Spermatozoa capacitation is a complex process that requires specific ionic and energetic conditions to support biochemical alterations leading to motility hyperactivation. However, human sperm capacitation is still poorly understood. Herein, we studied the effects of glucose on human sperm capacitation. Healthy men seminal samples (n = 55) were submitted to a density gradient centrifugation and incubated in capacitating conditions in the absence or presence of increasing glucose concentrations (0, 5.5, 11, and 22 mM). Viability and total motility were accessed. Phosphotyrosine levels were measured. Mitochondrial activity and endogenous ROS production were evaluated. Oxidative stress-induced damage was analyzed. Culture media was collected and analyzed by ¹H-NMR. Our results show that glucose is essential for human sperm capacitation and motility. Notably, we observed that mitochondrial activity increased even in the absence of glucose. This increased mitochondrial activity was followed by a ROS overproduction, although no oxidative stress-induced damage was detected. Our results show that glucose is essential for capacitation but mitochondrial activation is independent from its stimuli. ROS overproduction may take part on a finely regulated signaling pathway that modulates or even activates capacitation. Taken together, our results constitute a paradigm shift on human sperm capacitation physiology.

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder affecting women of reproductive age, yet the molecular mechanisms influencing its pathophysiology remain poorly defined. A comprehensive prospective case-control study was conducted to elucidate the follicular fluid (FF) hormone and metabolite profile in women with PCOS and its implications for oocyte maturation and fertilization. The study involved 40 age- and body mass index (BMI)-matched women undergoing in vitro fertilization (IVF), including 20 diagnosed with PCOS and 20 controls with infertility due to tubal or male factors. A distinctive hormone profile in the FF of women with PCOS was identified, characterized by significantly higher anti-Müllerian hormone (AMH) levels (24.90±17.61 vs. 16.68±17.67 pmol/L, p=0.0039) and lower progesterone (8253±4748 vs. 25362±10862 ng/mL, p<0.0001) and estradiol levels (388.23±210.58 vs. 651.48±390.79 ng/mL, p=0.0208) compared to normoovulatory controls. Moreover, a metabolite fingerprint associated with glycolytic and mitochondrial dysfunction was observed, as evidenced by lower lactate (4575.44±1507.76 vs. 5595.34±1073.32 μmol/L, p=0.0182) and formate (64.51±16.06 vs. 75.81±16.63 μmol/L, p=0.0351) levels and higher citrate levels (136.93±52.53 vs. 109.15±24.17 μmol/L, p=0.0409) in the FF of women with PCOS. These findings suggest that the molecular profile of the FF in women with PCOS is related to granulosa cell glycolytic and mitochondrial dysfunction, which can have a negative impact on oocyte fertilization potential. The study provides an integrative analysis of the FF hormone and metabolite profile in women with PCOS, offering insights into the molecular mechanisms underlying the reproductive dysfunctions associated with this condition.

Embryo quality evaluation during in vitro development is a crucial factor for the success of assisted reproductive technologies (ARTs). However, the subjectivity inherent in the morphological evaluation by embryologists can introduce inconsistencies that impact the optimal embryo choice for transfer. To provide a more comprehensive evaluation of embryo quality, we undertook the integration of embryo metabolomics alongside standardized morphokinetic classification. The culture medium of 55 embryos (derived from 21 couples undergoing ICSI) was collected at two timepoints (days 3 and 5). Samples were split into Good (n = 29), Lagging (n = 19), and Bad (n = 10) according to embryo morphokinetic evaluation. Embryo metabolic performance was assessed by monitoring the variation in specific metabolites (pyruvate, lactate, alanine, glutamine, acetate, formate) using ¹H-NMR. Adjusted metabolite differentials were observed during the first 3 days of culture and found to be discriminative of embryo quality at the end of day 5. Pyruvate, alanine, glutamine, and acetate were major contributors to this discrimination. Good and Lagging embryos were found to export and accumulate pyruvate and glutamine in the first 3 days of culture, while Bad embryos consumed them. This suggests that Bad embryos have less active metabolic activity than Good and Lagging embryos, and these two metabolites are putative biomarkers for embryo quality. This study provides a more comprehensive evaluation of embryo quality and can lead to improvements in ARTs by enabling the selection of the best embryos. By combining morphological assessment and metabolomics, the selection of high-quality embryos with the potential to result in successful pregnancies may become more accurate and consistent.