DHCR7: A vital enzyme switch between cholesterol and vitamin D production

Key factors and potential drug combinations of nonalcoholic steatohepatitis: Bioinformatic analysis and experimental validation-based study

BACKGROUND

Nonalcoholic fatty liver disease and its advanced stage, nonalcoholic steatohepatitis (NASH), are the major cause of hepatocellular carcinoma (HCC) and other end-stage liver disease. However, the potential mechanism and therapeutic strategies have not been clarified. This study aimed to identify potential roles of miRNA/mRNA axis in the pathogenesis and drug combinations in the treatment of NASH.

METHODS

Microarray GSE59045 and GSE48452 were downloaded from the Gene Expression Omnibus and analyzed using R. Then we obtained differentially expressed genes (DE-genes). DAVID database was used for Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathway analysis. Protein-protein interaction (PPI) networks were used for the identification of hub genes. We found upstream regulators of hub genes using miRTarBase. The expression and correlation of key miRNA and its targets were detected by qPCR. Drug Pair Seeker was employed to predict drug combinations against NASH. The expression of miRNA and hub genes in HCC was identified in the Cancer Genome Atlas database and Human Protein Atlas database.

RESULTS

Ninety-four DE-genes were accessed. GO and KEGG analysis showed that these predicted genes were linked to lipid metabolism. Eleven genes were identified as hub genes in PPI networks, and they were highly expressed in cells with vigorous lipid metabolism. hsa-miR-335-5p was the upstream regulator of 9 genes in the 11 hub genes, and it was identified as a key miRNA. The hub genes were highly expressed in NASH models, while hsa-miR-335-5p was lowly expressed. The correlation of miRNA-mRNA was established by qPCR. Functional verification indicated that hsa-miR-335-5p had inhibitory effect on the development of NASH. Finally, drug combinations were predicted and the expression of miRNA and hub genes in HCC was identified.

CONCLUSIONS

In the study, potential miRNA-mRNA pathways related to NASH were identified. Targeting these pathways may be novel strategies against NASH.

A Mendelian randomization study on the role of serum parathyroid hormone and 25-hydroxyvitamin D in osteoarthritis

OBJECTIVE

Serum parathyroid hormone (PTH) and 25-hydroxyvitamin D [25(OH)D] have been demonstrated to be associated with pathogenesis and progression of osteoarthritis (OA). This study aimed to determine the potential causal relationship between serum PTH and 25(OH)D levels and risk of OA.

DESIGN

We applied the two-sample Mendelian randomization (MR) approach to estimate the causal roles of serum PTH and 25(OH)D on OA. The instrumental variables for serum PTH and 25(OH)D were derived from two large genome-wide association studies (GWAS), which included 29,155 and 79,366 individuals, respectively. Summary-level data for overall, hip and knee OA were extracted from a GWAS meta-analysis, including 455,221 individuals. All participants included in this study were from the European population.

RESULTS

An inverse association was observed between serum PTH levels and risk of OA (random-effects: Effect = 0.71; 95% CI: 0.54 to 0.92; fixed-effects: Effect = 0.71; 95% CI: 0.61 to 0.82). Stratified by site, serum PTH levels were found to be inversely associated with knee OA (random-effects: Effect = 0.53; 95% CI: 0.41 to 0.68; fixed-effects: Effect = 0.53; 95% CI: 0.41 to 0.68). However, there was no evidence of the causal effect of serum 25(OH)D levels on OA.

CONCLUSIONS

The present study indicates an inverse causal relationship between serum PTH concentrations and development of OA. Moreover, a site-specific association was also observed between serum PTH levels and knee OA. The potential mechanisms by which serum PTH affects OA need to be further investigated.

Selective ability of rat 7-Dehydrocholesterol reductase (DHCR7) to act on some 7-Dehydrocholesterol metabolites but not on lumisterol metabolites

7-Dehydrocholesterol reductase (DHCR7) catalyses the final step of cholesterol biosynthesis in the Kandutsch-Russel pathway, the reduction of 7-dehydrocholesterol (7DHC) to cholesterol. 7DHC can be acted on by a range of other enzymes including CYP27A1 and CYP11A1, as well as by UVB radiation, producing a number of derivatives including hydroxy-metabolites, some of which retain the C7-C8 double bond and are biologically active. These metabolites include lumisterol (L3) which is a stereoisomer of 7DHC produced in the skin by UVB radiation of 7DHC, as well as vitamin D3. The aim of this study was to test whether these metabolites could act as substrates or inhibitors of DHCR7 in rat liver microsomes. To initially screen the ability of these metabolites to interact with the active site of DHCR7, their ability to inhibit the conversion of ergosterol to brassicasterol was measured. Sterols that significantly inhibited this reaction included 7DHC (as expected), 20S(OH)7DHC, 27(OH)DHC, 8DHC, 20S(OH)L3 and 22(OH)L3 but not 7-dehydropregnenolone (7DHP), 25(OH)7DHC, L3 or vitamin D3 and its hydroxyderivatives. Sterols that inhibited ergosterol reduction were directly tested as substrates for DHCR7. 20S(OH)7DHC, 27(OH)DHC and 7-dehydrodesmosterol were confirmed to be substrates, giving the expected product with the C7-C8 double bond removed. No products were observed from 8DHC or 20S(OH)L3 indicating that these sterols are inhibitors and not substrates of DHCR7. The resistance of lumisterol and 7DHP to reduction by DHCR7 in cells will permit other enzymes to metabolise these sterols to their active forms retaining the C7-C8 double bond, conferring specificity to their biological actions.

Vitamin D and the risk for cancer: A molecular analysis

Uncontrolled overgrowth of cells, such as in cancer, is an unavoidable risk in life that affects nearly every second individual in industrialized countries. However, in part this risk can be controlled through lifestyle adjustments, such as the avoidance of smoking, unhealthy diet, obesity, physical inactivity and other cancer risk factors. A low vitaminD status is a risk in particular for cancers of colon, prostate, breast and leukocytes. VitaminD₃ is produced non-enzymatically, when the cholesterol precursor 7-dehydrocholesterol is exposed to UV-B from sunlight, i.e., all cholesterol synthesizing species, including humans, can make vitaminD₃. VitaminD endocrinology started some 550million years ago, when the metabolite 1α,25-dihydroxyvitaminD₃ and the transcription factor vitaminD receptor teamed up for regulating the expression of hundreds of target genes in a multitude of different tissues and cell types. Initially, these genes were focused on the control of energy homeostasis, which later also involved energy-demanding innate and adaptive immunity. Rapidly growing cells of the immune system as well as those of malignant tumors rely on comparable genes and pathways, some of which are modulated by vitaminD. Accordingly, vitaminD has anti-cancer effects both directly via controling the differentiation, proliferation and apoptosis of neoplastic cells as well as indirectly through regulating immune cells that belong to the microenvironment of malignant tumors. This review discusses effects of vitaminD on the epigenome and transcriptome of stromal and tumor cells, inter-individual variations in vitaminD responsiveness and their relation to the prevention and possible therapy of cancer.

Effects of sublethal concentration of metamifop on hepatic lipid metabolism in adult zebrafish (Danio rerio)

Metamifop (MET) is an effective herbicide that has been extensively used in paddy fields. Previous research demonstrated that MET was highly toxic to zebrafish embryos, and this threat has caused great concern; moreover, 0.40 mg/L MET elevated the hepatosomatic index (HSI) in adult zebrafish without lethal effect after 21 d of exposure. In this study, we further determined the detailed impacts of MET on adult zebrafish at sublethal concentrations (0.025, 0.10 and 0.40 mg/L). We found that 0.40 mg/L MET caused liver injury by increasing the activity of aspartate aminotransferase and alanine aminotransferase in plasma, the content of interleukin-1β, IL-6, tumor necrosis factor-α, and mRNA expression level of genes associated with inflammatory response in liver of adult zebrafish. The hepatic triglyceride (TG), free fatty acid and fatty acid synthase levels were significantly elevated in 0.40 mg/L MET-treated group (1.55-, 2.20- and 2.30-fold, respectively), and the transcript of lipid accumulation-related genes (fabp10, fas, acc, chrebp, dagt2 and agpat4) were upregulated. Meanwhile, the total cholesterol content was decreased by 0.48-fold, bile acid level was increased by 2.44-fold, and levels of cholesterol metabolism-related genes (apoa-1a, hmgcra, cyp51, dhcr7 and cyp7a1) were increased, suggesting cholesterol metabolism disorder occurred in zebrafish. Furthermore, analysis of lipidomics revealed that 0.40 mg/L MET significantly increased the abundance of 91 lipids, which mainly belonged to TG lipid class and were enriched in pathways of glycerolipid metabolism, cholesterol metabolism, etc. These results suggested that MET exposure at sublethal concentrations would induce hepatic inflammation and lipid metabolism disorders in adult zebrafish.

The Interdependency and Co-Regulation of the Vitamin D and Cholesterol Metabolism

Vitamin D and cholesterol metabolism overlap significantly in the pathways that contribute to their biosynthesis. However, our understanding of their independent and co-regulation is limited. Cardiovascular disease is the leading cause of death globally and atherosclerosis, the pathology associated with elevated cholesterol, is the leading cause of cardiovascular disease. It is therefore important to understand vitamin D metabolism as a contributory factor. From the literature, we compile evidence of how these systems interact, relating the understanding of the molecular mechanisms involved to the results from observational studies. We also present the first systems biology pathway map of the joint cholesterol and vitamin D metabolisms made available using the Systems Biology Graphical Notation (SBGN) Markup Language (SBGNML). It is shown that the relationship between vitamin D supplementation, total cholesterol, and LDL-C status, and between latitude, vitamin D, and cholesterol status are consistent with our knowledge of molecular mechanisms. We also highlight the results that cannot be explained with our current knowledge of molecular mechanisms: (i) vitamin D supplementation mitigates the side-effects of statin therapy; (ii) statin therapy does not impact upon vitamin D status; and critically (iii) vitamin D supplementation does not improve cardiovascular outcomes, despite improving cardiovascular risk factors. For (iii), we present a hypothesis, based on observations in the literature, that describes how vitamin D regulates the balance between cellular and plasma cholesterol. Answering these questions will create significant opportunities for advancement in our understanding of cardiovascular health.

Genetic disease is a common cause of bilateral childhood cataract in Denmark

Purpose: Bilateral childhood cataracts can be caused by a metabolic disease, constitute a part of a syndrome, run in families, be sporadic or iatrogenic. The amount of work-up needed to establish a cause is discussed and the aim of the present study was to evaluate causes of bilateral childhood cataract.Methods: Chart review of 211 Danish children with bilateral cataracts. Information on work-up was retrieved with special focus on general health, metabolic screening, evaluation for congenital infections and genetic testing.Results: Cataract was seen in combination with systemic disease in 40.8%, 29.4% had hereditary cataracts, 27.0% had isolated cataract, in 1.4% it was associated with ocular malformations and 1.4% had been born prematurely without any other sequelae than the cataract. A genetic cause could be demonstrated in 74 children.Conclusion: Systemic comorbidities are very common in children with cataract and are not always known prior to the diagnosis of cataract. Genetic evaluation, especially targeted analyses, provided a molecular genetic diagnosis in a large proportion of those tested but it also failed to provide a molecular genetic diagnosis in some patients with a family history suggesting autosomal dominant inheritance. Most importantly, in some patients, genetic work-up provided a diagnosis in patients where it had therapeutic consequences and where the systemic disease would have caused irreversible damage, had it not been treated timely. Given the high prevalence of systemic disease, it seems advisable to co-manage children with bilateral cataracts with a pediatrician and to include genetic evaluation as part of the work-up.

Association of Vitamin D, Zinc and Selenium Related Genetic Variants With COVID-19 Disease Severity

Background: COVID-19 pandemic has proved to be an unrelenting health threat for more than a year now. The emerging amount of data indicates that vitamin D, zinc and selenium could be important for clinical presentation of COVID-19. Here, we investigated association of genetic variants related to the altered level and bioavailability of vitamin D, zinc and selenium with clinical severity of COVID-19. Methods: We analyzed variants in genes significant for the status of vitamin D (DHCR7/NADSYN1 rs12785878, GC rs2282679, CYP2R1 rs10741657, and VDR rs2228570), zinc (PPCDC rs2120019) and selenium (DMGDH rs17823744) in 120 Serbian adult and pediatric COVID-19 patients using allelic discrimination. Furthermore, we carried out comparative population genetic analysis among European and other worldwide populations to investigate variation in allelic frequencies of selected variants. Results: Study showed that DHCR7/NADSYN rs12785878 and CYP2R1 rs10741657 variants were associated with severe COVID-19 in adults (p = 0.03, p = 0.017, respectively); carriers of DHCR7/NADSYN TG+GG and CYP2R1 GG genotypes had 0.21 and 5.9 the odds for developing severe disease, OR 0.21 (0.05-0.9) and OR 5.9 (1.4-25.2), respectively. There were no associations between selected genetic variants and disease severity in pediatric patients. Comparative population genetic analysis revealed that Serbian population had the lowest frequency of CYP2R1 rs10741657 G allele compared to other non-Finish Europeans (0.58 compared to 0.69 and 0.66 in Spanish and Italian population, respectively), suggesting that other populations should also investigate the relationship of CYP2R1 variant and the COVID-19 disease course. Conclusion: The results of the study indicated that vitamin D related genetic variants were implicated in severe COVID-19 in adults. This could direct prevention strategies based on population specific nutrigenetic profiles.

An intronic DHCR7 genetic polymorphism associates with vitamin D serum level and incidence of acute coronary syndrome

INTRODUCTION

Vitamin D deficiency has been linked to cardiovascular pathologies including acute coronary syndrome (ACS). Polymorphisms in vitamin D associated genes have been confounding to vitamin D serum levels and pathological predispositions. 7-hydrocholesterol is a common precursor in cholesterol and vitamin D synthesis. DHCR7/NADSYN1 genetic locus expresses 7-hydrocholesterol reductase (DHCR7), an enzyme that recruits 7-hydrocholesterol in cholesterol biosynthesis, and NAD synthetase 1 (NADSYN1), which participates in the hydroxylation of 25 hydroxyvitamin D.

AIM

This study aims to correlate two polymorphisms in the DHCR7/NADSYN1 genetic locus with levels of circulatory vitamin D and the presentation of ACS in an Egyptian population.

METHODS

In a case control study, 189 ACS patients and 106 healthy control subjects were genotyped for SNPs rs11606033 of the DHCR7 gene and rs2276360 of the NADSYN1 gene using the amplification-refractory mutation system (ARMS). The levels of 25(OH)D2 and 25(OH)D3 were measured using an in-house developed and validated ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) based protocol.

RESULTS

ACS patients have significantly lower levels of circulating vitamin D in comparison to healthy controls. Allele A of the DHCR7 polymorphism was found to correlate with serum vitamin D deficiency and incidence of ACS classes: NSTEMI, STEMI and unstable angina, when compared to allele G. On the other hand, the NADSYN1 polymorphism rs2276360 correlated with serum 25(OH)D3 deficiency. Yet, no significant correlation was found with incidences of ACS.

CONCLUSION

We conclude that rs11606033, which is an intronic SNP between exon 4 and exon 5 of the DHCR7 gene, influences vitamin D serum abundance and more importantly ACS incidence.

Anthropometric characteristics of 65 Polish Smith-Lemli-Opitz patients

Smith-Lemli-Opitz syndrome (SLOS) belongs to a group of multiple congenital anomaly/developmental delay disorders. Its primary cause lies in the defect in cholesterol biosynthesis-7-dehydrocholesterol reductase (DHCR7)-caused by pathogenic variants in the homonymous gene. Anthropometric anomalies, especially growth restriction and microcephaly, are among the most common physical manifestations of SLOS. There have been no studies analyzing the correlation between genotype, biochemical marker (7-dehydrocholesterol), and the birth and growth parameters for individuals with SLOS. This paper presents anthropometric data from the group of 65 Polish patients (aged 0.1 to 18 years) with Smith-Lemli-Opitz syndrome, with genotype and biochemical correlations for birth parameters, as well as growth in relation to molecular DHCR7 variants.

Vitamin D and lumisterol derivatives can act on liver X receptors (LXRs)

The interactions of derivatives of lumisterol (L3) and vitamin D3 (D3) with liver X receptors (LXRs) were investigated. Molecular docking using crystal structures of the ligand binding domains (LBDs) of LXRα and β revealed high docking scores for L3 and D3 hydroxymetabolites, similar to those of the natural ligands, predicting good binding to the receptor. RNA sequencing of murine dermal fibroblasts stimulated with D3-hydroxyderivatives revealed LXR as the second nuclear receptor pathway for several D3-hydroxyderivatives, including 1,25(OH)2D3. This was validated by their induction of genes downstream of LXR. L3 and D3-derivatives activated an LXR-response element (LXRE)-driven reporter in CHO cells and human keratinocytes, and by enhanced expression of LXR target genes. L3 and D3 derivatives showed high affinity binding to the LBD of the LXRα and β in LanthaScreen TR-FRET LXRα and β coactivator assays. The majority of metabolites functioned as LXRα/β agonists; however, 1,20,25(OH)3D3, 1,25(OH)2D3, 1,20(OH)2D3 and 25(OH)D3 acted as inverse agonists of LXRα, but as agonists of LXRβ. Molecular dynamics simulations for the selected compounds, including 1,25(OH)2D3, 1,20(OH)2D3, 25(OH)D3, 20(OH)D3, 20(OH)L3 and 20,22(OH)2L3, showed different but overlapping interactions with LXRs. Identification of D3 and L3 derivatives as ligands for LXRs suggests a new mechanism of action for these compounds.

Multifaceted Interaction Between Hepatitis B Virus Infection and Lipid Metabolism in Hepatocytes: A Potential Target of Antiviral Therapy for Chronic Hepatitis B

Hepatitis B virus (HBV) is considered a “metabolic virus” and affects many hepatic metabolic pathways. However, how HBV affects lipid metabolism in hepatocytes remains uncertain yet. Accumulating clinical studies suggested that compared to non-HBV-infected controls, chronic HBV infection was associated with lower levels of serum total cholesterol and triglycerides and a lower prevalence of hepatic steatosis. In patients with chronic HBV infection, high ALT level, high body mass index, male gender, or old age was found to be positively correlated with hepatic steatosis. Furthermore, mechanisms of how HBV infection affected hepatic lipid metabolism had also been explored in a number of studies based on cell lines and mouse models. These results demonstrated that HBV replication or expression induced extensive and diverse changes in hepatic lipid metabolism, by not only activating expression of some critical lipogenesis and cholesterolgenesis-related proteins but also upregulating fatty acid oxidation and bile acid synthesis. Moreover, increasing studies found some potential targets to inhibit HBV replication or expression by decreasing or enhancing certain lipid metabolism-related proteins or metabolites. Therefore, in this article, we comprehensively reviewed these publications and revealed the connections between clinical observations and experimental findings to better understand the interaction between hepatic lipid metabolism and HBV infection. However, the available data are far from conclusive, and there is still a long way to go before clarifying the complex interaction between HBV infection and hepatic lipid metabolism.

The Role of Vitamin D as a Biomarker in Alzheimer's Disease

Vitamin D and cognition is a popular association, which led to a remarkable body of literature data in the past 50 years. The brain can synthesize, catabolize, and receive Vitamin D, which has been proved to regulate many cellular processes in neurons and microglia. Vitamin D helps synaptic plasticity and neurotransmission in dopaminergic neural circuits and exerts anti-inflammatory and neuroprotective activities within the brain by reducing the synthesis of pro-inflammatory cytokines and the oxidative stress load. Further, Vitamin D action in the brain has been related to the clearance of amyloid plaques, which represent a feature of Alzheimer Disease (AD), by the immune cell. Based on these considerations, many studies have investigated the role of circulating Vitamin D levels in patients affected by a cognitive decline to assess Vitamin D’s eventual role as a biomarker or a risk factor in AD. An association between low Vitamin D levels and the onset and progression of AD has been reported, and some interventional studies to evaluate the role of Vitamin D in preventing AD onset have been performed. However, many pitfalls affected the studies available, including substantial discrepancies in the methods used and the lack of standardized data. Despite many studies, it remains unclear whether Vitamin D can have a role in cognitive decline and AD. This narrative review aims to answer two key questions: whether Vitamin D can be used as a reliable tool for diagnosing, predicting prognosis and response to treatment in AD patients, and whether it is a modifiable risk factor for preventing AD onset.

Integrative transcriptomic and metabonomic profiling analyses reveal the molecular mechanism of Chinese traditional medicine huankuile suspension on TNBS-induced ulcerative colitis

This study aimed to investigate the therapeutic mechanism of Huankuile suspension (HKL), a typical traditional Chinese medicine, on ulcerative colitis (UC) in a rat model. UC model was established by 2,4,6-trinitrobenzene sulfonic acid (TNBS) enema. Then, the rats were randomly divided into three groups: water treated group, HKL treated group and 5- amino salicylic acid (5-ASA) treated group. After 7 days treatment, the histological score in the HKL treated group was comparable with those in the control group. qRT-PCR and western blot demonstrated that HKL could significantly decreased pro-inflammatory cytokines, including TNF-α, IL-1β and IL-6, while having less effect on anti-inflammatory cytokines, including IL-4 and IL-10. Transcriptomic analysis identified 670 differentially expressed genes (DEGs) between HKL treated UC rats and water treated UC rats. These DEGs were mostly related with immune response. Besides, metabonomic profile revealed 136 differential metabolites which were significantly enriched in “pyrimidine metabolism”, “glutathione metabolism”, “purine metabolism” and “citrate cycle”. Finally, integrated analysis revealed that metabonomic pathways including “steroid hormone biosynthesis”, “pyrimidine metabolism”, “purine metabolism”, and “glutathione metabolism” were altered by HKL at both transcriptomic and metabonomic levels. HKL could inhibit inflammation and regulate bile metabolism, pyrimidine metabolism, purine metabolism, glutathione metabolism and citrate cycle.

Proteomic analysis from skin swabs reveals a new set of proteins identifying skin impairment in atopic dermatitis

Atopic Dermatitis (AD) is a common inflammatory skin disease characterized by skin and systemic inflammation, and barrier dysfunction. Herein, we investigate the proteomic profile of AD skin barrier to identify a unique signature with an easy-performed sampling approach. We enrolled 8 moderate-to-severe AD patients and 8 age- and gender-matched healthy controls. Swabs were obtained from non-lesional skin of retroauricular area and antecubital fold. Peptide mixtures obtained through protein precipitation and in-solution digestion were analysed using NanoLC-MS/MS. Label-free quantification and statistical analysis were conducted in MaxQuant and Perseus. Bioinformatics analysis was performed using Gene Ontology and STRING. We identified 908 proteins and 35 differentially expressed proteins were selected (fold change 2, FDR < 0.05). Particularly, AD skin showed downregulation of skin hydration factors, structural and epidermal proteins, abnormalities in protease-proteasome complex and lipid metabolism profile. Imbalance of antioxidant and inflammatory processes, along with TDRD15 upregulation was also observed. Our result showed partial overlap with skin biopsy/tape-strips studies, showing the reliability of our sampling approach which could be an easier method of detection of hallmark barrier proteins in AD. Furthermore, we displayed a new differentially expressed set of proteins, not yet explored in AD which can have a potential role in AD pathomechanisms.

Evolution, Expression Profile, Regulatory Mechanism, and Functional Verification of EBP-Like Gene in Cholesterol Biosynthetic Process in Chickens (Gallus Gallus)

The emopamil binding protein (EBP) is an important enzyme participating in the final steps of cholesterol biosynthesis in mammals. A predictive gene EBP-like, which encodes the protein with a high identity to human EBP, was found in chicken genome. No regulatory mechanisms and biological functions of EBP-like have been characterized in chickens. In the present study, the coding sequence of EBP-like was cloned, the phylogenetic trees of EBP/EBP-like were constructed and the genomic synteny of EBP-like was analyzed. The regulatory mechanism of EBP-like were explored with in vivo and in vitro experiments. The biological functions of EBP-like in liver cholesterol biosynthetic were examined by using gain- or loss-of-function strategies. The results showed that chicken EBP-like gene was originated from a common ancestral with Japanese quail EBP gene, and was relatively conservative with EBP gene among different species. The EBP-like gene was highly expressed in liver, its expression level was significantly increased in peak-laying stage, and was upregulated by estrogen. Inhibition of the EBP-like mRNA expression could restrain the expressions of EBP-like downstream genes (SC5D, DHCR24, and DHCR7) in the cholesterol synthetic pathway, therefore downregulate the liver intracellular T-CHO level. In conclusion, as substitute of EBP gene in chickens, EBP-like plays a vital role in the process of chicken liver cholesterol synthesis. This research provides a basis for revealing the molecular regulatory mechanism of cholesterol synthesis in birds, contributes insights into the improvement of the growth and development, laying performance and egg quality in poultry.

Vitamin D pathway-related gene polymorphisms and their association with metabolic diseases: A literature review

PURPOSE

Given that the relationship between vitamin D status and metabolic diseases such as obesity and type 2 diabetes (T2D) remains unclear, this review will focus on the genetic associations, which are less prone to confounding, between vitamin D-related single nucleotide polymorphisms (SNPs) and metabolic diseases.

METHODS

A literature search of relevant articles was performed on PubMed up to December 2019. Those articles that had examined the association of vitamin D-related SNPs with obesity and/or T2D were included. Two reviewers independently evaluated the eligibility for the inclusion criteria and extracted the data. In total, 73 articles were included in this review.

RESULTS

There is a lack of research focusing on the association of vitamin D synthesis-related genes with obesity and T2D; however, the limited available research, although inconsistent, is suggestive of a protective effect on T2D risk. While there are several studies that investigated the vitamin D metabolism-related SNPs, the research focusing on vitamin D activation, catabolism and transport genes is limited. Studies on CYP27B1, CYP24A1 and GC genes demonstrated a lack of association with obesity and T2D in Europeans; however, significant associations with T2D were found in South Asians. VDR gene SNPs have been extensively researched; in particular, the focus has been mainly on BsmI (rs1544410), TaqI (rs731236), ApaI (rs7975232) and FokI (rs2228570) SNPs. Even though the association between VDR SNPs and metabolic diseases remain inconsistent, some positive associations showing potential effects on obesity and T2D in specific ethnic groups were identified.

CONCLUSIONS

Overall, this literature review suggests that ethnic-specific genetic associations are involved. Further research utilizing large studies is necessary to better understand these ethnic-specific genetic associations between vitamin D deficiency and metabolic diseases.

Role of Metabolism in Bone Development and Homeostasis

Carbohydrates, fats, and proteins are the underlying energy sources for animals and are catabolized through specific biochemical cascades involving numerous enzymes. The catabolites and metabolites in these metabolic pathways are crucial for many cellular functions; therefore, an imbalance and/or dysregulation of these pathways causes cellular dysfunction, resulting in various metabolic diseases. Bone, a highly mineralized organ that serves as a skeleton of the body, undergoes continuous active turnover, which is required for the maintenance of healthy bony components through the deposition and resorption of bone matrix and minerals. This highly coordinated event is regulated throughout life by bone cells such as osteoblasts, osteoclasts, and osteocytes, and requires synchronized activities from different metabolic pathways. Here, we aim to provide a comprehensive review of the cellular metabolism involved in bone development and homeostasis, as revealed by mouse genetic studies.

An autonomous, but INSIG-modulated, role for the sterol sensing domain in mallostery-regulated ERAD of yeast HMG-CoA reductase

HMG-CoA reductase (HMGR) undergoes feedback-regulated degradation as part of sterol pathway control. Degradation of the yeast HMGR isozyme Hmg2 is controlled by the sterol pathway intermediate GGPP, which causes misfolding of Hmg2, leading to degradation by the HRD pathway; we call this process mallostery. We evaluated the role of the Hmg2 sterol sensing domain (SSD) in mallostery, as well as the involvement of the highly conserved INSIG proteins. We show that the Hmg2 SSD is critical for regulated degradation of Hmg2 and required for mallosteric misfolding of GGPP as studied by in vitro limited proteolysis. The Hmg2 SSD functions independently of conserved yeast INSIG proteins, but its function was modulated by INSIG, thus imposing a second layer of control on Hmg2 regulation. Mutant analyses indicated that SSD-mediated mallostery occurred prior to and independent of HRD-dependent ubiquitination. GGPP-dependent misfolding was still extant but occurred at a much slower rate in the absence of a functional SSD, indicating that the SSD facilitates a physiologically useful rate of GGPP response and implying that the SSD is not a binding site for GGPP. Nonfunctional SSD mutants allowed us to test the importance of Hmg2 quaternary structure in mallostery: a nonresponsive Hmg2 SSD mutant strongly suppressed regulation of a coexpressed, normal Hmg2. Finally, we have found that GGPP-regulated misfolding occurred in detergent-solubilized Hmg2, a feature that will allow next-level analysis of the mechanism of this novel tactic of ligand-regulated misfolding.

Vitamin D and Genetic Susceptibility to Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease affecting the central nervous system (CNS), resulting from the interaction among genetic, epigenetic, and environmental factors. Vitamin D is a secosteroid, and its circulating levels are influenced by environment and genetics. In the last decades, research data on the association between MS and vitamin D status led to hypothesize a possible role for hypovitaminosis D as a risk factor for MS. Some gene variants encoding proteins involved in vitamin D metabolism, transport, and function, which are responsible for vitamin D status alterations, have been related to MS susceptibility. This review explores the current literature on the influence of vitamin D-related genes in MS susceptibility, reporting all single-nucleotide polymorphisms (SNPs) investigated to date in 12 vitamin D pathway genes. Among all, the gene codifying vitamin D receptor (VDR) is the most studied. The association between VDR SNPs and MS risk has been reported by many Authors, with a few studies producing opposite results. Other vitamin D-related genes (including DHCR7/NADSYN1, CYP2R1, CYP27A1, CYP3A4, CYP27B1, CYP24A1, Megalin-DAB2-Cubilin, FGF-23, and Klotho) have been less investigated and achieved more conflicting evidence. Taken together, findings from the studies reviewed cannot clarify whether and to what extent vitamin D-related gene variants can influence MS risk.

Genetic variants of vitamin D metabolism-related DHCR7/NADSYN1 locus and CYP2R1 gene are associated with clinical features of Parkinson's disease

PURPOSE/AIM OF THE STUDY

Parkinson's disease (PD) is the second most common neurodegenerative disorder. Vitamin D deficiency is suggested to be related to PD. A genome-wide association study indicated that genes involved in vitamin D metabolism affect vitamin D levels. Among these genes, single nucleotide polymorphisms (SNPs) of the vitamin D receptor (VDR) and vitamin D binding protein (VDBP/GC) genes have also been demonstrated to be associated with PD risk. Our aim was to investigate the relevance of SNPs within the 7-dehydrocholesterol reductase/nicotinamide adenine dinucleotide synthetase 1 (DHCR7/NADSYN1) locus and vitamin D 25-hydroxylase (CYP2R1) gene, which encode important enzymes that play a role in the vitamin D synthesis pathway, with PD and its clinical features.

MATERIALS AND METHODS

Genotypes of 382 PD patients and 240 cognitively healthy individuals were evaluated by a LightSNiP assay for a total of 10 SNPs within the DHCR7/NADSYN1 locus and CYP2R1 gene.

RESULTS

There were no significant differences in the allele and genotype distributions of any of the SNPs between any patient groups and healthy subjects. However, our results indicated that all of the SNPs within the DHCR7/NADSYN1 locus and CYP2R1 gene, except rs1993116, were associated with clinical motor features of PD including initial predominant symptom, freezing of gait (FoG) and falls as well as disease stage and duration of the disease.

CONCLUSIONS

In conclusion, genetic variants of the DHCR7/NADSYN1 locus and the CYP2R1 gene might be related to the inefficient utilization of vitamin D independent from vitamin D levels, and it might result in differences in the clinical features of PD patients.

An Update on Vitamin D Metabolism

Vitamin D is a steroid hormone classically involved in the calcium metabolism and bone homeostasis. Recently, new and interesting aspects of vitamin D metabolism has been elucidated, namely the special role of the skin, the metabolic control of liver hydroxylase CYP2R1, the specificity of 1α-hydroxylase in different tissues and cell types and the genomic, non-genomic and epigenomic effects of vitamin D receptor, which will be addressed in the present review. Moreover, in the last decades, several extraskeletal effects which can be attributed to vitamin D have been shown. These beneficial effects will be here summarized, focusing on the immune system and cardiovascular system.

Skin colour and vitamin D: An update

Homo sapiens evolved in East Africa and had dark skin, hair, and eyes, in order to protect against deleterious consequences of intensive UV radiation at equatorial latitudes. Intensive skin pigmentation was thought to bear the risk of inefficient vitamin D3 synthesis in the skin. This initiated the hypothesis that within the past 75 000 years, in which humans migrated to higher latitudes in Asia and Europe, the need for vitamin D3 synthesis served as an evolutionary driver for skin lightening. In this review, we summarize the recent archeogenomic reconstruction of population admixture in Europe and demonstrate that skin lightening happened as late as 5000 years ago through immigration of lighter pigmented populations from western Anatolia and the Russian steppe but not primarily via evolutionary pressure for vitamin D3 synthesis. We show that variations in genes encoding for proteins being responsible for the transport, metabolism and signalling of vitamin D provide alternative mechanisms of adaptation to a life in northern latitudes without suffering from consequences of vitamin D deficiency. This includes hypotheses explaining differences in the vitamin D status and response index of European populations.

Mechanical stimulations can inhibit local and remote tumor progression by downregulating WISP1

Mechanical stimulations can prevent bone loss, but their effects on the tumor-invaded bone or solid tumors are elusive. Here, we evaluated the effect of knee loading, dynamic loads applied to the knee, on metastasized bone and mammary tumors. In a mouse model, tumor cells were inoculated to the mammary fat pad or the proximal tibia. Daily knee loading was then applied and metabolic changes were monitored mainly through urine. Urine samples were also collected from human subjects before and after step aerobics. The result showed that knee loading inhibited tumor progression in the loaded tibia. Notably, it also reduced remotely the growth of mammary tumors. In the urine, an altered level of cholesterol was observed with an increase in calcitriol, which is synthesized from a cholesterol derivative. In urinary proteins, knee loading in mice and step aerobics in humans markedly reduced WNT1-inducible signaling pathway protein 1, WISP1, which leads to poor survival among patients with breast cancer. In the ex vivo breast cancer tissue assay, WISP1 promoted the growth of cancer fragments and upregulated tumor-promoting genes, such as Runx2, MMP9, and Snail. Collectively, the present preclinical and human study demonstrated that mechanical stimulations, such as knee loading and step aerobics, altered urinary metabolism and downregulated WISP1. The study supports the benefit of mechanical stimulations for locally and remotely suppressing tumor progression. It also indicated the role of WISP1 downregulation as a potential mechanism of loading-driven tumor suppression.

Vitamin D genes influence MS relapses in children

OBJECTIVE

The aim of this study was to determine whether a vitamin D genetic risk score (vitDGRS) is associated with 25-hydroxyvitamin D (25(OH)D) level and multiple sclerosis (MS) relapses in children.

METHODS

DNA samples were typed for single nucleotide polymorphisms (SNPs) from four genes previously identified to be associated with 25(OH)D levels. SNPs with strong associations with 25(OH)D after multiple comparison correction were used to create a genetic risk score (vitDGRS). Cox regression models tested associations of vitDGRS with relapse hazard.

RESULTS

Two independent SNPs within or near GC and NADSYN1/DHCR7 genes were strongly associated with 25(OH)D levels in the discovery cohort (n = 182) after Bonferroni correction. The vitDGRS of these SNPs explained 4.5% of the variance of 25(OH)D level after adjustment for genetic ancestry. Having the highest versus lowest vitDGRS was associated with 11 ng/mL lower 25(OH)D level (95% confidence interval (CI) = -17.5, -4.5, p = 0.001) in the discovery cohort. Adjusting for ancestry, sex, disease-modifying therapy (DMT), and HLA-DRB1*15 carrier status, the highest versus lowest vitDGRS was associated with 2.6-fold (95% CI = 1.37, 5.03, p = 0.004) and 2.0-fold (95% CI = 0.75, 5.20, p = 0.16) higher relapse hazard in the discovery and replication cohorts, respectively.

CONCLUSION

The vitDGRS identifies children at greater risk of relapse. These findings support a causal role for vitamin D in MS course.

The cholesterol synthesis enzyme lanosterol 14α-demethylase is post-translationally regulated by the E3 ubiquitin ligase MARCH6

Cholesterol synthesis is a tightly controlled pathway, with over 20 enzymes involved. Each of these enzymes can be distinctly regulated, helping to fine-tune the production of cholesterol and its functional intermediates. Several enzymes are degraded in response to increased sterol levels, whilst others remain stable. We hypothesised that an enzyme at a key branch point in the pathway, lanosterol 14α-demethylase (LDM) may be post-translationally regulated. Here, we show that the preceding enzyme, lanosterol synthase is stable, whilst LDM is rapidly degraded. Surprisingly, this degradation is not triggered by sterols. However, the E3 ubiquitin ligase membrane-associated ring-CH-type finger 6 (MARCH6), known to control earlier rate-limiting steps in cholesterol synthesis, also control levels of LDM and the terminal cholesterol synthesis enzyme, 24-dehydrocholesterol reductase. Our work highlights MARCH6 as the first example of an E3 ubiquitin ligase that targets multiple steps in a biochemical pathway and indicates new facets in the control of cholesterol synthesis.

Reactive Sterol Electrophiles: Mechanisms of Formation and Reactions with Proteins and Amino Acid Nucleophiles

Radical-mediated lipid oxidation and the formation of lipid hydroperoxides has been a focal point in the investigation of a number of human pathologies. Lipid peroxidation has long been linked to the inflammatory response and more recently, has been identified as the central tenet of the oxidative cell death mechanism known as ferroptosis. The formation of lipid electrophile-protein adducts has been associated with many of the disorders that involve perturbations of the cellular redox status, but the identities of adducted proteins and the effects of adduction on protein function are mostly unknown. Both cholesterol and 7-dehydrocholesterol (7-DHC), which is the immediate biosynthetic precursor to cholesterol, are oxidizable by species such as ozone and oxygen-centered free radicals. Product mixtures from radical chain processes are particularly complex, with recent studies having expanded the sets of electrophilic compounds formed. Here, we describe recent developments related to the formation of sterol-derived electrophiles and the adduction of these electrophiles to proteins. A framework for understanding sterol peroxidation mechanisms, which has significantly advanced in recent years, as well as the methods for the study of sterol electrophile-protein adduction, are presented in this review.

The Estrogen-Responsive Transcriptome of Female Secondary Sexual Traits in the Gulf Pipefish

Sexual dimorphism often results from hormonally regulated trait differences between the sexes. In sex-role-reversed vertebrates, females often have ornaments used in mating competition that are expected to be under hormonal control. Males of the sex-role-reversed Gulf pipefish (Syngnathus scovelli) develop female-typical traits when they are exposed to estrogens. We aimed to identify genes whose expression levels changed during the development and maintenance of female-specific ornaments. We performed RNA-sequencing on skin and muscle tissue in male Gulf pipefish with and without exposure to estrogen to investigate the transcriptome of the sexually dimorphic ornament of vertical iridescent bands found in females and estrogen-exposed males. We further compared differential gene expression patterns between males and females to generate a list of genes putatively involved in the female secondary sex traits of bands and body depth. A detailed analysis of estrogen-receptor binding sites demonstrates that estrogen-regulated genes tend to have nearby cis-regulatory elements. Our results identified a number of genes that differed between the sexes and confirmed that many of these were estrogen-responsive. These estrogen-regulated genes may be involved in the arrangement of chromatophores for color patterning, as well as in the growth of muscles to achieve the greater body depth typical of females in this species. In addition, anaerobic respiration and adipose tissue could be involved in the rigors of female courtship and mating competition. Overall, this study generates a number of interesting hypotheses regarding the genetic basis of a female ornament in a sex-role-reversed pipefish.

New aspects of vitamin D metabolism and action - addressing the skin as source and target

Vitamin D has a key role in stimulating calcium absorption from the gut and promoting skeletal health, as well as many other important physiological functions. Vitamin D is produced in the skin. It is subsequently metabolized to its hormonally active form, 1,25-dihydroxyvitamin D (1,25(OH)₂D), by the 1-hydroxylase and catabolized by the 24-hydroxylase. In this Review, we pay special attention to the effect of mutations in these enzymes and their clinical manifestations. We then discuss the role of vitamin D binding protein in transporting vitamin D and its metabolites from their source to their targets, the free hormone hypothesis for cell entry and HSP70 for intracellular transport. This is followed by discussion of the vitamin D receptor (VDR) that mediates the cellular actions of 1,25(OH)₂D. Cell-specific recruitment of co-regulatory complexes by liganded VDR leads to changes in gene expression that result in distinct physiological actions by 1,25(OH)₂D, which are disrupted by mutations in the VDR. We then discuss the epidermis and hair follicle, to provide a non-skeletal example of a tissue that expresses VDR that not only makes vitamin D but also can metabolize it to its hormonally active form. This enables vitamin D to regulate epidermal differentiation and hair follicle cycling and, in so doing, to promote barrier function, wound healing and hair growth, while limiting cancer development.

Sputum and blood transcriptomics characterisation of the inhaled PDE4 inhibitor CHF6001 on top of triple therapy in patients with chronic bronchitis

Background

Although phosphodiesterase-4 (PDE4) inhibitors have been shown to reduce COPD exacerbation rate, their biological mechanism of action is not completely elucidated at the molecular level. We aimed to characterise the whole genome gene expression profile of the inhaled PDE4-inhibitor CHF6001 on top of triple therapy in sputum cells and whole blood of patients with COPD and chronic bronchitis.

Methods

Whole genome gene expression analysis was carried out by microarray in 54 patients before and after 32 days treatment with CHF6001 800 and 1600 μg and placebo twice daily (BID) in a randomised crossover study.

Results

CHF6001 had a strong effect in sputum, with 1471 and 2598 significantly differentially-expressed probe-sets relative to placebo (p-adjusted for False Discovery Rate < 0.05) with 800 and 1600 μg BID, respectively. Functional enrichment analysis showed significant modulation of key inflammatory pathways involved in cytokine activity, pathogen-associated-pattern-recognition activity, oxidative stress and vitamin D with associated inhibition of downstream inflammatory effectors. A large number of pro-inflammatory genes coding for cytokines and matrix-metalloproteinases were significantly differentially expressed for both doses; the majority (> 87%) were downregulated, including macrophage inflammatory protein-1-alpha and 1-beta, interleukin-27-beta, interleukin-12-beta, interleukin-32, tumour necrosis factor-alpha-induced-protein-8, ligand-superfamily-member-15, and matrix-metalloproteinases-7,12 and 14. The effect in blood was not significant.

Conclusions

Inhaled PDE4 inhibition by CHF6001 on top of triple therapy in patients with COPD and chronic bronchitis significantly modulated key inflammatory targets and pathways in the lung but not in blood. Mechanistically these findings support a targeted effect in the lung while minimising unwanted systemic class-effects.

Trial registration

ClinicalTrial.gov, EudraCT, 2015–005550-35. Registered 15 July 2016.

Vitamin D: Newer Concepts of Its Metabolism and Function at the Basic and Clinical Level

The interest in vitamin D continues unabated with thousands of publications contributing to a vast and growing literature each year. It is widely recognized that the vitamin D receptor (VDR) and the enzymes that metabolize vitamin D are found in many cells, not just those involved with calcium and phosphate homeostasis. In this mini review I have focused primarily on recent studies that provide new insights into vitamin D metabolism, mechanisms of action, and clinical applications. In particular, I examine how mutations in vitamin D metabolizing enzymes-and new information on their regulation-links vitamin D metabolism into areas such as metabolism and diseases outside that of the musculoskeletal system. New information regarding the mechanisms governing the function of the VDR elucidates how this molecule can be so multifunctional in a cell-specific fashion. Clinically, the difficulty in determining vitamin D sufficiency for all groups is addressed, including a discussion of whether the standard measure of vitamin D sufficiency, total 25OHD (25 hydroxyvitamin) levels, may not be the best measure-at least by itself. Finally, several recent large clinical trials exploring the role of vitamin D supplementation in nonskeletal diseases are briefly reviewed, with an eye toward what questions they answered and what new questions they raised.

Vitamin D and Multiple Sclerosis: An Open-Ended Story

Multiple Sclerosis (MS) is a chronic inflammatory autoimmune disease of the Central Nervous System (CNS). Genetic, epigenetic and environmental factors interact together, contributing to the complex pathogenesis of the disease. In the last decades, the role of hypovitaminosis D on MS risk was hypothesised. Several factors drive the regulation of vitamin D status, including genetics. The current review summarises the literature evidence on the association between vitamin D and MS, with a focus on the genetic polymorphisms in vitamin D-related genes. The variants of the genes codifying Vitamin D Receptor (VDR), Vitamin D Binding Protein (VDBP) and CYP enzymes have been investigated, but the findings are controversial. Only a few studies have addressed the role of DHCR7 polymorphisms in MS risk.

UV increases skin-derived 1α,25-dihydroxyvitamin D3 production, leading to MMP-1 expression by altering the balance of vitamin D and cholesterol synthesis from 7-dehydrocholesterol

The skin is a unique site in the human body that has the capacity to synthesize the active form of vitamin D, 1α,25-dihydroxyvitamin D₃ (1α,25(OH)₂D₃), from 7-dehydrocholesterol (7DHC) upon UV irradiation. Keratinocytes express both 25-hydroxylase (CYP27A1 and CYP2R1) and 1α-hydroxylase (CYP27B1), critical enzymes involved in active vitamin D synthesis. Here, we investigated the effect of skin-derived 1α,25(OH)₂D₃, synthesized purely within the keratinocytes, on MMP-1 expression. Treatment of human epidermal keratinocytes with 1α,25(OH)₂D_3, but not 7DHC or 25OHD₃, significantly increased MMP-1 expression. UV irradiation increases 1α,25(OH)₂D₃ levels, and ketoconazole inhibits UV-induced production of 1α,25(OH)₂D₃. Upregulation of MMP-1 by UV was reversed by inhibition of 1α,25(OH)₂D₃ synthesis using ketoconazole or CYP27B1 siRNA. In keratinocytes, 7DHC is a substrate for both cholesterol and 1α,25(OH)₂D₃ synthesis. We demonstrated that UV irradiation leads to decreased expression of DHCR7 (7-dehydrocholesterol reductase), the enzyme that converts 7DHC to cholesterol. Inhibition of DHCR7 with its inhibitor BM15766 decreased cholesterol synthesis and increased UV-induced MMP-1 expression, which was attenuated by ketoconazole. These findings suggest that UV-induced reduction of DHCR7 leads to a decrease in cholesterol synthesis, thereby increasing 7DHC availability for 1α,25(OH)₂D₃ production, which enhances MMP-1 expression. Finally, UV irradiation in human skin in vivo significantly increased CYP27B1 mRNA and decreased DHCR7 mRNA expression. Taken together, we demonstrate here that skin-derived 1α,25(OH)₂D₃ significantly increases MMP-1 expression in human keratinocytes, a previously unappreciated function of 1α,25(OH)₂D_3. Moreover, UV irradiation upregulates the enzyme CYP27B1, which leads to 1α,25(OH)₂D₃ synthesis, but downregulates the cholesterol-producing enzyme DHCR7, both of which collectively lead to increased MMP-1 expression in human keratinocytes. This pathway may be exploited to develop a novel cutaneous anti-aging agent that blocks local cutaneous 1α,25(OH)₂D₃ synthesis.

Associations of cholesterol and vitamin D metabolites with the risk for development of high grade colorectal cancer

Background

Vitamin D deficiency is repeatedly reported in colorectal cancer (CRC). Since cholesterol and vitamin D share common precursor 7-dehydrocholesterol (7-DHC), it would be important to explore the associations of key vitamin D metabolites and serum lipid parameters in patients with high and low grade CRC. The aim of this study was to analyze relationships between serum 25(OH)D3, 24,25(OH)2D3 and 7-DHC levels and serum lipids in patients with CRC, and to evaluate their potential for prediction of risk for development of high grade CRC.

Methods

We recruited 82 patients CRC and 77 controls. 7-DHC, 25(OH)D3 and 24,25(OH)2D3 were quantified by LC-MS/MS methods.

Results

7-DHC, 25(OH)D3 and vitamin D metabolic ratio (VDMR) were significantly lower in CRC patients than in control group (P<0.001, P<0.010, P<0.050 and P<0.050, respectively). 25(OH)D3 levels were higher in patients with grade I CRC when compared to grade II (P<0.050). All vitamin D metabolites positively correlated with total cholesterol (TC) concentration in CRC patients. 25(OH)D3 was significant predictor of increased CRC risk (P<0.010). After adjustment for TC concentration, 25(OH)D3 lost its predictive abilities. However, 25(OH)D3 remained significant predictor of poorly differentiated type of cancer (P<0.050).

Conclusions

We found significant positive association between vitamin D status and serum total cholesterol. Although low 25(OH)D3 was found to be a significant risk factor for CRC development, the obtained results primarily suggest profound impact of cholesterol level on vitamin D status in CRC. However, our results suggest that low 25(OH)D3 might independently contribute to development of poorly differentiated tumor.

Vitamin D and evolution: Pharmacologic implications

Vitamin D₃ is produced non-enzymatically when the cholesterol precursor 7-dehydrocholesterol is exposed to UV-B, i.e., evolutionary the first function of the molecule was that of an UV-B radiation scavenging end product. Vitamin D endocrinology started when some 550 million years ago first species developed a vitamin D receptor (VDR) that binds with high affinity the vitamin D metabolite 1α,25-dihydroxyvitamin D₃. VDR evolved from a subfamily of nuclear receptors sensing the levels of cholesterol derivatives, such as bile acids, and controlling metabolic genes supporting cellular processes, such as innate and adaptive immunity. During vertebrate evolution, the skeletal and adaptive immune system showed in part interesting synchronous development although adaptive immunity is evolutionary older. There are bidirectional osteoimmune interactions between the immune system and bone metabolism, the regulation of both is under control of vitamin D. This diversity of physiological functions explains the pleiotropy of vitamin D signaling and opens the potential for various pharmacological applications of vitamin D as well as of its natural and synthetic derivatives. The overall impact of vitamin D on human health is demonstrated by the fact that the need for its efficient synthesis served in European hunter and gatherers as an evolutionary driver for increased 7-dehydrocholesterol levels, while light skin was established far later via populations from Anatolia and the northern Caucasus entering Europe 9000 and 5000 years ago, respectively. The later population settled preferentially in northern Europe and we hypothesize that that the introduction of high vitamin D responsiveness was an essential trait for surviving dark winters without suffering from the detrimental consequences of vitamin D deficiency.

Association of Vitamin D Pathway Genetic Variation and Thyroid Cancer

Vitamin D is mostly known for its role in bone and calcium metabolism. However, studies have suggested that it also has inhibitory effects on tumor development and progression. Genetic variants close to genes that encode crucial enzymes for the synthesis (DHCR7 rs12785878), metabolism (CYP2R1 rs2060793) and degradation (CYP24A1 rs6013897) of vitamin D have been associated with serum levels of vitamin D. The aim of this case-control study was to determine the effect of these variants in the vitamin D pathway on the susceptibility to thyroid cancer. Five hundred patients with differentiated thyroid cancer and 500 controls were genotyped for the DHCR7 rs12785878, CYP2R1 rs2060793, and CYP24A1 rs6013897 variants. Genotype and allele frequencies were compared between patients and controls. The DHCR7 rs12785878 minor allele was associated with thyroid cancer under an additive (OR 1.38, 95% CI 1.15–1.65, p = 0.0004) and codominant (OR 1.88, 95% CI 1.30–2.74, p = 0.0021) model. These findings suggest that DHCR7 polymorphisms may be associated with an increased risk of thyroid cancer due to an effect of this gene on circulating vitamin D levels.

Structural basis for human sterol isomerase in cholesterol biosynthesis and multidrug recognition

3-β-hydroxysteroid-Δ8, Δ7-isomerase, known as Emopamil-Binding Protein (EBP), is an endoplasmic reticulum membrane protein involved in cholesterol biosynthesis, autophagy, oligodendrocyte formation. The mutation on EBP can cause Conradi-Hunermann syndrome, an inborn error. Interestingly, EBP binds an abundance of structurally diverse pharmacologically active compounds, causing drug resistance. Here, we report two crystal structures of human EBP, one in complex with the anti-breast cancer drug tamoxifen and the other in complex with the cholesterol biosynthesis inhibitor U18666A. EBP adopts an unreported fold involving five transmembrane-helices (TMs) that creates a membrane cavity presenting a pharmacological binding site that accommodates multiple different ligands. The compounds exploit their positively-charged amine group to mimic the carbocationic sterol intermediate. Mutagenesis studies on specific residues abolish the isomerase activity and decrease the multidrug binding capacity. This work reveals the catalytic mechanism of EBP-mediated isomerization in cholesterol biosynthesis and how this protein may act as a multi-drug binder.

Vitamin D Receptor Polymorphism and DHCR7 Contribute to the Abnormal Interplay Between Vitamin D and Lipid Profile in Rheumatoid Arthritis

Emerging evidence suggests a role for 7-dehydrocholesterol reductase (DHCR7) in the crosstalk between cholesterol and vitamin D. Our aim was to evaluate the impact of vitamin D-related polymorphisms and DHCR7 levels in the association between vitamin D deficiency and altered lipid profile in rheumatoid arthritis (RA). Serum 25(OH)-vitamin D, DHCR7 levels and vitamin D-related polymorphisms (VDR-rs2228570, CYP27A1-rs933994, CYP2R1-rs10741657 and DHCR7-rs12785878) were analyzed in 211 RA patients,94 controls and in a prospective cohort of 13 RA patients undergoing TNFα-blockade. Vitamin D was decreased in RA (p < 0.001), correlated to HDL-cholesterol (r = 0.217, p < 0.001) and total-/HDL-cholesterol ratio (r = -0.227, p = 0.004). These correlations were restricted to the VDR-rs2228570 status. Vitamin D deficiency was associated with lower HDL-cholesterol (p = 0.028), higher tender (p = 0.005) and swollen (p = 0.002) joint counts, higher DAS28 (p = 0.018) and HAQ (p = 0.024) in AG/AA-patients but not in their GG-counterparts. The associations among DHCR7, vitamin D and lipid profile followed a seasonal pattern, decreased DHCR7 (p = 0.008) and vitamin D (p < 0.001) and increased total-cholesterol (p = 0.025) being found in winter/spring. Increasing vitamin D upon TNFα-blockade paralleled RA clinical improvement (r = -0.610, p = 0.027) and DHCR7 elevation (r = 0.766, p = 0.002). In conclusion, vitamin D-related polymorphisms and DHCR7 are pivotal to understand the complex, seasonal associations between vitamin D and lipid profile in RA.

Cholesterol increases protein levels of the E3 ligase MARCH6 and thereby stimulates protein degradation

The E3 ligase membrane-associated ring-CH-type finger 6 (MARCH6) is a polytopic enzyme bound to the membranes of the endoplasmic reticulum. It controls levels of several known protein substrates, including a key enzyme in cholesterol synthesis, squalene monooxygenase. However, beyond its own autodegradation, little is known about how MARCH6 itself is regulated. Using CRISPR/Cas9 gene-editing, MARCH6 overexpression, and immunoblotting, we found here that cholesterol stabilizes MARCH6 protein endogenously and in HEK293 cells that stably express MARCH6. Conversely, MARCH6-deficient HEK293 and HeLa cells lost their ability to degrade squalene monooxygenase in a cholesterol-dependent manner. The ability of cholesterol to boost MARCH6 did not seem to involve a putative sterol-sensing domain in this E3 ligase, but was abolished when either membrane extraction by valosin-containing protein (VCP/p97) or proteasomal degradation was inhibited. Furthermore, cholesterol-mediated stabilization was absent in two MARCH6 mutants that are unable to degrade themselves, indicating that cholesterol stabilizes MARCH6 protein by preventing its autodegradation. Experiments with chemical chaperones suggested that this likely occurs through a conformational change in MARCH6 upon cholesterol addition. Moreover, cholesterol reduced the levels of at least three known MARCH6 substrates, indicating that cholesterol-mediated MARCH6 stabilization increases its activity. Our findings highlight an important new role for cholesterol in controlling levels of proteins, extending the known repertoire of cholesterol homeostasis players.

Transcriptional profiling identifies novel regulators of macrophage polarization

Macrophages are key inflammatory immune cells that display dynamic phenotypes and functions in response to their local microenvironment. Major advances have occurred in understanding the transcriptional, epigenetic, and functional differences in various macrophage subsets by in vitro modeling and gene expression and epigenetic profiling for biomarker discovery. However, there is still no standardized protocol for macrophage polarization largely due to the lack of thorough validation of macrophage phenotypes following polarization. In addition, transcriptional regulation is recognized as a major mechanism governing differential macrophage polarization programs and as such, many genes have been identified to be associated with each macrophage subset. However, the functional role of many of these genes in macrophage polarization is still unknown. Moreover, the role of other regulatory mechanisms, such as DNA methylation, in macrophage polarization remains poorly understood. Here, we employed an optimized model of human M1 and M2 macrophage polarization which we used for large-scale transcriptional and DNA methylation profiling. We were unable to demonstrate a role for DNA methylation in macrophage polarization, as no significant changes were identified. However, we observed significant changes in the transcriptomes of M1 and M2 macrophages. Additionally, we identified numerous novel differentially regulated genes involved in macrophage polarization, including CYBB and DHCR7 which we show as important regulators of M1 and M2 macrophage polarization, respectively. Taken together, our improved in vitro human M1 and M2 macrophage model provides new understandings of the regulation of macrophage polarization and candidate macrophage biomarkers.

Neuroprotection by Heat Shock Factor-1 (HSF1) and Trimerization-Deficient Mutant Identifies Novel Alterations in Gene Expression

Heat shock factor-1 (HSF1) protects neurons from death caused by the accumulation of misfolded proteins by stimulating the transcription of genes encoding heat shock proteins (HSPs). This stimulatory action depends on the association of trimeric HSF1 to sequences within HSP gene promoters. However, we recently described that HSF-AB, a mutant form of HSF1 that is incapable of either homo-trimerization, association with HSP gene promoters, or stimulation of HSP expression, protects neurons just as efficiently as wild-type HSF1 suggesting an alternative neuroprotective mechanism that is activated by HSF1. To gain insight into the mechanism by which HSF1 and HSF1-AB protect neurons, we used RNA-Seq technology to identify transcriptional alterations induced by these proteins in either healthy cerebellar granule neurons (CGNs) or neurons primed to die. When HSF1 was ectopically-expressed in healthy neurons, 1,211 differentially expressed genes (DEGs) were identified with 1,075 being upregulated. When HSF1 was expressed in neurons primed to die, 393 genes were upregulated and 32 genes were downregulated. In sharp contrast, HSF1-AB altered expression of 13 genes in healthy neurons and only 6 genes in neurons under apoptotic conditions, suggesting that the neuroprotective effect of HSF1-AB may be mediated by a non-transcriptional mechanism. We validated the altered expression of 15 genes by QPCR. Although other studies have conducted RNA-Seq analyses to identify HSF1 targets, our study performed using primary neurons has identified a number of novel targets that may play a special role in brain maintenance and function.

Bi-allelic Mutations in LSS, Encoding Lanosterol Synthase, Cause Autosomal-Recessive Hypotrichosis Simplex

Hypotrichosis simplex (HS) is a rare form of hereditary alopecia characterized by childhood onset of diffuse and progressive scalp and body hair loss. Although research has identified a number of causal genes, genetic etiology in about 50% of HS cases remains unknown. The present report describes the identification via whole-exome sequencing of five different mutations in the gene LSS in three unrelated families with unexplained, potentially autosomal-recessive HS. Affected individuals showed sparse to absent lanugo-like scalp hair, sparse and brittle eyebrows, and sparse eyelashes and body hair. LSS encodes lanosterol synthase (LSS), which is a key enzyme in the cholesterol biosynthetic pathway. This pathway plays an important role in hair follicle biology. After localizing LSS protein expression in the hair shaft and bulb of the hair follicle, the impact of the mutations on keratinocytes was analyzed using immunoblotting and immunofluorescence. Interestingly, wild-type LSS was localized in the endoplasmic reticulum (ER), whereas mutant LSS proteins were localized in part outside of the ER. A plausible hypothesis is that this mislocalization has potential deleterious implications for hair follicle cells. Immunoblotting revealed no differences in the overall level of wild-type and mutant protein. Analyses of blood cholesterol levels revealed no decrease in cholesterol or cholesterol intermediates, thus supporting the previously proposed hypothesis of an alternative cholesterol pathway. The identification of LSS as causal gene for autosomal-recessive HS highlights the importance of the cholesterol pathway in hair follicle biology and may facilitate novel therapeutic approaches for hair loss disorders in general.

Recovery of lipid metabolic alterations in hepatitis C patients after viral clearance: Incomplete restoration with accelerated ω-oxidation

BACKGROUND

How hepatitis C virus (HCV)-associated lipid metabolic alterations recover after sustained virological response (SVR) remains elusive.

OBJECTIVE

The aforementioned recovery pattern was investigated.

METHODS

In a prospective cohort study of 438 chronic hepatitis C (CHC) patients with SVR after anti-HCV therapy, 164 sex- and age-matched genotype I (G1) and G2 patients underwent paired-serum liquid chromatography-tandem mass spectrometry analyses before and 24 weeks after therapy. Subjects without CHC served as controls (n = 100).

RESULTS

CHC patients had lower baseline lipid levels than controls. Among CHC patients, pre-therapy total cholesterol levels were positively associated with HCV RNA levels; G1 patients had higher pre-therapy HCV RNA levels than G2 patients. Repeated measures analysis of variance of CHC patients showed that lathosterol, lanosterol, total hydroxysphingomyelin, and total phosphatidylcholines levels, and total dicarboxyacylcarnitine/total acylcarnitine (indicators of ω-oxidation) and pre-β-lipoprotein ratios elevated 24 weeks after therapy compared with the levels before therapy. Levels of total lysophosphatidylcholines and α- and β-lipoprotein ratios decreased. Subgroup analyses showed elevated 7-dehydrocholesterol and lanosterol levels, particularly in G2 and male patients, who had broader spectra of altered phosphatidylcholines and acylcarnitines than G1 and female patients, respectively. Compared with controls, CHC patients had higher post-therapy levels of total lysophosphatidylcholines and hydroxysphingomyelins and ratios of total dicarboxyacylcarnitines/total acylcarnitines but lower cholesterol levels.

CONCLUSIONS

At 24 weeks after therapy, accelerated cholesterol biosynthesis, hepatic lipid export, ω-oxidation, and decreased systemic inflammation were noted in CHC patients with SVR, with greater efficiency in G2 and male patients. Regardless, HCV-associated lipid metabolic alterations required >24 weeks for restoration or were incompletely reversible after SVR.

Smith-Lemli-Opitz Syndrome in a newborn infant with developmental abnormalities and low endogenous cholesterol

BACKGROUND

Patients with Smith-Lemli-Opitz Syndrome (SLOS) have defective endogenous cholesterol synthesis, and present with decreased cholesterol levels and multiple developmental dysmorphologies.

CASE DESCRIPTION

A newborn infant with normal XY karyotype and normal microarray was born with multiple developmental defects and ambiguous genitalia. The patient was diagnosed with SLOS, following biochemical genetic analysis of serum 7-DHC concentrations. The clinical course of the patient was further complicated by the comorbidities associated with SLOS and the bacterial infections.

CONCLUSION

We provide a detailed biochemical profile of the SLOS patient. The report can help us further understand the pathological impacts of cholesterol synthesis deficiency and provide relevant clinical management with outcome of this rare genetic disorder.

Computational Investigation of the Missense Mutations in DHCR7 Gene Associated with Smith-Lemli-Opitz Syndrome

Smith-Lemli-Opitz syndrome (SLOS) is a cholesterol synthesis disorder characterized by physical, mental, and behavioral symptoms. It is caused by mutations in 7-dehydroxycholesterolreductase gene (DHCR7) encoding DHCR7 protein, which is the rate-limiting enzyme in the cholesterol synthesis pathway. Here we demonstrate that pathogenic mutations in DHCR7 protein are located either within the transmembrane region or are near the ligand-binding site, and are highly conserved among species. In contrast, non-pathogenic mutations observed in the general population are located outside the transmembrane region and have different effects on the conformational dynamics of DHCR7. All together, these observations suggest that the non-classified mutation R228Q is pathogenic. Our analyses indicate that pathogenic effects may affect protein stability and dynamics and alter the binding affinity and flexibility of the binding site.

Fetal and Maternal Genetic Variants Influencing Neonatal Vitamin D Status

OBJECTIVE

Several genetic polymorphisms determine vitamin D status. We aimed to estimate the strength of association of established 25-hydroyxvitamin D (25OHD)-associated variants in the mother and in the fetus, with 25OHD concentration in newborn umbilical cord plasma.

METHODS

We randomly selected 578 mother and child dyads from the prospective Norwegian Mother and Child Cohort study. 25OHD was assayed in maternal samples taken shortly after delivery and in cord samples. We genotyped the mother and child for single nucleotide polymorphisms in or near GC, DHCR7, CYP2R1, and CYP24A1, previously confirmed to be associated with 25OHD, and computed genetic risk score (GRS). The genetic associations were replicated in an independent sample of 594 subjects.

RESULTS

Although both fetal and maternal GRS were associated with cord 25OHD, only fetal GRS remained significantly associated with cord 25OHD in a regression model with maternal and fetal GRS simultaneously (1.6 nmol/L per fetal 25OHD-increasing allele; 95% confidence interval, 0.6 to 2.5, P = 0.0001). Two fetal single nucleotide polymorphisms in the GC gene (rs2282679 and rs222040) were the strongest genetic predictors of cord 25OHD [4.0 (2.1 to 5.9) and 3.0 (1.3 to 4.8) nmol/L per fetal allele, P < 0.001], followed by rs12785878 in DHCR7 [2.0 (0.1 to 3.8) nmol/L, P = 0.037]. The independent replication sample gave similar results. With fetal genotype included in a regression model with environmental factors, R2 for cord 25OHD was 0.28.

CONCLUSIONS

We show that fetal 25OHD-modifying genotype was a stronger predictor of cord 25OHD than corresponding maternal genotype. This raises interesting questions about fetal acquisition and placental transfer of 25OHD.