Radjesh J. Bisoendial

Restoration of Endothelial Function by Increasing High-Density Lipoprotein in Subjects With Isolated Low High-Density Lipoprotein

Background Loss‐of‐function mutations in the ATP‐binding cassette (ABCA)‐1 gene locus are the underlying cause for familial hypoalphalipoproteinemia, providing a human isolated low‐HDL model. In these familial hypoalphalipoproteinemia subjects, we evaluated the impact of isolated low HDL on endothelial function and the vascular effects of an acute increase in HDL. Methods and Results In 9 ABCA1 heterozygotes and 9 control subjects, vascular function was assessed by venous occlusion plethysmography. Forearm blood flow responses to the endothelium‐dependent and ‐independent vasodilators serotonin (5HT) and sodium nitroprusside, respectively, and the inhibitor of nitric oxide synthase NG‐monomethyl‐Larginine (L‐NMMA) were measured. Dose‐response curves were repeated after systemic infusion of apolipoprotein A‐I/phosphatidylcholine (apoA‐I/PC) disks. At baseline, ABCA1 heterozygotes had decreased HDL levels (0.4±0.2 mmol/L; P<0.05), and their forearm blood flow responses to both 5HT (maximum, 49.0±10.4%) and L‐NMMA (maximum, ‐22.8±22.9%) were blunted compared with control subjects (both P≤0.005). Infusion of apoA‐I/PC disks increased plasma HDL to 1.3±0.4 mmol/L in ABCA1 heterozygotes, which resulted in complete restoration of vasomotor responses to both 5HT and L‐NMMA (both P≤0.001). Endothelium‐independent vasodilation remained unaltered throughout the protocol. Conclusions In ABCA1 heterozygotes, isolated low HDL is associated with endothelial dysfunction, attested to by impaired basal and stimulated NO bioactivity. Strikingly, both parameters were completely restored after a single, rapid infusion of apoA‐I/PC. These findings indicate that in addition to its long‐term role within reverse cholesterol transport, HDL per se also exerts direct beneficial effects on the arterial wall. (Circulation. 2003;107:2944‐2948.)

Activation of Inflammation and Coagulation After Infusion of C-Reactive Protein in Humans

C-reactive protein (CRP) has been postulated to play a causal part in atherosclerosis and its acute complications. We assessed the effects of CRP-infusion on coagulation and inflammatory pathways to determine its role in atherothrombotic disease. Seven male volunteers received an infusion on two occasions, containing 1.25 mg/kg recombinant human CRP (rhCRP) or diluent, respectively. CRP-concentrations rose after rhCRP-infusion from 1.9 (0.3 to 8.5) to 23.9 (20.5 to 28.1) mg/L, and subsequently both inflammation and coagulation were activated. This sequence of events suggests that CRP is not only a well known marker of cardiovascular disease, but is also probably a mediator of atherothrombotic disease.

C-reactive protein is a mediator of cardiovascular disease

C-reactive protein is postulated to embody an index that can reflect cardiovascular risk and can be used to independently predict major cardiovascular events and mortality. On the other hand, credible experimental data have become available that demonstrate the abundant presence of C-reactive protein in atherosclerotic lesions and, moreover, identify C-reactive protein as an initiator of several pathogenic pathways that can cause atherogenic changes. Consequently, there has been a paradigm shift in which C-reactive protein is no longer regarded as merely an indicator of cardiovascular risk, but increasingly considered a direct partaker in the pathogenesis of atherosclerotic cardiovascular disease. These data underscore the need to explore risk-reducing interventions that selectively inhibit C-reactive protein activity as a novel strategy to prevent clinical manifestations of atherosclerosis.

Effects of CRP infusion on endothelial function and coagulation in normocholesterolemic and hypercholesterolemic subjects

C-reactive protein (CRP) has been suggested to exert direct adverse effects on the vasculature in experimental setups, including endothelial dysfunction and proinflammatory changes. Here, we assessed the consequences of 1.25 mg/kg highly purified recombinant human CRP, administered as an intravenous bolus, in six patients with familial hypercholesterolemia (FH) and six normocholesterolemic subjects. Endothelium-dependent and -independent vasoreactivity to serotonin and nitroprusside, respectively, were assessed using venous occlusion plethysmography before and after CRP infusion. For biochemical analyses, blood was drawn at different time points. At baseline, FH patients showed blunted endothelium-dependent vasodilation (maximum, 89.2 ± 30.0% vs. 117.7 ± 13.1% in normolipidemic subjects; P = 0.037). Procoagulant activity was also higher in FH patients, illustrated by increased prothrombin fragment 1+2 (F1+2) levels (P = 0.030) and plasminogen activator inhibitor type-1 (PAI-1) activity (P = 0.016). Upon CRP challenge, endothelium-dependent vasodilator capacity further deteriorated in FH patients (P = 0.029), whereas no change in vascular reactivity was observed in normolipidemic subjects. Additionally, coagulation activation was augmented in FH patients compared with normolipidemic subjects (P = 0.009 for F1+2 levels; P = 0.018 and P = 0.003 for PAI-1 antigen and activity, respectively). No difference in inflammatory responses was observed between groups. In hypercholesterolemic patients, CRP aggravates endothelial dysfunction and also evokes augmented procoagulant responses. These findings suggest that particularly in hypercholesterolemia, CRP-lowering strategies should be considered in addition to LDL reduction.

Measurement of subclinical atherosclerosis: beyond risk factor assessment.

Purpose of review Assessment of subclinical atherosclerosis using the current available noninvasive imaging modalities holds promise for individual cardiovascular risk management and monitoring efficacy of therapeutic interventions (i.e. surrogate end-points). The present review addresses benefits and limitations of flow-mediated dilatation, intima-media thickness, electron-beam computed tomography and magnetic resonance coronary angiography. Recent findings Both carotid intima-media thickness and peripheral flow-mediated dilatation correlate inversely with cardiovascular risk factors and coronary artery disease. They have been shown to carry predictive value for future cardiovascular events, but clinical application of both intima-media thickness and flow-mediated dilatation demands further methodological maturation of these techniques. Intima thickening has been successfully targeted in numerous intervention trials, but determination of an explicit threshold value beyond which cardiovascular risk significantly increases will facilitate its utility as a routine clinical tool. Electron-beam computed tomography can accurately detect and quantify coronary artery calcification (an established marker of the total coronary plaque burden). However, lack of evidence of its additional predictive power for future coronary events warrants for further research. Finally, magnetic resonance coronary angiography appears to be a promising technique, integrating both functional and anatomical aspects of coronary artery disease. Properly designed studies are needed to determine its value in clinical practice. Summary Various noninvasive imaging techniques have recently emerged that may find applications in clinical research. However, before widespread clinical utilization, further technical refinement of all of the cited imaging modalities is mandatory. It will be a challenge over the coming few years to clarify whether improvements in surrogate end-points can directly be translated into improved outcomes.

C-Reactive Protein Elicits White Blood Cell Activation in Humans

OBJECTIVE Consistent epidemiologic evidence suggests that acute infections increase the risk for acute cardiovascular events. We tested in humans whether activation of peripheral leukocytes in reaction to the administration of recombinant human C-reactive protein (rhCRP) may provide a mechanism for infectious diseases to promote atherosclerotic disease. METHODS AND RESULTS By using quantitative real-time polymerase chain reaction analysis, whole-blood expression profiles were analyzed for 95 inflammatory markers before and after infusion of 1.25 mg/kg rhCRP in 5 male volunteers. Relevant transcript levels were measured at baseline and 4 and 8 hours after rhCRP-infusion. CRP caused significant up-regulation of matrix metalloproteinase (MMP)-9, monocyte chemoattractant protein (MCP)-1, plasminogen activator urokinase, macrophage inflammatory protein 1 alpha, and nuclear factor of kappa B inhibitor mRNAs in peripheral leukocytes. mRNA up-regulation of MMP-9 and MCP-1 was 17- and 11-fold, respectively. The corresponding increase in plasma protein levels of MMP-9 (78+/-32 ng/mL to 109+/-41 ng/mL; P=.014) and MCP-1 (312+/-92 pg/mL to 2590+/-898 pg/mL; P=.007) closely mirrored mRNA findings. Also, in whole-blood culture stimulation assays, CRP induced proinflammatory changes. Notably, heat inactivation abolished the capacity of CRP to evoke these proinflammatory changes, excluding a role for contaminants within the purified CRP preparation. CONCLUSION CRP elicits activation of peripheral leukocytes with ensuing secretion of plaque-destabilizing mediators. These findings are consistent with the hypothesis that infectious diseases trigger manifestations of atherosclerosis, in which CRP elevation might contribute to the onset of cardiovascular events.

Consequences of Cholesteryl Ester Transfer Protein Inhibition in Patients With Familial Hypoalphalipoproteinemia

To the Editor: A large proportion of clinical events cannot be prevented during statin therapy, which calls for novel drug targets to further improve cardiovascular outcome. In particular, HDL-increasing strategies hold great promise. The impact of decreased HDL-C on cardiovascular disease (CVD)-related morbidity and mortality has been sharply delineated in individuals affected by familial hypoalphalipoproteinemia (FHA).1 HDL exerts multiple antiatherogenic actions beyond its role in reverse cholesterol transport, comprising antiinflammatory, antioxidative, and direct vascular effects.2 Whereas current strategies to raise HDL-C are limited, novel CETP-inhibitors are capable of mediating significant HDL-C elevation.3,4 Therefore, we evaluated the effects of CETP inhibition on lipid metabolism and markers of oxidation in subjects with FHA. Subjects were recruited from a Dutch population-based study to identify genes that control HDL-C levels,1 meeting the following criteria: (1) plasma HDL-C level below 10th percentile for age and sex; (2) absence of secondary lipid disorders; and (3) high likelihood of inherited low HDL (defined as HDL-C below 10th percentile in at least one first-degree family member). Nineteen FHA patients (13 men and 6 women; mean±SD age: 42.9±13.9 years), all free of overt macrovascular disease, were enrolled in the study. In 9 of these subjects the underlying defect was defined: heterozygosity for an apolipoprotein A-I (L178P) mutation,1 whereas in the remainder this genetic defect was excluded. The study protocol was approved …

Apolipoprotein A-I Increases Insulin Secretion and Production From Pancreatic β-Cells via a G-Protein-cAMP-PKA-FoxO1–Dependent Mechanism

Objective— Therapeutic interventions that increase plasma levels of high-density lipoproteins and apolipoprotein A-I (apoA-I) A-I, the major high-density lipoprotein apolipoprotein, improve glycemic control in people with type 2 diabetes mellitus. High-density lipoproteins and apoA-I also enhance insulin synthesis and secretion in isolated pancreatic islets and clonal &bgr;-cell lines. This study identifies the signaling pathways that mediate these effects. Approach and Results— Incubation with apoA-I increased cAMP accumulation in Ins-1E cells in a concentration-dependent manner. The increase in cAMP levels was inhibited by preincubating the cells with the cell-permeable, transmembrane adenylate cyclase inhibitor, 2′5′ dideoxyadenosine, but not with KH7, which inhibits soluble adenylyl cyclases. Incubation of Ins-1E cells with apoA-I resulted in colocalization of ATP-binding cassette transporter A1 with the G&agr;s subunit of a heterotrimeric G-protein and a G&agr;s subunit-dependent increase in insulin secretion. Incubation of Ins-1E cells with apoA-I also increased protein kinase A phosphorylation and reduced the nuclear localization of forkhead box protein O1 (FoxO1). Preincubation of Ins-1E cells with the protein kinase A–specific inhibitors, H89 and PKI amide, prevented apoA-I from increasing insulin secretion and mediating the nuclear exclusion of FoxO1. Transfection of Ins-1E cells with a mutated FoxO1 that is restricted to the nucleus confirmed the requirement for FoxO1 nuclear exclusion by blocking insulin secretion in apoA-I–treated Ins-1E cells. ApoA-I also increased Irs1, Irs2, Ins1, Ins2, and Pdx1 mRNA levels. Conclusions— ApoA-I increases insulin synthesis and secretion via a heterotrimeric G-protein-cAMP-protein kinase A-FoxO1–dependent mechanism that involves transmembrane adenylyl cyclases and increased transcription of key insulin response and &bgr;-cell survival genes.

The Prothrombotic State in Rheumatoid Arthritis: An Additive Risk Factor for Adverse Cardiovascular Events

Rheumatoid arthritis (RA) has been recognized to increase cardiovascular morbidity and mortality independent of established risk factors. The chronic inflammatory state, a hallmark of RA, is considered an autonomous risk factor, whereas components of innate and adaptive immunity are believed to contribute to the onset of acute cardiovascular events. Several studies have suggested that RA confers a prothrombotic state featured by abnormalities in coagulation and fibrinolytic systems together with an altered state of platelet reactivity. It is conceivable that these findings may be partly instrumental for the observed increased risk for adverse cardiovascular events in RA. Therapeutic strategies aimed at attenuating the inflammatory disease activity and intervening at the point of cross-talk between mediators of inflammation and thrombogenesis may help reduce cardiovascular disease burden in patients with RA.

Reduced fecal sterol excretion in subjects with familial hypoalphalipoproteinemia

BACKGROUND Fecal bile acid and neutral sterol excretion are the obligate endpoints of the reverse cholesterol transport pathway (RCT). In studies in mice, no evidence was found for a relation between HDL-cholesterol (HDL-c) levels and fecal sterol excretion. In this study, we have evaluated this relationship in patients with isolated low HDL-c versus controls. RESULTS Fecal sterol excretion was studied in 12 subjects with familial hypoalphalipoproteinemia (FHA) and 11 healthy controls. Compared to the controls (8.9+/-6.3mg/kg/day), neutral sterol excretion was significantly lower in the FHA group (4.0+/-2.4mg/kg/day). Fecal bile acid excretion showed a similar pattern. Across the groups, a strong positive correlation between HDL-c and fecal neutral sterol excretion was found (r=0.53; p=0.01). CONCLUSIONS Isolated low HDL-c levels in humans are associated with reduced fecal sterol excretion suggesting that in humans HDL regulates the final step in the RCT pathway at low HDL-c levels.