Delta-6 Desaturase Research Articles

Non-conjugated cis/trans 18:2 in Beef Fat are Mainly Δ-9 Desaturation Products of trans-18:1 Isomers.

Human liver cells (HepG2) were cultured with individual trans (t) 18:1 including t6-, t12-, t13-, t14-, t15- and t16-18:1, and retention times of their Δ-9 desaturation products were determined using 100-m biscyanopropyl-polysiloxane and SLB-IL111 columns. Corresponding peaks were found in beef adipose tissues known to have different delta-9 desaturase activities. Further lines of evidence indicating the presence of Δ-9 desaturation products of t-18:1 isomers in beef fat were developed by analysis of fatty acid methyl esters (FAME) fractionated using Ag+-TLC, and by GC/MS. Some of the Δ-9 desaturation products of t-18:1 have been previously identified in ruminant fat (c9, t12- and c9, t13-18:2). Some of the Δ-9 desaturation products of t-18:1 (c9, t14- and c9, t15-18:2) have been previously tentatively identified as different fatty acids, and for the first time we provide evidence of the presence of c9, t16-18:2, and where t6, c9-18:2 may elute during analysis of FAME from beef fat.

A Novel Selective Inhibitor of Delta-5 Desaturase Lowers Insulin Resistance and Reduces Body Weight in Diet-Induced Obese C57BL/6J Mice.

Obesity is now recognized as a state of chronic low-grade inflammation and is called as metabolic inflammation. Delta-5 desaturase (D5D) is an enzyme that metabolizes dihomo-γ-linolenic acid (DGLA) to arachidonic acid (AA). Thus, D5D inhibition increases DGLA (precursor to anti-inflammatory eicosanoids) while decreasing AA (precursor to pro-inflammatory eicosanoids), and could result in synergistic improvement in the low-grade inflammatory state. Here, we demonstrate reduced insulin resistance and the anti-obesity effect of a D5D selective inhibitor (compound-326), an orally active small-molecule, in a high-fat diet-induced obese (DIO) mouse model. In vivo D5D inhibition was confirmed by determining changes in blood AA/DGLA profiles. In DIO mice, chronic treatment with compound-326 lowered insulin resistance and caused body weight loss without significant impact on cumulative calorie intake. Decreased macrophage infiltration into adipose tissue was expected from mRNA analysis. Increased daily energy expenditure was also observed following administration of compound-326, in line with sustained body weight loss. These data indicate that the novel D5D selective inhibitor, compound-326, will be a new class of drug for the treatment of obese and diabetic patients.

Omega-6 polyunsaturated fatty acids, serum zinc, delta-5- and delta-6-desaturase activities and incident metabolic syndrome.

The associations of n-6 polyunsaturated fatty acids (PUFA) with metabolic syndrome have been poorly explored. We investigated the associations of the serum n-6 PUFA and the activities of enzymes involved in the PUFA metabolism, delta-5-desaturase (D5D) and delta-6-desaturase (D6D) with risk of incident metabolic syndrome. We also investigated whether zinc, a cofactor for these enzymes, modifies these associations. A prospective follow-up study was conducted on 661 men who were aged 42-60 years old at baseline in 1984-1989 and who were re-examined in 1998-2001. Men in the highest versus the lowest serum total omega-6 PUFA tertile had a 70% lower multivariate-adjusted risk of incident metabolic syndrome [odds ratio (OR) = 0.30; 95% confidence interval (CI) = 0.18-0.51, Ptrend < 0.001]. Inverse associations were also observed for linoleic acid, arachidonic acid and D5D activity. By contrast, men in the highest tertile of D6D activity had an 84% higher risk (OR = 1.84; 95% CI = 1.15-2.94, Ptrend = 0.008). Similar associations were observed with many of the metabolic syndrome components at the re-examinations. Most associations were attenuated after adjustment for body mass index. Finally, the associations of D6D and LA were stronger among those with a higher serum zinc concentration. Higher serum total n-6 PUFA, linoleic acid and arachidonic acid concentrations and D5D activity were associated with a lower risk of developing metabolic syndrome and higher D6D activity was associated with a higher risk. The role of zinc also needs to be investigated in other populations.

310 - Knocking Down Delta-5 Desaturase and Exploiting High Expression Level of COX-2 to Inhibit Cancer Migration and Invasion

Our recent research has shown that knockdown of delta-5 desaturase (D5D, a key enzyme that converts dihomo-γ-linolenic acid to arachidonic acid) and treatment dihomo-γ-linolenic exerted growth inhibitory effect on both colon and pancreatic cancer cells (Xu Y et al, FRBM 96: 67-77, 2016 and Yang X et al, FRBM 97: 342-350, 2016) due to formation of an anti-cancer byproduct 8-hydroxyoctanoic acid (8-HOA) from COX-catalyzed peroxidation. Here, we further tested whether knockdown of D5D could also be used to inhibit cancer migration and invasion using colon cancer cell line HCA-7 colony 29 and pancreatic cancer cell line BxPC-3 (both express high levels of COX-2). Cell migration and invasion were assessed by wound healing assay and transwell assay along with western blot to investigate the possible molecular mechanism. Our results showed that promoted 8-HOA formation in cancer cells via knocking down D5D (shRNA transfection) can significantly inhibit cell migration. D5D knockdown can also significantly improve the efficacies of 5-flurouracil and gemcitabine on colon and pancreatic cancer cell migration and invasion. The underlying mechanism might be that 8-HOA, serving as histone deacetylase inhibitor, downregulates MMP-2 and 9, consequently leading to altered expression in key proteins involved in epithelial mesenchymal transition (EMT) e.g. E-cadherin and vimentin. For the first time, we demonstrated high COX expression in cancers could be taken advantage to inhibit cancer cell migration and invasion. The research outcome may provide us a promising strategy for cancer metastasis by taking advantage of abundant ω-6 fatty acids in daily diet and exploiting the high COX expression level in cancer (a paradigm shifting concept). This work supported by NIH R15CA195499 and Sanford Health-NDSU Collaborative Research Seed Grant Program.

Delta-6 desaturase activity during the first year of life in preterm infants

Term neonates have high delta-6 desaturase (D6D) activity, which is important for regulating polyunsaturated fatty acid's (PUFA) nutritional status. The aim was to investigate D6D activity in preterm infants and its postnatal changes. Forty-three appropriate-for-gestational-age infants were included. PUFA in red blood cells was analyzed at birth and at one, six, and 12 months of age. D6D activity was estimated by 20:3n-6/18:2n-6 ratio. At birth, preterm infants had D6D activity as high as that of term infants; D6D activity declined to about one-third at one month, then further decreased to about one-sixth at six months and remained stable until 12 months. The postnatal change in arachidonic acid exhibited a similar pattern to that of D6D activity; however, docosahexaenoic acid showed a transient decrease at one month and recovered to the cord blood level at six months. D6D may regulate PUFA profile in preterm infants, especially during the early postnatal period.

Association of desaturase activity and C-reactive protein in European children.

Desaturase enzymes influence the fatty acid (FA) composition of body tissues and their activity affects the conversion rate of saturated to monounsaturated FA and of polyunsaturated FA (PUFA) to long-chain PUFA. Desaturase activity has further been shown to be associated with inflammation. We investigate the association between delta-9 (D9D), delta-6 (D6D) and delta-5 desaturase (D5D) activity and high-sensitive C-reactive protein (CRP) in young children. In the IDEFICS (Identification and prevention of dietary- and lifestyle-induced health effects in children and infants) cohort study children were examined at baseline (T0) and after 2 y (T1). D9D, D6D, and D5D activities were estimated from T0 product-precursor FA ratios. CRP was measured at T0 and T1. In a subsample of 1,943 children with available information on FA, CRP, and covariates, the cross-sectional and longitudinal associations of desaturase activity and CRP were analyzed. Cross-sectionally, a D9D increase of 0.01 units was associated with a 11% higher risk of having a serum CRP ≥ Percentile 75 (P75) (OR, 99% CI: 1.11 (1.01; 1.22)) whereas D6D and D5D were not associated with CRP. No significant associations were observed between baseline desaturase activity and CRP 2 y later. Cross-sectionally, our results indicate a positive association of D9D and CRP independent of weight status. High D9D activity may increase the risk of subclinical inflammation which is associated with metabolic disorders. As D9D expression increases with higher intake of saturated FA and carbohydrates, dietary changes may influence D9D activity and thus CRP. However, it remains to be investigated whether there is a causal relationship between D9D activity and CRP.

T-3364366 Targets the Desaturase Domain of Delta-5 Desaturase with Nanomolar Potency and a Multihour Residence Time.

Delta-5 desaturase (D5D) catalyzes the conversion from dihomo-gamma linoleic acid (DGLA) to arachidonic acid (AA). DGLA and AA are common precursors of anti- and pro-inflammatory eicosanoids, respectively, making D5D an attractive drug target for inflammatory-related diseases. Despite several reports on D5D inhibitors, their biochemical mechanisms of action (MOAs) remain poorly understood, primarily due to the difficulty in performing quantitative enzymatic analysis. Herein, we report a radioligand binding assay to overcome this challenge and characterized T-3364366, a thienopyrimidinone D5D inhibitor, by use of the assay. T-3364366 is a reversible, slow-binding inhibitor with a dissociation half-life in excess of 2.0 h. The long residence time was confirmed in cellular washout assays. Domain swapping experiments between D5D and D6D support [(3)H]T-3364366 binding to the desaturase domain of D5D. The present study is the first to demonstrate biochemical MOA of desaturase inhibitors, providing important insight into drug discovery of desaturase enzymes.

SCD1 deficiency protects mice against ethanol-induced liver injury

Stearoyl-CoA desaturase 1 (SCD1) is a delta-9 fatty acid desaturase that catalyzes the synthesis of mono-unsaturated fatty acids (MUFA). SCD1 is a critical control point regulating hepatic lipid synthesis and β-oxidation. Scd1 KO mice are resistant to the development of diet-induced non-alcoholic fatty liver disease (NAFLD). Using a chronic-binge protocol of ethanol-mediated liver injury, we aimed to determine if these KO mice are also resistant to the development of alcoholic fatty liver disease (AFLD).Mice fed a low-fat diet (especially low in MUFA) containing 5% ethanol for 10days, followed by a single ethanol (5g/kg) gavage, developed severe liver injury manifesting as hepatic steatosis. This was associated with an increase in de novo lipogenesis and inflammation. Using this model, we show that Scd1 KO mice are resistant to the development of AFLD. Scd1 KO mice do not show accumulation of hepatic triglycerides, activation of de novo lipogenesis nor elevation of cytokines or other pro-inflammatory markers. Incubating HepG2 cells with a SCD1 inhibitor induced a similar resistance to the effect of ethanol, confirming a role for SCD1 activity in mediating ethanol-induced hepatic injury.Taken together, our study shows that SCD1 is a key player in the development of AFLD and associated deleterious effects, and suggests SCD1 inhibition as a therapeutic option for the treatment of this hepatic disease.

Elevation of the Yields of Very Long Chain Polyunsaturated Fatty Acids via Minimal Codon Optimization of Two Key Biosynthetic Enzymes.

Eicosapentaenoic acid (EPA, 20:5Δ5,8,11,14,17) and Docosahexaenoic acid (DHA, 22:6Δ4,7,10,13,16,19) are nutritionally beneficial to human health. Transgenic production of EPA and DHA in oilseed crops by transferring genes originating from lower eukaryotes, such as microalgae and fungi, has been attempted in recent years. However, the low yield of EPA and DHA produced in these transgenic crops is a major hurdle for the commercialization of these transgenics. Many factors can negatively affect transgene expression, leading to a low level of converted fatty acid products. Among these the codon bias between the transgene donor and the host crop is one of the major contributing factors. Therefore, we carried out codon optimization of a fatty acid delta-6 desaturase gene PinD6 from the fungus Phytophthora infestans, and a delta-9 elongase gene, IgASE1 from the microalga Isochrysis galbana for expression in Saccharomyces cerevisiae and Arabidopsis respectively. These are the two key genes encoding enzymes for driving the first catalytic steps in the Δ6 desaturation/Δ6 elongation and the Δ9 elongation/Δ8 desaturation pathways for EPA/DHA biosynthesis. Hence expression levels of these two genes are important in determining the final yield of EPA/DHA. Via PCR-based mutagenesis we optimized the least preferred codons within the first 16 codons at their N-termini, as well as the most biased CGC codons (coding for arginine) within the entire sequences of both genes. An expression study showed that transgenic Arabidopsis plants harbouring the codon-optimized IgASE1 contained 64% more elongated fatty acid products than plants expressing the native IgASE1 sequence, whilst Saccharomyces cerevisiae expressing the codon optimized PinD6 yielded 20 times more desaturated products than yeast expressing wild-type (WT) PinD6. Thus the codon optimization strategy we developed here offers a simple, effective and low-cost alternative to whole gene synthesis for high expression of foreign genes in yeast and Arabidopsis.

Application of a delta-6 desaturase with α-linolenic acid preference on eicosapentaenoic acid production in Mortierella alpina.

BackgroundDelta-6 desaturase (FADS6) is a key bifunctional enzyme desaturating linoleic acid (LA) or α-linolenic acid (ALA) in the biosynthesis of polyunsaturated fatty acids (PUFAs). In previous work, we analyzed the substrate specificity of two FADS6 enzymes from Mortierella alpina ATCC 32222 (MaFADS6) and Micromonas pusilla CCMP1545 (MpFADS6), which showed preference for LA and ALA, respectively. We also clarified the PUFA profiles in M. alpina, where these lipids were synthesized mainly via the ω6 pathway and rarely via the ω3 pathway and as a result contained low ALA and eicosapentaenoic acid (EPA) levels.ResultTo enhance EPA production in M. alpina by favoring the ω3 pathway, a plasmid harboring the MpFADS6 gene was constructed and overexpressed in a uracil-auxotrophic strain of M. alpina using the Agrobacterium tumefaciens-mediated transformation (ATMT) method. Our results revealed that the EPA production reached 80.0 ± 15.0 and 90.4 ± 9.7 mg/L in MpFADS6 transformants grown at 28 and at 12 °C, respectively. To raise the level of ALA, free form fatty acid was used as exogenous substrate, which increased the EPA production up to 114.5 ± 12.4 mg/L. To reduce the cost of EPA production in M. alpina, peony seed oil (PSO) and peony seed meal (PSM) were used as source of ALA, and EPA production was improved to 149.3 ± 7.8 and 515.29 ± 32.66 mg/L by supplementing with 0.1 % PSO and 50 g/L PSM, respectively. The EPA yield was further increased to 588.5 ± 29.6 mg/L in a 5-L bioreactor, which resulted in a 26.2-fold increase compared to EPA production in wild-type M. alpina. In this work, we have significantly enhanced EPA production through overexpression of a FADS6 desaturase with preference for ALA, combined with supplementation of its substrate.ConclusionAn ALA-preferring FADS6 from M. pusilla CCMP1545 was applied to enhance EPA production in M. alpina. By exogenous addition of peony seed oil or peony seed meal, EPA production was further increased in flasks and fermenters. This research also highlights the value of peony seed meal which can be converted to a high value-added product containing EPA, and as a way to increase the EPA/AA ratio in M. alpina.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0516-5) contains supplementary material, which is available to authorized users.

Fatty acid desaturase 1 knockout mice are lean with improved glycemic control and decreased development of atheromatous plaque.

Delta-5 desaturase (D5D) and delta-6 desaturase (D6D), encoded by fatty acid desaturase 1 (FADS1) and FADS2 genes, respectively, are enzymes in the synthetic pathways for ω3, ω6, and ω9 polyunsaturated fatty acids (PUFAs). Although PUFAs appear to be involved in mammalian metabolic pathways, the physiologic effect of isolated D5D deficiency on these pathways is unclear. After generating >4,650 knockouts (KOs) of independent mouse genes and analyzing them in our high-throughput phenotypic screen, we found that Fads1 KO mice were among the leanest of 3,651 chow-fed KO lines analyzed for body composition and were among the most glucose tolerant of 2,489 high-fat-diet-fed KO lines analyzed by oral glucose tolerance test. In confirmatory studies, chow- or high-fat-diet-fed Fads1 KO mice were leaner than wild-type (WT) littermates; when data from multiple cohorts of adult mice were combined, body fat was 38% and 31% lower in Fads1 male and female KO mice, respectively. Fads1 KO mice also had lower glucose and insulin excursions during oral glucose tolerance tests along with lower fasting glucose, insulin, triglyceride, and total cholesterol levels. In additional studies using a vascular injury model, Fads1 KO mice had significantly decreased femoral artery intima/media ratios consistent with a decreased inflammatory response in their arterial wall. Based on this result, we bred Fads1 KO and WT mice onto an ApoE KO background and fed them a Western diet for 14 weeks; in this atherogenic environment, aortic trees of Fads1 KO mice had 40% less atheromatous plaque compared to WT littermates. Importantly, PUFA levels measured in brain and liver phospholipid fractions of Fads1 KO mice were consistent with decreased D5D activity and normal D6D activity. The beneficial metabolic phenotype demonstrated in Fads1 KO mice suggests that selective D5D inhibitors may be useful in the treatment of human obesity, diabetes, and atherosclerotic cardiovascular disease.

Cloning, expression and functional analysis of a delta 6-desaturase gene from the silkworm, Bombyx mori L.

Delta 6-fatty acid desaturase is a membrane-bound enzyme, which is the rate-limiting factor in the biosynthesis of polyunsaturated fatty acids. In this study, a novel delta 6-desaturase gene was cloned from Bombyx mori (BmD6DES). Sequencing analysis revealed that BmD6DES has an open reading frame of 1357bp that encodes 448 amino acids. Heterologous expression in yeast demonstrated that BmD6DES could synthesize γ-linolenic acid (GLA, 18:3, Δ6,9,12) by utilizing the endogenous substrate linoleic acid (LA, 18:2, Δ9,12). We found that BmD6DES transcripts were distributed in almost all B. mori tissues, with high expression levels observed at the 5th instar larval, pupal, and adult moth stages. A functional analysis of BmD6DES was performed by measuring mRNA levels after temperature stress, fungal infection, and RNA interference (RNAi). The results indicated that the highest expression of BmD6DES was observed at low temperatures (0°C) and 6h to 36h after fungal infection. qPCR analysis demonstrated that BmD6DES mRNA levels in pupa after BmD6DES RNAi treatment were significantly reduced from 12h to 72h compared to those in the control group. Our findings suggest that BmD6DES not only induces the formation of the third carbon–carbon double bond in the LA carbon chain, but also leads to sensitivity to low-temperature stress and fungal infection. These results imply that BmD6DES is a key gene in the γ-linolenic acid pathway during B. mori development.

An insect with a delta-12 desaturase, the jewel wasp Nasonia vitripennis, benefits from nutritional supply with linoleic acid.

The availability of linoleic acid (LA; C18:2(∆9,12)) is pivotal for animals. While vertebrates depend on a nutritional supply, some invertebrates, including the parasitic wasp Nasonia vitripennis, are able to synthesize LA from oleic acid (OA; C18:1(∆9)). This raises the question as to whether these animals nevertheless benefit from the additional uptake of LA with the diet. LA plays an important role in the sexual communication of N. vitripennis because males use it as a precursor for the synthesis of an abdominal sex pheromone attracting virgin females. We reared hosts of N. vitripennis that were fed diets enriched in the availability of stearic acid (SA: C18:0), OA or LA. N. vitripennis males developing on the different host types clearly differed in both the fatty acid composition of their body fat and sex pheromone titres. Males from LA-enriched hosts had an almost fourfold higher proportion of LA and produced significantly more sex pheromone than males from SA (2.2-fold) and OA (1.4-fold) enriched hosts, respectively. Our study demonstrates that animals being able to synthesize important nutrients de novo may still benefit from an additional supply with their diet.

Hexadecenoic Fatty Acid Isomers in Human Blood Lipids and Their Relevance for the Interpretation of Lipidomic Profiles.

Monounsaturated fatty acids (MUFA) are emerging health biomarkers, and in particular the ratio between palmitoleic acid (9cis-16:1) and palmitic acid (16:0) affords the delta-9 desaturase index that is increased in obesity. Recently, other positional and geometrical MUFA isomers belonging to the hexadecenoic family (C16 MUFA) were found in circulating lipids, such as sapienic acid (6cis-16:1), palmitelaidic acid (9trans-16:1) and 6trans-16:1. In this work we report: i) the identification of sapienic acid as component of human erythrocyte membrane phospholipids with significant increase in morbidly obese patients (n = 50) compared with age-matched lean controls (n = 50); and ii) the first comparison of erythrocyte membrane phospholipids (PL) and plasma cholesteryl esters (CE) in morbidly obese patients highlighting that some of their fatty acid levels have opposite trends: increases of both palmitic and sapienic acids with the decrease of linoleic acid (9cis,12cis-18:2, omega-6) in red blood cell (RBC) membrane PL were reversed in plasma CE, whereas the increase of palmitoleic acid was similar in both lipid species. Consequentially, desaturase enzymatic indexes gave different results, depending on the lipid class used for the fatty acid content. The fatty acid profile of morbidly obese subjects also showed significant increases of stearic acid (C18:0) and C20 omega-6, as well as decreases of oleic acid (9cis-18:1) and docosahexaenoic acid (C22:6 omega-3) as compared with lean healthy controls. Trans monounsaturated and polyunsaturated fatty acids were also measured and found significantly increased in both lipid classes of morbidly obese subjects. These results highlight the C16 MUFA isomers as emerging metabolic marker provided that the assignment of the double bond position and geometry is correctly performed, thus identifying the corresponding lipidomic pathway. Since RBC membrane PL and plasma CE have different fatty acid trends, caution must also be used in the choice of lipid species for the interpretation of lipidomic profiles.

Risk of secondary lymphedema in breast cancer survivors is related to serum phospholipid fatty acid desaturation.

Secondary lymphedema is a common irreversible side effect of breast cancer surgery. We investigated if risk of secondary lymphedema in breast cancer survivors was related to changes in serum phospholipid fatty acid composition. Study subjects were voluntarily recruited into the following three groups: breast cancer survivors who had sentinel lymph node biopsy without lymphedema (SLNB), those who had auxillary lymph node dissection without lymphedema (ALND), and those who had ALND with lymphedema (ALND + LE). Body mass index (BMI), serum lipid profiles, bioimpedance data with single-frequency bioimpedance analysis (SFBIA), and serum phospholipid compositions were analyzed and compared among the groups. BMI, serum total cholesterol (total-C), and low-density lipoprotein cholesterol (LDL-C) and SFBIA ratios increased only in the ALND + LE. High polyunsaturated fatty acids (PUFAs) and high C20:4 to C18:2 n-6 PUFAs (arachidonic acid [AA]/linoleic acid [LA]) was detected in the ALND and ALND + LE groups compared to SLNB. The ALND + LE group showed increased activity indices for delta 6 desaturase (D6D) and D5D and increased ratio of AA to eicosapentaenoic acid (AA/EPA) compared to the ALND and SLNB groups. Correlation and regression analysis indicated that D6D, D5D, and AA/EPA were associated with SFBIA ratios. We demonstrated that breast cancer survivors with lymphedema had elevated total PUFAs, fatty acid desaturase activity indices, and AA/EPA in serum phospholipids. Our findings suggested that desaturation extent of fatty acid composition might be related to the risk of secondary lymphedema in breast cancer survivors.

Supplementation with dietary EPA/DHA influences red blood cell fatty acid desaturase estimates and reflects tissue changes in fatty acids in systemic organs

Delta‐5‐desaturase (D5D) and delta‐6‐desaturase (D6D) are critical in polyunsaturated fatty acid (PUFA) metabolism. D5D and D6D catalyze the conversion of linoleic acid (LA) into arachidonic acid (AA) and that of alpha‐linolenic acid (ALA) into eicosapentaenoic acid (EPA). Altered PUFA desaturation (i.e., increased D6D and decreased D5D) can exacerbate inflammatory responses. Supplementation with the long chain PUFAs (LCPUFAs) EPA and DHA can influence PUFA metabolism and decrease pro‐inflammatory responses. Furthermore, changes in D5D and D6D activity are associated with obesity, type‐2 diabetes, and dysregulated metabolism. The objective of this study was to determine how increasing dietary EPA and DHA alters the D5D and D6D enzyme activity estimates (EAEs) in the RBC (red blood cell) and systemic tissues. In this study, mice were fed control plus three diets with increasing percent of energy (%en) derived from EPA+DHA. Dietary levels reflected recommended intakes of fish/fish oil by the American Heart Association. These doses translated to 0.1%en, 0.675%en, and 1.8%en from dietary EPA+DHA. Phospholipid (PL) fatty acids (FAs) were isolated from heart, skeletal muscle, spleen, lung, adipose tissue, and RBCs. PL FAs were converted to FA methyl esters and analyzed using gas chromatography. D5D and D6D EAEs were calculated using the ratio of arachidonic/dihomo‐gamma linolenic acid (DGLA) and DGLA/linoleic acid, respectively. We observed a positive correlation between RBC D5D EAEs and tissue D5D EAEs across all tissues. RBC D6D EAEs were positively correlated with muscle and negatively correlated with adipose D6D EAEs. D5D and D6D EAEs varied with EPA+DHA supplementation. When comparing the control vs the 1.8%en EPA+DHA diets, a significant decrease in D5D EAE was observed in heart (−42.51%), lung (−54.99%), spleen (−51.46%), and adipose (−78.06%). No significant difference was observed in muscle D5D EAE. Muscle D6D EAE significantly decreased (−39.95%). In adipose tissue, D6D was significantly increased compared to control (+97.80%). No significant dietary effect on D6D EAE was observed in heart, lung, or spleen with supplementation. RBC desaturase EAEs are reflective of tissue desaturase EAEs. Interestingly, RBC desaturase EAEs remained reflective of tissue desaturase EAEs despite changes in mean D5D and D6D EAEs after EPA+DHA supplementation. The high correlation between RBC desaturase EAEs and tissue desaturase EAEs with increasing dietary EPA and DHA, indicates RBC D5D and D6D EAEs are accurate non‐invasive methods to assess tissue PUFA metabolism. Future studies should investigate the usefulness of RBC desaturases in assessing tissues desaturases in disease models such as obesity, type‐2 diabetes, and metabolic syndrome and how EPA+DHA may alter fatty acid metabolism to favor an anti‐inflammatory profile.Support or Funding InformationResearch Support: NIH R03CA142000

FADS2 Over expression Promotes Metabolic Syndrome in Mice: Influence of Maternal Dietary Polyunsaturated Fatty Acid Composition

Accumulating evidence from human and animal studies indicates that risk of developing metabolic syndrome (MSx) is strongly influenced by maternal genotype and the nutritional environment encountered during fetal and early postnatal development. In addition to the well‐established effects of over nutrition, the fatty acid composition of the diet, particularly the n6:n3 polyunsaturated fatty acid (PUFA) ratio, has been postulated to play an important role in the development of MSx. However, results from dietary PUFA intervention studies on metabolic health have been inconsistent, perhaps in part due to individual and population differences in endogenous PUFA metabolism. Indeed, common FADS2 haplotypes and elevated serum indices of PUFA metabolism by its gene product, delta‐6 desaturase (D6D), also predict obesity and MSx in children and adult populations, though any causal relationship remains to be established. To directly investigate the effect of FADS2 expression on metabolic phenotype, we generated mice with global transgenic over expression of FADS2 (CMV promoter), backcrossed for 8 generations on a FVB background. FADS2‐tg mice exhibit elevated serum and tissue PUFA product/precursor ratios reflective of systemic D6D hyperactivity similar to those associated with FADS2 haplotypes and cardiometabolic risk in epidemiological studies. When maintained on a standard chow diet (Harlan 2918; 18% Kcals Fat), FADS2‐tg mice develop progressive obesity, glucose intolerance, insulin resistance and hyperlipidemia beginning at 1–2 months of age compared to age‐matched FVB wild‐type (WT) mice on the same chow diet. Importantly, linoleic acid (18:2n6) represents the majority (91%) of PUFA in 2918 chow, generating a dietary n6:n3 PUFA ratio of &gt;10:1, similar to the modern “western” diet. Based on clinical evidence for potentially beneficial effects of perinatal n3‐PUFA supplementation on infant metabolic status, we tested the hypothesis that reducing this ratio to ~3:1 in the maternal diet of FADS2‐tg mice would attenuate development of MSx in her offspring. FADS2‐tg females were fed 2918 chow supplemented with 2% flaxseed oil (providing ~1% w/w n3 α‐linolenic acid; ALA) beginning 2 weeks prior to pairing with a WT male until litters were weaned. Offspring were maintained on the standard 2918 chow diet after weaning, and compared to litters from the same mother without ALA supplementation. Interestingly, maternal ALA supplementation significantly normalized weight gain and glucose tolerance to near WT levels in male, but not female, offspring for up to 2 months post weaning on the chow diet. Food intake was similar across groups, actually trending higher in the offspring from the ALA supplemented pregnancy. Taken together, these studies suggest a causal link between FADS2 expression and the development of MSx, and reveal sex‐specific benefits of prenatal n3‐PUFA supplementation in this context. The cellular mechanisms responsible for MSx induced by FADS2 over expression, and its suppression by maternal ALA supplementation, are currently being investigated in our laboratory.Support or Funding InformationSupported by grants from the USDA and Colorado Agricultural Experimental Station to AJC.

Relationship between Body Mass Index, C-Peptide, and Delta-5-Desaturase Enzyme Activity Estimates in Adult Males.

Obesity, in particular abdominal obesity, alters the composition of plasma and tissue fatty acids (FAs), which contributes to inflammation and insulin resistance. FA metabolism is modulated by desaturases and may affect adipokine and insulin secretion. Therefore, we examined relationships between adipokines, a marker of insulin production, and plasma FA desaturase enzyme activity estimates (EAEs) in obesity. Plasma phospholipid (PPL) FAs were isolated from 126 males (ages 48 to 65 years), derivatized, and analyzed using gas chromatography. Delta-6 desaturase (D6D) and delta-5 desaturase (D5D) EAEs were calculated as the ratio of PPL 20:3/18:2 and 20:4/20:3, respectively. In body mass index (BMI) and waist circumference (WC) adjusted polytomous logistic regression analyses, PPL FAs and FA desaturase EAEs were associated with C-peptide and adiponectin. Individuals with elevated D6D EAEs were less likely (OR 0.33) to have serum adiponectin concentrations > 5.37 μg/mL, compared with adiponectin concentrations ≤ 3.62 μg/mL. Individuals with increased D5D EAEs were less likely (OR 0.8) to have C-peptide concentrations ≥ 3.32 ng/mL, and > 1.80 and ≤ 3.29 ng/mL, compared with those with C-peptide ≤ 1.76 ng/mL. The proinflammatory cytokine tumor necrosis factor-α (TNF- α) was positively associated with C-peptide, but TNF- α was not associated with the D5D EAE. C-peptide and adiponectin concentrations are associated with specific PPL FAs and FA desaturase EAEs. The relationship between C-peptide concentrations and D5D EAEs remained significant after adjusting for BMI, WC, and TNF-α. Thus, future research should investigate whether D5D inhibition may occur through a C-peptide mediated pathway.

Chronic pancreatitis and the composition of plasma phosphatidylcholine fatty acids

Chronic pancreatitis (CP) is an irreversible inflammatory disorder characterized by the destruction of both exocrine and endocrine tissue. There is growing evidence that dysregulation of fatty acid (FA) metabolism is connected with many diseases; however, there are few data concerning FA composition in CP. Therefore, we analyzed FA profiles in plasma phosphatidylcholines in 96 patients with CP and in 108 control subjects (CON).The patients with CP had, in comparison with CON, increased sum of monounsaturated FA (ΣMUFA) and decreased content of polyunsaturated FA (PUFA) in both n-6 and n-3 families. Moreover, CP patients had increased indexes for delta-9, delta-6 desaturases, and fall in activity of delta-5 desaturase. Increased ratio of 16:1n-7/18:2n-6 (marker of essential n-6 FA deficiency), was more prevalent among CP patients.These changes implicated decreased fat intake, including n-3 as well as n-6 PUFA, and intrinsic changes in FA metabolism due to the alteration of delta desaturase activities.

Polymorphisms in FADS1 and FADS2 alter plasma fatty acids and desaturase levels in type 2 diabetic patients with coronary artery disease.

BackgroundTo explore whether plasma fatty acids and SNPs in the fatty acid desaturase (FADS) gene associated with type 2 diabetes (T2D) and coronary artery disease (CAD).MethodsIn this cross-sectional study, we utilized gas chromatography–mass spectrometric analysis and the high-resolution melting method to detect plasma fatty acids and SNPs respectively (rs174537G>T, rs174616C>T, rs174460T>C, and rs174450A>C) in 234 T2D, 200 CAD, 185 T2D&CAD patients, and 253 healthy controls.ResultsWe found that T2D&CAD patients had the highest plasma arachidonic acid, dihomo-gamma-linolenic acid and delta-6 desaturase, and the lowest stearic acid, linolenic acid, and saturated fatty acids; plasma eicosapentaenoic acid and docosahexaenoic acid elevated in T2D patients, but significantly reduced in CAD patients. Moreover, T2D patients with rs174537 GG genotype were at risk of developing T2D&CAD (odds ratio (OR) 1.763; 95 % CI 1.143–2.718; p = 0.010), with elevated plasma LDL-cholesterol, arachidonic acid, and delta-6 desaturase.ConclusionsOur results show that SNPs in FADS gene (particularly rs174537) associate with plasma fatty acids and desaturase levels in patients with both T2D and CAD, which maybe increases the risk of CAD in diabetic patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-016-0834-8) contains supplementary material, which is available to authorized users.