Characterization of the human omega-oxidation pathway for omega-hydroxy-very-long-chain fatty acids

Very-long-chain fatty acids (VLCFAs) have long been known to be degraded exclusively in peroxisomes via beta-oxidation. A defect in peroxisomal beta-oxidation results in elevated levels of VLCFAs and is associated with the most frequent inherited disorder of the central nervous system white matter, X-linked adrenoleukodystrophy. Recently, we demonstrated that VLCFAs can also undergo omega-oxidation, which may provide an alternative route for the breakdown of VLCFAs. The omega-oxidation of VLCFA is initiated by CYP4F2 and CYP4F3B, which produce omega-hydroxy-VLCFAs. In this article, we characterized the enzymes involved in the formation of very-long-chain dicarboxylic acids from omega-hydroxy-VLCFAs. We demonstrate that very-long-chain dicarboxylic acids are produced via two independent pathways. The first is mediated by an as yet unidentified, microsomal NAD(+)-dependent alcohol dehydrogenase and fatty aldehyde dehydrogenase, which is encoded by the ALDH3A2 gene and is deficient in patients with Sjogren-Larsson syndrome. The second pathway involves the NADPH-dependent hydroxylation of omega-hydroxy-VLCFAs by CYP4F2, CYP4F3B, or CYP4F3A. Enzyme kinetic studies show that oxidation of omega-hydroxy-VLCFAs occurs predominantly via the NAD(+)-dependent route. Overall, our data demonstrate that in humans all enzymes are present for the complete conversion of VLCFAs to their corresponding very-long-chain dicarboxylic acids

Cytisine-Linked Isoflavonoid Antineoplastic Agents for the Treatment of Cancer

Cytisine-linked isoflavonoids, or pharmaceutically acceptable salts thereof or pharmaceutically acceptable compositions thereof, are useful for the treatment of conditions in which cells have a reliance on peroxisomal HSD17B4 to degrade very long chain fatty acids and provide necessary energy for cell proliferation, such as is seen in colorectal cancer and prostate cancer, for example

Elongation of long-chain fatty acids in rabbitfish Siganus canaliculatus: Cloning, functional characterisation and tissue distribution of Elovl5- and Elovl4-like elongases

Elongases of very long-chain fatty acids (Elovl) catalyse the rate-limiting step of the elongation pathway that results in net 2 C elongation of pre-existing fatty acyl chains. As the biosynthesis of long-chain polyunsaturated fatty acids (LC-PUFA) is particularly relevant in fish, Elovl involved in the pathway have been investigated in various studies. Here we report the molecular cloning, functional characterisation and tissue distribution of two distinct elovl-like cDNAs isolated from the herbivorous marine teleost Siganus canaliculatus. Unlike the carnivorous marine fish previously investigated, we hypothesise that the rabbitfish has an enhanced LC-PUFA biosynthetic capability as previously anticipated in a former study on fatty acyl desaturases (Fad). The results of the present study showed that rabbitfish expresses at least two elovl cDNAs, which have high homology in sequence and function to Elovl5 and Elovl4 elongases that have been investigated previously in other fish species. Furthermore, the results confirm that the activities of the Elovl5 and Elovl4 enzymes enable rabbitfish to perform all the elongation reactions required for the biosynthesis of the physiologically essential C20-22 LC-PUFA including eicosapentaenoic (20:5n-3), arachidonic (20:4n-6) and docosahexaenoic (22:6n-3, DHA) acids, as well as the less common very long-chain fatty acids (greater than C24). Rabbitfish is thus the first marine teleost in which genes encoding Fad and Elovl enzymes, with all the activities required for the production of DHA from C18 PUFA, have been characterised. Highlights Rabbitfish possess at least two fatty acid elongases. The elongases were functionally characterised as Elovl5 and Elovl4 types.  The elongases possess all the activities necessary for the biosynthesis of DHA.  Elovl4 is capable of synthesising very long-chain fatty acids up to C36 in length.  Rabbitfish represent a marine fish not dependent upon dietary EPA and DH

ELOVL3 is an important component for early onset of lipid recruitment in brown adipose tissue

Journal ArticleDuring the recruitment process of brown adipose tissue, the mRNA level of the fatty acyl chain elongase Elovl3 is elevated more than 200-fold in cold-stressed mice. We have obtained Elovl3-ablated mice and report here that, although cold-acclimated Elovl3-ablated mice experienced an increased heat loss due to impaired skin barrier, they were unable to hyperrecruit their brown adipose tissue. Instead, they used muscle shivering in order to maintain body temperature. Lack of Elovl3 resulted in a transient decrease in the capacity to elongate saturated fatty acyl-CoAs into very long chain fatty acids, concomitantly with the occurrence of reduced levels of arachidic acid (C20:0) and behenic acid (C22:0) in brown adipose tissue during the initial cold stress. This effect on very long chain fatty acid synthesis could be illustrated as a decrease in the condensation activity of the elongation enzyme. In addition, warmacclimated Elovl3-ablated mice showed diminished ability to accumulate fat and reduced metabolic capacity within the brown fat cells. This points to ELOVL3 as an important regulator of endogenous synthesis of saturated very long chain fatty acids and triglyceride formation in brown adipose tissue during the early phase of the tissue recruitment

The role of very long chain fatty acids in Arabidopsis growth and development

Very long chain fatty acids (VLCFAs) are essential to Arabidopsis growth and development. VLCFAs are found in sphingolipids, glycerophospholipids, triacylglycerols, suberin and cuticular waxes. VLCFAs are synthesized by the addition of 2 carbons from malonyl-CoA to pre-existing acyl-CoAs to produce chain lengths of greater than 18 carbon atoms. VLCFA synthesis involves four consecutive reactions that are catalysed by the microsomal Fatty Acid Elongase. In Arabidopsis the first reaction is catalysed by one of 21 different Keto-CoA Synthases (KCS) with diverse levels of expression and overlapping tissue specificities. The other three enzymes are ubiquitously expressed throughout the plant, and form the core components of the elongase. Lipidomic profiling has been performed on roots and shoots of plants with reduced levels of VLCFAs. Mutants of the core components of the elongase were analysed along with herbicides that inhibit a number of KCS enzymes, this allowed the whole elongase complex to be analysed. Differences were seen in the lipidomic profiles of the different elongase mutants and between the roots and shoots of the same mutants. This has revealed correlations between phenotypic differences and lipidomic changes giving insight into which lipid classes might be responsible for the various phenotypes. A forward genetic screen has been conducted in the Arabidopsis cer10-1 mutant to identify novel genes involved in VLCFA metabolism. CER10 encodes for the fourth component of the elongase complex. One suppressor mutant that has been identified has flower buds and fertility comparable to wild type plants but still displays the reduced size of the cer10-1 mutant. The second suppressor mutant identified showed restored size of aerial organs but the flower buds remained fused. Whole genome sequencing allowed localisation of these suppressor mutations on Chromosome 3. Partial biochemical characterisation of these mutants revealed interesting changes in their acyl-CoA and cuticular lipid profiles

Molecular Cloning and functional characterization of a putative Elovl4 gene and its expression in response to dietary fatty acid profiles in orange-spotted grouper Epinephelus coioides

Elongase of very long-chain fatty acids (Elovl) 4 probably plays a crucial role in marine fish species, where lack of Elovl2 has been considered as one possible reason for their low long-chain polyunsaturated fatty acids' (LC-PUFAs) biosynthetic capability. Elongase of very long-chain fatty acids 4 is the most recent member of the Elovl family that has been investigated in fish. Here, we report the molecular cloning and functional characterization of putativeelovl4cDNA isolated from marine teleost,Epinephelus coioides, and its expression in response to dietary n-3 LC-PUFA and docosahexaenoic acid (DHA) to eicosapentaenoic acid (EPA) ratio. Theelovl4cDNA of grouper was 2341bp including 301bp of 5′-untranslated region (UTR), 918bp of the coding region that encodes 305 amino acids (AA) and 1122bp of 3′UTR. Heterologous expression in yeast demonstrated that grouper Elovl4 could elongate saturated fatty acids (FA), especially 24:0 and 26:0, up to 36:0. Also, grouper Elovl4 effectively converted C20 and C22 polyunsaturated FAs to elongated polyenoic products up to C36. Tissue distribution analysis revealed that Elovl4 were widely transcribed in various tissues with the highest level in eye, brain and testis as described in other teleosts. The transcript level ofelovl4was significantly affected by dietary n-3 LC-PUFA and high LC-PUFA level repressess its expression. However, the ratio of DHA to EPA had no significant influence on its expression. These results may contribute to better understanding the LC-PUFA biosynthetic pathway in this fish species