This is a cross-sectional controlled study evaluating 22 A-T patients of both genders, between 3 and 27 years of age, who were diagnosed with probable A-T (clinical phenotype classical) according to the criteria of the European Society for Immunodeficiencies (ESID) [18, 19].
The control group was recruited from a Primary Health Care Service and composed of 18 healthy volunteers matched by age and gender.
The Research Ethics Committee from the Federal University of São Paulo and financed by The São Paulo Research Foundation - FAPESP n º 2015/13308-9.
The demographic, clinical, and treatment data were obtained from the patients’ charts. The family history risk of atherosclerosis was assessed for patients and controls.
At the time of sample collection, none of the subjects had an acute infectious disease, nor had they been using corticosteroids for at least 3 months; one patient was using antifungal drug and five were using antibiotics.
Anthropometric assessment and food intake
The anthropometric assessment involved measurements of weight, height, mid-upper arm circumference (MUAC), and skinfold thickness (tricipital, subscapular, bicipital, and sacroiliac) as proposed by the World Health Organization (WHO) and Frisancho (1990) [20, 21]. The patients who were unable to stand upright had their weight measured in the wheelchair, on a specific scale for wheelchair-users (Micheletti - capacity 1100 lbs - serial: 2161058). Recumbent height was measured with the patient lying on a flat and firm surface, using an inextensible tape graduated in centimeters.
To assess the body mass index (BMI) and height for age (H/A) of children and adolescents, expressed as Z-scores, the WHO [22] criteria and the classification proposed by De Onis et al. were adopted [23]. For adults, the cut-off point of the WHO for BMI was used [20]. The sum of skinfold thickness and MUAC was used to estimate children’s body composition [24-26]. While for adults, the estimation of body composition was based on the sum of the four different skinfolds [27]. The body fat percentage was classified according to Deurenberg et al and Lohman [25, 26].
The pubertal stage was evaluated according to Marshall and Tanner [28].
The assessment of food intake was performed using a 24 h dietary recall (R24hs), applied 3 times, with an interval of 15 days between them. The calculation of nutrients was performed using the Software Dietwin ®, comparing the cases to the controls [29, 30].
Considering that food composition tables available in some software do not have complete data on Se content in food, these data were included manually based on the article by Ferreira et al. (2002) [31]. Only one of A-T patients had feeding tubes.
Biochemical Assessment
After 8-hour fasting, blood was collected by peripheral venipuncture to analyze plasma selenium, erythrocyte glutathione peroxidase activity, lipid profile, apolipoproteins A-1 and B (Apo A-1, Apo B), oxidized LDL (LDLox), malondialdehyde (MDA), ultra-sensitive C-reactive protein (us-CRP), adiponectin, insulin, glucose, aspartate aminotransferase (AST), alanine transaminase (ALT), and gamma-glutamyl transpeptidase (Gamma GT).
All analyzes were performed using standard methods and good practice in clinical analysis. For determination of plasma selenium levels, the method used was atomic absorption spectrophotometry by graphite oven, with a detection limit of 1.0 mcg/L and linearity of 400.0 µg/L. The coefficient of variance was 0.8%. us-CRP was determined using the turbidimetric-immunological method (Roche). The measurement range is 1.0 to 200 mg/L. The variation coefficient was 1.3%. GPx activity was determined by the method based on that of Paglia and Valentine. (RANDOX). The method is linear up to a concentration of 925 U/L. The sensitivity was 75 U/L and the coefficient of variance was 3.4%. The lipid peroxidation was determined by the TBARS method (thiobarbituric acid-reactive substances) which is based on the reaction of malondialdehyde (MDA), a compound formed by the oxidation of lipids, with thiobarbituric acid (TBA) and is given in MDA equivalents, according to Satoh (1978) [32].
For classification of selenium levels, the cut-off point ≤ 46 µg/L was adopted for inadequacy. Glutathione peroxidase activity values lower than 4171 U/L were considered inadequate.
The lipid profile, including triglyceride, total cholesterol and high-density lipoprotein cholesterol (HDL-c) was measured by enzymatic-colorimetric tests. Low-density lipoprotein cholesterol (LDL-c) and very-low-density lipoprotein cholesterol (VLDL-c) were calculated using the formula by Friedewald et al. (1972) [33].
For classification, the cut-off points suggested by the American Academy of Pediatrics [34] and the National Cholesterol Education Program (NCEP) [35] were adopted. The presence of dyslipidemia was considered when the TC> 170 mg / dL for children / adolescents and> 200 mg / dL for adults and / or LDL-c> 110 mg / dL for children / adolescents and> 129 mg / dL for adults and / or triglycerides> 100 mg / dL for children / adolescents and> 150 mg / dL for adults and / or HDL-c <35 mg / dL for children / adolescents, <40 mg / dL for women and <50 mg / dL for men.
The non-HDL-c (NHDL-c) values were obtained by subtracting the HDL-c rates from the TC levels and classified according to Bogalusa [36] and NCEP. The following atherogenic indices were also calculated: total cholesterol/ HDL-c, Apo B/Apo A-1, LDL-c/Apo B, LDL-c/HDL-c [37], HDL-c/Apo A-1 [38].
Apo A-1 and Apo B were measured using kits of turbidimetric methods for human Apo A-1 and Apo B (Roche, Indianapolis, IN, USA) and oxidized LDL, (ELISA)PRO (Wuhan Fine Biological Technology Co, Wuhan, China).
Glycemia was measured by enzymatic reference method with hexokinase, while insulin was quantified by electrochemiluminescence. Using the fasting glucose and insulin values, the HOMA-IR (Homeostasis Model Assessment of Insulin Resistance) rate was calculated utilizing the following formula: HOMA-IR = fasting glucose (mmol / L) x fasting insulin (µU / mL) / 22.5. HOMA-IR was considerably elevated when > 3.16 [39].
To evaluate cardiovascular risk we consider inflammatory, oxidative stress and lipid status biomarkers.
Statistical Analysis
The SPSS 25.0 statistical package was used for statistical analysis. In the descriptive and bivariate analysis, categorical variables were presented in absolute and percentage numbers, and compared using the Chi-square test or Fisher’s exact test. Most continuous variables showed a non-parametric distribution and was decided to present them as medians and interquartile intervals and compare them using the Mann-Whitney test. The correlation between glutathione peroxidase activity and selenium levels was evaluated with Spearman test (rho).
The area under the ROC curve (AUC) along with the corresponding 95% confidence interval (CI). One ROC curve was reported to assess the discriminatory power between the variables studied which had a difference between groups in the univariate analysis. Lastly, a multi-ROC curve was generated for evaluated the discriminatory power of variable related to oxidative stress (glutathione peroxidase activity, malondialdehyde levels and group) and lipid biomarkers (oxidized LDL, Non-HDL cholesterol, Apo A-1/HDL-c, Apo B / Apo A-1 and group) in relation to selenium levels (≤ 46 µg/L e > 46 µg/L).
For multivariate analysis was used linear regression (ENTER method) with selenium (logarithm) as the dependent variable. The independent variables included in the model were those that had clinical relevance and those that showed a statistically significant difference in the bivariate analysis, excluding those in which collinearity was detected (correlation> 0.8). Thus, the model was built with group, age, us C-reactive protein, oxidized LDL, malondialdehyde, apoliprotein B/apoliprotein A-1, glutathione peroxidase activity and alanine aminotransferase.
A p-value less than 0.05 was considered statistically significant.