Yan Ni

Diabetic ketoacidosis (DKA) stands as the most common acute hyperglycaemic complication in children with type 1 diabetes (T1D) and remains associated with considerable morbidity and mortality. Although gut dysbiosis has been reported in newly diagnosed T1D, the gut microbiota and microbial metabolites during DKA onset remain poorly characterized. Shotgun metagenomic sequencing was performed on fecal samples from 96 newly diagnosed T1D children, including 32 presenting with DKA upon admission. Short-chain fatty acids (SCFAs) were quantified using gas chromatography/mass spectrometry (GC/MS). Comparative and correlation analyses were conducted to explore differences in gut microbial composition, SCFA levels, and their association with clinical indicators of DKA severity. Children with DKA exhibited distinct gut microbial compositions, with marked β-diversity separation from non-DKA individuals. The DKA group was characterized by an enrichment of potential pathogens and a significant depletion of SCFA-producing genera, including Anaerobutyricum, Dialister, Ruminococcus, Roseburia, Dorea, and Butyricicoccus. Correspondingly, fecal SCFA levels were significantly reduced in the DKA group. Moreover, SCFAs and their producing bacteria were strongly correlated with clinical indices of DKA severity. Mediation analysis suggested that reductions in SCFAs, particularly propionic acid and butyric acid, were associated with metabolic alterations linking SCFA-producing bacteria to DKA. This study provides a comprehensive characterization of gut microbiota and SCFA alterations in T1D children at DKA onset. The depletion of SCFA-producing bacteria and their metabolites reflects metabolic disturbances associated with DKA, and highlights SCFAs and their producers as candidate metabolic features warranting further validation as biomarkers and therapeutic targets.

Background: Metabolic dysfunction-associated steatotic liver disease (MASLD) is a prevalent pediatric disorder with limited treatment options, primarily due to an incomplete understanding of its molecular drivers. Recent research underscores the role of microbial guilds in metabolic health, but the mechanisms by which dysbiosis driven by core species and co-abundant symbionts disrupt metabolic homeostasis in pediatric MASLD remain unclear. Results: Here, we conducted integrated metagenomic and metabolomic analyses on 285 pediatric subjects including MASLD patients, obese and healthy controls. The gut dysbiosis in MASLD was characterized by a depletion of Phocaeicola vulgatus , Bacteroides uniformis , Parabacteroides distasonis , and Bacteroides thetaiotaomicron . Co-abundance network analysis, integrating our cohort with four public datasets, identified these species as core guild members associated with MASLD. Microbial enrichment analysis showed significant disruptions in carbohydrate metabolism, particularly the downregulation of the tricarboxylic acid (TCA) cycle, fructose and sucrose metabolism, and pentose and glucuronate interconversions. P. vulgatus and B. uniformis were identified as dominant species linked to the downregulation of KEGG orthologs (KOs) in these disrupted pathways that were inversely correlated with hepatic injury biomarkers. CAZyme database analysis further emphasized P. vulgatus as the primary contributor to glycoside hydrolases involved in monosaccharide utilization. Finally, both untargeted and targeted metabolomics analysis validated a disrupted metabolic network centered on the TCA cycle and monosaccharide metabolism in pediatric MASLD. Conclusion: Our findings suggest the core guild species P. vulgatus and B. uniformis may serve as critical regulators of carbohydrate metabolism in pediatric MASLD, offering potential mechanistic targets for gut microbiome-based interventions.

Secondary bile acids are generated from the metabolism of primary bile acids by intestinal flora and play important roles in lipid digestion, regulation of metabolic homeostasis, and intestinal-hepatic axis signaling. Recent studies indicate that lithocholic acid (LCA) and its derivatives (e.g., 3-oxoLCA and isoLCA) are significantly dysregulated in inflammatory bowel disease, nonalcoholic fatty liver disease, and hepatocellular carcinoma. Consequently, LCA species are emerging as promising biomarkers and potential targets for early diagnosis. This review systematically summarizes the metabolic pathways of LCA species, their distribution and concentrations in human blood, urine, and fecal samples, as well as the progress of recent research studies on enterohepatic disorders, which will serve as a reference for the development of new diagnostic and therapeutic methods in the future.

Excessive dietary fructose consumption is a significant contributor to the development of metabolic dysfunction‐associated steatotic liver disease (MASLD). However, the role of the intestinal fructose transporter, glucose transporter 5 (GLUT5), in this process remains poorly understood. This study aimed to investigate the potential use of GLUT5 as a novel therapeutic target for MASLD. Eight‐week‐old male C57BL/6J wild‐type (WT) mice were fed a high‐fat diet (HFD) or a high‐fat diet supplemented with 10% or 25% fructose in drinking water (HFF) for 8 weeks to investigate the effects of high‐fructose intake on MASLD development. To further elucidate the role of GLUT5, we utilized an intestine‐specific GLUT5 knockout ( Slc2a5 ‐IKO) mouse model with HFF diet intervention to evaluate the protective effects of GLUT5 inhibition against high‐fructose‐induced liver injury. Additionally, the GLUT5 transporter inhibitor, 2,5‐anhydro‐D‐mannitol (2,5‐AM), was administered to HFF‐fed WT mice to validate the alleviating effect on MASLD. The intestinal expression of GLUT5, liver and intestinal histology, and serum biochemical parameters were analyzed. Intestinal GLUT5 expression was significantly upregulated in WT mice fed HFF for 8 weeks, which developed impaired liver function and metabolic abnormalities. Compared with WT mice, liver damage was significantly attenuated in Slc2a5 ‐IKO mice with the 8‐week HFF diet plan. Furthermore, we demonstrated that the GLUT5 inhibitor, 2,5‐AM, effectively suppressed intestinal GLUT5 expression and ameliorated the progression of MASLD in WT mice. Intestinal GLUT5 represents a potential therapeutic target for mitigating high‐fructose‐induced MASLD.

Recent advances in microbiome-targeted therapies have uncovered immunomodulatory bacterial taxa with strain-specific therapeutic potential; however, the microbial signatures driving exclusive enteral nutrition (EEN) efficacy, particularly protective microbiota, and their mechanistic links to therapeutic outcomes remain uncharacterized in pediatric inflammatory bowel disease (IBD). Elucidating these microbial determinants and their functional pathways is critical for advancing targeted probiotic strategies in children. A cohort of treatment-naïve pediatric Crohn's disease (CD) patients and age-matched healthy controls (HC) were enrolled. Fecal samples were collected from both HC and CD patients during active phase and remission following EEN therapy. Metagenomic sequencing, qPCR validation, and targeted bile acid (BA) analysis were conducted to identify candidate protective strains and potential impacts on BA homeostasis. Mechanistic investigations were conducted using dextran sulfate sodium (DSS)- and trinitrobenzene sulfonic acid (TNBS)-induced colitis model in male mice. The relative abundance of Ruminococcus torques (R. torques) demonstrated significant depletion in active CD cases (p = 0.02) compared to HC, which was restored after EEN treatment at remission status (p < 0.001). Its level was negatively correlated with the disease severity index (PCDAI r=-0.64; CDEIS r=-0.70) and positively correlated with the secondary to primary BA ratio (r = 0.27). In murine models, R. torques supplementation attenuated colitis severity through enhancing epithelial integrity (claudin-3, 3.3-fold; occludin, 7.5-fold), suppressing pro-inflammatory mediators (TNF-α, -44%; IL-6, -71%), regulating BA metabolism (secondary/unconjugated BAs, 29%) and autophagy pathway (LC3-II/LC3-I ratio, -1.8-fold). Our findings demonstrated R. torques as a novel microbial therapeutic candidate for IBD management. The anti-colitis mechanisms involve the modulation of BA metabolic homeostasis, epithelial barrier reinforcement, and inflammation resolution.

The onset of puberty is increasingly observed at earlier ages in children, especially in girls with obesity, a trend that predisposes them to long-term metabolic and reproductive disorders in adulthood. Bile acids have emerged as pivotal signaling molecules in both metabolic and reproductive disorders, but remain unexplored in the early onset of puberty in children. Herein, we find elevated levels of muricholic acid (MCA) species in the serum of girls with central precocious puberty, which strongly correlate with indices of hypothalamic–pituitary–gonadal axis activation and can reach peak levels during puberty among healthy children. Intriguingly, reduction of MCA species can lead to decreased expression of gonadotropin-releasing hormone (GnRH) and delay the early onset of puberty, while elevated MCA levels induced premature sexual development in female mice. Mechanistically, we demonstrated that MCA had strong activation effects on Takeda G-protein-coupled receptor 5 (TGR5), and MCA enhanced GnRH expression in GnRH neurons through activation of the TGR5-PI3K/Akt-mTOR signaling pathway. Our findings reveal a link between metabolic status and reproductive maturation, highlighting MCA as a potential therapeutic target for managing early puberty initiation.

The rising prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) poses a significant global public health challenge. Bile acids (BAs), synthesized in the liver and further metabolized in the gut, are essential in maintaining host metabolic homeostasis. Bile salt hydrolase (BSH), an enzyme produced by the gut microbiota, catalyzes the hydrolysis of conjugated BAs, thus regulating the balance between primary and secondary BAs. Growing evidence suggests that BSH activity is intricately linked to the pathogenesis of MASLD. This review comprehensively examines the structural and functional properties of BSH enzymes, their distribution among gut microbial communities, and current methodologies for assessing BSH expression and activity. Furthermore, it highlights the alterations in BSH observed in MASLD and explores the potential mechanistic pathways involved, offering a foundation for the development of novel diagnostic and therapeutic strategies.

Background The diagnosis of central precocious puberty (CPP) relies on a gonadotropin releasing hormone stimulation test to assess the activation of the hypothalamic–pituitary–gonadal axis; this is costly and painful. Bile acids (BAs) have emerged as pivotal signaling molecules in the reproductive system. This study aimed to identify circulating BA profile signatures and explored if they may serve as biomarkers for CPP diagnosis in girls. Methods We enrolled 431 girls, including 241 in the training cohort and 190 in the validation cohort. Participants were divided into four groups based on their body mass index Z-score and whether they were diagnosed with CPP. Ultra-performance liquid chromatography coupled with tandem mass spectrometry was performed to quantify 38 serum BAs. Results There were 18 individual BAs that were statistically different between CPP and non-CPP counterparts. The majority of these BAs (14/18) correlated significantly with sex-related hormones (P < 0.05). In girls with normal weight (NW), a logistic regression model combining chenodeoxycholic acid, tauroα-muricholic acid, and 6-ketolithocholic acid achieved an area under the receiver operating characteristic curve (AUC) of 0.885. For girls who were overweight/obese (OB), hyocholic acid and taurohyocholic acid enhanced the diagnostic efficiency of basal luteinizing and follicle stimulating hormones to an AUC value 0.914. In validation cohort, 75.34% NW girls and 84.09% OB girls were accurately classified. Conclusions Serum BA profiles of CPP girls showed significant changes that were associated with serum sex-related hormone levels. BA profiles could be potential biomarkers in CPP diagnosis and screening.

Conjugated lithocholic acid (LCA) plays a critical role in the development of metabolic dysfunction‐associated steatotic liver disease (MASLD). In this process, hepatocyte inflammation‐caused upregulation of its receptor, Takeda G protein‐coupled receptor 5 (TGR5) is a crucial factor. Serum bile acid profiling shows an increase in conjugated LCA, which correlates with disease severity. Depletion of Gpbar1 in hepatocytes significantly protects against the progression from MASLD to metabolic dysfunction‐associated steatohepatitis (MASH) that is related to conjugated LCA. In vivo and in vitro experiments indicate that TGR5 activation in hepatocytes promotes lipotoxicity‐induced cell death and inflammation by suppressing de novo carnitine biosynthesis. Mechanistically, TGR5 binding to CD36 facilitates E3 ubiquitin ligase TRIM21 recruitment, leading to the degradation of BBOX1, a crucial enzyme in de novo carnitine biosynthesis. Targeting TGR5 therapeutically can restore carnitine biosynthesis, which may offer a potent strategy to prevent or reverse the transition from MASLD to MASH.

Objective: Diabetic ketoacidosis (DKA) stands as the most common acute hyperglycaemic complication with a relatively high mortality rate among children diagnosed with type 1 diabetes (T1D). Previous studies have shed light on gut dysbiosis in newly-onset T1D children, but research targeting the gut microbiota and microbial metabolites in patients with DKA remains scarce. Methods: Shotgun metagenomic analysis was conducted on fecal samples from 96 newly diagnosed T1D children, including 32 patients who presented with DKA upon admission. Short-chain fatty acids (SCFAs) were quantified using gas chromatography/mass spectrometry (GC/MS). Comparative analyses were performed on the gut microbiome and SCFA levels between DKA and non-DKA subgroups. Results: Gut microbiota composition differed between DKA and non-DKA groups. While alpha-diversity remained consistent, beta-diversity showed marked differences between the two groups, and the phyla Firmicutes and Bacteroidetes exhibited predominance in the DKA group. DKA was associated with increased potential pathogens and a significant depletion of SCFA-producing genera ( Anaerobutyricum , Dialister , Ruminococcus , Roseburia , Dorea , and Butyricicoccus ), accompanied by reduced SCFA levels. Further correlation analysis revealed strong associations between SCFAs, SCFA-producing microbiota, and disease severity indicators. Propionic acid and butyric acid mediated the association between SCFA-producing bacteria and DKA. Conclusion: This study first reported reductions in SCFAs and SCFA-producing bacteria in the fecal samples of T1D children at DKA onset. Our findings highlight SCFAs and their producers as protective biomarkers of DKA and suggest that targeting gut microbiota and SCFA metabolism may offer a potential therapeutic strategy for DKA. Importance: While gut microbiota imbalances have been linked to type 1 diabetes (T1D), little is known about the role of gut microbes and their metabolites during acute diabetic ketoacidosis (DKA), an acute and life-threatening complication. This study examined the gut microbiome and levels of short-chain fatty acids (SCFAs) in fecal samples from children with new-onset T1D with and without DKA. DKA was characterized by distinct microbial signatures, including increased potential pathogens, a loss of beneficial SCFA-producing bacteria, and consistently lower SCFA levels. These changes closely correlated with indicators of disease severity, and further mediation analysis revealed the role of SCFAs in linking gut microbiota to DKA. These findings suggest that SCFAs and their producers may serve as protective markers for DKA, highlighting the potential of microbiome-based interventions to improve outcomes in children facing this critical complication.