Role of plasma amino acids and gaba in alcoholic and non-alcoholic fatty liver disease-a pilot study

Efficacy of Rhamnus utilis Decne. Aqueous extract in mice with acute alcoholic liver injury and metabolomic study

Rhamnus utilis Decne. (Family Rhamnaceae Juss.) leaf is commonly prepared as a anti-inflammatory herbal medicine and used for tea production. To investigate the mechanism of Rhamnus utilis Decne. aqueous extract (RDAE) against acute alcoholic liver disease (ALD) in mice. The ALD mouse (Male ICR) model was induced via intragastric administration of 52 % alcohol. Mice in each group were treated by gavage once daily with the RDAE (1.12, 2.25, 4.500 g/kg). The expression of proteins involved in the MAPKs/NF-κB/COX-2-iNOS pathway was measured by western blotting. Non-targeted metabolomics was used to determine metabolic profiles and critical pathways, while targeted metabolomics validated key amino acid metabolites. After administration of RDAE, the body mass of mice was significantly increased. The liver index was significantly decreased. Meanwhile, the serum levels of AST, ALT, TG, TC, MDA, TNF-α, IL-1β and IL-6 were significantly decreased (P < 0.05, P < 0.01), but GSH level was inversely increased (P < 0.05). Metabolomic analysis revealed nine major pathways involved in the therapeutic effect of RDAE, including fructose and mannose metabolism. The levels of 7 amino acids including leucine, proline and alanine/sarcosine were significantly upregulated. Additionally, protein levels of p-NF-κB (p65)/NF-κB (p65), p-ERK1/2/ERK1/2, p-JNK/JNK, p-p38/p38, COX-2 and iNOS were significantly decreased (P < 0.01, P < 0.05). RDAE is used to treat acute ALD by improving lipid metabolism, inhibiting the expression of pro-inflammatory cytokines and regulating MAPKs/NF-κB/COX-2-iNOS signalling pathway. These findings provide valuable insights for acute ALD therapy based on traditional Chinese medicine (TCM).

Association between serum trace element, mineral, and amino acid levels with non-alcoholic fatty liver disease (NAFLD) in adult women

The objective of the present study is assessment of serum trace element and amino acid levels in non-alcoholic fatty liver disease (NAFLD) patients with subsequent evaluation of its independent associations with markers of liver injury and metabolic risk.

MATERIALS AND METHODS

140 women aged 20-90 years old with diagnosed NAFLD and 140 healthy women with a respective age range were enrolled in the current study. Analysis of serum and hair levels of trace elements and minerals was performed with inductively-coupled plasma mass-spectrometry (ICP-MS). Serum amino acid concentrations were evaluated by high-pressure liquid chromatography (HPLC) with UV-detection. In addition, routine biochemical parameters including liver damage markers, alanine aminotransferase (ALT) and gamma-glutamyltransferase (GGT), were assessed spectrophotometrically.

RESULTS

The findings demonstrated that patients with NAFLD were characterized by higher ALT, GGT, lactate dehydrogenase (LDH) and cholinesterase (CE) activity, as well as increased levels of total cholesterol, low-density lipoprotein cholesterol, triglycerides, and uric acid. NAFLD patients were characterized by reduced serum and hair Co, Se, and Zn levels, as well as hair Cu content and serum Mn concentrations in comparison to controls. Circulating Ala, Cit, Glu, Gly, Ile, Leu, Phe, and Tyr levels in NAFLD patients exceeded those in the control group. Multiple linear regression demonstrated that serum and hair trace element levels were significantly associated with circulating amino acid levels after adjustment for age, BMI, and metabolic parameters including liver damage markers.

CONCLUSION

It is proposed that altered trace element handling may contribute to NAFLD pathogenesis through modulation of amino acid metabolism.

Continuous production of gamma aminobutyric acid by engineered and immobilized Escherichia coli whole-cells in a small-scale reactor system

γ-Amino butyric acid (GABA) is a non-proteinogenic amino acid and a human neurotransmitter. Recently, increasing demand for food additives and biodegradable bioplastic monomers, such as nylon 4, has been reported. Consequently, considerable efforts have been made to produce GABA through fermentation and bioconversion. To realize bioconversion, wild-type or recombinant strains harboring glutamate decarboxylase were paired with the cheap starting material monosodium glutamate, resulting in less by-product formation and faster production compared to fermentation. To increase the reusability and stability of whole-cell production systems, this study used an immobilization and continuous production system with a small-scale continuous reactor for gram-scale production. The cation type, alginate concentration, barium concentration, and whole-cell concentration in the beads were optimized and this optimization resulted in more than 95 % conversion of 600 mM monosodium glutamate to GABA in 3 h and reuse of the immobilized cells 15 times, whereas free cells lost all activity after the ninth reaction. When a continuous production system was applied after optimizing the buffer concentration, substrate concentration, and flow rate, 165 g of GABA was produced after 96 h of continuous operation in a 14-mL scale reactor. Our work demonstrates the efficient and economical production of GABA by immobilization and continuous production in a small-scale reactor.

Three Klebsiella species as potential pathobionts generating endogenous ethanol in a clinical cohort of patients with auto-brewery syndrome: a case control study

BACKGROUND

Patients with auto-brewery syndrome (ABS) become inebriated after the ingestion of an alcohol-free, high-carbohydrate diet. Our previous work has shown that high-alcohol-producing (HiAlc) Klebsiella pneumoniae can generate excessive endogenous ethanol and cause non-alcoholic fatty liver disease (NAFLD). Therefore, it is reasonable to speculate that such bacteria might play an important role in the pathogenesis of ABS.

METHODS

The characteristics and metabolites of the intestinal flora from a clinical cohort of patients with ABS were analysed during different stages of disease and compared to a group of healthy controls. An in vitro culture system of relevant samples was used for screening drug sensitivity and ABS-inducing factors. Rabbit intestinal and murine models were established to verify if the isolated strains could induce ABS in vivo.

FINDINGS

We observed intestinal dysbiosis with decreased abundance of Firmicutes and increased of Proteobacteria in patients with ABS compared with healthy controls. The abundance of the genus Klebsiella in Enterobacteriaceae was strongly associated with fluctuations of patient's blood alcohol concentration. We isolated three species of HiAlc Klebsiella from ABS patients, which were able to induce ABS in mice. Monosaccharide content was identified as a potential food-related inducing factor for alcohol production. Treatments with antibiotics, a complex probiotic preparation and a low-carbohydrate diet not only alleviated ABS, but also erased ABS relapse during the follow-up observation of one of the patients.

INTERPRETATION

Excessive endogenous alcohol produced by HiAlc Klebsiella species was an underlying cause of bacterial ABS. Combined prescription of appropriate antibiotics, complex probiotic preparation and a controlled diet could be sufficient for treatment of bacteria-caused ABS.

FUNDING

The funders are listed in the acknowledgement.

Integrative transcriptomics and metabolomics explore the mechanism of kaempferol on improving nonalcoholic steatohepatitis

Kaempferol has been confirmed to be effective in improving metabolic diseases such as diabetes and obesity. However, its effect and mechanism in nonalcoholic steatohepatitis (NASH) are unclear. We aim to confirm whether kaempferol could improve NASH and find the corresponding differential genes and metabolites. Transcriptomics combined with metabolomics was used to investigate the alterations in genes and metabolites expression after kaempferol treatment in mice with high-fat-diet-induced NASH. The results showed that kaempferol reduced the level of alanine transaminase (ALT), low-density lipoprotein cholesterol (LDL-C), and total cholesterol (TC) in serum and triglyceride (TG), lipid droplets, and inflammatory cell infiltration in liver. Further, 277 differentially expressed genes (DEGs) were identified through liver transcriptomics and the five most obvious DEGs were found to be CYP2b9, Cyp4a12b, Mup17, Mup7, and Mup16, which revealed that HFD induced fatty acid degradation, ribosome, and glyoxylic acid and dicarboxylic acid metabolism. Nine serum metabolites (methylcysteine, l-tryptophan, adrenic acid, d-2-hydroxyglutaric acid, tartaric acid, p-cresol sulfate, l-alanine, l-tryosine, and glutaconic acid) and 3 liver differential metabolites (gallic acid, γ-lindenic acid, and l-phenylalanine) were also identified, while the pathways were mainly involved in phenylalanine, tyrosine, and tryptophan biosynthesis; and phenylalanine metabolism. Integrating transcriptomics and metabolomics analyses indicated that kaempferol possesses the ability to improve NASH associated with energy metabolism, lipid metabolism, oxidative stress, and inflammation-related pathways. This study provides a powerful means of multiomics data integration and reveals the potent therapy and biomarkers for kaempferol.

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.

Targeted Metabolomics Identifies Differential Serum and Liver Amino Acids Biomarkers in Rats with Alcoholic Liver Disease

To investigate changes in serum and hepatic levels of amino acids in ALD and to provide novel evidence and approaches for the prevention and treatment of ALD. Twenty specific pathogen-free SD male rats were devided into two groups, ten for the control group, and ten for the model group. Serum biochemical markers, including alanine aminotransferase, aspartate aminotransferase, laminin and hyaluronidase were measured. Histological analysis of liver tissues was performed. Serum and liver amino acids levels were quantitatively determined by ultra-high-performance liquid chromatography-tandem quadrupole mass spectrometry (UPLC-TQMS)-based targeted metabolomics. Compared with the normal group, ALD rats showed an obvious increase in the levels of β-alanine, alanine, serine, ornithine, tyrosine and the tyrosine ratio, while there was a decrease in arginine levels, the BTR ratio and Fischer's ratio in serum. Additionally, ALD rats exhibited a significant increase in the levels of cysteine and putrescine, while there was a decrease in sarcosine, β-alanine, serine, proline, valine, threonine, ornithine, lysine, histidine, tyrosine, symmetric dimethylarginine, methionine, isoleucine and methionine-sulfoxide levels in liver tissues compared with the normal group. The serum and liver amino acids showed significant changes in ALD rats and can be considered as potential specific diagnostic biomarkers for ALD.

Quantification of aminobutyric acids and their clinical applications as biomarkers for osteoporosis

Osteoporosis is a highly prevalent chronic aging-related disease that frequently is only detected after fracture. We hypothesized that aminobutyric acids could serve as biomarkers for osteoporosis. We developed a quick, accurate, and sensitive screening method for aminobutyric acid isomers and enantiomers yielding correlations with bone mineral density (BMD) and osteoporotic fracture. In serum, γ-aminobutyric acid (GABA) and (R)-3-aminoisobutyric acid (D-BAIBA) have positive associations with physical activity in young lean women. D-BAIBA positively associated with hip BMD in older individuals without osteoporosis/osteopenia. Lower levels of GABA were observed in 60–80 year old women with osteoporotic fractures. Single nucleotide polymorphisms in seven genes related to these metabolites associated with BMD and osteoporosis. In peripheral blood monocytes, dihydropyrimidine dehydrogenase, an enzyme essential to D-BAIBA generation, exhibited positive association with physical activity and hip BMD. Along with their signaling roles, BAIBA and GABA might serve as biomarkers for diagnosis and treatments of osteoporosis.

Wang et al. develop an LC/MS based screening method to separate and quantify aminobutyric acids isoforms. Applying it to osteoporosis clinical studies, their method yields important correlations with bone mineral density and osteoporotic fracture and highlight the role of γ-aminobutyric acid and β-aminoisobutyric acid as biomarkers for osteoporosis.

Neurochemical Evidence of Preclinical and Clinical Reports on Target-Based Therapy in Alcohol Used Disorder

Alcohol use disorder (AUD) is a chronic relapsing disorder, which enforces a person to compulsively seek alcohol, restricting control over alcohol intake leads to emergence of an undesired emotional state during abstinence. There are recent advances for better understanding of neurocircuitry involved in the pathophysiology of AUD. Alcohol interaction with neuronal membrane proteins results in changes in neuronal circuits. It is also linked with the potential medication and their clinical validation concerning their pharmacological targets for alcoholic abstinence. This review covers research work from the past few decades on the therapeutic advances on treatment of alcohol dependence; further detailing the fundamental neurochemical mechanisms after alcohol administration. It also covers interaction of alcohol with GABAergic, glutaminergic, dopaminergic, serotonergic and opioid systems. This review further elaborated the neurobiology of noradrenergic, cholinergic and cannabinoid systems and their interaction with AUD. Elaborative information of potential drug targets under current exploration for AUD treatment with their mechanisms are reported here along with clinical outcomes and the associated side effects.

Insulin resistance and metabonomics analysis of fatty liver haemorrhagic syndrome in laying hens induced by a high-energy low-protein diet

Fatty liver haemorrhagic syndrome (FLHS) is a widespread metabolic disease in laying hens that causes a decrease in egg production and even death. Insulin resistance is a major contributor to the pathogenesis of nonalcoholic fatty liver disease. However, the relationship between FLHS and the insulin resistance mechanisms underlying FLHS is not well elucidated. Therefore, we established an FLHS model induced by feeding a high-energy low-protein diet. In the current study, we found that the fasting glucose and insulin concentrations were elevated in the FLHS group compared with the control group during the experimental period. The results of the oral glucose tolerance test (OGTT) and insulin sensitivity test (IST) showed a high level of insulin resistance in the FLHS model. InsR, 4EBP-1, Glut-1 and Glut-3 mRNA expression were decreased, and TOR, S6K1, and FOXO1 were elevated (P < 0.05). Metabolomic analysis with GC/MS identified 46 differentially expressed metabolites between these two groups, and of these, 14 kinds of metabolism molecules and 32 kinds of small metabolism molecules were decreased (P < 0.05). Further investigation showed that glucose, lipid and amino acid metabolism blocks in the progression of FLHS by GO functional and pathway analysis. Overall, these results suggest that insulin resistance participated in FLHS; comprehensively, metabolites participated in the dysregulated biological process.

Ursodeoxycholic acid exerts hepatoprotective effects by regulating amino acid, flavonoid, and fatty acid metabolic pathways

INTRODUCTION

Ursodeoxycholic acid (UDCA) is an intestinal bacterial metabolite with hepatoprotective effects. However, molecular mechanisms underlying its effects remain unclear.

OBJECTIVES

The aim of this study was to investigate the mechanisms underlying the therapeutic effects of UDCA by using global metabolomics analyses in healthy subjects.

METHODS

Healthy Korean men were administered UDCA at dosage of 400, 800, or 1200 mg daily for 2 weeks. Serum samples were collected and used for liver function tests and to determine miR-122 expression levels. Urinary and plasma global metabolomics analyses were conducted using a liquid chromatography system coupled with quadrupole-time-of-flight mass spectrometry (LC/QTOFMS) and gas chromatography-TOFMS (GC/TOFMS). Unsupervised multivariate analysis (principal component analysis) was performed to identify discriminative markers before and after treatment.

RESULTS

Alanine transaminase score and serum miR-122 levels decreased significantly after 2 weeks of treatment. Through LC- and GC-based metabolomic profiling, we identified 40 differential metabolites in plasma and urine samples.

CONCLUSIONS

Regulation of liver function scores and metabolic alternations highlight the potential hepatoprotective action of UDCA, which were primarily associated with amino acid, flavonoid, and fatty acid metabolism in healthy men.

Dietary Nucleotides Supplementation and Liver Injury in Alcohol-Treated Rats: A Metabolomics Investigation

Background: Previous studies suggested that nucleotides were beneficial for liver function, lipid metabolism and so on. The present study aimed to investigate the metabolic response of dietary nucleotides supplementation in alcohol-induced liver injury rats. Methods: Five groups of male Wistar rats were used: normal control group (basal diet, equivalent distilled water), alcohol control group (basal diet, 50% alcohol (v/v)), dextrose control group (basal diet, isocaloric amount of dextrose), and 0.04% and 0.16% nucleotides groups (basal diet supplemented with 0.4 g and 1.6 g nucleotides kg⁻¹ respectively, 50% alcohol (v/v)). The liver injury was measured through traditional liver enzymes, expression of oxidative stress markers and histopathological examination. Ultra-performance liquid chromatography quadrupole-time-flight mass spectrometry (UPLC-Q-TOF-MS) was applied to identify liver metabolite profiles. Results: Nucleotides supplementation prevented the progression of hepatocyte steatosis. The levels of total proteins, globulin, alanine aminotransferase, aspartate aminotransferase, total cholesterol triglyceride, as well as the oxidative stress markers altered by alcohol, were improved by nucleotides supplementation. Elevated levels of liver bile acids (glycocholic acid, chenodeoxyglycocholic acid, and taurodeoxycholic acid), as well as lipids (stearic acid, palmitic acid, oleic acid, phosphatidylcholine, and lysophosphatidylethanolamine) in alcohol-treated rats were reversed by nucleotides supplementation. In addition, supplementation with nucleotides could increase the levels of amino acids, including valyl-Leucine, l-leucine, alanyl-leucine and l-phenylalanine. Conclusion: These data indicate potential biomarkers and confirm the benefit of dietary nucleotides on alcoholic liver injury.

(1)H-Nuclear Magnetic Resonance-Based Plasma Metabolic Profiling of Dairy Cows with Fatty Liver

Fatty liver is a common metabolic disorder of dairy cows during the transition period. Historically, the diagnosis of fatty liver has involved liver biopsy, biochemical or histological examination of liver specimens, and ultrasonographic imaging of the liver. However, more convenient and noninvasive methods would be beneficial for the diagnosis of fatty liver in dairy cows. The plasma metabolic profiles of dairy cows with fatty liver and normal (control) cows were investigated to identify new biomarkers using ¹H nuclear magnetic resonance. Compared with the control group, the primary differences in the fatty liver group included increases in β-hydroxybutyric acid, acetone, glycine, valine, trimethylamine-N-oxide, citrulline, and isobutyrate, and decreases in alanine, asparagine, glucose, γ-aminobutyric acid glycerol, and creatinine. This analysis revealed a global profile of endogenous metabolites, which may present potential biomarkers for the diagnosis of fatty liver in dairy cows.

γ-Aminobutyric acid ameliorates fluoride-induced hypothyroidism in male Kunming mice

AIM

This study evaluated the protective effects of γ-aminobutyric acid (GABA), a non-protein amino acid and anti-oxidant, against fluoride-induced hypothyroidism in mice.

MAIN METHODS

Light microscope sample preparation technique and TEM sample preparation technique were used to assay thyroid microstructure and ultrastructure; enzyme immunoassay method was used to assay hormone and protein levels; immunohistochemical staining method was used to assay apoptosis of thyroid follicular epithelium cells.

KEY FINDINGS

Subacute injection of sodium fluoride (NaF) decreased blood T4, T3 and thyroid hormone-binding globulin (TBG) levels to 33.98 μg/l, 3 2.8 ng/ml and 11.67 ng/ml, respectively. In addition, fluoride intoxication induced structural abnormalities in thyroid follicles. Our results showed that treatment of fluoride-exposed mice with GABA appreciably decreased metabolic toxicity induced by fluoride and restored the microstructural and ultrastructural organisation of the thyroid gland towards normalcy. Compared with the negative control group, GABA treatment groups showed significantly upregulated T4, T3 and TBG levels (42.34 μg/l, 6.54 ng/ml and 18.78 ng/ml, respectively; P<0.05), properly increased TSH level and apoptosis inhibition in thyroid follicular epithelial cells.

SIGNIFICANCE

To the best of our knowledge, this is the first study to establish the therapeutic efficacy of GABA as a natural antioxidant in inducing thyroprotection against fluoride-induced toxicity.

The metabolomic window into hepatobiliary disease

The emergent discipline of metabolomics has attracted considerable research effort in hepatology. Here we review the metabolomic data for non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), cirrhosis, hepatocellular carcinoma (HCC), cholangiocarcinoma (CCA), alcoholic liver disease (ALD), hepatitis B and C, cholecystitis, cholestasis, liver transplantation, and acute hepatotoxicity in animal models. A metabolomic window has permitted a view into the changing biochemistry occurring in the transitional phases between a healthy liver and hepatocellular carcinoma or cholangiocarcinoma. Whether provoked by obesity and diabetes, alcohol use or oncogenic viruses, the liver develops a core metabolomic phenotype (CMP) that involves dysregulation of bile acid and phospholipid homeostasis. The CMP commences at the transition between the healthy liver (Phase 0) and NAFLD/NASH, ALD or viral hepatitis (Phase 1). This CMP is maintained in the presence or absence of cirrhosis (Phase 2) and whether or not either HCC or CCA (Phase 3) develops. Inflammatory signalling in the liver triggers the appearance of the CMP. Many other metabolomic markers distinguish between Phases 0, 1, 2 and 3. A metabolic remodelling in HCC has been described but metabolomic data from all four Phases demonstrate that the Warburg shift from mitochondrial respiration to cytosolic glycolysis foreshadows HCC and may occur as early as Phase 1. The metabolic remodelling also involves an upregulation of fatty acid β-oxidation, also beginning in Phase 1. The storage of triglycerides in fatty liver provides high energy-yielding substrates for Phases 2 and 3 of liver pathology. The metabolomic window into hepatobiliary disease sheds new light on the systems pathology of the liver.