The Gut Microbiome and Abiotic Factors as Potential Determinants of Postprandial Glucose Responses: A Single-Arm Meal Study

The gut microbiome has combined with other person-specific information, such as blood parameters, dietary habits, anthropometrics and physical activity, been found to predict personalised postprandial glucose responses (PPGR) to various foods. Yet, the contributions of specific microbiome taxa, measures of fermentation, and abiotic factors in the colon to glycaemic control remain elusive. We tested whether PPGR 60 minutes after a standardised breakfast was associated with gut microbial α-diversity (primary outcome), and explored whether postprandial responses of glucose and insulin were associated with specific microbiome taxa, colonic fermentation as reflected by faecal short-chain fatty acids (SCFAs) and breath hydrogen and methane exhalation, as well as abiotic factors including faecal pH, faecal water content, faecal energy density, intestinal transit time (ITT), and stool consistency. A single-arm meal trial was conducted. 31 healthy (24 female and seven male) subjects consumed a standardised evening meal and a subsequent standardised breakfast (1499 kJ) where blood was collected for analysis of postprandial glucose and insulin responses. PPGR to the same breakfast varied across the healthy subjects. The largest inter-individual variability in PPGR was observed 60 minutes after the meal, but was not associated with gut microbial α-diversity. In addition, no significant associations were observed between postprandial responses and specific taxa of the gut microbiome, measures of colonic fermentation, ITT or other abiotic factors, respectively. However, fasting glucose concentrations were negatively associated with ITT, and fasting insulin was positively associated with fasting breath hydrogen. In conclusion, the gut microbiome, measures of colonic fermentation and abiotic factors were not shown to be significantly associated with variability in postprandial responses, suggesting that contributions of the gut microbiome, colonic fermentation and abiotic factors to PPGR may be subtle in healthy adults.