The effect of borage oil consumption on the composition of individual phospholipids in human platelets

Assessment of Polyunsaturated Fatty Acids on COVID-19-Associated Risk Reduction

Pooled evidence conveys the association between polyunsaturated fatty acids and infectious disease. SARS-CoV-2, an enveloped mRNA virus, was also reported to interact with polyunsaturated fatty acids. The present review explores the possible mode of action, immunology, and consequences of these polyunsaturated fatty acids during the viral infection. Polyunsaturated fatty acids control protein complex formation in lipid rafts associated with the function of two SARS-CoV-2 entry gateways: angiotensin-converting enzyme-2 and cellular protease transmembrane protease serine-2. Therefore, the viral entry can be mitigated by modulating polyunsaturated fatty acids contents in the body. α-Linolenic acid is the precursor of two clinically important eicosanoids eicosapentaenoic acid and docosahexaenoic acid, the members of ω-3 fats. Resolvins, protectins, and maresins derived from docosahexaenoic acid suppress inflammation and augment phagocytosis that lessens microbial loads. Prostaglandins of 3 series, leukotrienes of 5 series, and thromboxane A₃ from eicosapentaenoic acid exhibit anti-inflammatory, vasodilatory, and platelet anti-aggregatory effects that may also contribute to the control of pre-existing pulmonary and cardiac diseases. In contrast, ω-6 linoleic acid-derived arachidonic acid increases the prostaglandin G₂, lipoxins A₄ and B₄, and thromboxane A₂. These cytokines are pro-inflammatory and enhance the immune response but aggravate the COVID-19 severity. Therefore, the rational intake of ω-3-enriched foods or supplements might lessen the complications in COVID-19 and might be a preventive measure.

Graphic Abstract

Platelet lipidome: Dismantling the "Trojan horse" in the bloodstream

The platelet-lipid chapter in the story of atherothrombosis is an old one, recapitulated and revised in many contexts. For decades several stimulating facets have been added to it, both unraveling and increasing the perplexity of platelet-lipid interplay and its pathophysiological consequences. The recent paradigm shift in our perspective has evolved with lipidomic analysis of the intraplatelet compartment and platelet releasate. These investigations have disclosed that platelets are in constant interaction with circulatory lipids, often reflected in their lipid repertoire. In addition, they offer a shielded intracellular space for oxidative lipid metabolism generating "toxic" metabolites that escape degradation by plasma lipases and antioxidant defense, circulate undetected by conventional plasma lipid profile, and deposited at atherosclerotic lesions or thrombus. Lipidomics divulges this silent invader in platelet vehicles, thereby providing potential biomarkers of pathologic manifestations and therapeutic targets to be exploited, which is surmised in this review.

A mini review of nervonic acid: Source, production, and biological functions

Nervonic acid (NA) has attracted considerable attention because of its close relationship with brain development. Sources of NA include oil crop seeds, oil-producing microalgae, and other microorganisms. Transgenic technology has also been applied to improve the sources and production of NA. NA can be separated and purified by urea adduction fractionation, molecular distillation, and crystallization. Studies on NA functionality involved treatments for demyelinating diseases and acquired immunodeficiency syndrome, as well as prediction of mortality due to cardiovascular diseases and chronic kidney disease. This mini review focuses on the sources, production, and biological functions of NA and provides prospective trends in the investigation of NA.

Regulation of platelet function and thrombosis by omega-3 and omega-6 polyunsaturated fatty acids

Thrombosis is the most common underlying pathology responsible for morbidity and mortality in cardiovascular disease (CVD). Platelet adhesion, activation, and aggregation play central roles in hemostasis; however, the same process may also cause thrombosis and vessel occlusion at the site of ruptured atherosclerotic lesions leading to heart attack and stroke. ω-3 and ω-6 polyunsaturated fatty acids (PUFAs) are an essential component of the platelet phospholipid membrane and play a major role in many aspects of platelet function. Dietary supplementation of ω-3 and ω-6 PUFAs has long been used to slow the progression of CVD and to prevent acute cardiovascular events. Despite this, the role of ω-3 and ω-6 PUFAs and their oxylipin metabolites in platelet function remains controversial due to the lack in our understanding of the mechanistic regulation controlling platelet reactivity in vitro and substantial evidence for PUFA regulation of thrombotic events in vivo. In this review, we will outline the role of platelet physiology in hemostasis and the effect of ω-3 and ω-6 PUFAs on platelet function, with special emphasis on in vivo effects on hemostasis and thrombosis due to the role of PUFAs and their bioactive lipids in circulation. Further, recent mechanistic insights and evidence for cardio-protective effects of PUFAs and their bioactive lipids will be discussed.

The emerging role of oxylipins in thrombosis and diabetes

The prevalence of cardiovascular disease (CVD), the leading cause of death in the US, is predicted to increase due to the shift in age of the general population and increase in CVD risk factors such as obesity and diabetes. New therapies are required to decrease the prevalence of CVD risk factors (obesity and diabetes) as well as reduce atherothrombosis, the major cause of CVD related mortality. Oxylipins, bioactive metabolites derived from the oxygenation of polyunsaturated fatty acids, play a role in the progression of CVD risk factors and thrombosis. Aspirin, a cyclooxygenase-1 inhibitor, decreases atherothrombotic associated mortality by 25%. These potent effects of aspirin have shown the utility of modulating oxylipin signaling pathways to decrease CVD mortality. The role of many oxylipins in the progression of CVD, however, is still uncertain or controversial. An increased understanding of the role oxylipins play in CVD risk factors and thrombosis could lead to new therapies to decrease the prevalence of CVD and its associated mortality.

Dietary fat in relation to erythrocyte fatty acid composition in men

Erythrocyte membrane fatty acid (EMFA) composition is used in the validation of food frequency questionnaires (FFQ) and the evaluation of dietary fat quality. In this cross-sectional study we aimed to investigate associations of diet with EMFA. Altogether, 1,033 randomly selected Finnish men, aged from 47 to 75 years filled in a FFQ and their EMFA composition was analyzed. Marine polyunsaturated fatty acid (PUFA) intake correlated positively with erythrocyte eicosapentaenoic and docosahexaenoic acids (r(s) = 0.415 and r(s) = 0.340, respectively, P < 0.001) and inversely with all n-6 PUFA analyzed (P < 0.001). PUFA intake from spreads and cooking fats correlated positively with alpha-linolenic (ALA), linoleic (LNA) and nervonic acids (r(s) = 0.229, r(s) = 0.160 and r(s) = 0.143, respectively, P < 0.001). Milk fat intake was associated with myristic and behenic acids (r(s) = 0.186 and r(s) = 0.132, respectively P < 0.001). Butter users had lower ALA and LNA proportions (mol%) than non-users (0.16 ± 0.04 vs. 0.19 ± 0.05, P < 0.001 and 7.77 ± 1.02 vs. 8.12 ± 1.11, P = 0.001). Higher PUFA intake from meat was related to decreased long-chain n-3 (P < 0.001) and increased n-6 PUFA (P < 0.001) proportions. In conclusion, EMFA composition reflects particularly well the intakes of n-3 PUFA, whereas other associations remained lower. Yet, all main sources of dietary fat were related with EMFA. The dietary effect on the nervonic acid proportion was confirmed.

Investigations of human platelet-type 12-lipoxygenase: role of lipoxygenase products in platelet activation

Human platelet-type 12-lipoxygenase (12-LOX) has recently been shown to play an important role in regulation of human platelet function by reacting with arachidonic acid (AA). However, a number of other fatty acids are present on the platelet surface that, when cleaved from the phospholipid, can be oxidized by 12-LOX. We sought to characterize the substrate specificity of 12-LOX against six essential fatty acids: AA, dihomo-γ-linolenic acid (DGLA), eicosapentaenoic acid (EPA), α-linolenic acid (ALA), eicosadienoic acid (EDA), and linoleic acid (LA). Three fatty acids were comparable substrates (AA, DGLA, and EPA), one was 5-fold slower (ALA), and two showed no reactivity with 12-LOX (EDA and LA). The bioactive lipid products resulting from 12-LOX oxidation of DGLA, 12-(S)-hydroperoxy-8Z,10E,14Z-eicosatrienoic acid [12(S)-HPETrE], and its reduced product, 12(S)-HETrE, resulted in significant attenuation of agonist-mediated platelet aggregation, granule secretion, αIIbβ3 activation, Rap1 activation, and clot retraction. Treatment with DGLA similarly inhibited PAR1-mediated platelet activation as well as platelet clot retraction. These observations are in surprising contrast to our recent work showing 12(S)-HETE is a prothrombotic bioactive lipid and support our hypothesis that the overall effect of 12-LOX oxidation of fatty acids in the platelet is dependent on the fatty acid substrates available at the platelet membrane.

Gamma-linolenate reduces weight regain in formerly obese humans

The purpose of this study was to determine whether gamma-linolenate (GLA) supplementation would suppress weight regain following major weight loss. Fifty formerly obese humans were randomized into a double-blind study and given either 890 mg/d of GLA (5 g/d borage oil) or 5 g/d olive oil (controls) for 1 y. Body weight and composition and adipose fatty acids of fasting subjects were assessed at 0, 3, 12, and 33 mo. After 12 subjects in each group had completed 1 y of supplementation, weight regain differed between the GLA (2.17 +/- 1.78 kg) and control (8.78 +/- 2.78 kg) groups (P < 0.03). The initial study was terminated, and all remaining subjects were assessed over a 6-wk period. Unblinding revealed weight regains of 1.8 +/- 1.6 kg in the GLA group and 7.6 +/- 2.1 kg in controls for the 13 and 17 subjects, respectively, who completed a minimum of 50 wk in the study. Weight regain did not differ in the remaining 10 GLA and 5 control subjects who completed <50 wk in the study. In a follow-up study, a subgroup from both the original GLA (GLA-GLA, n = 9) and the original control (Control-GLA, n = 14) populations either continued or crossed over to GLA supplementation for an additional 21 mo. Interim weight regains between 15 and 33 mo were 6.48 +/- 1.79 kg and 6.04 +/- 2.52 kg for the GLA-GLA and Control-GLA groups, respectively. Adipose triglyceride GLA levels increased 152% (P < 0.0001) in the GLA group at 12 mo, but did not increase further after 33 mo of GLA administration. In conclusion, GLA reduced weight regain in humans following major weight loss, suggesting a role for essential fatty acids in fuel partitioning in humans prone to obesity.

Gamma-linolenic acid in borage oil reverses epidermal hyperproliferation in guinea pigs

As dietary sources of gamma-linolenic acid [GLA; 18:3(n-6)], borage oil (BO; 24-25 g/100 g GLA) and evening primrose oil (PO; 8-10 g/100 g GLA) are efficacious in treating skin disorders. The triglycerol stereospecificity of these oils is distinct, with GLA being concentrated in the sn-2 position of BO and in the sn-3 position of PO. To determine whether the absolute level and/or the triglycerol stereospecificity of GLA in oils affect biological efficacy, epidermal hyperproliferation was induced in guinea pigs by a hydrogenated coconut oil (HCO) diet for 8 wk. Subsequently, guinea pigs were fed diets of PO, BO or a mixture of BO and safflower oil (SO) for 2 wk. The mixture of BO and SO (BS) diet had a similar level of GLA as PO but with sn-2 stereospecificity. As controls, two groups were fed SO and HCO for 10 wk. Epidermal hyperproliferation was reversed by all three oils in the order of BO > BS > PO. However, proliferation scores of group PO were higher than of the normal control group, SO. The accumulations of dihomo-gamma-linolenic acid [DGLA; 20:3(n-6)], an elongase product of GLA, into phospholipids and ceramides, of 15-hydroxyeicosatrienoic acid (15-HETrE), the potent antiproliferative metabolite of DGLA, and of ceramides, the major lipid maintaining epidermal barrier, in the epidermis of group BO were greater than of groups BS and PO. Group BS had higher levels of DGLA, 15-HETrE and ceramides than group PO. With primary dependence on absolute levels, our data demonstrate that the antiproliferative efficacy of GLA in the epidermis is preferably exerted from sn-2 stereospecificity of GLA in BO.

Differential metabolism of dihomo-gamma-linolenic acid and arachidonic acid by cyclo-oxygenase-1 and cyclo-oxygenase-2: implications for cellular synthesis of prostaglandin E1 and prostaglandin E2

Prostaglandin (PG) E(1) has been shown to possess anti-inflammatory properties and to modulate vascular reactivity. These activities are sometimes distinct from those of PGE(2), suggesting that endogenously produced PGE(1) may have some beneficial therapeutic effects compared with PGE(2). Increasing the endogenous formation of PGE(1) requires optimization of two separate processes, namely, enrichment of cellular lipids with dihomo-gamma-linolenic acid (20:3 n-6; DGLA) and effective cyclo-oxygenase-dependent oxygenation of substrate DGLA relative to arachidonic acid (AA; 20:4 n-6). DGLA and AA had similar affinities (K(m) values) and maximal reaction rates (V(max)) for cyclo-oxygenase-2 (COX-2), whereas AA was metabolized preferentially by cyclo-oxygenase-1 (COX-1). To overcome the kinetic preference of COX-1 for AA, CP-24879, a mixed Delta(5)/Delta(6) desaturase inhibitor, was used to enhance preferential accumulation of DGLA over AA in cells cultured in the presence of precursor gamma-linolenic acid (18:3 n-6). This protocol was tested in two cell lines and both yielded a DGLA/AA ratio of approx. 2.8 in the total cellular lipids. From the enzyme kinetic data, it was calculated that this ratio should offset the preference of COX-1 for AA over DGLA. PGE(1) synthesis in the DGLA-enriched cells was increased concurrent with a decline in PGE(2) formation. Nevertheless, PGE(1) synthesis was still substantially lower than that of PGE(2). It appears that employing a dietary or a combined dietary/pharmacological paradigm to augment the cellular ratio of DGLA/AA is not an effective route to enhance endogenous synthesis of PGE(1) over PGE(2), at least in cells/tissues where COX-1 predominates over COX-2.

The effect of a Tropaeolum speciosum oil supplement on the nervonic acid content of sphingomyelin in rat tissues

The lipids of Tropaeolum speciosum (T. speciosum) are a rich source of naturally occurring nervonic acid (24:1n-9). We report that adding a T. speciosum oil supplement to a semi-purified diet significantly increased the amount of 24:1n-9 in liver and heart, but not brain, sphingomyelin (SM) of young rats. The bioavailability of 24:1n-9 from the lipids of T. speciosum was similar to that of 24:1n-9 ethyl ester in this rat bioassay.

Effect of borage oil consumption on fatty acid metabolism, transepidermal water loss and skin parameters in elderly people

Human skin is not able to biosynthesize gamma-linolenic acid (GLA, 18:3omega6) from the precursor linoleic acid (LA), or arachidonic acid (AA) from dihomo-gamma-linolenic acid (DHGLA). Dietary supplementation with GLA-rich seed oil of borage skips the step of hepatic 6-desaturation of fatty acids (FA) and, therefore, compensates the lack of these essential FA in conditions with impaired activity of delta 6-desaturase. Twenty-nine healthy elderly people (mean age 68.6 years), received a daily dose of 360 or 720 mg GLA for 2 months, using Borage oil in gelatine capsules (Quintesal 180, manufacturer Galderma Laboratorium GmbH, Freiburg, Germany). The effects of fatty acids derived from ingested borage oil capsules on skin barrier function were assessed by measurement of transepidermal water loss (TEWL). The consumption of borage oil induced a statistically significant improvement of cutaneous barrier function in the elderly people, as reflected in a mean decrease of 10.8% in the transepidermal water loss. Thirty-four percent of the people noted itch before borage oil consumption and 0% afterwards. Dry skin was claimed to be reduced from 42 to 14%, but no significant alteration of skin hydration was measured. The FA-composition of erythrocyte membrane phospholipids demonstrated an increase of GLA (+70%) and DHGLA (+18%) and a reduction of saturated and monounsaturated FA. There was no significant alteration in nervonic acid or in AA content, but an increase in the DHGLA/AA ratio (+23%). Thus, the consumption of borage oil by elderly people lead to alteration of FA metabolism and improved skin function.

Gamma-linolenic acid does not augment long-chain polyunsaturated fatty acid omega-3 status

Augmentation of long chain polyunsaturated omega3 fatty acid (LCPUFA omega3) status can be reached by consumption of fish oil or by improvement of the conversion of alpha-linolenic acid (ALA) to LCPUFA omega3. Since gamma-linolenic acid (GLA) might activate the rate-limiting delta-6 desaturation, we investigated whether GLA augments LCPUFA omega3 status. Eight adults received 1.4 g GLA for 4 weeks and subsequently 2.2 g ALA+1.4 g GLA daily during another 4 weeks. Another seven adults received a daily oral dose of 2.2 g ALA for 4 weeks, and subsequently 2.2 g ALA+1.4 g GLA during another 4 weeks. ALA, or ALA+GLA, did not significantly augment EPA and DHA contents. We conclude that the LCPUFA omega3 status can not be improved by supplementation of low dose GLA, neither by co-supplementation of ALA. Poor conversion of ALA to LCPUFA omega3 may be caused by preferential beta-oxidation of ALA, negative feedback of arachidonic acid from the omnivorous diet, or by the low dietary ALA/LA ratio.

Effects of feeding Lunaria oil rich in nervonic and erucic acids on the fatty acid compositions of sphingomyelins from erythrocytes, liver, and brain of the quaking mouse mutant

Feeding an oil from Lunaria biennis rich in 22:1n-9 and 24:1n-9 to homozygous quaking (qk.qk) mice caused a large increase in the percentage of 24:1n-9 and corresponding decreases in the percentage of 24:0 and 22:0 in sphingomyelins from liver, erythrocytes, and milk. Brain sphingomyelin from 2-wk-old qk.qk pups born to qk.qk mothers maintained on the Lunaria oil had essentially normal percentage of 24:1n-9 and 18:0, in contrast to pups born to mothers maintained on a control oil rich in 18:1n-9 whose brain sphingomyelin had a markedly reduced percentage of 24:1n-9 and an increased percentage of 18:0. After 2 wk and up to and beyond weaning, the qk.qk pups from Lunaria-fed mothers weaned on to the Lunaria diet had a markedly decreased percentage of 24:1n-9 in their brain sphingomyelin, accompanied by an increased percentage of 18:0, as compared to heterozygous quaking mice. However, the percentage of 24:1n-9 in brain sphingomyelin in qk.qk pups weaned on to the Lunaria diet continued throughout this period (2-8 wk postbirth) to be significantly higher than in qk.qk pups weaned on to the control diet. We conclude that dietary 24:1n-9 influences the fatty acid composition of brain sphingomyelin in qk.qk mice, but only via the mother in pre- or early postnatal animals. We further consider that the dietary effects may be elicited mainly in the sphingomyelin of nonmyelinated brain cells, and that the nervonic acid in myelin sphingomyelin may be formed mainly by chain elongation in oligodendrocytes from shorter chain fatty acid precursors.

Dietary gamma-linolenic acid enhances mouse macrophage-derived prostaglandin E1 which inhibits vascular smooth muscle cell proliferation

We previously demonstrated that macrophages isolated from mice fed gamma-linolenic acid (GLA)-enriched diets reduce vascular smooth muscle cell (SMC) proliferation in a cyclooxygenase-dependent fashion and may therefore favorably modulate the atherogenic process. The present study was conducted to elucidate the mechanism(s) by which dietary GLA influences the ability of macrophages to modulate SMC growth programs. Resident peritoneal macrophages were isolated from C57BL/6 female mice fed diets containing variable GLA compositions at 10% (wt/wt), treated with various antibodies and co-cultured with cycling naive vascular SMC isolated from nonpurified diet-fed mice. Smooth muscle cell proliferation and intracellular cAMP levels were measured after co-culture. In parallel experiments, cycling naive vascular SMC isolated from nonpurified diet-fed mice were dosed with exogenous prostaglandin E1 (PGE1 ) for various periods and challenged with cycloheximide for 4 h (8-12 h after PGE1 addition), and intracellular cAMP levels were measured at various time points. Macrophages isolated from mice fed GLA-enriched dietary oils significantly reduced SMC proliferation in co-culture compared with controls (macrophages from mice fed a corn oil diet containing no GLA). Anti-PGE1 antiserum treatment (1:50 or 1:100) blocked the ability of GLA-enriched macrophages to down-regulate SMC proliferation, a response reversed by exogenous PGE1 treatment. Macrophages isolated from mice fed GLA-enriched dietary oils elevated SMC intracellular cAMP levels in a biphasic fashion. In addition, exogenous PGE1 (1 nmol/L to 10 micromol/L) exerted a similar biphasic cAMP response in SMC, and the second phase of cAMP elevation was antagonized by cycloheximide. In conclusion, dietary GLA enhances mouse macrophage-derived prostaglandin E1, which inhibits vascular SMC proliferation.

Dietary very long chain fatty acids directly influence the ratio of tetracosenoic (24:1) to tetracosanoic (24:0) acids of sphingomyelin in rat liver

Twenty-one groups of weanling male Wistar rats were fed semipurified diets containing 5% (w/w) of different dietary fats. After 2 wk, liver sphingomyelin (SM) fatty acid composition was determined. The ratio of 24:1 to 24:0 in liver SM varied over a tenfold range in response to dietary fat type. Step-wise multiple regression analysis indicated that dietary 24:1, 24:0, and 22:1 were the most significant factors in predicting the 24:1/24:0 ratio of liver SM. The mathematical relation between the dietary fatty acid composition and liver SM 24:1/24:0 was y = 1.88 (24:1) -1.49 (24:0) +0.21 (22:1) +0.01 (18:1) +0.26, r2 = 0.95, P < 0.0001. These results were confirmed by a second experiment in which the rats were fed olive oil-based diets supplemented with various fatty acid ethyl esters.

Human platelets have cholesteryl ester hydrolytic activity resulting in esterification of [1-14C]oleate to individual phospholipids of platelets

Human platelet cholesteryl ester hydrolytic (CEH) activity was determined toward cholesteryl [1-14C]oleate resulting in esterification of [1-14C]oleate to individual platelet phospholipids: choline-containing phospholipids (PC); ethanolamine-containing phospholipids (PE); phosphatidylserine (PS); phosphatidylinositol (PI); and sphingomyelin (SPH). Liberation of [1-14C]oleate and esterification of [1-14C]oleate to platelet phospholipids was enhanced by 100 nM iloprost (a stable analogue of prostacyclin that increases platelet cyclic adenosine monophosphate (c-AMP)), inhibited by 30 microM H-89 (N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide)) (a specific c-AMP dependent protein kinase (CADPK) inhibitor) and 500 microM 2',5' dideoxyadenosine (DDA) (an inhibitor of iloprost-induced rise in platelet c-AMP), but unaffected by 150 mM choloroquine diphosphate. These observations suggest that the CEH activity is mediated by a CADPK phosphorylation of an enzyme with the phosphorylated state representing the active form of the enzyme and that the CEH activity is extralysosomal.

Nervonic acid and demyelinating disease

Demyelination in adrenoleukodystrophy (ALD) is associated with an accumulation of very long chain saturated fatty acids such as 26:0 stemming from a genetic defect in the peroxisomal beta oxidation system responsible for the chain shortening of these fatty acids. Long chain monoenoic acids such as erucic acid, 22:1(n-9), can normalise elevated serum levels of 26:0 in ALD by depressing their biosynthesis from shorter chain saturated fatty acids. Sphingolipids from post mortem ALD brain have decreased levels of nervonic acid, 24:1(n-9), and increased levels of stearic acid, 18:0. Increased levels of 26:0 are accompanied by decreased nervonic acid biosynthesis in skin fibroblasts from ALD patients. Sphingolipids from post mortem MS brain have the same decreased 24:1(n-9) and increased 18:0 seen in post mortem ALD brain. The 24:1(n-9) content of sphingomyelin is depressed in erythrocytes from multiple sclerosis (MS) patients. Defects in the microsomal biosynthesis of very long chain fatty acids including 24:1(n-9) in 'jumpy' and 'quaking' mice are accompanied by impaired myelination. An impairment in the provision of nervonic acid in demyelinating diseases is indicated, suggesting that dietary therapy with oils rich in very long chain monenoic acid fatty acids may be beneficial in such conditions.