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Abstract Although the toxic effect of Sedentary behavior (SED) on bone health has been demonstrated in the previous study, the underlying mechanisms of SED, or break SED to bone health remain unclear. In this study, we aim to investigate the effects of sedentary behavior (SED) on bone health, as well as the potential favor effects of moderate to vigorous physical activity (MVPA) and periodic interruptions of SED. To simulate SED, we used small Plexiglas cages (20.0 × 9.0 × 10.0 cm) to restrict animal movement. Short bursts of exercise to break SED and continuous long-term exercise were also designed. After an 8-weeks period of SED, we observed decreased bone mass and bone microstructure. Specifically, there was a notable decrease in the bone mineral density (BMD), bone surface (BS) and cortical thickness (Ct.Th) significantly reduced in cortical bone. In the trabecular bone, parameters such as trabecular separation (Tb.Sp), trabecular number (Tb.N), BS, connectivity density (Conn.D), BS/BV, bone volume/tissue volume (BV/TV), degree of anisotropy (DA), and structural model index (SMI) were also significantly reduced. In addition, we detected an increase in serum tartrate-resistant acid phosphatase (TRAP) levels in SED rats at both 4 and 8 weeks. At 8 weeks, the osteoclast number and surface with TRAP-staining were significantly increased, however, the OPG mRNA and proteins level were significantly decreased. After daily short bouts exercise and long-term exercise, we observed improvements in bone mass and microstructure. These improvements included increasing BMD and BV/TV of cortical bone, and improving Conn.D, BV/TV, DA and SMI of trabecular. Meanwhile, we found that, at 4 and 8 weeks, there was an increase in serum ALP. At 8 weeks, the mineralized nodules surface with Alizarin Red S-staining, and OPG mRNA and proteins level in bone tissue were significantly increased. Our findings suggest that SED leads to alterations in the bone mass and microstructure, which are associated with the changes in the OPG protein and bone remodeling. Exercise, whether in short daily bouts or continuous long-term sessions, can ameliorate the harmful effects of SED. Similarly, the changes in bone mass and microstructure from exercise are also associated with the changes in the OPG protein and bone remodeling by upregulated osteoblast activity to bone formation. Overall, our findings indicate the importance of physical activity in maintaining bone health and preventing the negative impacts of prolonged SED.

Abstract Sedentary behavior (SED) research is currently receiving increasing attention in the field of public health. While it has been shown to have negative effects on cardiovascular or metabolic health, there is limited knowledge regarding the relationship between SED and bone health in children, adolescents, and young adults. Thus, the purpose of this review is to investigate the associations between SED and bone health status, specifically bone mass, microstructure, and strength. A comprehensive literature search was conducted across five electronic databases, including EMBASE, PubMed, Medline, Cochrane, Web of Science and CNKI. The inclusion criteria were as follows: healthy participants aged 24 years or younger, with measured SED and measured bone outcomes. The quality of the included articles was assessed using the National Institute of Health Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. After excluding, the final sample included 25 cross-sectional, 9 observational and 2 both cross-sectional and longitudinal studies. Among these, seven were rated as ‘high quality’, twenty-three were rated as ‘moderated quality’, and six were rated as ‘low quality’ according to the quality assessment criteria. After summarizing the evidence, we found no strong evidence to support an association between BMC or BMD and SED, even when considering gender or adjusting for moderate-to-vigorous physical activity (MVPA). However, a strong level of evidence was found indicating a negative relationship between objectively measured SED and cortical bone mineral density (Ct.BMD) in the tibia or stiffness index (SI) in the Calcaneus across all age groups. While the association between adverse bone health outcomes and SED still cannot be confirmed due to insufficient evidence, these findings suggest that bone microstructure and strength may be more sensitive to SED than bone mass. Thus, further evidence is needed to fully understand the connection between sedentary behavior and bone health, particularly regarding the relationship between SED and bone strength.

To investigate the physiological mechanisms of salt stress mitigated by exogenous sucrose, Arabidopsis thaliana seedlings grown on Murashige and Skoog medium were treated with 3 % (m/v) sucrose combined with 75, 150, and 225 mM NaCl for 3 d. Our results show that increased salinity significantly decreased the survival rate, fresh mass, content of proteins, chlorophyll a (Chl a), and chlorophyll b (Chl b), and activities of antioxidant enzymes, whereas enhanced the content of malondialdehyde. However, the treatment with sucrose significantly enhanced salt stress tolerance in the Arabidopsis seedlings by decreasing lipid peroxidation and increasing the activities of superoxide dismutase, peroxidase, and catalase, the content of proteins, Chl a, Chl b, anthocyanins, and the transcription of genes involved in anthocyanin biosynthesis. Thus, sucrose might reduce ROS-induced oxidative damage by enhancing activities of antioxidant enzymes and the content of anthocyanins, thereby preventing membrane peroxidation and denaturation of biomolecules.