Anti-Lipoprotein Lipase Antibody as a Useful Marker for Plaque Vulnerability in Patients with Stable Angina.

AIMS: Identifying patients with vulnerable plaque who have poor prognosis among those with coronary artery disease (CAD) is crucial to deciding future therapeutic interventions. We previously reported that male CAD patients with low anti-apolipoprotein B-100 autoantibody (anti-apoB-100 Ab) levels were at an increased risk of developing unstable plaque lesions. This study focused on the autoantibodies against lipoprotein lipase (LPL), a key enzyme in triglyceride metabolism, which is another risk factor for atherosclerosis, and investigated their association with plaque characteristics. METHODS: We measured serum anti-LPL Ab levels using a homemade enzyme-linked immunosorbent assay in 80 male CAD patients. Coronary plaque properties were evaluated using iMAP®-intravascular ultrasound. RESULTS: Serum anti-LPL Ab levels were not correlated with plaque burden but were significantly negatively and positively correlated with fibrotic and necrotic plaques, respectively. High-risk patients with low anti-apoB-100 Ab levels were divided into groups according to their anti-LPL Ab levels. The group with high anti-LPL Ab levels exhibited more necrotic plaques and fewer fibrotic plaques as well as higher remnant-like lipoprotein particle levels than the group with low anti-LPL Ab levels. CONCLUSIONS: Serum anti-LPL Ab levels can serve as a marker of plaque instability in CAD patients and can help identify higher-risk cases when combined with anti-apoB-100 Ab levels.

Anti-Apo B-100 Autoantibody is a Marker of Unstable Coronary Plaque.

AIMS: Cardiovascular diseases (CVD) are a global leading cause of mortality. However, few biomarkers are available to predict future coronary plaque rupture. We have recently demonstrated that low levels of anti-apolipoprotein B-100 autoantibody (anti-apo B-100 Ab) correlated with an increased CVD risk in Japanese patients with diabetes. In the present study, we examined the relationship between serum anti-apo B-100 Ab levels and coronary plaque characteristics in patients undergoing elective percutaneous coronary intervention (PCI). METHODS: We conducted iMAP®-intravascular ultrasound (IVUS) in 88 Japanese male patients undergoing elective PCI, and the five consecutive slices of IVUS images at the center of the most stenotic culprit lesion were used for identifying the plaque characteristics. The serum levels of anti-apo B-100 Ab against synthetic peptides (p45 or p210) were measured using a homemade enzyme-linked immunosorbent assay. RESULTS: Serum IgG levels of anti-apo B-100 Ab against both native p45 and p210 (IgG N-p45 and IgGN-p210) and malondialdehyde (MDA)-modified p45 and p210 (IgGMDA-p45 or IgGMDA-p210) showed a negative correlation with plaque burden in total male patients undergoing elective PCI. Additionally, both IgGN-p45 and IgGN-p210, but neither IgGMDA-p45 nor IgGMDA-p210, correlated negatively with necrotic and positively with fibrotic components of iMAP®-IVUS plaque characteristics in the patients with ＜1 month statin treatment before elective PCI ("statin-untreated" group). There was no significant correlation between anti-apo B-100 Ab and any plaque characteristics in the patients with statin treatment for 1 month or more before elective PCI ("statin-treated" group). CONCLUSION: Measuring serum levels of anti-apo B-100 Ab might be helpful in the evaluation of unstable coronary plaque in male CVD patients without statin treatment.

Atheroprotective Roles of Adiponectin via CCL2 Inhibition.

AIM: Adiponectin (APN) exhibits different atheroprotective effects, and we have previously reported that APN function is modulated by its binding proteins, E-selectin ligand 1, Mac-2 binding protein, and cystatin C. In the present study, we aimed to identify a novel atheroprotective mechanism of APN via C-C motif chemokine 2 (CCL2). METHODS: We conducted iMAP®-intravascular ultrasound (IVUS) in 111 Japanese male patients with stable angina. The plaque characteristics were determined where "plaque burden" [(EEM CSA - lumen CSA)/(EEM CSA)×100 (%)] ＞50%, and their correlation with serum CCL2 and APN levels was analyzed. Using western blot analysis, the effects of APN on the biological effects of CCL2 were examined in their mutual binding by co-immunoprecipitation assay, the monocyte migration, and the phosphorylation of MAP kinases. RESULTS: In a clinical study, we found that the percentage of plaque in the culprit lesion was correlated positively with serum CCL2 and negatively with serum APN levels, with significance. We identified CCL2 as a novel APN-binding serum protein using immunoprecipitation and western blot analysis. CCL2-induced phosphorylation of MAP kinases and monocyte migration was significantly attenuated by APN in vitro. CONCLUSION: The opposite association of APN and CCL2 on the percentage of coronary plaque might be caused by their direct interaction and competitive functions on monocyte migration.

Cystatin C-Adiponectin Complex in Plasma Associates with Coronary Plaque Instability.

AIM: Adiponectin (APN) is an adipocyte-derived bioactive molecule with antiatherogenic properties. We previously reported that cystatin C (CysC) abolished the anti-atherogenic effects of APN. We aimed to elucidate the clinical significance of CysC-APN complex in patients with coronary artery disease (CAD). METHODS: We enrolled 43 stable CAD male patients to examine the relationship between CysC-APN complex and coronary plaque characteristics. Serum was immunoprecipitated by the anti-APN antibody and immunoblotted by the anti-CysC antibody to demonstrate the presence of CysC-APN complexes in vivo. To confirm their binding in vitro, HEK293T cell lysates overexpressing myc-APN and FLAG-CysC were immunoprecipitated with an anti-myc or anti-FLAG antibody, followed by immunoblotting with an anti-APN or anti-CysC antibody. RESULTS: CysC was identified as a specific co-immunoprecipitant with APN by the anti-APN antibody in human serum. In vitro, FLAG-CysC was co-immunoprecipitated with myc-APN by the anti-myc antibody and myc-APN was co-immunoprecipitated with FLAG-CysC by the anti-FLAG antibody. Among CAD patients, serum CysC-APN complex levels negatively correlated with fibrotic components of coronary plaques and positively correlated with either necrotic or lipidic plus necrotic components. Plaque burden negatively correlated with serum APN levels but not serum CysC-APN complex levels. Serum CysC levels had no association with plaque characteristics. In multivariate analysis, CysC-APN complex levels were identified as the strongest negative factor for fibrotic components and the strongest positive factor for both necrotic and lipidic plus necrotic components. CONCLUSION: Measuring serum CysC-APN complex levels is helpful for evaluating coronary plaque instability in CAD patients.

Intramolecular interaction of SUR2 subtypes for intracellular ADP-Induced differential control of K(ATP) channels.

ATP-sensitive K+ (K(ATP)) channels are composed of sulfonylurea receptors (SURs) and inwardly rectifying Kir6.2-channels. The C-terminal 42 amino acid residues (C42) of SURs are responsible for ADP-induced differential activation of K(ATP) channels in SUR-subtypes. By examining ADP-effect on K(ATP) channels containing various chimeras of SUR2A and SUR2B, we identified a segment of 7 residues at central portion of C42 critical for this phenomenon. A 3-D structure model of the region containing the second nucleotide-binding domain (NBD2) of SUR and C42 was developed based on the structure of HisP, a nucleotide-binding protein forming the bacterial Histidine transporter complex. In the model, the polar and charged residues in the critical segment located within a distance that allows their electrostatic interaction with Arg1344 at the Walker-A loop of NBD2. Therefore, the interaction might be involved in the control of ADP-induced differential activation of SUR2-subtype K(ATP) channels.

Marked elevation of serum M2BP-adiponectin complex in men with coronary artery disease.

BACKGROUND AND AIMS: Adiponectin (APN) is an adipocyte-derived bioactive molecule with anti-diabetic and anti-atherogenic properties. Although the anti-diabetic effects of APN are mediated by AdipoR1 and AdipoR2, the anti-atherogenic mechanisms of APN remain unclear. The aim of this study was to determine the serum molecule inhibiting APN functions. METHODS AND RESULTS: By immunoprecipitation with an anti-APN antibody and mass spectrometry, we identified Mac-2 binding protein (M2BP) as a novel serum APN-binding protein. The association of M2BP and APN was confirmed using reconstituted proteins in vitro. Serum M2BP-APN complex levels were markedly higher in male patients with coronary artery disease (CAD) than in healthy subjects. M2BP abrogated the suppressive effects of APN on tumour necrosis factor (TNF)-α-induced inflammation in vascular endothelial cells. CONCLUSIONS: The increment of serum M2BP-APN complex could be a novel risk factor for CAD, through the abolishment of the anti-atherogenic effects of APN.

Impact of Remnant Lipoprotein on Coronary Plaque Components.

AIM: Intravascular ultrasound (IVUS) is a useful modality for visualizing atherosclerotic lesions in coronary arteries, not only for the degree of arterial luminal stenosis but also for the plaque composition within the vessel walls. We aimed to determine the relationship between the clinical parameters and coronary plaque characteristics evaluated by IVUS in patients with stable angina under medical treatment. METHODS: Plaque measurements within the coronary arteries were collected by coronary angiography and iMAP-IVUS in 40 men with stable angina. The serum remnant-like cholesterol (RemL-C) was measured using homogeneous assays and serum adiponectin and omentin-1 levels were measured by enzyme-linked immunosorbent assays. RESULTS: The iMAP-IVUS analysis of the coronary arteries demonstrated that the plaque cross-sectional area (CSA) was 11.0±3.5 mm(2). Plaque CSA positively correlated with body mass index and negatively correlated with the serum adiponectin levels. Both areal and volumetric analyses of the plaque characteristics demonstrated that the serum RemL-C level was a positive determinant for %Necrosis and the negative determinant for %Fibrosis of the plaques. Neither serum high-density lipoprotein cholesterol nor low-density lipoprotein cholesterol levels correlated with the proportion of any plaque components. Additionally, the RemL-C/triglyceride ratio positively correlated with %Lipid significantly in the areal analysis. CONCLUSION: Elevation of the serum RemL-C levels in the patients with stable angina may link to coronary plaque vulnerability, which is characterized by high necrotic and low fibrotic components.

[Molecular biology of ion channels in the heart].

Cardiac action potential is generated and maintained by several types of ion channels, such as sodium, calcium, potassium, chloride and non-selective cation channels. Mutation of cardiac ion channels could result in life-threatening arrhythmia. To date, the successful cloning of ion channels has revealed their molecular structure and function. Molecular biological and electrophysiological studies have developed general concepts for understanding properties of these channels, such as gating mechanism, kinetics of activation and inactivation, ion selectivity and pharmacological properties. These findings may provide possibilities for genotype-specific or gene-targeted therapies. This review focuses on the molecular properties and functional roles of cardiac ion channels.

Nateglinide, a D-phenylalanine derivative lacking either a sulfonylurea or benzamido moiety, specifically inhibits pancreatic beta-cell-type K(ATP) channels.

A novel antidiabetic agent, nateglinide, is a D-phenylalanine derivative lacking either a sulfonylurea or benzamido moiety. We examined with the patch-clamp method the effect of nateglinide on recombinant ATP-sensitive K(+) (K(ATP)) channels expressed in human embryonic kidney 293T cells transfected with a Kir6.2 subunit and either of a sulfonylurea receptor (SUR) 1, SUR2A, and SUR2B. In inside-out patches, nateglinide reversibly inhibited the spontaneous openings of all three types of SUR/Kir6.2 channels. Nateglinide inhibited SUR1/Kir6.2 channels with high and low affinities (K(i) = 75 nM and 114 microM) but SUR2A/Kir6.2 and SUR2B/Kir6.2 channels only with low affinity (K(i) = 105 and 111 microM, respectively). Nateglinide inhibited the K(ATP) current mediated by Kir6.2 lacking C-terminal 26 amino acids only with low affinity (K(i) = 290 microM) in the absence of SUR. Replacement of serine at position 1237 of SUR1 to tyrosine [SUR1(S1237Y)] specifically abolished the high-affinity inhibition of SUR1/Kir6.2 channels by nateglinide. MgADP or MgUDP (100 microM) augmented the inhibitory effect of nateglinide on SUR1/Kir6.2 but not SUR1(S1237Y)/Kir6.2 or SUR2A/Kir6.2 channels. This augmenting effect of MgADP was also observed with the SUR1/Kir6.2(K185Q) channel, which was not inhibited by MgADP, but not with the SUR1(K1384A)/Kir6.2 channel, which was not activated by MgADP. These results indicate that therapeutic concentrations of nateglinide (approximately 10 microM) may selectively inhibit pancreatic type SUR1/Kir6.2 channels through SUR1, especially when the channel is activated by intracellular MgADP, even though the agent does not contain either a sulfonylurea or benzamido moiety.