Insulin resistance functionally limits endothelium-dependent coronary vasodilation in nondiabetic patients
ABSTRACT Insulin resistance (IR) is now considered to be a risk factor for coronary arterial atherosclerosis and is likely to be involved in a limited endothelium-dependent vasodilatory function in peripheral circulation. We investigated whether IR impairs endothelial vasodilator function in the noninfarcted coronary artery. In 14 nondiabetic patients (10 males, 66 +/- 6 years) who were selected from 214 patients underwent IR evaluation by glucose clamp, a Doppler flow wire was used to measure coronary flow changes (percent volume flow index, %VFI) during intracoronary administration of papaverin (10 mg) and stepwise administration of acetylcholine (Ach; 1, 3, 10 microg/ml per minute) into the non-infarcted left circumflex coronary artery. Insulin resistance was comparatively evaluated by an euglycemic hyperinsulinemic glucose clamp (M value, mg/m(2) per minute) or by a 75g-oral glucose tolerance test (120-min immunoreactive insulin; 120' IRI, pmol/l). Eight patients (57%) were defined as having IR on the basis of results obtained by both the glucose clamp method (M values <167 mg/m(2) per minute) and 120' IRI (>384 pmol/l). There was no difference between papaverin-induced %VFI increases in IR and non-IR subjects (328% +/- 43% vs. 361% +/- 87%). However, IR subjects showed significantly lower Ach-induced %VFI increases in a dose-dependent manner (P < 0.05), especially when low (1 microg/ml per minute) and moderate (3 microg/ml per minute) doses of Ach were used (165% +/- 18% or 248% +/- 29% in non-IR subjects vs. 130% +/- 20% or 183% +/- 41% in IR subjects, P < 0.001, respectively). Moreover, %VFI increase at a low dose of Ach infusion significantly correlated with M values or 120' IRI ([%VFI Ach 1 microg] = 85.9 + 0.35 [M values], r = 0.58, P = 0.038; [%VFI Ach 1 microg] = 176.8 - 0.47.[120' IRI], r = -0.57, P = 0.035). Insulin resistance limits endothelium-dependent coronary vasodilation in association with the severity of IR in non-diabetic patients.
- SourceAvailable from: Jesus Castillo[Show abstract] [Hide abstract]
ABSTRACT: We hypothesized that Angiotensin II (Ang II), like other circulating hormones, acts exclusively intravascularly. To activate or block solely intravascular Ang II receptors, Ang II and its peptide receptor blocker saralasin (Sar) were covalently coupled to a inert polymer (POL, MW >4000 kD) forming Ang II-POL and Sar-POL. These two nonpermeable polymers, Ang II and Sar, were intracoronarily administered into the isolated, saline-perfused rat hearts. Ang II-POL and Ang II caused a dose-dependent ventricular positive inotropic (+I) and vasoconstrictor effects (+V) which were blocked by Sar. Sar-POL blocked their +I but not their +V. Thus, Ang II and Ang II-POL act on endothelial luminal receptors through paracrine mechanisms. +I were blocked solely by purinoceptor antagonists and paralleled by augmented venous release of ATP degradation products (adenosine, inosine and hypoxanthine). In contrast, +V were blocked solely by aspirin, indomethacin or a thromboxane A2 receptor antagonist. Intracoronary administration of ATP-gamma-S and U46169, a purinergic, and TXA2 agonists, respectively, mimicked +I and +V. The results indicate that ATP is the paracrine inotropic mediator while thromboxane A2 is the vasoconstrictor mediator. Thus, the +I and +V distinct effects by intracoronary Ang II indicate that its diverse mechanism of action along the coronary vascular tree may be due to a functionally heterogeneous endothelium.Vascular Pharmacology 05/2004; 41(4-5):147-58. DOI:10.1016/j.vph.2004.08.002 · 4.62 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Etiopathogenesis of coronary artery ectasia (CAE), which is defined as abnormal dilatation of a segment of the coronary artery to 1.5 times of an adjacent normal coronary artery segment, is unclear. However, it is speculated that CAE develops in the atherosclerosis process through degeneration of coronary artery media layer. Our objective in this study is to compare levels of adiponectin between cases with CAE and normal coronary anatomy, and to examine whether adiponectin plays a role in CAE etiopathogenesis. The study registered a total of 66 cases, consisting of CAE cases (group 1, n = 36) and cases with normal coronary anatomy (group 2, n = 30). Taking coronary artery diameters of the control group cases as the reference, patients with abnormal segments 1.5 times larger than the adjacent segments were accepted as CAE. Serum adiponectin levels were 4.31 +/- 2.02 microg/ml in group 1 and 6.73 +/- 4.0 microg/ml in group 2 (P = 0.02). High-sensitivity C-reactive protein was 4.8 +/- 3.8 mg/l in group 1 and 3.6 +/- 3.4 mg/l in group 2 (P > 0.05). There was a negative correlation between ectatic coronary artery diameter and plasma adiponectin level (P = 0.03; r = -0.339). It was known that adiponectin levels dropped in atherosclerotic heart disease. In this study we found low plasma adiponectin levels in acquired CAE, attributed to atherosclerosis. Therefore, we think that adiponectin might be playing a role in etiopathogenesis and progression of CAE. This in turn may indicate that hypo-adiponectinemia may be useful in revealing a realized risk in CAE. However, larger, randomized, multicenter studies are required to examine the role of adiponectin in the development of CAE.Heart and Vessels 03/2009; 24(2):84-9. DOI:10.1007/s00380-008-1087-0 · 2.11 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Angiotensin II (Ang II), the major effector hormone of the renin-angiotensin system (RAS), has an important role in the regulation of vascular and renal homeostasis. Clinical and pharmacological studies have recently shown that Ang II is a critical promoter of insulin resistance and diabetes mellitus type 2. Ang II exerts its actions on insulin-sensitive tissues such as liver, muscle and adipose tissue where it has effects on the insulin receptor (IR), insulin receptor substrate (IRS) proteins and the downstream effectors PI3K, Akt and GLUT4. The molecular mechanisms involved have not been completely identified, but the role of serine/threonine phosphorylation of the IR and IRS-1 proteins in desensitization of insulin action has been well established. The purpose of this review is to highlight recent advances in the understanding of Ang II actions which lead to the development of insulin resistance and its implications for diabetes.Molecular and Cellular Endocrinology 04/2009; 302(2):128-39. DOI:10.1016/j.mce.2008.12.011 · 4.24 Impact Factor