Reducing Undercarboxylated Osteocalcin With Vitamin K Supplementation Does Not Promote Lean Tissue Loss or Fat Gain Over 3 Years in Older Women and Men: A Randomized Controlled Trial

Osteocalcin (OC) is a vitamin K–dependent protein synthesized during bone formation. Mice injected with the undercarboxylated form of OC (ucOC) had more skeletal muscle mass and less fat mass than sham‐treated controls, suggesting a unique metabolic role for ucOC. UcOC decreases in response to vitamin K supplementation. Our objective was to determine the effect of reducing ucOC on change in lean tissue and fat mass in older community‐dwelling adults ( n  = 401, mean ± SD 69 ± 6 years) using data from a randomized controlled trial of vitamin K supplementation. Over 3 years, serum ucOC was reduced by 58% in women and by 61% in men randomized to vitamin K, whereas in the control group, ucOC decreased by 1% in women and 4% in men (supplementation*time p  < 0.001 in men and women). However, there were no differences in the change in appendicular lean mass (calculated as arm lean mass + leg lean mass) or total body fat mass between women randomized to vitamin K and control over 3 years (supplementation*time p values all ≥ 0.18) or between men randomized to vitamin K and control (supplementation*time p values all ≥ 0.54). Consistent with these findings, ucOC was not associated cross‐sectionally with appendicular lean mass or fat mass in men or women after adjustment for total OC at baseline (all p  ≥ 0.12). These findings indicate the undercarboxylated form of OC is not implicated in age‐related changes in skeletal muscle or adipose tissue mass in older community‐dwelling adults. © 2016 American Society for Bone and Mineral Research.