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.

The sodium intake modifies the renin-aldosterone and blood pressure changes associated with moderately low energy diets

Thirty middle-aged, moderately obese men with untreated mild hypertension were allocated to two groups of 15 men each. Both groups were placed on energy-reduced diets (5.1 MJ/day) for 9-11 weeks which resulted in similar losses of body mass (8.5 kg). In group I the low energy diet was supplemented with sodium chloride leading to no change in urinary sodium excretion. During dieting there were significant reductions of plasma renin activity (PRA) and urinary excretion of noradrenaline and aldosterone. Heart rate but not mean arterial pressure (MAP) decreased significantly. Then followed a period of sodium restriction which resulted in a significant decrease in MAP and an increase in aldosterone excretion. In group II there was a reduction of sodium intake by about 80 mmol as judged from determinations of urinary sodium excretion. In this group the energy restriction was not accompanied by any changes in PRA or urinary excretion of aldosterone, whereas urinary noradrenaline excretion, heart rate and MAP decreased significantly. Urinary adrenaline excretion remained unchanged. It is concluded that the hypotensive response to moderate energy and sodium reduction cannot be explained by changes in the renin-aldosterone. system.

Body composition, intraerythrocyte sodium content, volume regulation and blood pressure during moderate sodium restriction in hypertensive men

Eleven moderately obese middle-aged male outpatients with untreated mild hypertension reduced their sodium intake by about 120 mmol per day during 4-6 weeks. Diastolic blood pressure was then significantly reduced in comparison with a matched control group. The reduction of urinary sodium excretion was significantly correlated to the change in mean arterial pressure. Mean body mass showed a small significant decrease, although there were no significant changes in total body water or body fat as determined from measurements of 40K and tritiated water. Nor did mean extracellular water or plasma volume (Evan's blue) show any significant change. The decrease in urinary sodium excretion was associated with increases in plasma renin activity and urinary aldosterone excretion, while a sympathetic nervous natriuretic index (urinary dopamine to noradrenaline excretion ratio) decreased. The low sodium diet period was followed by a period of energy reduction as well as sodium restriction for 15 weeks. Mean body mass was then reduced by about 8 kg. The systolic but not the diastolic blood pressure showed a significant decrease. The intraerythrocyte content of water, sodium and potassium did not change significantly during any of the diet periods. We conclude that moderate sodium restriction lowered the blood pressure and affected the renin-aldosterone and sympathetic nervous system to retain sodium which might explain the constancy of the plasma volume.

Effect of a moderately energy- and salt-reduced diet on body compartments and blood pressure control in obese men with mild hypertension

Ten middle-aged moderately obese men with untreated mild hypertension were studied during a 6-week weight maintenance period and a 9-week period on a diet containing 5 MJ when body mass decreased by 8.4 kg (SE 1.4). According to urinary sodium excretion there was a mean reduction of 89 mmol/day (SE 16) in sodium intake. Mean arterial pressure fell by 2.5 to 14.1 mmHg (95% confidence interval) which was correlated to the reduction of body mass. The sympathetic nervous activity diminished with decreasing noradrenaline excretion and heart rate. There were no changes in the renin-aldosterone system. Estimation of the body composition with a four-compartment model utilizing determinations of body mass, total body potassium and total body water (TBW) showed reductions of body fat (8.4 kg (SE 1.4] and body cell mass (BCM) (2.4 kg (SE 0.6], but not of TBW. Extracellular water (ECW) increased significantly as judged from ECW/BCM calculations. Plasma volume was determined by Evan's blue and did not change significantly. We suggest that the observed changes in body composition represent one aspect of the adjustment to a weight reducing diet, while blood pressure is lowered by another mechanism in the adaptive response to dieting, i.e. reduction in sympathetic nervous activity.

Cellular sodium turnover in obese hypertensive men

Seventeen moderately obese middle-aged male outpatients with untreated mild hypertension (OH) and 47 normotensive men with normal weight (C) were investigated with respect to intraerythrocyte electrolytes, transmembrane sodium fluxes, PRA and urinary excretion of aldosterone (U-ALDO). There was no difference between the groups in intraerythrocyte sodium but red cell potassium was significantly elevated in OH compared to C. Sodium influx and the rate constant for sodium efflux were also significantly higher in OH. There was a significant positive correlation between sodium influx and U-ALDO (r = 0.56, p less than 0.05).

Measurement of lower-leg volume change by quantitative computed tomography

BACKGROUND

Lower-leg edema is a common symptom in many diseases. A precise method with low variability for measurement of edema is warranted in order to obtain optimal conditions for investigation of treatment effects.

PURPOSE

To evaluate computed tomography for precise measurement of lower-leg muscle and adipose tissue volumes using a very low level of effective radiation dose.

MATERIAL AND METHODS

Eleven volunteers were examined three times during 1 day, either as two consecutive examinations in the morning and one single examination in the afternoon, or as one examination in the morning and two in the afternoon. Eleven scans with computed tomography were made at each examination, and lower-leg volumes were calculated from automatically measured scan areas and interscan distances. Volumes for muscle, adipose tissue, and bone were calculated separately. Minimal radiation dose was used.

RESULTS

Mean difference between the repeated examinations was -0.1 ml for total volume, -1.4 ml for muscle, and 1.6 ml for adipose tissue volume. The corresponding 95% confidence intervals were -6.5 to 6.0 ml, -3.5 to 6.5 ml, and -7.0 to 4.0 ml, respectively. The resulting effective dose was 0.5 microSv to one leg.

CONCLUSION

Computed tomography can be used as a precise quantitative method to measure small volume changes of the lower leg as a whole, and separately for muscle and adipose tissue. The results were obtained with a negligible effective dose, lower than that delivered by modern fan-beam dual-energy X-ray absorptiometry whole-body examinations and equal to a few hours of background radiation.

Urokinase-type plasminogen activator receptor is associated with macrophages and plaque rupture in symptomatic carotid atherosclerosis

There is a strong correlation between macrophage infiltration and plaque instability in recently symptomatic carotid atherosclerotic plaques, and it is hypothesised that mechanisms related to macrophages may be involved in plaque vulnerability and rupture. We previously found high expression of urokinase-type plasminogen activator receptor (UPAR) in human macrophages. The aim of this study was to investigate whether UPAR co-localises with macrophages in symptomatic carotid plaques, and whether UPAR expression is associated with plaque rupture. Real-time RT-PCR assays showed that UPAR expression levels were high in monocyte-derived macrophages and in carotid endarterectomies compared with a tissue panel. Serial transverse sections were prepared from carotid endarterectomies from 12 symptomatic patients, and analyzed with immunohistochemical staining for UPAR and for CD68-positive macrophages, and with histopathological assessment. UPAR co-localised with CD68-positive macrophages, with a high correlation (r=0.90, p<0.001) between immunostained areas in 12 carotid endarterectomies from symptomatic patients. High degrees of UPAR and CD68 staining were found in sections around the bifurcation level where rupture was most common, while low degrees of staining were found in sections of the common carotid artery end of the endarterectomy (p<0.05). Higher degrees of UPAR staining were observed in ruptured plaque sections compared with non-ruptured sections. In conclusion, UPAR was highly expressed in monocyte-derived macrophages and in symptomatic carotid plaques, UPAR co-localised with macrophages in carotid symptomatic plaques and UPAR was predominantly found in ruptured plaque segments. These findings support the hypothesis that UPAR is related to plaque rupture in symptomatic atherosclerotic lesions.

Cell death-inducing DFF45-like effector C is reduced by caloric restriction and regulates adipocyte lipid metabolism

Members of the cell death-inducing DFF45-like effector (CIDE) gene family have been shown to regulate lipid metabolism. In this article, we report that the third member of the human CIDE family, CIDEC, is down-regulated in response to a reduced caloric intake. The down-regulation was demonstrated by microarray and real-time polymerase chain reaction analysis of subcutaneous adipose tissue in 2 independent studies on obese patients undergoing treatment with a very low calorie diet. By analysis of CIDEC expression in 65 human tissues, we conclude that human CIDEC is predominantly expressed in subcutaneous adipocytes. Together, these observations led us to investigate the effect of decreased CIDEC expression in cultured 3T3-L1 adipocytes. Small interfering RNA-mediated knockdown of CIDEC resulted in an increased basal release of nonesterified fatty acids, decreased responsiveness to adrenergic stimulation of lipolysis, and increased oxidation of endogenous fatty acids. Thus, we suggest that CIDEC is a regulator of adipocyte lipid metabolism and may be important for the adipocyte to adapt to changes in energy availability.

Increased lipolysis by secretory phospholipase A(2) group V of lipoproteins in diabetic dyslipidaemia

BACKGROUND

Lipolysis of lipoproteins by secretory phospholipase A(2) group V (sPLA(2)-V) promotes inflammation, lipoprotein aggregation and foam cell formation--all considered as atherogenic mechanisms.

OBJECTIVE

In this study, we compared the susceptibility to sPLA(2)-V lipolysis of VLDL and LDL from individuals with type 2 diabetes and the metabolic syndrome (T2D-MetS) and from healthy controls. Design. VLDL and LDL were isolated from 38 T2D-MetS subjects and 38 controls, treated pair-wise. Extent of sPLA(2)-V lipolysis was measured as release of nonesterified free fatty acids (NEFA). In a subset of the subjects, lipoprotein composition was determined as a relationship between lipid and apolipoprotein components.

RESULTS

Mean paired increase in sPLA(2)-V lipolysis after 1 h for T2D-MetS versus control was 2.0 micromol NEFA l(-1) for VLDL (P = 0.004) and 0.75 micromol NEFA l(-1) for LDL (P = 0.001). There were also substantial differences in lipoprotein composition between the groups. T2D-MetS VLDL had higher triglyceride and cholesterol contents than control VLDL. T2D-MetS LDL was smaller and contained more triglycerides and less cholesterol than control LDL. Both VLDL and LDL from T2D-MetS subjects also contained more apolipoprotein CIII per particle.

CONCLUSION

VLDL and LDL from T2D-MetS individuals were more susceptible to sPLA(2)-V lipolysis than those from control individuals. This may result in elevated levels of NEFA and lysophosphatidylcholine, both in circulation and in LDL, possibly contributing to the elevated inflammatory state and increased risk of cardiovascular diseases seen in these individuals.

Expression profiling of macrophages from subjects with atherosclerosis to identify novel susceptibility genes

Although a number of environmental risk factors for atherosclerosis have been identified, heredity seems to be a significant independent risk factor. The aim of our study was to identify novel susceptibility genes for atherosclerosis. The screening process consisted of three steps. First, expression profiles of macrophages from subjects with atherosclerosis were compared to macrophages from control subjects. Secondly, the subjects were genotyped for promoter region polymorphisms in genes with altered gene expression. Thirdly, a population of subjects with coronary heart disease and control subjects were genotyped to test for an association with identified polymorphisms that affected gene expression. Twenty-seven genes were differentially expressed in both macrophages and foam cells from subjects with atherosclerosis. Three of these genes, IRS2, CD86 and SLC11A1 were selected for further analysis. Foam cells from subjects homozygous for the C allele at the -765C-->T SNP located in the promoter region of IRS2 had increased gene expression compared to foam cells from subjects with the nonCC genotype. Also, macrophages and foam cells from subjects homozygous for allele 2 at a repeat element in the promoter region of SLC11A1 had increased gene expression compared to macrophages and foam cells from subjects with the non22 genotype. Genotyping of 512 pairs of subjects with coronary heart disease (CHD) and matched controls revealed that subjects homozygous for C of the IRS2 SNP had an increased risk for CHD; odds ratio 1.43, p=0.010. Immunohistochemical staining of human carotid plaques showed that IRS2 expression was localised to macrophages and endothelial cells in vivo. Our method provides a reliable approach for identifying susceptibility genes for atherosclerosis, and we conclude that elevated IRS2 gene expression in macrophages may be associated with an increased risk of CHD.

Circulating matrix metalloproteinase 9 levels in relation to sampling methods, femoral and carotid atherosclerosis

OBJECTIVES

To examine whether circulating levels of matrix metalloproteinase 9 (MMP-9) were associated with ultrasound-assessed intima-media thickness (IMT) and echolucent plaques in the carotid and femoral arteries. To examine preanalytical sources of variability in MMP-9 concentrations related to sampling procedures.

SUBJECTS AND DESIGN

Plasma and serum MMP-9 levels were compared with ultrasound assessed measures of femoral and carotid atherosclerosis, in a cross-sectional study of 61-year-old men (n = 473). Preanalytical sources of variability in MMP-9 levels were examined in 10 healthy subjects. Main outcome measures were circulating levels of MMP-9 in serum and plasma, IMT of the carotid and femoral arteries, and plaque status based on size and echolucency.

SETTING

Research unit at university hospital.

RESULTS

Plasma concentrations of total and active MMP-9 were associated with femoral artery IMT independently of traditional cardiovascular risk factors, and were higher in subjects with moderate to large femoral plaques. Plasma MMP-9 concentration was higher in men with echolucent femoral plaques (P = 0.006) compared with subjects without femoral plaques. No similar associations were found for carotid plaques. MMP-9 concentrations were higher in serum than in plasma, and higher when sampling was performed with Vacutainer than with syringe. MMP-9 levels in serum were more strongly associated with peripheral neutrophil count compared with MMP-9 levels in plasma.

CONCLUSIONS

Plasma MMP-9 levels were associated with atherosclerosis in the femoral artery, and total MMP-9 concentration was higher in men with echolucent femoral plaques. The choice of sample material and sampling method affect the measurements of circulating MMP-9 levels.

Baseline ICAM-1 and VCAM-1 are increased in initially healthy middle-aged men who develop cardiovascular disease during 6.6 years of follow-up

The objective of the present study was to investigate if there was a difference in baseline serum concentrations of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) between groups with and without cardiovascular events during a mean follow-up of 6.6 years in a group of initially healthy 58-year-old men. A further aim was to examine if high serum concentrations of ICAM-1 and VCAM-1 were associated with carotid and femoral artery plaque occurrence, separately. Men with cardiovascular events during follow-up had higher median serum ICAM-I and VCAM-I than those without events (P < .05). The median of serum ICAM-I and VCAM-1 in the event group was used as the cutoff level, and in those with ICAM-1 and VCAM-1 above the cutoff value, there was an increased risk of having a plaque in the femoral artery (OR = 2.8, 95% CI = 1.8-4.3; and OR = 1.6, 95% CI = 1.1-2.5, respectively).

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.

Angiotensin type 2 receptor is expressed in human atherosclerotic lesions

Objective. Expression of the angiotensin type 2 receptor (AT2-receptor) occurs in many animal models of atherosclerosis. However, its expression in human plaques and its functional role remains undetermined.This study examined AT2-receptor expression in human atherosclerotic plaque and also explored its potentially important functional role in atherosclerosis.

Material and methods. We analysed carotid atherosclerotic plaques obtained from 14 Caucasian patients who had previously carotid artery stenosis. Half of all subjects undergone endarterectomy for symptomatic carotid artery stenosis. Half of all subjects received treatment with an angiotensin receptor blocker (ARB) (n=7); the remaining subjects received no intervention in the renin-angiotensin system (n=7). Immunohistochemistry measured tissue expression of smooth muscle cells (α-actin), macrophages (CD68 antibody), collagen (picro-sirius), and AT2-receptor (AT2-receptor antibody).

Results. AT2-receptor expression occurred consistently in all specimens. Although cellular localisation varied, AT2-receptor expression levels correlated with macrophage levels (p<0.01). Compared to conventional treatment, ongoing ARB treatment affected neither AT2-receptor levels nor plaque composition.

Conclusions. AT2-receptor is expressed in human atherosclerotic plaque. Furthermore, we detected no functionally important role of AT2-receptor expression and found no evidence that ARB treatment regulates AT2-receptor expression.

Relations of adipose tissue CIDEA gene expression to basal metabolic rate, energy restriction, and obesity: population-based and dietary intervention studies

CONTEXT

Cell death-inducing DNA fragmentation factor-alpha-like effector A (CIDEA) could be a potential target for the treatment of obesity via the modulation of metabolic rate, based on the findings that CIDEA inhibits the brown adipose tissue uncoupling process in rodents.

OBJECTIVES

Our objects were to investigate the putative link between CIDEA and basal metabolic rate in humans and to elucidate further the role of CIDEA in human obesity.

DESIGN

We have explored CIDEA gene expression in adipose tissue in two different human studies: a cross-sectional and population-based study assessing body composition and metabolic rate (Mölndal Metabolic study, n = 92); and a longitudinal intervention study of obese subjects treated with a very low calorie diet (VLCD) (VLCD study, n = 24).

RESULTS

The CIDEA gene was predominantly expressed in adipocytes as compared with other human tissues. CIDEA gene expression in adipose tissue was inversely associated with basal metabolic rate independently of body composition, age, and gender (P = 0.014). The VLCD induced an increase in adipose tissue CIDEA expression (P < 0.0001) with a subsequent decrease in response to refeeding (P < 0.0001). Reduced CIDEA gene expression was associated with a high body fat content (P < 0.0001) and high insulin levels (P < 0.01). No dysregulation of CIDEA expression was observed in individuals with the metabolic syndrome when compared with body mass index-matched controls. In a separate sample of VLCD-treated subjects (n = 10), uncoupling protein 1 expression was reduced during diet (P = 0.0026) and inversely associated with CIDEA expression (P = 0.0014).

CONCLUSION

The findings are consistent with the concept that CIDEA plays a role in adipose tissue energy expenditure.