J.J. Emeis

C-reactive protein, a hepatic acute phase protein largely regulated by circulating levels of interleukin-6, predicts coronary heart disease incidence in healthy subjects. We have shown that subcutaneous adipose tissue secretes interleukin-6 in vivo. In this study we have sought associations of levels of C-reactive protein and interleukin-6 with measures of obesity and of chronic infection as their putative determinants. We have also related levels of C-reactive protein and interleukin-6 to markers of the insulin resistance syndrome and of endothelial dysfunction. We performed a cross-sectional study in 107 nondiabetic subjects: (1) Levels of C-reactive protein, and concentrations of the proinflammatory cytokines interleukin-6 and tumor necrosis factor-alpha, were related to all measures of obesity, but titers of antibodies to Helicobacter pylori were only weakly and those of Chlamydia pneumoniae and cytomegalovirus were not significantly correlated with levels of these molecules. Levels of C-reactive protein were significantly related to those of interleukin-6 (r=0.37, P<0.0005) and tumor necrosis factor-alpha (r=0.46, P<0.0001). (2) Concentrations of C-reactive protein were related to insulin resistance as calculated from the homoeostasis model assessment model, blood pressure, HDL, and triglyceride, and to markers of endothelial dysfunction (plasma levels of von Willebrand factor, tissue plasminogen activator, and cellular fibronectin). A mean standard deviation score of levels of acute phase markers correlated closely with a similar score of insulin resistance syndrome variables (r=0.59, P<0.00005), this relationship being weakened only marginally by removing measures of obesity from the insulin resistance score (r=0.53, P<0.00005). These data suggest that adipose tissue is an important determinant of a low level, chronic inflammatory state as reflected by levels of interleukin-6, tumor necrosis factor-alpha, and C-reactive protein, and that infection with H pylori, C pneumoniae, and cytomegalovirus is not. Moreover, our data support the concept that such a low-level, chronic inflammatory state may induce insulin resistance and endothelial dysfunction and thus link the latter phenomena with obesity and cardiovascular disease.

In 328 type 2 diabetic patients followed for 9.0 years (mean), we investigated whether endothelial dysfunction and chronic inflammation (estimated from plasma markers) can explain the association between (micro)albuminuria and mortality. Of the patients, 113 died. Mortality was increased in patients with baseline microalbuminuria or macroalbuminuria (odds ratios as compared with normoalbuminuria, 1.78 [P < 0.05] and 2.86 [P < 0.01]) and in patients with soluble vascular cell adhesion molecule 1 in the third tertile and C-reactive protein in the second and third tertiles (odds ratios as compared with the first tertile, 2.05 [ P < 0.01], and 1.80 [P < 0.05] and 2.92 [ P < 0.01]). These associations were mutually independent. The mean yearly change in urinary albumin excretion was 9.4%; in von Willebrand factor, 8.1%; in tissue-type plasminogen activator, 2.8%; in soluble vascular cell adhesion molecule 1, 5.2%; in soluble E-selectin, -2.3%; in C-reactive protein, 3.8%; and in fibrinogen, 2.3%. The longitudinal development of urinary albumin excretion was significantly and independently determined by baseline levels of and the longitudinal development of BMI, systolic blood pressure, serum creatinine, glycated hemoglobin and plasma von Willebrand factor (baseline only), soluble E-selectin (baseline only), tissue-type plasminogen activator, C-reactive protein, and fibrinogen. The longitudinal developments of markers of endothelial function and inflammation were interrelated. In type 2 diabetes, increased urinary albumin excretion, endothelial dysfunction, and chronic inflammation are interrelated processes that develop in parallel, progress with time, and are strongly and independently associated with risk of death.

Increased levels of von Willebrand factor (vWf) and C-reactive protein (CRP) predict cardiovascular mortality in selected populations. It is uncertain whether vWf and CRP predict mortality in a general population and whether vWf and CRP predict mortality through similar pathways. This study investigated the association of vWf and CRP with cardiovascular and all-cause mortality among diabetic and nondiabetic subjects. An age-, sex-, and glucose tolerance-stratified sample (n=631) of a population-based cohort aged 50 to 75 years was followed prospectively for 5 years. After 5 years of follow-up, 58 subjects had died (24 of cardiovascular causes). vWf (>1.56 IU/mL) and CRP (>2.84 mg/L) levels in the upper tertile were associated with, respectively, a 3- and 2-fold increase in cardiovascular mortality after adjustment for age, sex, and glucose tolerance status. Analyses in nondiabetic and diabetic subjects separately gave similar results. After further adjustment for hypertension, levels of HDL cholesterol and triglyceride, smoking habits, ischemic heart disease, and peripheral arterial disease, the relative risks (RRs) were 3.0 (95% CI 1.2 to 7.9) for vWf and 1.4 (95% CI 0.6 to 3.5) for CRP. When both vWf and CRP were included in the latter multivariate analysis, the RRs were 3.0 (95% CI 1.1 to 7.9) for vWf and 1.3 (95% CI 0.5 to 3.4) for CRP. The association between vWf and risk of cardiovascular mortality was independent of blood group (O versus non-O) and, moreover, similar among subjects with different blood groups. Repeating the analyses for all-cause mortality gave similar results for CRP. For vWf, the RR was 2.0 (95% CI 1.1 to 3.5) after adjustment for all other risk factors. Increased levels of vWf are independently associated with cardiovascular and all-cause mortality in both diabetic and nondiabetic subjects. The association between increased levels of CRP and cardiovascular mortality was partly explained by other risk factors. Mutual adjustment of vWf and CRP did not markedly change the results, favoring the hypothesis that vWf and CRP predict mortality through different pathways.

Membrane-bound vascular cell adhesion molecule 1 (VCAM-1) allows the tethering and rolling of monocytes and lymphocytes as well as firm attachment and transendothelial migration of leukocytes. Soluble forms of VCAM (sVCAM-1) may serve as monitors of increased expression of membrane-bound VCAM-1 and thus may reflect progressive formation of atherosclerotic lesions. Levels of sVCAM-1 have been found to be increased among type 2 diabetic as compared with nondiabetic subjects. To study the association of plasma sVCAM-1 concentration and risk of cardiovascular and all-cause mortality among nondiabetic and diabetic subjects, we investigated an age-, sex-, and glucose-tolerance-stratified sample (n = 631) of a population-based cohort aged 50-75 years that was followed prospectively. Plasma levels of sVCAM-1 were determined in frozen -70 degrees C baseline samples. After 7.4 years (mean) of follow-up, 107 (17%) subjects had died (42 of cardiovascular causes). In the entire group, increased sVCAM-1 levels were significantly associated with increased risk of cardiovascular mortality (relative risks [RRs] per 100 ng/ml sVCAM-1 increase, 1.10 [1.05-1.15] after adjustment for age, sex, and glucose tolerance status). This RR was somewhat diminished by further adjustment for the presence of hypertension and cardiovascular disease; levels of total, HDL, and LDL cholesterol and homocysteine; the presence of microalbuminuria (a putative marker of endothelial dysfunction); levels of von Willebrand factor (a marker of endothelial dysfunction) and C-reactive protein (a marker of low-grade inflammation); and estimates of glomerular filtration rate. However, the RR remained statistically significant. The RR among type 2 diabetic subjects was 1.13 (1.07-1.20) per 100 ng/ml sVCAM-1 increase after adjustment for age and sex, which was somewhat higher but not significantly different from the RR in nondiabetic subjects (P value for interaction term, 0.12). Further adjustment for other risk factors gave similar results. In conclusion, levels of sVCAM-1 are independently associated with the risk of cardiovascular mortality in type 2 diabetic subjects and therefore might be useful for identifying subjects at increased cardiovascular risk. Increased plasma sVCAM-1 levels may reflect progressive formation of atherosclerotic lesions, or sVCAM-1 itself may have bioactive properties related to cardiovascular risk. Our data, however, argue against the hypotheses of sVCAM-1 levels simply being a marker of endothelial dysfunction, of low-grade inflammation, or of an impaired renal function.