Metabolic syndrome (MetS) is intricately linked to dysregulation of gut microbiota and host metabolomes. Here, we first find that a purified citrus polymethoxyflavone-rich extract (PMFE) potently ameliorates high-fat diet (HFD)–induced MetS, alleviates gut dysbiosis, and regulates branched-chain amino acid (BCAA) metabolism using 16S rDNA amplicon sequencing and metabolomic profiling. The metabolic protective effects of PMFE are gut microbiota dependent, as demonstrated by antibiotic treatment and fecal microbiome transplantation (FMT). The modulation of gut microbiota altered BCAA levels in the host serum and feces, which were significantly associated with metabolic features and actively responsive to therapeutic interventions with PMFE. Notably, PMFE greatly enriched the commensal bacterium Bacteroides ovatus, and gavage with B. ovatus reduced BCAA concentrations and alleviated MetS in HFD mice. PMFE may be used as a prebiotic agent to attenuate MetS, and target-specific microbial species may have unique therapeutic promise for metabolic diseases.

Gut microbiota dysbiosis is associated with the development of rheumatoid arthritis (RA). Sinomenine (SIN) is an effective immunosuppressive and anti-inflammatory drug used for treating RA, but how SIN regulates gut microbiota to alleviate RA remains underexplored. To identify the critical gut microbial species and microbial metabolites associated with the RA-protective effects of SIN, the microbiota-dependent anti-RA effects of SIN were assessed by 16S rRNA gene sequencing, antibiotic treatment, and fecal microbiota transplantation. Metabolomics analysis, transcriptional analysis, and targeted bacteria/metabolites gavage were conducted to explore how SIN regulates gut microbiota to reduce the severity of RA. SIN could restore intestinal microbial balance by mainly modulating the abundance of Lactobacillus, and significantly relieve collagen-induced arthritis (CIA) symptoms in a gut microbiota-dependent manner. SIN significantly elevated microbial tryptophan metabolites indole-3-acrylic acid (IA), indole-3-propionic acid (IPA), and indole-3-acetic acid (IAA). Tryptophan metabolites supplementation could activate aryl hydrocarbon receptor (AhR) and regulate Th17/Treg balance in CIA rats. Intriguingly, SIN relieved the arthritis symptoms involving the enrichment of two beneficial anti-CIA Lactobacillus species, L. paracasei and L. casei by mono-colonization. The promising therapeutic function of SIN was mostly attributed to the activation of AhR by explicitly targeting the Lactobacillus and microbial tryptophan metabolites. The intestinal bacterium L. paracasei and L. casei may be used to reduce the severity of CIA.

Background: As new biomarkers of coronary artery diseases (CAD) emerge via metabolomics, the underlying functional mechanisms remain to be elucidated. Functional metabolomics aims to translate metabolomics-derived biomarkers to disease mechanisms. Methods: A cohort of 2324 patients who underwent coronary angiography from 4 independent centers was studied. A combination of ultra–performance liquid chromatography and quadrupole time-of-flight mass spectrometry in the negative ion mode was used for untargeted analysis of metabolites in plasma. Significant differential metabolites were identified by cross-comparisons with and within CAD types, including normal coronary artery, nonobstructvie coronary atherosclerosis, stable angina, unstable angina, and acute myocardial infarction. A tandem liquid chromatography-mass spectrometry–based approach using isotope-labeled standard addition was subsequently performed for targeted analysis of the metabolic marker N -acetylneuraminic acid (Neu5Ac). A functional metabolomics strategy was proposed to investigate the role of Neu5Ac in the progression of CAD by using in vitro and in vivo models. Results: We identified a total of 36 differential metabolites, 35 of which were confirmed with reference compounds. Elevation of Neu5Ac was observed in plasma during CAD progression in center 1 ( P =4.0e-64, n=2019) and replicated in 3 independent centers (n=305). The increased level of Neu5Ac in plasma was confirmed by accurate targeted quantification. Mechanistically, Neu5Ac was able to trigger myocardial injury in vitro and in vivo by activation of the Rho/Rho-associated coiled-coil containing protein kinase signaling pathway through binding to RhoA and Cdc42, but not Rac1. Silencing neuraminidase-1, the enzyme that regulates Neu5Ac generation, ameliorated oxygen-glucose deprivation–induced injury in cardiomyocytes and ligation/isoprenaline-induced myocardial ischemia injury in rats. Pharmacological inhibition of neuraminidase by anti-influenza drugs, oseltamivir and zanamivir, also protected cardiomyocytes and the heart from myocardial injury. Conclusions: Functional metabolomics identified a key role for Neu5Ac in acute myocardial infarction, and targeting neuraminidase-1 may represent an unrecognized therapeutic intervention for CAD.