Serum bile acid level and fatty acid composition in Chinese children with non-alcoholic fatty liver disease

Role of intestinal flora in the development of nonalcoholic fatty liver disease in children

In China, 45% of adolescents with obesity develop fatty liver disease, a condition that increases the long-term risk of developing cirrhosis and liver cancer. Although the factors triggering nonalcoholic fatty liver disease (NAFLD) vary in children, the composition of intestinal microflora has been found to play an increasingly important role. However, evidence is limited on the prevalence of nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH) in Chinese children. Therefore, this study aimed to evaluate the fecal microbiome of Chinese children with NAFLD and further analyze the potential of flora in regulating NAFLD-related symptoms and metabolic functions. Specifically, the study applied a 16S rRNA and metagenomic sequencing to the fecal samples of pediatric patients with NAFLD, NASH, and NAFL, as well as healthy controls, to explore the correlation among NAFLD-related indexes, metabolic pathways, and gut flora. The findings showed that some fecal microbiota had a negative correlation with body mass index, and various NAFLD-related bacteria, including Lachnoclostridium, Escherichia-Shigella, and Faecalibacterium prausnitzii, were detected. Consequently, the study concluded that the variation in gut microbiota might be more important in improving NAFLD/NASH compared with single species, providing a microbiota diagnostic profile of NAFLD/NASH.IMPORTANCEThis study aims to characterize the gut microbiota in Chinese children with nonalcoholic fatty liver disease (NAFLD) through 16S rRNA and metagenomic sequencing. The results highlight the association between fecal microbiota and NAFLD in Chinese children, demonstrating distinct characteristics compared to adults and children from other countries. Based on the sequencing data from our cohort's fecal samples, we propose a microbiota model with a high area under the curve for distinguishing between NAFLD and healthy individuals. Furthermore, our follow-up study reveals that changes in the relative abundance of microbial biomarkers in this model are consistent with variations in patients' body mass index. These findings suggest the potential utility of the microbiota model and microbial biomarkers for diagnosing and treating NAFLD in children.

The Beneficial Effects of Dietary Astragali Radix Are Related to the Regulation of Gut Microbiota and Its Metabolites

Astragali Radix (AR) or its extract has been used as an herbal medicine and dietary supplement in China, Europe, and the United States. The gut microbiota could provide new insights for exploring dietary supplements' underlying mechanism on organisms. However, no reports have focused on the regulatory effect of AR on the gut microbiota as a dietary supplement. In this study, healthy ICR mice of either sex were divided into AR and control (CON) groups and given AR water extract (4.55 mg/kg·day-1) or saline by gavage for 14 days, respectively. Then 16S rRNA gene sequencing and ultra-high-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry-based fecal metabolomics were integrated to investigate the benefits of dietary AR. Weighted gene coexpression network analysis was also introduced to investigate the metabolites with highly synergistic changes. AR supplementation influenced the structure of intestinal microflora, especially enriching short-chain fatty acid-producing bacteria g_Coprobacillus, g_Prevotella, and g_Parabacteroides. AR also significantly altered the fecal metabolome, mainly related to amino acid metabolism, nucleotide metabolism, and bile acid (BA) metabolism. Moreover, the increased secondary BAs and BA-sulfates might closely relate to intestinal microflora. These findings provide valuable insights for future research of dietary AR as a functional food.

The gut microbiota metabolite glycochenodeoxycholate activates TFR-ACSL4-mediated ferroptosis to promote the development of environmental toxin-linked MAFLD

Metabolic dysfunction-associated fatty liver disease (MAFLD) has become the most common chronic liver disorders in the world, and yet has no approved pharmacotherapy due to the etiology is complex. In the last ten years, increasing evidence have identified the environmental pollutants as risk factors for MAFLD. However, the underlying mechanism remains unclear. Our study found that bromoacetic acid (BAA, a typical kind of environmental toxin) increased triglycerides and total cholesterol levels as well as induced obvious hepatic steatosis and inflammation. The lipidomics showed that ferroptosis was implicated in the environmental toxin-linked MAFLD. Besides, the analysis of microbial metabolomics showed significant change of gut microbiome in BAA groups and the content of gut microbiota metabolite (glycochenodeoxycholate, GCDCA) increased sharply. In vitro study, we observed features of ferroptotic cells by transmission electron microscopy after BAA/GCDCA treatment. Besides, we demonstrated that BAA/GCDCA significantly increased iron contents, with upregulating transferrin receptor (TFR) and acyl-CoA synthetase long-chain family 4 (ACSL4) expression levels. By contrast, iron chelator or silencing TFR relieved BAA/GCDCA-induced lipid metabolism disorder and inflammation. What's more, the interaction between TFR and ACSL4 was also identified. Taken together, we found that, in response to environmental toxin, gut microbiota metabolite GCDCA activates TFR-ACSL4-mediated ferroptosis, which triggered subsequent lipid metabolism disorder and inflammation. Moreover, these findings firstly highlighted the functional relevance among ferroptosis, lipid metabolism and gut microbiota metabolite during environmental pollutant exposure, which shed light on the deep mechanism of environmental toxin-related MAFLD, providing potential targets for the prevention of MAFLD.

Roles of Palmitoleic Acid and Its Positional Isomers, Hypogeic and Sapienic Acids, in Inflammation, Metabolic Diseases and Cancer

In the last few years, the monounsaturated hexadecenoic fatty acids are being increasingly considered as biomarkers of health with key functions in physiology and pathophysiology. Palmitoleic acid (16:1n-7) and sapienic acid (16:1n-10) are synthesized from palmitic acid by the action of stearoyl-CoA desaturase-1 and fatty acid desaturase 2, respectively. A third positional isomer, hypogeic acid (16:1n-9) is produced from the partial β-oxidation of oleic acid. In this review, we discuss the current knowledge of the effects of palmitoleic acid and, where available, sapienic acid and hypogeic acid, on metabolic diseases such as diabetes, cardiovascular disease, and nonalcoholic fatty liver disease, and cancer. The results have shown diverse effects among studies in cell lines, animal models and humans. Palmitoleic acid was described as a lipokine able to regulate different metabolic processes such as an increase in insulin sensitivity in muscle, β cell proliferation, prevention of endoplasmic reticulum stress and lipogenic activity in white adipocytes. Numerous beneficial effects have been attributed to palmitoleic acid, both in mouse models and in cell lines. However, its role in humans is not fully understood, and is sometimes controversial. Regarding sapienic acid and hypogeic acid, studies on their biological effects are still scarce, but accumulating evidence suggests that they also play important roles in metabolic regulation. The multiplicity of effects reported for palmitoleic acid and the compartmentalized manner in which they often occur, may suggest the overlapping actions of multiple isomers being present at the same or neighboring locations.

Role of bile acids in overweight and obese children and adolescents

Bile acids (BAs) are amphipathic molecules synthetized in the liver. They are primarily involved in the digestion of nutrients. Apart from their role in dietary lipid absorption, BAs have progressively emerged as key regulators of systemic metabolism and inflammation. In the last decade, it became evident that BAs are particularly important for the regulation of glucose, lipid, and energy metabolism. Indeed, the interest in role of BA in metabolism homeostasis is further increased due to the global public health increase in obesity and related complications and a large number of research postulating that there is a close mutual relationship between BA and metabolic disorders. This strong relationship seems to derive from the role of BAs as signaling molecules involved in the regulation of a wide spectrum of metabolic pathways. These actions are mediated by different receptors, particularly nuclear farnesoid X receptor (FXR) and Takeda G protein coupled receptor 5 (TGR5), which are probably the major effectors of BA actions. These receptors activate transcriptional networks and signaling cascades controlling the expression and activity of genes involved in BA, lipid and carbohydrate metabolism, energy expenditure, and inflammation. The large correlation between BAs and metabolic disorders offers the possibility that modulation of BAs could be used as a therapeutic approach for the treatment of metabolic diseases, including obesity itself. The aim of this review is to describe the main physiological and metabolic actions of BA, focusing on its signaling pathways, which are important in the regulation of metabolism and might provide new BA -based treatments for metabolic diseases.

Serum Bile Acid Profiles Improve Clinical Prediction of Nonalcoholic Fatty Liver in T2DM patients

Background: The present study aimed to assess the ability of serum bile acid profiles to predict the development of nonalcoholic fatty liver (NAFL) in type 2 diabetes mellitus (T2DM) patients. Methods: Using targeted ultraperformance liquid chromatography (UPLC) coupled with triple quadrupole mass spectrometry (TQ/MS), we compared serum bile acid levels in T2DM patients with NAFL (n = 30) and age- and sex-matched T2DM patients without NAFL (n = 36) at the first time. Second, an independent cohort study of T2DM patients with NAFL (n = 17) and age- and sex-matched T2DM patients without NAFL (n = 20) was used to validate the results. The incremental benefits of serum biomarkers, clinical variables alone, or with biomarkers were then evaluated using receiver operating characteristic (ROC) curves and decision curve analysis. The area under the curve (AUC), integrated discrimination improvement (IDI), and net reclassification improvement (NRI) were used to evaluate the biomarker predictive abilities. Results: The serum bile acid profiles in T2DM patients with NAFL were significantly different from T2DM patients without NAFL, as characterized by the significant elevation of LCA, TLCA, TUDCA, CDCA-24G, and TCDCA, which may be potential biomarkers for the identification of NAFL in T2DM patients. Based on the improvement in AUC, IDI, and NRI, the addition of 5 bile acids to a model with clinical variables statistically improved its predictive value. Similar results were found in the validation cohort. Conclusions: These results highlight that the detected biomarkers may contribute to the progression of NAFL in T2DM patients, and these biomarkers particularly in combination may help in the diagnosis of NAFL and allow earlier intervention in T2DM patients.

Efficacy of Weight Reduction on Pediatric Nonalcoholic Fatty Liver Disease: Opportunities to Improve Treatment Outcomes Through Pharmacotherapy

Obesity is the single greatest risk factor for nonalcoholic fatty liver disease (NAFLD). Without intervention, most pediatric patients with NAFLD continue to gain excessive weight, making early, effective weight loss intervention key for disease treatment and prevention of NAFLD progression. Unfortunately, outside of a closely monitored research setting, which is not representative of the real world, lifestyle modification success for weight loss in children is low. Bariatric surgery, though effective, is invasive and can worsen NAFLD postoperatively. Thus, there is an evolving and underutilized role for pharmacotherapy in children, both for weight reduction and NAFLD management. In this perspective article, we provide an overview of the efficacy of weight reduction on pediatric NAFLD treatment, discuss the pros and cons of currently approved pharmacotherapy options, as well as drugs commonly used off-label for weight reduction in children and adolescents. We also highlight gaps in, and opportunities for, streamlining obesity trials to include NAFLD assessment as a valuable, secondary, therapeutic outcome measure, which may aid drug repurposing. Finally, we describe the already available, and emerging, minimally-invasive biomarkers of NAFLD that could offer a safe and convenient alternative to liver biopsy in pediatric obesity and NAFLD trials.

Sex-Specific Metabolite Biomarkers of NAFLD in Youth: A Prospective Study in the EPOCH Cohort

CONTEXT

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in developed nations. There are currently no accurate biomarkers of NAFLD risk in youth.

OBJECTIVE

Identify sex-specific metabolomics biomarkers of NAFLD in a healthy cohort of youth.

DESIGN/SETTING

This prospective study included 395 participants of the EPOCH cohort in Colorado, who were recruited 2006-2009 ("T1 visit") and followed for 5 years ("T2 visit"). We entered 767 metabolites measured at T1 into a reduced rank regression model to identify the strongest determinants of hepatic fat fraction (HFF) at T2, separately for boys and girls. We compared the capacity of metabolites versus conventional risk factors (overweight/obesity, insulin, alanine transaminase, aspartate transaminase) to predict NAFLD (HFF ≥5%) and high HFF (fourth vs first quartile) using area under the receiver operating characteristic curve (AUC).

RESULTS

Prevalence of NAFLD was 7.9% (8.5% of boys, 7.1% of girls). Mean ± SD HFF was 2.5 ± 3.1%. We identified 13 metabolites in girls and 10 metabolites in boys. Metabolites were in lipid, amino acid, and carbohydrate metabolism pathways. At T1, the metabolites outperformed conventional risk factors in prediction of high HFF but not NAFLD. At T2, the metabolites were superior to conventional risk factors as predictors of high HFF (AUC for metabolites vs conventional risk factors for boys: 0.9565 vs 0.8851, P = 0.02; for girls: 0.9450 vs 0.8469, P = 0.02) with similar trends for NAFLD, although the differences were not significant.

CONCLUSIONS

The metabolite profiles identified herein are superior predictors of high HFF when assessed 5 years prior and concurrently in a general-risk setting.

An improved detection and identification strategy for untargeted metabolomics based on UPLC-MS

Untargeted metabolomics provides a comprehensive investigation of metabolites and enables the discovery of biomarkers. Improvements in sample preparation, chromatographic separation and raw data processing procedure greatly enhance the metabolome coverage. In addition, database-dependent software identification is also essential, upon which enhances the identification confidence and benefits downstream biological analysis. Herein, we developed an improved detection and identification strategy for untargeted metabolomics based on UPLC-MS. In this work, sample preparation was optimized by considering chemical properties of different metabolites. Chromatographic separation was done by two different columns and MS detection was performed under positive and negative ion modes regarding to the different polarities of metabolites. According to the characteristics of the collected data, an improved identification and evaluation strategy was developed involving fragment simulation and MS/MS library search based on two commonly used databases, HMDB and METLIN. Such combination integrated information from different databases and was aimed to enhance identification confidence by considering the rationality of fragmentation, biological sources and functions comprehensively. In addition, decision tree analysis and lab-developed database were also introduced to assist the data processing and enhance the identification confidence. Finally, the feasibility of the developed strategy was validated by liver samples of obesity mice and controls. 238 metabolites were accurately detected, which was beneficial for the subsequent biomarker discovery and downstream pathway analysis. Therefore, the developed strategy remarkably facilitated the identification accuracy and the confirmation of metabolites in untargeted metabolomics.

Gypenosides regulate farnesoid X receptor-mediated bile acid and lipid metabolism in a mouse model of non-alcoholic steatohepatitis

Background

Gypenosides (Gyp) are the main ingredient of the Chinese medicine, Gynostemma pentaphyllum. They are widely used in Asia as a hepatoprotective agent. Here, we elucidated the mechanism of Gyp in non-alcoholic steatohepatitis (NASH) with a focus on farnesoid X receptor (FXR)-mediated bile acid and lipid metabolic pathways.

Methods

NASH was induced in mice by high-fat diet (HFD) feeding, while mice in the control group were given a normal diet. At the end of week 10, HFD-fed mice were randomly divided into HFD, HFD plus Gyp, and HFD plus obeticholic acid (OCA, FXR agonist) groups and were given the corresponding treatments for 4 weeks. Next, we analyzed the histopathological changes as well as the liver triglyceride (TG) level and serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), fasting blood glucose (FBG), fasting insulin (FINS), TG, total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) levels as well as the bile acid profile. We carried out RT-PCR and western blotting to detect HFD-induced alterations in gene/protein expression related to bile acid and lipid metabolism.

Results

The HFD group had histopathological signs of hepatic steatosis and vacuolar degeneration. The liver TG and serum ALT, AST, FBG, FINS, TC, and LDL-C levels as well as the total bile acid level were significantly higher in the HFD group than in the control group (P < 0.01). In addition, we observed significant changes in the expression of proteins involved in bile acid or lipid metabolism (P < 0.05). Upon treatment with Gyp or OCA, signs of hepatic steatosis and alterations in different biochemical parameters were significantly improved (P < 0.05). Further, HFD-induced alterations in the expression genes involved in bile acid and lipid metabolism, such as CYP7A1, BSEP, SREBP1, and FASN, were significantly alleviated.

Conclusions

Gyp can improve liver lipid and bile acid metabolism in a mouse model of NASH, and these effects may be related to activation of the FXR signaling pathway.

Is the Fatty Acids Profile in Blood a Good Predictor of Liver Changes? Correlation of Fatty Acids Profile with Fatty Acids Content in the Liver

BACKGROUND

Existing data show a correlation between the profile of fatty acids, liver, and blood. Therefore, the aim of our study was to investigate the correlation between the fatty acids profile in blood pallets and the liver.

METHODS

The experiment was performed on 60 eight-week-old male Sprague-Dawley rats. The study group (n = 30, 5 groups, 6 rats each) received a cholesterol diet; the control group (n = 30, 5 groups, 6 rats each) received standard food for laboratory rats. The rats from both the study and control groups were sacrificed after 2, 4, 8, 12, and 16 weeks of dietary exposure. The fatty acids profile was measured using gas chromatography (GC).

RESULTS

In both the control and study group, the highest correlations were observed in palmitoleic acid (RHO = 0.68), heptadecanoic acid (RHO = 0.65), vaccenic acid (RHO = 0.72), eicosapentaenoic acid (RHO = 0.68), docosapentaenoic acid (RHO = 0.77), and docosahexaenoic (RHO = 0.77). Among liver indexes, the highest correlations were desaturase-18 (0.61).

CONCLUSIONS

Fatty acids profile is a sensitive marker of the development of potentially pathological changes in the liver. The potential markers of fatty liver are: oleic acid, vaccenic acid, EPA, DHA, docosapentaenoic acid, and desaturase index (SCD-18 index).

The Liver as an Endocrine Organ-Linking NAFLD and Insulin Resistance

The liver is a dynamic organ that plays critical roles in many physiological processes, including the regulation of systemic glucose and lipid metabolism. Dysfunctional hepatic lipid metabolism is a cause of nonalcoholic fatty liver disease (NAFLD), the most common chronic liver disorder worldwide, and is closely associated with insulin resistance and type 2 diabetes. Through the use of advanced mass spectrometry "omics" approaches and detailed experimentation in cells, mice, and humans, we now understand that the liver secretes a wide array of proteins, metabolites, and noncoding RNAs (miRNAs) and that many of these secreted factors exert powerful effects on metabolic processes both in the liver and in peripheral tissues. In this review, we summarize the rapidly evolving field of "hepatokine" biology with a particular focus on delineating previously unappreciated communication between the liver and other tissues in the body. We describe the NAFLD-induced changes in secretion of liver proteins, lipids, other metabolites, and miRNAs, and how these molecules alter metabolism in liver, muscle, adipose tissue, and pancreas to induce insulin resistance. We also synthesize the limited information that indicates that extracellular vesicles, and in particular exosomes, may be an important mechanism for intertissue communication in normal physiology and in promoting metabolic dysregulation in NAFLD.

Ursodeoxycholic Acid Alters Bile Acid and Fatty Acid Profiles in a Mouse Model of Diet-Induced Obesity

Ursodeoxycholic acid (UDCA) is a bile acid (BA) approved by the U.S. Food and Drug Administration for the treatment of primary biliary cholangitis. It is also the major active component of bear bile used in traditional Chinese medicine to reduce fever, remove toxins, and treat liver and eye ailments. In addition, UDCA and its conjugated form have been evaluated for their potential to improve symptoms of metabolic diseases, but the results have been inconclusive. To address this issue, in this study, we investigated the effects of orally administered UDCA on mice with diet-induced obesity, including the BA and free fatty acid (FFA) profiles of serum, liver, and epididymis and brown adipose tissues. We found that UDCA treatment significantly improved most metabolic indices; tauroursodeoxycholic acid (TUDCA) and taurolithocholic acid (TLCA) contents were increased in all examined tissues, whereas saturated FA levels were decreased, and n-3 polyunsaturated fatty acid (n-3 PUFA) levels were increased in most tissues. A correlation analysis showed that the concentrations of UDCA and its derivatives were positively correlated with that of n-3 PUFA. To clarify the mechanism by which UDCA alters FFA profiles, we analyzed the expression levels of genes involved in FFA biosynthesis, uptake, and oxidation and found that FFA biosynthesis and uptake were inhibited while FFA oxidation was stimulated by UDCA treatment. Additionally, amino acid-conjugated derivatives of UDCA, such as TUDCA and TLCA, altered FFA profiles by modulating FFA biosynthesis, uptake, and oxidation. These findings provide evidence that UDCA can alleviate metabolic dysfunction and could therefore be effective in the treatment of obesity.

Gut Microbiota-Derived Mediators as Potential Markers in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a common, multifactorial, and poorly understood liver disease whose incidence is globally rising. During the past decade, several lines of evidence suggest that dysbiosis of intestinal microbiome represents an important factor contributing to NAFLD occurrence and its progression into NASH. The mechanisms that associate dysbiosis with NAFLD include changes in microbiota-derived mediators, deregulation of the gut endothelial barrier, translocation of mediators of dysbiosis, and hepatic inflammation. Changes in short chain fatty acids, bile acids, bacterial components, choline, and ethanol are the result of altered intestinal microbiota. We perform a narrative review of the previously published evidence and discuss the use of gut microbiota-derived mediators as potential markers in NAFLD.

Response of fibroblast growth factor 19 and bile acid synthesis after a body weight-adjusted oral fat tolerance test in overweight and obese NAFLD patients: a non-randomized controlled pilot trial

Background

Non-alcoholic fatty liver disease (NAFLD) is common both in obese and overweight patients. Fibroblast growth factor 19 (FGF19), an intestinal hormone, could play a role in the complex pathogenesis of NAFLD. The aim of our study was to investigate responses of FGF19 and bile acid (BA) synthesis after a body weight-adjusted oral fat tolerance test (OFTT) in overweight and obese NAFLD patients.

Methods

For this study, we recruited 26 NAFLD patients; 14 overweight (median BMI 28.3 kg/m²), 12 obese (35.3 kg/m²) and 16 healthy controls (24.2 kg/m²). All individuals received 1 g fat (Calogen®) per kg body weight orally. Serum concentrations of FGF19 were determined by ELISA. Concentrations of BAs and BA synthesis marker 7α-hydroxy-4-cholesten-3-one (C4) were measured by gas chromatography-mass spectrometry and high-performance liquid chromatography, respectively; all at 0 (baseline), 2, 4 and 6 h during the OFTT.

Results

BMI correlated negatively with fasting FGF19 concentrations (rho = − 0.439, p = 0.004). FGF19 levels of obese NAFLD patients were significantly (p = 0.01) lower in the fasting state (median 116.0 vs. 178.5 pg/ml), whereas overweight NAFLD patients had significantly (p = 0.004) lower FGF19 concentrations 2 h after the fat load (median 163.0 vs. 244.5 pg/ml), and lowest values at all postprandial time points as compared to controls. Baseline BA concentrations correlated positively with FGF19 values (rho = 0.306, p = 0.048). In all groups, we observed BA increases during the OFTT with a peak at 2 h but no change in C4 levels in overweight/obese NAFLD patients.

Conclusions

Reduced basal gastrointestinal FGF19 secretion and decreased postprandial response to oral fat together with blunted effect on BA synthesis indicate alterations in intestinal or hepatic FXR signaling in overweight and obese NAFLD subjects. The precise mechanism of FGF19 signaling after oral fat load needs further evaluation.

Trial registration

We have registered the trial retrospectively on 30 Jan 2018 at the German clinical trials register (http://www.drks.de/), and the following number has been assigned DRKS00013942.

Electronic supplementary material

The online version of this article (10.1186/s12876-018-0805-z) contains supplementary material, which is available to authorized users.