Association of heart failure and its comorbidities with loss of life expectancy

Objective Estimating survival can aid care planning, but the use of absolute survival projections can be challenging for patients and clinicians to contextualise. We aimed to define how heart failure and its major comorbidities contribute to loss of actuarially predicted life expectancy. Methods We conducted an observational cohort study of 1794 adults with stable chronic heart failure and reduced left ventricular ejection fraction, recruited from cardiology outpatient departments of four UK hospitals. Data from an 11-year maximum (5-year median) follow-up period (999 deaths) were used to define how heart failure and its major comorbidities impact on survival, relative to an age–sex matched control UK population, using a relative survival framework. Results After 10 years, mortality in the reference control population was 29%. In people with heart failure, this increased by an additional 37% (95% CI 34% to 40%), equating to an additional 2.2 years of lost life or a 2.4-fold (2.2–2.5) excess loss of life. This excess was greater in men than women (2.4 years (2.2–2.7) vs 1.6 years (1.2–2.0); p<0.001). In patients without major comorbidity, men still experienced excess loss of life, while women experienced less and were non-significantly different from the reference population (1 year (0.6–1.5) vs 0.4 years (−0.3 to 1); p<0.001). Accrual of comorbidity was associated with substantial increases in excess lost life, particularly for diabetes, chronic kidney and lung disease. Conclusions Comorbidity accounts for the majority of lost life expectancy in people with heart failure. Women, but not men, without comorbidity experience survival close to reference controls

Inferring Pathway Activity toward Precise Disease Classification

The advent of microarray technology has made it possible to classify disease states based on gene expression profiles of patients. Typically, marker genes are selected by measuring the power of their expression profiles to discriminate among patients of different disease states. However, expression-based classification can be challenging in complex diseases due to factors such as cellular heterogeneity within a tissue sample and genetic heterogeneity across patients. A promising technique for coping with these challenges is to incorporate pathway information into the disease classification procedure in order to classify disease based on the activity of entire signaling pathways or protein complexes rather than on the expression levels of individual genes or proteins. We propose a new classification method based on pathway activities inferred for each patient. For each pathway, an activity level is summarized from the gene expression levels of its condition-responsive genes (CORGs), defined as the subset of genes in the pathway whose combined expression delivers optimal discriminative power for the disease phenotype. We show that classifiers using pathway activity achieve better performance than classifiers based on individual gene expression, for both simple and complex case-control studies including differentiation of perturbed from non-perturbed cells and subtyping of several different kinds of cancer. Moreover, the new method outperforms several previous approaches that use a static (i.e., non-conditional) definition of pathways. Within a pathway, the identified CORGs may facilitate the development of better diagnostic markers and the discovery of core alterations in human disease

Novel Paracrine Action of Endothelium enhances Glucose Uptake in Muscle and Fat

Rationale: A hallmark of type 2 diabetes is insulin resistance, which leads to increased endothelial cell production of superoxide and a simultaneous reduction in availability of the vasoprotective signalling radical, nitric oxide (NO). We recently demonstrated in preclinical models that type 2 diabetes simultaneously causes resistance to insulin like growth factor-1 (IGF-1) mediated glucose lowering and endothelial NO release. Objective: To examine the effect of insulin and IGF-1 resistance specifically in endothelial cells in vivo. Methods and Results: We generated mice expressing mutant IGF-1 receptors (mIGF-1R), which form non-functioning hybrid receptors with native insulin receptors (IR) and IGF-1R, directed to endothelial cells under control of the Tie2 promoter-enhancer. Despite endothelial cell insulin and IGF-1 resistance, mutant IGF-1R endothelial cell over-expressing mice (mIGFREO) had enhanced insulin and IGF-1 mediated systemic glucose disposal, lower fasting free fatty acids and triglycerides. In hyperinsulinaemic-euglycaemic clamp studies, mIGFREO had increased glucose disposal and increased glucose uptake into muscle and fat, in response to insulin. mIGFREO had increased NADPH oxidase 4 (Nox4) expression due to reduced expression of the microRNA, miR-25. Consistent with increased Nox4, mIGFREO endothelial cells generated increased hydrogen peroxide (H2O2), with no increase in superoxide. Treatment with catalase, a dismutase restored insulin tolerance to wild type levels in mIGFREO. Conclusions: Combined insulin and IGF-1 resistance restricted to the endothelium leads to a potentially favourable adaptation in contrast to pure insulin resistance, with increased Nox4-derived H2O2 generation mediating enhanced whole-body insulin sensitivity

Nox2 NADPH oxidase has a critical role in insulin resistance-related endothelial cell dysfunction.

Insulin resistance is characterized by excessive endothelial cell generation of potentially cytotoxic concentrations of reactive oxygen species. We examined the role of NADPH oxidase (Nox) and specifically Nox2 isoform in superoxide generation in two complementary in vivo models of human insulin resistance (endothelial specific and whole body). Using three complementary methods to measure superoxide, we demonstrated higher levels of superoxide in insulin-resistant endothelial cells, which could be pharmacologically inhibited both acutely and chronically, using the Nox inhibitor gp91ds-tat. Similarly, insulin resistance-induced impairment of endothelial-mediated vasorelaxation could also be reversed using gp91ds-tat. siRNA-mediated knockdown of Nox2, which was specifically elevated in insulin-resistant endothelial cells, significantly reduced superoxide levels. Double transgenic mice with endothelial-specific insulin resistance and deletion of Nox2 showed reduced superoxide production and improved vascular function. This study identifies Nox2 as the central molecule in insulin resistance-mediated oxidative stress and vascular dysfunction. It also establishes pharmacological inhibition of Nox2 as a novel therapeutic target in insulin resistance-related vascular disease