Lower insulin sensitivity as an independent risk factor for carotid wall thickening in normotensive, non-diabetic, non-smoking normal weight and obese premenopausal women

Impaired fasting plasma glucose is a risk indicator of interventricular septum thickening among non-diabetic subjects with obesity

AIMS

To evaluate whether progressively higher fasting plasma glucose (FPG) is associated to thickening of the interventricular septum (IVS) among non-diabetic subjects with obesity.

METHODOLOGY

We studied 227 consecutive non diabetic patients (155 women and 72 men, age range 18-72 years) with overweight or obesity (BMI ≥ 25 Kg/m2), taking no medication or supplement. Hormonal, metabolic and routine laboratory parameters were collected. Echocardiography and ultrasonography echo-color Doppler of intima-media thickness of the common carotid artery (IMT-CCA) were performed to evaluate intima-media thickness of the common carotid artery (IVST) and early signs of atherosclerosis, respectively, in all enrolled subjects.

RESULTS

Of the 227 subjects, 48.9% had higher IVST values. Age (p 0.04), waist circumference (p 0.01), systolic (p < 0.01) and diastolic blood pressure (p < 0.01), FPG (p < 0.01), insulin (p 0.04), HOMA IR (p = 0.01), uric acid (p < 0.01) serum levels, IMT-CCA (p < 0.01), and left atrial diameter (LAD) (p < 0.01) were significantly higher in subjects with pathological IVST. Logistic regression models demonstrated an independent relation of FPG to IVST, both in semi and fully adjusted models (ORs 1.045 and 1.039, respectively). Moreover, graph presentation of the ORs and 95% CIs by FPG quintiles showed a positive risk trend for pathological IVST.

CONCLUSIONS

Higher FPG levels represent an independent sensitive predictor of IVS thickening in subjects with obesity, even before overt diabetes. These results emphasize the importance of preventive management of the diabetes risk in obesity.

Task force on: 'Early markers of atherosclerosis: influence of age and sex'

Atherosclerosis and its complications are the most important causes of death all over the world, especially in Western countries. Diet habits, modern stress life, smoking, sedentary way of life and an involvement of genetic pattern of individuals lead to a sure degeneration of quality of life increasing the risk of atherosclerosis development. For this reason, the main purpose of actual medicine is to identify all the markers that could allow the physicians to evaluate the first moments of the development of this dangerous pathological process. The aim is to reduce the speed of its evolution, trying to delay indefinitely the risk coming from the morphological alterations of the vessels. 'Endothelium function' could allow physicians to detect the first moment of the natural history of atherosclerosis process. Its impairment is the first step in the degeneration of vascular structures. Many methods [flow-mediated vasodilatation (FMD); antero-posterior abdominal aorta diameter (APAO); intima-media thickness of the common carotid artery (CCA-IMT); arterial stiffness; and so on] try to evaluate its function, but many limitations come from general population characteristics. A standardization of the methods should take into account individuals' peculiarities. Two elements, not modifiable, should be taken into account for vascular evaluation: age and sex. The aim of this review is to outline the linkage among age, sex and instrumental evaluation of patients considered for a noninvasive assessment of their cardiovascular risk profile.

Clinical significance of glycated hemoglobin in the acute phase of ST elevation myocardial infarction

In population-based studies, including diabetic and nondiabetic cohorts, glycated hemoglobin A1c (HbA1c) has been reported as an independent predictor of all-cause and cardiovascular disease mortality. Data on the prognostic role of HbA1c in patients with acute myocardial infarction (MI) are not univocal since they stem from studies which mainly differ in patients' selection criteria, therapy (thrombolysis vs mechanical revascularization) and number consistency. The present review is focused on available evidence on the prognostic significance of HbA1c measured in the acute phase in patients with ST-elevation myocardial infarction (STEMI) submitted to primary percutaneous coronary intervention (PCI). We furthermore highlighted the role of HbA1c as a screening tool for glucose intolerance in patients with STEMI. According to available evidence, in contemporary cohorts of STEMI patients submitted to mechanical revascularization, HbA1c does not seem to be associated with short and long term mortality rates. However, HbA1c may represent a screening tool for glucose intolerance from the early phase on in STEMI patients. On a pragmatic ground, an HbA1c test has several advantages over fasting plasma glucose or an oral glucose tolerance test in an acute setting. The test can be performed in the non-fasting state and reflects average glucose concentration over the preceding 2-3 mo. We therefore proposed an algorithm based on pragmatic grounds which could be applied in STEMI patients without known diabetes in order to detect glucose intolerance abnormalities from the early phase. The main advantage of this algorithm is that it may help in tailoring the follow-up program, by helping in identifying patients at risk for the development of glucose intolerance after MI. Further validation of this algorithm in prospective studies may be required in the contemporary STEMI population to resolve some of these uncertainties around HbA1c screening cutoff points.

Is there evidence of early vascular disease in patients with obstructive sleep apnoea without known comorbidities? Preliminary findings

We evaluated early atherosclerotic lesions in 20 non-smokers with newly diagnosed Obstructive Sleep Apnoea (OSA) and without known comorbidities by measuring common carotid artery intima media thickness (CCA-IMT), transcranial Doppler ultrasound (TCD), and ankle brachial index (ABI). These were compared with 20 healthy age- and BMI-matched controls. In OSA patients, CCA-IMT was not significantly higher vs. controls (0.74±0.17 vs. 0.66±0.12 mm, p=0.201) and it was positively correlated with neck circumference (r=0.466, p=0.039), arousal index (r=0.663, p=0.001), gamma-glutamyl transpeptidase activity (r=0.474, p=0.035) while it was negatively correlated with Forced Expiratory Volume in 1 sec (r=-0.055, p=0.012). No difference was noted between patients and controls in terms of vascular stenosis on TCD examination, while asymptomatic peripheral artery disease was found in one patient with OSA. In conclusion, OSA patients without known comorbidities exhibit a non-significant increase in CCA-IMT without further evidence of vascular disease, but additional experience in a larger patient series is needed.

Insulin resistance is associated with significant clinical atherosclerosis in nondiabetic patients with acute myocardial infarction

OBJECTIVE

The prevalence of insulin resistance (IR) is increasing worldwide because of increasing age, obesity, and physical inactivity. Emerging evidence supports a direct proatherogenic effect of IR on the coronary vasculature, but the relation between IR and angiographic atherosclerosis in a real-world clinical setting is uncertain. In this work, we assessed whether IR is independently associated with clinically significant angiographic atherosclerosis in nondiabetic individuals.

APPROACH AND RESULTS

We examined the association between IR and the extent of coronary atherosclerosis determined by angiography in 1073 nondiabetic patients surviving acute myocardial infarction. Patients were divided into quartiles on the basis of the homeostasis model assessment grading of IR, and associations between IR and multivessel coronary artery disease, defined as ≥ 2 arteries with ≥ 70% stenosis (or ≥ 50% left main stenosis), were analyzed in bivariate and multivariable modeling. Overall, the cohort had a median age of 56 years; 28.9% women and 21.8% nonwhite. The crude prevalence of multivessel coronary artery disease was 37.8%, 42.3%, 47.2%, and 48.0% for homeostasis model assessment grading of IR quartiles 1, 2, 3, and 4, respectively (P(trend) = 0.009). In multivariable modeling, compared with quartile 1, both quartile 3 (relative risk [95% confidence interval], 1.31 [1.07-1.60]) and quartile 4 (1.29 [1.03-1.60]) were independently associated with multivessel coronary artery disease. Covariates in the model included patient demographic and clinical characteristics and metabolic factors (low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, triglyceride, glycosylated hemoglobin, and high-sensitivity C-reactive protein).

CONCLUSIONS

We demonstrate an independent association between IR and multivessel coronary artery disease in nondiabetic postmyocardial infarction patients. Our findings strengthen the experimental evidence for a direct atherogenic effect of IR independent of glucose control and other components of the metabolic syndrome.

Correlation between coronary artery disease severity, left ventricular mass index and carotid intima media thickness, assessed by radio-frequency

Background

Intima-media thickness of the common carotid artery (CCA-IMT) is a validated marker of systemic atherosclerosis process. The aim of this study was to evaluate the association between coronary artery disease (CAD), left ventricular hypertrophy (LVH) and CCA-IMT, assessed by Radio Frequency-Quality Intima Media Thickness (^RFQIMT) method, the next generation of IMT real-time measurement, based on the direct analysis of the radiofrequency signal and endowed with high accuracy and reproducibility in early detection of arterial wall thickness.

Methods

115 patients (76 men, mean age: 65.1 ± 12 years) referred to our department and shown significant (≥ 70% luminal obstruction) stenosis at least in one major epicardial coronary artery were studied. Coronary angiograms were divided for severity and extent of the disease: 79 patients (69%) had one, 24 patients (21%) two, 12 patients (10%) three major epicardial coronary arteries with ≥ 70% stenosis. All patients underwent echocardiography and carotid ultrasound examination, assessed by RF.

Results

Dividing ^RFQIMT data in tertiles, dyslipidaemia (31 patients with IMT ≥ 1.20 mm vs 16 with IMT = 0.91-1.19 vs 25 with IMT ≤ 0.9, p = 0.004), LVMI (153.5 ± 20.6 g/m² in IMT ≥ 1.20 mm vs 131.2 ± 8.4 g/m² in IMT = 0.91-1.19 mm vs 114.3 ± 11.1 g/m² in IMT ≤ 0.9 mm, P < 0.001) and number of high stenosed coronary arteries (IMT ≥ 1.20 mm population more often showed three vessel diseases than IMT ≤ 0.90 mm one, P < 0.001) seemed to be significantly related to CCA-IMT increases. Furthermore, LVMI is positively related to IMT (r = 0.91; P < 0.001). In a multivariate regression model (R² = 0.88), ^RFQIMT remained significantly associated with the dyslipidemia (regression coefficient ± standard error [SE]: 0.057 ± 0.023; p = 0.017), LVMI (regression coefficient ± SE: 0.01 ± 0.001; P < 0.0001) and number of damaged coronaries (regression coefficient ± SE: 0.0174 ± 0.028; P < 0.0001).

Conclusions

^RFQIMT is a sophisticated method for carotid ultrasound evaluation. Its evaluation in patients with at least one important major epicardial coronary vessel stenosis would help the accuracy in the general assessment of the number of coronary lesions in these patients.

Carotid artery intima-media thickness: normal and percentile values in the Italian population (camp study)

AIMS

Carotid intima-media thickness (IMT) is one of the best non-invasive parameters for evaluating previous vascular lesions and could be used to identify a preclinical stage of the atherosclerotic process. The aim of our research was to develop an epidemiological study of the normal mean values of IMT of the common carotid artery, adjusted for age and sex, in the Italian population.

METHODS AND RESULTS

In this multicenter study, a total of 1017 patients (596 males, mean age: 58.5 + 13.2 years) were enrolled at four different Italian centers. Inclusion criteria were the absence of cardiovascular risk factors or presence of not more than one. Patients underwent two-dimensional echo-color Doppler scanning of the carotid arteries, adopting a high-definition vascular echographic apparatus and a 11-3 MHz linear electronic probe. The arithmetical mean of the IMT value was calculated. Data obtained from this study show the carotid IMT changes in relation to age and sex. In particular, it grows higher with increasing age, and is always higher in men than in women.

CONCLUSION

In relation to the percentile distribution of the values in the population analyzed, the normal range of m-IMT could be established just on the basis of the patient's age and sex. In this way, the ultrasound scan operator can rely on a simple reference scheme. This will help to refine the use of carotid ultrasound as an excellent tool for detecting asymptomatic carotid alterations and patients at high risk for cerebral and cardiovascular 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.

Increased carotid IMT in overweight and obese women affected by Hashimoto's thyroiditis: an adiposity and autoimmune linkage?

BACKGROUND

Hashimoto's thyroiditis is the most important cause of hypothyroidism. It is a systemic disease that can even affect the cardiovascular system, by accelerating the atherosclerotic process. Aim of this study was to examine whether autoimmune thyroiditis has an effect on the intima-media thickness of the common carotid artery (IMT-CCT), independently of the thyroid function and well-known cardiovascular risk factors. Hashimoto's thyroiditis is a systemic disease. The aim is to examine whether autoimmune thyroiditis and adiposity can effect carotid IMT independently of thyroid hormones and cardiovascular risk factors.

METHODS

A total of 104 obese women (BMI > or = 25.0 kg/m-2), with FT3 and FT4 serum levels in the normal range and TSH levels < 4.5 microU/ml, were investigated. None of these patients was taking any kind of drug influencing thyroid function. Measurements were made of the IMT-CCT, BMI, waist circumference, blood pressure levels, as well as fasting TSH, FT3, FT4, anti-thyroid antibodies, insulin, fasting glycemia, triglycerides, total and HDL-cholesterol serum concentrations.

RESULTS

Of the 104 women, 30 (28.8%) were affected by autoimmune thyroiditis. Significantly higher values of IMT-CCT (p < 0.05), TSH (p < 0.05), and triglycerides (p < 0.05) were obtained, and significantly lower values of FT4 (p < 0.05), in patients with Hashimoto's thyroiditis as compared to those with a normal thyroid function. When examining the whole group together, at multiple regression analysis Hashimoto's thyroiditis maintained a positive association with the IMT (p < 0.001), independently of age, hypertension, BMI, and the fasting serum levels of TSH, FT3, FT4, insulin, fasting glycemia, triglycerides, total and HDL-cholesterol levels.

CONCLUSIONS

The present study shows that Hashimoto's thyroiditis is associated to an increased IMT only in overweight and obese, independently of the thyroid function, BMI and cardiovascular risk factors. These results suggest that Hashimoto's thyroiditis is a marker of evolution of the atherosclerosis if combined to adiposity.

Chronic insulin treatment suppresses PTP1B function, induces increased PDGF signaling, and amplifies neointima formation in the balloon-injured rat artery

We tested the hypothesis that hyperinsulinemia induces the suppression of protein tyrosine phosphatase 1B (PTP1B) function, leading to enhanced PDGF receptor (PDGFR) signaling and neointimal hyperplasia. Rats were implanted with insulin-releasing pellets or sham pellets. Blood glucose levels, insulin levels, food and water intake, body weights, and blood pressures were measured. Neointimal hyperplasia was assessed by computerized morphometry 14 days after carotid balloon injury. PTP1B protein expression in injured arteries was determined via Western blot analysis, whereas PTP1B activity was determined via an immunophosphatase assay. Serum insulin levels were two- to threefold greater in hyperinsulinemic rats, whereas systolic blood pressures, food and water intake, serum triglyceride levels, plasma cortisol levels, and urinary catecholamine levels were not affected. Fourteen days after injury, neointima-to-media area ratios were 0.89 +/- 0.23 and 1.35 +/- 0.22 in control and hyperinsulinemic rats, respectively (P < 0.01). PTP1B protein levels and total PTP1B activity in injured carotid arteries from the insulin-treated group were significantly decreased 7 or 14 days after injury, whereas PTP1B specific activity was decreased only 14 days after injury. These findings were associated with decreased PTP1B mRNA levels and increased PDGFR tyrosyl phosphorylation in insulin-treated rats. These observations support the hypothesis that hyperinsulinemia induces the suppression of PTP1B function, leading to enhanced PDGFR signaling and neointimal hyperplasia.

Chronic insulin treatment amplifies PDGF-induced motility in differentiated aortic smooth muscle cells by suppressing the expression and function of PTP1B

Hyperinsulinemia plays a major role in the pathogenesis of vascular disease. Restenosis occurs at an accelerated rate in hyperinsulinemia and is dependent on increased vascular smooth muscle cell movement from media to neointima. PDGF plays a critical role in mediating neointima formation in models of vascular injury. We have reported that PDGF increases the levels of protein tyrosine phosphatase PTP1B and that PTP1B suppresses PDGF-induced motility in cultured cells and that it attenuates neointima formation in injured carotid arteries. Others have reported that insulin enhances the mitogenic and motogenic effects of PDGF in cultured smooth muscle cells and that hyperinsulinemia promotes vascular remodeling. In the present study, we tested the hypothesis that insulin amplifies PDGF-induced cell motility by suppressing the expression and function of PTP1B. We found that chronic but not acute treatment of cells with insulin enhances PDGF-induced motility in differentiated cultured primary rat aortic smooth muscle cells and that it suppresses PDGF-induced upregulation of PTP1B protein. Moreover, insulin suppresses PDGF-induced upregulation of PTP1B mRNA levels, PTP1B enzyme activity, and binding of PTP1B to the PDGF receptor-beta, and it enhances PDGF-induced PDGF receptor phosphotyrosylation. Treatment with insulin induces time-dependent upregulation of phosphatidylinositol 3-kinase (PI3-kinase)-delta and activation of Akt, an enzyme downstream of PI3-kinase. Finally, inhibition of PI3-kinase activity, or its function, by pharmacological or genetic means rescues PTP1B activity in insulin-treated cells. These observations uncover novel mechanisms that explain how insulin amplifies the motogenic capacity of the pivotal growth factor PDGF.

Relationship between insulin resistance and left ventricular diastolic dysfunction in patients with impaired glucose tolerance and type 2 diabetes

AIM

The aim of this study was to explore the relationship between insulin resistance (IR) and the left ventricular diastolic function in patients with type 2 diabetes and subjects with impaired glucose tolerance (IGT).

METHODS

The study included 119 subjects who underwent oral glucose tolerance test (OGTT). IR was assessed using Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) and Quantitative Insulin Sensitivity Check Index (QUICKI). Left ventricular diastolic function was assessed using trans-thoracic Doppler echocardiography.

RESULTS

Based on the OGTT results, 29 subjects had normal glucose tolerance (NGT), 20 subjects had impaired glucose tolerance (IGT), and 70 patients had type 2 diabetes. There were significant differences among the patients in groups with NGT, IGT and diabetes regarding HOMA-IR (4.20 +/- 1.20 vs. 6.45 +/- 3.83 vs. 8.70 +/- 6.26; P < 0.001) and QUICKI (0.54 +/- 0.11 vs. 0.49 +/- 0.08 vs. 0.47 +/- 0.08; P < 0.001). In subjects with NGT, IGT and patients with diabetes, the pulsed Doppler transmitral variables were: E-wave (0.72 +/- 0.16 cm/s vs. 0.62 +/- 0.13 cm/s vs. 0.58 +/- 0.17 cm/s; P < 0.001), A-wave (0.61 +/- 0.13 cm/s vs. 0.62 +/- 0.11 cm/s vs. 0.71+/- 0.14 cm/s; P = 0.006) and E/A ratio (1.22 +/- 0.33 vs. 1.02 +/- 0.24 vs. 0.85 +/- 0.26; p < 0.001). The proportion of subjects with an E/A ratio <1 was 27.6% in the group with NGT, 55% in the group with IGT and 75.7% in the group with diabetes (P < 0.001). The E/A ratio correlated with HOMA-IR (r = -0.30, p = 0.001) and QUICKI (r = 0.37, p < 0.0001). Multiple linear regression model showed that IR (assessed by QUICKI) was an independent correlate of diastolic dysfunction (P = 0.034).

CONCLUSIONS

In subjects with impaired glucose tolerance and patients with type 2 diabetes, insulin resistance is associated with impaired diastolic function of the left ventricle.

Effects of obesity, body composition, and adiponectin on carotid intima-media thickness in healthy women

CONTEXT

Increased common carotid intima-media thickness (IMT) is predictive of coronary artery disease and stroke.

OBJECTIVE

In this study, we investigated common carotid IMT by obesity category in a cohort of healthy women without previously known cardiovascular disease.

DESIGN, SETTING, PARTICIPANTS, AND MAIN OUTCOME MEASURES

One hundred healthy women (aged 24-59 yr) from the general community enrolled in an observational study conducted at an academic medical center participated in the study. B-mode ultrasound imaging of the common carotid arteries was used to measure common carotid IMT in 99 subjects. Fat distribution was determined by computed tomography. Hormonal and inflammatory parameters related to cardiovascular disease and obesity were measured.

RESULTS

IMT was higher in obese [body mass index (BMI) >or= 30 kg/m(2)], compared with overweight women (BMI >or= 25 and < 30 kg/m(2)) [0.69 mm, interquartile range (IQR) 0.60-0.75 mm] vs. 0.62 mm [IQR 0.56-0.68 mm), P = 0.044] and in comparison with lean women (BMI < 25 kg/m(2)) [0.69 mm (IQR 0.60-0.75 mm) vs. 0.59 mm (IQR 0.54-0.67 mm), P = 0.016]. In multivariate modeling, age (beta = 0.0050 mm change in IMT per year of age, P = 0.003), smoking (beta = 0.0044 mm change in IMT per pack-year, P = 0.046), and sc abdominal adiposity (beta = 0.00026 mm change in IMT per square centimeter, P = 0.010) were positively associated with IMT, whereas adiponectin (beta = -0.0042 mm change in IMT per milligram per liter, P = 0.045) was negatively associated with IMT. Visceral adiposity (beta = 0.00048 mm change in IMT per square centimeter, P = 0.092) was not significantly associated with IMT after adjusting for age, race, smoking, sc abdominal adiposity, and adiponectin.

CONCLUSIONS

Obesity is associated with increased common carotid IMT in young and middle-aged women. Adiponectin and sc abdominal adiposity are associated with carotid IMT in this population.

Insulin resistance/compensatory hyperinsulinemia predict carotid intimal medial thickness in patients with essential hypertension

BACKGROUND AND AIM

Approximately 50% of subjects with essential hypertension (EH) are insulin resistant, and this defect in insulin action could contribute to increased cardiovascular disease (CVD) risk in these patients. To test this hypothesis, we attempted to see if there was a link between insulin resistance (IR) and carotid intimal medial thickness (IMT), an early index of CVD, in patients with essential hypertension.

METHODS AND RESULTS

Ultrasound quantification of carotid IMT was performed in 79 hypertensive patients, and 63 patients (31 m and 32 f), defined as being free of plaque (IMT < 1.3 mm), were further subdivided into normal (<1.0 mm) and thickened (1-1.3 mm) IMT groups. Subjects in the thickened IMT group were older and had significantly (p < 0.05) higher plasma concentrations of fasting insulin, nitric oxide (NO(x)) and intercellular adhesion molecule 1 (ICAM-1). However, the two groups were not significantly different in terms of blood pressure, overall or regional obesity, fasting lipid levels, uric acid, concentrations of other cellular adhesion molecules or levels of C-reactive protein. There were significant (p < 0.05) correlations in the whole population between IMT and age, fasting insulin and NO(x), and multiple regression analysis identified fasting insulin as an independent predictor of IMT.

CONCLUSIONS

The presence of increased IMT is significantly related to several metabolic and endothelial abnormalities associated with IR/hyperinsulinemia, and fasting insulin independently predicts the thickness of the intima-media layer. These results support the view that CVD risk is greatest in those patients with essential hypertension who are also IR/hyperinsulinemic.

Body composition and fat repartition in relation to structure and function of large arteries in middle-aged adults (the SU.VI.MAX study)

OBJECTIVE

To investigate associations of body composition assessed by bioimpedance analysis and anthropometric indicators of fat repartition with carotid structure and function.

DESIGN

Cross-sectional epidemiological study.

SUBJECTS

A total of 1014 middle-aged apparently healthy adults participating in the SU.VI.MAX study.

MEASUREMENTS

Body composition (fat mass, fat-free mass) was assessed by bioimpedance analysis and anthropometric indicators of fat repartition (waist circumference (WC); waist-hip-ratio (WHR)) were simultaneously collected. Carotid ultrasound examination included measurements of intima-media thickness (IMT) at the common carotid arteries (CCA) and assessment of atherosclerotic plaques in extracranial carotid arteries. Carotid-femoral pulse-wave velocity (PWV) was used as a marker of aortic stiffness.

RESULTS

In multivariate analyses adjusted for major known cardiovascular risk factors in addition to age, gender and height, fat-free mass, fat mass (FM), and WC were positively associated with CCA-IMT and lumen diameter. No significant association was found with occurrence of carotid plaques. PWV was only associated with WC. Associations of CCA-IMT and PWV with WC were not significant anymore after further adjustment on body mass index (BMI) or FM.

CONCLUSION

WC was the only measurement positively associated with both early atherosclerosis markers such as CCA-IMT and arterial stiffness. Although this association depends on overall adiposity, as assessed by the BMI, it emphasizes the importance of WC in clinical practice and prevention programs as a screening tool for individuals at risk for cardiovascular disease.

Direct effects of sex steroid hormones on adipose tissues and obesity

Sex steroid hormones are involved in the metabolism, accumulation and distribution of adipose tissues. It is now known that oestrogen receptor, progesterone receptor and androgen receptor exist in adipose tissues, so their actions could be direct. Sex steroid hormones carry out their function in adipose tissues by both genomic and nongenomic mechanisms. In the genomic mechanism, the sex steroid hormone binds to its receptor and the steroid-receptor complex regulates the transcription of given genes. Leptin and lipoprotein lipase are two key proteins in adipose tissues that are regulated by transcriptional control with sex steroid hormones. In the nongenomic mechanism, the sex steroid hormone binds to its receptor in the plasma membrane, and second messengers are formed. This involves both the cAMP cascade and the phosphoinositide cascade. Activation of the cAMP cascade by sex steroid hormones would activate hormone-sensitive lipase leading to lipolysis in adipose tissues. In the phosphoinositide cascade, diacylglycerol and inositol 1,4,5-trisphosphate are formed as second messengers ultimately causing the activation of protein kinase C. Their activation appears to be involved in the control of preadipocyte proliferation and differentiation. In the presence of sex steroid hormones, a normal distribution of body fat exists, but with a decrease in sex steroid hormones, as occurs with ageing or gonadectomy, there is a tendency to increase central obesity, a major risk for cardiovascular disease, type 2 diabetes and certain cancers. Because sex steroid hormones regulate the amount and distribution of adipose tissues, they or adipose tissue-specific selective receptor modulators might be used to ameliorate obesity. In fact, hormone replacement therapy in postmenopausal women and testosterone replacement therapy in older men appear to reduce the degree of central obesity. However, these therapies have numerous side effects limiting their use, and selective receptor modulators of sex steroid hormones are needed that are more specific for adipose tissues with fewer side effects.

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.

Effect of shift work on body mass index: results of a study performed in 319 glucose-tolerant men working in a Southern Italian industry

OBJECTIVE

To examine the influence of shift work on metabolic and cardiovascular risk factors in subjects working in an industry sited in Apulia, Southern Italy.

DESIGN

Cross-sectional study of metabolic effects of shift work in glucose tolerant workers in a chemical industry in southern Italy.

SUBJECTS

The subjects included 319 glucose tolerant male individuals, aged 35-60 y.

MEASUREMENTS

Anthropometric parameters (body mass index (BMI) and waist-to-hip ratio (WHR)), fasting concentrations of glucose, insulin, and lipids (total cholesterol, HDL-cholesterol, triglycerides), the sum of glucose levels during 75 g-oral glucose tolerance test (Sigma-OGTT), and systolic and diastolic blood pressure (SBP and DBP, respectively).

RESULTS

The prevalence of obesity was higher among shift workers compared to day workers, whereas body fat distribution was not different between the two groups. Shift workers had higher BMI than day workers, and shift working was associated with BMI, independently of age and work duration. Shift workers had significantly higher SBP levels, which were independently influenced by BMI, but not by shift work, thus suggesting that the difference in SBP may well be mediated by the increased body fatness.

CONCLUSION

In workers of an industry sited in Southern Italy, shift work may be directly responsible for increased body fatness and is indirectly associated with higher blood pressure levels and some features of metabolic syndrome.

Free testosterone plasma levels are negatively associated with the intima-media thickness of the common carotid artery in overweight and obese glucose-tolerant young adult men

OBJECTIVE

To evaluate the relation between free testosterone (FT) levels and the intima-media thickness of the common carotid artery (IMT-CCA) in overweight and obese glucose-tolerant (NGT) young adult men.

DESIGN

Cross-sectional study of FT and IMT-CCA in obese men.

SUBJECTS

A total of 127 overweight and obese NGT male individuals, aged 18-45 y.

MEASUREMENTS

FT plasma levels; IMT-CCA, as measured by high-resolution B-mode ultrasound imaging; central fat accumulation, as evaluated by waist circumference; body composition, as measured by bioimpedance analysis; insulin resistance, as calculated by homeostatic model assessment (HOMA(IR)); systolic and diastolic blood pressure; and fasting concentrations of glucose, insulin, and lipids.

RESULTS

IMT-CCA was positively correlated with age, body mass index (BMI), fat mass (FM), waist circumference, and fasting glucose concentrations, and inversely associated with FT levels. After multivariate analysis, IMT-CCA maintained an independent association with BMI, FM, and FT levels. This study indicates that IMT-CCA is negatively associated with FT levels, independent of age, total body fat, central fat accumulation, and fasting glucose concentrations in overweight and obese NGT patients.

CONCLUSION

Hypotestosteronemia may accelerate the development of atherosclerosis and increase the risk for CHD in obese men.

Physical activity, diet and cardiovascular disease risks in Chinese women

OBJECTIVE

To investigate the relationship between different types and levels of physical activity and cardiovascular disease risk factors, including oxidative stress, blood lipids and insulin resistance, in a healthy female population in China.

METHOD

Healthy women aged 35 to 65 years participated in this study. The habitual physical activity was evaluated by self-administered questionnaire (MOSPA). The dietary intakes of nutrients were calculated from 3-day recall records. Anthropometric data of each subject were measured, fasting blood samples were taken, and erythrocytes and serum were prepared for the measurement of erythrocyte superoxide dismutase activity, serum malondialdehyde, total antioxidant capacity, insulin, glucose and lipids (total cholesterol, triglycerides, apolipoprotein AI (apo A) and apolipoprotein B (apo B)) concentrations.

RESULTS

Low level of physical activity was related to a lower concentration of serum apo B, and higher energy expenditure from household physical activity had a reverse relationship with serum apo B and triglyceride levels. In the group with moderate occupational energy expenditure, the concentration of serum triglycerides was lower, but that of high-density lipoprotein was higher. Moderate energy expenditure (less than 1700 kcal day-1) from leisure-time physical activity was positively related to total antioxidant capacity and insulin sensitivity. However, heavy occupational physical activity may be not beneficial for the cardiovascular system.

CONCLUSION

This study indicates that leisure-time, moderate occupational and household physical activity levels decreased risk factors for cardiovascular disease.

Early carotid atherosclerosis in normotensive severe obese premenopausal women with low DHEA(S)

The aim of this study was to investigate the direct involvement of hyperinsulinaemia, DHEA and DHEA-S [DHEA(S)] in severe obesity in early carotid atherosclerosis, measured as intima-media thickness (IMT). Seventeen normotensive premenopausal women with very high BMI (43.5 +/- 1.6 kg/m2) were recruited for the study. Six women were also evaluated 12 months after laparoscopic adjustable silicone gastric banding (LASGB). Dietary intake, fasting plasma lipid profile, glycemic and insulinemic response to the OGTT, adrenal secretion, at baseline and after ACTH stimulation test, were measured. IMT, common carotid diameter (CD) and left ventricular mass index (LVMi) were measured by B-mode echotomography. All obese subjects showed higher fasting and stimulated insulin levels, but lower DHEA(S) levels than controls, showing a negative correlation between both fasting and stimulated insulin and DHEA(S), either at baseline or after ACTH testing. IMT was higher (p < 0.05) than controls, with a positive correlation with stimulated insulin (p < 0.05) and a strong negative correlation with DHEA(S) (p < 0.001). In a multiple linear regression analysis, insulin response to OGTT maintained an association with DHEA(S) independent of fasting insulin, while DHEA maintained the association with IMT independent of stimulated insulin (p < 0.0001). In the six patients evaluated 12 months after LASGB, fasting insulin levels decreased, while DHEA(S) levels increased (p < 0.05). In conclusion, an early cardiovascular involvement was detected in this group of severe obese with hyperinsulinaemia and low DHEA(S), even in the absence of other well known CVD risk factors.

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.

A low high density lipoprotein (HDL) level is associated with carotid artery intima-media thickness in asymptomatic members of low HDL families

Low serum high-density lipoprotein cholesterol (HDL-C) is a strong predictor of coronary heart disease (CHD). The aim of the present study was to evaluate the metabolic parameters predicting the atherosclerotic changes in asymptomatic members of low HDL-C families. We performed carotid B-mode ultrasonography with intima-media thickness (IMT) measurement for 89 asymptomatic members of Finnish low HDL-C families. The family members were categorized as affected or unaffected according to the 10th age-gender specific HDL-C percentile. In the affected group, the most marked decrease of HDL subclasses was observed for HDL2-C when compared with the unaffected (109% difference). In the partial correlation analyses, age and gender showed significant correlations with the mean IMT (for age, r=0.880, P<0.001, and for gender, r=-0.361, P=0.018). Importantly, HDL-C and HDL2-C were significantly inversely related to the mean carotid IMT, also after correction for age (for HDL-C, r=-0.186, P=0.043, for HDL2-C, r=-0.208, P=0.029, when adjusted for age). The correlation for HDL-C was significant also when adjusted for gender. In conclusion, low HDL-C is associated with increased carotid artery IMT in asymptomatic members of low HDL-C families.

The relationship between insulin resistance and cardiovascular risk factors in overweight/obese non-diabetic Asian adults: the 1992 Singapore National Health Survey

OBJECTIVE

Insulin resistance (IR) is associated with cardiovascular risk factors including hypertension, dyslipidemia, glucose intolerance and hyperuricemia. The relationship between IR and these cardiovascular risk factors in obese non-diabetic individuals is not well studied. We explore this relationship by comparing the cardiovascular risk factors among insulin-sensitive and insulin-resistant overweight/obese non-diabetic Asian adults in the 1992 National Health Survey of Singapore.

DESIGN AND MEASUREMENTS

A total of 3568 subjects were examined in the survey, which involved a combination of disproportionate stratified sampling and systematic sampling. Anthropometric measurements, level of physical activity, blood pressure, insulin, lipid profile, uric acid and standard 75 g oral glucose tolerance test were performed after a 10 h overnight fast. Subjects with diabetes were excluded from the analysis. Homeostasis model assessment (HOMA) was used to assess insulin sensitivity. Relative LDL size was derived from the formula LDL/ApoB. We defined insulin-sensitive individuals as having a HOMA value <1.479 (below median in individuals without diabetes; n=3226) and overweight/obesity as body mass index (BMI) >or=25.0 kg/m(2).

RESULTS

There were 156 insulin-sensitive (S) and 679 insulin-resistant (R) overweight/obese individuals, respectively. The groups did not differ in terms of gender and ethnic distribution and level of physical activity. However, subjects in group S were younger than those in group R (mean+/-s.d.; 40.1+/-12.1 vs 42.4+/-12.7 y; P<0.05). Group R individuals were also slightly more obese globally and centrally than group S (BMI=28.2+/-3.2 vs 27.1+/-2.8 kg/m(2); waist circumference (WC)=86.7+/-9.3 vs 82.5+/-8.3 cm; P<0.01). There were more subjects with impaired glucose tolerance (IGT) in group R than in group S (29.7 vs 16.0%; P<0.01). After adjustment for age and indices of global and regional obesity (ie BMI and WC), insulin-resistant individuals showed higher apolipoprotein B, triglyceride, fasting (FPG) and 2 h post-load plasma glucose (2hPG) but lower HDL and LDL size. Further adjustment for FPG, 2hPG and level of physical activity had minimal impact on the results.

CONCLUSIONS

Insulin-resistant overweight/obese non-diabetic Asian adults had greater burden of the cardiovascular dysmetabolic syndrome than insulin-sensitive overweight/obese individuals. This could not be fully explained by differences in global and regional obesity, glucose tolerance and level of physical activity.

Hyperinsulinemia and uterine perfusion in patients with polycystic ovary syndrome

OBJECTIVE

To determine whether hyperinsulinemia has a negative effect on uterine blood supply in patients with polycystic ovary syndrome (PCOS).

METHODS

Sixty-three patients with normal body mass index were included prospectively in the study: 48 had clinical and hormonal features of PCOS and 15 were normo-ovulatory. All patients underwent Doppler flow measurement of the uterine artery, and determination of serum concentrations of luteinizing hormone, follicle stimulating hormone, prolactin, estradiol, androgens, insulin and C-peptide during the early follicular phase of the menstrual cycle. The 48 PCOS-patients were divided into two groups according to the pulsatility index (PI) value of the uterine artery: Group 1, PI < 3; Group 2, PI >or= 3 and the groups were compared.

RESULTS

The mean PI of the uterine artery (3.01 +/- 1.0 vs. 1.93 +/- 0.3, respectively) and fasting levels of insulin (50.9 +/- 9.3 vs. 40.3 +/- 10.9) and C-peptide (366.9 +/- 118.4 vs. 243.6 +/- 120.3) of PCOS-patients were significantly higher than those of the control group. No correlation was found between insulinemia and C-peptide and PI of the uterine artery and no significant difference was found in insulin and C-peptide levels among the two groups of PCOS-affected patients. Only the serum level of dehydroepiandrosterone sulfate was significantly higher in Group 2, and a direct correlation was found between PI values of the uterine artery and DHEAS plasma levels.

CONCLUSION

Insulin and C-peptide do not seem to interfere with uterine perfusion in PCOS-affected patients.

The insulin tolerance test in morbidly obese patients undergoing bariatric surgery

OBJECTIVE

To assess the effect of massive weight loss in relation to insulin resistance and its correlation to changes in glycemic homeostasis and lipid profile in severely obese patients.

RESEARCH METHODS AND PROCEDURES

A prospective clinical intervention study was carried out with 31 morbidly obese women (body mass index: 54.2 +/- 8.8 kg/m(2)) divided into three groups according to their glucose tolerance test: 14 normal, 8 impaired glucose tolerance, and 9 type 2 diabetes. All subjects underwent an insulin tolerance test with intravenous bolus of 0.1 U insulin/kg body weight before silastic ring vertical gastroplasty Roux-en-Y gastric bypass surgery, and again at 2, 4, 6, and 12 months postoperatively. Fasting plasma glucose, hemoglobin A1c, and lipid profile were also evaluated.

RESULTS

A reduction of 68 +/- 15% in initial excess body weight was evident within 1 year. Along with weight loss, the following statistically significant changes were found: an increase in the insulin-sensitivity index (Kitt) and a decrease in fasting plasma glucose and hemoglobin A1c, most notably in the type 2 diabetes group. An overall improvement in lipid profile was observed in all three groups.

DISCUSSION

Bariatric surgery was an effective therapeutic approach for these obese patients because it reduced both weight and insulin resistance, along with improving metabolic parameters. Significant correlations were found between insulin resistance and metabolic improvements. Weight loss after bariatric surgery induced an improvement in metabolic fitness, related to the reduction in insulin resistance over a range of glucose tolerance statuses from normal to diabetic.

Plasma leptin is independently associated with the intima-media thickness of the common carotid artery

OBJECTIVE

To investigate whether intima-media thickness (IMT) of the common carotid artery (CCA), an early marker of asymptomatic atherosclerosis, is significantly and independently associated with plasma concentrations of leptin, an adipose tissue hormone that has recently been proposed as a cardiovascular risk factor in obese patients.

DESIGN

Cross-sectional sample of normal-weight and obese men and women.

SUBJECTS

One-hundred and twenty healthy subjects (52 men and 68 women), aged 18-45 y and with a wide range of BMI, were recruited for the study.

MEASUREMENTS

Fasting plasma leptin concentrations and the IMT of the CCA were measured in all subjects. Leptin concentrations were measured by radioimmunoassay and the IMT of the CCA was quantified by high resolution B-mode ultrasound imaging. Central fat (measured by waist circumference), smoking habits, blood pressure, insulin sensitivity (measured by the insulin tolerance test), and fasting plasma glucose, insulin and lipid pattern (cholesterol, HDL-cholesterol, triglycerides, LDL-cholesterol) were also measured.

RESULTS

IMT of the CCA was positively correlated with log leptin concentrations (P<0.005 in men and P<0.001 in women), body mass index (P<0.001 in men and women), waist circumference (P<0.001 in men and women), age (P<0.001 in men and P<0.05 in women), and negatively associated with insulin sensitivity in both sexes (P<0.05). IMT was also directly correlated with cholesterol (P<0.05), LDL-cholesterol (P<0.01) and systolic blood pressure in men (P<0.05), and with diastolic blood pressure levels in women (P<0.05). When a multiple linear regression model was used without body mass index (BMI), the correlation between leptin and IMT was maintained in both men (P<0.01) and women (P<0.005), independent of age, insulin sensitivity, smoking habits, systolic blood pressure, fasting glucose, triglycerides, cholesterol, LDL-cholesterol and HDL-cholesterol. By contrast, BMI-adjusted leptin concentrations were not significantly associated with IMT (Pc (partial correlation): 0.41 in men and 0.15 in women). Moreover, when BMI was entered into a multiple linear regression model without leptin, the correlation between BMI and IMT was maintained in both men (P<0.005) and women (P<0.01), independent of the same parameters.

CONCLUSION

Plasma leptin concentrations are independently associated with the IMT of the CCA, suggesting that the increase of adipose tissue mass (or leptin per se) may have an unfavourable influence on the development of atherosclerosis. However, the association between IMT and leptin seems to be dependent and/or confounded by the relationship between IMT and obesity.