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In this study, high-resolution 600-MHz 1H-NMR (nuclear magnetic resonance) spectroscopies were used to compare the urinary metabolic profiles of healthy humans and humans in a high-selenium area of China. NMR biomarkers for renal and liver lesions were observed by comparing the urine 1H-NMR spectra. In urinary excretion, the concentrations in human urine samples of formate, lactate, acetate, hippurate, and alanine in overexposure to selenium were increased, whereas citrate, creatine, and TMAO excretion were decreased compared with that of the healthy human—some of them even disappeared. An interesting result was the appearance of formate in urine, which has previously been shown to lead to acidosis and chronic renal failure and interfere with the lumen and proximal tubular cells. The level of creatine was associated with the seminal activity. The changes of acetate and citrate may explain the disorder of the cellular energy metabolism caused by selenium, and the changes of other amino acids were a result of the reuptake of these compounds that had been blocked in the glomerulus and proximal tubule. The results elucidate the renal/liver lesion in humans in high-selenium area by 1H-NMR spectroscopy and offer the molecular basic of selenium toxicity. [ABSTRACT FROM AUTHOR]

Selenium (Se) is an essential trace element in animals and human, however, excess Se intake can result in adverse health effects. Se supplementation increased glutathione peroxidase (GSH-Px) and thioredoxin reductase (TR) expressions in Se-deficient rats. However, little information is available on the relationship between Se overexposure on GSH-Px and TR mRNA levels and activities. In this study, the effects of Se overexposure on GSH-Px and TR mRNA levels and activities were investigated by reverse transcription-polymerase chain reaction (RT-PCR) and activity assay. Experimental groups of male Wistar rats were injected intraperitoneally (ip) with sodium selenite at doses of 20, 40, and 80 µg Se/kg/d for 15 d, respectively. Se levels were elevated dose-dependently in rat liver, kidney, and testis tissues. GSH-Px mRNA levels and activities in the liver and testis for rats injected with 20 µg Se/kg/d were increased significantly as compared with those in the control group. However, intraperitoneal injection of 40 and 80 µg Se/kg/d dramatically decreased GSH-Px mRNA expression and activity in liver and testis. The changes of TR mRNA level and activity in the liver and kidney were similar to those of GSH-Px in the liver and testis when supplemented with 40 and 80 µg Se/kg/d. There were no significant effects of Se status on kidney GSH-Px and testis TR expressions. The results suggested that Se overexposure had an adverse effect on GSH-Px and TR mRNA levels and activities, and there could be tissue differences in the regulation of selenoprotein levels. [ABSTRACT FROM AUTHOR]