Effects of Daily Physical Activity and Body Composition on Bone Turnover Markers in Young Adult Men

Presentation Number: SAT 336
Date of Presentation: April 2nd, 2016

Charlotte Verroken, Bruno Lapauw, Hans-Georg Zmierczak, Stefan Goemaere and Jean-Marc Kaufman*
Ghent University Hospital, Gent, Belgium

Abstract

BACKGROUND: Biochemical markers of bone turnover are higher in young adult men than in middle-aged men or young adult women. Nonetheless, little is known about the determinants of bone turnover in young men.

OBJECTIVE: We aimed to explore the associations of body composition, daily physical activity, and parameters reflecting mechanical loading with bone turnover in a cohort of healthy young men.

METHODS: A cross-sectional, population-based sibling-pair study was conducted in 1001 healthy men aged 25-45 years (mean age 34.5 ± 5.5 years). Bone turnover markers were measured from fasting serum samples using an electrochemiluminescence technique and include osteocalcin (OC) and procollagen type 1 amino-terminal propeptide (P1NP) as markers of bone formation, and C-terminal telopeptide of type 1 collagen (CTX) as a marker of bone resorption. Body composition (including whole body total fat and lean mass) was assessed using DXA. Physical activity levels at work, during sports activities, and during leisure time excluding sport were scored using the questionnaire as proposed by Baecke et al (1). Parameters reflecting mechanical loading include pQCT-derived muscle cross-sectional area (CSA) at the forearm and lower leg (66% from distal end point), grip strength, and biceps and quadriceps peak torque. Cross-sectional relationships were assessed using linear mixed-effects modeling.

RESULTS: Median OC, P1NP and CTX levels were 21.7 (25th–75th percentile 18.5-26.3) µg/L, 50.8 (41.7-63.7) µg/L and 0.41 (0.31-0.52) µg/L and correlated inversely with age (ß=-0.37 for OC, ß=-0.37 for P1NP and ß=-0.33 for CTX, p<0.001). In age and height-adjusted analyses, all bone turnover markers were inversely associated with fat mass (ß=-0.21, ß=-0.13 and ß=-0.19, p<0.001), and OC and CTX were inversely associated with lean mass (ß=-0.15 and ß=-0.09, p≤0.009). When fat and lean mass were both included in the regression models, only fat mass remained an independent determinant of the bone turnover markers (ß=-0.20, ß=-0.16 and ß=-0.21, all p<0.001). Sport index but not total physical activity correlated positively with the bone turnover markers after adjustment for age, height and body composition (ß=0.09, ß=0.11 and ß=0.07, p≤0.020). No associations were found between the bone turnover markers and muscle CSA, grip strength, or biceps or quadriceps peak torque.

CONCLUSION: Whereas bone turnover in healthy young men correlates inversely with the amount of fat mass and positively with physical activity levels during sports activities, it is not associated with the amount of lean mass or other parameters reflecting mechanical loading. These findings suggest that the relatively high levels of biochemical markers of bone turnover in young adult men may only for a minor part be explained by higher physical activity.

 

Nothing to Disclose: CV, BL, HGZ, SG, JMK