Specific Inhibition of Acyl-CoA Oxidase-1 by an Acetylenic Acid Improves Hepatic Lipid and Reactive Oxygen Species (ROS) Metabolism in Rats Fed a High Fat Diet

Fasting induces hepatic lipid accumulation by stimulating peroxisomal dicarboxylic acid oxidation

Fasting induces lipid accumulation in the liver, while the mechanisms by which fasting dysregulates liver fatty acid oxidation are not clear. Fatty acid ω-oxidation is induced in the fasting state, and administration of dicarboxylic acids to fasting animals decreases plasma ketone bodies. We hypothesized that endogenous dicarboxylic acids might play a role in controlling mitochondrial β-oxidation in fasting animals. A peroxisome proliferator-activated receptor-alpha agonist and an inhibitor for peroxisomal β-oxidation were administered to the fasting rats to investigate the role of dicarboxylic acids in liver fatty acid oxidation and lipid homeostasis. We observed that excessive β-oxidation of endogenous dicarboxylic acids by peroxisomes generated considerable levels of succinate in the liver. Excessive succinate oxidation subsequently increased the mitochondrial NADH/NAD⁺ ratio and led to an accumulation of 3-OH-CoA and 2-enoyl-CoA intermediates in the liver. This further induced feedback suppression of mitochondrial β-oxidation and promoted hepatic lipid deposition and steatosis. Specific inhibition of peroxisomal β-oxidation attenuated fasting-induced lipid deposition in the liver by reducing succinate production and enhancing mitochondrial fatty acid oxidation. We conclude that suppression of mitochondrial β-oxidation by oxidation of dicarboxylic acids serves as a mechanism for fasting-induced hepatic lipid accumulation and identifies cross talk between peroxisomal and mitochondrial fatty acid oxidation.

ACOX1, regulated by C/EBPα and miR-25-3p, promotes bovine preadipocyte adipogenesis

Acyl-coenzyme A oxidase 1 (ACOX1) is the first and rate-limiting enzyme in peroxisomal fatty acid β-oxidation of fatty acids. Previous studies have reported that ACOX1 was correlated with the meat quality of livestock, while the role of ACOX1 in intramuscular adipogenesis of beef cattle and its transcriptional and post-transcriptional regulatory mechanisms remain unclear. In the present study, gain-of-function and loss-of-function assays demonstrated that ACOX1 positively regulated the adipogenesis of bovine intramuscular preadipocytes. The C/EBPα-binding sites in the bovine ACOX1 promoter region at -1142 to -1129 bp, -831 to -826 bp, and -303 to -298 bp were identified by promoter deletion analysis and site-directed mutagenesis. Electrophoretic mobility shift assays (EMSA) and chromatin immunoprecipitation (ChIP) further showed that these three regions are C/EBPα-binding sites, both in vitro and in vivo, indicating that C/EBPα directly interacts with the bovine ACOX1 promoter and inhibits its transcription. Furthermore, the results from bioinformatics analysis, dual luciferase assay, site-directed mutagenesis, qRT-PCR, and Western blotting demonstrated that miR-25-3p directly targeted the ACOX1 3'UTR (3'UTR). Taken together, our findings suggest that ACOX1, regulated by transcription factor C/EBPα and miR-25-3p, promotes adipogenesis of bovine intramuscular preadipocytes via regulating peroxisomal fatty acid β-oxidation.

Dysregulated Provision of Oxidisable Substrates to the Mitochondria in ME/CFS Lymphoblasts

Although understanding of the biomedical basis of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is growing, the underlying pathological mechanisms remain uncertain. We recently reported a reduction in the proportion of basal oxygen consumption due to ATP synthesis by Complex V in ME/CFS patient-derived lymphoblast cell lines, suggesting mitochondrial respiratory inefficiency. This was accompanied by elevated respiratory capacity, elevated mammalian target of rapamycin complex 1 (mTORC1) signaling activity and elevated expression of enzymes involved in the TCA cycle, fatty acid β-oxidation and mitochondrial transport. These and other observations led us to hypothesise the dysregulation of pathways providing the mitochondria with oxidisable substrates. In our current study, we aimed to revisit this hypothesis by applying a combination of whole-cell transcriptomics, proteomics and energy stress signaling activity measures using subsets of up to 34 ME/CFS and 31 healthy control lymphoblast cell lines from our growing library. While levels of glycolytic enzymes were unchanged in accordance with our previous observations of unaltered glycolytic rates, the whole-cell proteomes of ME/CFS lymphoblasts contained elevated levels of enzymes involved in the TCA cycle (p = 1.03 × 10⁻⁴), the pentose phosphate pathway (p = 0.034, G6PD p = 5.5 × 10⁻⁴), mitochondrial fatty acid β-oxidation (p = 9.2 × 10⁻³), and degradation of amino acids including glutamine/glutamate (GLS p = 0.034, GLUD1 p = 0.048, GOT2 p = 0.026), branched-chain amino acids (BCKDHA p = 0.028, BCKDHB p = 0.031) and essential amino acids (FAH p = 0.036, GCDH p = 0.006). The activity of the major cellular energy stress sensor, AMPK, was elevated but the increase did not reach statistical significance. The results suggest that ME/CFS metabolism is dysregulated such that alternatives to glycolysis are more heavily utilised than in controls to provide the mitochondria with oxidisable substrates.

High fat suppresses SOD1 activity by reducing copper chaperone for SOD1 associated with neurodegeneration and memory decline

High fat consumption leads to reactive oxygen species (ROS) which is associated with age-progressive neurological disorders. Cu/Zn superoxide dismutase (SOD1) is a critical enzyme against ROS. However, the relationship between SOD1 and the high-fat-induced ROS and neurodegeneration is poorly known. Here we showed that, upon treatment with a saturated fatty acid palmitic acid (PA), the SOD1 activity was decreased in mouse neuronal HT-22 cell line accompanied by elevation of ROS, but not in mouse microglial BV-2 cell line. We further showed that PA decreased the levels of copper chaperone for SOD1 (CCS) in HT-22 cells, which promoted the nuclear import of SOD1 and decreased its activity. We demonstrated that the reduction of CCS is involved in the PA-induced decrease of SOD1 activity and elevation of ROS. In addition, compared with the adult mice fed with a standard diet, the high-fat-diet adult mice presented an increase of plasma free fatty acids, reduction of hippocampal SOD1 activity and CCS, mitochondrial degeneration and long-term memory decline. Taken together, our findings suggest that the high-fat-induced lower CCS level is essential for SOD1 suppression which may be associated with neurodegeneration and cognitive decline.

Anti-influenza A Virus Effects and Mechanisms of Emodin and Its Analogs via Regulating PPARα/γ-AMPK-SIRT1 Pathway and Fatty Acid Metabolism

The peroxisome proliferator-activated receptor (PPAR) α/γ-adenosine 5'-monophosphate- (AMP-) activated protein kinase- (AMPK-) sirtuin-1 (SIRT1) pathway and fatty acid metabolism are reported to be involved in influenza A virus (IAV) replication and IAV-pneumonia. Through a cell-based peroxisome proliferator responsive element- (PPRE-) driven luciferase bioassay, we have investigated 145 examples of traditional Chinese medicines (TCMs). Several TCMs, such as Polygonum cuspidatum, Rheum officinale Baillon, and Aloe vera var. Chinensis (Haw.) Berg., were found to possess high activity. We have further detected the anti-IAV activities of emodin (EMO) and its analogs, a group of common important compounds of these TCMs. The results showed that emodin and its several analogs possess excellent anti-IAV activities. The pharmacological tests showed that emodin significantly activated PPARα/γ and AMPK, decreased fatty acid biosynthesis, and increased intracellular ATP levels. Pharmaceutical inhibitors, siRNAs for PPARα/γ and AMPKα1, and exogenous palmitate impaired the inhibition of emodin. The in vivo test also showed that emodin significantly protected mice from IAV infection and pneumonia. Pharmacological inhibitors for PPARα/γ and AMPK signal and exogenous palmitate could partially counteract the effects of emodin in vivo. In conclusion, emodin and its analogs are a group of promising anti-IAV drug precursors, and the pharmacological mechanism of emodin is linked to its ability to regulate the PPARα/γ-AMPK pathway and fatty acid metabolism.

Replacing fish oil and astaxanthin by microalgal sources produced different metabolic responses in juvenile rainbow trout fed 2 types of practical diets

Dietary fish oil supplementation provides n-3 long-chained polyunsaturated fatty acids for supporting fish growth and metabolism and enriching fillet with eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; c22:6n-3). Two experiments were performed as a 3 × 2 factorial arrangement of dietary treatments for 16 wk to determine effects and mechanisms of replacing 0%, 50%, and 100% fish oil with DHA-rich microalgae in combination with synthetic vs. microalgal source of astaxanthin in plant protein meal (PM)- or fishmeal (FM)- based diets for juvenile rainbow trout (Oncorhynchus mykiss). Fish (22 ± 0.26 g) were stocked at 17/tank and 3 tanks/diet. The 100% fish oil replacement impaired (P < 0.0001) growth performance, dietary protein and energy utilization, body indices, and tissue accumulation of DHA and EPA in both diet series. The impairments were associated (P < 0.05) with upregulation of hepatic gene expression related to growth (ghr1and igf1) and biosynthesis of DHA and EPA (fads6 and evol5) that was more dramatic in the FM than PM diet-fed fish, and more pronounced on tissue EPA than DHA concentrations. The source of astaxanthin exerted interaction effects with the fish oil replacement on several measures including muscle total cholesterol concentrations. In conclusion, replacing fish oil by the DHA-rich microalgae produced more negative metabolic responses than the substitution of synthetic astaxanthin by the microalgal source in juvenile rainbow trout fed 2 types of practical diets.

The inflammatory environment mediated by a high-fat diet inhibited the development of mammary glands and destroyed the tight junction in pregnant mice

Long-term intake of a high-fat diet seriously affects the health of pregnant women and leads to increased levels of inflammation in the mammary gland. Therefore, to further explore the effect of a high-fat diet on mammary gland development and the tight junction (TJ) during pregnancy, we placed mice into two groups: a high-fat diet group and a control group. We detected the expression of proteins related to fat synthesis in the mammary gland by western blotting. The results showed that a high-fat diet could lead to an increase in fat synthesis in the mammary gland. Then, the inflammatory levels and acinar cell morphology in the mammary gland were detected by ELISA and H&E staining. We also measured the levels of MAPK and NF-κB signal pathway-related proteins by western blotting. The results showed that a high-fat diet activated the MAPK and NF-κB signaling pathways and promoted the expression of inflammatory factors. Finally, the development of the mammary gland and the integrity of the TJ were determined by immunohistochemistry, immunofluorescence and western blotting. The results showed that a high-fat diet inhibited the development of the mammary gland and the expression of tight junction proteins (TJs). Our study showed that a high-fat diet could promote the expression of inflammatory factors by activating the MAPK and NF-κB signaling pathways and could reshape the microenvironment through extramammary inflammation. Finally, a high-fat diet inhibited the development of the mammary gland during pregnancy and destroyed the integrity of the TJ.

Impaired peroxisomal fat oxidation induces hepatic lipid accumulation and oxidative damage in Nile tilapia

Many metabolic diseases in fish are often associated with lowered peroxisomal fatty acid (FA) β-oxidation. However, the physiological role of peroxisomal FA oxidation in lipid metabolism in fish still remains unclear. In the present study, a specific peroxisomal FA β-oxidation inhibitor, 10,12-tricosadiynoic acid (TDYA), was used to investigate the effects of impaired peroxisomal β-oxidation on growth performance, health status, and lipid metabolism in Nile tilapia. The results showed that the dietary TDYA treatment did not affect weight gain, but significantly decreased peroxisomal β-oxidation in the liver, and increased body fat accumulation. The fish with impaired peroxisomal β-oxidation exhibited higher contents of serum lipid and peroxidation products, and alanine aminotransferase activity, and significantly lowered hepatic activities of superoxide dismutase and catalase. The inhibited peroxisomal β-oxidation did not enhance mitochondrial β-oxidation activity, but compensatorily upregulated FA β-oxidation-related gene expression, and downregulated the gene expressions in lipolysis and lipogenesis. Taken together, TDYA treatment markedly induced lipid accumulation and hepatic oxidative damage via systemically depressing lipid catabolism and antioxidant capacity. Our findings reveal the pivotal roles of peroxisomal β-oxidation in maintaining health and lipid homeostasis in fish, and could be helpful in understanding metabolic diseases in fish.

High-fat but not normal-fat intake of extra virgin olive oil modulates the liver proteome of mice

PURPOSE

The metabolic benefits of the Mediterranean diet have been largely attributed to its olive oil content. Whether the ingested fat amount is relevant to these effects is not clear. We thus compared the effects of high-fat and normal-fat intake of extra-virgin olive oil (EVOO) on the liver proteome.

METHODS

Three groups of mice were fed for 12 weeks with either normal-fat diets containing either soybean oil (control, C) or EVOO (NO) or a high-fat EVOO diet (HO). Body weight and food intake were measured weekly and serum parameters were analyzed. The liver was processed for data-independent acquisition mass spectrometry-based proteomics. The differentially expressed proteins among the groups were submitted to pathway enrichment analysis.

RESULTS

The consumption of HO diet reduced food intake and serum triglycerides, while it preserved body weight gain, adiposity, and glycemia. However, it increased serum cholesterol and liver mass. The proteomic analysis showed 98 altered proteins, which were allocated in 27 significantly enriched pathways. The pathway analysis suggested stimulation of mitochondrial and peroxissomal β-oxidation, and inhibition of lipid synthesis and gluconeogenesis in the HO group. Although the NO group failed to show significant liver proteome alterations, it presented reduced body fat, body weight gain, and serum triglycerides and glucose levels.

CONCLUSION

The data indicate that the intake of the HO diet induced hepatic adjustments, which were partially successful in counteracting the detrimental outcomes of a high-fat feeding. Contrastingly, the NO diet had beneficial effects which were not accompanied by significant modifications on hepatic proteome.

Peroxisomal oxidation of erucic acid suppresses mitochondrial fatty acid oxidation by stimulating malonyl-CoA formation in the rat liver

Feeding of rapeseed (canola) oil with a high erucic acid concentration is known to cause hepatic steatosis in animals. Mitochondrial fatty acid oxidation plays a central role in liver lipid homeostasis, so it is possible that hepatic metabolism of erucic acid might decrease mitochondrial fatty acid oxidation. However, the precise mechanistic relationship between erucic acid levels and mitochondrial fatty acid oxidation is unclear. Using male Sprague-Dawley rats, along with biochemical and molecular biology approaches, we report here that peroxisomal β-oxidation of erucic acid stimulates malonyl-CoA formation in the liver and thereby suppresses mitochondrial fatty acid oxidation. Excessive hepatic uptake and peroxisomal β-oxidation of erucic acid resulted in appreciable peroxisomal release of free acetate, which was then used in the synthesis of cytosolic acetyl-CoA. Peroxisomal metabolism of erucic acid also remarkably increased the cytosolic NADH/NAD⁺ ratio, suppressed sirtuin 1 (SIRT1) activity, and thereby activated acetyl-CoA carboxylase, which stimulated malonyl-CoA biosynthesis from acetyl-CoA. Chronic feeding of a diet including high-erucic-acid rapeseed oil diminished mitochondrial fatty acid oxidation and caused hepatic steatosis and insulin resistance in the rats. Of note, administration of a specific peroxisomal β-oxidation inhibitor attenuated these effects. Our findings establish a cross-talk between peroxisomal and mitochondrial fatty acid oxidation. They suggest that peroxisomal oxidation of long-chain fatty acids suppresses mitochondrial fatty acid oxidation by stimulating malonyl-CoA formation, which might play a role in fatty acid-induced hepatic steatosis and related metabolic disorders.

Chemotherapy-associated liver injury in colorectal cancer

Patients with colorectal cancer (CRC) have benefited significantly from advances in multimodal treatment with significant improvements in long-term survival. More patients are currently being treated with surgical resection or ablation following neoadjuvant or adjuvant chemotherapy. However, several cytotoxic agents that are administered routinely have been linked to liver toxicities that impair liver function and regeneration. Recognition of chemotherapy-related liver toxicity emphasizes the importance of multidisciplinary planning to optimize care. This review aims to summarize current data on multimodal treatment concepts for CRC, provide an overview of liver damage caused by commonly administered chemotherapeutic agents, and evaluate currently suggested protective agents.

Nonalcoholic Fatty Liver Disease Pandemic Fuels the Upsurge in Cardiovascular Diseases

Cardiovascular diseases (CVDs) remain a leading cause of death worldwide. Among the major risk factors for CVD, obesity and diabetes mellitus have received considerable attention in terms of public policy and awareness. However, the emerging prevalence of nonalcoholic fatty liver disease (NAFLD), as the most common liver and metabolic disease and a cause of CVD, has been largely overlooked. Currently, the number of individuals with NAFLD is greater than the total number of individuals with diabetes mellitus and obesity. Epidemiological studies have established a strong correlation between NAFLD and an increased risk of CVD and CVD-associated events. Although debate continues over the causal relationship between NAFLD and CVD, many mechanistic and longitudinal studies have indicated that NAFLD is one of the major driving forces for CVD and should be recognized as an independent risk factor for CVD apart from other metabolic disorders. In this review, we summarize the clinical evidence that supports NAFLD as a risk factor for CVD epidemics and discuss major mechanistic insights regarding the acceleration of CVD in the setting of NAFLD. Finally, we address the potential treatments for NAFLD and their potential impact on CVD.

The different expression of glycogen phosphorylases in renal clear cell renal carcinoma and chromophobe renal carcinoma

BACKGROUND

The various pathogenesis between Clear cell renal carcinoma (CCRCC) and Chromophobe renal carcinoma (CHRCC) contributes to the different tumor growth rate and metastasis. In this study, we explored the distinct proteomic profiles between these two cancers and found different expression of glycogen phosphorylases in two cancers.

METHODS

We explored novel targets by proteomics. Five CCRCC cases and five CHRCC cases were selected for tandem mass tag-labeling liquid chromatography-mass spectroscopy (LC-MS). Gene ontology and KEGG pathway were applied for bioinformatic analysis. Glycogen phosphorylases were detected by Western blotting.

RESULTS

CHRCC were younger, more commonly female, and had larger tumors compared to those with CCRCC. 101 differentially expressed proteins (DEPs) in CCRCC and 235 DEPs in CHRCC were detected by LC-MS. It was found that disruption of metabolic pathways, epithelial cell differentiation, and cell response were the common characters for two tumor types. Activation of cell-cell adhesion and oxidation-reduction process stimulate CCRCC growth and epithelial cell differentiation and transferrin transport was involved in CHRCC growth, We also found that oxidative phosphorylation is activated in CHRCC and inhibited in CCRCC. More importantly, we found and confirmed that upregulation of glycogen phosphorylase liver type in CCRCC and glycogen phosphorylase brain type in CHRCC mediated differential glycogenolysis in the two tumor types, which could serve as potential therapeutic targets.

CONCLUSION

We found different expression of glycogen phosphorylases in CCRCC and CHRCC by quantitative proteomics, which provides potential therapeutic targets in the future.

Evaluation of the functional quality of rapeseed oil obtained by different extraction processes in a Sprague-Dawley rat model

The nutritional function of vegetable oil is influenced by different oil extraction methods. In this study, the effects of different processing techniques on the quality of rapeseed oil and animal lipid metabolism were evaluated. Results showed that rapeseed oil obtained by the aqueous enzymatic extraction (AEE) method had the highest polyphenol (152.08 ± 11.44 mg GAE per kg), α-tocopherol (208.97 ± 15.84 mg kg-1), and β-carotene (5.40 mg kg-1) contents and a better oxidation resistance. It was noted in an experiment on rats fed with diets containing rapeseed oils that AEE rapeseed oil reduces total cholesterol (TC), triacylglycerol (TG), low-density lipoprotein cholesterol (LDL-C), aspartate transaminase (ALT) and alanine transaminase (AST) in high-fat diet rats by 27.09%, 11.81%, 35.52%, 31.02% and 27.61%, respectively, and the body and liver weights of rats were decreased. mRNA expression indicated that AEE could significantly down-regulate fatty acid synthase (FAS) and up-regulate acyl-CoA oxidase 1 (ACOX1) gene expression levels (P < 0.05). These results suggested that the AEE method can increase the content of trace active substances in rapeseed oil and ameliorate chronic diseases induced by a high-fat diet.

Impairment of Fatty Acid Oxidation in Alveolar Epithelial Cells Mediates Acute Lung Injury

Profound impairment in cellular oxygen consumption, referred to as cytopathic dysoxia, is one of the pathological hallmarks in the lungs of patients with pathogen-induced acute lung injury (ALI). However, the underlying mechanism for this functional defect remains largely unexplored. In this study, we found that primary mouse alveolar epithelial cells (AECs) conducted robust fatty acid oxidation (FAO). More importantly, FAO was strikingly impaired in AECs of mice with LPS-induced ALI. The metabolic deficiency in these cells was likely due to decreased expression of key mediators involved in FAO and mitochondrial bioenergenesis, such as peroxisome proliferator-activated receptor γ coactivator (PGC)-1α, carnitine palmitoyltransferase 1A, and medium-chain acyl-CoA dehydrogenase (CAD). We found that treatment of alveolar epithelial line MLE-12 cells with BAL fluids from mice with ALI decreased FAO, and this effect was largely replicated in MLE-12 cells treated with the proinflammatory cytokine TNF-α, which was consistent with downregulations of PGC-1α, carnitine palmitoyltransferase 1A, long-chain CAD, and medium-chain CAD in the same treated cells. Furthermore, we found that the BAL fluids from ALI mice and TNF-α inhibited MLE-12 bioenergenesis and promoted cell apoptosis. In delineation of the role of FAO in ALI in vivo, we found that conditional ablation of AEC PGC-1α aggravated LPS-induced ALI. In contrast, fenofibrate, an activator of the PPAR-α/PGC-1α cascade, protected mice from this pathology. In summary, these data suggest that FAO is essential to AEC bioenergenesis and functional homeostasis. This study also indicates that FAO impairment-induced AEC dysfunction is an important contributing factor to the pathogenesis of ALI.

Updates to the n-3 polyunsaturated fatty acid biosynthesis pathway: DHA synthesis rates, tetracosahexaenoic acid and (minimal) retroconversion

N-3 polyunsaturated fatty acids (PUFA) and the numerous families of lipid mediators derived from them collectively regulate numerous biological processes. The mechanisms by which n-3 PUFA regulate biological processes begins with an understanding of the n-3 biosynthetic pathway that starts with alpha-linolenic acid (18:3n-3) and is commonly thought to end with the production of docosahexaenoic acid (DHA, 22:6n-3). However, our understanding of this pathway is not as complete as previously believed. In the current review we provide a background of the evidence supporting the pathway as currently understood and provide updates from recent studies challenging three central dogma of n-3 PUFA metabolism. By building on nearly three decades of research primarily in cell culture and oral dosing studies, recent evidence presented focuses on in vivo kinetic modelling and compound-specific isotope abundance studies in rodents and humans that have been instrumental in expanding our knowledge of the pathway. Specifically, we highlight three main updates to the n-3 PUFA biosynthesis pathway: (1) DHA synthesis rates cannot be as low as previously believed, (2) DHA is both a product and a precursor to tetracosahexaenoic acid (24:6n-3) and (3) increases in EPA in response to DHA supplementation are not the result of increased retroconversion.

The fatty acid oxidation enzyme long-chain acyl-CoA dehydrogenase can be a source of mitochondrial hydrogen peroxide

Fatty acid oxidation (FAO)-driven H₂O₂ has been shown to be a major source of oxidative stress in several tissues and disease states. Here, we established that the mitochondrial flavoprotein long-chain acyl-CoA dehydrogenase (LCAD), which catalyzes a key step in mitochondrial FAO, directly produces H₂O₂in vitro by leaking electrons to oxygen. Kinetic analysis of recombinant human LCAD showed that it produces H₂O₂ 15-fold faster than the related mitochondrial enzyme very long-chain acyl-CoA dehydrogenase (VLCAD), but 50-fold slower than a bona fide peroxisomal acyl-CoA oxidase. The rate of H₂O₂ formation by human LCAD is slow compared to its activity as a dehydrogenase (about 1%). However, expression of hLCAD in HepG2 cells is sufficient to significantly increase H₂O₂ in the presence of fatty acids. Liver mitochondria from LCAD−/− mice, but not VLCAD−/− mice, produce significantly less H₂O₂ during incubation with fatty acids. Finally, we observe highest LCAD expression in human liver, followed by kidney, lung, and pancreas. Based on our data, we propose that the presence of LCAD drives H₂O₂ formation in response to fatty acids in these tissues.

Fermented Cordyceps militaris Extract Ameliorates Hepatosteatosis via Activation of Fatty Acid Oxidation

Nonalcoholic fatty liver disease is a progressive disease involving the accumulation of lipid droplets in the liver. In this study, we investigated the anti-hepatosteatosis effects of fermented Cordyceps militaris extract (CME) in AML-12 hepatocytes. Although the levels of adenosine and cordycepin were reduced in the extracts of CM grown on germinated soybean (GSCE) and fermented CM grown on germinated soybean (GSC) by Pediococcus pentosaceus ON188 (ON188E), the expression of fatty acid oxidation (FAO) genes were upregulated only by GSC-ON188E treatment in a dose-dependent manner. In contrast, a lipogenic gene, stearoyl Coenzyme A desaturase 1, was downregulated by ON188E. Formation of intracellular lipid droplets by the addition of oleic acid was reduced by ON188E to levels observed in WY14643-treated cells. When cells were treated with ON188E, sphingosine kinase 2 mainly responsible for hepatic sphingosine 1-phosphate (S1P) synthesis was upregulated and S1P was elevated. Collectively, the fermented GSC extract activates FAO through elevation of S1P synthesis and has potential as a therapeutic for hepatosteatosis.

Diet-induced hepatic steatosis activates Ras to promote hepatocarcinogenesis via CPT1α

Aberrant activation of the RAS cascade ubiquitously occurs in human hepatocellular carcinomas (HCC), regardless of rare mutations of RAS. However, the association between the Ras cascade and hepatic steatosis during hepatocarcinogenesis remains under-investigated. Here, the variation in the constitutive activity of Ras signaling and HCC incidence was found in a nonalcoholic fatty liver disease (NAFLD)-HCC mouse model, and Ras activity was induced by hepatic steatosis. Even in hepatocyte-specific expression of Kras^G12D (Alb-Cre/Kras^G12D, Kras^hep) mice, mutagenic activation of Ras signaling was still significantly enhanced by NAFLD, with downregulation of negative regulators. Interestingly, hepatic steatosis could be alleviated by persistent activation of Ras, whereas Ras accelerated DNA damage and HCC progression through Carnitine palmitoyltransferase 1A (CPT1α). A close correlation between active Ras and CPT1α was also shown in clinical steatosis peri-tumor tissues of HCC samples and experimental models. CPT1α inhibitor etomoxir (ETO) largely ameliorated active Ras-drived HCC. These findings can provide a novel link between steatosis and Ras activity in liver cancer.

Proteomics analysis reveals a potential new target protein for the lipid-lowering effect of Berberine8998

Berberine8998 is a newly synthesized berberine derivative with better lipid-lowering activity and improved absorption. The objective of this study was to investigate the effects of berberine8998 on serum cholesterol and lipid levels in vivo and to examine the mechanisms involved. Hamsters on high-fat diet (HFD) were administered berberine or berberine8998 (50 mg·kg^-1·d^-1, ig) for 3 weeks. Berberine8998 administration significantly lowered the total cholesterol, triglycerides and LDL-C levels in HFD hamsters. Bioinformatics revealed that berberine and berberine8998 shared similar metabolic pathways and fatty acid metabolism was the predominant pathway. Western blot validation results showed that peroxisomal acyl-coenzyme A oxidase 1 (ACOX1) and long-chain fatty acid-CoA ligase 1 (ACSL1), two proteins involved in fatty acid metabolism, were expressed differently in the berberine8998 group than in the untreated group and the berberine treatment group. Biochemistry results showed that berberine8998 significantly lowered the non-esterified fatty acid (NEFA) levels, which may lead to a reduction in TG levels in the berberine8998 treatment group and the differences observed in proteomics analyses. Pharmacokinetic analysis conducted in rats. After administration of berberine or berberine8998 (50 mg/kg, ig), berberine8998 exhibited a remarkably improved absorption with increasing bioavailability by 6.7 times compared with berberine. These findings suggest that berberine8998 lowers cholesterol and lipid levels via different mechanisms than berberine, and its improved absorption makes it a promising therapeutic candidate for the treatment of hypercholesterolemia and obesity.

CD36 palmitoylation disrupts free fatty acid metabolism and promotes tissue inflammation in non-alcoholic steatohepatitis

BACKGROUND AND AIMS

Fatty acid translocase CD36 (CD36) is a membrane protein with multiple immuno-metabolic functions. Palmitoylation has been suggested to regulate the distribution and functions of CD36, but little is known about its significance in non-alcoholic steatohepatitis (NASH).

METHODS

Human liver tissue samples were obtained from patients undergoing liver biopsy for diagnostic purposes. CD36 knockout mice were injected with lentiviral vectors expressing wild-type CD36 or CD36 with mutated palmitoylation sites. Liver histology, immunofluorescence, mRNA expression profile, subcellular distributions and functions of CD36 protein were assessed.

RESULTS

The localization of CD36 on the plasma membrane of hepatocytes was markedly increased in patients with NASH compared to patients with normal liver and those with simple steatosis. Increased CD36 palmitoylation and increased localization of CD36 on the plasma membrane of hepatocytes were also observed in livers of mice with NASH. Furthermore, inhibition of CD36 palmitoylation protected mice from developing NASH. The absence of palmitoylation decreased CD36 protein hydrophobicity reducing its localization on the plasma membrane as well as in lipid raft of hepatocytes. Consequently, a lack of palmitoylation decreased fatty acid uptake and CD36/Fyn/Lyn complex in HepG2 cells. Inhibition of CD36 palmitoylation not only ameliorated intracellular lipid accumulation via activation of the AMPK pathway, but also inhibited the inflammatory response through the inhibition of the JNK signaling pathway.

CONCLUSIONS

Our findings demonstrate the key role of palmitoylation in regulating CD36 distributions and its functions in NASH. Inhibition of CD36 palmitoylation may represent an effective therapeutic strategy in patients with NASH.

LAY SUMMARY

Fatty acid translocase CD36 (CD36) is a multifunctional membrane protein which contributes to the development of liver steatosis. In the present study, we demonstrated that the localization of CD36 on the plasma membrane of hepatocytes is increased in patients with non-alcoholic steatohepatitis. Blocking the palmitoylation of CD36 reduces CD36 distribution in hepatocyte plasma membranes and protects mice from non-alcoholic steatohepatitis. The inhibition of CD36 palmitoylation not only improved fatty acid metabolic disorders but also reduced the inflammatory response in vitro and in vivo. The present study suggests that CD36 palmitoylation is important for non-alcoholic steatohepatitis development and inhibition of CD36 palmitoylation could be used to cure non-alcoholic steatohepatitis.

Ancestral TCDD Exposure Induces Multigenerational Histologic and Transcriptomic Alterations in Gonads of Male Zebrafish

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), the classic aryl hydrocarbon receptor (AhR) agonist, is a potent environmental toxicant and endocrine-disrupting chemical (EDC) with known developmental toxicity in humans, rodents, and fish. Early life exposure to some EDCs, including TCDD, is linked to the occurrence of adult-onset and multigenerational disease. Previous work exposing juvenile F0 zebrafish (Danio rerio) to 50 ppt (parts per trillion) TCDD during reproductive development has shown male-mediated transgenerational decreases in fertility (F0-F2) and histologic and transcriptomic alterations in F0 testes. Here, we analyzed male germline alterations in F1 and F2 adult fish, looking for changes in testicular histology and gene expression inherited through the male lineage that could account for decreased reproductive capacity. Testes of TCDD-lineage F1 fish displayed an increase in spermatogonia (immature germ cells) and decrease in spermatozoa (mature germ cells). No histological changes were present in F2 fish. Transcriptomic analysis of exposed F1 and F2 testes revealed alterations in lipid and glucose metabolism, oxidation, xenobiotic response, and sperm cell development and maintenance genes, all of which are implicated in fertility outcomes. Overall, we found that differential expression of reproductive genes and reduced capacity of sperm cells to mature could account for the reproductive defects previously seen in TCDD-exposed male zebrafish and their descendants, providing insight into the distinct multigenerational effects of toxicant exposure.

Decreased EDHF-mediated relaxation is a major mechanism in endothelial dysfunction in resistance arteries in aged mice on prolonged high-fat sucrose diet

High‐fat sucrose (HFS) diet in aged individuals causes severe weight gain (obesity) with much higher risk of cardiovascular diseases such as hypertension or atherosclerosis. Endothelial dysfunction is a major contributor for these vascular disorders. We hypothesize that prolonged ingestion of HFS diet by aged mice would accentuate endothelial dysfunction in the small resistance arteries. Male C57BL/6J mice at 12 weeks of age were divided into four groups and fed either normal chow (NC) or high‐fat sucrose diet (HFS). Young group received NC for 4 months, and high‐fat diet (HFD) for 3 months and 1 month HFS + 10% Sucrose (HFS diet). Aged mice received NC for 12 months. Aged HFS group received HFD for 4 months + 1 month HFD + 10% sucrose + 8 months HFD. Total body weight, plasma blood glucose levels, and glucose tolerance were determined in all groups. Isolated mesenteric arteries were assessed for arterial remodeling, myogenic tone, and vasomotor responses using pressure and wire myography. Both young and aged HFS mice showed impaired glucose tolerance (Y‐NC, 137 ± 8.5 vs. Y‐NC HFS, 228 ± 11.71; A‐NC, 148 ± 6.42 vs. A‐HFS, 225 ± 10.99), as well as hypercholesterolemia (Y‐NC 99.50 ± 6.35 vs. Y‐HFS 220.40 ± 16.34 mg/dL; A‐NC 108.6 ± vs. A‐HFS 279 ± 21.64) and significant weight gain (Y‐NC 32.13 ± 0.8 g vs. Y‐HFS 47.87 ± 2.18 g; A‐NC 33.72 vs. A‐HFS 56.28 ± 3.47 g) compared to both groups of mice on NC. The mesenteric artery from mice with prolonged HFS diet resulted in outward hypertrophic remodeling, increased stiffness, reduced myogenic tone, impaired vasodilation, increased contractility and blunted nitric oxide (NO) and EDH‐mediated relaxations. Ebselen, a peroxinitrite scavenger rescued the endothelium derived relaxing factor (EDHF)‐mediated relaxations. Our findings suggest that prolonged diet‐induced obesity of aged mice can worsen small resistance artery endothelial dysfunction due to decrease in NO and EDHF‐mediated relaxation, but, EDHF‐mediated relaxation is a major contributor to overall endothelial dysfunction.

Butein protects the nonalcoholic fatty liver through mitochondrial reactive oxygen species attenuation in rats

One of the worldwide metabolic health dilemma is nonalcoholic fatty liver diseases (NAFLD). Researchers are searching effective drug to manage NAFLD patients. One of the best way to manage the metabolic imperfection is through natural principal isolated from different sources. Butein, a natural compound known to have numerous pharmacological application. In the current study we assessed the therapeutic effect of butein administration on liver function tests, oxidative stress, antioxidants, lipid abnormalities, serum inflammatory cytokines, and mitochondrial reactive oxygen species levels, in rats with methionine-choline deficient (MCD) diet induced NAFLD. Male Wistar rats were treated with MCD diet with/without butein (200 mg/kg body wt. orally) for 6 weeks. The protective effect of butein, were evident from decreased transaminase activities, restoration of albumin, globulin, albumin/globulin ratio, and oxidants in serum (P < 0.01), further it improved liver antioxidant status (P < 0.01). Butein significantly lowered lipid profile parameters (P < 0.01), suppressed inflammatory cytokines (P < 0.01), and improved liver histology. Further to understand the possible mechanism behind the hepatoprotective and lipid lowering effect of butein, the activities of heme oxygenase (HO1), myeloperoxidase (MPO), and mitochondrial reactive oxygen species (ROS) were measured. We found that butein supplementation significantly decreased the activity of HO1 (P < 0.001), and increased the activity of MPO (P < 0.001). Furthermore butein attenuated mitochondrial ROS produced in NAFLD condition. Present study shows that butein supplementation restore liver function by altering liver oxidative stress, inflammatory markers, vital defensive enzyme activities, and mitochondrial ROS. In summary, butein has remarkable potential to develop effective hepato-protective drug. © 2018 BioFactors, 44(3):289-298, 2018.

Liraglutide reduces hepatic glucolipotoxicity‑induced liver cell apoptosis through NRF2 signaling in Zucker diabetic fatty rats

The primary aim of the present study was to evaluate the effects of liraglutide on glucolipotoxicity-induced liver cell apoptosis and the underlying mechanisms in Zucker diabetic fatty (ZDF) rats. The results revealed that liraglutide significantly decreased the body weight, hyperglycemia and hyperlipidemia of ZDF rats relative to those of Zucker lean (ZL) rats (P<0.05). Furthermore, the reduced liver cell apoptosis was observed in the ZDF rats following 6 weeks of liraglutide therapy. These data validated the beneficial effects of liraglutide on diabetic and obese ZDF rats. In addition, novel data was obtained that demonstrated that liraglutide treatment increased the expression of the antioxidant transcription factor nuclear factor-erythroid 2-related factor 2 (NRF2), as well as the transcription of downstream target genes, including nicotinamide adenine dinucleotide phosphate quinone dehydrogenase 1 and heme oxygenase-1 (P<0.05). Additionally, serum and hepatic GSH and SOD levels increased following liraglutide therapy (P<0.05). Hence, it was proposed that liraglutide may enhance the antioxidant activity of liver cells by activating the NRF2 signaling pathway, thereby reducing liver cell apoptosis induced by glucolipotoxicity in ZDF rats, which may shed light on the application of liraglutide in the treatment of diabetes- and obesity-induced liver injury.

Tyrosine Residues 232 and 401 Play a Critical Role in the Binding of the Cofactor FAD of Acyl-coA Oxidase

Acyl-coA oxidase (ACO) is an important flavoenzyme responsible for the first step of peroxisomal fatty acid β-oxidation. In this study, the roles of Tyr232 and Tyr401 in flavin adenine dinucleotide (FAD) binding and enzyme catalysis of ACO were explored using site-directed mutagenesis. For mutant proteins, different levels of activity loss were observed. Wavelength scanning of Y232 and Y401 mutant proteins indicated that there is no FAD binding in Y401S and Y401G mutant ACO. Structure analysis indicated that the phenolic hydroxyl and benzene ring of the side chain could stabilize FAD binding through hydrogen bonds network and hydrophobic pocket formation. These results indicated that these two tyrosine residues play a critical role in the FAD binding of ACO.

Expression enhancement in brown adipose tissue of genes related to thermogenesis and mitochondrial dynamics after administration of pepsin egg white hydrolysate

Pepsin egg white hydrolysate enhanced mitochondria proliferation on brown adipose tissue and thermogenesis. Reduced body weight and adiposity were observed.