Basal Diet Determined Long-Term Composition of the Gut Microbiome and Mouse Phenotype to a Greater Extent than Fecal Microbiome Transfer from Lean or Obese Human Donors

The Western dietary pattern can alter the gut microbiome and cause obesity and metabolic disorders. To examine the interactions between diet, the microbiome, and obesity, we transplanted gut microbiota from lean or obese human donors into mice fed one of three diets for 22 weeks: (1) a control AIN93G diet; (2) the total Western diet (TWD), which mimics the American diet; or (3) a 45% high-fat diet-induced obesity (DIO) diet. We hypothesized that a fecal microbiome transfer (FMT) from obese donors would lead to an obese phenotype and aberrant glucose metabolism in recipient mice that would be exacerbated by consumption of the TWD or DIO diets. Prior to the FMT, the native microbiome was depleted using an established broad-spectrum antibiotic protocol. Interestingly, the human donor body type microbiome did not significantly affect final body weight or body composition in mice fed any of the experimental diets. Beta diversity analysis and linear discriminant analysis with effect size (LEfSe) showed that mice that received an FMT from obese donors had a significantly different microbiome compared to mice that received an FMT from lean donors. However, after 22 weeks, diet influenced the microbiome composition irrespective of donor body type, suggesting that diet is a key variable in the shaping of the gut microbiome after FMT.