Lipoprotein Abnormalities Associated with Mild Impairment of Kidney Function in the Multi-Ethnic Study of Atherosclerosis

Background and objectives: Impaired kidney function is associated with increased risk for cardiovascular disease and may progress over time to end-stage renal disease. Abnormal lipoprotein metabolism has been implicated as a possible cause of these complications, but lipoproteins have not been described at the earliest stages of kidney disease.Design, setting, participants, & measurements: This study examined cross-sectional associations of serum cystatin C with conventional lipid measurements and detailed nuclear magnetic resonance lipoprotein measurements in the community-based Multi-Ethnic Study of Atherosclerosis. A total of 5109 participants with estimated glomerular filtration rate ≥60 ml/min per 1.73 m² were included in analyses.Results: Adjusting for age, gender, race/ethnicity, diabetes, impaired fasting glucose, BP, smoking, medications, body mass index, and albuminuria, greater cystatin C concentrations were associated with progressively unfavorable lipid and lipoprotein concentrations, including greater triglyceride concentration (+22 mg/dl, comparing fifth versus first quintiles of cystatin C) and lesser high-density lipoprotein cholesterol concentration (−7 mg/dl) but not with low-density lipoprotein cholesterol measured using conventional methods. When low-density lipoprotein particle subclasses were examined in more detail using nuclear magnetic resonance, greater cystatin C was associated with greater concentrations of atherogenic small low-density lipoprotein particles (+63 nmol/L) and intermediate-density lipoprotein particles (+6 nmol/L) and with a decrease in mean low-density lipoprotein particle size.Conclusions: Lipoprotein abnormalities are present with milder degrees of renal impairment than previously recognized, and abnormalities in low-density lipoprotein particle distribution may not be appreciated using conventional lipid measurements. These abnormalities may contribute to kidney disease progression and/or cardiovascular disease.Impaired kidney function is associated with increased risk for cardiovascular disease (1,2) and may progress over time to ESRD. Abnormal lipoprotein metabolism has been implicated as a possible cause of these complications (3,4). Moderate chronic kidney disease (CKD) is associated with elevated triglyceride and diminished HDL cholesterol concentrations (3–8). Total and LDL cholesterol concentrations have generally been reported to be unaltered in the setting of CKD (5–7); however, conventional lipid measurements do not fully capture relevant changes in lipoprotein distribution, particularly differences in LDL particle number and size (3,4). Moreover, lipid and lipoprotein concentrations have not been described at the earliest stages of kidney disease (before GFR falls below 60 ml/min per 1.73 m²), when the pathophysiologic processes that lead to atherosclerosis and CKD could already be developing.We examined associations of serum cystatin C with detailed nuclear magnetic resonance (NMR) lipoprotein measurements in the Multi-Ethnic Study of Atherosclerosis (MESA). Only participants with estimated GFR (eGFR) ≥60 ml/min per 1.73 m² were included in analyses, and individuals with clinical cardiovascular disease were excluded from MESA participation. Elevated serum cystatin C detects mild impairment of kidney function with greater sensitivity than eGFR calculated from serum creatinine (9–11). NMR quantifies lipoprotein particles by size, allowing characterization of particle number and size within classes of lipoproteins.     

Ex vivo expansion with stem cell factor and interleukin-11 augments both short-term recovery posttransplant and the ability to serially transplant marrow

The characterization of many cytokines involved in the control of hematopoiesis has led to intense investigation into their potential use in ex vivo culture to expand progenitor numbers. We have established the optimum ex vivo culture conditions that allow substantial amplification of transient engrafting murine stem cells and which, simultaneously, augment the ability to sustain serial bone marrow transplantation (BMT). Short-term incubation of unfractionated BM cells in liquid culture with stem cell factor (SCF) and interleukin-11 (IL- 11) produced a 50-fold amplification of clonogenic multipotential progenitors (CFU-A). Following such ex vivo expansion, substantially fewer cells were required to rescue lethally irradiated mice. When transplanted in cell doses above threshold for engraftment, BM cells expanded ex vivo resulted in significantly more rapid hematopoietic recovery. In a serial transplantation model, unmanipulated BM was only able to consistently sustain secondary BMT recipients, but BM expanded ex vivo has sustained quaternary BMT recipients that remain alive and well more than 140 days after 4th degree BMT. These results show augmentation of both short-term recovery posttransplant and the ability to serially transplant marrow by preincubation in culture with SCF and IL-11.     

CD34 expression is regulated reciprocally with adhesion molecules in vascular endothelial cells in vitro

Freshly cultured vascular endothelial cells express the CD34 antigen in a diffuse cell surface pattern with some concentration on microvilli. Expression is downregulated with proliferation in continuous culture and undetectable after nine population doublings but can be maintained by restraining cell proliferation and promoting cell contact. Expression of CD34 at the antigen and mRNA levels on early passage cells is rapidly downregulated by interleukin-1 beta (IL-1 beta), interferon-gamma (INF-gamma), and tumor necrosis factor-alpha (TNF- alpha) under conditions in which these ligands upregulate the adhesion molecules: endothelial leukocyte adhesion molecule 1 (ELAM-1) and intracellular adhesion molecule 1 (ICAM-1). This reciprocal pattern of expression and the topographic distribution of CD34 molecules on the lumenal interdigitated microprocesses of adjacent endothelial cells in vivo suggest that CD34 might have a negative modulating role on adhesion functions of endothelia.     

Biomarkers to predict recurrent cardiovascular disease: the Heart and Soul Study

Purpose

The study purpose was to evaluate the ability of 6 biomarkers to improve the prediction of cardiovascular events among persons with established coronary artery disease.

Background

Cardiovascular risk algorithms are designed to predict the initial onset of coronary artery disease but are less effective in persons with preexisting coronary artery disease.

Methods

We examined the association of N-terminal prohormone brain natriuretic peptide (Nt-proBNP), cystatin C, albuminuria, C-reactive protein (CRP), interleukin-6, and fibrinogen with cardiovascular events in 979 Heart and Soul Study participants with coronary artery disease after adjusting for demographic, lifestyle, and behavior variables; cardiovascular risk factors; cardiovascular disease severity; medication use; and left ventricular ejection fraction. The outcome was a composite of stroke, myocardial infarction, and coronary heart disease death during an average of 3.5 years of follow-up.

Results

During follow-up, 142 participants (15%) developed cardiovascular events. The highest quartiles (vs lower 3 quartiles) of 5 biomarkers were individually associated with cardiovascular risk after multivariate analysis: Nt-proBNP hazard ratio (HR) = 2.13 (95% confidence interval [CI], 1.43-3.18); cystatin C HR = 1.72 (95% CI, 1.10-2.70); albuminuria HR = 1.71 (95% CI, 1.15-2.54); CRP HR = 2.00 (95% CI, 1.40-2.85); and interleukin-6 HR = 1.76 (95% CI, 1.22-2.53). When all biomarkers were included in the multivariable analysis, only Nt-proBNP, albuminuria, and CRP remained significant predictors of events: HR = 1.88 (95% CI, 1.23-2.85), HR = 1.63 (95% CI, 1.09-2.43), and HR = 1.82 (95% CI, 1.24-2.67), respectively. The area under the receiver operator curve for clinical predictors alone was 0.73 (95% CI, 0.68-0.78); adding Nt-proBNP, albuminuria, and CRP significantly increased the area under the receiver operator curve to 0.77 (95% CI, 0.73-0.82, P <.005).

Conclusion

Among persons with prevalent coronary artery disease, biomarkers reflecting hemodynamic stress, kidney damage, and inflammation added significant risk discrimination for cardiovascular events.     

Arg-Gly-Asp-dependent occupancy of GPIIb/IIIa by applaggin: evidence for internalization and cycling of a platelet integrin

Using indirect immunofluorescence microscopy we examined the distribution and cycling of GPIIb/IIIa after binding to applaggin, a high-affinity Arg-Gly-Asp (RGD)--containing ligand. Resting, unfixed platelets were incubated with applaggin for 30 minutes at 37 degrees C, and bound applaggin was detected by an affinity-purified rabbit anti- applaggin antibody. Examination of intact cells showed a rim pattern for applaggin, consistent with its binding to the platelet surface. Staining of Triton X-100--permeabilized cells showed an intracellular pool of applaggin. Competition of applaggin binding by either AP-2, an anti-GPIIb/IIIa monoclonal antibody (MoAb) that blocks fibrinogen binding, or the synthetic peptide RGDW eliminated both surface and intracellular staining, indicating that applaggin is binding to GPIIb/IIIa in an RGD-dependent manner. Inhibition of platelet activation by PGE1 and theophylline had no effect on the observed staining patterns, indicating that cellular activation is not required for surface binding and subsequent internalization. To evaluate whether occupancy of functional binding sites on GPIIb/IIIa is required for internalization, we used mAb15, an anti-GPIIIa antibody that neither blocks fibrinogen binding nor induces the expression of ligand-induced binding sites on GPIIb/IIIa. In these studies mAb15 was internalized in a manner analogous to both AP-2 and applaggin, showing that occupancy of the RGD binding site is not required to initiate receptor internalization. To estimate the size of the newly internalized pool of applaggin, 125I-applaggin--binding studies were performed. Displacement of bound 125I-applaggin by excess unlabeled applaggin or EDTA showed that at least 17% of bound applaggin was nondisplaceable when binding was performed under conditions permitting membrane flow and internalization. These data indicate that GPIIb/IIIa is internalized in unstimulated platelets independent of cellular activation or occupancy of the functional binding site(s) of GPIIb/IIIa by RGD-containing ligands. Thus, internalization of GPIIb/IIIa may represent a mechanism by which the surface expression of this adhesion receptor is regulated.     

Recurrent pulmonary embolism after Greenfield filter placement

Three patients with documented recurrent pulmonary embolism with an inferior vena cava (IVC) Greenfield filter in place were examined with contrast-material-enhanced cavography. Mechanisms for recurrent pulmonary embolism were found to be propagation of thrombus through the filter struts, occlusion of the IVC at the level of the filter, and loss of contact of the filter hooks with a portion of the caval wall.