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Decreases in Circulating Uncarboxylated Osteocalcin Are Not Associated with HOMA‐IR Changes in Humans
Author(s) -
Centi Amanda,
Shea Kyla,
Gundberg Caren,
Saltzman Edward,
Booth Sarah
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.758.10
Subject(s) - osteocalcin , medicine , endocrinology , insulin resistance , chemistry , homeostatic model assessment , insulin , homeostasis , enzyme , alkaline phosphatase , biochemistry
Osteocalcin (OC) in its uncarboxylated form (ucOC) may improve glucose metabolism in mice. However, human data are equivocal. Vitamin K (VK) is the only known factor to reduce the proportion of circulating OC that is uncarboxylated. We hypothesized that a decrease in circulating ucOC through VK supplementation would increase insulin resistance (IR) measures in humans. Serum was collected from weight‐stable older and younger men and women (n=42) before and after 28d of VK supplementation (500 µg phylloquinone/d). All meals and beverages were provided to control for other nutrients. The primary outcome was defined as IR change assessed by the homeostatic model(HOMA‐IR). Total OC (tOC), ucOC and insulin were measured by radioimmuno assay. Glucose was measured by enzymatic kinetic method. Measured covariates were triglycerides, BMI, age group and sex. A repeated measures ANOVA was used to determine if decreases in ucOC increased HOMA‐IR. In response to VK supplementation, significant decreases in circulating ucOC (pre = 4.79 ± 2.61 ng/mL post = 1.59 ± 2.11 ng/mL, p<0.001) and tOC (pre = 9.19 ± 4.05 ng/mL post = 8.48 ± 3.86 ng/mL, p=0.015) were observed. However, there were no significant changes in HOMA‐IR (pre = 2.20 ± 0.98 post = 2.25 ± 1.12, p=0.78). Further, no differences in HOMA‐IR were observed between sexes (p=0.39) or age groups (p=0.20) in relation to decreases in circulating ucOC or tOC. The lack of association between changes in circulating ucOC and HOMA‐IR suggests that in humans, ucOC does not have a role in IR. Support: USDA ARS Cooperative Agreement No. 58‐1950‐7‐707, NIH/NIDDK No. 5R01DK069341‐03 and the A.S.P.E.N. Rhoads Research Foundation