Vitamin D Binding Protein Affects the Correlation of 25(OH)D and Frailty in the Older Men

The role of vitamin D in the link between physical frailty and cognitive function: A mediation analysis in community-dwelling Chinese older adults

Background

Physical frailty and cognitive aging have important influences on poor clinical outcomes in older adults. Many studies have investigated the association between frailty and cognitive function, but whether vitamin D mediates the association between frailty and cognitive function is unclear. We explored the mediating role of vitamin D on the cross-sectional association between physical frailty and cognitive function using data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS).

Methods

We analyzed data from 1944 subjects aged 60 years and older from the 2011 CLHLS cohort. Frailty status was identified by the Osteoporotic Fracture Study (SOF) index. The Chinese version of the Mini-Mental State Examination (MMSE) was used to assess cognitive function. Linear regression models were used to examine the association between frailty, vitamin D, and cognition, adjusted for a range of covariates. Mediation analyses tested the indirect effects of vitamin D on physical frailty and cognitive function.

Result

Physical frailty was negatively associated with vitamin D levels and scores on the MMSE, and vitamin D levels were positively associated with scores on the MMSE. Linear regression analysis showed that physical frailty and serum vitamin D concentration were significant predictors of cognitive function. Importantly, mediation analysis showed that serum vitamin D concentration significantly mediated the relationship between physical frailty and cognitive function.

Conclusion

The association between physical frailty and cognitive function appears to be mediated by vitamin D. Future studies should explore whether serum vitamin D concentrations may mediate the association between physical frailty and cognitive decline and whether this mediating role is moderated by other factors.

Association of GC Variants with Bone Mineral Density and Serum VDBP Concentrations in Mexican Population

Vitamin D-binding protein (VDBP) is encoded by the GC gene and is an active participant in the control of bone metabolism. However, the effect of its major variants on VDBP concentration and bone mineral density (BMD) remains unclear. Our aim was to analyze the effect of major GC variants on serum VDBP concentration and BMD. We recruited individuals from the Health Workers Cohort Study, which includes employees of the Mexican Institute of Social Security (IMSS). A total of 1853 adults were included. The single nucleotide polymorphisms (SNPs) rs7041 and rs4588 were genotyped to identify the three best characterized haplotypes of GC. Serum VBDP, 25(OH)D and BMD were also measured. Among women, the G allele of rs7041 was associated with higher VDBP and BMD compared to homozygous TT. The A allele of rs4588 was associated with lower VDBP and BMD compared to CC homozygous. In men, GC variants were only associated with VDBP levels. We did not observe an association between free/bioavailable 25(OH)D and BMD in men and women. Our results support an association of VDBP in bone health. The G and C alleles, from rs7041 and rs4588, respectively, are associated with high concentrations of VDBP and BMD in this sample of Mexican postmenopausal women.

Pinpointing a Role for Vitamin D in Frailty: A Time for Animal Models?

Frailty is a condition marked by greater susceptibility to adverse outcomes, including disability and mortality, which affects up to 50% of those 80 years of age and older. Concurrently, serum vitamin D insufficiency and deficiency, for which as many as 70% of older adults may be at risk, potentially play an important role in frailty onset and progression. Large population driven studies have uncovered associations between low serum vitamin D levels and higher incidence of frailty. However, attempts to apply vitamin D therapeutically to treat and/or prevent frailty have not yielded consistent support for benefits. Given the complexity and inconsistency arising from human studies involving vitamin D, our research group has recently published on animal models of vitamin D insufficiency. Combining our model with the emerging development of animal frailty assessment, we identified that higher than standard levels of vitamin D supplementation may delay frailty in mice. In this viewpoint article, we will discuss current knowledge regarding the importance of vitamin D in frailty progression, the emerging significance of animal models in addressing these relationships, and the future for pre-clinical and clinical research.

Can Serum Nitrosoproteome Predict Longevity of Aged Women?

Aging is characterized by increase in reactive oxygen (ROS) and nitrogen (RNS) species, key factors of cardiac failure and disuse-induced muscle atrophy. This study focused on serum nitroproteome as a trait of longevity by adopting two complementary gel-based techniques: two-dimensional differential in gel electrophoresis (2-D DIGE) and Nitro-DIGE coupled with mass spectrometry of albumin-depleted serum of aged (A, n = 15) and centenarian (C, n = 15) versus young females (Y, n = 15). Results indicate spots differently expressed in A and C compared to Y and spots changed in A vs. C. Nitro-DIGE revealed nitrosated protein spots in A and C compared to Y and spots changed in A vs. C only (p-value < 0.01). Nitro-proteoforms of alpha-1-antitripsin (SERPINA1), alpha-1-antichimotripsin (SERPINA3), ceruloplasmin (CP), 13 proteoforms of haptoglobin (HP), and inactive glycosyltransferase 25 family member 3 (CERCAM) increased in A vs. Y and C. Conversely, nitrosation levels decreased in C vs. Y and A, for immunoglobulin light chain 1 (IGLC1), serotransferrin (TF), transthyretin (TTR), and vitamin D-binding protein (VDBP). Immunoblottings of alcohol dehydrogenase 5/S-nitrosoglutathione reductase (ADH5/GSNOR) and thioredoxin reductase 1 (TRXR1) indicated lower levels of ADH5 in A vs. Y and C, whereas TRXR1 decreased in A and C in comparison to Y. In conclusion, the study identified putative markers in C of healthy aging and high levels of ADH5/GSNOR that can sustain the denitrosylase activity, promoting longevity.

Low Vitamin D Levels and Frailty Status in Older Adults: A Systematic Review and Meta-Analysis

Serum vitamin D deficiency is widespread among older adults and is a potential modifiable risk factor for frailty. Moreover, frailty has been suggested as an intermediate step in the association between low levels of vitamin D and mortality. Hence, we conducted a systematic review of the literature and meta-analysis to test the possible association of low concentrations of serum 25-hydroxyvitamin D (25(OH)D), a marker of vitamin D status, with frailty in later life. We reviewed cross-sectional or longitudinal studies evaluating populations of older adults and identifying frailty by a currently validated scale. Meta-analyses were restricted to cross-sectional data from studies using Fried’s phenotype to identify frailty. Twenty-six studies were considered in the qualitative synthesis, and thirteen studies were included in the meta-analyses. Quantitative analyses showed significant differences in the comparisons of frail (standardized mean difference (SMD)—1.31, 95% confidence interval (CI) (−2.47, −0.15), p = 0.0271) and pre-frail (SMD—0.79, 95% CI (−1.58, −0.003), p = 0.0491) subjects vs. non-frail subjects. Sensitivity analyses reduced heterogeneity, resulting in a smaller but still highly significant between-groups difference. Results obtained indicate that lower 25(OH)D levels are significantly associated with increasing frailty severity. Future challenges include interventional studies testing the possible benefits of vitamin D supplementation in older adults to prevent/palliate frailty and its associated outcomes.

A Comparison Study of Vitamin D Deficiency among Older Adults in China and the United States

Vitamin D deficiency is a common health concern worldwide. We aim to compare the prevalence of vitamin D deficiency among older adults (65+) in China and the United States (US). We used data from the 2011 wave of Chinese Longitudinal Healthy Longevity Survey (CLHLS) in China (n = 2180), and 2011–2014 National Health and Nutrition Examination Survey (NHANES) in the US (n = 2283). Serum 25-hydroxyvitamin D [25(OH)D] was measured and a level of under 30/50 nmol/L was defined as vitamin D severe deficiency/deficiency. Risk factors of vitamin D deficiency were examined by multivariate regression models. We found that the mean 25(OH)D concentration was lower in China than in the US (45.1 vs. 83.5 nmol/L), with Chinese elderly lower than American elderly for every age group. 70.3% in China and 17.4% in the US were considered as vitamin D deficiency (30.6% and 3.4% were considered as severe deficiency). Older age, females, ethnic minorities, higher household income, self-rated “very bad” health, and never drinkers, were statistically significant in predicting lower serum 25(OH)D levels in China. In the US, males, ethnic minorities, lower income, self-rated “very bad” health, physically inactive, overweight, and obese were related to lower serum 25(OH)D levels. Our findings suggest that different interventional strategies are needed to improve vitamin D deficiency and its associated negative health outcomes in China and the US.

Investigation of Vitamin D-Binding Protein Polymorphism Impact on Coronary Artery Disease and Relationship with Longevity: Own Data and a Review

The aim of the study was to assess the effect of vitamin D-binding protein (DBP) polymorphism on coronary artery disease (CAD). DBP phenotypes were identified in the groups: control (n = 306), men suffering from CAD (n = 154), and long-lived individuals (n = 108). Isoelectric focusing of DBP phenotypes in serum was performed on polyacrylamide gel. Distribution of DBP phenotypes in the study groups was found to be in Hardy-Weinberg equilibrium. Gc1s-1s phenotype and Gc1s allele frequency in CAD groups were significantly higher than in control, and Gc1s allele frequency was found significantly more often in CAD compared with long-lived group (p < 0.05). The Gc2 allele frequency in control was higher as compared with Gc2 frequency in CAD group (p < 0.05). The Gc2-2 phenotype was more frequent in long-lived survivors than in the CAD group (p < 0.05). It was found that the Gc1s allele significantly increased the risk of CAD with the odds ratio (OR) equal to 1.45 (p < 0.02) and showed Gc2 to be related with a decreased risk of CAD (OR = 0.69; p < 0.03). Authors review the role of DBP in resistance to atherosclerosis and cancer as the main longevity determinants.

Is the 25-Hydroxy-Vitamin D Serum Concentration a Good Marker of Frailty?

INTRODUCTION

The phenotype proposed by Fried and colleagues is a widely used operational definition of frailty defining such state of extreme vulnerability of older persons. Low serum 25-hydroxy-vitamin D (25(OH)D) has been suggested as biomarker of frailty in literature.

STUDY DESIGN

Cross-sectional.

OBJECTIVES

To explore the association of 25(OH)D concentrations with the frailty phenotype and its criteria.

METHODS

321 subjects referred by their general practitioner to a geriatric frailty clinic were assessed between January 1, 2013 and September 23, 2013. Adjusted logistic regression models were performed between serum concentrations of 25(OH)D and the frailty phenotype (global score as well as its specific criteria). Receivers operating curves were established in order to explore the existence of a possible threshold of vitamin D levels highly predictive of frailty.

RESULTS

Two hundred forty-one (75%) participants had 25(OH)D levels lower than 22 ng/ml. No significant association was reported between 25(OH)D levels and frailty. Among the five criteria of frailty, 25(OH)D was only associated with sedentariness (odds ratio 0.97 [95% confidence interval 0.95-0.99]).

CONCLUSION

In our sample, no association was found between 25(OH)D levels and phenotype of frailty or the different frailty criterion except for sedentariness.

Low 25-hydroxyvitamin D, but not the bioavailable fraction of 25-hydroxyvitamin D, is a risk factor for multiple sclerosis

BACKGROUND AND PURPOSE

Low 25-hydroxyvitamin D [25(OH)D] levels correlate with higher disease activity in patients with multiple sclerosis (MS). However, it is not clear whether low 25(OH)D levels directly contribute to increased disease activity or merely represent a consequence of reduced endogenous vitamin D synthesis in more disabled MS patients. Furthermore, recent data suggest that bioavailable vitamin D, which also integrates the levels of vitamin D binding proteins and albumin, could be a biologically more relevant parameter than 25(OH)D.

METHODS

Measured de-seasonalized 25(OH)D3 and vitamin D binding protein and calculated bioavailable and free vitamin D were compared in the baseline serum samples of 76 patients with clinically isolated syndrome enrolled in a longitudinal observational study and in 76 age- and sex-matched healthy controls (HC).

RESULTS

25(OH)D3 levels were lower in patients with clinically isolated syndrome (P = 0.002) than in HC, and more patients (8/76, 10.5%) than HC (1/76, 1.3%) had 25(OH)D3 levels <25 nmol/l (P = 0.03). In contrast, levels of 25(OH)D2, vitamin D binding protein and calculated levels of free and bioavailable vitamin D did not differ between the two groups.

CONCLUSIONS

Lower 25(OH)D3 levels already in the earliest phase of disease and in clinically hardly affected patients suggest that low 25(OH)D3 levels are rather a risk factor for than a consequence of MS. Nevertheless, because bioavailable vitamin D levels did not differ between the two groups, the mechanism underlying the association of 25(OH)D3 and MS does not appear to be related to reduced bioavailability of vitamin D.