Changes in Fecal Vitamin K Content are Associated with the Gut Microbiota

Emerging evidence suggests novel cardiometabolic roles for bacterially-synthesized vitamin K forms known as menaquinones (MK-n). Though gut bacteria synthesize MK-n, relationships between gut microbiota composition, MK-n biosynthesis, and cardiometabolic health have not been examined. To examine these relationships, MK-n and microbiota composition were measured in fecal samples collected from 77 Chinese adults (41 ± 7 y, BMI 32 ± 2 kg/m2) during a 23-wk diet intervention previously shown to alter gut microbiota composition and improve cardiometabolic health. Variability in fecal MK-n content was associated with gut microbiota composition, and longitudinal changes in the relative abundance of > 100 phylotypes were associated with altered fecal content of 蠅 1 individual MK-n. The strongest and most consistent relationships were between Prevotella spp. and MK-5, -11 -12, and -13, between Bacteroides spp. and MK-9 and -10, and between Eschericia/Shigella spp. and MK-8. Baseline fecal MK-9 content was inversely associated with BMI (r = -.30, P = 0.05) and HOMA-IR (r = -.37, P = 0.01). No other cross-sectional or longitudinal associations between fecal MK-n and cardiometabolic health biomarkers were observed. Findings suggest that variability in fecal MKn content is associated with the gut microbiota, and that diet-mediated changes in gut microbiota composition may alter gut MK-n content. The implications for human health merit further investigation. Funding: Dr. James Sadowski Memorial Internship, USDA contract #58-1950-7-707, National Nature Science Foundation of China.