Faculty Bibliography

Magnetic resonance (MR) imaging is becoming a pivotal diagnostic method to identify and characterize vulnerable atherosclerotic plaques. We previously reported a reconstituted high-density lipoprotein (rHDL) nanoparticle platform enriched with Gd-based amphiphiles as a plaque-specific MR imaging contrast agent. Further modification can be accomplished by inserting targeting moieties into this platform to potentially allow for improved intraplaque macrophage uptake. Since studies have indicated that intraplaque macrophage density is directly correlated to plaque vulnerability, modification of the rHDL platform may allow for better detection of vulnerable plaques. In the current study we incorporated a carboxyfluoresceine-labeled apolipoprotein E-derived lipopeptide, P2fA2, into rHDL. The in vitro macrophage uptake and in vivo MR efficacy were demonstrated using murine J774A.1 macrophages and the apolipoprotein E knock-out (apoE(-/-)) mouse model of atherosclerosis. The in vitro studies indicated enhanced association of murine macrophages to P2fA2 enriched rHDL (rHDL-P2A2) nanoparticles, relative to rHDL, using optical techniques and MR imaging. The in vivo studies showed a more pronounced and significantly higher signal enhancement of the atherosclerotic wall 24 h after the 50 micromol Gd/kg injection of rHDL-P2A2 relative to administration of rHDL. The normalized enhancement ratio for atherosclerotic wall of rHDL-P2A2 contrast agent injection was 90%, while that of rHDL was 53% 24 h post-injection. Confocal laser scanning microscopy revealed that rHDL-P2A2 nanoparticles co-localized primarily with intraplaque macrophages. The results of the current study confirm the hypothesis that intraplaque macrophage uptake of rHDL may be enhanced by the incorporation of the P2fA2 peptide into the modified HDL particle

High density lipoprotein (HDL) is an important natural nanoparticle that may be modified for biomedical imaging purposes. Here we developed a novel technique to create unique multimodality HDL mimicking nanoparticles by incorporation of gold, iron oxide, or quantum dot nanocrystals for computed tomography, magnetic resonance, and fluorescence imaging, respectively. By including additional labels in the corona of the particles, they were made multifunctional. The characteristics of these nanoparticles, as well as their in vitro and in vivo behavior, revealed that they closely mimic native HDL.

Impulse propagation in cardiac tissue is a complex process in which intercellular coupling through gap junction channels is a critical component. Connexin40 (Cx40) is an abundant gap junction protein that is expressed in atrial myocytes. Alterations in the expression of Cx40 have been implicated in atrial arrhythmogenesis. The purpose of the current study was to assess the role of Cx40 in atrial impulse propagation. High-resolution optical mapping was used to study conduction in the right and left atrial appendages of isolated Langendorff-perfused murine hearts. Wild-type (Cx40(+/+)), heterozygous (Cx40(+/-)), and knockout (Cx40(-/-)) mice, both adult and embryonic, were studied to assess the effects of reduced Cx40 expression on sinus node function and conduction velocity at different pacing cycle lengths (100 and 60 ms). In both adult and late-stage embryonic Cx40(+/+) mice, heterogeneity in CV was found between the right and left atrial appendages. Either partial (Cx40(+/-)) or complete (Cx40(-/-)) deletion of Cx40 was associated with the loss of conduction heterogeneity in both adult and embryonic mice. Additionally, sinus node impulse initiation was found to be ectopic in Cx40(-/-) mice at 15.5 days postcoitus, whereas Cx40(+/+) mice showed normal activation occurring near the crista terminalis. Our findings suggest that Cx40 plays an essential role in establishing interatrial conduction velocity heterogeneity in the murine model. Additionally, we describe for the first time a developmental requirement for Cx40 in normal sinus node impulse initiation at 15.5 days postcoitus

Pancreatic carboxyl ester lipase (CEL) is in the plasma of many mammals, including humans and rats, but not mice. In vitro, CEL hydrolyzes cholesterol esters of apolipoprotein B-containing lipoproteins (apo B-Lp). To study the effect of CEL on metabolism of apo B-Lp and atherosclerosis in vivo, apo E-knockout (EKO) mice, which have high plasma levels of apo B-Lp and are prone to atherosclerosis, were made to secrete CEL into plasma by introducing a transgene containing a liver-specific promoter and rat CEL complementary DNA. Plasma CEL activity in EKO-CEL mice was comparable with that found in rats. Evidence of modification of apo B-Lp by plasma CEL in vivo was an increase in the free cholesterol to cholesterol ester ratio of apo B-Lp from mice on chow or a Western-type diet. In addition, plasma total cholesterol levels were elevated in EKO-CEL mice, with the elevation found exclusively in the apo B-Lp fraction. Associated with the increase in steady-state apo B-Lp levels was an increase in the plasma half-life of very low-density lipoproteins (VLDL) in EKO-CEL mice, measured by the clearance rate of injected VLDL. Interestingly, despite the increase of apo B-Lp, the atherosclerotic lesion did not differ between EKO and EKO-CEL mice on a Western-type diet. In summary, our results demonstrate that plasma CEL modulates apo B-Lp metabolism in vivo, resulting in reduced VLDL clearance and elevated plasma cholesterol levels.

Cardiovascular disease is one of the prime causes of mortality throughout the world and there is a need for targeted and effective contrast agents to allow noninvasive imaging of the cholesterol-rich atherosclerotic plaques in arteries. A new, fully synthetic, high-density lipoprotein (HDL)-mimicking MRI contrast agent is developed, which enhances macrophage-rich areas of plaque in a mouse model of atherosclerosis by 94%. Confirmation of the targeting of this nanoparticulate agent is achieved using confocal microscopy by tracking a fluorescent lipid incorporated into the nanoparticle.

This article is designed for the general cardiologist, endocrinologist, and internist caring for patients with diabetes and coronary artery disease. Despite the burden of coronary disease in diabetics, little is known about the impact of commonly used oral hypoglycemic agents on cardiovascular outcomes. As the untoward effects of insulin resistance (IR) are increasingly recognized, there is interest in targeting this defect. Insulin resistance contributes to dyslipidemia, hypertension, inflammation, hypercoagulability, and endothelial dysfunction. The aggregate impact of this process is progression of systemic atherosclerosis and an increased risk of adverse cardiovascular outcomes. As such, much attention has been paid to the peroxisome-proliferator-activated receptor gamma (PPARg) agonists rosiglitazone and pioglitazone (thiazolidinediones [TZDs]). Many studies have demonstrated a beneficial effect on the atherosclerotic process; specifically, these agents have been shown to reduce markers of inflammation, retard progression of carotid intimal thickness, prevent restenosis after coronary stenting, and prevent cardiovascular death and myocardial infarction in 1 large trial. Such benefits come at the risk of fluid retention and heart failure (HF) exacerbation, and the net effect on plasma lipids is still poorly understood. Thus, the aggregate risk-benefit ratio is poorly defined. A recent meta-analysis has raised significant concerns regarding the overall cardiovascular safety of 1 particular PPARg agonist (rosiglitazone), prompting international debate and regulatory changes. This review scrutinizes the clinical evidence regarding the cardiovascular risks and benefits of PPARg agonists. Future studies of PPARg agonists, and other emerging drugs that treat IR and diabetes, must be designed to look at cardiovascular outcomes

Because the levels of secreted apolipoprotein B (apoB) directly correlate with circulating serum cholesterol levels, there is a pressing need to define how the biosynthesis of this protein is regulated. Most commonly, the concentration of a secreted, circulating protein corresponds to transcriptionally and/or translationally regulated events. By contrast, circulating apoB levels are controlled by degradative pathways in the cell that select the protein for disposal. This article summarizes recent findings on two apoB disposal pathways, endoplasmic reticulum (ER)-associated degradation and autophagy, and describes a role for post-ER degradation in the increased circulating lipid levels in insulin-resistant diabetics.

The authors recently reported a novel role for autophagy in late-stage quality control of a secreted protein, apolipoprotein-B(100) (apoB). Hepatocytes assemble this protein with triglycerides, cholesterol and other lipids into macromolecular complexes called lipoproteins. In what appears to be a normal response to diets rich in polyunsaturated fatty acids, which are readily peroxidized, apoB comes into contact with lipid peroxides in or after the Golgi apparatus. The protein becomes oxidatively damaged, aggregates, and is diverted out of the secretory pathway by autophagosomes, which deliver it to lysosomes for destruction. ApoB secretory control via autophagosomes is likely a key component of normal and pathological regulation of plasma lipoprotein levels, as well as a means for remarkably late-stage quality control of a secreted protein

AIM: The influence of metabolic syndrome (MS) on long-term mortality and morbidity in multi-vessel coronary artery disease (MV-CAD) is unclear. We studied the impact of MS on long-term outcomes in non-diabetic patients (NDM) with MV-CAD undergoing coronary revascularization in the Bypass Angioplasty Revascularization Investigation (BARI) trial and registry. METHODS: BARI trial and registry patients were separated into those with diabetes (DM) and those without. NDM fulfilling the NCEP definition of MS were identified. Ten year follow-up data were obtained on mortality, MI and development of diabetes. The data were analyzed using Cox proportional hazard modeling. RESULTS: In the BARI trial and registry 2962 NDM were identified. Of those, 510 patients had 3 or more components of the BARI-modified NCEP definition for MS, while 445 patients had 2 components of the definition and were classified as the 'mixed group'. Compared to patients without MS, both MS group (RR=3.2, p<0.0001) and the mixed group (RR=1.9, p=0.02) had a higher incidence of DM over the 10-year follow-up. Type 2 DM was found to be highly associated with 10-year mortality (RR=1.65, p<0.0001). However, there was no statistically significant difference in the rate of death or MI at 5 and 10 years between NDM with or without MS. In multivariate analysis, the presence of MS was not associated with 10-year mortality in the BARI population (RR=0.93, p=0.62). CONCLUSION: In this BARI follow-up study, we have affirmed the role of MS in predicting the development of diabetes in NDM at baseline. The 10-year risk of mortality and MI was not greater in NDM with MS who had MV-CAD and underwent revascularization, compared to patients without MS. Further studies to evaluate MS patients with MV-CAD undergoing coronary revascularization are warranted