Liver fatty acid composition in mice with or without nonalcoholic fatty liver disease

Microplastic-induced NAFLD: Hepatoprotective effects of nanosized selenium

Polystyrene microplastics (MPs) are persistent environmental pollutants commonly encountered in daily human life. Numerous studies have demonstrated their ability to induce liver damage, including oxidative stress, inflammation, and lipid accumulation. However, limited information exists regarding preventive measures against this issue. In our study, we investigated the potential preventive role of selenium nanoparticles (YC-3-SeNPs) derived from Yak-derived Bacillus cereus, a novel nanobiomaterial known for its antioxidant properties and lipid metabolism regulation. Using transcriptomic and metabolomic analyses, we identified key genes and metabolites associated with oxidative stress and lipid metabolism imbalance induced by MPs. Upregulated genes (Scd1, Fasn, Irs2, and Lpin) and elevated levels of arachidonic and palmitic acid accumulation were observed in MP-exposed mice, but not in those exposed to SeNPs. Further experiments confirmed that SeNPs significantly attenuated liver lipid accumulation and degeneration caused by MPs. Histological results and pathway screening validated our findings, revealing that MPs suppressed the Pparα pathway and Nrf2 pathway, whereas SeNPs activated both pathways. These findings suggest that MPs may contribute to the development of nonalcoholic fatty liver disease (NAFLD), while SeNPs hold promise as a future nanobio-product for its prevention.

Linseed Oil Attenuates Liver Inflammation, Fatty Acid Accumulation, and Lipid Distribution in Periportal and Perivenous Hepatocytes Induced by a High-Carbohydrate Diet in Mice

We evaluated whether linseed oil (LO) modulates the effects of a high-carbohydrate diet (HCD) on liver inflammation, fatty acid (FA) accumulation, and lipid distribution in periportal and perivenous hepatocytes. The control group (control high-carbohydrate diet [HCD-C]) received an HCD with lard and soybean oil as the lipid source. The L10 and L100 groups received the HCD with 10% and 100% of LO as the lipid source, respectively. The animals were killed by decapitation before (day 0) and after receiving the diets. Liver FA composition, inflammation, and fibrogenesis gene expression were evaluated. Also, the percentage of lipid-occupied area in periportal end perivenous hepatocytes were measured. The L100 group exhibited a higher (P < .05) liver amount of omega-3 polyunsaturated FA (n-3 PUFA) and lower (P < .05) amounts of saturated FA (SFA), monounsaturated FA (MUFA), and omega-6 polyunsaturated FA (n-6 PUFA) compared with L10 or HCD-C mice. On day 56, interleukin 10 and type IV collagen gene expression were significantly upregulated and downregulated, respectively in L100. Also, the L100 group showed lower (P < .05) FA accumulation (i.e., total FA, SFA, MUFA, and n-6 PUFA). Also, L10 and L100 presented lower (P < .05) percentage of high lipid-containing portion in periportal and perivenous hepatocytes. We concluded that LO attenuation of liver inflammation promoted by an HCD is associated with increased liver n-3 PUFA levels, so modulating FA composition, deposition, and distribution in periportal and perivenous hepatocytes.

Baicalein Prevents Fructose-Induced Hepatic Steatosis in Rats: In the Regulation of Fatty Acid De Novo Synthesis, Fatty Acid Elongation and Fatty Acid Oxidation

Non-alcoholic fatty liver disease (NAFLD), ranging from simple steatosis to non-alcoholic steatohepatitis (NASH), hepatic fibrosis and even hepatocellular carcinoma, is a liver disease worldwide without approved therapeutic drugs. Baicalein (BAL), a flavonoid compound extracted from the Traditional Chinese Medicine (TCM) Scutellariae Radix (Scutellaria baicalensis Georgi.), has been used in TCM clinical practice for thousands of years to treat liver diseases due to its "hepatoprotective effect". However, the underlying liver-protecting mechanisms remain largely unknown. Here, we found that oral administration of BAL significantly decreased excess serum levels of triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), aspartate aminotransferase (AST) as well as hepatic TG in fructose-fed rats. Attenuation of the increased vacuolization and Oil Red O staining area was evident on hepatic histological examination in BAL-treated rats. Mechanistically, results of RNA-sequencing, western-blot, real-time quantitative PCR (RT-qPCR) and hepatic metabolomics analyses indicated that BAL decreased fructose-induced excessive nuclear expressions of mature sterol regulatory element-binding protein 1c (mSREBP1c) and carbohydrate response element-binding protein (ChREBP), which led to the decline of lipogenic molecules [including fatty acid synthase (FASN), stearoyl-CoA desaturase 1 (SCD1), elongation of very long chain fatty acids 6 (ELOVL6), acetyl-CoA carboxylase (ACC)], accompanying with the alternation of hepatic fatty acids composition. Meanwhile, BAL enhanced fatty acid oxidation by activating AMPK/PGC1α signaling axis and PPARα signal pathway, which elicited high expression of carnitine palmitoyl transferase 1α (CPT1α) and Acyl-CoA oxidase 1 (ACO1) in livers of fructose-fed rats, respectively. BAL ameliorated fructose-induced hepatic steatosis, which is associated with regulating fatty acid synthesis, elongation and oxidation.

Changes in the Serum Fatty Acid Profile After Anhepatic Phase of Orthotopic Liver Transplantation Procedure

During orthotopic liver transplantation (OLT), the patients’ body remains deprived of this organ for some time, which could cause critical changes in the levels of various metabolites in the circulation, including fatty acids. Thus, the aim of this study was to determine whether the liver transplantation procedure leads to significant changes in the FA profile in serum lipids after the anhepatic phase. Our gas chromatography–mass spectrometry analysis revealed that after transplantation, serum levels of myristic and palmitic acids significantly decreased, whereas serum levels of very long-chain FAs containing 20 or more carbons in their chains were increased. These results indicate that the anhepatic phase during liver transplantation produces significant changes in serum fatty acid levels, and emphasizes the role of the liver in the metabolism of very long-chain fatty acids.

Assessment of hepatic fatty acids during non-alcoholic steatohepatitis progression using magnetic resonance spectroscopy

INTRODUCTION AND OBJECTIVES

Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of liver abnormalities including steatosis, steatohepatitis, fibrosis, and cirrhosis. Liver biopsy remains the gold standard method to determine the disease stage in NAFLD but is an invasive and risky procedure. Studies have previously reported that changes in intrahepatic fatty acids (FA) composition are related to the progression of NAFLD, mainly in its early stages. The aim of this study was to characterize the liver FA composition in mice fed a Choline-deficient L-amino-defined (CDAA) diet at different stages of NAFLD using magnetic resonance spectroscopy (MRS).

METHODS

We used in-vivo MRS to perform a longitudinal characterization of hepatic FA changes in NAFLD mice for 10 weeks. We validated our findings with ex-vivo MRS, gas chromatography-mass spectrometry and histology.

RESULTS

In-vivo and ex-vivo results showed that livers from CDAA-fed mice exhibit a significant increase in liver FA content as well as a change in FA composition compared with control mice. After 4 weeks of CDAA diet, a decrease in polyunsaturated and an increase in monounsaturated FA were observed. These changes were associated with the appearance of early stages of steatohepatitis, confirmed by histology (NAFLD Activity Score (NAS) = 4.5). After 10 weeks of CDAA-diet, the liver FA composition remained stable while the NAS increased further to 6 showing a combination of early and late stages of steatohepatitis.

CONCLUSION

Our results suggest that monitoring lipid composition in addition to total water/fat with MRS may yield additional insights that can be translated for non-invasive stratification of high-risk NAFLD patients.

The Myristic Acid:Docosahexaenoic Acid Ratio Versus the n-6 Polyunsaturated Fatty Acid:n-3 Polyunsaturated Fatty Acid Ratio as Nonalcoholic Fatty Liver Disease Biomarkers

It is well established that diets containing an increased omega-6 polyunsaturated fatty acid (n-6 PUFA) to omega-3 polyunsaturated fatty acid (n-3 PUFA) ratios are linked to inflammation and chronic diseases such as nonalcoholic fatty liver disease (NAFLD). However, the influence of an elevated n-6 PUFA:n-3 PUFA ratio in the tissues requires clarification. Herein, we identified primary experimental and clinical studies where it is possible to compare the performance of the myristic acid (Myr):docosahexaenoic acid (DHA) and n-6 PUFA:n-3 PUFA ratios in the liver and/or serum as potential NAFLD biomarkers. Articles were included if quantitative values of n-6 PUFA, n-3 PUFA, Myr, DHA, and information about liver inflammation or liver disease progression parameters were provided. Overall, most experimental (91.6%) and clinical studies (87.5%) reported higher Myr:DHA ratios associated with inflammation and/or NAFLD progression than the n-6 PUFA:n-3 PUFA ratio. We conclude that the Myr:DHA ratio represents a better biomarker of NAFLD than the n-6 PUFA:n-3 PUFA ratio. Future studies are necessary for verifying this observation.

The Obscure Effect of Tribulus terrestris Saponins Plus Inulin on Liver Morphology, Liver Fatty Acids, Plasma Glucose, and Lipid Profile in SD Rats with and without Induced Type 2 Diabetes Mellitus

Diabetes is a predictor of nonalcoholic fatty liver disease (NAFLD). There are data suggesting that Tribulus terrestris (TT) saponins act as antidiabetic agents and protect against NAFLD. The effect of saponins may be increased by fermentable fibers such as inulin. The aim of the present study was to investigate the influence of TT saponins and TT saponins plus inulin on the plasma lipid profile and liver fatty acids of rats with induced diabetes mellitus type 2 (T2DM). The study was performed on 36 male Sprague–Dawley rats divided into two main groups: control and diabetic. Animals of the diabetic (DM) group were fed a high-fat diet and injected with streptozotocin (low doses). Animals of the control group (nDM) were on a regular diet and were injected with buffer. After the injections, the animals were split into subgroups: three non-diabetic (nDM): (i) control (c-C); (ii) saponin-treated rats (C-Sap); (iii) rats treated with saponins + inulin (C-Sap + IN), and three diabetic subgroups (DM): (iv) control (c-DM); (v) saponin-treated rats (DM-Sap); (vi) rats treated with saponins + inulin (DM-Sap + IN). Liver fatty acids were extracted and analyzed by gas chromatography, and plasma glucose and lipids were measured. The study showed significant changes in liver morphology, liver fatty acids, plasma lipid profile, and plasma glucose. In summary, supplementation with TT saponins or saponins with inulin for one month decreased the level of steatosis in rats with induced type 2 diabetes. Moreover, there were favorable effects on the plasma lipid profile in the rats. However, additional supplementation with inulin had a negative effect on liver morphology (with a microvesicular type of steatosis) in the non-diabetes group. Moreover, supplementation with inulin had a negative effect on plasma glucose in both diabetic and non-diabetic rats. These data show that a diet enriched with fermentable fibers reveals different effects in different organisms, and not all sources and forms of fiber are beneficial to health.

Short-term changes in the serum metabolome after laparoscopic sleeve gastrectomy and Roux-en-Y gastric bypass

INTRODUCTION

Bariatric surgery is known to be the most effective treatment for weight loss in obese patients and for the rapid remission of obesity-related comorbidities. These short-term improvements result from not only limited digestion or absorption but also dynamic changes in metabolism throughout the whole body. However, short-term metabolism studies associated with bariatric surgery in Asian individuals have not been reported.

OBJECTIVES

The aim of this study was to investigate the short-term metabolome changes in the serum promoted by laparoscopic sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) and to determine the underlying mechanisms that affect obesity-related comorbidities.

METHODS

Serum samples were collected from Korean patients who underwent RYGB or SG before and 4 weeks after the surgery. Metabolomic and lipidomic profiling was performed using UPLC-Orbitrap-MS, and data were analyzed using statistical analysis.

RESULTS

Metabolites mainly related to amino acids, lipids (fatty acids, glycerophospholipids, sphingolipids, glycerolipids) and bile acids changed after surgery, and these changes were associated with the lowering of risk factors for obesity-related diseases such as nonalcoholic fatty liver disease (NAFLD), type 2 diabetes (T2D) and atherosclerosis. Interestingly, the number of significantly altered metabolites related to the lipid metabolism were greater in SG than in RYGB. Furthermore, the metabolites related to amino acid metabolism were significantly changed only after SG, whereas bile acid changed significantly only following RYGB.

CONCLUSION

These differences could result from anatomical differences between the two surgeries and could be related to the gut microbiota. This study provides crucial information to expand the knowledge of the common but different molecular mechanisms involved in obesity and obesity-related comorbidities affected by each bariatric procedure.

The Role of Fatty Acids in Non-Alcoholic Fatty Liver Disease Progression: An Update

Non-alcoholic fatty liver disease (NAFLD) is a major public health problem worldwide. NAFLD (both simple steatosis and steatohepatitis) is characterized by alterations in hepatic lipid metabolism, which may lead to the development of severe liver complications including cirrhosis and hepatocellular carcinoma. Thus, an exhaustive examination of lipid disorders in the liver of NAFLD patients is much needed. Mass spectrometry-based lipidomics platforms allow for in-depth analysis of lipid alterations in a number of human diseases, including NAFLD. This review summarizes the current research on lipid alterations associated with NAFLD and related complications, with special emphasis on the changes in long-chain and short-chain fatty acids levels in both serum and liver tissue, as well as in the hepatic expression of genes encoding the enzymes catalyzing lipid interconversions.

Lactobacillus casei YRL577 combined with plant extracts reduce markers of non-alcoholic fatty liver disease in mice

Probiotics and plant extracts are considered to prevent the development of non-alcoholic fatty liver disease (NAFLD). The present study explores the effects of using both probiotics and plant extracts on NAFLD. The present study evaluated the effects of plant extracts on lipid droplet accumulation and the growth of probiotics in vitro. A C57BL/6 mouse model was used to examine the effects of probiotics and plant extracts on NAFLD. Body weight and food intake were measured. The levels of serum lipids, oxidative stress and the liver injury index were determined using commercial kits. Haematoxylin and eosin staining, GC and real-time PCR were also used for analysis. The results revealed that administration of Lactobacillus casei YRL577 and L. paracasei X11 with resveratrol (RES) or tea polyphenols (TP) significantly reduced the levels of total cholesterol, TAG and LDL-cholesterol and increased the level of the HDL-cholesterol. The groups of L. casei YRL577 with RES and TP also regulated the liver structure, oxidative stress and injury. Furthermore, L. casei YRL577 with TP exhibited a more positive effect towards improving the NAFLD and increased the concentrations of the butyric acid than other three combined groups. L. casei YRL577 with TP up-regulated the mRNA levels of the farnesoid X receptor and fibroblast growth factor 15 and decreased the mRNA levels of the apical Na-dependent bile acid transporter. These findings showed that L. casei YRL577 + TP-modified genes in the intestinal bile acid pathway improved markers of NAFLD.

Calorie-Restricted Mediterranean and Low-Fat Diets Affect Fatty Acid Status in Individuals with Nonalcoholic Fatty Liver Disease

Lifestyle modifications are the main support of nonalcoholic fatty liver disease (NAFLD) therapy. Weight loss is one of the primary goals in NAFLD, but the effects of different calorie-restricted diets remain unclear. Thus, we evaluated the effects of two calorie-restricted diets—the Mediterranean diet (Med diet) and low-fat diet—on liver status, cardiometabolic markers, and fatty acid profiles in patients with NAFLD. Twenty-four overweight/moderately obese men were randomly assigned to consume one of these diets. Lipid levels, glucose, insulin, liver enzymes, steatosis, and fatty acid profiles of serum and erythrocytes phospholipids were assessed. After 3 months, all participants had a significant weight loss (>9%), with improvements in waist circumference, body fat %, index of visceral adiposity (VAI), lipid accumulation product, fatty liver (FLI), and hepatic steatosis (HSI) index (p < 0.001). Both diets significantly lowered triglycerides, total and LDL-cholesterol, liver enzymes, fasting glucose, insulin, and HOMA-IR index. Fatty acid profiles were enhanced after both diets, with a significantly decreased n-6/n-3 ratio. Participants on the Med diet had higher levels of HDL-cholesterol and monounsaturated and n-3 docosahexaenoic acids in serum phospholipids and lower levels of saturated fatty acids, triglycerides, TG/HDL ratio, and FLI when compared to participants on the low-fat diet. Our results indicate that dietary patterns and calorie restriction represent central therapeutic issues in the improvement of obesity-related cardiometabolic alterations that are involved in the mechanism of hepatic steatosis. The Med diet may contribute to disease treatment even more than the low-fat diet since it leads to decreased saturated and increased monounsaturated and n-3 polyunsaturated fatty acid status and improved FLI in NAFLD patients.

Lactobacillus casei YRL577 ameliorates markers of non-alcoholic fatty liver and alters expression of genes within the intestinal bile acid pathway

Non-alcoholic fatty liver disease (NAFLD) has become the main cause of end-stage liver disease. Probiotics have the potential effect of alleviating NAFLD. The aim of this study was to explore functional probiotics and their underlying mechanisms. The bile salt hydrolase (BSH) activity in thirty-four strains was determined in vitro. Then, C57BL/6 mice were used to explore the effects of probiotics on NAFLD. Body weight and food intake were measured, and serum lipid concentrations, oxidative stress and proinflammatory cytokines levels were determined using commercial kits. The expressions of intestinal bile acid pathway genes were evaluated via real-time PCR. The results showed that Lactobacillus casei YRL577 and L. paracasei X11 had higher BSH activity. L. casei YRL577 significantly reduced liver weight and liver index and could regulate the levels of lipid metabolism, oxidative stress and proinflammatory cytokines as compared with L. paracasei X11. Furthermore, the results indicated that L. casei YRL577 up-regulated the mRNA levels of farnesoid X receptor and fibroblast growth factor 15, whereas down-regulated the mRNA level of apical Na-dependent bile acid transporter. These findings suggested that L. casei YRL577 modified genes in the intestinal bile acid pathway which might contribute to the alleviation of NAFLD.

Orotic acid-treated hepatocellular carcinoma cells resist steatosis by modification of fatty acid metabolism

BACKGROUND

Orotic acid (OA) has been intensively utilized to induce fatty liver in rats. Although the capacity of OA to cause steatosis is species-specific, previous in vitro studies indicate that humans could also be susceptible to OA-induced fatty liver. The aim of the present study was to re-elucidate the potential of OA exposure to modulate the cellular mechanisms involved in both non-alcoholic fatty liver disease pathogenesis and cellular protection from lipid accumulation. In addition, alterations in detailed fatty acid (FA) profiles of cells and culture media were analyzed to assess the significance of lipid metabolism in these phenomena.

METHODS

In our experiments, human hepatocellular carcinoma HepG2 cells were exposed to OA. Bacterial endotoxin, lipopolysaccharide (LPS), was used to mimic hepatic inflammation. The lipogenic and inflammatory effects of OA and/or LPS on cells were assessed by labeling cellular lipids with Nile red stain and by performing image quantifications. The expression levels of key enzymes involved in de novo lipogenesis (DNL) and of inflammatory markers related to the disease development were studied by qRT-PCR. FA profiles of cells and culture media were determined from total lipids with gas chromatography-mass spectrometry.

RESULTS

Our data indicate that although OA possibly promotes the first stage of DNL, it does not cause a definite lipogenic transformation in HepG2 cells. Reduced proportions of 16:0, increased stearoyl-Coenzyme A desaturase 1 mRNA expression and relatively high proportions of 16:1n-7 suggest that active delta9-desaturation may limit lipogenesis and the accumulation of toxic 16:0. Inflammatory signaling could be reduced by the increased production of long-chain n-3 polyunsaturated FA (PUFA) and the active incorporation of certain FA, including 18:1n-9, into cells. In addition, increased proportions of 20:4n-6 and 22:6n-3, total PUFA and dimethyl acetal 18:0 suggest that OA exposure may cause increased secretion of lipoproteins and extracellular vesicles.

CONCLUSIONS

The present data suggest that, apart from the transcription-level events reported by previous studies, modifications of FA metabolism may also be involved in the prevention of OA-mediated steatosis. Increased delta9-desaturation and secretion of lipoproteins and extracellular vesicles could offer potential mechanisms for further studies to unravel how OA-treated cells alleviate lipidosis.

Effects of supplemental pine needles powder (Pinus brutia) on growth performance, breast meat composition, and antioxidant status in broilers fed linseed oil-based diets

This study was proposed to examine the effects of pine needles powder (Pinus brutia) supplementation on growth performance, breast meat composition, and antioxidant status in broilers fed linseed oil-based diets. For this purpose, a total of 210, Ross-308 1-day-old male broiler chicks were allocated to 5 experimental groups each containing 42 birds. Broilers were fed a linseed oil-based basal diet supplemented with 0% (control), 0.25% (P1), 0.50% (P2), 0.75% (P3), and 1% (P4) pine needles powder. During the 42-D feeding period, no significant differences were observed between experimental groups for body weight gain, feed intake, and feed conversion ratio; however, carcass yield was increased linearly with pine needles powder supplementation. No marked changes in the breast meat chemical composition were observed among experimental groups. Supplemental pine needles powder linearly decreased the malondialdehyde concentration in breast meat and liver tissues; however, 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity of breast meat samples remained unaffected. No significant variation was observed among experimental groups for superoxide dismutase enzyme activity in blood erythrocyte lysates, but blood serum total oxidation status tended to decrease with pine needles powder supplementation. In conclusion, results suggested that pine needles powder supplementation to broiler diets could be a viable option to improve the animal antioxidant status and meat oxidative stability; however, supplementation of Pinus brutia needles powder up to 1% into broiler diets was not sufficient to efficiently curb the fat-induced oxidation in meat. Further investigation is needed to determine the full antioxidant potential of pine needles powder supplementation in poultry by comparing different pine species, evaluating the bioavailability of their active compounds and determining most effective dietary concentration for broiler meat production without any adverse effects.

Fat and Sugar-A Dangerous Duet. A Comparative Review on Metabolic Remodeling in Rodent Models of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a common disease in Western society and ranges from steatosis to steatohepatitis to end-stage liver disease such as cirrhosis and hepatocellular carcinoma. The molecular mechanisms that are involved in the progression of steatosis to more severe liver damage in patients are not fully understood. A deeper investigation of NAFLD pathogenesis is possible due to the many different animal models developed recently. In this review, we present a comparative overview of the most common dietary NAFLD rodent models with respect to their metabolic phenotype and morphological manifestation. Moreover, we describe similarities and controversies concerning the effect of NAFLD-inducing diets on mitochondria as well as mitochondria-derived oxidative stress in the progression of NAFLD.

Lipid Related Genes Altered in NASH Connect Inflammation in Liver Pathogenesis Progression to HCC: A Canonical Pathway

Nonalcoholic steatohepatitis (NASH) is becoming a public health problem worldwide. While the number of research studies on NASH progression rises every year, sometime their findings are controversial. To identify the most important and commonly described findings related to NASH progression, we used an original bioinformatics, integrative, text-mining approach that combines PubMed database querying and available gene expression omnibus dataset. We have identified a signature of 25 genes that are commonly found to be dysregulated during steatosis progression to NASH and cancer. These genes are implicated in lipid metabolism, insulin resistance, inflammation, and cancer. They are functionally connected, forming the basis necessary for steatosis progression to NASH and further progression to hepatocellular carcinoma (HCC). We also show that five of the identified genes have genome alterations present in HCC patients. The patients with these genes associated to genome alteration are associated with a poor prognosis. In conclusion, using an integrative literature- and data-mining approach, we have identified and described a canonical pathway underlying progression of NASH. Other parameters (e.g., polymorphisms) can be added to this pathway that also contribute to the progression of the disease to cancer. This work improved our understanding of the molecular basis of NASH progression and will help to develop new therapeutic approaches.

Beyond the Scavenging of Reactive Oxygen Species (ROS): Direct Effect of Cerium Oxide Nanoparticles in Reducing Fatty Acids Content in an In Vitro Model of Hepatocellular Steatosis

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic accumulation of lipids. Antisteatotic effects of cerium oxide nanoparticles (CeO₂NPs) have recently been shown in animal models of liver disease. However, it is unclear whether the activity of CeO₂NPs is related solely to the decrease in oxidative stress or, in addition, they directly decrease liver fatty acid accumulation. To address this question, in this work, we used an in vitro model of hepatocellular steatosis, exposing HepG2 cells to oleic and palmitic acid. Cell uptake of CeO₂NPs and their effect on oxidative stress and viability of hepatic cells cultured with H₂O₂ were also evaluated. Results show that CeO₂NPs were uptaken by HepG2 cells and reduced oxidative stress and improved cell viability. Treatment with oleic and palmitic acid increased lipogenesis and the content of different fatty acids. CeO₂NPs reduced palmitic and stearic acid and most fatty acids consisting of more than 18 carbon atoms. These effects were associated with significant changes in elongase and desaturase activity. In conclusion, CeO₂NPs directly protected HepG2 cells from cell injury in oxidative stress conditions and reduced fatty acid content in steatotic conditions by inducing specific changes in fatty acid metabolism, thus showing potential in the treatment of NAFLD.

Procyanidin B2 ameliorates free fatty acids-induced hepatic steatosis through regulating TFEB-mediated lysosomal pathway and redox state

Procyanidin B2, a naturally occurring phenolic compound, has been reported to exert multiple beneficial functions. However, the effect of procyanidin B2 on free fatty acids (FFAs)-induced hepatic steatosis remains obscure. The present study is therefore aimed to elucidate the protective effect of procyanidin B2 against hepatic steatosis and its underlying mechanism. Herein, we reported that procyanidin B2 attenuated FFAs-induced lipid accumulation and its associated oxidative stress by scavenging excessive ROS and superoxide anion radicals, blocking loss of mitochondrial membrane potential, restoring glutathione content, and increasing activity of antioxidant enzymes (GPx, SOD and CAT) in hepatocytes. Procyanidin B2 mechanistically promoted lipid degradation via modulation of transcription factor EB (TFEB), a master regulator of lysosomal pathway. Molecular docking analysis indicated a possible ligand-binding position of procyanidin B2 with TFEB. In addition, administration of procyanidin B2 resulted in a significant reduction of hepatic fat accumulation in high-fat diet (HFD)-induced obese mice, and also ameliorated HFD-induced metabolic abnormalities, including hyperlipidemia and hyperglycemia. It was confirmed that procyanidin B2 prevented HFD-induced hepatic fat accumulation through down-regulating lipogenesis-related gene expressions (PPARγ, C/EBPα and SREBP-1c), inhibiting pro-inflammatory cytokines production (IL-6 and TNF-α) and increasing antioxidant enzymes activity (GPx, SOD and CAT). Moreover, hepatic fatty acids analysis indicated that procyanidin B2 caused a significant increase in the levels of palmitic acid, oleic acid and linoleic acid. Intriguingly, procyanidin B2 restored the decreased nuclear TFEB expression in HFD-induced liver steatosis and up-regulated its target genes involved in lysosomal pathway (Lamp1, Mcoln, Uvrag), which suggested a previously unrecognized mechanism of procyanidin B2 on ameliorating HFD-induced hepatic steatosis. Taken together, our results demonstrated that procyanidin B2 attenuated FFAs-induced hepatic steatosis through regulating TFEB-mediated lysosomal pathway and redox state, which had important implications that modulation of TFEB might be a potential therapeutic strategy for hepatic steatosis and procyanidin B2 could represent a promising novel agent in the prevention and treatment of non-alcoholic fatty liver disease (NAFLD).

Coagonist of glucagon-like peptide-1 and glucagon receptors ameliorates nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is often associated with obesity and type 2 diabetes. Coagonists of glucagon-like peptide-1 receptor (GLP-1R) and glucagon receptor (GCGR) are under clinical investigation for the treatment of obesity and type 2 diabetes. In this study, we have demonstrated the effect of a balanced coagonist in the treatment of NAFLD using mouse models. GLP-1R agonist exendin-4, glucagon, and coagonist (Aib2 C24 chimera2) were administered to C57BL6/J mice, in which NAFLD was induced by carbon tetrachloride (CCl₄) treatment after high-fat diet (HFD) feeding, and choline-deficient, L-amino-acid-defined HFD (CDAHFD) feeding. Repeated dose administration of coagonist significantly attenuated liver inflammation and steatosis induced by acute and long-term treatment with CCl₄ in HFD-fed mice. Coagonist markedly attenuated the CDAHFD-induced expression of TIMP-1, MMP-9, TNF-α, MCP-1, COL1A1, and α-SMA. It also inhibited progression of hepatic steatosis and fibrosis in mice. Exendin-4 was better than glucagon, but coagonist was most effective in reduction of hepatic inflammation as well as steatosis. Coagonist of GLP-1R and GCGR improved NAFLD in C57BL6/J mice. This effect is mediated by reduction in lipotoxicity and inflammation in liver.

Involvement of Porphyromonas gingivalis in the progression of non-alcoholic fatty liver disease

BACKGROUND AND AIMS

The risk factors in the progression of nonalcoholic fatty liver disease (NAFLD) have not been fully clarified. Porphyromonas gingivalis (P.g) has been considered to be a confounding risk factor for systemic diseases. We aimed to evaluate the effect of P.g infection on risk of progression to NASH.

METHODS

(1) Serum IgG antibody titers against P.g fimbriae (fimA) in 200 biopsy-proven NAFLD patients were measured by ELISA and compared with histological findings. (2) C57BL/6J mice were fed a control diet (CD) or high-fat diet (HFD) with or without P.g-odontogenic infection and analyzed histologically. Mouse livers were analyzed using CE-TOFMS and LC-TOFMS.

RESULTS

(1) A significant correlation between fibrosis progression and antibody titers against P.g possessing fimA type 4 was identified (P = 0.0081). Multivariate analysis identified older age and type 4 P.g-positivity as risk factors for advanced fibrosis. (2) Fibrosis and steatosis were more severe in HFD P.g(+) mice compared with HFD P.g(-) mice. In metabolome analysis, fatty acid metabolism was significantly disrupted with HFD in P.g-infected mouse livers. Monounsaturated/saturated fatty acid ratios were significantly higher in the HFD P.g(+) group than in the HFD P.g(-) group (P < 0.05). Moreover, expression levels of SCD1 and ELOVL6 were significantly reduced.

CONCLUSIONS

These results suggest that P.g infection is an important risk factor for pathological progression in NAFLD. Increase in the monounsaturated/saturated fatty acid ratio may be an important change that facilitates progression of NAFLD.

Dietary DHA/EPA Ratio Changes Fatty Acid Composition and Attenuates Diet-Induced Accumulation of Lipid in the Liver of ApoE-/- Mice

Diets containing various docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) ratios protect against liver damage in mice fed with a high-fat diet (HFD). However, it is unclear whether these beneficial roles of DHA and EPA are associated with alterations of fatty acid (FA) composition in the liver. This study evaluated the positive impacts of n-6/n-3 polyunsaturated fatty acids (PUFAs) containing different DHA/EPA ratios on HFD-induced liver disease and alterations of the hepatic FA composition. ApoE^-/- mice were fed with HFDs with various ratios of DHA/EPA (2 : 1, 1 : 1, and 1 : 2) and an n-6/n-3 ratio of 4 : 1 for 12 weeks. After treatment, the serum and hepatic FA compositions, serum biochemical parameters, liver injury, and hepatic lipid metabolism-related gene expression were determined. Our results demonstrated that dietary DHA/EPA changed serum and hepatic FA composition by increasing contents of n-6 and n-3 PUFAs and decreasing amounts of monounsaturated fatty acids (MUFAs) and the n-6/n-3 ratio. Among the three DHA/EPA groups, the DHA/EPA 2 : 1 group tended to raise n-3 PUFAs concentration and lower the n-6/n-3 ratio in the liver, whereas DHA/EPA 1 : 2 tended to raise n-6 PUFAs concentration and improve the n-6/n-3 ratio. DHA/EPA supplementation reduced the hepatic impairment of lipid homeostasis, oxidative stress, and the inflammatory responses in HFD-fed mice. The DHA/EPA 2 : 1 group had lower serum levels of total cholesterol, triglycerides, and low-density lipoprotein cholesterol and higher levels of adiponectin than HFD group. The DHA/EPA 1 : 2 group had elevated serum levels of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase, without significant change the expression of genes for inflammation or hepatic lipid metabolism among the three DHA/EPA groups. The results suggest that DHA/EPA-enriched diet with an n-6/n-3 ratio of 4 : 1 may reverse HFD-induced nonalcoholic fatty liver disease to some extent by increasing n-6 and n-3 PUFAs and decreasing the amount of MUFAs and the n-6/n-3 ratio.

Dietary omega-3 and omega-6 polyunsaturated fatty acids modulate hepatic pathology

Recent evidence has suggested that dietary polyunsaturated fatty acids (PUFAs) modulate inflammation; however, few studies have focused on the pathobiology of PUFA using isocaloric and isolipidic diets and it is unclear if the associated pathologies are due to dietary PUFA composition, lipid metabolism or obesity, as most studies compare diets fed ad libitum. Our studies used isocaloric and isolipidic liquid diets (35% of calories from fat), with differing compositions of omega (ω)-6 or long chain (Lc) ω-3 PUFA that were pair-fed and assessed hepatic pathology, inflammation and lipid metabolism. Consistent with an isocaloric, pair-fed model we observed no significant difference in diet consumption between the groups. In contrast, the body and liver weight, total lipid level and abdominal fat deposits were significantly higher in mice fed an ω-6 diet. An analysis of the fatty acid profile in plasma and liver showed that mice on the ω-6 diet had significantly more arachidonic acid (AA) in the plasma and liver, whereas, in these mice ω-3 fatty acids such as eicosapentaenoic acid (EPA) were not detected and docosahexaenoic acid (DHA) was significantly lower. Histopathologic analyses documented that mice on the ω-6 diet had a significant increase in macrovesicular steatosis, extramedullary myelopoiesis (EMM), apoptotic hepatocytes and decreased glycogen storage in lobular hepatocytes, and hepatocyte proliferation relative to mice fed the Lc ω-3 diet. Together, these results support PUFA dietary regulation of hepatic pathology and inflammation with implications for enteral feeding regulation of steatosis and other hepatic lesions.

Lipid oxidation products in the pathogenesis of non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is the major public health challenge for hepatologists in the twenty-first century. NAFLD comprises a histological spectrum ranging from simple steatosis or fatty liver, to steatohepatitis, fibrosis, and cirrhosis. It can be categorized into two principal phenotypes: (1) non-alcoholic fatty liver (NAFL), and (2) non-alcoholic steatohepatitis (NASH). The mechanisms of NAFLD progression consist of lipid homeostasis alterations, redox unbalance, insulin resistance, and inflammation in the liver. Even though several studies show an association between the levels of lipid oxidation products and disease state, experimental evidence suggests that compounds such as reactive aldehydes and cholesterol oxidation products, in addition to representing hallmarks of hepatic oxidative damage, may behave as active players in liver dysfunction and the development of NAFLD. This review summarizes the processes that contribute to the metabolic alterations occurring in fatty liver that produce fatty acid and cholesterol oxidation products in NAFLD, with a focus on inflammation, the control of insulin signalling, and the transcription factors involved in lipid metabolism.

Lipidomics for studying metabolism

Many thousands of lipid species exist and their metabolism is interwoven via numerous pathways and networks. These networks can also change in response to cellular environment alterations, such as exercise or development of a disease. Measuring such alterations and understanding the pathways involved is crucial to fully understand cellular metabolism. Such demands have catalysed the emergence of lipidomics, which enables the large-scale study of lipids using the principles of analytical chemistry. Mass spectrometry, largely due to its analytical power and rapid development of new instruments and techniques, has been widely used in lipidomics and greatly accelerated advances in the field. This Review provides an introduction to lipidomics and describes some common, but important, cellular metabolic networks that can aid our understanding of metabolic pathways. Some representative applications of lipidomics for studying lipid metabolism and metabolic diseases are highlighted, as well as future applications for the use of lipidomics in studying metabolic pathways.

Hepatic and serum lipid signatures specific to nonalcoholic steatohepatitis in murine models

Nonalcoholic fatty liver (NAFL) is a precursor of nonalcoholic steatohepatitis (NASH), a condition that may progress to cirrhosis and hepatocellular carcinoma. Markers for diagnosis of NASH are still lacking. We have investigated lipid markers using mouse models that developed NAFL when fed with high fat diet (HFD) or NASH when fed using methionine choline deficient diet (MCDD). We have performed a comprehensive lipidomic analysis on liver tissues as well as on sera from mice fed HFD (n = 5), MCDD (n = 5) or normal diet as controls (n = 10). Machine learning approach based on prediction analysis of microarrays followed by random forests allowed identifying 21 lipids out of 149 in the liver and 14 lipids out of 155 in the serum discriminating mice fed MCDD from HFD or controls. In conclusion, the global approach implemented allowed characterizing lipid signatures specific to NASH in both liver and serum from animal models. This opens new avenue for investigating early and non-invasive lipid markers for diagnosis of NASH in human.

Fads1 and 2 are promoted to meet instant need for long-chain polyunsaturated fatty acids in goose fatty liver

Global prevalence of non-alcoholic fatty liver disease (NAFLD) constitutes a threat to human health. Goose is a unique model of NAFLD for discovering therapeutic targets as its liver can develop severe steatosis without overt injury. Fatty acid desaturase (Fads) is a potential therapeutic target as Fads expression and mutations are associated with liver fat. Here, we hypothesized that Fads was promoted to provide a protection for goose fatty liver. To test this, goose Fads1 and Fads2 were sequenced. Fads1/2/6 expression was determined in goose liver and primary hepatocytes by quantitative PCR. Liver fatty acid composition was also analyzed by gas chromatography. Data indicated that hepatic Fads1/2/6 expression was gradually increased with the time of overfeeding. In contrast, trans-C18:1n9 fatty acid (Fads inhibitor) was reduced. However, enhanced Fads capacity for long-chain polyunsaturated fatty acid (LC-PUFA) synthesis was not sufficient to compensate for the depleted LC-PUFAs in goose fatty liver. Moreover, cell studies showed that Fads1/2/6 expression was regulated by fatty liver-associated factors. Together, these findings suggest Fads1/2 as protective components are promoted to meet instant need for LC-PUFAs in goose fatty liver, and we propose this is required for severe hepatic steatosis without liver injury.

Toll-like receptor 7 affects the pathogenesis of non-alcoholic fatty liver disease

Recently, a possible link between toll-like receptor 7 (TLR7) and liver disease was suggested, although it was limited to fibrosis. Based on this report, we investigated whether TLR7 has a pivotal role in non-alcoholic fatty liver disease (NAFLD). The TLR7 signaling pathway, which is activated by imiquimod (TLR7 ligand) naturally, induced autophagy and released insulin-like growth factor 1 (IGF-1) into medium from hepatocytes. Lipid accumulation induced by unsaturated fatty acid (UFA; arachidonic acid:oleic acid = 1:1) in hepatocytes, was attenuated in TLR7 and autophagy activation. Interestingly, TLR7 activation attenuated UFA-induced lipid peroxidation products, such as malondialdehyde (MDA) and 4-Hydroxy-2-Nonenal (4-HNE). To clarify a possible pathway between TLR7 and lipid peroxidation, we treated hepatocytes with MDA and 4-HNE. MDA and 4-HNE induced 2-folds lipid accumulation in UFA-treated hepatocytes via blockade of the TLR7 signaling pathway's IGF-1 release compared to only UFA-treated hepatocytes. In vivo experiments carried out with TLR7 knockout mice produced results consistent with in vitro experiments. In conclusion, TLR7 prevents progression of NAFLD via induced autophagy and released IGF-1 from liver. These findings suggest a new therapeutic strategy for the treatment of NAFLD.

Susceptibility of Different Mouse Wild Type Strains to Develop Diet-Induced NAFLD/AFLD-Associated Liver Disease

Although non-alcoholic and alcoholic fatty liver disease have been intensively studied, concerning pathophysiological mechanisms are still incompletely understood. This may be due to the use of different animal models and resulting model-associated variation. Therefore, this study aimed to compare three frequently used wild type mouse strains in their susceptibility to develop diet-induced features of non-alcoholic/alcoholic fatty liver disease. Fatty liver disease associated clinical, biochemical, and histological features in C57BL/6, CD-1, and 129Sv WT mice were induced by (i) high-fat diet feeding, (ii) ethanol feeding only, and (iii) the combination of high-fat diet and ethanol feeding. Hepatic and subcutaneous adipose lipid profiles were compared in CD-1 and 129Sv mice. Additionally hepatic fatty acid composition was determined in 129Sv mice. In C57BL/6 mice dietary regimens resulted in heterogeneous hepatic responses, ranging from pronounced steatosis and inflammation to a lack of any features of fatty liver disease. Liver-related serum biochemistry showed high deviations within the regimen groups. CD-1 mice did not exhibit significant changes in metabolic and liver markers and developed no significant steatosis or inflammation as a response to dietary regimens. Although 129Sv mice showed no weight gain, this strain achieved most consistent features of fatty liver disease, apparent from concentration alterations of liver-related serum biochemistry as well as moderate steatosis and inflammation as a result of all dietary regimens. Furthermore, the hepatic lipid profile as well as the fatty acid composition of 129Sv mice were considerably altered, upon feeding the different dietary regimens. Accordingly, diet-induced non-alcoholic/alcoholic fatty liver disease is most consistently promoted in 129Sv mice compared to C57BL/6 and CD-1 mice. As a conclusion, this study demonstrates the importance of genetic background of used mouse strains for modeling diet-induced non-alcoholic/alcoholic fatty liver disease.

Active Lactobacillus rhamnosus LA68 or Lactobacillus plantarum WCFS1 administration positively influences liver fatty acid composition in mice on a HFD regime

Active administration of Lactobacilli positively influences liver fatty acid composition in mice on a HFD regime.

Immunohistochemical determination of the extracellular matrix modulation in a rat model of choline-deprived myocardium: the effects of carnitine

Choline has been identified as an essential nutrient with crucial role in many vital biological functions. Recent studies have demonstrated that heart dysfunction can develop in the setting of choline deprivation even in the absence of underlying heart disease. Matrix metalloproteinases (MMPs) are responsible for extracellular matrix degradation, and the dysregulation of MMP-2 and MMP-9 has been involved in the pathogenesis of various cardiovascular disorders. The aim of the study was to investigate the role of MMPs and their inhibitors (TIMPs), in the pathogenesis of choline deficiency-induced cardiomyopathy, and the way they are affected by carnitine supplementation. Male Wistar Albino adult rats were divided into four groups and received standard or choline-deficient diet with or without L-carnitine in drinking water (0.15% w/v) for 1 month. Heart tissue immunohistochemistry for MMP-2, MMP-9, TIMP-1, and TIMP-2 was performed. Choline deficiency was associated with suppressed immunohistochemical expression of MMP-2 and an increased expression of TIMP-2 compared to control, while it had no impact on TIMP-1. MMP-9 expression was decreased without, however, reaching statistical significance. Carnitine did not affect MMP-2, MMP-9, TIMP-1 or TIMP-2 expression. The pattern of TIMP and MMP modulation observed in a choline deficiency setting appears to promote fibrosis. Carnitine, although shown to suppress fibrosis, does not seem to affect MMP-2, MMP-9, TIMP-1 or TIMP-2 expression. Further studies will be required to identify the mechanism underlying the beneficial effects of carnitine.

Effects of Fatty Acids on CYP2A5 and Nrf2 Expression in Mouse Primary Hepatocytes

Abnormal fatty acid metabolism is observed throughout nonalcoholic fatty liver disease (NAFLD) pathogenesis, and fatty acid storage is an important inducing factor in insulin resistance, lipid oxidation, hepatic cell damage, and inflammation. During NAFLD pathogenesis, changes in blood and liver contents of different fatty acid types also vary. Cytochrome P450 2A5 (CYP2A5), an important enzyme in mouse liver, metabolizes many drugs and activates multiple pro-carcinogens with widely varying structures. According to the changes in liver fatty acid profiles observed in NAFLD animal models developed in our laboratory and others, saturated (PA/palmitic, and SA/stearic acids) and unsaturated (OA/oleic, LA/linoleic, ALA/α-linolenic and AA/arachidonic acids) fatty acids were selected to induce mouse primary hepatocytes, at concentrations under 1 mM, as detected by MTT assay. After 24 h treatment with various fatty acid concentrations and types, CYP2A5 mRNA and protein amounts, and enzyme activity were determined by real-time PCR, Western blot, and Coumarin 7-hydroxylation, respectively. Meanwhile, Nrf2 mRNA and protein levels were evaluated by real-time PCR and Western blot. The results indicated that saturated fatty acids are more potent in inducing CYP2A5 than unsaturated ones, except arachidonic acid. In addition, the changes in CYP2A5 expression were consistent with the alterations observed in Nrf2 expression, indicating that Nrf2 might play a regulatory role in CYP2A5 expression.

Changes in fatty acid composition in tissue and serum of obese cats fed a high fat diet

Background

Obesity and overweight have been frequently observed in dogs and cats in recent years as in humans. The compositions of fatty acids (FAs) in the accumulated lipids in tissues of obese animals may have important roles in the process and mechanisms related to the onset of metabolic disorders. The purpose of this study was to evaluate the effects of a high fat (HF) diet, which contained a higher proportion of saturated FAs, on FA metabolism and distribution in obese cats.

Cats (N = 12) were divided into control diet group (crude fat; 16.0 %) (n = 4) or a high fat (HF) diet group (crude fat; 23.9 %) (n = 8). The HF diet contained up to 60 % of calories from fat and was rich in stearic acid. Blood samples were collected at 0, 2, 4 and 6 weeks after the feeding. Adipose and liver tissues were collected at the 6^th week after feeding. We performed analysis of histological findings and fatty acid composition in serum and tissues.

Results

Body weights of the cats significantly increased in the HF group. The increased activities of hepatic enzymes and the accumulation of lipid droplets were found in hepatocytes in the HF group at the 6^th week after feeding.

In this study, the stearic acid (C18:0)-rich HF diet contained less oleic acid (C18:1n-9) and more linoleic acid (C18:2n-6) than the control. However, the composition of oleic acid in the liver was higher, and those of stearic acid and linoleic acid were lower in the HF group at the 6^th week after feeding. The higher oleic acid:stearic acid ratio suggests an increase in the conversion from saturated FA to mono-unsaturated FAs, which may reflect the hepatic storage of FAs as a relatively harmless form.

Conclusion

The stearic acid-rich HF diet increased hepatic lipid accumulation accompanied by the increased of hepatic oleic acid, increased serum oleic acid and activation of hepatic enzymes. These findings could be an important sign of early stages of dyslipidemia and hepatic damage. Also, the higher oleic acid:stearic acid ratio might be related to the increased activity of SCD-1, which suggests that the stearic acid-rich HF diet evoked hepatic lipogenesis in the feline liver.

Increased palmitate intake: higher acylcarnitine concentrations without impaired progression of β-oxidation

Palmitic acid (PA) is associated with higher blood concentrations of medium-chain acylcarnitines (MCACs), and we hypothesized that PA may inhibit progression of FA β-oxidation. Using a cross-over design, 17 adults were fed high PA (HPA) and low PA/high oleic acid (HOA) diets, each for 3 weeks. The [1-(13)C]PA and [13-(13)C]PA tracers were administered with food in random order with each diet, and we assessed PA oxidation (PA OX) and serum AC concentration to determine whether a higher PA intake promoted incomplete PA OX. Dietary PA was completely oxidized during the HOA diet, but only about 40% was oxidized during the HPA diet. The [13-(13)C]PA/[1-(13)C]PA ratio of PA OX had an approximate value of 1.0 for either diet, but the ratio of the serum concentrations of MCACs to long-chain ACs (LCACs) was significantly higher during the HPA diet. Thus, direct measurement of PA OX did not confirm that the HPA diet caused incomplete PA OX, despite the modest, but statistically significant, increase in the ratio of MCACs to LCACs in blood.

Peroxisomes compensate hepatic lipid overflow in mice with fatty liver

Major causes of lipid accumulation in liver are increased import or synthesis or decreased catabolism of fatty acids. The latter is caused by dysfunction of cellular organelles controlling energy homeostasis, i.e., mitochondria. Peroxisomes also appear to be an important organelle in lipid metabolism of hepatocytes, but little is known about their role in the development of non-alcoholic fatty liver disease (NAFLD). To investigate the role of peroxisomes alongside mitochondria in excessive hepatic lipid accumulation, we used leptin-resistant db/db mice on C57BLKS background, a mouse model that develops hyperphagia-induced diabetes with obesity and NAFLD. Proteome and gene expression analyses along with lipid analyses in the liver revealed differential expression of genes related to lipid metabolism and β-oxidation, whereas genes for peroxisomal proteins were predominantly regulated.

CONCLUSION

Our investigations show that in fatty liver disease in combination with obesity and diabetes, the hepatocyte-protecting organelle peroxisome is altered. Hence, peroxisomes might indicate a stage of pre-NAFLD, play a role in the early development of NAFLD and appear to be a potential target for treatment and prevention of NAFLD.

Characteristics of hepatic fatty acid compositions in patients with nonalcoholic steatohepatitis

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is closely related to insulin resistance and lipid metabolism. Recent studies have suggested that the quality of fat accumulated in the liver is associated with the development of nonalcoholic steatohepatitis (NASH). In this study, we investigated the fatty acid composition in liver tissue and its association with the pathology in NAFLD patients.

METHODS

One hundred and three patients diagnosed with NAFLD [simple steatosis (SS): 63, NASH: 40] were examined and their hepatic fatty acids were measured using gas chromatography. In addition, relationships between the composition and composition ratios of various fatty acids and patient backgrounds, laboratory test values, histology of the liver, and expression of fat metabolism-related enzymes were investigated.

RESULTS

The C16:1n7 content, the C16:1n7/C16:0 and C18:1n9/C18:0 ratios were increased and the C18:0/C16:0 ratio was decreased in the NASH group. The C18:0/C16:0 and C18:1n9/C18:0 ratios were associated with the steatosis score in liver tissue, and the C16:1n7/C16:0 ratio was associated with the lobular inflammation score. The expressions levels of genes: SCD1, ELOVL6, SREBP1c, FAS and PPARγ were enhanced in the NASH group. In multivariate analysis, the C18:0/C16:0 ratio was the most important factor that was correlated with the steatosis score. In contrast, the C16:1n7/C16:0 ratio was correlated with lobular inflammation.

CONCLUSION

The fatty acid composition in liver tissue and expression of genes related to fatty acid metabolism were different between the SS and NASH groups, suggesting that the acceleration of fatty acid metabolism is deeply involved in pathogenesis of NASH.

In vitro treatment of HepG2 cells with saturated fatty acids reproduces mitochondrial dysfunction found in nonalcoholic steatohepatitis

Activity of the oxidative phosphorylation system (OXPHOS) is decreased in humans and mice with nonalcoholic steatohepatitis. Nitro-oxidative stress seems to be involved in its pathogenesis. The aim of this study was to determine whether fatty acids are implicated in the pathogenesis of this mitochondrial defect. In HepG2 cells, we analyzed the effect of saturated (palmitic and stearic acids) and monounsaturated (oleic acid) fatty acids on: OXPHOS activity; levels of protein expression of OXPHOS complexes and their subunits; gene expression and half-life of OXPHOS complexes; nitro-oxidative stress; and NADPH oxidase gene expression and activity. We also studied the effects of inhibiting or silencing NADPH oxidase on the palmitic-acid-induced nitro-oxidative stress and subsequent OXPHOS inhibition. Exposure of cultured HepG2 cells to saturated fatty acids resulted in a significant decrease in the OXPHOS activity. This effect was prevented in the presence of a mimic of manganese superoxide dismutase. Palmitic acid reduced the amount of both fully-assembled OXPHOS complexes and of complex subunits. This reduction was due mainly to an accelerated degradation of these subunits, which was associated with a 3-tyrosine nitration of mitochondrial proteins. Pretreatment of cells with uric acid, an antiperoxynitrite agent, prevented protein degradation induced by palmitic acid. A reduced gene expression also contributed to decrease mitochondrial DNA (mtDNA)-encoded subunits. Saturated fatty acids induced oxidative stress and caused mtDNA oxidative damage. This effect was prevented by inhibiting NADPH oxidase. These acids activated NADPH oxidase gene expression and increased NADPH oxidase activity. Silencing this oxidase abrogated totally the inhibitory effect of palmitic acid on OXPHOS complex activity. We conclude that saturated fatty acids caused nitro-oxidative stress, reduced OXPHOS complex half-life and activity, and decreased gene expression of mtDNA-encoded subunits. These effects were mediated by activation of NADPH oxidase. That is, these acids reproduced mitochondrial dysfunction found in humans and animals with nonalcoholic steatohepatitis.

Dietary intake of palmitate and oleate has broad impact on systemic and tissue lipid profiles in humans

BACKGROUND

Epidemiologic evidence has suggested that diets with a high ratio of palmitic acid (PA) to oleic acid (OA) increase risk of cardiovascular disease (CVD).

OBJECTIVE

To gain additional insights into the relative effect of dietary fatty acids and their metabolism on CVD risk, we sought to identify a metabolomic signature that tracks with diet-induced changes in blood lipid concentrations and whole-body fat oxidation.

DESIGN

We applied comprehensive metabolomic profiling tools to biological specimens collected from 18 healthy adults enrolled in a crossover trial that compared a 3-wk high-palmitic acid (HPA) with a low-palmitic acid and high-oleic acid (HOA) diet.

RESULTS

A principal components analysis of the data set including 329 variables measured in 15 subjects in the fasted state identified one factor, the principal components analysis factor in the fasted state (PCF1-Fasted), which was heavily weighted by the PA:OA ratio of serum and muscle lipids, that was affected by diet (P < 0.0001; HPA greater than HOA). One other factor, the additional principal components analysis factor in the fasted state (PCF2-Fasted), reflected a wide range of acylcarnitines and was affected by diet in women only (P = 0.0198; HPA greater than HOA). HOA lowered the ratio of serum low-density lipoprotein to high-density lipoprotein (LDL:HDL) in men and women, and adjustment for the PCF1-Fasted abolished the effect. In women only, adjustment for the PCF2-Fasted eliminated the HOA-diet effect on serum total- and LDL-cholesterol concentrations. The respiratory exchange ratio in the fasted state was lower with the HPA diet (P = 0.04), and the diet effect was eliminated after adjustment for the PCF1-Fasted. The messenger RNA expression of the cholesterol regulatory gene insulin-induced gene-1 was higher with the HOA diet (P = 0.008).

CONCLUSIONS

These results suggest that replacing dietary PA with OA reduces the blood LDL concentration and whole-body fat oxidation by modifying the saturation index of circulating and tissue lipids. In women, these effects are also associated with a higher production and accumulation of acylcarnitines, possibly reflecting a shift in fat catabolism.

Nrf2 deletion causes "benign" simple steatosis to develop into nonalcoholic steatohepatitis in mice fed a high-fat diet

Background

Nonalcoholic fatty liver disease begins with the aberrant accumulation of triglyceride in the liver. Its spectrum includes the earliest stage of hepatic simple steatosis (SS), nonalcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma. Generally, hepatic SS is often self-limited; however 10%-30% of patients with hepatic SS progress to NASH. The cause(s) of the transition from SS to NASH are unclear. We aimed to test the contribution of nuclear erythroid 2-related factor 2 (Nrf2) on the progression of “benign” SS to NASH in mice fed a high fat diet. In doing so, we discovered the influence of fatty acid in that progression.

Method

The involvement of Nrf2 in defending against the development of NASH was studied in an experimental model induced by a high-fat diet. Wild-type and Nrf2-null mice were fed the diet. Their specimens were analyzed for pathology as well as for fatty acid content and ratios.

Result

In feeding the high-fat diet to the Wild-type and the Nrf2-null mice, the Wild-type mice increased hepatic fat deposition without inflammation or fibrosis (i.e., simple steatosis), while the Nrf2-null mice had significantly more hepatic steatosis and substantial inflammation, (i.e., nonalcoholic steatohepatitis). In addition, as a result of the high-fat diet, SFA (C20: 0, C22: 0) and MUFA (C18: 1, C20: 1) content in Nrf2-null mice were significantly higher than in Wild-type mice. In the Nrf2-null mice the PUFA/TFA ratio decreased; conversely, the MUFA/TFA ratio increased.

Conclusion

The deletion of Nrf2 causes “benign” SS to develop into NASH in mice fed with a high-fat diet, through prompt fatty acid accumulation and disruption of hepatic fatty acid composition in the liver.

Elevated oleic acid serum concentrations in patients suffering from alcohol dependence

Background

Alcohol-induced damages such as brain atrophy and fatty liver are closely related to a disturbed lipid metabolism. In animal models, a linkage between chronic alcohol consumption and changes in fatty acid (FA) composition in various organs and cells is well known and there is some indication that this phenomenon could be linked to behavioural alterations associated with alcohol addiction such as craving. However, the influence of ethanol on secretory FA has not been investigated so far. In this study, we therefore aimed at investigating whether there is a significant change of serum FA composition in patients suffering from alcohol dependence. We compared patients before and after treatment (detoxication) with control individuals who did not suffer from addiction. The roles of age, the duration and intensity of alcohol use and lifestyles were considered.

Methods

Serum FA was measured in 73 male ethanol dependent patients before and after alcohol withdrawal in an in-patient setting. Additionally, of this group, 45 patients were matched with 45 healthy male volunteers as controls.

Results

We found significant differences in the FA composition before and after detoxication as well as between patients and controls. After detoxication, the values changed towards the ones in healthy controls. The main finding during acute alcohol use was an increased oleic acid concentration above the level of the linoleic acid concentration.

Conclusions

An elevated oleic/linoleic acid ratio seems to be a state marker for acute alcohol use and may be a relevant trait marker during detoxification and possibly the subsequent therapeutic measures. The results of this pilot study need to be replicated in a larger study also including female patients. Further, the specificity of this potential biomarker needs to be determined.

Expression of cytochrome P450 2A5 in a C57BL/6J mouse model of nonalcoholic fatty liver disease

Cytochrome P450 2A5 (CYP2A5) expression is induced during the hepatotoxicity caused by various hepatotoxins and hepatitis. However, CYP2A5 expression during nonalcoholic fatty liver disease (NAFLD) is still unknown. In this study, serum biochemical parameters and liver histopathological analyses found that NAFLD had developed in C57BL/6J mice via administration of a high-fat diet continuously for 8 weeks. Subsequently, CYP2A5 expression was probed in the mice diagnosed with NAFLD that were treated with or without pyrazole, the inducer of chemical liver injury. It is shown that hepatic CYP2A5 mRNA, protein expression and coumarin 7-hydroxylase activity are enhanced with high-fat feed, and that pyrazole is able to further increase CYP2A5 expression and activity in mice with NAFLD. These results revealed that CYP2A5 is elevated during NAFLD and suggested that pyrazole and NAFLD act synergistically to induce the expression of CYP2A5 via an unclear mechanism.

Paraoxonase-1 deficiency is associated with severe liver steatosis in mice fed a high-fat high-cholesterol diet: a metabolomic approach

Oxidative stress is a determinant of liver steatosis and the progression to more severe forms of disease. The present study investigated the effect of paraoxonase-1 (PON1) deficiency on histological alterations and hepatic metabolism in mice fed a high-fat high-cholesterol diet. We performed nontargeted metabolomics on liver tissues from 8 male PON1-deficient mice and 8 wild-type animals fed a high-fat, high-cholesterol diet for 22 weeks. We also measured 8-oxo-20-deoxyguanosine, reduced and oxidized glutathione, malondialdehyde, 8-isoprostanes and protein carbonyl concentrations. Results indicated lipid droplets in 14.5% of the hepatocytes of wild-type mice and in 83.3% of the PON1-deficient animals (P < 0.001). The metabolomic assay included 322 biochemical compounds, 169 of which were significantly decreased and 16 increased in PON1-deficient mice. There were significant increases in lipid peroxide concentrations and oxidative stress markers. We also found decreased glycolysis and the Krebs cycle. The urea cycle was decreased, and the pyrimidine cycle had a significant increase in orotate. The pathways of triglyceride and phospholipid synthesis were significantly increased. We conclude that PON1 deficiency is associated with oxidative stress and metabolic alterations leading to steatosis in the livers of mice receiving a high-fat high-cholesterol diet.

Physiological and behavioural effects of fruit toxins on seed-predating versus seed-dispersing congeneric rodents

Fleshy, ripe fruits attract seed dispersers but also seed predators. Although many fruit consumers (legitimate seed dispersers as well as seed predators) are clearly exposed to plant secondary compounds (PSCs), their impact on the consumers’ physiology and foraging behaviour has been largely overlooked. Here, we document the divergent behavioural and physiological responses of three congeneric rodent species in the Middle East, seed dispersers versus seed predators, to fruit consumption. The fruit pulp of the desert plant Ochradenus baccatus contains high concentrations of glucosinolates (GLSs). These GLSs are hydrolyzed into active toxic compounds upon contact with the myrosinase enzyme released from seeds crushed during fruit consumption. Acomys russatus and A. cahirinus share a desert habitat. Acomys russatus acts as an O. baccatus seed predator, and A. cahirinus circumvents the activation of the GLSs by orally expelling vital seeds. We found that between the three species examined, A. russatus was physiologically most tolerant to whole fruit consumption and even A. minous, which is evolutionarily naïve to O. baccatus, exhibits greater tolerance to whole fruit consumption than A. cahirinus. However, like A. cahirinus, A. minous may also behaviourally avoid the activation of the GLSs by making a hole in the pulp and consuming only the seeds. Our findings demonstrate that seed predators have a higher physiological tolerance than seed dispersers when consuming fruits containing toxic PSCs. The findings also demonstrate the extreme ecological/evolutionary ability of this plant-animal symbiosis to shift from predation to mutualism and vice versa.