Polyunsaturated fatty acids: biotechnology

Polyunsaturated fatty acids like EPA and DHA have attracted a great attention due to their beneficial effects on human health. At present, fish oil is the major source of EPA and DHA. Various alternative sources are being explored to get these essential fatty acids. Genes encoding enzymes involved in the biosyntheses of PUFAs have been identified, cloned and gene prospecting becomes a novel method for enhanced PUFA production. Desaturase and elongase genes have important biotechnological appeal from genetic engineering point of view. This review highlights the research and results on such enzymes.     

Polyunsaturated fatty acids regulate Shiga toxin transport

Shiga toxin (Stx) is internalized by receptor-mediated endocytosis and transported retrogradely to the endoplasmic reticulum from where the enzymatically active part of the toxin is translocated to the cytosol. In this study, we have investigated the effect of polyunsaturated fatty acids (PUFA) on intoxication and retrograde transport of Stx. In HEp-2 cells, PUFA treatment inhibited Stx intoxication by a factor of 10. Moreover, both Stx internalization and endosome-to-Golgi transport were reduced by PUFA and these reductions can together explain the reduced toxicity. Also cholera toxin internalization was reduced by PUFA treatment. Finally, ricin and Pseudomonas exotoxin 1 cytotoxicity were not reduced by PUFA, demonstrating that PUFA do not cause a general block in retrograde transport to the endoplasmic reticulum. In conclusion, these results clearly demonstrate the importance of PUFA for Stx and cholera toxin trafficking.     

Polyunsaturated fatty acids are FXR ligands and differentially regulate expression of FXR targets

Polyunsaturated fatty acids (PUFAs) have been previously reported as agonists of peroxisome proliferatoractivated receptor and antagonists of the liver X receptor. The activities on these two nuclear receptors have been attributed to their beneficial effects such as improvement of dyslipidemia and insulin sensitivity and decrease of hepatic lipogenesis. Here we report that PUFAs are ligands of farnesoid X receptor (FXR), a nuclear receptor for bile acids. In a conventional FXR binding assay, arachidonic acid (AA, 20:4), docosahexaenoic acid (DA, 22:6), and linolenic acid (LA, 18:3) had an affinity of 2.6, 1.5, and 3.5 microM, respectively. In a cell-free coactivator association assay, AA, DA, and LA decreased FXR agonist-induced FXR activation with IC(50)s ranging from 0.9 to 4.7 microM. In HepG2 cells, PUFAs regulated the expression of two FXR targets, BSEP and kininogen, in an opposite fashion, although both genes were transactivated by FXR. All three PUFAs dose-dependently enhanced FXR agonist-induced BSEP expression but decreased FXR agonist-induced human kininogen mRNA. Saturated fatty acids such as stearic acid (SA, 18:0) and palmitic acid (PA, 16:0) did not bind to FXR and did not change BSEP or kininogen expression. The pattern of BSEP and kininogen regulation by PUFAs is closely similar to that of the guggulsterone, previously reported as a selective bile acid receptor modulator. Our results suggest that PUFAs may belong to the same class of FXR ligands as guggulsterone, and that the selective regulation of FXR targets may contribute to the beneficial effects of PUFAs in lipid metabolism.     

Polyunsaturated fatty acids,neuroinflammation and well being

The innate immune system of the brain is principally composed of microglial cells and astrocytes, which, once activated, protect neurons against insults (infectious agents, lesions, etc.). Activated glial cells produce inflammatory cytokines that act specifically through receptors expressed by the brain. The functional consequences of brain cytokine action (also called neuroinflammation) are alterations in cognition, mood and behaviour, a hallmark of altered well-being. In addition, proinflammatory cytokines play a key role in depression and neurodegenerative diseases linked to aging. Polyunsaturated fatty acids (PUFA) are essential nutrients and essential components of neuronal and glial cell membranes. PUFA from the diet regulate both prostaglandin and proinflammatory cytokine production. n-3 fatty acids are anti-inflammatory while n-6 fatty acids are precursors of prostaglandins. Inappropriate amounts of dietary n-6 and n-3 fatty acids could lead to neuroinflammation because of their abundance in the brain and reduced well-being. Depending on which PUFA are present in the diet, neuroinflammation will, therefore, be kept at a minimum or exacerbated. This could explain the protective role of n-3 fatty acids in neurodegenerative diseases linked to aging.     

Polyunsaturated fatty acids in male and female reproduction

In Westernized societies, average consumption of n-6 polyunsaturated fatty acids (PUFAs) far exceeds nutritional requirements. The ratio of n-6 to n-3 PUFAs is generally >10:1 whereas on a primitive human diet it was closer to 1:1. Diets fed to intensively farmed livestock have followed a similar trend. Both n-6 and n-3 PUFAs can influence reproductive processes through a variety of mechanisms. They provide the precursors for prostaglandin synthesis and can modulate the expression patterns of many key enzymes involved in both prostaglandin and steroid metabolism. They are essential components of all cell membranes. The proportions of different PUFAs in tissues of the reproductive tract reflect dietary consumption. PUFA supplements (particularly n-3 PUFAs in fish oil) are promoted for general health reasons. Fish oils may also benefit fertility in cattle and reduce the risk of preterm labor in women, but in both cases current evidence to support this is inconclusive. Gamma-linolenic acid containing oils can alter the types of prostaglandins produced by cells in vitro, but published data to support claims relating to effects on reproductive health are lacking. Spermatozoa require a high PUFA content to provide the plasma membrane with the fluidity essential at fertilization. However, this makes spermatozoa particularly vulnerable to attack by reactive oxygen species, and lifestyle factors promoting oxidative stress have clear associations with reduced fertility. Adequately powered trials that control for the ratios of different PUFAs consumed are required to determine the extent to which this aspect of our diets does influence our fertility.     

Bisphosphonates derived from fatty acids are potent growth inhibitors of Trypanosoma cruzi

We have investigated the effect of a series of bisphosphonates derived from fatty acids against Trypanosoma cruzi proliferation in in vitro assays. Some of these drugs proved to be potent inhibitors against the intracellular form of the parasite exhibiting IC50 values at the low micromolar level. As bisphosphonates are FDA clinically approved for treatment of bone resorption, their potential innocuousness makes them good candidates to control tropical diseases.     

Polyunsaturated fatty acids production with a solid-state column reactor

To investigate the potential production of polyunsaturated fatty acids (PUFAs), a solid-state column reactor of rice bran with Mortierella alpina was used. The optimal conditions for PUFAs production were rice bran supplementation with 3.75% (ww(-1)) nitrogen source at initial moisture content 57%, initial pH 6-7, aeration, and incubation at 20 degrees C for 5 days and then at 12 degrees C for 7 days. Each gram of substrate carbon yielded 127 mg of total PUFAs, 12 mg of eicosapentaenoic acid (EPA), 6 mg of arachidonic acid (AA), 5mg of alpha-linolenic acid (ALA), and 117 mg of linoleic acid (LA) after 12 days incubation. Aeration enhanced the productions of AA, EPA, and total PUFAs. Supplementation of the nitrogen source on the fourth day and then a shift to lower temperature on the fifth day increased EPA production.     

Polyunsaturated fatty acids are incorporated into maturating male mouse germ cells by lysophosphatidic acid acyltransferase 3

Long-chain polyunsaturated fatty acids (PUFAs) accumulate in mammalian testis during puberty and are essential for fertility. To investigate whether lysophospholipid acyltransferases determine the PUFA composition of testicular phospholipids during pubertal development, we compared their mRNA expression, in vitro activity, and specificity with the lipidomic profile of major phospholipids. The accumulation of PUFAs in phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine correlated with an induced lysophosphatidic acid acyltransferase (LPAAT)3 mRNA expression, increased microsomal LPAAT3 activity, and shift of LPAAT specificity to PUFA-coenzyme A. LPAAT3 was induced during germ cell maturation, as shown by immunofluorescence microscopy. Accordingly, differentiation of mouse GC-2spd(ts) spermatocytes into spermatides up-regulated LPAAT3 mRNA, increased the amount of polyunsaturated phospholipids, and shifted the specificity for the incorporation of deuterium-labeled docosahexaenoic acid toward phosphatidylcholine and phosphatidylethanolamine. Stable knockdown of LPAAT3 in GC-2spd(ts) cells significantly decreased microsomal LPAAT3 activity, reduced levels of polyunsaturated phosphatidylethanolamine species, and impaired cell proliferation/survival during geneticin selection. We conclude that the induction of LPAAT3 during germ cell development critically contributes to the accumulation of PUFAs in testicular phospholipids, thereby possibly affecting sperm cell production.     

Polyunsaturated fatty acids stimulate phosphatidylcholine synthesis in PC12 cells

The synthesis of phospholipids in mammalian cells is regulated by the availability of three critical precursor pools: those of choline, cytidine triphosphate and diacylglycerol. Diacylglycerols containing polyunsaturated fatty acids (PUFAs) apparently are preferentially utilized for phosphatide synthesis. PUFAs are known to play an important role in the development and function of mammalian brains. We therefore studied the effects of unsaturated, monounsaturated and polyunsaturated fatty acids on the overall rates of phospholipid biosynthesis in PC12 rat pheochromocytoma cells. Docosahexaenoic acid (DHA, 22:6n-3), eicosapentaenoic acid (EPA, 20:5n-3) and arachidonic acid (AA, 20:4n-6) all significantly stimulated the incorporation of (14)C-choline into total cellular phospholipids. In contrast, monounsaturated oleic acid (OA) and the saturated palmitic (PA) and stearic (SA) acids did not have this effect. The action of DHA was concentration-dependent between 5 and 50 microM; it became statistically significant by 3 h after DHA treatment and then increased over the ensuing 3 h. DHA was preferentially incorporated into phosphatidylethanolamine (PE) and phosphatidylserine (PS), while AA predominated in phosphatidylcholine (PC).     

n-3 Polyunsaturated fatty acids in animal models with neuroinflammation

Neuroinflammation is present in the majority of acute and chronic neurological disorders. Excess or prolonged inflammation in the brain is thought to exacerbate neuronal damage and loss. Identifying modulators of neuroinflammation is an active area of study since it may lead to novel therapies. Omega-3 polyunsaturated fatty acids (n-3 PUFA) are anti-inflammatory in many non-neural tissues; their role in neuroinflammation is less studied. This review summarizes the relationship between n-3 PUFA and brain inflammation in animal models of brain injury and aging. Evidence by and large shows protective effects of n-3 PUFA in models of sickness behavior, stroke, aging, depression, Parkinson's disease, diabetes, and cytokine- and irradiation-induced cognitive impairments. However, rigorous studies that test the direct effects of n-3 PUFA in neuroinflammation in vivo are lacking. Future research in this area is necessary to determine if, and if so which, n-3 PUFA directly target brain inflammatory pathways. n-3 PUFA bioactive metabolites may provide novel therapeutic targets for neurological disorders with a neuroinflammatory component.