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

Advances in Research on Marine-Derived Lipid-Lowering Active Substances and Their Molecular Mechanisms

Hyperlipidemia (HLP) is a metabolic disorder caused by abnormal lipid metabolism. Recently, the prevalence of HLP caused by poor dietary habits in the population has been increasing year by year. In addition, lipid-lowering drugs currently in clinical use have shown significant improvement in blood lipid levels, but are accompanied by certain side effects. However, bioactive marine substances have been shown to possess a variety of physiological activities such as hypoglycemic, antioxidant, antithrombotic and effects on blood pressure. Therefore, the hypolipidemic efficacy of marine bioactive substances with complex and diverse structures has also attracted attention. This paper focuses on the therapeutic role of marine-derived polysaccharides, unsaturated fatty acids, and bioactive peptides in HLP, and briefly discusses the main mechanisms by which these substances exert their hypolipidemic activity in vivo.

Does inclusion of bioactive n-3 PUFAs in parenteral nutrition benefit postoperative patients undergoing liver surgery? A systematic review and meta-analysis of randomised control trials

OBJECTIVES

This meta-analysis aims to evaluate the effect of n-3 polyunsaturated fatty acids (PUFAs) as a part of parenteral nutrition in patients undergoing liver surgery.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed, the Cochrane Central Register of Controlled Trials, Springer link, Web of Science, China National Knowledge Infrastructure and VIP Database.

ELIGIBILITY CRITERIA

We included randomised controlled trials (RCTs) and evaluated the outcomes of liver function, inflammatory reaction, the influence of certain markers of the immune system, and specific clinical indexes for patients undergoing liver surgery and receiving parenteral nutrition with n-3 PUFAs.

DATA EXTRACTION AND SYNTHESIS

The Cochrane Collaboration's tool was used to assess the risk of bias for each study. Findings were summarised in Grades of Recommendation, Assessment, Development and Evaluation evidence profiles and synthesised qualitatively.

RESULTS

Eight RCTs, including 748 patients (trial: 374; control: 374), were included in the meta-analysis. Compared with patients in the control group, the patients in the n-3 PUFA group who underwent liver surgery had significantly lower aspartate aminotransferase (mean difference, MD -42.72 (95% CI -71.91 to -13.52); p=0.004), alanine aminotransferase (MD -38.90 (95% CI -65.44 to -12.37); p=0.004), white cell count (MD -0.93 (95% CI -1.60 to -0.26); p=0.007) and IL-6 (MD -11.37 (95% CI -14.62 to -8.13); p<0.00001) levels and a higher albumin level (MD 0.42 (95% CI 0.26 to 0.57); p<0.00001). They also had fewer infection complications (OR 0.44 (95% CI 0.28 to 0.68); p=0.0003) and a shorter duration of hospital stay (MD -2.17 (95% CI -3.04 to -1.3); p<0.00001) than the controls. However, there were no significant differences in terms of total bilirubin, TNF-α, IL-2, IgA, IgG, IgM and CD3, biliary leakage and mortality between the two groups.

CONCLUSIONS

We found that n-3 PUFAs can benefit patients undergoing liver surgery by improving liver function and certain clinical indexes and decreasing related inflammation factors. However, there are limited RCTs on the application of n-3 PUFAs for patients undergoing liver surgery. Further evidence of the benefit of n-3 PUFAs in these patients warrants further exploration.

Roles of the peroxisome proliferator-activated receptors (PPARs) in the pathogenesis of nonalcoholic fatty liver disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of disease phenotypes which start with simple steatosis and lipid accumulation in the hepatocytes - a typical histological lesions characteristic. It may progress to non-alcoholic steatohepatitis (NASH) that is characterized by hepatic inflammation and/or fibrosis and subsequent onset of NAFLD-related cirrhosis and hepatocellular carcinoma (HCC). Due to the central role of the liver in metabolism, NAFLD is regarded as a result of and contribution to the metabolic abnormalities seen in the metabolic syndrome. Peroxisome proliferator-activated receptors (PPARs) has three subtypes, which govern the expression of genes responsible for energy metabolism, cellular development, inflammation, and differentiation. The agonists of PPARα, such as fenofibrate and clofibrate, have been used as lipid-lowering drugs in clinical practice. Thiazolidinediones (TZDs) - ligands of PPARγ, such as rosiglitazone and pioglitazone, are also used in the treatment of type 2 diabetes (T2D) with insulin resistance (IR). Increasing evidence suggests that PPARβ/δ agonists have potential therapeutic effects in improving insulin sensitivity and lipid metabolism disorders. In addition, PPARs ligands have been considered as potential therapeutic drugs for hypertension, atherosclerosis (AS) or diabetic nephropathy. Their crucial biological roles dictate the significance of PPARs-targeting in medical research and drug discovery. Here, it reviews the biological activities, ligand selectivity and biological functions of the PPARs family, and discusses the relationship between PPARs and the pathogenesis of NAFLD and metabolic syndrome. This will open new possibilities for PPARs application in medicine, and provide a new idea for the treatment of fatty liver and related diseases.

Monounsaturated fatty acid-enriched olive oil exacerbates chronic alcohol-induced hepatic steatosis and liver injury in C57BL/6J mice

Dietary oil composition determines the pathological processes of alcoholic fatty liver disease (AFLD). Oil rich in saturated fatty acids protects, whereas oil rich in polyunsaturated fatty acids aggravates the alcohol-induced liver injury. However, limited studies have been conducted to address how monounsaturated fatty acids (MUFAs) enriched oil controls the pathological development of AFLD. Therefore, this study was designed to evaluate the effect of MUFA-enriched extra virgin olive oil (OO) on AFLD. Twenty C57BL/6J mice were randomly allocated into four groups and fed modified Lieber-DeCarli liquid diets containing isocaloric maltose dextrin a non-alcohol or alcohol with corn oil and OO for four weeks. Dietary OO significantly exacerbated alcohol-induced liver dysfunction, evidenced by histological examinations and disturbed biochemical parameters. Dietary OO with alcohol decreased hormone-sensitive lipase (HSL), phosphorylated 5'-AMP-activated protein kinase (p-AMPK), and carnitine palmitoyltransferase-Iα (CPT1α) expression, and increased sterol regulatory element-binding protein-1c (SREBP-1c), diacylglycerol acyltransferase-2 (DGAT2), and very low-density lipoprotein receptor (VLDLR) expression in the liver. It also promoted the expression of hepatic interleukin-6 (IL-6) and hepatic tumour necrosis factor-alpha (TNF-α) at the transcriptional level. Additionally, adipose tissue lipolysis partially had an etiologic effect on alcohol-induced hepatic steatosis under OO pretreatment. In conclusion, MUFA-enriched OO exacerbated liver dysfunction in vivo. OO should be cautiously considered as a unique dietary oil source for individuals with AFLD.

Dietary camellia seed oil attenuates liver injury in mice chronically exposed to alcohol

Dietary fat composition is closely associated with the pathological development of alcoholic liver disease (ALD). Fat enriched with saturated fatty acids protects whereas with polyunsaturated fatty acids aggravates alcohol-induced liver injury. However, limited study has addressed how monounsaturated fatty acids (MUFAs) determines the pathological process of ALD. Our study was conducted to evaluate the effect of MUFAs-enriched-camellia seed oil (CSO) on alcohol-induced liver injury. The ALD model was established by feeding C57BL/6 mice with Lieber-DeCarli diet, and with either CSO or polyunsaturated fatty acids (PUFAs)-enriched-corn oil (CO) as fat source. After 4-week-intervention, CSO-feed rescued alcohol-induced liver injury compared to CO-feed, evidenced by measurements of plasma ALT activity, H&E stain, and hepatic cleaved-Caspase-3 expression. Besides, CSO-feed alleviated alcohol-induced oxidative stress, associated with NRF2 and Hif-1α expressions improvement. The reduction of F4/80 immunostaining and the decreased expressions of hepatic TNF-α and IL-6 suggested CSO-feed improved alcohol-induced inflammation. The mechanistic analysis showed that the inhibition of ASK1 and MAPKs might contribute to CSO-protected liver injury. Notably, we observed CSO-feed relieved the gut microbiota disturbance with the decreased Firmicutes and Turicibater, and the increased Bacteroidota, Alloprevotella, and Bacteroides, and reduced circulatory endotoxin level and lipolysis of adipose tissue, which are the known pathogenic factors in alcohol-induced liver injury. Unexpectedly, CSO induced more hepatic steatosis than CO-feed. In conclusion, CSO attenuated chronic alcohol consumption-induced liver injury but enhanced hepatic steatosis. CSO could be a potential dietary choice for alcoholic individuals with liver injury.

Disruption of Pituitary Gonadotrope Activity in Male Rats After Short- or Long-Term High-Fat Diets Is Not Associated With Pituitary Inflammation

Overnutrition is associated with the activation of inflammatory pathways in metabolically linked organs and an early hypothalamic inflammation is now known to disrupt the central control of metabolic function. Because we demonstrated that fatty acids (FA) target the pituitary and affect gonadotropin synthesis, we asked whether overnutrition induces pituitary inflammation that may contribute to obesity-associated disorders in the control of reproduction. We analyzed pituitary inflammation and hypothalamic-pituitary-testicular axis in male rats fed a short- (4 weeks) or long-term (20 weeks) high-fat diet. The effect of diet enrichment with the ω3 polyunsaturated FA, DHA, was also analyzed. After only 4 weeks and before weight gain of rats, high-fat diet caused a significant decrease in pituitary gonadotropin and hypothalamic GnRH transcript levels despite unchanged testosterone and inhibin B levels. Contrasting with the hypothalamus, there was no concomitant increases in gene expression of pituitary inflammatory mediators and even a reduction of prototypical cytokines such as interleukin-1β and TNF-α. No inflammation was still detected in the pituitary after 20 weeks although gonadotropin transcripts and circulating levels were still altered. Gonadotropins were the only pituitary hormones remaining affected at this stage of the regimen, underlying a differential susceptibility of pituitary lineages to metabolic disorders. DHA enrichment of the diet did not prevent alterations of gonadotrope activity due to either a long- or a short-term high-fat diet although it blocked early hypothalamic inflammation and attenuated several metabolic effects. Taken together, our findings suggest that high-fat diet-induced defects in gonadotrope activity in male rats occurred despite a lack of pituitary inflammation.