Objectives : The gut microbiome participates in host metabolic regulation. While the vast majority of microbiome research has focused on bacterial populations, other microorganisms also colonize the mammalian intestine and likely play functionally important roles in host metabolism. The objective of current study was to characterize the role of dietary composition and timing strategies upon gut fungal populations.
Methods : C57BL/6 male mice were randomized to a Chow diet or a high-fat diet (HFD) for 6 weeks, followed by a switch from HFD to 1) Chow (sChow), 2) Purified High Fiber – Daniel Fast (DF), 3) HFD ad lib, 4) HFD time restricted (TRF), 5) HFD alternative day fasting (ADF), or 6) HFD 60% caloric restriction (CR) for an additional 8 weeks. Ileal, cecal and serial fecal samples were collected for next generation sequencing of ITS2 rRNA to examine the gut mycobiome.
Results : We observed dramatic reductions in alpha diversity in fecal fungal populations when animals consumed the HFD compared with Chow. HFD resulted in dramatic reduction in the relative abundance of the fungal order Saccharomyces, with a concomitant increases in the genus Candida and Hanseniaspora. In response to dietary switch from HFD to Chow, fungal taxonomic composition, alpha, and beta diversity transitioned to a population clustering more similarity with Chow by weeks 4 and 8 of intervention. After 8 weeks on the respective dietary interventions, alpha diversity of the ileal, cecal and fecal fungal population in mice consuming DF or various HFD fasting protocols remained similar to the HFD controls. Saccharomycetales remained the dominant genus present in HFD and DF groups. However, amongst these groups, the DF group (fecal sample) showed the greatest increase in Saccharomyces, but time-restricted feeding protocols also showed increased levels of Saccharomyces.
While fasting protocols on HFD are associated with improved metabolic outcomes, these data demonstrate that – similar to microbial populations within the microbiome – diet remains the largest driver of microorganism community composition. To our knowledge, this is the first investigation into the role of dietary timing strategies upon the gut fungal communities ever reported.
Funding Sources : University of Memphis. Children's Foundation Research Institute, Memphis