A species of Coprococcus is related to BMI in patients who underwent malabsorptive bariatric surgery and its abundance is modified by magnesium and thiamin intake

Background: Morbid obesity is associated with metabolic alterations and the onset of type 2 diabetes. Patients who undergo a malabsorptive bariatric surgery show an important improvement in several clinical variables and a modification in the gut microbiota balance. In this study, we aimed to identify bacteria related to changes in the body mass index of patients who underwent a bariatric surgery and their relationship with nutrients intake. Results: There were differences in bacterial diversity in the gut microbiota of patients that underwent a bariatric surgery. The Shannon and Simpson indexes decrease after the surgery (p < 0.001) and the beta diversity indexes (Bray-Curtis, Weighted and Unweighted UniFrac) showed differences when comparing pre- and post-surgery (p = 0.001). The abundance of a species in the genus Coprococcus correlated positively with the intake of magnesium and thiamin in post-surgery individuals (rho = 0.816, pFDR = 0.029 and rho = 0.812, pFDR = 0.029, respectively) and was related to BMI in both groups (p = 0.043 pre-surgery and p = 0.036 post-surgery). The abundances of several bacteria belonging to the order Clostridiales, as well as an enrichment of vitamin B1 (thiamin) biosynthesis, sugar degradation, acetate production and some amino acids biosynthesis were higher before the surgery. Conclusions: The abundance of a species of the genus Coprococcus that showed inverse relationships with BMI in pre-surgery and post-surgery patients correlates with the intake of magnesium and thiamin in individuals that underwent a malabsorptive bariatric surgery. It indicates that the well-established beneficial effects of bariatric surgery on BMI may be amplified by modulating the intake of micronutrients and its effect on the gut bacterial.