Gammalinolenic acid and dihomogammalinolenic acid suppress the CD3-mediated signal transduction pathway in human T cells

Effect of evening primrose oil supplementation on lipid profile: A systematic review and meta-analysis of randomized clinical trials

BACKGROUND

Studies have shown that evening primrose oil (EPO) supplementation might be effective in improving lipid profile, however, the results are inconsistent. This study was performed to determine the direction and magnitude of the EPO effect on the lipid profile.

METHODS

PubMed, Scopus, Cochrane Library, Embase and Web of Science databases and Google Scholar were searched up to September-2019. Meta-analysis was performed using the random-effects model. Lipid profile including high-density lipoprotein (HDL), total cholesterol (TC), triglyceride (TG), and low-density lipoprotein (LDL) was considered as the primary outcome.

RESULTS

A total of 926 articles were identified through database searching, of which, six RCTs were included in the meta-analysis. There were six studies on HDL, TC, and TG and four studies on LDL. EPO supplementation had no significant effect on TC, TG, LDL, and HDL. However, in subgroup analysis, a significant reduction in TG at a dose of ≤4 g/day (weighted mean difference [WMD] = -37.28 mg/dl; 95% CI: -73.53 to -1.03, p = .044) and a significant increase in HDL in hyperlipidemic subjects (WMD = 5.468 mg/dl; 95% CI: 1.323 to 9.614, p = .010) was found.

CONCLUSION

Oral intake of EPO at a dose of ≤4 g/day significantly reduces serum TG levels and significantly increases HDL levels in hyperlipidemic subjects.

The effects of vitamin D and evening primrose oil co-supplementation on lipid profiles and biomarkers of oxidative stress in vitamin D-deficient women with polycystic ovary syndrome: A randomized, double-blind, placebo-controlled trial

PURPOSE OF THE STUDY

There was inconsistent evidence about the benefit of vitamin D plus evening primrose oil (EPO) supplement intake on lipid profiles and reduced oxidative stress among women with polycystic ovary syndrome (PCOS). The current study was performed to evaluate the effects of vitamin D plus EPO supplementation on lipid profiles and biomarkers of oxidative stress in vitamin D-deficient women with PCOS.

MATERIALS AND METHODS

This randomized, double-blind, placebo-controlled trial was performed among 60 vitamin D-deficient women with PCOS. Participants were randomly assigned into two groups to receive either 1000 IU vitamin D3 plus 1000 mg EPO (n = 30) or placebo (n = 30) for 12 weeks. Metabolic profiles were quantified at baseline and after the 12-week intervention.

RESULTS

Compared with the placebo group, women in vitamin D and EPO co-supplementation group had significant increases in serum 25-hydroxyvitamin D (25(OH)D) (+10.7 ± 8.4 vs. -0.5 ± 1.6 ng/mL, p < 0.001) and plasma total glutathione (GSH) (+62.7 ± 58.0 vs. -0.7 ± 122.7 µmol/L, p = 0.01), while there were significant decreases in triglycerides (-7.3 ± 23.8 vs. +6.9 ± 26.3 mg/dL, p = 0.03), very low-density lipoprotein (VLDL) cholesterol levels (-1.5 ± 4.7 vs. +1.4 ± 5.3 mg/dL, p = 0.03), total/high-density lipoprotein cholesterol ratio (-0.3 ± 0.4 vs. -0.02 ± 0.4, p = 0.02), and malondialdehyde (MDA) concentration (-0.4 ± 0.4 vs. +0.5 ± 1.8 µmol/L, p = 0.008).

CONCLUSION

Overall, vitamin D and EPO co-supplementation for 12 weeks among vitamin D-deficient women with PCOS significantly improved triglycerides, VLDL cholesterol, GSH, and MDA levels.

Vitamin D and Evening Primrose Oil Administration Improve Glycemia and Lipid Profiles in Women with Gestational Diabetes

Limited data are available assessing the effects of vitamin D and evening primrose oil (EPO) administration on markers of insulin resistance and lipid concentrations in gestational diabetes mellitus (GDM). This study was designed to evaluate the effects of vitamin D and EPO administration on insulin resistance and lipid concentrations among women with GDM. In this prospective randomized, double-blind, placebo-controlled clinical trial, 60 participants with GDM were divided into 2 groups of either 1000 IU vitamin D3 and 1000 mg EPO or placebo for 6 weeks. At the beginning and end of the study, fasting blood samples were obtained from the participants to measure related variables. After 6 weeks of intervention, changes in fasting plasma glucose (-3.6 ± 7.5 vs. +1.5 ± 11.4 mg/dL, P = 0.04), serum insulin concentrations (-2.0 ± 5.3 vs. +4.6 ± 10.7 µIU/mL, P = 0.004), homeostasis model of assessment (HOMA) insulin resistance (-0.5 ± 1.1 vs. +1.1 ± 2.5, P = 0.003), HOMA-B cell function (-7.7 ± 23.3 vs. +17.4 ± 42.9, P = 0.007) and the quantitative insulin sensitivity check index (+0.01 ± 0.02 vs. -0.01 ± 0.02, P = 0.007) in the vitamin D plus EPO group were significantly different from the placebo group. In addition, compared with the placebo, vitamin D and EPO supplementation resulted in significant reductions in serum TAG (-20.0 ± 54.3 vs. +34.3 ± 38.2 mg/dL, P < 0.001), VLDL (-4.0 ± 10.9 vs. +6.9 ± 7.6 mg/dL, P < 0.001), TC (-22.1 ± 32.6 vs. +5.3 ± 20.1 mg/dL, P < 0.001), LDL concentrations (-18.0 ± 25.5 vs. +1.8 ± 15.7 mg/dL, P = 0.001) and TC/HDL (-0.3 ± 0.4 vs. +0.3 ± 0.5 mg/dL, P < 0.001). We did not observe any significant effect of vitamin D and EPO supplementation on serum HDL concentrations.

CLINICAL TRIAL REGISTRATION NUMBER

http://www.irct.ir : IRCT201509115623N52.

Polyunsaturated Fatty Acid-derived lipid mediators and T cell function

Fatty acids are involved in T cell biology both as nutrients important for energy production as well as signaling molecules. In particular, polyunsaturated fatty acids are known to exhibit a range of immunomodulatory properties that progress through T cell mediated events, although the molecular mechanisms of these actions have not yet been fully elucidated. Some of these immune activities are linked to polyunsaturated fatty acid-induced alteration of the composition of cellular membranes and the consequent changes in signaling pathways linked to membrane raft-associated proteins. However, significant aspects of the polyunsaturated fatty acid bioactivities are mediated through their transformation to specific lipid mediators, products of cyclooxygenase, lipoxygenase, or cytochrome P450 enzymatic reactions. Resulting bioactive metabolites including prostaglandins, leukotrienes, and endocannabinoids are produced by and/or act upon T leukocytes through cell surface receptors and have been shown to alter T cell activation and differentiation, proliferation, cytokine production, motility, and homing events. Detailed appreciation of the mode of action of these lipids presents opportunities for the design and development of therapeutic strategies aimed at regulating T cell function.

Treatment of rheumatoid arthritis with marine and botanical oils: influence on serum lipids

The gap in mortality between patients with rheumatoid arthritis (RA) and the general population (1.5-3.0 fold risk) is increasing. This disparity is attributable mainly to cardiovascular disease (CVD), as the CVD risk is comparable to patients with diabetes mellitus. The purpose of this study is to determine whether borage seed oil rich in gamma-linolenic acid, fish oil rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), or the combination of both oils are useful treatments for dyslipidemia in patients with RA. We randomized patients into a double blind, 18 month trial. Mixed effects models were used to compare trends over time in serum lipids. No significant differences were observed between the three groups: All three treatment groups exhibited similar meaningful improvement in the lipid profile at 9 and 18 months. When all groups were combined, these treatments significantly reduced total and LDL-cholesterol and triglycerides, increased HDL-cholesterol, and improved the atherogenic index. All improvements observed at 9 months persisted at 18 months (P < 0.001 verses baseline). Conclusion. Marine and botanical oils may be useful treatment for rheumatoid arthritis patients who are at increased risk for cardiovascular disease compared to the general population.

Oral omega-6 essential fatty acid treatment in contact lens associated dry eye

PURPOSE

Symptoms of dry eye are commonly reported in contact lens wearers and are a frequent cause of non-tolerance. The purpose of the present study is to evaluate the effects of oral treatment with particular omega-6 fatty acids in the form of evening primrose oil (EPO) on subjective symptoms, ocular surface signs and tear film characteristic in patients with contact lens associated dry eye.

METHODS

The study design was randomised, double-masked and placebo controlled. 76 female soft contact lens wearers were treated for 6 months with either EPO or placebo (olive oil). Subjects underwent three examinations (baseline, 3 and 6 months). At each examination subjects were given a questionnaire relating to lens comfort and dry eye symptoms and underwent a series of tests of tear film characteristics (tear meniscus height, break-up time), meibomian gland function (lipid layer thickness and quality) and ocular surface parameters (hyperaemia and staining).

RESULTS

The EPO group showed a significant improvement in the specific symptom of 'dryness' at 3 and 6 months (p<0.01) and also a significant improvement in overall lens comfort at 6 months (p<0.01). Tear meniscus height was increased in the EPO group at 6 months relative to baseline (p<0.01), although all other objective signs were unchanged.

CONCLUSION

This study provides evidence for a beneficial effect of particular orally administered omega-6 fatty acids in alleviating dry eye symptoms and improving overall lens comfort in patients suffering from contact lens associated dry eye.

Heterologous production of dihomo-gamma-linolenic acid in Saccharomyces cerevisiae

To make dihomo-gamma-linolenic acid (DGLA) (20:3n-6) in Saccharomyces cerevisiae, we introduced Kluyveromyces lactis Delta12 fatty acid desaturase, rat Delta6 fatty acid desaturase, and rat elongase genes. Because Fad2p is able to convert the endogenous oleic acid to linoleic acid, this allowed DGLA biosynthesis without the need to supply exogenous fatty acids on the media. Medium composition, cultivation temperature, and incubation time were examined to improve the yield of DGLA. Fatty acid content was increased by changing the medium from a standard synthetic dropout medium to a nitrogen-limited minimal medium (NSD). Production of DGLA was higher in the cells grown at 15 degrees C than in those grown at 20 degrees C, and no DGLA production was observed in the cells grown at 30 degrees C. In NSD at 15 degrees C, fatty acid content increased up until day 7 and decreased after day 10. When the cells were grown in NSD for 7 days at 15 degrees C, the yield of DGLA reached 2.19 microg/mg of cells (dry weight) and the composition of DGLA to total fatty acids was 2.74%. To our knowledge, this is the first report describing the production of polyunsaturated fatty acids in S. cerevisiae without supplying the exogenous fatty acids.

Therapeutic effect of topical gamma-linolenic acid on refractory uremic pruritus

BACKGROUND

Pruritus is a bothersome symptom affecting up to 80% of dialysis patients. Lymphocyte and cytokine interaction has an important role in the pathogenesis of uremic pruritus. Gamma-linolenic acid (GLA) is associated with immune modulation of T lymphocytes and lymphokines. The aim of this study is to determine whether topical GLA can attenuate uremic pruritus.

METHODS

Seventeen dialysis patients with refractory uremic pruritus who passed the screening criteria entered a prospective, randomized, double-blind, placebo-controlled, crossover study. They stopped all antipruritic therapy at least 2 weeks before the study and were randomly assigned to treatment with either GLA 2.2% cream or placebo-based cream applied to the entire body after taking a bath once a day and to pruritic sites 3 times a day for 2 weeks, and then the reverse treatment after a 2-week washout period. Severity of pruritus was evaluated by using a traditional visual analogue scale (VAS) and a modified questionnaire method (pruritus score [PS]). Hemogram, aspartate and alanine aminotransferases, bilirubin, albumin, blood urea nitrogen, creatinine, calcium, phosphate, and intact parathyroid hormone were measured.

RESULTS

Sixteen patients completed the study; 1 patient was withdrawn because of an allergic skin reaction. There were no significant differences between groups except for sex distribution. Median VAS and PS values between groups did not differ significantly at baseline. There is a greater antipruritic effect of GLA based on evaluation with both the VAS and PS. There is persistence of a residual effect into the second treatment period after GLA treatment.

CONCLUSION

GLA-rich cream is better than placebo-based cream for alleviating uremic pruritus. It is a useful adjuvant in the management of refractory uremic pruritus.

Parturition and Hypocalcemia Blunts Calcium Signals in Immune Cells of Dairy Cattle

The stress of parturition in the dairy cow is associated with increased susceptibility to infectious disease. During the periparturient period the demands for calcium are increased; these increased demands for calcium can result in subclinical or clinical hypocalcemia. Periparturient cows also experience significant immune suppression. Because intracellular calcium signaling is a key early feature in immune cell activation, we have hypothesized that the increased demand for calcium in periparturient cows may adversely affect intracellular calcium stores of immune cells. This reduction in intracellular calcium stores in immune cells could blunt intracellular calcium release following an activating stimulus, contributing to the immune suppression seen in these animals. To test this hypothesis, peripheral mononuclear cells were obtained from 27 multiparous dairy cows spanning a period of 2 wk before and 2 wk after parturition. Following activation of these cells by anti-CD3 antibodies plus secondary antibodies, intracellular calcium release from intracellular stores was measured. The intracellular calcium released in response to the activation signal declined as calcium demand for lactation became more intense and recovered as plasma calcium normalized. Intracellular calcium stores in peripheral mononuclear cells, estimated by pretreating cells with pervanadate and ionomycin, significantly decreased at parturition and returned to normal levels as the cows' blood calcium returned to normal levels. Hypocalcemia, which is common in periparturient dairy cows, is associated with decreased intracellular calcium stores in peripheral mononuclear cells. Our data suggest that this is the cause of a blunted intracellular calcium release response to an immune cell activation signal. It is concluded that intracellular Ca stores decrease in peripheral blood mononuclear cells (PBMC) before parturition and development of hypocalcemia. This suggests that systemic calcium stress precedes measurable hypocalcemia, particularly in cows that will develop milk fever. Therefore, PBMC intracellular Ca stores are a more sensitive measure of calcium stresses in transition cow. This decrease in PBMC intracellular Ca stores before parturition and the development of hypocalcemia contributes to periparturient immune suppression.

Dietary gamma-linolenic acid dose-dependently modifies fatty acid composition and immune parameters in rats

gamma-linolenic acid (GLA) has been reported to improve several inflammatory disorders through regulation of eicosanoid production. However, since GLA is a precursor of arachidonic acid, it may bring about increasing tissue arachidonic acid levels with subsequent pro-inflammatory events. To explore this possibility, we examined the effect of high-dose GLA acid on the fatty acid profile of immune cells, leukotriene B4 production by peritoneal exudate cells and immunoglobulin productivity of mesenteric lymph node lymphocytes of Sprague-Dawley rats. Male rats were fed 10% fat diets containing graded levels, 0, 20, 40 and 60% of GLA for 3 weeks. The results showed the distinction in activity of metabolizing GLA between immune cells and liver. Thus, in immune cells such as mesenteric lymph node and spleen lymphocytes and peritoneal exudate cells, more dihomo-gamma-linolenic acid was found than in the liver. Leukotriene B4 production by peritoneal exudate cells was significantly suppressed when fed the highest level of GLA suggesting a lower risk of allergic reaction. Moreover, immunoglobulin productivity in mesenteric lymph node lymphocytes was promoted by dietary GLA. The present study indicates that a high dose of GLA may exert anti-inflammatory effects through suppression of leukotriene B4 release and strengthening of gut immune system, thus ameliorating allergic reaction.

Gammalinolenic acid, an unsaturated fatty acid with anti-inflammatory properties, blocks amplification of IL-1 beta production by human monocytes

Administration of gammalinolenic acid (GLA), an unsaturated fatty acid, reduces joint inflammation in patients with rheumatoid arthritis. Addition of GLA in vitro suppresses release of IL-1beta from human monocytes stimulated with LPS. LPS-induced IL-1beta release is followed by IL-1-induced IL-1beta release, an amplification process termed autoinduction. We show here with peripheral blood monocytes from normal volunteers and from patients with rheumatoid arthritis by using IL-1R antagonist to block autoinduction and IL-1alpha stimulation to simulate autoinduction that approximately 40% of IL-1beta released from LPS-stimulated cells is attributable to autoinduction and that GLA reduces autoinduction of IL-1beta while leaving the initial IL-1beta response to LPS intact. Experiments with cells in which transcription and protein synthesis were blocked suggest that GLA induces a protein that reduces pro-IL-1beta mRNA stability. IL-1beta is important to host defense, but the amplification mechanism may be excessive in genetically predisposed patients. Thus, reduction of IL-1beta autoinduction may be protective in some patients with endotoxic shock and with diseases characterized by chronic inflammation.

Polyunsaturated fatty acids inhibit T cell signal transduction by modification of detergent-insoluble membrane domains

Polyunsaturated fatty acids (PUFAs) exert immunosuppressive effects, but the molecular alterations leading to T cell inhibition are not yet elucidated. Signal transduction seems to involve detergent-resistant membrane domains (DRMs) acting as functional rafts within the plasma membrane bilayer with Src family protein tyrosine kinases being attached to their cytoplasmic leaflet. Since DRMs include predominantly saturated fatty acyl moieties, we investigated whether PUFAs could affect T cell signaling by remodeling of DRMs. Jurkat T cells cultured in PUFA-supplemented medium showed a markedly diminished calcium response when stimulated via the transmembrane CD3 complex or glycosyl phosphatidylinositol (GPI)- anchored CD59. Immunofluorescence studies indicated that CD59 but not Src family protein tyrosine kinase Lck remained in a punctate pattern after PUFA enrichment. Analysis of DRMs revealed a marked displacement of Src family kinases (Lck, Fyn) from DRMs derived from PUFA-enriched T cells compared with controls, and the presence of Lck in DRMs strictly correlated with calcium signaling. In contrast, GPI-anchored proteins (CD59, CD48) and ganglioside GM1, both residing in the outer membrane leaflet, remained in the DRM fraction. In conclusion, PUFA enrichment selectively modifies the cytoplasmic layer of DRMs and this alteration could underlie the inhibition of T cell signal transduction by PUFAs.

The effects of dietary lipids on gene expression and apoptosis

The beneficial effects of dietary FO with respect to autoimmune disease, CVD and some types of cancer are well established. Studies conducted over the last 10-15 years have established the potent effects of FO on gene expression in the previously mentioned diseases. The effects of dietary FO appear to be selective in nature, with the expression of individual genes simultaneously being increased, decreased or completely unaffected. In order to elucidate the molecular mechanism(s) involved, recent studies have focused on analysing the effects of the long-chain polyunsaturated n-3 fatty acids EPA and DHA which are highly enriched in FO and thought to be the primary mediators of its biological activity. Indeed, it has been found that EPA and DHA appear to both directly and indirectly modulate gene expression in vivo, depending on the gene examined. The direct effects of EPA and DHA are most probably mediated by their ability to bind to positive and/or negative regulatory transcription factors, while the indirect effects appear to be mediated through alterations in the generation of intracellular lipid second messengers (e.g. diacylglycerol and ceramide). Future studies need to be focused on further elucidation of the inter- and intracellular signalling events mediated by dietary n-3 fatty acids. Understanding the molecular mechanism(s) modified by dietary FO will ultimately lead to improved dietary strategies to aid in the prevention of autoimmune disease, CVD and/or certain types of cancer.

Importance of dietary gamma-linolenic acid in human health and nutrition

Considerable debate remains regarding the distinct biological activities of individual polyunsaturated fatty acids (PUFA). One of the most interesting yet controversial dietary approaches has been the possible prophylactic role of dietary gamma-linolenic acid (GLA) in treating various chronic disease states. This strategy is based on the ability of diet to modify cellular lipid composition and eicosanoid (cyclooxygenase and lipoxygenase) biosynthesis. Recent studies demonstrate that dietary GLA increases the content of its elongase product, dihomo-gamma-linolenic acid (DGLA), within cell membranes without concomitant changes in arachidonic acid (AA). Subsequently, upon stimulation, DGLA can be converted by inflammatory cells to 15-(S)-hydroxy-8,11,13-eicosatrienoic acid and prostaglandin E1. This is noteworthy because these compounds possess both anti-inflammatory and antiproliferative properties. Although an optimal feeding regimen to maximize the potential benefits of dietary GLA has not yet been determined, it is the purpose of this review to summarize the most recent research that has focused on objectively and reproducibly determining the mechanism(s) by which GLA may ameliorate health problems.

Lipids and the immune response

The effects of fatty acids on immune responses have been studied since the early 1970s, but much controversy still remains. The present review examines recent studies in both animals and in humans, and highlights some new and exciting ideas concerning the mechanism by which fatty acids may affect immune responses in both normal and pathological situations, an area which is likely to progress rapidly over the next few years.

Clinical use of lipids to control inflammatory disease

Selective dietary supplementation with lipids has long been used to influence the course of chronic inflammatory diseases. This review describes new aspects of the molecular mechanism of lipids to modulate leukocyte activity and highlights some recent clinical studies on therapeutic lipid administration. New promising advances in parenteral application of lipids as well as the impact on acute inflammatory disorders are discussed.