ELOVL5 Research Articles

Regulatory divergence of homeologous Atlantic salmon elovl5 genes following the salmonid-specific whole-genome duplication

Fatty acyl elongase 5 (elovl5) is a critical enzyme in the vertebrate biosynthetic pathway which produces the physiologically essential long-chain polyunsaturated fatty acids (LC-PUFA), docosahexenoic acid (DHA), and eicosapentenoic acid (EPA) from 18 carbon fatty acids precursors. In contrast to most other vertebrates, Atlantic salmon possess two copies of elovl5 (elovl5a and elovl5b) as a result of a whole-genome duplication (WGD) which occurred at the base of the salmonid lineage. WGDs have had a major influence on vertebrate evolution, providing extra genetic material, enabling neofunctionalization to accelerate adaptation and speciation. However, little is known about the mechanisms by which such duplicated homeologous genes diverge. Here we show that homeologous Atlantic salmon elovl5a and elovl5b genes have been asymmetrically colonised by transposon-like elements. Identical locations and identities of insertions are also present in the rainbow trout duplicate elovl5 genes, but not in the nearest extant representative preduplicated teleost, the northern pike. Both elovl5 salmon duplicates possessed conserved regulatory elements that promoted Srebp1- and Srebp2-dependent transcription, and differences in the magnitude of Srebp response between promoters could be attributed to a tandem duplication of SRE and NF-Y cofactor binding sites in elovl5b. Furthermore, an insertion in the promoter region of elovl5a confers responsiveness to Lxr/Rxr transcriptional activation. Our results indicate that most, but not all, transposon mobilisation into elovl5 genes occurred after the split from the common ancestor of pike and salmon, but before more recent salmonid speciations, and that divergence of elovl5 regulatory regions have enabled neofuntionalization by promoting differential expression of these homeologous genes.

Clinical and neuroradiological features of spinocerebellar ataxia 38 (SCA38)

IntroductionSCA38 (MIM 611805) caused by mutations within the ELOVL5 gene, which encodes an enzyme involved in the synthesis of long-chain fatty acids with a high and specific expression in Purkinje cells, has recently been identified. ObjectiveThe present study was aimed at describing the clinical and neuroimaging features, and the natural history of SCA38. MethodsWe extended our clinical and brain neuroimaging data on SCA38 including 21 cases from three Italian families. All had the ELOVL5 c.689G > T (p.Gly230Val) missense mutation. ResultsAge at disease onset was in the fourth decade of life. The presenting features were nystagmus (100% of cases) and slowly progressive gait ataxia (95%). Frequent signs and symptoms included pes cavus (82%) and hyposmia (76%); rarer symptoms were hearing loss (33%) and anxiety disorder (33%). The disease progressed with cerebellar symptoms such as limb ataxia, dysarthria, dysphagia, and ophtalmoparesis followed in the later stages by ophtalmoplegia. Peripheral nervous system involvement was present in the last phase of disease with sensory loss. Dementia or extrapyramidal signs were not detected. Significant loss of abilities of daily living was reported only after 20 years of the disease. Brain imaging documented cerebellar atrophy with sparing of cerebral cortex and no white matter disease. ConclusionsSCA38 is a rare form of inherited ataxia with characteristic clinical features, including pes cavus and hyposmia, that may guide genetic screening and prompt diagnosis in light of possible future therapeutic interventions.

Age-associated changes in DNA methylation across multiple tissues in an inbred mouse model

Epigenetic disruption has been implicated in many diseases of aging, and age-associated DNA methylation changes at specific genomic loci in humans are strongly correlated with chronological age. The aim of this study was to explore the specificity of selected age-associated differentially methylated positions (aDMPs) identified in human epidemiological studies by quantifying DNA methylation across multiple tissues in homologous regions of the murine genome. We selected four high-confidence aDMPs (located in the vicinity of the ELOVL2, GLRA1, MYOD1 and PDE4C genes) and quantified DNA methylation across these regions in four tissues (blood, lung, cerebellum and hippocampus) from male and female C57BL/6J mice, ranging in age from fetal (embryonic day 17) to 630 days. We observed tissue-specific age-associated changes in DNA methylation that was directionally consistent with those observed in humans. These findings lend further support to the notion that changes in DNA methylation are associated with chronological age and suggest that these processes are often conserved across tissues and between mammalian species. Our data highlight the relevance of utilizing model systems, in which environmental and genetic influences can be carefully controlled, for the further study of these phenomena.

Echium oil increased the expression of a Δ4 Fads2 fatty acyl desaturase and the deposition of n-3 long-chain polyunsaturated fatty acid in comparison with linseed oil in striped snakehead (Channa striata) muscle.

Despite the potential of vegetable oils as aquafeed ingredients, a major drawback associated with their utilization is the inferior level of beneficial n-3 long-chain polyunsaturated fatty acids (LC-PUFA). Echium oil (EO), which is rich in stearidonic acid (SDA, 18:4n-3), could potentially improve the deposition of n-3 LC-PUFA as the biosynthesis of LC-PUFA is enhanced through bypassing the rate-limiting ∆6 desaturation step. We report for the first time an attempt to investigate whether the presence of a desaturase (Fads2) capable of ∆4 desaturation activities and an elongase (Elovl5) will leverage the provision of dietary SDA to produce a higher rate of LC-PUFA bioconversion. Experimental diets were designed containing fish oil (FO), EO or linseed oil (LO) (100FO, 100EO, 100LO), and diets which comprised equal mixtures of the designated oils (50EOFO and 50EOLO) were evaluated in a 12-week feeding trial involving striped snakeheads (Channa striata). There was no significant difference in growth and feed conversion efficiency. The hepatic fatty acid composition and higher expression of fads2 and elovl5 genes in fish fed EO-based diets indicate the utilization of dietary SDA for LC-PUFA biosynthesis. Collectively, this resulted in a higher deposition of muscle eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) compared to LO-based diets. Dietary EO improved the ratio of n-3 LC-PUFA to n-6 LC-PUFA in fish muscle, which is desirable for human populations with excessive consumption of n-6 PUFA. This study validates the contribution of SDA in improving the content of n-3 LC-PUFA and the ratio of EPA to arachidonic acid (ARA, 20:4n-6) in a freshwater carnivorous species.

Inferring chronological age from DNA methylation patterns of human teeth.

Current methods to determine chronological age from modern and ancient remains rely on both morphological and molecular approaches. However, low accuracy and the lack of standardized protocols make the development of alternative methods for the estimation of individual's age even more urgent for several research fields, such as biological anthropology, biodemography, forensics, evolutionary genetics, and ancient DNA studies. Therefore, the aim of this study is to identify genomic regions whose DNA methylation level correlates with age in modern teeth. We used MALDI-TOF mass spectrometry to analyze DNA methylation levels of specific CpGs located in the ELOVL2, FHL2, and PENK genes. We considered methylation data from cementum, dentin and pulp of 21 modern teeth (from 17 to 77 years old) to construct a mathematical model able to exploit DNA methylation values to predict age of the individuals. The median difference between the real age and that estimated using DNA methylation values is 1.20 years (SD = 1.9) if DNA is recovered from both cementum and pulp of the same modern teeth, 2.25 years (SD = 2.5) if DNA is recovered from dental pulp, 2.45 years (SD = 3.3) if DNA is extracted from cementum and 7.07 years (SD = 7.0) when DNA is recovered from dentin only. We propose for the first time the evaluation of DNA methylation at ELOVL2, FHL2, and PENK genes as a powerful tool to predict age in modern teeth for anthropological applications. Future studies are needed to apply this method also to historical and relatively ancient human teeth.

Common genetic variation and survival after colorectal cancer diagnosis: a genome-wide analysis.

Genome-wide association studies have identified several germline single nucleotide polymorphisms (SNPs) significantly associated with colorectal cancer (CRC) incidence. Common germline genetic variation may also be related to CRC survival. We used a discovery-based approach to identify SNPs related to survival outcomes after CRC diagnosis. Genome-wide genotyping arrays were conducted for 3494 individuals with invasive CRC enrolled in six prospective cohort studies (median study-specific follow-up = 4.2-8.1 years). In pooled analyses, we used Cox regression to assess SNP-specific associations with CRC-specific and overall survival, with additional analyses stratified by stage at diagnosis. Top findings were followed-up in independent studies. A P value threshold of P < 5×10(-8) in analyses combining discovery and follow-up studies was required for genome-wide significance. Among individuals with distant-metastatic CRC, several SNPs at 6p12.1, nearest the ELOVL5 gene, were statistically significantly associated with poorer survival, with the strongest associations noted for rs209489 [hazard ratio (HR) = 1.8, P = 7.6×10(-10) and HR = 1.8, P = 3.7×10(-9) for CRC-specific and overall survival, respectively). No SNPs were statistically significantly associated with survival among all cases combined or in cases without distant-metastases. SNPs in 6p12.1/ELOVL5 were associated with survival outcomes in individuals with distant-metastatic CRC, and merit further follow-up for functional significance. Findings from this genome-wide association study highlight the potential importance of genetic variation in CRC prognosis and provide clues to genomic regions of potential interest.

Identification of human ELOVL5 enhancer regions controlled by SREBP

Fatty acid elongase 5 (ELOVL5) is an enzyme involved in the synthesis of polyunsaturated fatty acids. Sterol Regulatory Element-binding Protein (SREBP)-1 activates ELOVL5 and increases polyunsaturated fatty acid synthesis, which in turn negatively affects SREBP-1 expression. Thus, ELOVL5 has been established as an SREBP-1 target gene and an important component of the negative feedback loop of de novo lipogenesis. However, the human ELOVL5 promoter/enhancer has not been fully analyzed and the location of SREBP biding sites around the ELOVL5 gene has yet to be defined. Here we performed a detailed promoter/enhancer analysis of human ELOVL5 gene, and identified two new SREBP binding sites, one in the 10 kb upstream region and one in the exon 1. These two SRE motifs are conserved among mammals and the mechanism found in the present study by which SREBP activates ELOVL5 is considered to be common in mammals. Through these findings, we clarified the molecular mechanism how SREBP activates ELOVL5, an important regulator of de novo lipogenesis.

DNA Methylation Perturbations in Genes Involved in Polyunsaturated Fatty Acid Biosynthesis Associated with Depression and Suicide Risk

Polyunsaturated fatty acid (PUFA) status has been associated with neuropsychiatric disorders, including depression and risk of suicide. Long-chain PUFAs (LC-PUFAs) are obtained in the diet or produced by sequential desaturation and elongation of shorter-chain precursor fatty acids linoleic acid (LA, 18:2n-6) and α-linolenic acid (ALA, 18:3n-3). We compared DNA methylation patterns in genes involved in LC-PUFA biosynthesis in major depressive disorder (MDD) with (n = 22) and without (n = 39) history of suicide attempt, and age- and sex-matched healthy volunteers (n = 59). Plasma levels of selected PUFAs along the LC-PUFA biosynthesis pathway were determined by transesterification and gas chromatography. CpG methylation levels for the main human LC-PUFA biosynthetic genes, fatty acid desaturases 1 (Fads1) and 2 (Fads2), and elongation of very long-chain fatty acids protein 5 (Elovl5), were assayed by bisulfite pyrosequencing. Associations between PUFA levels and diagnosis or suicide attempt status did not survive correction for multiple testing. However, MDD diagnosis and suicide attempts were significantly associated with DNA methylation in Elovl5 gene regulatory regions. Also the relative roles of PUFA levels and DNA methylation with respect to diagnostic and suicide attempt status were determined by least absolute shrinkage and selection operator logistic regression analyses. We found that PUFA associations with suicide attempt status were explained by effects of Elovl5 DNA methylation within the regulatory regions. The observed link between plasma PUFA levels, DNA methylation, and suicide risk may have implications for modulation of disease-associated epigenetic marks by nutritional intervention.

Nutritional Regulation of the Rainbow Trout Long Chain‐Polyunsaturated Fatty Acid Biosynthetic Enzymes

Rainbow trout (Oncorhynchus mykiss) is a commercially important aquaculture species. The use of the vegetable oil‐derived omega‐3 polyunsaturated fatty acid (PUFA) α‐linolenic acid (18:3n‐3; ALA) instead of fish oil as a sustainable lipid source in feeds is being investigated. The metabolism of ALA to eicosapentaenoic acid (20:5n‐3; EPA) and docosahexaenoic acid (22:6n‐3; DHA) found in fish oil requires three desaturation and three elongation steps performed by the enzymes Δ6desaturase, Δ5desaturase, Elovl5 and Elovl2. However, the biosynthetic capabilities of rainbow trout are largely unknown. The objectives of this study were to (a) functionally characterise the elongases, Elovl5 and Elovl2, using a yeast expression system and (b) investigate the nutritional regulation of the desaturase and elongase enzymes in juvenile rainbow trout fed diets rich in ALA, EPA or DHA and any combination thereof. The Elovl5 activity was specific to C18–20 PUFA substrates and not C22 PUFA. In contrast, the Elovl2 activity was specific to C20‐22 PUFA only, with no activity for C18 PUFA. Furthermore, we determined the change in Δ6desaturase, Δ5desaturase, elovl5 and elovl2 gene expression in response to dietary omega‐3 PUFA. Our study was the first to identify an Elovl2 in rainbow trout and it is only the third Elovl2 to be functionally characterised from fish. This study has elucidated that rainbow trout is dependent on Elovl2 for docosapentaenoic acid (22:5n‐3; DPA) to 24:5n‐3 synthesis and ultimately DHA synthesis.

Dynamics of fatty acid metabolism in a cell line from southern bluefin tuna (Thunnus maccoyii)

Bluefin tunas are large predatory marine fish of great commercial value but little is known of their specific nutritional requirements. The three species are farmed in sea cages in Australia, the Mediterranean, Mexico and Japan where they are fed small oily fish sourced from wild-catch fisheries. This may not be sustainable and, therefore, it is important to investigate the possible consequences of the replacement of wild-catch fisheries products (fish oil and fish meal) with alternative oil and meal sources in feeds for these fish. To this end we have studied fatty acid metabolism in a recently developed southern bluefin tuna (SBT, Thunnus maccoyii) cell line designated SBT-E1. The predominant fatty acids in the total lipid of the SBT-E1 cells were 16:0, 18:0 and 18:1n−9. There were also substantial amounts of 20:4n−6, 22:5n−3 and 22:6n−3 but only very limited amounts of 18:2n−6, 18:3n−3 or 20:5n−3. The fatty acid composition of the cells reflected that of the culture medium except that 20:4n−6, 22:5n−3 and 22:6n−3 were substantially more abundant in the cells than in the medium. Fatty acid esterification occurred predominantly into phosphatidylcholine (PC) and phosphatidylethanolamine (PE), the two most abundant classes of lipids. The SBT-E1 cells showed very limited Δ6 fatty acyl desaturase (Fads) activity towards either 18:3n−3 or 18:2n−6 but substantial elongation of very long chain fatty acids (Elovl) activity towards 20:5n−3. The latter activity is usually attributable to an Elovl5 enzyme. Surprisingly though, there were much higher levels of Δ6 Fads compared with Elovl5 gene expression in the SBT-E1 cells, suggesting that a different Elovl enzyme may catalyse this reaction in SBT. The cells also showed substantial β-oxidation of 18:3n−3 and 20:5n−3 but much less activity towards 18:0, 18:1n−9 or 18:2n−6. These results may explain the high 22:6n−3 to 20:5n−3 ratios found in the SBT tissue lipids, especially in the phospholipids. The results are discussed in terms of the presumed nutritional requirements of bluefin tunas given their high trophic level in marine food webs.

Single nucleotide polymorphisms of Δ6-desaturase and Elovl5 segments and their associations with common carp (Cyprinus carpio) growth traits.

Highly unsaturated fatty acids (HUFAs) are crucial for the nutritional health, physiology, and reproduction of vertebrates. The Δ6-desaturase and Elovl5 elongase genes produce essential enzymes in the biosynthetic pathway of HUFAs. Single nucleotide polymorphism (SNP) analysis of genes functionally related to the growth traits of the common carp (Cyprinus carpio var. Jian) can provide useful information for common carp molecular breeding. In this study, we isolated two Δ6 Fad genes and two Elovl5 genes from the common carp. Polymerase chain reaction-restriction fragment length polymorphism was performed, and the genotypes of three SNPs (Δ6Fad-a intron 10_C73T, Δ6Fad-b intron 10_A56G, and Elovl5-a intron 5_C64A) in 712 individuals (383 females and 329 males) were detected. Correlation analysis between the genotypes and weight gain revealed that intron 10_C73T of Δ6Fad-a, intron 10_A56G of Δ6Fad-b, and intron 5_ C64A of Elovl5-a were significantly associated with common carp weight gain. Weight gain increased with the enrichment of molecular SNP markers, consistent with the characteristics of quantitative traits. Our results indicate that Δ6Fad and Elovl5 elongase genes could be candidate genes for the molecular breeding of the common carp. This study provides useful information for the improvement of this species.

Involvement of Genetic Variants Associated With Primary Open-Angle Glaucoma in Pathogenic Mechanisms and Family History of Glaucoma

To investigate the associations between the non-intraocular pressure (IOP)-related genetic variants (genetic variants associated with vulnerability of the optic nerve independent of IOP) and primary open-angle glaucoma (POAG), including normal-tension glaucoma (NTG) and high-tension glaucoma (HTG), and between the non-IOP-related genetic variants and a family history of glaucoma. Case-control study. Japanese patients with NTG (n = 213) and HTG (n = 212) and 191 control subjects were genotyped for 5 non-IOP-related genetic variants predisposing to POAG near the SRBD1, ELOVL5, CDKN2B/CDKN2B-AS1, SIX1/SIX6, and ATOH7 genes. The load of these genetic variants was compared between the control subjects and patients with NTG or HTG and between the POAG patients with and without a family history of glaucoma. The total number of POAG risk alleles and the product of the odds ratios (POAG risk) of these genetic variants were significantly larger (P < .0025) in patients with both NTG and HTG than in the control subjects, and were significantly larger (P = .0042 and P = .023, respectively) in POAG patients with a family history of glaucoma than in those without. As the number of relatives with glaucoma increased, the total number of risk alleles and the product of the odds ratios increased (P = .012 and P = .047, respectively). Non-IOP-related genetic variants contribute to the pathogenesis of HTG as well as NTG. A positive family history of glaucoma in cases of POAG is thought to reflect the influence of genetic variants predisposing to POAG.

Characteristics of LC-PUFA biosynthesis in marine herbivorous teleostSiganus canaliculatusunder different ambient salinities

The present study aimed to characterize the influence of salinity on the biosynthesis of long-chain polyunsaturated fatty acid (LC-PUFA) in rabbitfish Siganus canaliculatus. An eight-week feeding trial was performed in rabbitfish juveniles with diets containing fish oil (FO) or a blend of vegetable oils (perilla and Canola oils, VO) at two salinities, 32 and 10 ppt. The whole-body fatty acid mass balance (FAMB) method was used to evaluate the in vivo LC-PUFA biosynthetic activities, and the hepatic mRNA levels of Δ4 and Δ6/Δ5 fatty acyl desaturases (Fad) and elongase of very long-chain fatty acids (Elovl5) genes were determined by real-time quantitative PCR. The results showed that the ex novo production of LC-PUFA in fish receiving the VO diet was significantly higher than fish fed the FO diet at both salinities. Furthermore, LC-PUFA production at 10 ppt salinity was significantly higher than that at 32 ppt salinity in the VO dietary groups, whereas no effect of salinity was found in the FO dietary groups. Consistent with this, the calculated apparent in vivo desaturation and elongation activities were also higher in VO and low-salinity treatments. In addition, higher levels of Δ4 and Δ6/Δ5 fads mRNA expression were obtained at low salinity, which was consistent with the calculated enzyme activities. In contrast, the expression of elovl5 was lower than that of fads, and the levels were not consistent with the elongase activity. The results suggest that ambient salinity may affect the activity of the LC-PUFA biosynthetic pathway in rabbitfish through regulating fatty acyl desaturase and elongase activities, partly through a transcriptional control mechanism in the case of desaturases.

The SNP in the promoter region of the bovine ELOVL5 gene influences economic traits including subcutaneous fat thickness

Genetic analyses have contributed to improvements of economically important traits derived from adipose tissue such as fatty acid composition in beef. Elongation of very long chain fatty acids (ELOVL) genes encode for the enzymes that play an important role in elongation of long-chain fatty acids. In this study, we aimed to discover genetic polymorphisms of ELOVL gene family in cattle populations to develop genetic markers. As a result, five synonymous mutations were detected in the coding regions of the ELOVL1, ELOVL2, ELOVL3 and ELOVL5 genes. In addition, six mutations were identified in promoter region of the ELOVL5. Two of five mutations in the promoter region of ELOVL5 were expected to alter the ELOVL5 expression and influence the economic traits, because of the high synteny of the region which was essential for activation of Elovl5 in mouse. Therefore, we performed association analysis between the genotypes and traits and our result revealed that T allele of g.-110T>C in ELOVL5 gene promoter indicated significantly thinner subcutaneous fat thickness (TT, 2.39 cm; CT, 2.35 cm) than that of C allele (CC, 2.68 cm) in a Japanese Black population. Our results suggest that the g.-110T>C is a useful genetic marker for the breeding in beef cattle.

Methylation of ELOVL2 gene as a new epigenetic marker of age

The discovery of biomarkers able to predict biological age of individuals is a crucial goal in aging research. Recently, researchers' attention has turn toward epigenetic markers of aging. Using the Illumina Infinium HumanMethylation450 BeadChip on whole blood DNA from a small cohort of 64 subjects of different ages, we identified 3 regions, the CpG islands of ELOVL2, FHL2, and PENK genes, whose methylation level strongly correlates with age. These results were confirmed by the Sequenom's EpiTYPER assay on a larger cohort of 501 subjects from 9 to 99 years, including 7 cord blood samples. Among the 3 genes, ELOVL2 shows a progressive increase in methylation that begins since the very first stage of life (Spearman's correlation coefficient = 0.92) and appears to be a very promising biomarker of aging.

Genetic variation in fatty acid elongases is not associated with intermediate cardiovascular phenotypes or myocardial infarction

Elongases 2, 4 and 5, encoded by genes ELOVL2, ELOVL4 and ELOVL5, have a key role in the biosynthesis of very long chain polyunsaturated fatty acids (PUFAs). To date, few studies have investigated the associations between elongase polymorphisms and cardiovascular health. We investigated whether ELOVL polymorphisms are associated with adipose tissue fatty acids, serum lipids, inflammation and ultimately with nonfatal myocardial infarction (MI) in a Costa Rican population. MI cases (n=1650) were matched to population-based controls (n=1650) on age, sex and area of residence. Generalized linear and multiple conditional logistic regression models were used to assess the associations between seven common ELOVL polymorphisms and cardiometabolic outcomes. Analyses were replicated in The Nurses' Health Study (n=1200) and The Health Professionals Follow-Up Study (n=1295). Variation in ELOVL2, ELOVL4 and ELOVL5 was not associated with adipose tissue fatty acids, intermediate cardiovascular risk factors or MI. In the Costa Rica study, the number of the minor allele copies at rs2294867, located in the ELOVL5 gene, was associated with an increase in total and LDL cholesterol (adjusted P-values=0.001 and <0.0001 respectively). Additionally, the number of the minor allele copies at rs761179, also located in the ELOVL5 gene, was significantly associated with an increase in total cholesterol (adjusted P-value=0.04). However, the observed associations were not replicated in independent populations. Common genetic variants in elongases are not associated with adipose tissue fatty acids, serum lipids, biomarkers of systemic inflammation, or the risk of MI.

Association betweenSRBD1andELOVL5Gene Polymorphisms and Primary Open-Angle Glaucoma

The S1 RNA binding domain 1 (SRBD1) and elongation of long-chain fatty acids family member 5 (ELOVL5) have been reported to be susceptibility genes for early-onset normal-tension glaucoma (NTG). The present study we conducted to assess whether these genes were associated with primary open-angle glaucoma (POAG), including late-onset NTG and high-tension glaucoma (HTG). Three hundred seventy Japanese patients with POAG, including 158 NTG and 212 HTG patients and 191 control subjects were analyzed for SRBD1 (rs3213787) and ELOVL5 (rs735860) gene polymorphisms. The A allele frequencies of rs3213787 were significantly higher in NTG (98.4%, P = 0.0003) and HTG (97.6%, P = 0.0013) patients than in the control subjects (92.7%). The A allele frequency was significantly higher (P = 0.014), even though the NTG patients were limited to those diagnosed at ages older than 60 years. The POAG patients with the CC or CT risk genotypes of rs735860 were significantly older (P = 0.032, analysis of variance, P = 0.043 and P = 0.015, respectively) than were the POAG patients with the TT genotype, and the frequency of a family history of glaucoma in POAG patients with the CC risk genotype was significantly higher (P = 0.015) than that in POAG patients with the TT genotype. SRBD1 gene polymorphism is associated with the development of HTG as well as NTG, including late-onset NTG. Typical POAG associated with ELOVL5 gene polymorphism may have a late rather than an early onset.

Influences of low salinity and dietary fatty acids on fatty acid composition and fatty acid desaturase and elongase expression in red sea bream Pagrus major

This study investigated the effects of dietary fatty acids and water salinity on fatty acid composition and expression of the fatty acid desaturase (fads)-like and elongase (elovl)-like genes of red sea bream Pagrus major. Sequence and phylogenetic analyses revealed that the fads-like and elovl-like genes isolated in this study encoded fads6 and elovl5, respectively. There was no significant difference in growth performance or proximate composition of fish fed diets formulated with 100% fish oil (FO) (FO diet) or with 67% of FO substituted with canola oil (VO diet). Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) contents were significantly higher in liver of fish reared at 15 and 20 ppt than those at 33 ppt. The liver fatty acid desaturase gene transcript was detected by reverse-transcription polymerase chain reaction (RT-PCR) in liver of fish fed the VO diet at 15 ppt, but not at either 20 or 33 ppt. The elovl5 gene was clearly expressed in liver for all treatments. These results suggest that red sea bream could synthesize EPA and DHA from their precursors in liver and that EPA and DHA biosynthesis potency was stimulated at lower salinity.

Differentiation-related changes in lipid classes with long-chain and very long-chain polyenoic fatty acids in rat spermatogenic cells

In rat seminiferous tubules (ST), cells that contain polar and neutral lipids with long-chain polyenoic fatty acids (PUFA) and sphingomyelins (SM) and ceramides (Cer) with very long chain (VLC) PUFA of the n-6 series coexist. In this study, pachytene spermatocytes and round spermatids were isolated to determine how these lipids change during spermatogenesis. As the amount per cell of PUFA-rich glycerophospholipids (GPL) decreased with cell size, the 22:5/20:4 ratio increased with cell differentiation. The elovl2 and elovl5 genes, required for 22:5 formation, were expressed (mRNA) in both cell types. Residual bodies- particles with compacted organelles and materials discarded from late spermatids-concentrated cholesterol, 22:5-rich triacylglycerols, and GPL, including plasmalogens and phosphatidylserine. Species of SM and Cer with nonhydroxylated (n-) VLCPUFA (28:4, 30:5, and 32:5) predominated in pachytene spermatocytes, whereas species with the corresponding 2-hydroxy (2-OH) VLCPUFA prevailed in round spermatids. Thus, a dramatic increase in the 2-OH/n-VLCPUFA ratio in SM and Cer was a hallmark of differentiation. A substantial decrease of 2-OH SM occurred between spermatids and mature spermatozoa and 2-OH SM species were collected in residual bodies "en route" to Sertoli cells. Notably, spermatids and spermatozoa gained a significant amount of ceramides devoid of n-VLCPUFA but having 2-OH VLCPUFA as their main fatty acids.

Investigation of highly unsaturated fatty acid metabolism in the Asian sea bass, Lates calcarifer

Lates calcarifer, commonly known as the Asian sea bass or barramundi, is an interesting species that has great aquaculture potential in Asia including Malaysia and also Australia. We have investigated essential fatty acid metabolism in this species, focusing on the endogenous highly unsaturated fatty acid (HUFA) synthesis pathway using both biochemical and molecular biological approaches. Fatty acyl desaturase (Fad) and elongase (Elovl) cDNAs were cloned and functional characterization identified them as ∆6 Fad and Elovl5 elongase enzymes, respectively. The ∆6 Fad was equally active toward 18:3n-3 and 18:2n-6, and Elovl5 exhibited elongation activity for C18-20 and C20-22 elongation and a trace of C22-24 activity. The tissue profile of gene expression for ∆6 fad and elovl5 genes, showed brain to have the highest expression of both genes compared to all other tissues. The results of tissue fatty acid analysis showed that the brain contained more docosahexaenoic acid (DHA, 22:6n-3) than flesh, liver and intestine. The HUFA synthesis activity in isolated hepatocytes and enterocytes using [1-(14)C]18:3n-3 as substrate was very low with the only desaturated product detected being 18:4n-3. These findings indicate that L. calcarifer display an essential fatty acid pattern similar to other marine fish in that they appear unable to synthesize HUFA from C18 substrates. High expression of ∆6 fad and elovl5 genes in brain may indicate a role for these enzymes in maintaining high DHA levels in neural tissues through conversion of 20:5n-3.