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ESC heart failure 9(5), 3254-3263 (2022). doi:10.1002/ehf2.14004, Published by Wiley, Chichester

Supplemental Digital Content is available in the text., Objective— To establish the cellular source of plasma factor (F)XIII-A. Approach and Results— A novel mouse floxed for the F13a1 gene, FXIII-Aflox/flox (Flox), was crossed with myeloid- and platelet-cre–expressing mice, and cellular FXIII-A mRNA expression and plasma and platelet FXIII-A levels were measured. The platelet factor 4-cre.Flox cross abolished platelet FXIII-A and reduced plasma FXIII-A to 23±3% (P

Background Plasminogen activator inhibitor type 1 ( PAI ‐1) plays an essential role in the fibrinolysis system and thrombosis. Population studies have reported that blood PAI ‐1 levels are associated with increased risk of coronary heart disease ( CHD ). However, it is unclear whether the association reflects a causal influence of PAI ‐1 on CHD risk. Methods and Results To evaluate the association between PAI ‐1 and CHD , we applied a 3‐step strategy. First, we investigated the observational association between PAI ‐1 and CHD incidence using a systematic review based on a literature search for PAI ‐1 and CHD studies. Second, we explored the causal association between PAI ‐1 and CHD using a Mendelian randomization approach using summary statistics from large genome‐wide association studies. Finally, we explored the causal effect of PAI ‐1 on cardiovascular risk factors including metabolic and subclinical atherosclerosis measures. In the systematic meta‐analysis, the highest quantile of blood PAI ‐1 level was associated with higher CHD risk comparing with the lowest quantile (odds ratio=2.17; 95% CI: 1.53, 3.07) in an age‐ and sex‐adjusted model. The effect size was reduced in studies using a multivariable‐adjusted model (odds ratio=1.46; 95% CI : 1.13, 1.88). The Mendelian randomization analyses suggested a causal effect of increased PAI ‐1 level on CHD risk (odds ratio=1.22 per unit increase of log‐transformed PAI ‐1; 95% CI : 1.01, 1.47). In addition, we also detected a causal effect of PAI ‐1 on elevating blood glucose and high‐density lipoprotein cholesterol. Conclusions Our study indicates a causal effect of elevated PAI ‐1 level on CHD risk, which may be mediated by glucose dysfunction.

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 NG-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. Insulin-resistant type 2 diabetes characterized by perturbation of the insulin/IGF-1 system is a multisystem disorder of nutrient homeostasis, cell growth, and tissue repair (1). As a result, type 2 diabetes is a major risk factor for the development of a range of disorders of human health, including occlusive coronary artery disease (2), peripheral vascular disease (3), stroke (4), chronic vascular ulcers (5), proliferative retinopathy (6), and nephropathy (7). A key hallmark of these pathologies is endothelial cell dysfunction characterized by a reduction in bioavailability of the signaling radical nitric oxide (NO). In the endothelium, insulin binding to its tyrosine kinase receptor stimulates release of NO (8). Insulin resistance at a whole-body level (9,10) and specific to the endothelium (11) leads to reduced bioavailability of NO, indicative of a critical role for insulin in regulating NO bioavailability. The insulin receptor (IR) and IGF-1 receptor (IGF-1R) are structurally similar—both composed of two extracellular α and two transmembrane β subunits linked by disulfide bonds (12). As a result, IGF-1R and IR can heterodimerize to form insulin-resistant hybrid receptors composed of one IGF-1R-αβ complex and one IR-αβ subunit complex (13,14). We recently demonstrated that reducing IGF-1R (by reducing the number of hybrid receptors) enhances insulin sensitivity and NO bioavailability in the endothelium (15). To examine the effect of increasing IGF-1R specifically in the endothelium on NO bioavailability, endothelial repair, and metabolic homeostasis, we generated a transgenic mouse with targeted overexpression of the human IGF-1R in the endothelium (hIGFREO).

OBJECTIVE—In mice, haploinsufficiency of the IGF-1 receptor (IGF-1R+/2), at a whole-body level, increases resistance to inflammation and oxidative stress, but the underlying mechanisms are unclear. We hypothesized that by forming insulin-resistant heterodimers composed of one IGF-1Rab and one insulin receptor (IR), IRab complex in endothelial cells (ECs), IGF-1R reduces free IR, which reduces EC insulin sensitivity and generation of the antioxidant/anti-inflammatory signaling radical nitric oxide (NO). RESEARCH DESIGN AND METHODS—Using a number of complementary gene-modified mice with reduced IGF-1R at a whole-body level and specifically in EC, and complementary studies in EC in vitro, we examined the effect of changing IGF1R/IR stoichiometry on EC insulin sensitivity and NO bioavailability. RESULTS—IGF-1R+/2 mice had enhanced insulin-mediated glucose lowering. Aortas from these mice were hypocontractile to phenylephrine (PE) and had increased basal NO generation and augmented insulin-mediated NO release from EC. To dissect EC from whole-body effects we generated mice with EC-specific knockdown of IGF-1R. Aortas from these mice were also hypocontractile to PE and had increased basal NO generation. Whole-body and EC deletion of IGF-1R reduced hybrid receptor formation. By reducing IGF-1R in IR-haploinsufficient mice we reduced hybrid formation, restored insulin-mediated vasorelaxation in aorta, and insulin stimulated NO release in EC. Complementary studies in human umbilical vein EC in which IGF-1R was reduced using siRNA confirmed that reducing IGF-1R has favorable effects on NO bioavailability and EC insulin sensitivity. CONCLUSIONS—These data demonstrate that IGF-1R is a critical negative regulator of insulin sensitivity and NO bioavailability in the endothelium.

Acute physical stresses such as major surgery, insulin-induced hypoglycaemia and exercise are associated with acute increases in circulating concentrations of factor VIII and increases in fibrinolytic activity. The mechanisms involved in producing these responses are partly under hormonal control and there is evidence that the neurohormones adrenaline and arginine vasopressin mediate some of the changes. Adrenaline infusions in man produce increases in both factor VIII and fibrinolysis and the rise in factor VIII is blocked by pretreatment with propranolol. Receptor blockade with propranolol also prevents the rise in factor VIII associated with hypoglycaemia to support the view that adrenaline is an important mediator under these circumstances. The pituitary antidiuretic hormone, arginine vasopressin, produces similar changes in haemostasis at plasma concentrations above those required for its renal effects, but within the range commonly seen during certain physical stresses. However, studies in clinical models that produce increases in vasopressin without a concomitant increase in adrenaline concentrations show enhanced fibrinolysis but no change in factor VIII. Thus it seems that adrenaline and vasopressin have a role in the regulation of haemostasis associated with stress, although the role of vasopressin in the regulation of factor VIII is open to question.