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

Abstract

The gut microbiome has combined with other person-specific information, such as blood parameters, dietary habits, anthropometrics, and physical activity been found to predict personalized postprandial glucose responses (PPGRs) to various foods. Yet, the contributions of specific microbiome taxa, measures of fermentation, and abiotic factors in the colon to glycemic control remain elusive. We tested whether PPGRs 60 min after a standardized 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 fecal short-chain fatty acids (SCFAs), and breath hydrogen and methane exhalation, as well as abiotic factors including fecal pH, fecal water content, fecal energy density, intestinal transit time (ITT), and stool consistency. A single-arm meal trial was conducted. A total of 31 healthy (24 female and seven male) subjects consumed a standardized evening meal and a subsequent standardized breakfast (1,499 kJ) where blood was collected for analysis of postprandial glucose and insulin responses. PPGRs to the same breakfast varied across the healthy subjects. The largest inter-individual variability in PPGRs was observed 60 min 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. 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 PPGRs may be subtle in healthy adults.

Stool energy density is positively correlated to intestinal transit time and related to microbial enterotypes

“…Instead, we found higher alpha-diversity and higher levels of microbiota-derived proteolytic metabolites in faeces and urine among the R-type individuals compared to the B and P type, suggesting a more complex microbial ecosystem with increased colonic proteolysis in the R-type individuals. This could possibly be explained by the longer transit time in the R-type individuals, since we and others have previously shown that a long intestinal transit time is associated with both alpha-diversity and increased proteolytic fermentation [ 16 , 17 ], whereas a short transit time is associated with increased saccharolysis [ 33 ]. Here, we did also observe negative correlations between transit time and faecal acetate/propionate/butyrate, however no differences were found in these metabolites among enterotypes.…”

Advancing human gut microbiota research by considering gut transit time

“…106 Elevated concentrations of branched-chain fatty acids (BCFA) are positively associated with CTT in healthy adults. 107 BCFA such as isobutyrate, isovalerate, or 2-methylbutyrate are products of bacterial fermentation of branched-chain amino acids and has been positively correlated with the relative abundance of Coprococcus and Blautia. 107 Interestingly, a study that employed the SmartPill to measure gastrointestinal pH, showed that Coprococcus spp.…”

“…In obesity, accelerated gastric emptying and changes in the transit in the small intestine, as well as both constipation and diarrhoea, have been reported 212 213. Altered gut motility affects the time for nutrient absorption and may contribute to changes in hormonal responses and glucose homeostasis 107 213. A recent cohort study has shown associations between stool frequency and vascular and non-vascular diseases in a Chinese population 214.…”

Personal diet–microbiota interactions and weight loss

“…In this regard, intestinal transit time, which is the time food takes to travel through the gastrointestinal system, appears as a largely neglected, but a relevant factor. We and others have shown that both intestinal transit time and stool consistency, a proxy of intestinal transit time, are strongly associated with the gut microbiome composition (26)(27)(28)(29) . Indeed, population studies have reported that measures of transit time explain more of the gut microbiome variation than dietary and health markers (28,95) .…”

“…Similarly, it has been observed that adults who consume a high variety of plants have higher gut microbial diversity compared with adults who consume a low variety of plants (25) . However, a high microbiota diversity has also been linked to a firm stool consistency and long colonic transit time (26)(27)(28) , which is associated with increased proteolysis (27,29) . Therefore, a high gut microbiota diversity does not per se imply a healthy gut microbial ecosystem if it is merely a reflection of a slow intestinal system trending towards constipation.…”