Fatty acid desaturase 1/2 (FADS1 and FADS2), fatty acid desaturase indices, and their relationships with metabolic syndrome in female adults with first-episode schizophrenia after antipsychotic medications

OBJECTIVE

Although antipsychotics constitute the best treatment for patients with schizophrenia, this treatment class carries a high risk of metabolic disarrangements thus developing metabolic syndrome (MetS). Altered fatty acid (FA) composition and desaturase indices have been associated with several metabolic diseases, including MetS. Herein, we determined fatty acid desaturase 1 (FADS1) and FADS2 gene expressions, serum delta-5 desaturase (D5D) and D6D indices in female adults with first-episode schizophrenia after olanzapine medication, as well as their relationship with the incidence of MetS.

METHODS

This study prospectively recruited 120 female patients with first-episode schizophrenia who completed 6-month olanzapine medication. Among these female patients, 31 patients developed MetS and 89 patients did not.

RESULTS

The mRNA expression levels of FADS1 and FADS2 in patients were analyzed according to the presence of MetS and evaluation times with results of two-way ANOVAs (FADS1: PMetS = 0.0006, Ptime = 0.004, Pinteraction = 0.010; FADS2: PMetS = 0.012, Ptime < 0.0001, Pinteraction = 0.001). The D5D and D6D indices in patients were analyzed according to the presence of MetS and evaluation times with results of two-way ANOVAs (D5D: PMetS = 0.002, Ptime = 0.009, Pinteraction = 0.014; D6D: PMetS = 0.011, Ptime = 0.006, Pinteraction = 0.0001). The SCD-16 and SCD-18 indices in patients were analyzed according to the presence of MetS and evaluation times (SCD-16: PMetS = 0.005, Ptime = 0.009, Pinteraction = 0.016; SCD-18: PMetS = 0.037, Ptime = 0.382, Pinteraction = 0.163). The following multiple comparisons test showed the MetS exhibited reduced FADS1 mRNA expression and D5D index, increased FADS2 mRNA expression and D6D index, concomitant with an enhanced SCD-16 index, compared to the non-MetS did not after 6-month olanzapine medication.

CONCLUSION

The study suggests changes of FADS1, FADS2 expressions, and fatty acid desaturase indices including D5D, D6D, and SCD-16 may be associated with the development of MetS in female adults with first-episode schizophrenia after olanzapine medication.

The association between genetically elevated polyunsaturated fatty acids and risk of cancer

BACKGROUND

The causal relevance of polyunsaturated fatty acids (PUFAs) for risk of site-specific cancers remains uncertain.

METHODS

Using a Mendelian randomization (MR) framework, we assessed the causal relevance of PUFAs for risk of cancer in European and East Asian ancestry individuals. We defined the primary exposure as PUFA desaturase activity, proxied by rs174546 at the FADS locus. Secondary exposures were defined as omega 3 and omega 6 PUFAs that could be proxied by genetic polymorphisms outside the FADS region. Our study used summary genetic data on 10 PUFAs and 67 cancers, corresponding to 562,871 cases and 1,619,465 controls, collected by the Fatty Acids in Cancer Mendelian Randomization Collaboration. We estimated odds ratios (ORs) for cancer per standard deviation increase in genetically proxied PUFA exposures.

FINDINGS

Genetically elevated PUFA desaturase activity was associated (P < 0.0007) with higher risk (OR [95% confidence interval]) of colorectal cancer (1.09 [1.07-1.11]), esophageal squamous cell carcinoma (1.16 [1.06-1.26]), lung cancer (1.06 [1.03-1.08]) and basal cell carcinoma (1.05 [1.02-1.07]). There was little evidence for associations with reproductive cancers (OR = 1.00 [95% CI: 0.99-1.01]; Pheterogeneity = 0.25), urinary system cancers (1.03 [0.99-1.06], Pheterogeneity = 0.51), nervous system cancers (0.99 [0.95-1.03], Pheterogeneity = 0.92) or blood cancers (1.01 [0.98-1.04], Pheterogeneity = 0.09). Findings for colorectal cancer and esophageal squamous cell carcinoma remained compatible with causality in sensitivity analyses for violations of assumptions. Secondary MR analyses highlighted higher omega 6 PUFAs (arachidonic acid, gamma-linolenic acid and dihomo-gamma-linolenic acid) as potential mediators. PUFA biosynthesis is known to interact with aspirin, which increases risk of bleeding and inflammatory bowel disease. In a phenome-wide MR study of non-neoplastic diseases, we found that genetic lowering of PUFA desaturase activity, mimicking a hypothetical intervention to reduce cancer risk, was associated (P < 0.0006) with increased risk of inflammatory bowel disease but not bleeding.

INTERPRETATION

The PUFA biosynthesis pathway may be an intervention target for prevention of colorectal cancer and esophageal squamous cell carcinoma but with potential for increased risk of inflammatory bowel disease.

FUNDING

Cancer Resesrch UK (C52724/A20138, C18281/A19169). UK Medical Research Council (MR/P014054/1). National Institute for Health Research (NIHR202411). UK Medical Research Council (MC_UU_00011/1, MC_UU_00011/3, MC_UU_00011/6, and MC_UU_00011/4). National Cancer Institute (R00 CA215360). National Institutes of Health (U01 CA164973, R01 CA60987, R01 CA72520, U01 CA74806, R01 CA55874, U01 CA164973 and U01 CA164973).

Engineering and fermenter production of fungi GLA in Pichia pastoris GS115 using oil waste

γ-Linolenic acid (GLA) is an essential n-6 polyunsaturated fatty acid (PUFA) that has received considerable attention in human and animal feed. GLA is used in many nutritional and medicinal applications, such as the treatment of cancer, inflammatory disorders, and diabetes. Currently, plant seed is the primary dietary source of GLA that is not enough to utilize on an industrial scale. To generate a sustainable novel source of GLA, the gene of delta-6 desaturase, one of the essential enzymes in the GLA production pathway, was isolated from Mucor rouxii DSM1194 and expressed in P. pastoris GS115 by pPICZC vector. The recombinant yeast expressed the GLA up to 19.2% (72 mg/g) of total fatty acids. GLA production of recombinant yeast was studied in a fermenter by oil waste for 5 days, and results detected 6.3 g/l lipid, and 103 mg/g GLA was produced in 72 h. The present study may provide an opportunity to develop an alternative host for manufacturing GLA on an industrial scale.

Δ5 and Δ6 desaturase indices are not associated with zinc intake as determined by dietary assessment or modified by a zinc-FADS1 rs174547 SNP interaction in young Canadian adults

BACKGROUND

Zinc is an essential trace mineral that serves as a cofactor for the delta-5 and delta-6 desaturases (D5D, D6D) that are critical for long-chain polyunsaturated fatty acid (LC-PUFA) synthesis. While plasma zinc levels are generally reported to be associated with D5D and D6D indices in humans, it remains unclear if dietary zinc intake can be similarly associated with desaturase indices. Therefore, the present investigation examined if zinc intake determined by food frequency questionnaire (FFQ) is associated with desaturase indices in young Canadian adults. Additionally, we explored whether desaturase indices were modified by an interaction between dietary zinc intake and a common variant in the FADS1 gene.

METHODS

Dietary zinc intake (FFQ), plasma fatty acids (gas chromatography) and the FADS1 rs174547 polymorphism were analyzed in young men and women (n = 803) from the cross-sectional Toronto Nutrigenomics and Health Study. Product-to-precursor fatty acid ratios were used to determine desaturase enzyme indices (D5D = 20:4n-6/20:3n-6; D6D = 18:3n-6/18:2n-6). Individuals were grouped according to dietary zinc intake, as well as by their rs174547 genotype (TT vs. TC+CC). Data were analyzed by 1-way and 2-way ANCOVA.

RESULTS

Plasma fatty acids and D5D/D6D indices did not differ between individuals grouped according to dietary zinc intake. Further, the recently proposed biomarker of zinc intake, 20:3n-6/18:2n-6, was not associated with dietary zinc intake. Although the FADS1 rs174547 SNP was significantly associated with D5D and D6D indices in both men and women (p < 0.0001), we did not find evidence of a dietary zinc intake - FADS1 SNP interaction on D5D or D6D indices.

CONCLUSION

Dietary zinc intake, as determined using FFQs, does not predict differences in desaturase indices, irrespective of FADS1 genotype.

Influence of iron-deficient diets during gestation and lactation on cerebral fatty acids and eicosanoids in guinea pig offspring-Comparison of studies with different sources of dietary lipids

Previous studies showed that mild iron deficiency anaemia (IDA) induced by feeding an iron deficient (ID) diet to female guinea pigs during gestation and lactation to alters the auditory functions of the offspring when corn oil is the only source of dietary lipids. Conversely, feeding an ID diet with a dietary fatty acid composition similar to that of typical human western diets induced minor impairments. Since tissue fatty acid metabolism is affected by dietary iron, the current study measured the impacts of these ID diets (ID-corn and ID-west) compared to the corresponding iron-sufficient control diets (IS-corn and IS-west) on encephalum fatty acid metabolism in the offspring at post-natal day 24. IDA induced by the ID-corn diet resulted in significant increases in encephalum n-6 PUFA content, but IDA induced by the ID-west diet had little impact on fatty acid profiles compared to the IS-west group. Brain COX II protein expression and FADS2 mRNA expression were statistically unaffected in both experiments, but encephalum PGE₂ concentrations were significantly reduced in ID-west pups. These results suggest IDA studies during prenatal development should consider dietary lipid compositions.

Liver DNA methylation of FADS2 associates with FADS2 genotype

BACKGROUND

Non-alcoholic fatty liver disease has been associated with increased mRNA expression of FADS2 in the liver and estimated activity of delta-6 desaturase in serum, encoded by the FADS2 gene. Since DNA methylation in the FADS1/2/3 gene cluster has been previously linked with genetic variants and desaturase activities, we now aimed to discover factors regulating DNA methylation of the CpG sites annotated to FADS1/2 genes.

METHODS

DNA methylation levels in the CpG sites annotated to FADS2 and FADS1 were analyzed from liver samples of 95 obese participants of the Kuopio Obesity Surgery Study (34 men and 61 women, age 49.5 ± 7.7 years, BMI 43.0 ± 5.7 kg/m²) using the Infinium HumanMethylation450 BeadChip (Illumina). Associations between DNA methylation levels and estimated delta-6 and delta-5 desaturase enzyme activities, liver histology, hepatic mRNA expression, FADS1/2 genotypes, and erythrocyte folate levels were analyzed.

RESULTS

We found a negative correlation between DNA methylation levels of cg06781209 and cg07999042 and hepatic FADS2 mRNA expression (both p < 0.05), and with estimated delta-6 desaturase activity based on both liver and serum fatty acids (all p < 0.05). Interestingly, the methylation level of cg07999042 (p = 0.001) but not of cg06781209 (p = 0.874) was associated with FADS2 variant rs174616.

CONCLUSIONS

Genetic variants of FADS2 may contribute to the pathogenesis of non-alcoholic fatty liver disease by modifying DNA methylation.

Dietary EPA and DHA prevent changes in white adipose tissue omega-3 PUFA and oxylipin content associated with a Fads2 deficiency

Fatty acid desaturase 2 (Fads2) encodes the delta-6 desaturase (D6D) enzyme, which is rate-limiting for the endogenous production of omega-3 long-chain polyunsaturated fatty acids (LC-PUFA). Numerous studies have reported the cardiometabolic health benefits of omega-3 LC-PUFA. Humans carrying genetic variants in the FADS2 gene have reduced levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as oxylipins, in blood, erythrocytes and white adipose tissue (WAT). Similar findings have been reported in whole-body Fads2^-/- mice fed a diet deficient in omega-3 LC-PUFA. The objective of this study was to determine if a diet containing EPA and DHA would prevent the deficiencies in WAT lipid profiles seen in Fads2^-/- mice fed a diet containing only ALA. Male C57BL/6 J Fads2^-/- and wild type (WT) mice were fed a low fat (7% w/w) diet for 9 weeks containing either flaxseed oil + ARASCO (FD, containing~53% ALA) or menhaden oil (MD, containing~14% EPA and 10% DHA). Fads2^-/- mice fed an ALA-enriched diet had reduced body weight, little-to-no omega-3 LC-PUFA and a near complete loss of all omega-3 derived oxylipins in both epididymal and inguinal WAT (P<.05) compared to their WT counterparts, as well as altered expression of key regulators of the fatty acid desaturase pathway. However, Fads2^-/- mice fed a diet containing EPA and DHA prevented most of these changes. This study provides evidence that a diet containing EPA and DHA provides a nutritional strategy to prevent alterations in WAT lipid content caused by reduced D6D activity.

Fatty Acids as Useful Serological Markers for Crohn's Disease

BACKGROUND

We have previously reported that patients with Crohn's disease (CD) have a very specific erythrocyte membrane phospholipid fatty acid profile. The findings of this study suggest that the activities of enzymes involved in the metabolism of linoleic acid (LA), that is, delta-6 desaturase, are higher in CD patients than in healthy individuals.

METHODS

We evaluated the utilities of various fatty acid compositions of the plasma (p-) as new serological markers for CD compared to those of erythrocyte membranes (e-).

RESULTS

Fifty CD patients and 50 healthy individuals were enrolled. In both plasma and erythrocyte membranes, the weight percentages of palmitic acid (PA) were significantly higher, while those of LA were significantly lower in CD patients than in controls. Fatty acids with high sensitivity and specificity were p-PA (0.86 and 0.74) and e-PA (0.80 and 0.74). With PA and LA as a CD fatty acid index (CDFAi), that is, CDFAi = (PA/LA), the sensitivity and specificity of plasma CDFAi (p-CDFAi) and e-CDFAi were 0.80 and 0.80; and 0.82 and 0.88 respectively.

CONCLUSION

In CD patients, various fatty acids were specifically altered in both plasma and erythrocytes, and p-PA and p-CDFAi are potentially useful as new serological markers for CD.

Neither linoleic acid nor arachidonic acid promote white adipose tissue inflammation in Fads2-/- mice fed low fat diets

Dietary n-6 polyunsaturated fatty acids (PUFA) are widely perceived to promote inflammation and contribute to the development of chronic diseases. This dogma has been recently questioned due to evidence that n-6 PUFA, specifically linoleic acid (LA, 18:2n-6) and arachidonic acid (AA, 20:4n-6), do not appear to activate inflammatory signalling pathways when consumed in moderate amounts. However, delineating the independent roles of different dietary n-6 PUFA in vivo is challenging because LA is continuously converted into AA in a pathway regulated by the fatty acid desaturase 2 (Fads2) gene. The objective of this study was to investigate the independent roles of LA and AA on white adipose tissue (WAT) inflammatory signalling pathways using Fads2-/- mice. We hypothesized that dietary LA would not induce WAT inflammation, unless it was endogenously converted into AA. Male C57BL/6 wild-type (WT) and Fads2-/- mice were fed low-fat isocaloric diets containing either 7% corn oil w/w (CD, containing ~42% LA) or 7% ARASCO oil w/w (AD, containing ~27% AA) for 9 weeks. WAT inflammatory gene expression, protein levels, as well as phospholipid (PL) and triacylglycerol (TAG) fatty acid composition, were analyzed by RT-qPCR, western blots, and gas chromatography, respectively. Fads2-/- mice fed CD had high LA, but little-to-no GLA (18:3n-6), DGLA (20:3n-6), and AA in PLs and TAGs compared to their WT counterparts. In comparison, Fads2-/- and WT mice fed AD showed minimal differences in n-6 PUFA content in serum and WAT, despite having significantly more AA than CD-fed mice. No differences in gene expression for common inflammatory adipokines (e.g. Mcp-1, Ccl5, Tnfα) or key regulators of eicosanoid production (e.g. Cox-2, Alox-12, Alox-15) were detected in WAT between any of the diet and genotype groups. Furthermore, no differences in MCP-1, and total or phosphorylated STAT3 and p38 inflammatory proteins, were observed. Collectively, these results demonstrate that neither LA nor AA promote WAT inflammation when consumed as part of a low-fat diet. Therefore, the existing dogma surrounding n-6 PUFA and inflammation needs to be reconsidered.

Improved γ-linolenic acid production in Mucor circinelloides by homologous overexpressing of delta-12 and delta-6 desaturases

Background

γ-Linolenic acid (GLA) is important because of its nutritional value and medicinal applications. Although the biosynthetic pathways of some plant and microbial GLA have been deciphered, current understanding of the correlation between desaturases and GLA synthesis in oleaginous fungi is incomplete. In previous work, we found that a large amount of oleic acid (OA) had not been converted to linoleic acid (LA) or GLA in Mucor circinelloides CBS 277.49, which may be due to inadequate activities of the delta-12 or delta-6 desaturases, and thus leading to the accumulation of OA and LA. Thus, it is necessary to explore the main contributing factor during the process of GLA biosynthesis in M. circinelloides.

Results

To enhance GLA production in M. circinelloides, homologous overexpression of delta-12 and two delta-6 desaturases (named delta-6-1 and delta-6-2, respectively) were analyzed. When delta-6 desaturase were overexpressed in M. circinelloides, up to 43% GLA was produced in the total fatty acids, and the yield of GLA reached 180 mg/l, which were, respectively, 38 and 33% higher than the control strain.

Conclusion

These findings revealed that delta-6 desaturase (especially for delta-6-1 desaturase) plays an important role in GLA synthesis by M. circinelloides. The strain overexpressing delta-6-1 desaturase may have potential application in microbial GLA production.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-017-0723-8) contains supplementary material, which is available to authorized users.

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.

Transgenic expression of salmon delta-5 and delta-6 desaturase in zebrafish muscle inhibits the growth of Vibrio alginolyticus and affects fish immunomodulatory activity

Marine fish are an important nutritional source for highly polyunsaturated fatty acids (PUFAs). PUFA biosynthesis requires the following key enzymes: delta-4 (Δ-4) desaturase, delta-5 (Δ-5) desaturase, delta-6 (Δ-6) desaturase, delta-5 (Δ-5) elongase, and delta-6 (Δ-6) elongase. The effect of overexpressing delta-5 desaturase and/or delta-6 desaturase in zebrafish muscle has not previously been reported. Herein, we investigated the effects of these proteins on antibacterial and immunomodulatory activity in transgenic zebrafish infected with Vibrio alginolyticus. Overexpression of delta-5 and delta-6 desaturase enhanced antibacterial activity at 4 and 12 h after injection of bacteria into muscle, as compared to controls. Furthermore, expression of immune-related genes (IL-1β, IL-22, and TNF-α) was observed to be altered in transgenic fish after 4 h of bacterial infection, resulting in a significant decrease in the inflammatory response, as compared to control fish. These results demonstrate that muscle-specific expression of transgenic desaturases in zebrafish not only enhance PUFA production, but also enhance antibacterial and anti-inflammatory activity. Overall, these results identify delta-5 and delta-6 desaturase as novel candidate genes for use in aquaculture, to enhance both disease resistance and fish oil production.

Characterization of fatty acid delta-6 desaturase gene in Nile tilapia and heterogenous expression in Saccharomyces cerevisiae

Fatty acid delta-6 desaturase (fads2)-like gene from Nile tilapia (Oreochromis niloticus) was characterized and designated as oni-fads2. The Oni-FADS2 showed the typical structure of microsomal FADS2. The presence of oni-fads2 transcripts in unfertilized eggs demonstrated the maternal role of Nile tilapia in providing the oni-fads2 transcript in their eggs. In addition, the expression of oni-fads2 was detectable in embryos throughout the hatching stage. Real-time reverse transcription-PCR revealed that oni-fads2 was expressed at a high level in all the brain regions, liver, and testis. Recombinant yeast (RY) was generated by transformation of Saccharomyces cerevisiae with the plasmid containing oni-fads2 driven by the Gal1 promoter (pYoni-fads2). The conspicuous expression of RY was detectable by RT-PCR after induction with galactose for 24h. When RY was induced with galactose, it exhibited 39% and 7% of delta-6 desaturase (∆6) activity toward C18:2n6 and C18:3n3, respectively. Additionally, it displayed 4% of delta-5 desaturase (∆5) activity toward C20:3n6, indicating that Oni-FADS2 had ∆5 and ∆6 bifunction.

Treatment of ovariectomized rats with 17β-estradiol increases hepatic delta-6 desaturase enzyme expression and docosahexaenoic acid levels in hepatic and plasma phospholipids

Higher docosahexaenoic acid (DHA) in females compared with males suggests ovarian hormones increase DHA production. Eight-week old rats were ovariectomized or sham operated (SHAM), and ovariectomized rats were treated with implanted pellets providing 17β-estradiol (OVX+E), progesterone (OVX+P), both (OVX+PE) or neither (OVX) for 14 days. Immunoblot and fatty acid analysis were performed on all samples, and microarray analysis was performed on OVX and SHAM groups. Increased Δ6-desaturase in OVX relative to SHAM was observed by microarray (12% higher) and immunoblot (31% higher). OVX+E and OVX+PE rats had 39% and 42% higher Δ6-desaturase content, respectively, compared with OVX. OVX+E and OVX+PE also increased phospholipid DHA concentrations in liver (increase of 34% and 40%, respectively) and plasma (increase of 70% and 74%, respectively) relative to OVX. Progesterone exerted no effect on Δ6-desaturase or DHA. These results indicate that 17β-estradiol increases DHA through increased Δ6-desaturase, possibly explaining sex differences in DHA.