Hepatoprotective Effect of Oyster Peptide on Alcohol-Induced Liver Disease in Mice

Musculus senhousei peptides alleviated alcoholic liver injury via the gut-liver axis

Alcoholic liver injury has become a leading threat to human health, with complicated pathogenesis and limited therapeutic options. Our previous study showed that Musculus senhousei peptides (MSPs) exhibit protective potential against early-stage alcoholic liver injury, although the underlying mechanism is not yet clear. In this study, histopathological analysis, mRNA abundance of injury-associated biomarkers, the gut microbiota, and faecal metabolome were evaluated using a mouse model subjected to acute alcohol exposure, aiming to identify the mechanism by which MSP can alleviate alcoholic hepatotoxicity. The results showed that MSP intervention significantly ameliorated symptoms of liver injury (suppressed serum ALT increment, hepatic lipid accumulation, and neutrophil infiltration in liver tissue), and reversed the abnormal mRNA abundance of biomarkers associated with oxidative stress (iNOS), inflammation (TNF-α, IL-1β, MCP-1, TNF-R1, and TLR4), and apoptosis (Bax and Casp. 3) in the liver. Moreover, MSP improved intestinal barrier function by increasing the expression of tight junction proteins (Claudin-1 and Claudin-3). Further analysis of faecal microbiota and metabolome revealed that MSP promoted the growth of tryptophan-metabolizing bacteria (Clostridiales, Alistipes, and Odoribacter), leading to increased production of indole derivatives (indole-3-lactic acid and N-acetyltryptophan). These results suggested that MSPs may alleviate alcohol-induced liver injury targeting the gut-liver axis, and could be an effective option for the prevention of alcoholic liver injury.

Bioactive peptides as a novel strategy to prevent alcoholic liver injury

Alcohol intake has become one of the leading risks to human health and wellness, among which acute and/or chronic alcohol-induced liver injury is a leading threaten, with few therapeutic options other than abstinence. In recent years, studies suggested that certain bioactive peptides from food sources could represent natural and safe alternatives for the prevention of alcoholic liver injury. Hence, this chapter focus on the advanced research on bioactive peptides exerting hepatoprotective activity against alcoholic liver injury. The main sources of protein, strategies for the preparation of hepatoprotective hydrolysates and peptides, underlying mechanisms of peptides on hepatoprotection, and possible structure-activity relationship between peptides and hepatoprotective activity were summarized and discussed, aiming to give a systematic insight into the research progress of hepatoprotective peptides. However, more efforts would be needed to give a clearer insight into the underlying mechanisms and structure-activity relationship before using hepatoprotective peptides as functional food ingredients or dietary supplements.

The Role of Oxidative Stress in Alcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis of Preclinical Studies

Alcoholic Fatty Liver Disease (AFLD) is characterized by the accumulation of lipids in liver cells owing to the metabolism of ethanol. This process leads to a decrease in the NAD+/NADH ratio and the generation of reactive oxygen species. A systematic review and meta-analysis were conducted to investigate the role of oxidative stress in AFLD. A total of 201 eligible manuscripts were included, which revealed that animals with AFLD exhibited elevated expression of CYP2E1, decreased enzymatic activity of antioxidant enzymes, and reduced levels of the transcription factor Nrf2, which plays a pivotal role in the synthesis of antioxidant enzymes. Furthermore, animals with AFLD exhibited increased levels of lipid peroxidation markers and carbonylated proteins, collectively contributing to a weakened antioxidant defense and increased oxidative damage. The liver damage in AFLD was supported by significantly higher activity of alanine and aspartate aminotransferase enzymes. Moreover, animals with AFLD had increased levels of triacylglycerol in the serum and liver, likely due to reduced fatty acid metabolism caused by decreased PPAR-α expression, which is responsible for fatty acid oxidation, and increased expression of SREBP-1c, which is involved in fatty acid synthesis. With regard to inflammation, animals with AFLD exhibited elevated levels of pro-inflammatory cytokines, including TNF-a, IL-1β, and IL-6. The heightened oxidative stress, along with inflammation, led to an upregulation of cell death markers, such as caspase-3, and an increased Bax/Bcl-2 ratio. Overall, the findings of the review and meta-analysis indicate that ethanol metabolism reduces important markers of antioxidant defense while increasing inflammatory and apoptotic markers, thereby contributing to the development of AFLD.

Glucosamine attenuates alcohol-induced acute liver injury via inhibiting oxidative stress and inflammation

Alcohol liver disease (ALD) is a liver disease caused by long-term heavy drinking. Glucosamine (GLC) is an amino monosaccharide that plays a very important role in the synthesis of human and animal cartilage. GLC is commonly used in the treatment of mild to moderate osteoarthritis and has good anti-inflammatory and antioxidant properties. In this study, alcoholic injury models were constructed in mice and human normal hepatocyte L02 cells to explore the protective effect and mechanism of GLC on ALD. Mice were given GLC by gavage for 30 days. Liver injury models of both mice and L02 cells were produced by ethanol. Detecting the levels of liver injury biomarkers, lipid metabolism, oxidative stress biomarkers, and inflammatory factors through different reagent kits. Exploring oxidative and inflammatory pathways in mouse liver tissue through Western blot and RT-PCR. The results showed that GLC can significantly inhibit the abnormal increase of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), triglycerides (TG), total cholesterol (TC), very low density lipoprotein (VLDL), low-density lipoprotein cholesterol (LDL-C), and can significantly improve the level of high-density lipoprotein cholesterol (HDL-C). In addition, GLC intervention significantly improved alcohol induced hepatic oxidative stress by reducing the levels of malondialdehyde (MDA) and, increasing the levels of glutathione (GSH), catalase (CAT) and superoxide dismutase (SOD) in the liver. Further mechanisms suggest that GLC can inhibit the expression of ethanol metabolism enzyme cytochrome P4502E1 (CYP2E1), activate the antioxidant pathway Keap1/Nrf2/HO-1, down-regulate the phosphorylation of MAPK and NF-κB signaling pathways, and thus reduce the expression of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6). Therefore, GLC may be a significant candidate functional food for attenuating alcohol induced acute liver injury.

Protective Effect of Polyphenols, Protein, Peptides, and Polysaccharides on Alcoholic Liver Disease: A Review of Research Status and Molecular Mechanisms

Alcoholic liver disease (ALD) has emerged as an important public health problem in the world. The polyphenols, protein, peptides, and polysaccharides have attracted attention for prevention or treatment of ALD. Therefore, this paper reviews the pathogenesis of ALD, the relationship between polyphenols, peptides, polysaccharides, and ALD, and expounds the mechanism of gut microbiota on protecting ALD. It is mainly found that the hydroxyl group of polyphenols endows it with antioxidation to protect ALD. The ALD protection of bioactive peptides is related to amino acid composition. The ALD protection of polysaccharides is related to the primary structure. Meanwhile, polyphenols, protein, peptides, and polysaccharides prevent or treat ALD by antioxidation, anti-inflammatory, antiapoptosis, lipid metabolism, and gut microbiota regulation. This contribution provides updated information on polyphenols, protein, peptides, and polysaccharides in response to ALD, which will not only facilitate the development of novel bioactive components but also the future application of functional food raw materials will be promoted.

Hepatoprotective Effect of Albumin Peptide Fractions from Corn Germ Meal against Alcohol-Induced Acute Liver Injury in Mice

Acute alcoholic liver disease can cause serious liver damage. This study reports on the hepatoprotective effect of albumin peptide fractions from corn germ meal (MW < 1 kDa) (APF4) on acute alcohol hepatic damage in mice. In the mice model, the results indicated that APF4 at a dose of 800 mg/kg/bw could markedly boost alcohol metabolism, which was shown in the reduced duration of the loss of the righting reflex; the reduced level of blood alcohol concentration (BAC), cytochrome P450 2E1 (CYP2E1), alanine aminotransferase (ALT), aminotransferase (AST), triglycerides (TG), and malondialdehyde (MDA) (p < 0.01); the enhanced activity of aldehyde dehydrogenase (ALDH); and the superoxide dismutase (SOD) and glutathione (GSH) levels being increased by up to 84.02% and 193.22% (p < 0.01) compared to the control group. The antioxidant capability and lipid peroxidation inhibition activity of APF4 may be responsible for its protective effect against liver damage induced by alcohol. The findings suggested that APF4 had the hepatoprotective property against liver damage induced by alcohol.

Eighteen Novel Bioactive Peptides from Monkfish (Lophius litulon) Swim Bladders: Production, Identification, Antioxidant Activity, and Stability

In the study, papain was chosen from five proteases to hydrolyze proteins of monkfish swim bladders for effectively utilizing monkfish (Lophius litulon) processing byproducts, and the hydrolysis conditions of papain were optimized as hydrolysis temperature of 65 °C, pH 7.5, enzyme dose 2.5% and time 5 h using single-factor and orthogonal experiments. Eighteen peptides were purified from the swim bladder hydrolysate of monkfish by ultrafiltration and gel permeation chromatography methods and identified as YDYD, QDYD, AGPAS, GPGPHGPSGP, GPK, HRE, GRW, ARW, GPTE, DDGGK, IGPAS, AKPAT, YPAGP, DPT, FPGPT, GPGPT, GPT and DPAGP, respectively. Among eighteen peptides, GRW and ARW showed significant DPPH· scavenging activities with EC₅₀ values of 1.053 ± 0.003 and 0.773 ± 0.003 mg/mL, respectively; YDYD, QDYD, GRW, ARW and YPAGP revealed significantly HO· scavenging activities with EC₅₀ values of 0.150 ± 0.060, 0.177 ± 0.035, 0.201 ± 0.013, 0.183 ± 0.0016 and 0.190 ± 0.010 mg/mL, respectively; YDYD, QDYD, ARW, DDGGK and YPAGP have significantly O2-· scavenging capability with EC₅₀ values of 0.126 ± 0.0005, 0.112 ± 0.0028, 0.127 ± 0.0002, 0.128 ± 0.0018 and 0.107 ± 0.0002 mg/mL, respectively; and YDYD, QDYD and YPAGP showed strong ABTS⁺· scavenging ability with EC₅₀ values of 3.197 ± 0.036, 2.337 ± 0.016 and 3.839 ± 0.102 mg/mL, respectively. YDYD, ARW and DDGGK displayed the remarkable ability of lipid peroxidation inhibition and Ferric-reducing antioxidant properties. Moreover, YDYD and ARW can protect Plasmid DNA and HepG2 cells against H₂O₂-induced oxidative stress. Furthermore, eighteen isolated peptides had high stability under temperatures ranging from 25-100 °C; YDYD, QDYD, GRW and ARW were more sensitive to alkali treatment, but DDGGK and YPAGP were more sensitive to acid treatment; and YDYD showed strong stability treated with simulated GI digestion. Therefore, the prepared antioxidant peptides, especially YDYD, QDYD, GRW, ARW, DDGGK and YPAGP from monkfish swim bladders could serve as functional components applied in health-promoting products because of their high-antioxidant functions.

Antioxidant and anti-inflammatory agents in chronic liver diseases: Molecular mechanisms and therapy

Chronic liver disease (CLD) is a continuous process that causes a reduction of liver function lasting more than six months. CLD includes alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), chronic viral infection, and autoimmune hepatitis, which can lead to liver fibrosis, cirrhosis, and cancer. Liver inflammation and oxidative stress are commonly associated with the development and progression of CLD. Molecular signaling pathways such as AMP-activated protein kinase (AMPK), C-Jun N-terminal kinase, and peroxisome proliferator-activated receptors (PPARs) are implicated in the pathogenesis of CLD. Therefore, antioxidant and anti-inflammatory agents from natural products are new potent therapies for ALD, NAFLD, and hepatocellular carcinoma (HCC). In this review, we summarize some powerful products that can be potential applied in all the stages of CLD, from ALD/NAFLD to HCC. The selected agents such as β-sitosterol, curcumin, genistein, and silymarin can regulate the activation of several important molecules, including AMPK, Farnesoid X receptor, nuclear factor erythroid 2-related factor-2, PPARs, phosphatidylinositol-3-kinase, and lysyl oxidase-like proteins. In addition, clinical trials are undergoing to evaluate their efficacy and safety.

Preparation and Hepatoprotective Activities of Peptides Derived from Mussels (Mytilus edulis) and Clams (Ruditapes philippinarum)

Low molecular weight (<5 kDa) peptides from mussels (Mytilus edulis) (MPs) and the peptides from clams (Ruditapes philippinarum) (CPs) were prepared through enzymatic hydrolysis by proteases (dispase, pepsin, trypsin, alcalase and papain). Both the MPs and the CPs showed excellent in vitro scavenging ability of free radicals including OH, DPPH and ABTS in the concentration range of 0.625−10.000 mg/mL. By contrast, the MPs hydrolyzed by alcalase (MPs-A) and the CPs hydrolyzed by dispase (CPs-D) had the highest antioxidant activities. Furthermore, MPs-A and CPs-D exhibited protective capabilities against oxidative damage induced by H2O2 in HepG2 cells in the concentration range of 25−800 μg/mL. Meanwhile, compared with the corresponding indicators of the negative control (alcohol-fed) mice, lower contents of hepatic MDA and serums ALT and AST, as well as higher activities of hepatic SOD and GSH-PX were observed in experiment mice treated with MPs-A and CPs-D. The present results clearly indicated that Mytilus edulis and Ruditapes philippinarum are good sources of hepatoprotective peptides.

Bioactive Peptides from Skipjack Tuna Cardiac Arterial Bulbs: Preparation, Identification, Antioxidant Activity, and Stability against Thermal, pH, and Simulated Gastrointestinal Digestion Treatments

Cardiac arterial bulbs of Skipjack tuna (Katsuwonus pelamis) are rich in elastin, and its hydrolysates are high quality raw materials for daily cosmetics. In order to effectively utilizing Skipjack tuna processing byproducts-cardiac arterial bulbs and to prepare peptides with high antioxidant activity, pepsin was selected from six proteases for hydrolyzing proteins, and the best hydrolysis conditions of pepsin were optimized. Using ultrafiltration and chromatographic methods, eleven antioxidant peptides were purified from protein hydrolysate of tuna cardiac arterial bulbs. Four tripeptides (QGD, PKK, GPQ and GLN) were identified as well as seven pentapeptides (GEQSN, GEEGD, YEGGD, GEGER, GEGQR, GPGLM and GDRGD). Three out of them, namely the tripeptide PKK and the pentapeptides YEGGD and GPGLM exhibited the highest radical scavenging activities on 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and superoxide anion assays. They also showed to protect plasmid DNA and HepG2 cells against H₂O₂-induced oxidative stress. Furthermore, they exhibited high stability under temperature ranged from 20-100 °C, pH values ranged from 3-11, and they simulated gastrointestinal digestion for 240 min. These results suggest that the prepared eleven antioxidant peptides from cardiac arterial bulbs, especially the three peptides PKK, YEGGD, and GPGLM, could serve as promising candidates in health-promoting products due to their high antioxidant activity and their stability.