The LDL-Receptor and its Molecular Properties: From Theory to Novel Biochemical and Pharmacological Approaches in Reducing LDL-cholesterol

BACKGROUND

The Low-Density Lipoprotein (LDL) Receptor (LDL-R) is a transmembrane protein playing a crucial role in effective lipid homeostasis. Various therapeutic agents have been used in the management of dyslipidemias, however, the outcome of therapeutic target is debated.

OBJECTIVE

The aim of this review is to summarize and fully understand the current concept regarding LDL-R and its molecular properties, metabolic pathway, factors affecting LDL-R activity and all available pharmacological interventions. Additionally, non-lipid related properties of LDL-R are also referred.

METHODS

Literature from the PubMed database was extracted to identify papers between 1984 to 2017 regarding LDL-R and therapeutic agents on dyslipidemia management.

RESULTS

We analyzed basic data regarding agents associated with LDL-R (Sterol Regulating Element-Binding Proteins - SREBPs, Protein ARH, IDOL, Thyroid Hormones, Haematologic Disorders, Protein convertase subtilisin kexintype 9 - PCSK-9, ApoC-III) as well as non-lipid related properties of LDL-R, while all relevant (common and novel) pharmacological interventions (statins, fibrates, cholesterol absorption inhibitors, bile acid sequestrants and PCSK- 9) are also referred.

CONCLUSION

LDL-R and its molecular properties are involved in lipid homeostasis, so potentially sets the therapeutic goals in cardiovascular patients, which is usually debated. Further research is needed in order to fully understand its properties, as well as to find the potential pharmacological interventions that could be beneficial in cholesterol homeostasis and various morbidities in order to reach the most appropriate therapeutic goal.

Predicting the Risk of Rupture of Abdominal Aortic Aneurysms by Utilizing Various Geometrical Parameters: Revisiting the Diameter Criterion

The authors estimated noninvasively the wall stress distribution for actual abdominal aortic aneurysms (AAAs) in vivo on a patient-to-patient basis and correlated the peak wall stress (PWS) with various geometrical parameters. They studied 39 patients (37 men, mean age 73.7 ± 8.2 years) with an intact AAA (mean diameter 6.3 ± 1.7 cm) undergoing preoperative evaluation with spiral computed tomography (CT). Real 3-dimensional AAA geometry was obtained from image processing. Wall stress was determined by using a finite-element analysis. The aorta was considered isotropic with linear material properties and was loaded with a static pressure of 120.0 mm Hg. Various geometrical parameters were used to characterize the AAAs. PWS and each of the geometrical characteristics were correlated by use of Pearson's rank correlation coefficients. PWS varied from 10.2 to 65.8 N/cm2 (mean value 37.1 ± 9.9 N/cm2). Among the geometrical parameters, the PWS was well correlated with the mean centerline curvature, the maximum centerline curvature, and the maximum centerline torsion of the AAAs. The correlation of PWS with maximum diameter was nonsignificant. Multiple regression analysis revealed that the mean centerline curvature of the AAA was the only significant predictor of PWS and subsequent rupture risk. This noninvasive computational approach showed that geometrical parameters other than the maximum diameter are better indicators of AAA rupture.

The dependence of patient dose on factors relating to the technique and complexity of Interventional Cardiology procedures

Dose-area product (DAP) measurements were conducted for 168 coronary angiography (CA) and 89 single vessel percutaneous transluminal coronary angioplasty (PTCA) to examine the factors influencing patient dose beyond the X-ray exposure parameters. It was found that for CA, the DAP increases with the number of catheters used and with the number of vessels with stenosis. DAP values for patients with a prior bypass surgery, were higher compared to those without such a medical record to surgery. In PTCA, the use of coronary stents did not enhance the patient radiation dose significantly. Noticeable differences were found in the percentage contribution of each projection to the total DAP between the three types of single vessel PTCA. Finally low variations in DAP were found among the cardiologists performing both procedures.

Spontaneous chylous cardiac tamponade: a case report

Background

Chylous cardiac tamponade is a rare condition with little known cause.

Case presentation

A case of an otherwise healthy woman who admitted with dyspnea and palpitations is presented. She had a history of a painful flexion-hyperextension of the spine. Diagnostic evaluation proved a chylous pericardial effusion with a disruption of the anterior longitudinal spinal ligament. Video-assisted thoracic surgery with mass supradiaphragmatic ligation of the thoracic duct and pericardial window formation was carried out successfully and resulted in the complete cure of the patient's condition.

Conclusion

Chylous pericardial effusion and subsequent tamponade is a rare entity. Endoscopic surgery is offering a safe and effective treatment.

Differences in management of atrial fibrillation between cardiologists and non-cardiologists in Greece

INTRODUCTION

We aimed to assess trends in the management of atrial fibrillation (AF) at various levels of medical care in Greece and to compare the treatment practices of cardiologists to those of non-cardiologists.

METHODS

From January to May 2007, 500 questionnaires were mailed to cardiologists, internists and general practitioners, randomly selected from regional medical associations. Questions assessed management practices for paroxysmal, persistent and permanent AF.

RESULTS

A total of 309 physicians (194 cardiologists and 115 non-cardiologists) responded. Cardiologists showed no preference regarding the site of cardioversion of paroxysmal AF, whereas non-cardiologists tend to cardiovert paroxysmal AF in the emergency department. Intravenous amiodarone is the most frequently used antiarrhythmic agent for cardioversion by both groups (63% vs. 71%, p=NS). Cardiologists utilise propafenone or ibutilide more frequently than non-cardiologists (24% vs. 11%, p<0.05 and 10% vs. 2%, p<0.01 respectively), while 12% of non-cardiologists would use digitalis for cardioversion (vs. 0.5% of cardiologists, p<0.001). Cardiologists prescribe commonly, but less frequently than non-cardiologists (42% vs. 59%, p<0.01) an antiarrhythmic drug after the first episode of paroxysmal AF, propafenone being the most popular among cardiologists (66%) and amiodarone (33%) or digitalis (23%) among general practitioners/internists. Beta-blockers are considered as first choice agents for rate control among cardiologists, while non-cardiologists would prescribe mainly digitalis. Antiplatelet agents were suggested by most physicians after cardioversion of the first episode of AF in low-risk patients. Cardiologists prefer aspirin, while non-cardiologists would prescribe clopidogrel as first choice antiplatelet agent. Both groups would recommend anticoagulants in high risk patients; nevertheless, in elderly patients without other risk factors, anticoagulants are more often prescribed by cardiologists (79% vs. 50%, p<0.001).

CONCLUSIONS

Important differences exist in the management of AF between cardiologists and general practitioners/internists in Greece. Non-cardiologists overuse digitalis, underuse beta-blockers, prefer clopidogrel to aspirin and are reluctant to prescribe anticoagulants in the elderly.

Brain natriuretic peptide and the athlete's heart: a pilot study

BACKGROUND

The role of brain natriuretic peptide (BNP) in differentiating the athlete's heart from maladaptive cardiac hypertrophy is unclear.

METHODS

To address this issue, an integrated M mode, two-dimensional B mode and Doppler echocardiographical study were performed and plasma BNP levels were measured in 25 strength athletes, 25 patients with established hypertrophic cardiomyopathy (HCM) and 25 healthy volunteers.

RESULTS

Among athletes, BNP levels correlated negatively with the total training time (r = -0.79, p = 0.002) and positively with ejection fraction (r = 0.58, p = 0.049) and fractional shortening (r = 0.57, p = 0.049). A BNP cut-off value of 11.8 pg/ml had 88% specificity and 74% negative predictive value for the exclusion of HCM.

CONCLUSIONS

Brain natriuretic peptide might be useful as a preparticipation screening test in athletes.

Influence of oscillating flow on LDL transport and wall shear stress in the normal aortic arch

Lipid accumulation in the aortic wall is an important factor in the development of atherosclerosis. The Low Density Lipoprotein (LDL) at the surface of the endothelium in relation to Wall Shear Stress (WSS) in the normal human aortic arch under unsteady, normal flow and mass conditions was computationally analysed. Concave sides of the aortic arch exhibit, relatively to the convex ones, elevated LDL levels at the surface of the endothelium for all time steps. At the peak systolic velocity, the LDL level reaches a value 23.0% higher than that at entrance in the ascending-descending aorta region. The corresponding LDL levels at the surface of the endothelium for the near minimum entrance velocity instant reaches 26.0%. During the cardiac cycle, the highest area averaged normalized LDL taken up as compared to the lowest one is 0.69%. WSS plays an important role in the lipid accumulation. Low WSS regions are exposed to high LDL levels at the surface of the endothelium. Regions of elevated LDL levels do not necessarily co-locate to the sites of lowest WSS. The near wall paths of the velocities might be the most important factor for the elevated LDL levels at the surface of the endothelium.

Standardized arrangement for a guideline-driven treatment of the metabolic syndrome: the SAGE-METS study

AIM

To substantially increase awareness, treatment and effective control of the metabolic syndrome (MetS) and its components.

SUBJECTS AND METHODS

This is a pilot best practice implementation enhancement programme to reduce the estimated cardiovascular disease (CVD) risk in 628 MetS patients with or without diabetes or CVD by improving quality of care. A baseline visit was followed by action to improve adherence to lifestyle advice and drug treatment for CVD risk factors by physicians specifically trained to implement guidelines. Finally, after 6 months, a single-page form was completed, showing if patients were at CVD risk factor target. If not, there was an analysis of the reason why.

RESULTS

The programme was effective in improving utilization of evidence-based treatment in 628 MetS patients. There was a substantially greater patient perception of MetS, an enhancement in compliance with lifestyle advice and increased prescription of evidence-based medication, leading to a 48% (p < 0.0001) improvement in estimated CVD risk. There was a substantial increase in the number of subjects on target for specific CVD risk factors.

CONCLUSIONS

This is the first study to increase adherence to multiple interventions for all MetS components on an outpatient basis, in both primary care and teaching hospital settings. Physician and patient education, distribution of printed guidelines and brochures, and completion of a single-page form motivated both physicians and patients to achieve multiple CVD risk factor guideline goals. The absence of a control group is a limitation of this study. Further work is also needed to establish if the improvements observed are sustained on a long-term basis.

Inhibition of renin-angiotensin system and advanced glycation end products formation: a promising therapeutic approach targeting on cardiovascular diseases

Cardiovascular disease remains the leading cause of death worldwide. The renin-angiotensin-aldosterone system (RAAS) plays a key role in the regulation of blood pressure, through the actions of angiotensin (Ang) II. Excessive RAAS activity may lead to hypertension and associated target organ damage. Indeed, RAAS blockade with angiotensin converting enzyme inhibitors (ACEIs) and/or angiotensin receptor AT (1) blockers (ARBs) has proved to be successful treatment for arterial hypertension, heart failure and diabetes. Accumulating evidence suggests that arterial stiffness is an important and independent predictor of cardiovascular risk. More recently, a role for advanced glycation end-products (AGEs) in the development of arterial stiffening has been suggested. Advanced glycation end-products form by a nonenzymatic reaction between reducing sugars and biological proteins. Mechanisms underlying these alterations include AGE cross-linking of collagen and AGE interactions with circulating proteins and AGE receptors. New pharmacologic agents that prevent AGE formation, break cross-links, or block AGE receptors reduce vascular and myocardial stiffness, inhibit atherosclerotic plaque formation, and improve endothelial function. These agents promise to reduce the risk of isolated systolic hypertension, diastolic dysfunction, diabetes and thus, heart failure.

In-hospital and long-term prognostic value of fibrinogen, CRP, and IL-6 levels in patients with acute myocardial infarction treated with thrombolysis

Plasma fibrinogen, C-reactive protein (CRP), and interleukin-6 (IL-6) levels in patients with acute myocardial infarction (AMI) receiving thrombolysis have been related to prognosis. The aim of this study was to investigate the time course of plasma fibrinogen, CRP, and IL-6 levels during the in-hospital phase in patients with AMI receiving thrombolysis, and their relationship to in-hospital and prognosis after 12-months follow-up. In 40 patients presenting with AMI within 6 hours of symptom onset and treated with thrombolysis, plasma fibrinogen, CRP, and IL-6 levels were measured on admission and after 6, 12, 24, 48, and 72 hours; 7 days; and 6 months. Patients with other diseases that can alter fibrinogen, CRP, or IL-6 levels were excluded. Patients had a clinical follow-up at 6 and 12 months, and the following cardiac events were recorded: cardiac death, recurrent angina, recurrent AMI, and heart failure. Plasma fibrinogen concentrations decreased significantly (p <0.01 vs admission levels) at 12 hours (425 +/-94 vs 322 +/-132 mg/dL), started to increase at 24 hours, reached peak value at 72 hours (602 +/-209 mg/dL), remained elevated at 7 days, and were back to admission levels at 6 months (375 +/-79 mg/dL). CRP levels increased significantly at 12 hours (0.73 +/-0.43 vs 0.23 +/-0.11 mg/dL, p <0.01), reached peak value at 72 hours (7.66 +/-3.28 mg/dL), decreased significantly on day 7 (2.32 +/-1.17 mg/dL), and at 6 months were within normal limits (0.49 +/-0.29 mg/dL). IL-6 levels increased significantly at 6 hours (14.03 +/-8.13 vs 6.37 +/-3.88 pg/mL, p <0.05), reached peak value at 24 hours (59.49 +/-23.57 pg/mL), started to decrease at 48 hours, and at 6 months were within normal limits (2.25 +/-1.24 pg/mL). During the in-hospital phase 33 patients had an uneventful course and 7 patients had complications (3 post-AMI angina; 4 heart failure). During the 12-month follow-up period 28 patients had an uneventful course, and 12 patients had complications (1 cardiac death, 5 recurrent angina, 2 recurrent AMI, and 4 heart failure). Regarding the in-hospital prognosis, fibrinogen, CRP, and IL-6 levels were significantly higher (p <0.05) in patients with complications from 48 to 72 hours, from 12 hours until day 7, and from 6 hours until day 7, respectively. During the 12-month follow-up period fibrinogen, CRP, and IL-6 levels were significantly higher in patients with complications (at 48, 24, and 24 hours, respectively) only in the subgroup of patients who had complications within the first 6 months following AMI. Multivariate analysis showed that CRP at 48 hours was the most important factor related to in-hospital prognosis (p = 0.02), and ejection fraction followed by CRP at 24 hours (p = 0.02) to 6-month prognosis (p = 0.018). Fibrinogen, CRP, and IL-6 levels alter in patients with AMI receiving thrombolysis, and are related both to in-hospital and to 6-month follow-up prognosis.

Skin doses to patients undergoing coronary angiography in a Greek hospital

In this study, the skin dose (SD) to patients undergoing coronary angiography (CA) were measured with thermoluminescence dosemeters (TLD) attached to various anatomical locations on the patient's skin during 93 CA procedures in a Greek hospital. The dose-area product (DAP) for every radiological projection was also measured for each procedure. The SD values were measured to be in the range 2.4-427.5 mGy, lower than the 2 Gy dose threshold for transient erythema. No general correlation was observed between the SD and the total DAP.

Radiation exposure to cardiologists performing interventional cardiology procedures

Medical doctors, who practice interventional cardiology, receive a noticeable radiation dose. In this study, we measured the radiation dose to 9 cardiologists during 144 procedures (72 coronary angiographies and 70 percutaneus translumined coronary angioplasties) in two Greek hospitals. Absorbed doses were measured with TLD placed underneath and over the lead apron at the thyroid protective collar. Based on these measurements, the effective dose was calculated using the Niklason method. In addition, dose area product (DAP) was registered. The effective doses, E, were normalised to the total DAP measured in each procedure, producing the E/DAP index. The mean effective dose values were found to be in the range of 1.2-2.7 microSv while the mean E/DAP values are in the range of 0.010-0.035 microSv/Gycm2. The dependence of dose to the X-ray equipment, the exposure parameters and the technique of the cardiologist were examined. Taking under consideration the laboratories' annual workload, the maximum annual dose was estimated to be 1.9 and 2.8 mSv in the two hospitals.

Radiation doses to patients undergoing coronary angiography and percutaneous transluminal coronary angioplasty

A detailed study of radiation doses received by 168 patients who underwent coronary angiography (CAG) and 102 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) in two Greek hospitals is presented. Radiation dose was measured in terms of dose-area product (DAP). The contribution of fluoroscopy and cineradiography to the total DAP was examined separately for each radiological projection used in both procedures. Effective dose and doses to various organs were estimated with the help of the ODS-60 software. Total DAP was found to correlate linearly to fluoroscopy time and cine film length. Mean DAP values were found to be 80.8 +/- 28.0 Gy cm2 for CAG and 86.2 +/- 65.6 Gy cm2 for PTCAs, whereas the estimated mean values of effective dose were 20.9 +/- 7.5 and 23.2 +/- 18.1 mSv respectively. DAP to effective dose conversion coefficients were estimated to be 0.26 mSv/Gy cm2 for CAG and 0.27 mSv/Gy cm2 for PTCAs.

Suitability of venous and arterial conduits used for coronary artery bypass grafting in conjunction with coronary disease risk factors

BACKGROUND/STUDY OBJECTIVES: We studied patients undergoing coronary artery bypass grafting. Risk factors for coronary disease were studied in conjunction with the histopathologic findings of the grafts prior to implantation. Our aim was to correlate the histologic condition of the grafts and evaluate the morphological changes in conjunction with existing risk factors.

DESIGN/PATIENTS

In 10 candidates for surgical revascularization (nine males, mean age 60.8 years), the risk factor profile was studied (smoking, dyslipidaemia, hypertension, diabetes, family history) and the Body Mass Index was calculated. Of a total of 14 grafts, 10 were saphenous vein grafts and four left internal thoracic artery grafts. Histologic samples were studied under optical and electron microscopy. We studied the intima morphology and thickness, the width of the intercellular spaces, the texture of the subendothelial layer, the endothelial status, and the condition of the basal lamina. Histopathological changes were correlated with risk factors.

RESULTS

Histopathological changes were observed in the wall structure of all grafts. The most important changes were found in the venous grafts, notably: intima thickening, existence of foam cells in the intima, widening of the intercellular spaces, subendothelial oedema, degeneration and detachment of endothelial cells, and wide multilayered basal lamina. The co-existence of two or more risk factors seems to exarcerbate morphological changes.

CONCLUSION

Morphological changes are present principally in the walls of venous but also arterial conduits, even prior to implantation. These changes may be attributable to preparation techniques and preservation conditions of the grafts, but they could additionally be induced by coexisting risk factors. It is conceivable that these alterations could perhaps precipitate and accelerate atherosclerotic changes, inducing lumen narrowing or even occlusion of the graft postoperatively.