Different Forms of Selenium Unlocked: Investigating their Effects on Metabolism, Infertility, Reproduction, and Microbial Diversity

Abstract

This thesis aims to investigate the effects of selenium (Se) supplementation on various aspects of health and well-being, including thyroid function and metabolism, male reproductive health, and gut microbiome. The hypothesis posits that adequate supply of dietary Se, in its optimal chemical form and at the appropriate dosage, could have far-reaching benefits for overall health and well-being. The study had four main objectives: (1) to assess thyroid function by comparing the levels of T3, T4, and TSH hormones, as well as the levels of GPx1/4 and DIO1, (2) to investigate the effects of Se supplementation on male reproductive health, including sperm count, motility, and vitality, (3) to characterise histological changes in the testicular structure and determine the presence of selenoproteins GPx1/4 in testes through the use of Immunohistochemistry, and (4) to differentiate the differences in the gastrointestinal microbiome between mice that have been fed Se-supplemented diets and those that have been fed standard chow. The main findings of the study are as follows. First, the study found that the most effective outcomes of Se supplementation were observed with the use of Nanoparticle Selenium (NanoSe) and this was limited to the short-term where a beneficial adaptive response was evident before fading to the control metabolic state. Notably, Se in the form Diphenyl Deiselenide (DDS) showed distinct differences in metabolism and biochemistry. Further research is necessary to establish a comprehensive understanding of the potency of NanoSe over an extended time period. Second, the study indicates that the use of various forms of Se, such as Sodium Selenite (NaSe), Methyl-selenocysteine (Met), and NanoSe, can result in an increase in testicular weight, testosterone levels and an improvement in sperm count, motility, and other male reproductive parameters. Third, this study has demonstrated that NanoSe has the most efficacious results in terms of altering microbiome composition, while the chemical form of diphenyl diselenide (DDS) exhibits significantly differing results in metabolism and biochemical analyses. In conclusion, the findings of this thesis suggest that adequate supply of dietary Se, in its optimal chemical form and at the appropriate dosage, can have significant benefits for overall health and well-being. The results of this study have important implications for public health and highlight the need for further research to fully understand the long-term safety and efficacy of Se supplementation.