Reduced mechanical stress leads to bone loss, as evidenced by disuse osteoporosis in bedridden patients and astronauts. Osteocytes have been identified as major cells responsible for mechanotransduction; however, the mechanism underlying the response of bone to mechanical unloading remains poorly understood. In this study, we found that mechanical unloading of wildtype mice caused decrease of Wnt/b-catenin signaling activity accompanied by upregulation of Sost. To further analyze the causal relationship among these events, Sost gene targeting mice were generated. We showed that sclerostin selectively inhibited Wnt/ b-catenin in vivo, and sclerostin suppressed the activity of osteoblast and viability of osteoblasts and osteocytes. Interestingly, Sost 2/2 mice were resistant to mechanical unloading-induced bone loss. Reduction in bone formation in response to unloading was also abrogated in the mutant mice. Moreover, in contrast to wildtype mice, Wnt/b-catenin signaling was not altered by unloading in Sost 2/2 mice. Those data implied that sclerostin played an essential role in mediating bone response to mechanical unloading, likely through Wnt/ b-catenin signaling. Our findings also indicated sclerostin is a promising target for preventing disuse osteoporosis.

BackgroundDue to its high prevalence and associated sight-threatening pathologies, myopia has emerged as a major health issue in East Asia. The purpose was to test the impact on myopia development of a school-based intervention program aimed at increasing the time student spent outdoors.MethodsA total of 3051 students of two primary (grades 1-5, aged 6-11) and two junior high schools (grades 7-8, aged 12-14) in both urban and rural Northeast China were enrolled. The intervention group (n = 1735) unlike the control group (n = 1316) was allowed two additional 20-min recess programs outside the classroom. A detailed questionnaire was administered to parents and children. Uncorrected visual acuity (UCVA) was measured using an E Standard Logarithm Vision Acuity Chart (GB11533-2011) at baseline, 6-month and 1-year intervals. A random subsample (n = 391) participated in the clinic visits and underwent cycloplegia at the beginning and after 1 year.ResultsThe mean UCVA for the entire intervention group was significantly better than the entire control group after 1 year (P < 0.001). In the subgroup study, new onset of myopia and changes in refractive error towards myopia were direction during the study period was significantly lower in the intervention group than in the control group (3.70 % vs. 8.50 %, P = 0.048; -0.10 ± 0.65 D/year vs. -0.27 ± 0.52 D/year, P = 0.005). Changes in axial length and IOP were also significantly lower following the intervention group (0.16 ± 0.30 mm/year vs. 0.21 ± 0.21 mm/year, P = 0.034; -0.05 ± 2.78 mmHg/year vs. 0.67 ± 2.21 mmHg/year, P = 0.006).ConclusionsIncreasing outdoor activities prevented myopia onset and development, as well as axial growth and elevated IOP in children.Trial registrationCurrent controlled trials NCT02271373.Electronic supplementary materialThe online version of this article (doi:10.1186/s12886-015-0052-9) contains supplementary material, which is available to authorized users.

Background-Abdominal bloating and visible distention are common yet poorly understood symptoms. Epidemiological data distinguishing visible distention from bloating are not available. We aimed to evaluate the prevalence and potential risk factors for abdominal bloating and visible distention separately in a representative US population, and their association with other functional gastrointestinal disorders (FGIDs).