Resumo  Introdução: A queda da 25-hidroxivitamina D [25 (OH) D] na doença renal crônica (DRC) limita a capacidade renal de sintetizar a vitamina. A deficiência de vitamina D, (25(OH)D<20 ng/mL), é prevalente em pacientes com DRC e associada ao estresse oxidativo (EO). Avaliamos possível associação entre a deficiência de vitamina D e EO em pacientes pré-dialíticos.  Métodos: estudo transversal com 206 pacientes com DRC. Exames para 25(OH)D, 1,25(OH)2D, marcadores inflamatórios e EO foram adicionados àqueles de rotina, incluindo creatinina, albumina, cálcio, fósforo, fosfatase alcalina, iPTH, glicose, hemoglobina, ácido úrico, colesterol total , LDL, HDL e triglicerídeos.  Resultados: 55 pacientes com DRC tinham deficiência de vitamina D e os 149 tinham níveis normais da vitamina. Houve uma associação significativa entre a vitamina D e a taxa estimada de filtração glomerular (TFGe). Os níveis de homocisteína foram melhor previstos pela TFGe, gênero e idade; proteína C reativa de alta sensibilidade (hsCRP) por estadiamento e IMC; os metabólitos de óxido nítrico (NOx) aumentaram na doença tardia; a leptina foi influenciada pelo IMC, e mais alta em mulheres, assim como os níveis de adiponectina.  Conclusões: biomarcadores do EO não correlacionaram com a deficiência de vitamina D, mas houve aumento de NOx nos estágios 4-5 da DRC. Apesar dos grandes números de pacientes com DRC, de biomarcadores inflamatórios e EO usados neste estudo, não houve associação entre os níveis de vitamina D e a TFGe. Mais estudos são necessários para avaliar a influência do status da vitamina D no EO em pacientes com DRC em pré-diálise.

Abstract  Introduction: The progressive decline in 25-hydroxyvitamin D [25(OH)D] in chronic kidney disease (CKD) limits the kidney ability of synthesizing the vitamin. Vitamin D deficiency as defined by KDIGO (25(OH)D <20 ng/mL) is prevalent in CKD patients and associated to oxidative stress (OS). We studied a possible association between vitamin D deficiency and OS in pre-dialysis patients.  Methods: A cross-sectional study with 206 CKD patients was carried out. Laboratory tests for 25(OH)D, 1,25(OH)2D, inflammatory markers, and OS were added to routine tests including creatinine, albumin, calcium, phosphorus, alkaline phosphatase, iPTH, glucose, hemoglobin, uric acid, total cholesterol, LDL, HDL, and triglycerides.  Results: Vitamin D deficiency was present in 55 CKD patients and normal vitamin D levels were seen in 149 patients. There was a significant association between vitamin D and estimated glomerular filtration rate (eGRF). Homocysteine levels were best predicted by eGRF, sex, and age; high sensitivity C-reactive protein (hsCRP) by staging and BMI; nitric oxide metabolites (NOx) were increased in late disease; leptin was influenced by BMI and higher in women than man; and adiponectin levels were higher in women.  Conclusions: OS biomarkers were not correlated with vitamin D deficiency but increased NOx were seen in stages 4-5 CKD patients. Even though a relatively large number of CKD patients was included and a broad number of OS and inflammatory biomarkers were used in this studied we failed to find an association between vitamin D levels and eGRF. More studies are needed to evaluate the influence of vitamin D status in OS in pre-dialysis CKD patients.