Background/Aim: The pathogenesis of Nonalcoholic Fatty Liver Disease remains largely unknown, but oxidative stress seems to be involved. The aim of this study was to evaluate the role of oxidative stress in experimental hepatic steatosis induced by a choline‐deficient diet.Methods: Fatty liver disease was induced in Wistar rats by a choline‐deficient diet. The animals were randomized into three groups: I (G1) and II (G2), n=6 each ‐ fed with a choline‐deficient diet for four and twelve weeks respectively; Group III (control‐G3; n=6) ‐ fed with a standard diet for twelve weeks. Samples of plasma and liver were submitted to biochemical, histological and oxidative stress analysis. Variables measured included serum levels of aminotransferases (AST, ALT), cholesterol and triglycerides. Oxidative stress was measured by lucigenin‐enhanced luminescence and the concentration of hydroperoxides (CE‐OOH‐cholesteryl ester) in the liver tissue. Results: We observed moderate macro‐ and microvesicular fatty change in periportal zones G1 and G2 as compared to controls (G3). In G2, fatty change was more severe. The inflammatory infiltrate was scanty and no fibrosis was seen in any group. There was a significant increase of AST and triglycerides in G1 and G2 as compared to control group G3. The lucigenin‐amplified luminescence (cpm/mg/min × 10³) was significantly increased in G1 (1393±790) and G2 (7191±500) as compared to controls (513±170),p<0.05. The concentrations of CE‐OOH were higher in G1 (5.7±0.9 nmol/mg protein) as compared to control (2.6±0.7 nmol/mg protein),p<0.05. Conclusion: 1) Oxidative stress was found to be increased in experimental liver steatosis; 2) The production of reactive oxygen species was accentuated when liver steatosis was more severe; 3) The alterations produced by oxidative stress could be an important step in the pathogenesis of nonalcoholic fatty liver disease.

Thiol groups have been described as the main responsible for antioxidative effects of plasmatic proteins. Also, thiol serum levels have shown a positive correlation with total antioxidant capacity (TAC) in many studies. Measurement of TAC by substract oxidation-based methods have been widely used as a reference to measure antioxidant status; however, in many cases these methods are inexact or imprecise, usually when performed by manual procedures. In this paper we describe a simple automated procedure for the determination of total thiols in serum, which was based on Ellman’s method. It was correlated with several markers of oxidative/antioxidative status, such as TAC and thiobarbituric acid reactive substance test (TBARs). Serum thiol levels were correlated positively with TAC (r = 0.298, p < 0.001) and negatively with TBARs levels (r = -0.330, p < 0.001). The novel automated procedure for thiol groups measurement can be a great tool in estimation of antioxidant status together with TAC assay. This procedure makes the determination of total thiol groups in large scale possible in clinical chemistry or research laboratories where this approach is necessary. Os tióis são descritos como os principais responsáveis pelos efeitos antioxidantes das proteínas plasmáticas. Além disso, diversos estudos mostram uma correlação positiva entre os níveis séricos de tióis e a capacidade antioxidante total (CAT). A medida da CAT por métodos baseados na oxidação de substratos tem sido amplamente usada como referência na estimativa da capacidade antioxidante em amostras biológicas; porém, em muitos casos esses métodos são inexatos e imprecisos, principalmente quando realizados por procedimentos não-automatizados. Neste artigo descrevemos um procedimento automatizado simples para a determinação de tióis totais no soro, com base no conhecido método de Ellman. A dosagem dos tióis foi correlacionada com diversos marcadores da capacidade oxidante/antioxidante, como a CAT, o teste das substâncias reativas ao ácido tiobarbitúrico (TBARs) e os níveis de peróxidos totais. Os tióis correlacionaram-se positivamente com a CAT (r = 0,298; p < 0,001) e negativamente com os níveis de TBARs (r = - 0,330; p < 0,001). O procedimento aqui descrito para a dosagem de tióis pode ser uma ferramenta importante na medida da capacidade antioxidante juntamente com a dosagem da CAT. A utilização desse novo procedimento possibilita a determinação dos tióis totais em larga escala por laboratórios clínicos e de pesquisa onde essa demanda é necessária