Osteoporosis is a major cause of morbidity and mortality in older persons [1]. While prevalence is particularly high in women, osteoporosis is also common in men, and risk factors may be unique [2]. T50 is a novel serum-based marker that assesses the propensity to calcification [3].
When calcium and phosphate precipitation is initiated in serum, there is formation of primary calciprotein particles (CPPs) which are rich in calcium and phosphate and contain small quantities of proteins including albumin and fetuin-A. With time, these moeties transition to larger secondary CPPs that differ in calcium, phosphate, and protein content from the primary CPPs. Calciprotein particle maturation time (T50) is a measure of the time to transition from primary to secondary CPPs in serum in vitro [3]. Shorter T50 suggests greater propensity to calcify. A shorter T50 has been associated with risk of cardiovascular disease (CVD) and all-cause mortality in kidney transplant recipients [4] and CKD patients [5]. No study to our knowledge has evaluated the relationship of T50 with bone disease in those without kidney disease. This study was designed to examine the correlates of T50 and relationship to bone mineral density (BMD) in community-living older men.
We measured T50 among participants from The Osteoporotic Fractures in Men (MrOS) Study (http://mrosdata.sfcc-cpmc.net), a prospective observational cohort study of 5994 men at six sites across the US [6,7]. We took a random sample of 150 individuals, one had missing blood specimens, bringing our analytic sample to 149. We categorized individuals into tertiles of T50, and compared demographics and disease indicators across tertiles using analysis of variance and chi square tests, as appropriate. We utilized linear regression to evaluate the cross-sectional association between T50 and hip and spine BMD. The mean T50 was 336 ± 52 min. All participants were men, mean age was 74 ± 5 years, and 19% (n=29) had CVD. Participant demographics and clinical characteristics, stratified by tertile of T50 concentration, are shown in Table 1. Older men were more likely to have shorter T50. Kidney function tended to be lower in those with shorter T50, and the prevalence of CVD and low ankle brachial index were higher in this group, albeit these findings did not reach statistical significance. We found no statistically significant associations between T50 and total hip or total spine BMD in analyses adjusted for variables including age, BMI, kidney function, vitamin D, and PTH. (Table 2)
Table 1.
Selected characteristicsa by T50 tertiles in community-living older men (MrOs) (random sub-cohort only, n=149)
| T50 Tertile I | T50 Tertile II | T50 Tertile III | P-valuec | |
|---|---|---|---|---|
| T50 range (min) | 206–314 | 314–361 | 361–477 | |
| N | 50 | 50 | 49 | |
| Age (years) ± SD | 75.1 (±5.8) | 73.3 (±4.7) | 72.3 (±4.3) | 0.02 |
| Black, N (%) | 4 (8.0) | 2 (4.0) | 2 (4.1) | 0.15 |
| Clinical Center, N (%) | ||||
| Birmingham | 21 (42.0) | 19 (38.0) | 22 (44.9) | 0.78 |
| Portland | 29 (58.0) | 31 (62.0) | 27 (55.1) | |
| > High school education, N (%) | 42 (84.0) | 43 (86.0) | 35 (71.4) | 0.14 |
| BMI (kg/m2) ± SD | 27.7 (±3.9) | 27.8 (±3.8) | 27.0 (±3.5) | 0.48 |
| Alcohol intake (drinks/wk) ± SD | ||||
| <1 drink/week | 24 (48.0) | 26(53.1) | 24 (50.0) | 0.88 |
| 1+ drinks/week | 26 (52.0) | 23 (46.9) | 24 (40.0) | |
| Smoking status, N (%) | ||||
| Never | 10 (20.0) | 21 (42.0) | 20 (40.8) | 0.15 |
| Former | 37 (74.0) | 27 (54.0) | 27 (55.1) | |
| Current | 3 (6.0) | 2 (4.0) | 2 (4.1) | |
| Physical activity score ± SD | 146.5 (±83.7) | 159.3 (±84.6) | 161.2 (±66.5) | 0.60 |
| Prevalent CVD, N (%) | 10 (20.0) | 13 (26.0) | 6 (12.2) | 0.22 |
| ABI, N (%) | ||||
| <0.9 | 7 (14.0) | 2 (4.1) | 1 (2.0) | 0.11 |
| 0.9 to <1.4 | 42 (84.0) | 47 (95.9) | 47 (95.9) | |
| >=1.4 | 1 (2.0) | 0 | 1 (2.0) | |
| Hypertension, N (%) | 21 (42.0) | 23 (46.0) | 19 (38.8) | 0.77 |
| Diabetes, N (%) | 6 (12.0) | 11 (22.0) | 0 | <0.01 |
| eGFR (ml/min/1.73m2) ± SD | 75.5 (±18.2) | 82.6 (±15.1) | 82.3 (±18.0) | 0.07 |
| Calcium (mg/dL) ± SD | 9.3 (±0.4) | 9.2 (± 0.4) | 9.3 (±0.4) | 0.43 |
| Phosphate (mg/dL) ± SD | 3.2 (±0.5) | 3.2 (± 0.4) | 3.1 (±0.4) | 0.13 |
| PTH (pg/ml) ± SD | 33.4 (±16.3) | 31.2 (±13.2) | 29.2 (±9.9) | 0.32 |
| 25(OH) Vitamin D (ng/ml) ± SD | 22.9 (±8.3) | 23.7 (±7.5) | 24.3 (±6.8) | 0.65 |
| Mean total hip BMD (g/cm2) ± SD | 0.9 (±0.2) | 0.9 (+0.1) | 0.9 (±0.1) | 0.44 |
| Mean total spine BMD (g/cm2) ± SD | 1.0 (±0.2) | 1.0 (±0.2) | 1.0 (±0.2) | 0.99 |
Variables from baseline (not available at dental visit 1): education level, PASE score, CVD (stroke or MI), ABI, hypertension, diabetes, eGFR, Calcium, Phosphate, history of any fracture, history of hip fracture.
Table 2.
Linear regression of the association between T50 and total hip and total spine BMD
| Total hip BMD (g/cm2) | Beta (95% Cl) | P-value | |
|---|---|---|---|
| Model 1 | 0.000009 (−0.0004, 0.0004) | 0.97 | |
| Model 2 | <–0.0001 (−0.0005, 0.0005) | 1.00 | |
| Total spine BMD (g/cm2) | |||
| Model 1 | −0.0002 (−0.0007, 0.0004) | 0.50 | |
| Model 2 | <–0.0001 (−0.0007, 0.0006) | 0.91 | |
Model 1: Unadjusted
Model 2: Adjusted for age, race, clinical center, BMI, physical activity, PTH, vitamin D, eGFR, Calcium, and Phosphate
In conclusion, T50, a novel indicator of serum calcification propensity was not associated with BMD in a random sample from the MrOS study of community-living older men. Shorter T50 is a robust indicator for soft tissue calcification and cardiovascular disease in high risk populations. We observed non-significant trends between shorter T50 and higher prevalence of CVD and lower ankle brachial index in community-living men. These findings were not statistically significant but should be re-evaluated in larger study samples in future studies to determine if T50 may give insights to cardiovascular disease risk above and beyond traditional risk factors in the general population.
ACKNOWLEDGEMENTS
Dr. Alexander L. Bullen was supported by a Ruth L. Kirschstein training grant from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK; T32DK104717). Dr. Joachim H. Ix was supported by a midcareer mentoring award from the NIDDK (K24DK110427).
The Osteoporotic Fractures in Men (MrOS) Study is supported by National Institutes of Health funding. The following institutes provide support: the National Institute on Aging (NIA), the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), the National Center for Advancing Translational Sciences (NCATS), and NIH Roadmap for Medical Research under the following grant numbers: U01 AG027810, U01 AG042124, U01 AG042139, U01 AG042140, U01 AG042143, U01 AG042145, U01 AG042168, U01 AR066160, and UL1 TR000128.
Footnotes
CONFLICTS OF INTEREST
Andreas Pasch is an inventor of the T50-Test and co-founder, stock-holder, and employee of Calciscon Ltd., Nidau, Switzerland, which commercializes the T50-Test. Dr Orwoll has received research support from Lilly and Mereo Biopharma, and has provided consulting for Bayer. Alexander L Bullen, Cheryl A.M Anderson, Elizabeth R. Hooker, Deborah M. Kado, and Joachim H. Ix declare that they have no conflict of interest.
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