Urinary bone resorption biomarkers

Martini and Wood (2002) tested the bioavailability of 3 different sources of Ca in 12 healthy elderly subjects (9 women and 3 men of mean SEM age 70 3 and 76 6 years, respectively) in a 6-week crossover trial conducted in a Human Study Unit. Each Ca source supplied 1000 mg Ca/day and was ingested for 1 week with meals (as 500 mg Ca 2x/day), thus contributing to a high-Ca intake (1300 mg Ca/day). A low-Ca intake (300 mg Ca/day strictly from the basal diet) was adhered to for 1 week in-between each treatment. The Ca sources included skim milk, CCM-fortified OJ, and a dietary supplement of CaCOa. Assessment parameters were indirect measures predicted to reflect the relative bioavailability of Ca postprandially via an acute PTH suppression test (hourly for 4h). Longer-term responses to Ca supplementation were assessed via a number of urinary and serum hormone, mineral, and bone resorption biomarkers (i.e., vitamin D, Ca, phosphorus, and collagen t) e 1 N-telopeptide cross-links). 

Horiuchi et al., 2000 Japanese postmenopause n = 85 Women with a high soy protein intake showed less bone loss and higher BMD at the lumbar spine Biomarkers urinary deoxypyridinoline (bone resorption) decreased... 

During the last decade, commercially available kits have made available for plasma/serum and urinary biomarkers of bone formation and bone resorption. Some of the assays have been shown to be applicable in rats and dogs, but not all assays work across the species, and there is inherent variability with these markers. Some of the tests are listed in Table 6.6, and a number of references are provided. These tests will have a place in animal models, and they may be useful efficacy markers in the development of novel therapeutic agents. 

The AHRQ Report summarized numerous studies that evaluated the effects of soy products, including both protein and isoflavones, on various markers of bone health, such as bone mineral density (BMD) and biomarkers related to bone formation (bone-specific alkaline phosphatase and osteocalcin) and resorption (urinary hydroxyproline, urinary pyridinoline, and urinary deoxypyridinoline). In general, no effect of soy consumption on BMD or on biomarkers of bone formation resulted. Although a number of studies observed reductions in markers of bone resorption, these were restricted to only two biomarkers urinary pyridinoline and deoxypyridinoline. Moreover, the effects were not consistent across studies. The AHRQ report found no consistent evidence of dose-response effects for either soy isoflavones or soy protein on markers of bone turnover (Balk et al., 2005). 

Biomarkers of bone turnover (serum osteocalcin, urinary DPD, serum BAP, etc.), typically included in studies with 3-6 month intervention duration, are also inconsistent in their response to soy product interventions these studies are described in more detail elsewhere (Coxam 2008). Meta-analyses of these trials revealed a moderate decrease in the bone resorption marker, urinary DPD, n = 887) but there were no effects on serum BAP or serum osteocalcin (Taku et al. 2010b). Intervention studies that include fracture as an outcome variable would be the optimum route for making conclusive assessments of the efficacy of SI in the prevention of OP, but very large numbers of participants would be required to achieve adequate statistical power. In the absence of data of this quality, the only recommendation is that including SF in the diet will not adversely affect bone health and might yield skeletal benefits in the long term. 

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