PPARα-Deficient ob/ob Obese Mice Become More Obese and Manifest Severe Hepatic Steatosis Due to Decreased Fatty Acid Oxidation

PPARα suppresses low-intensity-noise-induced body weight gain in mice: the activated HPA axis plays an critical role

BACKGROUND

As the second most risky environmental pollution, noise imposes threats to human health. Exposure to high-intensity noise causes hearing impairment, psychotic disorders, endocrine modifications. The relationship among low-intensity noise, obesity and lipid-regulating nuclear factor PPARα is not yet clear.

METHODS

In this study, male wild-type (WT) and Pparα-null (KO) mice on a high-fat diet (HFD) were exposed to 75 dB noise for 12 weeks to explore the effect of low-intensity noise on obesity development and the role of PPARα. 3T3-L1 cells were treated with dexamethasone (DEX) and sodium oleate (OA) to verify the down-stream effect of hypothalamic-pituitary-adrenal (HPA) axis activation on the adipose tissues.

RESULTS

The average body weight gain (BWG) of WT mice on HFD exposed to noise was inhibited, which was not observed in KO mice. The mass and adipocyte size of adipose tissues accounted for the above difference of BWG tendency. In WT mice on HFD, the adrenocorticotropic hormone level was increased by the noise challenge. The aggravation of fatty liver by noise exposure occurred in both mouse lines, and the transport of hepatic redundant lipid to adipose tissues were similar. The lipid metabolism in adipose tissue driven by HPA axis accorded with the BWG inhibition in vivo, validated in 3T3-L1 adipogenic stem cells.

CONCLUSION

Chronic exposure to low-intensity noise aggravated fatty liver in both WT and KO mice. BWG inhibition was observed only in WT mice, which covered up the aggravation of fatty liver by noise exposure. PPARα mediates the activation of HPA axis by noise exposure in mice on HFD. Elevated adrenocorticotropic hormone (ACTH) promoted lipid metabolism in adipocytes, which contributed to the disassociation of BWG and fatty liver development in male WT mice. Summary of PPARα suppresses noise-induced body weight gain in mice on high-fat-diet. Chronic exposure to low-intensity noise exposure inhibited BWG by PPARα-dependent activation of the HPA axis.

Hepatocyte-Specific PEX16 Abrogation in Mice Leads to Hepatocyte Proliferation, Alteration of Hepatic Lipid Metabolism, and Resistance to High-Fat Diet (HFD)-Induced Hepatic Steatosis and Obesity

Obesity results in hepatic fat accumulation, i.e., steatosis. In addition to fat overload, impaired fatty acid β-oxidation also promotes steatosis. Fatty acid β-oxidation takes place in the mitochondria and peroxisomes. Usually, very long-chain and branched-chain fatty acids are the first to be oxidized in peroxisomes, and the resultant short chain fatty acids are further oxidized in the mitochondria. Peroxisome biogenesis is regulated by peroxin 16 (PEX16). In liver-specific PEX16 knockout (Pex16Alb-Cre) mice, hepatocyte peroxisomes were absent, but hepatocytes proliferated, and liver mass was enlarged. These results suggest that normal liver peroxisomes restrain hepatocyte proliferation and liver sizes. After high-fat diet (HFD) feeding, body weights were increased in PEX16 floxed (Pex16fl/fl) mice and adipose-specific PEX16 knockout (Pex16AdipoQ-Cre) mice, but not in the Pex16Alb-Cre mice, suggesting that the development of obesity is regulated by liver PEX16 but not by adipose PEX16. HFD increased liver mass in the Pex16fl/fl mice but somehow reduced the already enlarged liver mass in the Pex16Alb-Cre mice. The basal levels of serum triglyceride, free fatty acids, and cholesterol were decreased, whereas serum bile acids were increased in the Pex16Alb-Cre mice, and HFD-induced steatosis was not observed in the Pex16Alb-Cre mice. These results suggest that normal liver peroxisomes contribute to the development of liver steatosis and obesity.

Dysfunction of the Brown Adipose Organ in HFD-Obese Rats and Effect of Tart Cherry Supplementation

Obesity has a great impact on adipose tissue biology, based on its function as a master regulator of energy balance. Brown adipose tissue (BAT) undergoes remodeling, and its activity declines in obese subjects due to a whitening process. The anti-obesity properties of fruit extracts have been reported. The effects of tart cherry against oxidative stress, inflammation, and the whitening process in the BAT of obese rats were investigated. Intrascapular BAT (iBAT) alterations and effects of Prunus cerasus L. were debated in rats fed for 17 weeks with a high-fat diet (DIO), in DIO supplemented with seed powder (DS), and with seed powder plus the juice (DJS) of tart cherry compared to CHOW rats fed with a normo-caloric diet. iBAT histologic observations revealed a whitening process in DIO rats that was reduced in the DS and DJS groups. A modulation of uncoupling protein-1 (UCP-1) protein and gene expression specifically were detected in the obese phenotype. An upregulation of UCP-1 and related thermogenic genes after tart cherry intake was detected compared to the DIO group. Metabolic adjustment, endoplasmic reticulum stress, protein carbonylation, and the inflammatory microenvironment in the iBAT were reported in DIO rats. The analysis demonstrated an iBAT modulation that tart cherry promoted. In addition to our previous results, these data confirm the protective impact of tart cherry consumption on obesity.

Bacteroides and NAFLD: pathophysiology and therapy

Non-alcoholic fatty liver disease (NAFLD) is a prevalent chronic liver condition observed globally, with the potential to progress to non-alcoholic steatohepatitis (NASH), cirrhosis, and even hepatocellular carcinoma. Currently, the US Food and Drug Administration (FDA) has not approved any drugs for the treatment of NAFLD. NAFLD is characterized by histopathological abnormalities in the liver, such as lipid accumulation, steatosis, hepatic balloon degeneration, and inflammation. Dysbiosis of the gut microbiota and its metabolites significantly contribute to the initiation and advancement of NAFLD. Bacteroides, a potential probiotic, has shown strong potential in preventing the onset and progression of NAFLD. However, the precise mechanism by which Bacteroides treats NAFLD remains uncertain. In this review, we explore the current understanding of the role of Bacteroides and its metabolites in the treatment of NAFLD, focusing on their ability to reduce liver inflammation, mitigate hepatic steatosis, and enhance intestinal barrier function. Additionally, we summarize how Bacteroides alleviates pathological changes by restoring the metabolism, improving insulin resistance, regulating cytokines, and promoting tight-junctions. A deeper comprehension of the mechanisms through which Bacteroides is involved in the pathogenesis of NAFLD should aid the development of innovative drugs targeting NAFLD.

Effects of Chronic Sleep Restriction on Transcriptional Sirtuin 1 Signaling Regulation in Male Mice White Adipose Tissue

Chronic sleep restriction (CSR) is a prevalent issue in modern society that is associated with several pathological states, ranging from neuropsychiatric to metabolic diseases. Despite its known impact on metabolism, the specific effects of CSR on the molecular mechanisms involved in maintaining metabolic homeostasis at the level of white adipose tissue (WAT) remain poorly understood. Therefore, this study aimed to investigate the influence of CSR on sirtuin 1 (SIRT1) and the peroxisome proliferator-activated receptor γ (PPARγ) signaling pathway in the WAT of young male mice. Both genes interact with specific targets involved in multiple metabolic processes, including adipocyte differentiation, browning, and lipid metabolism. The quantitative PCR (qPCR) results demonstrated a significant upregulation of SIRT-1 and some of its target genes associated with the transcriptional regulation of lipid homeostasis (i.e., PPARα, PPARγ, PGC-1α, and SREBF) and adipose tissue development (i.e., leptin, adiponectin) in CSR mice. On the contrary, DNA-binding transcription factors (i.e., CEBP-β and C-myc), which play a pivotal function during the adipogenesis process, were found to be down-regulated. Our results also suggest that the induction of SIRT1-dependent molecular pathways prevents weight gain. Overall, these findings offer new, valuable insights into the molecular adaptations of WAT to CSR, in order to support increased energy demand due to sleep loss.

Roles of transmembrane protein 135 in mitochondrial and peroxisomal functions - implications for age-related retinal disease

Aging is the most significant risk factor for age-related diseases in general, which is true for age-related diseases in the eye including age-related macular degeneration (AMD). Therefore, in order to identify potential therapeutic targets for these diseases, it is crucial to understand the normal aging process and how its mis-regulation could cause age-related diseases at the molecular level. Recently, abnormal lipid metabolism has emerged as one major aspect of age-related symptoms in the retina. Animal models provide excellent means to identify and study factors that regulate lipid metabolism in relation to age-related symptoms. Central to this review is the role of transmembrane protein 135 (TMEM135) in the retina. TMEM135 was identified through the characterization of a mutant mouse strain exhibiting accelerated retinal aging and positional cloning of the responsible mutation within the gene, indicating the crucial role of TMEM135 in regulating the normal aging process in the retina. Over the past decade, the molecular functions of TMEM135 have been explored in various models and tissues, providing insights into the regulation of metabolism, particularly lipid metabolism, through its action in multiple organelles. Studies indicated that TMEM135 is a significant regulator of peroxisomes, mitochondria, and their interaction. Here, we provide an overview of the molecular functions of TMEM135 which is crucial for regulating mitochondria, peroxisomes, and lipids. The review also discusses the age-dependent phenotypes in mice with TMEM135 perturbations, emphasizing the importance of a balanced TMEM135 function for the health of the retina and other tissues including the heart, liver, and adipose tissue. Finally, we explore the potential roles of TMEM135 in human age-related retinal diseases, connecting its functions to the pathobiology of AMD.

Shenge Formula attenuates high-fat diet-induced obesity and fatty liver via inhibiting ACOX1

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease worldwide. Shenge Formula (SGF) is a traditional Chinese medicine that has been used in the clinical treatment of NAFLD, and its therapeutic potential in patients and NAFLD animal models has been demonstrated in numerous studies. However, its underlying mechanism for treating NAFLD remains unclear.

PURPOSE

The aim of this study was to investigate the mechanism of SGF in the treatment of NAFLD using the proteomics strategy.

METHODS

Ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS) was used to determine the main components of SGF. A mouse model of nonalcoholic fatty liver disease was constructed by feeding mice with a high-fat diet for 16 weeks. SGF was administered for an additional 8 weeks, and metformin was used as a positive control. Liver sections were subjected to histopathological assessments. LC-MS/MS was used for the label-free quantitative proteomic analysis of liver tissues. Candidate proteins and pathways were validated both in vivo and in vitro through qRT-PCR, western blot, and immunohistochemistry. The functions of the validated pathways were further investigated using the inhibition strategy.

RESULTS

Thirty-nine ingredients were identified in SGF extracts, which were considered to be key compounds in the treatment of NAFLD. SGF administration attenuated obesity and fatty liver by reducing the body weight and liver weight in HFD-fed mice. It also relieved HFD-induced insulin resistance. More importantly, hepatic steatosis was significantly attenuated by SGF administration both in vivo and in vitro. Proteomic profiling of mouse liver tissues identified 184 differential expressed proteins (DEPs) associated with SGF treatment. Bioinformatic analysis of DEPs revealed that regulating the lipid metabolism and energy consumption process of hepatocytes was the main role of SGF in NAFLD treatment. This also indicated that ACOX1 might be the potential target of SGF, which was subsequently verified both in vitro and in vivo. The results demonstrated that SGF inhibited ACOX1 activity, thereby activating PPARα and upregulating CPT1A expression. Increased CPT1A expression promoted mitochondrial β-oxidation, leading to reduced lipid accumulation in hepatocytes.

CONCLUSIONS

Overall, our findings confirmed the protective effect of SGF against NAFLD and revealed the underlying molecular mechanism of regulating lipid metabolism.

The effects of purslane consumption on blood pressure, body weight, body mass index, and waist circumference: a systematic review and meta-analysis of randomised controlled

The effects of purslane consumption on anthropometric measurements and blood pressure have been studied in numerous experiments. However, the research findings conflict with one another. In order to assess the impact of purslane on weight, body mass index (BMI), waist circumference (WC), systolic blood pressure (SBP), and diastolic blood pressure (DBP), this meta-analysis was carried out. Up until February 2023, PubMed, Web of Science, Scopus, Google Scholar, and the reference lists of the identified pertinent randomised controlled trials (RCTs) were all searched. The random-effects model was used to calculate the effect size and then to describe it as a weighted mean difference (WMD) and 95 % confidence interval (CI) (CRD42023427955). The systematic review was able to incorporate seven RCTs. Meta-analysis showed that purslane significantly decreased body weight (WMD): -0⋅73 kg, 95 % confidence interval (CI): -1⋅37, -0⋅09, P=0⋅025), BMI (WMD: -0⋅35 kg/m2, 95 % CI: -0⋅64, -0⋅07, P=0⋅016), and SBP (WMD: -3⋅64 mmHg, 95 % CI: -6⋅42, -0⋅87, P = 0⋅01), and for WC, there was no discernible effect (WMD: -0⋅86 cm; 95 % CI, -1⋅80 to 0⋅07; P = 0⋅06) and DBP (WMD: -0⋅36 mmHg; 95 % CI, -1⋅75 to 1⋅03; P = 0⋅61). Purslane consumption, especially in participants with a BMI of <30, might play a role in decreasing SBP, body weight, BMI, and WC. Purslane consumption significantly reduced body weight, BMI, and SBP; however, WC and DBP did not experience a reduction. More investigation is needed to verify the impact of purslane consumption on anthropometric parameters and blood pressure.

NPRA promotes fatty acid metabolism and proliferation of gastric cancer cells by binding to PPARα

Among cancers, gastric cancer (GC) ranks third globally in morbidity and mortality, particularly in East Asia. Natriuretic peptide receptor A (NPRA), a receptor for guanylate cyclase, plays important roles in regulating water and sodium balance. Recent studies have suggested that NPRA is involved in tumorigenesis, but its role in GC development remains unclear. Herein, we showed that the expression level of NPRA was positively correlated with gastric tumor size and clinical stage. Patients with high NPRA expression had a lower five-year survival rate than those with low expression, and NPRA was identified as an independent predictor of GC prognosis. NPRA knockdown suppressed GC cell proliferation, migration and invasion. NPRA overexpression enhanced cell malignant behavior. Immunohistochemistry of collected tumor samples showed that tumors with high NPRA expression had higher peroxisome proliferator-activated receptor α (PPARα) levels. In vivo and in vitro studies showed that NPRA promotes fatty acid oxidation and tumor cell metastasis. Co-IP showed that NPRA binds to PPARα and prevents PPARα degradation. PPARα upregulation under NPRA protection activates arnitine palmitoyl transferase 1B (CPT1B) to promote fatty acid oxidation. In this study, new mechanisms by which NPRA promotes the development of GC and new regulatory mechanisms of PPARα were identified.

Obesity-induced metabolic imbalance allosterically modulates CtBP2 to inhibit PPAR-alpha transcriptional activity

Maintenance of metabolic homeostasis is secured by metabolite-sensing systems, which can be overwhelmed by constant macronutrient surplus in obesity. Not only the uptake processes but also the consumption of energy substrates determine the cellular metabolic burden. We herein describe a novel transcriptional system in this context comprised of peroxisome proliferator-activated receptor alpha (PPARα), a master regulator for fatty acid oxidation, and C-terminal binding protein 2 (CtBP2), a metabolite-sensing transcriptional co-repressor. CtBP2 interacts with PPARα to repress its activity, and the interaction is enhanced upon binding to malonyl-CoA, a metabolic intermediate increased in tissues in obesity and reported to suppress fatty acid oxidation through inhibition of carnitine palmitoyltransferase 1 (CPT1). In line with our preceding observations that CtBP2 adopts a monomeric configuration upon binding to acyl-CoAs, we determined that mutations in CtBP2 that shift the conformational equilibrium toward monomers increase the interaction between CtBP2 and PPARα. In contrast, metabolic manipulations that reduce malonyl-CoA decreased the formation of the CtBP2/PPARα complex. Consistent with these in vitro findings, we found that the CtBP2/PPARα interaction is accelerated in obese livers while genetic deletion of CtBP2 in the liver causes derepression of PPARα target genes. These findings support our model where CtBP2 exists primarily as a monomer in the metabolic milieu of obesity to repress PPARα, representing a liability in metabolic diseases that can be exploited to develop therapeutic approaches.

Supplemental Clostridium butyricum modulates lipid metabolism by reshaping the gut microbiota composition and bile acid profile in IUGR suckling piglets

BACKGROUND

Intrauterine growth restriction (IUGR) can cause lipid disorders in infants and have long-term adverse effects on their growth and development. Clostridium butyricum (C. butyricum), a kind of emerging probiotics, has been reported to effectively attenuate lipid metabolism dysfunctions. Therefore, the objective of this study was to investigate the effects of C. butyricum supplementation on hepatic lipid disorders in IUGR suckling piglets.

METHODS

Sixteen IUGR and eight normal birth weight (NBW) neonatal male piglets were used in this study. From d 3 to d 24, in addition to drinking milk, the eight NBW piglets (NBW-CON group, n = 8) and eight IUGR piglets (IUGR-CON group, n = 8) were given 10 mL sterile saline once a day, while the remaining IUGR piglets (IUGR-CB group, n = 8) were orally administered C. butyricum at a dose of 2 × 10⁸ colony-forming units (CFU)/kg body weight (suspended in 10 mL sterile saline) at the same frequency.

RESULTS

The IUGR-CON piglets exhibited restricted growth, impaired hepatic morphology, disordered lipid metabolism, increased abundance of opportunistic pathogens and altered ileum and liver bile acid (BA) profiles. However, C. butyricum supplementation reshaped the gut microbiota of the IUGR-CB piglets, characterized by a decreased abundance of opportunistic pathogens in the ileum, including Streptococcus and Enterococcus. The decrease in these bile salt hydrolase (BSH)-producing microbes increased the content of conjugated BAs, which could be transported to the liver and function as signaling molecules to activate liver X receptor α (LXRα) and farnesoid X receptor (FXR). This activation effectively accelerated the synthesis and oxidation of fatty acids and down-regulated the total cholesterol level by decreasing the synthesis and promoting the efflux of cholesterol. As a result, the growth performance and morphological structure of the liver improved in the IUGR piglets.

CONCLUSION

These results indicate that C. butyricum supplementation in IUGR suckling piglets could decrease the abundance of BSH-producing microbes (Streptococcus and Enterococcus). This decrease altered the ileum and liver BA profiles and consequently activated the expression of hepatic LXRα and FXR. The activation of these two signaling molecules could effectively normalize the lipid metabolism and improve the growth performance of IUGR suckling piglets.

GLP-1 Receptor Agonists in Non-Alcoholic Fatty Liver Disease: Current Evidence and Future Perspectives

To date, non-alcoholic fatty liver disease (NAFLD) is the most frequent liver disease, affecting up to 70% of patients with diabetes. Currently, there are no specific drugs available for its treatment. Beyond their anti-hyperglycemic effect and the surprising role of cardio- and nephroprotection, GLP-1 receptor agonists (GLP-1 RAs) have shown a significant impact on body weight and clinical, biochemical and histological markers of fatty liver and fibrosis in patients with NAFLD. Therefore, GLP-1 RAs could be a weapon for the treatment of both diabetes mellitus and NAFLD. The aim of this review is to summarize the evidence currently available on the role of GLP-1 RAs in the treatment of NAFLD and to hypothesize potential future scenarios.

Transmembrane protein 135 regulates lipid homeostasis through its role in peroxisomal DHA metabolism

Transmembrane protein 135 (TMEM135) is thought to participate in the cellular response to increased intracellular lipids yet no defined molecular function for TMEM135 in lipid metabolism has been identified. In this study, we performed a lipid analysis of tissues from Tmem135 mutant mice and found striking reductions of docosahexaenoic acid (DHA) across all Tmem135 mutant tissues, indicating a role of TMEM135 in the production of DHA. Since all enzymes required for DHA synthesis remain intact in Tmem135 mutant mice, we hypothesized that TMEM135 is involved in the export of DHA from peroxisomes. The Tmem135 mutation likely leads to the retention of DHA in peroxisomes, causing DHA to be degraded within peroxisomes by their beta-oxidation machinery. This may lead to generation or alteration of ligands required for the activation of peroxisome proliferator-activated receptor a (PPARa) signaling, which in turn could result in increased peroxisomal number and beta-oxidation enzymes observed in Tmem135 mutant mice. We confirmed this effect of PPARa signaling by detecting decreased peroxisomes and their proteins upon genetic ablation of Ppara in Tmem135 mutant mice. Using Tmem135 mutant mice, we also validated the protective effect of increased peroxisomes and peroxisomal beta-oxidation on the metabolic disease phenotypes of leptin mutant mice which has been observed in previous studies. Thus, we conclude that TMEM135 has a role in lipid homeostasis through its function in peroxisomes.

The Synergistic Protective Effect of γ-Oryzanol (OZ) and N-Acetylcysteine (NAC) against Experimentally Induced NAFLD in Rats Entails Hypoglycemic, Antioxidant, and PPARα Stimulatory Effects

This study estimated that the combined effect of γ-Oryzanol and N-acetylcysteine (NAC) against high-fat diet (HFD)-induced non-alcoholic fatty liver disease (NAFLD) in rats also estimated some of their mechanisms of action. Adult male rats were divided into seven groups (n = 8 each) as control, control + NAC, control + γ-Oryzanol, HFD, HFD + NAC, HFD + γ-Oryzanol, and HFD + NAC + γ-Oryzanol. NAC was administered orally at a final concentration of 200 mg/kg, whereas γ-Oryzanol was added to diets at a concentration of 0.16. All treatments were conducted for 17 weeks and daily. Both NAC and γ-Oryzanol were able to reduce final body weights, fat weights, fasting glucose, fasting insulin, serum, and serum levels of liver function enzymes as well as the inflammatory markers such as tumor necrosis factor-α (TNF-α), interleukine-6 (IL-6), and leptin in HFD-fed rats. They also improved hepatic structure and glucose tolerance, increased adiponectin levels, and reduced serum and hepatic levels of triglycerides (TGs) and cholesterol (CHOL) in these rats. These effects were concomitant with a reduction in the hepatic levels of lipid peroxides (MDA) and serum levels of LDL-C, but also with an increment in the hepatic levels of superoxide dismutase (SOD) and glutathione (GSH). Interestingly, only treatment with γ-Oryzanol stimulated the mRNA levels of proliferator-activated receptor alpha (PPARα) and carnitine palmitoyltransferase 1 (CPT1) in the liver and white adipose tissue (WAT) of rats. Of note, the combination therapy of both drugs resulted in maximum effects and restored almost normal liver structure and basal levels of all the above-mentioned metabolic parameters. In conclusion, a combination therapy of γ-Oryzanol and NAC is an effective therapy to treat NAFLD, which can act via several mechanisms on the liver and adipose tissue.

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.

Preventive Effects of l-Glutamine on High-Fat Diet-Induced Metabolic Disorders Linking with Regulation of Intestinal Barrier Integrity, Hepatic Lipid Metabolism, and Gut Microbiota in Rats

The present study was conducted to investigate the effects of l-glutamine (Gln) on a high-fat diet (HFD)-induced lipid metabolic abnormality and explore its possible mechanisms. The results demonstrated that Gln administration reduced body weight, improved serum lipids, and decreased glucose tolerance in HFD-fed rats. Meanwhile, Gln administration alleviated liver injury, reduced the hepatic inflammatory response by inhibiting NLRP3 inflammasome activation, and decreased hepatic lipid accumulation by promoting VLDL secretion and fatty acid β-oxidation, as well as reduced bile acid synthesis by activating hepatic and ileal FXR in HFD-fed rats. Moreover, Gln administration restored HFD-induced intestinal barrier dysfunction, promoted intestinal fat absorption, suppressed intestinal inflammation, and also reshaped the gut microbiota composition in HFD-fed rats by downregulating the abundance of potential pathogens Escherichia-Shigella and upregulating the abundance of beneficial bacteria such as Akkermansia. To conclude, the present results showed that Gln may be a potential option for preventing HFD-induced metabolic disorders via the gut-liver axis.

Fenofibrate enhances lipid deposition via modulating PPARγ, SREBP-1c, and gut microbiota in ob/ob mice fed a high-fat diet

Obesity is characterized by lipid accumulation in distinct organs. Presently, fenofibrate is a commonly used triglyceride-lowering drug. This study is designed to investigate whether long-term fenofibrate intervention can attenuate lipid accumulation in ob/ob mouse, a typical model of obesity. Our data demonstrated that fenofibrate intervention significantly decreased plasma triglyceride level by 21.0%, increased liver index and hepatic triglyceride content by 31.7 and 52.1%, respectively, and elevated adipose index by 44.6% compared to the vehicle group. As a PPARα agonist, fenofibrate intervention significantly increased the expression of PPARα protein in the liver by 46.3% and enhanced the expression of LDLR protein by 3.7-fold. However, fenofibrate dramatically increased the expression of PPARγ and SREBP-1c proteins by ~2.1- and 0.9-fold in the liver, respectively. Fenofibrate showed no effects on the expression of genes-related to fatty acid β-oxidation. Of note, it significantly increased the gene expression of FAS and SCD-1. Furthermore, fenofibrate modulated the gut microbiota. Collectively, long-term fenofibrate induces lipid accumulation in liver and adipose tissues in ob/ob mice by enhancing the expression of adipogenesis-related proteins and gut microbiota. These data suggest that fenofibrate may have limited effects on attenuating lipid deposition in obese patients.

Hepatocyte Mitochondrial Dynamics and Bioenergetics in Obesity-Related Non-Alcoholic Fatty Liver Disease

PURPOSE OF THE REVIEW

Mitochondrial dysfunction has long been proposed to play a crucial role in the pathogenesis of a considerable number of disorders, such as neurodegeneration, cancer, cardiovascular, and metabolic disorders, including obesity-related insulin resistance and non-alcoholic fatty liver disease (NAFLD). Mitochondria are highly dynamic organelles that undergo functional and structural adaptations to meet the metabolic requirements of the cell. Alterations in nutrient availability or cellular energy needs can modify their formation through biogenesis and the opposite processes of fission and fusion, the fragmentation, and connection of mitochondrial network areas respectively. Herein, we review and discuss the current literature on the significance of mitochondrial adaptations in obesity and metabolic dysregulation, emphasizing on the role of hepatocyte mitochondrial flexibility in obesity and NAFLD.

RECENT FINDINGS

Accumulating evidence suggests the involvement of mitochondrial morphology and bioenergetics dysregulations to the emergence of NAFLD and its progress to non-alcoholic steatohepatitis (NASH). Most relevant data suggests that changes in liver mitochondrial dynamics and bioenergetics hold a key role in the pathogenesis of NAFLD. During obesity and NAFLD, oxidative stress occurs due to the excessive production of ROS, leading to mitochondrial dysfunction. As a result, mitochondria become incompetent and uncoupled from respiratory chain activities, further promoting hepatic fat accumulation, while leading to liver inflammation, insulin resistance, and disease's deterioration. Elucidation of the mechanisms leading to dysfunctional mitochondrial activity of the hepatocytes during NAFLD is of predominant importance for the development of novel therapeutic approaches towards the treatment of this metabolic disorder.

Fatty acids composition and in vivo biochemical effects of Aleurites moluccana seed (Candlenut) in obese wistar rats

BACKGROUND

Candlenut (CN) has been used indiscriminately for weight loss. In vivo effects of CN in different doses are scarce.

OBJECTIVE

To evaluate the effects of CN ingestion in obese rats.

DESIGN

Thirty animals (obese and non-obese) received one of three different types of treatments: placebo, CN ingestion in a popular therapeutic regimen (8 days with oral administration of 0.2 mg/kg followed by 20 days with doses of 0.4 mg/kg), and ingestion of a doubled popular dose-called 2CN. Treatment was maintained for 28 days.

RESULTS

The fatty acid profile of CN indicated mainly linolelaidic and palmitoleic acids. Rats receiving CN and 2CN showed reduced plasmatic levels of glucose and lipoproteins (p < 0.05). A dose-dependent carcass fat reduction was observed (p < 0.05). Blood levels of aspartate aminotransferase (AST) and gamma-glutamyl transferase (GGT) reduced with CN and increased with 2CN doses (p < 0.05). Alanine aminotransferase (ALT) and the atherogenic index remained similar among all treatments (p > 0.05). Hepatic vacuolation decreased with CN, but the 2CN dose produced mononuclear leucocyte infiltrate.

CONCLUSIONS

Although CN presented beneficial effects on the metabolism of rats, it also caused increased risk of liver damage.

Targeted inhibition of PPARα ameliorates CLA-induced hypercholesterolemia via hepatic cholesterol biosynthesis reprogramming

BACKGROUND & AIMS

Disruption of lipid metabolism is largely linked to metabolic disorders, such as hypercholesterolemia (HCL) and liver steatosis. While cholesterol metabolic re-programmers can serve as targets for relevant interventions. Here we explored the dietary conjugated linoleic acids (CLA)-induced HCL in mice and the molecular regulation behind it.

METHODS

A high dose of CLA supplementation in the diet was used to induce HCL in mice and was found to cause a hyper-activated cholesterol biosynthesis programme in the liver, leading to cholesterol metabolism dysregulation. The effects of a small-molecule drug targeting PPARα, i.e., GW6471 were studied in vivo in mice fed diets with CLA supplementation for 28 days, and in primary hepatocytes derived from HCL-mice in vitro.

RESULTS

We demonstrate that CLA induced HCL and liver steatosis through multiple pathways. Among which was the PPARα-mediated cholesterogenesis. It was found to cooperate with SREBP2 via binding to Hmgcr and Dhcr7 (genes encoding key enzymes of the cholesterol biosynthetic pathway) and recruits the histone marks H3K27ac and H3K4me1 and cofactors. PPARα inhibition disrupts its physical association with SREBP2 by blocking cobinding of PPARα and SREBP2 to the genomic DNA response element. We showed that NR RORγ functions as an essential mediator that facilitates the interaction of PPARα and SREBP2 to modulate the cholesterol biosynthesis genes expression.

CONCLUSIONS

Our study unravels that the small-molecule compound GW6471 exerts an attractive therapeutic effect for CLA-induced HCL, involving multiple pathways with the "PPARα-RORγ-SREBP2" being a potential complex player in this hepatic cholesterol biosynthesis programming.

Comparative Transcriptome Analysis Reveals That Exendin-4 Improves Steatosis in HepG2 Cells by Modulating Signaling Pathways Related to Lipid Metabolism

No therapy exists for non-alcoholic fatty liver disease (NAFLD). However, glucagon-like peptide receptor agonists (GLP-1RAs) showed a beneficial effect on NAFLD, although the underpinning mechanisms remain unclear due to their pleiotropic effects. We examined the implicated signaling pathways using comparative transcriptomics in a cell model of steatosis to overcome pleiotropy. We treated steatotic HepG2 cells with the GLP-1RA Exendin-4 (Ex-4). We compared the transcriptome profiles of untreated steatotic, and Ex-4-treated steatotic cells, and used Ingenuity Pathway Analysis (IPA) to identify the signaling pathways and associated genes involved in the protective effect of Ex-4. Ex-4 treatment significantly reduces steatosis. RNA-seq analysis revealed 209 differentially expressed genes (DEGs) between steatotic and untreated cells, with farnesoid X receptor/retinoid X receptor (FXR/RXR) (p = 8.9 × 10−7) activation being the top regulated canonical pathway identified by IPA. Furthermore, 1644 DEGs were identified between steatotic cells and Ex-4-treated cells, with liver X receptor/retinoid X receptor (LXR/RXR) (p = 2.02 × 10−7) and FXR/RXR (p = 3.28 × 10−7) activation being the two top canonical pathways. The top molecular and cellular functions between untreated and steatotic cells were lipid metabolism, molecular transport, and small molecular biochemistry, while organismal injury and abnormalities, endocrine system disorders, and gastrointestinal disease were the top three molecular and cellular functions between Ex-4-treated and steatotic cells. Genes overlapping steatotic cells and Ex-4-treated cells were associated with several lipid metabolism processes. Unique transcriptomic differences exist between steatotic cells and Ex-4-treated steatotic cells, providing an important resource for understanding the mechanisms that underpin the protective effect of GLP-1RAs on NAFLD and for the identification of novel therapeutic targets for NAFLD.

Homogenised and pasteurised human milk: lipid profile and effect as a supplement in the enteral diet of Wistar rats

The retention of human milk (HM) fat in nasogastric probes of infusion pumps can be observed during the feed of infants unable to suck at the mother's breast. The lack of homogenisation of HM could contribute to the fat holding. Therefore, the present study evaluated (i) the influence of homogenisation on milk fat retaining in infant feeding probes and (ii) the in vivo effect of the homogenisation on lipid absorption by Wistar rats. The animals were fed with HM treated following two processing conditions, that is, pasteurised and homogenised-pasteurised. The animals were randomly subdivided into four experimental groups: water-fed (control), pasteurised milk, homogenised-pasteurised milk and pasteurised-skimmed milk. The results of food consumption, mass body gain, corporate metrics and plasma blood levels of total cholesterol did not show any difference (P < 0·05) among the three types of HM used in the experiments. The liver, intestine and intra-abdominal adipose tissue of the four groups of animals presented normal and healthy histology. The composition of fatty acids in the brain tissue of animals fed with homogenised HM increased when compared with the groups fed with non-homogenised HM. These values were 11·08 % higher for arachidonic acids, 6·59 % for DAH and 47·92 % for nervous acids. The ingestion of homogenised HM promoted higher absorption of milk nutrients. Therefore, the addition of the homogenisation stage in HM processing could be an alternative to reduce fat retention in probes and to improve the lipids' absorption in the body.

Real ambient particulate matter-induced lipid metabolism disorder: Roles of peroxisome proliferators-activated receptor alpha

A growing body of evidence associated particulate matter (PM) exposure with lipid metabolism disorders, yet, the underlying mechanism remains to be elucidated. Among the major lipid metabolism modulators, peroxisome proliferator-activated receptor (PPAR) alpha plays an important role. In the current study, an individually ventilated cage (IVC) system was used to expose C57/B6 mice to real-ambient PM for six weeks, with or without co-treatment of PPAR alpha agonist WY14,643. The general parameters, liver and adipose tissue pathology, serum lipids, metal deposition and lipid profile of liver were assessed. The results indicated that six weeks of real-ambient PM exposure induced dyslipidemia, including increased serum triglycerides (TG) and decreased high density lipoprotein cholesterol (HDL-C) level, along with steatosis in liver, increased size of adipocytes in white adipose tissue (WAT) and whitening of brown adipose tissue (BAT). ICP-MS results indicated increased Cr and As deposition in liver. Lipidomics analysis revealed that glycerophospholipids and cytochrome P450 pathway were most significantly affected by PM exposure. Several lipid metabolism-related genes, including CYP4A14 in liver and UCP1 in BAT were downregulated following PM exposure. WY14,643 treatment alleviated PM-induced dyslipidemia, liver steatosis and whitening of BAT, while enhancing CD36, SLC27A1, CYP4A14 and UCP1 expression. In conclusion, PPAR alpha pathway participates in PM-induced lipid metabolism disorder, PPAR alpha agonist WY14,643 treatment exerted protective effects on PM-induced dyslipidemia, liver steatosis and whitening of BAT, but not on increased adipocyte size of WAT.

Bifidobacterium animalis subsp. lactis A6 Enhances Fatty Acid β-Oxidation of Adipose Tissue to Ameliorate the Development of Obesity in Mice

Fatty acid β-oxidation (FAO) is confirmed to be impaired in obesity, especially in adipose tissues. We previously proved that Bifidobacterium animalis subsp. lactis A6 (BAA6) had protective effects against diet-induced obesity. However, whether BAA6 enhances FAO to ameliorate the development of obesity has not been explored. After being fed with high-fat diet (HFD) for 9 weeks, male C57BL/6J mice were fed HFD or BAA6 for 8 weeks. In vitro study was carried out using 3T3-L1 adipocytes to determine the effect of BAA6 culture supernatant (BAA6-CM). Here, we showed that administration of BAA6 to mice fed with HFD decreased body weight gain (by 5.03 g) and significantly up-regulated FAO in epididymal adipose tissues. In parallel, FAO in 3T3-L1 cells was increased after BAA6-CM treatment. Acetate was identified as a constituent of BAA6-CM that showed a similar effect to BAA6-CM. Furthermore, acetate treatment activated the GPR43-PPARα signaling, thereby promoting FAO in 3T3-L1 cells. The levels of acetate were also elevated in serum and feces (by 1.92- and 2.27-fold) of HFD-fed mice following BAA6 administration. The expression levels of GPR43 and PPARα were increased by 55.45% and 69.84% after BAA6 supplement in the epididymal fat of mice. Together, these data reveal that BAA6 promotes FAO of adipose tissues through the GPR43-PPARα signaling, mainly by increasing acetate levels, leading to alleviating the development of obesity.

Detailed Molecular Mechanisms Involved in Drug-Induced Non-Alcoholic Fatty Liver Disease and Non-Alcoholic Steatohepatitis: An Update

Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are some of the biggest public health challenges due to their spread and increasing incidence around the world. NAFLD is characterized by intrahepatic lipid deposition, accompanied by dyslipidemia, hypertension, and insulin resistance, leading to more serious complications. Among the various causes, drug administration for the treatment of numerous kinds of diseases, such as antiarrhythmic and antihypertensive drugs, promotes the onset and progression of steatosis, causing drug-induced hepatic steatosis (DIHS). Here, we reviewed in detail the major classes of drugs that cause DIHS and the specific molecular mechanisms involved in these processes. Eight classes of drugs, among the most used for the treatment of common pathologies, were considered. The most diffused mechanism whereby drugs can induce NAFLD/NASH is interfering with mitochondrial activity, inhibiting fatty acid oxidation, but other pathways involved in lipid homeostasis are also affected. PubMed research was performed to obtain significant papers published up to November 2021. The key words included the class of drugs, or the specific compound, combined with steatosis, nonalcoholic steatohepatitis, fibrosis, fatty liver and hepatic lipid deposition. Additional information was found in the citations listed in other papers, when they were not displayed in the original search.

Shyy J. Hepatic Reduction in Cholesterol 25-Hydroxylase Aggravates Diet-induced Steatosis

BACKGROUND & AIMS

Cholesterol 25-hydroxylase (Ch25h), converting cholesterol to 25-hydroxycholesterol (25-HC), is critical in modulating cellular lipid metabolism and anti-inflammatory and antiviral activities. However, its role in nonalcoholic fatty liver disease remains unclear.

METHODS

Ch25h expression was detected in livers of ob/ob mice and E3 rats fed a high-fat diet (HFD). Gain- or loss-of-function of Ch25h was performed using Ch25h^+/+ (wild type [WT]) mice receiving AAV8-Ch25h or Ch25h knockout (Ch25h^-/-) mice. WT mice fed an HFD were administered with 25-HC. The Ch25h-LXRα-CYP axis was measured in primary hepatocytes isolated from WT and Ch25h^-/- mice.

RESULTS

We found that Ch25h level was decreased in livers of ob/ob mice and E3 rats fed an HFD. Ch25h^-/- mice fed an HFD showed aggravated fatty liver and decreased level of cytochrome P450 7A1 (CYP7A1), in comparison with their WT littermates. RNA-seq analysis revealed that the differentially expressed genes in livers of HFD-fed Ch25h^-/- mice were involved in pathways of positive regulation of lipid metabolic process, steroid metabolic process, cholesterol metabolic process, and bile acid biosynthetic process. As gain-of-function experiments, WT mice receiving AAV8-Ch25h or 25-HC showed alleviated NAFLD, when compared with the control group receiving AAV8-control or vehicle control. Consistently, Ch25h overexpression significantly elevated the levels of primary and secondary bile acids and CYP7A1 but decreased those of small heterodimer partner and FGFR4.

CONCLUSIONS

Elevated levels of Ch25h and its enzymatic product 25-HC alleviate HFD-induced hepatic steatosis via regulating enterohepatic circulation of bile acids. The underlying mechanism involves 25-HC activation of CYP7A1 via liver X receptor. These data suggest that targeting Ch25h or 25-HC may have therapeutic advantages against nonalcoholic fatty liver disease.

Reducing embryonic mtDNA copy number alters epigenetic profile of key hepatic lipolytic genes and causes abnormal lipid accumulation in adult mice

Adverse fetal environment, in particular a shortage or excess of nutrients, is associated with increased risks of metabolic diseases later in life. However, the molecular mechanisms underlying this developmental origin of adult diseases remain unclear. Here, we directly tested the role of mitochondrial stress in mediating fetal programming in mice by enzymatically depleting mtDNA in zygotes. mtDNA-targeted plasmid microinjection is used to reduce embryonic mtDNA copy number directly, followed by embryo transfer. Mice with reduced zygote mtDNA copy number were born morphologically normal and showed no accelerated body weight gain. However, at 5 months of age these mice showed markedly increased hepatic lipidosis and became glucose-intolerant. Hepatic mRNA and protein expressions of peroxisome proliferator-activated receptor α (Pparα), a key transcriptional regulator of lipid metabolism, were significantly decreased as a result of increased DNA methylation in its proximal regulatory region. These results indicate that perturbation of mitochondrial function around the periconceptional period causes hypermethylation and thus suppressed expression of PPARα in fetal liver, leading to impaired hepatic lipid metabolism. Our findings provide the first direct evidence that mitochondrial stress mediates epigenetic changes associated with fetal programming of adult diseases in a mammalian system.

CD38 Deficiency Protects Mice from High Fat Diet-Induced Nonalcoholic Fatty Liver Disease through Activating NAD+/Sirtuins Signaling Pathways-Mediated Inhibition of Lipid Accumulation and Oxidative Stress in Hepatocytes

Nonalcoholic fatty liver disease (NAFLD) is characterized by excessive lipid accumulation in hepatocytes. CD38 was initially identified as a lymphocyte surface antigen and then has been found to exist in a variety of cell types. Our previous studies showed that CD38-/- mice were resistant to high-fat diet (HFD)-induced obesity. However, the role and mechanism of CD38 in HFD-induced NAFLD is still unclear. Here, we reported that CD38-/- mice significantly alleviated HFD-induced hepatic steatosis. HFD or oleic acid (OA) remarkably increased the mRNA and protein expressions of CD38 in mouse hepatic tissues and primary hepatocytes or hepatic cell lines in vitro and in vivo, suggesting that CD38 might play a role in HFD-induced hepatic steatosis. We observed that CD38 deficiency markedly decreased HFD- or OA-induced the lipid accumulation and oxidative stress in CD38-/- livers or primary hepatocytes, respectively. In contrast, overexpression of CD38 in Hep1-6 cells aggravated OA-induced lipid accumulation and oxidative stress. Furthermore, CD38 deficiency markedly inhibited HFD- or OA-induced the expressions of NOX4, and increased the expression of PPARα, CPT1, ACOX1 and SOD2 in liver tissue and hepatocytes from CD38-/- mice, indicating that CD38 deficiency-mediated the enhancement of fatty acid oxidation and the inhibition of oxidative stress contributed to protecting NAFLD. More importantly, Ex527 (Sirt1 inhibitor) and 3-TYP (Sirt3 inhibitor) significantly enhanced OA-induced lipid accumulation and oxidative stress in CD38-/- primary hepatocytes, suggesting that the anti-lipid accumulation of CD38 deficiency might be dependent on NAD/Sirtuins-mediated enhancement of FAA β-oxidation and suppression of oxidative stress in hepatocytes. In conclusion, we demonstrated that CD38 deficiency protected mice from HFD-induced NAFLD by reducing lipid accumulation and suppressing oxidative stress via activating NAD/Sirtuins signaling pathways.

Mechanisms Mediating the Regulation of Peroxisomal Fatty Acid Beta-Oxidation by PPARα

In mammalian cells, two cellular organelles, mitochondria and peroxisomes, share the ability to degrade fatty acid chains. Although each organelle harbors its own fatty acid β-oxidation pathway, a distinct mitochondrial system feeds the oxidative phosphorylation pathway for ATP synthesis. At the same time, the peroxisomal β-oxidation pathway participates in cellular thermogenesis. A scientific milestone in 1965 helped discover the hepatomegaly effect in rat liver by clofibrate, subsequently identified as a peroxisome proliferator in rodents and an activator of the peroxisomal fatty acid β-oxidation pathway. These peroxisome proliferators were later identified as activating ligands of Peroxisome Proliferator-Activated Receptor α (PPARα), cloned in 1990. The ligand-activated heterodimer PPARα/RXRα recognizes a DNA sequence, called PPRE (Peroxisome Proliferator Response Element), corresponding to two half-consensus hexanucleotide motifs, AGGTCA, separated by one nucleotide. Accordingly, the assembled complex containing PPRE/PPARα/RXRα/ligands/Coregulators controls the expression of the genes involved in liver peroxisomal fatty acid β-oxidation. This review mobilizes a considerable number of findings that discuss miscellaneous axes, covering the detailed expression pattern of PPARα in species and tissues, the lessons from several PPARα KO mouse models and the modulation of PPARα function by dietary micronutrients.

Losartan Prevents Hepatic Steatosis and Macrophage Polarization by Inhibiting HIF-1α in a Murine Model of NAFLD

Hypoxia and hepatosteatosis microenvironments are fundamental traits of nonalcoholic fatty liver disease (NAFLD). Hypoxia-inducible factor-1α (HIF-1α) is a transcription factor that controls the cellular response to hypoxia and is activated in hepatocytes of patients with NAFLD, whereas the route and regulation of lipid droplets (LDs) and macrophage polarization related to systemic inflammation in NAFLD is unknown. Losartan is an angiotensin II receptor antagonist, that approved portal hypertension and related HIF-1α pathways in hepatic injury models. Here, we show that losartan in a murine model of NAFLD significantly decreased hepatic de novo lipogenesis (DNL) as well as suppressed lipid droplets (LDs), LD-associated proteins, perilipins (PLINs), and cell-death-inducing DNA-fragmentation-factor (DFF45)-like effector (CIDE) family in liver and epididymal white adipose tissues (EWAT) of ob/ob mice. Obesity-mediated macrophage M1 activation was also required for HIF-1α expression in the liver and EWAT of ob/ob mice. Administration of losartan significantly diminishes obesity-enhanced macrophage M1 activation and suppresses hepatosteatosis. Moreover, HIF-1α-mediated mitochondrial dysfunction was reversed in ob/ob mice treated with losartan. Together, the regulation of HIF-1α controls LDs protein expression and macrophage polarization, which highlights a potential target for losartan in NAFLD.

TSH attenuates fatty acid oxidation in hepatocytes by reducing the mitochondrial distribution of miR-449a/449b-5p/5194

The elevated thyroid-stimulating hormone (TSH) levels contribute to the abnormal expression/activity of several key hepatic lipid metabolism enzymes. Although miRNAs have been shown to play key roles in hepatic lipid metabolism and are found in isolated mitochondria, very little is known about the pathological and physiological significance of their mitochondrial distributions in regulating liver lipid metabolism. Here, we found that TSH significantly reduced the distribution of some miRNAs in mitochondria of hepatocytes, especially miR-449a, miR-449b-5p, and miR-5194. These three miRNAs inhibited their target genes PGC1B, ABCD1, ADIPOR1 and the downstream molecule PPARA. These effects synergistically suppressed fatty acid (FA) β-oxidation in mitochondria and peroxisomes and decreased the translocation of cytosolic very long chain fatty acids to peroxisomes, which noticeably reduced FA catabolism and promoted triglyceride accumulation in hepatocytes. This study reveals the functional significance of changed miRNA mitochondrial-cytoplasmic distribution in the regulation of hepatic lipid metabolism.

Protective Effect of Cudrania tricuspidata Extract against High-Fat Diet Induced Nonalcoholic Fatty Liver Disease through Nrf-2/HO-1 Pathway

Nonalcoholic fatty liver disease is the most common chronic disease affecting a wide range of the world’s population and associated with obesity-induced metabolic syndrome. It is possibly emerging as a leading cause of life-threatening liver diseases for which a drug with a specific therapeutic target has not been developed yet. Previously, there have been reports on the benefits of Cudrania tricuspidata (CT) for treating obesity and diabetes via regulation of metabolic processes, such as lipogenesis, lipolysis, and inflammation. In this study, we investigated the ameliorative effect of orally administered 0.25% and 0.5% (w/w) CT mixed with high-fat diet (HFD) to C57BL/6J mice for 7 weeks. It was found that body weight, fat mass, hepatic mass, serum glucose level, and liver cholesterol levels were significantly reduced after CT treatment. In CT-treated HFD-fed mice, the mRNA expression levels of hepatic lipogenic and inflammatory cytokine-related genes were markedly reduced, whereas the expression level of epididymal lipogenic genes was increased. The mRNA expression level of beta-oxidation and Nrf-2/HO-1 genes significantly increased in CT-treated obese mice livers. We propose that CT alleviates hepatic steatosis by reducing oxidative stress and inflammation.

Tart cherry (Prunus cerasus L.) dietary supplement modulates visceral adipose tissue CB1 mRNA levels along with other adipogenesis-related genes in rat models of diet-induced obesity

PURPOSE

There is increasing evidence for the involvement of dietary bioactive compounds in the cross-talk modulation of endocannabinoid system and some of the key regulators of transcriptional control for adipogenesis.

METHODS

We aimed to characterize the expression of cannabinoid CB1/CB2 receptors and fatty acid amide hydrolase (FAAH) along with selected adipogenesis-related genes (PPARγ, SREBP-1c and PREF-1), adipocyte-secreted factors (leptin and adiponectin), mitochondrial bioenergetic modulators (PGC-1A and UCP-2), and transient receptor potential vanilloid subtype 1 (TRPV1) and 2 (TRPV2) channels in visceral adipose tissue of rats fed with a high-fat diet (HFD) containing either tart cherry seeds alone or tart cherry seeds and juice for 17 weeks. The visceral adipose tissue was weighed and checked the expression of different markers by qRT-PCR, Western blot and immunohistochemistry.

RESULTS

Tart cherry supplements were able to downregulate the HFD-induced mRNA expression of CB1 receptor, SREBP-1c, PPARγ, leptin, TRPV1 and TRPV2 resulting in potential anti-adipogenic effects.

CONCLUSION

The present study points out that the intake of bioactive constituents of tart cherry may attenuate the effect of adipogenesis by acting directly on the adipose tissue and modulating the interplay between CB1, PPARγ and TRPV channel gene transcription.

Co-option of PPARα in the regulation of lipogenesis and fatty acid oxidation in CLA-induced hepatic steatosis

Nonalcoholic-fatty-liver-disease (NAFLD) is the result of imbalances in hepatic lipid partitioning and is linked to dietary factors. We demonstrate that conjugated linoleic acid (CLA) when given to mice as a dietary supplement, induced an enlarged liver, hepatic steatosis, and increased plasma levels of fatty acid (FA), alanine transaminase, and triglycerides. The progression of NAFLD and insulin resistance was reversed by GW6471 a small-molecule antagonist of peroxisome proliferator-activated receptor α (PPARα). Transcriptional profiling of livers revealed that the genes involved in FA oxidation and lipogenesis as two core gene programs controlled by PPARα in response to CLA and GW6471 including Acaca and Acads. Bioinformatic analysis of PPARα ChIP-seq data set and ChIP-qPCR showed that GW6471 blocks PPARα binding to Acaca and Acads and abolishes the PPARα-mediated local histone modifications of H3K27ac and H3K4me1 in CLA-treated hepatocytes. Thus, our findings reveal a dual role of PPARα in the regulation of lipid homeostasis and highlight its druggable nature in NAFLD.

High-fat diet induces fibrosis in mice lacking CYP2A5 and PPARα: a new model for steatohepatitis-associated fibrosis

Obesity is linked to nonalcoholic steatohepatitis. Peroxisome proliferator-activated receptor-α (PPARα) regulates lipid metabolism. Cytochrome P-450 2A5 (CYP2A5) is a potential antioxidant and CYP2A5 induction by ethanol is CYP2E1 dependent. High-fat diet (HFD)-induced obesity and steatosis are more severe in CYP2A5 knockout (cyp2a5^-/-) mice than in wild-type mice although PPARα is elevated in cyp2a5^-/- mice. To examine why the upregulated PPARα failed to prevent the enhanced steatosis in cyp2a5^-/- mice, we abrogate the upregulated PPARα in cyp2a5^-/- mice by cross-breeding cyp2a5^-/- mice with PPARα knockout (pparα^-/-) mice to create pparα^-/-/cyp2a5^-/- mice. The pparα^-/-/cyp2a5^-/- mice, pparα^-/- mice, and cyp2a5^-/- mice were fed HFD to induce steatosis. After HFD feeding, more severe steatosis was developed in pparα^-/-/cyp2a5^-/- mice than in pparα^-/- mice and cyp2a5^-/- mice. The pparα^-/-/cyp2a5^-/- mice and pparα^-/- mice exhibited comparable and impaired lipid metabolism. Elevated serum alanine transaminase and liver interleukin-1β, liver inflammatory cell infiltration, and foci of hepatocellular ballooning were observed in pparα^-/-/cyp2a5^-/- mice but not in pparα^-/- mice and cyp2a5^-/- mice. In pparα^-/-/cyp2a5^-/- mice, although redox-sensitive transcription factor nuclear factor erythroid 2-related factor 2 and its target antioxidant genes were upregulated as a compensation, thioredoxin was suppressed, and phosphorylation of JNK and formation of nitrotyrosine adduct were increased. Liver glutathione was decreased, and lipid peroxidation was increased. Interestingly, inflammation and fibrosis were all observed within the clusters of lipid droplets, and these lipid droplet clusters were all located inside the area with CYP2E1-positive staining. These results suggest that HFD-induced fibrosis in pparα^-/-/cyp2a5^-/- mice is associated with steatosis, and CYP2A5 interacts with PPARα to participate in regulating steatohepatitis-associated fibrosis.

Sweroside ameliorates NAFLD in high-fat diet induced obese mice through the regulation of lipid metabolism and inflammatory response

ETHNOPHARMACOLOGICAL RELEVANCE

Sweroside, an iridoid derived from Traditional Chinese Medicine, is an active component in Swertia pseudochinensis Hara. Swertia pseudochinensis Hara is first recorded in "Inner Mongolia Chinese Herb Medicine"and is considered as a folk medicine for treating hepatitis in northern China.

AIM OF THE STUDY

This study sought to elucidate the role of sweroside in high fat diet induced obesity and fatty liver by using mouse model and investigated the primary molecular mechanism via transcriptomics analysis.

MATERIALS AND METHODS

C57BL/6 mice were fed high-fat diet (HFD) for 14 weeks to induce obesity, hyperglycemia, and fatty liver. These mice were subsequently treated with HFD alone or mixed with sweroside (at a daily dosage of 60 mg per kg of BW, 120 mg per kg of BW and 240 mg per kg of BW) for 6 weeks. BW and food intake was monitored weekly. Biochemical and pathological analysis were conducted to investigate the effect of sweroside on NAFLD. RNA-sequence and RT-qPCR analysis were performed to analyze the potential mechanism.

RESULTS

The mice treated with sweroside were resistant to HFD-induced body weight gain, insulin resistance and hepatic steatosis. Ingenuity pathway analysis (IPA) demonstrated that hepatic gene networks related to lipid metabolism and inflammatory response were down-regulated in the HFD + sweroside group. PPAR-ɑ was located in the center of the hepatic gene network, and the significantly altered genes were CD36 and FGF21, which are related to hepatic inflammation and lipid metabolism. Consistently, upstream-regulators analysis revealed that the main enriched upstream-regulator was PPAR-ɑ.

CONCLUSION

Our results indicate that sweroside may ameliorate obesity with fatty liver via the regulation of lipid metabolism and inflammatory responses. The beneficial effects of sweroside might be closely associated with the regulation of PPAR-α.

Ginsenosides reduce body weight and ameliorate hepatic steatosis in high fat diet‑induced obese mice via endoplasmic reticulum stress and p‑STAT3/STAT3 signaling

Obesity has been increasing globally for over three decades. According to previous studies, dietary obesity is usually associated with endoplasmic reticulum stress (ERS) and STAT3 signaling, which result in interference with the homeostatic control of energy and lipid metabolism. Ginsenosides (GS) administered to mice will modulate adiposity and food intake; however, the mechanism of food inhibition is unknown. The aim of the present study was to investigate whether GS may inhibit ERS and regulate STAT3 phosphorylation in GT1‑7 cells (a mouse hypothalamus gonadotropin‑releasing hormone neuron cell line) and the hypothalamus in order to reduce the body weight and ameliorate hepatic steatosis in high fat diet (HFD)‑induced obese mice. In the present study, GS inhibited the appetite, reduced the body weight, visceral fat, body fat content and blood glucose, and ameliorated the glucose tolerance of the obese mice compared with HFD mice. In addition, the levels of aspartate aminotransferase and alanine aminotransferase, triglyceride (TG), leptin and insulin in the serum were reduced compared with HFD mice. There was less TG in the liver, but more in the feces compared with HFD mice. Using hematoxylin and eosin staining of HepG2 cells and liver tissues, GS were demonstrated to improve the non‑alcoholic fatty liver of the HFD‑induced obese mice and reduce the diameter of the fat cells compared with HFD mice. GS also increased oxygen consumption and carbon dioxide emissions in the metabolic cage data compared with HFD mice. In the GT1‑7 cells, GS alleviated the ERS induced by tunicamycin and enhanced the activation of the STAT3 phosphorylation pathway. Furthermore the ERS of the liver was relieved to achieve the aforementioned pharmacological effects. GS were used in the homeostatic control of the energy and lipid metabolism of a diet‑induced obesity model. In conclusion, present studies suggest that GS exert these effects by increasing STAT3 phosphorylation expression and reducing the ERS. Thus, GS reduce body weight and ameliorate hepatic steatosis in HFD‑induced obese mice.

Role of farnesoid X receptor in hepatic steatosis in nonalcoholic fatty liver disease

With the increased incidence of obesity, nonalcoholic fatty liver disease (NAFLD) has become a major global health concern. The pathogenesis of NAFLD has not yet been fully elucidated, and as few efficient pharmaceutical treatments are available for the condition, economic and medical burdens are heavy. Hepatic steatosis, as a precursor of NAFLD, plays a vital role in the pathological process of NAFLD. Hepatic steatosis is a consequence of lipid acquisition (i.e. free fatty acid uptake and de novo lipogenesis) exceeding lipid disposal (i.e. fatty acid oxidation and export as very-low-density lipoproteins). Therefore, restoring lipid homeostasis in the liver is an important therapeutic strategy of NAFLD. Farnesoid X receptor (FXR) is a major member of the ligand-activated nuclear receptor superfamily. Previous reviews have shown that FXR is a multipurpose receptor that plays an important role in regulating bile acid homeostasis, glucose and lipid metabolism, intestinal bacterial growth, and hepatic regeneration. This review focuses on the role of FXR in individual pathways that contribute to hepatic steatosis; it further demonstrates the molecular function of FXR in the pathogenesis of NAFLD.

Genetic polymorphisms of PPAR genes and human cancers: evidence for gene-environment interactions

Peroxisome proliferator-activated receptors (PPARs) are nuclear transcription factors that play a role in lipid metabolism, cell proliferation, terminal differentiation, apoptosis, and inflammation. Although several cancer models have been suggested to explain PPARs' involvement in tumorigenesis, however, their role is still unclear. In this review, we examined associations of the different PPARs, polymorphisms and various types of cancer with a focus on gene-environment interactions. Reviewed evidence suggests that functional genetic variants of the different PPARs may modulate the relationship between environmental exposure and cancer risk. In addition, this report unveils the scarcity of reliable quantitative environmental exposure data when examining these interactions, and the current gaps in studying gene-environment interactions in many types of cancer, particularly colorectal, prostate, and bladder cancers.

Dynamic repression by BCL6 controls the genome-wide liver response to fasting and steatosis

Transcription is tightly regulated to maintain energy homeostasis during periods of feeding or fasting, but the molecular factors that control these alternating gene programs are incompletely understood. Here, we find that the B cell lymphoma 6 (BCL6) repressor is enriched in the fed state and converges genome-wide with PPARα to potently suppress the induction of fasting transcription. Deletion of hepatocyte Bcl6 enhances lipid catabolism and ameliorates high-fat-diet-induced steatosis. In Ppara-null mice, hepatocyte Bcl6 ablation restores enhancer activity at PPARα-dependent genes and overcomes defective fasting-induced fatty acid oxidation and lipid accumulation. Together, these findings identify BCL6 as a negative regulator of oxidative metabolism and reveal that alternating recruitment of repressive and activating transcription factors to shared cis-regulatory regions dictates hepatic lipid handling.

CYP2A6 is associated with obesity: studies in human samples and a high fat diet mouse model

BACKGROUND/OBJECTIVES

CYP2A6 (CYP2A5 in mice) is mainly expressed in the liver. Hepatic CYP2A6 expression is increased in patients with non-alcoholic fatty liver disease (NAFLD). In mice, hepatic CYP2A5 is induced by high fat diet (HFD) feeding. Hepatic CYP2A5 is also increased in monosodium glutamate-induced obese mice. NAFLD is associated with obesity. In this study, we examined whether obesity is related to CYP2A6.

SUBJECTS/METHODS

Obesity genetic association study: The SAGE is a comprehensive genome-wide association study (GWAS) with case subjects having a lifetime history of alcohol dependence and control subjects never addicted to alcohol. We used 1030 control individuals with self-reported height and weight. A total of 12 single nucleotide polymorphisms (SNP) within the CYP2A6 gene were available. Obesity was determined as a BMI ≥30: 30-34.9 (Class I obesity) and ≥35 (Class II and III obesity). Animal experiment study: CYP2A5 knockout (cyp2a5-/-) mice and wild type (cyp2a5+/+) mice were fed HFD for 14 weeks. Body weight was measured weekly. After an overnight fast, the mice were sacrificed. Liver and blood were collected for biochemical assays.

RESULTS

Single marker analysis showed that three SNPs (rs8192729, rs7256108, and rs7255443) were associated with class I obesity (p < 0.05). The most significant SNP for obesity was rs8192729 (odds ratio (OR) = 1.94, 95% confidence intervals = 1.21-3.10, p = 0.00582). After HFD feeding, body weight was increased in cyp2a5-/- mice to a greater extent than in cyp2a5+/+ mice, and fatty liver was more pronounced in cyp2a5-/- mice than in cyp2a5+/+ mice. PPARα deficiency in cyp2a5-/- mice developed more severe fatty liver, but body weight was not increased significantly.

CONCLUSION

CYP2A6 is associated with human obesity; CYP2A5 protects against obesity and NAFLD in mice. PPARα contributes to the CYP2A5 protective effects on fatty liver but it opposes to the protective effects on obesity.

Reactive Oxygen Species Induces Lipid Droplet Accumulation in HepG2 Cells by Increasing Perilipin 2 Expression

Non-alcoholic fatty liver disease (NAFLD) has become the world's most common liver disease. The disease can develop liver fibrosis or even carcinomas from the initial hepatic steatosis, and this process is influenced by many factors. Reactive oxygen species (ROS), as potent oxidants in cells, have been reported previously to play an important role in the development of NAFLD progression via promoting neutral lipid accumulation. Here, we found that ROS can promote lipid droplet formation in hepatocytes by promoting perilipin2 (PLIN2) expression. First, we used different concentrations of hydrogen peroxide to treat HepG2 cells and found that the number of lipid droplets in the cells increased, however also that this effect was dose-independent. Then, the mRNA level of several lipid droplet-associated genes was detected with hydrogen peroxide treatment and the expression of PLIN2, PLIN5, and FSP27 genes was significantly up-regulated (p < 0.05). We overexpressed PLIN2 in HepG2 cells and found that the lipid droplets in the cells were markedly increased. Interference with PLIN2 inhibits ROS-induced lipid droplet formation, revealing that PLIN2 is a critical factor in this process. We subsequently analyzed the regulatory pathway and protein interaction network that is involved in PLIN2 and found that PLIN2 can regulate intracellular lipid metabolism through the PPARα/RXRA and CREB/CREBBP signaling pathways. The majority of the data indicated the correlation between hydrogen peroxide-induced PLIN2 and lipid droplet upregulation. In conclusion, ROS up-regulates the expression of PLIN2 in hepatocytes, whereas PLIN2 promotes the formation of lipid droplets resulting in lipid accumulation in liver tissues.

Molecular mechanisms of hepatic lipid accumulation in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is currently the world's most common liver disease, estimated to affect up to one-fourth of the population. Hallmarked by hepatic steatosis, NAFLD is associated with a multitude of detrimental effects and increased mortality. This narrative review investigates the molecular mechanisms of hepatic steatosis in NAFLD, focusing on the four major pathways contributing to lipid homeostasis in the liver. Hepatic steatosis is a consequence of lipid acquisition exceeding lipid disposal, i.e., the uptake of fatty acids and de novo lipogenesis surpassing fatty acid oxidation and export. In NAFLD, hepatic uptake and de novo lipogenesis are increased, while a compensatory enhancement of fatty acid oxidation is insufficient in normalizing lipid levels and may even promote cellular damage and disease progression by inducing oxidative stress, especially with compromised mitochondrial function and increased oxidation in peroxisomes and cytochromes. While lipid export initially increases, it plateaus and may even decrease with disease progression, sustaining the accumulation of lipids. Fueled by lipo-apoptosis, hepatic steatosis leads to systemic metabolic disarray that adversely affects multiple organs, placing abnormal lipid metabolism associated with NAFLD in close relation to many of the current life-style-related diseases.

Mitochondrial role in the neonatal predisposition to developing nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a global epidemic in obese children and adults, and the onset might have fetal origins. A growing body of evidence supports the role of developmental programming, whereby the maternal environment affects fetal and infant development, altering the risk profile for disease later in life. Human and nonhuman primate studies of maternal obesity demonstrate that risk factors for pediatric obesity and NAFLD begin in utero. The pathologic mechanisms for NAFLD are multifactorial but have centered on altered mitochondrial function/dysfunction that might precede insulin resistance. Compared with the adult liver, the fetal liver has fewer mitochondria, low activity of the fatty acid metabolic enzyme carnitine palmitoyl-CoA transferase-1, and little or no gluconeogenesis. Exposure to excess maternal fuels during fetal life uniquely alters hepatic fatty acid oxidation, tricarboxylic acid cycle activity, de novo lipogenesis, and mitochondrial health. These events promote increased oxidative stress and excess triglyceride storage, and, together with altered immune function and epigenetic changes, they prime the fetal liver for NAFLD and might drive the risk for nonalcoholic steatohepatitis in the next generation.

Functional Comparison of High and Low Molecular Weight Chitosan on Lipid Metabolism and Signals in High-Fat Diet-Fed Rats

The present study examined and compared the effects of low- and high-molecular weight (MW) chitosan, a nutraceutical, on lipid metabolism in the intestine and liver of high-fat (HF) diet-fed rats. High-MW chitosan as well as low-MW chitosan decreased liver weight, elongated the small intestine, improved the dysregulation of blood lipids and liver fat accumulation, and increased fecal lipid excretion in rats fed with HF diets. Supplementation of both high- and low-MW chitosan markedly inhibited the suppressed phosphorylated adenosine monophosphate (AMP)-activated protein kinase-α (AMPKα) and peroxisome proliferator-activated receptor-α (PPARα) protein expressions, and the increased lipogenesis/cholesterogenesis-associated protein expressions [peroxisome proliferator-activated receptor-γ (PPARγ), sterol regulatory element binding protein-1c and -2 (SREBP1c and SREBP2)] and the suppressed apolipoprotein E (ApoE) and microsomal triglyceride transfer protein (MTTP) protein expressions in the livers of rats fed with HF diets. Supplementation with both a low- and high-MW chitosan could also suppress the increased MTTP protein expression and the decreased angiopoietin-like protein-4 (Angptl4) expression in the intestines of rats fed with HF diets. In comparison between low- and high-MW chitosan, high-MW chitosan exhibits a higher efficiency than low-MW chitosan on the inhibition of intestinal lipid absorption and an increase of hepatic fatty acid oxidation, which can improve liver lipid biosynthesis and accumulation.