Alterations in the composition of the gut microbiota affect absorption of cholecalciferol in severe osteoporosis

IntroductionTo evaluate the relationship between the gut microbial composition and intestinal cholecalciferol absorption in patients with severe osteoporosis (SOP).Materials and MethodsEighteen patients with primary osteoporosis (OP) and 18 with SOP were included. Their clinical data were collected and their circulating concentrations of cholecalciferol and 25(OH)D3 were measured. Fecal samples were collected and their microbial contents were analyzed using 16S rDNA sequencing.ResultsThe age, sex, body mass index, and body mass of the participants did not differ between the groups. The prevalence of gastrointestinal symptoms in the participants with SOP was significantly higher than that in the participants with OP. There were significant differences in the 25(OH)D3 and cholecalciferol concentrations between participants with SOP or OP and there was a significant positive correlation between the concentrations of these substance. The diversity of the gut microbiota in participants with SOP was significantly higher than that in participants with OP. Firmicutes was more abundant in the SOP group and the ratio of Firmicutes/Bacteroidetes in participants with SOP was higher. Conversely, Bifidobacterium was significantly less abundant, as were the order and family it belongs to. At the species level, Bifidobacterium was the most significant difference between the two groups.ConclusionDifferences in the intestinal microecology, especially Bifidobacterium, are associated with differences in the absorption of cholecalciferol and in the circulating 25(OH)D3 concentration, which may influence the progression of OP to SOP.