A novel multiplex analysis of filaggrin polymorphisms: a universally applicable method for genotyping

Filaggrin Mutation Status and Prevention of Atopic Dermatitis with Maternal Probiotic Supplementation

The World Allergy Organization recommends probiotics in the prevention of atopic dermatitis in high-risk populations. Mutations in the filaggrin gene (FLG) result in an increased risk of atopic dermatitis through disruption of the skin keratin layer. This exploratory study investigated whether the preventive effect of maternal probiotics was evident in children with and without FLG mutations. DNA was collected from children (n =   228) from the Probiotic in the Prevention of Allergy among Children in Trondheim (ProPACT) study. Samples were analysed for 3 common FLG mutations (R501X, R2447X, and 2282del4). Overall, 7% of children had heterozygous FLG mutations; each child had only one of the 3 mutations. Mutation status had no association with atopic dermatitis (RR = 1.1; 95% CI 0.5 to 2.3). The risk ratio (RR) for having atopic dermatitis following maternal probiotics was 0.6 (95% CI 0.4 to 0.9) and RR was similar if the child expressed an FLG mutation (RR = 0.6; 95% CI 0.1 to 4.1) or wildtype FLG (RR = 0.6; 95% CI 0.4 to 0.9). The preventive  effect of probiotics for atopic dermatitis was also evident in children without FLG mutation. Larger confirmatory studies are needed.

The association between Staphylococcus aureus colonization on cheek skin at 2 months and subsequent atopic dermatitis in a prospective birth cohort

BACKGROUND

Staphylococcus aureus may worsen already established atopic dermatitis (AD), but its primary role in the aetiopathogenesis and severity of AD is unclear.

OBJECTIVES

To compare the prevalence of S. aureus colonization in early infancy in children who developed AD during the first 2 years of life with children who did not.

METHODS

In this prospective birth cohort study, which included 450 infants, we analysed bacterial swabs collected from cheek skin at 0 and 2 months of age. The development of AD, and its severity, was diagnosed by a physician and monitored prospectively for 2 years. Information on parental atopy, filaggrin gene mutation status and use of antibiotics and emollients was included in the analyses.

RESULTS

At birth, the occurrence of S. aureus colonization was similar in infants who developed subsequent AD and those who did not. At 2 months of age, S. aureus colonization was more common in children who later developed AD (adjusted hazard ratio 1.97, 95% confidence interval 1.21-3.19; P = 0.006). No association was found between S. aureus colonization and AD severity or age at onset.

CONCLUSIONS

It remains unknown whether colonization with S. aureus may directly increase the risk of AD, or whether it should be considered as secondary to skin barrier impairment or a skewed immune activity, but according to our findings, S. aureus colonization is more commonly increased at 2 months of age in children who later developed AD.

Reduced Skin Microbiome Diversity in Infancy Is Associated with Increased Risk of Atopic Dermatitis in High-Risk Children

It is currently unknown whether alterations in the skin microbiome exist before development of atopic dermatitis (AD). In this prospective Danish birth cohort of 300 children, we examined whether skin microbiome alterations during the first 2 months of life were associated with an increased risk of AD in the first 2 years and its severity after adjustment for environmental factors and selected skin chemokine and natural moisturizing factor levels. We found no overall association between the skin microbiome at birth and age 2 months and AD during the first 2 years of life. However, when restricting the analysis to children with at least one parent with atopy, a lower alpha diversity at age 2 months was associated with an increased risk of AD (adjusted hazard ratio = 1.7, 95% confidence interval = 1.1-2.6). We observed a stronger association in children where both parents had atopy (adjusted hazard ratio = 4.4, 95% confidence interval = 1.1-18.2). The putative pathogenic role of changes in the skin microbiome on AD risk remains uncertain but may play a role in those with an atopic predisposition.

Skin biomarkers predict development of atopic dermatitis in infancy

BACKGROUND

There is currently no insight into biomarkers that can predict the onset of pediatric atopic dermatitis (AD).

METHODS

Nested in a prospective birth cohort study that examined the occurrence of physician-diagnosed AD in 300 children, 44 random children with onset of AD in the first year of life were matched on sex and season of birth with 44 children who did not develop AD. Natural moisturizing factor (NMF), corneocyte surface protrusions, cytokines, free sphingoid bases (SBs) of different chain lengths and their ceramides were analyzed from tape strips collected at 2 months of age before onset of AD using liquid chromatography, atomic force microscopy, multiplex immunoassay, and liquid chromatography mass spectrometry, respectively.

RESULTS

Significant alterations were observed for four lipid markers, with phytosphingosine ([P]) levels being significantly lower in children who developed AD compared with children who did not (median 240 pmol/mg vs. 540 pmol/mg, p < 0.001). The two groups of children differed in the relative amounts of SB of different chain lengths (C17, C18 and C20). Thymus- and activation-regulated chemokine (TARC/CCL17) was slightly higher in children who developed AD, whereas NMF and corneocyte surface texture were similar. AD severity assessed by the eczema area and severity index (EASI) at disease onset was 4.2 (2.0;7.2). [P] had the highest prediction accuracy among the biomarkers (75.6%), whereas the combination of 5 lipid ratios gave an accuracy of 89.4%.

CONCLUSION

This study showed that levels and SB chain length were altered in infants who later developed AD, and that TARC/CCL17 levels were higher.

Skin TARC/CCL17 increase precedes the development of childhood atopic dermatitis

BACKGROUND

It is unknown whether skin biomarkers collected in infancy can predict the onset of atopic dermatitis (AD) and be used in future prevention trials to identify children at risk.

OBJECTIVES

This study sought to examine whether skin biomarkers can predict AD during the first 2 years of life.

METHODS

This study enrolled 300 term and 150 preterm children at birth and followed for AD until the age of 2 years. Skin tape strips were collected at 0 to 3 days and 2 months of age and analyzed for selected immune and barrier biomarkers. Hazard ratio (HR) with 95% confidence interval (CI) using Cox regression was calculated for the risk of AD.

RESULTS

The 2-year prevalence of AD was 34.6% (99 of 286) and 21.2% (25 of 118) among term and preterm children, respectively. Skin biomarkers collected at birth did not predict AD. Elevated thymus- and activation-regulated chemokine/C-C motif chemokine ligand 17 -levels collected at 2 months of age increased the overall risk of AD (HR: 2.11; 95% CI: 1.36-3.26; P = .0008) and moderate-to-severe AD (HR: 4.97; 95% CI: 2.09-11.80; P = .0003). IL-8 and IL-18 predicted moderate-to-severe AD. Low filaggrin degradation product levels increased the risk of AD (HR: 2.04; 95% CI: 1.32-3.15; P = .001). Elevated biomarker levels at 2 months predicted AD at other skin sites and many months after collection.

CONCLUSIONS

This study showed that noninvasively collected skin biomarkers of barrier and immune pathways can precede the onset of AD.

Differences in Occurrence, Risk Factors and Severity of Early-onset Atopic Dermatitis among Preterm and Term Children

This prospective birth cohort followed 150 preterm and 300 term newborns during the first year of life to assess possible differences in risk factors, age at onset, anatomical location, and severity of atopic dermatitis. Atopic dermatitis was diagnosed clinically, and severity was assessed using Eczema Area Severity Index (EASI). DNA was analysed for filaggrin gene mutations. Parents were asked about environmental exposures and emollient use. Atopic dermatitis during the first year of life was observed in 21.2% of children and was more common in term children compared with preterm children (26.7% vs 11.7%, p < 0.001), with lower age of onset (4 vs 6 months, p < 0.05) and more severe disease at onset (EASI: 4.8 vs 0.4, p < 0.0005). Environmental risk factors for atopic dermatitis were essentially similar for preterm and term born children, apart from winter and autumn births. Filaggrin gene mutations were less common in preterm than term children (4.1% vs 9.2%, p = 0.06).

Assessment of biomarkers in pediatric atopic dermatitis by tape strips and skin biopsies

BACKGROUND

The cytokine profile of atopic dermatitis (AD) depends on age, ethnicity, and disease severity. This study examined biomarkers in children with AD collected by tape strips and skin biopsies, and examined whether the levels differed with filaggrin genotype, disease severity, and food allergy.

METHODS

Twenty-five children aged 2-14 years with AD were clinically examined. Skin biopsies were collected from lesional skin and tape strips were collected from lesional and non-lesional skin. We analyzed natural moisturizing factor (NMF) and 17 immune markers represented by mRNA levels in skin biopsies and protein levels in tape strips. Common filaggrin gene mutations were examined in all children.

RESULTS

The cytokine profile in lesional skin was dominated by a T helper (Th) 2 response in skin biopsies, and by a general increase in innate inflammation markers (interleukin (IL)-1α, IL-1β, IL-8, IL-18) along with TARC and CTACK in tape strips. The levels of TARC, CTACK, IL-8, IL-18 showed significant correlation with AD severity in both lesional and non-lesional tape stripped skin, while no significant correlations were observed in skin biopsy data. In tape strips from lesional and non-lesional skin, the levels of NMF and selected cytokines differed significantly between children with and without FLG mutations and food allergy.

CONCLUSION

Sampling of the stratum corneum with non-invasive tape strips can be used to identify biomarkers that are associated with disease severity, food allergy and FLG mutations. Skin biopsies showed robust Th2 signature but was inferior for association analysis regarding severity.

'Barrier dysfunction in Atopic newBorns studY' (BABY): protocol of a Danish prospective birth cohort study

INTRODUCTION

Skin barrier development and dysfunction in premature and mature newborns is important for the risk of atopic dermatitis (AD).

METHODS AND ANALYSIS

The Barrier dysfunction in Atopic newBorns studY (BABY) Cohort is a prospective birth cohort study of 150 preterm children (gestational age (GA) below 37+0) and 300 term children (GA 37+0 to 41+6). Skin barrier is assessed through transepidermal water loss, tape stripping, Raman-spectroscopy and microbiome sampling. Clinical examinations are done and DNA from buccal swabs is collected for genetic analyses. Thymus size is assessed by ultrasound examination. Information on pregnancy, delivery, parental exposures and diseases are collected, and structured telephone interviews are conducted at 18 and 24 months to assess exogenous exposures in the child and onset of AD. Hanifin and Rajka criteria as well as The UK Working Party's Diagnostic Criteria for Atopic Dermatitis are used to diagnose AD. Severity of AD is assessed using the Eczema Area and Severity Index (EASI) and Patient Oriented Eczema Measure (POEM).

ETHICS AND DISSEMINATION

The study is approved by the scientific Ethical Committee of the Capital Region (H-16042289 and H-16042294).Outcomes will be presented at national and international conferences and in peer-reviewed publications.

Urinary excretion of phenols, parabens and benzophenones in young men: Associations to reproductive hormones and semen quality are modified by mutations in the Filaggrin gene

BACKGROUND

The filaggrin gene (FLG) encodes an epidermal protein, filaggrin, which is important for normal skin barrier functions. We previously showed that FLG loss-of-function mutation carriers have a higher internal exposure to some non-persistent chemicals such as certain phthalates and parabens, suggesting increased trans-epidermal penetration. Several groups of non-persistent chemicals are suspected endocrine disrupters with potential to affect testicular function.

OBJECTIVES

To investigate associations between exposure to non-persistent chemicals and testicular function in young Danish men with and without FLG mutations.

METHODS

We measured urinary concentrations of bisphenol A (BPA) and other simple phenols, parabens, and UV filters including benzophenones (BP-1, BP-3 and 4-HBP) in men genotyped for FLG R501X, 2282del4, and R2447X loss-of-function mutations; in total 65 mutation carriers and 130 non-carriers (controls) were included. Outcomes were markers of testicular function, assessed by serum reproductive hormones and semen quality.

RESULTS

We found that associations between urinary chemical concentrations and outcomes were different in cases and controls. Within the group of FLG mutation carriers, higher urinary concentrations of BPA, BP-1 and BP-3 were associated with higher testosterone and estradiol serum levels and lower FSH. Similar trends in hormone levels were observed for FLG mutation carriers with measurable levels of 4-HBP compared to those who had no detectable levels of urinary 4-HBP. Furthermore, those in the highest urinary BPA quartile had lower sperm motility than those in the lower quartiles. None of these associations were evident in the control group. In the control group, however, lower sperm motility and sperm concentration were observed in the men with detectable urinary 4-HBP compared to the men non-detectable urinary 4-HBP. We found no association between any parabens and outcomes, nor for the other measured phenols or UV filters.

CONCLUSIONS

Associations between male reproductive health parameters and urinary levels of BPA and benzophenones such as BP-3, BP-1 and 4-HBP were observed in FLG mutation carriers but not in controls from the same study population. This difference between FLG mutation carriers and non-carriers is not explained solely by differences in exposure levels of the examined compounds as e.g. BPA and 4-HBP urinary levels did not differ between the two groups. We hypothesise that effects of exposure to these compounds may be modulated in FLG mutation carriers by either different levels of co-exposures or by route of uptake, with a higher fraction of the uptake by dermal uptake.

Poor agreement in questionnaire-based diagnostic criteria for adult atopic dermatitis is a challenge when examining cardiovascular comorbidity

BACKGROUND

The association between atopic dermatitis (AD) and cardio-metabolic risk factors is not yet established. Furthermore, no validated questionnaire-based method of identifying adults with AD is currently available.

OBJECTIVES

To assess the cardio-metabolic risk in adults with a history of AD using 3 different questionnaire-based diagnostic criteria.

METHODS

We utilized data from a general population study including questionnaire data and objective measurements of 9656 Danish adults. To identify adults with a history of AD, we used a question regarding physician-diagnosed AD and 2 versions of the UK Working Party Diagnostic Criteria. Associations between AD status and cardio-metabolic endpoints were estimated using survey weighted logistic and linear regression analysis.

RESULTS

We identified 462 (4.8%) adults with self-reported physician-diagnosed AD, whereas 903 (9.4%) and 226 (2.3%) had AD according to the UK Working Party Criteria when at least 2 and 3of 4 minor criteria were fulfilled. The populations were not comparable in terms of occurrence of cardio-metabolic risk factors. For example, the prevalence of obesity was lower in participants with physician-diagnosed AD but overall higher in UK 2/4 and UK 3/4.

CONCLUSION

Due to the heterogeneity in the captured study populations in terms of the studied outcomes and absence of a gold standard, no conclusions regarding the cardio-metabolic risk in adults with AD in a general population could be made. This study serves as an example of the challenges that are often encountered in questionnaire-based epidemiologic studies and highlights the need of better definitions for this patient group.

Children with atopic dermatitis and frequent emollient use have increased urinary levels of low-molecular-weight phthalate metabolites and parabens

BACKGROUND

Parabens may be added to cosmetic and personal care products for preservation purposes. Low-molecular weight (LMW) phthalate diesters function as plasticizers, fixatives or solvents in such products, but may also be found in small quantities as contaminants from plastic containers.

OBJECTIVE

To evaluate the association between emollient use, atopic dermatitis and FLG mutations, respectively, with urinary concentrations of phthalate metabolites and parabens in Danish children.

METHODS

Eight hundred and forty-five Danish children 4-9 years of age were studied. Urinary concentrations of phthalate metabolites and parabens were determined, and children were genotyped for common FLG loss-of-function mutations. Information about atopic dermatitis and use of emollients was obtained from questionnaires completed by parents.

RESULTS

The prevalence of atopic dermatitis was 16.1%. Phthalate metabolite and paraben levels were generally higher in children with frequent use of emollients compared to uncommon users, reaching statistical significance for some LMW phthalates and parabens. While there was no association with common FLG mutations, children with atopic dermatitis had significantly higher urinary levels of one LMW phthalate and two parabens, respectively, when compared to children without atopic dermatitis.

CONCLUSION

Emollient use and atopic dermatitis were associated with modestly increased internal LMW phthalate and paraben exposure in 4-9 year old children. It is unknown whether the difference is explained by increased use of the specific emollients that are used to treat pruritic and inflamed skin, and/or whether the impaired skin barrier allows chemicals to penetrate more easily. Moreover, the putative toxicological burden is unknown.

Exposure to phenols, parabens and UV filters: Associations with loss-of-function mutations in the filaggrin gene in men from the general population

BACKGROUND

Filaggrin is an epidermal protein that is important for normal skin barrier functions. Up to 10% of Europeans and Asians carry filaggrin gene (FLG) loss-of function mutations that appear to facilitate trans-epidermal penetration of certain chemicals. We previously showed that mutation carriers have higher internal exposure to certain phthalates, compared to controls, and hypothesized that they could have increased trans-epidermal penetration of other chemicals.

OBJECTIVES

We investigated exposure to non-persistent chemicals in young Danish men with and without FLG mutations.

METHODS

Concentrations of eight simple phenols, six parabens and nine UV filters were analysed in urine from 65 FLG loss-of-function mutation carriers and 130 non-carriers (controls). Regression analyses, controlling for urinary dilution and confounders, were performed to estimate associations between FLG mutation status and chemical concentrations in urine.

RESULTS

FLG mutation carriers had 80% (13-180%) higher urinary concentrations of methyl paraben (MeP) and 91% (13-219%) higher concentrations of n-propyl paraben (n-PrP) than controls. For 13 compounds, levels were higher in FLG mutation carriers, although differences were only statistically significant for MeP and n-PrP. Combined statistical analysis of concentrations of all the 18 compounds that were detectable in >10% of subjects, suggested that concentrations were generally higher in mutation carriers (p=0.03).

CONCLUSION

FLG loss-of-function mutation carriers have a higher internal exposure to some non-persistent chemicals, independently of atopic dermatitis. This may be due to increased trans-epidermal absorption and/or higher exposure, and mutation carriers may constitute a group susceptible to increased absorption of chemicals and topical medication.

Filaggrin loss-of-function mutations, atopic dermatitis and risk of actinic keratosis: results from two cross-sectional studies

BACKGROUND

Common loss-of-function mutations in filaggrin gene (FLG) represent a strong genetic risk factor for atopic dermatitis (AD). Homozygous mutation carriers typically display ichthyosis vulgaris (IV) and many have concomitant AD. Previously, homozygous, but not heterozygous, filaggrin gene mutations have been associated with squamous cell carcinomas.

OBJECTIVE

The first objective was to examine the association between FLG mutations and actinic keratosis (AK). The second objective was to investigate the occurrence of AK in patients with IV and AD, respectively.

METHODS

FLG mutation status in patients with AK was compared with controls from the general population. Furthermore, based on nationwide data from Danish registers, we compared the risk of AK in patients with IV, AD and psoriasis, respectively.

RESULTS

The prevalence of homozygous FLG mutations was significantly higher in the AK group (n = 4, 0.8%) in comparison with the control group (n = 18, 0.2%), whereas the prevalence of heterozygous FLG mutations was lower. In hospital registry data, patients with AD exhibited an increased risk of AK than did psoriasis controls (adjusted OR 1.46; [95% CI 1.12-1.90]), whereas no difference in risk was observed between patients with IV and AD.

CONCLUSIONS

This study indicates an increased susceptibility to AK in individuals with homozygous, but not heterozygous, FLG mutations and in patients with AD compared to psoriasis. Whether a reduction or absence of epidermal filaggrin could contribute to the susceptibility to AK in patients with IV and AD is unknown and additional research is needed to further explore this relationship.

Filaggrin gene mutations and the distribution of filaggrin in oral mucosa of patients with oral lichen planus and healthy controls

BACKGROUND

Lichen planus (LP) is a chronic inflammatory disease of unknown aetiology affecting the skin and oral mucosa. Oral lichenoid lesions (OLLs), like oral contact reactions, may resemble oral lichen planus (OLP) both clinically and histopathologically. As OLP and OLL are hyperkeratotic diseases and filaggrin is essential to keratinization, the distribution of filaggrin may be altered in these lesions.

OBJECTIVES

To investigate whether patients with OLP/OLL have (i) altered distribution of filaggrin in the oral mucosa; (ii) a higher incidence of mutations in the filaggrin gene (FLG); (iii) active dermatoses, apart from cutaneous LP, than healthy controls; and (iv) patients with OLP/OLL and a defect in the FLG have more widespread oral lesions and report more symptoms than OLP/OLL patients without a concomitant defect in the FLG.

METHODS

Forty-nine Caucasian patients (42 women and 7 men, mean age 61.0 ± 10.3 years), with symptomatic OLP, OLL or stomatitis, and 29 matched healthy controls underwent a clinical oral and dermatological examination, oral mucosal biopsy and filaggrin genotyping (testing for R2447X, R501X, 2282del4). Smear tests for Candida spp. were performed in all patients to exclude oral candidiasis. Immunohistochemistry were performed using poly- and monoclonal filaggrin antibodies.

RESULTS

The immunoreactivity for filaggrin was significantly more intense in the oral mucosa in the patients with OLP/OLL compared with healthy controls (P = 0.000025). No difference was noted in the incidence of defects in the FLG and active dermatoses between patients and healthy controls. No difference was noted in extension and number of symptoms reported by patients with OLP/OLL with or without a concomitant defect in the FLG.

CONCLUSION

OLP/OLL is associated with an altered distribution of filaggrin in the oral mucosa independently of defects in the FLG. Patients with OLP/OLL did not display more active dermatoses other than cutaneous LP when compared to healthy controls.

Filaggrin gene loss-of-function mutations explain discordance of atopic dermatitis within dizygotic twin pairs

OBJECTIVES

This study was designed to examine the association between loss-of-function mutations in the filaggrin gene (FLG) and atopic dermatitis (AD) and asthma in adult twins.

METHODS

A previously well-characterized cohort of 575 adult twins were genotyped for the loss-of-function mutations in FLG (R501X, 2282del4 and R2447X) most common among northern Europeans. Subjects were examined for symptoms of atopic diseases as well as for lung function, airway responsiveness, and atopy.

RESULTS

In the whole population of twins, the risk for AD was significantly increased in individuals with FLG mutations in comparison with wild-type carriers (34.3% vs. 21.8%) after adjustment for possible confounders (odds ratio [OR] 1.92, 95% confidence interval [CI] 1.07-3.41; P = 0.028). A significant association was also observed for persistent AD (OR 2.10, 95% CI 1.02-4.36; P = 0.046). There were no significant differences in risk for asthma by FLG mutation status in individuals with and without AD, respectively (P-value for interaction, 0.595). In 11 dizygotic twin pairs discordant for FLG mutation status, risk for AD was higher in the twin carrying the FLG mutation (five of 11 [45.5%] twins had developed AD) than in the non-carrier co-twin (two of 11 [18.2%] twins had developed AD) (OR 2.50, 95% CI 0.45-13.85; P = 0.293). FLG status did not explain a significant proportion of the variation in AD (P = 0.328) or asthma (P = 0.321).

CONCLUSIONS

Filaggrin gene mutations are risk factors for the presence and persistence of AD and explain the discordance of AD within dizygotic twin pairs.

Distinct molecular signatures of mild extrinsic and intrinsic atopic dermatitis

Atopic dermatitis (AD) is a common inflammatory skin disease with underlying defects in epidermal function and immune responses. In this study, we used microarray analysis to investigate differences in gene expression in lesional skin from patients with mild extrinsic or intrinsic AD compared to skin from healthy controls and from lesional psoriasis skin. The primary aim was to identify differentially expressed genes involved in skin barrier formation and inflammation, and to compare our results with those reported for patients with moderate and severe AD. In contrast to severe AD, expression of the majority of genes associated with skin barrier formation was unchanged or upregulated in patients with mild AD compared to normal healthy skin. Among these, no significant differences in the expression of filaggrin (FLG) and loricrin at both mRNA and protein level were found in lesional skin from patients with mild AD, despite the presence of heterozygous FLG mutations in the majority of patients with mild extrinsic AD. Several inflammation-associated genes such as S100A9, MMP12, CXCL10 and CCL18 were highly expressed in lesional skin from patients with mild psoriasis and were also increased in patients with mild extrinsic and intrinsic AD similar to previous reports for severe AD. Interestingly, expression of genes involved in inflammatory responses in intrinsic AD resembled that of psoriasis more than that of extrinsic AD. Overall, differences in expression of inflammation-associated genes found among patients with mild intrinsic and extrinsic AD correlated with previous findings for patients with severe intrinsic and extrinsic AD.

Xerosis is associated with asthma in men independent of atopic dermatitis and filaggrin gene mutations

BACKGROUND

Epidermal filaggrin deficiency due to common filaggrin gene (FLG) mutations causes xerosis and strongly increases the risk of atopic dermatitis and even asthma. However, it is unknown whether xerosis independent of FLG mutations could also increase the risk of asthma.

OBJECTIVE

To evaluate whether generalized xerosis was associated with asthma, independent of atopic dermatitis and common FLG mutations in a cross-sectional study on adult Danes.

METHODS

A total of 3396 adults from the general population participated in a health examination. Lung function and serum-specific IgE levels to inhalant allergens were measured and information on xerosis and atopic diseases was obtained by means of a questionnaire. Participants were genotypes for the three most common FLG mutations in Northern Europeans: R501X, 2282del4 and R2447X.

RESULTS

Fully adjusted logistic regression analyses showed that asthma (either current or at some point in life) was significantly associated with reporting generalized xerosis (OR 1.32; 95% CI 1.02-1.72). The association was stronger in men (OR 1.79; 95% CI 1.13-2.84) when compared to women (OR 1.18; 95% CI 0.86-1.62). Furthermore, a significant association was observed between xerosis and 'allergic asthma' in men (OR 2.13; 95% CI 1.08-4.19).

CONCLUSION

Our findings indicate an association between xerosis and asthma in men independent of atopic dermatitis and FLG mutations. Both facilitated allergen sensitization and secondary degradation of filaggrin following T-helper cell 2 inflammation might be key elements to understanding this relationship.

Common filaggrin gene mutations and risk of cervical cancer

BACKGROUND

As carriers of filaggrin gene (FLG) mutations may have a compromised cervical mucosal barrier against human papillomavirus infection, our primary objective was to study their risk of cervical cancer.

METHODS

We genotyped 586 cervical cancer patients for the two most common FLG mutations, R501X and 2282del4, using blood from the Copenhagen Hospital Biobank, Denmark. Controls (n = 8050) were genotyped in previous population-based studies. Information on cervical cancer, mortality and emigration were obtained from national registers. Odds ratios (OR) were estimated by logistic regression with adjustment for age at blood sampling, and weighted by the genotype-specific inverse probability of death between diagnosis and sampling. Hazard ratios (HR) were estimated by Cox regression with time since diagnosis as underlying time, and with adjustment for age at diagnosis and stratification by cancer stage.

RESULTS

The primary results showed that FLG mutations were not associated with the risk of cervical cancer (6.3% of cases and 7.7% of controls were carriers; OR adjusted 0.81, 95% CI 0.57-1.14; OR adjusted+ weighted 0.96, 95% CI 0.58-1.57). Among cases, FLG mutations increased mortality due to cervical cancer (HR 4.55, 95% CI 1.70-12.2), however, the association was reduced after stratification by cancer stage (HR 2.53, 95% CI 0.84-7.59).

CONCLUSION

Carriage of FLG mutations was not associated with the risk of cervical cancer.

Skin pH, atopic dermatitis, and filaggrin mutations

BACKGROUND

The acidic pH of the skin plays a role in antimicrobial defense by regulating the bacterial skin flora and aspects of barrier. Filaggrin is a co-factor in maintaining a low skin pH because of its degradation into acidic amino acids. Accordingly, lack of filaggrin due to filaggrin mutations may influence skin pH.

OBJECTIVE

We aimed to determine the epidermal pH in different groups stratified by filaggrin mutations and atopic dermatitis. Further, we investigated the changes in pH according to severity of mutational status among patients with dermatitis, irrespective of skin condition.

METHODS

pH was measured with a multiprobe system pH probe (PH 905), and the study population was composed of 67 individuals, who had all been genotyped for 3 filaggrin mutations (R501X, 2282del4, R2447X).

RESULTS

We found no clear pattern in relation to filaggrin mutation carrier status. Individuals with wild-type filaggrin displayed both the most acidic and most alkaline values independent of concomitant skin disease; however, no statistical differences between the groups were found.

CONCLUSIONS

The lack of significant diversity in skin pH in relation to filaggrin mutation carrier status suggests that the effect of filaggrin mutations on skin pH is not pronounced.

Filaggrin loss-of-function mutations and incident cancer: a population-based study

BACKGROUND

Loss-of-function mutations in the filaggrin gene (FLG) could have opposing effects on cancer risk, as mutations are associated with both 10% higher serum vitamin D levels, which may protect against cancer, and with impaired skin barrier function, which may lead to higher cancer susceptibility.

OBJECTIVES

To investigate the association of the FLG genotype and cancer types in four population-based cohorts.

METHODS

A total of 13,376 individuals were genotyped for FLG mutations. Information on cancer was obtained from the Danish Cancer Registry. Persons with a history of cancer at baseline were excluded from prospective analyses.

RESULTS

There were 1339 incident cancers (median follow-up 11·4 years). The hazard ratios (HRs) and 95% confidence intervals (CIs) for FLG mutation carriers vs. wild types were: for any cancer (HR 0·95, 95% CI 0·78-1·16), any cancer excluding nonmelanoma skin cancer (NMSC) (HR 1·05, 95% CI 0·84-1·31), head and neck cancer (HR 1·72, 95% CI 0·71-4·15), colorectal cancer (HR 0·82, 95% CI 0·44-1·52), bronchus and lung cancer (HR 1·34, 95% CI 0·77-2·33), breast cancer (HR 0·58, 95% CI 0·30-1·14), uterine cancer (HR 0·42, 95% CI 0·06-3·10), prostate cancer (HR 1·09, 95% CI 0·61-1·94), urinary cancer (HR 1·30, 95% CI 0·51-3·29), malignant melanoma (HR 1·03, 95% CI 0·41-2·58) and NMSC (HR 0·70, 95% CI 0·47-1·05). Among participants aged over 60 years at baseline, we found statistically significant lower risks of all cancers and NMSC among FLG mutation carriers.

CONCLUSIONS

The only significant associations between FLG loss-of-function mutations and cancer were in subgroup analyses.

Associations of filaggrin gene loss-of-function variants and human papillomavirus-related cancer and pre-cancer in Danish adults

Purpose

Filaggrin proteins are expressed in the skin, oral cavity, oesophagus, and cervical mucose. Loss-of-function mutations in the filaggrin gene (FLG) reduce filaggrin expression and cause an impaired skin barrier function. We hypothesized that FLG mutation carriers would be more susceptible to human papillomavirus (HPV) infection and thus a higher risk of HPV-related cancer and pre-cancer. We investigated the association of the FLG genotype with incidence of HPV-related cancer of cervix, vagina, vulva, penis, anus and head and neck, and pre-cancer of the cervix.

Methods

We included 13,376 persons from four population-based studies conducted in the same background population in Copenhagen, Denmark. Participants were genotyped for the most common FLG mutations in Europeans. Information on cancer was obtained from The Danish Cancer Registry until 11 July 2011.

Results

There were 489 cases of prevalent and 97 cases of incident HPV-related cancer and pre-cancer (median follow-up 11.5 years). There was a statistically significant association between FLG genotype and incident HPV-related cancer and pre-cancer with a hazard ratio, HR = 2.1 (95% confidence intervals, CI: 1.2, 3.7) for FLG mutation carriers vs. wild types.

Conclusions

FLG loss-of-function mutations were associated with higher incidence of HPV-related cancers and pre-cancers that are potentially screening and vaccine preventable.

Associations of filaggrin gene loss-of-function variants with urinary phthalate metabolites and testicular function in young Danish Men

BACKGROUND

Filaggrin is an epidermal protein that is crucial for skin barrier function. Up to 10% of Europeans and 5% of Asians carry at least one null allele in the filaggrin gene (FLG). Reduced expression of filaggrin in carriers of the null allele is associated with facilitated transfer of allergens across the epidermis. We hypothesized that these individuals may have increased transdermal uptake of endocrine disruptors, including phthalates.

OBJECTIVES

We investigated urinary excretion of phthalate metabolites and testicular function in young men with and without FLG loss-of-function variants in a cross-sectional study of 861 young men from the general Danish population.

METHODS

All men were genotyped for FLG R501X, 2282del4, and R2447X loss-of-function variants. We measured urinary concentrations of 14 phthalate metabolites and serum levels of reproductive hormones. We also evaluated semen quality.

RESULTS

Sixty-five men (7.5%) carried at least one FLG-null allele. FLG-null carriers had significantly higher urinary concentrations of several phthalate metabolites, including a 33% higher concentration of MnBP (mono-n-butyl phthalate; 95% CI: 16, 51%). FLG-null variants were not significantly associated with reproductive hormones or semen quality parameters.

CONCLUSION

This study provides evidence that carriers of FLG loss-of-function alleles may have higher internal exposure to phthalates, possibly due to increased transepidermal absorption. FLG loss-of-function variants may indicate susceptible populations for which special attention to transepidermal absorption of chemicals and medication may be warranted.

No association between loss-of-function mutations in filaggrin and diabetes, cardiovascular disease, and all-cause mortality

BACKGROUND

Common loss-of-function mutations in the filaggrin gene (FLG) are a major predisposing risk factor for atopic disease due to reduced epidermal filaggrin protein levels. We previously observed an association between these mutations and type 2 diabetes and hypothesized that an inherited impairment of skin barrier functions could facilitate low-grade inflammation and hence increase the risk of diabetes and cardiovascular disease. We examined the association between loss-of-function mutations in FLG and diabetes, stroke, ischemic heart disease (IHD), and all-cause mortality in the general population.

METHODS

The R501X and 2282del4 loss-of function mutations in FLG were genotyped in four Danish study populations including a total of 13373 adults aged 15-77 years. Two of the studies also genotyped the R2447X mutation. By linkage to Danish national central registers we obtained information for all participants on dates of diagnoses of diabetes, stroke, and IHD, as well as all-cause mortality. Data were analyzed by Cox proportional hazard models and combined by fixed effect meta-analyses.

RESULTS

In meta-analyses combining the results from the four individual studies, carriage of loss-of-function mutations in FLG was not associated with incident diabetes (hazard ratio (HR) (95% confidence intervals (CI)) = 0.95 (0.73, 1.23), stroke (HR (95% CI) = 1.27 (0.97, 1.65), ischemic heart disease (HR (95%CI) = 0.92 (0.71, 1.19), and all-cause mortality (HR (95%CI) = 1.02 (0.83, 1.25)). Similar results were obtained when including prevalent cases in logistic regression models.

CONCLUSION

Our results suggest that loss-of-function mutations in FLG are not associated with type 2 diabetes, cardiovascular disease, and all-cause mortality. However, larger studies with longer follow-up are needed to exclude any associations.

Investigating the causal effect of vitamin D on serum adiponectin using a Mendelian randomization approach

BACKGROUND/OBJECTIVES

The aim was to examine the causal effect of vitamin D on serum adiponectin using a multiple instrument Mendelian randomization approach.

SUBJECTS/METHODS

Serum 25-hydroxy vitamin D (25(OH)D) and serum total or high molecular weight (HMW) adiponectin were measured in two Danish population-based studies: the Inter99 study (6405 adults, 30-60 years) conducted in 1999-2001, and the MONICA10 study (2656 adults, 41-71 years) conducted in 1993-1994.

RESULTS

In the Inter99 study, serum 25(OH)D was positively associated with total adiponectin (the effect estimate in % per doubling of 25(OH)D was 4.78, 95% CI: 1.96, 7.68, P<0.001). Using variations in the vitamin D-binding protein gene and the filaggrin gene as instrumental variables, the causal effect in % was estimated to 61.46, 95% CI: 17.51, 120.28, P=0.003 higher adiponectin per doubling of 25(OH)D. In the MONICA10 cohort, no significant association was observed between the serum concentrations of 25(OH)D and HMW adiponectin (the effect estimate in % per doubling of 25(OH)D was -1.51, 95% CI: -5.80, 2.98, P=0.50), although the instrumental variables analysis to some extent supported a positive causal association (the effect estimate in % per doubling of 25(OH)D was 37.13, 95% CI: -3.67, 95.20, P=0.080).

CONCLUSIONS

The results indicate a possible causal association between serum 25(OH)D and total adiponectin. However, the association was not replicated for HMW adiponectin. Thus, further studies are needed to confirm a causal relationship.

Vitamin D status, filaggrin genotype, and cardiovascular risk factors: a Mendelian randomization approach

Background

Vitamin D deficiency is associated with increased cardiovascular disease risk in observational studies. Whether these associations are causal is not clear. Loss-of-function mutations in the filaggrin gene result in up to 10% higher serum vitamin D concentrations, supposedly due to a decreased UV-protection of the keratinocytes. We used a Mendelian randomization approach to estimate the causal effect of vitamin D status on serum lipids, blood pressure, body mass index, waist circumference, and the metabolic syndrome.

Methods

Three population based studies were included, Monica10 (2,656 individuals aged 40–71 years), Inter99 (6,784 individuals aged 30–60 years), and Health2006 (3,471 individuals aged 18–69 years) conducted in 1993–94, 1999–2001, and 2006–2008, respectively. Participants were genotyped for the two most common filaggrin gene mutations in European descendants R501X and 2282del4, in all three studies and further for the R2447X mutation in the Inter99 and Health2006 studies. Filaggrin genotype was used as instrumental variable for vitamin D status. Baseline measurements of serum 25-hydroxyvitamin D were performed in all three studies.

Results

Instrumental variable analyses showed a 23.8% (95% confidence interval, CI 3.0, 48.6) higher HDL cholesterol level and a 30.5% (95% CI: 0.8, 51.3) lower serum level of triglycerides per doubling of vitamin D. These associations were, however, not statistically significant when applying the Bonferroni adjusted significance level. The remaining lipids showed non-significant changes in a favorable direction. Doubling of vitamin D gave a non-significantly lower odds ratio = 0.26 (95% CI: 0.06, 1.17) of the metabolic syndrome. There were no statistically significant causal effects of vitamin D status on blood pressure, body mass index, or waist circumference.

Conclusion

Our results support a causal effect of higher vitamin D status on a more favorable lipid profile, although more studies in other populations are needed to confirm our results.