Metabolic enhancers supporting 1-carbon cycle affect sperm functionality: an in vitro comparative study

Area of Science:

• Reproductive Biology
• Biochemistry
• Spermatozoa Physiology

Background:

• Spermatozoa are vulnerable to oxidative stress, impacting their function.
• Key antioxidants like hypotaurine and glutathione depend on cysteine availability.
• Cysteine synthesis is linked to the 1-carbon cycle (1-CC).

Purpose of the Study:

• To investigate the effects of 1-carbon cycle (1-CC) supporting compounds and N-acetyl-cysteine (NAC) on sperm functionality.
• To evaluate the impact on mitochondrial membrane potential (ΔΨM) and reactive oxygen species (ROS) production in human, bovine, and ascidian spermatozoa.

Main Methods:

• Incubation of spermatozoa with a 1-CC supporting treatment (TRT) or NAC.
• Comparison with control groups (CNTRL) incubated with medium alone.
• Assessment of mitochondrial membrane potential (ΔΨM), ROS production (H₂DCFDA, 2-OH Ethidium), and intracellular pH (pHᵢ) at 90 and 180 minutes.

Main Results:

• Both TRT and NAC significantly increased ΔΨM in human and bovine spermatozoa compared to controls.
• ROS production varied by species; bovine TRT group showed decreased ROS at 2-OH Ethidium.
• Intracellular pH (pHᵢ) remained largely unaffected, except in ascidian sperm where NAC lowered pHᵢ, reversed by NaHCO₃ buffering.

Conclusions:

• Supplementation supporting the 1-carbon cycle (1-CC) and N-acetyl-cysteine (NAC) alone enhance mammalian sperm kinetics, ΔΨM, and ROS production.
• Demonstrates direct in vitro effects of these compounds on sperm functionality.
• Highlights the role of 1-CC in maintaining sperm health under oxidative stress.