Levels of Adhesion Molecules Bear a Relationship to Triglyceride Levels in Type 2 Diabetic Subjects With Proven Silent Ischemia
By Adamikova, A Kojecky, V; Rybka, J; Svacina, S
Aim. The aim of the study was to examine the levels of adhesion molecules, high-sensitivity C-reactive protein (hs-CRP) and lipid spectrum of type 2 diabetic subjects with proven silent myocardial ischemia. Methods. We included in the study 19 patients with ischemia (Group 1) and 16 patients without ischemia (Group 2). We documented silent ischemia by an exercise-myocardial single photon emission computed tomography. We examined the levels of total cholesterol, high-density lipoprotein, low-density lipoprotein, triglycerides, vascular cell adhesion molecule 1, intercellular adhesion molecule 1, E-selectin, HbA^sub 1c^, microalbuminuria (MAU), hs-CRP and carotid intima-media thickness.
Results. The differences among the values of lipids, adhesion molecules, HbA^sub 1c^, hs-CRP, MAU between the groups were not statistically significant. E-selectin levels positively correlated with triglyceride levels in the group 1 (Spearman correlation, P
Conclusion. Statistically differences between the study groups were not significant. Levels of E-selectin positively correlated with high triglyceride levels in type 2 diabetic subjects with silent ischemia. This correlation documents a disturbance of the reverse cholesterol transport system.
[Int Angiol 2008;27:307-12]
Key words: Cell adhesion molecules – Triglycerides – Diabetes mellitus – Ischemia.
Cardiovascular disease ranks among the main causes of mortality and morbidity of patients of type 2 diabetes mellitus. The prevalence of coronary heart disease in type 2 diabetic subjects is reported as 26-35%. Fifty percent of deaths are due to coronary heart disease and 15% to brain strokes.1
According to current knowledge the inflammatory theory is moving into the forefront of pathogenesis of the process of atherosclerosis. There exists evidence of interconnection between the metabolic and immune systems.2 Metabolic imbalance leads to immune imbalance with starvation and immunosuppression on one hand and obesity and inflammatory diseases on the other. The current concept of atherogenesis, thus, involves participation of the immune system and chronic inflammation.3 Infiltration and retention of low- density lipoprotein (LDL) particles in the artery intima initiates an inflammatory response in the vascular wall. A key moment is the expression of adhesion molecules in the vascular endothelium. Leukocyte and monocyte adhesion and their migration to subendothelial areas occur at the location of the activated endothelial cells through the adhesion molecules.4 Macrophage antigens activate specific T-cells for the production of cytokines (e.g. interferon-gamma, interleukin-1, tumor necrosis factor [TNF]), which influence the origin of inflammation. These cytokines also induce production of interleukin6, while interleukin-6 stimulates the creation of acute phase reactants in the liver (C-reactive protein [CRP], serum amyloid A and fibrinogen). Interleukin-1 and TNF are produced by various tissues as a response to infection and also by patients with metabolic syndromes.5 Observation of the individual parts of this cascade can aid in clinical diagnosis and assessment of therapy.6-8 The aim of the study was to examine the relationship between conventional and inflammatory factors of the process of atherosclerosis of type 2 diabetic subjects with proven silent ischemia.
Materials and methods
The patients were enrolled in the study on the basis of positive microalbuminuria (MAU). These values were obtained from screening of patients with diabetes during their regular diabetic outpatient visits.
We observed 35 asymptomatic type 2 diabetic subjects without cardiovascular disease in the study, who, according to an exercise myocardial single photon emission computed tomography (SPECT), were subdivided into two groups. In group 1 (n=19; average age: 55.68+- 7.56 years; body mass index [BMI]: 30.03+-4.07), silent myocardial and lower limb ischemia was proven, while in group 2 (n=16; average age: 56.13+-6.48 years; BMI: 30.34+-4.85) without proven myocardial and lower limb silent ischemia.
Silent ischemia was proven by an exercise myocardial SPECT, followed by planar scintigraphy of both lower limbs on gamma camera antero-posterior and postero-anterior views. Resting scintigraphy followed by planar imaging at the same site were performed in the next stage.9-11 None of the patients smoked cigarettes, and all were treated for hypertension. Antihypertensive therapies in both groups were comparable.
Both groups were compared according to atherosclerotic markers, both traditional and inflammatory. Total cholesterol, LDL and high- density lipoprotein (HDL) cholesterol, and triglycerides were assessed on a Hitachi 911 biochemical analyzer. High-sensitivity CRP (hs-CRP) was analyzed on a Hitachi 911 analyzer using immunoturbidimetric tests from Orion Diagnostica, Finland. Intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1) and E-selectin were analyzed using Instant ELISA from Bender MedSystems, Austria.
We further observed glycosylated hemoglobin HbA^sub 1c^ and MAU as further markers of the early stadium of atherosclerosis. Diabetes control was assessed using HbA^sub 1c^ levels.
All subjects underwent measurements of the carotid artery intima- media thickness (IMT) by high-resolution real-time B mode ultrasonography with a 7.5 MHz linear transducer (ImagePoint HP, USA). The left carotid arteries were investigated in longitudinal projections. The examination included the segment of the left common carotid artery 1 cm under the carotid bulb. Areas with calcified plaques were avoided. IMT was defined as the distance between the leading edge of the first echogenic line (lumen intima interface) and the second echogenic line (media-adventitia interface) of the far wall. Three measurements were averaged to give the mean IMT. The measurements were carried out by the same independent ultrasonographic physician.
Data were expressed as mean +- standard deviation. Comparisons between the groups were carried out using the Mann-Whitney U-test. Values of P
Both groups were matched by age and BMI: 1) Group 1: n=19; mean age: 55.68+-7.56 years; BMI: 30.03+-4.07; 2) Group 2: n=16; mean age: 56.13+-6.48 years; BMI: 30.34+-4.85. In the course of the MannWhitney U-test, proof of statistically significant differences was obtained only for a difference of the carotid IMT, which was greater in Group 1 (IMT: 1.09+-0.28 mm vs 0.6+-0.11 mm; P
Both groups of type 2 diabetic subjects were matched by age and BMI. We did not prove statistically significant differences between the group with silent ischemia and without ischemia at the levels of total cholesterol, HDL and LDL cholesterol, triglycerides, MAU and hs-CRP. Both groups were also comparable as to diabetes control according to glycosylated hemoglobin HbA^sub 1c^. Levels of adhesion molecules VCAM-1, ICAM-1 and E-selectin also did not demonstrate any statistically significant differences between the groups with and without silent ischemia. In the group with silent ischemia, we documented statistically significantly greater carotid IMT.
The study proved correlation between levels of the inflammatory marker E-selectin and triglyceride levels in the diabetic group with proven silent ischemia. We did not prove this relation in the patient group without silent ischemia.
The relations between levels of inflammatory and traditional markers and the incidence of cardiovascular disease are the subject of a whole line of studies.12, 13 In the Women’s Health Study, Ridker et al.14-16 reported that levels of CRP was a stronger predictor than LDL cholesterol levels. Comparing CRP levels of at least 3 mg/L with those of /=18 years, who were participants in the National Health and Nutrition Examination Survey (NHANES) 1999-2000. The subjects were classified as having diabetes, the metabolic syndrome or neither; further in individual groups by low (3 mg/L) CRP levels. Logistic regression examined the odds of cardiovascular disease by its condition and CRP group. In this cross-sectional analysis, those with diabetes and high CRP are 7 times more likely to have cardiovascular disease than those with neither metabolic syndrome nor diabetes, but low CRP.
In the Atherosclerosis Risk in Communities Study, Ballantyne et al.18 reported a relative risk of coronary heart disease of 1.72 (95% CI: 1.24 to 2.39) among subjects with a CRP level of at least 3 mg/L, as compared with subjects with a level of
In our study, no proof was ascertained of a statistically significant difference between levels of hs-CRP and adhesion molecules in the group of diabetic subjects. However, average levels of hsCRP in both groups with and without proven silent myocardial and lower limb ischemia exceeded 3 mg/L. These levels document the high risk of coronary events of diabetic subjects in agreement with reports from literature. Activation of endothelial cells and of monocytes/macrophages plays an important role in atherogenesis and in the vulnerability of atherosclerotic plaques, and thus can influence the rapid progression of coronary disease. Adhesion molecules represent a major factor in the disruption of the atheromatic plaque and the origin of acute coronary syndrome or in diabetic subjects with silent ischemia.19, 20
E-selectin mediates the first step in leukocyte adhesion at the locus of inflammation. The ICAM-1 and VCAM-1 enable a strong bond of leukocytes and their penetration into the vascular wall.
Some clinical studies 21 were concerned with inflammatory markers and the risk of progression of stabilized coronary heart disease. Zouridakis et al21 proved that at hs-CRP, neopterin, soluble ICAM-1 (sICAM-1), matrix metalloproteinase-9 and past history of instable angina pectoris were independent predictors of rapid progression of coronary disease.
Further studies examined levels of adhesion molecules and the risk of progression of peripheral atherosclerosis in the population.22-27 In the Edinburgh Artery Study the authors22 studied the levels of CRP, interleukin-6, ICAM-1, VCAM-1 and E-selectin and their relation to the progression of lower limb atherosclerosis according to measurement of ankle-brachial index (ABI). At baseline, a significant trend was found between higher plasma levels of CRP and the increasing severity of peripheral arterial disease after adjustment for baseline cardiovascular risk factors. Interleukin6 at baseline was associated with progressive atherosclerosis at 5 years, and CRP, interleukin-6, and ICAM-1 were associated with changes at 12 years, independently of baseline ABI, cardiovascular risk factors, and baseline cardiovascular disease. Only interleukin-6 showed more consistent results and stronger independent predictive value than other inflammatory markers.
Our study group of type 2 diabetic subjects with silent myocardial as well as lower limb ischemia demonstrated by a prolonged exercise SPECT into the periphery. In this group, we were interested in the correlation of inflammatory markers and other conventional risk factors. We proved correlation of E-selectin with triglyceride levels. This association was not found in the group without silent ischemia. We also did not find any correlation with the other factors for the other adhesion molecules ICAM-1 and VCAM- 1. Lack of correlation between ICAM-1, VCAM-1 and triglyceride levels in the group of patients with silent ischemia may be due to a small size of patient population currently studied, as well as due to an apparently stronger involvement of E-selectin which is the first step in the inflammatory cascade. The exchange of cholesterol esters from HDL with triglycerides and phospholipids from very LDL and chylomicrons, mediated by cholesterolestertransferprotein (CETP), is augmented during hypertriglyceridemia.
The increased risk is explained by the enrichment of triacylglycerol lipoproteins by cholesterol and inefficiency of cholesterol reverse transport.28 This transport system moderates lipid uptake into the arterial walls and has a key function in lipid accumulation.
Diabetes is associated with disturbances in the lipid metabolism, and these patients are highly susceptible to atherosclerosis. Little is known about the association between CETP, C-629A gene polymorphism and cardiovascular disease in these patients.
In the group of diabetic subjects with proven silent myocardial and lower limb ischemia, we also found a statistically significantly greater IMT of the left common carotid. In a line of studies,29-33 a positive correlation of the IMT of the common carotids and incidence of cardiovascular occurrences was proven. The increasing level of the cardiovascular events is associated with the statistically significant augmentation of the IMT carotid.
For the time being, a limitation of our observations is the relatively small group.
In summary, the proven correlation of levels of the adhesion molecule E-selectin and triglycerides of asymptomatic type 2 diabetic patients with myocardial and lower limb ischemia documents a disturbance of the reverse cholesterol transport system, which plays a key role in lipid accumulation and in the progression of atherosclerosis. Other differences between the study groups were not statistically significant. These results document evidence that patients with diabetes are at a high risk for developing cardiovascular diseases. Observation of mutual relations of inflammatory marker levels and traditional risk factors of atherosclerosis may prospectively influence therapeutic intervention strategies used with these patients.
Some results of this study were presented at the 41st Annual Meeting of the EASD in Athens, Greece, 12-15 September 2005.
Acknowledgements.-We wish to thank Dr. Spendlikova for biochemical processing of inflammatory markers.
Received on April, 28, 2006; accepted for publication on January 10, 2007.
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A. ADAMIKOVA 1, V. KOJECKY 1, J. RYBKA 1, S. SVACINA 2
1 Diabetes Center, WHO Collaborating Center, Bata Hospital, Zlin, Czech Republic
2 First Faculty of Medicine, Charles University, Prague, Czech Republic
Address reprint requests to: A. Adamikova, MD, Diabetes Center, WHO Collaborating Center, Bata Hospital, Havlickovo nabr. 600, 762 75 Zlin, Czech Republic.
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