Circulating levels of inflammatory markers predict change in bone mineral density and resorption in older adults: a longitudinal study.

CONTEXT: IL-1, IL-6, and TNF-alpha play an important role in the pathogenesis of osteoporosis in animals; however, evidence that these play a similar role in bone loss in human studies is limited. OBJECTIVE: Our objective was to determine the associations between serum markers of inflammation and changes in bone mineral density (BMD) and urinary pyridinoline (PYR) to creatinine (Cr) ratio over 2.9 yr in older adults. METHODS: A total of 168 randomly selected subjects (mean 63 yr, range 52-78, 48% female) was studied. BMD was measured by dual-energy x-ray absorptiometry at baseline (mean T score: -0.18 to -0.61) and 2.9 yr later. Serum high-sensitivity (hs) C-reactive protein (CRP), IL-6, TNF-alpha, and the urinary PYR/Cr ratio were measured on both occasions. RESULTS: The mean annual loss of BMD was 0.15, 0.15, and 0.34% at total body, spine, and hip, respectively. Change in total body BMD was associated with baseline hs-CRP, IL-6, and TNF-alpha, as well as change in hs-CRP (beta: -0.41%/U, 95% confidence interval -0.68%, -0.15%) and IL-6 (beta: -0.62%/U, 95% confidence interval -1.01%, -0.23%). If these markers were put in the same predictive model, only IL-6 remained largely unchanged. Changes in other BMD sites were significantly predicted by IL-6 (hip and spine) and TNF-alpha (spine only). Finally, change in the PYR/Cr ratio was positively associated baseline IL-6, hs-CRP, and their changes (all P < 0.05) in women, but not men. CONCLUSIONS: Variation within the low levels of inflammatory markers observed in this study, especially IL-6, predicts bone loss and resorption, suggesting that targeted antiinflammatory therapy has potential for the prevention of osteoporosis.

A prospective study of urinary electrolytes and bone turnover in adolescent males.

BACKGROUND & AIMS: The role of excessive salt on bone metabolism in children is uncertain. The aim of this 6-week prospective study was to describe the association between urinary electrolytes and bone turnover markers in a convenience sample of adolescent boys (N = 136, mean age 16 yr). METHODS: Urinary electrolytes (sodium, potassium, calcium and magnesium) were assessed on spot overnight urines on three occasions to minimise regression dilution bias. Bone turnover was assessed by bone specific alkaline phosphatase (BAP) and urinary pyridinoline (PYR) at baseline and follow up. RESULTS: In multivariate analysis, urinary sodium (but not other electrolytes) was positively associated with both PYR and BAP both before and after taking short-term growth into account (both p < 0.05) and explained 3-6% of the variation in bone turnover markers. Urinary sodium was associated with urinary magnesium (r = +0.26, p < 0.05) but only weakly with calcium (r = +0.18, p = 0.08). Urinary potassium was significantly associated with urinary magnesium (r = -0.24, p < 0.05). CONCLUSION: High urinary sodium (which largely reflects dietary sodium intake in our location) results in a high bone turnover state in adolescent boys which is most likely detrimental for bone. Other urinary electrolytes are not related to bone turnover but may influence bone via other pathways.