Association of Intima-Media Thickness Measured at the Common Carotid Artery With Incident Carotid Plaque: Individual Participant Data Meta-Analysis of 20 Prospective Studies

Background The association between common carotid artery intima-media thickness (CCA-IMT) and incident carotid plaque has not been characterized fully. We therefore aimed to precisely quantify the relationship between CCA-IMT and carotid plaque development. Methods and Results We undertook an individual participant data meta-analysis of 20 prospective studies from the Proof-ATHERO (Prospective Studies of Atherosclerosis) consortium that recorded baseline CCA-IMT and incident carotid plaque involving 21 494 individuals without a history of cardiovascular disease and without preexisting carotid plaque at baseline. Mean baseline age was 56 years (SD, 9 years), 55% were women, and mean baseline CCA-IMT was 0.71 mm (SD, 0.17 mm). Over a median follow-up of 5.9 years (5th-95th percentile, 1.9-19.0 years), 8278 individuals developed first-ever carotid plaque. We combined study-specific odds ratios (ORs) for incident carotid plaque using random-effects meta-analysis. Baseline CCA-IMT was approximately log-linearly associated with the odds of developing carotid plaque. The age-, sex-, and trial arm-adjusted OR for carotid plaque per SD higher baseline CCA-IMT was 1.40 (95% CI, 1.31-1.50; I²=63.9%). The corresponding OR that was further adjusted for ethnicity, smoking, diabetes, body mass index, systolic blood pressure, low- and high-density lipoprotein cholesterol, and lipid-lowering and antihypertensive medication was 1.34 (95% CI, 1.24-1.45; I²=59.4%; 14 studies; 16 297 participants; 6381 incident plaques). We observed no significant effect modification across clinically relevant subgroups. Sensitivity analysis restricted to studies defining plaque as focal thickening yielded a comparable OR (1.38 [95% CI, 1.29-1.47]; I²=57.1%; 14 studies; 17 352 participants; 6991 incident plaques). Conclusions Our large-scale individual participant data meta-analysis demonstrated that CCA-IMT is associated with the long-term risk of developing first-ever carotid plaque, independent of traditional cardiovascular risk factors.

Predictive value for cardiovascular events of common carotid intima media thickness and its rate of change in individuals at high cardiovascular risk - Results from the PROG-IMT collaboration

AIMS

Carotid intima media thickness (CIMT) predicts cardiovascular (CVD) events, but the predictive value of CIMT change is debated. We assessed the relation between CIMT change and events in individuals at high cardiovascular risk.

METHODS AND RESULTS

From 31 cohorts with two CIMT scans (total n = 89070) on average 3.6 years apart and clinical follow-up, subcohorts were drawn: (A) individuals with at least 3 cardiovascular risk factors without previous CVD events, (B) individuals with carotid plaques without previous CVD events, and (C) individuals with previous CVD events. Cox regression models were fit to estimate the hazard ratio (HR) of the combined endpoint (myocardial infarction, stroke or vascular death) per standard deviation (SD) of CIMT change, adjusted for CVD risk factors. These HRs were pooled across studies. In groups A, B and C we observed 3483, 2845 and 1165 endpoint events, respectively. Average common CIMT was 0.79mm (SD 0.16mm), and annual common CIMT change was 0.01mm (SD 0.07mm), both in group A. The pooled HR per SD of annual common CIMT change (0.02 to 0.43mm) was 0.99 (95% confidence interval: 0.95-1.02) in group A, 0.98 (0.93-1.04) in group B, and 0.95 (0.89-1.04) in group C. The HR per SD of common CIMT (average of the first and the second CIMT scan, 0.09 to 0.75mm) was 1.15 (1.07-1.23) in group A, 1.13 (1.05-1.22) in group B, and 1.12 (1.05-1.20) in group C.

CONCLUSIONS

We confirm that common CIMT is associated with future CVD events in individuals at high risk. CIMT change does not relate to future event risk in high-risk individuals.

Insulin Sensitivity and Hemostatic Factors in Clinically Healthy 58-year-old Men

The objective of this cross-sectional study was to investigate the relationship between factors of the coagulation- and fibrinolysis systems and insulin sensitivity in 104 clinically healthy, 58-years-old men. Insulin sensitivity (hyperinsulinemic euglycemic clamp) adjusted for lean body mass, the metabolic syndrome according to a suggested definition, and different factors in the coagulation- and fibrinolysis system were determined. Subjects with the metabolic syndrome were characterised by increases in PAI-1 activity, tPA antigen, protein C and protein S and low concentrations of tPA activity. Insulin sensitivity was independently and reversibly associated with PAI-1 (p = 0.014) and directly with tPA activity (p = 0.001). Insulin sensitivity was also significantly negatively associated with protein S and protein C and several components in the metabolic syndrome, however not remaining significant in multivariate analyses. Protein C and protein S were significantly associated with PAI-1 activity, tPA activity (negatively), tPA antigen and antithrombin III. In conclusion, the data indicated that insulin resistance and several of the clustering components in the metabolic syndrome are accompanied by increased plasma concentrations of the anticoagulatory proteins C and S which may represent a mechanism which counteracts the concomitantly occurring hypofibrinolysis.

Carotid intima-media thickness progression and risk of vascular events in people with diabetes: results from the PROG-IMT collaboration

OBJECTIVE

Carotid intima-media thickness (CIMT) is a marker of subclinical organ damage and predicts cardiovascular disease (CVD) events in the general population. It has also been associated with vascular risk in people with diabetes. However, the association of CIMT change in repeated examinations with subsequent CVD events is uncertain, and its use as a surrogate end point in clinical trials is controversial. We aimed at determining the relation of CIMT change to CVD events in people with diabetes.

RESEARCH DESIGN AND METHODS

In a comprehensive meta-analysis of individual participant data, we collated data from 3,902 adults (age 33-92 years) with type 2 diabetes from 21 population-based cohorts. We calculated the hazard ratio (HR) per standard deviation (SD) difference in mean common carotid artery intima-media thickness (CCA-IMT) or in CCA-IMT progression, both calculated from two examinations on average 3.6 years apart, for each cohort, and combined the estimates with random-effects meta-analysis.

RESULTS

Average mean CCA-IMT ranged from 0.72 to 0.97 mm across cohorts in people with diabetes. The HR of CVD events was 1.22 (95% CI 1.12-1.33) per SD difference in mean CCA-IMT, after adjustment for age, sex, and cardiometabolic risk factors. Average mean CCA-IMT progression in people with diabetes ranged between -0.09 and 0.04 mm/year. The HR per SD difference in mean CCA-IMT progression was 0.99 (0.91-1.08).

CONCLUSIONS

Despite reproducing the association between CIMT level and vascular risk in subjects with diabetes, we did not find an association between CIMT change and vascular risk. These results do not support the use of CIMT progression as a surrogate end point in clinical trials in people with diabetes.

Inflammatory markers and extent and progression of early atherosclerosis: Meta-analysis of individual-participant-data from 20 prospective studies of the PROG-IMT collaboration

BACKGROUND

Large-scale epidemiological evidence on the role of inflammation in early atherosclerosis, assessed by carotid ultrasound, is lacking. We aimed to quantify cross-sectional and longitudinal associations of inflammatory markers with common-carotid-artery intima-media thickness (CCA-IMT) in the general population.

METHODS

Information on high-sensitivity C-reactive protein, fibrinogen, leucocyte count and CCA-IMT was available in 20 prospective cohort studies of the PROG-IMT collaboration involving 49,097 participants free of pre-existing cardiovascular disease. Estimates of associations were calculated within each study and then combined using random-effects meta-analyses.

RESULTS

Mean baseline CCA-IMT amounted to 0.74 mm (SD = 0.18) and mean CCA-IMT progression over a mean of 3.9 years to 0.011 mm/year (SD = 0.039). Cross-sectional analyses showed positive linear associations between inflammatory markers and baseline CCA-IMT. After adjustment for traditional cardiovascular risk factors, mean differences in baseline CCA-IMT per one-SD higher inflammatory marker were: 0.0082 mm for high-sensitivity C-reactive protein (p < 0.001); 0.0072 mm for fibrinogen (p < 0.001); and 0.0025 mm for leucocyte count (p = 0.033). 'Inflammatory load', defined as the number of elevated inflammatory markers (i.e. in upper two quintiles), showed a positive linear association with baseline CCA-IMT (p < 0.001). Longitudinal associations of baseline inflammatory markers and changes therein with CCA-IMT progression were null or at most weak. Participants with the highest 'inflammatory load' had a greater CCA-IMT progression (p = 0.015).

CONCLUSION

Inflammation was independently associated with CCA-IMT cross-sectionally. The lack of clear associations with CCA-IMT progression may be explained by imprecision in its assessment within a limited time period. Our findings for 'inflammatory load' suggest important combined effects of the three inflammatory markers on early atherosclerosis.

Neuronal and glia-related biomarkers in cerebrospinal fluid of patients with acute ischemic stroke

BACKGROUND

Cerebral ischemia promotes morphological reactions of the neurons, astrocytes, oligodendrocytes, and microglia in experimental studies. Our aim was to examine the profile of CSF (cerebrospinal fluid) biomarkers and their relation to stroke severity and degree of white matter lesions (WML).

METHODS

A total of 20 patients (mean age 76 years) were included within 5–10 days after acute ischemic stroke (AIS) onset. Stroke severity was assessed using NIHSS (National Institute of Health stroke scale). The age-related white matter changes (ARWMC) scale was used to evaluate the extent of WML on CT-scans. The concentrations of specific CSF biomarkers were analyzed.

RESULTS

Patients with AIS had significantly higher levels of NFL (neurofilament, light), T-tau, myelin basic protein (MBP), YKL-40, and glial fibrillary acidic protein (GFAP) compared with controls; T-Tau, MBP, GFAP, and YKL-40 correlated with clinical stroke severity, whereas NFL correlated with severity of WML (tested by Mann–Whitney test).

CONCLUSIONS

Several CSF biomarkers increase in AIS, and they correlate to clinical stroke severity. However, only NFL was found to be a marker of degree of WML.

Heart dysfunction in patients with acute ischemic stroke or TIA does not predict all-cause mortality at long-term follow-up

BACKGROUND

Despite heart failure being a substantial risk factor for stroke, few studies have evaluated the predictive value of heart dysfunction for all-cause mortality in patients with acute ischemic stroke, in particular in the elderly. The aim of this study was to investigate whether impaired heart function in elderly patients can predict all-cause mortality after acute ischemic stroke or transient ischemic attack (TIA).

METHODS

A prospective long-term follow-up analysis was performed on a hospital cohort consisting of n = 132 patients with mean age 73 ± 9 years, presenting with acute ischemic stroke or transient ischemic attack, without atrial fibrillation. All patients were examined by echocardiography during the hospital stay. Data about all-cause mortality were collected at the end of the follow-up period. The mean follow-up period was 56 ± 22 months.

RESULTS

In this cohort, 58% of patients with acute ischemic stroke or TIA had heart dysfunction. Survival analysis showed that heart dysfunction did not predict all-cause mortality in this cohort. Furthermore, in multivariate regression analysis age (HR 5.401, Cl 1.97-14.78, p < 0.01), smoking (HR 3.181, Cl 1.36-7.47, p < 0.01), myocardial infarction (HR 2.826, Cl 1.17-6.83, p < 0.05) were independent predictors of all-cause mortality.

CONCLUSION

In this population with acute ischemic stroke or TIA and without non-valvular atrial fibrillation, impaired heart function does not seem to be a significant predictor of all-cause mortality at long-term follow-up.

Electrocardiographic abnormalities and elevated cTNT at admission for intracerebral hemorrhage: predictors for survival?

BACKGROUND

Cerebrovascular lesions are often associated with electrocardiographic (ECG) abnormalities. The main purpose of this work was to investigate the prognostic value of ECG abnormalities and/or elevated cardiac troponin (cTNT) on admission in patients with nontraumatic intracerebral hemorrhage (ICH).

METHODS

Ninety-seven consecutive patients with ICH were included. The predictive value of ECG abnormalities and increased TNT on survival were evaluated using Cox proportional hazard model.

RESULTS

The most frequently observed ECG abnormalities were the presence of a Q wave (39.6%), followed by prolonged QTc (>0.44 s; 35.4%), which was an independent predictor for long-term mortality (P = 0.019). No difference in QTc was observed between patients with right versus left ICH. Increased cTNT levels at admission had no prognostic value.

CONCLUSION

Various ECG changes were common in patients presenting with an ICH, but only prolonged QTc was found to be an independent predictor of poor survival during follow-up after ICH.

Comparative evaluation of treatment with low-dose aspirin plus dipyridamole versus aspirin only in patients with acute ischaemic stroke

BACKGROUND

Previous studies have suggested that pre-stroke treatment with low-dose aspirin (A) could reduce the severity of acute ischaemic stroke, but less is known on the effect of pre-stroke treatment with a combination of aspirin and dipyridamole (A + D) and post-stroke effects of these drugs. The aim of the present study was to evaluate the effect of this drug combination on acute and long-term prognosis of ischaemic stroke.

METHODS

Patients without atrial fibrillation admitted to the stroke unit with acute ischaemic stroke (n = 554) or TIA (n = 108) were studied during acute hospital care and up to 12 months after discharge from hospital.

RESULTS

Prior to acute stroke 62 patients were treated with A + D while 247 patients were treated with A only. No beneficial effects of the combination A + D compared to A only were noted on stroke severity and/or acute in-hospital mortality. However, survival analysis by Cox-proportional hazard model demonstrated lower 12-months all-cause mortality in patients discharged with A + D (n = 275) compared with patients on A only (HR, 0.52; CI, 0.32-0.86; p = 0.011; n = 262) after adjusting for age, baseline NIHSS, previous stroke, previous myocardial infarction and type 2 diabetes. We also noted a tendency towards lower all-cause mortality at 3 months with use of A + D, but this was not statistically significant (p = 0.12).

CONCLUSIONS

Pre-stroke treatment with a combination of low-dose A + D does not reduce the severity of acute stroke, nor does it reduce the acute in-hospital mortality. However, treatment with A + D at discharge from hospital is seemingly associated with lower long-term mortality compared with A only, contrary to the results from previous randomised studies. However, our results must be interpreted with extreme caution considering the non-randomised study design.

Apolipoprotein B/Apolipoprotein A-I in Relation to the Metabolic Syndrome and Change in Carotid Artery Intima-Media Thickness During 3 Years in Middle-Aged Men

Background and Purpose— The apolipoprotein B (apoB)/apolipoprotein A-I (apoA-I) ratio is a measure of the relationship between different lipoprotein particles and a powerful predictor of coronary death. The aim was to examine whether apoB/apoA-I was associated with the metabolic syndrome (MetS) at baseline and also with the future change in carotid artery intima-media thickness (IMT).

Methods— In 313 58-year-old men, carotid artery IMT was measured bilaterally by high-resolution B-mode ultrasound at baseline and after 3 years of follow-up. Serum apolipoprotein concentrations and the components of MetS were measured at study entry.

Results— ApoB/apoA-I showed statistically significant associations with body mass index, waist-to-hip ratio, high-density lipoprotein (HDL) cholesterol, triglycerides, low-density lipoprotein (LDL) particle size, insulin, and diastolic blood pressure. Two thirds of the patients with MetS had high apoB/apoA-I ratios (>0.90) compared with one third of those without the syndrome ( P <0.001). The IMT change was associated with apoB, total cholesterol, LDL cholesterol, triglycerides, and inversely with HDL cholesterol and LDL particle size at entry, and there was a strong colinearity between these variables. The subjects with apoB/apoA-I above the first tertile (0.74) had a 20-μm-higher (95% CI, 7 to 33) annual increase in IMT compared with those below this level after adjustment for blood pressure and smoking.

Conclusions— The apoB/apoA-I ratio was strongly associated with MetS and its components at baseline. ApoB/apoA-I at baseline was related to the change in carotid artery IMT during 3 years of follow-up. There was a strong colinearity between apoB/apoA and the atherogenic lipids.

Erythrocyte sodium/lithium countertransport is associated with thrombotic and fibrinolytic factors in 58-year-old men

The metabolic syndrome, in which insulin resistance is the core feature, is associated both with dysregulation of thrombosis/fibrinolysis and erythrocyte sodium/lithium countertransport (SLC). To investigate this further we designed a cross-sectional study to examine whether factors involved in coagulation- and fibrinolysis systems were associated with SLC independently of insulin resistance in 93 58-year-old men. SLC was in univariate analysis positively correlated with PAI-1 activity (r = 0.35, p <0.01), tPA antigen (r = 0.38, p <0.01), von Willebrand factor (r = 0.25, p <0.05), protein S (r = 0.26, p <0.05), and C (r = 0.30, p <0.01), and negatively associated with tPA activity(r = -0.28, p <0.01). Since these correlations could be influenced by the components of the metabolic syndrome itself, a separate analysis with adjustment for glucose infusion rate (GIR), plasma insulin, body fat, sagittal diameter of the abdomen (SD) and log serum triglyceride concentration (TG) was conducted. Then SLC was associated with tPA antigen independent of GIR, plasma insulin, body fat, SD and TG. SLC was also associated with protein C independent of GIR, insulin, body fat and SD but not TG. In conclusion, we found a relationship between SLC and the fibrinolytic system that was not related to the metabolic syndrome.

Endothelium-dependent flow-mediated vasodilatation, insulin resistance and the metabolic syndrome in 60-year-old men

OBJECTIVES

To evaluate the endothelium-dependent flow-mediated vasodilatation (FMD) in the brachial artery and to study the relationship to insulin sensitivity and to the metabolic syndrome in 60-year-old clinically healthy men.

SUBJECTS

The men were randomly selected from the general population (n = 55). The subjects with the metabolic syndrome were defined according to a definition proposed by a working group associated with the World Health Organization (WHO).

METHODS

Ultrasound images for measurement of lumen diameter of the brachial artery were recorded before and after reactive hyperaemia induced by occlusion of the artery, both with and without ischaemic hand exercise during the occlusion. Insulin-mediated glucose uptake was determined by euglycaemic hyperinsulinaemic clamp as a measure of insulin sensitivity.

RESULTS

The FMD was in the total group 3.2% when hyperaemia was induced by occlusion only and 8.7% after occlusion plus ischaemic hand exercise (P < 0.001, n = 51). However, no relationship was observed between any measure of FMD and insulin-mediated glucose uptake (r = -0.05 and r = 0.06, n = 47, P > 0.30). Furthermore, subjects with the metabolic syndrome (n = 13) did not differ in any measure of FMD compared with those with no risk factors (n = 11).

CONCLUSION

In this study the ultrasound method to evaluate endothelial function did not show that low insulin sensitivity or the metabolic syndrome were associated with impaired FMD in otherwise clinically healthy 60-year-old men.

Insulin, insulin propeptides and intima-media thickness in the carotid artery in 58-year-old clinically healthy men. The Atherosclerosis and Insulin Resistance study (AIR)

AIMS

To examine the relationship between specific (intact) insulin, insulin propeptides and subclinical atherosclerosis.

METHODS

A cross-sectional study based on a stratified sampling of randomly selected, clinically healthy 58-year-old men (n = 391). Ultrasound examinations of the carotid arteries were performed with measurement of intima-media thickness (IMT) in the common carotid artery and in the carotid artery bulb. Fasting, cross-reacting plasma insulin (RIA), specific (intact) insulin, proinsulin, 32,33 split proinsulin and C-peptide were measured.

RESULTS

Plasma concentrations of cross-reacting plasma insulin, specific insulin, proinsulin, 32,33 split proinsulin and C-peptide were univariately associated with common carotid artery IMT. Established risk factors such as blood pressure, smoking, apoB, triglycerides, body mass index (BMI), and waist--hip ratio were also related to IMT. After adjustment for smoking, apoB, blood pressure and triglycerides, cross-reacting plasma insulin, proinsulin and C-peptide but not specific insulin and split 32,33 proinsulin remained associated with carotid artery IMT. No associations remained after adjustment for BMI.

CONCLUSIONS

Fasting plasma proinsulin, C-peptide, and insulin by cross-reacting RIA was associated with common carotid artery IMT independent of several conventional risk factors for atherosclerosis. The multicollinearity between the insulin peptides and propeptides makes it difficult to clarify the exact role of each peptide.

Carotid and femoral atherosclerosis, cardiovascular risk factors and C-reactive protein in relation to smokeless tobacco use or smoking in 58-year-old men

Objectives. To examine the associations between smokeless tobacco use, smoking, cardiovascular risk factors, inflammation and ultrasound-assessed measures of atherosclerosis in the carotid and femoral arteries. Subjects. The study was performed in a population-based sample of clinically healthy men (n = 391) all 58 years old. Exclusion criteria were cardiovascular or other clinically overt diseases or continuous medication with cardiovascular drugs. Methods. The habits of smoking and oral moist snuff use were assessed by questionnaires. C-reactive protein (CRP) was assessed by high sensitive enzyme-linked immunosorbent assay (ELISA). Intima-media thickness (IMT) in the carotid bulb, the common carotid artery and the common femoral artery and plaque occurrence were measured by ultrasound. Results. The use of oral moist snuff was associated with serum triglycerides and waist-hip ratio (WHR), but not with CRP or ultrasound-assessed measures of subclinical atherosclerosis. Smoking, on the other hand, was associated with CRP, the components in the metabolic syndrome and IMT as well as plaques in the carotid and femoral arteries. In comparison to never-smokers the current smokers had higher values of WHR, triglycerides, C-reactive protein and IMT in carotid bulb and femoral artery. Ex-smokers were in general more obese and had a femoral IMT that was in-between that of never-smokers and current smokers. Conclusions. Tobacco smoking, but not oral moist snuff use, was associated with carotid and femoral artery IMT, and increased levels of CRP. Current smoking was also associated with abdominal obesity. Ex-smokers though, are generally more obese. Smoking was also associated with hyperinsulinaemia, dyslipidaemia and high blood pressure, i.e. the metabolic syndrome. The inhaled smoke from the combustion of tobacco seems to be an important aetiological factor in the atherosclerotic process.

The metabolic syndrome, smoking, and antibodies to oxidized LDL in 58-year-old clinically healthy men

BACKGROUND AND AIM

The aim was to examine whether the metabolic syndrome (as recently defined), its various components, and smoking were associated with circulating antibodies to oxidized low-density lipoproteins (IgG- and IgM-Ox-LDLAb) and malondialdehyde-treated LDL (IgG- and IgM-MDA-LDLAb) (ELISA) in a population sample of clinically healthy 58-year-old men (n = 391).

METHODS AND RESULTS

LDL peak particle size (gradient gel electrophoresis) and antibody titers were measured in all patients. Trend analysis showed significantly higher IgG-Ox-LDLAb and IgG-MDA-LDLAb titers across the range of men with none of the criteria defining metabolic syndrome (n = 77), those with > or = 1 criterion (n = 252) and those fulfilling the criteria (n = 62), which remained after adjustment for smoking. IgG-Ox-LDLAb was associated with plasma insulin, body mass index (BMI), the waist/hip ratio (WHR) and smoking. IgG-MDA-LDLAb was, in addition, related to diastolic blood pressure, serum triglycerides and a small LDL peak particle size. The IgM antibody titers only inversely correlated with smoking.

CONCLUSIONS

High serum titers of IgG antibodies to oxidized LDL and MDA-treated LDL were associated with the metabolic syndrome and smoking. Several of the factors in the metabolic syndrome were related to the IgG antibody titers to modified LDL. The high degree of intercorrelation among these factors makes it difficult to clarify the independent role of any specific factor.

Intact insulin, insulin propeptides, and intima-media thickness in the femoral artery in 58-year-old clinical healthy men--the Atherosclerosis and Insulin Resistance Study

The aim of this study was to examine the association between intact insulin, insulin propeptides, and femoral artery intima-media thickness. The design was a cross-sectional study and the study group (n = 391) consisted of randomly recruited clinically healthy 58-year-old Swedish men. The intima-media thickness of the common femoral artery was measured with ultrasound. Fasting plasma insulin; intact insulin; proinsulin; 32,33 split-proinsulin; and C-peptide concentrations were assessed. The results showed that the common femoral artery intima-media thickness correlated significantly and univariately with waist-hip ratio, systolic blood pressure, serum total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, ApoB, low-density lipoprotein peak particle size, and cigarette years. Furthermore, of intact insulin and insulin propeptides, only intact insulin and C-peptide were univariately associated with common femoral artery intima-media thickness (r= 0.14, p < 0.01; r= 0.18, p < 0.01; respectively). In a multiple regression analysis, common femoral artery intima-media thickness was independently associated with systolic blood pressure (beta-coefficient = 0.004, p = 0.002), ApoB (beta-coefficient = 0.338, p < 0.001 ) and cigarette years (beta-coefficient = 0.0004, p < 0.001), (R2= 25%, p<O0.00). In conclusion, smoking, systolic blood pressure, and ApoB but not insulin or insulin propeptides were independently associated with femoral atherosclerosis.

Sodium/lithium countertransport, insulin resistance, insulin peptides and microalbuminuria in clinically healthy 58-year-old men

The activity of the erythrocyte transport system, sodium/lithium countertransport (SLC), has been linked to the metabolic syndrome characterized by insulin resistance and compensatory hyperinsulinaemia. We measured SLC and insulin sensitivity with the euglycaemic hyperinsulinaemic clamp method in a patient sample (n = 93) randomly selected from a large clinically healthy group of 58-year-old men (n = 818). The lipid profile, blood pressure, body mass index (BMI) and insulin were also analysed. There was a significant difference (P < 0.001) in SLC between subjects with the metabolic syndrome (n = 19) and subjects without any components of this syndrome (n = 20). There was a highly significant correlation between SLC and BMI, waist/hip ratio, total body fat mass, serum triglycerides, plasma insulin, proinsulin split products and C-peptide in a univariate analysis. There was also a significant correlation between SLC and insulin sensitivity measured as insulin-mediated glucose uptake (P < 0.01). In multiple regression analysis, only two of the variables showing univariate significance were independently correlated to SLC, i.e. serum triglycerides (P < 0.001) and BMI (P < 0.01). The subjects with a SLC value in the highest tertile had a 6-fold higher prevalence of insulin resistance (low-insulin-mediated glucose uptake) as compared with those with a SLC value in the lowest tertile. We conclude that, in clinically healthy 58-year-old men from the general population, erythrocyte SLC is closely linked to metabolic syndrome, in particular to obesity, triglycerides and insulin resistance.

Low-density lipoprotein particle size, insulin resistance, and proinsulin in a population sample of 58-year-old men

The relationship between insulin sensitivity and low-density lipoprotein (LDL) peak particle size was examined in 104 clinically healthy 58-year-old men recruited from the general population. Insulin sensitivity was measured by the euglycemic hyperinsulinemic clamp method with adjustment for lean body mass. LDL peak particle size was determined by gradient gel electrophoresis, and insulin, proinsulin, and 32,33 split proinsulin were determined by 2-site immunoradiometric assays. The results showed that 16 subjects (15%) had pattern B, with a predominance of small LDL particles. These cases and a small LDL peak particle size were characterized by the features of the insulin resistance syndrome, ie, general and central obesity, elevated diastolic blood pressure, low serum concentrations of high-density lipoprotein (HDL) and apolipoprotein A1 (apoA1), increases in serum triglycerides and circulating insulin peptides, and low insulin-mediated glucose uptake. The correlation between insulin sensitivity and LDL peak particle size was significant (r = .33, P = .001) and independent of obesity. In a traditional multiple regression analysis, LDL peak particle size was independently associated not with insulin-mediated glucose uptake but with circulating triglycerides and HDL cholesterol, which together explained 67% of the variability in LDL particle size (P = .000). Of all insulin peptides, only proinsulin showed an independent relation to LDL peak particle size, but it disappeared after adjustment for other variables. We conclude that a small LDL particle size was associated with insulin resistance among these clinically healthy men, but this was not independent of serum triglycerides and HDL cholesterol. Serum proinsulin was more directly related to LDL particle size than insulin.

Antibodies to oxidized LDL in relation to intima-media thickness in carotid and femoral arteries in 58-year-old subjectively clinically healthy men

Antibody (Ab) titers to oxidized low density lipoprotein (OxLDL) have been found to be independent predictors of the progression of carotid atherosclerosis. Ab titers against OxLDL may be related to the entire burden of atherosclerosis in the vascular tree or, more specifically, to the disease process in different arterial regions. Therefore, the aim of the present study was to investigate the relationship between IgG and IgM titers to modified LDL and intima-media thickness (IMT) in the carotid and femoral arteries in subjectively clinically healthy 58-year-old men. IMT was measured by ultrasound, and Ab titers to modified LDL were measured by ELISA. The results showed that the common carotid artery IMT was associated with elevated titers of IgG-OxLDL Ab and independently with systolic blood pressure, smoking, and body mass index. The femoral artery IMT showed a negative correlation to IgM-OxLDL Ab and independent associations with smoking, systolic blood pressure, and total cholesterol. To summarize, in 58-year-old subjectively clinically healthy men recruited from the general population, there was a positive association between IgG-OxLDL Ab and IMT in the common carotid artery and a negative association between IgM-OxLDL Ab and IMT in the common femoral artery. However, these associations were not independent of other risk factors.

Insulin resistance and intima-media thickness in the carotid and femoral arteries of clinically healthy 58-year-old men. The Atherosclerosis and Insulin Resistance Study (AIR)

OBJECTIVE

To examine whether insulin resistance was associated with ultrasound-assessed measures of atherosclerosis in men with varying degrees of obesity.

DESIGN

A random selection of subjects from the general population were divided into quintiles of a body mass index/blood glucose score that was shown to be a valid and reproducible index of the degree of insulin sensitivity as assessed by the clamp technique. Every fourth man in quintiles 1 and 5 and every 20th man in quintiles 2-4 (in total, 104 men) were selected for an ultrasound examination of the carotid and femoral arteries and a euglycaemic hyperinsulinaemic clamp examination, adjusted for fat-free mass.

SETTING

A university hospital.

SUBJECTS

A total of 104 clinically healthy 58-year-old men of Swedish ancestry.

RESULTS

The mean common carotid artery intima-media thickness (IMT), but not the common femoral IMT, correlated significantly with glucose infusion rate (GIR) (r = - 0.20, P < 0.05), systolic blood pressure (r = 0.20, P < 0.05), pulse pressure (r = 0.23 P < 0.01), heart rate (r = 0.20, P < 0.05), HDL cholesterol (r = - 0.18, P < 0.05), log triglycerides (r = 0.28, P < 0.01), apoA1 (r = - 0.20, P < 0.05), apoB (r = 0.21, P < 0.05), LDL particle size (r = - 0.22, P < 0.05) and plasma insulin (r = 0.20, P < 0.05). In a multiple regression, common carotid IMT was independently associated with log triglycerides (beta = 0.25, P = 0.012) and pulse pressure (beta = 0.21, P = 0.031) (R2 = 8.7%, P = 0.005)

CONCLUSIONS

Insulin sensitivity, measured with the gold standard euglycaemic hyperinsulinaemic clamp method, showed similar associations with ultrasound-assessed measures of atherosclerosis in the carotid arteries as established cardiovascular risk factors, but only triglycerides and pulse pressure contributed independently to the variability in the common carotid intima-media thickness.

Insulin sensitivity and hemostatic factors in clinically healthy 58-year-old men

The objective of this cross-sectional study was to investigate the relationship between factors of the coagulation- and fibrinolysis systems and insulin sensitivity in 104 clinically healthy, 58-years-old men. Insulin sensitivity (hyperinsulinemic euglycemic clamp) adjusted for lean body mass, the metabolic syndrome according to a suggested definition, and different factors in the coagulation- and fibrinolysis system were determined. Subjects with the metabolic syndrome were characterised by increases in PAI-1 activity, tPA antigen, protein C and protein S and low concentrations of tPA activity. Insulin sensitivity was independently and reversibly associated with PAI-1 (p = 0.014) and directly with tPA activity (p = 0.001). Insulin sensitivity was also significantly negatively associated with protein S and protein C and several components in the metabolic syndrome, however not remaining significant in multivariate analyses. Protein C and protein S were significantly associated with PAI-1 activity, tPA activity (negatively), tPA antigen and antithrombin III. In conclusion, the data indicated that insulin resistance and several of the clustering components in the metabolic syndrome are accompanied by increased plasma concentrations of the anticoagulatory proteins C and S which may represent a mechanism which counteracts the concomitantly occurring hypofibrinolysis.

The metabolic syndrome, LDL particle size, and atherosclerosis: the Atherosclerosis and Insulin Resistance (AIR) study

An operative definition of the metabolic syndrome has been suggested by a working group associated with the World Health Organization in 1998. The aim of this study was to examine whether small, low density lipoprotein (LDL) particle size was associated with the metabolic syndrome and with subclinical atherosclerosis as measured by ultrasound in the carotid and femoral arteries. The study was performed in a population-based sample of clinically healthy men (N=391), all 58 years old and not undergoing any treatment with cardiovascular drugs. Exclusion criteria were cardiovascular or other clinically overt diseases or continuous medication with cardiovascular drugs. The results showed that subjects characterized by the metabolic syndrome (n=62) had a thicker mean intima-media complex (IMT) in both the carotid and femoral arteries (0.86 versus 0.77 mm, P:<0.001, and 1.03 versus 1. 00 mm, P:=0.022, respectively) and also lower mean values for LDL particle size (25.78 versus 26.80 nm, respectively, P:<0.001) compared with subjects with no risk factors (n=77). The group with the metabolic syndrome (n=62) also had higher mean values for serum cholesterol and heart rate. In the whole study group (N=391), there were significant but weak negative relationships between small LDL particle size, increasing IMT, and increasing cross-sectional intima-media area of the carotid and femoral arteries and also negative relationships between LDL particle size and plaque occurrence and size in the carotid and femoral arteries. In summary, this is the first large-scale study to demonstrate a relationship between the clustering of risk factors that constitute the metabolic syndrome and a small LDL particle size pattern and the occurrence of preclinical atherosclerosis in the carotid and femoral arteries, as assessed by the ultrasound technique, in healthy 58-year-old men recruited from the general population.

The euglycemic hyperinsulinemic clamp examination: variability and reproducibility

The aim was to examine the reproducibility of the euglycemic hyperinsulinemic clamp method. From a random population sample of 60-year-old clinically healthy men, 32 subjects with varying degrees of insulin sensitivity were recruited. Conventional 2-h clamp examinations were carried out at an interval of 2 weeks. Insulin was infused intravenously (priming for 10 min and thereafter 1.0 mU/kg body wt/min). Glucose was infused concomitantly aiming at a whole blood glucose of 5 mmol/L. The glucose infusion rate (GIR) was adjusted for body weight or fat free mass (FFM), the latter measured with dual-energy X-ray absorptiometry. During the final hour of each examination (60-120 min) the mean whole blood glucose concentrations were 5.06+/-0.15 and 5.09+/-0.17 mmol/L, respectively. Of the different time intervals studied, the glucose infusion rate during the final hour (GIR60-120) showed the highest correlation and lowest coefficient of variation (GIR60-120 adjusted by FFM: r=0.70, coefficient of variation=14.7%). Adjustment of GIR for weight instead of FFM underestimated insulin sensitivity in obese men. GIR60-120 adjusted for FFM tended to increase during the second examination. The measurement error was constant across all GIR. In summary, the euglycemic hyperinsulinemic clamp method has a coefficient of variation around 15%. The glucose infusion rate should be adjusted for fat free mass.

Computerized measurement of LDL particle size in human serum. Reproducibility studies and evaluation of LDL particle size in relation to metabolic variables and the occurrence of atherosclerosis

OBJECTIVES

The main aims of the present research project were to develop and evaluate a new software program for evaluation of LDL particle size applied to the gradient gel electrophoresis methodology without the use of previous ultracentrifugation, and to investigate the relationships among LDL particle size, metabolic variables and atherosclerosis, as measured by ultrasound, in subjects with different degrees of insulin resistance.

METHODS

LDL particle size was determined by polyacrylamide gradient gel electrophoresis.

RESULTS

Coefficient of variation for between-assay experiments was 0.3% (r = 0.99) for measurement of LDL peak particle size. LDL peak particle size was negatively correlated to serum triglycerides, apolipoprotein B, fasting insulin, BMI and diastolic blood pressure and positively correlated to HDL. Furthermore, subjects with moderate to large plaques in the carotid artery had smaller LDL particles compared to subjects without plaques.

CONCLUSIONS

This project resulted in a highly reproducible, computerized method for the analysis of LDL particle size. The data suggest that it is possible to assess LDL particle size in serum without the use of previous ultra-centrifugation. LDL particle size was associated with metabolic variables and the occurrence of moderate to large plaques in the carotid artery.