Aim: The critical role of hyperinsulinemia, independent of hyperglycemia, in the pathogenesis of atherosclerosis has not been fully determined. We investigated the association between secretion patterns of insulin after oral glucose load and the severity of coronary artery disease (CAD) in patients with normal glucose tolerance (NGT). Methods: We enrolled 116 subjects with NGT from 243 patients who had undergone coronary angiography and a standard 75-g oral glucose tolerance test. The patients were divided into 0-vessel, single-vessel and multi-vessel disease groups on the basis of the severity of CAD. Results: The 2-h insulin levels in the multi-vessel disease group (p=0.005) and the single-vessel disease group (p<0.05) were significantly higher than those in the 0-vessel disease group. Multivariate analysis revealed that the levels of 2-h insulin were an independent variable for the presence of CAD (p=0.02) after adjustment for gender and the presence of each criterion of metabolic syndrome using the definition of the International Diabetes Federation. Conclusion: A slight but significant increase in prolonged insulin secretion, which is associated with the early stage of insulin resistance, in subjects with NGT, may play an important role in the pathogenesis of atherosclerosis.
Aim: Macrophage migration inhibitory factor (MIF) is known as a pro-inflammatory cytokine that regulates a broad spectrum of inflammatory reactions. MIF is expressed in vascular smooth muscle cells (VSMCs), and inhibition of the progression of atherosclerosis was observed in MIF-deficient atherosclerotic mice. However, the functional role of MIF in VSMCs has not been elucidated. The aim of this study was to investigate the role of MIF on the migration of VSMCs. Methods: Cultured rat A10 cells, derived from rat embryonic aortic smooth muscle cells, were stimulated with oxLDL, and the effect of MIF knockdown on oxLDL-mediated migration of A10 cells was analyzed. Results: Intracellular MIF content was significantly increased and a marked increase of MIF concent-ration was observed in the supernatant of A10 cells treated with oxLDL. The migration of A10 cells was significantly accelerated by the stimulation of recombinant MIF in a dose-dependent manner. Notably, knockdown of intracellular MIF by siRNA abolished oxLDL-induced migration of A10 cells. Conclusion: These findings suggest that MIF acts on the migration of VSMCs in an autocrine and paracrine fashion. MIF appears to be a novel target for the prevention of cardiovascular events.
Aim: ApoA-I and HDL promote cellular cholesterol efflux in the early stages of the reverse cholesterol transport (RCT) pathway. A low plasma HDL-C level is characteristic of atherogenic dyslipidemia in patients with type 2 diabetes. We evaluated plasma lipid levels and the expression of factors related to RCT in type 2 diabetic patients, and the effects of an HMG-CoA reductase inhibitor, simvastatin, were studied. Methods: Messenger RNA (mRNA) expression in circulating mononuclear cells was analyzed by reverse transcription-polymerase chain reaction (RT-PCR), focusing on the following factors: liver X receptor α (LXR α), ATP-binding cassette A1 (ABCA1), scavenger receptor class B type 1 (SR-B1), apolipoprotein E (ApoE), apolipoprotein A-1 (ApoA-1), caveolin, and cholesterol ester transfer protein (CETP). Type 2 diabetic subjects (n=29) were divided into three subgroups: patients with normolipidemia (DM group, n=11), patients with untreated hyperlipidemia (DMHL group, n=10), and those with hyperlipidemia treated with simvastatin 5-10mg/day (DMST group, n=8). The control group (CNT group) included seven healthy volunteers. Results: Simvastatin treatment significantly increased plasma levels of ApoA-I compared to the other three groups. Simvastatin treatment improved the expression of mRNA for LXRα, ABCA1, and ApoA-I compared with DMHL or control groups. Conclusion: Our data suggest that RCT may be reduced in type 2 diabetic patients with hyperlipidemia, and simvastatin may be able to improve reverse cholesterol transport for this population of diabetic patients.
Aim: Atherosclerotic lesions are reported to be hypoxic. Since hypoxia is known to induce the production of growth factors, such as vascular endothelial growth factor (VEGF), we examined the implication of hypoxia-induced VEGF in the proliferation of human coronary artery smooth muscle cells (CASMCs). Methods: Cells were cultured under hypoxic conditions (1% O2, 5% CO2) and several responses were measured. Results: Under hypoxic conditions, the mRNA and protein levels of VEGF, and the mRNA level of VEGF receptor-1 (VEGFR-1) increased with an increase in hypoxia-inducible factor-1α (HIF-1α) protein, and considerable amounts of VEGF were secreted. Hypoxia enhanced the incorporation of [3H]-thymidine by CASMCs, which was completely inhibited by a neutralizing antibody against VEGF. A neutralizing antibody against NADPH-cytochrome P-450 reductase (NPR), which contributes to the stabilization of HIF-1α, also attenuated hypoxia-stimulated proliferation. In NPR-knockdown cells, the expression of VEGF, proliferation, and transcriptional activity were attenuated, whereas in NPR-overexpressing cells, they were enhanced. Conclusion: Hypoxia-induced proliferation of CASMCs is mediated through the expressions of VEGF and VEGFR-1 in an autocrine mechanism. Their expressions are dependent on the stabilization of HIF-1α, which is regulated by NPR. We suggest that hypoxia and hypoxia-induced VEGF expression are involved in the pathogenesis of progressive atherosclerosis.
Aim: The aim of this study was to evaluate the anti-atherogenic outcomes of pioglitazone, a thiazolidinedione derivative, in type 2 diabetic patients. Methods: Eight patients with poor diabetic control were treated with 15 mg of pioglitazone for 4 months. Blood samples were collected monthly, and the levels of fasting plasma glucose (FPG), HbA1c, and lipids, such as triglycerides, total cholesterol, low-density lipoprotein-cholesterol, and high-density lipoprotein-cholesterol, were measured. Other parameters, including immunorecative insulin (IRI), remnant-like particle-cholesterol (RLP-C), adiponectin, plasminogen activator inhibitor type 1 (PAI-1), tumor necrosis factor (TNF)- α , leptin, brain natriuretic peptide (BNP), and high-sensitivity (hs)-C-reactive protein (CRP), were examined at the beginning and end of the study. In addition, clinically adverse side-effects were evaluated. Results: Treatment with pioglitazone significantly decreased the levels of HbA1c, FPG, the homeostasis model assessment of insulin resistance (HOMA-IR) index, RLP-C, PAI-1, TNF- α , and hs-CRP, but not the level, IRI, lipids, or leptin. In contrast, adverse side-effects, including body weight gain, liver dysfunction and edema, were not observed during this study. Conclusion: These results strongly suggested that treatment with pioglitazone has a greater clinical benefit for the prevention of atherosclerosis, including coronary heart diseases, without any adverse side-effects.
Aim: Preβ1-HDL is involved in the initial step of cholesterol efflux from peripheral cells and plays an important role in reverse cholesterol transport. We studied the effect of pitavastatin on the HDL subfraction profile, preβ1-HDL concentration and its disappearance rate. Methods: Twenty-nine hypercholesterolemic patients were treated with pitavastatin at 2 mg/day for 4 weeks, and plasma levels of total cholesterol (TC), triglyceride, HDL-cholesterol (C), HDL2-C, HDL3-C, preβ1-HDL, LCAT activity, and CETP mass were assayed. The preβ1-HDL disappearance rate was determined as the difference in preβ1-HDL concentration before and after incubation at 37°C for 90 min divided by the pre-incubation preβ1-HDL concentration. Results: Pitavastatin led to significant decreases in TC by 26.9% and LDL-C by 39.8%. HDL-C and HDL2-C increased significantly by 6.0% and 9.0%, respectively, but there was no significant change in HDL3-C. Preβ1-HDL concentration significantly decreased (-8.7%; p<0.05); however, its disappearance rate significantly increased (13.0%; p<0.05). There were significant decreases in both LCAT activity and CETP mass. Conclusion: Although pitavastatin decreased plasma preβ1-HDL concentration, it increased the preβ1-HDL disappearance rate. These data suggest that pitavastatin might promote the early step of reverse cholesterol transport.