Coronary artery disease risk predicted by insulin resistance, plasma lipids, and hypertension in people without diabetes

The risk of carotid plaque instability in patients with metabolic syndrome is higher in women with hypertriglyceridemia

Background

Metabolic syndrome certainly favors growth of carotid plaque; however, it is uncertain if it determines plaque destabilization. Furthermore, it is likely that only some components of metabolic syndrome are associated with increased risk of plaque destabilization. Therefore, we evaluated the effect of different elements of metabolic syndrome, individually and in association, on carotid plaques destabilization.

Methods

A total of 186 carotid endarterectomies from symptomatic and asymptomatic patients were histologically analysed and correlated with major cardiovascular risk factors.

Results

Metabolic syndrome, regardless of the cluster of its components, is not associated with a significant increase in risk of plaque destabilization, rather with the presence of stable plaques. The incidence of unstable plaques in patients with metabolic syndrome is quite low (43.9 %), when compared with that seen in the presence of some risk factors, but significantly increases in the subgroup of female patients with hypertriglyceridemia, showing an odds ratio of 3.01 (95% CI, 0.25–36.30).

Conclusions

Our data may help to identify patients with real increased risk of acute cerebrovascular diseases thus supporting the hypothesis that the control of hypertriglyceridemia should be a key point on prevention of carotid atherosclerotic plaque destabilization, especially in post-menopausal female patients.

Coagulation F13A1 V34L, fibrinogen and homocysteine versus conventional risk factors in the pathogenesis of MI in young persons

BACKGROUND

The pathogenesis of myocardial infarction (MI) involves environmental and genetic risk factors, with the latter putatively playing significant roles in younger patients. Genetic variability in coagulation factors comprises one such group. The coagulation factor 13 subunit A (F13A1) Val34Leu polymorphism (rs5985) has yielded variable findings in literature, with no prior South Asian data.

METHODS

We studied the frequency of this polymorphism using the amplification-created restriction-enzyme site (ACRES) polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) in 101 MI patients aged below 40 years and 103 controls along with plasma fibrinogen and serum homocysteine levels.

RESULTS

The distribution of Val/Val, Val/Leu and Leu/Leu genotypes was similar among cases (72.3%, 26.7% and 1.0%) and controls (78.6%, 19.4% and 1.9%, respectively). Val and Leu allele frequencies were 85.6% and 14.4% among patients and 88.3% and 11.7% among controls, respectively (p = .416). Mean plasma fibrinogen was higher in patients vis-à-vis controls (3.1 versus 3.7 g/l; p < .001) but homocysteine was elevated in both patients (52%) and controls (67%) (p = .225). Multivariate analysis revealed hypertension (p < .001, OR 6.16) and smoking (p < .001, OR 5.48) to impart strongest risk followed by positive family history, plasma fibrinogen levels and male gender.

CONCLUSIONS

Despite its small sample size, this first South Asian study suggests neither protective nor deleterious effects of the F13A1 Val34Leu polymorphism on the risk of MI in young persons. The Leu allele frequency is intermediate to that reported from the West and the Far East. Traditional risk factors contribute greatly to risk even in younger MI patients in South Asia.

Relationship of Insulin Resistance to Prevalence and Progression of Coronary Artery Calcification Beyond Metabolic Syndrome Components: Shiga Epidemiological Study of Subclinical Atherosclerosis

OBJECTIVE

The association between insulin resistance (IR) and coronary artery calcification (CAC) has been uncertain after adjustment for metabolic syndrome components. We aimed to evaluate whether IR is associated with CAC prevalence or progression independently of metabolic syndrome components.

APPROACH AND RESULTS

We conducted a population-based study in a random sample of Japanese men aged 40 to 79 years and determined IR using the homeostasis model assessment of insulin resistance (HOMA-IR). The associations of HOMA-IR and other diabetic parameters per 1-SD increase with CAC prevalence and progression were evaluated using multivariable logistic regression. Of 1006 total participants at baseline (mean age, 64±10 years), CAC prevalence was observed in 646 (64.2%), and of 789 participants at follow-up (mean duration, 4.9±1.3 years), CAC progression was observed in 365 (46.3%). After adjustment for covariates including metabolic syndrome components, higher HOMA-IR was independently associated with CAC prevalence (adjusted odds ratio 1.34, 95% confidence interval 1.10-1.63; P=0.003) and progression (odds ratio 1.32, 95% confidence interval 1.09-1.60; P=0.004). In participants without diabetes mellitus, positive associations were similarly observed (prevalence: odds ratio 1.29, 95% confidence interval 1.04-1.60; P=0.022; and progression: odds ratio 1.25, 95% confidence interval 1.01-1.55; P=0.042), whereas glucose and hemoglobin A1c were not associated with CAC prevalence and progression.

CONCLUSIONS

Higher IR was associated with CAC prevalence and progression independently of metabolic syndrome components in Japanese men and also in those without diabetes mellitus. Among diabetic measures, IR and fasting insulin, but not glucose and hemoglobin A1c, predicted CAC progression in men without diabetes mellitus.

Coronary artery calcification in obese youth: what are the phenotypic and metabolic determinants?

OBJECTIVE

Obesity in adolescence has been associated with increased risk for coronary heart disease in adulthood. This study evaluated subclinical atherosclerosis in obese youth and the underlying risk factors.

RESEARCH DESIGN AND METHODS

Ninety obese adolescents (37 normal glucose tolerant, 27 prediabetes, and 26 type 2 diabetes) underwent evaluation of coronary artery calcifications (CACs) by electron beam computed tomography, aortic pulse wave velocity (PWV), carotid intima-media thickness (IMT), lipids, leptin, inflammatory markers, and body composition (DEXA). A total of 68 underwent evaluation of insulin sensitivity (IS) (hyperinsulinemic-euglycemic clamp) and abdominal adiposity (computed tomography).

RESULTS

A total of 50% had CACs (CAC+: Agatston CAC score ≥1). CAC+ youth had higher BMI, fat mass, and abdominal fat, with no difference in sex, race, IS per fat-free mass (ISFFM), glucose tolerance, PWV, or IMT compared with the CAC- group. PWV was inversely related to IS. In multiple regression analyses with age, race, sex, HbA1c, BMI (or waist circumference), ISFFM, diastolic blood pressure, non-HDL cholesterol, and leptin as independent variables, BMI (or waist) (R(2) = 0.41; P = 0.001) was the significant determinant of CAC; leptin (R(2) = 0.37; P = 0.034) for PWV; and HbA1c, race, and age (R(2) = 0.34; P = 0.02) for IMT.

CONCLUSIONS

Early in the course of obesity, there is evidence of CAC independent of glycemia. The different biomarkers of subclinical atherosclerosis appear to be differentially modulated, adiposity being the major determinant of CAC, hyperglycemia, age, and race for IMT, and leptin and IS for arterial stiffness. These findings highlight the increased cardiovascular disease risk in obese youth and the need for early interventions to reverse obesity and atherosclerosis.

Insulin resistance independently predicts the progression of coronary artery calcification

BACKGROUND

Change in coronary artery calcification is a surrogate marker of subclinical coronary artery disease (CAD). In the only large prospective study, CAD risk factors predicted progression of coronary artery calcium (CAC).

METHODS

We measured CAC at enrollment and after 24 months in a community-based sample of 869 healthy adults aged 60 to 72 years who were free of clinical CAD. We assessed predictors of the progression of CAC using univariate and multivariate models after square root transformation of the Agatston scores. Predictors tested included age, sex, race/ethnicity, smoking status, body mass index, family history of CAD, C-reactive protein and several measures of diabetes, insulin levels, blood pressure, and lipids.

RESULTS

The mean age of the cohort was 66 years, and 62% were male. The median CAC at entry was 38.6 Agatston units and increased to 53.3 Agatston units over 24 months (P < .01). The CAC progression was associated with white race, diabetes, dyslipidemia, hypertension, lower diastolic blood pressure, and higher pulse pressure. After controlling for these variables, higher fasting insulin levels independently predicted CAC progression.

CONCLUSIONS

Insulin resistance, in addition to the traditional cardiac risk factors, independently predicts progression of CAC in a community-based population without clinical CAD.

A triglyceride/high-density lipoprotein ratio > or = 3.5 is associated with an increased burden of coronary artery disease on cardiac catheterization

An elevated triglyceride (TG)/high-density lipoprotein (HDL) ratio has been described as a predictor of insulin resistance and cardiovascular events. We evaluated whether a TG/HDL ratio > or = 3.5 was associated with the burden of coronary artery disease (CAD) on cardiac catheterization. A retrospective chart review of 156 consecutive adults presenting to the Montefiore Medical Center Emergency Department with symptoms of unstable angina and no known history of CAD who underwent cardiac catheterization as part of their index hospitalization was performed. TG and HDL data were available in 100 patients within 6 months prior to admission and no more than 24 hours after presentation. A priori, a burden of CAD score was developed. On multivariate analysis, a TG/HDL ratio > or = 3.5 was associated with the burden of CAD (odds ratio, 2.87; 95% confidence interval, 1.03-7.96; p = 0.04). Further study is warranted.

[Metabolic syndrome in patients with coronary heart disease. Results of using different diagnostic criteria]

A unified definition of metabolic syndrome, considered a common feature of cardiovascular risk, is lacking. The aim of this study was to compare the prevalence of this syndrome in patients with ischemic heart disease using two diagnostic criteria: the European Group of Resistance to Insulin and the National Cholesterol Education Program. We designed an observational, cross-sectional study of the factors that make up metabolic syndrome in subjects diagnosed with coronary heart disease. A total of 169 patients aged 35 to 79 years were studied (129 men and 40 women). With the European group criterion the percentage of patients with metabolic syndrome was 43.7%, whereas the American group criterion yielded a prevalence of 40.8% (no significant difference). The prevalence of metabolic syndrome among patients with ischemic heart disease is high. The diagnostic criteria used are similar and do not differ significantly, although diagnostic concordance was only 50%.

[Prevalence of metabolic syndrome in patients with coronary heart disease]

BACKGROUND AND OBJECTIVE

We aimed to know the prevalence of classical cardiovascular risk factors, hyperinsulinism, insulin resistance and metabolic syndrome (MS) in a population with coronary heart disease (CHD) as compared with a population without personal or familial history of cardiovascular risk factors.

SUBJECTS AND METHOD

This was an observational and transversal study of cardiovascular risk factors making up the MS in an adult population. 367 subjects aged 35-79 years (268 men and 99 women) were studied; 185 had CHD (141 men and 44 women) and 182 (127 men and 55 women) were included as a control population. 82 individuals of the control group who had no MS components were selected for the calculation of parameters of hyperinsulinism and the HOMA (Homeostasis Model Assessment) index in order to evaluate the insulin resistance.

RESULTS

As compared with the control group, patients with CHD showed higher blood pressure (systolic and dyastolic), body mass index (BMI), triglicerydes and apo B100 concentrations, and lower HDL-c and apo A1 values. They also exhibited higher values of glycemia and insulinemia and consequently a higher HOMA index. The values of insulin and HOMA (percentil 75), obtained from the selected group for this purpose, were 12 U/ml and 3.03, respectively. In the CHD population, 38.28% (95% CI, 31.13-45.95) had hyperinsulinism, 47.02% (95% CI, 39.70-54.47) had insulin resistance (HOMA) and 41.08% (95% CI, 33.98-48.55) had MS.

CONCLUSIONS

There was a high prevalence of cardiovascular risk factors in the CHD population. Patients with CHD have higher hyperinsulinism and insulin resistance as well as a greater prevalence of MS. Despite treatment, a clear association exists between MS and CHD in both men and women.

Insulin, proinsulin and insulin resistance status in relation to lipid profiles among school children in Taiwan-The Taipei Children Heart Study

PURPOSE

Evidence suggests that there may be a metabolic syndrome characterized by hyperinsulinemia or insulin resistance associated with increased cardiovascular disease risk. The purpose of this study is to evaluate insulin, proinsulin or insulin resistance to determine which is the best parameter to predict lipid profiles among children in Taiwan.

METHODS

After multi-stage sampling, we randomly included 852 school children (415 boys and 437 girls) with a mean age of 13 yr in this study. We measured insulin and intact proinsulin levels by RIA (<0.2% cross-reactivity) and estimated insulin resistance index (IRI) using the homeostatic model assessment (HOMA) method. We used standard methods to measure atherosclerotic lipid profiles including total cholesterol (CHOL), triglyceride (TG), HDL-C, apolipoprotein A (ApoA), apolipoprotein B (ApoB), and lipoprotein[a] and calculated LDL-C and TCHR (total cholesterol to HDL-C ratio) levels.

RESULTS

Girls had higher CHOL, LDL-C, ApoA and ApoB levels than boys (p < 0.001). There was no significant difference in insulin, proinsulin and IRI status between boys and girls. Among boys, insulin, proinsulin and IRI were positively correlated with TG, ApoB and TCHR and negatively related to HDL-C. Among girls, these associations were attenuated and became insignificantly for TCHR and HDL-C. After adjusting for potential confounders, IRI and insulin were still positively associated with TG and ApoB levels and negatively associated with HDL-C in boys. However, in girls, proinsulin and insulin were positively associated with TG only. Finally, in the stepwise regression analyses, IRI was a better predictor of TG, HDL-C, and ApoB than insulin or proinsulin in boys. However, in girls, proinsulin was a stronger predictor than insulin or IRI for TG and TCHR.

CONCLUSION

From this study, we found that IRI (in boys) and proinsulin (in girls) levels are generally more significant and stronger parameters than insulin for predicting lipid profiles among children in Taiwan.

Fat distribution and insulin sensitivity in postmenopausal women: influence of hormone replacement

OBJECTIVE

To examine cross-sectionally the influence of hormone replacement therapy (HRT) on the relationship between body composition and insulin sensitivity (Si).

RESEARCH METHODS AND PROCEDURES

Subjects were 57 early postmenopausal white women, 33 receiving HRT and 24 controls. Body composition was estimated using DXA and computed tomography scans at the abdomen and mid-thigh. Si was assessed by a frequently sampled intravenous glucose tolerance test with minimal model analysis.

RESULTS

Compared with nonusers, HRT users had lower visceral adipose tissue, fasting serum glucose, and fasting insulin. Total body fat and unadjusted Si did not differ between groups. Visceral adipose tissue mass (VATM) was the only body-fat compartment significantly associated with Si (r(2) = 0.43, p < 0.0001) in a model including total-body fat, upper-trunk fat, subcutaneous abdominal fat mass, leg fat, and mid-thigh low-density lean tissue. Lean body mass was positively correlated with Si among HRT users and tended to be negatively correlated among nonusers. HRT status also affected the relationship between VATM and Si such that, relative to nonusers, HRT users had lower Si across lower VATM levels, but higher Si across higher VATM.

DISCUSSION

These results suggest that in postmenopausal women, VATM is uniquely related to Si. HRT affects the relationship between VATM and Si and between lean body mass and Si. These interactions should be considered in future studies.

Obesity and sarcopenia after menopause are reversed by sex hormone replacement therapy

OBJECTIVE

Menopause is linked to an increase in fat mass and a decrease in lean mass exceeding age-related changes, possibly related to reduced output of ovarian steroids. In this study we examined the effect of combined postmenopausal hormone replacement therapy (HRT) on the total and regional distribution of fat and lean body mass.

RESEARCH METHODS AND PROCEDURES

Sixteen healthy postmenopausal women (age: 55 +/- 3 years) were studied in a placebo-controlled, crossover study and were randomized to 17beta estradiol plus cyclic norethisterone acetate (HRT) or placebo in two 12-week periods separated by a 3-month washout. Total and regional body composition was measured by DXA at baseline and in the 10th treatment week in both periods. Changes were compared by a paired Student's t test.

RESULTS

The change in body weight during HRT was equal to the change during placebo (-24.6 g vs. -164 g, p = 0.42), but relative fat mass was significantly reduced (-0.5% vs. +1.24%, p < 0.01). During HRT, compared with during placebo, lean body mass increased (+347 g vs. -996 g, p < 0.01) and total fat mass decreased (-400 g vs. +836 g, p = 0.06). Total bone mineral content increased (+28.9 g vs. -4.4 g, p = 0.04) and abdominal fat decreased (-185 g vs. +253 g, p = 0.04) during HRT compared with placebo.

DISCUSSION

HRT is linked to the reversal of both menopause-related obesity and loss of lean mass, without overall change in body weight. The increase in lean body mass during HRT is likely explained by muscle anabolism, which in turn, prevents disease in the elderly.

[Diabetes mellitus, inflammation and coronary atherosclerosis: current and future perspectives]

Type 2 diabetes mellitus is a condition associated with an increased risk of coronary artery disease. This condition is currently reaching epidemic proportions in the Western world. Epidemiological studies have shown that insulin resistance and the constellation of metabolic alterations associated with type 2 diabetes mellitus such as dyslipidaemia, systemic hypertension, obesity and hypercoagulability, have an effect on the premature onset and severity of atherosclerosis. Albeit direct, the link between insulin resistance and atherogenesis is rather complex. It is likely that its complexity relates to the interaction between genes that predispose to insulin resistance and genes that independently regulate lipid metabolism, coagulation processes and biological responses of the arterial wall. The rapid development of molecular biology in recent years has resulted in a better understanding of the immune and inflammatory mechanisms that underlie insulin resistance and atherosclerosis. For example, it is known that nuclear transcription factors such as nuclear factor kappa beta and peroxisome proliferator-activated receptor are involved in atherosclerosis. The former modulates gene expression which encodes pro-inflammatory proteins vital for the development of the atheromatous plaque. In the presence of insulin resistance there are multiple activating factors that could explain the early onset and severity of atherosclerosis. Glitazones, the new oral antidiabetic drugs and agonists of peroxisome proliferator-activated receptor, have been shown to improve peripheral insulin sensitivity and to also delay atherosclerosis progression in experimental models. Their beneficial effects have been linked to their anti-inflammatory effect.