Meeting Abstract
Diet exerts a major influence on the composition and function of the gut microbiota and, therefore, host-microbial symbiosis. Thirteen-lined ground squirrels have seasonal metabolic cycles comprised of summer feeding – providing substrates for squirrel and microbiota metabolism – and winter fasting – when hibernators metabolize primarily stored fat and microbes have access only to host-derived metabolic substrates (e.g., mucins). To assess how seasonal dietary change affects the hibernator-gut microbe symbiosis, we used stable isotope assisted metabolomics to assess the capacity of the gut microbiota in degrading substrates and generating metabolites that are incorporated into the squirrel metabolome. After oral gavage of active season and hibernating (aroused) squirrels with 13C-inulin (a substrate mammals cannot degrade), changes in 13C:12C (δ13C) are monitored in exhaled CO2. We found that increases in δ13C after 13C-inulin gavage are high and similar in spring and summer squirrels, lower in aroused hibernators, and abolished when squirrels are pretreated with microbiota-depleting antibiotics. NMR analysis reveals multiple 13C-labeled metabolites in gut contents, blood and liver of summer and hibernating squirrels including short chain fatty acids, β-hydroxybutyrate and carnitine, among others. Cluster analysis (PLSDA) indicates that liver 13C-metabolites separate by season and by presence/absence of antibiotics. This approach provides a pathway for a molecular-based exploration of the seasonally changing hibernator-microbe symbiosis. Supported by NSF 1558044.
