High levels of IgM against methylglyoxal-modified apolipoprotein B100 are associated with less coronary artery calcification in patients with type 2 diabetes

OBJECTIVE

  Advanced glycation end products (AGE) have been implicated in diabetic vascular complications through activation of pro-inflammatory genes. AGE-modified proteins are also targeted by the immune system resulting in the generation of AGE-specific autoantibodies, but the association of these immune responses with diabetic vasculopathy remains to be fully elucidated. The aim of this study was to determine whether antibodies against apolipoprotein B100 modified by methylglyoxal (MGO-apoB100) are associated with coronary atherosclerosis in patients with type 2 diabetes.

METHODS

  We measured antibodies against MGO-apoB100 in plasma from 497 type 2 diabetic patients without clinical signs of cardiovascular disease. Severity of coronary disease was assessed as coronary artery calcium (CAC) imaging. Immunoglobulin (Ig)M and IgG levels recognizing MGO-apoB100 were determined by enzyme-linked immunosorbent assay.

RESULTS

  Anti-MGO-apoB100 IgM antibody levels were higher in subjects with a low to moderate CAC score (≤400 Agatston units) than in subjects with a high score (>400 Agatston units; 136.8±4.4 vs. 101.6± 7.4 arbitrary units (AU), P<0.0001) and in subjects demonstrating no progression of CAC during 30 months of follow-up (136.4±5.7 vs. 113.9 ± 6.2 AU in subjects with progression, P<0.0001). Subjects with a family history of premature myocardial infarction had lower levels of anti-MGO-apoB100 IgM. Female subjects had higher levels of anti-MGO-apoB100 antibodies and lower CAC than men. Accordingly, high levels of IgM against MGO-apoB100 are associated with less severe and a lower risk of progression of coronary disease in subjects with type 2 diabetes.

CONCLUSIONS

Although conclusions regarding causal relationships based on epidemiological observations need to be made with caution, our findings suggest the possibility that anti-MGO-apoB100 IgM may be protective in diabetic vasculopathy.

Effects of intensive insulin therapy alone and in combination with pioglitazone on body weight, composition, distribution and liver fat content in patients with type 2 diabetes

AIM

To evaluate the effects of intensive insulin therapy alone and with added pioglitazone on body weight, fat distribution, lean body mass (LBM) and liver fat in type 2 diabetic patients.

METHODS

Twenty-five insulin-treated, obese patients with type 2 diabetes were randomized to addition of pioglitazone 45 mg (n = 12) or placebo (n = 13) and treated intensively for 12-16 weeks. Dual-energy X-ray absorptiometry/abdominal computed tomography scans were performed before/after treatment. LBM, visceral/subcutaneous adipose tissue (VAT/SAT) and liver/spleen (L/S) attenuation ratios were measured pre-/posttreatment (a ratio <1 represents fatty liver).

RESULTS

Intensive insulin alone and insulin + pioglitazone significantly improved glycaemic control (7.8 ± 0.3 to 7.2 ± 0.3% and 7.6 ± 0.3 to 7.1 ± 0.4%, respectively). Body weight gain was greater with insulin + pioglitazone (4.9 ± 4.5 kg) versus insulin therapy alone (1.7 ± 0.7 kg). SAT increased significantly with pioglitazone + insulin therapy (393.9 ± 48.5 to 443.2 ± 56.7 cm(2) , p < 0.01) compared to a non-significant increase with insulin therapy alone (412.9 ± 42.5 to 420.8 ± 43.8 cm(2) ). VAT decreased non-significantly in both groups (240.3 ± 41.7 to 223.8 ± 38.1 cm(2) with insulin + pioglitazone and 266.6 ± 27.4 to 250.5 ± 22.2 cm(2) with insulin therapy). LBM increased significantly by 1.92 ± 0.74 kg with insulin + pioglitazone treatment. The L/S attenuation ratio in the placebo + insulin group decreased from 1.08 ± 0.1 to 1.04 ± 0.1 (p = ns) and increased from 1.00 ± 0.1 to 1.08 ± 0.05 (p = 0.06) in the pioglitazone + insulin group.

CONCLUSIONS

Intensification of insulin therapy in type 2 diabetic patients causes modest weight gain and no change in body fat distribution, LBM or liver fat. In contrast, the addition of pioglitazone, at equivalent glycaemia, increases weight gain, fat mass and SAT; increases LBM and tends to decrease liver fat. These changes in fat distribution may contribute to the beneficial effects of pioglitazone, despite greater weight gain.

Vaccines modulating lipoprotein autoimmunity as a possible future therapy for cardiovascular disease

Current strategies for prevention of cardiovascular disease focus on risk factor intervention. Although these have been proven both safe and effective results from randomized clinical trials suggest that it is difficult to achieve relative risk reductions exceeding 40% with this approach. To further improve efficacy future therapies must aim at targeting the actual disease process in the arterial wall. Emerging evidence have identified an important role of the immune system in atherosclerosis and suggest that modulation of autoimmune responses against oxidized LDL and other antigens in the atherosclerotic plaque represent one possible new approach to disease prevention. Oxidized LDL is targeted by both antibody-mediated and cellular immune responses and as much as 10% of the T cells in atherosclerotic plaques are oxidized LDL-specific. Immune activation in the atherosclerotic plaque is primarily of the pro-inflammatory Th1-type and inhibition Th1 immunity reduces atherosclerosis in experimental animals. Atherosclerosis vaccines based on antigens derived from LDL have been developed to modulate these processes. Their mechanisms of action remain to be full characterized but may involve expression of protective antibodies that facilitate the removal of oxidized LDL and antigen-specific regulatory T cells that counteract Th1 autoimmunity against oxidized LDL. In this review we will discuss the possibilities and challenges encountering the translation of immune-modulatory therapy for atherosclerosis from the experimental stage into the clinic.

Associations between autoantibodies against apolipoprotein B-100 peptides and vascular complications in patients with type 2 diabetes

AIMS/HYPOTHESIS

Oxidation of LDL in the arterial extracellular matrix is a key event in the development of atherosclerosis and autoantibodies against oxidised LDL antigens reflect disease severity and the risk of developing acute cardiovascular events. Since type 2 diabetes is associated with increased oxidative stress, we tested the hypothesis that autoantibodies against oxidised LDL antigens are biomarkers for vascular complications in diabetes.

METHODS

We studied 497 patients with type 2 diabetes without clinical signs of coronary heart disease. Oxidised LDL autoantibodies were determined by ELISA detecting IgG and IgM specific for native and malondialdehyde (MDA)-modified apolipoprotein B-100 peptides p45 and p210. The severity of coronary disease was assessed as the coronary artery calcium score.

RESULTS

Patients affected by retinopathy had significantly higher levels of IgG against MDA-p45 and MDA-p210. In contrast, high levels of autoantibodies against the corresponding native peptides were associated with less coronary calcification and a lower risk of progression of coronary disease.

CONCLUSIONS/INTERPRETATION

Our observations suggest that LDL oxidation is involved in the pathogenesis of diabetic retinopathy and that autoantibodies against apolipoprotein B peptides may act as biomarkers for both micro- and macrovascular complications in diabetes.

Anatomical and visual outcome of stages 4 and 5 retinopathy of prematurity

AIM

To describe our experience in surgical management of stages 4 and 5 retinopathy of prematurity (ROP) and assess its anatomical and visual outcome.

MATERIALS AND METHODS

This study is a retrospective, interventional, consecutive case series. It involved 33 eyes of 29 infants. The data were retrieved retrospectively for each case from their medical records. All the eyes underwent primary vitrectomy with additional procedures like scleral buckling (two eyes), lensectomy (14 eyes), subretinal fluid drainage (two eyes), and one case of corneal transplant (open sky vitrectomy). The anatomical and visual outcome was reviewed at the final follow-up.

RESULTS

The mean gestational age was 29.7 weeks (range 25-34 weeks) and mean birth weight was 1332 g (range 650-2050 g). Anatomical success for stage 4A was defined as complete retinal attachment with undistorted or minimally distorted posterior pole. For stage 4B, partial residual retinal detachment and for stage 5 at least posterior pole attachment. Visual acuity was measured in anatomically successful eyes that were cooperative. The anatomical outcome was 90% (9/10 eyes) for stage 4A, 44.4% (4/9 eyes) for stage 4B, and 14.3% (2/14) for stage 5. The mean follow-up was 19.1 months. Posterior retinotomy was the commonest complication for stage 4B (66.7%).

CONCLUSION

Anatomical and visual success was the best for stage 4A ROP. Surgery for stage 4A can halt progression to stages 4B or 5 ROP. Aggressive peeling of posterior membranes should be avoided for stage 4B. Anatomical and visual outcome is very poor for stage 5.

Apolipoprotein A-I/HDL Infusion Therapy for Plaque Stabilization-Regression: A Novel Therapeutic Approach

LDL-lowering therapies, predominantly involving statins, have been shown to significantly reduce cardiovascular events in asymptomatic subjects as well as in subjects with clinically established atherosclerotic cardiovascular disease. However, despite statin therapy, significant number of cardiovascular events continue to occur indicating the need for additional targets for atherosclerosis management. A number of pre-clinical studies have suggested that several HDL based therapies have the potential to stabilize or regress atherosclerosis consistent with epidemiologic evidence of an inverse relationship between coronary heart disease and HDL cholesterol levels. One such therapeutic approach involves direct infusion of HDL or HDL like molecules for rapid remodeling and stabilization of atherosclerosis. Pre-clinical and proof of concept type preliminary clinical studies suggest the feasibility and potential efficacy of this emerging new therapeutic paradigm.

Haplotypes in the lipoprotein lipase gene influence high-density lipoprotein cholesterol response to statin therapy and progression of atherosclerosis in coronary artery bypass grafts

Lipoprotein lipase (LPL) hydrolyzes circulating triglycerides (TGs). We previously showed that 3'-end haplotypes in the LPL gene influence atherosclerosis and insulin resistance. This study asked whether these LPL haplotypes influence response to lipid-lowering therapy among 829 subjects from the Post-Coronary Artery Bypass Graft trial. Lipid profiles were obtained at baseline and 4-5 years after treatment with lovastatin. Haplotypes were based on 12 SNPs. The fourth most frequent haplotype, 12-4, was associated with a decreased increment in high-density lipoprotein-cholesterol (HDL-C) following treatment. Haplotypes 12-6, 12-7 and 12-8 were each associated with increased HDL-C response to therapy, and haplotype 12-2 with decreased TG response. The most common haplotype, 12-1, was protective against graft worsening or occlusion. Haplotype 12-4 reduced HDL-C response to lovastatin, possibly consistent with our prior observations of this haplotype as predisposing to coronary artery disease. LPL may influence atherosclerosis risk through pleiotropic effects on each aspect of the metabolic syndrome.

Increasing High-Density Lipoprotein Cholesterol in Dyslipidemia by Cholesteryl Ester Transfer Protein Inhibition

Reduced HDL cholesterol may be a risk factor comparable in importance to increased LDL cholesterol. Interventions that raise HDL are antiatherosclerotic, presumably through acceleration of reverse cholesterol transport and by antioxidant and antiinflammatory effects. In the hypercholesterolemic rabbit, HDL levels can be increased by >50% by inhibition of cholesteryl ester transfer protein (CETP), a molecule that plays a central role in HDL metabolism. This HDL-raising effect is antiatherosclerotic in moderately severe hyperlipidemia but appears to be ineffective in the presence of severe hypertriglyceridemia. In humans, mutations resulting in CETP inhibition have been associated with both reduced and increased risk of atherosclerosis. Proposed explanations for these apparently disparate observations are that the antiatherosclerotic effect of CETP inhibition varies with either the metabolic milieu or the degree of CETP inhibition. We now have pharmacological inhibitors of CETP that are capable of increasing HDL by as much as 50% to 100% in humans. The importance of this development is that reduced HDL is a risk factor independent of LDL and that these new agents alter HDL by a magnitude comparable to that of statins on LDL. Clinical trials, now beginning, will need to identify the patient subsets in which CETP inhibition may be more or less effective.

Platelet-induced expression of tissue factor procoagulant activity in freshly isolated human mononuclear cells: implications for experimental use

Monocytes express tissue factor (TF) as a result of cytokine stimulation or endothelial adherence. We evaluated monocyte-platelet interaction in vitro as another trigger for monocyte TF enhancement in human mononuclear cells isolated by density gradient centrifugation from peripheral blood. Cell TF procoagulant activity (TF-PCA) was quantitated by a one-stage recalcification clotting time assay. Platelets were counted and identified by whole blood flow cytometry as CD61 positive particles, activated platelets were characterized by P-Selectin (CD62) expression, and monocytes by surface CD14 expression. A significant correlation between normalized TF-PCA of isolated mononuclear cells and platelet count was shown (r = 0.43, P < 0.001). Percentage of activated platelets in baseline samples was 4.2 +/- 3.5 while adenosine diphosphate (ADP) increased platelet positivity to 34 +/- 17% (P < 0.001). After isolation, 52 +/- 12% of platelets within suspensions were activated (P < 0.0001). Percentage of CD62-positive monocytes (CD14+ particles) increased from baseline 5% to 13 +/- 6% in ADP-stimulated samples to 53 +/- 17% after isolation (P < 0.001). These findings suggest that density gradient centrifugation activates platelets and that an adhesive interaction between monocytes and platelets may promote TF-PCA expression in isolated mononuclear suspensions. Enhanced monocyte TF expression as a result of an activated platelet-monocyte interaction seems to be an important laboratory effect requiring consideration when utilizing this technique in an experimental setup.

The VIVA trial: Vascular endothelial growth factor in Ischemia for Vascular Angiogenesis

BACKGROUND

Recombinant human vascular endothelial growth factor protein (rhVEGF) stimulates angiogenesis in animal models and was well tolerated in Phase I clinical trials. VIVA (Vascular endothelial growth factor in Ischemia for Vascular Angiogenesis) is a double-blind, placebo-controlled trial designed to evaluate the safety and efficacy of intracoronary and intravenous infusions of rhVEGF.

METHODS AND RESULTS

A total of 178 patients with stable exertional angina, unsuitable for standard revascularization, were randomized to receive placebo, low-dose rhVEGF (17 ng x kg(-1) x min(-1)), or high-dose rhVEGF (50 ng x kg(-1) x min(-1)) by intracoronary infusion on day 0, followed by intravenous infusions on days 3, 6, and 9. Exercise treadmill tests, angina class, and quality of life assessments were performed at baseline, day 60, and day 120. Myocardial perfusion imaging was performed at baseline and day 60. At day 60, the change in exercise treadmill test (ETT) time from baseline was not different between groups (placebo, +48 seconds; low dose, +30 seconds; high dose, +30 seconds). Angina class and quality of life were significantly improved within each group, with no difference between groups. By day 120, placebo-treated patients demonstrated reduced benefit in all three measures, with no significant difference compared with low-dose rhVEGF. In contrast, high-dose rhVEGF resulted in significant improvement in angina class (P=0.05) and nonsignificant trends in ETT time (P=0.15) and angina frequency (P=0.09) as compared with placebo.

CONCLUSIONS

rhVEGF seems to be safe and well tolerated. rhVEGF offered no improvement beyond placebo in all measurements by day 60. By day 120, high-dose rhVEGF resulted in significant improvement in angina and favorable trends in ETT time and angina frequency.

The role of inflammation in plaque disruption and thrombosis

Most of the serious clinical manifestations (such as unstable angina, acute MI, and many cases of sudden death) of coronary atherosclerosis result from thrombosis, usually occurring on a disrupted atherosclerotic plaque. Plaques prone to disruption have large lipid-rich cores with evidence of cap-thinning and active inflammation. Inflammatory cells may contribute to both plaque disruption and subsequent thrombosis. Here we review the evidence for the involvement of inflammation in plaque disruption and thrombosis and the potential clinical implications of this pathophysiologic paradigm.

Acute coronary syndrome caused by coronary artery dissection mimicking acute plaque rupture

When a middle-aged, nonpregnant female patient with no coronary risk factors presents with chest pain, what are the red flags for unusual causes? This case report provides important diagnostic clues as well as progressive therapeutic steps to solving a potentially life-threatening problem.

Toll-like receptor-4 is expressed by macrophages in murine and human lipid-rich atherosclerotic plaques and upregulated by oxidized LDL

BACKGROUND

Inflammation is implicated in atherogenesis and plaque disruption. Toll-like receptor 2 (TLR-2) and TLR-4, a human homologue of drosophila Toll, play an important role in the innate and inflammatory signaling responses to microbial agents. To investigate a potential role of these receptors in atherosclerosis, we assessed the expression of TLR-2 and TLR-4 in murine and human atherosclerotic plaques.

METHODS AND RESULTS

Aortic root lesions of high-fat diet-fed apoE-deficient mice (n=5) and human coronary atherosclerotic plaques (n=9) obtained at autopsy were examined for TLR-4 and TLR-2 expression by immunohistochemistry. Aortic atherosclerotic lesions in all apoE-deficient mice expressed TLR-4, whereas aortic tissue obtained from control C57BL/6J mice showed no TLR-4 expression. All 5 lipid-rich human plaques expressed TRL-4, whereas the 4 fibrous plaques and 4 normal human arteries showed no or minimal expression. Serial sections and double immunostaining showed TLR-4 colocalizing with macrophages both in murine atherosclerotic lesions and at the shoulder region of human coronary artery plaques. In contrast to TLR-4, none of the plaques expressed TLR-2. Furthermore, basal TLR-4 mRNA expression by human monocyte-derived macrophages was upregulated by ox-LDL in vitro.

CONCLUSIONS

Our study demonstrates that TLR-4 is preferentially expressed by macrophages in murine and human lipid-rich atherosclerotic lesions, where it may play a role to enhance and sustain the innate immune and inflammatory responses. Moreover, upregulation of TLR-4 in macrophages by oxidized LDL suggests that TLR-4 may provide a potential pathophysiological link between lipids and infection/inflammation and atherosclerosis.

Structural determinants of binding and specificity in transforming growth factor-receptor interactions

Transforming growth factor (TGF-beta) protein families are cytokines that occur as a large number of homologous proteins. Three major subgroups of these proteins with marked specificities for their receptors have been found-TGF-beta, activin/inhibin, and bone morphogenic protein. Although structural information is available for some members of the TGF-beta family of ligands and receptors, very little is known about the way these growth factors interact with the extracellular domains of their cell surface receptors, especially the type II receptor. In addition, the elements that are the determinants of binding and specificity of the ligands are poorly understood. The structure of the extracellular domain of the receptor is a three-finger fold similar to some toxin structures. Amino acid exchanges between multiply aligned homologous sequences of type II receptors point to a residue at the surface, specifically finger 1, as the determinant of ligand specificity and complex formation. The "knuckle" epitope of ligands was predicted to be the surface that interacts with the type II receptor. The residues on strands beta2, beta3, beta7, beta8 and the loop region joining beta2 and beta3 and joining beta7 and beta8 of the ligands were identified as determinants of binding and specificity. These results are supported by studies on the docking of the type II receptor to the ligand dimer-type I receptor complex.

Comparison of fasting and postprandial plasma lipoproteins in subjects with and without coronary heart disease

Plasma lipoprotein levels, including remnant-like particle (RLP) cholesterol and RLP triglycerides, were assessed in fasting (12 hours) and postprandial (PP) (4 hours after a fat-rich meal) states in 88 patients with coronary heart disease (CHD) and 88 controls. All lipoproteins were assessed by direct methods. We hypothesized that patients with CHD would have greater percent increases in their triglyceride levels, RLP cholesterol, and RLP triglycerides, in response to a fat-rich meal. In the fasting state, triglycerides, RLP cholesterol, RLP triglycerides, and low-density lipoprotein (LDL) cholesterol levels were all significantly higher in cases versus controls by 51%, 35%, 39%, and 40%, respectively. These levels were 57%, 37%, 64%, and 37% higher in the PP state, respectively. Mean high-density lipoprotein (HDL) cholesterol values were 27% lower in cases in both the fasting and PP states. After eating, triglycerides, RLP cholesterol, and RLP triglycerides increased 64%, 71%, and 290% in controls, respectively, whereas in cases these levels increased by 71%, 94%, and 340%, respectively (all p <0.0001). Percent increases in the PP state were not significantly different in cases versus controls. Following the fat-rich meal, LDL and HDL cholesterol decreased by 5% and 4% in controls, and by 7% and 6% in patients, with no significant difference in percent changes between groups. Fasting values correlated very highly with PP values for all parameters (all p <0.0001). Our data indicate that although patients with CHD have higher fasting and PP levels of triglycerides, RLP cholesterol, and RLP triglycerides than controls, the response (percent increase) to a fat-rich meal is comparable in both groups. Thus, a feeding challenge is not essential for assessment of these lipoproteins. Moreover, it is not necessary to obtain a fasting sample to assess direct LDL and HDL cholesterol.

Structural understanding of the transmembrane domains of inositol triphosphate receptors and ryanodine receptors towards calcium channeling

Inositol 1,4,5-triphosphate receptors (Insp(3)Rs) and ryanodine receptors (ryRs) act as cationic channels transporting calcium ions from the endoplasmic reticulum to cytosol by forming tetramers and are proteins localized to the endoplasmic reticulum (ER). Despite the absence of classical calcium-binding motifs, calcium channeling occurs at the transmembrane domain. We have investigated putative calcium binding motifs in these sequences. Prediction methods indicate the presence of six transmembrane helices in the C-terminal domain, one of the three domains conserved between Insp(3)R and ryR receptors. The recently identified crystal structure of the K(+) channel, which also forms tetramers, revealed that two transmembrane helices, an additional pore helix and a selectivity filter are responsible for selective K(+) ion channeling. The last three TM helices of Insp(3)R and ryR are particularly well conserved and we found analogous pore helix and selectivity filter motif in these sequences. We obtained a three-dimensional structural model for the transmembrane tetramer by extrapolating the distant structural similarity to the K(+) channels.

Intravenous magnesium in experimental stent thrombosis in swine

We investigated the effects of magnesium on acute platelet-dependent stent thrombosis in an ex vivo porcine arteriovenous shunt model of high-shear blood flow. Control nitinol stents were expanded to 2 mm in diameter in a tubular perfusion chamber interposed in the shunt and exposed to flowing arterial blood at a shear rate of 2100 s(-1) for 20 minutes (n=156 perfusion runs in 10 swine). Animals were treated with intravenous heparin or MgSO(4) alone (2 g bolus over 20 minutes, followed by 2 g/h infusion) and combined heparin plus MgSO(4) in random fashion. Effects on thrombus weight (TW), platelet aggregation, bleeding time, activated clotting time, mean arterial blood pressure, and heart rate were quantified. Data points in the magnesium-treated animals were examined within 20 minutes after bolus (Mg-early) and >40 minutes after bolus (Mg-late). Stent TW (20+/-3 mg, pretreatment) was reduced by 42+/-21%, 47+/-19%, 48+/-16%, 67+/-12%, and 86+/-8% in the groups treated with Mg-early alone, Mg-late alone, heparin alone, heparin+Mg-early, and heparin+Mg-late, respectively (all P<0.001 versus pretreatment, P<0.001 for heparin+Mg-early and Mg-late versus heparin or magnesium alone, and P<0.05 for heparin+Mg-late versus heparin+Mg-early, ANOVA). Magnesium had no significant effect on platelet aggregation, activated clotting time, or bleeding time. There were no significant effects on heart rate or mean arterial blood pressure. The serum magnesium level was inversely correlated with TW (r=-0.70, P=0.002). In conclusion, treatment with intravenous MgSO(4) produced a time-dependent inhibition of acute stent thrombosis under high-shear flow conditions without any hemostatic or significant hemodynamic complications. Thus, magnesium may be an effective agent for preventing stent thrombosis.