Background: Emerging evidence suggests that faecal microbiome has an important role in energy homeostasis and glucose metabolism. To our knowledge, no previous studies have investigated associations between faecal microbiome and insulin sensitivity and secretion using gold-standard methods, in overweight or obese, otherwise healthy adults.
Methods: We investigated whether faecal microbiome (16S rRNA sequencing; QIIME software) was associated with: body mass index (BMI) and gold-standard measures of insulin sensitivity (M-value; hyperinsulinaemic-euglycaemic clamps) and insulin secretion (intravenous glucose tolerance test) in 38 overweight or obese individuals. Differences in microbiome composition were compared between overweight versus obese individuals (BMI 25-29.9 vs ≥30 kg/m2) as well as between insulin-resistant versus insulin-sensitive individuals (M<4.7 vs M≥4.7 mg/kg/min).
Results: Genus Prevotella was higher in abundance, and genus Streptococcus was lower in abundance in the overweight (n=18) compared to obese (n=20) group (linear discriminant analysis [LDA] > 3.0). The insulin resistant group (n=14) had more abundant genus Dialister and less abundant genus Clostridium compared to the insulin sensitive group (n=23) (LDA > 3.0). Order Clostridiales was negatively and genus Dialister was positively associated with insulin secretion (rho=-0.58, p<0.0001 and rho=0.52, p<0.0001, respectively). No significant differences in overall bacterial community structure and diversity were observed.
Conclusion: Our findings suggest that faecal microbiome is related to insulin sensitivity and secretion in overweight or obese adults. Studies need to confirm whether faecal microbiome contributes to increased insulin resistance and development of type 2 diabetes, and if modulation of microbiome can reduce type 2 diabetes risk.