Endothelial Function In Hypercholesterolemia Research Articles

Protective effect of insulin-like growth factor-1 on vascular endothelial function in hypercholesterolemia and the underlying mechanism

To investigate the relationship between insulin-like growth factor-1 (IGF-1) in the serum and the vascular endothelial function in patients with hypercholesterolemia and the underlying mechanism. We examined the flow-mediated arterial diastolic function (FMD), the levels of IGF-1, asymmetric dimethylarginine (ADMA), NO, and the activity of nitric oxide synthase (NOS) in the serum from 25 patients with hypercholesterolemia and from healthy controls. An endothelial cell injury model was established by incubation of the human umbical vein endothelial cells (HUVECs) with oxidized low-density lipoprotein (ox-LDL) for 24 hours. Cells were treated with IGF-1 30 min before ox-LDL treatment. The levels of ADMA, NOS, and NO in the cell supernatant, the activity of dimethylarginine dimethylamine hydrolase (DDAH) in the cell lysate were measured. Beta-galactosidase staining was used to assess the degree of endothelial cell senescence by calculating the senescence rate of cells. Compared with the control group, the FMD, the levels of IGF-1 and NO, and the activity of NOS in the serum from patients with hypercholesterolemia decreased significantly accompanied with a dramatic increase at ADMA level. Multiple linear regression analysis showed that the change in IGF-1 was positively correlated with FMD while the change in ADMA was negatively correlated with FMD. Compared with the control group, ox-LDL treatments significantly decreased the activities of DDAH and NOS, and the level of NO, accompanied with an increase in ADMA. Betagalactosidase staining showed that the senescence rate of cells increased in the ox-LDL group. The effect of ox-LDL on HUVECs was significantly attenuated at the presence of IGF-1. The decrease in IGF-1 in the peripheral blood may contribute to vascular endothelial dysfunction in patients with hypercholesterolemia. IGF-1 can protect HUVECs against ox-LDL-induced senescence, which is likely involved in the regulation of DDAH/ADMA pathway.

Impaired endothelial function may be due to decreased aortic tetrahydrobiopterin, assessed by a new flow-mediated vasodilation in vivo in hypercholesterolemic/atherogenic mice

Tetrahydrobiopterin (BH4) is an important cofactor for endothelial nitric oxide synthase activity. The relationship between endothelial function in vivo and aortic BH4 level is not fully understood, however. In the present study, we aimed to clarify whether reduction of aortic BH4 levels contributes to endothelial dysfunction in vivo using spontaneously hyperlipidemic mice. To estimate endothelial function in vivo and in real-time state, we developed a flow-mediated vasodilation (FMV) method in mice, which measured changes in the diameter of the femoral artery in response to increased blood flow. C57BL/6 mice and apoE/low-density lipoprotein receptor double knock-out mice were fed a low-fat diet (LFD) or a high-fat diet (HFD) for 12 weeks from 6 weeks of age. HFD feeding impaired FMV in double knock-out mice, but not in C57BL/6 mice. Furthermore, HFD feeding reduced plasma NOx concentration and aortic BH4 level in double knock-out mice. Conversely, exogenous injection of BH4 (2 mg/kg) markedly increased aortic BH4 levels and restored endothelial function. In conclusion, we demonstrated that HFD feeding impaired nitric oxide-mediated endothelial function and reduced BH4 level in vivo, and that acute augmentation of aortic BH4 levels improved endothelial function. These findings indicate that BH4 is a critical determinant of nitric oxide-mediated endothelial function in hypercholesterolemia.

Acute inhibition of the endogenous xanthine oxidase improves renal hemodynamics in hypercholesterolemic pigs

Hypercholesterolemia (HC), a major risk factor for onset and progression of renal disease, is associated with increased oxidative stress, potentially causing endothelial dysfunction. One of the sources of superoxide anion is xanthine oxidase (XO), but its contribution to renal endothelial function in HC remains unclear. We tested the hypothesis that XO modulates renal hemodynamics and endothelial function in HC pigs. Four groups (n = 23) of female domestic pigs were studied 12 wk after either normal (n = 11) or HC diet (n = 12). Oxidative stress was assessed by plasma isoprostanes and oxidized LDL, and the XO system by plasma uric acid, urinary xanthine, and renal XO expression (by immunoblotting and immunohistochemistry). Renal hemodynamics and function were studied with electron beam-computed tomography before and after endothelium-dependent (ACh) and -independent (sodium nitroprusside) challenge, during a concurrent intrarenal infusion of either oxypurinol or saline (n = 5-6 in each group). HC showed elevated oxidative stress, higher plasma uric acid (23.8 +/- 3.8 vs. 6.2 +/- 0.8 microM/mM creatinine, P = 0.001), lower urinary xanthine, and greater renal XO expression compared with normal. Inhibition of XO in HC significantly improved the blunted responses to ACh of cortical perfusion (13.5 +/- 12.1 and 37.2 +/- 10.6%, P = 0.01 and P = not significant vs. baseline, respectively), renal blood flow, and glomerular filtration rate; restored medullary perfusion; and improved the blunted cortical perfusion response to sodium nitroprusside. This study demonstrates that the endogenous XO system is activated in swine HC. Furthermore, it suggests an important role for XO in regulation of renal hemodynamics, function, and endothelial function in experimental HC.

Artichoke juice improves endothelial function in hyperlipemia

Artichoke extracts have been shown to produce various pharmacological effects, such as the inhibition of cholesterol biosynthesis and of LDL oxidation. Endothelial dysfunction represents the first stage of atherosclerotic disease; it is usually evaluated in humans by a noninvasive ultrasound method as brachial flow-mediated vasodilation (FMV) and by the determination of several humoral markers such as vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and E-selectin. Aim of the study was to investigate the effects of dietary supplementation with artichoke juice on brachial FMV of hyperlipemics. We studied 18 moderately hyperlipemic patients (LDL cholesterol > 130 <200 mg/dl and/or triglycerides >150 <250 mg/dl) of both genders and 10 hyperlipemic patients, matched for age, sex and lipid parameters. All subjects were under isocaloric hypolipidic diet. A basal determination of serum lipids, soluble VCAM-1, ICAM-1, E-selectin and brachial FMV was performed. Thereafter patients were given 20 ml/die of frozen artichoke juice. The same parameters were repeated after 6 weeks. After artichoke treatment there was an increase of triglycerides (156 ± 54 vs 165 ± 76 mg/dL, p < 0.05) and a reduction of total cholesterol (261 ± 37 vs 244 ± 38 mg/dL, p < 0.05) and LDL cholesterol (174 ± 31 vs 160 ± 34 mg/dL, p < 0.05). Controls showed a significant decrease in total and LDL cholesterol (respectively: 267 ± 22 vs 249 ± 20 mg/dL and 180 ± 24 vs 164 ± 23 mg/dL, both p < 0.001). After artichoke there was a decrease in VCAM-1(1633 ± 1293 vs 1139 ± 883 ng/mL, p < 0.05) and ICAM-1(477 ± 123 vs 397 ± 102 ng/mL, p < 0.05), brachial FMV increased (3.3 ± 2.7 vs 4.5 ± 2.4%, p < 0.01), while controls did not exhibit significant changes in VCAM-1, ICAM-1, E-selectin and brachial FMV. Univariate analysis showed that, in artichoke patients, changes of VCAM-1 and ICAM-1 were significantly related to changes in brachial FMV (respectively: r = −0.66 and r = −0.62; both p < 0.05). In conclusion, artichoke dietary supplementation seems to positively modulate endothelial function in hypercholesterolemia.

Long-term treatment with nifedipine modulates procoagulant marker and C-C chemokine in hypertensive patients with type 2 diabetes mellitus

In type 2 diabetes mellitus, there is increased risk of nephropathy and cardiovascular complications and the incidence of renal failure increases in advanced stages of the disease. Nifedipine, a dihydropyridine-type calcium antagonist, improves endothelial function in hypercholesterolemia by enhancing nitric oxide function, and increases endothelial nitric oxide bioavailability by antioxidative mechanisms. We administered nifedipine, 50 mg/day, to the hypertensive patients for 12 months. There were no other changes in any of the patient's pharmacologic regimen during nifedipine treatment. Clinical and biochemical data obtained before and after nifedipine administration were compared. All markers were measured by ELISA. The levels of platelet activation markers (CD62P, CD63, PAC-1, and Annexin V), microparticles (PDMP and MDMP), RANTES and soluble adhesion markers (sP-selectin and sVCAM-1) differed in the control group and the hypertension group. The levels of these markers were also different in hypertensive patients with and without type 2 diabetes but were unchanged in patients without diabetes in comparison to the control group. However, the concentrations of MDMPs, chemokines, and soluble adhesion markers in hypertensive patients without type 2 diabetes decreased significantly following nifedipine treatment, although the level of RANTES was unchanged. Systolic blood pressure correlated with CD62P, CD63, annexin V, and RANTES levels, and diastolic blood pressure with CD62P and annexin V levels. The effect of nifedipine on platelet activation markers and C-C chemokines in the present study indicates potential effectiveness of calcium antagonist therapy for hypertensive patients with type 2 diabetes.

Antioxidant improves smooth muscle sarco/endoplasmic reticulum Ca(2+)-ATPase function and lowers tyrosine nitration in hypercholesterolemia and improves nitric oxide-induced relaxation.

Antioxidants improve endothelial function in hypercholesterolemia (HC); however, whether this includes improvement of the vascular smooth muscle response to NO is unknown. NO relaxes arteries, in part, by stimulating Ca(2+) uptake via sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) in aortic smooth muscle, and HC impairs SERCA function and the response to NO. HC induces oxidative stress, which could impair SERCA function. To study the effect of antioxidants, which are known to improve endothelium-dependent relaxation in HC, smooth muscle SERCA activity and NO-induced relaxation were studied in rabbits fed normal chow or a 0.5% cholesterol diet for 13 weeks. The antioxidant t-butylhydroxytoluene (BHT, 1%) was mixed with the HC diet in the last 3 weeks. HC impaired acetylcholine- and NO-induced relaxation, and these were restored by BHT. After inhibiting SERCA with thapsigargin, no difference existed in NO-induced relaxation among the three groups. Reduced aortic SERCA activity in HC was restored by BHT without changing SERCA protein expression. 3-Nitrotyrosine was notably increased in the media of the HC aorta, where it colocalized with SERCA. Tyrosine-nitrated SERCA protein was immunoprecipitated in the aortas of HC rabbits, where it was decreased by BHT, and it was also detected in the aortas of atherosclerotic humans. Thus, the antioxidant reverses impaired smooth muscle SERCA function in HC, and this is correlated with the improved relaxation to NO. These beneficial effects may depend on reducing the direct effects on SERCA of reactive oxygen species that are augmented in HC.

Simvastatin preserves coronary endothelial function in hypercholesterolemia in the absence of lipid lowering.

Recent evidence suggests that some benefit from the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors may occur independent of lipid lowering. We aimed to determine the effect of simvastatin on coronary endothelial function, endothelial NO synthase (eNOS) expression, and oxidative stress in experimental hypercholesterolemia (HC) in the absence of cholesterol lowering. Pigs were randomized to 3 experimental groups: normal diet (N group), high cholesterol diet (HC group), and HC diet with simvastatin (HC+S group) for 12 weeks. Low density lipoprotein cholesterol was similarly increased in the HC and HC+S groups compared with the N group. In vitro analysis of coronary large- and small-vessel endothelium-dependent vasorelaxation was performed. The mean vasorelaxation of epicardial vessels to bradykinin was significantly attenuated in the HC group compared with the N group (32.3+/-1.2% versus 42.9+/-1.6%, respectively; P<0.0001). This attenuation was significantly reversed in the HC+S group (38.7+/-1.5%, P<0.005 versus HC group). The maximal vasorelaxation to substance P was significantly attenuated in the HC group compared with the N group (50.5+/-11.9% versus 79.3+/-5.3%, respectively; P<0.05). This attenuated response was normalized in the HC+S group (74.9+/-4.1%, P<0.05 versus HC group). The maximal arteriolar vasorelaxation to bradykinin was also significantly attenuated in the HC group compared with the N group (71.9+/-4.9% versus 96.8+/-1.34%, respectively; P<0.005). This was reversed in the HC+S group (98.4+/-0.6%, P<0.0001 versus HC group). Western blotting of coronary tissue homogenates for eNOS demonstrated a decrease in protein levels in the HC group compared with the N group, with normalization in the HC+S group. Elevation of plasma F(2)-isoprostanes and thiobarbituric acid-reactive substances, markers of oxidative stress, occurred in the HC compared with the N group. These changes were reversed in the HC+S group. In summary, simvastatin preserves endothelial function in coronary epicardial vessels and arterioles in experimental HC (in the absence of cholesterol lowering) in association with an increase in coronary eNOS levels and a decrease in oxidative stress. These alterations may play a role in the reduction in cardiac events after treatment with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors.

Nifedipine improves endothelial function in hypercholesterolemia, independently of an effect on blood pressure or plasma lipids.

Dihydropyridine calcium antagonists have been shown to retard atherogenesis in animal models and to prevent the development of early angiographic lesions in human coronary arteries. Endothelial dysfunction is an early event in the pathogenesis of cardiovascular disease. We investigated whether nifedipine could improve endothelial function in hypercholesterolemia, independently of changes in blood pressure or plasma lipids. First, we compared in vivo forearm vascular responses to the endothelium-dependent and independent vasodilators serotonin (5-HT) and sodium nitroprusside (SNP) in 11 patients with familial hypercholesterolemia before and after 6-weeks treatment with nifedipine GITS (60 mg, OD) and in 12 matched controls. In a subgroup of six control subjects forearm vascular function was also assessed before and after 6-weeks nifedipine GITS treatment. In vitro, we subsequently explored possible mechanisms underlying the effect of nifedipine on endothelial function. We investigated the effects of nifedipine on both NO production by recombinant endothelial NO synthase (eNOS) and endothelial cells, using 3H-arginine conversion, as well as on superoxide generation by endothelial cell lysates, using lucigenin enhanced chemiluminescence. In hypercholesterolemia 5-HT-induced vasodilation was impaired (47 +/- 9% increase in forearm bloodflow vs. 99 +/- 8% in controls). Treatment with nifedipine completely restored 5-HT-induced vasodilation (113 +/- 13%), whereas it did not influence basal forearm vasomotion or SNP-induced vasodilation. Nifedipine did not alter forearm vascular responses in control subjects and did not alter blood pressure or plasma lipids. In vitro, we found no direct effect of nifedipine on NO production by recombinant eNOS or endothelial cells. However, we did observe a reduction in endothelial superoxide generation. Our data show that nifedipine improves endothelial function in hypercholesterolemia. It is suggested from our in vitro experiments that this effect is due to reduced NO degradation.

Combination of vitamins C and E alters the response to coronary balloon injury in the pig.

Restenosis is the major limitation of the long-term success of percutaneous transluminal coronary angioplasty. The process of restenosis involves repair of vascular injury and remodeling of vessel architecture. Therapeutic interventions that improve vascular function may therefore be beneficial in the treatment of restenosis. Antioxidants such as probucol and vitamins C and E have proved effective in improving endothelial function in hypercholesterolemia, inhibiting lipid accumulation in animal models of atherosclerosis, and decreasing cardiovascular mortality in humans. Forty-two female domestic swine were divided into four study groups: control (n = 12); vitamin C (500 mg/d, group C, n = 9); vitamin E (1000 U/d, group E, n = 10); and vitamins C and E (500 mg/d + 1000 U/d, group C+E, n = 11) before oversized balloon injury of the left anterior descending and circumflex coronary arteries. Vitamins were administered 7 days before balloon injury and continued until the swine were killed 14 days after injury. Significant differences in morphometric parameters were present only in group C+E, with increases in vessel and lumen area in the segment with maximal injury. Although there was no decrease in intima area or in maximal intima thickness, the ratio of intima area to vessel area was significantly reduced, consistent with a positive effect in group C+E. Graphic analysis of the relationship between initial vessel injury (using internal elastic lamina fracture length/lumen perimeter) and vessel response to injury (using intima area/vessel area) for all segments showed improved indices for group C+E (P < .005). The beneficial effect of vitamins correlated with changes in lipid redox state. Low-density lipoprotein (LDL) thiobarbituric acid-reactive substances showed an approximately 70% decrease in all treatment groups, and the lag phase for LDL-conjugated diene formation was significantly increased, with group C+E > group E > group C. The combination of vitamins C and E improved vascular response to injury because of an apparent beneficial effect on vascular remodeling. The fact that the combination of vitamins C+E was better than vitamin E or vitamin C alone is consistent with the ability of vitamin C to improve the antioxidant effect of vitamin E, suggesting that the improved vessel response was due to a change in redox state. This study suggests an important role for oxygen radicals in the vascular response to injury and suggests that vascular remodeling and intimal proliferation are important to the restenotic process.