Serum β-2 microglobulin is a marker of high bone remodelling in elderly women

Abstract

β-2 microglobulin ( β2m), the water soluble extrinsic light chain of class I MHC, has been recently isolated from the adult bone culture medium. Serum β2m plays a role as a bone-derived growth factor regulating both osteoblast and osteoclast cell activity. Serum β2m has been proposed as a bone remodeling biological marker in high bone turnover conditions. The purpose of our study was to determine the relationship between β2m and vitamin D status in post-menopausal women. We have studied 44 healthy women from 20 to 80 years with normal hepatic and renal function, without diabetes mellitus and/or inflammatory, tumoral or infectious diseases. We measured the serum levels of calcium, phosphorus, parathyroid hormone (PTH), vitamin D binding protein (DBP), 25-OHD 3 (calcidiol), 1,25(OH) 2D 3 (calcitriol) and β2m. Serum β2m levels increased with age ( r=0.54, P<0.001). Post-menopausal women had higher serum levels than pre-menopausal women of β2m (1.76±0.22 mg/l vs. 1.35±0.2 mg/l, P<0.01); PTH (61.5±7.5 ng/ml vs. 39±6 ng/ml, P<0.001) and lower serum levels of 25-OHD 3 (7.5±2.3 ng/ml vs. 18.2±2.5 ng/ml, P<0.001). Moreover, serum levels of β2m were negatively correlated with 25-OHD 3 ( r=−0.34, P<0.05) and with ionized calcium ( r=−0.45, P<0.01) and positively with PTH ( r=0.48, P<0.01). These results support the role of β2m as a regulator of bone metabolism and its potential use as a marker of high bone turnover in post-menopausal women, specially in elderly women with vitamin D deficiency and secondary hyperparathyroidism.