Dairy product intake modifies gut microbiota composition among hyperinsulinemic individuals.

Purposes: The objectives of this study were to investigate differences in gut microbiota (GM) composition after high dairy intake (HD) compared to adequate dairy intake (AD) and to correlate GM composition variations with the change in glycemic parameters in hyperinsulinemic subjects.
Methods: In this crossover study, 10 hyperinsulinemic adults were randomized to HD (≥ 4 servings/day) or AD (≤ 2 servings/day) for 6 weeks, separated by a 6-week washout period. Fasting insulin and glucose levels were measured after each intervention. Insulin resistance was calculated with the homeostasis model assessment of insulin resistance (HOMA-IR). GM was determined with 16S rRNA-based high-throughput sequencing at the end of each intervention. Paired t test, correlations and machine learning analyses were performed.
Results: Endpoint glycemic parameters were not different between HD and AD intake. After HD compared with AD intake, there was a decrease in the abundance of bacteria in Roseburia and Verrucomicrobia (p = 0.04 and p = 0.02, respectively) and a trend for an increase abundance in Faecalibacteria and Flavonifractor (p = 0.05 and p = 0.06, respectively). The changes in abundance of Coriobacteriia, Erysipelotrichia, and Flavonifractor were negatively correlated with the change in HOMA-IR between the AD and HD phases. Furthermore, a predictive GM signature, including Anaerotruncus, Flavonifractor, Ruminococcaceae, and Subdoligranulum, was related to HOMA-IR.
Conclusion: Overall, these results suggest that HD modifies the abundance of specific butyrate-producing bacteria in Firmicutes and of bacteria in Verrucomicrobia in hyperinsulinemic individuals. In addition, the butyrate producing bacteria in Firmicutes phylum correlate negatively with insulin resistance.