Mucosa-associated microbiota in the jejunum of patients with morbid obesity: alterations in states of insulin resistance and metformin treatment.

BACKGROUND

Stool samples have been widely used to evaluate gut microbiota; however, little is known about the composition of human small intestinal microbiota and the alterations provoked by insulin resistance.

OBJECTIVE

To describe the composition of jejunal microbiota in morbidly obese patients, as well as its link with insulin resistance and metformin treatment.

SETTING

Virgen de la Victoria University Hospital and Regional University Hospital, Málaga, Spain.

METHODS

Jejunal biopsies from 46 morbidly obese patients were analyzed by next-generation sequencing method. Patients were classified in the following 3 groups: low homeostasis model assessment of insulin resistance index (HOMA-IR) value, high HOMA-IR value, and metformin-treated type 2 diabetes patients (T2D-metf).

RESULTS

Richness (q = .011) together with Proteobacteria (W = 2), Fusobacteria (W = 2), and Bacteroidetes (W = 1) phyla were significantly higher in high HOMA-IR compared with low HOMA-IR group. At family level, several differences were found between low HOMA-IR and T2D-metf group, being the most important the higher abundance of Halomonadacea in T2D-metf group (W = 22). PICRUSt analysis showed that predicted genes involved in trimethylamine-N-oxide biosynthesis pathway could be increased in jejunal microbiota of T2D-metf group compared with the low HOMA-IR group, while indole biosynthesis pathway could be increased in the low HOMA-IR group compared with the high HOMA-IR group.

CONCLUSION

An increase in richness and an enrichment in Proteobacteria, Fusobacteria, and Bacteroidetes was observed in jejunal from morbidly obese patients with high insulin resistance. Halomonadaceae family was significantly increased in metformin-treated patients. Functional analysis of predicted metagenome suggests that trimethylamine-N-oxide biosynthesis pathway could be increased in the jejunal microbiota of T2D-meft group, while indole biosynthesis pathway could be increased in low HOMA-IR group. These results contribute to the increase in the scarce knowledge about the mucosal microbiota of the hardly accessible small intestine.