Arg972 Insulin receptor substrate-1 is associated with decreased serum angiotensin-converting enzyme 2 levels in acute myocardial infarction patients: in vivo and in vitro evidence

Relationship between circulating levels of angiotensin-converting enzyme 2-angiotensin-(1-7)-MAS axis and coronary heart disease

As a counter-regulatory arm of the renin angiotensin system (RAS), the angiotensin-converting enzyme 2-angiotensin-(1–7)-MAS axis (ACE2-Ang-(1–7)-MAS axis) plays a protective role in cardiovascular diseases. However, the link between circulating levels of ACE2-Ang-(1–7)-Mas axis and coronary atherosclerosis in humans is not determined. The object of present study was to investigate the association of circulating levels of ACE2, Ang-(1–7) and Ang-(1–9) with coronary heart disease (CHD) defined by coronary angiography (CAG). 275 patients who were referred to CAG for the evaluation of suspected CHD were enrolled and divided into two groups: CHD group (diameter narrowing ≥ 50%, n = 218) and non-CHD group (diameter narrowing < 50%, n = 57). Circulating ACE2, Ang-(1–7) and Ang-(1–9) levels were detected by enzyme-linked immunosorbent assay (ELISA). In females, circulating ACE2 levels were higher in the CHD group than in the non-CHD group (5617.16 ± 5206.67 vs. 3124.06 ± 3005.36 pg/ml, P = 0.009), and subgroup analysis showed the significant differences in ACE2 levels between the two groups only exist in patients with multi-vessel lesions (P = 0.009). In multivariate logistic regression, compared with the people in the lowest ACE2 quartile, those in the highest quartile had an OR of 4.33 (95% CI 1.20–15.61) for the CHD (P for trend = 0.025), the OR was 5.94 (95% CI 1.08–32.51) for the third ACE2 quartile and 9.58 (95% CI 1.61–56.95) for the highest ACE2 quartile after adjusting for potential confounders (P for trend = 0.022). However, circulating Ang-(1–7) and Ang-(1–9) levels had no significant differences between the two groups. In males, there were no significant differences in the levels of ACE2-Ang-(1–7)-MAS axis between two groups. Together, circulating ACE2 levels, but not Ang-(1–7) and Ang-(1–9) levels, significantly increased in female CHD group when compared with non-CHD group, increased ACE2 was independently associated with CHD in female and in patients with multi-vessel lesions even after adjusting for the confounding factors, indicating that ACE2 may participate as a compensatory mechanism in CHD.

Understanding Key Mechanisms of Exercise-Induced Cardiac Protection to Mitigate Disease: Current Knowledge and Emerging Concepts

The benefits of exercise on the heart are well recognized, and clinical studies have demonstrated that exercise is an intervention that can improve cardiac function in heart failure patients. This has led to significant research into understanding the key mechanisms responsible for exercise-induced cardiac protection. Here, we summarize molecular mechanisms that regulate exercise-induced cardiac myocyte growth and proliferation. We discuss in detail the effects of exercise on other cardiac cells, organelles, and systems that have received less or little attention and require further investigation. This includes cardiac excitation and contraction, mitochondrial adaptations, cellular stress responses to promote survival (heat shock response, ubiquitin-proteasome system, autophagy-lysosomal system, endoplasmic reticulum unfolded protein response, DNA damage response), extracellular matrix, inflammatory response, and organ-to-organ crosstalk. We summarize therapeutic strategies targeting known regulators of exercise-induced protection and the challenges translating findings from bench to bedside. We conclude that technological advancements that allow for in-depth profiling of the genome, transcriptome, proteome and metabolome, combined with animal and human studies, provide new opportunities for comprehensively defining the signaling and regulatory aspects of cell/organelle functions that underpin the protective properties of exercise. This is likely to lead to the identification of novel biomarkers and therapeutic targets for heart disease.

IRS proteins and diabetic complications

IRS proteins are cellular adaptor molecules that mediate many of the key metabolic actions of insulin. When tyrosine is phosphorylated by the activated insulin receptor, IRS proteins recruit downstream effectors, such as phosphoinositide 3-kinase and mitogen-activated protein kinase, in order to elicit cellular responses such as glucose uptake, lipid metabolism and cell proliferation. There are two main IRS proteins in humans (IRS1 and IRS2), both of which are widely expressed. Given their central role in the insulin signalling pathway, it is not surprising that male mice lacking Irs1 or Irs2 present with elevated blood glucose or type 2 diabetes, respectively. For reasons yet to be identified, female Irs2 (-/-) mice do not develop type 2 diabetes. A number of organs are affected by complications of diabetes; macrovascular complications include stroke and coronary artery disease, while nephropathy, neuropathy and retinopathy fall into the category of microvascular complications. Given the serious consequences of these complications on patient morbidity and mortality, it is essential to identify the molecular pathogenesis underlying diabetic complications, with a view to improving therapeutic intervention and patient outcomes. A number of recently published papers have converged on the hypothesis that the loss of insulin signalling and IRS proteins is instrumental to the development and/or progression of diabetic complications. This review will summarise some highlights from the published work in which this hypothesis is discussed.

Arg⁹⁷² insulin receptor substrate-1 inhibits endothelial nitric oxide synthase expression in human endothelial cells by upregulating microRNA-155

The dysregulation of nitric oxide (NO) synthesis attributable to the abnormal expression/activity of endothelial NO synthase (eNOS) is considered to be a major characteristic of insulin-resistant states, as well as an essential contributor to the pathogenesis of cardiovascular diseases. The Arg972 insulin receptor substrate-1 (IRS-1) is associated with insulin resistance. In the present study, we investigated the association between Arg972 IRS-1 and eNOS expression/activity in human subjects and in primary cultures of human endothelial cells. Data from 832 human subjects revealed that heterozygous and homozygous Arg972 IRS-1 carriers had significantly lower levels of plasma eNOS and nitrite/nitrate than the homozygous wild-type (WT) IRS-1 carriers. Human umbilical vein endothelial cells (HUVECs) established from delivering mothers expressing heterozygous Arg972 IRS-1 had significantly lower eNOS expression/activity and higher miR-155 levels than those expressing WT homozygous IRS-1. The overexpression of IRS-1 and Arg972 IRS-1 in the HUVECs, respectively, decreased and increased the miR-155 expression level. In addition, the overexpression of IRS-1 in the HUVECs significantly increased eNOS expression; this effect was reversed by transfection with mature miR-155 mimic or treatment with the selective phosphatidylinositol-3 kinase (PI3K) inhibitor, BKM120. On the other hand, the overexpression of Arg972 IRS-1 markedly decreased eNOS expression and this effect was reversed by transfection with antagomir-155. On the whole, our in vivo data demonstrate that Arg972 IRS-1 is associated with decreased plasma eNOS and nitrite/nitrate levels in human subjects. Our in vitro data demonstrate that Arg972 IRS-1 inhibits eNOS expression in human endothelial cells by upregulating miR-155 expression through the impairment of PI3K signaling. The present study provides new insight into the pathophysiological role of Arg972 IRS-1 in cardiovascular diseases.