Microbiome Metagenomics in High-Fat Diet-Fed Mice Reveals Altered Microbial Metabolic Pathways Related to AMD

Abstract

Purpose : The link between the gut microbiome and age-related macular degeneration (AMD) is not completely understood, but gut dysbiosis has been implicated in AMD pathogenesis. Our team previously showed that high-fat diet (HFD) intake induces changes in gut microbiota composition (gut dysbiosis), alters the retinal and choroidal transcriptome, and exacerbates choroidal neovascularization in mouse models. However, little is known about how HFD changes the functional profiles of microbes. The purpose of this study is to use shotgun metagenomics to determine the effect of HFD consumption on microbial metabolic pathways, thereby clarifying the link between HFD-induced gut dysbiosis and AMD.

Methods : C57BL/6 mice were placed on either a ND or 23% HFD for 8 weeks (4 mice/group). For shotgun metagenomic analysis, DNA was extracted from fecal pellets and Illumina compatible libraries were generated using the QIAseq FX Library Kit. Sequencing runs were performed on the Illumina NextSeq platform. Abundant microbial genes were identified and biological pathways associated with these genes were determined using the Kyoto Encyclopedia of Genes and Genomes.

Results : Between HFD and ND mice, we identified 29 significantly altered microbial metabolic pathways based on the Kruskal-Wallis Rank Sum Test (p-value < 0.05). The most significantly upregulated pathway in HFD mice was the biosynthesis of heparan sulfate (implicated in AMD pathogenesis due to its interaction with complement factor H). In contrast, significantly down-regulated pathways in HFD mice include N-glycan biosynthesis (important for intestinal barrier function), primary/secondary bile acid (BA) biosynthesis (BAs inhibit AMD features in vitro), polyphenol biosynthesis (protects against oxidative stress), glycerophospholipid metabolism (similarly altered in AMD patients), and sucrose/galactose metabolism (key for maintaining retinal homeostasis). Compared to HFD mice, ND mice exhibited significantly decreased degradation of terpenoids (eg, geraniol), a group of compounds with geroprotective properties.

Conclusions : HFD intake significantly dysregulates microbial metabolic pathways involving the metabolism of lipids, carbohydrates, amino acids, glycans, and terpenoids. Therefore, a HFD not only modulates gut microbiome composition, but is also associated with alterations in key microbial metabolic pathways that overlap with AMD pathogenesis.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.