Serum and synovial fluid vitamin D metabolites and rheumatoid arthritis

Higher Vitamin D Levels before Methotrexate Therapy Initiation Are Associated with Lower Subsequent Mortality in Patients with Rheumatoid Arthritis

(1) Vitamin D deficiency is associated with mortality in the general population and has been observed in one rheumatoid arthritis (RA) cohort. Here, we investigate the relationship between 25-hydroxyvitamin D (25(OH)D) levels before methotrexate (MTX) therapy initiation in patients with RA and the subsequent all-cause mortality in a national Veterans Affairs (VA) cohort. (2) This is a retrospective study on RA patients time-oriented around the initial MTX prescription and 25(OH)D levels before starting MTX. We examined survival in patients with 25(OH)D levels > 50 nmol/L and ≤50 nmol/L using the Cox Proportional Hazard Model and fully adjusted for risk factors. (3) In total, 15,109 RA patients were included in the nationwide cohort. RA patients with 25(OH)D levels > 50 nmol/L before starting MTX had a 28% reduced risk of mortality when compared to those with levels ≤ 50 nmol/L (HR: 0.72, CI: 0.64-0.80, p < 0.001) after adjusting for traditional risk factors. (4) In this national RA cohort receiving standard-of-care MTX, patients with 25(OH)D levels > 50 nmol/L have a lower subsequent mortality when compared to those with 25(OH)D levels ≤ 50 nmol/L. It remains to be determined whether increasing Vitamin D levels in RA patients initially found to be Vitamin D deficient impacts their all-cause mortality.

1,25-Dihydroxyvitamin D regulates macrophage activation through FBP1/PKR and ameliorates arthritis in TNF-transgenic mice

1,25-Dihydroxyvitamin D (1,25(OH)₂D₃) has immunomodulatory activity and its deficiency correlates with rheumatoid arthritis (RA) incidence. Whether 1,25(OH)₂D₃ modulates macrophage activation or protects against RA remains unclear. We demonstrate that 1,25(OH)₂D₃ suppresses M1 macrophage polarization and CD80, IL-6, CXCL10, IFIT1, IFI44, and double-stranded RNA-dependent protein kinase R (PKR) expression in the macrophages of RA patients. In phorbol 12-myristate 13-acetate-induced THP-1 cells, 1,25(OH)₂D₃ upregulates fructose-1,6-bisphosphatase 1 (FBP1) expression through direct promoter interaction. FBP1 interacts with PKR and promotes PKR ubiquitination degradation. SiR-FBP1 transfection impairs 1,25(OH)₂D₃ action and suppresses IL-6, CXCL10, IFIT1, IFI27, and IFI44 expression in macrophages, whereas siR-PKR transfection impairs siR-FBP1 activity in 1,25(OH)₂D₃-treated macrophages. 1,25(OH)₂D₃ treatment ameliorates the clinical signs of arthritis in tumor necrosis factor-transgenic mice, inhibits M1 polarization and marker expression, and promotes FBP1 expression in mononuclear cells isolated from swollen joints; thus, 1,25(OH)₂D₃ suppresses M1 macrophage activation through FBP1/PKR and ameliorates arthritis by restoring the macrophage subtype.

Determination of a Serum 25-Hydroxyvitamin D Reference Ranges in Japanese Adults Using Fully Automated Liquid Chromatography-Tandem Mass Spectrometry

BACKGROUND

Despite an increasing interest in vitamin D status, a reference range of the nutrient has not been fully established. This is partly due to a paucity of standardized measuring systems with high throughput. In addition, the range may vary by populations and may change with modernization of lifestyles.

OBJECTIVES

This study aims to calculate the current reference concentration of 25-hydroxyvitamin D (25(OH)D) among healthy people living in an urban area in Japan.

METHODS

A newly developed fully automated liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) system was used to measure serum 25(OH)D concentrations. Reproducibility was assessed by measuring standardized samples. Accuracy was validated by comparing with commercially available immunoassays. Then, mass screening was conducted targeting participants who received medical checkups in Tokyo from April 2019 to March 2020, and the reference ranges were calculated.

RESULTS

The coefficients of variations of interoperator and interday reproducibility were 4.1%-8.5% and 3.7%-8.0% for 25-hydroxyvitamin D₂ (25(OH)D2) and 4.7%-7.0% and 4.0%-6.9% for 25-hydroxyvitamine D3, respectively. The measured total 25(OH)D concentrations correlated well with those measured by immunoassays. In total, 5518 participants were measured for 25(OH)D concentrations, among whom 98% showed inadequate concentrations (<30 ng/mL). The reference ranges of total 25(OH)D for female, male, and total participants were 7-30 ng/mL, 5-27 ng/mL, and 6-29 ng/mL, respectively. After excluding those with abnormal renal and liver function, the range was 6-30 ng/mL.

CONCLUSIONS

The high prevalence of vitamin D insufficiency among seemingly healthy population may be attributed to lifestyle characteristics of people living in urban areas of Japan, including spending less time outdoors and lower intake of traditional foods. Longitudinal follow-up and mass screenings targeting different population will help elucidate reasons for discrepancies between official guidelines and the observed concentrations, to which the well-validated measurement system is essential.

Nutrients and rheumatoid arthritis: From the perspective of neutrophils

Neutrophils are considered as core immune cells involve in the early stage of rheumatoid arthritis (RA) and participate in the disease progression. The underlining mechanisms include the elevated chemotaxis and infiltration of neutrophils, the increase in the reactive oxygen species and the promotion of neutrophil extracellular traps formation. Accumulating studies demonstrated the important role of nutrients intake played in the initiation and progression of RA. This study summarized the effects of several macronutrients and micronutrients on regulating RA through the modulation of activated neutrophils and appealed for a healthy diet in RA-risk individuals as well as RA patients.

Metabolomic analysis in spondyloarthritis: A systematic review

Spondyloarthritis (SpA) is a group of rheumatic diseases that cause joint inflammation. Accumulating studies have focused on the metabolomic profiling of SpA in recent years. We conducted a systematic review to provide a collective summary of previous findings on metabolomic profiling associated with SpA. We systematically searched PubMed, Medline, Embase and Web of Science for studies on comparisons of the metabolomic analysis of SpA patients and non-SpA controls. The Newcastle-Ottawa Scale (NOS) was used to assess the quality of the included articles. From 482 records identified, 31 studies were included in the analysis. A number of metabolites were differentially distributed between SpA and non-SpA cases. SpA patients showed higher levels of glucose, succinic acid, malic acid and lactate in carbohydrate metabolism, higher glycerol levels and lower fatty acid (especially unsaturated fatty acid) levels in lipid metabolism, and lower levels of tryptophan and glutamine in amino acid metabolism than healthy controls. Both conventional and biological therapy of SpA can insufficiently reverse the aberrant metabolism state toward that of the controls. However, the differences in the results of metabolic profiling between patients with SpA and other inflammatory diseases as well as among patients with several subtypes of SpA are inconsistent across studies. Studies on metabolomics have provided insights into etiological factors and biomarkers for SpA. Supplementation with the metabolites that exhibit decreased levels, such as short-chain fatty acids (SCFAs), has good treatment prospects for modulating immunity. Further studies are needed to elucidate the role of disordered metabolic molecules in the pathogenesis of SpA.

Sample preparation techniques for extraction of vitamin D metabolites from non-conventional biological sample matrices prior to LC-MS/MS analysis

The determination of vitamin D metabolites as status marker or for diagnostic purposes is almost entirely conducted from blood serum or plasma. Other biological matrices, however, have also interested researchers, for two main reasons: (1) alternative matrices may allow non-invasive sampling, permit easier sample transfer and require less demanding storage conditions; and (2) the levels of vitamin D metabolites in other body compartments may further aid the understanding of vitamin D metabolism and function. Thus, the development of reliable and efficient sample preparation protocols for sample matrices other than serum/plasma, which will remove potential interferences and selectively extract the targeted metabolites, is of great importance. This review summarizes sample preparation methods for measurement of vitamin D metabolites using liquid chromatography-(tandem)mass spectrometry in more than ten different human tissues, including hair, saliva, adipose tissue, brain and others.

Autoimmune disease and interconnections with vitamin D

Vitamin D has well-documented effects on calcium homeostasis and bone metabolism but recent studies suggest a much broader role for this secosteroid in human health. Key components of the vitamin D system, notably the vitamin D receptor (VDR) and the vitamin D-activating enzyme (1α-hydroxylase), are present in a wide array of tissues, notably macrophages, dendritic cells and T lymphocytes (T cells) from the immune system. Thus, serum 25-hydroxyvitamin D (25D) can be converted to hormonal 1,25-dihydroxyvitamin D (1,25D) within immune cells, and then interact with VDR and promote transcriptional and epigenomic responses in the same or neighbouring cells. These intracrine and paracrine effects of 1,25D have been shown to drive antibacterial or antiviral innate responses, as well as to attenuate inflammatory T cell adaptive immunity. Beyond these mechanistic observations, association studies have reported the correlation between low serum 25D levels and the risk and severity of human immune disorders including autoimmune diseases such as inflammatory bowel disease, multiple sclerosis, type 1 diabetes and rheumatoid arthritis. The proposed explanation for this is that decreased availability of 25D compromises immune cell synthesis of 1,25D leading to impaired innate immunity and over-exuberant inflammatory adaptive immunity. The aim of the current review is to explore the mechanistic basis for immunomodulatory effects of 25D and 1,25D in greater detail with specific emphasis on how vitamin D-deficiency (low serum levels of 25D) may lead to dysregulation of macrophage, dendritic cell and T cell function and increase the risk of inflammatory autoimmune disease.

Physiological levels of 25-hydroxyvitamin D3 induce a suppressive CD4+ T cell phenotype not reflected in the epigenetic landscape

1,25-dihydroxyvitamin D3 (1,25(OH)₂ D₃ ), the active metabolite of vitamin D3 has a strong impact on the differentiation and function of immune cells. Here we analyzed the influence of its precursor 25-hydroxyvitamin D3 (25(OH)D₃ ) on the differentiation of human CD4⁺ T cells applying physiological concentrations in vitro. Our data show that 25(OH)D₃ is converted to its active form 1,25(OH)₂ D₃ by T cells, which in turn supports FOXP3, CD25 and CTLA-4 expression and inhibits IFN-γ production. These changes were not reflected in the demethylation of the respective promoters. Furthermore, we investigated the impact of vitamin D3 metabolites under induced Treg polarization conditions using TGF-β. Surprisingly, no additive effect but a decreased percentage of FOXP3 expressing cells was observed. However, the combination of 25(OH)D₃ or 1,25(OH)₂ D₃ together with TGF-β further upregulated CD25 and CTLA-4 and significantly increased soluble CTLA-4 and IL-10 secretion whereas IFN-γ expression of iTreg was decreased. Our data suggest that physiological levels of 25(OH)D₃ act as potent modulator of human CD4⁺ T cells and autocrine or paracrine production of 1,25(OH)₂ D₃ by T cells might be crucial for the local regulation of an adaptive immune response. However, since no epigenetic changes are detected by 25(OH)D₃ a rather transient phenotype is induced.

Vitamin D and the Immune System in Menopause: A Review

Menopause is a normal phenomenon in a woman’s life cycle involving multiple health-related issues that contribute to physical instability. Changes in the immune system in postmenopausal women are caused by estrogen deprivation along with age. Increased proinflammatory serum marker levels, cytokine responses in body cells, decreased CD4 T and B lymphocyte levels, and natural killer cell cytotoxic activity are also observed during postmenopause. Moreover, vitamin D, in addition to its classical effects on calcium homeostasis and bone density, plays an important role. Current evidence indicates that vitamin D regulates innate and adaptive immune responses; however, vitamin D deficiency is linked to increased autoimmune activity and infection susceptibility. This review provides an overview of the consequences of immune alterations as an outcome of aging in postmenopausal women and the benefit of vitamin D supplementation.

Placental uptake and metabolism of 25(OH)vitamin D determine its activity within the fetoplacental unit

Pregnancy 25-hydroxyvitamin D [25(OH)D] concentrations are associated with maternal and fetal health outcomes. Using physiological human placental perfusion and villous explants, we investigate the role of the placenta in regulating the relationships between maternal 25(OH)D and fetal physiology. We demonstrate active placental uptake of 25(OH)D₃ by endocytosis, placental metabolism of 25(OH)D₃ into 24,25-dihydroxyvitamin D₃ and active 1,25-dihydroxyvitamin D [1,25(OH)₂D₃], with subsequent release of these metabolites into both the maternal and fetal circulations. Active placental transport of 25(OH)D₃ and synthesis of 1,25(OH)₂D₃ demonstrate that fetal supply is dependent on placental function rather than simply the availability of maternal 25(OH)D₃. We demonstrate that 25(OH)D₃ exposure induces rapid effects on the placental transcriptome and proteome. These map to multiple pathways central to placental function and thereby fetal development, independent of vitamin D transfer. Our data suggest that the underlying epigenetic landscape helps dictate the transcriptional response to vitamin D treatment. This is the first quantitative study demonstrating vitamin D transfer and metabolism by the human placenta, with widespread effects on the placenta itself. These data demonstrate a complex interplay between vitamin D and the placenta and will inform future interventions using vitamin D to support fetal development and maternal adaptations to pregnancy.

Value of combination of 25-(OH)-D3, IL-6, and cyclic peptide containing citrulline antibodies in different stages of rheumatoid arthritis

OBJECTIVE

To determine the value of a combination of 25-hydroxyvitamin D3 (25-(OH)-D3), interleukin-6 (IL-6), and cyclic peptide containing citrulline (CCP) antibodies in the acute stage and remission stage of patients with rheumatoid arthritis (RA).

METHODS

A retrospective analysis was made on 80 RA patients who received treatment in Wenjiang District People's Hospital of Chengdu from February 2017 to February 2020. According to their condition, they were identified as acute-stage patients (n=48) or remission-stage patients (n=32). In addition, 40 healthy individuals who received physical examination in our hospital during the same period were enrolled in a control group. Serum 25-(OH)-D3, IL-6, and CCP antibodies in all enrolled participants were quantified, and their levels were compared between RA patients at the acute stage and those at the remission stage before therapy, and also between patients with different efficacy after 3 months of therapy. The correlations of serum 25-(OH)-D3, IL-6, and CCP antibodies with disease activity score in 28 joints (DAS-28) were analyzed. A corresponding joint receiver operating characteristic (ROC) curve was drawn to analyze the diagnostic value of the combination of 25-(OH)-D3, IL-6, and CCP antibodies in the staging of RA patients, and logistic regression was used to establish an efficacy risk model.

RESULTS

The highest serum 25-(OH)-D3 level was found in the control group, followed by the remission-stage patients and then acute-stage patients from high to low (all P<0.05), and the lowest levels of serum IL-6 and CCP antibodies were also found in the control group, followed by the remission-stage patients and then the acute-stage patients from low to high (all P<0.05). The Pearson's test revealed a negative correlation of 25-(OH)-D3 with DAS-28 and a positive correlation of IL-6 and CCP antibodies with DAS-28. According to ROC curve-based analysis, the area under the joint curve of 25-(OH)-D3, IL-6, and CCP antibodies was >0.9. After therapy, patients showed an increase in 25-(OH)-D3 and decreases in IL-6 and CCP antibodies (all P<0.05). The logistic model confirmed that the area under the ROC curve of RA affecting the efficacy on patients was >0.8.

CONCLUSION

A combination of 25-(OH)-D3, IL-6, and CCP antibodies can be adopted as a diagnostic indicator in acute and remission stages of RA. A risk factor model of clinical efficacy in RA patients can help us effectively identify high-risk patients before therapy and take intervention measures early.

Analysis of Vitamin D Components in Serum of Minors by UHPLC-MS/MS

Serum 25-hydroxyvitamin D [25(OH)D] concentration represents the body's reserves of vitamin D, which is mostly used by clinicians to evaluate the storage status of vitamin D in the body. The present study aimed to investigate the serum vitamin D components in different health status of minors to correctly evaluate the vitamin D storage in vivo. A total of 2,270 minors were included in the study, which was divided into healthy group (1,204 cases) and disease group (1,066 cases, including 270 short stature, 433 respiratory infections, 175 malnutrition and 188 tic disorder subjects). The levels of 25-hydroxyvitamin D₂ [25(OH)D₂] and 25-hydroxyvitamin D₃ [25(OH)D₃] were measured by UHPLC-MS/MS in all subjects, and the 25(OH)D₃ activity equivalents [25(OH)D₃-AE] and 25(OH)D were calculated. In addition, the 3-epi-25-hydroxyvitamin D₃ [3-epi-25(OH)D₃] concentrations of 278 subjects (including 147 healthy and 131 disease subjects) were measured by random sampling. 25(OH)D₂, 25(OH)D₃, 25(OH)D and 25(OH)D₃-AE levels in disease group were significantly lower than those in healthy group (p<0.001). According to the level of 25(OH)D, the sufficiency of vitamin D [25(OH)D≥30 ng/mL] was 65.4% in healthy group and 50.5% in disease group. When the 25(OH)D₂ activity was converted into 25(OH)D₃-AE, 53.2% of the patients in the healthy group had sufficiency vitamin D, and 39.1% in the disease group. The 3-epi-25(OH)D₃ level in the disease group was significantly lower than that in the healthy group (p<0.001). Not only the 25(OH)D, but also the both of 25(OH)D₂ and 25(OH)D₃ levels may overestimate the vitamin D status in subjects. For accurate evaluation, at least the serum levels of 25(OH)D₂, 25(OH)D₃ and 3-epi-25(OH)D₃ should be determined simultaneously.

Influence of Seasonal Vitamin D Changes on Clinical Manifestations of Rheumatoid Arthritis and Systemic Sclerosis

Vitamin D [1,25(OH)2D-calcitriol] is basically a steroid hormone with pleiotropic biologic effects, and its impact on the regulation of immune system may influence several clinical conditions. Calcidiol (25OHD), as precursor of calcitriol, derives, for the most part (80%), from cutaneous cholesterol (7-dehydrocholesterol) under the action of UV-B (sunlight). Consequently, serum concentrations fluctuate during the year following the circannual rhythm of sun exposition. We will update about the available evidence regarding the complex influence of seasonal vitamin D changes on two different chronic connective tissue diseases, namely rheumatoid arthritis (RA) and systemic sclerosis (SSc). Notably, RA is an emblematic model of autoimmune disease with prevalent joint inflammatory features, while SSc is mainly an autoimmune progressive pro-fibrotic disease. However, in both conditions, low serum concentrations of 25OHD are involved in the pathogenesis of the diseases, and emerging data report their impact on clinical manifestations.

Vitamin D: Current Challenges between the Laboratory and Clinical Practice

Vitamin D is a micronutrient with pleiotropic effects in humans. Due to sedentary lifestyles and increasing time spent indoors, a growing body of research is revealing that vitamin D deficiency is a global problem. Despite the routine measurement of vitamin D in clinical laboratories and many years of efforts, methods of vitamin D analysis have yet to be standardized and are burdened with significant difficulties. This review summarizes several key analytical and clinical challenges that accompany the current methods for measuring vitamin D. According to an external quality assessment, methods and laboratories still produce a high degree of variability. Structurally similar metabolites are a source of significant interference. Furthermore, there is still no consensus on the normal values of vitamin D in a healthy population. These and other problems discussed herein can be a source of inconsistency in the results of research studies.

In sickness and in health: pivotal role of vitamin D

Within the last several years, frequency of vitamin D testing has multiplied substantially all over the world, since it has been shown to have an important role in many diseases and conditions. Even though liquid chromatography - tandem mass spectrometry (LC-MS/MS) has been identified as "gold standard" method for vitamin D measurement, most laboratories still use immunochemistry methods. Besides analytical problems (hydrophobicity, low circulating concentrations, ability to bind to lipids, albumins and vitamin D binding protein, presence of multiple vitamin D metabolites and variable ratios of 25(OH)D₂ and 25(OH)D₃ in the blood), vitamin D shows great preanalytical variability, since its concentration is drastically influenced by seasonal changes, exposure to sun, type of clothes or sun block creams. Vitamin D is mostly measured in serum or plasma, but new studies are showing importance of measuring vitamin D in pleural effusions, breast milk, urine, synovial fluid and saliva. Besides the main role in calcium homeostasis and bone metabolism, many studies linked vitamin D deficiency with cancer, cardiovascular diseases, diabetes, fertility and many other conditions. However, even though initial observational studies indicated that supplementation with vitamin D might be beneficial in disease development and progression; first results of well-designed randomized controlled prospective studies did not find differences in frequency of cardiovascular events or invasive cancer between patients taking vitamin D supplementation compared to placebo. In the light of these recent findings, validity of excessive vitamin D testing remains an open question.

Vitamin D as a Key Player in Modulating Rheumatoid Arthritis-derived Immune Response

Rheumatoid arthritis (RA) is a systemic inflammatory disease with chronic nature of joints related to autoimmunity. Vitamin D was found to modulate cell growth, function of immune cells and anti-inflammatory action. The aims of that study were to investigate serum level of vitamin D and some cytokines and to identify the correlation between vitamin D and these cytokines in RA. Totally 40 RA patients without vitamin D supplement were involved in this study. Serum level of vitamin D, interleukin-6 (IL-6), IL-10, IL-35, C-reactive protein (CRP) and tumor necrosis factor α (TNF-α), all of them were measure in all patients by enzyme-linked immunosorbent assay (ELISA). Patients were classified according to Vitamin D levels into two groups; RA patients with Vit. D deficiency (n=25) and RA patients with Vit. D sufficiency (n=15). IL-6 was lower significantly (P = 0.03) in RA patients with Vit. D sufficiency than RA patients with Vit. D deficiency. IL-10 and IL-35 were higher significantly (P = 0.0234, P = 0.0356 respectively) in RA patients with Vit. D sufficiency than RA patients with Vit. D deficiency. Vit. D was significantly positively correlated with both IL-10 (r = 0.4516, P = 0.0034) and IL-35 (r = 0.3424, P = 0.0329) and negatively correlated with IL-6 (r = -0.3188, P = 0.0479). Sufficient serum level of Vit. D is correlated with higher level of anti-inflammatory cytokines (IL-10 and IL-35) and lower level of IL-6. This support the immunomodulatory effect of Vit. D in RA.

Clinical Significance of Analysis of Vitamin D Status in Various Diseases

Vitamin D plays a role not only in the proper functioning of the skeletal system and the calcium-phosphate equilibrium, but also in the immune system, the cardiovascular system and the growth and division of cells. Although numerous studies have reported on the analysis of vitamin D status in various groups of patients, the clinical significance of measurements of vitamin D forms and metabolites remains ambiguous. This article reviews the reports analyzing the status of vitamin D in various chronic states. Particular attention is given to factors affecting measurement of vitamin D forms and metabolites. Relevant papers published during recent years were identified by an extensive PubMed search using appropriate keywords. Measurement of vitamin D status proved to be a useful tool in diagnosis and progression of metabolic syndrome, neurological disorders and cancer. High performance liquid chromatography coupled with tandem mass spectrometry has become the preferred method for analyzing the various forms and metabolites of vitamin D in biological fluids. Factors influencing vitamin D concentration, including socio-demographic and biochemical factors as well as the genetic polymorphism of the vitamin D receptor, along with vitamin D transporters and enzymes participating in vitamin D metabolism should be considered as potential confounders of the interpretation of plasma total 25(OH)D concentrations.

Vitamin D and early rheumatoid arthritis

BACKGROUND

Previous studies have linked rheumatoid arthritis (RA) risk and disease activity with vitamin D-deficiency (low serum 25-hydroxyvitamin D (25OHD)), but a causal role for vitamin D in RA is still unclear, with conflicting results from many previous studies, partly due to heterogeneity in study design and patient populations. In this study we aimed to (1) analyse serum 25OHD in early inflammatory arthritis, (2) compare 25OHD with disease activity and fatigue in early RA and (3) determine whether low 25OHD is associated with progression to RA.

METHODS

An analysis of 790 patients recruited to the Birmingham Early Inflammatory Arthritis Cohort and followed longitudinally to determine clinical outcomes. The following were recorded at baseline: demographic data, duration of symptoms, duration of early morning stiffness (EMS), tender and swollen joint counts, Visual Analogue Scale (VAS) pain/fatigue/EMS, PHQ-9, HAQ and FACIT-Fatigue scores, DAS28-ESR, DAS28-CRP, CRP, ESR, anti-CCP antibody status, rheumatoid factor status, and serum 25OHD (ng/ml). Diagnosis was recorded at 0 and 12 months onwards as either RA, Undifferentiated Inflammatory Arthritis (UIA; synovitis not meeting other classification/diagnostic criteria), Clinically Suspect Arthralgia (CSA; arthralgia of an inflammatory type without synovitis), or Other.

RESULTS

Baseline demographic data were similar between all groups, with median symptom duration of 16.8-34.0 days. Baseline 25OHD was not significantly different between groups [median, interquartile range (IQR): RA 46.7, 30.0-73.3; UIA 51.4, 30.0-72.3; CSA 47.7, 30.3-73.0; Other 39.9, 28.6-62.2]. In RA (n = 335), there were no significant differences between 25OHD and measures of disease activity or fatigue. No association between 25OHD and progression from UIA or CSA to RA was observed.

CONCLUSIONS

There was no clear association between serum 25OHD and baseline diagnosis, RA disease activity, or progression from UIA or CSA to RA. Future studies of other vitamin D metabolites may better define the complex role of vitamin D in RA.

Dietary Habits and Nutrition in Rheumatoid Arthritis: Can Diet Influence Disease Development and Clinical Manifestations?

Rheumatoid arthritis (RA) is a systemic, autoimmune disease characterized by joint involvement, with progressive cartilage and bone destruction. Genetic and environmental factors determine RA susceptibility. In recent years, an increasing number of studies suggested that diet has a central role in disease risk and progression. Several nutrients, such as polyunsaturated fatty acids, present anti-inflammatory and antioxidant properties, featuring a protective role for RA development, while others such as red meat and salt have a harmful effect. Gut microbiota alteration and body composition modifications are indirect mechanisms of how diet influences RA onset and progression. Possible protective effects of some dietary patterns and supplements, such as the Mediterranean Diet (MD), vitamin D and probiotics, could be a possible future adjunctive therapy to standard RA treatment. Therefore, a healthy lifestyle and nutrition have to be encouraged in patients with RA.

Vitamin D, Autoimmune Disease and Rheumatoid Arthritis

Vitamin D has been reported to influence physiological systems that extend far beyond its established functions in calcium and bone homeostasis. Prominent amongst these are the potent immunomodulatory effects of the active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3). The nuclear vitamin D receptor (VDR) for 1,25-(OH)2D3 is expressed by many cells within the immune system and resulting effects include modulation of T cell phenotype to suppress pro-inflammatory Th1 and Th17 CD4+ T cells and promote tolerogenic regulatory T cells. In addition, antigen-presenting cells have been shown to express the enzyme 1α-hydroxylase that converts precursor 25-hydroxyvitamin D3 (25-OHD3) to 1,25-(OH)2D3, so that immune microenvironments are able to both activate and respond to vitamin D. As a consequence of this local, intracrine, system, immune responses may vary according to the availability of 25-OHD3, and vitamin D deficiency has been linked to various autoimmune disorders including rheumatoid arthritis (RA). The aim of this review is to explore the immune activities of vitamin D that impact autoimmune disease, with specific reference to RA. As well as outlining the mechanisms linking vitamin D with autoimmune disease, the review will also describe the different studies that have linked vitamin D status to RA, and the current supplementation studies that have explored the potential benefits of vitamin D for prevention or treatment of RA. The overall aim of the review is to provide a fresh perspective on the potential role of vitamin D in RA pathogenesis and treatment.

Vitamin D Measurement, the Debates Continue, New Analytes Have Emerged, Developments Have Variable Outcomes

The demand for measurement of vitamin D metabolites for clinical diagnosis and to advance our understanding of the role of vitamin D in human health has significantly increased in the last decade. New developments in technologies employed have enabled the separation and quantification of additional metabolites and interferences. Also, developments of immunoassays have changed the landscape. Programmes and materials for assay standardisation, harmonisation and the expansion of the vitamin D external quality assurance scheme (DEQAS) with the provision of target values as measured by a reference measurement procedure have improved standardisation, quality assurance and comparability of measurements. In this article, we describe developments in the measurement of the commonly analysed vitamin D metabolites in clinical and research practice. We describe current analytical approaches, discuss differences between assays, their origin, and how these may be influenced by physiological and experimental conditions. The value of measuring metabolites beyond 25 hydroxyvitamin D (25(OH)D), the marker of vitamin D status, in routine clinical practice is not yet confirmed. Here we provide an overview of the value and application of the measurement of 1,25 dihydroxyvitamin D, 24,25 dihydroxyvitamin D and free 25OHD in the diagnosis of patients with abnormalities in vitamin D metabolism and for research purposes.

Vitamin D-binding protein as a biomarker to confirm specific clinical diagnoses

Introduction: Vitamin D-binding protein (DBP) performs a variety of functions as a transporter for various ligands and takes part in a number of systemic and local physiological and pathological processes. The knowledge about the pathomechanisms of this protein involvement justifies its use as a biomarker to confirm specific clinical diagnoses suggested by nonspecific signs and symptoms.Areas covered: DBP has properties of both systemic laboratory parameters measured in the blood plasma and specific parameters measured in variety of physiological fluids to assess local changes in specific body organs. Articles published in English between 1993 and 2019 were searched for in PubMed using terms DBP, vitamin D, and metabolites, inflammation. DBP is a transport protein and a regulator of immune and inflammatory processes.Expert opinion: DBP capacity for transporting numerous ligands and co-involvement of DBP in immune and inflammatory processes suggest that DBP may be used in laboratory diagnostics as a specific parameter to confirm pathomechanisms of several systemic diseases and local conditions. Changes in the concentration of DBP present in a variety of clinical material may provide valuable information for use in assessing the severity and treatment of pathological processes.

Vitamin D and autoimmune disease

Vitamin D as a part of the endocrine system is an important component in the interaction between the kidney, bone, parathyroid hormone, and the intestine, which maintains extracellular calcium level within normal limits, in order to keep the vital physiologic process and skeletal integrity. Vitamin D is also associated with hypertension, muscular function, immunity, and ability to encounter infection, autoimmune disease, and cancer. The role of vitamin D in immunity is a feedback reaction of paracrine to eliminate inflammation or to influence CD4 T-cell differentiation and or to increase the function of T suppressor cell or combination between both. The active form of vitamin D produces and maintains self immunologic tolerance, some studies show that 1,25(OH)2D inhibits induction of disease in autoimmune encephalomyelitis, thyroiditis, type-1 diabetes mellitus, inflammatory bowel disease (IBD), systemic lupus erythematosus, and collagen-induced arthritis and Lyme arthritis.