SNPs of the FADS Gene Cluster are Associated with Polyunsaturated Fatty Acids in a Cohort of Patients with Cardiovascular Disease

Adult medication-free schizophrenic patients exhibit long-chain omega-3 Fatty Acid deficiency: implications for cardiovascular disease risk

Deficiency in long-chain omega-3 (LCn - 3) fatty acids, eicosapentaenoic acid (EPA, 20:5n - 3) and docosahexaenoic acid (DHA, 22:6n - 3), has been implicated in the pathoetiology of cardiovascular disease, a primary cause of excess premature mortality in patients with schizophrenia (SZ). In the present study, we determined erythrocyte EPA + DHA levels in adult medication-free patients SZ (n = 20) and age-matched healthy controls (n = 24). Erythrocyte EPA + DHA composition exhibited by SZ patients (3.5%) was significantly lower than healthy controls (4.5%, -22%, P = 0.007). The majority of SZ patients (72%) exhibited EPA+DHA levels ≤4.0% compared with 37% of controls (Chi-square, P = 0.001). In contrast, the omega-6 fatty acid arachidonic acid (AA, 20:4n - 6) (+9%, P = 0.02) and the AA:EPA + DHA ratio (+28%, P = 0.0004) were significantly greater in SZ patients. Linoleic acid (18:2n - 6) was significantly lower (-12%, P = 0.009) and the erythrocyte 20:3/18:2 ratio (an index of delta6-desaturase activity) was significantly elevated in SZ patients. Compared with same-gender controls, EPA + DHA composition was significantly lower in male (-19%, P = 0.04) but not female (-13%, P = 0.33) SZ patients, whereas the 20:3/18:2 ratio was significantly elevated in both male (+22%, P = 0.008) and female (+22%, P = 0.04) SZ patients. These results suggest that the majority of SZ patients exhibit low LCn - 3 fatty acid levels which may place them at increased risk for cardiovascular morbidity and mortality.

Elevated immune-inflammatory signaling in mood disorders: a new therapeutic target?

Converging translational evidence has implicated elevated immune-inflammatory signaling activity in the pathoetiology of mood disorders, including major depressive disorder and bipolar disorder. This is supported in part by cross-sectional evidence for increased levels of proinflammatory eicosanoids, cytokines and acute-phase proteins during mood episodes, and prospective longitudinal evidence for the emergence of mood symptoms in response to chronic immune-inflammatory activation. In addition, mood-stabilizer and atypical antipsychotic medications downregulate initial components of the immune-inflammatory signaling pathway, and adjunctive treatment with anti-inflammatory agents augment the therapeutic efficacy of antidepressant, mood stabilizer and atypical antipsychotic medications. Potential pathogenic mechanisms linked with elevated immune-inflammatory signaling include perturbations in central serotonin neurotransmission and progressive white matter pathology. Both heritable genetic factors and environmental factors including dietary fatty-acid composition may act in concert to sustain elevated immune-inflammatory signaling. Collectively, these data suggest that elevated immune-inflammatory signaling is a mechanism that is relevant to the pathoetiology of mood disorders, and may therefore represent a new therapeutic target for the development of more effective treatments.

Indices of fatty acid desaturase activity in healthy human subjects: effects of different types of dietary fat

Δ9-Desaturase (stearoyl-CoA desaturase 1, SCD-1) regulates the desaturation of SFA, mainly stearic and palmitic, to MUFA. Δ6-Desaturase (D6D) and Δ5-desaturase (D5D) are involved in the metabolism of linoleic and α-linolenic acid to polyunsaturated metabolites. The objective of the present study was to study the effects of different types of dietary fat on indices of fatty acid desaturase (FADS) activity (evaluated as product:precursor ratios) in plasma and skeletal muscle in human subjects. A high SCD-1 index has been related to obesity and metabolic disorders, while the D5D index is associated with insulin sensitivity. Fatty acid composition of serum and skeletal muscle lipids was analysed by GLC during a randomised, controlled, 3-month dietary intervention in healthy subjects. A comparison of the effects of a diet containing butter fat (SFA, n 17) with a diet containing monounsaturated fat (MUFA, n 17), keeping all other dietary components constant, showed a reduced SCD-1 activity index by 20% on the MUFA diet compared with the SFA diet assessed in serum cholesteryl esters. The D6D and D5D indices remained unaffected. Supplementation with long-chain n-3 fatty acids reduced the SCD-1 index by a similar magnitude while the D6D index decreased and the D5D index increased. It is concluded that changes in the type of fat in the diet affect the indices of FADS activity in serum and skeletal muscle in human subjects. The desaturase activity indices estimated from the serum lipid ester composition are significantly related to corresponding indices studied in skeletal muscle phospholipids.

Interaction between a common variant in FADS1 and erythrocyte polyunsaturated fatty acids on lipid profile in Chinese Hans

Little is known about the associations of FADS1 genetic variants with circulating levels of PUFA and lipids in Asian populations who have a different dietary pattern and dyslipidemia prevalence compared with Western populations. In a population-based sample of 3,210 unrelated Han Chinese living in Beijing and Shanghai, we examined a FADS1 genetic variant, rs174550, in relation to blood PUFA and lipid levels. C-allele of rs174550 was significantly associated with levels of erythrocyte PUFAs in upstream and downstream pathways of delta-5 desaturase (D5D) (P ≤ 0.003). Moreover, rs174550 C-allele was associated with a lower HDL cholesterol level (P = 0.02) in total population and a higher triglyceride level (P = 0.0002) in Beijing residents. Interestingly, erythrocyte levels of 18:2n-6 and 18:3n-3 modified the effect of rs174550 on HDL cholesterol level: stronger associations between rs174550 C-allele and lower HDL cholesterol levels were exhibited when erythrocyte 18:2n-6 or 18:3n-3 level was low (P for interaction = 0.02 and 0.03, respectively). These data suggested that FADS1 genetic variant was associated with circulating PUFA and lipid levels and that its effect on HDL cholesterol might depend on PUFA status in the Han Chinese population.

FADS gene polymorphisms confer the risk of coronary artery disease in a Chinese Han population through the altered desaturase activities: based on high-resolution melting analysis

Objective

We explored the desaturase activities and the correlation of fatty acid desaturases (FADS) gene single nucleotide polymorphisms (SNPs) with plasma fatty acid in coronary artery disease (CAD) patients in a Chinese Han population.

Methods

Plasma fatty acids were measured by gas chromatography in CAD patients (n = 505) and a control group (n = 510). Five SNPs in the FADS gene were genotyped with high-resolution melting (HRM) methods.

Results

After adjustment, D6D activity, assessed as arachidonic acid (AA, C20:4n-6)/linoleic acid (LA, C18:2n-6), was higher in CAD patients (p<0.001). D9D activity, which was estimated as the ratio of palmitoleic acid (C16:1)/palmitic acid (C16:0) or oleic acid (C18:1n-9) to stearic acid (C18:0), was also increased (p<0.001). The genotype distributions of rs174537 G>T and rs174460 C>T were different between the two groups. The rs174537 T allele was associated with a lower risk of CAD [OR 0.743, 95% CI (0.624, 0.884), p = 0.001]. Carriers of the rs174460 C allele were associated with a higher risk of CAD [OR 1.357, 95% CI (1.106, 1.665), p = 0.003].

Conclusions

We firstly report that the rs174460 C allele is associated with a higher risk of CAD, and confirm that the rs174537 T allele is associated with a lower risk of CAD. Our results indicate that FADS gene polymorphisms are likely to influence plasma fatty acid concentrations and desaturase activities.

Dietary oils and FADS1-FADS2 genetic variants modulate [13C]α-linolenic acid metabolism and plasma fatty acid composition

BACKGROUND

Desaturation of dietary α-linolenic acid (ALA) to omega-3 (n-3) long-chain fatty acids (FAs) is mediated through FA desaturases (FADS1-FADS2) and may be influenced by dietary FA composition.

OBJECTIVE

We investigated the effects of diets enriched in flaxseed oil (FXCO) or high-oleic acid canola oil (HOCO) compared with a Western diet (WD) and FADS1-FADS2 single nucleotide polymorphisms (SNPs) on plasma FAs and [U-(13)C]ALA metabolism.

DESIGN

In a randomized crossover design, 36 hyperlipidemic subjects consumed 3 isoenergetic diets enriched in FXCO (20.6 g ALA/d), HOCO (2.4 g ALA/d), or WD (1.3 g ALA/d) for 4 wk. On day 27, blood was sampled 0, 24, and 48 h after the subjects (n = 26) consumed 45 mg [U-(13)C]ALA. The subjects were genotyped for 4 FADS SNPs.

RESULTS

FXCO increased (P < 0.001) plasma ALA, EPA, and docosapentaenoic acid (DPA), with no change in DHA compared with the HOCO or WD diets. At 24 and 48 h, [U-(13)C]ALA recovered as plasma [(13)C]EPA and [(13)C]DPA were lower (P < 0.001) after the FXCO diet than after the HOCO and WD diets. No change in [(13)C]DHA was observed between diets. Minor allele homozygotes of rs174545, rs174583, rs174561, and rs174537 had lower (P < 0.05) plasma EPA, arachidonic acid (AA), EPA/ALA, and AA/linoleic acid compositions and lower (P < 0.05) plasma [(13)C]EPA enrichment at 24 and 48 h in comparison with carriers of the major allele after all diets. SNPs were not associated with plasma composition of DHA or [(13)C]DHA enrichment.

CONCLUSION

An increase in ALA intake resulting in increased plasma EPA composition may be cardioprotective, especially in minor allele homozygotes. This trial was registered at www.clinicaltrials.gov as NCT00927199.

Genetic variation at the FADS1-FADS2 gene locus influences delta-5 desaturase activity and LC-PUFA proportions after fish oil supplement

Delta-5 and delta-6 desaturases (D5D and D6D) are key enzymes in endogenous synthesis of long-chain PUFAs. In this sample of healthy subjects (n = 310), genotypes of single nucleotide polymorphisms (SNPs) rs174537, rs174561, and rs3834458 in the FADS1-FADS2 gene cluster were strongly associated with proportions of LC-PUFAs and desaturase activities estimated in plasma and erythrocytes. Minor allele carriage associated with decreased activities of D5D (FADS1) (5.84 × 10(-19) ≤ P ≤ 4.5 × 10(-18)) and D6D (FADS2) (6.05 × 10(-8) ≤ P ≤ 4.20 × 10(-7)) was accompanied by increased substrate and decreased product proportions (0.05 ≤ P ≤ 2.49 × 10(-16)). The significance of haplotype association with D5D activity (P = 2.19 × 10(-17)) was comparable to that of single SNPs, but haplotype association with D6D activity (P = 3.39 × 10(-28)) was much stronger. In a randomized controlled dietary intervention, increasing eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) intake significantly increased D5D (P = 4.0 × 10(-9)) and decreased D6D activity (P = 9.16 × 10(-6)) after doses of 0.45, 0.9, and 1.8 g/day for six months. Interaction of rs174537 genotype with treatment was a determinant of D5D activity estimated in plasma (P = 0.05). In conclusion, different sites at the FADS1-FADS2 locus appear to influence D5D and D6D activity, and rs174537 genotype interacts with dietary EPA+DHA to modulate D5D.

Current status on genome-metabolome-wide associations: an opportunity in nutrition research

Genome-wide association studies (GWASs) have become a very important tool to address the genetic origin of phenotypic variability, in particular associated with diseases. Nevertheless, these types of studies provide limited information about disease etiology and the molecular mechanisms involved. Recently, the incorporation of metabolomics into the analysis has offered novel opportunities for a better understanding of disease-related metabolic deregulation. The pattern emerging from this work is that gene-driven changes in metabolism are prevalent and that common genetic variations can have a profound impact on the homeostatic concentrations of specific metabolites. A particularly interesting aspect of this work takes into account interactions of environment and lifestyle with the genome and how this interaction translates into changes in the metabolome. For instance, the role of PYROXD2 in trimethylamine metabolism points to an interaction between host and microbiome genomes (host/microbiota). Often, these findings reveal metabolic deregulations, which could eventually be tuned with a nutritional intervention. Here we review the development of gene-metabolism association studies from a single-gene/single-metabolite to a genome-wide/metabolome-wide approach and highlight the conceptual changes associated with this ongoing transition. Moreover, we report some of our recent GWAS results on a cohort of 265 individuals from an ethnically diverse population that validate and refine previous findings on gene-urine metabolism interactions. Specifically, our results confirm the effect of PYROXD2 polymorphisms on trimethylamine metabolism and suggest that a previously reported association of N-acetylated compounds with the ALMS1/NAT8 locus is driven by SNPs in the ALMS1 gene.

Association between polymorphisms in the fatty acid desaturase gene cluster and the plasma triacylglycerol response to an n-3 PUFA supplementation

Eicosapentaenoic and docosahexaenoic acids have been reported to have a variety of beneficial effects on cardiovascular disease risk factors. However, a large inter-individual variability in the plasma lipid response to an omega-3 (n-3) polyunsaturated fatty acid (PUFA) supplementation is observed in different studies. Genetic variations may influence plasma lipid responsiveness. The aim of the present study was to examine the effects of a supplementation with n-3 PUFA on the plasma lipid profile in relation to the presence of single-nucleotide polymorphisms (SNPs) in the fatty acid desaturase (FADS) gene cluster. A total of 208 subjects from Quebec City area were supplemented with 3 g/day of n-3 PUFA, during six weeks. In a statistical model including the effect of the genotype, the supplementation and the genotype by supplementation interaction, SNP rs174546 was significantly associated (p = 0.02) with plasma triglyceride (TG) levels, pre- and post-supplementation. The n-3 supplementation had an independent effect on plasma TG levels and no significant genotype by supplementation interaction effects were observed. In summary, our data support the notion that the FADS gene cluster is a major determinant of plasma TG levels. SNP rs174546 may be an important SNP associated with plasma TG levels and FADS1 gene expression independently of a nutritional intervention with n-3 PUFA.

Variants in CPT1A, FADS1, and FADS2 are Associated with Higher Levels of Estimated Plasma and Erythrocyte Delta-5 Desaturases in Alaskan Eskimos

The delta-5 and delta-6 desaturases (D5D and D6D), encoded by fatty acid desaturase 1 (FADS1) and 2 (FADS2) genes, respectively, are rate-limiting enzymes in the metabolism of ω-3 and ω-6 fatty acids. The objective of this study was to identify genes influencing variation in estimated D5D and D6D activities in plasma and erythrocytes in Alaskan Eskimos (n = 761) participating in the genetics of coronary artery disease in Alaska Natives (GOCADAN) study. Desaturase activity was estimated by product: precursor ratio of polyunsaturated fatty acids. We found evidence of linkage for estimated erythrocyte D5D (eD5D) on chromosome 11q12-q13 (logarithm of odds score = 3.5). The confidence interval contains candidate genes FADS1, FADS2, 7-dehydrocholesterol reductase (DHCR7), and carnitine palmitoyl transferase 1A, liver (CPT1A). Measured genotype analysis found association between CPT1A, FADS1, and FADS2 single-nucleotide polymorphisms (SNPs) and estimated eD5D activity (p-values between 10⁻²⁸ and 10⁻⁵). A Bayesian quantitative trait nucleotide analysis showed that rs3019594 in CPT1A, rs174541 in FADS1, and rs174568 in FADS2 had posterior probabilities > 0.8, thereby demonstrating significant statistical support for a functional effect on eD5D activity. Highly significant associations of FADS1, FADS2, and CPT1A transcripts with their respective SNPs (p-values between 10⁻⁷⁵ and 10⁻⁷) in Mexican Americans of the San Antonio Family Heart Study corroborated our results. These findings strongly suggest a functional role for FADS1, FADS2, and CPT1A SNPs in the variation in eD5D activity.

Interactions between dietary n-3 fatty acids and genetic variants and risk of disease

Nutritional genomics has undergone rapid development and the concept is now very popular with the general public. Therefore, there is increasing demand for knowledge on adapting dietary composition to the genome. Our aim has been to undertake a systematic review so as to find out the level of evidence existing on whether the effects of n-3 fatty acids on health can be modulated by genetic variation. A systematic literature search was conducted on studies that jointly analyse the effect of one or more genetic variants in candidate genes and n-3 fatty acids. Both observational and experimental studies were included. Results are classified in accordance with whether the study was undertaken on intermediate phenotypes (plasma lipid concentrations, glucose, inflammation markers, anthropometric measurements) or disease phenotypes (cancer, cardiovascular diseases, metabolic syndrome, etc) and whether it was experimental or observational. A wide diversity of genetic variants and little consistency in the publication of replication studies was found. Greater consistency was observed in studies that involved the FADS1 and FADS2 locus in the determination of n-3 fatty acid concentrations in biological samples. Most of the studies were designed to measure gene-diet interactions and not diet-gene interactions. Despite the fact that multiple studies have shown statistically significant interactions between n-3 fatty acids and certain genetic variants on intermediate and disease phenotypes, the individual level of evidence is very low and recommendations cannot be made on increasing or reducing the intake of n-3 fatty acids based on each individual's genotype.

Fatty acids as biocompounds: their role in human metabolism, health and disease: a review. part 2: fatty acid physiological roles and applications in human health and disease

BACKGROUND

This is the second of two review parts aiming at describing the major physiological roles of fatty acids, as well as their applications in specific conditions related to human health.

RESULTS

The review included the current literature published in Pubmed up to March 2011. In humans, fatty acids are a principle energy substrate and structural components of cell membranes (phospholipids) and second messengers. Fatty acids are also ligands of nuclear receptors affecting gene expression. Longer-chain (LC) polyunsaturated fatty acids (PUFA), including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid are precursors of lipid mediators such as eicosanoids (prostaglandins, leukotrienes, thromboxanes), resolvins and neuroprotectins. Lipid mediators produced by EPA and DHA (LC n-3 PUFA; mainly found in oily fish) are considered as inflammation-resolving, and thus, fish oil has been characterised as antiinflammatory. Recommendations for EPA plus DHA intake from oily fish vary between 250-450 mg/day. Dietary reference values for fat vary between nutrition bodies, but mainly agree on a low total and saturated fat intake. The existing literature supports the protective effects of LC n-3 PUFA (as opposed to n-6 PUFA and saturated fat) in maternal and offspring health, cardiovascular health, insulin sensitivity, the metabolic syndrome, cancer, critically ill patients, and immune system disorders.

CONCLUSION

Fatty acids are involved in multiple pathways and play a major role in health. Further investigation and a nutrigenomics approach to the effects of these biocompounds on health and disease development are imperative and highlight the importance of environmental modifications on disease outcome.

FADS1 FADS2 gene cluster, PUFA intake and blood lipids in children: results from the GINIplus and LISAplus studies

BACKGROUND

Elevated cholesterol levels in children can be a risk factor for cardiovascular diseases in later life. In adults, it has been shown that blood lipid levels are strongly influenced by polymorphisms in the fatty acid desaturase (FADS) gene cluster in addition to nutritional and other exogenous and endogenous determinants. Our aim was to investigate whether lipid levels are determined by the FADS genotype already in children and whether this association interacts with dietary intake of n-3 fatty acids.

METHODS

The analysis was based on data of 2006 children from two German prospective birth cohort studies. Total cholesterol, HDL, LDL and triglycerides were measured at 10 years of age. Six single nucleotide polymorphisms (SNPs) of the FADS gene cluster were genotyped. Dietary n-3 fatty acid intake was assessed by food frequency questionnaire. Linear regression modeling was used to assess the association between lipid levels, n-3 fatty acid intake and FADS genotype.

RESULTS

Individuals carrying the homozygous minor allele had lower levels of total cholesterol [means ratio (MR) ranging from 0.96 (p = 0.0093) to 0.98 (p = 0.2949), depending on SNPs] and LDL [MR between 0.94 (p = 0.0179) and 0.97 (p = 0.2963)] compared to homozygous major allele carriers. Carriers of the heterozygous allele showed lower HDL levels [β between -0.04 (p = 0.0074) to -0.01 (p = 0.3318)] and higher triglyceride levels [MR ranging from 1.06 (p = 0.0065) to 1.07 (p = 0.0028)] compared to homozygous major allele carriers. A higher n-3 PUFA intake was associated with higher concentrations of total cholesterol, LDL, HDL and lower triglyceride levels, but these associations did not interact with the FADS1 FADS2 genotype.

CONCLUSION

Total cholesterol, HDL, LDL and triglyceride concentrations may be influenced by the FADS1 FADS2 genotype already in 10 year old children. Genetically determined blood lipid levels during childhood might differentially predispose individuals to the development of cardiovascular diseases later in life.

Genetic adaptation of fatty-acid metabolism: a human-specific haplotype increasing the biosynthesis of long-chain omega-3 and omega-6 fatty acids

Omega-3 and omega-6 long-chain polyunsaturated fatty acids (LC-PUFAs) are essential for the development and function of the human brain. They can be obtained directly from food, e.g., fish, or synthesized from precursor molecules found in vegetable oils. To determine the importance of genetic variability to fatty-acid biosynthesis, we studied FADS1 and FADS2, which encode rate-limiting enzymes for fatty-acid conversion. We performed genome-wide genotyping (n = 5,652 individuals) and targeted resequencing (n = 960 individuals) of the FADS region in five European population cohorts. We also analyzed available genomic data from human populations, archaic hominins, and more distant primates. Our results show that present-day humans have two common FADS haplotypes-defined by 28 closely linked SNPs across 38.9 kb-that differ dramatically in their ability to generate LC-PUFAs. No independent effects on FADS activity were seen for rare SNPs detected by targeted resequencing. The more efficient, evolutionarily derived haplotype appeared after the lineage split leading to modern humans and Neanderthals and shows evidence of positive selection. This human-specific haplotype increases the efficiency of synthesizing essential long-chain fatty acids from precursors and thereby might have provided an advantage in environments with limited access to dietary LC-PUFAs. In the modern world, this haplotype has been associated with lifestyle-related diseases, such as coronary artery disease.

Fatty Acid desaturase gene variants, cardiovascular risk factors, and myocardial infarction in the costa rica study

Genetic variation in fatty acid desaturases (FADS) has previously been linked to long-chain polyunsaturated fatty acids (PUFAs) in adipose tissue and cardiovascular risk. The goal of our study was to test associations between six common FADS polymorphisms (rs174556, rs3834458, rs174570, rs2524299, rs174589, rs174627), intermediate cardiovascular risk factors, and non-fatal myocardial infarction (MI) in a matched population based case–control study of Costa Rican adults (n = 1756). Generalized linear models and multiple conditional logistic regression models were used to assess the associations of interest. Analyses involving intermediate cardiovascular risk factors and MI were also conducted in two replication cohorts, The Nurses’ Health Study (n = 1200) and The Health Professionals Follow-Up Study (n = 1295). In the Costa Rica Study, genetic variation in the FADS cluster was associated with a robust linear decrease in adipose gamma-linolenic, arachidonic, and eicosapentaenoic fatty acids, and significant or borderline significant increases in the eicosadienoic, eicosatrienoic, and dihomo-gamma-linolenic fatty acids. However, the associations with adipose tissue fatty acids did not translate into changes in inflammatory biomarkers, blood lipids, or the risk of MI in the discovery or the replication cohorts. In conclusion, fatty acid desaturase polymorphisms impact long-chain PUFA biosynthesis, but their overall effect on cardiovascular health likely involves multiple pathways and merits further investigation.

Polyunsaturated fatty acid metabolism in prostate cancer

Polyunsaturated fatty acids (PUFA) play important roles in the normal physiology and in pathological states including inflammation and cancer. While much is known about the biosynthesis and biological activities of eicosanoids derived from ω6 PUFA, our understanding of the corresponding ω3 series lipid mediators is still rudimentary. The purpose of this review is not to offer a comprehensive summary of the literature on fatty acids in prostate cancer but rather to highlight some of the areas where key questions remain to be addressed. These include substrate preference and polymorphic variants of enzymes involved in the metabolism of PUFA, the relationship between de novo lipid synthesis and dietary lipid metabolism pathways, the contribution of cyclooxygenases and lipoxygenases as well as terminal synthases and prostanoid receptors in prostate cancer, and the potential role of PUFA in angiogenesis and cell surface receptor signaling.

Genome-wide association study identifies novel loci associated with circulating phospho- and sphingolipid concentrations

Phospho- and sphingolipids are crucial cellular and intracellular compounds. These lipids are required for active transport, a number of enzymatic processes, membrane formation, and cell signalling. Disruption of their metabolism leads to several diseases, with diverse neurological, psychiatric, and metabolic consequences. A large number of phospholipid and sphingolipid species can be detected and measured in human plasma. We conducted a meta-analysis of five European family-based genome-wide association studies (N = 4034) on plasma levels of 24 sphingomyelins (SPM), 9 ceramides (CER), 57 phosphatidylcholines (PC), 20 lysophosphatidylcholines (LPC), 27 phosphatidylethanolamines (PE), and 16 PE-based plasmalogens (PLPE), as well as their proportions in each major class. This effort yielded 25 genome-wide significant loci for phospholipids (smallest P-value = 9.88×10⁻²⁰⁴) and 10 loci for sphingolipids (smallest P-value = 3.10×10⁻⁵⁷). After a correction for multiple comparisons (P-value<2.2×10⁻⁹), we observed four novel loci significantly associated with phospholipids (PAQR9, AGPAT1, PKD2L1, PDXDC1) and two with sphingolipids (PLD2 and APOE) explaining up to 3.1% of the variance. Further analysis of the top findings with respect to within class molar proportions uncovered three additional loci for phospholipids (PNLIPRP2, PCDH20, and ABDH3) suggesting their involvement in either fatty acid elongation/saturation processes or fatty acid specific turnover mechanisms. Among those, 14 loci (KCNH7, AGPAT1, PNLIPRP2, SYT9, FADS1-2-3, DLG2, APOA1, ELOVL2, CDK17, LIPC, PDXDC1, PLD2, LASS4, and APOE) mapped into the glycerophospholipid and 12 loci (ILKAP, ITGA9, AGPAT1, FADS1-2-3, APOA1, PCDH20, LIPC, PDXDC1, SGPP1, APOE, LASS4, and PLD2) to the sphingolipid pathways. In large meta-analyses, associations between FADS1-2-3 and carotid intima media thickness, AGPAT1 and type 2 diabetes, and APOA1 and coronary artery disease were observed. In conclusion, our study identified nine novel phospho- and sphingolipid loci, substantially increasing our knowledge of the genetic basis for these traits.

Phospho- and sphingolipids are integral to membrane formation and are involved in crucial cellular functions such as signalling, membrane fluidity, membrane protein trafficking, neurotransmission, and receptor trafficking. In addition to severe monogenic diseases resulting from defective phospho- and sphingolipid function and metabolism, the evidence suggests that variations in these lipid levels at the population level are involved in the determination of cardiovascular and neurologic traits and subsequent disease. We took advantage of modern laboratory methods, including microarray-based genotyping and electrospray ionization tandem mass spectrometry, to hunt for genetic variation influencing the levels of more than 350 phospho- and sphingolipid phenotypes. We identified nine novel loci, in addition to confirming a number of previously described loci. Several other genetic regions provided substantial evidence of their involvement in these traits. All of these loci are strong candidates for further research in the field of lipid biology and are likely to yield considerable insights into the complex metabolic pathways underlying circulating phospho- and sphingolipid levels. Understanding these mechanisms might help to illuminate factors leading to the development of common cardiovascular and neurological diseases and might provide molecular targets for the development of new therapies.

FADS gene cluster modulates the effect of breastfeeding on asthma. Results from the GINIplus and LISAplus studies

BACKGROUND

  The protective effect of breastfeeding (BF) on the development of asthma has been widely recognized, even if not all results have been consistent. Gene variants of the FADS gene cluster have a major impact on fatty acid composition in blood and in breast milk. Therefore, we evaluated the influence of the FADS1 FADS2 gene cluster polymorphisms on the association between BF and asthma.

METHODS

  The analysis was based on data (N=2245) from two German prospective birth cohort studies. Information on asthma and BF during the first 6 months was collected using questionnaires completed by the parents. Logistic regression modelling was used to analyse the association between exclusive BF and ever having asthma stratified by genotype.

RESULTS

  In the stratified analyses, BF for 3 or 4 months after birth had a protective effect for heterozygous and homozygous carriers of the minor allele (adjusted odds ratio between 0.37 (95% CI: 0.18-0.80) and 0.42 (95% CI: 0.20-0.88). Interaction terms of BF with genotype were significant and ranged from -1.17 (P-value: 0.015) to -1.33 (0.0066). Moreover, heterozygous and homozygous carriers of the minor allele who were exclusively breastfed for 5 or 6 months after birth had a reduced risk of asthma [0.32 (0.18-0.57) to 0.47 (0.27-0.81)] in the stratified analyses. For individuals carrying the homozygous major allele, BF showed no significant effect on the development of asthma.

CONCLUSIONS

  The association between exclusive BF and asthma is modified by the genetic variants of FADS genotypes in children.

Polyunsaturated fatty acid levels in blood during pregnancy, at birth and at 7 years: their associations with two common FADS2 polymorphisms

Minor alleles of polymorphisms in the fatty acid desaturase (FADS) gene cluster have been associated with reduced desaturation of the precursor polyunsaturated fatty acids (FAs) in small studies. The effects of these polymorphisms during progressive developmental stages have not previously been reported. Data from blood samples for 4342 pregnant women, 3343 umbilical cords reflecting the newborn's blood supply and 5240 children aged 7 years were analysed to investigate the associations of polyunsaturated FAs with rs1535 and rs174575-two polymorphisms in the FADS2 gene. Strong positive associations were observed between the minor G allele for these two markers, especially rs1535, and the substrates linoleic (18:2n-6) and α-linolenic (18:3n-3) acid. Negative associations were observed for the more highly unsaturated FAs such as arachidonic acid (20:4n-6), timnodonic acid (EPA, 20:5n-3) and cervonic acid (DHA, 22:6n-3). Bivariable genetic associations using the mother and child genotypes suggested that the newborn metabolism had a greater capacity to synthesize the more highly unsaturated omega-6 FAs than the more highly unsaturated omega-3 FAs. Nevertheless, despite the immaturity of the neonate, there was evidence that synthesis of DHA was occurring. However, by 7 years, no associations were observed with the maternal genotype. This suggested that the children's FA levels were related only to their own metabolism with no apparent lasting influences of the in utero environment.

A case-control study between the gene polymorphisms of polyunsaturated fatty acids metabolic rate-limiting enzymes and coronary artery disease in a Chinese Han population

To investigate the association between the polymorphisms of fatty acid desaturase 1 (FADS1), fatty acid desaturase 2 (FADS2) and elongation of very long chain fatty acids like 2 (ELOVL2) gene and coronary artery disease (CAD) in a Chinese Han population. Three single nucleotide polymorphisms (SNPs) from these genes were genotyped using PCR-based restriction fragment length polymorphism analysis in 199 CAD cases and 192 controls of Han Chinese origin. rs174556 in the FADS1 gene showed allelic (P=0.002) and genotypic (P=0.030) association with the disease, while there was no disease association for the other two SNPs. The frequency of rs174556 minor allele (T) was significantly higher in the case group than the control group. The trans phase gene-gene interaction analysis showed that the combined genotype of rs174556 (T/T) and rs3756963 (T/T) was weakly associated with the disease (P=0.043). rs174556 in the FADS1 gene is very likely to be associated with CAD in the Chinese Han population.

Influence of FADS polymorphisms on tracking of serum glycerophospholipid fatty acid concentrations and percentage composition in children

BACKGROUND

Tracking of fatty acid (FA) contribution to plasma or serum lipids over time was shown in children and adults. However, the potential role of FADS gene variants has not been investigated.

METHODS AND PRINCIPAL FINDINGS

Serum GP FA composition of 331 children aged 2 and 6 years, participating in an ongoing birth cohort study, was analyzed. Correlation coefficients were estimated to describe FA tracking over 4 years and to assess the influence of FADS variants on tracking. We found low to moderate tracking (r = 0.12-0.49) of FA compositions and concentration between 2 and 6 years. Concentration changes of total monounsaturated FA and total saturated FA over time correlated closely (r = 0.79) but percentage values were unrelated (r = -0.02). Tracking for n-6 long chain polyunsaturated fatty acid (LC-PUFA) concentrations was lower in subjects homozygous for the major allele of FADS variants and higher in carriers of at least one minor allele, whereas for total n-3 LC-PUFA concentrations and compositions this was vice versa. For individual n-3 PUFA inconsistent results were found.

CONCLUSIONS AND SIGNIFICANCE

Serum GP FA composition shows low to moderate tracking over 4 years with a higher tracking for LC-PUFA metabolites than for their precursor FA. Serum PUFA levels and their tracking seem to be more influenced by lipid and lipoprotein metabolism than by FA specific pathways.

FADS gene variants modulate the effect of dietary fatty acid intake on allergic diseases in children

BACKGROUND

The association between dietary fatty acid intake and the development of atopic diseases has been inconsistent. This could be due to inter-individual genetic differences in fatty acid metabolism.

OBJECTIVE

The aim of the current study was to assess the influence of FADS1 FADS2 gene cluster polymorphisms on the association between dietary fatty acid intake and atopic diseases and allergic sensitization in 10-year-old children.

METHODS

The analysis was based on data from two German prospective birth cohort studies. Data on margarine and fatty acid intake were collected using a food frequency questionnaire. Information on atopic diseases was collected using a questionnaire completed by the parents. Specific IgE against common food and inhalant allergens were measured. Six variants of the FADS1 FADS2 gene cluster (rs174545, rs174546, rs174556, rs174561, rs174575 and rs3834458) were tested. Logistic regression modelling, adjusted for gender, age, maternal education level and study centre, was used to analyse the association between fatty acid intake and atopic diseases stratified by genotype.

RESULTS

No significant association was found between the six FADS single nucleotide polymorphisms (SNPs) and allergic diseases or atopic sensitization. The total n-3/total n-6 ratio was positive associated with an increased risk of hayfever in homozygous major allele carriers ranging from an adjusted odds ratios of 1.25 (95%-CI: 1.00-1.57) to 1.31 (95%-CI: 1.01-1.69) across the six tested SNPs although this association was not significant anymore after correcting for multiple testing. Daily margarine intake was significantly associated with asthma [1.17 (1.03-1.34) to 1.22 (1.06-1.40)] in individuals carrying the homozygous major allele. This association was also significant after correcting for multiple testing.

CONCLUSIONS & CLINICAL RELEVANCE

The association between dietary intake of fatty acids and allergic diseases might be modulated by FADS gene variants in children.

Differences in arachidonic acid levels and fatty acid desaturase (FADS) gene variants in African Americans and European Americans with diabetes or the metabolic syndrome

Over the past 50 years, increases in dietary n-6 PUFA, such as linoleic acid, have been hypothesised to cause or exacerbate chronic inflammatory diseases. The present study examines an individual's innate capacity to synthesise n-6 long-chain PUFA (LC-PUFA) with respect to the fatty acid desaturase (FADS) locus in Americans of African and European descent with diabetes or the metabolic syndrome. Compared with European Americans (EAm), African Americans (AfAm) exhibited markedly higher serum levels of arachidonic acid (AA) (EAm 7·9 (sd 2·1), AfAm 9·8 (sd 1·9) % of total fatty acids; P < 2·29 × 10⁻⁹) and the AA:n-6-precursor fatty acid ratio, which estimates FADS1 activity (EAm 5·4 (sd 2·2), AfAm 6·9 (sd 2·2); P = 1·44 × 10⁻⁵). In all, seven SNP mapping to the FADS locus revealed strong association with AA, EPA and dihomo-γ-linolenic acid (DGLA) in the EAm. Importantly, EAm homozygous for the minor allele (T) had significantly lower AA levels (TT 6·3 (sd 1·0); GG 8·5 (sd 2·1); P = 3·0 × 10⁻⁵) and AA:DGLA ratios (TT 3·4 (sd 0·8), GG 6·5 (sd 2·3); P = 2·2 × 10⁻⁷) but higher DGLA levels (TT 1·9 (sd 0·4), GG 1·4 (sd 0·4); P = 3·3 × 10⁻⁷) compared with those homozygous for the major allele (GG). Allele frequency patterns suggest that the GG genotype at rs174537 (associated with higher circulating levels of AA) is much higher in AfAm (0·81) compared with EAm (0·46). Similarly, marked differences in rs174537 genotypic frequencies were observed in HapMap populations. These data suggest that there are probably important differences in the capacity of different populations to synthesise LC-PUFA. These differences may provide a genetic mechanism contributing to health disparities between populations of African and European descent.

Bimodal distribution of polyunsaturated fatty acids in schizophrenia suggests two endophenotypes of the disorder

BACKGROUND

There is conflicting evidence of whether polyunsaturated fatty acids (PUFA) in red blood cells are bimodally distributed in schizophrenia. The purpose of this study was to examine the distribution of PUFA, as well as its links to plausible causal factors.

METHODS

A 16-week cohort study and a case-control study as part of a randomized controlled trial. Ninety-nine patients with DSM-IV schizophrenia, schizoaffective disorder, or schizophreniform disorder, aged 18 to 39, were consecutively included at admission to psychiatric departments of nine Norwegian hospitals. Fatty acids were measured in 97 of these patients and in 20 healthy control subjects. The primary outcome measure was the bimodality test statistic T, assessed by a χ(2) test of the likelihood of one or two normal distributions of PUFA.

RESULTS

At baseline, levels of polyunsaturated fatty acids were highly significantly bimodally distributed among patients. One third of patients constituted a group (low PUFA) who had PUFA levels at one fifth (p < .001) of those in high PUFA patients and healthy control subjects, which did not differ. Bimodality was mainly accounted for by docosahexaenoic acid and arachidonic acid. Bimodality was confirmed after 16 weeks. α-tocopherol was a robust predictor of PUFA at both occasions. Desaturase and elongase indexes differed between PUFA groups. Smoking, gender, antipsychotic medication, and dietary factors did not explain the bimodal distribution.

CONCLUSIONS

Red blood cell PUFA were bimodally distributed among acutely ill patients with schizophrenia and schizoaffective disorder. Endogenous deficiencies of redox regulation or synthesis of long-chain PUFA in the low PUFA group may explain our findings.

FADS1 genetic variability interacts with dietary α-linolenic acid intake to affect serum non-HDL-cholesterol concentrations in European adolescents

Two rate-limiting enzymes in PUFA biosynthesis, Δ5- and Δ6-desaturases, are encoded by the FADS1 and FADS2 genes, respectively. Genetic variants in the FADS1-FADS2 gene cluster are associated with changes in plasma concentrations of PUFA, HDL- and LDL-cholesterol, and TG. However, little is known about whether dietary PUFA intake modulates these associations, especially in adolescents. We assessed whether dietary linoleic acid (LA) or α-linolenic acid (ALA) modulate the association between the FADS1 rs174546 polymorphism and concentrations of PUFA, other lipids, and lipoproteins in adolescents. Dietary intakes of LA and ALA, FADS1 rs174546 genotypes, PUFA levels in serum phospholipids, and serum concentrations of TG, cholesterol, and lipoproteins were determined in 573 European adolescents from the HELENA study. The sample was stratified according to the median dietary LA (≤9.4 and >9.4 g/d) and ALA (≤1.4 and >1.4 g/d) intakes. The associations between FADS1 rs174546 and concentrations of PUFA, TG, cholesterol, and lipoproteins were not affected by dietary LA intake (all P-interaction > 0.05). Similarly, the association between the FADS1 rs174546 polymorphism and serum phospholipid concentrations of ALA or EPA was not modified by dietary ALA intake (all P-interaction > 0.05). In contrast, the rs174546 minor allele was associated with lower total cholesterol concentrations (P = 0.01 under the dominant model) and non-HDL-cholesterol concentrations (P = 0.02 under the dominant model) in the high-ALA-intake group but not in the low-ALA-intake group (P-interaction = 0.01). These results suggest that dietary ALA intake modulates the association between FADS1 rs174546 and serum total and non-HDL-cholesterol concentrations at a young age.

Genetic loci associated with plasma phospholipid n-3 fatty acids: a meta-analysis of genome-wide association studies from the CHARGE Consortium

Long-chain n-3 polyunsaturated fatty acids (PUFAs) can derive from diet or from α-linolenic acid (ALA) by elongation and desaturation. We investigated the association of common genetic variation with plasma phospholipid levels of the four major n-3 PUFAs by performing genome-wide association studies in five population-based cohorts comprising 8,866 subjects of European ancestry. Minor alleles of SNPs in FADS1 and FADS2 (desaturases) were associated with higher levels of ALA (p = 3 x 10⁻⁶⁴) and lower levels of eicosapentaenoic acid (EPA, p = 5 x 10⁻⁵⁸) and docosapentaenoic acid (DPA, p = 4 x 10⁻¹⁵⁴). Minor alleles of SNPs in ELOVL2 (elongase) were associated with higher EPA (p = 2 x 10⁻¹²) and DPA (p = 1 x 10⁻⁴³) and lower docosahexaenoic acid (DHA, p = 1 x 10⁻¹⁵). In addition to genes in the n-3 pathway, we identified a novel association of DPA with several SNPs in GCKR (glucokinase regulator, p = 1 x 10⁻⁸). We observed a weaker association between ALA and EPA among carriers of the minor allele of a representative SNP in FADS2 (rs1535), suggesting a lower rate of ALA-to-EPA conversion in these subjects. In samples of African, Chinese, and Hispanic ancestry, associations of n-3 PUFAs were similar with a representative SNP in FADS1 but less consistent with a representative SNP in ELOVL2. Our findings show that common variation in n-3 metabolic pathway genes and in GCKR influences plasma phospholipid levels of n-3 PUFAs in populations of European ancestry and, for FADS1, in other ancestries.

Fish intake, erythrocyten-3 fatty acid status and metabolic health in Danish adolescent girls and boys

Marinen-3 long-chain PUFA (n-3 LCPUFA) may have a beneficial effect on several aspects of the metabolic syndrome (dyslipidaemia, insulin resistance, hypertension and abdominal obesity). The metabolic syndrome is increasing in prevalence during adolescence, but only few studies have investigated the effects ofn-3 LCPUFA in adolescence. The present study examines associations between fish intake (assessed by a 7 d pre-coded food diary), erythrocyte (RBC) DHA status (analysed by GC) and metabolic syndrome measures (anthropometry, blood pressure and plasma lipids, insulin and glucose) in 109 17-year-old children from the Copenhagen Birth Cohort Study. Of the children, 8 % were overweight or obese and few showed signs of the metabolic syndrome, but all the metabolic syndrome variables were correlated. Median fish intake was 10·7 (interquartile range 3·6–21·2) g/d. Boys tended to have a higher fish intake (P = 0·052), but girls had significantly higher RBC levels of DHA (P = 0·001). Sex and fish intake explained 37 % of the variance in RBC-DHA (P < 0·001). After adjusting for confounders, high DHA status was found to be significantly correlated with higher systolic blood pressure (P = 0·014) and increased fasting insulin (P = 0·018), but no adverse association was observed with the mean metabolic syndromez-score. Overall, the present study showed the expected association between fish intake and RBC-DHA, which in contrast to our expectations tended to be associated with a poorer metabolic profile. Whether these results reflect the physiological function ofn-3 LCPUFA, lifestyle factors associated with fish intake in Denmark, or mere chance remains to be investigated.

Polymorphisms in FADS1 and FADS2 alter desaturase activity in young Caucasian and Asian adults

Recent evidence indicates that genetic variation in fatty acid desaturases 1 and 2 (FADS1 and FADS2) is associated with changes in plasma fatty acid profiles; however, the association with altered desaturase activity has not been examined in different ethnic populations. The present study examined whether genetic variation in the FADS gene cluster regulates desaturase activity in two populations of young Canadian adults (Caucasian and Asian) and whether altered desaturase activity was reflected in both n-3 and n-6 fatty acid profiles. FADS1 and FADS2 were genotyped in a random subset of participants (Caucasian, n=78; Asian, n=69) from the Toronto Nutrigenomics and Health study using MALDI-TOF mass spectrometry, and plasma fatty acids were measured by gas chromatography. Desaturase activities were estimated using the following fatty acid ratios: γ-linoleic acid to linoleic acid (GLA:LA), arachidonic acid to linoleic acid (AA:LA), arachidonic acid to dihomo-γ-linoleic acid (AA:DGLA), and eicosapentaneoic acid to α-linolenic acid (EPA:ALA). Nineteen single nucleotide polymorphisms (SNPs) were examined, and several SNPs (9 in Caucasians and 8 in Asians) were associated with various desaturase activities. The most significant association detected was between the FADS1 rs174547 SNP and AA:LA in both Caucasians (p=4.0 × 10(-8)) and Asians (p=5.0 × 10(-5)). Although the minor allele for this SNP differed between Caucasians (T) and Asians (C), carriers of the C allele had a lower desaturase activity than carriers of the T allele in both groups. To determine whether rs174547 was a dominant SNP in the FADS gene cluster, we constructed an additional model which included this SNP as a covariate. Only one SNP (rs498793 in FADS2) remained associated with the EPA:ALA ratio (p=1.1 × 10(-5)) in Asians. This study shows that genetic variation in the FADS gene cluster (in particular rs174547) can alter desaturase activity in subjects of Caucasians and Asian descent.

The impact of FADS genetic variants on ω6 polyunsaturated fatty acid metabolism in African Americans

Background

Arachidonic acid (AA) is a long-chain omega-6 polyunsaturated fatty acid (PUFA) synthesized from the precursor dihomo-gamma-linolenic acid (DGLA) that plays a vital role in immunity and inflammation. Variants in the Fatty Acid Desaturase (FADS) family of genes on chromosome 11q have been shown to play a role in PUFA metabolism in populations of European and Asian ancestry; no work has been done in populations of African ancestry to date.

Results

In this study, we report that African Americans have significantly higher circulating levels of plasma AA (p = 1.35 × 10^-48) and lower DGLA levels (p = 9.80 × 10^-11) than European Americans. Tests for association in N = 329 individuals across 80 nucleotide polymorphisms (SNPs) in the Fatty Acid Desaturase (FADS) locus revealed significant association with AA, DGLA and the AA/DGLA ratio, a measure of enzymatic efficiency, in both racial groups (peak signal p = 2.85 × 10^-16 in African Americans, 2.68 × 10^-23 in European Americans). Ancestry-related differences were observed at an upstream marker previously associated with AA levels (rs174537), wherein, 79-82% of African Americans carry two copies of the G allele compared to only 42-45% of European Americans. Importantly, the allelic effect of the G allele, which is associated with enhanced conversion of DGLA to AA, on enzymatic efficiency was similar in both groups.

Conclusions

We conclude that the impact of FADS genetic variants on PUFA metabolism, specifically AA levels, is likely more pronounced in African Americans due to the larger proportion of individuals carrying the genotype associated with increased FADS1 enzymatic conversion of DGLA to AA.

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.

Fatty acid desaturase (FADS) gene polymorphisms and insulin resistance in association with serum phospholipid polyunsaturated fatty acid composition in healthy Korean men: cross-sectional study

Background

We investigated the relationship between fatty acid desaturase (FADS) gene polymorphisms and insulin resistance (IR) in association with serum phospholipid polyunsaturated fatty acid (FA) composition in healthy Korean men.

Methods

Healthy men (n = 576, 30 ~ 79 years old) were genotyped for rs174537 near FADS1 (FEN1-10154G>T), FADS2 (rs174575C>G, rs2727270C>T), and FADS3 (rs1000778C>T) SNPs. Dietary intake, serum phospholipid FA composition and HOMA-IR were measured.

Results

Fasting insulin and HOMA-IR were significantly higher in the rs174575G allele carriers than the CC homozygotes, but lower in the rs2727270T allele carriers than the CC homozygotes. The proportion of linoleic acid (18:2ω-6, LA) was higher in the minor allele carriers of FEN1-10154G>T, rs174575C>G and rs2727270C>T than the major homozygotes, respectively. On the other hand, the proportions of dihomo-γ-linolenic acid (20:3ω-6, DGLA) and arachidonic acid (20:4ω-6, AA) in serum phospholipids were significantly lower in the minor allele carriers of FEN1-10154 G>T carriers and rs2727270C>T than the major homozygotes respectively. AA was also significantly lower in the rs1000778T allele carriers than the CC homozygotes. HOMA-IR positively correlated with LA and DGLA and negatively with AA/DGLA in total subjects. Interestingly, rs174575G allele carriers showed remarkably higher HOMA-IR than the CC homozygotes when subjects had higher proportions of DLGA (≥1.412% in total serum phospholipid FA composition) (P for interaction = 0.009) or of AA (≥4.573%) (P for interaction = 0.047).

Conclusion

HOMA-IR is associated with FADS gene cluster as well as with FA composition in serum phospholipids. Additionally, HOMA-IR may be modulated by the interaction between rs174575C>G and the proportion of DGLA or AA in serum phospholipids.

Genetic variants in the FADS gene cluster are associated with arachidonic acid concentrations of human breast milk at 1.5 and 6 mo postpartum and influence the course of milk dodecanoic, tetracosenoic, and trans-9-octadecenoic acid concentrations over the duration of lactation

BACKGROUND

Breastfeeding is considered an optimal nutritional source of n-6 (omega-6) and n-3 (omega-3) fatty acids (FAs) for the proper visual and cognitive development of newborn children. In addition to maternal nutrition as an important regulator of FA concentrations, first results exist on an association of breast-milk FAs with single nucleotide polymorphisms (SNPs) in the FADS gene cluster, which encodes the rate-limiting enzymes in the elongation-desaturation pathway of long-chain polyunsaturated fatty acids (LC-PUFAs).

OBJECTIVE

We analyzed the influence of FADS SNPs on breast-milk FA concentrations and their time course during lactation in the Ulm Birth Cohort study, which comprised 772 nursing mothers at 1.5 mo after giving birth, and in a subset of 463 mothers who were still breastfeeding at 6 mo postpartum.

DESIGN

We conducted linear regression analysis of 8 FADS SNPs with FA concentrations at both time points separately and assessed the genotype effect over time in a longitudinal analysis by using a generalized estimating equation regression model.

RESULTS

We observed significant associations of FADS genotypes with arachidonic acid (AA) concentrations and the 20:4n-6/20:3n-6 ratio at both time points but no association of FADS SNPs with the time course of AA concentrations. A longitudinal analysis of FAs other than LC-PUFAs by genotype over time showed associations for dodecanoic acid, cis-15-tetracosenoic acid, and trans-9-octadecenoic acid.

CONCLUSIONS

Maternal FADS genotypes are associated with breast-milk AA concentrations and might therefore influence the supply of this FA for children. Furthermore, our data indicate an interrelation between the LC-PUFA pathway and saturated and monounsaturated FAs.

Genetic variants of the fatty acid desaturase gene cluster predict amounts of red blood cell docosahexaenoic and other polyunsaturated fatty acids in pregnant women: findings from the Avon Longitudinal Study of Parents and Children

BACKGROUND

Blood and tissue long-chain polyunsaturated fatty acid (LC-PUFA) amounts, which have been associated with early development and lifelong health, depend on dietary intake and endogenous conversion of precursor fatty acids (FAs) by the enzymes Δ⁵-desaturase and Δ⁶-desaturase. Polymorphisms in the desaturase encoding genes FADS1 and FADS2 have been associated with several n-6 (omega-6) and n-3 (omega-3) FAs and especially with arachidonic acid (AA) amounts. Associations with docosahexaenoic acid (DHA), which is considered particularly important for brain and retina development, are hardly existent.

OBJECTIVE

We explored the relation between FADS gene cluster polymorphisms and red blood cell (RBC) FA amounts in > 4000 pregnant women participating in the Avon Longitudinal Study of Parents and Children.

DESIGN

Linear regression analysis of 17 single nucleotide polymorphisms (SNPs) in the FADS gene cluster was conducted with RBC phospholipid FAs from 6711 samples from 4457 women obtained throughout pregnancy (mean ± SD gestational age: 26.8 ± 8.2 wk).

RESULTS

Independent of dietary effects, the minor alleles were consistently positively associated with precursor FAs and negatively associated with LC-PUFAs and product:substrate ratios of the n-6 (AA:linoleic acid ratio) and n-3 (eicosapentaenoic acid:α-linolenic acid ratio) pathways. In contrast to previous studies, we also showed significant inverse associations with DHA. Similar but weaker associations were shown for the FADS3 SNP rs174455.

CONCLUSIONS

FADS genotypes influence DHA amounts in maternal RBC phospholipids and might affect the child's DHA supply during pregnancy. It is highly likely that a gene product of FADS3 has a desaturating activity.

A defect in Δ6 and Δ5 desaturases may be a factor in the initiation and progression of insulin resistance, the metabolic syndrome and ischemic heart disease in South Asians

The high incidence of insulin resistance and the metabolic syndrome in South Asians remains unexplained. I propose that a defect in the activity of Δ⁶ and Δ⁵ desaturases and consequent low plasma and tissue concentrations of polyunsaturated fatty acids such as γ-linolenic acid (GLA), dihomo-γ-linolenic acid (DGLA), arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and formation of their anti-inflammatory products prostaglandin E₁ (PGE₁), prostacyclin (PGI₂), PGI₃, lipoxins, resolvins, protectins, maresins and nitrolipids could be responsible for the high incidence of insulin resistance, the metabolic syndrome and ischemic heart disease (IHD) in South Asians. This proposal is supported by the observation that South Asian Indians have lower plasma and tissue concentrations of GLA, DGLA, AA, EPA and DHA, the precursors of PGE₁, PGI₂, PGI₃, lipoxins, resolvins, protectins, and nitrolipids, the endogenous molecules that prevent platelet aggregation, vasoconstriction, thrombus formation, leukocyte activation and possess anti-inflammatory action and thus, are capable of preventing the development of insulin resistance, atherosclerosis, hypertension, type 2 diabetes mellitus and premature ischemic heart disease. Genetic predisposition, high carbohydrate intake, lack of exercise, tobacco use and low birth weight due to maternal malnutrition suppress the activity of Δ⁶ and Δ⁵ desaturases that leads to low plasma and tissue concentrations of polyunsaturated fatty acids and their products. This implies that adequate provision of polyunsaturated fatty acids and co-factors needed for their metabolism, and efforts to enhance the formation of their beneficial metabolites PGE₁, PGI₂, PGI₃, lipoxins, resolvins, protectins, maresins and nitrolipids could form a novel approach in the prevention and management of these diseases in this high-risk population.

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.

Interactions between the APOA5 -1131T>C and the FEN1 10154G>T polymorphisms on ω6 polyunsaturated fatty acids in serum phospholipids and coronary artery disease

We determined the contribution of the combination of FEN1 10154G>T with the most significant association in the analysis of plasma arachidonic acid (AA, 20:4ω6) and the APOA5-1131T>C on phospholipid ω6PUFA and coronary artery disease (CAD). Patients with CAD (n = 807, 27-81 years of age) and healthy controls (n = 1123) were genotyped for FEN1 10154G>T and APOA5-1131T>C. We found a significant interaction between these two genes for CAD risk (P = 0.007) adjusted for confounding factors. APOA5-1131C allele carriers had a higher CAD risk [odds ratio (OR):1.484, 95% confidence interval (CI):1.31-1.96; P = 0.005] compared with APOA5-1131TT individuals in the FEN1 10154GG genotype group but not in the FEN1 10154T allele group (OR:1.096, 95%CI:0.84-1.43; P = 0.504). Significant interactions between these two genes were also observed for the AA proportion (P = 0.04) and the ratio of AA/linoleic acid (LA, 18:2ω6) (P = 0.004) in serum phospholipids of controls. The APOA5-1131C allele was associated with lower AA (P = 0.027) and AA/LA (P = 0.014) only in controls carrying the FEN1 10154T allele. In conclusion, the interaction between these genes suggests that the FEN1 10154T variant allele decreases AA and AA/LA in the serum phospholipids of carriers of the APOA5-1131C allele, but contributes no significant increase in CAD risk for this population subset despite their increased triglylcerides and decreased apoA5.

Genetic variation of the FADS1 FADS2 gene cluster and n-6 PUFA composition in erythrocyte membranes in the European Prospective Investigation into Cancer and Nutrition-Potsdam study

Delta-5 (D5D) and delta-6 (D6D) desaturases are key enzymes in PUFA metabolism. Several factors (e.g. hyperglycaemia, hypertension, blood lipids, statins and fatty acids in diet and biological tissues) may influence desaturase activity. The goals were to evaluate the associations between variation in genes encoding these desaturases (FADS1 and FADS2) and blood concentrations of n-6 PUFA and estimated D5D and D6D activities (evaluated as product/precursor ratio), and to investigate whether other factors influencing the activity of desaturases modify these associations. A random sample of 2066 participants from the European Prospective Investigation into Cancer and Nutrition-Potsdam study (n 27 548) was utilised in the analyses. Crude and adjusted associations between rs174546 genotypes (reflecting genetic variation in the FADS1 FADS2 gene cluster), n-6 PUFA in erythrocytes and estimated desaturase activities were evaluated using multiple linear regression. Potential effect modification was determined by performing stratified analyses and evaluating interaction terms. We found rs174546 genotypes to be related to linoleic (r² 0·060), γ-linolenic (r² 0·041), eicosadienoic (r² 0·034), arachidonic (r² 0·026), docosatetraenoic acids (r² 0·028), estimated D6D activity (r² 0·052) and particularly strongly to dihomo-γ-linolenic acid (DGLA, r² 0·182) and D5D activity (r² 0·231). We did not observe effect modifications with regard to the estimated D5D activity, DGLA and arachidonic acid (AA) for most of the factors evaluated; however, the genetic effect on D5D activity and DGLA may be modified by the dietary n-6:n-3-ratio (P-values for interaction: 0·008 and 0·002), and the genetic effect on DGLA and AA may be modified by lipid-lowering medication (P-values for interaction: 0·0004 and 0·006). In conclusion, genetic variation in the FADS1 FADS2 gene cluster affects n-6 PUFA profiles in erythrocytes reflecting altered D5D activity.

Genetic variants in the metabolism of omega-6 and omega-3 fatty acids: their role in the determination of nutritional requirements and chronic disease risk

The tissue composition of polyunsaturated fatty acids is important to health and depends on both dietary intake and metabolism controlled by genetic polymorphisms that should be taken into consideration in the determination of nutritional requirements. Therefore at the same dietary intake of linoleic acid (LA) and alpha-linolenic acid (ALA), their respective health effects may differ due to genetic differences in metabolism. Delta-5 and delta-6 desaturases, FADS1 and FADS2, respectively, influence the serum, plasma and membrane phospholipid levels of LA, ALA and long-chain polyunsaturated fatty acids during pregnancy, lactation, and may influence an infant's IQ, atopy and coronary heart disease (CHD) risk. At low intakes of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), polymorphisms at the 5-lipoxygenase (5-LO) level increase the risk for CHD whereas polymorphisms at cyclooxgenase-2 increase the risk for prostate cancer. At high intakes of LA the risk for breast cancer increases. EPA and DHA influence gene expression. In future, intervention studies on the biological effects of LA, ALA and LC-PUFAs, and the effects of genetic variants in FADS1 and FADS2, 5-LO and cyclooxygenase-2 should be taken into consideration both in the determination of nutritional requirements and chronic disease risk. Furthermore, genome-wide association studies need to include environmental exposures and include diet in the interaction between genetic variation and disease association.

Lipophilic compound-mediated gene expression and implication for intervention in reactive oxygen species (ROS)-related diseases: mini-review

In addition to exhibiting antioxidant properties, conjugated linoleic acid (CLA) and vitamin E may modulate gene expression of endogenous antioxidant enzymes. Depending on cellular microenvironments, such modulation reflects either antioxidant or prooxidant outcomes. Although epidemiological/experimental studies have indicated that CLA and vitamin E have health promoting properties, recent findings from clinical trials have been inconclusive. Discrepancies between the results found from prospective studies and recent clinical trials might be attributed to concentration-dependent cellular microenvironment alterations. We give a perspective of possible molecular mechanisms of actions of these lipophilic compounds and their implications for interventions of reactive oxygen species (ROS)-related diseases.

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.

Dietary n-3 and n-6 polyunsaturated fatty acid intake interacts with FADS1 genetic variation to affect total and HDL-cholesterol concentrations in the Doetinchem Cohort Study

BACKGROUND

The delta-5 and delta-6 desaturases, encoded by the FADS1 and FADS2 genes, are rate-limiting enzymes in polyunsaturated fatty acid (PUFA) biosynthesis. Single nucleotide polymorphisms in the FADS gene cluster region have been associated with both PUFA concentrations in plasma or erythrocyte membrane phospholipids and cholesterol concentrations in recent genome-wide association studies.

OBJECTIVE

We examined whether genetic variations in the FADS gene cluster region interact with dietary intakes of n-3 (omega-3) and n-6 (omega-6) PUFAs to affect plasma total, HDL-, and non-HDL-cholesterol concentrations.

DESIGN

Dietary intakes of n-3 and n-6 PUFAs, plasma concentrations of total and HDL cholesterol, and rs174546, rs482548, and rs174570 in the FADS gene cluster region were measured in 3575 subjects in the second survey of the Doetinchem Cohort Study.

RESULTS

Significant associations between rs174546 genotypes and total and non-HDL-cholesterol concentrations were observed in the group with a high intake of n-3 PUFAs (> or =0.51% of total energy; P = 0.006 and 0.047, respectively) but not in the low-intake group (P for interaction = 0.32 and 0.51, respectively). The C allele was associated with high total and non-HDL-cholesterol concentrations. Furthermore, the C allele was significantly associated with high HDL-cholesterol concentrations in the group with a high intake of n-6 PUFAs (> or =5.26% of total energy, P = 0.004) but not in the group with a low intake (P for interaction = 0.02).

CONCLUSION

Genetic variation in the FADS1 gene potentially interacts with dietary PUFA intakes to affect plasma cholesterol concentrations, which should be investigated further in other studies.

Genetic variation in lipid desaturases and its impact on the development of human disease

Perturbations in lipid metabolism characterize many of the chronic diseases currently plaguing our society, such as obesity, diabetes, and cardiovascular disease. Thus interventions that target plasma lipid levels remain a primary goal to manage these diseases. The determinants of plasma lipid levels are multi-factorial, consisting of both genetic and lifestyle components. Recent evidence indicates that fatty acid desaturases have an important role in defining plasma and tissue lipid profiles. This review will highlight the current state-of-knowledge regarding three desaturases (Scd-1, Fads1 and Fads2) and their potential roles in disease onset and development. Although research in rodent models has provided invaluable insight into the regulation and functions of these desaturases, the extent to which murine research can be translated to humans remains unclear. Evidence emerging from human-based research demonstrates that genetic variation in human desaturase genes affects enzyme activity and, consequently, disease risk factors. Moreover, this genetic variation may have a trans-generational effect via breastfeeding. Therefore inter-individual variation in desaturase function is attributed to both genetic and lifestyle components. As such, population-based research regarding the role of desaturases on disease risk is challenged by this complex gene-lifestyle paradigm. Unravelling the contribution of each component is paramount for understanding the inter-individual variation that exists in plasma lipid profiles, and will provide crucial information to develop personalized strategies to improve health management.

FADS1 FADS2 gene variants modify the association between fish intake and the docosahexaenoic acid proportions in human milk

BACKGROUND

The genes encoding Delta(5)- and Delta(6)-desaturases (FADS1 FADS2 gene cluster) were reported to be associated with n-3 (omega-3) and n-6 (omega-6) fatty acid proportions in human plasma, tissues, and milk. Docosahexaenoic acid (DHA) can be supplied especially by dietary fish or fish oil and synthesized from alpha-linolenic acid through a pathway involving these desaturases.

OBJECTIVE

We evaluated whether FADS gene variants modify the effect of maternal fish and fish-oil intake on plasma and milk DHA proportions.

DESIGN

FADS1 rs174561, FADS2 rs174575, and intergenic rs3834458 single nucleotide polymorphisms were genotyped in 309 women from the KOALA Birth Cohort Study in The Netherlands. Plasma was collected at 36 wk of pregnancy, and milk was collected at 1 mo postpartum. Fish and fish-oil intake was assessed by using a food-frequency questionnaire at 34 wk of pregnancy and updated for the week of milk collection. Gene-diet interactions were tested by linear regression analysis.

RESULTS

DHA proportions were lower in women homozygous for the minor allele than in women who were homozygous for the major allele (DHA proportions in plasma phospholipids: P < 0.01; DHA proportions in milk: P < 0.05). Fish intake ranged from 0 to 2.5 portions of fatty fish/wk, and 12 women took fish-oil supplements during pregnancy. DHA proportions in plasma phospholipids increased with increasing fish and fish-oil intake, irrespective of the genotype. DHA proportions in milk increased only with fish and fish-oil intake in the major-allele carriers.

CONCLUSION

Lower proportions of DHA in milk from women who were homozygous for the minor allele could not be compensated for by increasing fish and fish-oil intake, possibly because of limited incorporation into milk.