Oxidation of remnant-like particles from serum of diabetic patients, patients with ischemic heart disease and normal subjects

Atherogenic postprandial remnant lipoproteins; VLDL remnants as a causal factor in atherosclerosis

Oxidized LDL (Ox-LDL) and chylomicron (CM) remnants have been suggested to be the most atherogenic lipoproteins that initiate and exacerbate coronary atherosclerosis. In this review, we propose a hypothesis of the causal lipoproteins in atherosclerosis based on our recent findings on postprandial remnant lipoproteins (RLP). Plasma RLP-C and RLP-TG increased significantly after food intake, especially a fat load. More than 80% of the TG increase after the fat load consisted of the TG in RLP, which contained significantly greater apoB100 than apoB48 particles as VLDL remnants. The majority of the LPL in non-heparin plasma was found in RLP as an RLP-LPL complex and released into the circulation after hydrolysis. Plasma LPL did not increase after food intake, which may have caused the partial hydrolysis of CM and VLDL as well as the significant increase of RLP-TG in the postprandial plasma. LPL was inversely correlated with the RLP particle size after food intake. We showed that VLDL remnants are the major atherogenic lipoproteins in the postprandial plasma associated with insufficient LPL activity and a causal factor in the initiation and progression of atherosclerosis. We also propose "LPL bound TG-rich lipoproteins" as a new definition of remnant lipoproteins based on the findings of the RLP-LPL complex in the non-heparin plasma.

Immunological detection of large oxidized lipoproteins in hypertriglyceridemic serum

BACKGROUND

Triglyceride-rich, low-density lipoproteins (TG-rich LDL) have been reported as an oxidized lipoprotein species in patients with severe liver disease. Using TG-rich LDL as an immunogen, we obtained a monoclonal antibody (G11-6) that reacted with TG-rich LDL from patients with liver disease and with metal-oxidized LDL only in the early process of the oxidation reaction. This study determined the G11-6-reactive lipoproteins in hypertriglyceridemic serum.

METHODS

Serum samples from healthy volunteers (n = 12) and hypertriglyceridemic patients (n = 9) were fractionated by gel filtration and subjected to a sandwich enzyme-linked immunosorbent assay (ELISA) using G11-6 and polyclonal anti-apolipoprotein B antibodies.

RESULTS

Small LDL and larger lipoproteins reacted with G11-6. G11-6-reactive small LDL was identified in both the healthy subjects and hypertriglyceridemic patients, whereas G11-6-reactive larger lipoproteins were found only in the hypertriglyceridemic patients.

CONCLUSIONS

G11-6 is a useful tool for detecting increased large oxidized lipoproteins in hypertriglyceridemic patients.

The oxidative modification hypothesis of atherosclerosis: The comparison of atherogenic effects on oxidized LDL and remnant lipoproteins in plasma

A tremendous number of articles on oxidized LDL (Ox-LDL) and scavenger receptor in macrophage have been published since Steinberg proposed Ox-LDL hypothesis as the major cause of atherosclerosis. This hypothesis has provided strong support for the efficacy of LDL lowering drugs, indicating that lowering LDL means lowering Ox-LDL in vivo. This manuscript proposed a new oxidative modification hypothesis that remnant lipoproteins determined as remnant-like lipoprotein particles (RLP), not LDL are the major oxidized lipoproteins in plasma, resulting from the plasma concentration of these oxidized lipoproteins. Remnant lipoproteins may play a pivotal role for the initiation of atherosclerosis via lectin-like oxidized LDL receptor-1 (LOX-1) in endothelial cells. Isolated remnant lipoproteins were found to be oxidized or susceptible to be oxidized in plasma, not necessary to be further oxidized in vitro as Ox-LDL. High similarity of proatherogenic and proinflammatory properties of isolated Ox-LDL and remnant lipoporteins have been reported and predicted the presence of similar oxidized phospholipids in both lipoproteins as bioactive components. These results suggest the possibility that reducing plasma remnant lipoproteins rather than LDL should be the target for hyperlipidemic therapy especially in patients with metabolic syndrome for the prevention of endothelial dysfunction in the initiation of atherosclerosis.

Postprandial Increase in Plasma Concentrations of Remnant-Like Particles: An Independent Risk Factor for Restenosis after Percutaneous Coronary Intervention

Postprandial increase in remnant lipoprotein concentrations has been suggested as an important atherogenic factor. However, the influence of these remnants on the development of restenosis after percutaneous coronary intervention (PCI) remains to be examined. The present study was designed to address this point. In 60 consecutive patients with successful PCI, the influences of possible risk factors on the development of restenosis, including remnant-like particles (RLP) cholesterol (RLP-C) and triglyceride (RLP-TG), were examined. While mean concentrations of RLP-C and RLP-TG were normal in fasting state, postprandial change in RLP-C concentrations was a significant and independent risk factor for restenosis after PCI. The calculated cut-off index (COI) for the change was +64%. When the patients were divided into 2 groups according to this COI, minimal lumen diameter (MLD) and reference coronary diameter were comparable before and immediately after PCI between the high- (COI < 64%) and the low- (COI < 64%) responders. However, follow-up coronary angiography 3 to 6 months after PCI demonstrated that MLD, late loss, and loss index were all worse in the high responders compared with the low responders. These results indicate that post-prandial increase in RLP-C concentrations is an independent risk factor for restenosis after successful PCI, even in patients with normal fasting RLP-C levels.

Exhaled carbon monoxide levels elevated in diabetes and correlated with glucose concentration in blood: a new test for monitoring the disease?

PURPOSE

In diabetes, the interaction of glycated proteins with their cell-surface binding sites leads to oxidative stress and induction of the stress protein heme oxygenase (HO)-1. Considering that carbon monoxide (CO) is a product of HO activity, we studied the level of exhaled CO as a marker of oxidative stress in diabetes.

METHODS

Eight patients with insulin-dependent diabetes mellitus (type 1) (4 men, 4 women; [mean +/- SEM] age, 50 +/- 8 years) were studied, of whom 2 had peripheral neuropathy and 1 had renal failure. Sixteen patients with non-insulin-dependent diabetes mellitus (type 2) (5 men, 11 women; age 63 +/- 8 years) were studied, of whom 2 had peripheral neuropathy. Glycosylated hemoglobin (HbA(1)c) levels were higher (7.4 +/- 0.3%) in patients with type 1 (mean duration of the disease, 20 +/- 5 years) than in type 2 (4.9 +/- 0.4%; p < 0.05; mean duration of the disease, 11 +/- 2 years). All of the patients were lifelong nonsmokers.

RESULTS

Levels of exhaled CO were higher in patients with diabetes (type 1, 4.0 +/- 0.7 ppm; type 2, 5.0 +/- 0.4 ppm) when compared to 37 nonsmoking healthy subjects (20 men, 17 women; age, 33 +/- 3 years) (2.9 +/- 0.2 ppm; p < 0.05). There was a positive correlation between exhaled CO levels and the incidence of glycemia in all subjects (r = 0.52, p < 0.05) and the duration of diabetes (r = 0.48, p < 0.05), but there was not a strong correlation with concentrations of HbA(1)c (r = 0.06, p = 0.8). In addition, an oral glucose tolerance test was performed in five healthy nonsmoking volunteers (three men; age, 33 +/- 4 years). The maximal glucose increase (from 3.9 +/- 0.2 to 5.5 +/- 0.1 mmol/L at 15 min; p < 0.05) was associated with a significant increase in exhaled CO concentration (from 3.0 +/- 0.5 to 6.3 +/- 1.0 ppm; p < 0. 05). Both parameters returned to the baseline at 40 min after glucose administration.

CONCLUSIONS

Elevated levels of exhaled CO in diabetes may reflect HO-1 induction and oxidative stress. The measurement of CO may be a new tool for disease monitoring.