Lactobacillus rhamnosus GG Promotes Intestinal Vitamin D Absorption by Upregulating Vitamin D Transporters in Senile Osteoporosis

Intestinal absorption of vitamin D is an important way to improve the vitamin D level in senile osteoporosis (SOP). There is a link between oral probiotics and vitamin D, but the mechanism is still unclear. We aimed to evaluate whether Lactobacillus rhamnosus GG culture supernatant (LCS) can affect cholecalciferol absorption, transport, and hydroxylation in SOP, and explore underlying mechanisms. In the study, specific-pathogen-free SAMP6 mice were randomly divided into an experimental group administered undiluted LCS and a control group administered normal drinking water. Furthermore, levels of cholecalciferol absorption were compared between Caco-2 cells cultured with varying concentrations of cholecalciferol and stimulated with LCS or de Man, Rogosa, and Sharpe (MRS) broth (control). Similarly, LCS-stimulated HepG2 cells were compared with MRS-stimulated HepG2 cells. Finally, protein levels of VD transporters in small intestine tissues and Caco-2 cells, as well as vitamin D-binding protein and 25-hydroxylase in liver tissues and HepG2 cells, were detected by western blot. The results showed that plasma concentrations of cholecalciferol and 25OHD3 were higher in mice of the LCS group compared with the control group, and these values were positively correlated. With the addition of LCS, cholecalciferol uptake was increased with 0.5 μM or 10 μM cholecalciferol in the medium. Protein levels of CD36 and NPC1L1 were higher in the LCS group compared with the control group, while SR-BI protein was decreased, both in vitro and in vivo. In conclusion, LCS can promotes intestinal absorption cholecalciferol by affecting protein levels of VD transporters and improves 25OHD3 levels in SOP.