Osteocalcin carboxylation is not associated with body weight or percent fat changes during weight loss in post-menopausa
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ORIGINAL ARTICLE
Osteocalcin carboxylation is not associated with body weight or percent fat changes during weight loss in post-menopausal women Amanda J. Centi1 • Sarah L. Booth1 • Caren M. Gundberg2 • Edward Saltzman1 Barbara Nicklas3 • M. Kyla Shea1
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Received: 20 December 2014 / Accepted: 27 April 2015 Ó Springer Science+Business Media New York 2015
Abstract Osteocalcin (OC) is a vitamin K-dependent bone protein used as a marker of bone formation. Mouse models have demonstrated a role for the uncarboxylated form of OC (ucOC) in energy metabolism, including energy expenditure and adiposity, but human data are equivocal. The purpose of this study was to determine the associations between changes in measures of OC and changes in body weight and percent body fat in obese, but otherwise healthy post-menopausal women undergoing a 20-week weight loss program. All participants received supplemental vitamins K and D and calcium. Body weight and body fat percentage (%BF) were assessed before and after the intervention. Serum OC [(total (tOC), ucOC, percent uncarboxylated (%ucOC)], and procollagen type 1N-terminal propeptide (P1NP; a measure of bone formation) were measured. Women lost an average of 10.9 ± 3.9 kg and 4 %BF. Serum concentrations of tOC, ucOC, %ucOC, and P1NP did not significantly change over the twenty-week intervention, nor were these measures associated with changes in weight (all p [ 0.27) or %BF (all p [ 0.54). Our data do not support an association between any serum measure of OC and weight or %BF loss in post-
Electronic supplementary material The online version of this article (doi:10.1007/s12020-015-0618-6) contains supplementary material, which is available to authorized users. & Sarah L. Booth [email protected] 1
Human Nutrition Research Center on Aging, Tufts University, 711 Washington Street, Boston, MA 02111, USA
2
Yale School of Medicine, 153 College Street, New Haven, CT, USA
3
Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC, USA
menopausal women supplemented with nutrients implicated in bone health. Keywords Body fat
Osteocalcin Vitamin K Weight loss
Introduction Osteocalcin (OC) is a vitamin K (VK)-dependent protein found primarily in bone. It is synthesized in osteoblasts [1] and undergoes a VK-dependent post-translational modification that results in carboxylation of specific glutamate residues. In its carboxylated (cOC) form, OC binds to hydroxyapatite in bone [2]. Serum concentrations of OC have been used to assess bone formation [3], whereas the percent of OC that is not carboxylated (%ucOC) is used as a measure of VK status [4]. Although the Adequate Intake for VK in the form of phylloquinone (vitamin K1) has been established at 120 and 90 lg phylloquinone per day for men and women, respectively, intakes of 100 lg phylloquinone per day do not result in complete carboxylation of osteocalcin [5]. Based on studies in mice, OC, specifically the uncarboxylated (ucOC) form, regulates energy metabolism, including energy expenditu
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