Table 2.
Associations of Total and Free 25(OH)D With Biomarkers at Baseline and 12 Months
| Baseline | 12 months | |||||||
|---|---|---|---|---|---|---|---|---|
| Total 25(OH)D (nmol/L) | Free 25(OH)D (pmol/L) | Total 25(OH)D (nmol/L) | Free 25(OH)D (pmol/L) | |||||
| β coefficient | p value | β coefficient | p value | β coefficient | p value | β coefficient | p value | |
| Plasma calcium and renal function markers | ||||||||
| Albumin (g/L) | 0.004 | 0.44 | n/a | n/a | −0.003 | 0.72 | n/a | n/a |
| Adjusted calcium (mmol/L) | 0.000 | 0.34 | 0.001 | 0.46 | −0.001 | <0.05 | −0.002 | <0.05 |
| Serum phosphate (mmol/L) | 0.001 | 0.08 | 0.003 | 0.18 | 0.000 | 0.84 | 0.003 | 0.18 |
| Cystatin C (mg/L) | 0.000 | 0.50 | −0.002 | 0.425 | 0.000 | 0.88 | 0.004 | 0.19 |
| Serum creatinine (μmol/L) | 0.027 | 0.58 | 0.169 | 0.47 | −0.074 | 0.23 | −0.424 | 0.10 |
| eGFR (mL/min per 1.73 m2) | 0.026 | 0.50 | 0.144 | 0.43 | −0.141 | <0.01 | −0.710 | <0.001 |
| Klotho (pg/mL) | −1.398 | 0.40 | −7.066 | 0.37 | −1.606 | 0.10 | −1.771 | 0.66 |
| cFGF23 (RU/mL) | −0.433 | <0.001 | −1.741 | <0.01 | −0.203 | 0.10 | −0.396 | 0.45 |
| iFGF23 (pg/mL) | 0.107 | 0.22 | 0.227 | 0.50 | 0.047 | 0.68 | 0.485 | 0.31 |
| iFGF23/cFGF23 | −0.023 | <0.05 | −0.104 | <0.05 | −0.005 | 0.21 | −0.006 | 0.74 |
| Vitamin D metabolism markers | ||||||||
| 24,25(OH)2D (nmol/L) | 0.126 | <0.001 | 0.559 | <0.001 | 0.124 | <0.001 | 0.452 | <0.001 |
| 1,25(OH)2D (pmol/L) | 0.425 | <0.001 | 1.964 | <0.001 | 0.130 | 0.15 | 0.268 | 0.49 |
| 1,25(OH)2D:24,25(OH)2D | −0.916 | <0.001 | −0.114 | <0.001 | −0.010 | 0.73 | −0.015 | 0.91 |
| DBP (mg/L) | 0.439 | <0.01 | n/a | n/a | 0.803 | <0.001 | n/a | n/a |
| PTH (pg/mL) | −0.360 | <0.001 | −1.612 | <0.001 | −0.121 | 0.09 | −0.752 | <0.05 |
| Wnt signaling pathway markers | ||||||||
| SOST (pmol/L) | 0.020 | 0.76 | 0.237 | 0.45 | 0.014 | 0.86 | 0.634 | <0.05 |
| DKK1 (pmol/L) | 0.000 | 0.99 | −0.03 | 0.89 | 0.035 | 0.55 | 0.194 | 0.46 |
| OPG (pmol/L) | 0.002 | 0.76 | −0.016 | 0.53 | 0.005 | 0.51 | 0.024 | 0.45 |
| sRANKL (pmol/L) | 0.000 | 0.90 | 0.000 | 0.79 | 0.000 | 0.78 | 0.000 | 0.66 |
| sRANKL/OPG | 0.000 | 0.88 | 0.000 | 0.82 | 0.000 | 0.85 | 0.000 | 0.94 |
| Bone density and metabolism | ||||||||
| Hip BMD (g/m2) | 0.001 | <0.01 | 0.006 | <0.01 | 0.001 | 0.10 | 0.003 | 0.14 |
| Hip BMC (g) | 0.053 | <0.05 | 0.298 | <0.01 | 0.036 | 0.16 | 0.121 | 0.27 |
| FN BMD (g/m2) | 0.001 | <0.05 | 0.005 | <0.01 | 0.001 | 0.14 | 0.003 | 0.11 |
| FN BMC (g) | 0.007 | <0.05 | 0.039 | <0.01 | 0.000 | 0.99 | 0.000 | 0.99 |
| BAP (μg/L) | −0.019 | <0.05 | −0.096 | <0.05 | 0.006 | 0.72 | 0.038 | 0.58 |
| CTX (ng/mL) | 0.000 | 0.61 | −0.002 | 0.43 | 0.000 | 0.51 | −0.001 | 0.73 |
| PINP (μg/L) | −0.034 | 0.42 | −0.202 | 0.32 | −0.031 | 0.63 | −0.014 | 0.96 |
| PINP/CTX | 0.007 | 0.93 | −0.005 | 0.99 | −0.137 | 0.26 | −0.315 | 0.54 |
25(OH)2D = 1,25‐dihydroxy vitamin D; 24,25(OH)2D = 24,25‐dihydroxy vitamin D; 25(OH)D = 25‐hydroxy vitamin D; BAP = bone‐specific alkaline phosphatase; BMC = bone mineral content; BMD = bone mineral density; cFGF23 and iFGF23 = c‐terminal and intact fibroblast growth factor‐23, respectively; CTX = C‐terminal telopeptide; DBP = vitamin D binding protein; DKK1 = Dickkopf‐related protein 1; eGFR = estimated glomerular filtration rate; FN = femoral neck; OPG = osteoprotegerin; PINP = procollagen 1 intact N‐terminal; PTH = parathyroid hormone; SOST = sclerostin; sRANKL = soluble receptor activator of NF‐κB ligand. Univariate linear regression analysis; the table displays the β coefficients and the ANOVA p value for the β coefficient. Regression analyses for variables derived from the independent variable were not conducted (ie, for free 25(OH)D, these were DBP, Alb, and total 25(OH)D) and for any of the ratios with total 25(OH)D).
β‐coefficients and associated p‐values from univariate linear regression analysis. Significant associations p<0.05 are indicted in bold.