Dietary fatty acids and bioactive fatty acid metabolites in alcoholic liver disease

The Octadecanoids: Synthesis and Bioactivity of 18-Carbon Oxygenated Fatty Acids in Mammals, Bacteria, and Fungi

The octadecanoids are a broad class of lipids consisting of the oxygenated products of 18-carbon fatty acids. Originally referring to production of the phytohormone jasmonic acid, the octadecanoid pathway has been expanded to include products of all 18-carbon fatty acids. Octadecanoids are formed biosynthetically in mammals via cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P450 (CYP) activity, as well as nonenzymatically by photo- and autoxidation mechanisms. While octadecanoids are well-known mediators in plants, their role in the regulation of mammalian biological processes has been generally neglected. However, there have been significant advancements in recognizing the importance of these compounds in mammals and their involvement in the mediation of inflammation, nociception, and cell proliferation, as well as in immuno- and tissue modulation, coagulation processes, hormone regulation, and skin barrier formation. More recently, the gut microbiome has been shown to be a significant source of octadecanoid biosynthesis, providing additional biosynthetic routes including hydratase activity (e.g., CLA-HY, FA-HY1, FA-HY2). In this review, we summarize the current field of octadecanoids, propose standardized nomenclature, provide details of octadecanoid preparation and measurement, summarize the phase-I metabolic pathway of octadecanoid formation in mammals, bacteria, and fungi, and describe their biological activity in relation to mammalian pathophysiology as well as their potential use as biomarkers of health and disease.

Investigating the correlation between polyunsaturated fatty acids intake and non-invasive biomarkers of liver fibrosis

BACKGROUND

Polyunsaturated fatty acids (PUFAs) have potentially beneficial effects on the liver tissue. Noninvasive biomarkers, including imaging techniques and blood-based biomarkers, are important tools for assessing liver fibrosis. This study aims to investigate the relationship between dietary intake of PUFAs and noninvasive biomarkers for liver fibrosis in the general population.

METHODS

The National Health and Nutrition Examination Survey 2017-2018 (NHANES 2017-2018) datasets were used. Fibrosis-4 index (FIB-4), FIB-8, and Fatty Liver Index (FLI) were calculated for each subject. The fibrosis groups were compared based on their intake of PUFA. The correlation between each score and PUFA intake was calculated. Correlation analysis was performed.

RESULTS

A total of 5087 subjects (50.36% female) with a mean age of 49.37 ± 12.14 were evaluated. The mean of median liver stiffness measurement (LSM) was 5.92 ± 5.20 kPa (kPa). The mean PUFA intake was reported as 20.2 ± 13.9 gm. Fibrosis (F) grouping revealed that 190 subjects had F3, and 154 F4. HDL had a significant correlation with Docosapentaenoic acid (DPA) intake (r = -0.038, p = 0.007). Moreover, AST and ALT had a significant correlation with Docosahexaenoic acid (DHA) intake (r = 0.033 and 0.059, p = 0.019 and < 0.001, respectively). FIB-4 and FIB-8 had no correlation with PUFA intake. FLI had a significant correlation with DPA acid (r = 0.062, p < 0.001).

CONCLUSION

A significant correlation between FLI, and PUFA intake suggests that increasing PUFA consumption could have a positive impact on liver health.

Diet modifies the association between alcohol consumption and severe alcohol-related liver disease incidence

It is elusive why some heavy drinkers progress to severe alcohol-related liver disease (ALD) while others do not. This study aimed to investigate if the association between alcohol consumption and severe ALD is modified by diet. This prospective study included 303,269 UK Biobank participants. Alcohol consumption and diet were self-reported. The diet score was created from 4 items selected using LASSO. Cox proportional hazard model showed that the diet score was monotonically associated with severe ALD risk, adjusted for sociodemographics, lifestyle factors, and alcohol consumption. Relative excess risk due to interaction analysis indicated that having a higher ALD diet score and a higher alcohol consumption simultaneously confers to 2.44 times (95% CI: 1.06-3.83) higher risk than the sum of excess risk of each factor. In this work, we show that people who have a poor diet might be more susceptible to severe ALD due to alcohol consumption.

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.

Integration of the Exogenous Tuning of Thraustochytrid Fermentation and Sulfur Polymerization of Single-Cell Oil for Developing Plant-like Oils

In this study, we have demonstrated a bioprocessing approach encompassing the exogenous addition of low-molecular-weight compounds to tune the fatty acid (FA) profile in a novel thraustochytrid strain to produce desirable FAs. Maximum lipid recovery (38%, dry wt. biomass) was obtained at 1% Tween 80 and 0.25 mg/L of Vitamin B12. The transesterified lipid showed palmitic acid (C16, 35.7% TFA), stearic acid (C18, 2.1% TFA), and oleic acid (C18:1, 18.7% TFA) as the main components of total FAs, which are mainly present in plant oils. Strikingly, D-limonene addition in the fermentation medium repressed the production of polyunsaturated fatty acid (PUFAs). Sulfur-polymerization-guided lipid separation revealed the presence of saturated (SFAs, 53% TFA) and monounsaturated fatty acids (MUFAs, 46.6% TFA) in thraustochytrid oil that mimics plant-oil-like FA profiles. This work is industrially valuable and advocates the use of sulfur polymerization for preparation of plant-like oils through tuneable thraustochytrid lipids.

Dietary fatty acid patterns and risk of oesophageal squamous cell carcinoma

Background

To characterize and examine the associations between dietary fatty acid intake patterns and the risk of oesophageal squamous cell carcinoma (ESCC).

Methods

A total of 422 patients and 423 controls were recruited. Dietary fatty acids were entered into a factor analysis. Multivariable logistic regression and restricted cubic spline were used to evaluate the risk of ESCC specific for different dietary fatty acid patterns (FAPs). A forest plot was applied to show the association between FAPs and ESCC risk after stratification by lifestyle exposure factors (tobacco smoking, alcohol drinking, pickled food, fried food, hot food, hard food).

Results

The factor analysis generated four major fatty acid patterns: a medium- and long-chain SFA (MLC-SFA) pattern; an even-chain unsaturated fatty acid (EC-UFA) pattern, a saturated fatty acid (SFA) pattern and an n-3 long-chain polyunsaturated fatty acid (n-3 LC-PUFA) pattern. In the multivariate-adjusted model, the odds ratios (ORs) with 95% confidence intervals (CIs) of ESCC were 2.07 (1.31, 3.26) and 0.53 (0.34, 0.81) for the highest versus the lowest tertiles of the EC-UFA pattern and n-3 LC-PUFA pattern, respectively. The MLC-SFA and SFA patterns were not associated with ESCC. An association between FAPs and ESCC risk after stratification by lifestyle exposure factors was also observed.

Conclusions

Our study indicates that the EC-UFA pattern and n-3 LC-PUFA pattern intake are associated with ESCC, providing a potential dietary intervention for ESCC prevention.

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.

A dipeptidyl peptidase IV inhibitory peptide relieves palmitic acid-induced endoplasmic reticulum stress in HepG2 cells independent of inhibiting dipeptidyl peptidase IV activity

The peptide VLATSGPG (VLA) is known to inhibit dipeptidyl peptidase IV (DPP-IV), although its mechanism in relieving endoplasmic reticulum (ER) stress is unclear. In this study, we found that treating HepG2 cells with 1.0 mM VLA reduced DPP-IV activity by 73.7 ± 4.8% without changing the DPP-IV mRNA expression level. In addition, 1.0 and 0.5 mM VLA alleviated palmitic acid (PA)-induced cell death and intracellular calcium imbalances. The levels of apoptosis-related proteins (caspase-3, caspase-9, and CHOP) were reduced by VLA treatment, which was presumed to be related to ER stress. Further studies confirmed that VLA alleviated PA-induced morphological damage to the ER and reduced the levels of the ER stress marker proteins (BIP, p-PERK, and p-IRE1α). VLA alleviated PA-induced ER stress in HepG2 cells independent of DPP-IV enzymatic activity inhibition. These findings have implications for developing novel treatment approaches for liver diseases caused by ER stress.

Fat-1 Transgenic Mice With Augmented n3-Polyunsaturated Fatty Acids Are Protected From Liver Injury Caused by Acute-On-Chronic Ethanol Administration

Alcohol-associated liver disease (ALD) is the leading cause of liver disease worldwide, and alcohol-associated hepatitis (AH), a severe form of ALD, is a major contributor to the mortality and morbidity due to ALD. Many factors modulate susceptibility to ALD development and progression, including nutritional factors such as dietary fatty acids. Recent work from our group and others showed that modulation of dietary or endogenous levels of n6-and n3-polyunsaturated fatty acids (PUFAs) can exacerbate or attenuate experimental ALD, respectively. In the current study, we interrogated the effects of endogenous n3-PUFA enrichment in a mouse model which recapitulates features of early human AH using transgenic fat-1 mice which endogenously convert n6-PUFAs to n3-PUFAs. Male wild type (WT) and fat-1 littermates were provided an ethanol (EtOH, 5% v/v)-containing liquid diet for 10 days, then administered a binge of EtOH (5 g/kg) by oral gavage on the 11^th day, 9 h prior to sacrifice. In WT mice, EtOH treatment resulted in liver injury as determined by significantly elevated plasma ALT levels, whereas in fat-1 mice, EtOH caused no increase in this biomarker. Compared to their pair-fed controls, a significant EtOH-mediated increase in liver neutrophil infiltration was observed also in WT, but not fat-1 mice. The hepatic expression of several cytokines and chemokines, including Pai-1, was significantly lower in fat-1 vs WT EtOH-challenged mice. Cultured bone marrow-derived macrophages isolated from fat-1 mice expressed less Pai-1 and Cxcl2 (a canonical neutrophil chemoattractant) mRNA compared to WT when stimulated with lipopolysaccharide. Further, we observed decreased pro-inflammatory M1 liver tissue-resident macrophages (Kupffer cells, KCs), as well as increased liver T regulatory cells in fat-1 vs WT EtOH-fed mice. Taken together, our data demonstrated protective effects of endogenous n3-PUFA enrichment on liver injury caused by an acute-on-chronic EtOH exposure, a paradigm which recapitulates human AH, suggesting that n3-PUFAs may be a viable nutritional adjuvant therapy for this disease.

Associations Between Erythrocyte Membrane Fatty Acid Compositions and Biomarkers of Vascular Health in Adults With Type 1 Diabetes With and Without Insulin Resistance: A Cross-Sectional Analysis

OBJECTIVES

The aim of this study was to assess the relationship between specific erythrocyte fatty acid levels and vascular health in type 1 diabetes (T1D) with and without insulin resistance (IR).

METHODS

We analyzed baseline pretreatment data in a subset of 23 patients with T1D from a previously published randomized controlled trial consisting of comprehensive erythrocyte-derived fatty acid profiles and a panel of inflammation-associated endothelial markers. Estimated glucose disposal rate was used to identify and categorize patients with IR. We utilized principal component analysis (PCA) to cluster vascular biomarkers to compute a single "vascular signal" and utilized univariate linear regression models to investigate the association with IR and fatty acid profiles.

RESULTS

Subjects with IR displayed significantly higher levels of linoleic acid (p=0.001), lower levels of eicosapentaenoic acid (EPA) (p<0.001), lower levels of omega-3 polyunsaturated fatty acid (n-3PUFA) (p<0.006) and an increased omega-6 (n-6)PUFA:n-3PUFA ratio (p=0.001). IR was associated with significantly higher linoleic acid levels, total n-6PUFA and an increased ratio of n-6PUFA:n-3PUFA, and negatively associated with arachidonic acid and EPA levels, total saturated fatty acid and total n-3PUFA. The PCA-derived vascular biomarker cluster was positively associated with linoleic acid and n-6PUFA:n-3PUFA ratio, and inversely associated with EPA.

CONCLUSIONS

Specific erythrocyte membrane fatty acid compositions are associated with impaired vascular health and IR in adults with T1D. These findings suggest that IR and risk of associated complications may be influenced by specific fatty acid profiles, and thus potentially modified by the selective targeting of dietary fatty acids.

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.

Regulatory effect of volatile compounds in fermented alcoholic beverages on gut microbiota and serum metabolism in a mouse model

Ethanol (EtOH) is the main risk factor for alcoholic liver disease. However, fermented alcoholic beverages contain not only ethanol but also various volatile compounds. Currently, the effects of volatile compounds in ethanol-containing fermented beverages on gut microbiota and host metabolism are largely unclear. To fill this gap, we constructed an 8-week mice model using three types of Baijiu (a traditional fermented alcoholic beverage), sterile water and ethanol as controls. Results revealed that three types of Baijiu contain various volatiles, mainly belonging to esters, alcohols, and acids. All of Baijiu caused the lower levels of liver injury in mice than EtOH (at the same EtOH concentration) by phenotypic, biochemical and pathological analysis. We observed that Baijiu volatiles affect the gut microbiota structure and serum metabolomic patterns of mice. Compared with EtOH, Baijiu feeding profoundly increased the relative abundance of Lactobacillus (the highest relative abundance in the Baijiu-fed group was 11.16 ± 1.52%, and in the EtOH-fed group it was 1.80 ± 0.66%). Esters, acids and phenols in volatiles showed strong positive correlations (P < 0.01, R > 0.6) with Lactobacillus. Moreover, Baijiu feeding significantly (P < 0.05) enriched serum metabolites related to bioenergy (i.e., D-glucose, the highest fold change was 1.16) and anti-inflammatory activity (i.e., arachidonic acid, the highest fold change was 1.43) as compared to EtOH. Finally, the microbial and metabolic function analysis showed that volatiles will enhance the citrate cycle and biosynthesis of unsaturated fatty acid pathways. Overall, these data demonstrated the potential of volatile compounds for attenuating the progress of alcoholic liver disease by regulating the gut microbiota and host metabolism.

Differences and Correlations of Morphological Characteristics and Fatty Acid Profiles of Seeds of Toona sinensis

Toona sinensis (A.Juss.) M.Roem., a multi-purpose tree of Meliaceae, is widely distributed and intensively cultivated in Asia, yet its high yielding, lipid-rich seeds are rarely exploited. The present study systematically analyzed the differences and correlations of seed morphological characteristics and fatty acid (FA) profiles of 62 representative T. sinensis germplasms distributed across northern to southern China. T. sinensis seeds were rich in total FAs (TFA, 107.03-176.18 mg/g). Additionally, linoleic acid (54.69-100.59 mg/g), α-linolenic acid (ALA, 22.47-45.02 mg/g), oleic acid (OA, 5.12-23.94 mg/g), palmitic acid (6.87-14.14 mg/g), stearic acid (SA, 3.13-6.57 mg/g) and elaidic acid (1.70-2.88 mg/g) were the major FAs measured by GC/MS analysis. Size (average width of 3.94±0.01 mm and length of 5.79±0.02 mm) and mass (average thousand-seed weight of 10.52±0.17 g) were greater in T. sinensis seeds collected south than north of 30° latitude. These traits were also positively correlated with unsaturated FA content and negatively related to SA and saturated FA contents (P<0.05). Significant positive correlations were found between seed length and polyunsaturated FA (R² =0.370) and ALA levels (R² =0.296), as well as between thousand-seed weight and monounsaturated FAs (R² =0.309) and OA levels (R² =0.297) (P<0.05). Seventeen T. sinensis germplasms gathered by cluster analysis as cluster IV were determined as desirable for oil processing due to their higher TFA and ALA contents and greater seed size and mass than others. Generally, the wider, heavier, and especially longer seeds of T. sinensis contain much higher levels of FAs, especially ALA, and are the more promising sources for breeding and the oil processing industry.

Predictors of steroid non-response and new approaches in severe alcoholic hepatitis

Severe alcoholic hepatitis (SAH) remains a disease with high mortality. Steroid is the main stay and has been shown to give modest 28-day survival benefit in carefully selected patients, but no 90-day survival benefit. Since non-responders have high incidence of infections and increased mortality, it would be worthwhile to identify them before starting steroid therapy. A high and rising bilirubin, urinary acetyl carnitine >2,500 ng/mL, high asiloglycoprotein positive microparticles, and specific features in liver biopsy could predict steroid non-response at baseline. There is an ever-growing need to find new and effective therapies for SAH patients. Besides aggressive nutrition, granulocyte colony stimulating factor, fecal microbiota transplantation, and plasma exchange appear promising therapies and provide a hope for steroid ineligible or steroid non-responsive patients. Suppression of hepatic inflammation, preventing new bacterial or fungal infections, and enhancing liver regeneration will remain the key targets for next generation therapies.