Vitamin D receptor expression in human muscle tissue decreases with age

Vitamin D augments insulin secretion via calcium influx and upregulation of voltage calcium channels: Findings from INS-1 cells and human islets

Vitamin D (VD) has been implicated in regulating insulin secretion and pancreatic β-cell function. Yet, the underlying molecular mechanism of VD in glucose homeostasis is not fully understood. This study investigates the effect of VD in regulating insulin secretion and pancreatic β-cell function. INS-1 β-cells were treated with VD to assess cell viability, reactive oxygen species production (ROS), insulin secretion, glucose uptake, proliferation, gene expression alterations, mitochondria metabolism, calcium influx, as well as the effects of antidiabetic drugs on VDR expression. Additionally, RNA sequencing from human pancreatic islets were utilized to examine VDR expression in relation to clinical parameters such as HbA1c, BMI, age, and gender. VD treatment enhanced glucose-stimulated insulin secretion and elevated intracellular calcium levels without affecting insulin content, glucose uptake, ROS production, proliferation, or mitochondrial metabolism. Expression levels of key β-cell function genes, including Ins, Pdx1, and Glut2, remained unchanged with VD treatment. However, genes associated with calcium channels were upregulated. Cell exposure to rosiglitazone and dexamethasone elevated VDR expression in INS-1 cells, while metformin and insulin had no effect. RNA-seq analysis in human islets showed that VDR expression levels in human islets were significantly higher than in other metabolic tissues and were notably reduced in hyperglycemic donors compared to normoglycemic individuals. Furthermore, VDR expression positively correlated with several genes regulating voltage-gated calcium channels. In conclusion, the study indicates that VD plays a significant role in enhancing insulin secretion through modulation of intracellular calcium dynamics, highlighting its potential therapeutic implications for managing type 2 diabetes.

Exploring the impact of vitamin D-related genetic variants on muscular fitness changes in middle-aged and older adults in Kosovo

Introduction

Age-related decline in muscle strength and performance significantly impact morbidity and mortality. Various factors including genetics have been investigated to better understand this decline. This study aimed to investigate longitudinal changes in physical performance and strength and their association with genetic variants in genes involved in the vitamin D pathway.

Methods

This longitudinal study was conducted in the Prishtina region, Kosovo, with community-dwelling adults over 40 years of age. Genomic DNA was extracted from saliva samples to assess single nucleotide polymorphisms in the vitamin D receptor (VDR) gene (rs7975232, rs2228570, rs731236, also referred to as ApaI, FokI, and TaqI, respectively) and the vitamin D binding protein (GC) gene (rs4588, rs2282679). Physical performance was assessed by isometric handgrip strength, 30-s chair stand, timed up and go and 6-min walk test. Vitamin D levels were assessed from blood samples only at follow-up.

Results

A total of 138 participants (65.1 ± 9.0 years, 52.2% female) were included. Over a 2.7-year period, significant declines in the 30-s chair stand test (p < 0.001) and timed up and go performance (p < 0.001) were observed, whereas BMI increased. Only female participants experienced a decrease in handgrip strength (p < 0.001). Genotyping showed significant associations of the ApaI variant with changes in BMI and handgrip strength. Participants with the minor CC genotype showed a greater increase in BMI and a greater decrease in absolute and relative handgrip strength. No significant interactions were observed for FokI and TaqI in the VDR gene, or rs4588 and rs2282679 in the GC gene. Vitamin D deficiency (<50 nmol/L) was prevalent in 47.5% of participants, with significant differences in 25(OH)D levels observed between genotypes of the GC gene (rs4588, p = 0.039; rs2282679, p = 0.036).

Conclusion

Physical fitness declined significantly over time, with female participants experiencing a greater decline in handgrip strength. The ApaI variant in the VDR gene was associated with changes in muscle strength, while variants in the GC gene were associated with vitamin D levels. These findings suggest that genetic factors related to the vitamin D pathway may contribute to the age-related decline in muscle strength. Therefore, genetic predisposition should be considered when developing individual interventions for healthy aging.

Vitamin D status and its determinants in German elite athletes

PURPOSE

This study investigated elite German athletes to (1) assess their serum 25(OH)D levels and the prevalence of insufficiency, (2) identify key factors influencing serum 25(OH)D levels, and (3) analyze the association between serum 25(OH)D levels and handgrip strength.

METHODS

In this cross-sectional study, a total of 474 athletes (231 female), aged 13-39 years (mean 19.3 years), from ten Olympic disciplines were included. Serum 25(OH)D levels were analyzed via liquid chromatography-mass spectrometry, and 17 single nucleotide polymorphisms (SNPs) related to vitamin D metabolism were determined using leukocyte DNA. Grip strength was measured unimanually using a hand-held dynamometer. Multiple linear regressions were used to analyze the influence of SNPs, age, sex, season (summer vs. winter), and discipline (indoor vs. outdoor) on 25(OH)D status. Linear regression analyzed the relationship between handgrip strength and serum 25(OH)D levels.

RESULTS

In total, 55.5% (n = 263) of athletes demonstrated insufficient serum 25(OH)D levels (< 30 ng/mL, < 75 nmol/L), with 16% (n = 76) showing levels below 20 ng/mL (50 nmol/L). After correction for multiple testing, significant influences on 25(OH)D levels were observed for the C allele of VDBP rs7041 (AC Genotype: β ^  = 7.46, p < .001; CC Genotype: β ^  = 6.23, p = .001). Age (all p < .01) and discipline (indoor vs. outdoor; all p < .05) also influenced serum 25(OH)D levels. Furthermore, serum 25(OH)D was positively associated with handgrip strength ( β ^ = 0.01, p < .001).

CONCLUSION

A high prevalence of insufficient 25(OH)D levels (< 30 ng/mL, < 75 nmol/L) was observed. We identified certain genetic variants as well as age and discipline as predictors of serum 25(OH)D levels. This knowledge may guide individualized diagnostic, nutritional, and supplementation strategies.

Age but not vitamin D is related to sarcopenia in vitamin D sufficient male elderly in rural China

This study aimed to identify the correlation of serum 25(OH)D level with sarcopenia and its components in Chinese elderly aged 65 years and above from rural areas. A total of 368 Chinese elderly aged 65 years and above in rural areas were enrolled. Indicators of muscle mass and strength, including the appendicular skeletal muscle mass (ASM), skeletal muscle index (SMI) and hand grip strength (HGS) were measured. Physical performance was assessed by the Short Physical Performance Battery (SPPB). Serum 25(OH)D levels were measured using the liquid chromatography with tandem mass spectrometry. Correlations of serum 25(OH)D level with sarcopenia and its components in Chinese elderly were identified by the binary logistic regression and linear regression analyses. The median serum 25(OH)D level was 34.80 ng/ml, and significantly higher in men than in women (40.70 ng/ml vs. 27.30 ng/ml). The prevalence of sarcopenia in our cohort was 21.5%, and higher in men than in women (29.4% vs. 10.8%). The serum 25(OH)D level was not correlated with sarcopenia, HGS and SPPB score in either male or female elderly. Positive correlations of age with sarcopenia, low HGS and low SPPB score were observed in male elderly, while significant correlations were not observed in females. Correlation analyses of sarcopenia components revealed that age was negatively correlated with SMI and gait speed in male elderly, but negatively correlated with the gait speed and positively correlated with the time to complete 5 sit-to-stand movements in female elderly. In conclusion, rural Chinese elderly have relatively high vitamin D level and prevalence of sarcopenia. Age but not serum 25(OH)D level is significantly correlated with sarcopenia in vitamin D sufficient male elderly.

Effects of Supplemental Vitamin D3, Omega-3 Fatty Acids on Physical Performance Measures in the VITamin D and OmegA-3 TriaL

CONTEXT

Declining muscle strength and performance in older adults are associated with falls, fractures, and premature death.

OBJECTIVE

This work aimed to determine whether supplementation with vitamin D3 or omega-3 fatty acids vs placebo for 2 years improves physical performance measures.

METHODS

VITamin D and OmegA-3 TriaL (VITAL) was a double-blinded, placebo-controlled randomized trial of supplemental vitamin D3 and/or omega-3 fatty acids vs placebo in the prevention of cancer and cardiovascular disease in 25 871 US adults. This ancillary study was completed in a New England subcohort that had in-person evaluations at baseline and 2-year follow-up. This study was conducted with 1054 participants (age: men ≥50 and women ≥55 years) at the Center for Clinical Investigations in Boston. Interventions included a 2 × 2 factorial design of supplemental vitamin D3 (cholecalciferol, 2000 IU/day) and/or marine omega-3 fatty acids (1 g/day). Main outcome measures included 2-year changes in physical performance measures of grip strength, walking speed, standing balance, repeated chair stands, and Timed-up and Go (TUG).

RESULTS

At 2 years, all randomized groups showed worsening walking speeds and TUG. There were no differences in changes in grip strength, walking speeds, Short Physical Performance Battery (composite of walking speed, balance, and chair stands), and TUG between the vitamin D3-treated and the placebo-treated groups and between the omega-3-treated and the placebo-treated groups. Effects overall did not vary by sex, age, body mass index, or baseline measures of total or free 25-hydroxyvitamin D (25[OH]D) or plasma omega-3 index; TUG slightly worsened with vitamin D supplementation, compared to placebo, in participants with baseline total 25(OH)D levels above the median (P = .01; P for interaction = .04).

CONCLUSION

Neither supplemental vitamin D3 nor marine omega-3 fatty acids for 2 years improved physical performance in this generally healthy adult population.

A Snapshot of Vitamin D Status, Performance, Blood Markers, and Dietary Habits in Runners and Non-Runners

BACKGROUND

Vitamin D can influence athletic performance and infection risk. This study aimed to investigate vitamin D status, hematochemical factors, anthropometric and performance parameters, and dietary habits in runners (n = 23) and sedentary healthy individuals (non-runners, n = 22) during the autumn season.

METHODS

Both groups had their serum 25-Hydroxyvitamin D (ng/mL) levels, blood and performance parameters, and dietary habits measured.

RESULTS

Serum 25-Hydroxyvitamin D levels were significantly lower in non-runners (runners: males 30.0 ± 5.6, females 31.2 ± 5.2 vs. non-runners: males, 22.8 ± 6.5, females 24.7 ± 6.5 ng/mL, p < 0.001). White blood cells, monocyte, and neutrophil levels were higher in non-runners for both males and females. Among the subjects, 23 had optimal vitamin D levels (>29 ng/mL), while 22 had insufficient/deficient levels (<29 ng/mL), with a higher prevalence of insufficiency in non-runners compared to runners (63.6% vs. 34.8%; p = 0.053). Maximal isometric force and jump height were equal in both groups, but VO2max was higher in runners. Linear regression analysis identified monocyte count as the only predictor of vitamin D levels for both males (y = -24.452 x + 40.520; R2 = 0.200; p = 0.015) and females (y = -33.409 x + 45.240; R2 = 0.368; p = 0.003).

CONCLUSIONS

This study highlights significant differences in vitamin D status between runners and non-runners, with runners exhibiting higher serum 25-Hydroxyvitamin D levels, although this finding is likely due to the increased sun exposure that runners receive. It also provides valuable insights into the vitamin D status of healthy young sedentary individuals and runners, enhancing the understanding of how physical activity influences vitamin D levels.

Effect of serum 25-hydroxyvitamin D level on quadriceps strength: a systematic review and meta-analysis

BACKGROUND

Vitamin D deficiency has been linked to poor muscle function, cartilage degeneration, and the development of knee osteoarthritis. However, the impact of serum 25-hydroxyvitamin D [25(OH)D] level on quadriceps muscle strength remains inconclusive, largely due to variations in study designs, differences in study populations, and the influence of confounding factors such as co-supplementation with other vitamins. The existing literature presents mixed findings, highlighting the need for a comprehensive evaluation of the available evidence.

PURPOSE

This systematic review and meta-analysis aim to summarise.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

Searches were conducted using Medline (Ovid), Embase (Ovid), CINAHL (EBSCOhost), and SPORTDiscus (EBSCOhost), which aimed to summarise recent (published after 2000 and before March 1st, 2024) studies reporting the effects of serum 25(OH)D levels on quadriceps strength. Appraisal tool for Cross-Sectional Studies (AXIS) for cross-sectional studies and Quality in Prognosis Studies (QUIPS) for longitudinal studies. Results from the AXIS and QUIPS tools were used for GRADE quality assessment. The review was carried out using PRIMSA guidelines and registered in PROSPERO (ID: CRD42022313240).

RESULTS

Four hundred studies were screened and 28 studies with 5752 participants were included. 28 published studies (24 cross-sectional and 4 longitudinal) were identified. Key results supported the significant positive correlation between serum 25(OH)D levels and isokinetic quadriceps strength at 180°/s in elderly and athletic populations with a correlation coefficient of 0.245 (95%CI: 0.078-0.398, p = 0.004). However, no significant correlation was found with isometric quadriceps strength or isokinetic strength at 60°/s (r = 0.190, p = 0.085). There was only a weak negative correlation with MVC.

CONCLUSION

This review found a statistically significant positive correlation between serum 25(OH)D levels and isokinetic quadriceps strength. This has important clinical implications, especially in the elderly cohort, with higher 25(OH)D levels being associated with a reduced incidence of falls and fragility fractures.

Associations between serum 25-hydroxyvitamin D and prognosis of chronic kidney disease: a prospective cohort study

BACKGROUND AND OBJECTIVES

25-hydroxyvitamin D [25(OH)D] deficiency is prevalent in patients with chronic kidney disease (CKD), the associations between serum 25(OH)D levels and mortality in patients with CKD remain unclear, and this study aimed to explore these associations further.

METHODS

4989 participants with CKD were enrolled in the study, and the Cox regression model was used to assess the effects of serum 25(OH)D concentrations on mortality risk. A restricted cubic spline model was used to explore the dose-response relationships, and threshold effect analysis was performed based on inflection points identified by a two-piecewise linear regression model. In addition, subgroup and sensitivity analyses were employed.

RESULTS

1255 participants died during a mean follow-up period of 70 months. Compared with the 25(OH)D-deficient group, the fully adjusted hazard ratios and 95% confidence intervals for the 25(OH)D-adequate group were 0.631 (0.545, 0.730) for all-cause mortality, 0.569 (0.435, 0.743) for cardiovascular mortality, 0.637 (0.461, 0.878) for hypertension mortality, and cancer mortality was 0.596 (0.426, 0.834). The inflection points of serum 25(OH)D concentration affecting all-cause and cardiovascular mortality were 89 nmol/L, and 107 nmol/L, respectively. Subgroup analyses and interaction tests suggested that the effects varied across populations. The results of sensitivity analyses indicated a reliable correlation.

CONCLUSION

We found an association between serum 25(OH)D concentrations and the prognosis of patients with CKD as a reliable predictor of early intervention and intensive care.

Vitamin D and Sarcopenia in the Senior People: A Review of Mechanisms and Comprehensive Prevention and Treatment Strategies

This article reviews the mechanisms and prevention strategies associated with vitamin D and sarcopenia in older adults. As a geriatric syndrome, sarcopenia is defined by a notable decline in skeletal muscle mass and strength, which increases the risk of adverse health outcomes such as falls and fractures. Vitamin D, an essential fat-soluble vitamin, is pivotal in skeletal muscle health. It affects muscle function through various mechanisms, including regulating calcium and phosphorus metabolism, promoting muscle protein synthesis, and modulation of muscle cell proliferation and differentiation. A deficiency in vitamin D has been identified as a significant risk factor for the development of sarcopenia in older adults. Many studies have demonstrated that low serum vitamin D levels are significantly associated with an increased risk of sarcopenia. While there is inconsistency in the findings, most studies support the importance of vitamin D in maintaining skeletal muscle health. Vitamin D influences the onset and progression of sarcopenia through various pathways, including the promotion of muscle protein synthesis, the regulation of mitochondrial function, and the modulation of immune and inflammatory responses. Regarding the prevention and treatment of sarcopenia, a combination of nutritional, exercise, and pharmacological interventions is recommended. Further research should be conducted to elucidate the molecular mechanism of vitamin D in sarcopenia, to study genes related to sarcopenia, to perform large-scale clinical trials, to investigate special populations, and to examine the combined application of vitamin D with other nutrients or drugs. A comprehensive investigation of the interconnection between vitamin D and sarcopenia will furnish a novel scientific foundation and productive strategies for preventing and treating sarcopenia. This, in turn, will enhance the senior people's quality of life and health.

Vitamin D add on the standard treatment for myasthenia gravis symptoms following total gastrectomy: a case report

BACKGROUND

Myasthenia gravis (MG) is a long-term autoimmune disorder that affects the neuromuscular junction, causing muscle weakness and fatigue as its primary clinical features. Vitamin D is crucial for both the autoimmune response and skeletal muscle function.

CASE PRESENTATION

Here, we presented a case report documenting the substantial improvement in symptoms experienced by a patient who underwent subtotal gastrectomy for gastric cancer following high-dose Vitamin D supplementation. The patient developed generalized MG two months after the surgery and did not respond adequately to pyridostigmine therapy, experiencing a progressive deterioration of the condition. A significant reduction in vitamin D concentration was observed following subtotal gastrectomy. In response, high-dose vitamin D supplementation was administered to the patient. Within one week of treatment, swallowing symptoms improved, enabling the consumption of a small amount of liquid food. By the second week, substantial swallowing and neck function improvements were evident. After one month, the patient regained the ability to straighten the neck while walking and consumed a regular diet despite persistent difficulties chewing hard food.

CONCLUSIONS

This case underscores the therapeutic potential of vitamin D in alleviating MG symptoms, particularly in individuals with compromised vitamin D levels following gastrectomy. The observed improvements present a new perspective on the possible involvement of vitamin D supplementation in the management of postoperative MG cases.

Role of Myostatin in Rheumatoid Arthritis: A Review of the Clinical Impact

Rheumatoid arthritis (RA) is a chronic inflammatory disease that affects synovial joints and that frequently involves extra-articular organs. A multiplicity of interleukins (IL) participates in the pathogenesis of RA, including IL-6, IL-1β, transforming growth factor-beta (TGF-β), and tumor necrosis factor (TNF)-α; immune cells such as monocytes, T and B lymphocytes, and macrophages; and auto-antibodies, mainly rheumatoid factor and anti-citrullinated protein antibodies (ACPAs). Skeletal muscle is also involved in RA, with many patients developing muscle wasting and sarcopenia. Several mechanisms are involved in the myopenia observed in RA, and one of them includes the effects of some interleukins and myokines on myocytes. Myostatin is a myokine member of the TGF-β superfamily; the overproduction of myostatin acts as a negative regulator of growth and differentiates the muscle fibers, limiting their number and size. Recent studies have identified abnormalities in the serum myostatin levels of RA patients, and these have been found to be associated with muscle wasting and other manifestations of severe RA. This review analyzes recent information regarding the relationship between myostatin levels and clinical manifestations of RA and the relevance of myostatin as a therapeutic target for future research.

Association between vitamin D status, physical performance, sex, and lifestyle factors: a cross-sectional study of community-dwelling Kosovar adults aged 40 years and older

PURPOSE

Vitamin D status and its association with age-related decline in physical performance and strength have already been highlighted in various ways, but data on the situation in developing countries are scarce. This study aimed to investigate vitamin D status, its association with muscle mass and function, and other potential determinants such as age, sex, lifestyle factors (physical activity, dietary behavior), self-perceived health status, medication intake, education and financial situation in adults from Kosovo.

METHODS

This cross-sectional study included 297 participants (54.5% women), aged ≥ 40 years. Serum 25-hydroxyvitamin D (25(OH)D) concentration, hand grip strength and physical performance tests, body composition, vitamin D dietary intake and knowledge were assessed. The interaction between serum 25(OH)D status, lifestyle factors and muscle traits was investigated.

RESULTS

Vitamin D deficiency (< 50 nmol/L) was observed in 47.5% of the total population, of whom 14.7% of them were severely deficient (< 30 nmol/L). No associations were found between 25(OH)D concentration and age. Daily dietary intake of vitamin D was low (1.89 ± 0.67 µg) and 87.6% of individuals did not take vitamin D supplements. However, vitamin D supplementation was the only variable that added statistical significance (p < 0.05) to the prediction of vitamin D status (3.8%). On the other hand, age, medication intake and vitamin D level contributed significantly to the overall regression model, explaining 24.9% of the 30-s chair stand performance as an indicator of lower-body strength endurance.

CONCLUSION

Vitamin D deficiency is highly prevalent among community-dwelling adults in Kosovo and low serum 25(OH)D has been associated with low muscle strength. This implies an urgent need for the development of comprehensive prevention strategies, focusing on pharmacological (supplementation) but also on non-pharmacological strategies such as education, food fortification or lifestyle advices.

Exercise-induced vitamin D receptor and androgen receptor mediate inhibition of IL-6 and STAT3 in muscle

Background

Skeletal muscle produces interleukin-6 (IL-6) during exercise as a myokine. Although IL-6 is required for skeletal muscle regeneration, its action increases the expression of myostatin and other proteins involved in muscle atrophy, resulting in skeletal muscle atrophy. In this study, we clarified the effects exercise-induced vitamin D receptor (VDR) and androgen receptor (AR) expression on IL-6 and signal transducer and activator of transcription 3 (STAT3) in vivo and in vitro.

Method

C2C12 myotubes were subjected to electric pulse stimulation (EPS) in vitro. To evaluate VDR and AR function, a VDR/AR agonist and antagonist were administered before EPS to C2C12 myotubes. C57BL6 mice underwent 4 weeks of exercise. The expression levels of proteolytic-associated genes, including CCAAT/enhancer-binding protein delta (C/EBPδ) and myostatin, were measured by quantitative real-time polymerase chain reaction, and phosphorylated and total STAT3 levels were measured by Western blot analysis.

Result

The expression of VDR and AR mRNA was induced following EPS in C2C12 myotubes. IL-6 mRNA expression was also increased with a peak at 6 h after EPS and p-STAT3/STAT3 ratio reciprocally decreased. Although VDR/AR agonist administration decreased IL-6 mRNA expression and p-STAT3/STAT3 ratio, these two endpoints increased after treatment with VDR/AR antagonist, respectively. Exercise in mice also increased the expression of VDR/AR and IL-6 mRNA and decreased p-STAT3/STAT3 ratio.

Conclusion

Exercise-induced VDR and AR expression results in the suppression of IL-6 mRNA and STAT3 phosphorylation in skeletal muscle.

The Global Prevalence of Vitamin D Deficiency in the Elderly: A Meta-analysis

Background

Vitamin D deficiency is widely prevalent among the elderly, posing significant health risks. This study aims to determine the global prevalence of vitamin D deficiency in the elderly.

Methods

A systematic review and meta-analysis was conducted, examining databases including Scientific Information Database (SID), Medline (PubMed), ScienceDirect, Scopus, Embase, and Google Scholar until January 2023. The publication bias of the studies was assessed using the I2 test of heterogeneity and the Egger test.

Results

The prevalence of vitamin D deficiency, defined as levels below 20 ng or 50 nmol was found to be 59.7% (95% CI 45.9-72.1). Furthermore, a review of six studies involving 6748 elderly individuals showed a prevalence of 27.5% (95% CI 21.8-34.1) for deficiency defined between 20 and 30 ng or 50-75 nmol. Additionally, a meta-analysis of seven studies with a sample size of 6918 elderly individuals reported a prevalence of 16% (95% CI 10.2-24.1) for deficiency defined above 30 nmol or 75 nmol.

Conclusion

The results of the present study reveal that the prevalence of vitamin D deficiency among the elderly is high and requires the attention of health policymakers at the World Health Organization to prioritize extensive information dissemination and screening to mitigate the adverse effects on their quality of life.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43465-023-01089-w.

Association between sarcopenia and new-onset chronic kidney disease among middle-aged and elder adults: findings from the China Health and Retirement Longitudinal Study

BACKGROUND

Sarcopenia is a senile syndrome of age-related muscle loss. It is thought to affect the development of chronic kidney disease and has a serious impact on the quality of life of the elder adults. Little is known about the association between sarcopenia and new-onset chronic kidney disease in middle-aged and elder adults. Using nationally representative data from the China Health and Retirement Longitudinal Study (CHARLS), we conducted a longitudinal analysis to investigate the association between sarcopenia status and new-onset chronic kidney disease in middle-aged and elder adults in China.

METHODS

The study population consisted of 3676 participants aged 45 or older selected from 2011 CHARLS database who had no history of chronic kidney disease at the baseline and completed the follow-up in 2015. A multivariate cox regression model was employed to examine the association between sarcopenia and the incidence of new-onset chronic kidney disease.

RESULTS

Followed up for 4 years, a total of 873 (22.5%) new cases of chronic kidney disease occurred. Among them, participants diagnosed with sarcopenia (HR1.45; 95% CI 1.15-1.83) were more likely to develop new-onset chronic kidney disease than those without sarcopenia. Similarly, patients with sarcopenia were more likely to develop new-onset chronic kidney disease than those with possible sarcopenia (HR 1.27; 95%CI 1.00-1.60). Subgroup analysis revealed that elder adults aged between 60 and 75 years old (HR 1.666; 95%CI 1.20-22.28), with hypertension (HR 1.57; 95%CI 1.02-2.40), people with sarcopenia had a significantly higher risk of developing new-onset chronic kidney disease than those without sarcopenia (all P < 0.05).

CONCLUSION

Middle-aged and elder adults diagnosed with sarcopenia have a higher risk of developing new-onset chronic kidney disease.

Role of vitamin D for orthodontic tooth movement, external apical root resorption, and bone biomarker expression and remodeling: A systematic review

Objective

: This systematic review aimed to evaluate the correlation between vitamin D levels and the rate of tooth movement, external apical root resorption, bone biomarker expression, and bone remodeling.

Methods

: Three databases (PubMed, Scopus, and Web of Science) were systematically searched from inception until 14th March 2023 to identify studies investigating the correlation between orthodontic tooth movement and vitamin D in animals and humans. The quality assessment was made in accordance with the Joanna Briggs Institute Critical Appraisal Checklist.

Results

: Overall, 519 records were identified, and 19 were selected for the qualitative synthesis. Eleven studies investigated the effect of local administration (injections in the periodontal ligament, to the gingiva distal to the teeth, or submucosae palatal area) and systemic administration (oral supplementation) of vitamin D on tooth movement, external apical root movement, pro-inflammatory cytokines, and bone remodeling factors. The remaining eight studies investigated the correlation between serum vitamin D levels and salivary vitamin D levels on bone turnover markers and tooth movement.

Conclusions

: The findings of this systematic review support that vitamin D3 local injections might increase the rate of tooth movement via the receptor activator of the nuclear factor-kB/osteoprotegerin axis. However, the non-uniform study designs and the different protocols and outcome methods make it challenging to draw reliable conclusions.

Vitamin D levels and the risk of overactive bladder: a systematic review and meta-analysis

CONTEXT

Overactive bladder is treated mainly with behavioral and drug therapy, and symptoms of urinary frequency and incontinence are challenging to eliminate. There is thus a continuous unmet need for new drugs with a substitution effect mechanism.

OBJECTIVE

It not known whether vitamin D deficiency can lead to overactive bladder or urinary incontinence or whether vitamin D supplementation alleviates bladder symptoms. This comprehensive systematic review with meta-analysis was conducted to determine whether overactive bladder is associated with vitamin D deficiency.

DATA SOURCES

The PubMed and Cochrane Library databases were searched systematically up to July 3, 2022.

DATA EXTRACTION

Initially, 706 articles were identified in the literature search, of which 13 were included in the systematic review: 4 randomized controlled trials, 3 cohort studies, 3 cross-sectional studies, and 3 case-control studies.

DATA ANALYSIS

An increased risk of overactive bladder and urinary incontinence was observed with vitamin D deficiency (odds ratio [OR] = 4.46; 95%CI, 1.03-19.33; P = 0.046 and OR = 1.30; 95%CI, 1.01-1.66; P = 0.036, respectively). Vitamin D levels were relatively low in patients with overactive bladder or urinary incontinence (SMD = -0.33; 95%CI, -0.61 to -0.06, P = 0.019). On the basis of existing data, the risk of urinary incontinence was reduced by 66% after vitamin D supplementation (OR = 0.34; 95%CI, 0.18-0.66; P = 0.001). Egger test was conducted to assess publication bias, and the results were tested for robustness using a sensitivity analysis.

CONCLUSIONS

Vitamin D deficiency increases the risk of overactive bladder and urinary incontinence, and vitamin D supplementation reduces the risk of urinary incontinence. The development of new strategies to prevent or alleviate bladder symptoms is crucial. Vitamin D supplementation may be gaining recognition as an effective strategy for prevention or alleviation of bladder symptoms such as overactive bladder and incontinence.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42022351443.

Pathophysiology of sarcopenia: Genetic factors and their interplay with environmental factors

Sarcopenia is a geriatric disorder characterized by a progressive decline in muscle mass and function. This disorder has been associated with a range of adverse health outcomes, including fractures, functional deterioration, and increased mortality. The pathophysiology of sarcopenia is highly complex and multifactorial, involving both genetic and environmental factors as key contributors. This review consolidates current knowledge on the genetic factors influencing the pathogenesis of sarcopenia, particularly focusing on the altered gene expression of structural and metabolic proteins, growth factors, hormones, and inflammatory cytokines. While the influence of environmental factors such as physical inactivity, chronic diseases, smoking, alcohol consumption, and sleep disturbances on sarcopenia is relatively well understood, there is a dearth of studies examining their mechanistic roles. Therefore, this review emphasizes the interplay between genetic and environmental factors, elucidating their cumulative role in exacerbating the progression of sarcopenia beyond their individual effects. The unique contribution of this review lies in synthesizing the latest evidence on the genetic factors and their interaction with environmental factors, aiming to inform the development of novel therapeutic or preventive interventions for sarcopenia.

Vitamin D3 Exerts Beneficial Effects on C2C12 Myotubes through Activation of the Vitamin D Receptor (VDR)/Sirtuins (SIRT)1/3 Axis

The onset of sarcopenia is associated with a decline in vitamin D receptor (VDR) expression, wherein reduced VDR levels contribute to muscle atrophy, while heightened expression promotes muscle hypertrophy. Like VDR, the age-related decline in protein deacetylase sirtuin (SIRT) expression is linked to the development of sarcopenia and age-related muscle dysfunction. This study aimed to investigate whether the VDR agonist 1,25-dihydroxyvitamin D3 (1,25VD3) exerts beneficial effects on muscles through interactions with sirtuins and, if so, the underlying molecular mechanisms. Treatment of 1,25VD3 in differentiating C2C12 myotubes substantially elevated VDR, SIRT1, and SIRT3 expression, enhancing their differentiation. Furthermore, 1,25VD3 significantly enhanced the expression of key myogenic markers, including myosin heavy chain (MyHC) proteins, MyoD, and MyoG, and increased the phosphorylation of AMPK and AKT. Conversely, VDR knockdown resulted in myotube atrophy and reduced SIRT1 and SIRT3 levels. In a muscle-wasting model triggered by IFN-γ/TNF-α in C2C12 myotubes, diminished VDR, SIRT1, and SIRT3 levels led to skeletal muscle atrophy and apoptosis. 1,25VD3 downregulated the increased expression of muscle atrophy-associated proteins, including FoxO3a, MAFbx, and MuRF1 in an IFN-γ/TNF-α induced atrophy model. Importantly, IFN-γ/TNF-α significantly reduced the mtDNA copy number in the C2C12 myotube, whereas the presence of 1,25VD3 effectively prevented this decrease. These results support that 1,25VD3 could serve as a potential preventive or therapeutic agent against age-related muscle atrophy by enhancing the VDR/SIRT1/SIRT3 axis.

Vitamin D deficiency contributes to overtraining syndrome in excessive trained C57BL/6 mice

Overtraining syndrome is a condition resulting from excessive training load associated with inadequate recovery and poor sleep quality, leading to performance decrements and fatigue. Here we hypothesized that vitamin D (VitD) deficiency is a lead factor in the development of the overtraining syndrome. To test this hypothesis, two groups of 60-week-old C57BL/6 mice followed a 16-week excessive eccentric-based overtraining by excessive downhill running with or without dietary VitD depletion (EX and EX-D- groups). Two control groups were trained by uphill running at the same load with or without VitD depletion (CX and CX-D- groups). Handgrip strength decreased throughout the protocol for all groups but the decrease was sharper in EX-D- group (VitD × training, p = 0.0427). At the end of the protocol, the mass of Triceps brachii muscle, which is heavily stressed by eccentric contractions, was reduced in eccentric-trained groups (training effect, p = 0.0107). This atrophy was associated with a lower concentration of the anabolic myokine IL-15 (training effect, p = 0.0314) and a tendency to a higher expression of the atrogene cathepsin-L (training effect, p = 0.0628). VitD depletion led to a 50% decrease of the fractional protein synthesis rate in this muscle (VitD effect, p = 0.0004) as well as decreased FGF21 (VitD effect, p = 0.0351) and increased osteocrin (VitD effect, p = 0.038) concentrations that would lead to metabolic defects. Moreover, the proportion of anti-inflammatory Th2 lymphocytes was significantly decreased by the combination of eccentric training with VitD depletion (vitD × training, p = 0.0249) suggesting a systemic inflammation. Finally, exploratory behavior time of mice was decreased by VitD depletion (VitD effect, p = 0.0146) suggesting a cognitive dysfunction. Our results suggest that VitD deficiency exacerbates the effects of overtraining.

The Role of Nutrition in the Treatment of Sarcopenia in Old Patients: From Restoration of Mitochondrial Activity to Improvement of Muscle Performance, a Systematic Review

Sarcopenia is an age-related disease characterized by loss of muscle strength, mass and performance. Malnutrition contributes to sarcopenia pathogenesis. The aim of this systematic review is to analyze existing evidence on the efficacy of nutritional supplementation on muscle and mitochondrial health among sarcopenic or malnourished older adults. We included randomized controlled trials (RCTs) assessing the effect of branched-chain amino acid (BCAA), vitamin D and/or omega-3 polyunsaturated fatty acid (PUFA) on muscle mass, strength and performance and/or on mitochondrial activity and redox state in older sarcopenic and/or malnourished adults. The literature search was on MEDLINE, Embase and Cochrane Central, restricted to articles published in the last 10 years (2012-2022). Twelve RCTs with a total of 1337 subjects were included. BCAA with vitamin D significantly ameliorates appendicular muscle mass (4 RCTs), hand grip strength (4 RCTs), gait speed (3 RCTs), short physical performance battery (3 RCTs) or chair stand test (3 RCTs) among six out of nine RCTs. BCAA alone (2 RCTs) or PUFA (1 RCT) were not effective in improving muscle health. Mitochondrial function was significantly improved by the administration of BCAA alone (1 RCT) or in association with vitamin D (1 RCT). In conclusion, BCAA in association with vitamin D may be useful in the treatment of sarcopenia and boost mitochondrial bioenergetic and redox activity. PROSPERO CRD42022332288.

Linear and Nonlinear Associations Between Vitamin D and Grip Strength: A Mendelian Randomization Study in UK Biobank

BACKGROUND

Low vitamin D status is a widespread phenomenon. Similarly, muscle weakness, often indicated by low grip strength, is another public health concern; however, the vitamin D-grip strength relationship is equivocal. It is important to understand whether variation in vitamin D status causally influences muscle strength to elucidate whether supplementation may help prevent/treat muscle weakness.

METHODS

UK Biobank participants, aged 37-73 years, with valid data on Vitamin D status (circulating 25-hydroxyvitamin D [25(OH)D] concentration) and maximum grip strength were included (N = 368,890). We examined sex-specific cross-sectional associations between 25(OH)D and grip strength. Using Mendelian randomization (MR), we estimated the strength of the 25(OH)D-grip strength associations using genetic instruments for 25(OH)D as our exposure. Crucially, because potential effects of vitamin D supplementation on strength could vary by underlying 25(OH)D status, we allowed for nonlinear relationships between 25(OH)D and strength in all analyses.

RESULTS

Mean (SD) of 25(OH)D was 50 (21) nmol/L in males and females. In cross-sectional analyses, there was evidence of nonlinear associations between 25(OH)D and strength, for example, compared to males with 50 nmol/L circulating 25(OH)D, males with 75 nmol/L had 0.36 kg (0.31,0.40) stronger grip; males with 25 nmol/L had 1.01 kg (95% confidence interval [CI]: 0.93, 1.08) weaker grip. In MR analyses, linear and nonlinear models fitted the data similarly well, for example, 25 nmol/L higher circulating 25(OH)D in males was associated with 0.25 kg (-0.05, 0.55) greater grip (regardless of initial 25(OH)D status). Results were similar, albeit weaker, for females.

CONCLUSIONS

Using two different methods to triangulate evidence, our findings suggest moderate to small causal links between circulating 25(OH)D and grip strength.

"Diet for the prevention and management of sarcopenia"

Sarcopenia is a geriatric condition characterized by a progressive loss of skeletal muscle mass and strength, with an increased risk of adverse health outcomes (e.g., falls, disability, institutionalization, reduced quality of life, mortality). Pharmacological remedies are currently unavailable for preventing the development of sarcopenia, halting its progression, or impeding its negative health outcomes. The most effective strategies to contrast sarcopenia rely on the adoption of healthier lifestyle behaviors, including adherence to high-quality diets and regular physical activity. In this review, the role of nutrition in the prevention and management of sarcopenia is summarized. Special attention is given to current "blockbuster" dietary regimes and agents used to counteract age-related muscle wasting, together with their putative mechanisms of action. Issues related to the design and implementation of effective nutritional strategies are discussed, with a focus on unanswered questions on the most appropriate timing of nutritional interventions to preserve muscle health and function into old age. A brief description is also provided on new technologies that can facilitate the development and implementation of personalized nutrition plans to contrast sarcopenia.

Association of Vitamin D Receptor Gene Polymorphisms with Cardiometabolic Phenotypes in Hispanics: A Life Course Approach

The vitamin D receptor (VDR) is vital for maintaining calcium and phosphate balance and regulating bone metabolism. Recent research has suggested that VDR also plays an essential role in metabolic diseases. Previous studies on non-Hispanic whites have shown that VDR single nucleotide polymorphisms (SNP) are associated with cardiometabolic phenotypes. However, the association between VDR SNPs and cardiometabolic traits in Hispanics remains unclear. This study investigated the association between VDR SNPs and cardiometabolic phenotypic data in self-reported Hispanics (n = 1610) from the Arizona Insulin Resistance registry and Sangre Por Salud Biobank. The study population was predominantly female (66.4%) with a mean age of 40 ± 14 years (n = 121 <18 years) and an average body mass index (BMI) of 29.8 ± 6.3 kg/m2. We performed a genotyping association analysis of VDR SNPs (Taq1-rs731236, Fok1-rs2228570 and Apa1-rs7975232) with cardiometabolic traits using linear regression models. The results showed that Taq1 and Apa1 were strongly associated with systolic blood pressure (SBP) in children (<18 years), while Fok1 was associated with measures of adiposity, including fat mass, waist circumference, and BMI. In age-stratified adult (≥18 years) models, Taq1 was strongly associated with hemoglobin A1c, while Apa1 was associated with BMI and fasting glucose. Fok1 had no significant associations in the adult models. In conclusion, the VDR SNPs were associated with several cardiometabolic phenotypes in this Hispanic sample, but the type and strength of the associations varied by age group.

Sarcopenia in youth

Recent research has revealed causes other than aging that may induce sarcopenia in young people, contrary to the long-studied age-dependent reduction in muscular mass and function. The risk of sarcopenia begins in early adulthood, resulting in exaggerated muscle dysfunction in later life. Despite its clinical significance, research on youth-onset sarcopenia is still in its infancy. Due to a paucity of epidemiologic data and standardized criteria for sarcopenia in youth, determining the prevalence of sarcopenia in the young population remains challenging. Based on the evidence, >1 in every 10 young adults of most ethnicities is estimated to have sarcopenia. This review summarizes the possible etiologies of sarcopenia in young populations, including metabolic syndrome, physical inactivity, inadequate nutrition, inherent and perinatal factors, vitamin D deficiency, endocrinopathy, an imbalance of gut microbiota, neuromuscular diseases, organ failure, malignancy, and other inflammatory disorders. This is the first review of the current knowledge on the importance, prevalence, diagnosis, and causes of sarcopenia in youth.

An Integrated Approach to Skeletal Muscle Health in Aging

A decline in muscle mass and function represents one of the most problematic changes associated with aging, and has dramatic effects on autonomy and quality of life. Several factors contribute to the inexorable process of sarcopenia, such as mitochondrial and autophagy dysfunction, and the lack of regeneration capacity of satellite cells. The physiologic decline in muscle mass and in motoneuron functionality associated with aging is exacerbated by the sedentary lifestyle that accompanies elderly people. Regular physical activity is beneficial to most people, but the elderly need well-designed and carefully administered training programs that improve muscle mass and, consequently, both functional ability and quality of life. Aging also causes alteration in the gut microbiota composition associated with sarcopenia, and some advances in research have elucidated that interventions via the gut microbiota-muscle axis have the potential to ameliorate the sarcopenic phenotype. Several mechanisms are involved in vitamin D muscle atrophy protection, as demonstrated by the decreased muscular function related to vitamin D deficiency. Malnutrition, chronic inflammation, vitamin deficiencies, and an imbalance in the muscle-gut axis are just a few of the factors that can lead to sarcopenia. Supplementing the diet with antioxidants, polyunsaturated fatty acids, vitamins, probiotics, prebiotics, proteins, kefir, and short-chain fatty acids could be potential nutritional therapies against sarcopenia. Finally, a personalized integrated strategy to counteract sarcopenia and maintain the health of skeletal muscles is suggested in this review.

The benefits of Vitamin D in the COVID-19 pandemic: biochemical and immunological mechanisms

In December 2019, a new infectious complication called CoronaVirus Infectious Disease-19, briefly COVID-19, caused by SARS-COV-2, is identified in Wuhan, China. It spread all over the world and became a pandemic. In many individuals who had suffered SARS-COV-2 infection, cytokine storm starts through cytokine overproduction and leads to Acute Respiratory Syndrome (ARS), organ failure, and death. According to the obtained evidence, Vitamin D (VitD) enhances the ACE2/Ang(1-7)/MasR pathway activity, and it also reduces cytokine storms and the ARS risk. Therefore, VitD intake may be beneficial for patients with SARS-COV-2 infection exposed to cytokine storm but do not suffer hypotension. In the present review, we have explained the effects of VitD on the renin-angiotensin system (RAS) function and angiotensin-converting enzyme2 (ACE2) expression. Furthermore, we have reviewed the biochemical and immunological effects of VitD on immune function in the underlying diseases and its role in the COVID-19 pandemic.

Vitamin D3 Supplementation: Comparison of 1000 IU and 2000 IU Dose in Healthy Individuals

Background: Scientific studies point to a significant global vitamin D deficiency. The recommended dose of vitamin D for the adult population in Central Europe is 800–2000 IU/day. The aim of our study was to determine whether doses of 1000 IU or 2000 IU of vitamin D3 are adequate to achieve the sufficiency reference values of [25(OH)D]. Methods: Seventy-two healthy volunteers, average age twenty-two, took part in the study. The study was conducted from October to March in order to eliminate intra-dermal vitamin D production. Vitamin D3 in an oleaginous mixture was used. The participants used either 1000 IU or 2000 IU/daily for two 60-day periods with a 30-day break. Results: The dose of 1000 IU, taken for 60 days, increased vitamin D levels relatively little. Furthermore, serum vitamin D levels decreased in the 30 days following the cessation of supplementation. Taking 2000 IU daily led to a sharp increase in serum levels which plateaued 30 days after the subjects stopped using vitamin D3 drops. Conclusions: Both doses, taken daily, can help maintain adequate vitamin D levels during the winter months. A daily dose of 2000 IU, however, maintained the desired levels of vitamin D for a longer period.

Age-related muscle anabolic resistance: inevitable or preventable?

Age-related loss of muscle mass, strength, and performance, commonly referred to as sarcopenia, has wide-ranging detrimental effects on human health, the ramifications of which can have serious implications for both morbidity and mortality. Various interventional strategies have been proposed to counteract sarcopenia, with a particular emphasis on those employing a combination of exercise and nutrition. However, the efficacy of these interventions can be confounded by an age-related blunting of the muscle protein synthesis response to a given dose of protein/amino acids, which has been termed "anabolic resistance." While the pathophysiology of sarcopenia is undoubtedly complex, anabolic resistance is implicated in the progression of age-related muscle loss and its underlying complications. Several mechanisms have been proposed as underlying age-related impairments in the anabolic response to protein consumption. These include decreased anabolic molecular signaling activity, reduced insulin-mediated capillary recruitment (thus, reduced amino acid delivery), and increased splanchnic retention of amino acids (thus, reduced availability for muscular uptake). Obesity and sedentarism can exacerbate, or at least facilitate, anabolic resistance, mediated in part by insulin resistance and systemic inflammation. This narrative review addresses the key factors and contextual elements involved in reduction of the acute muscle protein synthesis response associated with aging and its varied consequences. Practical interventions focused on dietary protein manipulation are proposed to prevent the onset of anabolic resistance and mitigate its progression.

Bmi-1 Overexpression Improves Sarcopenia Induced by 1,25(OH)2 D3 Deficiency and Downregulates GATA4-Dependent Rela Transcription

Sarcopenia increases with age, and an underlying mechanism needs to be determined to help with designing more effective treatments. This study aimed to determine whether 1,25(OH)₂ D₃ deficiency could cause cellular senescence and a senescence-associated secretory phenotype (SASP) in skeletal muscle cells to induce sarcopenia, whether GATA4 could be upregulated by 1,25(OH)₂ D₃ deficiency to promote SASP, and whether Bmi-1 reduces the expression of GATA4 and GATA4-dependent SASP induced by 1,25(OH)₂ D₃ deficiency in skeletal muscle cells. Bioinformatics analyses with RNA sequencing data in skeletal muscle from physiologically aged and young mice were conducted. Skeletal muscles from 2-month-old young and 2-year-old physiologically aged wild-type (WT) mice and 8-week-old WT, Bmi-1 mesenchymal transgene (Bmi-1^Tg ), Cyp27b1 homozygous (Cyp27b1^-/- ), and Bmi-1^Tg Cyp27b1^-/- mice were observed for grip strength, cell senescence, DNA damage, and NF-κB-mediated SASP signaling of skeletal muscle. We found that muscle-derived Bmi-1 and vitamin D receptor (VDR) decreased with physiological aging, and DNA damage and GATA4-dependent SASP activation led to sarcopenia. Furthermore, 1,25(OH)₂ D₃ deficiency promoted DNA damage-induced GATA4 accumulation in muscles. GATA4 upregulated Rela at the region from -1448 to -1412 bp at the transcriptional level to cause NF-κB-dependent SASP for aggravating cell senescence and muscular dysfunction and sarcopenia. Bmi-1 overexpression promoted the ubiquitination and degradation of GATA4 by binding RING1B, which prevented cell senescence, SASP, and dysfunctional muscle, and improved sarcopenia induced by 1,25(OH)₂ D₃ deficiency. Thus, Bmi-1 overexpression improves sarcopenia induced by 1,25(OH)₂ D₃ deficiency, downregulates GATA4-dependent Rela transcription, and sequentially inhibits GATA4-dependent SASP in muscle cells. Therefore, Bmi-1 overexpression could be used for translational gene therapy for the ubiquitination of GATA4 and prevention of sarcopenia. © 2023 American Society for Bone and Mineral Research (ASBMR).

Serum Vitamin D Level Correlations With Tissue Vitamin D Level and Muscle Performance Before and After Rotator Cuff Repair

BACKGROUND

There is a lack of studies about serum and tissue vitamin D levels of the rotator cuff muscle on muscle power, fatty degeneration, and healing failure after rotator cuff repair (RCR). Furthermore, no studies have evaluated vitamin D receptor proteins in the rotator cuff that show a close association with serum vitamin D levels.

PURPOSE

To evaluate the correlations between serum vitamin D and tissue vitamin D as well as perioperative variables of arthroscopic RCR.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

From March 2017 to October 2017, a total of 36 patients who underwent RCR were prospectively enrolled, and supraspinatus muscle tissue was obtained during surgery to analyze tissue vitamin D levels. Serum vitamin D levels were checked preoperatively and at 6 months and 1 year postoperatively. Tissue vitamin D levels were assessed using liquid chromatography, and the vitamin D receptor was measured by western blotting. Isokinetic muscle performance test (IMPT; peak torque and torque deficiency compared with the opposite shoulder) results and fatty degeneration of the rotator cuff using the Goutallier classification were assessed preoperatively and at 1 year after surgery. The American Shoulder and Elbow Surgeons score and Constant score were collected at 2 years after surgery. Healing failure of the repaired rotator cuff was analyzed by magnetic resonance imaging at 1 year after surgery.

RESULTS

Overall, only three patients (8.3%) had serum vitamin D sufficiency (>20 ng/mL). Among 36 patients, 26 patients returned for their 1-year follow-up. Lower preoperative serum vitamin D levels resulted in lower serum vitamin D levels at 6 months and 1 year postoperatively (all P < .05). Lower preoperative and 1-year postoperative serum vitamin D levels resulted in more torque deficiency on the IMPT in abduction than higher preoperative and 1-year postoperative serum vitamin D levels (all P < .05). Tissue vitamin D levels had a strong correlation with preoperative serum vitamin D levels (P = .001). Lower tissue vitamin D levels were associated with lower peak torque on the IMPT in abduction (P = .043) and a tendency of lower peak torque on the IMPT in external rotation (P = .077) at 1 year postoperatively. There was no correlation between tissue and serum vitamin D levels and functional outcomes, fatty degeneration, and healing failure after surgery (all P > .05). The vitamin D receptor showed no correlation with any variables (all P > .05).

CONCLUSION

Lower preoperative serum vitamin D levels had a strong correlation with lower tissue vitamin D levels and lower serum vitamin D levels at 1 year after surgery. Furthermore, the patients with lower serum vitamin D levels showed more weakness of muscle power perioperatively. The results of this study emphasized the association between vitamin D levels and rotator cuff muscle power.

Clinical Trial to Assess Physiology and Activity of Masticatory Muscles of Complete Denture Wearer Following Vitamin D Intervention

Background and Objectives: Little information is available on the role of Vitamin D as a micro-nutrient deficiency with masticatory muscle efficiency and its effect on the function of removable prosthesis. The aim of this study was to evaluate the role of vitamin D on masticatory muscle activity among completely edentulous patients and its effect on the retention of removable complete dentures (RCDs). Materials and Methods: A non-randomized clinical control trial was conducted on completely edentulous patients (60.53 ± 7.01 years) in the Indian population between 2017 and 2019. Subjects were evaluated for temporomandibular disorders according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD). Serum Vitamin D (S Vit D) levels, Ultrasonography (USG), and surface Electromyography (sEMG) readings of the masseter muscle were recorded at enrolment (Level 0), after 3 months of Vitamin D therapy (Level 3), and after consecutive 3 months of maintenance therapy, i.e., after 6 months from baseline (Level 6). The fabrication of new RCDs was done for all after the enrolment, and the retention of RCDs was assessed by asking a question regarding denture retention and asking respondents to mark their satisfaction on a 5-point Likert scale. Data were analysed using ANOVA, Paired'-test and Pearson correlation coefficients. A p-value less than 0.05 indicated a statistically significant association. Results: Between enrolment and a six-month follow-up, S Vit D levels showed an increase from 16.03 ± 5.68 ng/mL to 31.35 ± 9.28 ng/mL, showing an increase of 15.32 ± 9.38 ng/mL (95.57% rise). Statistically significant values were observed for USG and sEMG. Conclusions: Results showed that S Vit D affects masticatory muscle activity by improving its thickness and boosting its tonicity. Healthy muscles assist in the retention of RCDs, consequently aiding in mastication, speech, and phonetics, hence improving patient satisfaction. Clinical implication: Acknowledging the fact that the prevalence of Vitamin D deficiency is worldwide. We suggest Vitamin D therapy as a nutritional intervention among the elderly completely edentulous population, following dietary counselling, and consider Vitamin D therapy to be an adjunct to nutritional counselling for improving masticatory muscle activity and efficiency, which aids in RCD retention and stability. Consequently, improving oral health-related quality of life for individuals.

Differential effects of vitamin D on upper and lower body fat-free mass: potential mechanisms

Vitamin D insufficiency is a global health concern and low vitamin D status is regularly associated with reduced muscle mass and sarcopenia in observational research. Recent research using Mendelian randomization (MR) has highlighted the potentially causal positive effect of serum vitamin D (25(OH)D) on total, trunk and upper body appendicular fat-free mass (FFM). However, no such effect was found in lower body FFM, a result that mirrors the outcomes of some vitamin D intervention studies. Here we review the current literature on vitamin D, muscle mass and strength and discuss some potential mechanisms for the differing effects of vitamin D on upper and lower body FFM. In particular, differences in distribution of the vitamin D receptor as well as androgen receptors, in the upper and lower body musculature, will be discussed.

Are Skeletal Muscle Changes during Prolonged Space Flights Similar to Those Experienced by Frail and Sarcopenic Older Adults?

Microgravity exposure causes several physiological and psychosocial alterations that challenge astronauts' health during space flight. Notably, many of these changes are mostly related to physical inactivity influencing different functional systems and organ biology, in particular the musculoskeletal system, dramatically resulting in aging-like phenotypes, such as those occurring in older persons on Earth. In this sense, sarcopenia, a syndrome characterized by the loss in muscle mass and strength due to skeletal muscle unloading, is undoubtedly one of the most critical aging-like adverse effects of microgravity and a prevalent problem in the geriatric population, still awaiting effective countermeasures. Therefore, there is an urgent demand to identify clinically relevant biological markers and to underline molecular mechanisms behind these effects that are still poorly understood. From this perspective, a lesson from Geroscience may help tailor interventions to counteract the adverse effects of microgravity. For instance, decades of studies in the field have demonstrated that in the older people, the clinical picture of sarcopenia remarkably overlaps (from a clinical and biological point of view) with that of frailty, primarily when referred to the physical function domain. Based on this premise, here we provide a deeper understanding of the biological mechanisms of sarcopenia and frailty, which in aging are often considered together, and how these converge with those observed in astronauts after space flight.

Lack of significant seasonal association between serum 25(OH)D concentration, muscle mass and strength in postmenopausal women from the D-FINES longitudinal study

The aim of the present study was to assess the seasonal relationship between serum 25(OH)D concentration, lean mass and muscle strength. This was a secondary data analysis of a subgroup of 102 postmenopausal women participating in the 2006-2007 D-FINES (Vitamin D, Food Intake, Nutrition and Exposure to Sunlight in Southern England) study. The cohort was assessed as two age subgroups: <65 years (n=80) and ≥65 years (n=22). Outcome measures included lean mass (DXA), muscle strength (handgrip dynamometry) and serum 25(OH)D concentration (enzymeimmunoassay). Derived outcomes included appendicular skeletal muscle mass (ASM) and relative appendicular skeletal muscle index (RASM). Sarcopenia status was assessed using the European Working Group on Sarcopenia in Older People 2018 criteria. Non-parametric partial correlation using BMI as a covariate was used to evaluate the study aims. There were no statistically significant associations between total lean mass, ASM or RASM and 25(OH)D in any group at any season. There was a trend for handgrip strength to be positively associated with serum 25(OH)D concentration. There was a trend showing a higher prevalence of sarcopenia in women ≥65 years. Sarcopenia status appeared transient for five women. In conclusion, the present study found no significant association between vitamin D status and functional indicators of musculoskeletal health, which were additionally not affected by season.

Serum vitamin D status and circulating irisin levels in older adults with sarcopenia

Background

Emerging evidence suggests sarcopenia, which is involved in the serum vitamin D deficiency and development of abnormal muscle metabolism, is predominately centered in the general older population. In the present study, we aimed to explore the relationship between the level of serum vitamin D and irisin concentrations in the older adults with sarcopenia.

Methods

A cross-sectional study was conducted which included 422 sarcopenia participants (146 males and 276 females). Sarcopenia was assessed according to the recommended diagnostic criteria of the Asia Working Group for Sarcopenia (AWGS). The levels of serum 25-hydroxyvitamin D (25(OH)D), 25-hydroxyvitamin D₂ (25(OH)D₂) and 25-hydroxyvitamin D₃ (25(OH)D₃) were determined by LC-MS/MS. Irisin levels were measured by enzyme-linked immunosorbent assay (ELISA). The relationship between serum concentration of vitamin D and irisin were determined using multiple linear regression analysis.

Results

After adjustment for potential confounding factors, a significant and positive relationship between changes in irisin across 25(OH)D, and 25(OH)D₃ was observed (standard regression coefficients of 0.150 and 0.151, respectively, P < 0.05). However, no significant relationship was observed between serum vitamin D concentrations and irisin levels in males.

Conclusions

This study demonstrated that a higher level of serum vitamin D is independently related to the increment of irisin in sarcopenia females, not in males. These investigations need to be verified in other large-scale prospective studies.

Influence of vitamin D on sarcopenia pathophysiology: A longitudinal study in humans and basic research in knockout mice

BACKGROUND

Vitamin D is an essential nutrient in musculoskeletal function; however, its relationship to sarcopenia remains ambiguous, and the mechanisms and targets of vitamin D activity have not been elucidated. This study aimed to clarify the role of vitamin D in mature skeletal muscle and its relationship with sarcopenia.

METHODS

This epidemiological study included 1653 community residents who participated in both the fifth and seventh waves of the National Institute for Longevity Sciences, Longitudinal Study of Aging and had complete background data. Participants were classified into two groups: vitamin D-deficient (serum 25-hydroxyvitamin D < 20 ng/mL) and non-deficient (serum 25-hydroxyvitamin D ≥ 20 ng/mL); they underwent propensity-score matching for background factors (age, sex, height, weight, comorbidities, smoker, alcohol intake, energy intake, vitamin D intake, steps, activity, season and sarcopenia). Changes in muscle strength and mass over the 4-year period were compared. For basic analysis, we generated Myf6^CreERT2 Vitamin D Receptor (VDR)-floxed (Vdr^mcKO ) mice with mature muscle fibre-specific vitamin D receptor knockout, injected tamoxifen into 8-week-old mice and analysed various phenotypes at 16 weeks of age.

RESULTS

Grip strength reduction was significantly greater in the deficient group (-1.55 ± 2.47 kg) than in the non-deficient group (-1.13 ± 2.47 kg; P = 0.019). Appendicular skeletal muscle mass reduction did not differ significantly between deficient (-0.05 ± 0.79 kg) and non-deficient (-0.01 ± 0.74 kg) groups (P = 0.423). The incidence of new cases of sarcopenia was significantly higher in the deficient group (15 vs. 5 cases; P = 0.039). Skeletal muscle phenotyping of Vdr^mcKO mice showed no significant differences in muscle weight, myofibre percentage or myofibre cross-sectional area; however, both forelimb and four-limb muscle strength were significantly lower in Vdr^mcKO mice (males: forelimb, P = 0.048; four-limb, P = 0.029; females: forelimb, P < 0.001; four-limb, P < 0.001). Expression profiling revealed a significant decrease in expression of sarcoendoplasmic reticulum Ca²⁺ -ATPase (SERCA) 1 (P = 0.019) and SERCA2a (P = 0.049) genes in the Vdr^mcKO mice. In contrast, expression of non-muscle SERCA2b and myoregulin genes showed no changes.

CONCLUSIONS

Vitamin D deficiency affects muscle strength and may contribute to the onset of sarcopenia. Vitamin D-VDR signalling has minimal influence on the regulation of muscle mass in mature myofibres but has a significant influence on muscle strength.

Vitamin D status modulates mitochondrial oxidative capacities in skeletal muscle: role in sarcopenia

Skeletal muscle mitochondrial function is the biggest component of whole-body energy output. Mitochondrial energy production during exercise is impaired in vitamin D-deficient subjects. In cultured myotubes, loss of vitamin D receptor (VDR) function decreases mitochondrial respiration rate and ATP production from oxidative phosphorylation. We aimed to examine the effects of vitamin D deficiency and supplementation on whole-body energy expenditure and muscle mitochondrial function in old rats, old mice, and human subjects. To gain further insight into the mechanisms involved, we used C2C12 and human muscle cells and transgenic mice with muscle-specific VDR tamoxifen-inducible deficiency. We observed that in vivo and in vitro vitamin D fluctuations changed mitochondrial biogenesis and oxidative activity in skeletal muscle. Vitamin D supplementation initiated in older people improved muscle mass and strength. We hypothesize that vitamin D supplementation is likely to help prevent not only sarcopenia but also sarcopenic obesity in vitamin D-deficient subjects.

Vitamin D, exercise, and immune health in athletes: A narrative review

Vitamin D exerts important extra-skeletal effects, exhibiting an exquisite immune regulatory ability, affecting both innate and adaptive immune responses through the modulation of immunocyte function and signaling. Remarkably, the immune function of working skeletal muscle, which is fully recognized to behave as a secretory organ with immune capacity, is under the tight control of vitamin D as well. Vitamin D status, meaning hormone sufficiency or insufficiency, can push toward strengthening/stabilization or decline of immune surveillance, with important consequences for health. This aspect is particularly relevant when considering the athletic population: while exercising is, nowadays, the recommended approach to maintain health and counteract inflammatory processes, “too much” exercise, often experienced by athletes, can increase inflammation, decrease immune surveillance, and expose them to a higher risk of diseases. When overexercise intersects with hypovitaminosis D, the overall effects on the immune system might converge into immune depression and higher vulnerability to diseases. This paper aims to provide an overview of how vitamin D shapes human immune responses, acting on the immune system and skeletal muscle cells; some aspects of exercise-related immune modifications are addressed, focusing on athletes. The crossroad where vitamin D and exercise meet can profile whole-body immune response and health.

Dietary supplementation of 25-hydroxycholecalciferol as an alternative to cholecalciferol in swine diets: A review

25-hydroxycholecalciferol (25-OHD₃ ) formed via hepatic hydroxylation from vitamin D, cholecalciferol, represents the precursor of the biologically active vitamin D hormone, 1,25-dihydroxyvitamin D. Due to a higher absorption rate and the omission of one hydroxylation, dietary supplementation of 25-OHD₃ instead of vitamin D₃ is considered to be more efficient as plasma concentrations of 25-OHD₃ are increased more pronounced. The present review summarises studies investigating potential beneficial effects on mineral homeostasis, bone metabolism, health status and performance in sows, piglets and fattening pigs. Results are inconsistent. While most studies could not demonstrate any or only a slight impact of partial or total replacement of vitamin D₃ by 25-OHD₃ , some experiments indicated that 25-OHD₃ might alter physiological processes when animals are challenged, for example, by a restricted mineral supply.

The Relationship Between Vitamin D and Activity of Daily Living in the Elderly

Objective

To analyze the association between vitamin D and the performance of activity of daily living in the elderly.

Methods

A total of 94 patients over the age of 65 were eligible to participate if they had undergone a bone mineral density test and if they were in a stable health condition. Subjects were further divided into two groups according to activity of daily living (ADL): the score over 40 of the patients as the high ADL group and the below as the low ADL group.

Results

According to univariate analysis, the mean of total hip T score, serum creatinine/cystatin C ratio (CCR), and vitamin D were significantly different between the two groups (P=0.024, 0.008, 0.010). Multivariate ORs showed that the CCR (OR: 0.948; 95%CI: 0.910–0.989; P=0.013) and vitamin D (OR: 865; 95%CI: 0.752–0.994; P=0.047) were inversely associated with having low ADL. Furthermore, on multiple linear regression analysis, the Barthel ADL index was related to geriatric nutritional risk index (GNRI), CCR and vitamin D but independent of patients’ age with the slope of 0.732, 0.539, and 0.689 separately, reflected the stronger relative within the variables.

Conclusion

We demonstrated that there is a negative correlation of CCR and vitamin D with having low ADL in elderly population. Monitoring the trend of serum vitamin D and CCR, may have a role in the early detection of low ADL with loss of muscle mass and strength in the population of the elderly.

Advances in Our Understanding of the Mechanism of Action of Drugs (including Traditional Chinese Medicines) for the Intervention and Treatment of Osteoporosis

Osteoporosis (OP) is known as a silent disease in which the loss of bone mass and bone density does not cause obvious symptoms, resulting in insufficient treatment and preventive measures. The losses of bone mass and bone density become more severe over time and an only small percentage of patients are diagnosed when OP-related fractures occur. The high disability and mortality rates of OP-related fractures cause great psychological and physical damage and impose a heavy economic burden on individuals and society. Therefore, early intervention and treatment must be emphasized to achieve the overall goal of reducing the fracture risk. Anti-OP drugs are currently divided into three classes: antiresorptive agents, anabolic agents, and drugs with other mechanisms. In this review, research progress related to common anti-OP drugs in these three classes as well as targeted therapies is summarized to help researchers and clinicians understand their mechanisms of action and to promote pharmacological research and novel drug development.

The Vitamin D/Vitamin D receptor (VDR) axis in muscle atrophy and sarcopenia

Muscle atrophy and sarcopenia (the term given to the age-related decline in muscle mass and function), influence an individuals risk of falls, frailty, functional decline, and, ultimately, impaired quality of life. Vitamin D deficiency (low serum levels of 25-hydroxyvitamin D (25(OH)D₃)) has been reported to impair muscle strength and increase risk of sarcopenia. The mechanisms that underpin the link between low 25(OH)D₃ and sarcopenia are yet to be fully understood but several lines of evidence have highlighted the importance of both genomic and non-genomic effects of active vitamin D (1,25-dihydroxyvitamin D (1,25(OH)₂D₃)) and its nuclear vitamin D receptor (VDR), in skeletal muscle functioning. Studies in vitro have demonstrated a key role for the vitamin D/VDR axis in regulating biological processes central to sarcopenic muscle atrophy, such as proteolysis, mitochondrial function, cellular senescence, and adiposity. The aim of this review is to provide a mechanistic overview of the proposed mechanisms for the vitamin D/VDR axis in sarcopenic muscle atrophy.

Effect of Calcifediol on Physical Performance and Muscle Strength Parameters: A Systematic Review and Meta-Analysis

There is general agreement that optimal vitamin D status is necessary for bones, muscles, and general health, particularly in older adults, who are at higher risk of negative consequences of vitamin D deficiency, including sarcopenia; vitamin D supplementation is proposed as a potential intervention to mitigate sarcopenia. Several RCTs have reported that calcifediol (25(OH)D) was more potent than cholecalciferol in increasing plasma 25(OH)D. The present systematic review and meta-analysis aimed to summarize the effects of calcifediol on physical performance and muscle strength. We searched databases from inception to 1 January 2022 for studies investigating calcifediol on physical performance or muscle strength parameters. We calculated the difference between the means of follow-up vs. baseline data using standardized mean differences (SMD) and their 95% confidence intervals (CIs); a random-effect model was considered for all of the analyses. Seven RCTs were included in the meta-analysis. Calcifediol significantly improved gait speed (SMD = 2.500; 95%CI = 1.768−3.223; p < 0.0001); handgrip strength (n = 5446 participants, SMD = 0.532; 95%CI: 0.305−0.758; p < 0.0001; I2 = 20.2%); and leg extension (n = 4318 participants, SMD = 0.641; 95%CI: 0.346 to 0.935; p < 0.0001; I2 = 18.8%;) vs. baseline values. In conclusion, in this systematic review and meta-analysis, we observed that calcifediol may have a positive effect on muscle strength parameters, with less evidence on physical performance. These data further indicate the importance of vitamin D and, in particular, of calcifediol, not only on bone metabolism but also on muscle parameters and sarcopenia.

Correlation of Vitamin D3, PAI-1, and HCG Hormone in Pre- and Post-Menopausal in Babylon Province

Background

Menopause is a unique event in women's life it usually occurs naturally, most often after age 50 when woman has not menstruated in 12 consecutive months. This study was planned to assess the relationship between Vitamin D3 level, PAI-1 and HCG in Babylon women at age <50 years as pre-menopausal and> 50 years as post-menopausal.

Methods

The sample were selected from a group of pre- and post-menopausal women, 30 and 50 respectively. All the tests were evaluated to measure Vitamin D3 level, PAI-1 and HCG level. The sample was collected between July 2019 and January 2020 at Merjan medical city GIT and Liver Center, Babylon province, Iraq.

Results

The result of current study revealed that there are significant differences in vitamin D3 level in various age categories within postmenopausal women (p= 0.02) also there is no significant differences in PAI-1 and HCG with in these two groups, p= 0.08 and 0.07, respectively. Also, there is significant negative correlation between vitamin D3 and PAI-1 in postmenopausal women (p. value is 0.01).

Conclusion

Indeed, postmenopausal women regarded as elderly, but they have sufficient vitamin D3 and normal PAI-I levels as markers for normal non fibrosis status.

Systemic ablation of vitamin D receptor leads to skeletal muscle glycogen storage disorder in mice

BACKGROUND

Vitamin D deficiency leads to pathologies of multiple organ systems including skeletal muscle. Patients with severe vitamin D deficiency exhibit muscle weakness and are susceptible to frequent falls. Mice lacking a functional vitamin D receptor (VDR) develop severe skeletal muscle atrophy immediately after weaning. But the root cause of myopathies when vitamin D signalling is impaired is unknown. Because vitamin D deficiency leads to metabolic changes as well, we hypothesized that the skeletal muscle atrophy in mice lacking VDR may have a metabolic origin.

METHODS

We analysed wild-type (WT) mice as well as vitamin D receptor null (vdr-/-) mice for skeletal muscle proteostasis, energy metabolism, systemic glucose homeostasis, and muscle glycogen levels. Dysregulation of signalling pathways as well as the glycogen synthesis and utilization machinery were also analysed using western blots. qRT-PCR assays were performed to understand changes in mRNA levels.

RESULTS

Skeletal muscles of vdr-/- exhibited higher expression levels of muscle-specific E3 ubiquitin ligases and showed increased protein ubiquitination, suggesting up-regulation of protein degradation. Foxo1 transcription factor was activated in vdr-/- while Foxo3 factor was unaffected. Fasting protein synthesis as well as mTORC1 pathways were severely down-regulated in vdr-/- mice. Skeletal muscle ATP levels were low in vdr-/- (0.58 ± 0.18 μmol/mL vs. 1.6 ± 0.0.14 μmol/mL, P = 0.006), leading to increased AMPK activity. Muscle energy deprivation was not caused by decreased mitochondrial activity as we found the respiratory complex II activity in vdr-/- muscles to be higher compared with WT (0.29 ± 0.007 mU/μL vs. 0.16 ± 0.005 mU/μL). vdr-/- mice had lower fasting blood glucose levels (95 ± 14.5 mg/dL vs. 148.6 ± 6.1 mg/dL, P = 0.0017) while they exhibited hyperlactataemia (7.42 ± 0.31 nmol/μL vs. 4.95 ± 0.44 nmol/μL, P = 0.0032), suggesting systemic energy deficiency in these mice. Insulin levels in these mice were significantly lower in response to intraperitoneal glucose injection (0.69 ± 0.08 pg/mL vs. 1.11 ± 0.09 pg/mL, P = 0.024). Skeletal muscles of these mice exhibit glycogen storage disorder characterized by increased glycogen accumulation. The glycogen storage disorder in vdr-/- muscles is driven by increased glycogen synthase activity and decreased glycogen phosphorylase activity. Increased glycogenin expression supports higher levels of glycogen synthesis in these muscles.

CONCLUSIONS

The results presented show that lack of vitamin D signalling leads to a glycogen storage defect in the skeletal muscles, which leads to muscle energy deprivation. The inability of vdr-/- skeletal muscles to use glycogen leads to systemic defects in glucose homeostasis, which in turn leads to proteostasis defects in skeletal muscles and atrophy.

Association Between Vitamin D Supplementation and Fall Prevention

BACKGROUND

Falls occur frequently among older individuals, leading to high morbidity and mortality. This study was to assess the efficacy of vitamin D in preventing older individuals from falling.

METHODS

We searched the PubMed, Cochrane Library, and EMBASE databases systematically using the keywords "vitamin D" and "fall" for randomized controlled trials (RCTs) comparing the effects of vitamin D with or without calcium supplements with those of a placebo or no treatment on fall incidence in adults older than 50 years. A meta-analysis was performed to calculate risk ratios (RRs), absolute risk differences (ARDs) and 95% CIs with random-effects models.

RESULTS

A total of 38 RCTs involving 61 350 participants fulfilled the inclusion criteria. Compared with placebo, high-dose vitamin D (≥ 700 IU) can prevent falls [RR, 0.87 (95% CI 0.79 to 0.96); ARD, -0.06 (95% CI, -0.10 to -0.02)]. Low-dose vitamin D (<700 IU) was not significantly associated with falls. Subgroup analysis showed that supplemental calcium, 25(OH) D concentration and frequency influenced the effect of vitamin D in preventing falls. Sensitivity analysis showed that vitamin D prevented falls, which was consistent with the primary analysis. In addition, the active form of vitamin D also prevented falls.

CONCLUSION

In this meta-analysis of RCTs, doses of 700 IU to 2000 IU of supplemental vitamin D per day were associated with a lower risk of falling among ambulatory and institutionalized older adults. However, this conclusion should be cautiously interpreted, given the small differences in outcomes.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/, identifier CRD42020179390.

Vitamin D Supplementation Improves Handgrip Strength in Postmenopausal Women: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

INTRODUCTION

In postmenopausal women, vitamin D deficiency (as defined by the circulating level of 25(OH)D being below 20 ng/ml (50 nmol/L)) is a regular occurrence. The effect of vitamin D supplementation on the muscle function of postmenopausal women has been controversial. This systematic review and meta-analysis of randomized controlled trials (RCTs) examines and summarizes the effects of vitamin D supplementation on the muscular strength and mobility of postmenopausal women.

METHODS

RCTs that met the inclusion criteria for this study were identified by searching PubMed, EMBASE, and the Cochrane Library. Postmenopausal women who were included in the study were exposed to RCTs assessing the effectiveness of vitamin D supplements. Meta-analysis data were extracted by two independent reviewers and screened for methodological quality. RCTs that did not meet the minimum requirement for assessment were excluded. In the meta-analysis, the effect size (weighted mean differences, WMD) of handgrip strength (HGS) and timed-up and go test (TUG) with a 95% confidence interval (CI) was obtained to compare reported results across the included RCTs.

RESULTS

A total of 19 trials were included in this systematic review, among which 13 trials were eligible for the meta-analysis. In the 13 included studies, supplementing with vitamin D produced a weighted mean difference of 0.876 kg (95% CI = 0.180 to 1.571, P = 0.014, I² = 68.5%) for HGS, a measurement of muscle strength. However, an insignificant decrease of 0.044 s was observed after analyzing the TUG (95% CI = -0.979 to 0.892, P = 0.927, I² = 95%). According to subgroup analysis, vitamin D supplementation increased HGS in patients over the age of 60 (P = 0.001), in those without calcium supplementation (P = 0.032), and in those whose baseline vitamin D level was greater than 75 nmol/L (30 ng/ml) (P = 0.003).

CONCLUSIONS

Taking into account the studies in this systematic review, vitamin D supplementation improved muscle strength in postmenopausal women. However, an insignificant result was demonstrated in terms of mobility after vitamin D supplementation.

Threshold for Relationship between Vitamin D and Parathyroid Hormone in Chinese Women of Childbearing Age

Background: The aim of this study was to assess the relationship between serum 25-hydroxyvitamin D [25(OH)D] and serum intact parathyroid hormone (PTH) in Chinese childbearing women, and to estimate the optimum threshold of 25(OH)D that maximally inhibits the PTH, which is considered to be the optimal status for vitamin D sufficiency. Methods: Serum samples were selected from the biological samples' bank of the Chinese Chronic Diseases and Nutrition Survey (CCDNS) 2015. The serum 25(OH)D concentration was determined by liquid chromatography tandem mass spectrometry and the serum PTH was determined by electronic chemiluminescence. Simple linear and partial correlation analysis, locally weighted regression smooth scatterplot (LOESS), nonlinear least squares estimation (NLS), and segmented regression (SR) were utilized to estimate the relationship of 25(OH)D and PTH, and to determine the threshold of 25(OH)D. Results: A total of 1568 serum samples of 25(OH)D concentration and PTH concentration were analyzed. A significant inverse relationship between 25(OH)D and PTH concentration was observed below 15.25 (14.22-16.28) ng/mL, and PTH decreased slowly with the increase of 25(OH)D above 16.75 (15.43-18.06) ng/mL after adjusting by age, latitude, city type, season, corrected calcium, and phosphorus. A very short plateau of PTH was found at 15.25 ng/mL and 16.75 ng/mL in terms of 25(OH)D according to LOESS, NLS, and SR. Conclusions: The serum 25(OH)D was negatively correlated with the serum PTH. The threshold of VitD sufficiency was found in the range of 14.22-18.06 ng/mL in terms of serum 25(OH)D concentration for Chinese childbearing women aged 18-44 years old.