Dysbiosis in Patients with Chronic Kidney Disease: Let Us Talk About Vitamin K

This narrative review aimed to summarize the current evidence on the connection between dysbiosis and vitamin K deficiency in patients with chronic kidney disease (CKD). The presence of dysbiosis (perturbations in the composition of the microbiota) has been described in several non-communicable diseases, including chronic kidney disease, and it has been hypothesized that dysbiosis may cause vitamin K deficiency. Patients with CKD present both vitamin K deficiency and gut dysbiosis; however, the relationship between gut dysbiosis and vitamin K deficiency remains to be addressed.Recently, few studies in animals have demonstrated that a dysbiotic environment is associated with low production of vitamin K by the gut microbiota. Vitamin K plays a vital role in blood coagulation as well as in the cardiovascular and bone systems. It serves as a cofactor for γ-glutamyl carboxylases and thus is essential for the post-translational modification and activation of vitamin K-dependent calcification regulators, such as osteocalcin, matrix Gla protein, Gla-rich protein, and proteins C and S. Additionally, vitamin K executes essential antioxidant and anti-inflammatory functions. Dietary intake is the main source of vitamin K; however, it also can be produced by gut microbiota. This review discusses the effects of uremia on the imbalance in gut microbiota, vitamin K-producing bacteria, and vitamin K deficiency in CKD patients, leading to a better understanding and raising hypothesis for future clinical studies.