Insulin resistance and angiographical characteristics of coronary atherosclerosis

Differential associations of angiographic extent and severity of coronary artery disease with asymmetric dimethylarginine but not insulin resistance in non-diabetic men with stable angina: a cross-sectional study

Background

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthesis inhibitor, and insulin resistance (IR) have been implicated in atherogenesis. Our aim was to estimate relations between ADMA, the magnitude of IR and angiographic indices of extent and severity of coronary atherosclerosis in non-diabetic men with stable coronary artery disease (CAD).

Methods

We studied 151 non-diabetic men (mean age 57 ± 11 years) with stable angina, obstructive CAD (at least 1 luminal diameter stenosis of ≥70% in major coronary segments) and without heart failure, and 34 age-matched controls free of ≥50% coronary narrowings. The following CAD indices were computed: the number of major epicardial vessels with ≥70% stenosis, Sullivan extent score representing a proportion of the visible coronary tree with vessel wall irregularities, and Gensini score which reflects both CAD severity and extent, yet assigning a heavier weight to proximal segments and to the more severe narrowings by a non-linear point system. An estimate of IR was derived by homeostasis model assessment (HOMA-IR) from fasting insulin and glucose.

Results

Among the CAD patients, the proportions of subjects with 1-vessel, 2- vessel and 3-vessel CAD were 26%, 25% and 49%, respectively. ADMA levels were higher in patients with obstructive CAD compared to the controls (0.51 ± 0.10 vs. 0.46 ± 0.09 μmol/L [SD], P = 0.01), whereas HOMA-IR was similar (median, 3.2 [interquartile range: 2.4–4.9] vs. 2.9 [2.3–4.7], P = 0.2). Within the CAD group, ADMA increased across ascending quartiles of Sullivan score (Spearman’s rho = 0.23, P = 0.004), but not with Gensini score (rho = 0.12, P = 0.15) or the number of vessels involved (rho = 0.08, P = 0.3). ADMA correlated to log-transformed Sullivan score (Pearson's r = 0.21, P = 0.008), which was only slightly attenuated upon multivariate adjustment (β = 0.19 ± 0.08 [SEM], P = 0.015). HOMA-IR did not differ according to any measure of angiographic CAD (P ≥ 0.2). ADMA and log (HOMA-IR) were mutually unrelated (r = 0.07, P = 0.4).

Conclusions

ADMA is associated with diffuse but not focal coronary atherosclerosis in non-diabetic men with stable CAD irrespectively of the degree of IR. The independent relationship between ADMA and coronary atherosclerotic burden may contribute to the well-recognized prognostic effect of ADMA in CAD.

Postchallenge responses of nitrotyrosine and TNF-alpha during 75-g oral glucose tolerance test are associated with the presence of coronary artery diseases in patients with prediabetes

BACKGROUND

Meta-analysis has demonstrated an exponential relationship between 2-hr postchallenge hyperglycemia and coronary artery disease (CAD). Pulsatile hyperglycemia can acutely increase proinflammatory cytokines by oxidative stress. We hypothesized that postchallenge proinflammatory and nitrosative responses after 75 g oral glucose tolerance tests (75 g-OGTT) might be associated with CAD in patients without previously recognized type 2 diabetes mellitus (T2DM).

METHODS

Serial changes of plasma glucose (PG), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and nitrotyrosine levels were analyzed during 75 g-OGTT in 120 patients (81 male; age 62 ± 11 years) before coronary angiography. Patients were classified as normal (NGT; 42%), impaired (IGT; 34%) and diabetic (T2DM; 24%) glucose tolerance by 75 g-OGTT.

RESULTS

Postchallenge hyperglycemia elicited TNF-α, IL-6 and nitrotyrosine levels time-dependently, and 2-hr median levels of TNF-α (7.1 versus 6.4 pg/ml; P < 0.05) and nitrotyrosine (1.01 versus 0.83 μmol/l; P < 0.05), but not IL-6 or PG, were significantly higher in patients with CAD in either IGT or T2DM groups. After adjusting risk factors and glucose tolerance status, 2-hr nitrotyrosine in highest quartiles (OR: 3.1, P < 0.05) remained an independent predictor of CAD by logistic regression analysis.

CONCLUSIONS

These results highlight postchallenge proinflammatory and nitrosative responses by 75 g-OGTT, rather than hyperglycemia per se, are associated with CAD in patients without previous recognized diabetes.

Insulin resistance is associated with the metabolic syndrome and is not directly linked to coronary artery disease

BACKGROUND

Insulin resistance (IR) is the key feature of the metabolic syndrome (MetS). Its association with directly visualized coronary atherosclerosis is unclear. We hypothesised that insulin resistance is associated with both angiographically determined coronary artery disease (CAD) and with the MetS.

METHODS

In 986 consecutive patients undergoing coronary angiography for the evaluation CAD, IR was determined by the HOMA index; the MetS was defined according to NCEP-ATPIII criteria; and significant CAD was diagnosed when coronary stenoses ≥50% were present.

RESULTS

HOMA IR scores were higher in MetS patients than in subjects without the MetS (4.9±6.4 vs. 2.2±2.0; p<0.001). HOMA IR did not differ significantly between patients with significant CAD and those who did not have significant CAD. When both, the presence of MetS and of significant CAD were considered, HOMA IR was significantly higher in patients with the MetS both among those who had significant CAD (4.9±6.8 vs. 2.2±1.8; p<0.001) and among those who did not have significant CAD (5.0±5.8 vs. 2.1±2.3; p<0.001), it did not differ significantly between patients with significant CAD and subjects without significant CAD among patients with the MetS nor among those without MetS. Similar results were obtained with the IDF definition of the MetS.

CONCLUSION

IR is significantly associated with the MetS but not with angiographically determined CAD. IR may play a greater role in the eventual precipitation of thrombosis than in the gradual progression of atherosclerosis.

The Relationship between Glucose Tolerance and Severity of Coronary Artery Disease Using the Gensini Score

Consecutive patients (n = 235) with coronary ischemia were studied; 69 patients (29%) had diabetes. An oral glucose tolerance test (OGTT) was administered to the 166 patients without diabetes; 76 (46%) had normal glucose tolerance (group I = NGT), 68 (41%) had impaired glucose tolerance ([IGT] group II = IGT), and 22 (13%) had diabetic glucose tolerance (DGT). The DGT patients were added to the known diabetics forming (Group III; n = 91). Multivessel disease was significantly more prevalent in group III; 30 patients (43%) in group I, 32 patients (51%) in group II, and 57 patients (69%) in group III ( P = .002). Gensini scores were 43.20 ± 24.92 in group I, 54.22 ± 42.61 in group II, and 60.59 ± 38.21 in group III. ( P = .037) The severity of coronary artery disease is related to abnormal glucose tolerance. Patients with IGT could be neglected in terms of interventions focused to improve risk factors.

Association of human carboxypeptidase E exon5 gene polymorphisms with angiographical characteristics of coronary atherosclerosis in a Chinese population

AIM

To explore the association between 801C>T and 847C>T polymorphisms of the human carboxypeptidase E (CPE) gene exon5, which could cause hyperproinsulinemia, and the angiographical characteristics of coronary atherosclerosis.

METHODS

In total, 1044 consecutive patients who underwent coronary angiography for suspected or known coronary atherosclerosis were examined with respect to their genotypes, insulin, proinsulin level, and other risk factors of coronary atherosclerosis. The angiographical characteristics of coronary atherosclerosis (ie the severity of coronary heart disease) were defined by Gensinios score (GS) system.

RESULTS

The results showed that the genotype frequencies of CC, CT, and TT at 801C>T locus were significantly different among the patients of the 4 groups who were classified by quartile values of GS (P=0.033). However, the frequency of the 847T allele was 0 for all the patients. The ordinal logistic regression analysis revealed that the increased risk of angiographical characteristics of coronary atherosclerosis were associated with CPE 801CT/TT variant genotypes [adjusted odds ratio (OR)=1.23, 95% confidence interval (CI) =0.93-1.63 for 801CT and adjusted OR=3.13, 95% CI=1.18-8.28 for 801TT] compared with the 801CC wild-type homozygotes. A stratification analysis showed that the effects of the CPE 801TT genotype were more evident among subgroups with relatively older (> or = 60 years) patients, males, and smokers. Furthermore, an analysis of covariance controlling age, sex, and body mass index indicated that differences of blood glucose, insulin, insulin resistance, and the proinsulin level between 801C>T genotype groups were not statistically significant.

CONCLUSION

These findings indicate that the 801C>T polymorphism in the CPE exon5 gene may contribute to the angiographical characteristics of coronary atherosclerosis in the Chinese population.

Impact of Abnormal Glucose Tolerance, Hypertension and Other Risk Factors on Coronary Artery Disease

BACKGROUND

The degree to which abnormal glucose tolerance contributes to the development of coronary artery disease (CAD) has not been clarified in Japanese. The relationship between abnormal glucose tolerance and severity of coronary artery stenosis, as well as the contributions of hypertension, diabetes and other risk factors for CAD to recurrence of the disease, were investigated in the present study.

METHODS AND RESULTS

The subjects were 474 consecutive patients (mean age: 63.8+/-11.3 years) with suspected CAD who were admitted to Sapporo Medical University Hospital during April 1, 1997 to March 31, 2004. The coronary index and stenosis score were higher in subjects with diabetes mellitus (DM) and in subjects with impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) than in subjects with normal glucose tolerance (NGT). Ischemic episodes recurred during the observation period (mean 2.5 years) in 61 of 341 patients diagnosed as having CAD. In the follow-up subjects, systolic blood pressure (SBP) was significantly higher in the recurrence group than in the non-recurrence group, and SBP was a significant variable in logistic regression analysis after adjustment for age, gender, hemoglobin A1c, total cholesterol, body mass index, smoking history, family history and stenosis score. The relative risk of recurrence became 1.7-fold higher with a rise in SBP of 10 mmHg (95% confidence interval: 1.252-2.250). Analysis of the relationship between glucose tolerance and recurrence showed that the rate of recurrence was higher in patients with IFG+IGT+DM than in those with NGT.

CONCLUSIONS

CAD progresses not only in patients with DM but also in those with IGT. The rate of recurrence of ischemic episodes increases in individuals with IGT or DM, and suggesting that hypertension is a risk factor for recurrence of ischemic episodes. Management of glucose tolerance and blood pressure is therefore important for prevention of CAD in Japanese.

The effect of insulin resistance on prognosis of non-diabetic patients who underwent percutaneous coronary intervention

Insulin resistance is an important risk factor for coronary artery disease. However, there has been no data regarding its clinical effect on the outcomes of percutaneous coronary intervention (PCI) in non-diabetic patients. We analyzed 98 non-diabetic consecutive patients (59+/-11.5 yr, male:female=63:35) who underwent elective coronary angiography. The patients were divided into two groups: Group I (n=71; the value of HOMA-IR [homeostasis model assessment of insulin resistance] <2.6) and Group II (n=27; the value of HOMA-IR > or = 2.6). In-hospital and 30-day major adverse cardiac events (MACE) were compared between the two groups. The concentrations of fasting insulin and triglyceride were significantly higher in Group II than in Group I. Significant correlations were observed between the value of HOMA-IR and body mass index (r=0.489, p<0.001), levels of total cholesterol (r=0.204, p=0.045), triglyceride (r=0.334, p=0.001) and apolipoprotein B (r=0.212, p=0.038). PCI was performed in 59 patients (60.2%). In-hospital and 30-day MACE were higher in Group II than Group I (2.4% vs. 27.8%, p=0.008; 2.4% vs. 27.8%, p=0.008). Multivariate analysis revealed that the value of HOMA-IR > or = 2.6 was an independent predictor of MACE. Increased HOMA-IR level is an important prognostic indicator in non-diabetic patients underwent PCI.

Relationship between true fasting plasma insulin level and angiographic characteristics of coronary atherosclerosis

BACKGROUND

Reports about the relationships between specific insulin concentration and coronary heart disease risk are controversial.

HYPOTHESIS

The objective of this study was to examine the association between insulin level and the severity of coronary atherosclerosis.

METHODS

The study population consisted of 507 consecutive patients (376 men and 131 women) who underwent coronary angiography for suspected or known coronary atherosclerosis. The patients' habits of smoking and drinking were investigated, and anthropometric measurements including body mass index, systolic and diastolic blood pressures, as well as plasma measurements including lipids and blood glucose were taken. The true insulin level was measured using a highly sensitive two-site sandwich ELISA. The severity of coronary atherosclerosis was defined by the Gensini score system. The statistical methods including Kruskal-Wallis test, chi-square analysis, Spearman correlation analysis, and multivariate stepwise linear regression analysis were employed to explore the relationship between specific insulin level and coronary atherosclerosis.

RESULTS

When the Gensini score was examined as a categorical variable classified by tertile values, subjects with a high Gensini score had significantly higher values of fasting plasma specific insulin level (p = 0.022). The Spearman correlation analysis suggest that the Gensini score correlated significantly with true insulin (mIU/l) (r = 0.095, p = 0.033). However, the results from the multivariate stepwise linear regression analysis show that the association between specific insulin level and severity of coronary atherosclerosis lost its significance.

CONCLUSIONS

The level of plasma fasting specific insulin was associated significantly with the severity of coronary atherosclerosis, as measured by Gensini score, but hyperinsulinemia showed no association with the severity of coronary atherosclerosis in multivariate analyses.

Increased fasting plasma insulin concentrations are associated with the severity of angiographic coronary artery disease

Fasting plasma insulin concentrations were obtained in 82 patients (51 men and 31 women), mean age 60 +/- 11 years, with a body mass index >25 kg/m(2) who had coronary angiography because of suspected symptomatic coronary artery disease (CAD). Obstructive CAD was diagnosed if there was >50% obstruction of > or =1 vessel. Of 82 patients, 37 (45%) had left main or 3-vessel CAD, 22 (27%) had 2-vessel CAD, 9 (11%) had 1-vessel CAD, and 14 (17%) had no obstructive CAD. Among the 4 groups, there was no significant difference in gender, age, dyslipidemia, and smoking. Hypertension (p = 0.0003), diabetes mellitus (p = 0.035), and increased fasting plasma insulin concentration (p < 0.0001) were significantly associated with the severity of CAD. Stepwise ordinal logistic regression analysis identified increased fasting plasma insulin concentrations in these obese subjects as a significant independent risk factor for the severity of angiographic CAD (p < 0.0001).

Post-challenge hyperinsulinaemia rather than hyperglycaemia is associated with the severity of coronary artery disease in patients without a previous diagnosis of diabetes mellitus

OBJECTIVE

To ascertain the prevalence of abnormal glucose metabolism in patients with coronary artery disease (CAD) but no previous diagnosis of diabetes mellitus (DM) and to examine the relation between the severity of CAD and responses of glucose and insulin to the glucose tolerance test.

METHODS AND RESULTS

Abnormalities of glucose metabolism and insulin response were analysed in 144 patients with CAD without a previous diagnosis of DM who underwent both coronary arteriography and 75 g oral glucose tolerance test. The proportions of impaired and diabetic glucose tolerance were very high (39% for impaired and 21% for diabetic glucose tolerance); only 40% had normal glucose tolerance. The parameters of glucose metabolism were not associated with the number of diseased coronary arteries or the presence of previous myocardial infarction (MI). However, the insulin concentration at 60 minutes or 120 minutes after glucose challenge, insulin area, and the ratio of insulin to glucose area were significantly higher in patients with significant coronary stenosis and with previous MI. Fasting glucose concentration and most conventional risk factors did not predict post-challenge hyperinsulinaemia.

CONCLUSION

Patients with CAD without a previous diagnosis of DM had a high prevalence of abnormal glucose tolerance. Post-challenge hyperinsulinaemia was associated with the number of diseased coronary arteries and the presence of previous MI. The insulin response to the glucose challenge test requires further investigation as a potential risk factor for CAD and a potential target for intervention.

Anatomy of coronary disease in diabetic patients: an explanation for poorer outcomes after percutaneous coronary intervention and potential target for intervention

There are over 1.3 million known diabetic patients in the UK and a similar number who have the disease undiagnosed. Over 90% have non-insulin dependent diabetes mellitus usually characterised by insulin resistance and adult onset. Over half of all diabetic patients die of coronary disease and account for over a fifth of percutaneous coronary intervention (PCI) revascularisation procedures. Despite recent therapeutic advances such as new antiplatelet treatments and drug eluting stents, outcomes for diabetic patients after PCI are still significantly worse than for non-diabetic patients. This article summarises what is known about the pattern and severity of diabetic coronary disease, what mechanisms are responsible for these differences, and whether this information can help explain the poorer prognosis for these patients after PCI and form the basis of interventions to improve outcome.

Role of adiponectin in insulin-resistant hypertension and atherosclerosis

Insulin resistance is one of the major risk factors associated with development of hypertension and atherosclerosis. Recent studies have shown that adiponectin, an adipocyte-derived hormone, may be involved in insulin resistance and development of atherosclerosis in diabetes patients. The aim of this study was to examine adiponectin levels in patients with essential hypertension to determine the relationships between adiponectin levels and insulin sensitivity and to examine the relationship of adiponectin with pulse wave velocity (PWV) in a general population based on the results of an epidemiological survey in Japan. In a clinical study, 20 normotensives (NT) and 30 non-treated essential hypertensives (EHT) were hospitalized, and euglycemic hyperinsulinemic glucose clamp (GC) was performed to evaluate insulin sensitivity defined as M value. EHT were divided into insulin-resistant EHT (EHT-R) and insulin-nonresistant EHT (EHT-N) according to the mean -1 SD of the M value of NT as a cut-off point. Fasting plasma glucose (FPG), immunoreactive insulin (IRI), and adiponectin concentrations were measured. There were no significant differences in body mass index (BMI) or FPG among the NT, EHT-N, and EHT-R groups. The M value and adiponectin concentration in EHT-R were significantly lower than those in the NT or EHT-N. The IRI level in the EHT-R was significantly higher than those in the other groups. A positive correlation between adiponectin concentration and M value was found in all subjects, and adiponectin concentration and M value were found to be significant determinants of each other in multiple regression analysis. In an epidemiological study, we studied 391 male inhabitants of rural communities in Hokkaido, Japan. Systolic blood pressure (SBP), BMI, FPG, IRI, and adiponectin were measured in all subjects early in the morning. Homeostasis model assessment (HOMA) values were calculated as an index of insulin sensitivity, and PWV was used as an index of atherosclerosis. A negative correlation between HOMA values and adiponectin concentration was found in all of the subjects. Multiple regression analysis revealed that adiponectin was a significant determinant for PWV in subjects less than 70 years of age. The results of the clinical study indicate that EHT-R had not only hyperinsulinemia but also a low concentration of adiponectin. The results of multiple regression analysis for determinants of degree of PWV using data obtained in the epidemiological study suggest that adiponectin plays a role in antiatherosclerosis, partly through improvement of insulin resistance.

Postchallenge hyperglycemia but not hyperinsulinemia is associated with angiographically documented coronary atherosclerosis in Korean subjects

Although hyperinsulinemia has attracted considerable attention as a possible risk factor for coronary artery disease (CAD), previous studies have not shown consistent results. Hyperglycemia could be an alternative explanation for the association between type 2 diabetes and atherosclerosis. Since previous studies have been mostly lacking coronary angiographic data, we analyzed the relationship between the presence and severity of coronary atherosclerosis based on angiography and hyperinsulinemia or hyperglycemia. Two hundred and thirty subjects underwent coronary angiography and a 75-g oral glucose tolerance test. Age, sex, waist-to-hip ratio, postchallenge 1-h and 2-h glucose levels, plasma triglyceride and HDL-cholesterol levels were different between those with or without CAD. However, there was no significant difference in the plasma insulin levels, area of insulin under the curve, and the ratio of the insulin- and glucose areas between the groups with and without CAD. Multiple logistic regression analysis including fasting-, 1-h, and 2-h glucose values and a variety of atherosclerosis risk factors showed that age, sex and postchallenge 2-h glucose levels were independent determinants of the presence of CAD. These results suggest that coronary atherosclerosis might be associated with postchallenge hyperglycemia, but not with hyperinsulinemia in Korean subjects.

Role of hypertension, dyslipidemia and diabetes mellitus in the development of coronary atherosclerosis in Japan

The present study evaluated the effect of hypertension (HT), dyslipidemia and diabetes mellitus (DM) on the development of coronary atherosclerosis in the Japanese population, using a cross-sectional study of 433 patients (254 men and 179 women) aged 30 years or older who underwent coronary angiography for suspected or known coronary heart disease angina at 5 cardiology departments in the Fukuoka area between September 1996 and August 1997. Patients with a disease duration of 6 months or more were excluded. The main outcome measure was angiographically defined coronary artery stenosis and was found to a significant degree in 146 patients (33.7%). HT, DM, low levels of high-density lipoprotein cholesterol (HDL-C) and hypertriglyceridemia remained as significant coronary artery disease (CAD) risk factors even after controlling for age, sex, hospital, smoking, alcohol use, body mass index and leisure time physical activity. However, hypercholesterolemia was not a significant risk factor after adjusting for these variables. After controlling for these variables, DM, low HDL-C and hypertriglyceridemia were significant CAD risk factors for men, but only DM was a significant CAD risk factor in women. These results indicate that in Japan DM, low HDL-C and hypertriglyceridemia may be more important CAD risk factors than hypercholesterolemia.