Interactive effects of blueberry supplementation and GPR109A deletion on gut microbiome profiles in mice

Blueberry‐supplemented (BB) diets in rodent models have shown to improve skeletal mass, glucose tolerance and endothelial function. In addition to the bioactive and dietary fibre components of these diets, effects of blueberries may be in part via modulation and action of the gut microbiome. However, few studies have characterized gut microbiome composition following BB supplementation. Since phenolic acids and gut microbiota‐derived short‐chain fatty acids (SCFAs) such as butyrate can bind and activate GPR109A (nicotinic acid receptor) signaling, we examined the interactive roles of GPR109A and BB‐supplementation on microbiome profiles in mice. Male GPR109A global knockouts and WT littermates were fed control or BB‐supplemented diets (5% w/w) for 4 weeks (n=10). All diets were based on the AIN‐93G formulation and contained 19% calories from protein, 17% from fat and 64% from carbohydrates. Body weight, body composition (non‐invasively via Echo MRI) and food intake were measured weekly and did not differ between groups within the study period. At the end of 4 wk serum, liver, adipose tissue depots and cecal contents were collected for further analysis. Microbial community profiling was conducted by sequencing the 16S rRNA (V4 region) followed by analysis using QIIME. BB‐diet fed mice showed greater a‐diversity (OTU richness) in both WT and GPR109A‐KO. Interestingly, GPR109A loss per se was associated with significantly lower a‐diversity relative to WT mice (p<0.05). Principal coordinate analysis of b‐diversity values showed highly significant effects of both genotype and diet (p<0.00001). BB diets affected abundance of 15 genera in WT mice, of which only 5 genera were also affected in GRP109A KO with BB‐treatment (p<0.05, two‐way ANOVA). However, BB diets in GPR109A KO altered 7 genera uniquely suggesting significant genotype‐diet interactions. Two‐way ANOVA analysis showed BB‐diets increased Bacteroidetes and decreased Firmicutes phyla (p<0.001) in both WT and KO mice. OTU abundance of genera including Facklamia, Clostridium, Coprococcus, Dorea , and Ruminoccous was affected by both diet and genotype of mice (p<0.01). LEfSE analysis confirmed enrichment of phyla Bacteroidetes with BB‐diets. Predictive functional metagenomics analysis using PiCRUST identified alterations of pathways involving immune and bacterial response, protein digestion, amino acid metabolism and xenobiotics biodegradation to be affected by genotype and BB‐diet. Associations between alterations in microbial abundance and diet‐associated changes in adipose tissue and liver gene expression will also be presented. Overall, these results suggest changes in microbial community structure with BB‐diets and also reveal novel host genotype dependent alterations in the microbiome. Support USDA CRIS 6206‐51000‐010‐05S Support or Funding Information Support USDA CRIS 6206‐51000‐010‐05S