This breakthrough could finally unlock male birth control

 Researchers at Michigan State University have identified a molecular "switch" that boosts sperm energy just before they attempt to fertilize an egg. The finding could improve infertility treatments and support the development of safe, nonhormonal male birth control options.

"Sperm metabolism is special since it's only focused on generating more energy to achieve a single goal: fertilization," said Melanie Balbach, an assistant professor in the Department of Biochemistry and Molecular Biology and senior author of the study.

Before ejaculation, mammalian sperm remain in a low energy state. Once inside the female reproductive tract, they rapidly transform. They begin swimming more forcefully and adjust the outer membranes that will eventually interact with the egg. These changes demand a sudden and significant rise in energy production.

"Many types of cells undergo this rapid switch from low to high energy states, and sperm are an ideal way to study such metabolic reprogramming," Balbach said. She joined MSU in 2023 to expand her pioneering work on sperm metabolism.

Tracking the Fuel That Powers Fertilization

Earlier in her career at Weill Cornell Medicine, Balbach helped show that blocking a critical sperm enzyme caused temporary infertility in mice. That discovery highlighted the possibility of nonhormonal male birth control.

Although scientists understood that sperm require large amounts of energy to prepare for fertilization, the exact mechanism behind this surge remained unclear until now.

Working with collaborators at Memorial Sloan Kettering Cancer Center and the Van Andel Institute, Balbach's team developed a method to follow how sperm process glucose, a sugar they absorb from their surroundings and use as fuel.

By mapping glucose's chemical path inside the cell, the researchers identified clear differences between inactive sperm and those that had been activated.

"You can think of this approach like painting the roof of a car bright pink and then following that car through traffic using a drone," Balbach explained.

"In activated sperm, we saw this painted car moving much faster through traffic while preferring a distinct route and could even see what intersections the car tended to get stuck at," she said.

Using resources such as MSU's Mass Spectrometry and Metabolomics Core, the team assembled a detailed picture of the multi step, high energy process sperm rely on to achieve fertilization.

Source: ScienceDaily