Background: The essential micronutrient Selenium (Se) is critical for human health. The thyroid gland contains the highest Se concentration; seleno-proteins are responsible for thyroid hormone (TH) synthesis. Moderate Se-deficiency may impact seleno-protein function and impair TH synthesis leading to metabolic disorders and infertility. While Se supplementation improves clinical outcomes, there is no consensus on the correct dose and form of dietary Se for humans, leading to conflicting guidelines on optimal dietary Se concentrations.
Aims: This project provided male C57BL/6 mice standard chow (control, 0.3ppm/kg) and three dietary Se forms (chow-containing selenite (NaSe, 5ppm/kg), methylselenocysteine (Met 10ppm/kg) and diphenyl diselenide (DDS 15ppm/kg)) to assess their potential in thyroid/reproductive health, and body metabolism.
Methods and Results: EchoMRI studies revealed that the DDS diet decreased body weight significantly including lean and fat mass. However, circulating TH levels in the same mice was identical to the controls as determined by quantitative ELISA, which suggests that reduced lean/fat masses were likely due to lower food intake rather than enhanced metabolism. By contrast, mice fed with dietary NaSe and Met trended to lower fat mass, although lean mass/body weight were comparable to the control. These outcomes suggest enhanced body metabolism in mice receiving dietary NaSe and Met, as a corresponding elevation in TH and thyroid-stimulating hormone (TSH) was observed in these same mice. Interestingly, NaSe and Met diets caused significant increase in sperm motility consistent with enhanced testicular function, while mice taking the DDS diet showed significantly lower testicular weight, sperm count and motility compared to NaSe, Met and control.
Conclusions: Taken together, our data indicate that dietary NaSe and Met improved thyroid/testicular function, enhanced body metabolism and weight loss with a concomitant enhancement of factors affecting male fertility, further studies are warranted to evaluate the levels, activities, and seleno-toxicity with reference to thyroid/testicular functions.