Optimal protective hypothermia in arrested mammalian hearts.

Many therapeutic hypothermia recommendations have been reported, but the information supporting them is sparse, and reveals a need for the data of target therapeutic hypothermia (TTH) from well-controlled experiments. The core temperature ≤35°C is considered as hypothermia, and 29°C is a cooling injury threshold in pig heart in vivo. Thus, an optimal protective hypothermia (OPH) should be in the range 29-35°C. This study was conducted with a pig cardiopulmonary bypass preparation to decrease the core temperature to 29-35°C range at 20 minutes before and 60 minutes during heart arrest. The left ventricular (LV) developed pressure, maximum of the first derivative of LV (dP/dtmax), cardiac power, heart rate, cardiac output, and myocardial velocity (Vmax) were recorded continuously via an LV pressure catheter and an aortic flow probe. At 20 minutes of off-pump during reperfusion after 60 minutes arrest, 17 hypothermic hearts showed that the recovery of Vmax and dP/dtmax established sigmoid curves that consisted of two plateaus: a good recovery plateau at 29-30.5°C, the function recovered to baseline level (BL) (Vmax=118.4%±3.9% of BL, LV dP/dtmax=120.7%±3.1% of BL, n=6); another poor recovery plateau at 34-35°C (Vmax=60.2%±2.8% of BL, LV dP/dtmax=28.0%±5.9% of BL, p<0.05, n=6; ), which are similar to the four normothermia arrest (37°C) hearts (Vmax=55.9%±4.8% of BL, LV dP/dtmax=24.5%±2.1% of BL, n=4). The 32-32.5°C arrest hearts showed moderate recovery (n=5). A point of inflection (around 30.5-31°C) existed at the edge of a good recovery plateau followed by a steep slope. The point presented an OPH that should be the TTH. The results are concordant with data in the mammalian hearts, suggesting that the TTH should be initiated to cool core temperature at 31°C.

Darapladib: an emerging therapy for atherosclerosis.

Despite a reduction in cardiovascular risk conferred by therapies that modify circulating lipids, a need remains for novel treatments to further decrease the occurrence of complications of atherosclerotic cardiovascular diseases. Lipoprotein-associated phospholipase-A(2) is an important regulator of lipid metabolism and inflammation that circulates with lipoprotein particles and is carried into the arterial wall with low-density lipoprotein particles during the progression of atherosclerosis. Within the vessel wall, lipoprotein-associated phospholipase-A(2) releases small molecules that stimulate macrophage recruitment and evolution to foam cells, leading to plaque vulnerability. Epidemiologic studies demonstrate that elevated circulating levels of lipoprotein-associated phospholipase-A(2) predict an increased risk of myocardial infarction and stroke, whereas histologic examination of diseased human coronary arteries reveals intense presence of the enzyme in atherosclerotic plaques that are prone to rupture. These considerations suggest lipoprotein-associated phospholipase-A(2) as a promising therapeutic target, and a specific inhibitor, darapladib, has been under development for this application. This review summarizes the completed preclinical and early phase clinical studies that underlie two recently commenced phase III clinical trials that will investigate the efficacy and safety of darapladib in nearly 13,000 individuals with coronary heart disease. When completed, these trials should provide important insights into the utility of darapladib to reduce myocardial infarction, stroke and cardiovascular death.

Effects of intensive blood-pressure control in type 2 diabetes mellitus.

BACKGROUND: There is no evidence from randomized trials to support a strategy of lowering systolic blood pressure below 135 to 140 mm Hg in persons with type 2 diabetes mellitus. We investigated whether therapy targeting normal systolic pressure (i.e., <120 mm Hg) reduces major cardiovascular events in participants with type 2 diabetes at high risk for cardiovascular events. METHODS: A total of 4733 participants with type 2 diabetes were randomly assigned to intensive therapy, targeting a systolic pressure of less than 120 mm Hg, or standard therapy, targeting a systolic pressure of less than 140 mm Hg. The primary composite outcome was nonfatal myocardial infarction, nonfatal stroke, or death from cardiovascular causes. The mean follow-up was 4.7 years. RESULTS: After 1 year, the mean systolic blood pressure was 119.3 mm Hg in the intensive-therapy group and 133.5 mm Hg in the standard-therapy group. The annual rate of the primary outcome was 1.87% in the intensive-therapy group and 2.09% in the standard-therapy group (hazard ratio with intensive therapy, 0.88; 95% confidence interval [CI], 0.73 to 1.06; P=0.20). The annual rates of death from any cause were 1.28% and 1.19% in the two groups, respectively (hazard ratio, 1.07; 95% CI, 0.85 to 1.35; P=0.55). The annual rates of stroke, a prespecified secondary outcome, were 0.32% and 0.53% in the two groups, respectively (hazard ratio, 0.59; 95% CI, 0.39 to 0.89; P=0.01). Serious adverse events attributed to antihypertensive treatment occurred in 77 of the 2362 participants in the intensive-therapy group (3.3%) and 30 of the 2371 participants in the standard-therapy group (1.3%) (P<0.001). CONCLUSIONS: In patients with type 2 diabetes at high risk for cardiovascular events, targeting a systolic blood pressure of less than 120 mm Hg, as compared with less than 140 mm Hg, did not reduce the rate of a composite outcome of fatal and nonfatal major cardiovascular events. (ClinicalTrials.gov number, NCT00000620.)

Effects of cardiac autonomic dysfunction on mortality risk in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial.

OBJECTIVE: Intensive therapy targeting normal blood glucose increased mortality compared with standard treatment in a randomized clinical trial of 10,251 participants with type 2 diabetes at high-risk for cardiovascular disease (CVD) events. We evaluated whether the presence of cardiac autonomic neuropathy (CAN) at baseline modified the effect of intensive compared with standard glycemia treatment on mortality outcomes in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial participants. RESEARCH DESIGN AND METHODS: CAN was assessed by measures of heart rate variability (HRV) and QT index (QTI) computed from 10-s resting electrocardiograms in 8,135 ACCORD trial participants with valid measurements (mean age 63.0 years, 40% women). Prespecified CAN definitions included a composite of the lowest quartile of HRV and highest QTI quartile in the presence or absence of peripheral neuropathy. Outcomes were all-cause and CVD mortality. Associations between CAN and mortality were evaluated by proportional hazards analysis, adjusting for treatment group allocation, CVD history, and multiple prespecified baseline covariates. RESULTS: During a mean 3.5 years follow-up, there were 329 deaths from all causes. In fully adjusted analyses, participants with baseline CAN were 1.55-2.14 times as likely to die as participants without CAN, depending on the CAN definition used (P < 0.02 for all). The effect of allocation to the intensive group on all-cause and CVD mortality was similar in participants with or without CAN at baseline (P(interaction) > 0.7). CONCLUSIONS: Whereas CAN was associated with increased mortality in this high-risk type 2 diabetes cohort, these analyses indicate that participants with CAN at baseline had similar mortality outcomes from intensive compared with standard glycemia treatment in the ACCORD cohort.

Darapladib, a reversible lipoprotein-associated phospholipase A2 inhibitor, for the oral treatment of atherosclerosis and coronary artery disease.

Darapladib, under development by GlaxoSmithKline plc, is a novel inhibitor of lipoprotein-associated phospholipase A2 (PLA2), an enzyme that may link lipid metabolism with inflammation, leading to the increased stability of atherosclerotic plaques present in the major arteries. Darapladib exhibits favorable pharmacokinetics, minimal predicted drug-drug interactions, sustained blood levels with once-daily oral dosing and limited inhibition of other PLA2 isozymes. Preclinical studies in diabetic-hypercholesterolemic swine (useful for the study of human atherosclerosis mechanisms) demonstrated that darapladib attenuated the progression of arterial plaques to a higher-risk phenotype by reducing the number of inflammatory macrophages within plaques and dampening T-cell responses. Two phase II clinical trials demonstrated sustained lipoprotein-associated PLA2 inhibition with daily oral dosing, and favorable effects on markers of inflammation and plaque stability. Phase III trials are ongoing to assess the safety and efficacy of darapladib in reducing adverse clinical events in patients with atherosclerosis.

Emerging inflammatory markers for assessing coronary heart disease risk.

Although assessment of traditional coronary heart disease risk factors can often stratify individuals into low- or high-risk categories, additional means are needed to more precisely classify people clinically defined as intermediate-risk, to guide the intensity of risk-reducing therapies. The recognition that inflammatory pathways are important in the progression of atherosclerosis and its complications has prompted investigation to identify circulating risk markers that may be useful in risk stratification. This article summarizes recent studies on the current use of an emerging group of inflammatory markers: soluble CD-40 ligand, interleukin-18, myeloperoxidase, B-type natriuretic peptides, secretory phospholipase A(2), lipoprotein-associated phospholipase A(2), and C-reactive protein. The demonstration that lowering C-reactive protein along with low-density lipoprotein cholesterol with statins reduces events beyond cholesterol lowering alone suggests that titration of therapies using other emerging inflammatory markers may further reduce the toll of atherosclerosis in adult populations.

Review of the evidence for the clinical utility of lipoprotein-associated phospholipase A2 as a cardiovascular risk marker.

A substantial body of peer-reviewed studies has been published validating the role of inflammation in atherogenesis and supporting lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) as a cardiovascular risk marker independent of and additive to traditional risk factors. As with elevated high-sensitivity C-reactive protein, an elevated Lp-PLA(2) level approximately doubles the risk for primary and secondary cardiovascular events. Interestingly, when both inflammatory markers are increased together, they provide an even greater predictive capability to help identify very-high-risk individuals who would benefit most from aggressive lipid-lowering therapy. High levels of Lp-PLA(2) are present in inflamed, rupture-prone plaques, and it appears that Lp-PLA(2) is released from these plaques into the circulation. Over 25 prospective epidemiologic studies have demonstrated the association of elevated Lp-PLA(2) levels with future coronary events and stroke-11 of 12 prospective studies have shown a statistically significant association between elevated Lp-PLA(2) and primary coronary or cardiovascular events, 12 of 13 have shown a statistically significant association with recurrent coronary or cardiovascular events, and 6 studies have shown a positive association with stroke. Lp-PLA(2) should be viewed today as an important cardiovascular risk marker whose utility is as an adjunct to the major risk factors to adjust absolute risk status and thereby modify low-density lipoprotein cholesterol goals. The low biologic fluctuation and high vascular specificity of Lp-PLA(2) makes it possible to use a single measurement in clinical decision making, and it also permits clinicians to follow the Lp-PLA(2) marker serially. Ultimately, Lp-PLA(2) may also be classified as a risk factor, but this should not detract from its utility today as a risk marker.

Consensus panel recommendation for incorporating lipoprotein-associated phospholipase A2 testing into cardiovascular disease risk assessment guidelines.

A consensus panel was formed to review the rapidly emerging literature on the vascular-specific inflammatory marker lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) and to update recommendations for the appropriate use of this novel biomarker in clinical practice. The recommendations of the panel build on guidelines of the Adult Treatment Panel III (ATP III) and the American Heart Association/Centers for Disease Control (AHA/CDC) for cardiovascular risk assessment. Consistent with the ATP III guideline recommendations for the use of inflammatory markers, Lp-PLA(2) is recommended as an adjunct to traditional risk assessment in patients at moderate and high 10-year risk. A simplified framework for traditional Framingham risk factor assessment is proposed. As a highly specific biomarker for vascular inflammation, elevated Lp-PLA(2) levels should prompt consideration of increasing the cardiovascular risk category from moderate to high or high to very high risk, respectively. Because intensification of lifestyle changes and low-density lipoprotein (LDL) cholesterol lowering is beneficial in high-risk patients, regardless of baseline LDL cholesterol levels, consideration should be given to lowering the LDL cholesterol target by 30 mg/dL (1 mg/dL = 0.02586 mmol/L) in patients with high levels of Lp-PLA(2). Lp-PLA(2) is recommended as a diagnostic test for vascular inflammation to better identify patients at high or very high risk who will benefit from intensification of lipid-modifying therapies. However, at this time Lp-PLA(2) cannot be recommended as a target of therapy.

Use of biomarkers to develop treatment strategies for atherosclerosis.

This review focuses on the recent progress in and future prospects for the widened use of biomarkers of inflammation to modify lipid treatment goals in individuals assessed according to traditional risk factors to be at moderate or higher risk for clinical cardiovascular disease events. Elevated blood levels of high-sensitivity C-reactive protein or lipoprotein-associated phospholipase A(2) independently predict increased risk after adjustment for an individual's clinical risk status. When elevated individually, each is associated with an approximate doubling of risk for primary or recurrent cardiovascular events. Fourteen major studies, encompassing healthy adults, patients with chronic coronary heart disease, and those with a recent coronary event or stroke, are reviewed, demonstrating the consistent predictive value of these biomarkers across the risk spectrum. When both inflammatory markers are increased, they provide an even greater predictive capability to identify especially high-risk individuals who would benefit most from aggressive lipid-modifying therapies.

Rationale and design for the blood pressure intervention of the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial.

The Action to Control Cardiovascular Disease in Diabetes (ACCORD) blood pressure trial is an unmasked, open-label, randomized trial with a sample size of 4,733 participants. This report describes the rationale, design, and methods of the blood pressure interventions in ACCORD. Participants eligible for the blood pressure trial are randomized to 1 of 2 groups with different treatment goals: systolic blood pressure <120 mm Hg for the more intensive goal and systolic blood pressure <140 mm Hg for the less intensive goal. The primary outcome measure for the trial is the first occurrence of a major cardiovascular disease (CVD) event, specifically nonfatal myocardial infarction or stroke, or cardiovascular death during a follow-up period ranging from 4-8 years. The ACCORD blood pressure trial should provide the first definitive clinical trial data on the possible benefit of treating to a more aggressive systolic blood pressure goal in reducing CVD events in patients with diabetes mellitus.

Activation of IKKbeta by glucose is necessary and sufficient to impair insulin signaling and nitric oxide production in endothelial cells.

Hyperglycemic impairment of nitric oxide (NO) production by endothelial cells is implicated in the effect of diabetes to increase cardiovascular disease risk, but the molecular basis for this effect is unknown. In skeletal muscle, diabetes induces activation of inhibitor kappaB kinase (IKKbeta), a key cellular mediator of the response to inflammatory stimuli, and this impairs insulin signal transduction via the insulin receptor substrate-phosphatidylinositol 3-OH kinase (IRS-1/PI3-kinase) pathway. Since activation of endothelial nitric oxide synthase (eNOS) is dependent on IRS-1/PI3-kinase signaling, we hypothesized that activation of IKKbeta may contribute to the effect of glucose to impair NO production. Here, we show that exposure of bovine aortic endothelial cells to high glucose (25 mM) for 24 h impaired insulin-mediated tyrosine phosphorylation of IRS-1, serine phosphorylation of Akt, activation of eNOS, and production of NO. High glucose treatment also activated IKKbeta, and pretreatment with aspirin, a pharmacological inhibitor of IKKbeta, prevented both glucose-induced IKKbeta activation and the effect of high glucose to impair insulin-mediated NO production. These adverse responses to glucose were also blocked by selective inhibition of IKKbeta signaling via overexpression of a kinase-inactive form of the enzyme. Conversely, overexpression of wild-type IKKbeta recapitulated the deleterious effect of high glucose on insulin-mediated activation of eNOS. These data demonstrate that activation of IKKbeta plays a critical and novel role to mediate the deleterious effects of high glucose on endothelial cell function.

Free fatty acid impairment of nitric oxide production in endothelial cells is mediated by IKKbeta.

OBJECTIVE: Free fatty acids (FFA) are commonly elevated in diabetes and obesity and have been shown to impair nitric oxide (NO) production by endothelial cells. However, the signaling pathways responsible for FFA impairment of NO production in endothelial cells have not been characterized. Insulin receptor substrate-1 (IRS-1) regulation is critical for activation of endothelial nitric oxide synthase (eNOS) in response to stimulation by insulin or fluid shear stress. METHODS AND RESULTS: We demonstrate that insulin-mediated tyrosine phosphorylation of IRS-1 and serine phosphorylation of Akt, eNOS, and NO production are significantly inhibited by treatment of bovine aortic endothelial cells with 100 micromol/L FFA composed of palmitic acid for 3 hours before stimulation with 100 nM insulin. This FFA preparation also increases, in a dose-dependent manner, IKKbeta activity, which regulates activation of NF- kappaB, a transcriptional factor associated with inflammation. Similarly, elevation of other common FFA such as oleic and linoleic acid also induce IKKbeta activation and inhibit insulin-mediated eNOS activation. Overexpression of a kinase inactive form of IKKbeta blocks the ability of FFA to inhibit insulin-dependent NO production, whereas overexpression of wild-type IKKbeta recapitulates the effect of FFA on insulin-dependent NO production. CONCLUSIONS: Elevated levels of common FFA found in human serum activate IKKbeta in endothelial cells leading to reduced NO production, and thus may serve to link pathways involved in inflammation and endothelial dysfunction.

Immunocytochemical detection of phosphatidylinositol 3-kinase activation by insulin and leptin.

Intracellular signaling mediated by phosphatidylinositol 3-kinase (PI3K) is important for a number of cellular processes and is stimulated by a variety of hormones, including insulin and leptin. A histochemical method for assessment of PI3K signaling would be an important advance in identifying specific cells in histologically complex organs that are regulated by growth factors and peptide hormones. However, current methods for detecting PI3K activity require either homogenization of the tissue or cells or the ability to transfect probes that bind to phosphatidylinositol 3,4,5 trisphosphate (PIP3), the reaction product of PI3K catalysis. Here we report the validation of an immunocytochemical method to detect changes in PI3K activity, using a recently developed monoclonal antibody to PIP3, in paraformaldehyde-fixed bovine aortic endothelial cells (BAECs) in culture and in hepatocytes of intact rat liver. Treatment with either insulin or leptin increased BAEC PIP3 immunoreactivity, and these effects were blocked by pretreatment with PI3K inhibitors. Furthermore, infusion of insulin into the hepatic portal vein of fasted rats caused an increase of PIP3 immunostaining in hepatocytes that was associated with increased serine phosphorylation of the downstream signaling molecule protein kinase B/Akt (PKB/Akt). We conclude that immunocytochemical PIP3 staining can detect changes in PI3K activation induced by insulin and leptin in cell culture and intact liver.