Bone mass, vitamin D levels and immunosuppressive treatment in patients with liver transplant and risedronate treatment

Abstract

As bone matures type I collagen undegoes β isomerisation at the DG motif of the CTX epitope. Measurements of αCTX and βCTX allow us to distinguish between bone turnover in newly formed and mature bone, respectively. In states of pathologically high bone turnover such as Paget's and malignant bone diseases, there is a relatively greater increase in the resorption of newly formed bone. Treatment of these with bisphosphonates results in a relatively greater decrease in the resorption of newly formed bone. The aims were to investigate 1) the relative increase in αCTX in postmenopausal osteoporosis and 2) the relative decrease in αCTX with bisphosphonate treatment. We recruited 60 postmenopausal women (mean age 68: range 55-85) with a BMD T-score of <2.5 or <1 and a fracture. They were randomised into 3 treatment groups: ibandronate (n=19), alendronate (n=23) and risedronate (n=18). 75 healthy premenopausal women (mean age 38: range 30-45) were recruited. We measured α and βCTX (Nordic Biosciences Diagnostics, Copenhagen, Denmark) in second morning void urine samples and serum βCTX (Roche Diagnostics, Pensberg, Germany). The median urinary α and βCTX and serum βCTX were significantly lower in healthy premenopausal compared to postmenopausal osteoporotic women at baseline 62%, 110% and 65% respectively (P<0.0001). The median urinary α and βCTX and serum βCTX showed a significant decrease by 68%, 88%, and 79% from baseline respectively (P<0.0001) after 13 weeks of treatment. The α/β CTX ratio increased by 62% (P<0.05). We conclude that resorption of type I collagen in postmenopausal osteoporosis is greater compared to healthy premenopausal women. There is no relative greater increase in the resorption of newly formed bone. With bisphosphonate treatment, the resorption of type I collagen is decreased after 13 weeks of treatment, but there is no greater decrease in the relative resorption of newly formed bone. In fact, there is a preferential decrease in the resorption of mature bone.