Bone Turnover Markers and Osteokines in Adolescent Female Athletes of High- and Low-Impact Sports Compared With Nonathletic Controls.

This study examined differences in resting concentrations of markers of bone formation and resorption, and osteokines between female adolescent (12-16 y) swimmers, soccer players, and nonathletic controls. Resting, morning blood samples were obtained after an overnight fast from 20 swimmers, 20 soccer players, and 20 nonathletic controls, matched for age. carboxyl-terminal cross-linking telopeptide of type I collagen (CTX), amino-terminal propeptide of type I collagen (P1NP), total osteocalcin (OC), sclerostin, osteoprotegerin (OPG), and receptor activator of nuclear factor kappa B ligand (RANKL) were analyzed in serum. After controlling for percent body fat, there were no significant differences between swimmers and nonathletic controls in any of the measured markers. In contrast, soccer players had significantly higher P1NP (89.5 [25.6] ng·mL-1), OC (57.6 [22.9] ng·mL-1), and OPG (1052.5 [612.6] pg·mL-1) compared with both swimmers (P1NP: 66.5 [20.9] ng·mL-1; OC: 24.9 [12.5] ng·mL-1; OPG: 275.2 [83.8] pg·mL-1) and controls (P1NP: 58.5 [16.2] ng·mL-1; OC: 23.2 [11.9] ng·mL-1; OPG: 265.4 [97.6] pg·mL-1), with no differences in CTX, sclerostin, and RANKL. These results suggest that bone formation is higher in adolescent females engaged in high-impact sports like soccer compared with swimmers and controls.

Twelve weeks of a diet and exercise intervention alters the acute bone response to exercise in adolescent females with overweight/obesity.

Introduction: Exercise and consumption of dairy foods have been shown to improve bone mineralization. However, little is known about the magnitude and timing of their synergistic effects on markers and regulators of bone metabolism in response to acute exercise in adolescent females with obesity, a population susceptible to altered bone metabolism and mineral properties. This study examined the influence of twelve weeks of exercise training and nutritional counselling on the bone biochemical marker response to acute exercise and whether higher dairy consumption could further influence the response. Methods: Thirty adolescent females (14.3 ± 2.0 years) with overweight/obesity (OW/OB) completed a 12-week lifestyle modification intervention involving exercise training and nutritional counselling. Participants were randomized into two groups: higher dairy intake (RDa; 4 servings/day; n = 14) or low dairy intake (LDa; 0-2 servings/d; n = 16). Participants performed one bout of plyometric exercise (5 circuits; 120 jumps) both pre- and post-intervention. Blood samples were taken at rest, 5 min and 1 h post-exercise. Serum sclerostin, osteocalcin (OC), osteoprotegerin (OPG), receptor activator nuclear factor kappa B ligand (RANKL), and C-terminal telopeptide of type 1 collagen (ßCTX) concentrations were measured. Results: While there was an overall increase in sclerostin pre-intervention from pre to 5 min post-exercise (+11% p = 0.04), this response was significantly decreased post-intervention (-25%, p = 0.03) independent of dairy intake. The OPG:RANKL ratio was unresponsive to acute exercise pre-intervention but increased 1 h post-exercise (+2.6 AU; p < 0.001) post-intervention. Dairy intake did not further influence these absolute responses. However, after the 12-week intervention, the RDa group showed a decrease in the relative RANKL post-exercise response (-21.9%; p < 0.01), leading to a consistent increase in the relative OPG:RANKL ratio response, which was not the case in the LDa group. There was no influence of the intervention or dairy product intake on OC, OPG, or ßCTX responses to acute exercise (p > 0.05). Conclusion: A lifestyle modification intervention involving exercise training blunts the increase in sclerostin and can augment the increase in OPG:RANKL ratio to acute exercise in adolescent females with OW/OB, while dairy product consumption did not further influence these responses.

Testing the Functional Model of Bone Development: Direct and Mediating Role of Muscle Strength on Bone Properties in Growing Youth.

This study examines the functional model of bone development in peri-pubertal boys and girls. Specifically, we implemented a mixed-longitudinal design and hierarchical structural models to provide experimental evidence in support of the conceptual functional model of bone development, postulating that the primary mechanical stimulus of bone strength development is muscle force. To this end, we measured radial and tibial bone properties (speed of sound, SOS), isometric grip and knee extensors strength, bone resorption (urinary NTX concentration), body mass index (BMI), somatic maturity (years from peak height velocity) and skeletal maturity (bone age) in 180 children aged 8-16 years. Measurements were repeated 2-4 times over a period of 3 years. The multilevel structural equation modeling of 406 participant-session observations revealed similar results for radial and tibial SOS. Muscle strength (i.e., grip strength for the radial and knee extension for tibial model) and NTX have a significant direct effect on bone SOS (ß = 0.29 and -0.18, respectively). Somatic maturity had a direct impact on muscle strength (ß = 0.24) and both a direct and indirect effect on bone SOS (total effect, ß = 0.30). Physical activity and BMI also had a significant direct impact on bone properties, (ß = 0.06 and -0.18, respectively), and an additional significant indirect effect through muscle strength (ß = 0.01 and 0.05, respectively) with small differences per bone site and sex. Muscle strength fully mediated the impact of bone age (ß = 0.14) while there was no significant effect of energy intake on either muscle strength or bone SOS. In conclusion, our results support the functional model of bone development in that muscle strength and bone metabolism directly affect bone development while the contribution of maturity, physical activity, and other modulators such as BMI, on bone development is additionally modulated through their effect on muscle strength.

Dairy product intake decreases bone resorption following a 12-week diet and exercise intervention in overweight and obese adolescent girls.

BACKGROUND: We examined whether increased dairy intake was associated with changes in the levels of bone-related biochemical markers in overweight/obese adolescent girls undergoing a 12-week diet and exercise intervention. METHODS: Thirty-five girls were assigned to a low dairy group (LDa; 0-2 servings/day; n = 16) or a higher dairy group (RDa; 4 servings/day; n = 19). Morning, fasted/resting blood samples were collected before and after the intervention and serum concentrations of procollagen-type-1-N-terminal-propeptide (P1NP), ß-isomerized-C-terminal-cross-linking-telopeptides (ß-CTX), osteocalcin (OC), 25-hydroxyvitamin-D, sclerostin and parathyroid hormone were measured. RESULTS: At baseline, there were no significant differences between groups in any bone variable. Changes (∆) over time in ß-CTΧ (p = 0.035; interaction) and OC (p = 0.015; interaction) were significantly different between groups characterized by decreases in RDa and increases in LDa. P1NP and P1NP:ß-CTX ratio decreased in both groups (main time effects: p = 0.003, p = 0.041, respectively). ∆ß-CTX (r = -0.37; p = 0.028) and ∆OC (r = -0.39; p = 0.021) were correlated with average number of dairy servings consumed during the study and with each other (r = 0.45; p = 0.006). ∆OC was not correlated with ∆P1NP (r = 0.19; p = 0.27). CONCLUSIONS: Our results suggest that the osteogenic response to a diet and exercise program in this population can be improved with increased dairy intake via a decrease in bone resorption. IMPACT: We demonstrated that bone resorption significantly decreased over the intervention period in the group consuming adequate levels of dairy products compared to the group consuming little to no dairy products. Change in bone resorption was negatively correlated with average number of dairy servings consumed during the study. Our results suggest that the osteogenic response to a diet and exercise program in this population can be improved with increased dairy intake via a decrease in bone resorption. This is the first study to date to assess changes in bone marker status following a lifestyle intervention with exercise and different intakes of dairy products in a sample of OW/OB adolescent girls. We provide evidence that increased dairy product intake is associated with beneficial changes in circulating levels of bone-related biochemical markers in these girls undergoing a 12-week lifestyle (nutrition counseling and exercise training) intervention program. The main impact of our work relates particularly to the recent changes to Canada's food guide. Using the old recommendations, we demonstrated that the inclusion of 3-4 servings of mixed dairy foods per day improved bone health (primarily as a decrease in resorption) in OW/OB adolescent girls and that this level of dairy product intake appears appropriate and should still be encouraged for this age group. We also demonstrated that adolescent girls, a group that usually does not sufficiently consume dairy products, also improved their BMI percentile and nutrient intake with the inclusion of dairy products in their diets.

First-year university is associated with greater body weight, body composition and adverse dietary changes in males than females.

BACKGROUND: The transition from high school to university life is a critical time for change, often accompanied by the adoption of negative lifestyle habits including unhealthy nutrition. The purpose of this longitudinal study was to identify sex-specific changes in dietary intake and diet quality, and associated changes in body weight and composition during first-year university. METHODS: Three-hundred and one students (n = 229 females) completed food frequency questionnaires, and had their body weight, body composition, waist and hip circumference measured at the beginning and end of first-year university. Repeated-measures ANOVAs with covariate adjustments were used with variables for sex (between group) and time (within group) to assess these changes. RESULTS: Students gained body weight and fat during the year (p<0.001). Body mass Index (BMI) also significantly increased (p = 0.032). Males gained more weight (Male:3.8 kg; Female:1.8 kg), fat mass (Male:2.7 kg; Female:1.5 kg), lean mass (Male:1.1 kg; Female:0.3 kg) and BMI (Male:1.2 kg/m2; Female:0.7 kg/m2; p≤0.001 for interactions), and had greater increases in waist circumference (Male:2.7 cm; Female:1.1 cm) and waist:hip ratio (Male:0.02; Female:0.004; p<0.05 for interactions) than females. Energy intake remained the same over the year in both sexes, accompanied by an increase in alcohol (ethanol) in both sexes but more so in males than females (p = 0.011 interaction). Diet quality decreased, characterized by a reduced intake of healthy foods/beverages (p<0.05) in both sexes such as yogurt, cheese, oatmeal, breads, rice, pasta, vegetables, green salad, fruits, steak, fish, nuts and milk, and an increased consumption of unhealthy foods and beverages (p<0.05) such as donuts/cakes, fried chicken, beer and liquor. Significant interactions between sexes indicated that males displayed a more adverse and lower quality eating pattern which included greater intakes of donuts/cakes, fried chicken, beer and liquor, as well as decreased intakes of eggs and vegetables compared to females. Lastly, some dietary intake changes significantly correlated with fat mass and waist circumference change indicating that poor dietary choices were associated with increased adiposity. CONCLUSIONS: Our study demonstrated that during first-year university, both male and female students undergo unfavorable changes in nutrition and body weight/composition that significantly differ between sexes, with males showing more adverse changes. Our results can be used to inform effective sex-specific strategies and interventions to improve dietary habits during the transition to university life.

Mechanical, biochemical, and dietary determinants of the functional model of bone development of the radius in children and adolescents.

This study examined the degree to which various mechanical, biochemical, and dietary factors are related to nonweight bearing bone properties in 172 healthy peri-pubertal children (age, 11.7 ± 2.0 years). Dominant radial speed of sound (rSOS) was measured by transaxial quantitative ultrasound at distal radius. Potential modulating factors included somatic maturity offset (years from age of peak height velocity), grip strength, forearm lean cross-sectional area (CSA), physical activity, nutritional intake, and amino-terminal cross-linking propeptide (NTx), reflecting bone resorption. In a hierarchical regression, grip strength adjusted for CSA was the second most important predictor of rSOS after the maturity offset (ß = 0.22 and ß = 0.33, respectively; R2 = 0.16). When relative grip strength was added to the model the contribution of sex was no longer significant. Calcium intake was a significant predictor of rSOS only after NTx was accounted for in the model (ß = 0.17, R2 = 0.21). This may suggest that calcium's effects on the muscle-bone unit may be modulated through bone resorption. In the final model, relative grip strength together with maturity offset, dietary calcium, and NTx explained up to 21% of the variance in rSOS in this cohort of children. Therefore, during the peri-pubertal stage, size-adjusted forearm muscle strength is related to radial bone strength after controlling for maturity, with calcium intake having a potential indirect association through NTx.

The effect of adiposity on the relationship between indicators of maturity in peri-pubertal children.

BACKGROUND: Although the relation between body fatness and maturation has been the subject of much research, somatic maturity as assessed by sex-specific regression equations, has yet to be investigated in a population of overweight and obese children. AIM: To examine whether adiposity affects the relationship between somatic and skeletal maturity in peri-pubertal children and if increased adiposity is related to earlier maturation. SUBJECTS AND METHODS: A total of 172 girls and boys (12.8 ± 0.9 years of age) participated in the study. Participants were categorized as normal weight (NW, < 85(th) percentile) or overweight/obese (OW/OB, ≥ 85(th) percentile) based on body mass index and matched for chronological and skeletal age. Skeletal age was assessed across the radial and ulnar epiphyses using quantitative ultrasound. Somatic maturity was assessed as years from age of peak height velocity (aPHV), estimated using prediction equations. Peripheral adiposity was determined by the sum of two skin-folds. RESULTS: Years from aPHV was significantly higher (p < 0.001) in OW/OB girls, but not in OW/OB boys. Skeletal age was associated with years from aPHV in NW and OW/OB boys (r = 0.87 vs 0.86, p < 0.001) and girls (r = 0.83 vs 0.72, p < 0.001). Among peri-pubertal youth of similar chronological and skeletal age, OW/OB girls were more somatically mature than their NW peers. CONCLUSION: It is concluded that excess peripheral adiposity in girls may affect the estimated somatic maturity, as reflected in years from aPHV.

Factors associated with bone turnover and speed of sound in early and late-pubertal females.

This cross-sectional study examines whether maturity, body composition, physical activity, dietary intake, and hormonal concentrations are related to markers of bone turnover and tibial speed of sound (tSOS) in premenarcheal (n = 20, 10.1 ± 1.1 years) and postmenarcheal girls (n = 28, aged 15.0 ± 1.4 years). Somatic maturity was evaluated using years from age of peak height velocity (aPHV). Daily dietary intake was assessed with a 24-h recall interview, and moderate to very vigorous physical activity (MVPA) was measured using accelerometry. Plasma levels of 25-OH vitamin D, serum levels of insulin-like growth-factor 1 (IGF-1) and leptin, and serum levels of bone turnover markers including osteocalcin (OC), bone-specific alkaline phosphatase (BAP) and cross-linked N-teleopeptide of type I collagen (NTX) were measured using ELISA. OC, BAP, and NTX were significantly higher while IGF-1 and tSOS were lower in the premenarcheal group. The premenarcheal girls were more active and had higher daily energy intake relative to their body mass but there were no group differences in body mass index percentile. Maturity predicted 40%-57% of the variance in bone turnover markers. Additionally, daily energy intake was a significant predictor of OC, especially in the postmenarcheal group. IGF-1 and MVPA were significant predictors of BAP in the group as a whole. However, examined separately, IGF-1 was a predictor of BAP in the premenarcheal group while MVPA was a predictor in the postmenarcheal group. Adiposity and leptin were both negative predictors of tSOS, with leptin being specifically predictive in the postmenarcheal group. In conclusion, while maturity was the strongest predictor of bone markers and tSOS, dietary intake, physical activity, body composition, and hormonal factors further contribute to the variance in bone turnover and bone SOS in young Caucasian females. Further, the predicting factors of bone turnover and tSOS were different within each maturity group.

Quantitative bone ultrasound measurements in young females 14-23 years of age.

AIM: This study examined how transaxial quantitative ultrasound (QUS) measurements differed in young females between 14 and 23 years of age and if body composition and behavioral factors, namely, oral contraceptive (OC) use, physical activity, and calcium intake, influenced these measurements. METHODS: Participants (n = 595) were classified as nonusers or users of OC. QUS measurements were performed at the distal radius and midtibia, and the bone speed of sound (SOS) was recorded for each site. Body mass index (BMI) was calculated from body mass and height. Physical activity and dietary calcium intake were assessed using standardized questionnaires. RESULTS: Bone SOS increased significantly with increasing age (r(2) = 0.28 and 0.20 for radius and tibia, respectively, p < 0.05) but slower after age 18. OC use was not significantly associated with the QUS measurements, yet there was a significant age-by-OC use interaction (p < 0.05) for SOS of the tibia. For the nonusers of OC, age, BMI, and calcium intake were significant predictors of tibia SOS, explaining 24% of the variance in tibial SOS scores, whereas among the OC users, only age and BMI were significant predictors of tibial SOS, explaining 18% of the variance with no other variables entering in the model. Age was the only predictor of radius SOS in both groups. QUS scores increased steadily from 14 to 23 years of age in young females. CONCLUSIONS: OC use was associated with lower tibial SOS scores in early adulthood but not during adolescence, suggesting that OC use possibly may interfere with the bone development of the tibia. Furthermore, daily calcium intake demonstrated a positive relationship with the tibial SOS only in the nonusers of OC; however, this relationship was reversed for BMI irrespective of OC use.

Bone speed of sound, bone turnover and IGF-I in adolescent synchronized swimmers.

This pilot study compared bone speed of sound (SOS), bone turnover and insulin-like growth factor 1 (IGF-1) between 20 Caucasian, postmenarcheal, adolescent synchronized swimmers (SS) and 20 aged- and maturity-matched nonswimmers (NS). Daily dietary intake and physical activity levels were also assessed. Bone SOS was measured by quantitative ultrasound. Blood samples were analyzed for osteocalcin, cross-linked N-teleopeptide of type I collagen (NTx), IGF-I and 25-OH vitamin D. Although no differences in bone SOS or turnover markers were observed between groups, the lower IGF-1 and vitamin D intake found in synchronized swimmers, in combination with their higher strenuous activity levels, should be further explored.

Correlates of mucosal immunity and upper respiratory tract infections in girls.

In this study we examined whether salivary hormones, physical activity and adiposity were correlated with secretory immunoglobulin A (sIgA) and frequency of upper respiratory tract infections (URTI) in 43 early-pubertal and 59 late-pubertal girls. Physical activity was measured using accelerometers and relative body fat was assessed using bioelectrical impendence. Resting saliva samples were obtained between 1500 and 1800 hr and assayed for sIgA, cortisol and testosterone. Participants completed a one-month health log to record URTI frequency. Early-pubertal girls were more physically active, had less adiposity, but lower concentrations of sIgA than late-pubertal adolescents (122.7 +/- 91.6 vs 201.9 +/- 102.9 pg/ml, respectively). The frequency of URTI was similar in the two groups. Neither sIgA nor URTI were correlated with salivary hormones, physical activity or adiposity within the early-pubertal girls. In the late-pubertal group, sIgA was negatively associated (r = -0.44; p < 0.05) with cortisol, and positively associated (r = 0.41; p < 0.05) with the testosterone to cortisol ratio. These results suggest that mucosal immunity increases with pubertal maturation, while higher cortisol is associated with lower mucosal immunity in adolescents.