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)

Increased Vascularization in the Vulnerable Upstream Regions of Both Early and Advanced Human Carotid Atherosclerosis

BACKGROUND

Vascularization of atherosclerotic plaques has been linked to plaque vulnerability. The aim of this study was to test if the vascularization was increased in upstream regions of early atherosclerotic carotid plaques and also to test if the same pattern of vascularization was seen in complicated, symptomatic plaques.

METHODS

We enrolled 45 subjects with early atherosclerotic lesions for contrast enhanced ultrasound and evaluated the percentage of plaque area in a longitudinal ultrasound section which contained contrast agent. Contrast-agent uptake was evaluated in both the upstream and downstream regions of the plaque. We also collected carotid endarterectomy specimens from 56 subjects and upstream and downstream regions were localized using magnetic resonance angiography and analyzed using histopathology and immunohistochemistry.

RESULTS

Vascularization was increased in the upstream regions of early carotid plaques compared with downstream regions (30% vs. 23%, p = 0.033). Vascularization was also increased in the upstream regions of advanced atherosclerotic lesions compared with downstream regions (4.6 vs. 1.4 vessels/mm2, p = 0.001) and was associated with intra-plaque hemorrhage and inflammation.

CONCLUSIONS

Vascularization is increased in the upstream regions of both early and advanced plaques and is in advanced lesions mainly driven by inflammation.

Apolipoprotein B/apolipoprotein A-I ratio and apolipoprotein B: long-term predictors of myocardial infarction in initially healthy middle-aged men--a 13-year follow-up

We investigated whether serum concentrations of apolipoprotein (apo) B and apoA-I and the apoB/apoA-I ratio provided predictive information on myocardial infarction (MI) and ischemic stroke during 13 years of follow-up in a group of initially clinically healthy 58-year-old men, free from previous cardiovascular disease, diabetes, other established disease, or treatment with cardiovascular drugs. Multivariate logistic regression analysis showed that the apoB/apoA-I ratio and apoB were significant and independent determinants of MI (exponentiation of the B coefficient [Exp(β)] 3.1, 95% confidence interval [CI] 1.6-6.3, P=.001, Exp(β) 2.8, 95% CI 1.1-7.7, P=.045, respectively). The area under the receiver-operating characteristics curve as a relative measure of test efficiency was highest and significant for both apoB/apoA-I ratio and apoB (area under the curve=0.75, P<.001). In conclusion, the apoB/apoA-I ratio and apoB are independent risk factors for MI and has the highest efficiencies for predicting MI in initially healthy middle-aged men.

Insulin induces human acyl-coenzyme A: cholesterol acyltransferase1 gene expression via MAP kinases and CCAAT/enhancer-binding protein α

Insulin resistance characterized by hyperinsulinemia is associated with increased risk of atherosclerosis. Acyl-coenzyme A: cholesterol acyltransferase (ACAT) is an intracellular enzyme involved in cellular cholesterol homeostasis and in atherosclerotic foam cell formation. To investigate the relationship between hyperinsulinemia and atherosclerosis, we investigated whether insulin induced ACAT1 gene expression and found that insulin up-regulated ACAT1 mRNA, protein and enzyme activity in human THP-1 cells and THP-1-derived macrophages. Moreover, luciferase assays revealed that insulin enhanced the ACAT1 gene P1 promoter activity but not the P7 promoter. To explore the molecular mechanisms involved, deletion analysis of the human ACAT1 P1 promoter revealed an insulin response element (IRE) upstream of the P1 promoter (from -603 to -580), EMSA experiments demonstrated that CCAAT/enhancer binding protein α(C/EBPα) bound to the P1 promoter IRE. Insulin-induced ACAT1 upregulation was blocked by the presence of PD98059 (an inhibitor of extracellular signal-regulated kinase, ERK) and SB203580 (an inhibitor of p38 mitogen-activated protein kinase, p38MAPK) but not by Wortmannin (an inhibitor of phosphatidylinositol 3-kinase, PI3K) or U73122 (an inhibitor of phospholipase C-γ, PLCγ). These studies demonstrate that insulin promotes ACAT1 gene expression at the transcriptional level. The molecular mechanism of insulin action is mediated via interaction of the functional IRE upstream of the ACAT1 P1 promoter with C/EBPα and is MAPK-dependent.

Moderate Intensities of Leisure-Time Physical Activity Are Associated With Lower Levels of High-Sensitivity C-Reactive Protein in Healthy Middle-Aged Men

Circulating C-reactive protein (CRP), reflective of systemic chronic low-grade inflammation, is a marker associated with cardiovascular disease (CVD). One of the mechanisms through which physical activity might promote cardiovascular health is by preventing changes in inflammation biomarkers, such as CRP. The present study examined the association of self-reported physical activity with an inflammation biomarker, high-sensitivity CRP (hs-CRP), in a population-based cohort of clinically healthy 58-year-old men. Compared with a sedentary lifestyle both moderate (1.81 [0.94-3.69] vs 1.28 [0.55-2.90] mg/L; P < .05) and vigorous physical activity (1.81 [0.94-3.69] vs 0.88 [0.42-1.81] mg/L; P < .001) were associated with decrease in hs-CRP levels. In summary, we identified an association between self-reported leisure time physical activity and hs-CRP in a cross-sectional study of healthy 58-year-old men, with decreased levels of CRP by increased intensities of physical activity.

Increased Leisure-Time Physical Activity is Associated With Lower Prevalence of the Metabolic Syndrome in 64-Year Old Women With Impaired Glucose Tolerance

The metabolic syndrome (MetS) is characterized by a cluster of factors that confer an increased risk of cardiovascular morbidity as well as mortality. It is established that physical activity (PA) has a protective role in cardiovascular morbidity and mortality, mainly through favorable effects on traditional risk factors such as body mass and blood pressure. We assessed the prevalence of MetS in a population-based sample of 64-year-old women with impaired glucose tolerance (IGT) with respect to leisure-time PA (LTPA). The results showed an inverse linear association ( P < .05) between LTPA and MetS in this group. In conclusion, this study suggests that an increased PA level has an important role in preventing MetS in women with IGT.

Increasing leisure time physical activity is associated with less prevalence of the metabolic syndrome in healthy middle-aged men

The metabolic syndrome (MetS) is characterized by a constellation of factors that confer an increased risk for cardiovascular morbidity and mortality. It is well-known that physical activity (PA) has a protective role on cardiovascular morbidity and mortality, mainly through its favorable effects on traditional risk factors such as body mass and blood pressure (BP). We assessed the prevalence of MetS in a population-based sample of 58-year-old men with respect to leisure-time PA and also to occupational PA. The results showed an inverse linear association (P < .05) between leisure time physical activity (LTPA) and MetS in this group. In conclusion, this study suggests that PA has an important role in controlling MetS.

Human oral, gut, and plaque microbiota in patients with atherosclerosis

Periodontal disease has been associated with atherosclerosis, suggesting that bacteria from the oral cavity may contribute to the development of atherosclerosis and cardiovascular disease. Furthermore, the gut microbiota may affect obesity, which is associated with atherosclerosis. Using qPCR, we show that bacterial DNA was present in the atherosclerotic plaque and that the amount of DNA correlated with the amount of leukocytes in the atherosclerotic plaque. To investigate the microbial composition of atherosclerotic plaques and test the hypothesis that the oral or gut microbiota may contribute to atherosclerosis in humans, we used 454 pyrosequencing of 16S rRNA genes to survey the bacterial diversity of atherosclerotic plaque, oral, and gut samples of 15 patients with atherosclerosis, and oral and gut samples of healthy controls. We identified Chryseomonas in all atherosclerotic plaque samples, and Veillonella and Streptococcus in the majority. Interestingly, the combined abundances of Veillonella and Streptococcus in atherosclerotic plaques correlated with their abundance in the oral cavity. Moreover, several additional bacterial phylotypes were common to the atherosclerotic plaque and oral or gut samples within the same individual. Interestingly, several bacterial taxa in the oral cavity and the gut correlated with plasma cholesterol levels. Taken together, our findings suggest that bacteria from the oral cavity, and perhaps even the gut, may correlate with disease markers of atherosclerosis.

Erythrocyte sodium-lithium countertransport activity is inversely correlated to adiponectin, retinol binding protein 4 and body height

BACKGROUND

We have previously described that the sodium/lithium countertransport (SLC) in the erythrocyte cell membrane is closely linked to obesity and insulin resistance. Adiponectin and retinol-binding protein 4 (RBP-4) are believed to affect obesity and insulin resistance. In the present study, we aimed to further characterize the relationship between SLC, inflammatory markers, adiponectin and RBP-4.

METHODS

We included 93 clinically healthy 58-year-old men selected to display variations in insulin sensitivity. High sensitivity C-reactive protein (hs-CRP), TNF-alpha, soluble TNF-alpha-receptors (sTNFR) 1 and 2, IL-6 and RBP-4 were measured using antibody-based techniques. Adiponectin was determined by a radioimmunoassay kit. The lithium concentration in the special flux medium was measured by atomic absorption spectrophotometry.

RESULTS

In univariate analyses, SLC correlated negatively with RBP-4 (r(s) = -0.256, p = -0.017) and to adiponectin (r(s) = -0.316, p = 0.003) and positively with TNF-alpha (r(s) = 0.346, p = 0.001) and hs-CRP (r(s) = 0.288, p = 0.005). There were no statistically significant correlations with sTNFR 1 or 2 or IL-6. SLC was negatively associated to body height (r(s) = -0.256, p = 0.013).

CONCLUSIONS

We are the first to report that SLC correlates negatively with adiponectin and RBP-4. This finding is intriguing, as adiponectin is anti-inflammatory and anti-diabetic whereas RBP-4 supposedly decreases insulin sensitivity. We also observed a negative association between SLC activity and body height indicating that SLC activity is not primarily influenced by fat mass. The positive association of SLC with markers of inflammatory activity such as TNF-alpha and hs-CRP is in line with the proposed link between inflammation and insulin resistance.

Moderate physical activity is associated with lower ApoB/ApoA-I ratios independently of other risk factors in healthy, middle-aged men

Low-density lipoprotein is recognized as a primary vascular risk factor. However, recent data favor apolipoprotein (apo)B and apoA-I as risk factors with higher predictive values than conventional lipids. We investigated how leisure-time physical activity relates to the serum apoB/apoA-I ratio in middle-aged men. The results showed that compared with a sedentary lifestyle, moderate physical activity was associated with a decreased apoB/apoA-I ratio (1.01 ± 0.28 vs 0.87 ± 0.24, P < .05) and increased apoA-I levels (1.30 ± 0.20 g/L vs 1.43 ± 0.22 g/L, P < .05), whereas vigorous activity was required to observe a reduction in apoB levels (1.27 ± 0.28 g/L vs 1.14 ± 0.24 g/L, P < .05). A covariate analysis showed that leisure time physical activity was also associated with reduced apoB/apoA-I ratios after adjustment for smoking, systolic blood pressure and waist circumference. Importantly, this association was seen at moderate levels of physical activity, supporting the notion that some activity is better than none.

Ankle-Brachial Index Should Be Measured in Both the Posterior and the Anterior Tibial Arteries in Studies of Peripheral Arterial Disease

Lower extremity peripheral artery disease (PAD) is a powerful predictor of cardiovascular events and mortality. The ankle-brachial index (ABI) is an objective and standard diagnostic method to diagnose PAD (an ABI ≤ 0.9 is considered pathological). The American Heart Association (AHA) and the American College of Cardiology (ACC) recommend using both the posterior and anterior tibial arteries when assessing ABI. We investigated whether there was a difference in the diagnosis of PAD if the ABI was measured in the posterior or the anterior tibial arteries. The results showed that among participants with ABI ≤0.9, between 30% and 40% would not get a PAD diagnosis if the ABI was measured in only 1 of the arteries. In conclusion, this study emphasizes the importance of measuring the ABI in both the posterior tibial and the anterior tibial arteries when diagnosing PAD.

Albuminuria within the normal range and ultrasound-assessed atherosclerosis in the AIR study: a 9-year follow-up of 58-year-old clinically healthy men

BACKGROUND

Microalbuminuria, traditionally defined as 30-300 mg urinary albumin/24 h, predicts renal impairment and cardiovascular disease. Studies suggest that also a far lower urinary albumin excretion (UAE) can predict clinical outcome. Intima media thickness (IMT) is an established estimate of atherosclerosis. In this study, we investigated the predictive value of UAE within the normal rate (UAE-n) for the progression of IMT in the carotid and femoral arteries.

METHODS

We included 325 clinically healthy men with normoalbuminuria. Anthropometrics, urine and blood samples were taken and IMT in the carotid and femoral arteries were assessed by B-mode ultrasound at baseline and after 3 and 9 years. The annual progression rate of IMT (r-IMT) was calculated.

RESULTS

UAE-n correlated with carotid IMT at baseline and after 3 and 9 years, but not with r-IMT. In a regression analysis, only HDL and baseline IMT remained as statistically significant co-variates to mean IMT at 9 years. IMT in the femoral artery and r-IMT at any time-point did not correlate to baseline UAE.

CONCLUSION

UAE-n was associated with carotid IMT after 3 and 9 years but not r-IMT or with femoral artery IMT. Carotid IMT after 9 years' follow-up was independently related to baseline IMT and HDL cholesterol. In this cohort of 58-year-old men, our interpretation is that UAE-n is not associated with the increase in carotid and femoral artery IMT observed after 9 years.

High apoB/apoA-I ratio is associated with increased progression rate of carotid artery intima-media thickness in clinically healthy 58-year-old men: experiences from very long-term follow-up in the AIR study

OBJECTIVES

The aim of the present study was to investigate the relationship between atherosclerotic progression rate as measured by carotid artery IMT during very long-term follow-up in clinically healthy men and a number of baseline risk factors of potential importance for atherosclerosis progression including apoA-I, apoB, apoB/apoA-I ratio, other lipid variables including LDL particle size, body composition variables, blood pressure, smoking, fasting blood glucose and insulin, and also hsCRP.

BACKGROUND

Low-density lipoprotein (LDL) is associated with increased carotid IMT progression rate during long-term follow-up, whereas the relationship between newer biomarkers such as apoB/apoA-I ratio and carotid artery IMT progression rate has been less investigated.

METHODS

58-year-old men identified by screening in the community (n=391) with varying degrees of obesity and insulin sensitivity were examined with high-resolution B-mode ultrasound at baseline and after 3, and 8.9 years of follow-up (n=305 investigated after 8.9 years). The carotid arteries were examined bilaterally, and the mean intima-thickness was calculated for 10mm sections of the composite of common carotid arteries and bulbs (IMT(composite)). Serum levels of apoB and apoA-I were measured using a turbidimetric method. Uni- and multi-variable analyses were performed to study the relationship between carotid IMT(composite) progression rate and risk factors.

RESULTS

In a multi-variable analysis including all baseline variables only the apoB/apoA-I ratio (p=0.003; beta=0.181, standard error=0.003) and serum insulin (p=0.026; beta=-0.133, standard error=0.000) was significantly related to IMT(composite) progression rate.

CONCLUSION

The results indicate that apoB/apoA-I ratio is an important risk factor for predicting atherosclerotic progression rate during very long-term follow-up in clinically healthy middle-aged men.

Increased apoB/apoA-I Ratio is Predictive of Peripheral Arterial Disease in Initially Healthy 58-Year-old Men during 8.9 Years of Follow-up

The aim of the present study was to investigate, if increased levels of apoB/apoA-I ratios are associated with future peripheral arterial disease as measured by ankle-brachial index. Increased apoB/apoA-I levels are defined as 0.9, which has been suggested for men, and as 0.63, which has observed to be associated with plaques in the femoral artery. The study was performed in a cohort of initially clinically healthy 58-year-old men living in the city of Göteborg, Sweden. The group with an apoB/apoA-I ratio ≥0.9 had a significantly increased risk of having PAD during 8.9 years of follow-up than the group below that level (OR: 2.15 CI: 1.21 to 3.82, p < 0.01). When applying the lower apoB/apoA-I cut off, results showed that the group with a level >0.63 had more than a three-fold risk of future PAD compared to the group ≤0.63 (OR: 3.28 CI: 1.14 to 9.40, p < 0.05).

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).

Proinsulin:insulin and insulin:glucose ratios as predictors of carotid plaque growth: a population-based 7 year follow-up of the Tromsø Study

AIMS/HYPOTHESIS

Proinsulin is increased in persons at cardiovascular risk. Increased secretion of proinsulin relative to insulin has been suggested as a sign of defective conversion of proinsulin to insulin and C-peptide and is associated with beta cell dysfunction. It has also been suggested that proinsulin has more of a pro-atherogenic effect than insulin, the levels of which are also increased in the insulin resistance state. In this prospective population-based study, we examined whether the proinsulin:insulin ratio (PIR) or insulin:glucose ratio (IGR, an insulin resistance surrogate) predicted carotid plaque size in nondiabetic participants.

MATERIALS AND METHODS

The study included 1,859 men and 1,998 women aged 25-82 years from the Tromsø Study, who were examined with B-mode high resolution ultrasound at baseline in 1994-1995 and at follow-up in 2001-2002. All images were computer processed to yield mm(2) measures of plaque. Proinsulin and insulin were measured at baseline. All analyses were stratified for sex.

RESULTS

After adjusting for age, baseline plaque area, BMI, cholesterol, HDL-cholesterol, HbA(1c), IGR, albumin:creatinine ratio, fibrinogen, BP and lifestyle factors (tobacco smoking, alcohol consumption, physical activity), PIR was significantly associated with plaque size at follow-up in women but not men. For each SD in the PIR in women, the mean plaque area increased by 0.97 mm(2) (95% CI 0.44-1.50). IGR was not associated with carotid plaque size.

CONCLUSIONS/INTERPRETATION

The PIR is associated with progressive carotid artery plaque size in women.

Measures of insulin sensitivity

Many approaches may be taken in the assessment of insulin sensitivity in humans. The euglycemic hyperinsulinemic glucose clamp and measurement of steady-state plasma glucose are direct but time- and resource-intensive approaches. Alternative approaches, including calculations based on fasting plasma insulin and glucose levels or analyses of glucose and insulin levels after intravenous or oral glucose administration, are useful but provide only modest correlation with the primary analyses. Surrogate measures of insulin sensitivity may be found in body mass index, waist circumference, or serum triglyceride or C-reactive peptide determination. New, innovative isotopic approaches now being developed offer the potential to characterize whole-body glucose metabolism in a fashion that may eventually allow routine clinical testing of insulin sensitivity.

Insulin resistance, the metabolic syndrome, diabetes, and cardiovascular disease risk in women with PCOS

Polycystic ovary syndrome is the most common endocrinopathy of reproductive aged women affecting 6-10% of the population. Traditionally considered a reproductive disorder manifesting as chronic anovulation, infertility, and hyperandrogenism, management has primarily focused on short-term reproductive outcomes. Recently, however, significant metabolic aspects in conjunction with longer-term health sequealae of PCOS have been recognized. The metabolic features are primarily related to underlying insulin resistance (IR), which is now understood to play an important role in both the pathogenesis and long-term sequelae of PCOS.

Circulating oxidized low-density lipoprotein is associated with echolucent plaques in the femoral artery independently of hsCRP in 61-year-old men

OBJECTIVES

The aim of the study was to test the hypothesis that circulating markers of inflammation (high-sensitive C-reactive protein, hsCRP) and oxidative modification of lipids (oxidized low-density lipoprotein, oxLDL) were associated with the occurrence of echolucent rather than echogenic femoral artery plaques in a cross-sectional population based cohort of 513, 61-year-old men.

BACKGROUND

The relationships between circulating oxLDL, hsCRP and the occurrence of echolucent plaques in the femoral artery have not previously been investigated.

METHODS

The levels of circulating oxLDL and hsCRP were determined in plasma by ELISA. Plaque occurrence, size and echogenicity were measured by B-mode ultrasound in the right femoral artery. Assessment of plaque echogenicity was based on the classification (grades 1-4) proposed by Gray-Weale et al.

RESULTS

A higher frequency of echolucent femoral plaques was observed in subjects with the metabolic syndrome and current smokers (p=0.01 and p<0.001, respectively) as well as with increasing levels of oxLDL and hsCRP (p=0.002 and p=0.005, respectively). In a multiple logistic regression analysis oxLDL and current smokers turned out to be independent associated with the presence of echolucent femoral artery plaques.

CONCLUSIONS

The results of the present study support our hypothesis that circulating oxLDL is a marker of an unstable echolucent plaque phenotype in the femoral artery in man.

apoB/apoA–I ratio is related to femoral artery plaques and is predictive for future cardiovascular events in healthy men

OBJECTIVES

The aim of the present study was to investigate the association between serum concentrations of apoB, apoA-I and the apoB/apoA-I ratio and future cardiovascular events in a group of healthy 58-year-old men during 6.6 years of follow-up. A further aim was to investigate the concentrations of apoB, apoA-I and the apoB/apoA-I ratio to the association of plaque occurrence in the carotid and femoral arteries.

BACKGROUND

Previous studies have shown that the apoB/apoA-I ratio is an important cardiovascular risk factor, whereas the association between apoB/apoA-I ratio and presence of atherosclerotic plaques in the carotid and femoral arteries has been less investigated.

METHODS

The carotid and femoral arteries were examined by high-resolution B-mode ultrasound in 391, 58-year-old men identified by screening in the city of Göteborg, Sweden. Assessment of plaque occurrence and measurement of apolipoproteins (apoA-I and apoB) was performed.

RESULTS

Subjects with an apoB/apoA-I ratio >/=0.9 had a significantly increased risk to suffer a cardiovascular event during 6.6 years of follow-up (OR 3.07, 95% CI 1.22-7.71), while no difference in risk for cardiovascular events was observed for subjects with LDL cholesterol >3.4 mmol/L compared to subjects <3.4 mmol/L (OR 1.04, 95% CI 0.37-2.46). A greater risk for plaques in the femoral artery was also observed in subjects with an apoB/apoA-I ratio >/=0.9 compared to subjects <0.9 (OR 3.06, 95% CI 1.22-7.70). In a multiple logistic regression model, both elevated apoB/apoA-I ratio and plaque occurrence in the femoral artery were of significant importance for cardiovascular events during follow-up.

CONCLUSIONS

The results showed that the apoB/apoA-I ratio was associated with arteriosclerosis in the femoral artery, and predicted future cardiovascular events. These observations, and the fact that apoB and apoA-I can be measured in the non-fasting state with high precision, in combination with the finding that LDL cholesterol did not predict cardiovascular disease, support results from other studies that the apoB/apoA-I ratio may be a superior risk marker for cardiovascular disease.

Insulin resistance, the metabolic syndrome, diabetes, and cardiovascular disease risk in women with PCOS

Polycystic ovary syndrome is the most common endocrinopathy of reproductive aged women affecting 6-10% of the population. Traditionally considered a reproductive disorder manifesting as chronic anovulation, infertility, and hyperandrogenism, management has primarily focused on short-term reproductive outcomes. Recently, however, significant metabolic aspects in conjunction with longer-term health sequealae of PCOS have been recognized. The metabolic features are primarily related to underlying insulin resistance (IR), which is now understood to play an important role in both the pathogenesis and long-term sequelae of PCOS.

Regulation and splicing of scavenger receptor class B type I in human macrophages and atherosclerotic plaques

BACKGROUND

The protective role of high-density lipoprotein (HDL) in the cardiovascular system is related to its role in the reverse transport of cholesterol from the arterial wall to the liver for subsequent excretion via the bile. Scavenger receptor class B type I (SR-BI) binds HDL and mediates selective uptake of cholesterol ester and cellular efflux of cholesterol to HDL. The role of SR-BI in atherosclerosis has been well established in murine models but it remains unclear whether SR-BI plays an equally important role in atherosclerosis in humans. The aim of this study was to investigate the expression of SR-BI and its isoforms in human macrophages and atherosclerotic plaques.

METHODS

The effect of hypoxia and minimally modified low-density lipoprotein (mmLDL), two proatherogenic stimuli, on SR-BI expression was studied in human monocyte-derived macrophages from healthy subjects using real-time PCR. In addition, SR-BI expression was determined in macrophages obtained from subjects with atherosclerosis (n = 15) and healthy controls (n = 15). Expression of SR-BI isoforms was characterized in human atherosclerotic plaques and macrophages using RT-PCR and DNA sequencing.

RESULTS

SR-BI expression was decreased in macrophages after hypoxia (p < 0.005). In contrast, SR-BI expression was increased by exposure to mmLDL (p < 0.05). There was no difference in SR-BI expression in macrophages from patients with atherosclerosis compared to controls. In both groups, SR-BI expression was increased by exposure to mmLDL (p < 0.05). Transcripts corresponding to SR-BI and SR-BII were detected in macrophages. In addition, a third isoform, referred to as SR-BIII, was discovered. All three isoforms were also expressed in human atherosclerotic plaque. Compared to the other isoforms, the novel SR-BIII isoform was predicted to have a unique intracellular C-terminal domain containing 53 amino acids.

CONCLUSION

We conclude that SR-BI is regulated by proatherogenic stimuli in humans. However, we found no differences between subjects with atherosclerosis and healthy controls. This indicates that altered SR-BI expression is not a common cause of atherosclerosis. In addition, we identified SR-BIII as a novel isoform expressed in human macrophages and in human atherosclerotic plaques.

The metabolic syndrome in middle-aged men according to different definitions and related changes in carotid artery intima-media thickness (IMT) during 3 years of follow-up

OBJECTIVES

To examine the occurrence over time of the metabolic syndrome (MetS) according to different definitions and the relation to change during follow-up in carotid artery intima-media thickness (IMT), measured by ultrasound.

DESIGN

A cohort of 316, originally 58-year-old men, initially free of diabetes and cardiovascular disease, was followed for 3.2 +/- 0.2 years. IMT was measured bilaterally by high-resolution B-mode ultrasound at baseline and follow-up. The MetS was classified according to slightly modified World Health Organization (WHO) and National Cholesterol Education Program (NCEP) criteria.

RESULTS

In 88% WHO and NCEP definitions resulted in identical classifications. IMT was larger both at baseline and after 3 years in men fulfilling the criteria for the MetS, according to either of the definitions, compared to those without factors in the syndrome. Men who fulfilled the WHO criteria for the MetS, at the initial and final examination showed a statistically significant increase in carotid artery IMT during the study [76 (95% CI: 14-130) microm, n = 37]. Men fulfilling the WHO criteria for the MetS at baseline tended to have a larger annual increase in IMT than those not fulfilling the criteria or having no risk factors in the syndrome.

CONCLUSIONS

More than 10% of the men had the MetS both at baseline and after 3 years, and this was associated with an increase in IMT using the WHO definition. Several of the components included in the MetS deteriorated during follow-up, i.e. body mass index (BMI), waist-to-hip ratio (WHR), waist circumference, blood glucose and blood pressure.

Non-stenotic echolucent ultrasound-assessed femoral artery plaques are predictive for future cardiovascular events in middle-aged men

OBJECTIVES

The aim of the present study was to examine the relationship between plaque occurrence, plaque size and plaque echogenicity, assessed by B-mode ultrasound, in the femoral artery and the development of clinical cardiovascular disease.

BACKGROUND

The relationship between carotid atherosclerosis assessed by B-mode ultrasound and cardiovascular disease has been thoroughly investigated. In comparison, the femoral arteries have received much less attention.

METHODS

The femoral artery was examined by high-resolution B-mode ultrasound in 391, 58-year-old men identified by screening in the city of Goteborg, Sweden. Assessment of plaque occurrence, plaque size (no, small, or moderate/large) and plaque characteristics in terms of echogenicity (no, echogenic or echolucent) were performed.

RESULTS

Subjects with a plaque present in the femoral artery at study baseline had a three-fold increase in odds ratio (OR 3.04, 95%, CI 1.24-7.42) for having a cardiovascular event during 6.6 years of follow-up compared to subjects without plaque. After adjustment for cardiovascular risk factors (LDL, triglycerides, systolic blood pressure and smoking) there was a borderline significant association between plaque occurrence and cardiovascular disease (OR = 2.64, p = 0.055). Plaque size could be demonstrated to be associated with cardiovascular events (p = 0.012, for trend). The results also showed that in this group of men, the risk of having a cardiovascular event was to a large extent confined to those with an echolucent plaque at baseline. However, no significant difference in risk prediction was seen between echogenic and echolucent plaques, respectively.

CONCLUSIONS

This is the first study to show that the presence of non-stenotic plaques in the femoral artery in middle-aged men without prior cardiovascular events has a predictive value for future cardiovascular events. The relationship was attenuated by adjustment for traditional cardiovascular risk factors. Data also indicates that plaque echolucency predicts increased risk.

Proinsulin concentration is an independent predictor of all-cause and cardiovascular mortality: an 11-year follow-up of the Hoorn Study

OBJECTIVE

High proinsulin concentration may be a better predictor for cardiovascular disease (CVD) mortality than insulin concentration. Previous observations may have been confounded by glucose tolerance status or lack of precision because of high intraindividual variability. We investigated the longitudinal relation of means of duplicate measurements of insulin and proinsulin with all-cause and CVD mortality in a population-based cohort taking glucose tolerance status into account.

RESEARCH DESIGN AND METHODS

Fasting and post-75-g glucose-load (2-h) glucose, insulin, and proinsulin values were determined in duplicate on separate days in 277 participants with normal glucose metabolism, 208 participants with impaired glucose metabolism, and 119 newly detected patients with type 2 diabetes of the Hoorn Study. Insulin resistance and beta-cell function were estimated by homeostasis model assessment (HOMA-IR and HOMA-B, respectively), and the fasting proinsulin-to-insulin ratio was calculated. Subjects were followed with respect to mortality until January 2003.

RESULTS

Fasting proinsulin levels were significantly associated with all-cause and CVD mortality. The hazard ratios (HRs) per increase in interquartile range adjusted for age and sex were 1.21 (95% CI 1.04-1.42) for all-cause mortality and 1.33 (1.06-1.66) for CVD mortality. Adjustment for glucose tolerance status and HOMA-IR did not substantially change the associations.

CONCLUSIONS

Fasting proinsulin was associated with all-cause and CVD mortality, independent of glucose tolerance status and insulin resistance and largely independent of other CVD risk factors. Proinsulin might play a role in the relationship between insulin resistance and CVD.

The reciprocal association of adipocytokines with insulin resistance and C-reactive protein in clinically healthy men

In experimental models, adiponectin improves and tumor necrosis factor alpha (TNF- alpha ) impairs insulin action, and the expression of these adipocytokines seems to have a reciprocal regulation. The aim was to examine whether in a cross-sectional study, associations supporting this concept may be found in 58-year-old clinically healthy men, and also the relation to C-reactive protein (CRP). In 102 men, euglycemic hyperinsulinemic clamp was used to assess glucose infusion rate (GIR). Total body fat (dual-energy x-ray absorptiometry), plasma adiponectin (radioimmunoassay), TNF-alpha , and CRP (enzyme-linked immunosorbent assay) were measured. Adiponectin correlated positively to GIR (r=0.33, P<.001) and negatively to total fat mass (r=-0.29, P=.004), whereas TNF- alpha showed reverse associations (r=-0.31, P<.01, and r=0.31, P<.01). Adiponectin and TNF- alpha were negatively correlated (-0.28, P=.006). An interaction term (TNF- alpha /adiponectin ratio) and body fat together explained 31.3% (P<.001) in GIR variability. The odds ratio for having insulin resistance was 9.3 (95% CI, 2.2-38.9) in subjects with TNF-alpha values above and adiponectin levels below the median, as compared to subjects with TNF- alpha values below and adiponectin levels above the median. Total fat and TNF-alpha , but not adiponectin, were significantly associated with log CRP (R2=20%, P<.001). In conclusion, this study in man showed that plasma adiponectin and TNF-alpha were independently and reversely associated with insulin resistance. C-reactive protein levels were related to TNF-alpha and obesity.

IRIS II Study: Sensitivity and specificity of intact proinsulin, adiponectin, and the proinsulin/adiponectin ratio as markers for insulin resistance

OBJECTIVE

This study was performed to compare the specificity and sensitivity of intact proinsulin, adiponectin, and their ratio (proinsulin/adiponectin) in the prediction of insulin resistance as assessed by the homeostasis model assessment (HOMA) score (> or =2 = resistant).

RESEARCH DESIGN AND METHODS

Using a cross-sectional approach, 500 orally treated patients with type 2 diabetes (272 women, 238 men; mean +/- SD age, 64.8 +/- 11.6 years; hemoglobin A1c, 7.0 +/- 1.5%; disease duration, 5.8 +/- 6.1 years) were investigated. Various cutoffs for body mass index-adjusted adiponectin and proinsulin/adiponectin were compared with the established cutoff value of 10 pmol/L for fasting proinsulin.

RESULTS

Fasting proinsulin correlated more closely with the HOMA score (r = 0.560, P < 0.001) than fasting adiponectin (r = -0.204, P < 0.001) or proinsulin/adiponectin (r = 0.355, P < 0.001). For proinsulin, specificity and sensitivity for insulin resistance in correlation to the HOMA score results were 96% and 70%, respectively. At a comparable specificity level to proinsulin, adiponectin did not reach a comparable sensitivity (14%), while the proinsulin/adiponectin ratio almost reached the same sensitivity (65%). Overall, patients with elevated proinsulin had a higher prevalence of micro- and macrovascular disease [odds ratio 1.47 (adiponectin, 1.08; proinsulin/ adiponectin, 1.48) and 1.34 (adiponectin, 1.32; proinsulin/adiponectin, 1.27), respectively].

CONCLUSIONS

Elevation of fasting intact proinsulin seems to be the more specific marker for insulin resistance and increased cardiovascular risk than suppression of fasting adiponectin. Formation of the ratio does not lead to a further increase in the predictive value.

Oxidized low-density lipoprotein in plasma is a prognostic marker of subclinical atherosclerosis development in clinically healthy men

OBJECTIVE

To investigate the association between plasma oxidized low-density lipoprotein (OxLDL) and the progress of clinically silent atherosclerosis, as measured by ultrasound in the carotid arteries.

DESIGN

Prospective, observational study with more than 3 years of follow-up.

SETTING

One-centre study at university hospital.

MATERIAL AND METHODS

The subjects (n = 326) were obtained by stratified sampling from a population sample of men who were 58 years old at baseline. Carotid artery intima-media thickness (IMT) was measured bilaterally by high-resolution B-mode ultrasound at baseline and after follow-up. Plasma OxLDL cholesterol concentrations and conventional cardiovascular risk factors were measured at study entry. Automated measurements of IMT were performed. Plaque occurrence and size were assessed (plaque status). Plasma OxLDL at entry was measured by a specific monoclonal antibody, mAb-4E6.

RESULTS

OxLDL at entry, but not LDL cholesterol, was associated with the number and size of plaques at follow-up (P = 0.008), also after adjustment for plaque status at entry (P = 0.033). The plasma OxLDL concentration at entry was associated with change in carotid artery IMT (r = 0.17; P = 0.002) and in a stepwise multiple regression analysis this association remained after adjustment for other cardiovascular risk factors (P = 0.005).

CONCLUSIONS

These results provide new information, supporting the concept that circulating OxLDL was associated with the silent phase of atherosclerosis progression in clinically healthy men independently of conventional risk factors.

Vascular dysfunction and autonomic neuropathy in Type 2 diabetes

AIMS

To test the hypothesis that arterial dysfunction in Type 2 diabetes is related to autonomic neuropathy.

METHODS

Arterial function and autonomic neuropathy were assessed over two consecutive days in 45 Type 2 diabetic and control subjects. Systemic arterial compliance (SAC), arterial stiffness (pulse-wave velocity, PWV) and carotid intima thickness (IMT) were assessed; these markers reflect early vascular disease and predict clinical vascular events. Autonomic neuropathy was assessed using heart rate variability with continuous ECG recording during various breathing and postural manoeuvres and an overall autonomic score was generated. Fasting metabolic parameters including glucose, insulin, HbA(1c) and lipid profile were measured.

RESULTS

Autonomic neuropathy tests were all repeatable in diabetic subjects. Compared with controls, diabetic subjects had arterial dysfunction with increased PWV (P = 0.009), IMT (P < 0.001) and reduced SAC (P = 0.053). After adjustment for age, central PWV correlated with fasting insulin (r(2) = 0.45, P < 0.05) and autonomic score (r(2) = 0.44, P < 0.05), peripheral PWV correlated with autonomic score (r(2) = 0.51, P < 0.005) and IMT correlated with fasting insulin (r(2) = 0.5, P < 0.005). The presence of autonomic neuropathy correlated with fasting insulin (P = 0.015), but not age, duration diabetes, lipids or blood pressure.

CONCLUSION

Using repeatable measures of autonomic neuropathy and vascular function in Type 2 diabetic subjects, we have demonstrated associations between autonomic neuropathy, vascular dysfunction and hyperinsulinaemia. This may help to explain the excess cardiovascular mortality seen in diabetic subjects with autonomic neuropathy.

Preclinical atherosclerosis and inflammation in 61-year-old men with newly diagnosed diabetes and established diabetes

OBJECTIVE

The aim of this study was to investigate the occurrence of subclinical atherosclerosis and underlying mechanisms in men with newly diagnosed diabetes and established diabetes compared with healthy control subjects.

RESEARCH DESIGN AND METHODS

In a population-based study of 61-year-old Caucasian men (n = 271) with established diabetes (n = 50) and newly diagnosed diabetes (n = 24) and healthy control subjects (n = 197), standard risk factors and highly sensitive (hs) C-reactive protein (CRP) were measured. Ultrasound measurements of intima-media thickness (IMT) were performed bilaterally in the common carotid artery, and a composite measure was calculated from common carotid and carotid bulb IMT (composite IMT). The plaque status was assessed.

RESULTS

Composite IMT and carotid plaque size increased gradually among the healthy control subjects, newly diagnosed diabetic patients, and established diabetic patients (P for trend < or =0.001, respectively). CRP was higher in newly and established diabetes (NS between diabetes groups) compared with healthy control subjects (P < 0.001). Total cholesterol levels were lower in newly diagnosed diabetes (5.51 +/- 1.13 mmol/l, P < 0.05) and established diabetes (5.45 +/- 1.15 mmol/l, P < 0.01) compared with those of healthy control subjects (5.77 +/- 1.03 mmol/l). In men with diabetes (n = 74), diabetes onset status (newly diagnosed versus established), waist-to-hip ratio (WHR), and serum triglycerides, but not CRP, explained 16% of the variance in composite IMT.

CONCLUSIONS

This is the first study to show increased preclinical atherosclerotic changes (IMT and plaque size) and increased inflammation (hs-CRP) in men with newly diagnosed diabetes as well as in patients with established diabetes compared with healthy control subjects. WHR, diabetes onset status (newly diagnosed versus established), and triglycerides, but not CRP, were independent correlates of carotid artery IMT in men with diabetes.

Nontraditional risk factors for cardiovascular disease in diabetes

People with type 2 diabetes are disproportionately affected by cardiovascular disease (CVD), compared with those without diabetes. Traditional risk factors do not fully explain this excess risk, and other "nontraditional" risk factors may be important. This review will highlight the importance of nontraditional risk factors for CVD in the setting of type 2 diabetes and discuss their role in the pathogenesis of the excess CVD morbidity and mortality in these patients. We will also discuss the impact of various therapies used in patients with diabetes on nontraditional risk factors.

Plasma ghrelin, body fat, insulin resistance, and smoking in clinically healthy men: the atherosclerosis and insulin resistance study

The purpose of the study was to examine whether insulin sensitivity was associated with fasting plasma ghrelin concentrations in a population-based sample of 58-year-old clinically healthy Caucasian men. The methods used were dual-energy x-ray absorptiometry (DXA) for measurement of body composition and a conventional euglycemic hyperinsulinemic clamp, measuring glucose infusion rate (GIR) that was adjusted for fat-free mass. Plasma ghrelin was measured by radioimmunoassay. The results showed that ghrelin was not associated with GIR adjusted for fat-free mass or with GIR adjusted for body mass, and body fat, or waist circumference. Plasma ghrelin correlated negatively to body fat (-0.46, P<.001) and waist circumference (-0.45, P<.001). Ghrelin was also inversely related to systolic and diastolic blood pressure (r=-.29 and r=-0.34, respectively, P<.01) and positively to high-density lipoprotein (HDL) cholesterol (0.33, P<.01), and low-density lipoprotein (LDL) particle size (0.34, P<.001), but these associations did not remain after adjustment for body fat. Plasma ghrelin was associated with current smoking independent of waist circumference. Among current smokers, circulating plasma concentrations were higher in those who had smoked during the hour preceding the blood sample than those who had smoked 2 to 12 hours ago (P=.043). The conclusion is that whole body insulin sensitivity was not associated with plasma ghrelin concentrations. Body fatness was the strongest determinant of circulating ghrelin. It was found that acute smoking may affect ghrelin levels.