Association of fatty acids in serum phospholipids with hay fever, specific and total immunoglobulin E

Shared Genetic Liability Between Major Depressive Disorder and Atopic Diseases

Objectives

Deciphering the genetic relationships between major depressive disorder (MDD) and atopic diseases (asthma, hay fever, and eczema) may facilitate understanding of their biological mechanisms as well as the development of novel treatment regimens. Here we tested the genetic correlation between MDD and atopic diseases by linkage disequilibrium score regression.

Methods

A polygenic overlap analysis was performed to estimate shared genetic variations between the two diseases. Causal relationships between MDD and atopic diseases were investigated using two-sample bidirectional Mendelian randomization analysis. Genomic loci shared between MDD and atopic diseases were identified using cross-trait meta-analysis. Putative functional genes were evaluated by fine-mapping of transcriptome-wide associations.

Results

The polygenic analysis revealed approximately 15.8 thousand variants causally influencing MDD and 0.9 thousand variants influencing atopic diseases. Among these variants, approximately 0.8 thousand were shared between the two diseases. Mendelian randomization analysis indicates that genetic liability to MDD has a causal effect on atopic diseases (b = 0.22, p = 1.76 × 10^-6), while genetic liability to atopic diseases confers a weak causal effect on MDD (b = 0.05, p = 7.57 × 10^-3). Cross-trait meta-analyses of MDD and atopic diseases identified 18 shared genomic loci. Both fine-mapping of transcriptome-wide associations and analysis of existing literature suggest the estrogen receptor β-encoding gene ESR2 as one of the potential risk factors for both MDD and atopic diseases.

Conclusion

Our findings reveal shared genetic liability and causal links between MDD and atopic diseases, which shed light on the phenotypic relationship between MDD and atopic diseases.

Shared Genetic Liability Between Major Depressive Disorder and Atopic Diseases

OBJECTIVES

Deciphering the genetic relationships between major depressive disorder (MDD) and atopic diseases (asthma, hay fever, and eczema) may facilitate understanding of their biological mechanisms as well as the development of novel treatment regimens. Here we tested the genetic correlation between MDD and atopic diseases by linkage disequilibrium score regression.

METHODS

A polygenic overlap analysis was performed to estimate shared genetic variations between the two diseases. Causal relationships between MDD and atopic diseases were investigated using two-sample bidirectional Mendelian randomization analysis. Genomic loci shared between MDD and atopic diseases were identified using cross-trait meta-analysis. Putative functional genes were evaluated by fine-mapping of transcriptome-wide associations.

RESULTS

The polygenic analysis revealed approximately 15.8 thousand variants causally influencing MDD and 0.9 thousand variants influencing atopic diseases. Among these variants, approximately 0.8 thousand were shared between the two diseases. Mendelian randomization analysis indicates that genetic liability to MDD has a causal effect on atopic diseases (b = 0.22, p = 1.76 × 10^-6), while genetic liability to atopic diseases confers a weak causal effect on MDD (b = 0.05, p = 7.57 × 10^-3). Cross-trait meta-analyses of MDD and atopic diseases identified 18 shared genomic loci. Both fine-mapping of transcriptome-wide associations and analysis of existing literature suggest the estrogen receptor β-encoding gene ESR2 as one of the potential risk factors for both MDD and atopic diseases.

CONCLUSION

Our findings reveal shared genetic liability and causal links between MDD and atopic diseases, which shed light on the phenotypic relationship between MDD and atopic diseases.

FADS2 polymorphisms are associated with plasma arachidonic acid and estimated desaturase-5 activity in a cross-sectional study

Polymorphisms in FADS genes are associated with plasma long-chain polyunsaturated fatty acids (LC-PUFA) and modulate omega-6/omega-3 balance. We hypothesized that the FADS2 gene variants will be associated with lower product-to-precursor ratio in the fatty acid metabolic pathways. Thus, we explored FADS2 rs174593, rs174616, and rs174576 effects on plasma phospholipid fatty acid profile, markers of desaturase activities, and risk factors in a sample of apparently healthy Serbian adults. Food and nutrient intake data were compiled through 24 h recalls. Plasma phospholipid fatty acid content was assessed by gas-chromatography. Estimated desaturase activities were calculated as conversion rates towards LC-PUFA in omega-6 pathway. During the selection of FADS2 polymorphisms, we accounted for their positional and functional aspect. Genotyping was performed by Real-Time PCR. Multivariable-adjusted general linear and hierarchical regression models were applied. Study subjects (mean age = 40 ± 7 years, 70% who were overweight) had a median dietary omega-6/omega-3 ratio of 16.29. Alternative allele frequencies were 33%, 36%, and 51% for rs174593, rs174576, and rs174616, respectively. Addition of FADS2 alternative alleles was associated with lower plasma arachidonic acid (AA, C20:4 n-6, P < .001) and estimated desaturase-5 activity (P < .001), irrespective of gender, age, daily polyunsaturated/saturated fatty acid intake, and obesity. The rs174576 association with AA withstood multiple testing and additional adjustments for other variants (multivariable-adjusted β = -1.14 [95% CI: -2.25, -0.43]). None of the variants was associated with dietary intake, serum lipids, or obesity. We observed inverse associations between FADS2 variants and plasma AA but not omega-3 fatty acids in Serbian subjects, with rs174576 exhibiting the strongest relation.

Prenatal Omega-3 and Omega-6 Polyunsaturated Fatty Acids and Childhood Atopic Dermatitis

BACKGROUND

Atopic dermatitis is a common childhood disease, potentially influenced by prenatal nutritional exposures such as polyunsaturated fatty acids (PUFAs).

OBJECTIVE

In a racially diverse cohort, we hypothesized that childhood atopic dermatitis would be associated with higher prenatal omega-6 (n-6) and lower omega-3 (n-3) PUFAs.

METHODS

We included mother-child dyads, births 2006 to 2011, enrolled in the University of Tennessee Health Sciences Center Conditions Affecting Neurocognitive Development in Early Childhood cohort. Primary exposures included second trimester plasma n-3 and n-6 PUFA status and the ratio of the two (n-6:n-3). We assessed child current atopic dermatitis symptoms in the previous 12 months at age approximately 4 to 6 years. We investigated the association between PUFA exposures and atopic dermatitis using multivariable logistic regression, adjusting for potential confounders. We assessed for effect modification by maternal prenatal smoking, atopic disease history, and child sex.

RESULTS

Among 1131 women, 67% were African American and 42% had an atopic disease history; 17% of children had atopic dermatitis. Higher prenatal n-6 PUFAs were associated with increased relative odds of child atopic dermatitis (adjusted odds ratio: 1.25; confidence interval: 1.01-1.54 per interquartile range difference), and interaction models demonstrated that this association was seen in dyads in which the women had a history of atopic disease. Neither prenatal n-3 PUFAs nor n-6:n-3 were associated with child atopic dermatitis.

CONCLUSION

In this racially diverse cohort, higher second trimester n-6 PUFAs were associated with atopic dermatitis in children of women with atopy. PUFAs may represent a modifiable risk factor for atopic dermatitis, particularly in individuals with a familial predisposition.

Association of Polymorphism in Fatty Acid Desaturase Gene with the Risk of Type 2 Diabetes in Iranian Population

Background:

The type 2 diabetes is one of the most common autoimmune diseases. Due to a key role in the metabolism of unsaturated fatty acids such as arachidonic acid, one of the most important precursors of immunity mediators, fatty acid desaturase (FADS) genes could have an important impact in the development of type 2 diabetes.

Materials and Methods:

This study aimed to determine the relationship between polymorphisms rs174537 in FADS1 gene and rs174575 in FADS2 gene with type 2 diabetes in Iranian population. After extracting genomic DNA, the locations of mutations and allele types were identified with high-resolution melting (HRM)-polymerase chain reaction method. Then, association between these mutations with metabolic syndrome, dyslipidemia, and type 2 diabetes was investigated using χ² correlation coefficients for variables and logistic regression.

Results:

The results showed that among 50 diabetic participants, 68% of patients have the mutant allele for rs174537 in FADS1 gene. This rate is 26% for rs174575 in FADS2 gene. Based on the results, it seems that participants having rs174537 mutant allele are more prone to become diabetic but it has a beneficial effect on total and low-density lipoprotein cholesterol and participants having rs174575 mutant are less prone to become diabetic, and also, it leads to higher triglycerides and body mass index (obesity).

Conclusions:

Detecting FADS1 and FADS2, gene polymorphisms using HRM can be an anticipating tool for making decision on initiating lifestyle modifications to prevent type 2 diabetes.

Serum Phospholipid Fatty Acid Composition in Cystic Fibrosis Patients with and without Liver Cirrhosis

Background/Aims: Cystic fibrosis (CF) liver disease is the third most frequent cause of death in CF patients. Although it alters fatty acid (FA) metabolism, data concerning the profile of FA in CF patients with liver cirrhosis is lacking. This study aimed to assess the FA composition of serum phospholipids in CF patients with and without liver cirrhosis. Methods: The study comprised 25 CF patients with liver cirrhosis and 25 without it. We assessed Z-scores for body height and weight, lung function, exocrine pancreatic sufficiency and colonization with Pseudomonas aeruginosa. FAs' profile of serum glycerophospholipids was quantified by gas chromatography mass spectrometry. Results: In CF patients with liver cirrhosis, the levels of C16:0 were higher and the amounts of C20:2n-6, C20:3n-6, C20:4n-6, and all the n-3 polyunsaturated FAs (PUFAs) (C18:3n-3, C20:5n-3, C22:5n-3, C22:6n-3) were lower than those in CF subjects without liver cirrhosis. The n-6/n-3, C20:4n-6/C18:2n-6, total n-6/C18:2n-6, C20:5n-3/C18:3n-3 and total n-3/C18:3n-3 ratios did not differ between the 2 groups. Conclusions: Liver cirrhosis may associate with profound abnormalities in the composition of serum glycerophospholipids FAs in CF patients. None of the analyzed clinical factors could explain the greater prevalence of low levels of PUFAs in this CF subgroup.

Effects of omega-3 on matrix metalloproteinase-9, myoblast transplantation and satellite cell activation in dystrophin-deficient muscle fibers

In Duchenne muscular dystrophy (DMD), lack of dystrophin leads to progressive muscle degeneration, with DMD patients suffering from cardiorespiratory failure. Cell therapy is an alternative to life-long corticoid therapy. Satellite cells, the stem cells of skeletal muscles, do not completely compensate for the muscle damage in dystrophic muscles. Elevated levels of proinflammatory and profibrotic factors, such as metalloproteinase 9 (MMP-9), impair muscle regeneration, leading to extensive fibrosis and poor results with myoblast transplantation therapies. Omega-3 is an anti-inflammatory drug that protects against muscle degeneration in the mdx mouse model of DMD. In the present study, we test our hypothesis that omega-3 affects MMP-9 and thereby benefits muscle regeneration and myoblast transplantation in the mdx mouse. We observe that omega-3 reduces MMP-9 gene expression and improves myoblast engraftment, satellite cell activation, and muscle regeneration by mechanisms involving, at least in part, the regulation of macrophages, as shown here with the fluorescence-activated cell sorting technique. The present study demonstrates the benefits of omega-3 on satellite cell survival and muscle regeneration, further supporting its use in clinical trials and cell therapies in DMD.

Prenatal determinants of cord blood total immunoglobulin E levels in Mexican newborns

Asthma and allergic diseases have increased worldwide; however, etilogic factors for this increase are still poor. Prenatal consumptions of fatty acids are hypothesized, although few clinical trials in developing countries have been performed. This study was designed to identify predictors of immunoglobulin E (IgE) levels in cord blood of Mexican newborns. Total IgE was measured in umbilical cord blood from 613 infants whose mothers participated in a double-blind randomized controlled trial of 400 mg of docosahexaenoic acid or placebo from 18 to 22 weeks gestation through delivery. During pregnancy, information on sociodemographic characteristics, environmental exposures, and perceived maternal stress were obtained; a maternal blood sample was also collected to determine atopy via specific IgE levels. Logistic regression models were used to identify the main prenatal predictors of detectable total IgE levels in cord blood. IgE was detectable in cord blood from 344 (53.7%) infants; the main predictors in multivariate analyses were maternal atopy (odds ratio [OR] = 1.69; 95% CI, 1.19-2.42; p < 0.05) and pesticide use in the home (OR = 1.49; 95% CI, 1.04-2.14; p < 0.05). When stratified by maternal atopy, season of birth was a significant predictor in the atopic group only (OR = 2.48; 95% CI, 1.00-6.16; p < 0.05), and pesticide use was a significant predictor for infants born to nonatopic mothers (OR = 1.64; 95% CI, 1.07-2.51; p < 0.05). No differences were seen in the proportion of infants with detectable IgE by treatment group. Prenatal supplementation with omega-3 polyunsaturated fatty acid did not alter the detectable cord blood IgE levels. Maternal atopy and pesticide use during pregnancy are strong predictors of cord blood IgE levels in newborns. Clinical trial NCT00646360, www.clinicaltrials.gov.

Influence of genotype on the modulation of gene and protein expression by n-3 LC-PUFA in rats

It is becoming increasingly apparent that responsiveness to dietary fat composition is heterogeneous and dependent on the genetic make-up of the individual. The aim of this study was to evidence a genotype-related differential effect of n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) on the modulation of hepatic genes involved in cholesterol metabolism. Fourteen spontaneously hypertensive (SH) rats, which present a naturally occurring variation in the gene encoding for sterol responsive element binding protein 1 (SREBP-1), contributing to their inherited variation in lipid metabolism, and 14 Wistar-Kyoto (WK) rats were fed a control diet or an n-3 LC-PUFA enriched diet for 90 days. Plasma lipid profile, total lipid fatty acid composition in plasma and liver, and the expression of SREBP-1 and 2, 3-hydroxy-3-methyl-glutaryl-CoA reductase, low-density lipoprotein receptor, and acyl-CoA:cholesterol acyltransferase 2 encoding genes and proteins were determined. The positive effect of the enriched diet on the serum lipid profile, particularly on total cholesterol and triglyceride level, was clearly evidenced in both WK and SH rats, but n-3 LC-PUFA acted through a different modulation of gene and protein expression that appeared related to the genetic background. Our study evidences a different transcriptional effect of specific nutrients related to genetic variants.

n-3 Fatty acids inhibit transcription of human IL-13: implications for development of T helper type 2 immune responses

Fish oil supplementation during pregnancy has been associated with lower levels of cord blood IL-13, suggesting that the administration of n-3 fatty acids may attenuate the development of allergic disease. The present study aimed to investigate the mechanism by which n-3 fatty acid administration influences the production of IL-13. Pregnant BALB/c mice were fed nutritionally complete high-fat diets (15 %, w/w) with an n-3 fatty acid-enriched (DHA 1 %, w/w) or control diet (0 % DHA) immediately following delivery. Pups were exposed during suckling and weaned to the maternal diet for the remainder of the study. The production of IL-13, IL-4, IL-10 and interferon-γ from the splenocytes of ovalbumin (ova)-sensitised animals was assessed following in vitro ova stimulation or unstimulated conditions. Human T helper type 2 (Th2) cells were mitogen-stimulated in the presence or absence of DHA (10 μM) and assessed for IL-13 and IL-4 expression using intracellular flow cytometry. The influence on transcriptional activation was studied using a human IL-13 promoter reporter construct and electromobility shift assay. Ova-activated splenocytes from DHA-fed mice produced less IL-13 (57.2 (se 21.7) pg/ml) and IL-4 (7.33 (SE 3.4) pg/ml) compared with cells from the animals fed the control diet (161.5 (SE 45.0), P< 0.05; 33.2 (SE 11.8), P< 0.05). In vitro, DHA inhibited the expression of IL-13 protein from human Th2 cells as well as transcriptional activation and binding of the transcription factors cyclic AMP response element binding and activating transcription factor 2 to the human IL-13 promoter. These data indicate the potential of n-3 fatty acids to attenuate IL-13 expression, and suggest that they may subsequently reduce allergic sensitisation and the development of allergic disease.

Determinants of DHA levels in early infancy: differential effects of breast milk and direct fish oil supplementation

INTRODUCTION

Although omega (n)-3 long-chain polyunsaturated fatty acids (LCPUFA), particularly docosahexaenoic acid (DHA), intakes are important during infancy, the optimal method of increasing infant status remains unclear. We hypothesized that high-dose infant fish oil supplementation would have greater relative effects upon n-3 LCPUFA status at six months of age than breast milk fatty acids.

PATIENTS AND METHODS

Infants (n=420) were supplemented daily from birth to six months with fish oil or placebo. In a subset of infants, LCPUFA levels were measured in cord blood, breast milk and in infant blood at 6 months.

RESULTS

DHA levels increased in the fish oil group relative to placebo (p<05). Breast milk DHA was the strongest predictor of infant erythrocyte DHA levels (p=<001). This remained significant after adjustment for cord blood DHA, supplementation group and adherence.

CONCLUSION

In this cohort, breast milk DHA was a greater determinant of infant erythrocyte n-3 LCPUFA status, than direct supplementation with fish oil.

Polyunsaturated fatty acid intake and prevalence of eczema and rhinoconjunctivitis in Japanese children: the Ryukyus Child Health Study

Background

The recent increase in the prevalence of allergic disorders might be a consequence of increased intake of n-6 polyunsaturated fatty acids (PUFAs) and reduced intake of n-3 PUFAs. The current cross-sectional study examined the association between intake levels and the prevalence of eczema and rhinoconjunctivitis in Japanese children.

Methods

Subjects were 23,388 schoolchildren aged 6-15 years residing in Okinawa. The presence of eczema and/or rhinoconjunctivitis was determined according to the criteria of the International Study of Asthma and Allergies in Childhood. A brief diet history questionnaire for children and adolescents was administered to acquire information on dietary factors. Adjustment was made for age, sex, residential municipality, number of siblings, smoking in the household, body mass index, paternal and maternal history of allergic diseases, and paternal and maternal educational level.

Results

The prevalences of eczema and rhinoconjunctivitis in the previous 12 months were 7.0% and 8.0%, respectively. Consumption of PUFAs, n-3 PUFAs, α-linolenic acid, n-6 PUFAs, and linoleic acid was positively associated with the prevalence of eczema: the adjusted odds ratios (ORs) between extreme quintiles (95% confidence intervals [CIs], P for trend) were 1.26 (1.07-1.48, 0.04), 1.31 (1.11-1.54, 0.009), 1.31 (1.12-1.55, 0.003), 1.26 (1.07-1.48, 0.01), and 1.27 (1.08-1.49, 0.01), respectively. Arachidonic acid intake was independently inversely related to eczema: the adjusted OR between extreme quintiles was 0.81 (0.69-0.95, 0.0008). Eczema was not associated with eicosapentaenoic or docosahexaenoic acid intake, or with the ratio of n-3 to n-6 PUFA intake. Only arachidonic acid intake was statistically significantly related to the prevalence of rhinoconjunctivitis, showing a clear inverse linear trend: the adjusted OR between extreme quintiles was 0.86 (0.74-0.997, 0.03).

Conclusions

Consumption of n-3 and n-6 PUFAs, especially α-linolenic acid and linoleic acid, may be positively associated with eczema. Arachidonic acid intake may be inversely related to eczema and rhinoconjunctivitis.

Genetic variation in polyunsaturated fatty acid metabolism and its potential relevance for human development and health

Blood and tissue contents of polyunsaturated fatty acid (PUFA) and long-chain PUFA (LC-PUFA) are related to numerous health outcomes including cardiovascular health, allergies, mental health and cognitive development. Evidence has accumulated to show that in addition to diet, common polymorphisms in the fatty acid desaturase (FADS) gene cluster have very marked effects on human PUFA and LC-PUFA status. Recent results suggest that in addition to fatty acid desaturase 1 and fatty acid desaturase 2, the gene product of fatty acid desaturase 3 is associated with desaturating activity. New data have become available to show that FADS single nucleotide polymorphisms (SNPs) also modulate docosahexaenoic acid status in pregnancy as well as LC-PUFA levels in children and in human milk. There are indications that FADS SNPs modulate the risk for allergic disorders and eczema, and the effect of breastfeeding on later cognitive development. Mechanisms by which FADS SNPs modulate PUFA levels in blood, breast milk and tissues should be explored further. More studies are required to explore the effects of FADS gene variants in populations with different ethnic backgrounds, lifestyles and dietary habits, and to investigate in greater depth the interaction of gene variants, diet and clinical end points, including immune response and developmental outcomes. Analyses of FADS gene variants should be included into all sizeable cohort and intervention studies addressing biological effects of PUFA and LC-PUFA in order to consider these important confounders, and to enhance study sensitivity and precision.

Variants of the FADS1 FADS2 gene cluster, blood levels of polyunsaturated fatty acids and eczema in children within the first 2 years of life

Background

Association of genetic-variants in the FADS1-FADS2-gene-cluster with fatty-acid-composition in blood of adult-populations is well established. We analyze this genetic-association in two children-cohort-studies. In addition, the association between variants in the FADS-gene-cluster and blood-fatty-acid-composition with eczema was studied.

Methods and Principal Findings

Data of two population-based-birth-cohorts in the Netherlands and Germany (KOALA, LISA) were pooled (n = 879) and analyzed by (logistic) regression regarding the mutual influence of single-nucleotide-polymorphisms (SNPs) in the FADS-gene-cluster (rs174545, rs174546, rs174556, rs174561, rs3834458), on polyunsaturated fatty acids (PUFA) in blood and parent-reported eczema until the age of 2 years. All SNPs were highly significantly associated with all PUFAs except for alpha-linolenic-acid and eicosapentaenoic-acid, also after correction for multiple-testing. All tested SNPs showed associations with eczema in the LISA-study, but not in the KOALA-study. None of the PUFAs was significantly associated with eczema neither in the pooled nor in the analyses stratified by study-cohort.

Conclusions and Significance

PUFA-composition in young children's blood is under strong control of the FADS-gene-cluster. Inconsistent results were found for a link between these genetic-variants with eczema. PUFA in blood was not associated with eczema. Thus the hypothesis of an inflammatory-link between PUFA and eczema by the metabolic-pathway of LC-PUFAs as precursors for inflammatory prostaglandins and leukotrienes could not be confirmed by these data.

High-throughput analysis of total plasma fatty acid composition with direct in situ transesterification

Background

Plasma fatty acid (FA) composition reflects dietary intake and endogenous turnover and is associated with health outcomes on a short and long term basis. The total plasma FA pool represents the composition of all FA containing lipid fractions. We developed a simplified and affordable high-throughput method for the analysis of total plasma FA composition, suitable for large studies.

Methodology/Principal Findings

The total lipid FA from 100 µl plasma is transferred in situ into methyl esters, avoiding initial extraction and drying steps. The fatty acid methyl esters are extracted once and analyzed by gas chromatography. For the new direct in situ transesterification method optimal, reaction parameters were determined. Intra-assay analysis (n = 8) revealed coefficients of variation below 4% for FA contributing more than 1% to total FA.

Conclusions/Significance

The results show good agreement with FA concentrations obtained by a reference method. The new direct in situ transesterification method is robust and simple. Sample preparation time and analysis costs are reduced to a minimum. This method is an economically and ecologically superior alternative to conventional methods for assessing plasma FA status in large studies.

Omega-3 polyunsaturated fatty acids and bronchial inflammation in grass pollen allergy after allergen challenge

RATIO: Asthma is a major public health problem, with bronchial inflammation as the therapeutic target. The role of dietary fish oil derived polyunsaturated fatty acids (PUFAs) in allergic inflammation is controversial. Most asthmatics suffer from mild disease and non-pharmacologic interventions are attractive. This study investigates the anti-inflammatory potential of nutritional PUFAs in an experimentally induced bronchial inflammation.

METHODS

We examined 38 grass pollen allergic asthmatics and 19 controls. History of dietary PUFA intake was compared with levels of PUFAs in erythrocyte membranes, and stratified according to low (25th quartile; Q25) and high (75th quartile; Q75) ratios of omega-3 (n-3) to omega-6 (n-6) PUFAs as a surrogate for anti-inflammatory (Q75) or proinflammatory (Q25) effects. Bronchial inflammation was simulated with one-step inhalation of grass pollen. Bronchial response (exhaled nitric monoxide, eNO as surrogate for inflammation, decrease of FEV(1)) was correlated with levels of PUFAs in erythrocyte membranes.

RESULTS

Ratios of n-3/n-6 PUFA were significantly lower in asthmatics than in healthy controls. Levels of eNO were significantly higher in Q25 asthmatics than in Q75 asthmatics (p = 0.040). There was a trend of higher bronchial hyperreactivity in Q25 asthmatics (median PD(20) 0.27 vs. 0.14; n.s.), induced by specific bronchial challenge with grass pollen (FEV(1) decrease 16.7 vs. 23.1%; n.s.).

CONCLUSION

When stratifying for erythrocyte membrane PUFA content as a surrogate for alimentary intake, we found mild effects on bronchial allergic inflammation. Future intervention studies with pharmacological PUFA doses appear suitable to clarify dietary PUFA role as an adjunctive intervention to the established treatment of asthma. ClinicalTrials.gov No. NCT00519740.

Role of FADS1 and FADS2 polymorphisms in polyunsaturated fatty acid metabolism

Tissue availability of polyunsaturated fatty acids (PUFAs) depends on dietary intake and metabolic turnover and has a major impact on human health. Strong associations between variants in the human genes fatty acid desaturase 1 (FADS1, encoding Delta-5 desaturase) and fatty acid desaturase 2 (FADS2, encoding Delta-6 desaturase) and blood levels of PUFAs and long-chain PUFAs (LC-PUFAs) have been reported. The most significant associations and the highest proportion of genetically explained variability (28%) were found for arachidonic acid (20:4n-6), the main precursor of eicosanoids. Subjects carrying the minor alleles of several single nucleotide polymorphisms had a lower prevalence of allergic rhinitis and atopic eczema. Therefore, blood levels of PUFAs and LC-PUFAs are influenced not only by diet, but to a large extent also by genetic variants common in a European population. These findings have been replicated in independent populations. Depending on genetic variants, requirements of dietary PUFA or LC-PUFA intakes to achieve comparable biological effects may differ. We recommend including analyses of FADS1 and FADS2 polymorphism in future cohort and intervention studies addressing biological effects of PUFAs and LC-PUFAs.

Do FADS genotypes enhance our knowledge about fatty acid related phenotypes?

Several physiological processes, such as visual and cognitive development in early life, are dependent on the availability of long-chain polyunsaturated fatty acids (LC-PUFAs). Furthermore, the concentration of LC-PUFAs in phospholipids has been associated with numerous complex diseases like cardiovascular disease, atopic disease and metabolic syndrome. The level and composition of LC-PUFAs in the human body is mainly dependent on their dietary intake or on the intake of fatty acid precursors, which are endogenously elongated and desaturated to physiologically active LC-PUFAs. The delta-5 and delta-6 desaturase are the most important enzymes in this reaction cascade. In the last few years, several studies have reported an association between single nucleotide polymorphisms (SNPs) in the two desaturase encoding genes (FADS1 and FADS2) and the concentration of omega-6 and omega-3 fatty acids. This shows that beside nutrition, genetic factors play an important role in the regulation of LC-PUFAs as well. This review focuses on current knowledge of the impact of FADS genotypes on LC-PUFA and lipid metabolism and discusses their influence on infant intellectual development, neurological conditions, metabolic disease as well as cardiovascular disease.

Genetic variation in CRTh2 influences development of allergic phenotypes

BACKGROUND

Allergic disorders are characterized by an increase in the Th2 cytokines IL-4, IL-5 and IL-13, produced primarily by Th2 cells. These cells are marked by the expression of CRTh2 (chemoattractant receptor-homologous molecule expressed on Th2 cells), a receptor for prostaglandin D(2). As genetic variation plays a significant role in the predisposition for allergic disorders, we investigated the influence of single nucleotide polymorphisms (SNPs) in CRTh2.

METHODS

In a large study population of German children (n = 4264) from the International Study of Asthma and Allergy in Children (ISAAC II), six polymorphisms in CRTh2 were genotyped. Statistical analyses were performed using single SNP and haplotype analyses.

RESULTS

Uncorrected associations among -6373G>A, +1431G>C and +1538A>G were observed with a number of allergic phenotypes (P < 0.05). After correction, association between +1431C and specific IgE to food allergens remained significant (P = 0.04). Associations of haplotype (H)3 (containing +1538G) with reduced risk for asthma and H2 (containing +1431C) with increased risk for specific IgE to food allergens also remained significant after correction for multiple testing (P = 0.004).

CONCLUSIONS

Genetic variation within CRTh2 modifies the development of allergic sensitization and asthma in a population of German children.

Vitamin E intake in relation to allergic sensitization and IgE serum concentration

BACKGROUND

A protective role of dietary vitamin E intake on disorders related to the immune system, such as allergic diseases, has been suggested. However, results from epidemiological studies are conflicting.

OBJECTIVES

The aim of present study was to analyze whether dietary vitamin E intake is related to the prevalence of allergic sensitization and total serum IgE concentrations in adult subjects.

METHODS

The present study population consisted of 366 adults aged 29 to 54 years participating in the German centers of the European Community Respiratory Health Survey (ECRHS) II, Erfurt and Hamburg. A validated food frequency questionnaire was used to gather information on dietary vitamin E intake. Total serum IgE concentrations and specific IgE to common allergens were analyzed by using the Pharmacia CAP System. Allergic sensitization was defined as specific serum IgE concentration > or = 0.35 kU/l.

RESULTS

The risk for allergic sensitization was substantially decreased in the middle quartiles (aOR: 0.42; 95% CI: 0.22-0.81) and the highest quartile (aOR: 0.22; 95% CI: 0.08-0.60) of total dietary vitamin E intake, after adjustment for potential confounders. Total serum IgE concentration was not statistically significantly associated with dietary vitamin E intake.

CONCLUSIONS

The findings of this study suggest that dietary vitamin E intake might play a protective role in the development of allergic sensitization.

Common genetic variants of the FADS1 FADS2 gene cluster and their reconstructed haplotypes are associated with the fatty acid composition in phospholipids

Fatty acid composition in membranes plays an important role in cellular processes and has shown to be associated with the aetiology of several complex diseases in humans. We report strong associations between variants in the human delta-5 and delta-6 desaturase genes FADS1 FADS2 and fatty acid composition in serum phospholipids. Eighteen polymorphisms located in this gene cluster were genotyped in 727 adults from Erfurt, a German centre of the European Community Respiratory Health Survey. The cluster is located at chromosome 11q12-11q13.1, a region repeatedly found to be linked with atopy and other complex diseases. Polymorphisms and statistically reconstructed haplotypes of FADS1 and the upstream region of FADS2 showed strongest associations with the level of the direct precursor of inflammatory eicosanoids, the n-6 fatty acid arachidonic acid (C20:4n-6), also strong associations with levels of the n-6 fatty acids C18:2n-6, C18:3n-6, C20:2n-6, C20:3n-6, C22:4n-6 and of the n-3 fatty acids C18:3n-3, C20:5n-3 and C22:5n-3 (P-values < 1.0 x 10(-13)). Carriers of the rare alleles of several SNPs and their respective haplotypes had a lower prevalence of allergic rhinitis and atopic eczema. No association was found for total and specific IgE levels.