Novel Paracrine Action of Endothelium Enhances Glucose Uptake in Muscle and Fat.

[Figure: see text].

The IGF-1 receptor and regulation of nitric oxide bioavailability and insulin signalling in the endothelium.

The insulin-like growth factor-1 receptor (IGF-1R), like the insulin receptor (IR), plays a significant role in determining bioavailability of the critical signalling molecule nitric oxide (NO) and hence, modulates endothelial cell function, particularly in response to stimulation with insulin. In particular, the ability of the IGF-1R to form hybrid receptors with the IR appears to be highly significant in determining the sensitivity of the endothelial cell to insulin. This review will examine the structure of the IGF-1R and how this, with particular reference to the ability of the IGF-1R and the IR to form hybrid receptors, may have an effect both on endothelial cell function and the development of cardiovascular disease.

Reduction of heart failure guideline-directed medication during hospitalization: prevalence, risk factors, and outcomes.

AIMS: Optimal management of heart failure with reduced ejection fraction (HFrEF) includes titration of guideline-directed medical therapy (GDMT) to the highest tolerated dose within the licensed range. During hospitalization, GDMT doses are often significantly altered, although it is unknown whether the cause of hospitalization influences this. METHODS AND RESULTS: We recruited 711 people with stable HFrEF from specialist heart failure clinics and prospectively assessed events occurring during first unplanned hospitalization. Dose changes of ACE inhibitors or angiotensin receptor blockers (ACEi/ARB), beta-blockers, mineralocorticoid receptor antagonists, and loop diuretics were recorded during 414 hospitalizations, categorized as due to decompensated heart failure, other cardiovascular causes, infection, or other non-cardiovascular causes. Most hospitalizations resulted in no change to GDMT. ACEi/ARB dose was reduced in 21% of hospitalizations and was more common during non-cardiovascular hospitalization (25.4% vs. 13.9%; P = 0.005). ACEi/ARB dose reduction was associated with older age and lower left ventricular ejection fraction at study recruitment, and poorer renal function, lower systolic blood pressure, higher serum potassium, and less frequent care from a cardiologist during admission. People experiencing ACEi/ARB reduction had worse age-adjusted survival after discharge, without differences in heart failure re-hospitalization. De-escalation of beta-blockers occurred in 8% of hospitalizations, most often due to other non-cardiovascular causes; this was not associated with post-discharge survival or re-hospitalization with heart failure. CONCLUSIONS: De-escalation of HFrEF GDMT is more common during non-cardiovascular hospitalization and for ACEi/ARB is associated with reduced survival. Post-discharge care plans should include robust plans to consider re-escalation of GDMT in these cases.

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.

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.

Novel role of the IGF-1 receptor in endothelial function and repair: studies in endothelium-targeted IGF-1 receptor transgenic mice.

We recently demonstrated that reducing IGF-1 receptor (IGF-1R) numbers in the endothelium enhances nitric oxide (NO) bioavailability and endothelial cell insulin sensitivity. In the present report, we aimed to examine the effect of increasing IGF-1R on endothelial cell function and repair. To examine the effect of increasing IGF-1R in the endothelium, we generated mice overexpressing human IGF-1R in the endothelium (human IGF-1R endothelium-overexpressing mice [hIGFREO]) under direction of the Tie2 promoter enhancer. hIGFREO aorta had reduced basal NO bioavailability (percent constriction to N(G)-monomethyl-l-arginine [mean (SEM) wild type 106% (30%); hIGFREO 48% (10%)]; P < 0.05). Endothelial cells from hIGFREO had reduced insulin-stimulated endothelial NO synthase activation (mean [SEM] wild type 170% [25%], hIGFREO 58% [3%]; P = 0.04) and insulin-stimulated NO release (mean [SEM] wild type 4,500 AU [1,000], hIGFREO 1,500 AU [700]; P < 0.05). hIGFREO mice had enhanced endothelium regeneration after denuding arterial injury (mean [SEM] percent recovered area, wild type 57% [2%], hIGFREO 47% [5%]; P < 0.05) and enhanced endothelial cell migration in vitro. The IGF-1R, although reducing NO bioavailability, enhances in situ endothelium regeneration. Manipulating IGF-1R in the endothelium may be a useful strategy to treat disorders of vascular growth and repair.