Gut microbiota dysbiosis and altered short-chain fatty acid biosynthetic pathways in Chinese children with obesity and nonalcoholic fatty liver disease

Background Nonalcoholic fatty liver disease (NAFLD), recently reclassified as metabolic dysfunction-associated steatotic liver disease (MASLD), is the most prevalent chronic liver disease in children, affecting 13% of the general pediatric population and up to 47% of children with obesity worldwide. Gut microbiota dysbiosis contributes to NAFLD pathogenesis through the gut-liver axis, yet the interplay between microbial communities and host metabolic regulators, particularly angiopoietin-like protein 4 (ANGPTL4), remains incompletely characterized. Methods Eighty-nine Chinese children aged 5–15 years were enrolled, including 29 healthy controls (Con), 39 with simple obesity (OB), and 21 with obesity and NAFLD. Gut microbiota was profiled by 16S rRNA gene sequencing (V3–V4 region) and analyzed using QIIME2 and MicrobiomeAnalyst. Functional prediction employed PICRUSt2 referencing MetaCyc pathways. Serum ANGPTL4, leptin, adiponectin, and interleukin-6 were measured. Results Chao1 species richness differed significantly among groups (F = 4.98, p = 0.009), while Shannon diversity did not (F = 2.22, p = 0.115). Beta diversity (PERMANOVA, F = 2.87, R 2 = 0.063, p = 0.002) differed significantly among groups, although PERMDISP indicated heterogeneous dispersion (F = 6.62, p = 0.002). LEfSe analysis identified enrichment of short-chain fatty acid (SCFA)-producing genera (Bacteroides, Alistipes, Oscillospira, Parabacteroides) in healthy controls, while Megamonas, Blautia, Coprococcus, and Dorea characterized the NAFLD group. ANCOM-BC2 identified significant enrichment of Megamonas in the NAFLD group (q = 0.005 vs Con). PICRUSt2 predicted lower abundance of nine SCFA-related pathways in the obesity groups compared with controls. After FDR correction, Bacteroides-ANGPTL4 was the most significant correlation (r = 0.460, q < 0.001), and four additional associations survived correction. In hierarchical regression, Bacteroides remained independently associated with ANGPTL4 after adjustment for age, BMI, sex, and Tanner stage (β = 0.254, p = 0.016, ΔR 2 = 0.057), although this association was attenuated after additional adjustment for group status (β = 0.204, p = 0.058). Conclusion Chinese children with obesity and NAFLD exhibit gut microbial dysbiosis characterized by reduced species richness, depletion of SCFA-producing genera, and lower predicted abundance of SCFA-related pathways. The independent association between Bacteroides and ANGPTL4 suggests a potential microbiota-host metabolic link that may be associated with hepatic lipid metabolism.