© 2004 by the American Diabetes Association, Inc.
Acute Respiratory Viral Infections Aggravate Arterial Endothelial Dysfunction in Children With Type 1 Diabetes
1 Division of Pediatric Cardiology, Lund University Hospital, Lund, Sweden Address correspondence and reprint requests to Petru Liuba, PhD, MD, Pediatric Cardiology, Lund University Hospital, 221 85 Lund, Sweden. E-mail: petru.liuba{at}pedi.lu.se
Abbreviations: CRP, C-reactive protein FMD, flow-mediated dilatation GTN, glyceryl-trinitrate vWF, von Willebrand antigen
Despite improvements in therapy for children with type 1 diabetes, the prevalence of cardiovascular morbidity in adulthood due to accelerated atherosclerosis remains significant (1). Similar to other cardiovascular risk factors, the diabetic state facilitates arterial endothelial injury, a primary event in the pathogenesis of atherosclerosis (2). Although several pediatric studies have reported an association of diabetes with arterial endothelial dysfunction (3,4), pathogenic animal studies have suggested that even though this disease predisposes to endothelial dysfunction and atherosclerosis, it might not be sufficient to cause them (5). Notably, type 1 diabetes increases the propensity for both chronic and acute infections in part by weakening the immune mechanisms (6). The risk is particularly increased for respiratory tract infections, but other infections have also been associated with diabetes (7). Furthermore, diabetic patients are at greater risk for infection-related mortality (8), and the excess risk appears to be linked to cardiovascular diseases (9). In the present study, we investigated whether viral respiratory tract infections in children with type 1 diabetes might impose an additional burden on the arterial endothelial function.
A total of 26 children (aged 618 years, mean [±SD] age 14 ± 3 years) with type 1 diabetes (duration 6 ± 3 years) were recruited. Of these, 11 children had a clinically manifested upper respiratory tract infection (body temperature >38°C and flu-like symptoms) 68 weeks before the study day. None of the children who had the infection required antibiotic treatment or hospitalization. Ten age- and weight-matched healthy children served as control subjects. None of the control subjects and remaining diabetic children had a history of infection or other acute inflammatory disease within the preceding 3 months. Exclusion criteria were clinically manifested angiopathy, hypertension, obesity (BMI >25 kg/m2), smoking, pregnancy, and early coronary heart disease among first-degree relatives. The study was approved by the Lund University ethics committee. Weight and blood pressure were measured on the ultrasound day. Venous samples were collected from the diabetic children following the ultrasound study. Data on age, diabetes duration, and mean HbA1c (3 months before the study) were obtained from the registry of the outpatient diabetes clinic.
Blood analyses
Endothelium-dependent and -independent reactivity of the brachial artery
Statistical analyses
Clinical and metabolic profile With the exception of vWF, which was higher in the diabetic children who had infection (P < 0.05), no differences in the studied variables were noted between the infection and noninfection diabetic children (Table 1). Overall, in diabetic children, a direct correlation was noted between oxidized LDL and CRP (r = 0.5, P = 0.03).
Baseline diameter and GTN-induced and flow-mediated dilatation of brachial artery Neither the baseline diameter nor the GTN-induced dilatory responses of the brachial artery (Table 1) differed between the groups (P > 0.5). In contrast, diabetic children who had infection had significantly lower FMD than diabetic children without infection (P < 0.01) and control subjects (P < 0.001) (Table 1). In the infection group, FMD was inversely related to orosomucoid (r = 0.8, P < 0.05). The FMD of the entire diabetic group (infected and noninfected children) was 5.6 ± 2% and inversely correlated with vWF (r = 0.4, P < 0.05), CRP (r = 0.6, P = 0.01), and LDL cholesterol (r = 0.6, P < 0.01).
The present study provides suggestive evidence that acute respiratory viral infections could aggravate the arterial endothelial dysfunction in children with type 1 diabetes, as indicated by the significantly lower FMD and higher vWF in the postinfection diabetic children. In keeping with other studies (3,4), we found that FMD of the brachial artery is profoundly altered in children with diabetes, and this appears to be mediated in part by a low-grade systemic inflammation (defined by high-sensitivity CRP and elevated LDL cholesterol levels), as suggested by their inverse correlation with FMD. Recurrent acute respiratory infections are more common in diabetic patients, seemingly as a consequence of impaired immunity (8). Acute infections could cause short-lasting inflammatory responses with subsequent endothelial damage, which, depending on the number of infections in time and presence of additional cardiovascular risk factors (e.g., diabetes), might be critical to atherosclerosis development (11). Indeed, earlier pediatric studies have suggested that various types of acute infections could elicit proatherogenic changes in arterial structure (12). The main limitation of this study resides in the small sample size, which could have influenced the statistical power. The cross-sectional nature of this study precludes conclusions with regard to the possible implications of the infection-related endothelial changes in the pathogenesis of atherosclerosis in diabetic children. However, in view of the central role of endothelial dysfunction in the development of atherosclerosis and its multifactorial etiology, it is conceivable that augmentation of endothelial dysfunction by infections could further increase the susceptibility to accelerated atherosclerosis in the diabetes milieu. This issue needs to be addressed by future large-scale prospective studies.
This study was supported by grants from the Swedish Royal Physiographic Society (to P.L.), Anna-Lisa and Sven-Eric Lundgrens Foundation for Medical Research (to P.L.), Barndiabetesfonden (to S.S.), and Lund University Hospital (to P.L.). We thank Annica Maxedius, RN, for excellent technical assistance. We also acknowledge Irén Tiberg, RN, and Annette Leger, RN, for their support in patient recruitment.
A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances. Received for publication June 10, 2004. Accepted for publication July 21, 2004.
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