Development of new enzyme-linked immunosorbent assay for oxidized lipoprotein(a) by using purified human oxidized lipoprotein(a) autoantibodies as capture antibody

Elevated serum β2-glycoprotein-I-lipoprotein(a) complexes levels are associated with the presence and complications in type 2 diabetes mellitus

AIMS

To examine the serum levels of β2-glycoprotein I-lipoprotein(a) complexes [β2-GPI-Lp(a)] in type 2 diabetes mellitus (T2DM) patients and evaluate the association of the complexes with complications in T2DM.

METHODS

Fifty two T2DM patients (22 with complications and 30 free of complications) and 52 age/gender-matched healthy controls were studied. Serum concentrations of β2-GPI-Lp(a) and ox-Lp(a) were measured by "sandwich" ELISAs and their associations with complications were examined using multiple linear regression.

RESULTS

Mean serum β2-GPI-Lp(a) (1.19 ± 0.30 U/mL vs. 0.89 ± 0.20 U/mL, p<0.001) and ox-Lp(a) concentrations (13.34 ± 11.73 mg/L vs. 5.26 ± 3.34 mg/L, p<0.001) were both significantly higher in T2DM than in controls. The area under the ROC curve (AUC) for β2-GPI-Lp(a) and ox-Lp(a) was 0.725 and 0.738, respectively. β2-GPI-Lp(a) levels were markedly higher in patients with complications than those without complication (1.39 ± 0.28 U/mL vs. 1.04 ± 0.31 U/mL, p<0.01), whereas no marked difference was found in ox-Lp(a). In multivariate regression analysis, the association between β2-GPI-Lp(a) and complications remained significant (β=0.249, p<0.05, respectively) after adjustments were made for other traits.

CONCLUSIONS

Elevated β2-GPI-Lp(a) may reflect chronic underlying pathophysiological processes involved in development of complications of T2DM.

Increased serum levels of β₂-GPI-Lp(a) complexes and their association with premature atherosclerosis in patients with rheumatoid arthritis

BACKGROUND

Our recent study found the existence of complexes of β₂-glycoprotein I (β₂-GPI) with lipoprotein(a)[Lp(a)] in circulation and the complex concentrations were increased in sera of systemic lupus erythematosus patients. The concentration of β₂-GPI-Lp(a) and its relationship with premature atherosclerosis were evaluated in rheumatoid arthritis (RA) patients.

METHODS

Serum concentrations of β₂-GPI-Lp(a) were measured in 53 active RA patients and 40 healthy controls by a "sandwich" ELISA. β₂-GPI-ox-LDL, ox-Lp(a), ox-LDL and anti-β₂-GPI were also measured by ELISAs. In addition, inflammatory markers were examined.

RESULTS

Serum β₂-GPI-Lp(a) (1.12±0.25 U/ml vs. 0.87±0.19 U/ml, P<0.0001) and β₂-GPI-ox-LDL (1.01±0.20 U/ml vs. 0.80±0.08 U/ml, P<0.0001) concentrations in RA were both significantly higher than those of controls. Ox-Lp(a) (8.38±6.69 mg/l vs. 5.49±4.31 mg/l, P<0.05) and ox-LDL (0.68±0.65 mg/l vs. 0.37±0.13 mg/l, P=0.001) were also higher in RA than in controls. The area under the ROC curve (AUC) for β₂-GPI-Lp(a) (0.787) was larger than for ox-Lp(a) (0.731). AUC of β₂-GPI-ox-LDL (0.858) was also larger than for ox-LDL (0.785). β₂-GPI-Lp(a) and β₂-GPI-ox-LDL were positively correlated with ox-Lp(a), ox-LDL and CRP, respectively.

CONCLUSIONS

β₂-GPI-Lp(a) complex concentrations increased in active RA. Inflammation and oxidative stress in RA contribute to the increase of ox-Lp(a) and subsequently the formation of β₂-GPI-Lp(a).

The association between blood glucose and oxidized lipoprotein(a) in healthy young women

Background

Oxidized lipoproteins play important roles in the atherosclerotic processes. Oxidized lipoprotein(a) (oxLp(a)) may be more potent in atherosclerotic pathophysiology than native Lp(a), a cardiovascular disease-relevant lipoprotein. Increased blood glucose concentrations can induce oxidative modification of lipoproteins. The aim of this study was to investigate the association between circulating oxLp(a) and cardiometabolic variables including blood glucose in healthy volunteers within the normal range of blood glucose.

Methods

Several cardiometabolic variables and serum oxLp(a) (using an ELISA system) were measured among 70 healthy females (mean age, 22 years).

Results

Lp(a) and glucose were significantly and positively correlated with oxLp(a) in simple correlation test. Furthermore, a multiple linear regression analysis showed oxLp(a) to have a weakly, but significantly positive and independent correlation with only blood glucose (β = 0.269, P < 0.05).

Conclusions

These results suggest that increased glucose may enhance the oxidization of Lp(a) even at normal glucose levels.

Percutaneous coronary intervention results in acute increases in native and oxidized lipoprotein(a) in patients with acute coronary syndrome and stable coronary artery disease

OBJECTIVE

To investigate possible changes of native and oxidized lipoprotein(a) [ox-Lp(a)] levels after percutaneous coronary intervention (PCI).

DESIGN AND METHODS

Lp(a), ox-Lp(a), and Lp(a) immune complexes (IC) and autoantibody levels were studied in 111 patients with acute coronary syndrome (ACS) and 68 patients with stable coronary artery disease (CAD) before and after PCI.

RESULTS

Compared with pre-PCI, Lp(a), ox-Lp(a), and Lp(a)-IC levels acutely increased, while the autoantibody decreased in both the ACS and stable CAD patients. They all returned toward baseline by 1 to 2 days. The absolute change of ox-Lp(a) was found positively related with both the diameter of stenosis (R=0.273, P=0.004) and the number of vessel disease (R=0.312, P=0.001) in the ACS patients, while not in the stable CAD patients.

CONCLUSION

PCI results in acute plasma increases of ox-Lp(a) and Lp(a). Ox-Lp(a) may be present in ruptured or permeable plaques and be released into the circulation by PCI.

Elevated concentrations of oxidized lipoprotein(a) are associated with the presence and severity of acute coronary syndromes

OBJECTIVE

To investigate possible mechanisms and association of increased oxidized Lp(a) [ox-Lp(a)] levels with presence and extent of acute coronary syndromes (ACS).

METHODS

Ox-Lp(a) levels were studied in 96 patients with ACS, 89 patients with stable coronary artery disease (CAD), and 100 control subjects.

RESULTS

Compared to control, ox-Lp(a) levels increased in stable CAD patients (P<0.001), and especially in ACS (P<0.001) (ACS, 16.29+/-13.80 microg/ml; stable CAD, 10.04+/-10.32 microg/ml; control, 7.10+/-9.16 microg/ml). The ratio of ox-Lp(a) to Lp(a) was higher in the ACS than those in the stable CAD (P<0.05) and control (P<0.001). Ox-Lp(a) levels were found associated with a graded increase in extent of angiographically documented CAD in the ACS (R=0.275, P=0.007), while not in the stable CAD (R=0.090, P=0.402). Multiple linear regression analysis found ox-Lp(a) (beta=0.271, P=0.019), age (beta=0.244, P=0.038) and TG (beta=0.213, P=0.070) accounted for 11.1% of the variation in the extent of angiographically documented CAD in ACS patients; Lp(a) (beta=0.415, P=0.000) and extent of CAD (beta=0.193, P=0.071) accounted for 21.5% of that in ox-Lp(a) levels.

CONCLUSION

Elevated ox-Lp(a) levels are associated with presence and severity of ACS, and may be useful for identification of patients with ACS.

Plasma oxidized lipoprotein(a) and its immune complexes are present in newborns and children

BACKGROUND

Oxidized Lp(a) [ox-Lp(a)] has been reported to play more potent roles than native Lp(a) in atherosclerosis. We investigated the distribution characteristics of plasma ox-Lp(a) and Lp(a) immune complex [Lp(a)-IC] levels in newborns and children.

METHODS

Plasma ox-Lp(a) and Lp(a)-IC levels were measured in 747 children and 30 cord blood by ELISAs.

RESULTS

The mean levels of Lp(a), ox-Lp(a) and Lp(a)-IC were much lower in newborns than in children (P<0.001), and increased rapidly to that in children after birth. The distributions of Lp(a), ox-Lp(a) and Lp(a)-IC were skewed toward low values in children, no difference of their levels was found in each of the 13year groups. The levels of ox-Lp(a) correlated positively with total and LDL cholesterol, Lp(a) and Lp(a)-IC; Lp(a)-IC correlated positively with sex, total and LDL cholesterol, Lp(a) and ox-Lp(a), respectively. Multiple linear regression analysis showed Lp(a) and Lp(a)-IC accounted for 42% of the variation in ox-Lp(a) levels, and ox-Lp(a) accounted for 30% of that in Lp(a)-IC.

CONCLUSIONS

The fact that ox-Lp(a) and Lp(a)-IC are present in newborns and children suggests that oxidized lipoproteins play an initiating role in atherosclerotic process.

Native, oxidized lipoprotein(a) and lipoprotein(a) immune complex in patients with active and inactive rheumatoid arthritis: plasma concentrations and relationship to inflammation

BACKGROUND

Several studies suggest that lipoprotein (a) [Lp(a)] act as acute phase reactant and be associated with early atherosclerosis in rheumatoid arthritis (RA). Oxidized Lp(a) [ox-Lp(a)] and Lp(a) immune complex (IC) concentrations both increased in patients with coronary heart disease. We investigated Lp(a), ox-Lp(a) and Lp(a)-IC concentrations in RA patients and to explore the relationships with inflammatory disease activity markers.

METHODS

Plasma Lp(a), ox-Lp(a) and Lp(a)-IC concentrations, and inflammatory markers were analyzed in 54 patients with RA, including 23 active and 21 inactive RA, and 60 control subjects.

RESULTS

Lp(a) and ox-Lp(a) concentrations in active RA were higher than those in both inactive RA and control; Lp(a)-IC concentrations in active RA were also higher than inactive RA, while no difference was found in Lp(a), ox-Lp(a) and Lp(a)-IC concentrations between inactive RA and control. Lp(a) concentrations were found positively correlated with ox-Lp(a) and Lp(a)-IC concentrations, respectively; ox-Lp(a) concentrations were also related with Lp(a)-IC. Lp(a), ox-Lp(a) and Lp(a)-IC were all found positively related with C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), respectively.

CONCLUSIONS

Native, oxidized Lp(a) and Lp(a)-IC concentrations increased in active RA patients. Inflammation may induce the changes of Lp(a), resulting in increased ox-Lp(a) and Lp(a)-IC, and may play an important role in atherosclerosis.