Fatty Acid Desaturase Gene Cluster Research Articles

Impact of FADS genotype on polyunsaturated fatty acid content in human milk extracellular vesicles: A genetic association study.

Extracellular vesicles in human milk are critical in supporting newborn growth and development. Bioavailability of dietary extracellular vesicles may depend on the composition of membrane lipids. Single-nucleotide polymorphisms (SNPs) in the fatty acid desaturase gene cluster impact the content of long-chain polyunsaturated fatty acids in human milk phospholipids. This study investigated the relation between variation in FADS1 and FADS2 with the content of polyunsaturated fatty acids in extracellular vesicles from human milk. Milk was obtained from a cohort of mothers (N = 70) at 2-4 weeks of lactation. SNPs in the FADS gene locus were determined using pyrosequencing for rs174546 in FADS1 and rs174575 in FADS2. Quantitative lipidomic analysis of polyunsaturated fatty acids in human milk and extracellular vesicles from human milk was completed by gas chromatography-mass spectrometry. The rs174546 and rs174575 genotypes were independent predictors of the arachidonic acid content in extracellular vesicles. The rs174546 genotype also predicted eicosapentaenoic acid and docosahexaenoic acid in extracellular vesicles. The reduced content of long-chain polyunsaturated fatty acids in extracellular vesicles in human milk may be due to lower fatty acid desaturase activity in mothers who are carriers of the A allele in rs174546 or the G allele in rs174575. The polyunsaturated fatty acid composition of milk extracellular vesicles is predicted by the FADS genotype. These findings yield novel insights regarding extracellular vesicle content and composition that can inform the design of future research to explore how lipid metabolites impact the bioavailability of human milk extracellular vesicles.

Metabolomic Investigation of Major Depressive Disorder Identifies a Potentially Causal Association With Polyunsaturated Fatty Acids

BackgroundMetabolic differences have been reported between individuals with and without major depressive disorder (MDD), but their consistency and causal relevance have been unclear. MethodsWe conducted a metabolome-wide association study of MDD with 249 metabolomic measures available in the UK Biobank (n = 29,757). We then applied two-sample bidirectional Mendelian randomization and colocalization analysis to identify potentially causal relationships between each metabolite and MDD. ResultsA total of 191 metabolites tested were significantly associated with MDD (false discovery rate–corrected p < .05), which decreased to 129 after adjustment for likely confounders. Lower abundance of omega-3 fatty acid measures and a higher omega-6 to omega-3 ratio showed potentially causal effects on liability to MDD. There was no evidence of a causal effect of MDD on metabolite levels. Furthermore, genetic signals associated with docosahexaenoic acid colocalized with loci associated with MDD within the fatty acid desaturase gene cluster. Post hoc Mendelian randomization of gene-transcript abundance within the fatty acid desaturase cluster demonstrated a potentially causal association with MDD. In contrast, colocalization analysis did not suggest a single causal variant for both transcript abundance and MDD liability, but rather the likely existence of two variants in linkage disequilibrium with one another. ConclusionsOur findings suggest that decreased docosahexaenoic acid and increased omega-6 to omega-3 fatty acids ratio may be causally related to MDD. These findings provide further support for the causal involvement of fatty acids in MDD.

Investigation of FADS Gene Cluster Single Nucleotide Polymorphisms in End-Stage Renal Disease Compared With Normal Controls.

End-stage renal disease (ESRD) is a public health problem with a high burden. The condition is associated with abnormalities in lipid metabolism. The fatty acid desaturase (FADS) gene cluster includes three genes that are significantly correlated with a number of pathologic conditions related to abnormal lipid levels. In the current study, we genotyped rs174556, rs99780, and rs7115739 single nucleotide polymorphisms within the FADS cluster in a population of ESRD patients and healthy controls. The rs174556 of the FADS1 gene and rs99780 of the FADS2 gene were not associated with the risk of ESRD in any inheritance model. However, the rs7115739 of FADS3 was associated with the risk of ESRD in all models except for the recessive model. The T allele of this SNP was significantly less prevalent among cases compared with controls [odds ratio (OR) (95% CI) = 0.44 (0.25–0.77), P value = 0.004]. GT and TT genotypes has been shown to decrease the risk of ESRD in a codominant model [OR (95% CI) = 0.49 (0.26–0.92) and OR (95% CI) = 0.18 (0.02–1.6), respectively; P value = 0.019]. In the dominant model, GT + TT status was associated with lower risk of ESRD [OR (95% CI) = 0.45 (0.24–0.82), P value = 0.0078]. Assessment of association between this SNP and risk of ESRD in an overdominant model revealed that GT genotype decreases the risk of this condition [OR (95% CI) = 0.5 (0.27–0.94), P value = 0.029]. Taken together, the rs7115739 of FADS3 is suggested as a putative modulator of the risk of ESRD in the Iranian population.

Long-Chain Polyunsaturated Fatty Acids, Homocysteine at Birth and Fatty Acid Desaturase Gene Cluster Polymorphisms Are Associated with Children’s Processing Speed up to Age 9 Years

Both pre- and early postnatal supplementation with docosahexaenoic acid (DHA), arachidonic acid (AA) and folate have been related to neural development, but their long-term effects on later neural function remain unclear. We evaluated the long-term effects of maternal prenatal supplementation with fish-oil (FO), 5-methyltetrahydrofolate (5-MTHF), placebo or FO + 5-MTHF, as well as the role of fatty acid desaturase (FADS) gene cluster polymorphisms, on their offspring’s processing speed at later school age. This study was conducted in NUHEAL children at 7.5 (n = 143) and 9 years of age (n = 127). Processing speed tasks were assessed using Symbol Digit Modalities Test (SDMT), Children Color Trails Test (CCTT) and Stroop Color and Word Test (SCWT). Long-chain polyunsaturated fatty acids, folate and total homocysteine (tHcy) levels were determined at delivery from maternal and cord blood samples. FADS and methylenetetrahydrofolate reductase (MTHFR) 677 C > T genetic polymorphisms were analyzed. Mixed models (linear and logistic) were performed. There were significant differences in processing speed performance among children at different ages (p < 0.001). The type of prenatal supplementation had no effect on processing speed in children up to 9 years. Secondary exploratory analyses indicated that children born to mothers with higher AA/DHA ratio at delivery (p < 0.001) and heterozygotes for FADS1 rs174556 (p < 0.05) showed better performance in processing speed at 9 years. Negative associations between processing speed scores and maternal tHcy levels at delivery were found. Our findings suggest speed processing development in children up to 9 years could be related to maternal factors, including AA/DHA and tHcy levels, and their genetic background, mainly FADS polymorphism. These considerations support that maternal prenatal supplementation should be quantitatively adequate and individualized to obtain better brain development and mental performance in the offspring.

Early nutrition in combination with polymorphisms in fatty acid desaturase gene cluster modulate fatty acid composition of cheek cells' glycerophospholipids in school-age children.

Variants in the human genes of fatty acid (FA) desaturase 1 (FADS1), 2 (FADS2) and 3 (FADS3) are associated with PUFA blood levels. We explored if maternal prenatal supplementation and children's genetic variation in seventeen SNP of the FADS1, FADS2 and FADS3 gene cluster influence twenty-one of the most relevant cheek cells' derived FA in glycerophospholipids (GPL-FA). The study was conducted in 147 Spanish and German mother-children pairs participating in the Nutraceuticals for a Healthier Life (NUHEAL) study at 8, 9 and 9·5 years. Linear and mixed model longitudinal regression analyses were performed. Maternal fish-oil (FO) or FO+5-methyltetrahydrofolate (5-MTHF) supplementation during pregnancy was associated with a significant decrease of arachidonic acid (AA) concentrations in cheek cell GPL in the offspring, from 8 to 9·5 years; furthermore, maternal FO+5-MTHF supplementation was associated with higher n-6 docosapentaenoic acid concentrations in their children at age 8 years. FADS1 rs174556 polymorphism and different FADS2 genotypes were associated with higher concentrations of linoleic and α-linolenic acids in children; moreover, some FADS2 genotypes determined lower AA concentrations in children's cheek cells. It is suggested an interaction between type of prenatal supplementation and the offspring genetic background driving GPL-FA levels at school age. Prenatal FO supplementation, and/or with 5-MTHF, seems to stimulate n-3 and n-6 FA desaturation in the offspring, increasing long-chain PUFA concentrations at school age, but depending on children's FADS1 and FADS2 genotypes. These findings suggest potential early nutrition programming of FA metabolic pathways, but interacting with children's FADS polymorphisms.

The association of fatty acid desaturase gene polymorphisms on long-chain polyunsaturated fatty acid composition in Indonesian infants

ABSTRACTBackgroundAdequate availability of long-chain polyunsaturated fatty acids (LC-PUFAs) is important for human health from pregnancy to adulthood. Previous studies on fatty acid desaturase (FADS) gene single-nucleotide polymorphisms (SNPs) have been performed predominantly in Western populations and showed that FADS SNPs had a marked impact on LC-PUFA composition in blood and tissues.ObjectivesWe aimed to investigate the influence of fetal FADS genotypes on LC-PUFA composition in umbilical artery plasma lipids in Indonesian infants.DesignWe performed a cross-sectional study to assess for these associations.ResultsA total of 12 cord plasma n–6 (ω-6) and n–3 (ω-3) fatty acids were analyzed for associations with 18 FADS gene cluster SNPs from 390 women with single parturition from the Indonesian Prospective Study of Atopic Dermatitis in Infants (ISADI). Fetal FADS genotypes influenced cord plasma LC-PUFA composition, but, in contrast to previous studies from Western populations, the quantitatively predominant SNPs were associated with lower LC-PUFA content.ConclusionTo our knowledge, this study was the first in South East Asia on FADS genotypes and arterial cord blood fatty acids to show an association between fetal LC-PUFA composition and fetal FADS SNPs. The FADS genotype distribution differs markedly between different geographical populations. This trial was registered at clinicaltrials.gov as NCT02401178.

The combined effects of FADS gene variation and dietary fats in obesity-related traits in a population from the far north of Sweden: the GLACIER Study.

BackgroundRecent analyses in Greenlandic Inuit identified six genetic polymorphisms (rs74771917, rs3168072, rs12577276, rs7115739, rs174602, and rs174570) in the fatty acid desaturase gene cluster (FADS1-FADS2-FADS3) that are associated with multiple metabolic and anthropometric traits. Our objectives were to systematically assess whether dietary polyunsaturated fat acid (PUFA) intake modifies the associations between genetic variants in the FADS gene cluster and cardiometabolic traits and to functionally annotate top ranking candidates to estimate their regulatory potential.MethodsData analyses consisted: interaction analyses between the six candidate genetic variants and dietary PUFA intake; gene-centric joint analyses to detect interaction signals in the FADS region; haplotype block-centric joint tests across 30 haplotype blocks in the FADS region to refine interaction signals; functional annotation of top loci. These analyses were undertaken in Swedish adults from the GLACIER Study (N=5,160); data on genetic variation and eight cardiometabolic traits was used.ResultsInteractions were observed between rs174570 and n-6 PUFA intake on fasting glucose (Pint=0.005) and between rs174602 and n-3 PUFA intake on total cholesterol (Pint=0.001). Gene-centric analyses demonstrated a statistically significant interaction effect for FADS and n-3 PUFA on triglycerides (P=0.005) considering genetic main effects as random. Haplotype analyses revealed three blocks (Pint<0.011) that could drive the interaction between FADS and n-3 PUFA on triglycerides; Functional annotation of these regions showed that each block harbours a number of highly functional regulatory variants; FADS2 rs5792235 demonstrated the highest functionality score.ConclusionsThe association between FADS variants and triglycerides may be modified by PUFA intake. The intronic FADS2 rs5792235 variant is a potential causal variant in the region having the highest regulatory potential. However, our results suggest that haplotypes may harbour multiple functional variants in a region, rather than a single variant.

Tissue-specific impact of FADS cluster variants on FADS1 and FADS2 gene expression.

Omega-6 (n-6) and omega-3 (n-3) long (≥ 20 carbon) chain polyunsaturated fatty acids (LC-PUFAs) play a critical role in human health and disease. Biosynthesis of LC-PUFAs from dietary 18 carbon PUFAs in tissues such as the liver is highly associated with genetic variation within the fatty acid desaturase (FADS) gene cluster, containing FADS1 and FADS2 that encode the rate-limiting desaturation enzymes in the LC-PUFA biosynthesis pathway. However, the molecular mechanisms by which FADS genetic variants affect LC-PUFA biosynthesis, and in which tissues, are unclear. The current study examined associations between common single nucleotide polymorphisms (SNPs) within the FADS gene cluster and FADS1 and FADS2 gene expression in 44 different human tissues (sample sizes ranging 70–361) from the Genotype-Tissue Expression (GTEx) Project. FADS1 and FADS2 expression were detected in all 44 tissues. Significant cis-eQTLs (within 1 megabase of each gene, False Discovery Rate, FDR<0.05, as defined by GTEx) were identified in 12 tissues for FADS1 gene expression and 23 tissues for FADS2 gene expression. Six tissues had significant (FDR< 0.05) eQTLs associated with both FADS1 and FADS2 (including artery, esophagus, heart, muscle, nerve, and thyroid). Interestingly, the identified eQTLs were consistently found to be associated in opposite directions for FADS1 and FADS2 expression. Taken together, findings from this study suggest common SNPs within the FADS gene cluster impact the transcription of FADS1 and FADS2 in numerous tissues and raise important questions about how the inverse expression of these two genes impact intermediate molecular (such a LC-PUFA and LC-PUFA-containing glycerolipid levels) and ultimately clinical phenotypes associated with inflammatory diseases and brain health.

Δ-5 Fatty Acid Desaturase FADS1 Impacts Metabolic Disease by Balancing Proinflammatory and Proresolving Lipid Mediators.

Human genetic variants near the FADS (fatty acid desaturase) gene cluster (FADS1-2-3) are strongly associated with cardiometabolic traits including dyslipidemia, fatty liver, type 2 diabetes mellitus, and coronary artery disease. However, mechanisms underlying these genetic associations are unclear. Here, we specifically investigated the physiological role of the Δ-5 desaturase FADS1 in regulating diet-induced cardiometabolic phenotypes by treating hyperlipidemic LDLR (low-density lipoprotein receptor)-null mice with antisense oligonucleotides targeting the selective knockdown of Fads1. Fads1 knockdown resulted in striking reorganization of both ω-6 and ω-3 polyunsaturated fatty acid levels and their associated proinflammatory and proresolving lipid mediators in a highly diet-specific manner. Loss of Fads1 activity promoted hepatic inflammation and atherosclerosis, yet was associated with suppression of hepatic lipogenesis. Fads1 knockdown in isolated macrophages promoted classic M1 activation, whereas suppressing alternative M2 activation programs, and also altered systemic and tissue inflammatory responses in vivo. Finally, the ability of Fads1 to reciprocally regulate lipogenesis and inflammation may rely in part on its role as an effector of liver X receptor signaling. These results position Fads1 as an underappreciated regulator of inflammation initiation and resolution, and suggest that endogenously synthesized arachidonic acid and eicosapentaenoic acid are key determinates of inflammatory disease progression and liver X receptor signaling.

Can polymorphisms in the fatty acid desaturase (FADS) gene cluster alter the effects of fish oil supplementation on plasma and erythrocyte fatty acid profiles? An exploratory study.

The enzymes encoded by fatty acid desaturases (FADS) genes determine the desaturation of long-chain polyunsaturated fatty acids (LCPUFA). We investigated if haplotype and single nucleotide polymorphisms (SNPs) in FADS gene cluster can influence LCPUFA status in infants who received either fish oil or placebo supplementation. Children enrolled in the Infant Fish Oil Supplementation Study (IFOS) were randomly allocated to receive either fish oil or placebo from birth to 6 months of age. Blood was collected at 6 months of age for the measurement of fatty acids and for DNA extraction. A total of 276 participant DNA samples underwent genotyping, and 126 erythrocyte and 133 plasma fatty acid measurements were available for analysis. Twenty-two FADS SNPs were selected on the basis of literature and linkage disequilibrium patterns identified from the HapMap data. Haplotype construction was completed using PHASE. For participants allocated to the fish oil group who had two copies of the FADS1 haplotype consisting of SNP minor alleles, DHA levels were significantly higher compared to other haplotypes. This finding was not observed for the placebo group. Furthermore, for members of the fish oil group only, the minor homozygous carriers of all the FADS1 SNPs investigated had significantly higher DHA than other genotypes (rs174545, rs174546, rs174548, rs174553, rs174556, rs174537, rs174448, and rs174455). Overall results of this preliminary study suggest that supplementation with fish oil may only significantly increase DHA in minor allele carriers of FADS1 SNPs. Further research is required to confirm this novel finding.

Erythrocyte polyunsaturated fatty acid composition is associated with depression and FADS genotype in Caucasians

Background: Polyunsaturated fatty acids (PUFAs) play an important role in the pathophysiology of major depressive disorder (MDD), related, in part, to their role in inflammatory systems. The enzymes δ-5 and δ-6 desaturase are the rate-limiting steps in the metabolism of PUFAs and are encoded in the genes fatty acid desaturase (FADS) 1 and 2, respectively. Single nucleotide polymorphisms (SNPs) and haplotypes within the FADS gene cluster have been shown to influence PUFA composition.Aim: The objective of this study was to determine whether key omega-3 (n-3) and omega-6 (n-6) fatty acids may be associated with depression, and to explore the role of FADS genotype in PUFA variation.Methods: Four erythrocyte long chain (LC) fatty acids (linoleic acid [LA], α-linolenic acid [ALA], arachidonic acid [AA] and Eicosapentaenoic acid [EPA]), as well as six SNPs (rs174537, rs174547, rs174570, rs174575, rs498793 and rs3834458) within the FADS gene cluster were measured in a sample of 207 participants (154 with MDD versus 53 non-depressed controls).Results: The precursor LC-PUFAs LA and ALA appeared to be negatively associated with depression (P < 0.001 and P < 0.01, respectively), while AA:LA (surrogate measure of desaturase activity) was positively associated with depression (P < 0.01). No significant differences were noted in erythrocyte EPA, AA or AA:EPA between groups. Minor alleles of each SNP (excluding rs498793) were associated with variation in desaturase activity and LA. Both rs174537 and rs174547 were associated with ALA. No genotype was associated with EPA or AA. Minor alleles of rs174537 and rs174547 were significantly associated with lower odds of MDD (although significance was lost after correction for multiple comparisons).Conclusion: Precursor LC-PUFAs, LA and ALA, appear to be associated with MDD and potentially modulated by genetic variation in the FADS gene cluster. These results provide support for the consideration of PUFA composition, diet and FADS genetic variation in the pathophysiology of MDD.

A study of associations between early DHA status and fatty acid desaturase (FADS) SNP and developmental outcomes in children of obese mothers

DHA from diet or endogenous synthesis has been proposed to affect infant development, however, results are inconclusive. In this study, we aim to verify previously observed fatty acid desaturase gene cluster (FADS) SNP-specific associations with erythrocyte DHA status in 9-month-old children and sex-specific association with developmental outcomes. The study was performed in 166 children (55 % boys) of obese mothers. Erythrocyte fatty acid composition was analysed in blood-samples obtained at 9 months of age, and developmental outcomes assessed by the Ages and Stages Questionnaire at 3 years. Erythrocyte DHA level ranged from 4·4 to 9·9 % of fatty acids, but did not show any association with FADS SNP or other potential determinants. Regression analysis showed associations between erythrocyte DHA and scores for personal-social skills (β 1·8 (95 % CI 0·3, 3·3), P=0·019) and problem solving (β 3·4 (95 % CI 1·2, 5·6), P=0·003). A tendency was observed for an association in opposite direction between minor alleles (G-variant) of rs1535 and rs174575 and personal-social skills (P=0·062 and 0·068, respectively), which became significant when the SNP were combined based on their previously observed effect on erythrocyte DHA at 9 months of age (β 2·6 (95 % CI 0·01, 5·1), P=0·011). Sex-SNP interaction was indicated for rs174575 genotype on fine motor scores (P=0·016), due to higher scores among minor allele carrying girls (P=0·043), whereas no effect was seen among boys. In conclusion, DHA-increasing FADS SNP and erythrocyte DHA status were consistently associated with improved personal-social skills in this small cohort of children of obese mothers irrespective of sex, but the sample was too small to verify potential sex-specific effects.

Association of the FADS gene cluster with coronary artery disease and plasma lipid concentrations in the northern Chinese Han population

We investigated the association of single nucleotide polymorphisms (SNPs) in the fatty acid desaturase (FADS) gene cluster with coronary artery disease (CAD) in a case-control study and evaluated the possible influence of genetic variation on total cholesterol (TC) and triglyceride concentrations in the controls. In total, 497 CAD patients and 495 unrelated controls were genotyped for eight SNPs in the FADS gene cluster, and the blood lipid levels of subjects were measured. Three genetic models, including codominant, dominant and recessive, were used to analyze the genotypic relationship with CAD and plasma lipid levels. Single locus genotypic analysis revealed that rs1000778 in FADS3 under a recessive model (AA vs. GG-GA) was significantly associated with CAD adjusted for risk factors. The rs1000778 minor allele AA was associated with a lower risk of CAD (OR =0.37, 95% CI: 0.15–0.89, P=0.025). In the control group, there were significant differences in TC concentrations under a recessive genetic model for rs174575 (C/G) in FADS2 and for rs174450 (A/C) and rs7115739 (G/T) in FADS3 (P=0.053, 0.016 and 0.018, respectively). The rs1000778-G variant in FADS3 may contribute to the susceptibility of CAD, but the result needs to be further confirmed because of small sample size in our study. Genetic variations in FADS2 and FADS3 influence TC concentration in the northern Chinese Han population.

Alternative splicing generates novel Fads3 transcript in mice.

Fads3 is the third member of the fatty acid desaturase gene cluster; with at least eight evolutionarily conserved alternative transcripts (AT), having no clearly established function as are known for FADS2 and FADS1. Here we present identification of a novel Fads3 transcript in mice (Fads3AT9), characterize Fads3AT9 expression in mouse tissues and evaluate correlations with metabolite profiles. Total RNA obtained from mouse tissues is reverse-transcribed into cDNA and used as template for PCR reactions. Tissue fatty acids were extracted and quantified by gas chromatography. Sequencing analysis revealed complete absence of exon 2 resulting in an open reading frame of 1239bp, encoding a putative protein of 412 aa with loss of 37 aa compared to classical Fads3 (Fads3CS). FADS3AT9 retains all the conserved regions characteristic of front end desaturase (cytochrome b5 domain and three histidine repeats). Both Fads3CS and Fads3AT9 are ubiquitously expressed in 11 mouse tissues. Fads3AT9 abundance was greater than Fads3CS in pancreas, liver, spleen, brown adipose tissue and thymus. Fads3CS expression is low in pancreas while Fads3AT9 is over ten-fold greater abundance. The eicosanoid precursor fatty acid 20:4n-6, the immediate desaturation product of the Fads1 coded Δ5-desaturase, was highest in pancreas where Fads3CS is low. Changes in expression patterns and fatty acid profiles suggest that Fads3AT9 may play a role in the regulation and/or biosynthesis of long chain polyunsaturated fatty acids from precursors.

Association of polyunsaturated fatty acids in breast milk with fatty acid desaturase gene polymorphisms among Chinese lactating mothers

BackgroundThe fatty acid desaturase (FADS) controls polyunsaturated fatty acid (PUFA) synthesis in human tissues and breast milk. DesignEvaluate the influence of 10 single nucleotide polymorphisms (SNPs) and various haplotypes in the FADS gene cluster (FADS1, FADS2, FADS3) on PUFA concentration in the breast milk of 209 healthy Chinese women. PUFA concentrations were measured in breast milk using gas chromatography and genotyping was performed using the Sequenom Mass Array system. ResultsA SNP (rs1535) and 2-locus haplotypes (rs3834458-rs1535, rs1535-rs174575) in the FADS2 gene were associated with concentrations of γ-linoleic acid (GLA) and arachidonic acid (AA) in breast milk. Likewise, in the FADS1 gene, a 2-locus constructed haplotype (rs174547-rs174553) also affected GLA and AA concentration (P<0.05 for all). Minor allele carriers of the SNP and haplotypes described above had lower concentrations of GLA and AA. In the FADS2 gene, the 3-locus haplotype rs3834458-rs1535-rs174575, significantly affected concentrations of GLA but not AA. Pairwise comparison showed that individuals major homozygous for the SNP rs1000778 in the FADS3 gene had lower concentrations of ALA and linoleic acid (LA) in their breast milk. ConclusionPolymorphisms in the FADS gene cluster influence PUFA concentrations in the breast milk of Chinese Han lactating women.

Desaturase and elongase-limiting endogenous long-chain polyunsaturated fatty acid biosynthesis.

Endogenous synthesis of the long-chain polyunsaturated fatty acids (LCPUFAs) is mediated by the fatty acid desaturase (FADS) gene cluster (11q12-13.1) and elongation of very long-chain fatty acids 2 (ELOVL2) (6p24.2) and ELOVL5 (6p12.1). Although older biochemical work identified the product of one gene, FADS2, rate limiting for LCPUFA synthesis, recent studies suggest that polymorphisms in any of these genes can limit accumulation of product LCPUFA. Genome-wide association study (GWAS) of Greenland Inuit shows strong adaptation signals within FADS gene cluster, attributed to high omega-3 fatty acid intake, while GWAS found ELOVL2 associated with sleep duration, age and DNA methylation. ELOVL5 coding mutations cause spinocerebellar ataxia 38, and epigenetic marks were associated with depression and suicide risk. Two sterol response element binding sites were found on ELOVL5, a SREBP-1c target gene. Minor allele carriers of a 3 single nucleotide polymorphism (SNP) haplotype in ELOVL2 have decreased 22 : 6n-3 levels. Unequivocal molecular evidence shows mammalian FADS2 catalyzes direct Δ4-desaturation to yield 22 : 6n-3 and 22 : 5n-6. An SNP near FADS1 influences the levels of 5-lipoxygenase products and epigenetic alteration. Genetic polymorphisms within FADS and ELOVL can limit LCPUFA product accumulation at any step of the biosynthetic pathway.

Genetic variants in desaturase gene, erythrocyte fatty acids, and risk for type 2 diabetes in Chinese Hans

ObjectiveThe aim of this study was to examine the association of the genetic variants in the fatty acid desaturase (FADS) gene cluster with erythrocyte phospholipid fatty acids (PLFA), and their relation to risk for type 2 diabetes mellitus (T2DM) in Han Chinese. MethodsSeven hundred and fifty-eight patients with T2DM and 400 healthy individuals were recruited. The erythrocyte PLFA and single-nucleotide polymorphism were determined by standard method. ResultsMinor allele homozygotes and heterozygotes of rs174575 and rs174537 had lower PL 20:4 ω-6 levels in healthy individuals. Minor allele homozygotes and heterozygotes of rs174455 in FADS3 gene had lower levels of 22:5 ω-3, 20:4 ω-6, and Δ5desaturase activity in patients with T2DM. Erythrocyte membrane PL 18:3 ω-3 (P for trend = 0.002), 22:5 ω-3 (P for trend < 0.001), ω-3 polyunsaturated fatty acid (P for trend < 0.001), and ω-3:ω-6 (P for trend < 0.001) were significantly inversely associated with risk for T2DM. ConclusionGenetic variants in the FADS gene cluster are associated with altered erythrocyte PLFAs. High levels of PL 18:3 ω-3, 22:5 ω-3, and total ω-3 polyunsaturated fatty acid were associated with low risk for T2DM.

Interaction of Fatty Acid Genotype and Diet on Changes in Colonic Fatty Acids in a Mediterranean Diet Intervention Study

A Mediterranean diet increases intakes of n-3 and n-9 fatty acids and lowers intake of n-6 fatty acids. This can impact colon cancer risk as n-6 fatty acids are metabolized to proinflammatory eicosanoids. The purpose of this study was to evaluate interactions of polymorphisms in the fatty acid desaturase (FADS) genes, FADS1 and FADS2, and changes in diet on fatty acid concentrations in serum and colon. A total of 108 individuals at increased risk of colon cancer were randomized to either a Mediterranean or a Healthy Eating diet. Fatty acids were measured in both serum and colonic mucosa at baseline and after six months. Each individual was genotyped for four single-nucleotide polymorphisms in the FADS gene cluster. Linear regression was used to evaluate the effects of diet, genotype, and the diet by genotype interaction on fatty acid concentrations in serum and colon. Genetic variation in the FADS genes was strongly associated with baseline serum arachidonic acid (n-6) but serum eicosapentaenoic acid (n-3) and colonic fatty acid concentrations were not significantly associated with genotype. After intervention, there was a significant diet by genotype interaction for arachidonic acid concentrations in colon. Subjects who had all major alleles for FADS1/2 and were following a Mediterranean diet had 16% lower arachidonic acid concentrations in the colon after six months of intervention than subjects following the Healthy Eating diet. These results indicate that FADS genotype could modify the effects of changes in dietary fat intakes on arachidonic acid concentrations in the colon.

Polymorphisms, de novo lipogenesis, and plasma triglyceride response following fish oil supplementation

Interindividual variability in the response of plasma triglyceride concentrations (TG) following fish oil consumption has been observed. Our objective was to examine the associations between single-nucleotide polymorphisms (SNPs) within genes encoding proteins involved in de novo lipogenesis and the relative change in plasma TG levels following a fish oil supplementation. Two hundred and eight participants were recruited in the greater Quebec City area. The participants completed a six-week fish oil supplementation (5 g fish oil/day: 1.9-2.2 g eicosapentaenoic acid and 1.1 g docosahexaenoic acid. SNPs within SREBF1, ACLY, and ACACA genes were genotyped using TAQMAN methodology. After correction for multiple comparison, only two SNPs, rs8071753 (ACLY) and rs1714987 (ACACA), were associated with the relative change in plasma TG concentrations (P = 0.004 and P = 0.005, respectively). These two SNPs explained 7.73% of the variance in plasma TG relative change following fish oil consumption. Genotype frequencies of rs8071753 according to the TG response groups (responders versus nonresponders) were different (P = 0.02). We conclude that the presence of certain SNPs within genes, such as ACLY and ACACA, encoding proteins involved in de novo lipogenesis seem to influence the plasma TG response following fish oil consumption.

Polymorphisms in Fatty Acid Desaturase (FADS) Gene Cluster: Effects on Glycemic Controls Following an Omega-3 Polyunsaturated Fatty Acids (PUFA) Supplementation

Changes in desaturase activity are associated with insulin sensitivity and may be associated with type 2 diabetes mellitus (T2DM). Polymorphisms (SNPs) in the fatty acid desaturase (FADS) gene cluster have been associated with the homeostasis model assessment of insulin sensitivity (HOMA-IS) and serum fatty acid composition. Objective: To investigate whether common genetic variations in the FADS gene cluster influence fasting glucose (FG) and fasting insulin (FI) responses following a 6-week n-3 polyunsaturated fatty acids (PUFA) supplementation. Methods: 210 subjects completed a 2-week run-in period followed by a 6-week supplementation with 5 g/d of fish oil (providing 1.9 g–2.2 g of EPA + 1.1 g of DHA). Genotyping of 18 SNPs of the FADS gene cluster covering 90% of all common genetic variations (minor allele frequency ≥ 0.03) was performed. Results: Carriers of the minor allele for rs482548 (FADS2) had increased plasma FG levels after the n-3 PUFA supplementation in a model adjusted for FG levels at baseline, age, sex, and BMI. A significant genotype*supplementation interaction effect on FG levels was observed for rs482548 (p = 0.008). For FI levels, a genotype effect was observed with one SNP (rs174456). For HOMA-IS, several genotype*supplementation interaction effects were observed for rs7394871, rs174602, rs174570, rs7482316 and rs482548 (p = 0.03, p = 0.01, p = 0.03, p = 0.05 and p = 0.07; respectively). Conclusion: Results suggest that SNPs in the FADS gene cluster may modulate plasma FG, FI and HOMA-IS levels in response to n-3 PUFA supplementation.