, methanolic extract of Lysimachia candida Lindl. (250 mg/kg b. w. p. o.) was administrated to the rats daily for the next 17 weeks. Blood samples were collected at different time points to analyze fasting blood glucose levels and relevant biochemical parameters important for the assessment of metabolic disease phenotypes. Liquid chromatography-mass spectrometry (LC-MS) based metabolomics was done to study the dynamics of metabolic changes in the serum during disease progression and how the medicinally important plant extract treatment reversed the metabolic diseases. Multivariate data analysis approaches have been employed to understand the metabolome changes and disease pathology. This study has identified the interplay of some metabolic pathways that alter the disease progression and their reversal after administration of the plant extract. Different group of metabolites mainly bile acids, fatty acids, carnitines, and their derivatives were found to be altered in the diseased rats. However, all the metabolites identified between control and disease groups are mainly related to lipid metabolism. The results depict that the treatment with the above-mentioned plant extract improves the regulation of aberrant lipid metabolism, and reverses the metabolic syndrome phenotype. Therefore, the present study reveals the potential mechanism of the herbal extract to prevent metabolic syndrome in rats.

Protective effects of zingerone on high cholesterol diet-induced atherosclerosis through lipid regulatory signaling pathway

AIM

A high cholesterol diet (HCD) is known to cause metabolic dysregulation, oxidative stress, cardiovascular diseases and atherogenesis. Zingerone is a pharmacologically active component of dry ginger. Zingerone has been shown to have a wide range of pharmacological properties, including scavenging free radicals, high antioxidant activity, suppressing lipid peroxidation and anti-inflammatory. This study aimed to investigate the effects of Zingerone on HCD-induced atherosclerosis in rats.

METHODS

Animals were divided into four categories (n = 6). Group I: normal control, Group II: zingerone control (20 mg/kg b.wt.), group III: HCD-induced atherosclerosis, Group IV: HCD + zingerone, respectively, for 8 weeks.

RESULTS

The HCD-fed rats resulted in a significant increase in an atherosclerotic lesion, lipid peroxidation, lipid profile, high-density lipoprotein concentration, cardiac markers, body weight, reduced antioxidant status, and displayed atherosclerosis. These findings were conventional by up-regulated expression of lipid regulatory genes like sterol-regulatory-element-binding protein-c (SREBP-c), fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), acetyl-CoA synthetase (ACS), liver X receptor-alpha (LXR-α), and down-regulated expression of acetyl-CoA oxidase (ACO), peroxisome proliferator-activated receptor-alpha (PPAR-α) and carnitine palmitoyl transferase-1 (CPT-1) in HCD-fed rats. These significant changes were observed in the zingerone-treated rats for the last 4 weeks.

CONCLUSION

These findings suggest that zingerone reduced atherosclerosis by modulated the atherosclerotic lesion, lipid profile, antioxidant status and lipid regulatory gene expression in HCD-fed rats.

Icaritin ameliorates hepatic steatosis via promoting fatty acid β-oxidation and insulin sensitivity

AIM

This study aimed to reveal the effects of icaritin (ICT) on lipotoxicity induced by palmitate (PA) in hepatic cells and steatosis in high-fat diet (HFD)-fed mice as well as exploring the potential mechanisms.

MAIN METHODS

Primary mouse hepatocytes and human hepatoma Huh7 cells were used to evaluate ICT effect in vitro. HFD-fed mice were used to evaluate the ICT effect in vivo.

RESULTS

In vitro study indicated that ICT significantly rescued PA-induced steatosis, mainly through a combination of robust increased mitochondrial respiration, fatty acid oxidation and mildly decreased synthesis of fatty acid. An HFD-fed mouse model with 8 weeks HFD-fed showed metabolic disorders, while ICT application significantly reduced the weight, serum glucose levels, insulin resistance, hepatic steatosis level and adipose contents. In consistent with the observations in cell lines, ICT rescued the HFD-impaired functions and contents of key factors related to fatty acid β-oxidation through elevated expression of peroxisome proliferator-activated receptor α (PPARα). Meanwhile, it also reversed the decreased phosphoryl levels of AKT and glucogen synthase kinase 3 (GSK3β), leading to the improvement of insulin resistance.

SIGNIFICANCE

ICT administration had a therapeutic effect on PA- or HFD-induced hepatic steatosis and metabolic disorders. It may provide a novel strategy to construct preventive and therapeutic means for hepatic steatosis.

Effect of fenofibrate on proliferation of SMMC-7721 cells via regulating cell cycle

Liver cancer is a malignant cancer with great harmfulness. Fenofibrate is a peroxisome proliferation activated receptor (PPARα) agonist widely used in the treatment of dyslipidemia. Previous studies have shown that fenofibrate may promote cell proliferation, but the underlying mechanism has not been fully characterized. The aim of this study was to investigate the role of PPARα agonist fenofibrate in cell proliferation of SMMC-7721 cells compared with that of THLE-2 cells. SMMC-7721 and THLE-2 cells were treated with different concentrations of fenofibrate. Cell proliferation was analyzed by MTT, using flow cytometry for cell cycle analysis, and CyclinD1, Cyclin-dependent kinases2 (CDK2) and Proliferating Cell Nuclear Antigen (PCNA) were analyzed by Western blotting. RT-qPCR method was used to assess CDK2, CyclinD1 and PCNA mRNA levels. The results showed that 10^-9-10^-4 mol/L fenofibrate could induce cell growth and 10^-4, 10^-5, 10^-6 mol/L fenofibrate could reduce the number of G0/G1 phase cells and increased in the number of cells in S and G2/M phase of cell cycle in SMMC-7721 cells. Furthermore, fenofibrate could significantly increase the expression of cell cycle related protein (CyclinD1, CDK2)and cell proliferation related proteins (PCNA). The use of PPARα inhibitor MT886 inhibited cell cycle progression and promote tumor cell apoptosis. But fenofibrate had no obvious effect on THLE-2 cells. These results revealed the effect of fenofibrate on the cell cycle of liver cancer cells, and provided a reasonable explanation for studying how fenofibrate promotes cell proliferation.