Vitamin C, diclophenac, and L-arginine protect endothelium-dependent vasodilation against elevated circulating fatty acid levels in humans

Lipid Emulsions Containing Medium Chain Triacylglycerols Blunt Bradykinin-Induced Endothelium-Dependent Relaxation in Porcine Coronary Artery Rings

Lipid emulsions for parenteral nutrition are used to provide calories and essential fatty acids for patients. They have been associated with hypertriglyceridemia, hypercholesterolemia, and metabolic stress, which may promote the development of endothelial dysfunction in patients. The aim of the present study was to determine whether five different industrial lipid emulsions may affect the endothelial function of coronary arteries. Porcine coronary artery rings were incubated with lipid emulsions 0.5, 1, or 2% (v/v) for 30 min before the determination of vascular reactivity in organ chambers and the level of oxidative stress using electron paramagnetic resonance. Incubation of coronary artery rings with either Lipidem^®, Medialipid^® containing long- and medium-chain triacylglycerols (LCT/MCT), or SMOFlipid^® containing LCT, MCT, omega-9, and -3, significantly reduced the bradykinin-induced endothelium-dependent relaxation, affecting both the nitric oxide (NO) and endothelium-dependent hyperpolarization (EDH) components, whereas, Intralipid^® containing LCT (soybean oil) and ClinOleic^® containing LCT (soybean and olive oil) did not have such an effect. The endothelial dysfunction induced by Lipidem^® was significantly improved by indomethacin, a cyclooxygenase (COX) inhibitor, inhibitors of oxidative stress (N-acetylcysteine, superoxide dismutase, catalase) and transition metal chelating agents (neocuproine, tetrathiomolybdate, deferoxamine and L-histidine). Lipidem^® significantly increased the arterial level of oxidative stress. The present findings indicate that lipid emulsions containing LCT/MCT induce endothelial dysfunction in coronary artery rings by blunting both NO- and EDH-mediated relaxations. The Lipidem^®-induced endothelial dysfunction is associated with increased vascular oxidative stress and the formation of COX-derived vasoconstrictor prostanoids.

Correlation between serum free fatty acids levels and Gensini score in elderly patients with coronary heart disease

Objectives

To investigate the relationship between serum free fatty acids (FFAs) levels and the severity of coronary artery lesions in elderly patients with coronary heart disease (CAD).

Methods

A total of 172 elderly patients who underwent coronary angiography were divided into CAD group (n = 128) and non-CAD group (n = 44) according to the results of coronary angiography. Serum FFAs and lipid levels were measured and the Gensini score were calculated.

Results

No matter the differences between age, gender and the usage of statins or not, there was no statistical significance in FFAs levels (P > 0.05). In terms of the Gensini score, it was higher in patients aged 70–79 years than in patients 60–69 years old [15.00 (5.00, 34.00) vs. 10.00 (2.00, 24.00), P < 0.05], higher in men than women [14.00 (4.00, 34.00) vs. 7.00 (2.50, 19.75), P < 0.05], and higher in patients on statins [13.50 (4.25, 33.50) vs. 6.50 (2.00, 18.00), P < 0.05]. The serum FFAs levels [449.50 (299.00, 624.75) mEq/L vs. 388.00 (258.50, 495.25) mEq/L, P < 0.05] and Gensini score [17.50 (8.00, 41.75) vs. 1.00 (0, 5.00), P < 0.05] were higher in the CAD group than in the non-CAD group. In the CAD group, there was no statistical significance in FFAs levels among patients with different numbers of diseased coronary vessels (P > 0.05). Furthermore, the FFAs levels were positively correlated with the Gensini score (r = 0.394, P = 0.005). Regression analysis showed that the FFAs levels were related to the Gensini score independently after adjusting for the other risk factors.

Conclusions

The serum FFAs levels were associated with the Gensini score in elderly patients with CAD. It might indicate FFAs as a biomarker predicting the severity of coronary artery lesions.

High-fat diet alters prostanoid balance and perfusion in ischemic myocardium of naproxen-treated swine

BACKGROUND

The effect of nonsteroidal anti-inflammatory drugs (NSAIDs) on the cardiovascular system remains controversial, especially in patients with cardiovascular comorbidities. We used a swine model of chronic myocardial ischemia to investigate whether hypercholesterolemia alters the cardiovascular effects of the nonselective NSAID naproxen.

METHODS

Yorkshire swine were fed normal chow (NAP; n = 7) or a high-fat diet (HF-NAP; n = 8). Chronic myocardial ischemia was created in all animals by left circumflex ameroid constrictor placement. All swine were started on oral naproxen (440 mg/day) at the time of ameroid placement. After 7 weeks, myocardial perfusion and microvessel reactivity in the ischemic territory were assessed. Tissue levels of prostanoid metabolites 11-dehydrothromboxane B2 (11-d-TXB₂) and 6-keto-prostaglandin F1-α (6-k-PGF(1α)) were measured. Tissue was analyzed for capillary density and protein expression.

RESULTS

Myocardial perfusion was significantly decreased in the HF-NAP group both at rest and during ventricular pacing. Microvessel relaxation responses to sodium nitroprusside and adenosine 5'-diphosphate were similar between groups. Tissue 11-d-TXB₂ levels were similar between groups, but tissue 6-k-PGF(1α) was significantly decreased in the HF-NAP group (P = .001). Expression of thromboxane synthase was significantly higher in the HF-NAP group (P = .02), while prostacyclin synthase expression was significantly decreased in the HF-NAP group (P = .04). Capillary density was higher in the HF-NAP group (P = .005). Proangiogenic vascular endothelial growth factor (VEGF; P = .0002) and Akt (P = .01) were downregulated in the HF-NAP group.

CONCLUSION

A high-fat diet impairs tissue perfusion in ischemic myocardium of naproxen-treated swine by shifting the prostanoid balance to favor production of thromboxane over prostacyclin. Dietary modification may improve myocardial blood flow and alter the safety profile in chronically ischemic cardiac patients taking naproxen.

DHA-rich fish oil reverses the detrimental effects of saturated fatty acids on postprandial vascular reactivity

BACKGROUND

Experimental elevation of nonesterified fatty acids (NEFAs) impairs endothelial function, but the effect of NEFA composition is unknown.

OBJECTIVE

The objective was to test the effect of acute elevation of NEFAs enriched with either saturated fatty acids (SFAs) or SFAs with long-chain (LC) n-3 (omega-3) PUFAs on vascular function measured via flow-mediated dilatation (FMD), laser Doppler iontophoresis (LDI), and digital volume pulse (DVP).

DESIGN

In 59 subjects (30 men and 29 women), repeated oral fat feeding of either palm stearin (SFA) or palm stearin with DHA-rich fish oil (SFA + LC n-3 PUFA) was performed on 2 separate occasions with continuous heparin infusion to elevate NEFAs for a duration of 60 to 240 min. Vascular function was measured at baseline and at the end of NEFA elevation; venous blood was collected for measurement of lipids and circulating markers of endothelial function.

RESULTS

NEFA elevation during consumption of the SFA-rich drinks was associated with a marked impairment of FMD, whereas consumption of SFAs + LC n-3 PUFAs improved FMD response, with a mean (±SEM) difference of 2.06 ± 0.29% (P < 0.001). Positive correlations were found with percentage weight of LC n-3 PUFAs in circulating NEFAs and change in FMD response [Spearman's rho (r(s)) = 0.460, P < 0.001]. LDI measures increased during both treatments (P ≤ 0.026), and there was no change in DVP indexes.

CONCLUSIONS

The composition of NEFAs can acutely affect FMD. The beneficial effect of LC n-3 PUFAs on postprandial vascular function warrants further investigation but may be mediated by nitric oxide-independent mechanisms. This trial is registered at clinicaltrials.gov as NCT01351324.

Impaired endothelium-dependent vasodilatation is a novel predictor of mortality in intensive care

OBJECTIVE

Endothelial function may be impaired in critical illness. We hypothesized that impaired endothelium-dependent vasodilatation is a predictor of mortality in critically ill patients.

DESIGN

Prospective observational cohort study.

SETTING

Seventeen-bed adult intensive care unit in a tertiary referral university teaching hospital.

PATIENTS

Patients were recruited within 24 hrs of admission to the intensive care unit.

INTERVENTIONS

The SphygmoCor Mx system was used to derive the aortic augmentation index from radial artery pulse pressure waveforms. Endothelium-dependent vasodilatation was calculated as the change in augmentation index in response to an endothelium-dependent vasodilator (salbutamol).

MEASUREMENTS AND MAIN RESULTS

Demographics, severity of illness scores, and physiological parameters were collected. Statistically significant predictors of mortality identified using single regressor analysis were entered into a multiple logistic regression model. Receiver operator characteristic curves were generated. Ninety-four patients completed the study. There were 80 survivors and 14 nonsurvivors. The Simplified Acute Physiology Score II, the Sequential Organ Failure Assessment score, leukocyte count, and endothelium-dependent vasodilatation conferred an increased risk of mortality. In logistic regression analysis, endothelium-dependent vasodilatation was the only predictor of mortality with an adjusted odds ratio of 26.1 (95% confidence interval [CI], 4.3-159.5). An endothelium-dependent vasodilatation value of 0.5% or less predicted intensive care unit mortality with a sensitivity of 79% (CI, 59-88%) and specificity of 98% (CI, 94-99%).

CONCLUSIONS

In vivo bedside assessment of endothelium-dependent vasodilatation is an independent predictor of mortality in the critically ill. We have shown it to be superior to other validated severity of illness scores with high sensitivity and specificity.

Role of marginal vitamin C deficiency in atherogenesis: in vivo models and clinical studies

Vitamin C is a pivotal redox modulater in many biological reactions of which several remain poorly understood. Naturally, vitamin C has been the subject of many investigations over the past decades in relation to its possible beneficial effects on cardiovascular disease primarily based on its powerful yet general antioxidant properties. However, growing epidemiological, clinical and experimental evidence now suggests a more specific role of ascorbate in vasomotion and in the prevention of atherosclerosis. For example, in contrast to most other biological antioxidants, administration of vitamin C can apparently induce vasodilation. Millions of people worldwide can be diagnosed with vitamin C deficiency according to accepted definitions. In this perspective, the present review examines the evidence for a specific link between vitamin C deficiency and increased risk of atherosclerosis as well as the possible mechanisms by which vitamin C may exert its protective function.

Supplements of l-arginine attenuate the effects of high-fat meal on endothelial function and oxidative stress

BACKGROUND

Postprandial hypertriglyceridemia is known to cause endothelial dysfunction and increased oxidative stress. Oral supplements of l-arginine have been found to improve endothelial function. However, the effects of supplements of l-arginine on the influences of postprandial hypertriglyceridemia were not studied before.

METHODS

Forty young healthy men without any risk factors were equally divided into two groups. l-arginine group (age 22+/-1 years, body mass index 23.5+/-1.2 kg/m(2)) received a standard high-fat meal with 15 g oral l-arginine. Control group (age 22+/-1 years, body mass index 23.8+/-0.9 kg/m(2)) received a standard high-fat meal with placebo. A standard high-fat meal consisted of 900 kcal and 50 g of fat. Flow-mediated vasodilation (FMD), von Willebrand factor (vWF), p-Selectin, and glutathione peroxidase (GSH-Px) were measured before and 2 h after the high-fat meal.

RESULTS

Serum triglyceride levels were significantly increased 2 h after the high-fat meal in both groups. In the control group, FMD (10.5+/-1.2% vs. 6.8+/-1.4%, p<0.001) and GSH-Px (23.5+/-6.2 vs. 21.9+/-5.0 mug/ml, p=0.029) were significantly decreased after the high-fat meal. P-Selectin (20.0+/-7.7 vs. 25.9+/-10.5 mg/l, p=0.025) and vWF (731.2+/-131.5 vs. 934.9+/-133.8 mU/ml, p<0.001) were significantly increased after the high-fat meal. In the l-arginine group, FMD (10.3+/-1.3 vs. 9.3+/-0.9%, p<0.001) was slightly but significantly decreased after the high-fat meal but not GSH-Px (23.6+/-3.6 vs. 23.0+/-4.8%, p=0.468). P-Selectin (20.1+/-5.9 vs. 25.7+/-10.2 mg/l, p=0.001) and vWF (793.2+/-146.0 vs. 944.4+/-136.8 mU/ml, p<0.001) were significantly increased after the high-fat meal. Degree of FMD attenuation following the high-fat meal was significantly less in the l-arginine group (1.0+/-0.9 vs. 3.8+/-1.5%, p<0.001).

CONCLUSIONS

Concomitant supplements of l-arginine improved endothelial dysfunction and oxidative stress induced by postprandial hypertriglyceridemia. However, changes of p-Selectin and vWF were not affected by supplements of l-arginine with the high-fat meal.

Effect of fatty acids on endothelium-dependent relaxation in the rabbit aorta

The metabolic syndrome, Type II (non-insulin-dependent) diabetes and obesity are associated with endothelial dysfunction and increased plasma concentrations of NEFAs (non-esterified fatty acids; free fatty acids). The present study was undertaken to define the inhibitory effects of saturated NEFAs on EDR (endothelium-dependent relaxation). Experiments were performed in rings of rabbit aorta to establish (i) dose-response relationships, (ii) the effect of chain length, (iii) the effect of the presence of double bonds, (iv) reversibility and time course of inhibition, and (v) the effect on nitric oxide production. Aortic rings were incubated (1 h) with NEFA-albumin complexes derived from lauric (C(12:0)), myristic (C(14:0)), palmitic (C(16:0)), stearic (C(18:0)) and linolenic (C(18:3)) acids. EDR induced by acetylcholine (0.1-10 mumol/l) was measured after pre-contraction with noradrenaline. Inhibition of EDR was dose-dependent (0.5-2 mmol/l NEFA), and the greatest inhibition (51%) was observed with stearic acid (2 mmol/l). Lauric acid had the smallest inhibitory effect. The inhibitory effects were always reversible and were evident after 15 min of incubation. Linolenic acid caused a significantly lower inhibition of EDR than stearic acid. SOD (superoxide dismutase) restored the inhibitory effect caused by NEFAs, suggesting the involvement of ROS (reactive oxygen species) in removing nitric oxide. The nitric oxide concentration measured after exposure of the rings to acetylcholine was lower after incubation with NEFAs than with Krebs buffer alone. This finding is consistent with removal of nitric oxide by ROS. This claim was supported by the demonstration of increased concentrations of nitrated tyrosine in the rings incubated with NEFAs.

Molecular mechanisms of lipid-induced insulin resistance in muscle, liver and vasculature

Increased body fat content correlates with insulin resistance and is a key feature of type 2 diabetes. Excessive intake of fat results in deposition of lipids not only in fat tissue but also in skeletal muscle and liver. Subsequently, both plasma and intracellular concentrations of free fatty acids and their metabolites rise and activate signal transduction pathways, which will induce inflammation and impair insulin signalling. Furthermore, elevated circulating lipids impair endothelial function and fibrinolysis, which contributes to the development of vascular disease. Thus, therapeutic strategies aiming at reduction of (intracellular) lipid availability in skeletal muscle and liver and pharmacological modulation of the signalling pathways activated by increased lipid stores represent promising targets for future treatment of insulin resistance and prevention of its complications. This review focuses on the effects of increased lipid availability on the regulation of glucose metabolism in skeletal muscle and liver as well as on vascular function.

Effects of Intralipid infusion on hemorheology and peripheral resistance in neonates and children

Deleterious microcirculatory effects of Intralipid (IL) infusion may be caused by hemorheological or vascular effects. The aim of this investigation was to study vascular and hemorheological effects of IL in preterm and fullterm neonates and children. Ten preterm newborns, 10 fullterm neonates, and 10 children received an initial infusion of IL (0.6 g/kg) over 4 h. Calf blood flow (venous occlusion plethysmography), blood pressure (Dinamap), whole blood and plasma viscosity (capillary viscometer), red blood cell deformability (rheoscope), and erythrocyte aggregation (aggregometer) were measured before and after administration of IL. Plasma triglyceride levels showed the greatest increase in preterm infants. Whole blood viscosity decreased by about 10% in all three groups because of a similar reduction in hematocrit. Red blood cell aggregation decreased by about 20% after IL infusion. Blood pressure rose by 10%, and peripheral blood flow declined by about 10% in the three groups. Vascular hindrance, a calculation of blood pressure divided by blood flow and viscosity, was raised by about 20%, suggesting marked vasoconstriction of peripheral arteries. Vasoconstriction rather than hemorheological changes during infusion of IL may play a crucial role in the pathogenesis of circulatory alterations in parenterally-fed neonates.

Acute elevations of medium- and long-chain fatty acid have different impacts on endothelium-dependent vasodilation in humans

It has previously been shown that acute elevation of long-chain fatty acids (LCFA) impairs endothelium-dependent vasodilation (EDV) in humans. In this study, we tested the hypothesis that an elevation of both medium-chain fatty acids (MCFA) and LCFA affects the endothelium differently from LCFA elevation alone. Ten healthy volunteers received an intravenous infusion of Structolipid (structured TG, MCFA/LCFA ratio 1:1) and heparin for 2 h, while another 10 subjects received an infusion of Intralipid (LCFA only) and heparin. EDV and endothelium-independent vasodilation (EIDV) were studied in the forearm after local administration of methacholine chloride (2 and 4 microg/min) and sodium nitroprusside (5 and 10 microg/min). Forearm blood flow was determined by venous occlusion plethysmography. Intralipid and heparin increased circulating FA levels from 0.2 +/- 0.1 to 1.4 +/- 0.5 mmol/L (P < 0.001) and reduced EDV by 20% (P < 0.01). Although Structolipid and heparin increased circulating FA levels to a similar extent (from 0.4 +/- 0.1 to 1.8 +/- 0.4 mmol/L after 2 h), EDV was not significantly changed. EIDV increased slightly during both interventions (P < 0.05). In conclusion, an acute elevation of LCFA attenuated EDV, whereas an elevation of both MCFA and LCFA did not influence EDV. Thus, FA composition seems to be of importance for EDV in healthy humans.