Unravelling the molecular mechanisms underlying the lifestyle-associated decline in human fertility

• Main Author: Henriques, Magda Alexandra Carvalho
• Publication Date: 2024
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: http://hdl.handle.net/10773/41741
• topic: Human reproduction; Zebrafish; Mercury; Bioaccumulation; Lifestyle; Metabolism

Infertility is a disorder of the reproductive system, manifested by the inability to conceive after 12 months of unprotected sexual intercourse, affecting approximately 15-20% of couples of childbearing age. Globally, there has been a concerning decline in fertility rates. Although many causes have been identified for the majority of infertility cases, in approximately 30%, there is no apparent cause. Various studies suggest that idiopathic infertility may be associated with exposure to environmental pollutants and lifestyle factors. Among pollutants, mercury is considered one of the most toxic metals. Mercury can naturally occur in very low concentrations in the environment due to natural processes such as volcanic eruptions and erosion of the Earth's crust, as well as human activities like mining. Due to its tendency to bioaccumulate, even low concentrations of mercury can cause adverse effects, often irreversible. Studies have shown associations between mercury and the decline in human reproductive health, with higher levels of mercury found in the hair, blood, and urine of individuals with idiopathic infertility. Associations have also been observed between mercury levels and prolonged time to achieve pregnancy, spontaneous abortions, and menstrual changes. However, the molecular mechanisms underlying the effects of mercury on reproductive health remain unknown. This study aims to study the effects of mercury exposure and lifestyle on the reproductive health of the population in Aveiro. The results indicated a considerable mercury exposure in the Aveiro population, potentially leading to an increase in the percentage of sperm with morphological abnormalities and implications during foetal development. The study also demonstrated that lifestyle can negatively influence male reproductive function, specifically, tobacco consumption reducing seminal volume and total sperm count and inducing the activation of proteins involved in the cellular stress response. Furthermore, since it is not possible to assess the effects of mercury on human embryonic development and gonads, an animal model using zebrafish was employed in this study. The results revealed that mercury exposure induces molecular changes with the potential to compromise normal embryonic development. Additionally, the study showed that mercury induces molecular alterations in the zebrafish gonads, resulting in decreased expression of apolipoproteins essential for reproductive function and a decrease in proteins involved in the mitochondrial respiratory chain. Overall, the findings of this study provide valuable information regarding the impact of mercury and lifestyle factors on reproductive health and embryonic development.