A randomized-controlled, double-blind study of the impact of selenium supplementation on thyroid autoimmunity and inflammation with focus on the GPx1 genotypes.

PURPOSE: To analyze the impact of selenium supplementation on serum antiTPO levels and thyroid echogenicity in patients with CAT, evaluating the response in subgroups with different GPx1 genotypes. METHODS: CAT patients (n = 55) with positive antiTPO were randomized to selenomethionine (SeMet) 200 µg daily (n = 28) or placebo (n = 27) for 3 months. Assessments included GPx1 genotyping at baseline and serum levels of plasma selenium, erythrocyte GPx1 activity, antiTPO and thyroid echogenicity at baseline, and 3 and 6 months. RESULTS: In the SeMet group, the increase in plasma levels of selenium and erythrocyte GPx1 activity was similar among patients with different GPx1 genotypes. In the overall cohort, patients randomized to SeMet showed a 5 % decrease in antiTPO levels at 3 months (p = non-significant) and 20 % at 6 months (p < 0.001 versus 3 months). In contrast, patients in the placebo group did not show significant changes in antiTPO levels at any time point. Subgroup analysis showed that patients with different GPx1 genotypes presented comparable responses in antiTPO levels and echogenicity index to SeMet. CONCLUSIONS: Selenium supplementation decreased serum antiTPO levels in CAT patients, with similar response among patients with different GPx1 genotypes.

A follow-up study of the chronic kidney disease patients treated with Brazil nut: focus on inflammation and oxidative stress.

Brazil nut is the richest known food source of selenium. The supplementation with Brazil nut during 3 months was effective in reducing oxidative stress and inflammation in hemodialysis (HD) patients. However, there are no available data on the antioxidant effect after that supplementation. The objective of this work was to determine if the beneficial effects of one Brazil nut supplementation per day during 3 months for the HD patients could be sustained after 12 months. Twenty-nine HD patients (58.6 % men, 51.0 ± 3.3 years) from RenalCor Clinic, Rio de Janeiro, Brazil, were followed up 12 months after the supplementation study had finished. The plasma levels of antioxidant substances as selenium, glutathione peroxidase (GPx), 8-isoprostane, 8-hydroxy-2-deoxyguanosine (8-OHdG) and cytokines (tumour necrosis factor alpha (TNF-α) and interleukin-6 (IL-6)) were determined before, after 3 months of supplementation and after 12 months. After 3-months supplementation, cytokines, 8-OHdG and 8-isoprostane plasma levels have decreased and the activity of GPx and selenium plasma levels have increased significantly. Additionally, after 12 months, the values of 8-isoprostane, 8-OHdG and cytokines increased and the activity of GPx and selenium plasma levels decreased significantly. The levels of oxidative stress and inflammation biomarkers after 12 months increased compared to the basal levels. Consequently, it is necessary to motivate patients to adopt different dietary intake patterns.

Effect of Brazil nut supplementation on the blood levels of selenium and glutathione peroxidase in hemodialysis patients.

OBJECTIVE: In patients who have undergone hemodialysis, large amounts of reactive oxygen species (ROS) are produced and, at higher concentrations, ROS are thought to be involved in the pathogenesis of cardiovascular disease. It has been proposed that selenium (Se) may exert an antiatherogenic influence by reducing oxidative stress. The richest known food source of selenium is the Brazil nut (Bertholletia excelsa, family Lecythidaceae), found in the Amazon region. We evaluated the effect of Brazil nut supplementation on blood levels of Se and glutathione peroxidase (GSH-Px) activity in patients on hemodialysis. METHODS: A total of 81 patients on hemodialysis (52.0±15.2 y old, average time on dialysis 82.3±91.4 mo, body mass index 24.9±4.4 kg/m(2)) from the RenalCor and RenalVida Clinics in Rio de Janeiro, Brazil, were studied. All patients received one nut (around 5 g, averaging 58.1 µg Se/g) a day for 3 mo. The Se concentrations in the nuts and in plasma and erythrocytes were determined by atomic absorption spectrophotometry with hydride generation (Hitachi, Z-500). GSH-Px levels were measured using Randox commercial kits. RESULTS: Plasma Se (18.8±17.4 µg/L) and erythrocyte (72.4±37.9 µg/L) levels were below the normal range before nut supplementation. After supplementation, the plasma level increased to 104.0±65.0 µg/L and erythrocytes to 244.1±119.5 µg/L (P<0.0001). The activity of GSH-Px also increased after supplementation, from 46.6±14.9 to 55.9±23.6 U/g of hemoglobin (P<0.0001). Before supplementation, 11% of patients had GSH-Px activity below the normal range (27.5-73.6 U/g of hemoglobin). After supplementation, all patients showed GSH-Px activity within the normal range. CONCLUSION: The data revealed that the investigated patients presented Se deficiency and that the consumption of only one Brazil nut a day (5 g) during 3 mo was effective to increase the Se concentration and GSH-Px activity in these patients, thus improving their antioxidant status.