Sclerostin and Biomarkers of Bone Health, Energy and Vitamin D Status in Elite Male Athletes

Sclerostin is a hormone secreted by osteocytes that inhibits bone formation and is affected by mechanical loading. Few studies have investigated serum sclerostin levels in athletes and no investigations have focused on elite long-distance runners. PURPOSE: The aim of this study was to investigate serum levels of sclerostin in male and female long-distance runners and to explore their association with bone mineral density (BMD), bone turnover, energy and vitamin D status. METHODS: Twenty-five elite distance runners (23±6 yrs; M=13, F=12) had their BMD assessed by dual energy x-ray absorptiometry (DXA) and blood samples taken in the fasted state and before exercise on one occasion. Blood samples were analysed for serum sclerostin, N-terminal propeptide of procollagen type 1 (P1NP), C-terminal telopeptide of type 1 collagen (CTX), 25 hydroxy vitamin D [25(OH)D] and free triiodothyronine (fT3) levels. Comparisons between M and F were made using independent t-tests with Bonferroni correction. Analysis of covariance was used to control for potential confounders when making comparisons and Pearson correlations analysed variables for relationships. RESULTS: Serum sclerostin levels were not significantly different between males and females (0.45±0.10 ng/mL versus 0.41±0.12 ng/mL unpaired t-test, P=0.398). In males, serum sclerostin correlated positively with CTX (r=0.72, p=0.006) and fT3 (r=0.62, p=0.023) and this association remained significant after adjustments for age and weight. No other significant associations were observed for sclerostin and any other biomarkers. CONCLUSIONS: Serum sclerostin levels in elite distance runners were not influenced by sex, but were significantly associated with biomarkers of bone resorption and may be related to energy availability in elite male distance runners. Further research is needed to explore the clinical implications of measuring sclerostin in elite distance runners.