Ablation of Elovl6 protects pancreatic islets from high-fat diet-induced impairment of insulin secretion

ELOVL family member 6, elongation of very long-chain fatty acids (Elovl6) is a microsomal enzyme that regulates the elongation of C12–16 saturated and monounsaturated fatty acids and is related to the development of obesity-induced insulin resistance via the modification of the fatty acid composition. In this study, we investigated the role of systemic Elovl6 in the pancreatic islet and β-cell function. Elovl6 is expressed in both islets and β-cell lines. In mice fed with chow, islets of the Elovl6^−/− mice displayed normal architecture and β-cell mass compared with those of the wild-type mice. However, when fed a high-fat, high-sucrose (HFHS) diet, the islet hypertrophy in response to insulin resistance observed in normal mice was attenuated and glucose-stimulated insulin secretion (GSIS) increased in the islets of Elovl6^−/− mice compared with those of the wild-type mice. Enhanced GSIS in the HFHS Elovl6^−/− islets was associated with an increased ATP/ADP ratio and the suppression of ATF-3 expression. Our findings suggest that Elovl6 could be involved in insulin secretory capacity per β-cell and diabetes.     

Deletion of ELOVL5 leads to fatty liver through activation of SREBP-1c in mice

Elongation of very long chain fatty acids (ELOVL)5 is one of seven mammalian fatty acid condensing enzymes involved in microsomal fatty acid elongation. To determine the in vivo substrates and function of ELOVL5, we generated Elovl5(-/-) mice. Studies using liver microsomal protein from wild-type and knockout mice demonstrated that the elongation of gamma-linolenic (C18:3, n-6) to dihomo-gamma-linolenic (C20:3, n-6) and stearidonic (C18:4, n-3) to omega3-arachidonic acid (C20:4, n-3) required ELOVL5 activity. Tissues of Elovl5(-/-) mice accumulated the C18 substrates of ELOVL5 and the levels of the downstream products, arachidonic acid (C20:4, n-6) and docosahexaenoic acid (DHA, C22:6, n-3), were decreased. A consequence of decreased cellular arachidonic acid and DHA concentrations was the activation of sterol regulatory element-binding protein (SREBP)-1c and its target genes involved in fatty acid and triglyceride synthesis, which culminated in the development of hepatic steatosis in Elovl5(-/-) mice. The molecular and metabolic changes in fatty acid metabolism in Elovl5(-/-) mice were reversed by dietary supplementation with arachidonic acid and DHA. These studies demonstrate that reduced ELOVL5 activity leads to hepatic steatosis, and endogenously synthesized PUFAs are key regulators of SREBP-1c activation and fatty acid synthesis in livers of mice.     

ELOVL2 controls the level of n-6 28:5 and 30:5 fatty acids in testis, a prerequisite for male fertility and sperm maturation in mice

ELOVL2 is a member of the mammalian microsomal ELOVL fatty acid enzyme family, involved in the elongation of very long-chain fatty acids including PUFAs required for various cellular functions in mammals. Here, we used ELOVL2-ablated (Elovl2(-/-)) mice to show that the PUFAs with 24-30 carbon atoms of the ω-6 family in testis are indispensable for normal sperm formation and fertility in male mice. The lack of Elovl2 was associated with a complete arrest of spermatogenesis, with seminiferous tubules displaying only spermatogonia and primary spermatocytes without further germinal cells. Furthermore, based on acyl-CoA profiling, heterozygous Elovl2(+/-) male mice exhibited haploinsufficiency, with reduced levels of C28:5 and C30:5n-6 PUFAs, which gave rise to impaired formation and function of haploid spermatides. These new insights reveal a novel mechanism involving ELOVL2-derived PUFAs in mammals and previously unrecognized roles for C28 and C30 n-6 PUFAs in male fertility. In accordance with the function suggested for ELOVL2, the Elovl2(-/-) mice show distorted levels of serum C20 and C22 PUFAs from both the n-3 and the n-6 series. However, dietary supplementation with C22:6n-3 could not restore male fertility to Elovl2(+/-) mice, suggesting that the changes in n-6 fatty acid composition seen in the testis of the Elovl2(+/-) mice, cannot be compensated by increased C22:6n-3 content.     

Elovl5 regulates the mTORC2-Akt-FOXO1 pathway by controlling hepatic cis-vaccenic acid synthesis in diet-induced obese mice

Elevated hepatic expression of fatty acid elongase-5 (Elovl5) induces FoxO1 phosphorylation, lowers FoxO1 nuclear content, and suppresses expression of genes involved in gluconeogenesis (GNG). In this report, we define the molecular and metabolic basis of Elovl5 control of FoxO1 phosphorylation. Adenoviral-mediated (Ad-Elovl5) induction of hepatic Elovl5 in diet-induced obese, glucose-intolerant mice and HepG2 cells increased the phosphorylation of Akt2-S⁴⁷³ [mammalian target of rapamycin complex-2 (mTORC2) site], but not Akt2-T³⁰⁸ (PDK1 site). The Akt2 inhibitor Akti1/2 blocked Elovl5 induction of FoxO1-S²⁵⁶ phosphorylation in HepG2 cells. Elevated Elovl5 activity in liver and HepG2 cells induced rictor mRNA, rictor protein, and rictor-mTOR interaction, whereas rictor knockdown (siRNA) attenuated Elovl5 induction of Akt2-S⁴⁷³ and FoxO1-S²⁵⁶ phosphorylation in HepG2 cells. FA analysis revealed that the abundance of cis-vaccenic acid (18:1,n-7) was increased in livers of obese mice and HepG2 cells following Ad-Elovl5 infection. Treating HepG2 cells with Elovl5 substrates established that palmitoleic acid (16:1,n-7), but not γ-linolenic acid (18:3,n-6), induced rictor protein, Akt-S⁴⁷³, and FoxO1-S²⁵⁶ phosphorylation. Inhibition of FA elongation blocked 16:1,n-7 but not 18:1,n-7 induction of rictor protein and Akt-S⁴⁷³ and FoxO1-S²⁵⁶ phosphorylation. These results establish a novel link between Elovl5-mediated synthesis of 18:1,n-7 and GNG through the control of the mTORC2-Akt-FoxO1 pathway.     

New insight into the SSC8 genetic determination of fatty acid composition in pigs

Background

Fat content and fatty acid composition in swine are becoming increasingly studied because of their effect on sensory and nutritional quality of meat. A QTL (quantitative trait locus) for fatty acid composition in backfat was previously detected on porcine chromosome 8 (SSC8) in an Iberian x Landrace F₂ intercross. More recently, a genome-wide association study detected the same genomic region for muscle fatty acid composition in an Iberian x Landrace backcross population. ELOVL6, a strong positional candidate gene for this QTL, contains a polymorphism in its promoter region (ELOVL6:c.-533C < T), which is associated with percentage of palmitic and palmitoleic acids in muscle and adipose tissues. Here, a combination of single-marker association and the haplotype-based approach was used to analyze backfat fatty acid composition in 470 animals of an Iberian x Landrace F₂ intercross genotyped with 144 SNPs (single nucleotide polymorphisms) distributed along SSC8.

Results

Two trait-associated SNP regions were identified at 93 Mb and 119 Mb on SSC8. The strongest statistical signals of both regions were observed for palmitoleic acid (C16:1(n-7)) content and C18:0/C16:0 and C18:1(n-7)/C16:1(n-7) elongation ratios. MAML3 and SETD7 are positional candidate genes in the 93 Mb region and two novel microsatellites in MAML3 and nine SNPs in SETD7 were identified. No significant association for the MAML3 microsatellite genotypes was detected. The SETD7:c.700G > T SNP, although statistically significant, was not the strongest signal in this region. In addition, the expression of MAML3 and SETD7 in liver and adipose tissue varied among animals, but no association was detected with the polymorphisms in these genes. In the 119 Mb region, the ELOVL6:c.-533C > T polymorphism showed a strong association with percentage of palmitic and palmitoleic fatty acids and elongation ratios in backfat.

Conclusions

Our results suggest that the polymorphisms studied in MAML3 and SETD7 are not the causal mutations for the QTL in the 93 Mb region. However, the results for ELOVL6 support the hypothesis that the ELOVL6:c.-533C > T polymorphism has a pleiotropic effect on backfat and intramuscular fatty acid composition and that it has a role in the determination of the QTL in the 119 Mb region.     

Genome-Wide Association Analyses for Fatty Acid Composition in Porcine Muscle and Abdominal Fat Tissues

Fatty acid composition is an important phenotypic trait in pigs as it affects nutritional, technical and sensory quality of pork. Here, we reported a genome-wide association study (GWAS) for fatty acid composition in the longissimus muscle and abdominal fat tissues of 591 White Duroc×Erhualian F₂ animals and in muscle samples of 282 Chinese Sutai pigs. A total of 46 loci surpassing the suggestive significance level were identified on 15 pig chromosomes (SSC) for 12 fatty acids, revealing the complex genetic architecture of fatty acid composition in pigs. Of the 46 loci, 15 on SSC5, 7, 14 and 16 reached the genome-wide significance level. The two most significant SNPs were ss131535508 (P = 2.48×10⁻²⁵) at 41.39 Mb on SSC16 for C20∶0 in abdominal fat and ss478935891 (P = 3.29×10⁻¹³) at 121.31 Mb on SSC14 for muscle C18∶0. A meta-analysis of GWAS identified 4 novel loci and enhanced the association strength at 6 loci compared to those evidenced in a single population, suggesting the presence of common underlying variants. The longissimus muscle and abdominal fat showed consistent association profiles at most of the identified loci and distinct association signals at several loci. All loci have specific effects on fatty acid composition, except for two loci on SSC4 and SSC7 affecting multiple fatness traits. Several promising candidate genes were found in the neighboring regions of the lead SNPs at the genome-wide significant loci, such as SCD for C18∶0 and C16∶1 on SSC14 and ELOVL7 for C20∶0 on SSC16. The findings provide insights into the molecular basis of fatty acid composition in pigs, and would benefit the final identification of the underlying mutations.     

Hepatic Gluconeogenesis Is Enhanced by Phosphatidic Acid Which Remains Uninhibited by Insulin in Lipodystrophic Agpat2?/? Mice

In this study we examined the role of phosphatidic acid (PA) in hepatic glucose production (HGP) and development of hepatic insulin resistance in mice that lack 1-acylglycerol-3-phosphate O-acyltransferase 2 (AGPAT2). Liver lysophosphatidic acid and PA levels were increased ∼2- and ∼5-fold, respectively, in male Agpat2^−/− mice compared with wild type mice. In the absence of AGPAT2, the liver can synthesize PAs by activating diacylglycerol kinase or phospholipase D, both of which were elevated in the livers of Agpat2^−/− mice. We found that PAs C16:0/18:1 and C18:1/20:4 enhanced HGP in primary WT hepatocytes, an effect that was further enhanced in primary hepatocytes from Agpat2^−/− mice. Lysophosphatidic acids C16:0 and C18:1 failed to increase HGP in primary hepatocytes. The activation of HGP was accompanied by an up-regulation of the key gluconeogenic enzymes glucose-6-phosphatase and phosphoenolpyruvate carboxykinase. This activation was suppressed by insulin in the WT primary hepatocytes but not in the Agpat2^−/− primary hepatocytes. Thus, the lack of normal insulin signaling in Agpat2^−/− livers allows unrestricted PA-induced gluconeogenesis significantly contributing to the development of hyperglycemia in these mice.     

Depletion of ceramides with very long chain fatty acids causes defective skin permeability barrier function, and neonatal lethality in ELOVL4 deficient mice

Very long chain fatty acids (VLCFA), either free or as components of glycerolipids and sphingolipids, are present in many organs. Elongation of very long chain fatty acids-4 (ELOVL4) belongs to a family of 6 members of putative fatty acid elongases that are involved in the formation of VLCFA. Mutations in ELOVL4 were found to be responsible for an autosomal dominant form of Stargardt's-like macular dystrophy (STGD3) in human. We have previously disrupted the mouse Elovl4 gene, and found that Elovl4+/- mice were developmentally normal, suggesting that haploinsufficiency of ELOVL4 is not a cause for the juvenile retinal degeneration in STGD3 patients. However, Elovl4-/- mice died within several hours of birth for unknown reason(s). To study functions of ELOVL4 further, we have explored the causes for the postnatal lethality in Elovl4-/- mice. Our data indicated that the mutant mice exhibited reduced thickness of the dermis, delayed differentiation of keratinocytes, and abnormal structure of the stratum corneum. We showed that all Elovl4-/- mice exhibited defective skin water permeability barrier function, leading to the early postnatal death. We further showed that the absence of ELOVL4 results in depletion in the epidermis of ceramides with omega-hydroxy very long chain fatty acids (> or = C28) and accumulation of ceramides with non omega-hydroxy fatty acids of C26, implicating C26 fatty acids as possible substrates of ELOVL4. These data demonstrate that ELOVL4 is required for VLCFA synthesis that is essential for water permeability barrier function of skin.     

Altered Lipid Metabolism in Residual White Adipose Tissues of Bscl2 Deficient Mice

Mutations in BSCL2 underlie human congenital generalized lipodystrophy type 2 disease. We previously reported that Bscl2 ^−/− mice develop lipodystrophy of white adipose tissue (WAT) due to unbridled lipolysis. The residual epididymal WAT (EWAT) displays a browning phenotype with much smaller lipid droplets (LD) and higher expression of brown adipose tissue marker proteins. Here we used targeted lipidomics and gene expression profiling to analyze lipid profiles as well as genes involved in lipid metabolism in WAT of wild-type and Bscl2^−/− mice. Analysis of total saponified fatty acids revealed that the residual EWAT of Bscl2^−/− mice contained a much higher proportion of oleic_18:1n9 acid concomitant with a lower proportion of palmitic_16:0 acid, as well as increased n3- polyunsaturated fatty acids (PUFA) remodeling. The acyl chains in major species of triacylglyceride (TG) and diacylglyceride (DG) in the residual EWAT of Bscl2^−/− mice were also enriched with dietary fatty acids. These changes could be reflected by upregulation of several fatty acid elongases and desaturases. Meanwhile, Bscl2^−/− adipocytes from EWAT had increased gene expression in lipid uptake and TG synthesis but not de novo lipogenesis. Both mitochondria and peroxisomal β-oxidation genes were also markedly increased in Bscl2^−/− adipocytes, highlighting that these machineries were accelerated to shunt the lipolysis liberated fatty acids through uncoupling to dissipate energy. The residual subcutaneous white adipose tissue (ScWAT) was not browning but displays similar changes in lipid metabolism. Overall, our data emphasize that, other than being essential for adipocyte differentiation, Bscl2 is also important in fatty acid remodeling and energy homeostasis.     

In vivo hepatic lipid quantification using MRS at 7 Tesla in a mouse model of glycogen storage disease type 1a

The assessment of liver lipid content and composition is needed in preclinical research to investigate steatosis and steatosis-related disorders. The purpose of this study was to quantify in vivo hepatic fatty acid content and composition using a method based on short echo time proton magnetic resonance spectroscopy (MRS) at 7 Tesla. A mouse model of glycogen storage disease type 1a with inducible liver-specific deletion of the glucose-6-phosphatase gene (L-G6pc^−/−) mice and control mice were fed a standard diet or a high-fat/high-sucrose (HF/HS) diet for 9 months. In control mice, hepatic lipid content was found significantly higher with the HF/HS diet than with the standard diet. As expected, hepatic lipid content was already elevated in L-G6pc^−/− mice fed a standard diet compared with control mice. L-G6pc^−/− mice rapidly developed steatosis which was not modified by the HF/HS diet. On the standard diet, estimated amplitudes from olefinic protons were found significantly higher in L-G6pc^−/− mice compared with that in control mice. L-G6pc^−/− mice showed no noticeable polyunsaturation from diallylic protons. Total unsaturated fatty acid indexes measured by gas chromatography were in agreement with MRS measurements. These results showed the great potential of high magnetic field MRS to follow the diet impact and lipid alterations in mouse liver.     

Genome-Wide Association Study of Plasma Polyunsaturated Fatty Acids in the InCHIANTI Study

Polyunsaturated fatty acids (PUFA) have a role in many physiological processes, including energy production, modulation of inflammation, and maintenance of cell membrane integrity. High plasma PUFA concentrations have been shown to have beneficial effects on cardiovascular disease and mortality. To identify genetic contributors of plasma PUFA concentrations, we conducted a genome-wide association study of plasma levels of six omega-3 and omega-6 fatty acids in 1,075 participants in the InCHIANTI study on aging. The strongest evidence for association was observed in a region of chromosome 11 that encodes three fatty acid desaturases (FADS1, FADS2, FADS3). The SNP with the most significant association was rs174537 near FADS1 in the analysis of arachidonic acid (AA; p=5.95×10⁻⁴⁶). Minor allele homozygotes had lower AA compared to the major allele homozygotes and rs174537 accounted for 18.6% of the additive variance in AA concentrations. This SNP was also associated with levels of eicosadienoic acid (EDA; p=6.78×10⁻⁹) and eicosapentanoic acid (EPA; p=1.07×10⁻¹⁴). Participants carrying the allele associated with higher AA, EDA, and EPA also had higher low-density lipoprotein (LDL-C) and total cholesterol levels. Outside the FADS gene cluster, the strongest region of association mapped to chromosome 6 in the region encoding an elongase of very long fatty acids 2 (ELOVL2). In this region, association was observed with EPA (rs953413; p=1.1×10⁻⁶). The effects of rs174537 were confirmed in an independent sample of 1,076 subjects participating in the GOLDN study. The ELOVL2 SNP was associated with docosapentanoic and DHA but not with EPA in GOLDN. These findings show that polymorphisms of genes encoding enzymes in the metabolism of PUFA contribute to plasma concentrations of fatty acids.     

Lipid Biomarkers and Carbon Isotope Signatures of a Microbial (Beggiatoa) Mat Associated with Gas Hydrates in the Gulf of Mexico

White and orange mats are ubiquitous on surface sediments associated with gas hydrates and cold seeps in the Gulf of Mexico. The goal of this study was to determine the predominant pathways for carbon cycling within an orange mat in Green Canyon (GC) block GC 234 in the Gulf of Mexico. Our approach incorporated laser-scanning confocal microscopy, lipid biomarkers, stable carbon isotopes, and 16S rRNA gene sequencing. Confocal microscopy showed the predominance of filamentous microorganisms (4 to 5 μm in diameter) in the mat sample, which are characteristic of Beggiatoa. The phospholipid fatty acids extracted from the mat sample were dominated by 16:1ω7c/t (67%), 18:1ω7c (17%), and 16:0 (8%), which are consistent with lipid profiles of known sulfur-oxidizing bacteria, including Beggiatoa. These results are supported by the 16S rRNA gene analysis of the mat material, which yielded sequences that are all related to the vacuolated sulfur-oxidizing bacteria, including Beggiatoa, Thioploca, and Thiomargarita. The δ¹³C value of total biomass was −28.6‰; those of individual fatty acids were −29.4 to −33.7‰. These values suggested heterotrophic growth of Beggiatoa on organic substrates that may have δ¹³C values characteristic of crude oil or on their by-products from microbial degradation. This study demonstrated that integrating lipid biomarkers, stable isotopes, and molecular DNA could enhance our understanding of the metabolic functions of Beggiatoa mats in sulfide-rich marine sediments associated with gas hydrates in the Gulf of Mexico and other locations.     

Genetic loci associated with circulating levels of very long-chain saturated fatty acids

Very long-chain saturated fatty acids (VLSFAs) are saturated fatty acids with 20 or more carbons. In contrast to the more abundant saturated fatty acids, such as palmitic acid, there is growing evidence that circulating VLSFAs may have beneficial biological properties. Whether genetic factors influence circulating levels of VLSFAs is not known. We investigated the association of common genetic variation with plasma phospholipid/erythrocyte levels of three VLSFAs by performing genome-wide association studies in seven population-based cohorts comprising 10,129 subjects of European ancestry. We observed associations of circulating VLSFA concentrations with common variants in two genes, serine palmitoyl-transferase long-chain base subunit 3 (SPTLC3), a gene involved in the rate-limiting step of de novo sphingolipid synthesis, and ceramide synthase 4 (CERS4). The SPTLC3 variant at rs680379 was associated with higher arachidic acid (20:0 , P = 5.81 × 10⁻¹³). The CERS4 variant at rs2100944 was associated with higher levels of 20:0 (P = 2.65 × 10⁻⁴⁰) and in analyses that adjusted for 20:0, with lower levels of behenic acid (P = 4.22 × 10⁻²⁶) and lignoceric acid (P = 3.20 × 10⁻²¹). These novel associations suggest an inter-relationship of circulating VLSFAs and sphingolipid synthesis.     

Palmitoleate Reverses High Fat-induced Proinflammatory Macrophage Polarization via AMP-activated Protein Kinase (AMPK)

A rise in tissue-embedded macrophages displaying “M1-like” proinflammatory polarization is a hallmark of metabolic inflammation during a high fat diet or obesity. Here we show that bone marrow-derived macrophages (BMDM) from high fat-fed mice retain a memory of their dietary environment in vivo (displaying the elevated proinflammatory genes Cxcl1, Il6, Tnf, Nos2) despite 7-day differentiation and proliferation ex vivo. Notably, 6-h incubation with palmitoleate (PO) reversed the proinflammatory gene expression and cytokine secretion seen in BMDM from high fat-fed mice. BMDM from low fat-fed mice exposed to palmitate (PA) for 18 h ex vivo also showed elevated expression of proinflammatory genes (Cxcl1, Il6, Tnf, Nos2, and Il12b) associated with M1 polarization. Conversely, PO treatment increased anti-inflammatory genes (Mrc1, Tgfb1, Il10, Mgl2) and oxidative metabolism, characteristic of M2 macrophages. Therefore, saturated and unsaturated fatty acids bring about opposite macrophage polarization states. Coincubation of BMDM with both fatty acids counteracted the PA-induced Nos2 expression in a PO dose-dependent fashion. PO also prevented PA-induced IκBα degradation, RelA nuclear translocation, NO production, and cytokine secretion. Mechanistically, PO exerted its anti-inflammatory function through AMP-activated protein kinase as AMP kinase knockout or inhibition by Compound C offset the PO-dependent prevention of PA-induced inflammation. These results demonstrate a nutritional memory of BMDM ex vivo, highlight the plasticity of BMDM polarization in response to saturated and unsaturated fatty acids, and identify the potential to reverse diet- and saturated fat-induced M1-like polarization by administering palmitoleate. These findings could have applicability to reverse obesity-linked inflammation in metabolically relevant tissues.     

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.     

FADS genetic variants and ω-6 polyunsaturated fatty acid metabolism in a homogeneous island population

Long-chain polyunsaturated fatty acids (PUFA) orchestrate immunity and inflammation through their capacity to be converted to potent inflammatory mediators. We assessed associations of FADS gene cluster polymorphisms and fasting serum PUFA concentrations in a fully ascertained, geographically isolated founder population of European descent. Concentrations of 22 PUFAs were determined by gas chromatography, of which ten fatty acids and five ratios defining FADS1 and FADS2 activity were tested for genetic association against 16 single nucleotide polymorphisms (SNP) in 224 individuals. A cluster of SNPs in tight linkage disequilibrium in the FADS1 gene (rs174537, rs174545, rs174546, rs174553, rs174556, rs174561, rs174568, and rs99780) were strongly associated with arachidonic acid (AA) (P = 5.8 × 10⁻⁷ – 1.7 × 10⁻⁸) among other PUFAs, but the strongest associations were with the ratio measuring FADS1 activity in the ω-6 series (P = 2.11 × 10⁻¹³ – 1.8 × 10⁻²⁰). The minor allele across all SNPs was consistently associated with decreased ω-6 PUFAs, with the exception of dihomo-γ-linoleic acid (DHGLA), where the minor allele was consistently associated with increased levels. Our findings in a geographically isolated population with a homogenous dietary environment suggest that variants in the Δ-5 desaturase enzymatic step likely regulate the efficiency of conversion of medium-chain PUFAs to potentially inflammatory PUFAs, such as AA.