C18 hydroxy fatty acids as markers of lipid peroxidationex vivoandin vivo

Hydroxy fatty acids in the surface Earth system

Lipids are ubiquitous and highly abundant in a wide range of organisms and have been found in various types of environmental media. These molecules play a crucial role as organic tracers by providing a chemical perspective on viewing the material world, as well as offering a wealth of information on metabolic activities. Among the diverse lipid compounds, hydroxy fatty acids (HFAs) with one to multiple hydroxyl groups attached to the carbon chain stand out as important biomarkers for different sources of organic matter. HFAs are widespread in nature and are involved in biotransformation and oxidation processes in living organisms. The unique chemical and physical properties attributed to the hydroxyl group make HFAs ideal biomarkers in biomedicine and environmental toxicology, as well as organic geochemistry. The molecular distribution patterns of HFAs can be unique and diagnostic for a given class of organisms, including animals, plants, and microorganisms. Thus, HFAs can act as a valuable proxy for understanding the ecological relationships between different organisms and their environment. Furthermore, HFAs have numerous industrial applications due to their higher reactivity, viscosity, and solvent miscibility. This review paper integrates the latest research on the sources and chemical analyses of HFAs, as well as their applications in industrial/medicinal production and as biomarkers in environmental studies. This review article also provides insights into the biogeochemical cycles of HFAs in the surface Earth system, highlighting the importance of these compounds in understanding the complex interactions between living organisms and the environment.

Hydroxylated sphingolipid biosynthesis regulates photoreceptor apical domain morphogenesis

Apical domains of epithelial cells often undergo dramatic changes during morphogenesis to form specialized structures, such as microvilli. Here, we addressed the role of lipids during morphogenesis of the rhabdomere, the microvilli-based photosensitive organelle of Drosophila photoreceptor cells. Shotgun lipidomics analysis performed on mutant alleles of the polarity regulator crumbs, exhibiting varying rhabdomeric growth defects, revealed a correlation between increased abundance of hydroxylated sphingolipids and abnormal rhabdomeric growth. This could be attributed to an up-regulation of fatty acid hydroxylase transcription. Indeed, direct genetic perturbation of the hydroxylated sphingolipid metabolism modulated rhabdomere growth in a crumbs mutant background. One of the pathways targeted by sphingolipid metabolism turned out to be the secretory route of newly synthesized Rhodopsin, a major rhabdomeric protein. In particular, altered biosynthesis of hydroxylated sphingolipids impaired apical trafficking via Rab11, and thus apical membrane growth. The intersection of lipid metabolic pathways with apical domain growth provides a new facet to our understanding of apical growth during morphogenesis.

DHA concentration of red blood cells is inversely associated with markers of lipid peroxidation in men taking DHA supplement

An increase in the proportion of fatty acids with higher numbers of double bonds is believed to increase lipid peroxidation, which augments the risk for many chronic diseases. (n-3) Polyunsaturated fatty acids provide various health benefits, but there is a concern that they might increase lipid peroxidation. We examined the effects of docosahexaenoic acid [22:6 (n-3)] supplementation on lipid peroxidation markers in plasma and red blood cells (RBC) and their associations with red blood cell and plasma fatty acids. Hypertriglyceridemic men (n = 17 per group) aged 39–66 years participated in a double-blind, randomized, placebo-controlled, parallel study. They received no supplements for the first 8 days and then received 7.5 g/day docosahexaenoic acid oil (3 g/day docosahexaenoic acid) or olive oil (placebo) for 90 days. Fasting blood samples were collected 0, 45, and 91 days after supplementation. Docosahexaenoic acid supplementation did not change plasma or RBC concentrations of lipid peroxidation markers (total hydroxyoctadecadienoic acid, total hydroxyeicosatetraenoic acid, total 8-isoprostaglandin F_2α, 7α-hydroxycholesterol, 7β-hydroxycholesterol) when pre- and post-supplement values were compared. However, the post-supplement docosahexaenoic acid (DHA) concentration was inversely associated with RBC concentrations of ZE-HODE, EE-HODE, t-HODE, and total 8-isoprostaglandin F_2α, (p<0.05). RBC concentration of hydroxycholesterol was also inversely associated with DHA but it did not attain significance (p = 0.07). Our results suggest that increased concentration of DHA in RBC lipids reduced lipid peroxidation. This may be another health benefit of DHA in addition to its many other health promoting effects.

Similarities and differences between the effects of EPA and DHA on markers of atherosclerosis in human subjects

We have reviewed effects of long chain (LC) n-3 PUFA on markers of atherosclerosis in human subjects with a focus on individual effects of EPA and DHA. Initial results from epidemiological studies suggested that LC n-3 PUFA from fish oils (FO) reduced incidence of CVD; those results have been confirmed in interventional studies. Dietary intervention with n-3 PUFA decreased fasting and postprandial TAG, number of remnant-like chylomicron particles, large VLDL, and total and small dense LDL particles. It increased mean size of LDL particles by increasing number of large and decreasing those of small dense particles. With some exceptions, n-3 PUFA decreased blood pressure (BP) and heart rate (HR), flow-mediated dilation (FMD) and plasma concentrations of inflammatory markers. n-3 PUFA also decreased circulating adhesion molecules and intima-media thickness (IMT) in some but not other studies. For IMT, results varied with the sex and artery being examined. EPA effects on FMD are endothelial cell dependent, while those of DHA seem to be endothelial cell independent. Individually, both EPA and DHA decreased TAG and inflammatory markers, but only DHA decreased HR, BP and number of small dense LDL particles. Results varied because of dose and duration of n-3 PUFA, EPA:DHA, health status of subjects and other reasons. Future studies are needed to determine optimal doses of EPA and DHA individually, their synergistic, additive or antagonistic effects, and to understand underlying mechanisms. In conclusion, n-3 PUFA decreased several risk factors for atherosclerosis without any serious adverse effects.

Treatment of hypertension in metabolic syndrome subjects with amlodipine and olmesartan-effects on oxidized non-esterified free fatty acids and cytokine production

PURPOSE

Angiotensin II increases activation of oxidative signaling and vascular inflammatory gene expression, and interruption of the renin-angiotensin system has been considered more vasculoprotective than use of calcium channel antagonists and other anti-hypertensive therapies. Despite these putative mechanisms, amlodipine is equally efficacious as other therapies in reducing cardiovascular events.

METHODS

Double-blind, controlled trial, designed to investigate the effects of 2-months treatment with amlodipine and olmesartan on oxidized non-esterified fatty acids (ox-NEFA), and lipopolysaccharide-stimulated cytokine production in whole blood among 23 hypertensive subjects with the metabolic syndrome.

RESULTS

Treatment with olmesartan was no different than amlodipine in changing concentrations of total oxidized fatty acids (p = 0.37), total ox-NEFA (p = 0.43) and 9, 10, 11, 12, 13, 14, 15 and 16 ox-NEFA concentrations. In contrast, 8 ox-NEFA increased (median [interquartile ranges] by 45.2% [5.3 to 50.0] in olmesartan-treated subjects) compared with a decrease of 18.4% (-45.1-13.9) in amlodipine-treated subjects (p = 0.03). Lipopolysaccharide-stimulated cytokine production and levels of soluble cellular adhesion molecules did not change with either treatment.

CONCLUSION

Despite experimental data that demonstrates that angiotensin receptor antagonists reduce cellular oxidant stress and inflammation, olmesartan was not different than amlodipine in changing ox-NEFA and inflammatory markers in hypertensive subjects with the metabolic syndrome.

Lycopene, lutein and beta-carotene as determinants of LDL conjugated dienes in serum

Oxidative modification of low-density lipoprotein (LDL) in the vascular endothelium is considered to be important in the development of early atherosclerosis. The aim of this study was to investigate the main determinants of serum LDL conjugated dienes in women (n=124) and men (n=225). We focused on the influence of fat-soluble vitamins and carotenoids on the concentration of conjugated dienes in LDL. In multivariate linear regression models, including age, body mass index, diastolic blood pressure, symptomatic ischaemic heart disease (IHD) or IHD history, statin medication, leukocytes and serum triglycerides as covariates, plasma lycopene (standardized beta=-0.33; P=0.002) and lutein (standardized beta=-0.22; P=0.027) concentrations were the strongest determinants of serum LDL conjugated dienes in women, whereas plasma beta-carotene (standardized beta=-0.23; P=0.002) was the most important factor in men. Furthermore, statin medication, diastolic blood pressure, age and serum triglycerides were significant determinants of LDL conjugated dienes. The regression model with lycopene contributed to 29% in women and 15% in men with beta-carotene of the variation of serum LDL conjugated dienes. Results of the present study suggest that plasma lycopene, lutein and beta-carotene are the most powerful antioxidants for explaining the content of in vivo oxidatively modified LDL in serum.

Fenofibrate reduces lipoprotein associated phospholipase A2 mass and oxidative lipids in hypertriglyceridemic subjects with the metabolic syndrome

BACKGROUND

Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a macrophage-synthesized lipase that is primarily bound to small electronegative low-density lipoproteins (LDLs). Lipoprotein-associated phospholipase A2 oxidatively modifies LDL and generates the proinflammatory byproducts oxidized fatty acids (ox-FAs) and lysophosphatidylcholine. Fenofibrate reduces Lp-PLA2 mass; however, it remains unknown whether the anti-inflammatory effects of fenofibrate are related to changes in LDL subclasses.

METHODS

This was a randomized, double-blind, controlled clinical trial designed to investigate the effects of 3-month treatment with fenofibrate (160 mg/d) on Lp-PLA2 mass, LDL subclasses, and ox-FAs among 55 hypertriglyceridemic (> or = 1.7 and < 6.78 mmol/L) subjects with the metabolic syndrome.

RESULTS

Fenofibrate treatment lowered fasting Lp-PLA2 mass by 13.2% (-19.0 to -7.7) versus placebo (2.3% [-5.0 to 4.1], P = .0002) and total ox-FA by 15.5% (-34.2 to +1.4) versus an 11.5% increase with placebo (P = .0013). In age-, sex-, and treatment-adjusted models, changes in Lp-PLA2 mass were associated with reductions in chemical LDL cholesterol (r = 0.59, P < .01) and measured total LDL particles (LDL-Ps) (r = 0.64, P < .01) and small LDL-Ps (r = 0.57, P < .01). In models that included small LDL, effects of fenofibrate on Lp-PLA2 mass were attenuated (P = .125), but not in models that included LDL cholesterol (P < .0001) and LDL-Ps (P = .005). Changes in Lp-PLA2 mass were not significantly associated with changes in ox-FA or inflammatory markers.

CONCLUSIONS

Among hypertriglyceridemic subjects with the metabolic syndrome, fenofibrate therapy reduced Lp-PLA2 mass, and these changes were associated with fewer small LDL-Ps.

Fenofibrate reduces fasting and postprandial inflammatory responses among hypertriglyceridemia patients with the metabolic syndrome

OBJECTIVE

To examine the effects of fenofibrate (160mg/d) therapy on fasting and postprandial cytokine production in subjects with metabolic syndrome and hypertriglyceridemia.

RESEARCH DESIGN AND METHODS

Randomized, double-blind, controlled trial that compared the effects of 3-month therapy with placebo and fenofibrate on fasting and postprandial cytokine production in 55 subjects with metabolic syndrome and elevated fasting triglycerides (>or=1.7 and <6.78mmol/L).

RESULTS

Fenofibrate treatment reduced concentrations of monohydroxy fatty acids (OH-FA) by 15.5% (p=0.001), lipopolysaccharide activated monocyte chemotactic protein-1 (MCP-1/CCL2) production in fasting blood samples by 3.4% (p=0.01 vs. placebo), macrophage inflammatory protein-1alpha (MIP-1alpha/CCL3) by 3.5% (p=0.01), and interleukin-1beta (IL-1beta) by 2.5% (p=0.04). After a standardized fat load (50kg/m(2)), OH-FA were reduced by 31.0% (p<0.0001), MCP-1/CCL2 was reduced by 5.2% (p=0.002), MIP-1alpha/CCL3 by 3.9% (p=0.007), and IL-1beta by 3.4% (p=0.02). Reductions in MCP-1/CCL2, MIP-1alpha/CCL3, and IL-1beta production correlated with changes in fasting and postprandial large very low-density lipoprotein (VLDL) (all p<0.005) and small low-density lipoprotein (LDL) particles (all p<0.05). In stepwise regression models that included age, gender, weight change, and drug assignment, large VLDL particles were associated with reductions in postprandial MCP-1/CCL2 (p=0.042), MIP-1alpha/CCL3 (p=0.003), and IL-1beta (p=0.02).

CONCLUSIONS

This study reports that fenofibrate reduces whole blood production of inflammatory cytokines and hepatic-synthesized inflammatory proteins, and the anti-inflammatory effects of fenofibrate therapy involve VLDL- and LDL-mediated pathways.

Fenofibrate therapy ameliorates fasting and postprandial lipoproteinemia, oxidative stress, and the inflammatory response in subjects with hypertriglyceridemia and the metabolic syndrome

OBJECTIVE

The aim of this study was to determine the effects of fenofibrate (160 mg/day) on fasting and postprandial lipoproteins, oxidized fatty acids, and inflammatory mediators in subjects with hypertriglyceridemia and the metabolic syndrome.

RESEARCH DESIGN AND METHODS

Fifty-nine subjects with fasting hypertriglyceridemia (> or = 1.7 and < 6.9 mmol/l) and two or more of the Adult Treatment Panel III criteria for the metabolic syndrome were randomly assigned to fenofibrate (160 mg/day) or placebo in a double-blind, controlled clinical trial.

RESULTS

Fenofibrate treatment lowered fasting triglycerides (-46.1%, P < 0.0001) and postprandial (area under the curve) triglycerides (-45.4%, P < 0.0001) due to significant reductions in postprandial levels of large (-40.8%, P < 0.0001) and medium (-49.5%, P < 0.0001) VLDL particles. The number of fasting total LDL particles was reduced in fenofibrate-treated subjects (-19.0%, P = 0.0033) primarily due to reductions in small LDL particles (-40.3%, P < 0.0001); these treatment differences persisted postprandially. Fasting and postprandial oxidized fatty acids were reduced in fenofibrate-treated subjects compared with placebo-administered subjects (-15.3%, P = 0.0013, and 31.0%, P < 0.0001, respectively), and fenofibrate therapy lowered fasting and postprandial soluble vascular cell adhesion molecule-1 (VCAM-1) (-10.9%, P = 0.0005, and -12.0%, P = 0.0001, respectively) as well as fasting and postprandial soluble intercellular adhesion molecule-1 (ICAM-1) (-14.8%, P < 0.0001, and -15.3%, P < 0.0001, respectively). Reductions in VCAM-1 and ICAM-1 were correlated with reductions in fasting and postprandial large VLDL particles (P < 0.0001) as well as postprandial oxidized fatty acids (P < 0.0005).

CONCLUSIONS

Triglyceride-lowering therapy with fenofibrate reduced fasting and postprandial free fatty acid oxidation and inflammatory responses, and these antiatherosclerotic effects were most highly correlated with reductions in large VLDL particles.

Dark chocolate consumption increases HDL cholesterol concentration and chocolate fatty acids may inhibit lipid peroxidation in healthy humans

Cocoa powder is rich in polyphenols and, thus, may contribute to the reduction of lipid peroxidation. Our aim was to study the effects of long-term ingestion of chocolate, with differing amounts of polyphenols, on serum lipids and lipid peroxidation ex vivo and in vivo. We conducted a 3 week clinical supplementation trial of 45 nonsmoking, healthy volunteers. Participants consumed 75 g daily of either white chocolate (white chocolate, WC group), dark chocolate (dark chocolate, DC group), or dark chocolate enriched with cocoa polyphenols (high-polyphenol chocolate, HPC group). In the DC and HPC groups, an increase in serum HDL cholesterol was observed (11.4% and 13.7%, respectively), whereas in the WC group there was a small decrease (-2.9%, p < 0.001). The concentration of serum LDL diene conjugates, a marker of lipid peroxidation in vivo, decreased 11.9% in all three study groups. No changes were seen in the total antioxidant capacity of plasma, in the oxidation susceptibility of serum lipids or VLDL + LDL, or in the concentration of plasma F2-isoprostanes or hydroxy fatty acids. Cocoa polyphenols may increase the concentration of HDL cholesterol, whereas chocolate fatty acids may modify the fatty acid composition of LDL and make it more resistant to oxidative damage.