Suppression of acute ethanol-induced hepatic steatosis by docosahexaenoic acid is associated with downregulation of stearoyl-CoA desaturase 1 and inflammatory cytokines

Recent advances in anti-inflammation via AMPK activation

Inflammation is a complex physiological phenomenon, which is the body's defensive response, but abnormal inflammation can have adverse effects, and many diseases are related to the inflammatory response. AMPK, as a key sensor of cellular energy status, plays a crucial role in regulating cellular energy homeostasis and glycolipid metabolism. In recent years, the anti-inflammation effect of AMPK and related signalling cascade has begun to enter everyone's field of vision - not least the impact on metabolic diseases. A great number of studies have shown that anti-inflammatory drugs work through AMPK and related pathways. Herein, this article summarises recent advances in compounds that show anti-inflammatory effects by activating AMPK and attempts to comment on them.

Reduced incretin receptor trafficking upon activation enhances glycemic control and reverses obesity in diet-induced obese mice

Activation of incretin receptors by their cognate agonist augments sustained cAMP generation both from the plasma membrane as well as from the endosome. To address the functional outcome of this spatiotemporal signaling, we developed a nonacylated glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) receptor dual agonist I-M-150847 that reduced receptor internalization following activation of the incretin receptors. The incretin receptor dual agonist I-M-150847 was developed by replacing the tryptophan cage of exendin-4 tyrosine substituted at the amino terminus with the C-terminal undecapeptide sequence of oxyntomodulin that placed lysine 30 of I-M-150847 in frame with the corresponding lysine residue of GIP. The peptide I-M-150847 is a partial agonist of GLP-1R and GIPR; however, the receptors, upon activation by I-M-150847, undergo reduced internalization that promotes agonist-mediated iterative cAMP signaling and augments glucose-stimulated insulin exocytosis in pancreatic β cells. Chronic administration of I-M-150847 improved glycemic control, enhanced insulin sensitivity, and provided profound weight loss in diet-induced obese (DIO) mice. Our results demonstrated that despite being a partial agonist, I-M-150847, by reducing the receptor internalization upon activation, enhanced the incretin effect and reversed obesity.NEW & NOTEWORTHY Replacement of the tryptophan cage (Trp-cage) with the C-terminal oxyntomodulin undecapeptide along with the tyrosine substitution at the amino terminus converts the selective glucagon-like peptide-1 receptor (GLP-1R) agonist exendin-4 to a novel GLP-1R and GIPR dual agonist I-M-150847. Reduced internalization of incretin receptors upon activation by the GLP-1R and GIPR dual agonist I-M-150847 promotes iterative receptor signaling that enhances the incretin effect and reverses obesity.

N-3 Polyunsaturated Fatty Acids Protect against Alcoholic Liver Steatosis by Activating FFA4 in Kupffer Cells

Supplementation with fish oil rich in omega-3 polyunsaturated fatty acids (n-3 PUFAs) effectively reduces acute and chronic alcohol-induced hepatic steatosis. We aimed to find molecular mechanisms underlying the effects of n-3 PUFAs in alcohol-induced hepatic steatosis. Because free fatty acid receptor 4 (FFA4, also known as GPR120) has been found as a receptor for n-3 PUFAs in an ethanol-induced liver steatosis model, we investigated whether n-3 PUFAs protect against liver steatosis via FFA4 using AH7614, an FFA4 antagonist, and Ffa4 knockout (KO) mice. N-3 PUFAs and compound A (CpdA), a selective FFA4 agonist, reduced the ethanol-induced increase in lipid accumulation in hepatocytes, triglyceride content, and serum ALT levels, which were not observed in Ffa4 KO mice. N-3 PUFAs and CpdA also reduced the ethanol-induced increase in lipogenic sterol regulatory element-binding protein-1c expression in an FFA4-dependent manner. In Kupffer cells, treatment with n-3 PUFA and CpdA reversed the ethanol-induced increase in tumor necrosis factor-α, cyclooxygenase-2, and NLR family pyrin domain-containing 3 expression levels in an FFA4-dependent manner. In summary, n-3 PUFAs protect against ethanol-induced hepatic steatosis via the anti-inflammatory actions of FFA4 on Kupffer cells. Our findings suggest FFA4 as a therapeutic target for alcoholic hepatic steatosis.

Docosahexaenoic acid-loaded nanoparticles: A state-of-the-art of preparation methods, characterization, functionality, and therapeutic applications

Docosahexaenoic acid (DHA, C22:6 n-3), an omega-3 polyunsaturated fatty acid, offers several beneficial effects. DHA helps in reducing depression, autoimmune diseases, rheumatoid arthritis, attention deficit hyperactivity syndrome, and cardiovascular diseases. It can stimulate the development of brain and nerve, alleviate lipids metabolism-related disorders, and enhance vision development. However, DHA susceptibility to chemical oxidation, poor water solubility, and unpleasant order could restrict its applications for nutritional and therapeutic purposes. To avoid these drawbacks and enhance its bioavailability, DHA can be encapsulated using an effective delivery system. Several encapsulation methods are recognized, and DHA-loaded nanoparticles have demonstrated numerous benefits. In clinical studies, positive influences on the development of several diseases have been reported, but some assumptions are conflicting and need more exploration, since DHA has a systemic and not a targeted release at the required level. This might cause the applications of nanoparticles that could allow DHA release at the required level and improve its efficiency, thus resulting in a better controlling of several diseases. In the current review, we focused on researches investigating the formulation and development of DHA-loaded nanoparticles using different delivery systems, including low-density lipoprotein, zinc oxide, silver, zein, and resveratrol-stearate. Silver-DHA nanoparticles presented a typical particle size of 24 nm with an incorporation level of 97.67 %, while the entrapment efficiency of zinc oxide-DHA nanoparticles represented 87.3 %. By using zein/Poly (lactic-co-glycolic acid) stabilized nanoparticles, DHA's encapsulation level reached 84.6 %. We have also highlighted the characteristics, functionality and medical implementation of these nanoparticles in the treatment of inflammations, brain disorders, diabetes as well as hepatocellular carcinoma.

Click chemistry-based enrichment strategy for tracing cellular fatty acid metabolism by LC-MS/MS

Fatty acids (FAs), which were initially recognized as energy sources and essential building blocks of biomembranes, serve as the precursors of important signaling molecules. Tracing FA metabolism is essential to understanding the biochemical activity and role of FAs in physiological and pathological events. Inspired by the advances in click chemistry for protein enrichment, we herein established a click chemistry-based enrichment (CCBE) strategy for tracing the cellular metabolism of eicosapentaenoic acid (EPA, 20:5 n-3) in neural cells. Terminal alkyne-labeled EPA (EPAA) used as a surrogate was incubated with N2a, mouse neuroblastoma cells, and alkyne-labeled metabolites (ALMs) were selectively captured by an azide-modified resin via a Cu(I)-catalyzed azide-alkyne cycloaddition reaction for enrichment. After removing unlabeled metabolites, ALMs containing a triazole moiety were cleaved from solid-phase resins and subjected to liquid chromatography mass spectrometry (LC-MS) analysis. The proposed CCBE strategy is highly selective for capturing and enriching alkyne-labeled metabolites from the complicated matrices. In addition, this method can overcome current detection limits by enhancing MS sensitivity of targets, improving the chromatographic separation of sn-position glycerophospholipid regioisomers, facilitating structural characterization of ALMs by a specific MS/MS fragmentation signature, and providing versatile fluorescence detection of ALMs for cellular distribution. This CCBE strategy might be expanded to trace the metabolism of other FAs, small molecules, or drugs.

The Intestinal Microbiota in the Development of Chronic Liver Disease: Current Status

Chronic liver disease (CLD) is a significant global health burden, leading to millions of deaths annually. The gut-liver axis plays a pivotal role in this context, allowing the transport of gut-derived products directly to the liver, as well as biological compounds from the liver to the intestine. The gut microbiota plays a significant role in maintaining the health of the digestive system. A change in gut microbiome composition as seen in dysbiosis is associated with immune dysregulation, altered energy and gut hormone regulation, and increased intestinal permeability, contributing to inflammatory mechanisms and damage to the liver, irrespective of the underlying etiology of CLD. The aim of this review is to present the current knowledge about the composition of the intestinal microbiome in healthy individuals and those with CLD, including the factors that affect this composition, the impact of the altered microbiome on the liver, and the mechanisms by which it occurs. Furthermore, this review analyzes the effects of gut microbiome modulation on the course of CLD, by using pharmacotherapy, nutrition, fecal microbiota transplantation, supplements, and probiotics. This review opens avenues for the translation of knowledge about gut-liver interplay into clinical practice as an additional tool to fight CLD and its complications.

The effect of omega-3 fatty acids on alcohol-induced damage

Alcohol is the most widely consumed psychoactive substance in the world that has a severe impact on many organs and bodily systems, particularly the liver and nervous system. Alcohol use during pregnancy roots long-lasting changes in the newborns and during adolescence has long-term detrimental effects especially on the brain. The brain contains docosahexaenoic acid (DHA), a major omega-3 (n-3) fatty acid (FA) that makes up cell membranes and influences membrane-associated protein function, cell signaling, gene expression and lipid production. N-3 is beneficial in several brain conditions like neurodegenerative diseases, ameliorating cognitive impairment, oxidative stress, neuronal death and inflammation. Because alcohol decreases the levels of n-3, it is timely to know whether n-3 supplementation positively modifies alcohol-induced injuries. The aim of this review is to summarize the state-of-the-art of the n-3 effects on certain conditions caused by alcohol intake, focusing primarily on brain damage and alcoholic liver disease.

Lipid Aldehydes 4-Hydroxynonenal and 4-Hydroxyhexenal Exposure Differentially Impact Lipogenic Pathways in Human Placenta

Long chain polyunsaturated fatty acids (LCPUFAs), such as the omega-6 (n-6) arachidonic acid (AA) and n-3 docosahexanoic acid (DHA), have a vital role in normal fetal development and placental function. Optimal supply of these LCPUFAs to the fetus is critical for improving birth outcomes and preventing programming of metabolic diseases in later life. Although not explicitly required/recommended, many pregnant women take n-3 LCPUFA supplements. Oxidative stress can cause these LCPUFAs to undergo lipid peroxidation, creating toxic compounds called lipid aldehydes. These by-products can lead to an inflammatory state and negatively impact tissue function, though little is known about their effects on the placenta. Placental exposure to two major lipid aldehydes, 4-hydroxynonenal (4-HNE) and 4-hydroxyhexenal (4-HHE), caused by peroxidation of the AA and DHA, respectively, was examined in the context of lipid metabolism. We assessed the impact of exposure to 25 μM, 50 μM and 100 μM of 4-HNE or 4-HHE on 40 lipid metabolism genes in full-term human placenta. 4-HNE increased gene expression associated with lipogenesis and lipid uptake (ACC, FASN, ACAT1, FATP4), and 4-HHE decreased gene expression associated with lipogenesis and lipid uptake (SREBP1, SREBP2, LDLR, SCD1, MFSD2a). These results demonstrate that these lipid aldehydes differentially affect expression of placental FA metabolism genes in the human placenta and may have implications for the impact of LCPUFA supplementation in environments of oxidative stress.

Increased Expression of Hepatic Stearoyl-CoA Desaturase (SCD)-1 and Depletion of Eicosapentaenoic Acid (EPA) Content following Cytotoxic Cancer Therapy Are Reversed by Dietary Fish Oil

Cancer treatment evokes impediments to liver metabolism that culminate in fatty liver. This study determined hepatic fatty acid composition and expression of genes and mediators involved in lipid metabolism following chemotherapy treatment. Female rats bearing the Ward colon tumor were administered Irinotecan (CPT-11) +5-fluorouracil (5-FU) and maintained on a control diet or a diet containing eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) (2.3 g/100 g fish oil). Healthy animals provided with a control diet served as a reference group. Livers were collected one week after chemotherapy. Triacylglycerol (TG), phospholipid (PL), ten lipid metabolism genes, leptin, and IL-4 were measured. Chemotherapy increased TG content and reduced EPA content in the liver. Expression of SCD1 was upregulated by chemotherapy, while dietary fish oil downregulated its expression. Dietary fish oil down-regulated expression of the fatty acid synthesis gene FASN, while restoring the long chain fatty acid converting genes FADS2 and ELOVL2, and genes involved in mitochondrial β-oxidation (CPT1α) and lipid transport (MTTP1), to values similar to reference animals. Neither leptin nor IL-4 were affected by chemotherapy or diet. Depletion of EPA is associated with pathways evoking enhanced TG accumulation in the liver. Restoring EPA through diet may pose a dietary strategy to attenuate chemotherapy-associated impediments in liver fatty acid metabolism.

Environmental concentrations of benzophenone-3 disturbed lipid metabolism in the liver of clown anemonefish (Amphiprion ocellaris)

Benzophenone-3 (BP-3) often used as a UV filter in various products and an endocrine disruptor. In this work, we exposed the clown anemonefish to 10 μg/L and 50 μg/L BP-3 for 7 and 14 days. Liver histological, biochemical analysis, and transcriptome sequencing were used to explore the mechanism of the lipid metabolism disorder in the liver of three-month-old clown anemonefish treated with BP-3. The histological and biochemical analysis showed that BP-3 induces morphological changes and lipid droplet accumulation, and the lipid content, lipase, and antioxidant enzyme activity were abnormal. After treatment with 10 μg/L and 50 μg/L BP-3 for 7 days, the transcriptome analysis further demonstrated that the KEGG analysis revealed that the differentially expressed genes (DEGs) were mainly associated with fat digestion and absorption, PPAR signaling pathway, circadian rhythm, and mineral absorption pathways; After 10 μg/L and 50 μg/L of BP-3 exposure for 14 days, the KEGG analysis were mainly associated with circadian rhythm, circadian rhythm-fly, protein processing in the endoplasmic reticulum, and beta-alanine metabolism pathways. Several key genes were involved in the process of liver lipid metabolism, including CD36, APoA-Ⅰ, FABP, LPL, ACS, and PEPCK. The qRT-PCR validation results showed that eight genes (CYP8B1, FABP1, LPL, MGAT, PEPCK, PER1, PSMB4, PSME2) were significantly down-regulated, and the other two genes (Fbxl3, RXR) were significantly up-regulated after 7 days of BP-3 exposure. Similarly, eleven genes (AMPK, ARNTL, Bmal1, CASP3, CYC, CYP2J, CYP2U1, GSK3A, PEPCK, RAC1, RORA) were significantly up-regulated, and the other four genes (NR1D1, PER1, PTGDS, HLF) were significantly down-regulated after 14 days of BP-3 exposure. In conclusion, our results elucidate the physiological and molecular responses to BP-3 exposure in the liver lipid metabolism of clown anemonefish, and these findings reveal that the regulation of lipid metabolism is disturbed when clown anemonefish is exposed to UV filters.

Analysis of alcohol use, consumption of micronutrient and macronutrients, and liver health in the 2017-2018 National Health and Nutrition Examination Survey

BACKGROUND

Alcohol use is a major global healthcare burden that contributes to numerous adverse health outcomes, including liver disease. Many factors influence individual susceptibility to alcohol-associated diseases, including nutritional factors. The objective of the current study was to examine inter-relations among alcohol, dietary micronutrients and macronutrient consumption, and liver health by analyzing data from the 2017-2018 National Health and Nutrition Examination Survey (NHANES).

METHODS

Based on self-reported alcohol consumption, NHANES respondents were assigned to one of four categories: never drinkers (lifetime abstainers), non-drinkers (past-year abstainers), moderate drinkers (1/2 drinks per day for females/males, respectively), and heavy drinkers (>1/>2 drinks per day for females/males, respectively, and/or frequent binge drinking). Survey-weighted regression analyses (adjusted for gender, age, race, education, and body mass index) were performed to examine associations between alcohol intake, dietary, and liver health characteristics.

RESULTS

Individuals categorized as heavy drinkers were significantly younger, most often well-educated males with low incidences of diabetes and other comorbidities. They consumed the most overall calories and various micronutrients, indicating a diet that was not necessarily nutrient poor. Neither moderate nor heavy drinkers had liver steatosis or fibrosis as measured by liver elastography, although heavy drinkers had modestly elevated plasma biomarkers of liver injury, including ALT, AST, and GGT, compared with the other groups.

CONCLUSIONS

Our findings suggest that the category of heavy drinkers in the 2017-2018 NHANES consisted of generally healthy individuals with high-energy intake and no evidence of liver steatosis or fibrosis. However, slightly increased plasma liver markers may indicate a risk of future progression to more advanced stages of liver disease over time in some individuals. Several limitations should be considered when interpreting these data, including the potential misclassification of drinking categories and the lack of standardized cutoff scores for fatty liver as assessed by elastography, among others.

Dietary Goji Shapes the Gut Microbiota to Prevent the Liver Injury Induced by Acute Alcohol Intake

Diet is a major driver of the structure and function of the gut microbiota, which influences the host physiology. Alcohol abuse can induce liver disease and gut microbiota dysbiosis. Here, we aim to elucidate whether the well-known traditional health food Goji berry targets gut microbiota to prevent liver injury induced by acute alcohol intake. The results showed that Goji supplementation for 14 days alleviated acute liver injury as indicated by lowering serum aspartate aminotransferase, alanine aminotransferase, pro-inflammatory cytokines, as well as lipopolysaccharide content in the liver tissue. Goji maintained the integrity of the epithelial barrier and increased the levels of butyric acid in cecum contents. Furthermore, we established the causal relationship between gut microbiota and liver protection effects of Goji with the help of antibiotics treatment and fecal microbiota transplantation (FMT) experiments. Both Goji and FMT-Goji increased glutathione (GSH) in the liver and selectively enriched the butyric acid-producing gut bacterium Akkermansia and Ruminococcaceae by using 16S rRNA gene sequencing. Metabolomics analysis of cecum samples revealed that Goji and its trained microbiota could regulate retinoyl β-glucuronide, vanillic acid, and increase the level of glutamate and pyroglutamic acid, which are involved in GSH metabolism. Our study highlights the communication among Goji, gut microbiota, and liver homeostasis.

Pathogenesis of Alcohol-Associated Fatty Liver: Lessons From Transgenic Mice

Alcohol-associated liver disease (ALD) is a major public health issue that significantly contributes to human morbidity and mortality, with no FDA-approved therapeutic intervention available. The health burden of ALD has worsened during the COVID-19 pandemic, which has been associated with a spike in alcohol abuse, and a subsequent increase in hospitalization rates for ALD. A key knowledge gap that underlies the lack of novel therapies for ALD is a need to better understand the pathogenic mechanisms that contribute to ALD initiation, particularly with respect to hepatic lipid accumulation and the development of fatty liver, which is the first step in the ALD spectrum. The goal of this review is to evaluate the existing literature to gain insight into the pathogenesis of alcohol-associated fatty liver, and to synthesize alcohol’s known effects on hepatic lipid metabolism. To achieve this goal, we specifically focus on studies from transgenic mouse models of ALD, allowing for a genetic dissection of alcohol’s effects, and integrate these findings with our current understanding of ALD pathogenesis. Existing studies using transgenic mouse models of ALD have revealed roles for specific genes involved in hepatic lipid metabolic pathways including fatty acid uptake, mitochondrial β-oxidation, de novo lipogenesis, triglyceride metabolism, and lipid droplet formation. In addition to reviewing this literature, we conclude by identifying current gaps in our understanding of how alcohol abuse impairs hepatic lipid metabolism and identify future directions to address these gaps. In summary, transgenic mice provide a powerful tool to understand alcohol’s effect on hepatic lipid metabolism and highlight that alcohol abuse has diverse effects that contribute to the development of alcohol-associated fatty liver disease.

Myriocin Treatment Reverses Alcohol-Induced Alterations in Polyunsaturated Fatty Acid-Containing Phospholipid Expression in the Liver

Chronic heavy alcohol exposure causes steatohepatitis manifested by abnormal intra-hepatocyte accumulation of lipid and parenchymal inflammation. Attendant alterations in polyunsaturated fatty acid (PUFA)-containing phospholipids could cause alcoholic liver disease (ALD) to progress by promoting oxidative stress, inflammation, and fibrogenesis. Previously we showed that myriocin, a serine palmitoyltransferase inhibitor, ameliorates experimental alcohol-induced steatohepatitis. However, the surprising overall therapeutic responses suggested that myriocin's targets may go beyond sphingolipids. To this end, the present study examines the effects of myriocin on hepatic composition of docosahexaenoic acid (DHA)- and arachidonic acid (AA)-containing phospholipids in an experimental model of ALD. A chronic+binge ethanol exposure model was generated by feeding Long Evans rats with ethanol-containing diets (24% caloric content) for 8 weeks and simultaneously binge gavage administering 2 g/kg ethanol on Tuesdays, Thursdays and Saturdays during Weeks 6-8. Myriocin was administered by i.p. injection on Mondays, Wednesdays, and Fridays of Weeks 3-8. Control rats were studied in parallel. Upon euthanasia, the livers were harvested to examine ethanol- and/or myriocin-modulation of hepatic lipids using matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS). Results were analyzed statistically by two-way analysis of variance and depicted with data bar plots and heatmaps. Chronic+binge ethanol exposures significantly increased hepatic expression of AA-containing phospholipids including PE(36:4) (P = .005), PE(38:4) (P = .03), and PI(38:4) (P = .04) and reduced DHA-containing phospholipids including PS(40:6) (P = .03) and PE(40:6) (P = .04) relative to control. Myriocin partially reversed ethanol's effects on hepatic PUFA expression by decreasing PE(36:4) (P = .004) and increasing PS(40:6) (P = .04) and PI(40:6) (P = .0003) relative to ethanol-exposed rats. Ethanol-mediated alterations in hepatic PUFA-containing phospholipids may contribute to hepatic oxidative and inflammatory injury by increasing AA and fibrogenesis by inhibiting DHA. The results suggest that Myriocin may help reduce or prevent long-term and progressive liver injury stemming from excessive chronic+binge ethanol consumption.

DHA Suppresses Hepatic Lipid Accumulation via Cyclin D1 in Zebrafish

With the widespread use of high-fat diets (HFDs) in aquaculture, fatty livers are frequently observed in many fish species. The aim of this study was to investigate if docosahexaenoic acid (DHA) could be used to reduce the fatty liver in zebrafish generated by a 16% soybean oil-HFD over 2 weeks of feeding. The DHA was added to iso-lipidic HFD at 0.5, 1.0, and 2.0% of diet. Supplementation of DHA reduced growth and feed efficiency in a dose dependent manner being lowest in the HFDHA2.0 group. Hepatic triglyceride (TG) in zebrafish fed 0.5% DHA-supplemented HFD (HFDHA0.5) was significantly lower than in the HFD control. Transcriptional analyses of hepatic genes showed that lipid synthesis was reduced, while fatty acid β-oxidation was increased in the HFDHA0.5 group. Furthermore, the expression of Cyclin D1 in liver of zebrafish fed HFDHA0.5 was significantly reduced compared to that in fish fed HFD. In zebrafish liver cells, Cyclin D1 knockdown and blocking of Cyclin D1-CDK4 signal led to inhibited lipid biosynthesis and elevated lipid β-oxidation. Besides, DHA-supplemented diet resulted in a rich of Proteobacteria and Actinobacteriota in gut microbiota, which promoted lipid β-oxidation but did not alter the expression of Cyclin D1 in germ-free zebrafish model. In conclusion, DHA not only inhibits hepatic lipid synthesis and promotes lipid β-oxidation via Cyclin D1 inhibition, but also facilitates lipid β-oxidation via gut microbiota. This study reveals the lipid-lowering effects of DHA and highlights the importance of fatty acid composition when formulating fish HFD.

A New Perspective on Fish Oil: The Prevention of Alcoholic Liver Disease

The mechanisms of alcoholic liver diseases (ALD) are very complex and interrelated, including abnormal lipid metabolism, oxidative stress, and gut-derived endotoxin pathway. On the other hand, fish oil is rich in n-3 polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which decrease blood triglyceride concentration in hypertriglycemia patients and show protective effects against fatty liver. However, there is limited evidence from studies of the relationship between fish oil and ALD based on the viewpoint of the intestinal integrity and microflora. Therefore, this review discusses the mechanism of amelioration for ALD by fish oil. Based on our previous studies, partial replacement of olive oil by fish oil in alcohol-containing liquid diet ameliorated the liver damage including fatty liver and inflammation in rats. Based on these results, the mechanisms of hepatoprotective effects due to fish oil substitution were discussed in three parts, such as regulating lipid metabolism, decreasing oxidative stress and maintaining intestinal health. First of all, we found that fish oil substitution increased plasma adiponectin levels, and then increasing MCAD and CPT-1 mRNA levels to accelerate fatty acid oxidation in liver, then further prevent ethanol-induced hepatosteatosis in rats with chronic alcohol-feeding. Fish oil replacement also enhanced hepatic autophagy flux, which enhanced lipid degradation, then inhibited lipid accumulation in liver. Secondly, the appreciable proportion of fish oil decreased lipid peroxidation by reducing the protein expression of cytochrome p450 2E1 in chronic alcohol-feeding rats. We also speculated that the appropriate proportion of n-6 and n-3 PUFAs is very important for preventing alcoholic liver disease. At last, substituting fish oil for olive oil normalized the intestinal permeability and fecal microbiota composition, thus providing a low plasma endotoxin level and inflammatory responses, which exert ameliorative effects on ethanol-induced liver injuries in rats.

Increased lipogenesis is critical for self-renewal and growth of breast cancer stem cells: Impact of omega-3 fatty acids

Aberrant lipid metabolism has recently been recognized as a new hallmark of malignancy, but the characteristics of fatty acid metabolism in breast cancer stem cells (BCSC) and potential interventions targeting this pathway remain to be addressed. Here, by using the in vitro BCSC models, mammosphere‐derived MCF‐7 cells and HMLE‐Twist‐ER cells, we found that the cells with stem cell‐like properties exhibited a very distinct profile of fatty acid metabolism compared with that of their parental cancer cells, characterized by increased lipogenesis, especially the activity of stearoyl‐CoA desaturase 1 (SCD1) responsible for the production of monounsaturated fatty acids, and augmented synthesis and utilization of the omega‐6 arachidonic acid (AA). Suppression of SCD1 activity by either enzyme inhibitors or small interfering RNA (siRNA) knockdown strikingly limited self‐renewal and growth of the BCSC, suggesting a key role for SCD1 in BCSC proliferation. Furthermore, elevated levels of SCD1 and other lipogenic enzymes were observed in human breast cancer tissues relative to the noncancer tissues from the same patients and correlated with the pathological grades. Interestingly, treatment of BCSC with omega‐3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid, effectively downregulated the expression of the lipogenic enzymes and markedly suppressed BCSC self‐renewal and growth. Dietary supplementation of nude mice bearing BCSC‐derived tumors with omega‐3 fatty acids also significantly reduced their tumor load. These findings have demonstrated that increased lipogenesis is critical for self‐renewal and growth of BCSC, and that omega‐3 fatty acids are effective in targeting this pathway to exert their anticancer effect.

Beneficial effects of an endogenous enrichment in n3-PUFAs on Wnt signaling are associated with attenuation of alcohol-mediated liver disease in mice

Alcohol-associated liver disease (ALD) is a major human health issue for which there are limited treatment options. Experimental evidence suggests that nutrition plays an important role in ALD pathogenesis, and specific dietary fatty acids, for example, n6 or n3-PUFAs, may exacerbate or attenuate ALD, respectively. The purpose of the current study was to determine whether the beneficial effects of n3-PUFA enrichment in ALD were mediated, in part, by improvement in Wnt signaling. Wild-type (WT) and fat-1 transgenic mice (that endogenously convert n6-PUFAs to n3) were fed ethanol (EtOH) for 6 weeks followed by a single LPS challenge. fat-1 mice had less severe liver damage than WT littermates as evidenced by reduced plasma alanine aminotransferase, hepatic steatosis, liver tissue neutrophil infiltration, and pro-inflammatory cytokine expression. WT mice had a greater downregulation of Axin2, a key gene in the Wnt pathway, than fat-1 mice in response to EtOH and LPS. Further, there were significant differences between WT and fat-1 EtOH+LPS-challenged mice in the expression of five additional genes linked to the Wnt signaling pathway, including Apc, Fosl1/Fra-1, Mapk8/Jnk-1, Porcn, and Nkd1. Compared to WT, primary hepatocytes isolated from fat-1 mice exhibited more effective Wnt signaling and were more resistant to EtOH-, palmitic acid-, or TNFα-induced cell death. Further, we demonstrated that the n3-PUFA-derived lipid mediators, resolvins D1 and E1, can regulate hepatocyte expression of several Wnt-related genes that were differentially expressed between WT and fat-1 mice. These data demonstrate a novel mechanism by which n3-PUFAs can ameliorate ALD.

Diet-Regulating Microbiota and Host Immune System in Liver Disease

The gut microbiota has been known to modulate the immune responses in chronic liver diseases. Recent evidence suggests that effects of dietary foods on health care and human diseases are related to both the immune reaction and the microbiome. The gut-microbiome and intestinal immune system play a central role in the control of bacterial translocation-induced liver disease. Dysbiosis, small intestinal bacterial overgrowth, translocation, endotoxemia, and the direct effects of metabolites are the main events in the gut-liver axis, and immune responses act on every pathways of chronic liver disease. Microbiome-derived metabolites or bacteria themselves regulate immune cell functions such as recognition or activation of receptors, the control of gene expression by epigenetic change, activation of immune cells, and the integration of cellular metabolism. Here, we reviewed recent reports about the immunologic role of gut microbiotas in liver disease, highlighting the role of diet in chronic liver disease.

Quantitative analysis of n-3 polyunsaturated fatty acids and their metabolites by chemical isotope labeling coupled with liquid chromatography - mass spectrometry

n-3 polyunsaturated fatty acids (PUFAs) and their metabolites play the crucial role in a wide range of physiologic and pathologic processes, including cardiovascular, neurodegenerative diseases, and inflammation-associated disorders. However, the quantitative analysis of n-3 PUFAs and their metabolites, oxylipins, is obstructed by high structural similarity, poor ionization efficiency and low abundance. In this study, a sensitive method was developed to quantify 28 n-3 PUFAs/oxylipins using chemical isotope labeling coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Standards labeled with cholamine-d₉ were used as one-to-one internal standards to achieve accurate quantification. The cholamine-d₀-derivatized biological samples were mixed with cholamine d₉-labeled standards for LC-MS/MS with multiple reaction monitoring. After cholamine derivatization, both MS sensitivity and chromatographic performance of n-3 PUFAs/oxylipins were substantially improved. Furthermore, the relationship between retention time and substituent position of regioisomers, and their fragmentation patterns were investigated, which may facilitate the identification of unknown oxylipins. Additionally, the developed method was applied to quantify the target n-3 PUFAs/oxylipins in serum and brain tissue from fish oil-supplemented mice, which exhibited its great potential and practicability. Collectively, this sensitive and reliable method may facilitate the elucidation of the roles of n-3 PUFAs/oxylipins in the physiological and pathological processes.

A mini-review of the rodent models for alcoholic liver disease: shortcomings, application, and future prospects

Rodents are the most common models in studies of alcoholic liver disease (ALD). Although several rodents ALD models have been established and multiple mechanisms have been elucidated based on them, these models have some non-negligible shortcomings, specifically only inducing early stage (mainly steatosis, slight to moderate steatohepatitis) but not the whole spectrum of human ALD. The resistance of rodents to advanced ALD has been suggested to be due to the physiological differences between rodents and human beings. Previous studies have reported significant interstrain differences in the susceptibility to ethanol-induced liver injury and in the manifestation of ALD (such as different alteration of lipid profiles). Therefore, it would be interesting to characterize the manifestation of ethanol-induced liver damage in various rodents, which may provide a recommendation to investigators of ALD. Furthermore, more severe ALD models need to be established for the study of serious ALD forms, which may be achieved by using genetic modified rodents.

Metabolomics Study of Serum from a Chronic Alcohol-Fed Rat Model Following Administration of Defatted Tenebrio molitor Larva Fermentation Extract

We have previously showed that defatted mealworm fermentation extract (MWF) attenuates alcoholic liver injury by regulating lipid, inflammatory, and antioxidant metabolism in chronic alcohol-fed rats. The current metabolomics study was performed to monitor biochemical events following the administration of MWF (daily for eight weeks) to a rat model of alcoholic liver injury by gas chromatography-tandem mass spectrometry (GC-MS/MS). The levels of 15 amino acids (AAs), 17 organic acids (OAs), and 19 free fatty acids (FFAs) were measured in serum. Analysis of variance (ANOVA), principal component analysis (PCA), and partial least squares discriminant analysis (PLS-DA) were used to compare the levels of 51 metabolites in serum. In particular, 3-hydroxybutyric acid (3-HB), pyroglutamic acid (PG), octadecanoic acid, and docosahexaenoic acid (DHA) were evaluated as high variable importance point (VIP) scores and PCA loading scores as determined by PLS-DA and PCA, and these were significantly higher in the MWF and silymarin groups than in the EtOH group. MWF showed a protective effect from alcohol-induced liver damage by elevating hepatic β-oxidation activity, and serum 3-HB levels were significantly higher in the MWF group than in the EtOH control group. Glycine levels were higher in the MWF group than in the EtOH group, and PG levels (related to glutathione production) were also elevated, indicating a reduction in alcohol-related oxidative stress. In addition, MWF is protected from alcohol-induced inflammation and steatosis by increasing serum DHA, palmitic, and octadecanoic acid levels as compared with the EtOH group. These results suggest that MWF might attenuate alcoholic liver disease, due to its anti-inflammatory and antioxidant effects by up-regulating hepatic β-oxidation activity and down-regulating liver FFA uptake.

Oxidation of fish oil exacerbates alcoholic liver disease by enhancing intestinal dysbiosis in mice

The role of n-3 polyunsaturated fatty acids (PUFAs) in alcoholic liver disease (ALD) has been controversial. N-3 PUFA oxidation in animal feeding stuffs was rarely concerned, likely contributing to inconsistent outcomes. Here, we report the impacts of oxidized fish oil (OFO) on ALD in C57BL/6 mice. Alcohol exposure increased plasma aminotransferase levels and hepatic inflammation. These deleterious effects were ameliorated by unoxidized FO but exacerbated by OFO. Sequencing analysis showed the accentuated intestinal dysbiosis and the increased proportion of Proteobacteria in OFO-fed mice. Intestinal sterilization by antibiotics completely abolished OFO-aggravated liver injury. Additionally, alcohol exposure leads to the greater increase in plasma endotoxin and decrease in intestinal tight junction protein expressions in OFO-fed mice. Stabilization of intestinal barrier by obeticholic acid markedly blunted OFO-aggravated liver injury in alcohol-fed mice. These results demonstrate that OFO exacerbates alcoholic liver injury through enhancing intestinal dysbiosis, barrier dysfunction, and hepatic inflammation mediated by gut-derived endotoxin.

Feng et al. show that oxidized fish oil exacerbates alcoholic liver injury in mice by enhancing intestinal dysbiosis, barrier dysfunction, and hepatic inflammation that is mediated by gut-derived endotoxin. This study suggests that n-3 polyunsaturated fatty acids enriched in fish oil should be kept from oxidation to exert their health benefits.

Gender Difference on the Effect of Omega-3 Polyunsaturated Fatty Acids on Acetaminophen-Induced Acute Liver Failure

Acetaminophen (APAP) toxicity is the leading cause of drug-induced liver failure, which is closely related to mitochondrial dysfunction and oxidative damage. Studies in clinical trials and in animal models have shown that omega-3 polyunsaturated fatty acids (n-3 PUFAs) affect the progression of various types of liver damage. Interestingly, the sex-dependent effect of n-3 PUFAs on human health has also been well documented. However, it is unknown whether supplementation of n-3 PUFAs modulates the pathogenesis of APAP-induced liver failure with sex-specificity. Our results showed that both endogenous and exogenous n-3 PUFAs significantly aggravated the APAP-induced liver injury in male mice, whereas the opposite effects were observed in females. In vivo and in vitro studies demonstrated that estrogen contributes to the gender difference in the regulation of n-3 PUFAs on APAP overdose. We found that n-3 PUFA-mediated regulation of hepatic oxidative stress response and autophagy upon APAP challenge is distinct between male and female mice. Moreover, we provided evidence that β-catenin signaling activation is responsible for the sex-dependent regulation of APAP hepatotoxicity by n-3 PUFAs. Together, these findings indicated that supplementation with n-3 PUFAs displays sex-differential effect on APAP hepatotoxicity and could have profound significance in the clinical management for drug-induced liver injury.

Hepatoprotective effects of gamma-aminobutyric acid-enriched fermented Hovenia dulcis extract on ethanol-induced liver injury in mice

BACKGROUND

Various extracts of Hovenia dulcis have been commonly used in Asia for cases of alcohol-related disorders. Fermentation is reported to enhance the level and biological activities of various bio-constituents of plant extracts. Therefore, this study was undertaken to evaluate the effects of fermented H. dulcis extract (FHDE) on ethanol-induced liver injury in mice.

METHODS

FHDE was prepared using Bacillus subtilis and Lactobacillus plantarum. The effects of FHDE on ethanol-induced liver injury were evaluated in C57BL/6 N CrSlc mice. A mixed feed preparation containing the fermented extract with and without ethanol was given to mice for 29 days, according to its group. At the end of the experiment, blood and liver samples were collected from all mice in the group. Plasma biochemical analysis and histopathological investigation were performed to evaluate the impacts of treatment on the biomarkers of hepatic damage and inflammatory changes. Besides, the expression of genes that regulate the activities of enzymes associated with alcohol metabolism, antioxidant activity, and fatty acid oxidation was assessed using a quantitative real-time polymerase chain reaction. Moreover, the amino acid contents and the active ingredients of the extract were evaluated before and after fermentation.

RESULTS

Fermentation resulted in a marked increase and decrease in the amount of Gamma-Amino-n-butyric acid (GABA) and glutamic acid, respectively. FHDE enhanced the body weight gain of mice compared to ethanol. Besides, plasma levels of triglyceride, low-density lipoprotein, the activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were significantly (P < 0.05) reduced in the FHDE-treated groups relative to the ethanol-treated control. FHDE upregulated the expression of genes associated with enzymes involved in alcohol dehydrogenation (Adh1 and Aldh2), antioxidant activity (SOD and CAT), and fatty acid oxidation (PPAR-α and PGC-1α). However, the expressions of Cytochrome peroxidase Cyp2E1 and genes related to lipogenesis (SREBP-1c, FAS, SCD-1, and ACC) were significantly (P < 0.05) downregulated following treatment with the FHDE. Histopathological investigation demonstrated a slight degree of inflammatory cell infiltration and occasional fatty changes in the FHDE-treated groups.

CONCLUSION

The GABA-enriched fermented H. dulcis extract prevented ethanol-induced hepatic damage by enhancing the antioxidant defense system, fatty acid oxidation, and reducing lipogenesis.

Cryptotanshinone from the Salvia miltiorrhiza Bunge Attenuates Ethanol-Induced Liver Injury by Activation of AMPK/SIRT1 and Nrf2 Signaling Pathways

Cryptotanshinone (CT), a diterpene that is isolated from Salvia miltiorrhiza Bunge, exhibits anti-cancer, anti-oxidative, anti-fibrosis, and anti-inflammatory properties. Here, we examined whether CT administration possess a hepatoprotective effect on chronic ethanol-induced liver injury. We established a chronic alcohol feeding mouse model while using C57BL/6 mice, and examined the liver sections with hematoxylin-eosin (H&E) and Oil Red O (ORO) staining. Further, we analyzed the lipogenesis, fatty acid oxidation, oxidative stress, and inflammation genes by using quantitative polymerase chain reaction (qPCR) and immunoblotting in in vivo, and in vitro while using HepG2 and AML-12 cells. CT treatment significantly ameliorated ethanol-promoted hepatic steatosis, which was consistent with the decreased hepatic triglyceride levels. Interestingly, CT activated the phosphorylation of AMP-activated protein kinase (AMPK), sirtuin 1 (SIRT1), and nuclear factor E2-related factor 2 (Nrf2) proteins. Importantly, compound C (AMPK inhibitor) significantly blocked the CT-mediated reduction in TG accumulation, but not Ex52735 (SIRT1 inhibitor), which suggested that CT countering ethanol-promoted hepatic steatosis is mediated by AMPK activation. Furthermore, CT significantly inhibited cytochrome P450 2E1 (CYP2E1) and enhanced both the expression of antioxidant genes and hepatic glutathione levels. Finally, CT inhibited the ethanol-induced inflammation in ethanol-fed mice and HepG2 cells. Overall, CT exhibits a hepatoprotective effect against ethanol-induced liver injury by the inhibition of lipogenesis, oxidative stress, and inflammation through the activation of AMPK/SIRT1 and Nrf2 and the inhibition of CYP2E1. Therefore, CT could be an effective therapeutic agent for treating ethanol-induced liver injury.

Fish oil up-regulates hepatic autophagy in rats with chronic ethanol consumption

In this study, we examined the regulation of autophagy by fish oil in rats under ethanol-containing diets. Thirty male Wistar rats (8-week-old) were divided into six groups and fed a control diet or an ethanol-containing diet, which was adjusted with fish oil to replace 25% or 57% of the olive oil. After 8 weeks, rats in the E (ethanol diet) group showed the significantly higher plasma aspartate transaminase (AST) and alanine transaminase (ALT) activities, protein expression of cytochrome P450 2E1 (CYP2E1), and levels of hepatic inflammatory cytokines. However, all of those items had significantly decreased in the EF25 (ethanol with 25% fish oil) and EF57 (ethanol with 57% fish oil) groups. As to autophagic indicators, protein expressions of mammalian target of rapamycin (mTOR), Unc-51-like autophagy activating kinase 1 (ULK1) and p62 were significantly increased in the E group. Conversely, the protein expressions of light chain 3II (LC3II)/LC3I and Beclin1 were significantly decreased in the E group. On the other hand, protein expressions of phosphorylated Akt, mTOR, ULK1, and p62 were down-regulated, protein expressions of LC3II/LC3I and Beclin1 were conversely up-regulated in the EF25 and EF57 groups. Fish oil activated hepatic autophagy via inhibiting the Akt signaling pathway, which exerted protective effects against ethanol-induced liver injury in rats.

Maternal Eicosapentaenoic Acid Feeding Decreases Placental Lipid Deposition and Improves the Homeostasis of Oxidative Stress Through a Sirtuin-1 (SIRT1) Independent Manner

SCOPE

Maternal obesity has been associated with increased placental lipotoxicity and impaired mitochondrial function. Sirtuin-1 (SIRT1) is an important regulator of both lipid metabolism and mitochondrial biogenesis. The present study aims to determine whether supplementation of the maternal diet with eicosapentaenoic acid (EPA) can decrease placental lipid deposition and improve antioxidant ability, in a SIRT1-dependent manner.

METHODS AND RESULTS

Pregnant SIRT1^+/- mice (mated with male SIRT1^+/- ) are fed a high-fat diet consisting of 60% of the kcal from fat, or an equienergy EPA diet for 18.5 d. Supplementation with EPA significantly changes maternal plasma, placental and fetal fatty acid composition, and decreases placental and fetal lipid content. In addition, placental antioxidant capacity and lipid peroxidation products are increased, placental uncoupling protein 1 (UCP1) and PPARγ coactivator-1 α (PGC1α) expression are activated, and mitochondrial swelling decreases. While SIRT1 deficiency has little effect on placental fatty acid composition and lipid content, decreased fetal lipid deposition is observed, placental PGC1α expression decreases, mitochondrial swelling increases, and placental total superoxide dismutase (T-SOD) activity increases. Both EPA and SIRT1 have no effect on BODIPY-FL-C16 uptake. Interestingly, there is no significant interaction between diet and genotype.

CONCLUSION

Maternal EPA feeding decreases placental lipid deposition and improves placental oxidative stress homeostasis independent of SIRT1.

Omega-3 fatty acid decreases oleic acid by decreasing SCD-1 expression in the liver and kidney of a cyclosporine-induced nephropathy rat model

Aim: Stearoyl-CoA desaturase (SCD)-1 and elongase-6 (Elovl-6) are associated with fatty acid (FA) synthesis. We evaluated the effect of omega-3 FA on erythrocyte membrane FA contents through SCD-1 and Elovl-6 expression in the liver and kidney of a cyclosporine (CsA)-induced rat model.

Methods: Male Sprague Dawley rats were divided into control, CsA, and CsA treated with omega-3 FA groups. We measured SCD-1 and Elovl-6 expression levels via western blot and immunohistochemistry analysis.

Results: Erythrocyte membrane oleic acid content was lower in the CsA with omega-3 FA group compared to the CsA group. Compared to the control group, CsA-induced rats showed elevated SCD-1 expression in the kidney and liver, which omega-3 FA treatment reversed. Elovl-6 expression was increased in the liver, but decreased in the kidney in CsA group compared to control, which omega-3 FA treatment also reversed.

Conclusions: Omega-3 FA supplementation decreased erythrocyte membrane oleic acid content by modulating SCD-1 and Elovl-6 expression in the kidney and liver of CsA-induced rats.

Amelioration of CCl4-Induced Hepatotoxicity in Rabbits by Lepidium sativum Seeds

The current study aimed to evaluate the probable protective effect of Lepidium sativum seeds (LSS) against CCl₄ induced hepatic injury in New-Zealand rabbits. Rabbits were randomly divided into two main groups; group-A (noninjured group, n=15) was divided to subgroups A1 (untreated control) and A2 and A3 which received 200 & 400 mg/kg bw of LSS, respectively, in their diet daily. Group-B (injured group, n=30) were subcutaneously injected with CCl₄ (0.5 ml/kg bw) starting from day one of the experiment and were equally divided into 3 subgroups: B1 received normal standard diet and B2 & B3 received 200 & 400 mg/kg bw of LSS, respectively, in their diet daily. Five rabbits of all subgroups were decapitated 5 and 10 weeks after experimental running. Biochemical analysis revealed significant decrease in serum levels of transaminases, γ-GT, ALP, total bilirubin, cholesterol, triglycerides associated with significant increase in the serum levels of T protein and albumin of 200 and 400 mg/kg bw of LSS protected rabbits for 5 and 10 weeks as compared with CCl₄ treated rabbits. Oxidative stress and depressed antioxidant system of the liver tissues were markedly obvious in the CCl₄ treated group. LSS administration reversed these results towards normalization. Histopathological examination of LSS protected rabbits (200 mg/kg bw of LSS for 10 weeks) showed improvement of the histoarchitectural changes of the liver induced by CCl₄ to the normal aspect, showing regenerating hepatocytes with no steatosis, discrete chronic venous congestion, and discrete inflammatory infiltrate. The current findings provide new evidence that LSS could reverse the hepatotoxic effects of CCl₄ and repair the liver functions.

n-3 Polyunsaturated fatty acids for the management of alcoholic liver disease: A critical review

Excess alcohol exposure leads to alcoholic liver disease (ALD), a predominant cause of liver-related morbidity and mortality worldwide. In the past decade, increasing attention has been paid to understand the association between n-3 polyunsaturated fatty acids (n-3 PUFAs) and ALD. In this review, we summarize the metabolism of n-3 PUFAs, animal model of ALD, and the findings from recent studies determining the role of n-3 PUFAs in ALD as a possible treatment. The animal models of acute ethanol exposure, chronic ethanol exposure and chronic-plus-single binge ethanol feeding have been widely used to explore the impact of n-3 PUFAs. Although the results of studies regarding the role of n-3 PUFAs in ALD have been inconsistent or controversial, increasing evidence has demonstrated that n-3 PUFAs may be useful in alleviating alcoholic steatosis and alcohol-induced liver injury through multiple mechanisms, including decreased de novo lipogenesis and lipid mobilization from adipose tissue, enhanced mitochondrial fatty acid β-oxidation, reduced hepatic inflammation and oxidative stress, and promoted intestinal homeostasis, positively suggesting that n-3 PUFAs might be promising for the management of ALD. The oxidation of n-3 PUFAs ex vivo in an experimental diet was rarely considered in most n-3 PUFA-related studies, likely contributing to the inconsistent results. Thus, the role of n-3 PUFAs in ALD deserves greater research efforts and remains to be evaluated in randomized, placebo-controlled clinic trial. ABBREVIATION AA arachidonic acid ACC acetyl-CoA carboxylase ACLY ATP-citrate lyase ACO acyl-CoA oxidase ALA α-linolenic acid ALD alcoholic liver disease ALP alkaline phosphatase ALT alanine aminotransferase AMPK AMP-activated protein kinase AST aspartate aminotransferase ATGL adipose triglyceride lipase cAMP cyclic adenosine 3',5'-monophosphate COX cyclooxygenases CPT1 carnitine palmitoyltransferase 1 CYP2E1 cytochrome P450 2E1 DGAT2 diacylglycerol acyltransferase 2 DGLA dihomo-γ-linolenic acid DHA docosahexaenoic acid DPA docosapentaenoic acid DTA docosatetraenoic acid EPA eicosapentaenoic acid ER endoplasmic reticulum ETA eicosatetraenoic acid FAS fatty acid synthase FATPs fatty acid transporter proteins GLA,γ linolenic acid GPR120 G protein-coupled receptor 120 GSH glutathione; H&E haematoxylin-eosin; HO-1 heme oxygenase-1; HSL hormone-sensitive lipase; IL-6 interleukin-6 iNOS nitric oxide synthase LA linoleic acid LBP lipopolysaccharide binding protein LOX lipoxygenases LXR liver X receptor LXREs LXR response elements MCP-1 monocyte chemotactic protein-1 MTP microsomal triglyceride transfer protein MUFA monounsaturated fatty acids MyD88 myeloid differentiation factor 88 n-3 PUFAs omega-3 polyunsaturated fatty acid NAFLD nonalcoholic fatty liver disease NASH nonalcoholic steatohepatitis NF-κB transcription factor nuclear factor κB PDE3B phosphodiesterase 3B PPAR peroxisome proliferator-activated receptor ROS reactive oxygen species RXR retinoid X receptor SCD-1 stearyl CoA desaturase-1 SDA stearidonic acid SFA saturated fatty acids SIRT1 sirtuin 1 SOD superoxide dismutase SREBP sterol regulatory element-binding protein TB total bilirubin TC total cholesterol TG triacylglycerol TLR4 Toll-like receptor-4 TNF-α tumor necrosis factor-α VLDLR very low-density lipoprotein receptor WT wild type; ZO-1 zonula occludens-1.

Substitution of linoleic acid with α-linolenic acid or long chain n-3 polyunsaturated fatty acid prevents Western diet induced nonalcoholic steatohepatitis

Imbalance in the n-6 polyunsaturated fatty acids (PUFA) and n-3 PUFA in the Western diet may increase the risk of nonalcoholic fatty liver disease (NAFLD). This study investigates the impact of substitution of linoleic acid with α-linolenic acid (ALA) or long chain (LC) n-3 PUFA and hence decreasing n-6:n-3 fatty acid ratio on high fat, high fructose (HFHF) diet induced nonalcoholic steatohepatitis (NASH). Male Sprague-Dawley rats were divided into four groups and fed control diet, HFHF diet (n-6:n-3 ratio of 200), HFHF diet with ALA (n-6:n-3 ratio of 2) or HFHF diet with LC n-3 PUFA (n-6:n-3 ratio of 5) for 24 weeks. Rats fed HFHF diet with n-6:n-3 ratio of 200 resulted in hepatic steatosis, induced glucose intolerance, insulin resistance and oxidative stress accompanied by increase in markers of inflammation, plasma lipids and aminotransferase levels. Histopathological examination of liver further confirmed the establishment of NASH. ALA and LC n-3 PUFA supplementation prevented hepatic steatosis and dyslipidemia by inhibiting lipogenesis and increasing insulin sensitivity. Furthermore, n-3 PUFA supplementation attenuated hepatic oxidative stress by restoring antioxidant status, decreased inflammation and preserved hepatic architecture. These finding suggest that decreasing n-6:n-3 ratio prevented HFHF induced NASH by attenuating oxidative stress and inflammation.

Chronic high-dosage fish oil exacerbates gut-liver axis injury in alcoholic steatohepatitis in mice: the roles of endotoxin and IL-4 in Kupffer cell polarization imbalance

In the present study, intestinal tight junctions (TJs) and Kupffer cell polarization were investigated in an alcoholic steatohepatitis (ASH) mouse model to uncover the potential side effects of overexposure to fish oil or omega-3 fatty acids. The mice were fed ad libitum with a liquid diet containing ethanol and fish oil. In the meantime, ethanol was given every 5-7 days by gavage to simulate binge drinking. After the 7^th binge, steatosis, necrosis, inflammatory infiltration, and bridging fibrosis were observed in the liver by histological staining. After the 13^th binge, the inducers, markers and other downstream genes/proteins of the Kupffer cell M1/M2 phenotype in the liver, serum, and small intestine were analysed. The results suggested that a chronic high dosage of fish oil alone reduced the mRNA levels of most genes tested and showed a tendency to damage the intestinal zonula occludens-1 localization and reduce the number of M2 Kupffer cells. Meanwhile, the combination of fish oil and ethanol damaged the intestinal TJs, resulting in an increased endotoxin level in the liver. Gut-derived endotoxin polarized Kupffer cells to the M1 phenotype, whereas the number of cells with the M2 phenotype (markers: CD163 and CD206) was decreased. Interleukin-4 (IL-4), an M2 Kupffer cell inducer, was also decreased. Moreover, in vitro experiments showed that IL-4 reversed eicosapentaenoic acid-induced CD163 and CD206 mRNA suppression in RAW 264.7 cells. Overall, our results showed that a chronic high dosage of fish oil exacerbated gut-liver axis injury in alcoholic liver disease in mice, and endotoxin/IL-4-induced Kupffer cell polarization imbalance might play an important role in that process.

Omega-3 polyunsaturated fatty acids ameliorate ethanol-induced adipose hyperlipolysis: A mechanism for hepatoprotective effect against alcoholic liver disease

Alcohol exposure induces adipose hyperlipolysis and causes excess fatty acid influx into the liver, leading to alcoholic steatosis. The impacts of omega-3 polyunsaturated fatty acids (n-3 PUFA) on ethanol-induced fatty liver are well documented. However, the role of n-3 PUFA in ethanol-induced adipose lipolysis has not been sufficiently addressed. In this study, the fat-1 transgenic mice that synthesizes endogenous n-3 from n-6 PUFA and their wild type littermates with an exogenous n-3 PUFA enriched diet were subjected to a chronic ethanol feeding plus a single binge as model to induce liver injury with adipose lipolysis. Additionally, the differentiated adipocytes from 3T3-L1 cells were treated with docosahexaenoic acid or eicosapentaenoic acid for mechanism studies. Our results demonstrated that endogenous and exogenous n-3 PUFA enrichment ameliorates ethanol-stimulated adipose lipolysis by increasing PDE3B activity and reducing cAMP accumulation in adipocyte, which was associated with activation of GPR120 and regulation of Ca²⁺/CaMKKβ/AMPK signaling, resultantly blocking fatty acid trafficking from adipose tissue to the liver, which contributing to ameliorating ethanol-induced adipose dysfunction and liver injury. Our findings identify that endogenous and exogenous n-3 PUFA enrichment ameliorated alcoholic liver injury by activation of GPR120 to suppress ethanol-stimulated adipose lipolysis, which provides the new insight to the hepatoprotective effect of n-3 PUFA against alcoholic liver disease.

Differential response of rat strains to obesogenic diets underlines the importance of genetic makeup of an individual towards obesity

Obesity, a multifactorial disorder, results from a chronic imbalance of energy intake vs. expenditure. Apart from excessive consumption of high calorie diet, genetic predisposition also seems to be equally important for the development of obesity. However, the role of genetic predisposition in the etiology of obesity has not been clearly delineated. The present study addresses this problem by selecting three rat strains (WNIN, F-344, SD) with different genetic backgrounds and exposing them to high calorie diets. Rat strains were fed HF, HS, and HFS diets and assessed for physical, metabolic, biochemical, inflammatory responses, and mRNA expression. Under these conditions: significant increase in body weight, visceral adiposity, oxidative stress and systemic pro-inflammatory status; the hallmarks of central obesity were noticed only in WNIN. Further, they developed altered glucose and lipid homeostasis by exhibiting insulin resistance, impaired glucose tolerance, dyslipidemia and fatty liver condition. The present study demonstrates that WNIN is more prone to develop obesity and associated co-morbidities under high calorie environment. It thus underlines the cumulative role of genetics (nature) and diet (nurture) towards the development of obesity, which is critical for understanding this epidemic and devising new strategies to control and manage this modern malady.

Chronic consumption of fructose in combination with trans fatty acids but not with saturated fatty acids induces nonalcoholic steatohepatitis with fibrosis in rats

PURPOSE

Consumption of Western diet high in fat and fructose has been attributed to the recent epidemic of nonalcoholic fatty liver disease (NAFLD). However, the impact of specific fatty acids on the progression of NAFLD to nonalcoholic steatohepatitis (NASH) is poorly understood. In the present study, we investigated the chronic effects of consumption of fructose in combination with saturated fatty acids (SFA) or trans fatty acids (TFA) on the development of NAFLD.

METHODS

Male Sprague-Dawley rats were randomly assigned to six isocaloric starch/high fructose (44% of calories), high fat (39% calories) diet containing either starch-peanut oil, fructose-peanut oil, fructose-palmolein, fructose-clarified butter, fructose-coconut oil or fructose-partially hydrogenated vegetable oil and fed for 24 weeks. Palmolein, clarified butter and coconut oil were used as the source of SFA whereas partially hydrogenated vegetable oil was used as the source of TFA. Peanut oil was used as the reference oil.

RESULTS

Long-term feeding of fructose in combination with SFA or TFA induced hepatic steatosis of similar extent associated with upregulation of stearoyl CoA desaturase-1. In contrast, fructose in combination with TFA induced NASH with fibrosis as evidenced by upregulation of hepatic proinflammatory cytokine and fibrogenic gene expression, increased hepatic oxidative stress and adipocytokine imbalance. Histopathological analysis revealed the presence of NASH with fibrosis. Further, peanut oil prevented the development of NAFLD in fructose-fed rats.

CONCLUSION

Fructose in combination with TFA caused NASH with fibrosis by inducing oxidative stress and inflammation, whereas, fructose in combination with SFA caused simple steatosis, suggesting that the type of fatty acid is more important for the progression of NAFLD.

Low-ω3 Fatty Acid and Soy Protein Attenuate Alcohol-Induced Fatty Liver and Injury by Regulating the Opposing Lipid Oxidation and Lipogenic Signaling Pathways

Chronic ethanol-induced downregulation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) and upregulation of peroxisome proliferator-activated receptor gamma coactivator 1-beta (PGC1β) affect hepatic lipid oxidation and lipogenesis, respectively, leading to fatty liver injury. Low-ω3 fatty acid (Low-ω3FA) that primarily regulates PGC1α and soy protein (SP) that seems to have its major regulatory effect on PGC1β were evaluated for their protective effects against ethanol-induced hepatosteatosis in rats fed with Lieber-deCarli control or ethanol liquid diets with high or low ω3FA fish oil and soy protein. Low-ω3FA and SP opposed the actions of chronic ethanol by reducing serum and liver lipids with concomitant decreased fatty liver. They also prevented the downregulation of hepatic Sirtuin 1 (SIRT1) and PGC1α and their target fatty acid oxidation pathway genes and attenuated the upregulation of hepatic PGC1β and sterol regulatory element-binding protein 1c (SREBP1c) and their target lipogenic pathway genes via the phosphorylation of 5' adenosine monophosphate-activated protein kinase (AMPK). Thus, these two novel modulators attenuate ethanol-induced hepatosteatosis and consequent liver injury potentially by regulating the two opposing lipid oxidation and lipogenic pathways.

Critical Roles of Kupffer Cells in the Pathogenesis of Alcoholic Liver Disease: From Basic Science to Clinical Trials

Alcoholic liver disease (ALD) encompasses a spectrum of liver injury ranging from steatosis to steatohepatitis, fibrosis, and finally cirrhosis. Accumulating evidences have demonstrated that Kupffer cells (KCs) play critical roles in the pathogenesis of both chronic and acute ALD. It has become clear that alcohol exposure can result in increased hepatic translocation of gut-sourced endotoxin/lipopolysaccharide, which is a strong M1 polarization inducer of KCs. The activated KCs then produce a large amount of reactive oxygen species (ROS), pro-inflammatory cytokines, and chemokines, which finally lead to liver injury. The critical roles of KCs and related inflammatory cascade in the pathogenesis of ALD make it a promising target in pharmaceutical drug developments for ALD treatment. Several drugs (such as rifaximin, pentoxifylline, and infliximab) have been evaluated or are under evaluation for ALD treatment in randomized clinical trials. Furthermore, screening pharmacological regulators for KCs toward M2 polarization may provide additional therapeutic agents. The combination of these potentially therapeutic drugs with hepatoprotective agents (such as zinc, melatonin, and silymarin) may bring encouraging results.

Endogenous n-3 Fatty Acids Alleviate Carbon-Tetrachloride-Induced Acute Liver Injury in Fat-1 Transgenic Mice

n-3 polyunsaturated fatty acids (PUFAs) are beneficial for numerous models of liver diseases. The probable protective effects of n-3 PUFA against carbon-tetrachloride- (CCl₄-) induced acute liver injury were evaluated in a fat-1 transgenic mouse that synthesizes endogenous n-3 from n-6 PUFA. Fat-1 mice and their WT littermates were fed a modified AIN93 diet containing 10% corn oil and were injected intraperitoneally with a single dose of CCl₄ or vehicle. CCl₄ challenge caused severe liver injury in WT mice, as indicated by serum parameters and histopathological changes, which were remarkably ameliorated in fat-1 mice. Endogenous n-3 PUFA decreased the elevation of oxidative stress induced by CCl₄ challenge, which might be attributed to the activation of Nrf2/keap1 pathway. Additionally, endogenous n-3 PUFA reduces hepatocyte apoptosis via suppressing MAPK pathway. These findings indicate that n-3 PUFA has potent protective effects against acute liver injury induced by CCl₄ in mice, suggesting that n-3 PUFA can be used for the prevention and treatment of liver injury.

Dietary α-linolenic acid-rich flaxseed oil prevents against alcoholic hepatic steatosis via ameliorating lipid homeostasis at adipose tissue-liver axis in mice

Low levels of n-3 polyunsaturated fatty acids (PUFAs) in serum and liver tissue biopsies are the common characteristics in patients with alcoholic liver disease. The α-linolenic acid (ALA) is a plant-derived n-3 PUFA and is rich in flaxseed oil. However, the impact of ALA on alcoholic fatty liver is largely unknown. In this study, we assessed the potential protective effects of ALA-rich flaxseed oil (FO) on ethanol-induced hepatic steatosis and observed that dietary FO supplementation effectively attenuated the ethanol-induced hepatic lipid accumulation in mice. Ethanol exposure stimulated adipose lipolysis but reduced fatty acid/lipid uptake, which were normalized by FO. Our investigations into the corresponding mechanisms demonstrated that the ameliorating effect of FO might be associated with the lower endoplasmic reticulum stress and normalized lipid metabolism in adipose tissue. In the liver, alcohol exposure stimulated hepatic fatty acid uptake and triglyceride synthesis, which were attenuated by FO. Additionally, dietary FO upregulated plasma adiponectin concentration, hepatic adiponectin receptor 2 expression, and the activation of hepatic adenosine monophosphate-activated protein kinase. Collectively, dietary FO protects against alcoholic hepatic steatosis by improving lipid homeostasis at the adipose tissue-liver axis, suggesting that dietary ALA-rich flaxseed oil might be a promising approach for prevention of alcoholic fatty liver.

Fish Oil Reduces Hepatic Injury by Maintaining Normal Intestinal Permeability and Microbiota in Chronic Ethanol-Fed Rats

The aim of this study was to investigate the ameliorative effects of fish oil on hepatic injury in ethanol-fed rats based on the intestinal permeability and microbiota. Rats were assigned to 6 groups and fed either a control diet or an ethanol diet such as C (control), CF25 (control with 25% fish oil), CF57 (control with 57% fish oil), E (ethanol), EF25 (ethanol with 25% fish oil), and EF57 (ethanol with 57% fish oil) groups. Rats were sacrificed at the end of 8 weeks. Plasma aspartate aminotransferase (AST) and aminotransferase (ALT) activities, hepatic cytokines, and plasma endotoxin levels were significantly higher in the E group. In addition, hepatic histopathological analysis scores in the E group were significantly elevated. Rats in the E group also showed increased intestinal permeability and decreased numbers of fecal Bifidobacterium. However, plasma AST and ALT activities and hepatic cytokine levels were significantly lower in the EF25 and EF57 groups. Histological changes and intestinal permeability were also improved in the EF25 and EF57 groups. The fecal Escherichia coli numbers were significantly lower, but fecal Bifidobacterium numbers were significantly higher in the EF25 and EF57 groups.

Effect of ω-3 supplementation on placental lipid metabolism in overweight and obese women

BACKGROUND

The placentas of obese women accumulate lipids that may alter fetal lipid exposure. The long-chain omega-3 fatty acids (n–3 FAs) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) alter FA metabolism in hepatocytes, although their effect on the placenta is poorly understood.

OBJECTIVE

We aimed to investigate whether n–3 supplementation during pregnancy affects lipid metabolism in the placentas of overweight and obese women at term.

DESIGN

A secondary analysis of a double-blind randomized controlled trial was conducted in healthy overweight and obese pregnant women who were randomly assigned to DHA plus EPA (2 g/d) or placebo twice a day from early pregnancy to term. Placental FA uptake, esterification, and oxidation pathways were studied by measuring the expression of key genes in the placental tissue of women supplemented with placebo and n–3 and in vitro in isolated trophoblast cells in response to DHA and EPA treatment.

RESULTS

Total lipid content was significantly lower in the placentas of overweight and obese women supplemented with n–3 FAs than in those supplemented with placebo (14.14 ± 1.03 compared with 19.63 ± 1.45 mg lipid/g tissue; P < 0.05). The messenger RNA expression of placental FA synthase (FAS) and diacylglycerol O-acyltransferase 1 (DGAT1) was negatively correlated with maternal plasma enrichment in DHA and EPA (P < 0.05). The expression of placental peroxisome proliferator–activated receptor γ (r = −0.39, P = 0.04) and its target genes DGAT1 (r = −0.37, P = 0.02) and PLIN2 (r = −0.38, P = 0.04) significantly decreased, with an increasing maternal n–3:n–6 ratio (representing the n–3 status) near the end of pregnancy. The expression of genes that regulate FA oxidation or uptake was not changed. Birth weight and length were significantly higher in the offspring of n–3-supplemented women than in those in the placebo group (P < 0.05), but no differences in the ponderal index were observed. Supplementation of n–3 significantly decreased FA esterification in isolated trophoblasts without affecting FA oxidation.

CONCLUSION

Supplementing overweight and obese women with n–3 FAs during pregnancy inhibited the ability of the placenta to esterify and store lipids. This trial was registered at clinicaltrials.gov as NCT00957476.

Alcoholic Liver Disease: Update on the Role of Dietary Fat

Alcoholic liver disease (ALD) spans a spectrum of liver pathology, including fatty liver, alcoholic steatohepatitis, and cirrhosis. Accumulating evidence suggests that dietary factors, including dietary fat, as well as alcohol, play critical roles in the pathogenesis of ALD. The protective effects of dietary saturated fat (SF) and deleterious effects of dietary unsaturated fat (USF) on alcohol-induced liver pathology are well recognized and documented in experimental animal models of ALD. Moreover, it has been demonstrated in an epidemiological study of alcoholic cirrhosis that dietary intake of SF was associated with a lower mortality rates, whereas dietary intake of USF was associated with a higher mortality. In addition, oxidized lipids (dietary and in vivo generated) may play a role in liver pathology. The understanding of how dietary fat contributes to the ALD pathogenesis will enhance our knowledge regarding the molecular mechanisms of ALD development and progression, and may result in the development of novel diet-based therapeutic strategies for ALD management. This review explores the relevant scientific literature and provides a current understanding of recent advances regarding the role of dietary lipids in ALD pathogenesis.

Endogenously elevated n-3 polyunsaturated fatty acids alleviate acute ethanol-induced liver steatosis

Effective means for the prevention of alcohol-induced liver disease, a global health problem, have yet to be developed. We evaluated whether the high endogenous levels of omega-3 polyunsaturated acids (n-3 PUFA) in fat-1 transgenic mice could protect them against acute ethanol-induced liver steatosis. We induced alcoholic liver steatosis in 9-week-old male heterozygous fat-1 mice and their wild-type (WT) male littermates through three oral gavages of 60% ethanol at 4.7 g/kg body weight. Hepatic lipid accumulation was significantly increased in both alcohol treatment groups, but by much less in the fat-1 group compared with the WT group. Fat-1 mice exhibited significantly lower levels of total hepatic/plasma TG and plasma alanine aminotransferase activity. Accordingly, hepatic expression of lipogenesis-related genes (e.g., SREBP-1c, FAS, and SCD-1) and plasma levels of inflammatory cytokines (e.g., IL-6, TNF-α, and MCP-1) were reduced in the fat-1 mice. Furthermore, decreased hepatic expression of cytochrome P450 2E1 (CYP2E1) and increased hepatic levels of PPAR-α and HO-1 were observed in the fat-1 mice, compared to the WT mice. These findings show that elevated tissue n-3 PUFA protect against acute ethanol-induced liver steatosis in fat-1 mice, possibly through the down-regulation of hepatic lipogenesis, inflammatory response, and oxidative stress.