The present study shows a prevalence of 32% of subclinical atherosclerosis in childhood-onset systemic lupus erythematosus. Similar data were reported in a five-year follow-up prospective study, with 32% of adult SLE patients displaying evidence of carotid atherosclerosis, compared to 4% in healthy controls [31]. To our knowledge, no other study has yet assessed the prevalence of subclinical atherosclerosis in cSLE based on percentiles of CIMT normality and few studies have assessed the atherosclerosis risk factors in cSLE patients [4, 6, 32-33].
Atherosclerosis begins in childhood. The PDAY study (Pathobiological Determinants of Atherosclerosis in Youth), which collected data from over 3,000 autopsies in 10 to 15 years-old subjects who died from trauma, reported that nearly 100% had atherosclerotic lesions in aorta and 50% in coronary arteries [34]. In particular, pediatric patients with chronic inflammatory disease and chronic kidney disease are at high risk to manifest cardiovascular diseases before the age of 30 years [35]. Thus, cSLE patients need special attention in the surveillance for atherosclerosis and it is important to evaluate the arterial health status of these children and adolescents to prevent atherosclerosis progression.
In our study, traditional risk factors, including dyslipidemia, uncontrolled hypertension, obesity, diabetes and contraceptive use, were frequently observed in cSLE and no patient had adequate food intake. Only one patient had the recommended regular physical activity level [15]. In a previous study, Salomão et al showed that Brazilian cSLE patients have worse nutritional status based on lipid and proteomic profiles, homocysteine and folate levels and higher BMI and WC when compared to healthy controls [36]. The same was observed in another Brazilian study where adolescent lupus patients exhibited higher levels of total cholesterol, VLDL, triglycerides and homocysteine compared to healthy controls [37]. Abad et al. evaluated the impact of nutritional intervention in these patients. The nutritional intervention in a group of adolescents with lupus for less than 9 months decreased their energy consumption and intake of macronutrients such as carbohydrates, total fat, and saturated fat and had a protective effect against the increase in fat mass [38]. Therefore, the control of traditional risk factors, mainly with nutritional guidance and incentive to physical activity, is the first step towards the prevention of cardiovascular diseases.
Endothelial dysfunction, assessed by arterial compliance and distensibility, and arterial structure deterioration, assessed by CIMT, are early events in the development of cardiovascular disease [7]. Controversial results have been reported in relation to endothelial function analysis (brachial artery flow-mediated dilation) in childhood lupus. Some studies showed no differences on endothelial function between the control and lupus subjects [37,39], whereas others, mainly studies in adults [32,40] have shown decreased flow-mediated dilation in lupus patients compared to control subjects. The CIMT exam has limitations represented by being difficult to perform, especially in children, due to the arterial size, to obtain precise measurements and the need to perform measurements at the same time during the cardiac cycle [7].
Assessment of CIMT with high-resolution B-mode ultrasonography has emerged as one of the most powerful tools for the evaluation of subclinical atherosclerosis [7].
In the present study, both the absolute values and normality percentiles of the ultrasound measurements were analyzed, to minimize the limitation of not having a control group and normal reference values for the Brazilian population. The two analysis obtained similar results regarding the correlation between CIMT in mm or subclinical atherosclerosis by percentiles [25-28]: in the univariate analysis the associations with SLEDAI-2k > 5, estimated CrCl < 75 ml / min / 1.73 m2, protein to creatinine ratio > 0.2 were statistically significant. The presence of uncontrolled hypertension and short stature were associated only with the media of CIMT in mm and the cholesterol with subclinical atherosclerosis group by percentiles. Only the SLEDAI-2k > 5 maintained significant correlation after the adjusted models.
In the Atherosclerosis Prevention in Pediatric Lupus Erythematosus (APPLE) study, both traditional (increasing age, higher BMI, male sex and higher low-density lipoprotein) and nontraditional risk factors (longer SLE duration, increased creatinine clearance, proteinuria, azathioprine use and prednisone doses) were associated with increased CIMT in 221 lupus patients under 21 years. Vitamin D deficiency was independently associated with elevated hsCRP, a marker of inflammation, which predicts cardiovascular disease risk [6]. In our study, in univariate analysis, only cholesterol levels had a significant association with subclinical atherosclerosis with respect to traditional risk factors and only one patient exhibited vitamin D deficiency.
Although the exact mechanism of atherosclerosis in lupus is not clearly defined, there is evidence that an imbalance between endothelial damage and atheroprotective mechanism seems to be a central event. Insults lead to endothelial damage, and several cytokines and adhesion molecules are involved in this process [41- 45].
Neither increased hsCRP nor plasma levels of the cytokines, most frequently correlated with atherosclerosis in previous studies in lupus, including interleukins (IL), IL-1alpha, IL-1beta, IL-6, IL-10, IL-17; interferon (IFN) alpha and gamma, adhesion molecules, vascular cell adhesion molecule (VCAM-1), intercellular adhesion molecule-1 (ICAM-1) or P-selectin, exhibited significant associations with subclinical atherosclerosis. The small sample size may explain the apparently contradictory results in relation to cytokines in our study.
However, moderate to severe disease activity score was an independent risk factor, suggesting that active inflammation may play a role in subclinical atherosclerosis progression. It is possible that other markers of inflammation may be involved, since atherosclerosis is a chronic multifactorial inflammatory disease [46, 47].
Unlike the APPLE study, our study shows no association between CIMT and use of immunosuppressive drugs, such as azathioprine and prednisone, including current and cumulative doses. Since all patients were using hydroxychloroquine, it was not possible to assess a beneficial effect of the drug on serum lipids, as in previous studies [48].
Regarding disease activity, Baragetti et al., considering SLEDAI changes in a longitudinal study, showed that most patients who develop carotid atherosclerosis are characterized by persistent or worsened disease activity during the five-year observation period, independently of traditional risk factors. In addition, specific T cells subsets such CD4+ CCR5+T cells were independently associated with development of carotid atherosclerosis in SLE patient in this study [31]. Su-Angka et al. reported no significant differences in CIMT between 102 patients with cSLE disease activity and the control group (inactive lupus) [32]. The differences between our study and Su-Angka's report may be related to the age of patients, since they included younger patients, mean 12 (10.8-15.6) years old in their study in comparison to ours, 13.9 (6.4-19.5) years old. In addition, their report excluded patients with other atherosclerosis risk factors, such as diabetes mellitus and family history of hypercholesterolemia.
The renal involvement, with the highest scores in the disease activity index, has been associated with CIMT. Falashi et al. evaluated twenty-six cSLE patients and reported that patients with nephrotic-range proteinuria have significantly higher CIMT than those without proteinuria [4]. History of lupus nephritis and hypertension were correlated with CIMT in a seven-year surveillance in another SLE study that showed no difference in progression of subclinical atherosclerosis between patients with mild lupus and control subjects [49]. On the other hand, Sharma et al. reported no significant differences in CIMT between 102 SLE patients with and without nephritis, although the nephritis group exhibited a higher SLEDAI score, more persistent inflammation and, consequently, higher risk to developed arterial injury leading to early end-organ damage [50]. In our study estimated CrCl < 75 ml/ min / 1.73 m2 and moderate to severe range proteinuria were associated with CIMT, although no significant association was found after the adjusted models.
Huang et al., in a six-year period longitudinal study, reported that lymphopenia at diagnosis and higher baseline levels of serum creatinine and C-reactive protein are positively associated with progression of CIMT, but only lymphopenia is consistently associated with progression of CIMT in multivariable analysis [33]. Our study showed no specific association with hematological changes and CIMT. However, despite the different results among the studies, they invariably show associations between clinical and laboratory findings and disease activity. Thus, adequate control of disease activity, in addition to monitoring traditional risk factors, is essential to prevent atherosclerosis in cSLE.
Despite great diversity in the studied population and the ethnic origin of cSLE patients, it is agreed that lupus patients are at high risk of developing atherosclerosis, regardless of traditional risk factors.
Longitudinal studies with long time follow up and standardization of validated measurement procedures for the studied population are necessary. Until now, most studies, including ours, correlate active lupus and / or factors related to disease activity with a higher incidence of subclinical atherosclerosis or rapid progression to atherosclerosis.
The CIMT is a non-invasive, reproducible, low cost, and high accuracy tools for the evaluation of subclinical atherosclerosis. But, until now, no standard recommendation is available for monitoring patients for the progression of atherosclerosis with this method in clinical practice, including periodic assessment time [6]. However, international clinical trials were able to demonstrate a significant decrease in CIMT within 1 year with diet and exercise intervention [52] and 2 years after statin therapy intervention [53]. Thus, one year is already sufficient for changes in CIMT values. Although longitudinal studies, with a long time follow up and standardization of validated measurement procedures are necessary, we recommend checking the risk factors for atherosclerosis of cSLE patients, including disease activity, at every medical visit, and assessment of the CIMT at least every two years.
The early institution of measures to prevent atherosclerosis progression, decreasing long-term cardiovascular complications, could provide a better quality of life and longer survival to our patients.
Our study has limitations that include a small sample size, cross-sectional design and absence of a control group. However, to our knowledge, this is the first study that uses the normative percentile values for CIMT in children and adolescents with lupus to categorize them into two groups, with and without subclinical atherosclerosis. Our data clearly show an adequate and strong association between the mean CIMT in mm, a marker of subclinical atherosclerosis, and disease activity in cSLE.