Lifetime changes in gut microbiota and metabolite composition in high-fat diet-induced obesity in apolipoprotein A-IV gene knockout mice

AbstractIntroduction: Apolipoprotein A-IV (ApoA-IV) is a glycoprotein predominantly synthesized in the small intestine in response to dietary lipid intake. Recent studies have highlighted its involvement in gut-brain signaling and its interaction with hormones including leptin and cholecystokinin. Moreover, ApoA-IV has been implicated in modulating the gut microbiota, which is increasingly recognized as a key player in metabolic health and disease. However, chronic high-fat diet (HFD) consumption appears to impair ApoA-IV signaling and disrupt gut microbial balance, contributing to obesity and insulin resistance.Aim: The aim of this study was to investigate the role of ApoA-IV in shaping the gut microbiota and associated metabolic profiles throughout the lifespan of mice exposed to a HFD. Using ApoA-IV-deficient mice, we sought to elucidate the interplay between ApoA-IV, gut microbial composition, and metabolite production in the context of diet-induced obesity.Material and methods: At six weeks of age, ApoA-IV-KO and wild type (WT) mice were fed either a normal diet (ND) or HFD, and fecal samples were collected at weeks 0, 12, 28, 56, and 84 (n=126) for microbiota and branched-chain amino acids (BCAAs) and short-chain fatty acids (SCFAs) and profiling using 16S rRNA gene sequencing and GC-MS.Results: ApoA-IV deficiency modulated gut microbiota dynamics and metabolite profiles during aging and HFD exposure. Lifespan was longest in ApoA-IV-KO mice on a ND, while HFD reduced survival across genotypes. Microbiota analysis at weeks 0, 12, 28, and 84 revealed diet and age-dependent shifts, including altered abundance of Akkermansia, reduced Monoglobus, and elevated Firmicutes/Bacteroidetes ratio in ApoA-IV-KO mice on HFD. Metabolomic profiling showed that HFD had a stronger impact than genotype, with early and persistent increases in BCAAs and reductions in SCFAs, particularly in WT mice from week 28, and in ApoA-IV-KO mice from week 12. In old age (week 84), microbiota composition converged between genotypes on ND, although significant differences in metabolite profiles under HFD persisted, suggesting compensatory microbial mechanisms in ApoA-IV deficiency.Conclusions: Diet exerted a stronger influence on microbiota composition and metabolite profiles than genotype, with HFD inducing persistent changes across the lifespan. ApoA-IV deficiency delayed early microbial and metabolic shifts and shaped distinct responses to dietary stress. Despite age-related convergence in microbiota structure, genotype-specific differences in metabolite profiles and SCFA bacteria correlations persisted into old age, highlighting the lasting impact of ApoA-IV on host metabolic adaptation.