Adolescent testosterone, muscle mass and glucose metabolism: evidence from the 'Children of 1997' birth cohort in Hong Kong.

AIMS: Diabetes rates are high in Asia despite relatively low rates of obesity, which might be related to lower muscle mass. Muscle mass plays an important role in glucose metabolism. Peak muscle mass is obtained in late adolescence. We tested the hypothesis that pubertal testosterone is negatively associated with glucose metabolism mediated by muscle mass. METHODS: Participants aged 15 years (278 boys and 223 girls) were recruited from the Hong Kong's 'Children of 1997' birth cohort in 2012. Multivariable linear regression with multiple imputation and inverse probability weighting was used to examine the adjusted associations of pubertal testosterone with skeletal muscle index, body fat percentage, fasting glucose, insulin and homeostasis model of assessment - insulin resistance. RESULTS: Total testosterone was negatively associated with fasting glucose (-0.008, 95% confidence interval -0.015 to -0.002), insulin (-0.43, 95% confidence interval -0.56 to -0.30) and insulin and homeostasis model of assessment - insulin resistance (-0.09, 95% confidence interval -0.12 to -0.06) adjusted for sex, birth weight, highest parental education, mother's place of birth and physical activity. These associations were attenuated by additional adjustment for skeletal mass index or body fat percentage. CONCLUSIONS: Adolescent glucose metabolism may be influenced by testosterone, perhaps partially via skeletal muscle mass.

Genetic diversity analysis of faba bean (Vicia faba L.) germplasms using sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

To investigate genetic diversity and relationships of 101 faba bean (Vicia faba L.), landraces and varieties from different provinces of China and abroad were analyzed by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE). A total of 2625 unambiguous and stable bands from 101 germplasms were detected, and 36 different bands were classified according to the electrophoretic mobility patterns of the proteins as determined by the SDS-PAGE analysis, of which 16 were polymorphic. Besides the common bands, the protein bands of 92, 75, 62, 40, 34, 17, and 13 kDa presented the highest frequencies of 92.08, 90.10, 99.01, 95.05, 95.05, 98.02, and 95.05%, respectively. The other 29 polymorphic protein bands showed higher polymorphism with 16.09 polymorphic bands in average. The genetic similarity of the 101 genotypes tested varied from 0.6111 to 0.9722, with an average of 0.7122. Cluster analysis divided the 101 genotypes into six major clusters, which was consistent with the systematic classification of faba bean done in previous studies. The overall results indicated that SDS-PAGE was a useful tool for genetic diversity analysis and laid a solid foundation for future faba bean breeding.

Caffeine inhibits the viability and osteogenic differentiation of rat bone marrow-derived mesenchymal stromal cells.

BACKGROUND AND PURPOSE: Caffeine is consumed extensively in Europe and North America. As a risk factor for osteoporosis, epidemiological studies have observed that caffeine can decrease bone mineral density, adversely affect calcium absorption and increase the risk of bone fracture. However, the exact mechanisms have not been fully investigated. Here, we examined the effects of caffeine on the viability and osteogenesis of rat bone marrow-derived mesenchymal stromal cells (rBMSCs). EXPERIMENTAL APPROACH: Cell viability, apoptosis and necrosis were quantified using thymidine incorporation and flow cytometry. Sequential gene expressions in osteogenic process were measured by real-time PCR. cAMP, alkaline phosphatase and osteocalcin were assessed by immunoassay, spectrophotometry and radioimmunoassay, respectively. Mineralization was determined by calcium deposition. KEY RESULTS: After treating BMSCs with high caffeine concentrations (0.1-1mM), their viability decreased in a concentration-dependent manner. This cell death was primarily due to necrosis and, to a small extent, apoptosis. Genes and protein sequentially expressed in osteogenesis, including Cbfa1/Runx2, collagen I, alkaline phosphatase and its protein, were significantly downregulated except for osteocalcin and its protein. Moreover, caffeine inhibited calcium deposition in a concentration- and time-dependent manner, but increased intracellular cAMP in a concentration-dependent manner. CONCLUSIONS AND IMPLICATIONS: By suppressing the commitment of BMSCs to the osteogenic lineage and selectively inhibiting gene expression, caffeine downregulated some important events in osteogenesis and ultimately affected bone mass.