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Objective: Sarcopenia in older adults is closely related to vitamin D deficiency and reduced levels of physical activity, but little has been reported on the interaction between physical activity and the positive effects of vitamin D. The purpose of this study was to explore the interactive effect of vitamin D and physical activity on muscle mass and function through animal experiments and population surveys. Methods: Male 4‐week‐old C57BL/6J mice were fed different purified diets: a vitamin D‐deficient diet (with increased calcium and phosphorus to prevent the effects of abnormal mineral levels on muscle) or a 1,25‐dihydroxyvitamin D3 (1,25D)‐supplemented diet. After 24 weeks on the assigned diets, the mice were immobilized. The level of skeletal muscle atrophy in the mice was determined by grip strength, gastrocnemius (GA) muscle mass and muscle fiber cross‐sectional area (CSA); additionally, the protein expression levels of FOXO3a and the E3 ubiquitin ligases MuRF1 and MAFbx were detected. A cross‐sectional study included data from 4139 older adults (64.9% women, 67.9 ± 6.7 years) as part of a survey in Shenyang, Northeast China. The associations of serum 25(OH)D3 and physical activity with timed up and go test (TUG) performance, handgrip strength, calf circumference, and body muscle mass were assessed by a linear regression analysis that was adjusted for covariates. Results: In activity‐limited mice, vitamin D deficiency accelerated the decrease in GA muscle weight, muscle fiber CSA, and grip strength and increased the protein expression of MuRF1, MAFbx, and FOXO3a (all P < 0.05). In addition, 1,25D supplementation may inhibit the grip‐strength reduction induced by limited activity (P = 0.069). Serum 25(OH)D3 and physical activity were linearly related to TUG time (P < 0.001) and handgrip strength (P < 0.05) after adjustment for sex, age, body mass index (BMI), education level, smoking status, and serum calcium level. Serum 25(OH)D3 and physical activity had interactive effects on TUG (P < 0.001) and handgrip strength (P < 0.05) but not calf circumference or body muscle mass in older adults. Conclusions: The effect of vitamin D on muscle strength and physical performance depends on physical activity level in the elderly. It is recommended that older adults strive to avoid both physical inactivity and vitamin D deficiency. Because physical inactivity and vitamin D deficiency may exacerbate muscle atrophy, the biological mechanism may involve synergistic effects of vitamin D and physical activity on the promotion of muscle protein ubiquitination and degradation. [ABSTRACT FROM AUTHOR]

Aims. Previous evidence has demonstrated an increased fracture risk among the population with type 2 diabetes mellitus (T2DM). This study investigated the prevalence of bone fractures in elderly subjects (with and without type 2 diabetes) and identified any fracture risk factors, especially the risk factors for common known fractures in particular diabetic populations. Methods. This cross-sectional study was conducted with community-dwelling people over 60 years old in nine communities from the city of Shenyang, which is the capital of Northeast China's Liaoning Province. A total of 3430 elderly adults (2201 females, mean ± standard deviation age 68.16 ± 6.1 years; 1229 males, 69.16 ± 6.7 years) were included. Our study measured the heel bone mineral density (BMD) and used the timed "up and go" (TUG) test and other indicators. In addition, we performed logistic regression analysis to explore the risk factors for fractures in the general population and the diabetic population and to analyze the differences. Results. The results revealed that a total of 201 elderly persons (5.8%), with an average age of 70.05 ± 6.54 years, suffered from a history of fragility fractures, which affected more females (74.6%) than males (p = 0.001). The prevalence of fractures in the T2DM population was 7.3%, which was much higher than the 5.2% in non-T2DM population (p < 0.05). In the non-T2DM population, the BMD was lower and the TUG time was longer in the fracture group than in the nonfracture group (p < 0.001). However, in the T2DM population, the BMD and TUG values were similar between the fracture group and the nonfracture group (p > 0.05). Logistic regression analysis showed that the female sex (OR 1.835), TUG time > 10.2 s (OR 1.602), and T ‐ score ≤ − 2.5 (OR 1.750) were independent risk factors for fragility fractures in the non-T2DM population, but they were not risk factors in the T2DM population. Conclusions. This study found that low BMD and slow TUG time were independent risk factors for fractures in non-T2DM patients, while no associations were found in the T2DM population. Patients with T2DM have a higher risk for fractures even when they have sufficient BMD and a short TUG time. TUG and BMD underestimated the risk for fractures in the T2DM population. [ABSTRACT FROM AUTHOR]

Background and objective: Oxidative stress has been demonstrated to be a mechanism that leads to bone mass reduction, and according to many studies, serum uric acid (UA) is a strong endogenous antioxidant that can protect bone mineral density (BMD). To date, there have been no large-scale, cross-sectional studies based on the population in northeast China to assess the relationship between serum UA and BMD. Therefore, we examined the association between serum UA and BMD among a Chinese population older than 60 years old in northeast China. Methods: This research was a cross-sectional study of 3465 Chinese individuals over 60 years old in nine communities from the city of Shenyang, which is the capital of northeast China's Liaoning Province. Participants were stratified into three groups by serum UA or BMD levels, and then Pearson's correlation analysis and multiple regression analysis were used to study the relationship between serum UA and BMD. Results: We found that participants with higher serum UA levels had significantly greater BMD and T-values compared to those of participants with lower serum UA levels. After adjusting for confounding factors, Pearson's correlation analysis and multiple regression analysis showed that higher serum UA levels remained associated with higher BMD levels (P<0.05). In different models, the prevalence of osteoporosis (OP) among participants with higher serum UA levels was reduced by 23% to 26% (P<0.05) compared to that in individuals with lower serum UA levels. In addition, serum UA levels were negatively correlated with estimated glomerular filtration rate (eGFR) and positively correlated with 25-hydroxy vitamin D3 [25-(OH)D3] (P<0.05). Conclusion: We concluded that higher serum UA levels are associated with greater BMD, and serum UA might have a protective effect on bone metabolism due to its antioxidant properties. [ABSTRACT FROM AUTHOR]