Evolving Role of Vitamin D in Immune-Mediated Disease and Its Implications in Autoimmune Hepatitis

Prognostic Significance of Severe Vitamin D Deficiency in Patients with Primary Sclerosing Cholangitis

Vitamin D deficiency has been linked with adverse events in various liver diseases. The present study aimed to recognize the association between severe vitamin D deficiency and disease progression, hepatobiliary malignancies, liver-related mortality, and the need for liver transplantation in primary sclerosing cholangitis (PSC). Patients with a diagnosis of PSC (n = 354), followed by the autoimmune liver disease clinic at the University of Alberta, were included. Patients with vitamin D levels < 25 nmol/L were defined as severely deficient. Univariate and multivariate analyses were conducted using the Cox proportional hazards regression models. The mean vitamin D level was 59 ± 2 nmol/L, and 63 patients (18%) had a severe vitamin D deficiency. Patients with a severe vitamin D deficiency were 2.5 times more likely to experience hepatobiliary malignancies (HR 2.55, 95% CI, 1.02-6.40, p = 0.046). A severe vitamin D deficiency at diagnosis (HR 1.82, 95% CI, 1.05-3.15, p = 0.03) and persistent deficiencies over time (HR 2.26, 95% CI, 1.17-4.37, p = 0.02) were independently associated with a higher risk of poor clinical liver outcomes. A severe vitamin D deficiency at diagnosis and persistent deficiency at longitudinal assessments were associated with liver-related mortality or the need for liver transplantation.

An Update on the Effects of Vitamin D on the Immune System and Autoimmune Diseases

Vitamin D intervenes in calcium and phosphate metabolism and bone homeostasis. Experimental studies have shown that 1,25-dihydroxyvitamin D (calcitriol) generates immunologic activities on the innate and adaptive immune system and endothelial membrane stability. Low levels of serum 25-hydroxyvitamin D (25(OH)D) are associated with an increased risk of developing immune-related diseases such as psoriasis, type 1 diabetes, multiple sclerosis, and autoimmune diseases. Various clinical trials describe the efficacy of supplementation of vitamin D and its metabolites for treating these diseases that result in variable outcomes. Different disease outcomes are observed in treatment with vitamin D as high inter-individual difference is present with complex gene expression in human peripheral blood mononuclear cells. However, it is still not fully known what level of serum 25(OH)D is needed. The current recommendation is to increase vitamin D intake and have enough sunlight exposure to have serum 25(OH)D at a level of 30 ng/mL (75 nmol/L) and better at 40–60 ng/mL (100–150 nmol/L) to obtain the optimal health benefits of vitamin D.

Role of Vitamin D in Liver Disease and Complications of Advanced Chronic Liver Disease

Vitamin D is a crucial nutrient with many pleiotropic effects on health and various chronic diseases. The purpose of this review is to provide a detailed report on the pathophysiological mechanisms underlying vitamin D deficiency in patients with chronic liver disease, addressing the different liver etiologies and the condition of advanced chronic liver disease (cirrhosis) with related complications. To date, patients with liver disease, regardless of underlying etiology, have been shown to have reduced levels of vitamin D. There is also evidence of the predictive role of vitamin D values in complications and progression of advanced disease. However, specific indications of vitamin D supplementation are not conclusive concerning what is already recommended in the general population. Future studies should make an effort to unify and validate the role of vitamin D supplementation in chronic liver disease.

Vitamin D–VDR Novel Anti-Inflammatory Molecules—New Insights into Their Effects on Liver Diseases

There is consistent evidence that vitamin D deficiency is strongly associated with liver dysfunction, disease severity, and poor prognosis in patients with liver disease. Vitamin D and its receptor (VDR) contribute to the regulation of innate and adaptive immune responses. The presence of genetic variants of vitamin D- and VDR-associated genes has been associated with liver disease progression. In our recent work, we summarized the progress in understanding the molecular mechanisms involved in vitamin D–VDR signaling and discussed the functional significance of VDR signaling in specific cell populations in liver disease. The current review focuses on the complex interaction between immune and liver cells in the maintenance of liver homeostasis and the development of liver injury, the interplay of vitamin D and VDR in the development and outcome of liver disease, the role of vitamin D- and VDR-associated genetic variants in modulating the occurrence and severity of liver disease, and the therapeutic value of vitamin D supplementation in various liver diseases. The association of the vitamin D–VDR complex with liver dysfunction shows great potential for clinical application and supports its use as a prognostic index and diagnostic tool.

Epigenetic Aspects and Prospects in Autoimmune Hepatitis

The observed risk of autoimmune hepatitis exceeds its genetic risk, and epigenetic factors that alter gene expression without changing nucleotide sequence may help explain the disparity. Key objectives of this review are to describe the epigenetic modifications that affect gene expression, discuss how they can affect autoimmune hepatitis, and indicate prospects for improved management. Multiple hypo-methylated genes have been described in the CD4⁺ and CD19⁺ T lymphocytes of patients with autoimmune hepatitis, and the circulating micro-ribonucleic acids, miR-21 and miR-122, have correlated with laboratory and histological features of liver inflammation. Both epigenetic agents have also correlated inversely with the stage of liver fibrosis. The reduced hepatic concentration of miR-122 in cirrhosis suggests that its deficiency may de-repress the pro-fibrotic prolyl-4-hydroxylase subunit alpha-1 gene. Conversely, miR-155 is over-expressed in the liver tissue of patients with autoimmune hepatitis, and it may signify active immune-mediated liver injury. Different epigenetic findings have been described in diverse autoimmune and non-autoimmune liver diseases, and these changes may have disease-specificity. They may also be responses to environmental cues or heritable adaptations that distinguish the diseases. Advances in epigenetic editing and methods for blocking micro-ribonucleic acids have improved opportunities to prove causality and develop site-specific, therapeutic interventions. In conclusion, the role of epigenetics in affecting the risk, clinical phenotype, and outcome of autoimmune hepatitis is under-evaluated. Full definition of the epigenome of autoimmune hepatitis promises to enhance understanding of pathogenic mechanisms and satisfy the unmet clinical need to improve therapy for refractory disease.

Serum 25-hydroxyvitamin D and C-reactive protein and plasma von Willebrand concentrations in 23 dogs with chronic hepatopathies

BACKGROUND

Serum concentrations of 25-hydroxyvitamin D (25(OH)VD) and C-reactive protein (CRP) and von Willebrand's factor (vWF) concentration correlate with histopathologic disease grade and stage in chronic inflammatory and fibrotic hepatopathies (CH) in humans.

OBJECTIVES

To evaluate serum 25(OH)VD and serum CRP concentrations and plasma vWF concentration and determine if they correlate with histopathologic and biochemical variables in dog with CH.

ANIMALS

Twenty-three client-owned dogs with a histopathologic diagnosis of CH were prospectively enrolled.

METHODS

Blood samples were collected before liver biopsy. Correlations between biomarkers and clinical pathological and histopathologic variables were evaluated using Pearson's or Spearman's test.

RESULTS

Serum 25(OH)VD concentration (median, 213 nmol/L; range, 42-527 nmol/L) was negatively correlated with serum aspartate aminotransferase activity (AST; rho = -0.59, P < .01), polymorphonuclear neutrophil count (PMN; r = -0.46, P < .05), and positively correlated with serum albumin concentration (r = 0.69, P < .001). Serum CRP concentration (median, 7.4 μg/L; range, 1-44.9 μg/L) was positively correlated with overall histopathologic necroinflammatory activity (r = 0.78, P < .001) and fibrosis score (rho = 0.49, P < .05). Plasma vWF concentration (median, 73.3%; range, 15-141%) was positively correlated with fibrosis score (r = 0.53, P < .05) and prothrombin time (rho = 0.67, P < .01), and negatively correlated with serum albumin concentration (r = -0.73, P < .001).

CONCLUSION AND CLINICAL IMPORTANCE

In dogs with CH, serum 25(OH)VD concentration was negatively correlated with disease activity, whereas serum CRP concentration and plasma vWF concentration were positively correlated with histopathologic grade and stage. Our results provide preliminary evidence that these biomarkers may be useful to assess grade and stage of CH in dogs in the absence of liver biopsy.

Vitamin D Is Associated with Clinical Outcomes in Patients with Primary Biliary Cholangitis

Vitamin D (VD) deficiency has been associated with clinical outcomes in patients with chronic liver disease. This study aims to identify the prevalence of VD deficiency in patients with primary biliary cholangitis (PBC) and its association with treatment response to ursodeoxycholic acid (UDCA), cirrhosis development, and liver-related events (mortality and liver transplantation). Two hundred and fifty-five patients with PBC diagnosis were evaluated. Patients with VD levels below 50 nmol/L were defined as deficient. Treatment response to UDCA was defined according to the Toronto criteria. Independent risk factors were identified using binary logistic and Cox regression analysis. The mean level of serum VD was 77 ± 39 nmol/L, and 64 patients (25%) were VD deficient. Incomplete response to UDCA was more prevalent in VD-deficient patients compared to their counterparts (45% vs. 22%; p < 0.001). The risk of cirrhosis development (hazard ratio (HR) 1.93; 95% confidence interval (CI) 1.17–3.19, p = 0.01) and liver-related mortality or need for liver transplantation (HR 3.33, 95% CI, 1.57–7.07, p = 0.002) was higher in VD-deficient patients after adjusting for confounders. Vitamin D deficiency is frequent in patients with PBC and is associated with incomplete response to UDCA, cirrhosis development, and liver-related mortality or need for liver transplantation.

Vitamin D supplementation for autoimmune hepatitis: A need for further investigation

Autoimmune hepatitis is a chronic liver disease harboring an autoimmune basis and progressive character. Despite still obscurity in etiology and pathogenesis, some evidence supports the importance of sustaining the immune system. Vitamin D is a lipo-soluble vitamin, which has been identified as decreased in our body. It is often due to the daily habit change and decrease of individual sun exposure due to the increase of the ultraviolet-induced potential melanocytic transformation. Here, we emphasize the importance of vitamin D supplementation in patients affected with liver disease.

Potential roles of vitamin D binding protein in attenuating liver injury in sepsis

BACKGROUND

In sepsis, vitamin D binding protein (VDBP) has been shown to be low-expressed. The current study examined the relationship between serum VDBP level and liver injury in sepsis patients, as well as in a mouse model for sepsis and in cultured liver epithelial cell line exposed to lipopolysaccharide (LPS).

METHODS

The human study included 78 sepsis patients and 50 healthy volunteers. Sepsis patients were categorized into sepsis survivor group (n = 43) and sepsis non-survivor group (n = 35) based on 28-day mortality for data analysis. Adult male C57BL/6 mice were subjected to cecal ligation and puncture (CLP). Serum samples were collected on day 1, 3, 5 and 7 to determine the levels of VDBP, 25-hydroxyvitamin D [25(OH)D₃], 1,25-dihydroxyvitamin D [1,25(OH)₂D₃], interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α). Potential protective effects of VDBP overexpression against LPS-induced liver damage were examined in cultured THLE2 cells.

RESULTS

Serum levels of VDBP, 25(OH)D₃, and 1,25(OH)₂D₃ were significantly lower in sepsis patients vs. the healthy control (P < 0.001), as well as in the sepsis non-survivor group vs. the sepsis survivor group (P < 0.001, P = 0.0338, or P = 0.0013, respectively). Lower serum VDBP level was associated with higher Acute Physiology and Chronic Health Evaluation (APACHE) II score (r = - 0.2565, P = 0.0234) and Sequential Organ Failure Assessment score (r = - 0.3522, P = 0.0016), but lower serum albumin (ALB, r = 0.4628, P < 0.001) and total protein (TP, r = 0.263, P = 0.02). In CLP mice, there was a 5-day period of serum VDBP reduction, followed by return towards the baseline on day 7. VDBP was also decreased in LPS-treated THLE2 cells (P < 0.001). VDBP overexpression reduced LPS-induced THLE2 damage. Reduced damage was associated with decreased oxidative stress and inactivation of the c-Jun N-terminal kinase signaling pathway.

CONCLUSION

VDBP may be protective against sepsis-induced liver injury.

Vitamin D levels in Greek patients with systemic lupus erythematosus

OBJECTIVES

Vitamin D deficiency has been observed in autoimmune rheumatic diseases, such as rheumatoid arthritis. The aim was to study vitamin D in patients with systemic lupus erythematosus (SLE) and its relationship with disease activity.

METHODS

In a cohort of 45 patients with SLE, 41 females and 4 males, aged 47.07 ± 2.17 years (mean ± SEM), and range = 21-79 years, 25(OH)D₃ levels were determined by electrochemiluminescence. C₃ and C₄ levels were also analyzed. SLE disease activity was estimated by SLEDAI-2K. Observations were also performed in a control group matched for age and sex.

RESULTS

In this cohort of SLE patients, 25(OH)D₃ levels were 40.36 ± 2.41 nmol/L (mean ± SEM) as opposed to 60.98 ± 4.28 nmol/L in the control group (p < 0.001, Student's t test). Vitamin D levels were related to C₃ (p < 0.001, linear regression analysis), correlation coefficient 0.106, r² = 0.011, and C₄ (p < 0.001); correlation coefficient 0.316 and r² = 0.100; and inversely related to disease activity (p < 0.001), correlation coefficient -0.572 and r² = 0.327. 25(OH)D₃ levels were 17.73 ± 1.20 nmol/L and 12.24 ± 0.93 nmol/L, in the groups without and with renal involvement, respectively (p = 0.001, Student's t test).

CONCLUSIONS

Vitamin D levels are low in SLE patients and are inversely related to disease activity. Routine screening for vitamin D levels should be performed in SLE patients.

Vitamin D and Folate as Predictors of MMSE in Alzheimer's Disease: A Machine Learning Analysis

Vitamin D (VD) and micronutrients, including folic acid, are able to modulate both the innate and the adaptive immune responses. Low VD and folic acid levels appear to promote cognitive decline as in Alzheimer’s disease (AD). A machine learning approach was applied to analyze the impact of various compounds, drawn from the blood of AD patients, including VD and folic acid levels, on the Mini-Mental State Exam (MMSE) in a cohort of 108 patients with AD. The first analysis was aimed at predicting the MMSE at recruitment, whereas a second investigation sought to predict the MMSE after a 4 year follow-up. The simultaneous presence of low levels of VD and folic acid allow to predict MMSE, suggestive of poorer cognitive function. Such results suggest that the low levels of VD and folic acid could be associated with more severe cases of cognitive impairment in AD. It could be hypothesized that simultaneous supplementation of VD and folic acid could slow down the progression of cerebral degeneration at least in a subset of AD individuals.

Cholangiopathy aggravation is caused by VDR ablation and alleviated by VDR-independent vitamin D signaling in ABCB4 knockout mice

BACKGROUND & AIMS

Cholangiopathies are chronic liver diseases in which damaged cholangiocytes trigger a proinflammatory and profibrotic reaction. The nuclear vitamin D receptor (VDR) is highly expressed in cholangiocytes and exerts immune-regulatory functions in these cells. In the present study, we examined the protective function of VDR and other vitamin D signaling pathways in chronic cholangiopathy and cholangiocytes.

METHODS

Vdr was invalidated in Abcb4 knockout mice, a widely used animal model of chronic cholangiopathy. The impact of vitamin D signaling on cholangiopathy features was examined in vivo and in cholangiocytes (primary and cell lines).

RESULTS

Cholangiopathy features (i.e, cholestasis, ductular reaction and fibrosis) were aggravated in Vdr;Abcb4 double knockout mice compared to the Abcb4 simple knockout, and associated with an overexpression of proinflammatory factors. The proinflammatory phenotype of cholangiocytes was also exacerbated following VDR silencing in vitro. The expression of proinflammatory factors and the severity of cholangiopathy were reduced in the double knockout mice treated with the vitamin D analog calcipotriol or with vitamin D. In vitro, the inflammatory response to TNFα was significantly reduced by calcipotriol in biliary cells silenced for VDR, and this effect was abolished by co-silencing the plasma membrane receptor of vitamin D, protein disulfide-isomerase A3 (PDIA3).

CONCLUSIONS

Our results demonstrate an anti-inflammatory role of VDR signaling in cholangiocytes and cholangiopathy. They also provide evidence for PDIA3-mediated anti-inflammatory effects of vitamin D and vitamin D analog in these settings.

An insight into the mechanism and molecular basis of dysfunctional immune response involved in cholestasis

Cholestasis is one of the most common clinical symptom of liver diseases. If patients do not receive effective treatment, cholestasis can evolve into liver fibrosis, cirrhosis and ultimately liver failure requiring liver transplantation. Currently, only ursodeoxycholic acid, obeticholic acid and bezafibrate are FDA-approved drugs, thereby requiring a breakthrough in new mechanisms and therapeutic development. Inflammation is one of the common complications of cholestasis. Hepatic accumulation of toxic hydrophobic bile acids is a highly immunogenic process involving both resident and immigrating immune cells. And the resulting inflammation may further aggravate hepatocyte injury. Though, great investigations have been made in the immune responses during cholestasis, the relationship between immune responses and cholestasis remains unclear. Moreover, scarce reviews summarize the immune responses during cholestasis and the efficacy of therapies on immune response. The main purpose of this paper is to review the existing literature on dysfunctional immune response during cholestasis and the effect of treatment on immune response which may provide an insight for researchers and drug development.

Low Vitamin D Status Is Associated with Inflammation in Patients with Chronic Obstructive Pulmonary Disease

Vitamin D deficiency is associated with increased risks of chronic obstructive pulmonary disease (COPD). Nevertheless, the mechanisms remain unknown. This study analyzed the correlations between vitamin D levels and inflammation in COPD patients. One hundred and one patients with COPD and 202 control subjects were enrolled. Serum 25(OH)D level and inflammatory cytokines were detected. Serum 25(OH)D was decreased and inflammatory cytokines were increased in COPD patients. According to forced expiratory volume in 1 s, COPD patients were divided into three grades. Furthermore, serum 25(OH)D was gradually decreased in COPD patients ranging from grade 1-2 to 4. Serum 25(OH)D was inversely associated with inflammatory cytokines in COPD patients. Further analysis found that NF-κB and AP-1 signaling were activated in COPD patients. Besides, inflammatory signaling was gradually increased in parallel with the severity of COPD. By contrast, pulmonary nuclear vitamin D receptor was decreased in COPD patients. In vitro experiments showed that 1,25(OH)₂D₃ inhibited LPS-activated inflammatory signaling in A549 cells (human lung adenocarcinoma cell). Mechanically, 1,25(OH)₂D₃ reinforced physical interactions between vitamin D receptor with NF-κB p65 and c-Jun. Our results indicate that vitamin D is inversely correlated with inflammatory signaling in COPD patients. Inflammation may be a vital mediator of COPD progress in patients with low vitamin D levels.

Vitamin D Therapy in Adults With Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Vitamin D deficiency has been implicated in the pathogenesis of inflammatory bowel disease. Emerging literature suggests that optimization of vitamin D levels may be associated with improvements in disease activity and quality of life. We conducted a meta-analysis exploring the effect of vitamin D on serum 25-hydroxyvitamin D (s-25[OH]D) levels, clinical improvement, and biomarkers.

METHODS

MEDLINE, EMBASE, the Cochrane Library, and sources for grey literature were searched from inception until September 2019. The primary outcome was s-25(OH)D mean differences. Heterogeneity was assessed using the χ 2 test and the I2 statistic. Review Manager software v. 5.3 was used.

RESULTS

Twelve randomized controlled trials (n = 611) and 4 observational studies (n = 359) were included in the meta-analysis. On average, in the randomized controlled trials, vitamin D supplementation increased s-25(OH)D levels by 15.50 ng/mL (95% confidence interval [CI], 11.08-19.92, P ≤ 0.00001, I2 = 90%) and in observational studies they increased by 18.39 ng/mL (95% CI, 8.91-27.88, P = 0.0001, I2 = 82%). Subgroup analyses between vitamin D and placebo groups revealed that vitamin D increased s-25(OH)D by 14.85 ng/mL (95% CI, 9.96-19.73, P ≤ 0.00001, I2 = 90%) and when high doses of vitamin D were compared with low doses, high doses increased s-25(OH)D by 18.27 ng/mL (95% CI, 5.44-31.10, P = 0.005, I2 = 90%). The Harvey Bradshaw Index improved by -1.47 points (95% CI, -2.47 to -0.47, P = 0.004, I2 = 0%) and the high-sensitivity C-reactive protein decreased by -1.58 mg/L (95% CI, -2.95 to -0.21, P = 0.02, I2 = 0%).

CONCLUSIONS

Vitamin D supplementation in patients with IBD and vitamin D deficiency is effective at correcting vitamin D levels and is associated with improvement in clinical and biochemical disease activity scores.

Vitamin D supplementation improves anxiety but not depression symptoms in patients with vitamin D deficiency

OBJECTIVE

Epidemiological evidence indicated a relationship between vitamin D (VD) and depression with anxiety, but their therapeutic relationship has not been fully elucidated. This study aimed to examine whether VD supplementation would relieve symptoms in patients with depression and anxiety with low serum 25-hydroxy VD [25(OH) D] levels.

METHOD

Participants with low 25(OH)D levels were randomized to control or daily VD group and were followed up for 6 months. Serum concentrations of 25(OH) D were measured using commercial kits. Psychological symptoms were evaluated with the Hamilton Depression Rating Scale-17 (HAMD-17), Revised Social Anhedonia Scale (RSAS), Revised Physical Anhedonia scale (RPAS), and Hamilton Anxiety Rating Scale-14 (HAMA-14). The trial was listed in the trial registration (http://www.medresman.org.cn/uc/index.aspx; NTR number: ChiCTR2000030130).

RESULTS

In this clinical population, no significant difference in depression symptoms was detected between VD group and control group at both baseline and at the endpoint of our study. The HAMD-17, RSAS, and RPAS scores did not change significantly between VD and control groups from baseline to endpoint (all p > .05). However, there was a significant difference in time effect of the total HAMA-14 scores between the two groups (β [95% Cl] = -2.235 [-3.818, -0.653], p = .006).

CONCLUSIONS

Vitamin D supplementation could improve the anxiety symptoms but not depressive symptoms in depressive patients with low VD level after the 6-month intervention.

A Brief Review of the Effects of Vitamin D on Multiple Sclerosis

Multiple sclerosis (MS) is characterized as an autoimmune disease affecting the central nervous system. It is one of the most common neurological disorders in young adults. Over the past decades, increasing evidence suggested that hypovitaminosis D is a contributing factor to the risk of developing MS. From different risk factors contributing to the development of MS, vitamin D status is of particular interest since it is not only a modifiable risk factor but is also associated with MS disease activity. MS patients with lower serum vitamin D concentrations were shown to have higher disease activity. However, this finding does not demonstrate causality. In this regard, prospective vitamin D supplementation studies missed statistical significance in its primary endpoints but showed promising results in secondary outcome measures or post hoc analyses. An explanation for missed primary endpoints may be underpowered trials. Besides vitamin D supplementation as a potential add-on to long-term immunotherapeutic treatment, a recent laboratory study of our group pointed toward a beneficial effect of vitamin D to improve the efficacy of glucocorticoids in relapse therapy. In the following article, we will briefly review the effects of vitamin D on MS by outlining its effects on the immune and nervous system and by reviewing the association between vitamin D and MS risk as well as MS disease activity. We will also review the effects of vitamin D supplementation on MS risk and MS disease activity.

Pathophysiological Role and Therapeutic Implications of Vitamin D in Autoimmunity: Focus on Chronic Autoimmune Diseases

Vitamin D is a pleiotropic secosteroid yielding multiple actions in human physiology. Besides the canonical regulatory activity on bone metabolism, several non-classical actions have been described and the ability of vitamin D to partake in the regulation of the immune system is particularly interesting, though far stronger and convincing evidence has been collected in in vitro as compared to in vivo studies. Whether vitamin D is able to regulate at physiological concentrations the human immune system remains unproven to date. Consequently, it is not established if vitamin D status is a factor involved in the pathogenesis of immune-mediated diseases and if cholecalciferol supplementation acts as an adjuvant for autoimmune diseases. The development of autoimmunity is a heterogeneous process, which may involve different organs and systems with a wide range of clinical implications. In the present paper, we reviewed the current evidences regarding vitamin D role in the pathogenesis and management of different autoimmune diseases.

Vitamin D-Cathelicidin Axis: at the Crossroads between Protective Immunity and Pathological Inflammation during Infection

Vitamin D signaling plays an essential role in innate defense against intracellular microorganisms via the generation of the antimicrobial protein cathelicidin. In addition to directly binding to and killing a range of pathogens, cathelicidin acts as a secondary messenger driving vitamin D-mediated inflammation during infection. Recent studies have elucidated the biological and clinical functions of cathelicidin in the context of vitamin D signaling. The vitamin D-cathelicidin axis is involved in the activation of autophagy, which enhances antimicrobial effects against diverse pathogens. Vitamin D studies have also revealed positive and negative regulatory effects of cathelicidin on inflammatory responses to pathogenic stimuli. Diverse innate and adaptive immune signals crosstalk with functional vitamin D receptor signals to enhance the role of cathelicidin action in cell-autonomous effector systems. In this review, we discuss recent findings that demonstrate how the vitamin D-cathelicidin pathway regulates autophagy machinery, protective immune defenses, and inflammation, and contributes to immune cooperation between innate and adaptive immunity. Understanding how the vitamin D-cathelicidin axis operates in the host response to infection will create opportunities for the development of new therapeutic approaches against a variety of infectious diseases.

Serum vitamin D status in sick cats with and without cholestatic liver disease

OBJECTIVES

Vitamin D deficiency accompanies chronic cholestatic liver disease (CLD) in humans. The vitamin D status of cats with CLD is unknown. The objectives of this study were to describe serum vitamin D concentrations in cats with CLD and to determine if they correlated with indices of liver disease severity.

METHODS

Thirty-six cats with CLD, defined by increases in serum bilirubin and serum alanine aminotransferase, and 23 sick cats with non-hepatobiliary diseases were prospectively enrolled. Serum 25-hydroxyvitamin D (25[OH]D), parathyroid hormone (PTH) and ionized calcium were measured. Signalment, clinical signs, comorbidities, diet history, serum bilirubin, liver enzyme activity, albumin, phosphorus, white blood cell count, prothrombin time and final hepatic cytologic/histopathologic diagnosis, when available, were recorded.

RESULTS

Median serum 25(OH)D levels were similar in cats with CLD (89.5 nmol/l; range 21-112 nmol/l) and sick cats (89.0 nmol/l; range 49-115 nmol/l). Overall 12/36 (33%) cats with CLD and 4/23 (17%) sick cats had 25(OH)D levels below the lower limit of the reference interval (<65 nmol/l). Median PTH concentrations in cats with CLD were significantly higher (0.95 pmol/l; range 0-11.3 pmol/l) than in sick cats (0.70 pmol/l; range 0.5-6 pmol/l). In cats with CLD, 6/36 (17%) had high PTH levels in contrast to only 1/23 (4%) sick cats. In cats with CLD, 25(OH)D concentrations did not correlate with serum bilirubin, albumin or serum liver enzymes but were moderately negatively correlated with white blood cell count (r = - 0.402, P = 0.013). Cats with hepatic lipidosis had the highest prevalence of 25(OH)D concentrations that fell below the reference interval.

CONCLUSIONS AND RELEVANCE

Many cats with CLD have serum 25(OH)D concentrations below the lower limit of the reference interval. Further study is warranted to determine the clinical relevance and whether supplementation would provide benefits.

Examining pathogenic concepts of autoimmune hepatitis for cues to future investigations and interventions

BACKGROUND

Multiple pathogenic mechanisms have been implicated in autoimmune hepatitis, but they have not fully explained susceptibility, triggering events, and maintenance or escalation of the disease. Furthermore, they have not identified a critical defect that can be targeted. The goals of this review are to examine the diverse pathogenic mechanisms that have been considered in autoimmune hepatitis, indicate investigational opportunities to validate their contribution, and suggest interventions that might evolve to modify their impact. English abstracts were identified in PubMed by multiple search terms. Full length articles were selected for review, and secondary and tertiary bibliographies were developed. Genetic and epigenetic factors can affect susceptibility by influencing the expression of immune regulatory genes. Thymic dysfunction, possibly related to deficient production of programmed cell death protein-1, can allow autoreactive T cells to escape deletion, and alterations in the intestinal microbiome may help overcome immune tolerance and affect gender bias. Environmental factors may trigger the disease or induce epigenetic changes in gene function. Molecular mimicry, epitope spread, bystander activation, neo-antigen production, lymphocytic polyspecificity, and disturbances in immune inhibitory mechanisms may maintain or escalate the disease. Interventions that modify epigenetic effects on gene expression, alter intestinal dysbiosis, eliminate deleterious environmental factors, and target critical pathogenic mechanisms are therapeutic possibilities that might reduce risk, individualize management, and improve outcome. In conclusion, diverse pathogenic mechanisms have been implicated in autoimmune hepatitis, and they may identify a critical factor or sequence that can be validated and used to direct future management and preventive strategies.

Regulation of the Immune Balance During Allogeneic Hematopoietic Stem Cell Transplantation by Vitamin D

One of the most promising therapeutic approaches for numerous hematological malignancies represents the allogeneic hematopoietic stem cell transplantation (allo-HSCT). One major complication is the development of the life-threatening graft-vs.-host disease (GvHD) which limits beneficial effects of graft-vs.-leukemia (GvL) responses during allo-HSCT. Strengthening GvL effects without induction of severe GvHD is essential to decrease the relapse rate after allo-HSCT. An interesting player in this context is vitamin D₃ since it has modulatory capacity in both preventing GvHD and boosting GvL responses. Current studies claim that vitamin D₃ induces an immunosuppressive environment by dendritic cell (DC)-dependent generation of regulatory T cells (Tregs). Since vitamin D₃ is known to support the antimicrobial defense by re-establishing the physical barrier as well as releasing defensins and antimicrobial peptides, it might also improve graft-vs.-infection (GvI) effects in patients. Beyond that, alloreactive T cells might be attenuated by vitamin D₃-mediated inhibition of proliferation and activation. Despite the inhibitory effects of vitamin D₃ on T cells, anti-tumor responses of GvL might be reinforced by vitamin D₃-triggered phagocytic activity and antibody-based immunotherapy. Therefore, vitamin D₃ treatment does not only lead to a shift from a pro-inflammatory toward a tolerogenic state but also promotes tumoricidal activity of immune cells. In this review we focus on vitamin D₃ and its immunomodulatory effects by enhancing anti-tumor activity while alleviating harmful allogeneic responses in order to restore the immune balance.

Vitamin D and autoimmune diseases

The prevalence of autoimmune diseases (ADs) has increased over the past few decades. Vitamin D deficiency is a common factor in many of these diseases, whose etiology remains poorly understood. The objective of this study was to review published data on the role of vitamin D in ADs. Vitamin D insufficiency has been described as an important factor in the development of some ADs, generally attributed to the key role of this vitamin in the immune system. Most studies show that adequate supplementation can prevent and improve the development of some of these diseases, although the optimal vitamin D dose remains controversial. We highlight the importance of measuring serum vitamin D levels of the population and developing strategies to improve and maintain levels with no health risks.

The upside-downside nature of Vitamin D signaling in liver

Discussion of the potential contradictory effects of vitamin D receptor signaling in a mouse model of autoimmune hepatitis.

Emerging role of vitamin D in autoimmune diseases: An update on evidence and therapeutic implications

Vitamin D plays a key role in in calcium homeostasis and, thus, provides an important support in bone growth by aiding in the mineralization of the collagen matrix. However, vitamin D performs various immunomodulatory, anti-inflammatory, antioxidant and anti-fibrotic actions. Autoimmune diseases result from an aberrant activation of the immune system, whereby the immune response is directed against harmless self-antigens. Does vitamin D play a role in the pathophysiology of autoimmune diseases? And, if so, what is its role? In the last decade, researchers' interest in vitamin D and its correlations with autoimmune diseases has considerably increased. We conducted a literature review, covering the period January 1, 2009 through March 30, 2019, in PubMed. We analyzed more than 130 studies in order to find a correlation between vitamin D levels and its effect upon several autoimmune diseases. The analysis demonstrated an inverse association between vitamin D and the development of several autoimmune diseases, such as SLE, thyrotoxicosis, type 1 DM, MS, iridocyclitis, Crohn's disease, ulcerative colitis, psoriasis vulgaris, seropositive RA, polymyalgia rheumatica. International multicenter study could allow us to confirm the data already present in the literature in the single clinical studies and to evaluate when to effectively supplement vitamin D in patients who do not take corticosteroids.

Vitamin D supplementation for the prevention or depletion of side effects of therapy with alemtuzumab in multiple sclerosis

PURPOSE OF REVIEW

Not only the multiple sclerosis specialist but also the general neurologist and primary care practitioner are increasingly aware of possible adverse events (AEs) by treatment with alemtuzumab (over 47% risk of secondary autoimmune-mediated diseases). Vitamin D supplementation's effect (VDS) to reduce these autoimmune AEs is poorly performed in routine practice. This article seeks to justify why this simple, inexpensive, patient-friendly therapy should be seriously discussed.

RECENT FINDINGS

Patients who have developed autoimmunity also show a high basal level of IL-21, a cytokine which increases the growth of auto-reactive T-cells. For side effects such as thyroid dysfunction, autoimmune thrombocytopenia, autoimmune hemolytic anemia, autoimmune hepatitis, diabetes mellitus type 1, and alopecia areata/alopecia totalis, VDS may have an impact on the immunological mechanism, in particular lowering levels of IL-17 and IL-21.

SUMMARY

The potential role of vitamin D in influencing autoimmune diseases is evident. If a life-threatening side-effect can be prevented by high-dose VDS, it is ethical to initiate this add-on therapy despite contradictory results in studies on the effectiveness of VDS.