Vitamin D inhibits development of liver fibrosis in an animal model but cannot ameliorate established cirrhosis

1α,25(OH)2D3 Regulates the TGF-β1/Samd Signaling Pathway Inhibition of Hepatic Stellate Cell Activation

To investigate the effect of 1α,25(OH)2D3 on hepatic stellate cells and the mechanism of the TGF-β1/Smad signaling pathway.LX2 cells were treated with TGF-β1 and different concentrations of 1α,25(OH)2D3. Cell proliferation was assessed using the CCK8 assay to determine the optimal concentration of 1α,25(OH)2D3 activity. The cell cycle and apoptotic rates were evaluated using flow cytometry. The expressions of Samd2, Samd3, Samd4, and Samd7 was assessed by western blotting, whereas the expression of MMP1, MMP13, and TIMP-1 was detected by qPCR.Compared with the control group, the 1α,25(OH)2D3 group had a higher apoptotic rate of LX2 cells, the cell cycle was blocked from the G1 stage to the S stage, the expressions of Samd2, Samd7, MMP1, and MMP13 increased, while the expressions of Samd3, Samd4, and TIMP-1 decreased.1α,25(OH)2D3 inhibits hepatic stellate cell activation and exerts anti-hepatic fibrosis effects by downregulating the expression of Samd3, Samd4, TIMP-1 and upregulating the expression of Samd2, Samd4, MMP1, and MMP13.

Retinoid X receptor heterodimers in hepatic function: structural insights and therapeutic potential

Nuclear receptors (NRs) are key regulators of multiple physiological functions and pathological changes in the liver in response to a variety of extracellular signaling changes. Retinoid X receptor (RXR) is a special member of the NRs, which not only responds to cellular signaling independently, but also regulates multiple signaling pathways by forming heterodimers with various other NR. Therefore, RXR is widely involved in hepatic glucose metabolism, lipid metabolism, cholesterol metabolism and bile acid homeostasis as well as hepatic fibrosis. Specific activation of particular dimers regulating physiological and pathological processes may serve as important pharmacological targets. So here we describe the basic information and structural features of the RXR protein and its heterodimers, focusing on the role of RXR heterodimers in a number of physiological processes and pathological imbalances in the liver, to provide a theoretical basis for RXR as a promising drug target.

Relationship among serum 25-hydroxyvitamin D, fibrosis stage, genetic susceptibility, and risk of severe liver disease

OBJECTIVES

The prospective association between vitamin D and new-onset severe liver disease is still uncertain. The aim of this study was to assess the association of serum 25-hydroxyvitamin D (25(OH)D) with new-onset severe liver disease and to evaluate whether fibrosis stage, as assessed by the fibrosis- 4 (FIB-4) scores and genetic risk for liver cirrhosis may modify this association.

METHODS

The study included 439 807 participants without liver diseases at baseline from the UK Biobank. Serum 25(OH)D concentrations were measured using the chemiluminescent immunoassay method. The primary outcome was new-onset severe liver disease, a composite definition of compensated or decompensated liver cirrhosis, liver failure, hepatocellular carcinoma, and liver-related death.

RESULTS

During a median follow-up of 12 y, 4510 participants developed new-onset severe liver disease. Overall, there was an inverse association of serum 25(OH)D with new-onset severe liver disease (per SD increment, adjusted hazard ratio [HR], 0.87; 95% confidence interval, 0.84-0.91). Similarly, serum 25(OH)D (per SD increment) was significantly and inversely associated with new-onset compensated cirrhosis, decompensated cirrhosis, liver failure, and liver-related death, respectively, with HRs ranging from 0.75 to 0.87. No significant association was found for hepatocellular carcinoma. Furthermore, there was a stronger inverse association between serum 25(OH)D and severe liver disease among those with a higher FIB-4 score (≥2.67, 1.3 to <2.67, and <1.3; Pinteraction < 0.001). However, the genetic risks for liver cirrhosis, calculated using 12 related single nucleotide polymorphisms, did not significantly modify the association between serum 25(OH)D and severe liver disease (Pinteraction = 0.216).

CONCLUSIONS

Lower serum 25(OH)D concentrations were significantly associated with a greater risk for new-onset severe liver disease, especially in participants with higher FIB-4 scores.

Compensated liver cirrhosis: Natural course and disease-modifying strategies

Compensated liver cirrhosis (CLC) is defined as cirrhosis with one or more decompensating events, such as ascites, variceal haemorrhage, or hepatic encephalopathy. Patients with CLC are largely asymptomatic with preserved hepatic function. The transition from CLC to decompensated cirrhosis occurs as a result of a complex interaction between multiple predisposing and precipitating factors. The first decompensation event in CLC patients is considered a significant turning point in the progression of cirrhosis, as it signals a drastic decline in median survival rates from 10-12 years to only 1-2 years. Furthermore, early cirrhosis has the potential to regress as liver fibrosis is a dynamic condition. With the advent of effective non-invasive tools for detecting hepatic fibrosis, more and more patients with CLC are currently being recognised. This offers clinicians a unique opportunity to properly manage such patients in order to achieve cirrhosis regression or, at the very least, prevent its progression. There are numerous emerging approaches for preventing or delaying decompensation in CLC patients. A growing body of evidence indicates that treating the underlying cause can lead to cirrhosis regression, and the use of non-selective beta-blockers can prevent decompensation by lowering portal hypertension. Additionally, addressing various cofactors (such as obesity, diabetes, dyslipidaemia, and alcoholism) and precipitating factors (such as infection, viral hepatitis, and hepatotoxic drugs) that have a detrimental impact on the natural course of cirrhosis may benefit patients with CLC. However, high-quality data must be generated through well-designed and adequately powered randomised clinical trials to validate these disease-modifying techniques for CLC patients. This article discussed the natural history of CLC, risk factors for its progression, and therapeutic approaches that could alter the trajectory of CLC evolution and improve outcomes.

Gene Polymorphisms and Biological Effects of Vitamin D Receptor on Nonalcoholic Fatty Liver Disease Development and Progression

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, with increasing prevalence worldwide. The genetic and molecular background of NAFLD pathogenesis is not yet clear. The vitamin D/vitamin D receptor (VDR) axis is significantly associated with the development and progression of NAFLD. Gene polymorphisms may influence the regulation of the VDR gene, although their biological significance remains to be elucidated. VDR gene polymorphisms are associated with the presence and severity of NAFLD, as they may influence the regulation of adipose tissue activity, fibrosis, and hepatocellular carcinoma (HCC) development. Vitamin D binds to the hepatic VDR to exert its biological functions, either by activating VDR transcriptional activity to regulate gene expression associated with inflammation and fibrosis or by inducing intracellular signal transduction through VDR-mediated activation of Ca²⁺ channels. VDR activity has protective and detrimental effects on hepatic steatosis, a characteristic feature of NAFLD. Vitamin D-VDR signaling may control the progression of NAFLD by regulating immune responses, lipotoxicity, and fibrogenesis. Elucidation of the genetic and molecular background of VDR in the pathophysiology of NAFLD will provide new therapeutic targets for this disease through the development of VDR agonists, which already showed promising results in vivo.

The effect of high oral loading dose of cholecalciferol in non-alcoholic fatty liver disease patients. A randomized placebo controlled trial

Background and Aim: Non-alcoholic fatty liver (NAFLD) is one of the most common progressive metabolic disorders worldwide. There are increasing scientific interests nowadays for the association between vitamin D status and Non-alcoholic fatty liver. Earlier studies have revealed that vitamin D deficiency is highly prevalent in Non-alcoholic fatty liver patients that contributes to poor outcomes. Hence, the present study aimed to assess the efficacy and safety of oral cholecalciferol on Non-alcoholic fatty liver patients.

Subjects and Methods: This study was conducted on 140 patients that were randomized either to group 1 that received the standard conventional therapy in addition to placebo or group 2 that received the standard conventional therapy in addition to cholecalciferol during the 4 months study period.

Results: At the end of the study group 2 revealed significant decrease (p &lt; 0.05) in the mean serum level of TG, LDL-C, TC, hsCRP as compared to their baseline results and group 1 results. Additionally, a significant improvement in the serum levels of ALT (p = 0.001) was seen in group 2 at the end of the study when compared to group 1. Whereas group 1 did not show any change in these parameters when compared to group 2 and their baseline results.

Conclusion: Cholecalciferol was shown to have beneficial effects on serum ALT levels, hsCRP levels and lipid profile of NAFLD patients.

Clinical Trial Registration:https://prsinfo.clinicaltrials.gov/prs-users-guide.html, identifier NCT05613192

Incomplete response to ursodeoxycholic acid in primary biliary cholangitis: criteria, epidemiology, and possible mechanisms

INTRODUCTION

As a common autoimmune disease with the characteristic of early complication, primary biliary cholangitis (PBC) leads to an increasing number of mortalities among people with end-stage liver disease (ESLD) waiting for liver transplantation. Ursodeoxycholic acid (UDCA) is the only approved first-line medicine for PBC, and a good response to treatment could acquire an ideal prognosis. Patients with poor UDCA response usually have more adverse outcomes and worse survival, therefore, the management of this group become a major consideration.

AREAS COVERED

Due to the complexity of race and environment for PBC, different criteria for UDCA response exhibit various predictive performances. Factors affecting UDCA response conditions include gender, age, ethnicity, serum indicators, auto-antibodies, and autoimmune comorbidities, while no agreement has been reached. In this review, we mainly focus on cellular senescence, immune-mediated damage, and vitamin D deficiency as possible mechanisms for UDCA non-responders.

EXPERT OPINION

The pathogenesis of PBC has yet to be clarified. Immunology-related mechanisms and therapy targets ought to be the main effort made for further study. Irrespective of the response condition, UDCA is recommended for routine administration in all PBC patients without contraindication. Ongoing clinical trials of second-line and additional therapy exhibit promising prospects.

Missing Causality and Heritability of Autoimmune Hepatitis

BACKGROUND

Autoimmune hepatitis has an unknown cause and genetic associations that are not disease-specific or always present. Clarification of its missing causality and heritability could improve prevention and management strategies.

AIMS

Describe the key epigenetic and genetic mechanisms that could account for missing causality and heritability in autoimmune hepatitis; indicate the prospects of these mechanisms as pivotal factors; and encourage investigations of their pathogenic role and therapeutic potential.

METHODS

English abstracts were identified in PubMed using multiple key search phases. Several hundred abstracts and 210 full-length articles were reviewed.

RESULTS

Environmental induction of epigenetic changes is the prime candidate for explaining the missing causality of autoimmune hepatitis. Environmental factors (diet, toxic exposures) can alter chromatin structure and the production of micro-ribonucleic acids that affect gene expression. Epistatic interaction between unsuspected genes is the prime candidate for explaining the missing heritability. The non-additive, interactive effects of multiple genes could enhance their impact on the propensity and phenotype of autoimmune hepatitis. Transgenerational inheritance of acquired epigenetic marks constitutes another mechanism of transmitting parental adaptations that could affect susceptibility. Management strategies could range from lifestyle adjustments and nutritional supplements to precision editing of the epigenetic landscape.

CONCLUSIONS

Autoimmune hepatitis has a missing causality that might be explained by epigenetic changes induced by environmental factors and a missing heritability that might reflect epistatic gene interactions or transgenerational transmission of acquired epigenetic marks. These unassessed or under-evaluated areas warrant investigation.

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.

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.

Liver Steatosis: A Marker of Metabolic Risk in Children

Obesity is one of the greatest health challenges affecting children of all ages and ethnicities. Almost 19% of children and adolescents worldwide are overweight or obese, with an upward trend in the last decades. These reports imply an increased risk of fat accumulation in hepatic cells leading to a series of histological hepatic damages gathered under the acronym NAFLD (Non-Alcoholic Fatty Liver Disease). Due to the complex dynamics underlying this condition, it has been recently renamed as 'Metabolic Dysfunction Associated Fatty Liver Disease (MAFLD)', supporting the hypothesis that hepatic steatosis is a key component of the large group of clinical and laboratory abnormalities of Metabolic Syndrome (MetS). This review aims to share the latest scientific knowledge on MAFLD in children in an attempt to offer novel insights into the complex dynamics underlying this condition, focusing on the novel molecular aspects. Although there is still no treatment with a proven efficacy for this condition, starting from the molecular basis of the disease, MAFLD's therapeutic landscape is rapidly expanding, and different medications seem to act as modifiers of liver steatosis, inflammation, and fibrosis.

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 D3 supplementation alleviates chemically-induced cirrhosis-associated hepatocarcinogenesis

Vitamin D₃ (VD₃) deficiency has been associated with increased risk for cirrhosis and hepatocellular carcinoma, a highly incident malignant neoplasia worldwide. On the other hand, VD₃ supplementation has shown some beneficial effects in clinical studies and rodent models of chronic liver disease. However, preventive effects of dietary VD₃ supplementation in cirrhosis-associated hepatocarcinogenesis is still unknow. To investigate this purpose, male Wistar rats submitted to a combined diethylnitrosamine- and thioacetamide-induced model were concomitantly supplemented with VD₃ (5,000 and 10,000 IU/kg diet) for 25 weeks. Liver samples were collected for histological, biochemical and molecular analysis. Serum samples were used to measure 25-hydroxyvitamin D [25(OH)D] and alanine aminotransferase levels. Both VD₃ interventions decreased hepatic collagen deposition and pro-inflammatory p65 protein levels, while increased hepatic antioxidant catalase and glutathione peroxidase activities and serum 25(OH)D, without a clear dose-response effect. Nonetheless, only the highest concentration of VD₃ increased hepatic protein levels of VD receptor, while decreased the number of large preneoplastic glutathione-S-transferase- (>0.5 mm²) and keratin 8/18-positive lesions, as well the multiplicity of hepatocellular adenomas. Moreover, this intervention increased hepatic antioxidant Nrf2 protein levels and glutathione-S-transferase activity. In summary, dietary VD₃ supplementation - in special the highest intervention - showed antifibrotic and antineoplastic properties in chemically-induced cirrhosis-associated hepatocarcinogenesis. The positive modulation of Nrf2 antioxidant axis may be mechanistically involved with these beneficial effects, and may guide future clinical studies.

Relationship of Vitamin D Deficiency and Fatty Liver in Children as Defined by Multiple Imaging and Histologic Endpoints

Objectives

The relationship between vitamin D deficiency (VDD) and pediatric nonalcoholic fatty liver disease (NAFLD) remains uncertain due to conflicting results and few studies with histologic endpoints. We therefore used multiple imaging and histologic NAFLD endpoints to more comprehensively assess the association between VDD and NAFLD in a large pediatric population.

Methods

Data were obtained from an ongoing pediatric NAFLD study in Bronx, NY. Briefly, overweight and obese children aged 2-18 years with alanine aminotransferase (ALT) levels ≥ 35 U/L were serially enrolled. Liver biopsy was obtained in accordance with clinical guidelines. All participants had liver imaging, namely, controlled attenuation parameter (CAP; Echosens, France) to assess steatosis and, to assess fibrosis, vibration controlled transient elastography (VCTE; FibroScan™, Echosens, France) and acoustic radiation force impulse (ARFI; Philips, Netherlands) imaging. Levels of 25-hydroxyvitamin D were measured serologically.

Results

N=276 (88%) of 315 participants had 25-OH vitamin D results, of whom 241 (87%) were Hispanic, 199 (72%) were male, and 92 (33%) underwent liver biopsy. VDD was univariately associated with high waist circumference (p=0.004), high-density lipoprotein level (p=0.01), season (p=0.009), and CAP score (p=0.01). In multivariate analysis, only waist circumference (p=0.0002) and biopsy inflammation grade (p=0.03) were associated with VDD, though the latter had not approximated statistical significance in univariate analysis (p=0.56). There was no association between VDD and hepatic steatosis, ballooning, NAFLD Activity Score, ARFI or VCTE elasticity scores.

Conclusions

VDD was not associated with NAFLD defined by imaging and histologic endpoints, except for a possible relation with histologic inflammation grade.

Nuclear Receptors in Liver Fibrosis

Nuclear receptors are ligand-activated transcription factors that regulate gene expression of a variety of key molecular signals involved in liver fibrosis. The primary cellular driver of liver fibrogenesis are activated hepatic stellate cells. Different NRs regulate the hepatic expression of pro-inflammatory and pro-fibrogenic cytokines that promote the transformation of hepatic stellate cells into fibrogenic myofibroblasts. Importantly, nuclear receptors regulate gene expression circuits that promote hepatic fibrogenesis and/or allow liver fibrosis regression. In this review, we highlight the direct and indirect influence of nuclear receptors on liver fibrosis, with a focus on hepatic stellate cells, and discuss potential therapeutic effects of nuclear receptor modulation in regard to anti-fibrotic and anti-inflammatory effects. Further research on nuclear receptors-related signaling may lead to the clinical development of effective anti-fibrotic therapies for patients with liver disease.

Yes-associated protein regulates the hepatoprotective effect of vitamin D receptor activation through promoting adaptive bile duct remodeling in cholestatic mice

Mounting clinical evidence has revealed that the vitamin D receptor (VDR) is associated with cholestatic liver injury, although the functions of VDR in this condition remain largely unexplored. Here, we investigated the effects of VDR activation on bile duct ligation (BDL) mice, and the underlying mechanisms were further investigated. A low-calcemic VDR agonist, paricalcitol (PAL, 200 ng/kg), was intraperitoneally injected into BDL mice every other day for 5 days or 28 days. Liver histology, liver function indicators, cholangiocyte proliferation, fibrosis scores, and inflammation were evaluated. Mice treated with PAL were rescued from the decreased survival rate induced by BDL and liver damage was reduced. Mechanistically, PAL promoted cholangiocyte proliferation, which was likely conducive to proliferating bile duct maturation and increased branching of bile ducts. PAL treatment also increased the expression of Yes-associated protein (YAP) and its target protein epithelial cell adhesion molecule (EpCam) and decreased the level of inactive cytoplasmic phosphorylated YAP. YAP knockdown abrogated PAL-induced primary bile duct epithelial cell proliferation, confirmed with YAP inhibitor administration. In addition, BDL-induced liver fibrosis and inflammatory cell infiltration were reduced by PAL treatment at both day 5 and day 28 post-BDL. In conclusion, VDR activation mitigates cholestatic liver injury by promoting adaptive bile duct remodeling through cholangiocytic YAP upregulation. Because PAL is an approved clinical drug, it may be useful for treatment of cholestatic liver disease. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The effect of 1,25-dihydroxyvitamin D3 on liver damage, oxidative stress, and advanced glycation end products in experimental nonalcoholic- and alcoholic- fatty liver disease

Background/aim

Oxidative stress and advanced glycation end products (AGEs) formation are proposed as effective mechanisms in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD). 1,25(OH)2D3 was proposed to have antioxidant, antiinflammatory and antiglycation properties. In this study, the effect of 1,25(OH)2D3 treatment on oxidative stress parameters and AGEs levels together with hepatic histopathology was investigated in high fructose (HFr) or ethanol (EtOH)-treated rats.

Materials and methods

Rats were treated with fructose (30%) or ethanol (5-20%) in drinking water with and without 1,25(OH)2D3 treatment (5 µg/kg two times a week) for 8 weeks. Insulin resistance (IR), oxidative stress parameters, AGEs, triglyceride (TG), and hydroxyproline (Hyp) levels together with histopathology were investigated in the liver.

Results

1,25(OH)2D3 decreased hepatic reactive oxygen species, lipid and protein oxidation products together with histopathological improvements in HFr- and EtOH-treated rats. 1,25(OH)2D3 treatment was observed to decrease significantly serum and hepatic AGEs in HFr group, and hepatic AGEs in EtOH group.

Conclusion

Our results clearly show that 1,25(OH)2 D3 treatment may be useful in the alleviation of hepatic lesions by decreasing glycooxidant stress in both NAFLD and ALD models created by HFr- and EtOH-treated rats, respectively.

Active Vitamin D3 Treatment Attenuated Bacterial Translocation via Improving Intestinal Barriers in Cirrhotic Rats

SCOPE

Pathological bacterial translocation from the disrupted intestinal barrier leads to substantial complications and mortality in liver cirrhosis. Vitamin D is reported as beneficial to gut barriers in some animal models. However, its effect on cirrhotic bacterial translocation is unknown. The authors aim to investigate the effects of calcitriol on bacterial translocation in cirrhotic rats.

METHODS AND RESULTS

Cirrhotic rats are administrated with a 2-week course of active vitamin D3 (calcitriol, 0.1 μg kg-1  per day) or vehicle by oral gavage after thioacetamide (TAA) injection for 16 weeks. Bacterial translocation, gut permeability, gut microbiota, and associated mechanisms are investigated. Calcitriol treatment significantly attenuates bacterial translocation and reduces intestinal permeability in TAA-induced cirrhotic rats. It upregulates the expressions of occludin in the small intestine and claudin-1 in the colon of cirrhotic rats directly independent of intrahepatic status. Even when a short period of calcitriol treatment do not reduce intestinal bacterial overgrowth, it induces a remarkable change of bacterial diversities and enrichment of Muribaculaceae, Bacteroidales, Allobaculum, Anaerovorax, and Ruminococcaceae.

CONCLUSION

Calcitriol treatment attenuates intestinal permeability, reduces bacterial translocation, and enriches potentially beneficial gut microbiota in cirrhotic rats that may enable it as a potential therapeutic agent to prevent cirrhotic complications.

The association between vitamin D-related gene polymorphisms and hepatitis B virus-related liver cirrhosis

Objectives

To investigate the relationship between vitamin D-related gene single nucleotide polymorphisms (SNPs) and hepatitis B-related liver cirrhosis.

Methods

This study included patients with chronic hepatitis B who were admitted to the Liver Research Center of the First Affiliated Hospital of Fujian Medical University from July 2012 to August 2016. SNPs rs1544410 and rs2228570 in the vitamin D receptor gene and rs2282679 in the vitamin D-binding protein gene were detected using the imLDR™ multiple SNP typing kit. Genotype and allele frequencies were compared between groups using the chi-square test or Fisher’s exact test.

Results

A total of 226 patients with hepatitis B virus (HBV) infection were enrolled, including 116 with HBV-related cirrhosis and 110 patients without. The distributions of vitamin D-related gene SNPs in both groups were in accordance with the Hardy–Weinberg equilibrium. There was no significant difference in the frequency or allelic distributions of rs1544410, rs2228570, and rs2282679 between the two groups. Additionally, the SNPs were not associated with the severity of cirrhosis.

Conclusion

No significant connection was identified between vitamin D-related SNPs and HBV-related liver cirrhosis.

The Impact of Vitamin D in Non-Alcoholic Fatty Liver Disease: A Cross-Sectional Study in Patients with Morbid Obesity

PURPOSE

We aimed to evaluate the association between vitamin D status and hepatic function parameters and scores: Fatty Liver Index (FLI, predictor of hepatic steatosis) and BARD (BMI, AST/ALT ratio and DM, predictor of hepatic fibrosis) in patients with morbid obesity.

PATIENTS AND METHODS

Cross-sectional study including patients with morbid obesity followed in our centre between January 2010 and July 2018. Patients with missing vitamin D levels or hepatic profile parameters were excluded. We divided the population according to two cut-offs of vitamin D levels (12ng/mL and 20ng/mL).

RESULTS

The included population (n=1124) had an average age of 43.3±10.7 years and 84.3% were female. Seventy-point eight percent of the population had vitamin D levels lower than 20ng/mL and 34.8% lower than 12ng/dL. Patients with lower vitamin D levels (<12ng/mL) had higher BMI, hip and waist circumferences and higher prevalence of hypertension. Higher FLI scores [OR= 0.77 (0.07), p<0.01] and ALP levels [β= -0.03 (-0.06, -0.01), p<0.01] associated to lower vitamin D levels.

CONCLUSION

Vitamin D deficiency is associated with a higher risk of hepatic steatosis in individuals with morbid obesity. Correction of vitamin D deficiency may have a beneficial role in the management of NAFLD in patients with morbid obesity.

Vitamin D alleviates liver fibrosis by inhibiting histidine-rich calcium binding protein (HRC)

BACKGROUND

Liver fibrosis may progress toward cirrhosis and cancer without effective therapy. Here, we investigated the underlying mechanism of Vitamin D as a therapeutic approach.

METHODS

Carbon tetrachloride (CCL4)-induced mice model and transforming growth factor-β1 (TGF-β1) induced human hepatic stellate cell line LX-2 were used in vivo and in vitro. The fibrotic profiles, degree of liver injury and HRC expression were assessed by histology, Western blot, immunohistochemistry and Real-Time PCR. The proliferation of cells transfected with HRC ^+/+ and HRC^-/- plasmids was detected by MTS and cell cycle methods.

RESULTS

Vitamin D significantly suppressed the expression of HRC in liver fibrosis model both in vivo and in vitro (P < 0.01). The cell with overexpression of HRC significantly increased TGF-β1/Smad3 expressions and the percentage of the S peak in cell cycle (P < 0.05). However, Vitamin D can significantly reverse the levels of TGF-β1, Smad3 and p-smad3 caused by HRC in vitro. Furthermore, the overexpression of HRC in cell lines can attenuate the function of Vitamin D, suggesting that VD played a role by regulating HRC. Mechanically, HRC as the target of VDR is detected by CHIP method.

CONCLUSIONS

Vitamin D can delay hepatic fibrosis by reducing activation of hepatic stellate cells and TGF-β/Smad signaling through negative regulation of HRC. The findings revealed the important regulatory effect of Vitamin D in hepatic stellate cells and provided new insights into the therapeutic function of Vitamin D on liver fibrosis.

Association of serum 25-hydroxyvitamin D levels with severe necroinflammatory activity and inflammatory cytokine production in type I autoimmune hepatitis

25-Hydroxyvitamin D [25(OH)D] has been reported to be associated with several chronic liver diseases. The relationship between 25(OH)D and autoimmune hepatitis (AIH) pathogenesis is incompletely understood. We investigated the association of serum total and free 25(OH)D levels with necroinflammatory activity and cytokine levels in 66 patients with AIH diagnosed in our hospital. The median age at AIH diagnosis was 57 years, and the male:female ratio was 7:59. The median serum total 25(OH)D level in therapy-naïve patients with AIH was 14.2 ng/mL (interquartile range [IQR], 11.4–17.9 ng/mL). Of the 66 patients with AIH, 36 had serum total 25(OH)D levels of < 15 ng/mL and were considered to have vitamin D deficiency, and 30 had serum total 25(OH)D levels of ≥ 15 ng/mL. Patients with acute-onset AIH had significantly lower serum total 25(OH)D levels than those with chronic-onset AIH. In particular, serum total 25(OH)D levels were significantly lower in patients with severe forms of AIH. Furthermore, the serum total 25(OH)D level was positively correlated with the serum albumin level and prothrombin time and negatively correlated with the serum total bilirubin level and necroinflammatory activity in AIH. Multivariate logistic regression analysis showed that the serum total 25(OH)D level was an independent factor for severe necroinflammatory activity. Interestingly, AIH patients with serum total 25(OH)D levels of < 15 ng/mL had higher levels of inflammatory cytokines such as interferon-γ and interleukin-33. Free 25(OH)D levels were correlated with total 25(OH)D levels, and the percentage of free 25(OH)D was significantly associated with necroinflammatory activity. In conclusion, 25(OH)D deficiency may play an important role in predicting AIH severity via inflammatory cytokine production.

Vitamin D and Metabolic Dysfunction-Associated Fatty Liver Disease (MAFLD): An Update

Non-alcoholic fatty liver disease (NAFLD) is the first cause of chronic liver disease worldwide; it ranges from simple steatosis to steatohepatitis (NASH) and, potentially, cirrhosis and hepatocarcinoma. NAFLD is also an independent risk factor for type 2 diabetes, cardiovascular diseases, and mortality. As it is largely associated with insulin resistance and related disorders, NAFLD has been recently re-named as Metabolic dysfunction-Associated Fatty Liver Disease (MAFLD). At present, there are no approved pharmacological treatments for this condition. Vitamin D is a molecule with extensive anti-fibrotic, anti-inflammatory, and insulin-sensitizing properties, which have been proven also in hepatic cells and is involved in immune-metabolic pathways within the gut–adipose tissue–liver axis. Epidemiological data support a relationship hypovitaminosis D and the presence of NAFLD and steatohepatitis (NASH); however, results from vitamin D supplementation trials on liver outcomes are controversial. This narrative review provides an overview of the latest evidence on pathophysiological pathways connecting vitamin D to NAFLD, with emphasis on the effects of vitamin D treatment in MAFLD by a nonsystematic literature review of PubMed published clinical trials. This article conforms to the Scale for Assessment of Narrative Review Articles (SANRA) guidelines. Evidence so far available supports the hypothesis of potential benefits of vitamin D supplementation in selected populations of NAFLD patients, as those with shorter disease duration and mild to moderate liver damage.

Is vitamin D receptor a druggable target for non-alcoholic steatohepatitis?

Nonalcoholic steatohepatitis (NASH) is a progressed stage of non-alcoholic fatty liver disease, and available therapeutic strategies for NASH are limited. Vitamin D receptor (VDR) is proposed as a druggable target for NASH due to the discovery of vitamin D deficiency in NASH patients. To date, vitamin D supplementation has not consistently conferred expected therapeutic benefits, raising the question of whether VDR can serve as a proper drug target for NASH. It is known that VDR can interact with other ligands such as bile acids in addition to vitamin D, and its expression can be induced by fatty acids, and insulin. It has also been shown that while activation of VDR in hepatic macrophages and hepatic stellate cells resulted in attenuation of hepatic inflammation and fibrosis, activation of VDR in hepatocytes could accelerate lipid accumulation. Thus, the multiplicity of VDR ligands, together with the cell type-specificity of VDR activation, must be taken into consideration in assessing the validity of VDR being a potential druggable target for NASH treatment. To this end, we have evaluated the relationship between VDR activation and various contributing factors, such as gut microbiota, bile acid, fatty acids, and insulin, in addition to vitamin D, with an expectation that a potential drug might be identified that can elicit VDR activation in a tissue- and/or cell type-specific manner and therefore achieving therapeutic benefits in NASH.

Role of diet and lifestyle modification in the management of nonalcoholic fatty liver disease and type 2 diabetes

Nonalcoholic fatty liver disease (NAFLD) is considered as the hepatic evidence of insulin resistance which is the hallmark of type 2 diabetes. NAFLD is considered as the risk factor for developing type 2 diabetes and has a high frequency of occurrence in those with existing type 2 diabetes. Compared with patients with only NAFLD or type 2 diabetes, these patients show a poor metabolic profile and increase mortality. Hence, effective treatment strategies are necessary. Here, we review the role of diet and lifestyle modification in the management of NAFLD and type 2 diabetes. Based on the available studies, it has been shown that the addition of any kind of physical activity or exercise is beneficial for patients with both NAFLD and type 2 diabetes. Proper dietary management leads to weight loss are also effective in improving metabolic parameters in patients with both NAFLD and type 2 diabetes. In conclusion, it is clear that increasing physical activity or exercise is effective in improving metabolic parameters in patients who are suffering with both NAFLD and type 2 diabetes.

Vitamin D Attenuates Loss of Endothelial Biomarker Expression in Cardio-Endothelial Cells

Vitamin D is associated with cardiovascular health through activating the vitamin D receptor that targets genes related to cardiovascular disease (CVD). The human cardiac microvascular endothelial cells (HCMECs) were used to develop mechanically and TGF-β1-induced fibrosis models, and the rat was used as the isoproterenol (ISO)-induced fibrosis model. The rats were injected with ISO for the first five days, followed by vitamin D injection for the consecutive three weeks before being sacrificed on the fourth week. Results showed that mechanical stretching reduced endothelial cell marker CD31 and VE-cadherin protein expressions, as well as increased α-smooth muscle actin (α-SMA) and fibronectin (FN). The transforming growth factor-β1 (TGF-β1) reduced CD31, and increased α-SMA and FN protein expression levels. Vitamin D presence led to higher protein expression of CD31, and lower protein expressions of α-SMA and FN compared to the control in the TGF-β1-induced fibrosis model. Additionally, protein expression of VE-cadherin was increased and fibroblast-specific protein-1 (FSP1) was decreased after vitamin D treatment in the ISO-induced fibrosis rat. In conclusion, vitamin D slightly inhibited fibrosis development in cell and animal models. Based on this study, the beneficial effect of vitamin D may be insignificant; however, further investigation of vitamin D’s effect in the long-term is required in the future.

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.

Serum 25-hydroxyvitamin-D and nonalcoholic fatty liver disease: Does race/ethnicity matter? Findings from the MESA cohort

BACKGROUND AND AIMS

Low serum 25-hydroxyvitamin D (25(OH)D) is associated with higher nonalcoholic fatty liver disease (NAFLD) risk in studies of mainly white participants. Significant racial/ethnic differences exist in serum 25(OH)D and NAFLD prevalence questioning extending this association to other racial/ethnic groups. We tested whether the association between serum 25(OH)D and NAFLD vary by race/ethnicity.

METHODS AND RESULTS

This was a cross-sectional analysis from the Multi-Ethnic Study of Atherosclerosis (MESA) that included 3484 participants (44% male; 38.4% Whites, 27.8% African-Americans, 23.5% Hispanics, and 10.3% Chinese-Americans) who had serum 25(OH)D and upper abdominal CT images available at baseline. Serum 25(OH)D was measured by high-performance liquid chromatography-tandem mass spectrometry. NAFLD was identified if liver-to-spleen Hounsfield-Unit ratio was <1. Whites had the highest 25(OH)D level and African-Americans had the lowest level (mean ± SD: 29.5 ± 10.4 vs.19.9 ± 9.1, respectively). Six hundred and eleven (17.5%) participants had NAFLD; Hispanics had the highest prevalence (26.2%) followed by Chinese-Americans (19.8%), Whites (15.8%) and African-Americans (11.7%), P < 0.0001. In adjusted model, the association of 25(OH)D with NAFLD differed by race/ethnicity (P < 0.0001). Negative association was only evident in Causations (OR (95% CI):1.23 (1.03, 1.47) per 1 SD lower serum 25(OH)D). For other racial/ethnic groups, BMI, triglycerides, diabetic status and/or smoking, but not serum 25(OH)D, were common independent risk factors for NAFLD.

CONCLUSIONS

The negative association between serum 25(OH)D and NAFLD in Whites may not be broadly generalizable to other racial/ethnic groups. Modifiable risk factors including BMI, triglycerides, diabetic status and/or smoking associate with NAFLD risk in non-white racial/ethnic groups beyond 25(OH)D.

Antifibrotic effects of hypocalcemic vitamin D analogs in murine and human hepatic stellate cells and in the CCl4 mouse model

Liver cirrhosis is a life-threatening consequence of liver fibrosis. The aim of this study was to investigate the antifibrotic potential of clinically available vitamin D analogs compared to that of calcitriol in vitro and in vivo. Murine hepatic stellate cells, Kupffer cells, and human LX-2 cells were treated with vitamin D analogs, and the profibrotic behavior of these cells was studied. In vivo liver fibrosis was induced using CCl₄ until measurable fibrosis was established. Animals were then treated with calcitriol and paricalcitol. Vitamin D and its analogs showed antifibrotic effects in vitro. Treatment with active vitamin D (calcitriol, CAL) and its analogs reduced the protein expression of α-smooth muscle actin (α-SMA) in mHSC. In human LX-2 cells alfacalcidol reduced transforming growth factor-β (TGF-β) induced platelet-derived growth factor receptor-β protein expression and contractility while paricalcitol (PCT), in its equipotent dose to CAL, reduced TGF-β induced α-SMA protein expression, and ACTA2 and TGF-β mRNA expression. No effects of a treatment with vitamin D and its analogs were observed in Kupffer cells. In vivo, PCT-treated mice had significantly lower calcium levels than CAL-treated mice. CAL and PCT reduced the hepatic infiltration of CD11b-positive cells and alanine transaminase levels, while PCT but not CAL significantly inhibited fibrosis progression, with a favorable side effect profile in the CCl₄ model. We conclude that hypocalcemic vitamin D analogs should be considered in future studies investigating vitamin D for the treatment of liver fibrosis.

NAFLD and Extra-Hepatic Comorbidities: Current Evidence on a Multi-Organ Metabolic Syndrome

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide and its incidence is definitely increasing. NAFLD is a metabolic disease with extensive multi-organ involvement, whose extra-hepatic manifestations include type 2 diabetes mellitus, cardiovascular disease, obstructive sleep apnea, chronic kidney disease, osteoporosis, and polycystic ovarian syndrome. Recently, further evidence has given attention to pathological correlations not strictly related to metabolic disease, also incorporating in this broad spectrum of systemic involvement hypothyroidism, psoriasis, male sexual dysfunction, periodontitis, and urolithiasis. The most common cause of mortality in NAFLD is represented by cardiovascular disease, followed by liver-related complications. Therefore, clinicians should learn to screen and initiate treatment for these extra-hepatic manifestations, in order to provide appropriate multidisciplinary assessments and rigorous surveillance. This review evaluates the current evidence regarding extra-hepatic associations of NAFLD, focusing on the pathogenic hypothesis and the clinical implications.

Overview of studies of the vitamin D/vitamin D receptor system in the development of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the world. NAFLD is known to be associated with obesity, type 2 diabetes, metabolic syndrome and increased cardiovascular events: for these reasons, it is becoming a global public health problem and represents an important challenge in terms of prevention and treatment. The mechanisms behind the pathogenesis of NAFLD are multiple and have not yet been completely unraveled; consequently, at moment there are not effective treatments. In the past few years a large body of evidence has been assembled that attributes an important role in hepatic aberrant fat accumulation, inflammation and fibrosis, to the vitamin D/vitamin D receptor (VD/VDR) axis, showing a strong association between hypovitaminosis D and the diagnosis of NAFLD. However, the data currently available, including clinical trials with VD supplementation, still provides a contrasting picture. The purpose of this editorial is to provide an overview of recent advances in the pathogenesis of NAFLD in relation to VD/VDR. Based on recent data from literature, we focused in particular on the hypothesis that VDR itself, independently from its traditional ligand VD, may have a crucial function in promoting hepatic fat accumulation. This might also offer new possibilities for future innovative therapeutic approaches in the management of NAFLD.

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.

The Efficacy of Vitamin D Supplementation against Nonalcoholic Fatty Liver Disease: A Meta-Analysis

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of liver disease worldwide. If this disease is not appropriately controlled, it can eventually cause chronic liver damage, including cirrhosis and hepatocellular carcinoma. Accordingly, the adoption of appropriate interventions to control NAFLD is important for any healthcare system. The aim of the present systematic review and meta-analysis was to clarify the effect of vitamin D supplementation on NAFLD. PubMed, Scopus, Science Direct, ISI Web of Science, and Google Scholar were systematically searched up to March 2019 to find clinical trials that examined the effects of vitamin D supplementation on liver enzyme levels in NAFLD patients. Means for liver enzymes and potential sources of heterogeneity were extracted. A subgroup analysis was performed to detect potential sources of interstudy heterogeneity. Nine trials (10 arms) comprising 467 participants were eligible for meta-analysis. The results from a pooled analysis did not reveal a significant effect of vitamin D intake on alanine aminotransferase (-2.88 U/L; 95% CI, -6.03 to 0.27; I² = 85%), aspartate aminotransferase (-0.10 U/L; 95% CI, -1.18 to 0.97; I² = 26%), and γ-glutamyltransferase levels (0.12 U/L; 95% CI, -5.94 to 6.18; I² = 38%). The meta-analysis suggested a significant reduction in alkaline phosphatase (-13.79 U/L; 95% CI, -22.13 to -5.45; I² = 72%) following vitamin D supplementation. This effect was robust in the subgroup in which > 3,000 IU/day vitamin D was administered (-19.74 U/L; 95% CI, -25.36 to -14.12; I² = 0.0%). The present meta-analysis does not suggest the efficacy of vitamin D supplementation on NAFLD treatment.

Association of vitamin D levels and vitamin D-related gene polymorphisms with liver fibrosis in patients with biopsy-proven nonalcoholic fatty liver disease

BACKGROUND

Vitamin D has promising anti-proliferative and anti-fibrotic properties, but its clinical utility in nonalcoholic fatty liver disease (NAFLD) is unclear.

AIMS

This study aimed to clarify the association between vitamin D levels, single nucleotide polymorphisms (SNPs) in vitamin D-related genes, and the histopathological severity of disease in patients with biopsy-proven NAFLD.

METHODS

SNPs in CYP2R1, DHCR7, vitamin D binding protein (GC), CYP27B1, and vitamin D receptor (VDR) were determined for 229 consecutive patients with biopsy-proven NAFLD.

RESULTS

In this study, vitamin D deficiency defined as 25-hydroxyvitamin-D₃ levels of ≤20 ng/mL was found in 151 patients (65.9%). Multivariate analysis revealed that cold season, advanced fibrosis, and CYP2R1 rs1993116 genotype non-AA were independent factors significantly associated with vitamin D deficiency. Old age (p = 5.05 × 10^-8), high body mass index (p = 2.13 × 10^-2), low total-cholesterol (p = 1.46 × 10^-4), low serum vitamin D level (p = 7.34 × 10^-3), and VDR rs1544410 genotype CC (p = 9.15 × 10^-3) were independent factors associated with advanced liver fibrosis.

CONCLUSION

Serum 25-hydroxyvitamin-D₃ levels and the VDR gene SNP were significantly and independently associated with the severity of liver fibrosis in patients with biopsy-proven NAFLD.

Vitamin D Improves Intestinal Barrier Function in Cirrhosis Rats by Upregulating Heme Oxygenase-1 Expression

Intestinal barrier dysfunction always accompanies cirrhosis in patients with advanced liver disease and is an important contributor facilitating bacterial translocation (BT), which has been involved in the pathogenesis of cirrhosis and its complications. Several studies have demonstrated the protective effect of Vitamin D on intestinal barrier function. However, severe cholestasis leads to vitamin D depletion. This study was designed to test whether vitamin D therapy improves intestinal dysfunction in cirrhosis. Rats were subcutaneously injected with 50% sterile CCl₄ (a mixture of pure CCl₄ and olive oil, 0.3 mL/100 g) twice a week for 6 weeks. Next, 1,25(OH)₂D₃ (0.5 µg/100 g) and the vehicle were administered simultaneously with CCl₄ to compare the extent of intestinal histologic damage, tight junction protein expression, intestinal barrier function, BT, intestinal proliferation, apoptosis, and enterocyte turnover. Intestinal heme oxygenase-1 (HO-1) expression and oxidative stress were also assessed. We found that vitamin D could maintain intestinal epithelial proliferation and turnover, inhibit intestinal epithelial apoptosis, alleviate structural damage, and prevent BT and intestinal barrier dysfunction. These were achieved partly through restoration of HO-1 and inhibition of oxidative stress. Taken together, our results suggest that vitamin D ameliorated intestinal epithelial turnover and improved the integrity and function of intestinal barrier in CCl₄-induced liver cirrhotic rats. HO-1 signaling activation was involved in these above beneficial effects.

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

Vitamin D has immunomodulatory, anti-inflammatory, antioxidant, and anti-fibrotic actions that may impact on the occurrence and outcome of immune-mediated disease. The goals of this review are to describe the nature of these expanded roles, examine the implications of vitamin D deficiency in autoimmune hepatitis, and identify opportunities for future investigation. Abstracts were identified in PubMed by multiple search terms. Full-length articles were selected for review, and secondary and tertiary bibliographies were developed. Vitamin D receptors are expressed on the principal cell populations involved in the innate and adaptive immune responses. Macrophages and dendritic cells can produce 1,25-dihydroxyvitamin D within the microenvironment. This active form of vitamin D can inhibit immune cell proliferation, promote an anti-inflammatory cytokine profile, expand regulatory T cells, enhance glucocorticoid actions, increase glutathione production, and inhibit hepatic stellate cells. Vitamin D deficiency has been commonly present in patients with immune-mediated liver and non-liver diseases, and it has been associated with histological severity, advanced hepatic fibrosis, and non-response to conventional glucocorticoid therapy in autoimmune hepatitis. Vitamin D analogues with high potency, low calcemic effects, and independence from hepatic hydroxylation are possible interventions. In conclusion, vitamin D has properties that could ameliorate immune-mediated disease, and vitamin D deficiency has been a common finding in immune-mediated liver and non-liver diseases, including autoimmune hepatitis. Loss of vitamin D-dependent homeostatic mechanisms may promote disease progression. Vitamin D analogues that are independent of hepatic hydroxylation constitute an investigational opportunity to supplement current management of autoimmune hepatitis.

Severe vitamin D deficiency is a prognostic biomarker in autoimmune hepatitis

BACKGROUND

Vitamin D deficiency has been implicated in the outcome of chronic liver disease.

AIM

To determine the frequency of severe vitamin D deficiency in autoimmune hepatitis (AIH), assess its association with treatment non-response, and evaluate the relationship between vitamin D status and liver-related mortality and need for transplantation.

METHODS

Two hundred and nine patients were evaluated by liver tissue examination at presentation. Serum vitamin D levels were determined, and serum levels <25 nmol/L (10 ng/mL) were considered severely deficient. Treatment non-response was defined as non-normalised aspartate aminotransferase/alanine aminotransferase and immunoglobulin G levels during conventional immunosuppressive therapy. Univariate and multivariate analyses were performed using binary logistic regression and Cox proportional hazards model.

RESULTS

The mean vitamin D level was 60 ± 38 nmol/L (range, 3-263 nmol/L), and 42 patients (20%) had severe vitamin D deficiency. Treatment non-response was more common in patients with severe vitamin D deficiency than in patients without (59% vs 41%, P = 0.04). Severe vitamin D deficiency was also independently associated with a higher risk of developing cirrhosis (HR 3.40; 95% CI 1.30-8.87, P = 0.01) and liver-related mortality or requirement for liver transplantation (LT; HR 5.26, 95% CI, 1.54-18.0, P = 0.008). Patients with persistent severe deficiency following vitamin D supplementation continued to have poor outcomes.

CONCLUSIONS

Severe vitamin D deficiency is associated with treatment non-response, progression to cirrhosis, and liver-related death or need for LT. Severe vitamin D deficiency is a prognostic biomarker in AIH.

Novel insights into the relationship between nonalcoholic fatty liver disease and osteoporosis

Excess fat deposition and insulin resistance are considered the main risk factors for nonalcoholic fatty liver disease (NAFLD), and therefore, not surprisingly, the global prevalence of NAFLD increases in parallel with both obesity and type 2 diabetes. Although deterioration of bone homeostasis in patients with NAFLD is commonly observed, its etiology has not been fully elucidated yet. It was shown in several studies that bone tissue seems to be independently associated with NAFLD. A mechanistic perspective puts the liver at the center of mutual interdependencies obviously involving adipose tissue and muscles and also the bone matrix and bone cells, which are relatively novel. In this review, various pathophysiological mechanisms and possible mediating molecules that may interplay between NAFLD and bone tissue are described. Chronic inflammation, vitamin D3, growth hormone, insulin-like growth factor 1, osteopontin, fetuin-A, irisin, osteocalcin, and osteoprotegerin from osteoblasts have been proposed as mediators of mutual interactions among the skeleton, fatty tissue, and liver. Although to date there are still many issues that have not been elucidated, growing evidence suggests that screening and surveillance of bone mineral density in patients with NAFLD should be considered in future strategies and guidelines for NAFLD management.

Generic chemoprevention of hepatocellular carcinoma

Chronic fibrotic liver disease caused by viral or metabolic etiologies is a high-risk condition for developing hepatocellular carcinoma (HCC). Even after curative treatment of early-stage HCC tumor, the carcinogenic microenvironment persists in the remnant diseased liver and supports the development of de novo HCC tumors (de novo HCC recurrence). Therefore, prevention of HCC development in patients at risk of not only first-primary but also second-primary HCC tumors is theoretically the most impactful strategy to improve patient prognosis. However, no such therapy has been established to date. One major challenge is the identification of clinically relevant targets that can be achieved by utilizing the reverse-engineering strategy of chemoprevention discovery, which integrates omics information from clinical cohorts with completed follow-up for cancer development. Clinical and experimental studies have suggested etiology-specific and generic candidate HCC chemoprevention strategies, including statins, antidiabetic drugs, selective molecular targeted agents, and dietary and nutritional substances. Clinical testing of the candidate compounds can be cost-effectively performed by combining it with HCC risk biomarker evaluation to specify the target patient population most likely to benefit from the therapy. Nontoxic, generic agents will have broad clinical applicability across the diverse HCC etiologies and clinical contexts and are expected to substantially improve the still dismal prognosis of HCC.

Animal models of portal hypertension

Chronic liver diseases ultimately lead to cirrhosis and portal hypertension (PHT). Indeed, PHT is a major cause of severe complications, while medical treatment is limited to non-selective beta blockers. Sophisticated animal models are needed to investigate novel treatment options for different etiologies of liver disease, effective anti-fibrotic agents as well as vasoactive drugs against PHT. In this review, we present some of the most common animal models of liver disease and PHT - including pre-hepatic, intra-hepatic and post-hepatic PHT in rodents. Methodology for induction, considerations for disease etiology, advantages and limitations and practical issues of these animal models are discussed. The appropriate and sensible use of animal models in preclinical research supporting the 3R concept of replacement, reduction and refinement is highlighted.

Under-Evaluated or Unassessed Pathogenic Pathways in Autoimmune Hepatitis and Implications for Future Management

Autoimmune hepatitis is a consequence of perturbations in homeostatic mechanisms that maintain self-tolerance but are incompletely understood. The goals of this review are to describe key pathogenic pathways that have been under-evaluated or unassessed in autoimmune hepatitis, describe insights that may shape future therapies, and encourage investigational efforts. The T cell immunoglobulin mucin proteins constitute a family that modulates immune tolerance by limiting the survival of immune effector cells, clearing apoptotic bodies, and expanding the population of granulocytic myeloid-derived suppressor cells. Galectins influence immune cell migration, activation, proliferation, and survival, and T cell exhaustion can be induced and exploited as a possible management strategy. The programmed cell death-1 protein and its ligands comprise an antigen-independent inhibitory axis that can limit the performance of activated T cells by altering their metabolism, and epigenetic changes can silence pro-inflammatory genes or de-repress anti-inflammatory genes that affect disease severity. Changes in the intestinal microbiota and permeability of the intestinal mucosal barrier can be causative or consequential events that affect the occurrence and phenotype of immune-mediated disease, and they may help explain the female propensity for autoimmune hepatitis. Perturbations within these homeostatic mechanisms have been implicated in experimental models and limited clinical experiences, and they have been favorably manipulated by monoclonal antibodies, recombinant molecules, pharmacological agents or dietary supplements. In conclusion, pathogenic mechanisms that have been implicated in other systemic immune-mediated and liver diseases but under-evaluated or unassessed in autoimmune hepatitis warrant consideration and rigorous evaluation.

Epigenetic changes and their implications in autoimmune hepatitis

BACKGROUND

The genetic risk of autoimmune hepatitis is insufficient to explain the observed risk, and epigenetic changes may explain disparities in disease occurrence in different populations within and between countries. The goal of this review was to examine how epigenetic changes induced by the environment or inherited as a phenotypic trait may affect autoimmune hepatitis and be amenable to therapeutic intervention.

MATERIALS AND METHODS

Pertinent abstracts were identified in PubMed by multiple search terms. The number of abstracts reviewed was 1689, and the number of full-length articles reviewed exceeded 150.

RESULTS

Activation of pro-inflammatory genes in autoimmune disease is associated with hypomethylation of deoxyribonucleic acid and modification of histones within chromatin. Organ-specific microribonucleic acids can silence genes by marking messenger ribonucleic acids for degradation, and they can promote inflammatory activity or immunosuppression. High circulating levels of the microribonucleic acids 21 and 122 have been demonstrated in autoimmune hepatitis, and they may increase production of pro-inflammatory cytokines. Microribonucleic acids are also essential for maintaining regulatory T cells. Drugs, pollutants, infections, diet and ageing can induce inheritable epigenetic changes favouring autoimmunity. Reversal is feasible by manipulating enzymes, transcription factors, gene-silencing molecules and toxic exposures or by administering methyl donors and correcting vitamin D deficiency. Gene targets, site specificity, efficacy and consequences are uncertain.

CONCLUSIONS

Potentially reversible epigenetic changes may affect the occurrence and outcome of autoimmune hepatitis, and investigations are warranted to determine the nature of these changes, key genomic targets, and feasible interventions and their consequences.

Vitamin D levels do not predict the stage of hepatic fibrosis in patients with non-alcoholic fatty liver disease: A PRISMA compliant systematic review and meta-analysis of pooled data

AIM

To investigate the relationship between 25-hydroxyvitamin D [25(OH)D] levels and fibrosis stage in patients with non-alcoholic fatty liver disease (NAFLD).

METHODS

Two individual reviewers identified relevant studies using the PubMed, EMBASE, Cochrane, and Scopus databases. Inclusion criteria were as follows: (1) Studies that evaluated adults with NAFLD and serum or plasma 25(OH)D levels; and (2) assessed fibrosis stage using liver biopsy. A rigorous analysis yielded six articles as having sufficient data to employ in evaluating the association of serum vitamin D levels in patients with NAFLD based on their liver fibrosis stage by histopathological analysis. The lead investigators of each of the six studies were contacted and the data were collected. To meta-analyze vitamin D levels in F0-F2 vs F3-F4 fibrosis, a random-effects meta-analysis fit using restricted maximum likelihood was applied. To examine trends across each stage of fibrosis with respect to vitamin D levels, a meta-regression was performed. P < 0.05 was considered statistically significant.

RESULTS

A total of 937 subjects from six studies were included in the final analysis to evaluate the association of serum vitamin D levels in patients with NAFLD based on their liver fibrosis stage by histopathological analysis. The lead investigators of each of the six studies were contacted and the data were collected. First, the investigators performed a meta-analysis to compare serum vitamin D levels in patients with NAFLD with stage F0-F2 compared to F3-F4, which did not show significance [meta-estimate of the pooled mean difference = -0.86, P = 0.08 (-4.17, 2.46)]. A meta-regression evaluation of serum vitamin 25 (OH)D levels across the individual stages (F0-F4) of fibrosis did not show an association for the six included studies.

CONCLUSION

Low vitamin D status is not associated with higher stages of liver fibrosis in patients with NAFLD.

Food components with antifibrotic activity and implications in prevention of liver disease

Increasing prevalence of nonalcoholic fatty liver disease (NAFLD) in parallel with the obesity epidemic has been a major public health concern. NAFLD is the most common chronic liver disease in the United States, ranging from fatty liver to steatohepatitis, fibrosis and cirrhosis in the liver. In response to chronic liver injury, fibrogenesis in the liver occurs as a protective response; however, prolonged and dysregulated fibrogenesis can lead to liver fibrosis, which can further progress to cirrhosis and eventually hepatocellular carcinoma. Interplay of hepatocytes, macrophages and hepatic stellate cells (HSCs) in the hepatic inflammatory and oxidative milieu is critical for the development of NAFLD. In particular, HSCs play a major role in the production of extracellular matrix proteins. Studies have demonstrated that bioactive food components and natural products, including astaxanthin, curcumin, blueberry, silymarin, coffee, vitamin C, vitamin E, vitamin D, resveratrol, quercetin and epigallocatechin-3-gallate, have antifibrotic effects in the liver. This review summarizes current knowledge of the mechanistic insight into the antifibrotic actions of the aforementioned bioactive food components.

Patients with Nonalcoholic Fatty Liver Disease Have a Low Response Rate to Vitamin D Supplementation

Background: Hypovitaminosis D is associated with an increased severity of nonalcoholic fatty liver disease (NAFLD), but reports on the response to cholecalciferol (vitamin D₃) supplementation are conflicting.Objective: The objective of this study was to determine if standard vitamin D₃ supplementation is effective in NAFLD with hypovitaminosis D.Methods: Sixty-five well-characterized adults [age (mean ± SD): 51.6 ± 12.3 y] with biopsy-proven NAFLD were screened. Forty-two patients (the ratio of men to women was 13:29) had hypovitaminosis D (plasma 25-hydroxyvitamin D [25(OH)D] <30 ng/mL). An observational study was performed in NAFLD patients with hypovitaminosis D treated with 2000 IU cholecalciferol (vitamin D₃) daily for 6 mo per clinical practice. Plasma 25(OH)D, hepatic and metabolic panels, and metabolic syndrome components were assessed before and after cholecalciferol supplementation. Body composition was measured by using bioelectrical impedance analysis. The primary outcome measure was plasma 25(OH)D ≥30 ng/mL at the end of the study. Secondary outcomes included change in serum transaminases, fasting plasma glucose, and insulin and homeostasis model assessment of insulin resistance (HOMA-IR). Chi-square, Student's t tests, correlation coefficient, and multivariate analysis were performed.Results: Twenty-six (61.9%) patients had nonalcoholic steatohepatitis (NASH), and 16 (38.1%) had hepatic steatosis. After 6 mo of cholecalciferol supplementation, plasma 25(OH)D ≥30 ng/mL was observed in 16 subjects (38.1%; responders) whereas the remaining 26 patients (61.9%) were nonresponders with plasma 25(OH)D <30 ng/mL. Significantly fewer (P < 0.01) patients with NASH were responders (4 of 26, 15.4%) than those with hepatic steatosis (12 of 16, 75%). Baseline fasting serum alanine aminotransferase, plasma glucose, and HOMA-IR were similar in the responders and nonresponders, but the NASH score on the liver biopsy was lower (16.5%) in the responders (P < 0.001). Nonresponders had a higher fat mass (10.5%) and lower fat-free mass (10.4%) than responders did. End-of-treatment alanine aminotransferase and HOMA-IR improved only in responders. The baseline HOMA-IR and histological NASH score were independent predictors of nonresponse to cholecalciferol supplementation.Conclusions: Daily supplementation with 2000 IU cholecalciferol for 6 mo did not correct hypovitaminosis D in the majority of patients with NASH. Further studies are needed to determine if higher doses are effective. This trial was registered at clinicaltrials.gov as 13-00153.

Immunity and Fibrogenesis: The Role of Th17/IL-17 Axis in HBV and HCV-induced Chronic Hepatitis and Progression to Cirrhosis

Cirrhosis is a common final pathway for most chronic liver diseases; representing an increasing burden worldwide and is associated with increased morbidity and mortality. Current evidence has shown that, after an initial injury, the immune response has a significant participation in the ongoing damage, and progression from chronic viral hepatitis (CVH) to cirrhosis, driving the activation and maintenance of main fibrogenic pathways. Among immune deregulations, those related to the subtype 17 of T helper lymphocytes (Th17)/interleukin-17 (IL-17) axis have been recognized as key immunopathological and prognostic elements in patients with CVH. The Th17/IL-17 axis has been found involved in several points of fibrogenesis chain from the activation of stellate cells, increased expression of profibrotic factors as TGF-β, promotion of the myofibroblastic or epithelial–mesenchymal transition, stimulation of the synthesis of collagen, and induction of imbalance between matrix metalloproteinases and tissue inhibitors of metalloproteinases (TIMPs). It also promotes the recruitment of inflammatory cells and increases the expression of proinflammatory cytokines such as IL-6 and IL-23. So, the Th17/IL-17 axis is simultaneously the fuel and the flame of a sustained proinflammatory and profibrotic environment. This work aims to present the immunopathologic and prognostic role of the Th17/IL-17 axis and related pathways in fibrogenesis and progression to cirrhosis in patients with liver disease due to hepatitis B virus (HBV) and hepatitis C virus (HCV).