RESUMO
The diagnosis of male infertility is based essentially on the patient's medical history and a standard semen analysis. However, the latter rarely provides information on the causes of a possible infertility, emphasizing the need to extend the analysis of the sperm function. Mitochondrial function has been associated with sperm function and dysfunction, the latter primarily through the production of excessive amounts of reactive oxygen species (ROS). We hypothesized that analysis of sperm mitochondrial metabolism together with sperm ROS production could be an additional tool to improve routine semen analysis, after appropriate validations. To test our hypothesis, we performed several experiments using a non-routine method (high-resolution respirometry, HRR) to access mitochondrial function. First, we investigated whether mitochondrial function is related to human sperm motility and morphology. When mitochondrial metabolism was challenged, sperm motility decreased significantly. Additionally, morphological abnormalities in the sperm mid-piece and mitochondria were associated with global sperm defects evaluated by routine methods. Subsequently, sperm mitochondrial function was assessed by HRR. Respiratory control ratio (RCR) was determined and evaluated in the context of classical sperm analysis. In parallel, sperm hydrogen peroxide (H2O2) production and seminal plasma (SP) antioxidant capacity were measured. The percentage of sperm with progressive motility correlated positively with RCR, SP antioxidant capacity, and negatively with the concentration of extracellular H2O2 production ([H2O2]). The percentage of normal sperm morphology correlated positively with RCR and negatively with [H2O2]. Sperm morphology did not correlate with seminal plasma antioxidant capacity. Furthermore, Receiver Operating Characteristic curves were used for the first time to test the diagnostic ability of RCR, [H2O2], and SP antioxidant capacity as binary classifiers. An RCR cut off value of 3.2 was established with a sensitivity of 73% and a specificity of 61%, using reference values considered normal or abnormal in routine semen analysis. The cut off value for [H2O2] was 0.2 µM/106 sperm (sensitivity = 65%, specificity = 60%). There were no reference values for SP antioxidant capacity that distinguished between abnormal and normal sperm samples. We conclude that sperm mitochondrial function indices in combination with [H2O2] may be useful tools to complement the routine semen analysis.
RESUMO
BACKGROUND: Over the last years, there has been an increasing concern about a global decline in men's fertility. Specifically, some evidence indicates that sperm quality has decreased over the last years. However, reports showing the changes in sperm quality with time are inconsistent. Part of the contradictions between studies is attributed to geographical differences. Surprisingly, few studies include data from South American countries, creating a bias in the conclusions. This study aims to determine how sperm quality has evolved over the past 30 years in Uruguay. For this purpose, 317 medical records from allegedly healthy sperm donor candidates, aged between 18 and 36 years old, who voluntarily requested to be considered as sperm donors between 1988 and 2019, were analyzed. The studied variables were the following sperm parameters: semen volume, sperm cell concentration, total sperm number, progressive motility, vitality, and sperm morphology. A correlative statistical analysis was performed between seminal parameter values and the year data were collected. RESULTS: We found a statistically significant decrease in sperm concentration and normal sperm morphology during the studied period. There was no decrease in vitality, seminal volume, and total progressive motility. Semen parameters were not associated with tobacco, drugs, or alcohol consumption. CONCLUSIONS: We conclude that the sperm quality of donor candidates in Uruguay decreased during this period. Further studies should be carried out to verify the occurrence of this phenomenon in the general population and find its possible causes.
RéSUMé: CONTEXTE: Au cours des dernières années, on s'est de plus en plus inquiété d'une baisse de la fertilité masculine. Plus précisément, certaines données indiquent que la qualité du sperme a diminué au cours des dernières années. Cependant, les rapports montrant les changements dans la qualité du sperme avec le temps sont incohérents. Une partie des contradictions entre les études est attribuée à des différences géographiques. Étonnamment, peu d'études ont inclue des données provenant de pays d'Amérique du Sud, ce qui crée un biais dans les conclusions. Cette étude vise à déterminer comment la qualité du sperme a évolué au cours des 30 dernières années en Uruguay. À cette fin, 317 dossiers médicaux de candidats donneurs de sperme prétendument en bonne santé, âgés de 18 à 36 ans, qui ont volontairement demandé à être considérés comme donneurs de sperme entre 1988 et 2019, ont été analysés. Les variables étudiées étaient les paramètres suivants du sperme: volume de sperme, concentration de cellules spermatiques, nombre total de spermatozoïdes, motilité progressive, vitalité, et morphologie des spermatozoïdes. Une analyse statistique corrélative a été effectuée entre les valeurs des paramètres séminaux et l'année de recueil des données. RéSULTATS: Nous avons trouvé une diminution statistiquement significative de la concentration de spermatozoïdes et de la morphologie normale des spermatozoïdes pendant la période étudiée. Il n'y a eu aucune diminution de la vitalité, du volume de sperme, et de la motilité progressive totale. Les paramètres du sperme n'étaient pas associés à la consommation de tabac, de drogues ou d'alcool. CONCLUSIONS: Nous concluons que la qualité du sperme des candidats donneurs en Uruguay a diminué au cours de cette période. D'autres études devraient être menées pour vérifier l'apparition de ce phénomène dans la population générale et en trouver les causes possibles.
