The effect of vitamin K1 supplementation on sensitivity and insulin resistance via osteocalcin in prediabetic women: a double-blind randomized controlled clinical trial

BACKGROUND/OBJECTIVES: A relationship between osteocalcin (OC) levels and factors associated with energy metabolism and insulin resistance has been reported recently. The aim of this study was to investigate whether modulation of ostecalcin isoforms via vitamin K1 supplementation would affect glucose metabolism or insulin sensitivity in prediabetic and premenopause women. SUBJECTS/METHODS: Eighty-two prediabetic women were randomized to consume vitamin K1 supplement (n = 39) or placebo (n = 43) for 4 weeks. Participants in the vitamin K1 supplement group received one pearl softgel capsule containing 1000 mu m of phylloquinone, and the placebo group received one placebo capsule daily for 4 weeks. Blood samples were collected at baseline and after the 4-week intervention period to quantify carboxylated OC (cOC), undercarboxylated OC (ucOC) and relevant variables. RESULTS: Phylloquinone supplementation increased the serum levels of cOC and decreased ucOC, compared with placebo (12.53 +/- 5.95 compared with 7.43 +/- 4.85 ng/ml and 2.47 +/- 1.91 compared with 4.79 +/- 2.43 ng/ml, respectively; P < 0.001). Furthermore, intake of phylloquinone supplement led to significant decreases in %ucOC (17.97 +/- 12.24 compared with 43.80 +/- 19.86) and 2-h post-oral glucose tolerance test (OGTT) glucose (7.32 +/- 1.50 compared with 8.62 +/- 1.45 mmol/l), and 2-h post-OGTT insulin level (80.34 +/- 42.24 compared with 112.43 +/- 53.19 mu IU/ml) and increased insulin sensitivity index (2.46 +/- 0.71 compared with 1.75 +/- 0.61) compared with placebo. Overall, a significant association was found between changes in %ucOC and changes in 2-h post-OGTT glucose (r = 0.308, P = 0.028). CONCLUSIONS: The results of this study demonstrated that vitamin K1 supplementation for 4 weeks did not affect insulin resistance in premenopausal and prediabetic women but had beneficial effects on glycemic status and insulin sensitivity.