Renin angiotensin system and ASCVD

25-hydroxyvitamin D is associated with adiposity and cardiometabolic risk factors in a predominantly vitamin D-deficient and overweight/obese but otherwise healthy cohort

Vitamin D deficiency has reached epidemic proportions worldwide and has recently been linked to cardiometabolic risk factors including obesity, insulin resistance, hypertension, dyslipidemia, as well as type 2 diabetes and cardiovascular disease. The objective of this study was to examine the associations between circulating 25-hydrovitamin D (25(OH)D) levels and cardiometabolic risk factors using direct measures of adiposity, glucose intolerance, and insulin resistance, as well as lipids, blood pressure, and plasma markers of inflammation. We measured circulating 25(OH)D, physical activity (International Physical Activity Questionnaire- IPAQ), anthropometry (body mass index (BMI), waist-to-hip ratio (WHR), % body fat (dual energy X-ray absorptiometry)), metabolic parameters (fasting and 2-h plasma glucose levels during oral glucose tolerance test; insulin sensitivity (M, hyperinsulinaemic-euglycaemic clamp), and cardiovascular and inflammatory profiles (blood pressure (BP), pulse pressure (PP), mean arterial pressure (MAP), plasma lipid levels, white blood cell count (WBC), and plasma high-sensitivity C-reactive protein levels (hsCRP)) in 111 healthy, non-diabetic adults (66 males/45 females; age 31.1±9.2years; % body fat 36.0±10.2%). Mean 25(OH)D was 39.8±19.8 nmol/L with no difference between genders (p=0.4). On univariate analysis, 25(OH)D was associated with% body fat (r=-0.27; p=0.005), 2-h glucose (r=-0.21; p=0.03), PP (r=0.26; p=0.006), and insulin sensitivity (r=0.20, p=0.04), but not with age, BMI, WHR, fasting glucose, BP, MAP, lipids, or inflammatory markers (all p>0.05). After adjusting for age and sex, 25(OH)D remained associated with% body fat (β=-0.12%; p=0.003), 2-h glucose (β=-0.13mmol/L; p=0.02), PP (β=0.12mmHg; p=0.009), and insulin sensitivity (β=0.22mg/kg/min; p=0.03), and became associated with fasting glucose (β=-0.04mmol/L; p=0.04) and hsCRP (β=-0.51mg/L; p=0.04). After adjusting for age, sex, and % body fat, 25(OH)D was no longer associated with insulin sensitivity, 2-h glucose, or hsCRP, but remained associated with fasting glucose (β=-0.05mmol/L; p=0.03) and PP (β=0.10mmHg; p=0.03). 25(OH)D remained associated with fasting glucose (β=-0.06mmol/L; p=0.02) after hsCRP and physical activity were added to the model with % body fat, age, and sex. ​These cross-sectional data suggest that associations between vitamin D and cardiometabolic risk among healthy, non-diabetic adults are largely mediated by adiposity. Large-scale intervention and mechanistic studies are needed to further investigate whether vitamin D has an independent role in the prevention and/or management of cardiometabolic risk and disease.

Role of cardiac renin angiotensin system in ischemia reperfusion injury and preconditioning of heart

Cardio-vascular diseases are the leading cause of morbidity and mortality. Ischemia is a state of oxygen deprivation in tissues, whereas reperfusion is restoration of blood flow in ischemic tissues. Myocardial damage of tissue during reperfusion after ischemic insult is known as myocardial ischemia–reperfusion (I/R) injury. It induces damage to cardiac muscle via increasing expression of oxygen, sodium and calcium ions which are responsible in the activation of proteases and cell death. Heart renin angiotensin system (RAS) plays an important role in the myocardial ischemia and reperfusion injury. Angiotensin (1–7) is responsible for vasodilation and angiotensin II for vasoconstriction. Here-in we reviewed how myocardial I/R injury sets in by up-regulation of angiotensin II that leads to increased infarct size, which can be reduced by the use of ACE inhibitors, ACE2 activators and angiotensin II antagonist.

Vitamin D supplementation for the prevention of type 2 diabetes in overweight adults: study protocol for a randomized controlled trial

Background

Despite Australia’s sunny climate, low vitamin D levels are increasingly prevalent. Sun exposure is limited by long working hours, an increase in time spent indoors, and sun protection practices, and there is limited dietary vitamin D fortification. While the importance of vitamin D for bone mineralization is well known, its role as a protective agent against chronic diseases, such as type 2 diabetes and cardiovascular disease, is less understood. Observational and limited intervention studies suggest that vitamin D might improve insulin sensitivity and secretion, mainly via its anti-inflammatory properties, thereby decreasing the risk of development and progression of type 2 diabetes. The primary aim of this trial is to investigate whether improved plasma concentrations of 25-hydroxyvitamin D (25(OH)D), obtained through vitamin D supplementation, will increase insulin sensitivity and insulin secretion. A secondary aim is to determine whether these relationships are mediated by a reduction in underlying subclinical inflammation associated with obesity.

Methods/Design

Fifty overweight but otherwise healthy nondiabetic adults between 18 and 60 years old, with low vitamin D levels (25(OH)D < 50 nmol/l), will be randomly assigned to intervention or placebo. At baseline, participants will undergo a medical review and anthropometric measurements, including dual X-ray absorptiometry, an intravenous glucose tolerance test, muscle and fat biopsies, a hyperinsulinemic euglycemic clamp, and questionnaires assessing diet, physical activity, sun exposure, back and knee pain, and depression. The intervention group will receive a first dose of 100,000 IU followed by 4,000 IU vitamin D (cholecalciferol) daily, while the placebo group will receive apparently identical capsules, both for a period of 16 weeks. All measurements will be repeated at follow-up, with the primary outcome measure expressed as a change from baseline in insulin sensitivity and secretion for the intervention group compared with the placebo group. Secondary outcome measures will compare changes in anthropometry, cardiovascular risk factors, and inflammatory markers.

Discussion

The trial will provide much needed clinical evidence on the impact of vitamin D supplementation on insulin resistance and secretion and its underlying mechanisms, which are relevant for the prevention and management of type 2 diabetes.

Trial registration

Clinicaltrials.gov ID: NCT02112721.

Role of ACE I/D gene polymorphisms on the effect of ramipril in inflammatory response and myocardial injury in patients undergoing coronary artery bypass grafts

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors block angiotensin II formation and release bradykinin, which is effective in the regulation of oxidoinflammatory injury. Some reports denote alterations in the effectiveness of ACE inhibitors in association with ACE insertion/deletion (I/D) gene polymorphisms. This study investigates the effects of ramipril on the oxidoinflammatory cytokines (IL-6, IL-8, TNF-alpha) and TnT (myocardial injury marker) and their alteration in association with ACE I/D gene polymorphisms.

METHODS

The study group (n = 51) patients received ramipril before coronary artery bypass grafting (CABG), while patients not receiving ramipril (n = 51) constituted the controls. TNFα, IL-6, and IL-8 were evaluated using ELISA and TnT by electrochemiluminescence methods before the induction of anesthesia (t1), at the 20th minute following cross-clamping (t2), at the end of the operation (t3), and at the 24th hour from the commencement of anesthesia (t4). Genotyping was performed by PCR.

RESULTS

Differences between the groups were significant at t4 for the TNFα and at t3 for IL-6 (p < 0.05). The TnT levels increased from t2 onward in the control group and were highest in t3. Changes in t3 and t4 values in both groups according to their t1 values were significant (p < 0.05). However, differences between the groups were insignificant (p > 0.05). The IL-6, IL-8, TNFα, and TnT serum levels had no correlation with the ACE I/D gene polymorphism.

CONCLUSION

Low cytokine and TnT levels in the study group, especially after cross-clamping, may indicate the protective effect of ramipril from oxidoinflammatory injury. This effect did not appear to be associated with the ACE I/D gene polymorphism.

A modern understanding of the traditional and nontraditional biological functions of angiotensin-converting enzyme

Angiotensin-converting enzyme (ACE) is a zinc-dependent peptidase responsible for converting angiotensin I into the vasoconstrictor angiotensin II. However, ACE is a relatively nonspecific peptidase that is capable of cleaving a wide range of substrates. Because of this, ACE and its peptide substrates and products affect many physiologic processes, including blood pressure control, hematopoiesis, reproduction, renal development, renal function, and the immune response. The defining feature of ACE is that it is composed of two homologous and independently catalytic domains, the result of an ancient gene duplication, and ACE-like genes are widely distributed in nature. The two ACE catalytic domains contribute to the wide substrate diversity of ACE and, by extension, the physiologic impact of the enzyme. Several studies suggest that the two catalytic domains have different biologic functions. Recently, the X-ray crystal structure of ACE has elucidated some of the structural differences between the two ACE domains. This is important now that ACE domain-specific inhibitors have been synthesized and characterized. Once widely available, these reagents will undoubtedly be powerful tools for probing the physiologic actions of each ACE domain. In turn, this knowledge should allow clinicians to envision new therapies for diseases not currently treated with ACE inhibitors.

The impact of vitamin D deficiency on diabetes and cardiovascular risk

PURPOSE OF REVIEW

To review the association between vitamin D deficiency and diabetes and cardiovascular risk.

RECENT FINDINGS

Vitamin D deficiency is newly recognized as a common condition of increasing prevalence worldwide. Clinically, vitamin D has an established role in calcium and bone metabolism and has recently been shown to be associated with increased risk of developing type 1 and type 2 diabetes mellitus and cardiovascular disease (CVD), as well as with cardiovascular risk factors such as hypertension and obesity. The molecular mechanisms of these associations remain incompletely understood. The active metabolite of vitamin D regulates transcription of multiple gene products with antiproliferative, prodifferentiative, and immunomodulatory effects. Although vitamin D deficiency is frequently unrecognized clinically, laboratory measurement is easy to perform and treatment of vitamin D deficiency is relatively well tolerated and inexpensive. Limited, yet promising, results of proof-of-concept intervention studies of using vitamin D in diabetes will be presented.

SUMMARY

The high prevalence of vitamin D deficiency and plausible molecular mechanisms linking this to diabetes and cardiovascular risk suggest treatment of vitamin D deficiency to prevent and/or treat diabetes is a promising field to explore.

Transforming growth factor beta in cardiovascular development and function

Transforming growth factor betas (TGFbetas) are pleiotropic cytokines involved in many biological processes. Genetic engineering and tissue explanation studies have revealed specific non-overlapping roles for TGFbeta ligands and their signaling molecules in development and in normal function of the cardiovascular system in the adult. In the embryo, TGFbetas appear to be involved in epithelial-mesenchymal transformations (EMT) during endocardial cushion formation, and in epicardial epithelial-mesenchymal transformations essential for coronary vasculature, ventricular myocardial development and compaction. In the adult, TGFbetas are involved in cardiac hypertrophy, vascular remodeling and regulation of the renal renin-angiotensin system. The evidence for TGFbeta activities during cardiovascular development and physiologic function will be given and areas which need further investigation will be discussed.

Modulating atherosclerosis through inhibition or blockade of angiotensin

Angiotensin-convertng enzyme (ACE) inhibitors are well recognized for their benefits in treating hypertension and congestive heart failure and preventing postmyocardial infarction heart failure or left ventricular (LV) dysfunction. Recently, blockade of the angiotensin II type 1 (AT1) receptor was shown to reduce cardiovascular events in hypertensive subjects with LV hypertrophy. Several lines of evidence are now converging to show that ACE inhibitors may affect the atherosclerotic process itself. Emerging clinical data indicate that angiotensin-receptor blockers (ARBs) may possibly modulate atherosclerosis as well. The antiatherogenic properties of ACE inhibitors and ARBs may derive from inhibition or blockade of angiotensin II, now recognized as an agent that increases oxidative stress.Angiotensin-converting enzyme inhibition and angiotensin-receptor blockade also increase endothelial nitric oxide formation, which improves endothelial function. In contrast to the effects of ARBs, the vascular effects of ACE inhibitors may, in part, be mediated by an increase in bradykinin. This article reviews some of the biologic mechanisms whereby ACE inhibitors and ARBs may modulate atherosclerosis.

Altered renin synthesis and secretion in the kidneys of heterozygous mice with a null mutation in the TGF-beta(2) gene

Transforming growth factors beta (TGF-betas) are peptides involved in autocrine and paracrine control of cell growth and differentiation. In the kidneys, TGF-beta(2) has been shown to localize specifically in renin-producing cells in various conditions stimulating the renin response. To test in vivo the functional role of TGF-beta(2), the renin response was investigated in mice heterozygous for a null mutation of the TGF-beta(2) gene, which had a twofold reduction in the amount of TGF-beta(2) mRNA. Although the increase in plasma renin concentration triggered by dehydration was not different from wild-type mice, renal renin mRNA and protein levels were higher in mutant mice under hydrated or dehydrated conditions. These data suggest that TGF-beta(2) exerts an inhibitory effect on renin synthesis and release from the juxtaglomerular apparatuses.

The hypertension-lipid connection: insights into the relation between angiotensin II and cholesterol in atherogenesis

Clinical data and experimental studies have established the important role of abnormal lipid metabolism in the causation of atherosclerosis and enthroned the hydroxymethylglutaryl coenzyme reductase inhibitors (statins) as a mainstay in management of patients with coronary heart disease. However, emerging experimental data underline the role of vascular renin-angiotensin systems in mediating the early stages of vascular endothelial dysfunction and inflammation as prerequisites for unleashing the cascade of cellular and molecular events that lead to the deposition of foam cells and their eventual progression to the atherosclerotic plaque. We discuss here the biological effects of statins and angiotensin II in the evolution of atherogenesis, underscoring possible links between statins and angiotensin receptor blockers. From the assessment of the commonality of effects resulting from the nonlipidic actions of statins and angiotensin II on the process of atherogenesis, we develop the argument that dyslipidemia may influence the ability to control blood pressure in hypertensive subjects and hypothesize that the combined use of statins and blockers of the renin-angiotensin system may have an additive effect in the management of hypertensive subjects.

Inflammatory pathways in atherosclerosis and acute coronary syndromes

Evidence from a broad range of studies demonstrates that atherosclerosis is a chronic disease that, from its origins to its ultimate complications, involves inflammatory cells (T cells, monocytes, macrophages), inflammatory proteins (cytokines, chemokines), and inflammatory responses from vascular cells (endothelial cell expression of adhesion molecules). Investigators have identified a variety of proteins whose levels might predict cardiovascular risk. Of these candidates, C-reactive protein, tumor necrosis factor-alpha, and interleukin-6 have been most widely studied. There is also the prospect of inflammation as a therapeutic target, with investigators currently debating to what extent the decrease in cardiovascular risk seen with statins, angiotensin-converting enzyme inhibitors, and peroxisome proliferator-activated receptor ligands derives from changes in inflammatory parameters. These advances in basic and clinical science have placed us on a threshold of a new era in cardiovascular medicine.