Relatively High Bone Mineral Density in Chinese Adolescent Dancers Despite Lower Energy Intake and Menstrual Disorder

Objective The effect of dietary restriction, intense exercise and menstrual dysfunction on bone mineral density remains controversial. The aim of this study was to assess the skeletal health status and relationship between bone mineral density and nutrient intake, menstrual status, estrogen level and other factos in Chinese adolescent dancers. Methods Sixty dancers and 77 healthy controls underwent measurements of bone density, body composition, and estrogen level. Nutrient intake, menstrual status and physical activity were assessed with questionnaires. The correlation between these factors were analyzed. Results The dancers under study had a significantly lean body mass index （18.3±1.4 kg/m^2 vs. 21.7±3.1 kg/m^2）, lower percentage of body fat （0.25±0.05 vs. 0.34±0.04） and later age at menarche （14.0±0.9 y vs. 13.0±1.3 y）, and the estrogen level, daily calorie and fat intake in them were also lower than in the controls. All the dancers undertook intensive physical activity every day and up to 69% of them suffered from irregular menarche. Yet they had relatively high BMD and BMC of the total body and legs than the controls after adjusting for BM1 and age. Site-specific BMD was positively correlated to BMI, body composition and training hours per week and negatively correlated to the age at menarche and menstrual frequency. Conclusions The relatively high BMD and BMC of the dancers at the total body and legs were probably caused by high levels of weight-bearing physical activity. To ameliorate disordered eating, especially low energy intake might be helpful to prevent the Triad and to improve the bone health in adolescent dancers.

Association between Adiponectin and Metabolic Syndrome in Older Adults from Major Cities of China

Objective To investigate the association between adiponectin and metabolic syndrome （MetS） and related diseases in older adults from major cities of China. Methods A total of 2 049 adults at the age of 60-96 years from18 major cities of China were enrolled in the study. Plasma adiponectin and insulin concentrations were measured. Insulin resistance was assessed by homeostasis model assessment of insulin resistance （HOMA-IR）. The definitions proposed by International Diabetes Federation （IDF） and American Heart Association/National Heart, Lung, and Blood/nstitute （AHA/NLHBI） were used to identify MetS. Results The adiponectin concentration increased with the advance of age and was higher in women than in men. The sex specific adiponectin concentration was inversely correlated with body mass index （BMI）, waist circumference, diastolic blood pressure, triglycerides, glucose and fasting blood insulin, and positively correlated with HDL-C （P〈0.001）. The adiponectin concentration decreased with increasing MetS components. Compared with the 4th sex-specific adiponectin quartile, the odds ratio （OR） for prevalent MetS-IDF and MetS-AHA/NLHBI in subjects of the 1st quartile group was 3.25 （95% CI： 2.24, 4.71） and 3.21 （95% CI： 2.26, 4.55）, respectively. The association was independent of age, sex, life-style factors, medication, family history of chronic diseases, BMI, and HOMA-IR, The OR for MetS was much higher than those of MetS components and its related diseases. Conclusion Adiponectin is strongly associated with MetS independent of insulin resistance and obesity in older adults from major cities in China. The adiponectin concentration is a useful predictor for the risk of MetS.

Correlation of Serum Leptin Level with Bone Mineral Density and Bone Turnover Markers in Chinese Adolescent Dancers

Objective To investigate plasma leptin concentrations in adolescent female dancers and to determine whether leptin has some effects on their bone mineral density （BMD） and bone turnover markers. Methods Sixty dancers aged 15-17 years and 77 healthy controls were enrolled in the study. Bone mineral density （BMD） and body composition were detected by dual energy X-ray absorptiometry. Serum leptin concentrations were measured by radioimmunoassay （RIA）. Two bone turnover markers, bone-specific alkaline phosphatase （BAP） and tartrate-resistant acid phosphatase（TRACP）, were determined by ELISA. Results The dancers had a lower fat mass and a lower leptin level than the controls, while they had a relatively higher BMD of the total body and legs after adjustment for BMI and age. The levels of bone resorption and formation of markers were higher in the dancers than in the controls. Leptin was positively correlated with BMI, body weight, fat mass, and percentage of body fat. In dancers, Leptin was positively correlated with the BMD of the total body and the left leg. However, after adjustment for BMI, no correlation of serum leptin concentrations with BMD values was found in either dancers or controls. Nor correlation was found between leptin and bone turnover markers after adjustment for BMI. Conelusion The leptin profile is different between the controls and the dancers with a lower BMI and a lower fat mass. Circulating plasma leptin level depends on BMI and is not a direct determinant of BMD in Chinese adolescent dancers.