Measurement of protein carbonyls in plasma of smokers and in oxidized LDL by an ELISA.
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Adult↗
Biomedical subjects
I Jialal
Publications and source records attributed to I Jialal.
alpha-Tocopherol enrichment of monocytes decreases agonist-induced adhesion to human endothelial cells.
BACKGROUND: Monocyte-endothelium adhesion is a crucial early event in atherogenesis. Several reports indicate that alpha-tocopherol (AT) is a potent antioxidant in plasma and LDL and also has intracellular effects that are antiatherogenic. Recently, it has been shown that AT supplementation results in decreased monocyte-endothelial cell adhesion. However, there is a paucity of data on the mechanisms by which AT inhibits adhesion of monocytes. We studied the effect of AT enrichment of a human monocytic cell line, U937, on adhesion to human umbilical vein endothelial cells (HUVECs). METHODS AND RESULTS: Both lipopolysaccharide (LPS)- and N-formyl-methionyl-leucyl-phenylalanine (FMLP)-stimulated U937 adhesion to HUVECs were studied. AT (50 and 100 micromol/L) significantly decreased adhesion of both LPS- and FMLP-stimulated U937 cells to HUVECs (LPS-treated cells, P<0.0125; FMLP-treated cells, P<0.05). Expression of the adhesion molecules CD11a, CD11b, CD11c, very late antigen-4 (VLA-4), and L-selectin, as assessed by flow cytometry, was increased in the stimulated U937 cells, and AT resulted in significant reduction in the expression of CD11b and VLA-4. In addition, activation of the transcription factor nuclear factor-kappaB (NF-kappaB), as assessed by gel shift assays, was inhibited by pretreatment with AT in LPS-treated U937 cells. CONCLUSIONS: AT significantly decreases adhesion of activated monocytes to endothelial cells by decreasing expression of CD11b and VLA-4 on monocytes, possibly by inhibiting the activation of NF-kappaB.
Cell Adhesion↗
Effects of increasing doses of alpha-tocopherol in providing protection of low-density lipoprotein from oxidation.
In this study, we tested whether 1,200 IU/day of alpha-tocopherol was more potent than 400 and 800 IU of alpha-tocopherol in decreasing low-density lipoprotein (LDL) oxidative susceptibility in a 2-month study. The decrease in LDL oxidation was significantly greater with 1,200 IU/day than 400 IU/day.
Antioxidants↗
Remnant-like particle cholesterol levels in patients with dysbetalipoproteinemia or coronary artery disease.
PURPOSE: Several studies have provided support for a proatherogenic role for remnant lipoproteins. Thus, the aim of this study was to compare remnant-like particle (RLP) cholesterol levels in patients with coronary artery disease who were normolipidemic with those in controls of similar age and gender. We also assessed the usefulness of measuring RLP-cholesterol levels in patients with type III dyslipidemia. SUBJECTS AND METHODS: Remnant-like particle cholesterol levels were measured in 63 normolipidemic men with coronary artery disease and 23 male controls of similar age as well as in 15 patients with type III dyslipidemia and 103 controls, using an immunoaffinity method. RESULTS: Remnant-like particle cholesterol levels were significantly increased in men with coronary artery disease compared with controls (7.6 +/- 3.8 mg/dL versus 5.7 +/- 1.9 mg/dL, P < 0.01). In patients with coronary artery disease, RLP-cholesterol levels were correlated with total triglyceride and nonhigh-density-lipoprotein (HDL) cholesterol levels, but not with HDL-cholesterol levels. RLP-cholesterol levels were significantly elevated in patients with type III dyslipidemia (median 119, range 31 to 240 mg/dL) compared with controls (median 5.6, range 2.2 to 10.5 mg/dL, P < 0.001). CONCLUSION: Normolipidemic men with coronary artery disease have increased levels of RLP-cholesterol that is not detected with conventional lipid screening. The RLP-cholesterol assay is a simple method for detecting high concentrations of remnant lipoproteins in patients with type III dyslipidemia.
Adult↗
Detection of oligoclonal bands in cerebrospinal fluid by immunofixation electrophoresis.
Multiple sclerosis is a severe demyelinating disease, the diagnosis of which is aided by biochemical tests, such as detection of oligoclonal immunoglobulin bands in the cerebrospinal fluid (CSF). Because interpretation of agarose gel electrophoresis (AGE) of CSF for oligoclonal bands is often equivocal, we compared immunofixation electrophoresis (IFE) with AGE for 124 consecutive CSF specimens submitted to the Parkland Memorial Hospital Clinical Chemistry Laboratory (Dallas, Tex) for detection of oligoclonal bands. Both methods used the Paragon Electrophoresis Systems (Beckman Instruments, Brea, Calif). Anti-IgG antisera was used exclusively on all specimens. Oligoclonal bands were identified in 23 specimens (18.5%), while the other 101 (81.5%) were interpreted as negative by both methods. Of the positive specimens, 17 (74%) were positive by both methods, 5 (22%) by IFE alone, and 1 (4%) by AGE alone. Of the 23 patients with positive specimens represented, 17 (74%) had been given a diagnosis of multiple sclerosis. The patient whose specimen was positive by AGE alone had a diagnosis of HIV infection with Guillain-Barré syndrome. The sensitivities (with 95% confidence intervals) of IFE and AGE were 73.9% (51.3-88.9) and 56.5% (34.9-76.1), respectively. The specificities of both methods were identical at 95.0% (88.3-98.2). Subjective assessment of the gels demonstrated that the IFE method is consistently easier to interpret than AGE. The IFE method seems to be superior in identifying oligoclonal bands and thus aiding in diagnosis of demyelinating disorders.
Acquired Immunodeficiency Syndrome↗
Evaluation of a rapid homogeneous method for direct measurement of high-density lipoprotein cholesterol.
We evaluated the performance of a direct Liquid N-geneous HDL-C assay (N-HDL; Genzyme Diagnostics, Cambridge, Mass) and compared it with a Centers for Disease Control and Prevention (CDC) modified reference procedure (M-REF) and phosphotungstic acid (PTA) precipitation method in patients with normotriglyceridemia (triglyceride level, <400 mg/dL) and hypertriglyceridemia (triglyceride level, > or =400 mg/dL). Excellent intra-assay and interassay coefficients of variation were obtained (<2.0%) using the N-HDL assay. The N-HDL and PTA assays correlated well with M-REF in normotriglyceridemic samples. In hypertriglyceridemic samples, however, the N-HDL method exhibited better correlation with M-REF than the PTA assay. In addition, compared with M-REF, the mean absolute percentage bias of N-HDL was lower than the PTA assay in normotriglyceridemic (4.9% vs 5.8%) and hypertriglyceridemic (5.4% vs 12.9%) samples. Hemolysis, ascorbic acid, and bilirubin did not interfere with the N-HDL assay. On the basis of these findings, the N-HDL assay compares favorably with the modified CDC reference method and seems superior to the PTA assay. It also has the advantage of being suited for complete automation and, thus, would prove useful in large clinical laboratories.
Cholesterol, HDL↗
The effects of alpha-tocopherol on critical cells in atherogenesis.
Low levels of alpha tocopherol have been associated with increased risk for coronary artery disease and increased intake has been shown to be protective. Data support a proatherogenic role for oxidized LDL in atherosclerosis and several studies show that alpha tocopherol decreases the susceptibility of LDL to oxidation. In addition, alpha tocopherol can partition in the artery wall in critical cells such as smooth muscle cells, monocyte-macrophages, endothelial cells, and platelets, exerting beneficial effects. In this review, the anti-atherogenic effects of alpha tocopherol on crucial cells in atherogenesis have been highlighted, such as the inhibition of smooth muscle cell proliferation, preservation of endothelial function, inhibition of monocyte-endothelial adhesion, inhibition of monocyte reactive oxygen species and cytokine release, and inhibition of platelet adhesion and aggregation.
Arteriosclerosis↗
Evolving lipoprotein risk factors: lipoprotein(a) and oxidized low-density lipoprotein.
Cardiovascular disease is the leading cause of morbidity and mortality in Westernized populations. Evolving lipoprotein risk factors include LDL oxidation and lipoprotein(a) [lp(a)]. Several lines of evidence support a role for oxidatively modified LDL in atherogenesis and its in vivo existence. There are both direct and indirect measures of oxidative stress. The most relevant direct measure of lipid peroxidation is urinary F2 isoprostanes. The most common indirect measure of LDL oxidation is quantifying the lag phase of copper-catalyzed LDL oxidation by assaying conjugated diene formation. Lp(a) is increased in patients with cardiovascular and cerebrovascular disease. However, not all prospective studies have confirmed a positive relationship between Lp(a) and cardiovascular events. Lp(a) appears to present three major problems: standardization of the assay, establishing its role in atherogenesis, and the lack of an effective therapy that can substantially lower Lp(a) concentrations. Thus, at the present time, Lp(a) concentrations should not be recommended for the general population but be reserved for patients with coronary artery disease without established risk factors, young patients with coronary artery disease or cerebrovascular disease, or a family history of premature atherosclerosis and family members of an index patient with increased concentrations of Lp(a). Although both LDL oxidation and Lp(a) are evolving risk factors for cardiovascular disease, more data are needed before they become part of the established lipoprotein repertoire.
Animals↗
Comparison of 2 homogeneous high-density lipoprotein cholesterol assays.
BACKGROUND: High-density lipoprotein cholesterol (HDL-C) is an independent inverse risk factor for coronary artery disease. Current methodologies for measurement of HDL-C in most clinical laboratories involve chemical precipitation-based methods. However, these methods are time-consuming, affected by high triglycerides, are not suitable for complete automation, and require a large sample size. New direct homogeneous methods are now available that do not have these constraints. DESIGN: We evaluated the performance of 2 direct homogeneous methods, Liquid N-geneous HDL-C assay (LN-HDL) and Boehringer Mannheim HDL Cholesterol assay (BM-HDL), and compared these methods against a modified Centers for Disease Control and Prevention reference method (MR-HDL) in 126 patients with normotriglyceridemia (triglycerides < 4.5 mmol/L, range 0.6-4.3 mmol/ L) and 50 patients with hypertriglyceridemia (triglycerides > or =4.5 mmol/L, range 4.5-18.8 mmol/L). RESULTS: Excellent precision profiles were exhibited by both homogeneous methods. Both LN-HDL and BM-HDL correlated well with MR-HDL in normotriglyceridemia (r = 0.98, slope = 0.93 and r = 0.97, slope = 1.0, respectively). However, compared with the modified reference method, the LN-HDL correlated better than the BM-HDL in hypertriglyceridemic samples (r = 0.97, slope = 1.0 and r = 0.91, slope = 0.9, respectively). The 1998 National Cholesterol Education Program guidelines for accuracy (bias < +/-5%) were met by LN-HDL in both normotriglyceridemic and hypertriglyceridemic samples (bias = 1.3% and 3.3%, respectively); however, BM-HDL failed to meet the National Cholesterol Education Program accuracy criteria in both triglyceride subgroups (bias = 8.2% and 11.3%, respectively). In addition, the total error for LN-HDL in both normotriglyceridemia (6.6%) and hypertriglyceridemia (8.6%) was well within the National Cholesterol Education Program guidelines for total error (< or =13%); BM-HDL exhibited a higher total error than LN-HDL in normotriglyceridemia (11.9%) and failed to meet the National Cholesterol Education Program guidelines in hypertriglyceridemia (15.0%). CONCLUSION: Although both homogeneous methods are precise, the LN-HDL assay is superior in accuracy to the BM-HDL assay when compared with the modified reference method.
Cholesterol↗
A more valid measurement of low-density lipoprotein cholesterol in diabetic patients.
PURPOSE: This study was conducted to determine if the direct low-density lipoprotein (LDL) cholesterol assay would provide a more valid measure of LDL cholesterol in diabetic patients compared with the Friedewald equation. PATIENTS AND METHODS: Fasting plasma from 148 diabetic patients, 40 with insulin-dependent diabetes (IDDM) and 108 with non-insulin dependent diabetes (NIDDM) with triglyceride levels < 400 mg/dL, were analyzed for LDL cholesterol using the Friedewald equation, the direct LDL assay, and beta-quantification. Forty-six diabetic patients with triglyceride levels > or = 400 mg/dL were also studied to determine the validity of the direct LDL cholesterol assay with hypertriglyceridemia. RESULTS: The friedewald equation and the direct LDL cholesterol assay correlated well with beta-quantification (r = 0.969 and r = 0.971, respectively) for LDL cholesterol determination in diabetic patients. Although the Friedewald equation in comparison with beta-quantification underestimated (8%) LDL cholesterol values in diabetic patients, the direct LDL cholesterol assay had a mean bias of < 1%. Also, the underestimation by the Friedewald equation exceeded 10% for the triglyceride subgroup of 200 to 400 mg/dL. Furthermore, the accuracy of the direct LDL cholesterol assay was superior to the Friedewald equation since LDL cholesterol levels determined by the two methods coincided within +/- 10% of beta-quantification in 85% and 68% of diabetic patients, respectively (P = 0.0005). Similar results for both the Friedewald equation and the direct LDL cholesterol assay in comparison with beta-quantification were seen when diabetic patients were subgrouped into IDDM and NIDDM. Also, the direct LDL cholesterol assay appeared to provide a reliable estimate in patients with triglycerides > or = 400 mg/dL. CONCLUSION: The results of our studies indicate that the direct LDL cholesterol assay is a more reliable and accurate method than the Friedewald formula for LDL cholesterol determination in diabetic patients and is more rapid and cost effective than the reference method.
Cholesterol, LDL↗
Bimonthly update: lipidology. Therapy and clinical trials.
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Anticholesteremic Agents↗
Dose-response comparison of RRR-alpha-tocopherol and all-racemic alpha-tocopherol on LDL oxidation.
Much data have accrued in support of the concept that oxidation of LDL is a key early step in atherogenesis. The most consistent data with respect to micronutrient antioxidants and atherosclerosis appear to relate to alpha-tocopherol (AT), the predominant lipid-soluble antioxidant in LDL. There are scant data on the direct comparison of RRR-AT and all-racemic (rac)-AT on LDL oxidizability. Hence, the aim of the present study was to examine the relative effects of RRR-AT and all-rac-AT on plasma antioxidant levels and LDL oxidation in healthy persons in a dose-response study. The effect of RRR-AT and all-rac-AT at doses of 100, 200, 400, and 800 IU/d on plasma and LDL AT levels and LDL oxidation was tested in a randomized, placebo-controlled study of 79 healthy subjects. Copper-catalyzed oxidation of LDL was monitored by measuring the formation of conjugated dienes and lipid peroxides over an 8-hour time course at baseline and again after 8 weeks. Plasma AT, lipid-standardized AT, and LDL AT levels rose in a dose-dependent fashion in both the RRR-AT and all-rac-AT groups compared with baseline. There were no significant differences in plasma, lipid-standardized, and LDL AT levels between RRR-AT and all-rac-AT supplementation at any dose comparison. The lag phases of oxidation were significantly prolonged with doses > or = 400 IU/d of RRR-AT and all-rac-AT, as measured by conjugated-dienes assay and at 400 IU/d of RRR-AT and 800 IU/d of both forms of AT by lipid peroxide assay. Again, there were no significant differences in the lag phase of oxidation at each dose for RRR-AT when compared with all-rac-AT. Also, there were no significant differences in LDL oxidation after in vitro enrichment of LDL with RRR-AT and all-rac-AT. Thus, supplementation with either RRR-AT or all-rac-AT resulted in similar increases in plasma and LDL AT levels at equivalent IU doses, and the degree of protection against copper-catalyzed LDL oxidation was only evident at doses > or = 400 IU/d for both forms.
Adult↗
Comparison of two assays for measuring LDL cholesterol.
The purpose of this study was to evaluate the LipiDirect assay (L-LDL) against the Direct LDL immunoseparation method (D-LDL) and beta quantification (BQ-LDL) for measurement of LDL cholesterol (LDL-C) in patients with normo- and hypertriglyceridemia. Samples from 156 patients [triglyceride (Tg) range 0.61-9.95 g/L] were assayed for LDL-C concentrations with the three methods. An additional seven patients with type III hyperlipidemia and 25 paired sera from fasting and nonfasting individuals also were analyzed by the three methods. Both assays displayed excellent precision. The mean LDL-C value from L-LDL was significantly higher than BQ-LDL and D-LDL in normo- and hypertriglyceridemic samples (P < 0.001). The mean absolute bias of L-LDL vs BQ-LDL was 12.7% for Tg < 4 g/L and 30.6% for Tg > or = 4 g/L, compared with 6.2% and 12.5%, respectively, for D-LDL. L-LDL correctly classified only 68% of patients with LDL-C < 1.30 g/L and 57% of patients with LDL-C between 1.30-1.59 g/L as compared with 98% and 93%, respectively, for D-LDL (P < 0.001). In patients with type III hyperlipidemia, L-LDL had a 130% positive bias with BQ-LDL as compared with a 14% negative bias for D-LDL. With all three methods there were no significant differences between samples from fasting and nonfasting individuals. On the basis of these findings, the D-LDL assay appears to be superior to the L-LDL assay.
Cholesterol, LDL↗
The effects of alpha tocopherol supplementation on monocyte function. Decreased lipid oxidation, interleukin 1 beta secretion, and monocyte adhesion to endothelium.
Low levels of alpha tocopherol are related to a higher incidence of cardiovascular disease and increased intake appears to afford protection against cardiovascular disease. In addition to decreasing LDL oxidation, alpha tocopherol may exert intracellular effects on cells crucial in atherogenesis, such as monocytes. Hence, the aim of this study was to test the effect of alpha tocopherol supplementation on monocyte function relevant to atherogenesis. Monocyte function was assessed in 21 healthy subjects at baseline, after 8 wk of supplementation with d-alpha tocopherol (1,200 IU/d) and after a 6-wk washout phase. The release of reactive oxygen species (superoxide anion, hydrogen peroxide), lipid oxidation, release of the potentially atherogenic cytokine, interleukin 1 beta, and monocyte-endothelial adhesion were studied in the resting state and after activation of the monocytes with lipopolysaccharide at 0, 8, and 14 wk. There was a 2.5-fold increase in plasma lipid-standardized and monocyte alpha tocopherol levels in the supplemented phase. After alpha tocopherol supplementation, there were significant decreases in release of reactive oxygen species, lipid oxidation, IL-1 beta secretion, and monocyte-endothelial cell adhesion, both in resting and activated cells compared with baseline and washout phases. Studies with the protein kinase C inhibitor, Calphostin C, suggest that the inhibition of reactive oxygen species release and lipid oxidation is due to an inhibition of protein kinase C activity by alpha tocopherol. Thus, this study provides novel evidence for an intracellular effect of alpha tocopherol in monocytes that is antiatherogenic.
Adult↗
Effect of ascorbate supplementation on low density lipoprotein oxidation in smokers.
The oxidative modification of low density lipoprotein (LDL) may play a role in the pathogenesis of atherosclerosis. Furthermore, evidence of oxidized LDL (ox-LDL) has been found in vivo. Supplementation of some animal models with antioxidants has been shown to retard the formation of aortic atherosclerosis. Ascorbate (vitamin C) is a highly potent aqueous-phase antioxidant in plasma, which has been shown in vitro to retard LDL oxidation. Cigarette smokers have reduced concentrations of ascorbate in their plasma, and their LDL may be more prone to oxidation. Hence, the objective of the present study was to examine the effect of ascorbate depletion and supplementation on the propensity of LDL to oxidize in smokers in a 6-week study. Nineteen healthy smokers followed a low ascorbate diet (< or = 30 mg/day) for 2 weeks, then were randomly assigned to receive placebo or 1000 mg ascorbate per day for 4 weeks. Blood was taken at 0 and 4 weeks of supplementation for study of LDL oxidative susceptibility. LDL was oxidized with 5 mumol/l copper. The ascorbate-supplemented group had significant increases in plasma ascorbate. The placebo group showed no change in the time course of LDL oxidation between 0 and 4 weeks. However, the ascorbate-supplemented group has a significant reduction in LDL oxidative susceptibility as measured by thiobarbituric acid-reactive substances (TBARS) and the formation of conjugated dienes. The ascorbate-supplemented group demonstrated significantly increased lag phase and decreased oxidation rate at 4 weeks compared to 0 weeks. No changes were found in the placebo group. The ascorbate-supplemented group showed no biochemical signs consistent with increased body iron stores. Supplementation of otherwise healthy smokers for 4 weeks with 1000 mg ascorbate per day resulted in increased plasma ascorbate and reduced LDL oxidative susceptibility.
Adult↗
Oxidized low-density lipoprotein and atherosclerosis.
Atherosclerosis is the leading cause of morbidity and mortality in western society. The most important risk factors for atherosclerosis include smoking, hypertension, dyslipidemia, diabetes and a family history of premature atherosclerosis. Several studies indicate that an increased plasma low density lipoprotein (LDL) cholesterol constitutes a major risk factor for atherosclerosis. Many data support a proatherogenic role for oxidized LDL, and its in vivo existence. The oxidative susceptibility of LDL is increased with established cardiovascular risk factors, such as diabetes, smoking and dyslipidemia. Supplementation with antioxidants such as ascorbate and alpha to copherol can decrease LDL oxidation as well as cardiovascular mortality and thus shows promise in the prevention of atherosclerosis
Antioxidants↗
Plasma oxidizability in Mexican-Americans and non-Hispanic whites.
Several lines of evidence support an atherogenic role for oxidized low-density lipoprotein (LDL). Previous studies have suggested that although Mexican-Americans have an increased rate of diabetes, obesity, elevated triglyceride levels, and low high-density lipoprotein (HDL) cholesterol levels, their rates of coronary heart disease (CHD) are similar or possibly lower than in non-Hispanic whites. Mexican-Americans have smaller, denser LDL than non-Hispanic whites. On the basis of this latter observation, we postulated that lipid peroxide (LPO) levels would be increased in Mexican-Americans. We examined the oxidizability of plasma in 50 Mexican-Americans and 50 non-Hispanic whites from the San Antonio Heart Study, a population-based study of diabetes and cardiovascular disease, at baseline and after coincubation with a metal-independent system (2'2'-azobis-2-amidinopropane hydrochloride [AAPH]) and a metal-dependent system (Fe2+/H2O2) of oxidation. LPO levels were measured by a modified fluorimetric assay. Vitamin E and plasma fatty acid composition were also determined. We found significantly higher LPO levels at baseline and after AAPH coincubation in Mexican-Americans than in non-Hispanic whites (baseline, 2.75 +/- .09 v 2.07 +/- .09 micromol/L, P < .001; post-AAPH, 5.49 +/- .14 v 5.07 +/-. .04 micromol/L, P = .037). However, no significant ethnic differences were seen after coincubation with Fe2+/H2O2. Diabetes and cigarette-smoking were also associated with higher LPO levels. Mexican-Americans also had lower levels of vitamin E (the predominant lipid-soluble antioxidant in plasma) than non-Hispanic whites, although these differences only partially explained the differences in susceptibility to oxidation. Plasma fatty acids were similar in Mexican-Americans and non-Hispanic whites, suggesting only small differences in diet composition. We conclude that LPO levels are higher in Mexican-Americans than in non-Hispanic whites, and that these results are only partially related to differences in vitamin E levels.
Adult↗
Oxidatively modified LDL and atherosclerosis: an evolving plausible scenario.
Much evidence has accumulated that implicates the oxidative modification of low-density lipoprotein (LDL) in the early stages of atherogenesis. The antioxidant nutrients alpha-tocopherol, ascorbic acid, and betacarotene have been shown to inhibit in vitro LDL oxidation. In addition, they have been shown to increase the resistance of LDL to oxidation when given to animals and humans. Because plasma levels of these nutrients can be increased by dietary supplementation with minimal side effects, they may show promise in the prevention of coronary artery disease.
Antioxidants↗