Lack of association of insulin resistance and carotid intimal medial thickness in non-diabetic Asian Indian subjects

Risk of atherosclerosis in women with polycystic ovary syndrome: a study from South India

Women with polycystic ovary syndrome (PCOS) often present for cosmetic and or reproductive symptoms; attention is generally not paid to the future risk of atherosclerosis for these women. Given that Asian Indians are insulin resistant and prone to metabolic syndrome at an earlier age, we assessed glucose/insulin ratio and intimal medial thickness (IMT) in young women with PCOS from south India. In this cross-sectional case control study, we assessed insulin resistance and carotid IMT in 40 women presenting with hyperandrogenic features of PCOS. Insulin resistance was assessed by fasting glucose/insulin ratio and IMT by the Doppler system with electrical linear transducer midfrequency of 12 MHz. Women with PCOS had higher fasting insulin levels (36.58 +/- 17.81 muU/mL, vs. 16.60 +/- 3.22 muU/mL in controls; p < 0.001), higher insulin resistance (glucose/insulin ratio 2.81 +/- 1.47 vs. 5.47 +/- 1.46 in controls; p < 0.001), and greater IMT (0.53 +/- 0.14 mm vs. 0.39 +/- 0.06 mm in controls; p < 0.001). Women with PCOS had a higher body mass index (BMI) (26.46 +/- 5.24 vs. 23.24 +/- 3.05 in controls; p < 0.001), and the differences between PCOS and controls persisted, even among those who had a BMI of less than 25. We concluded that South Indian women with the reproductive abnormalities of PCOS have greater insulin resistance and IMT, and therefore they must be advised about lowering the risk of future vascular disease.

Subclinical atherosclerosis and metabolic risk: role of body mass index and waist circumference

BACKGROUND

Carotid artery intima-media thickness (IMT) is greater in adults with elevated metabolic risk profiles. However, the influence of body mass index (BMI) or waist circumference (WC) on the relationship between IMT and metabolic risk is unclear.

METHODS

Adults from the Bogalusa Heart Study were classified as normal weight, overweight, or obese and into WC categories (men, low <94 cm, moderate 94-101.9 cm, high ≥102 cm; women, low <80 cm, moderate 80-87.9 cm, high ≥88 cm). Elevated metabolic risk was defined by cardiovascular risk factor clustering (≥2 abnormal risk factors or insulin resistance (upper quartile of homeostasis model of insulin resistance). Carotid ultrasound measurements were obtained and mean IMT was calculated. General linear models compared IMT between elevated versus normal metabolic risk groups, adjusting for sex, age, race/ethnicity, and either BMI or WC category.

RESULTS

Adults were 24-43 years of age (n = 991) and 41% had elevated metabolic risk (42% male, 28% African American, 38% obese). IMT (mm) was greater in adults with elevated metabolic risk (0.83 ± 0.007) versus normal risk (0.80 ± 0.006) whether adjusted by BMI or WC (both P < 0.0005). IMT was greater in adults with elevated compared to normal metabolic risk within normal-weight (0.84 ± 0.016 vs. 0.79 ± 0.008; P = 0.002), and obese adults (0.86 ± 0.009 vs. 0.80 ± 0.01; P = 0.03), but not significantly different between risk groups in overweight adults. Similar results were found when stratified by WC category.

CONCLUSION

Adults with elevated metabolic risk have greater IMT than those with normal risk in normal-weight, overweight, low WC, and high WC, but not significant for overweight or moderate WC categories.

Association between impaired glucose tolerance and carotid atherosclerosis: a study in 64-year-old women and a meta-analysis

BACKGROUND AND AIMS

Impaired glucose tolerance (IGT) is regarded as a transient metabolic state leading to type-2 diabetes, and is known to predict future risk of cardiovascular disease. This study was designed to investigate if IGT is associated with subclinical atherosclerosis.

METHODS AND RESULTS

In a population-based cohort of 64-year-old women, a group with IGT determined by repeated oral glucose tolerance tests (n=205) was compared with healthy women with normal glucose tolerance (NGT, n=188). Intima-media thickness (IMT) and plaques in the common carotid arteries (CCA) and bulbs were measured by ultrasound. The 95% confidence interval (CI) of the difference between the IGT and NGT groups was -0.03 to 0.03mm. There was no difference in carotid bulb IMT or in the occurrence, size, and characteristics of plaques between the IGT and NGT groups. A meta-analysis was used to calculate summary measures of 12 reviewed studies showing a difference of 0.030 (95% CI 0.012-0.048) mm in carotid IMT between IGT and NGT groups. Heterogeneity in IMT differences between studies was shown.

CONCLUSIONS

In our population-based cohort of 64-year-old women, IGT was not associated with increased occurrence of subclinical atherosclerosis. However, a meta-analysis of 12 studies, including our current study, showed that IGT was associated with a small increase in the CCA IMT.

ApoB/apoA-I ratio is related to femoral artery plaques in 64-year-old women also in cases with low LDL cholesterol

INTRODUCTION

The apolipoproteinB (apoB)/apolipoproteinA-I (apoA-I) ratio mirrors the number of pro-atherogenic and anti-atherogenic lipoprotein particles. This ratio may carry more information on risk for atherosclerosis than LDL in cohorts with impaired glucose tolerance. The aim was to examine the association between the apoB/apoA-I ratio and ultrasound-assessed atherosclerosis in the carotid and femoral arteries in women with varying degrees of glucose tolerance.

METHODS

Plaque occurrence, and intima-media thickness in the carotid and femoral arteries were examined by B-mode ultrasound in a random sample of 64-year-old women (n=646) living in Gothenburg, Sweden, representing different degrees of glucose intolerance (diabetes (n=234), impaired (n=212) and normal glucose tolerance (n=200)). Traditional risk factors and serum concentrations of apolipoproteins were analysed.

RESULTS

For subjects in the lowest LDL tertile, the risk of having a plaque in the femoral artery was three times greater for subjects in the highest apoB/apoA-I tertile compared to subjects in the lowest tertile (OR: 3.0, 95% CI: 1.2-7.5). A clear increase in the occurrence of femoral plaque was observed already at a cut-off value of 0.63 (OR: 1.8, 95% CI: 1.2-2.6). ApoB/apoA-I was also related to femoral plaque occurrence in women with low HbA1c. ApoB/A-I ratio was associated with carotid and femoral IMT but not carotid plaques.

CONCLUSION

The apoB/apoA-I ratio improved the identification of cases with femoral artery atherosclerosis in a cohort of women with varying degrees of glucose tolerance. Such cases could also be identified in women with normal LDL and HbA1c levels. The results indicate that an apoB/apoA-I ratio above 0.63 should be used as a marker of increased risk.

Insulin sensitivity as a risk factor for common carotid intima media thickness (IMT): its relation to atherosclerosis

INTRODUCTION

The relationship between insulin resistance and atherosclerosis (ATH) in non-diabetic hypertensive patients from the Asian Indian population remains poorly understood. To resolve this issue, the present study was designed to analyze whether insulin sensitivity in a non-diabetic individual is related to the development of ATH.(by using IMT as an index) and whether this relationship is dependent on the presence of other cardiovascular disease (CVD) risk factors such as dyslipidemia and hypertension.

METHODOLOGY

This study included 68 healthy controls with no diabetes and hypertension and 41 hypertensive patients who underwent four-point oral glucose tolerance test (OGTT) and intravenous glucose tolerance test (IVGTT). A biochemical profile, beta mode ultrasonography for intima media thickness of carotid artery, and ECG determination was carried out.

RESULTS

Hypertensive patients in our study exhibited significantly increased abdominal obesity. Blood pressure, fasting and 2 hr plasma glucose (4.62 +/- 0.08 and 5.55 +/- 0.17 mmol/l), and triglyceride (1.47 +/- 0.067 mmol/l) levels were compared to those of control subjects (p < 0.05). The fasting insulin levels and HOMA-IR were also significantly increased and Composite Insulin Sensitivity Index (CISI) reduced compared to controls with p < 0.01. Intima media thickness of the left (0.08 +/- 0.01) and right (0.069 +/- 0.008) CA were both significantly increased in hypertensives (p < 0.01). Correlation analysis showed that IMT of the left carotid artery was significantly associated with triglyceride levels (r = 0.813, p < 0.05) but not with insulin measures such as HOMA-IR and CISI.

CONCLUSION

Hyperinsulinemia was observed in our non-diabetic hypertensive patients, but no association was found between IMT and insulin resistance. That IMT of hypertensives was associated with triglyceride levels suggests that high levels of insulin may be related to the development of ATH indirectly through its effects on lipid metabolism in our population.

Vascular phenotype and subclinical inflammation in diabetic Asian Indians without overt cardiovascular disease

Although Asian Indian (AI) patients with diabetes mellitus type 2 (DM2) are at high risk for cardiovascular disease (CVD), not all patients develop CVD. The vascular phenotype of AI-DM2 without CVD has not been elucidated and may point to protective features. Using baseline data from a clinical trial we provide an initial description of vascular parameters in AI-DM2 compared to Europid Caucasian controls (ECs) matched for age and gender. Endpoints of the study were endothelial function, low-grade systemic inflammation (CRP) and carotid intima-media thickness (cIMT). AIs had longer duration of diabetes, worse glycemic control and more microangiopathy. Both groups demonstrated marked endothelial dysfunction. CRP levels were similar: 1.7 (4.9) mg/L in AIs and 2.8 (3.6) mg/L in ECs. cIMT values were significantly lower in AI-DM2 than EC-DM2 (0.655mm (0.12) versus 0.711mm (0.15), p=0.03). Multiple regression analysis showed that variability in CRP was mainly determined by waist circumference, not by ethnicity. In contrast, ethnicity was a significantly explanatory variable for cIMT. Vascular phenotype of AI-DM2 without CVD was characterized by endothelial dysfunction and relatively low levels of CRP, comparable to EC-DM2 controls. In contrast, lower cIMT values were observed in AI-DM2 despite longer duration of diabetes and worse metabolic control. We propose that mechanisms slowing its progression may have atheroprotective potential in AI-DM2.

Carotid intima-media thickness and stiffness in relation to type 2 diabetes in Chinese

We investigated carotid intima-media thickness (IMT) and quantitative carotid stiffness (QCS) index in relation to plasma glycosylated hemoglobin A(1C) (HbA(1C)) and duration of diabetes mellitus in 337 Chinese diabetic patients. In categorical analyses, carotid IMT was 710 mum in subjects with a duration of diabetes mellitus < or = 2 years, 760 micorm in subjects with a duration of diabetes mellitus more than two years and with plasma HbA(1C) < 6.5% (P < 0.05), and 790 microm in subjects with a duration of diabetes mellitus more than two years but with plasma HbA(1C) > or = 6.5% (P < 0.01). The corresponding values for QCS values were 4.5, 4.6 and 5.1 (P < 0.05), respectively. In multiple stepwise regression analyses carotid IMT was significantly associated with the duration of diabetes mellitus, systolic blood pressure and serum concentration of total cholesterol, whereas QCS was significantly associated with age, HbA(1C), systolic and diastolic blood pressure (P < 0.05). In conclusion, carotid IMT as a structural measure of arterial wall is increased in patients with a longer history of diabetes mellitus, whereas QCS as functional index is mainly influenced by the quality of blood glucose control.

Insulin resistance is associated with increased risk of major cardiovascular events in patients with preexisting coronary artery disease

BACKGROUND

Over the past years it has been recognized that insulin resistance (IR) is an independent risk factor for the development of diabetes, whereas its association with cardiovascular events remains controversial. The aim of our study was to explore the association between IR per se and cardiovascular events among patients with preexisting coronary artery disease.

METHODS

The mean follow-up period of this prospective study was 6.2 years. Metabolic and inflammatory parameters were analyzed from stored frozen plasma samples obtained at baseline from 2938 patients aged 45 to 74 years. The homeostatic index of IR (HOMA-IR) was calculated according to the homeostasis model assessment.

RESULTS

New major cardiovascular events (fatal and nonfatal myocardial infarction and sudden death) were recorded in 108 (11.1%) patients from the lowest IR tertile, in 147 (14.7%) from the intermediate tertile, and in 166 (17.2%) from the highest tertile (P = .0002). The linear trend for total and cardiac death across the tertiles of HOMA-IR was significant as well (P = .02 and P = .009, respectively). The highest age-adjusted rates for major cardiovascular events and new diabetes were found among patients within the top tertile of HOMA-IR (57% and 130% higher rates, respectively, tertile 3 vs tertile 1, P < .0001 for both). Multivariable analysis identified HOMA-IR (tertile 3 vs tertile 1) as an independent predictor of increased risk of major cardiovascular events and new diabetes with hazard ratios (95% CI) of 1.4 (1.1-1.8) and 1.5 (1.1-2.0), respectively.

CONCLUSIONS

Insulin resistance per se is an independent risk factor for cardiovascular events and new diabetes in patients with preexisting coronary artery disease.

Soluble CD40 ligand levels in otherwise healthy subjects with impaired fasting glucose

Unlike diabetes mellitus and impaired glucose tolerance, it is not clear whether the subjects with impaired fasting glucose (IFG) are at increased risk of atherosclerosis and cardiovascular diseases. The CD40-CD40 ligand interaction is involved in the mechanism of atherosclerosis. We investigated whether soluble CD40L (sCD40L) as well as high sensitive C-reactive protein (hsCRP) levels are increased in subjects with IFG having no confounding factors for inflammation or atherosclerosis. Twenty four IFG subjects with no additional disorders and 40 appropriate healthy controls were studied. sCD40L and hsCRP levels in the IFG and control groups were similar. Blood pressures, total and LDL-cholesterol, and triglyceride levels were also similar, whereas HDL-cholesterol was lower and HOMA-IR indexes were higher in the IFG group. Though the sample size was small, the present data show that sCD40L seems not to alter in subjects with IFG suggesting that it might not be an independent risk factor for atherosclerosis.

Serum ghrelin and carotid atherosclerosis in older Japanese people with metabolic syndrome

Ghrelin may play a role in the development of atherosclerosis. However, the effect of serum ghrelin on carotid intima-media thickness (cIMT) (well-established as a surrogate marker to atherosclerosis) in metabolic syndrome (MS), particularly among relatively older subjects, has still not been thoroughly investigated. A total of 101 subjects >60 years of age (mean age, 72.3 years) with MS were enrolled in the study to investigate the relationship between serum total ghrelin and B-mode ultrasonographic cIMT levels. There were significantly positive correlations between cIMT and both age and systolic BP, but cIMT was significantly inversely correlated to ghrelin levels. In the multiple regression analysis for cIMT adjusted by other measured parameters, ghrelin was a significant and independent factor along with age and systolic BP. These findings suggest that decreased ghrelin levels may be related to carotid atherosclerosis among older subjects with MS.

Intimal media thickness, glucose intolerance and metabolic syndrome in Asian Indians--the Chennai Urban Rural Epidemiology Study (CURES -22)

AIMS

The aim of the present study was to assess carotid intimal media thickness (IMT) in different grades of glucose intolerance and the metabolic syndrome (MS) in Asian Indians, a high-risk group for diabetes and coronary artery disease.

METHODS

Subjects with normal glucose tolerance (NGT) (n = 1600), impaired glucose tolerance (IGT) (n = 330), newly diagnosed diabetes (NDD) (n = 330) and known diabetes (KD) (n = 1170) were recruited from the Chennai Urban Rural Epidemiology Study (CURES), an ongoing study on a representative population of Chennai (formerly Madras), in southern India. Assessment of carotid IMT was performed using high-resolution B-mode ultrasonography. MS was defined using modified adult treatment parel (ATP) III guidelines. Subjects with self-reported diabetes, hypertension and dyslipidaemia were excluded from the analysis on MS.

RESULTS

Subjects with glucose intolerance had significantly higher mean carotid IMT values compared with subjects with normal glucose tolerance (NGT 0.69 +/- 0.12 mm, IGT 0.75 +/- 0.16 mm, NDD 0.79 +/- 0.19 mm and KD 0.87 +/- 0.24 mm, P < 0.001). Regression analysis showed that there was a linear increase in mean IMT values with increasing severity of glucose intolerance, even after adjusting for age and gender. Mean IMT values were higher in those with MS and increased with increase in number of metabolic abnormalities (subjects without any metabolic abnormality 0.66 +/- 0.12 mm, one abnormality 0.67 +/- 0.13 mm, two 0.70 +/- 0.12 mm, three 0.72 +/- 0.12 mm, four 0.77 +/- 0.15 mm, five 0.76 +/- 0.13 mm). Regression models showed MS to be associated with IMT, even after adjusting for age, gender and presence of diabetes (P = 0.021).

CONCLUSIONS

In Asian Indians, carotid IMT increases progressively with increasing severity of glucose intolerance and is also associated with the metabolic syndrome, independent of age, gender and presence of diabetes.

Carotid artery intima-media thickness in patients with Type 2 diabetes mellitus and impaired glucose tolerance: a systematic review

AIMS

To review the difference in carotid artery intima media thickness (IMT) between patients with Type 2 diabetes (DM) or impaired glucose tolerance (IGT), and control subjects.

METHODS

Systematic reviews were made in order to identify cross-sectional studies using the ultrasound method. The differences between IMT in DM or IGT and control subjects were calculated. Meta-analysis using random-effects modelling was used to calculate summary measures.

RESULTS

Twenty-three studies included 24,111 subjects; 4019 with DM and 1110 with IGT. In 20 of 21 studies, the diabetic patients had greater carotid artery IMT than the subjects in the control groups. The estimated mean difference in IMT was 0.13 (95% CI: 0.12-0.14) mm. Heterogeneity was observed and likely sources of variation were study size, diabetes duration, and ultrasound method. In three out of nine studies, the IGT patients had significant greater carotid artery IMT than the subjects in the control groups. The estimated mean difference in IMT was 0.04 (95% CI: 0.014-0.071) mm.

CONCLUSIONS

Type 2 diabetes was associated with an 0.13 mm increase in IMT compared with control subjects. In patients with IGT, the increase in IMT was about one-third of that observed in diabetes. The observed difference in IMT can be interpreted as if the diabetes patients were more than 10 years older than the control groups, and that the relative risks of myocardial infarction and stroke were increased by almost 40%, respectively.

The apoB/apoA-I ratio: a strong, new risk factor for cardiovascular disease and a target for lipid-lowering therapy--a review of the evidence

During the last several years interest has focused on the importance of the lipid-transporting apolipoproteins--apoB transports all potentially atherogenic very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL) and LDL particles, and apoA-I transports and acts as the major antiatherogenic protein in the HDL particles. The evidence for the apoB/apoA-I ratio being a strong, new risk factor for cardiovascular (CV) disease and a target for lipid-lowering therapy is reviewed. Results from clinical prospective studies and lipid-lowering trials in healthy subjects and in patients with different clinical manifestations of atherosclerosis are reported. Risk of nonfatal and fatal myocardial infarction and stroke, and manifestations of atherosclerosis documented by angiographic, ultrasound and other techniques has been related to conventional lipids and apolipoproteins (apo). The cholesterol balance determined as the apoB/apoA-I ratio has repeatedly been shown to be a better marker than lipids, lipoproteins and lipid ratios. The results indicate that the apoB/apoA-I ratio is a simple, accurate and new risk factor for CV disease--the lower the apoB/apoA-I ratio, the lower is the risk. Guidelines should be developed in order to recognize the important clinical risk information embedded in the apoB/apoA-I ratio.

Hyperglycaemia after glucose loading is a major predictor of preclinical atherosclerosis in nondiabetic subjects

OBJECTIVE

Carotid intima-media thickness (IMT) has proved to be an independent marker of preclinical atherosclerosis. The aim of this study was to determine whether carotid IMT is associated with the plasma glucose concentration in the fasting state, after loading with oral glucose, or with the insulin sensitivity index (ISI) in nondiabetic subjects with different levels of glucose intolerance and insulin resistance.

DESIGN

Cross-sectional study.

PATIENTS

A total of 160 nondiabetic subjects (147 from our obesity-overweight clinic and 13 healthy normal subjects) were included in the present study, among them 33 had normal glucose tolerance (NGT), 13 had impaired fasting glucose (IFG), 80 had impaired glucose tolerance (IGT) and 34 had both IFG and IGT.

MEASUREMENTS

Carotid IMT was assessed in the common carotid artery by a high-resolution B-mode ultrasound system. Plasma glucose was measured after fasting and at 30 min, 1, 2 and 3 h after a standard 75-g load of glucose. The ISI was calculated from the frequent sampling intravenous glucose tolerance test (FSIGT). Results The IMT values in the NGT group were lower than those in the IFG, IGT and IFG + IGT groups (P < 0.03). No statistical difference in IMT values was found among the latter three groups. Univariate correlation analyses showed that the IMT was positively associated with age, plasma glucose concentrations 1 and 2 h after glucose loading, and serum concentration of low density lipoprotein (LDL) cholesterol (r=0.39, 0.22, 0.25 and 0.18, respectively, P<0.05). Multiple regression analysis showed that only age, plasma glucose concentration 2 h after glucose loading, and LDL cholesterol appeared to be significant correlates of the IMT (P<0.0001), whereas the ISI was not.

CONCLUSIONS

In nondiabetic subjects with various degrees of glucose intolerance, there was a significant increase in IMT in those with IFG and IGT. Significant determinants of IMT, an indicator of preclinical atherosclerosis, include hyperglycaemia 2 h after a glucose load, age and LDL cholesterol, whereas fasting glucose concentration and the ISI were not significantly associated with IMT.

Arterial wall thickness is associated with insulin resistance in type 2 diabetic patients

The aim of the present study was to investigate the independent association of the intimal-medial thickness of carotid and femoral arteries (CA-IMT and FA-IMT), a marker of atheroscelosis, with insulin resistance in type 2 diabetic patients. We evaluated CA-IMT and FA-IMT by high-resolution ultrasonography and insulin resistance determined by euglycemic hyperinsulinemic clamp in 119 type 2 diabetic subjects, 71 males and 48 females (age, 54 +/- 12 (SD) years). In simple regression analyses, CA-IMT and FA-IMT were significantly inversely correlated with insulin sensitivity index (CA-IMT, r = -0.225, p = 0.010; FA-IMT, r = -0.186, p = 0.043, respectively). Multiple regression analysis was performed with the logarithm of CA-IMT or FA-IMT as a dependent variable and insulin sensitivity index as an independent variable along with known clinical risk factors. Insulin sensitivity index exhibited a significant independent contribution to log (CA-IMT) (beta = -0.204, p = 0.033) and to log (FA-IMT) (beta = -0.237, p = 0.010) in these models (CA-IMT, R(2) = 0.347, p < 0.0001; FA-IMT, R(2) = 0.398, p < 0.0001, respectively). In conclusion, insulin resistance is associated with both CA-IMT and FA-IMT in type 2 diabetic patients, suggesting that it is an independent risk factor for the development of atherosclerosis in type 2 diabetes.

Association between insulin resistance and carotid arteriosclerosis in subjects with normal fasting glucose and normal glucose tolerance

OBJECTIVE

We examined the possible association between insulin resistance and carotid arteriosclerosis in subjects who had both normal fasting glucose and normal glucose tolerance after intake of a glucose load.

METHODS AND RESULTS

Our subjects were individuals who underwent general health screening at our institute, which included carotid ultrasound and oral glucose tolerance testing. Of the 1238 subjects enrolled in our study, 738 (60%) were classified as normal, defined as a normal fasting glucose level and normal glucose tolerance, and 334 (27%) and 166 (13%) were classified as borderline and diabetic, respectively, according to the criteria of the Japan Diabetes Society. The homeostasis model assessment of insulin resistance (HOMA-IR) was used as the index to measure insulin resistance. In normal-type subjects, univariate analysis showed that insulin resistance, but not insulin secretion, was associated with the presence of carotid plaque. Multivariate analysis showed that HOMA-IR was positively associated with carotid plaque in normal-type subjects, with an odds ratio of 1.19 (95% confidence interval, 1.00 to 1.41; P<0.05).

CONCLUSIONS

These data suggest the possibility that the presence of higher insulin resistance could be a risk factor for carotid arteriosclerosis in subjects with normal fasting glucose and normal glucose tolerance.