Albumin-to-alkaline phosphatase ratio may be a better predictor of survival than sclerostin, dickkopf-1, osteopontin, osteoprotegerin and osteocalcin

Objectives

The value of biochemical markers of bone turnover (BTMs) in predicting survival and disease remains unclear. In a prospective study we evaluated the novel biomarkers for bone turnover sclerostin, dickkopf-1 (DKK-1), osteopontin (OPN), osteoprotegerin (OPG) and osteocalcin (OC), as well as a traditional biomarker, alkaline phosphatase (ALP) in relation to risk of mortality, cardiovascular events and fractures.

Participants

and Methods:Routine blood tests and serum BTMs, including ALP, were analyzed in patients with hip fracture n = 97, stroke n = 71 and healthy volunteers n = 83 (mean age 86, 83 and 77, respectively), followed for 7 years. Hazard Ratios (HR) were calculated for mortality, cardiovascular events and fractures in relation to these biomarkers. After adding the albumin-to-ALP ratio (AAPR) a post hoc analysis was performed.

Results

120 participants died during the study. In the entire group of patients and volunteers (n = 251) higher AAPR (HR 0.28, 95 % CI 0.14-0.59, p < 0.001) was associated with decreased mortality. OPN and OPG were associated with mortality risk only in the univariate statistical analysis. HR for high AAPR in relation to new cardiovascular events was borderline significant (HR 0.29, 95 % CI 0.08-1.06, p = 0.061). None of the examined biomarkers were associated with new fractures, nor with an increased risk of a new cardiovascular event.

Conclusions

AAPR may be a better predictor of mortality than the more novel BTMs, and higher AAPR could be associated with longer life expectancy. Further studies should determine the clinical usefulness of AAPR as a biomarker of mortality and cardiovascular disease.

Serum levels of the bone turnover markers dickkopf-1, sclerostin, osteoprotegerin, osteopontin, osteocalcin and 25-hydroxyvitamin D in Swedish geriatric patients aged 75 years or older with a fresh hip fracture and in healthy controls

BACKGROUND

Bone turnover markers have a potential clinical use in describing bone remodeling and in predicting fractures.

AIMS

In an elderly population ≥75 years with a fresh hip fracture, and in healthy controls, investigate bone turnover markers and their relation to each other, to vitamin D status and to bone mineral density (BMD).

METHODS

In a cross-sectional study serum levels of dickkopf-1 (DKK-1), sclerostin (SOST), osteoprotegerin (OPG), osteopontin (OPN), osteocalcin, 25-hydroxyvitamin D (25(OH)D) were analyzed in 89 Swedish patients with a fresh hip fracture and in 82 healthy volunteers. Serum levels of bone markers were determined by Luminex technique.

RESULTS

S-25-hydroxyvitamin D (S-25(OH)D) was decreased in patients compared to controls (48 ± 21 vs. 76 ± 25 nmol/L, p < 0.001). SOST, but none of the other bone turnover markers correlated with BMD (r = 0.50, p < 0.001). Compared with controls, higher levels of OPG (488 ± 1.4 vs. 191 ± 1.4 ng/L, p < 0.001), OPN (69 ± 1.7 vs. 19 ± 1.4 µg/L, p < 0.001), DKK-1 (273 ± 1.7 vs. 168 ± 1.7 ng/L, p < 0.001), and lower levels of osteocalcin (5.8 ± 3.5 vs. 9.5 ± 3.6 µg/L, p < 0.001), were found in the fracture group. Levels of OPG, DKK-1 and SOST in both groups were positively associated. S-25(OH)D concentration was not found to be strongly associated with any of the bone markers.

CONCLUSIONS

In contrast to findings in other studies, we found no strong correlation between 25(OH)D and the investigated bone markers. Both in patients with a fresh hip fracture and in healthy elderly, DKK-1, SOST and OPG appear to be associated. This suggests a relevance in these relationships meriting further investigation.

Contrasting effects of platelet-derived growth factor (PDGF) isomers on mitogenesis, contraction and intracellular calcium concentration in human vascular smooth muscle

The present study was aimed at characterizing the responses of human vascular smooth muscle to all three dimeric isomers of platelet-derived growth factor (PDGF-AA, -AB and -BB) in terms of mitogenesis, contraction and intracellular calcium concentration. The potential of interaction between PDGF and endothelin-1 (ET-1) was also investigated. All three PDGF isoforms (0.1-20 ng mL-1) stimulated DNA synthesis in cultured human coronary artery and saphenous vein vascular smooth muscle cells (VSMC), measured by [3H]thymidine incorporation. PDGF-AB and -BB elicited comparable large increases in DNA synthesis of maximum 595 +/- 149% (P = 0.001, n = 9) and 576 +/- 17% (P < 0.001, n = 5), respectively, whereas PDGF-AA was only weakly mitogenic (61 +/- 16% increase; P < 0.05, n = 3). At a threshold concentration, PDGF acted in synergy with ET-1 to enhance DNA synthesis (816 +/- 337% increase; P < 0.05, n = 7). In contrast to mitogenesis, none of the three PDGF isomers had any effect on contraction of human saphenous veins in vitro, nor did they affect the contractile response to ET-1, 5-HT or the thromboxane mimetic U46619. The effects of the three PDGF isomers on intracellular calcium ([Ca2+]i) rises in cultured human VSMC were heterogeneous, with PDGF-BB inducing the largest increase in [Ca2+]i (442 +/- 53 nmol L-1) vs. PDGF-AB (290 +/- 28 nmol L-1), whilst PDGF-AA had no effect. Both the responses to PDGF-AB and-BB relied upon intracellular calcium release, whilst only PDGF-AB showed additional dependence on influx of extracellular calcium. In summary, PDGF is strongly mitogenic and comitogenic with ET-1, despite not being a vasoconstrictor, for human VSMC. Also, human VSMC showed heterogeneous responses to the three PDGF isoforms. These results implicate PDGF, and in particular the PDGF receptor-beta, as important role players in the development of vascular smooth muscle-mediated intimal thickening in humans.