Nutritional status of selenium in overweight and obesity: A systematic review and meta-analysis.

BACKGROUND & AIMS: Selenium is an antioxidant and anti-inflammatory nutrient and regulates important physiological processes, such as carbohydrate and lipid metabolism, immune system actions, and adipocyte differentiation. Given these important functions, several studies have assessed the nutritional status of selenium to elucidate whether its homeostasis is impaired by excess adiposity, which in turn could contribute to the adipose tissue dysfunction and metabolic disorders. However, the results of these studies are quite controversial. Therefore, this systematic review and meta-analysis aimed to assess differences in the nutritional status of selenium in overweight/obese individuals. METHODS: We searched the PubMed, Scopus, Web of Science, Embase, Cochrane Library, and Virtual Health Library databases. Studies comparing overweight or obese individuals with eutrophic individuals and assessing at least one marker of selenium were included. Comprehensive Meta-Analysis software was used to perform meta-analysis. The effect size was calculated using the raw mean difference or the standardized mean difference, with 95% confidence interval and a p-value of <0.05. Heterogeneity was determined using the I2 index. Subgroup analyses were performed according to sex, body mass index (BMI), and selenium content in the soil. The protocol of this review was registered in the Prospective Register of Systematic Reviews (registration number: CRD42020185405). RESULTS: This systematic review included 73 articles, of which 65 articles were eligible for meta-analysis. There were no significant differences between the overweight/obesity and eutrophy groups in terms of dietary intake and plasma/serum levels of selenium and selenoprotein P levels. The activity of plasma/serum glutathione peroxidase was decreased in the overweight/obese children and adolescents; however, the difference was no statistically significant when the enzyme activity was analyzed in erythrocytes and whole blood. In the adult age group, overweight/obese individuals had decreased activity of both glutathione peroxidase isoforms compared to those individuals with eutrophy. In particular, the activity of erythrocyte glutathione peroxidase was significantly decreased in obese individuals and those living in regions with low-to-moderate selenium content in the soil. Regarding selenium excretion markers, overweight/obese individuals had lower levels of selenium in the urine and nails and a trend of higher levels of selenium in the hair than eutrophic individuals. CONCLUSIONS: In conditions of excess adiposity, the main alteration in the nutritional status of selenium is a decrease in glutathione peroxidase activity, particularly in adults with obesity. In addition, reduced levels of selenium in urine and nails can be found in overweight or obese individuals.

Effect of zinc supplementation on superoxide dismutase activity in patients with ulcerative rectocolitis.

INTRODUCTION: Ulcerative rectocolitis is characterized by diffuse mucosal inflammation and oxidative stress. Thus, the organism activates the antioxidant defence system in an attempt to reduce the excessive production of reactive oxygen species or neutralize them. OBJECTIVE: This study evaluated the effect of zinc supplementation on the activity of the enzyme superoxide dismutase (SOD) in patients with ulcerative rectocolitis. METHODS: The study included 24 patients, aged between 20 and 59 years and diagnosed with ulcerative rectocolitis, in the remission stage of the disease, who were divided into two groups: experimental - deficient in zinc (n=12) and control - normal or high zinc (n=12). Only the first group underwent supplement intervention, in the form of zinc gluconate (30 mg Zn/day), taken daily in the morning, fasted for 60 days. Plasma and erythrocyte zinc concentrations were determined by flame atomic absorption spectrophotometer. The erythrocyte SOD activity was determined in vitro according to the methodology recommended by the manufacturer Randox. RESULTS AND DISCUSSION: Zinc supplementation caused a significant increase in the plasma concentrations of the mineral, and showed a significant reduction in erythrocyte zinc, remaining within normal limits. The SOD activity was high in patients of both the experimental and control groups, with no difference after supplementation. CONCLUSION: This study demonstrates that zinc supplementation improves the homeostatic condition of the mineral, with no change in SOD activity, as a marker of oxidative stress in patients with ulcerative rectocolitis.

Introducción: La colitis ulcerosa se caracteriza por la inflamación difusa de la mucosa y el estrés oxidativo. De esta forma, el cuerpo activa el sistema de defensa antioxidante en un intento de reducir la producción excesiva de especies reactivas de oxígeno, así como poder neutralizarlos. Objetivo: Este estudio evaluó el efecto de la suplementación de zinc sobre la actividad de la enzima superóxido dismutasa en pacientes con colitis ulcerosa. Métodos: El estudio incluyó 24 pacientes, con edades comprendidas entre 20 y 59 años y con diagnóstico de colitis ulcerosa en fase de remisión de la enfermedad. Los pacientes fueron divididos en dos grupos: experimental - deficiencia de zinc (n = 12) y control - normales o con altos contenido de zinc (n = 12). El grupo experimental se sometió a tratamiento con suplemento de drogas, en forma de gluconato de zinc (30 mg Zn / día), administrada diariamente por la mañana en ayunas durante 60 días. Las concentraciones en plasma y los eritrocitos de zinc se determinaron por espectrofotometría de absorción atómica de llama. La actividad de la superóxido dismutasa (SOD) se determinó por el método de eritrocitos in vitro utilizando el kit de Randox. Resultados y Discusión: La suplementación de zinc causó un aumento significativo en las concentraciones plasmáticas de mineral y mostró una reducción significativa en los eritrocitos, permaneciendo dentro de los límites normales. La actividad de SOD fue mayor en los pacientes de los grupos experimentales y de control, sin diferencias después de la suplementación. Conclusión: El estudio evidenció que la administración de suplementos de zinc mejora la condición homeostática del mineral, sin ningún cambio en la actividad de SOD, como un marcador de estrés oxidativo en pacientes con colitis ulcerosa.