Associations Between Dietary Macronutrient Intake and the Gut Microbiome in Adults Undergoing Bariatric Surgery for Obesity

Objectives: To examine associations between macronutrient intakes prior to and following roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) bariatric surgeries with gut microbiome and related gene pathways. Methods: A cohort of 29 adults (27F, 2M) were studied. Participants recorded three-day food records prior to pre-operative and post-operative outpatient visits to a clinical research center. Macronutrient intake was determined using Nutrition Data System for Research (NDSR) software. Stool samples were collected with a commercial kit (OMNIgene-GUT, DNAGenotek Inc.). Mean daily macronutrient intakes, corrected per 1000 kcal or as % of total kcal intake, and Healthy Eating Index 2015 (HEI-2015) scores coupled with metagenomic data, were analyzed by multivariable associations and predictive methods. Cross-sectional and longitudinal nutrient intake and metagenomic data from pre- to post-operative visits were analyzed. Results: At the phylum level, pre-operative (n=29) Actinobacteria abundance was positively associated with monounsaturated fat (MUFA) intake. Synergistetes abundance was positively associated with soluble dietary fiber intake, and Proteobacteria were negatively linked with HEI-2015 scores. Post-operatively (n=19), Lentisphaerae were negatively associated with dietary glycemic index. Verrucomicrobia and Euryarchaeta were positively associated with MUFA intake, while Verrucomicrobia were negatively linked with polyunsaturated fat (PUFA) intake. Comparing pre- and post-operative periods longitudinally (n=19), Lentisphaerae and Verrucomicrobia abundance were negatively associated with the glycemic index, while Fusobacteria were positively associated with the glycemic index. Several functional gene pathways were positively linked to HEI-2015 scores (e.g., L-proline and glutamine biosynthesis), soluble fiber intake (e.g., arginine and ornithine metabolism) and insoluble fiber intake (e.g., L-proline and isoleucine metabolism), respectively. Conclusions: In adults undergoing bariatric surgery, intake of specific macronutrients and HEI-2015 diet quality scores were associated with several microbial phyla and related gene pathways. Associations between gut metagenomic indexes and macronutrient intake were modified by bariatric surgery. Funding Sources: Funded by the National Institutes of Health.