Influence of serum cholesterol on atherogenesis and intimal hyperplasia after angioplasty: inhibition by amlodipine

Temporal Relationship Between Changes in Serum Calcium and Hypercholesteremia and Its Impact on Future Brachial-Ankle Pulse Wave Velocity Levels

Background: The high levels of serum calcium and cholesterol are the important risk factors of cardiovascular disease (CVD), which frequently influence each other during the development of CVD. However, few studies have examined their temporal relationship to confirm the precursor, and it is still largely unknown whether and how their temporal relationship would influence the development of CVD. This study aimed to establish the temporal relationship between the changes in serum calcium and cholesterol using the longitudinal cohort data, and examine whether this temporal relationship influenced the arterial elasticity indicated by brachial-ankle pulse wave velocity (baPWV). Methods: This is a cohort study with a sample of 3,292 Chinese participants (aged 20-74 years) with 5.7 years follow-up. Serum calcium and cholesterol were measured at baseline and follow-up survey. The cross-lagged path analysis was used to examine their temporal relationship, and mediation analysis was performed to evaluate the potential mediating effect. Results: The cross-lagged path coefficients (β₂ values) from baseline serum calcium to follow-up cholesterol was significantly greater than the path coefficients (β₁ values) from baseline cholesterol to follow-up serum calcium (β₂ = 0.110 vs. β₁ = 0.047; P = 0.010) after adjusting for the multiple covariates. The path coefficients from baseline serum calcium to follow-up cholesterol in the participants with high baPWV was significantly greater than the participants with low baPWV (β₂ = 0.155 for high baPWV and β₂ = 0.077 for low baPWV, P = 0.028 for the difference between the β₂ values). Moreover, cholesterol partially mediated the association between the higher serum calcium and greater subsequent baPWV values, the percentage of the total effect mediated by cholesterol was estimated at 21.7%. Conclusion: Our findings indicate that increased serum calcium precedes increased in serum cholesterol, and this temporal relationship may contribute to the development of higher baPWV levels.

Natural history of β-cell adaptation and failure in type 2 diabetes

Type 2 diabetes mellitus (T2D) is a complex disease characterized by β-cell failure in the setting of insulin resistance. The current evidence suggests that genetic predisposition, and environmental factors can impair the capacity of the β-cells to respond to insulin resistance and ultimately lead to their failure. However, genetic studies have demonstrated that known variants account for less than 10% of the overall estimated T2D risk, suggesting that additional unidentified factors contribute to susceptibility of this disease. In this review, we will discuss the different stages that contribute to the development of β-cell failure in T2D. We divide the natural history of this process in three major stages: susceptibility, β-cell adaptation and β-cell failure, and provide an overview of the molecular mechanisms involved. Further research into mechanisms will reveal key modulators of β-cell failure and thus identify possible novel therapeutic targets and potential interventions to protect against β-cell failure.

Transauricular balloon angioplasty in rabbit thoracic aorta: a novel model of experimental restenosis

BACKGROUND

The aim of this study was to demonstrate a percutaneous transauricular method of balloon angioplasty in high-cholesterol fed rabbits, as an innovative atherosclerosis model.

METHODS

Twenty male New Zealand rabbits were randomly divided into two groups of ten animals, as follows: atherogenic diet plus balloon angioplasty (group A) and atherogenic diet alone (group B). Balloon angioplasty was performed in the descending thoracic aorta through percutaneous catheterization of the auricular artery. Eight additional animals fed regular diet were served as long term control. At the end of 9 week period, rabbits were euthanized and thoracic aortas were isolated for histological, immunohistochemical and biochemical analysis.

RESULTS

Atherogenic diet induced severe hypercholesterolemia in both group A and B (2802 ± 188.59 and 4423 ± 493.39 mg/dl respectively) compared to the control animals (55.5 ± 11.82 mg/dl; P < 0.001). Group A atherosclerotic lesions appeared to be more advanced histologically (20% type IV and 80% type V) compared to group B lesions (50% type III and 50% type IV). Group A compared to group B atherosclerotic lesions demonstrated similar percentage of macrophages (79.5 ± 9.56% versus 84 ± 12.2%; P = 0.869), more smooth muscle cells (61 ± 14.10% versus 40.5 ± 17.07; P = 0.027), increased intima/media ratio (1.20 ± 0.50 versus 0.62 ± 0.13; P = 0.015) despite the similar degree of intimal hyperplasia (9768 ± 1826.79 μm² versus 12205 ± 8789.23 μm²; P = 0.796), and further significant lumen deterioration (23722 ± 4508.11 versus 41967 ± 20344.61 μm²; P = 0.05) and total vessel area reduction (42350 ± 5819.70 versus 73190 ± 38902.79 μm²; P = 0.022). Group A and B animals revealed similar nitrated protein percentage (P = NS), but significantly higher protein nitration compared to control group (P < 0.01; P < 0.01, respectively). No deaths or systemic complications were reported.

CONCLUSION

Transauricular balloon angioplasty constitutes a safe, minimally invasive and highly successful model of induced atherosclerosis in hyperlipidaemic rabbits.

Seeding of endothelial cells on the luminal surface of a sheet model of cold-stored (at 4°C) sheep carotid arteries

Cold-stored arteries are biomaterials that potentially represent an abundant "off-the-shelf" source of vascular grafts for use in vascular surgery. One of the keys to reestablishing the antithrombogenic endothelial cell (EC) lining of cold-stored arterial grafts is to maximize the number of ECs that attach following seeding. In this study, the cold-stored sheep carotid artery is used as a substrate to determine the conditions that maximize EC adherence following seeding. The effect of serum concentration, duration of seeding incubation, seeding density, and period of cold storage on attachment of ECs following seeding of 4-week cold-stored sheep carotid arteries (n = 5 arteries), 8-week cold-stored sheep carotid arteries (n = 5 arteries), and 12-week cold-stored sheep carotid arteries (n = 5 arteries) was examined. Three experiments (serum concentration, time of incubation, and seeding density) were conducted to determine the conditions that maximized the number of cultured sheep carotid artery ECs that attached to cold-stored sheep carotid artery following seeding. A flat sheet model was used. Serum concentration (0%, 10%, 20%, and 30%) in the seeding suspension did not have a significant effect on overall EC adherence on 4-, 8-, and 12-week cold-stored arteries. Time of seeding incubation (30, 60, and 90 min) did not have a significant effect on overall EC adherence on 4-, 8-, and 12-week cold-stored arteries. Seeding density (500,000 cells/ml, 1,000,000 cells/ml, and 2,000,000 cells/ml) had a significant effect (p = 0.036) on overall EC adherence on 4-, 8-, and 12-week cold-stored arteries. The period of cold storage (4, 8, and 12 weeks) of the artery had a significant effect (p = 0.002, p < 0.0001, p < 0.0001 in serum, time, and seeding density experiments, respectively) on overall EC adherence following seeding. Pairwise comparisons of EC adherence revealed the following. In the serum experiment, EC adherence on 4-week cold-stored arteries was significantly greater than on 8-week cold-stored arteries (p = 0.003) and 12-week cold-stored arteries (p = 0.002). This effect was due largely to the significant difference between EC adherence on 4-week and 8-week cold-stored arteries (p = 0.0002) and between EC adherence on 4-week and 12-week cold-stored arteries (p = 0.0091) at 20% serum. In the time experiment, EC adherence on 4-week cold-stored arteries was significantly greater than on 12-week cold-stored arteries (p < 0.0001). In the seeding density experiment, EC adherence on 4-week cold-stored arteries was significantly greater than on 8-week cold-stored arteries (p < 0.0001) and 12-week cold-stored arteries (p < 0.0001). In the same experiment, EC adherence following seeding at a density of 1,000,000 cells/ml and 2,000,000 cells/ml was significantly greater (p = 0.03 and p = 0.02, respectively) than EC adherence following seeding at a density of 500,000 cells/ml. Thus, it was determined that 4-week cold-stored arteries were superior to 8- and 12-week cold-stored arteries in terms of the number of ECs that adhered. It was also determined that a seeding density of 1,000,000 or 2,000,000 cells/ml was superior to a seeding density of 500,000 cells/ml in terms of producing maximal EC attachment. The ideal conditions, from those examined, for maximizing EC attachment to cold-stored arteries were 4 weeks of cold storage, a serum concentration of 20%, a seeding density of 2,000,000 cells/ml, and a duration of incubation of 30-90 min.

Interaction between mild hypercholesterolemia, HDL-cholesterol levels, and angiotensin II in intimal hyperplasia in mice

Two month old C57BL/6 mice were placed on three different diets: 1) normal diet (NC; 0.025% cholesterol), 2) hypercholesterolemic Western-type diet (HC-W; 0.2% cholesterol), and 3) hypercholesterolemic Paigen-type diet (HC-P; 1.25% cholesterol plus 0.5% cholic acid). At 6 months of age, the animals underwent ligation of the left carotid artery and were randomly assigned to vehicle (PBS, subcutaneous) or angiotensin II (Ang II; 1.4 mg/kg/day, subcutaneous) treatment for 4 weeks. Low density lipoprotein-cholesterol levels were similarly increased in both HC diets (NC, 4 +/- 3 mg/dl; HC-W, 123 +/- 17 mg/dl; HC-P, 160 +/- 14 mg/dl). However, the levels of high density lipoprotein-cholesterol (HDL-C) were reduced only in animals fed the HC-P diet (NC, 82 +/- 6 mg/dl; HC-W, 79 +/- 7 mg/dl; HC-P, 58 +/- 7 mg/dl). In Ang II-treated mice, carotid artery ligation induced intimal smooth muscle cell proliferation to a similar extent in NC- and HP-W-fed animals. However, a significantly larger intimal area developed in ligated vessels from Ang II-treated mice fed the HC-P diet (3.6-fold higher than in Ang II-treated NC mice). Together, these results show the accelerating effect of mild hypercholesterolemia, reduced HDL-C levels, and Ang II on intimal hyperplasia after carotid artery ligation in mice.

A membrane defect in the pathogenesis of the Smith-Lemli-Opitz syndrome

The Smith-Lemli-Opitz syndrome (SLOS) is an often lethal birth defect resulting from mutations in the gene responsible for the synthesis of the enzyme 3beta-hydroxy-steroid-Delta7-reductase, which catalyzes the reduction of the double bond at carbon 7 on 7-dehydrocholesterol (7-DHC) to form unesterified cholesterol. We hypothesize that the deficiency in cholesterol biosynthesis and subsequent accumulation of 7-DHC in the cell membrane leads to defective composition, organization, dynamics, and function of the cell membrane. Using skin fibroblasts obtained from SLOS patients, we demonstrate that the SLOS membrane has increased 7-DHC and reduced cholesterol content and abnormal membrane fluidity. X-ray diffraction analyses of synthetic membranes prepared to mimic SLOS membranes revealed atypical membrane organization. In addition, calcium permeability is markedly augmented, whereas membrane-bound Na+/K+ATPase activity, folate uptake, inositol-1,4,5-trisphosphate signaling, and cell proliferation rates are markedly suppressed. These data indicate that the disturbance in membrane sterol content in SLOS, likely at the level of membrane caveolae, directly contributes to the widespread tissue abnormalities in this disease.