MALE FERTILITY: It would be at its peak 3 hours later

 Will this research from the Center for Reproductive Medicine at China Medical University (Li and Wang's lab), published in the journal Molecular and Cellular Proteomics, challenge the advice currently given by doctors in fertility clinics? Today, men who are trying to conceive are advised to abstain between conception efforts. But the team who worked with nearly 500 couples conclude that using sperm after a short period of abstinence of less than 3 hours increases the chances of conception.

 

The objective of the study was to determine whether the length of time a couple waits between conception efforts or fertility treatment cycle can impact success rates. Indeed, if today, doctors in fertility clinics advise rather to abstain between each treatment, Drs Da Li and XiuXia Wang, clinical researchers at the Center for Reproductive Medicine at Shengjing Hospital in Shenyang, suggest changing the IVF protocol.

 

The team worked with nearly 500 couples to determine whether the length of time a couple waited between conception efforts could alter their success rate.

 

Sperm is more fertile 3 hours after:

• the researchers confirm here the conclusions of previous studies showing that the sperm produced shortly after the most recent ejaculation, that is to say approximately 3 hours later, contains spermatozoa which are faster and more mobile than after an abstinence of several days;
• using a technique called mass spectrometry to examine the protein composition of samples, the team identifies major molecular differences. The majority of affected proteins are involved in cell adhesion, a function that sperm need to fuse with eggs.
• Differences between the two sample types are also seen in proteins involved in sperm motility and metabolism, particularly in proteins that regulate reactive oxygen species, a byproduct of cellular energy production. . Although reactive oxygen species are necessary for some normal sperm functions, an excess can damage sperm genetic material. The researchers point out that the longer the sperm, the more vulnerable they are to DNA damage by reactive oxygen, and this vulnerability is a barrier to their ability to form a viable embryo.

 

 

Do the observed changes affect fertility? The team proceeded, for IVF, as usual with the two types of samples, for the 500 couples, using them to generate and then implant embryos. While the “typical” live birth rate in a cohort of this size is around 30%, in the experimental cohort, linked to only a few hours of abstinence, the live birth rate is higher by a third.

 

Opt for frequent sex around the time of ovulation? These data suggest that couples with relatively normal (sperm) characteristics should have frequent intercourse around the time of ovulation. “It could make all the difference,” sum up the researchers. The team plans to continue working with patients and performing further research to better identify differences between sample types.

“Promising and exciting prospects for future parents”.

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MALE FERTILITY: Global warming also knocks out sperm

 Global warming harms male fertility, concludes this study from the University of East Anglia (UK) which shows, in particular, the deleterious effects of heat peaks on sperm. Work presented in the journal Nature Communications, carried out at this stage in insects, which specifies these negative effects on fertility from one generation to the next, and helps to explain the reduction in biodiversity and the extinction of certain species with global warming.

The research team hypothesizes that male infertility during heat waves could also help explain why climate change has such an impact on the reproduction and survival of different species. “We know that biodiversity is suffering with climate change, but the specific causes and sensitivities are difficult to pinpoint,” notes lead author Professor Matt Gage: “We show with this research that sperm function is a trait particularly sensitive to global warming.

 

Local extinctions of some species are known to occur when temperature changes become too intense. The explanation for these phenomena could be linked to sperm, suggests the study carried out on the beetle, a small red flour beetle (Tribolium castaneum). The insects were exposed to standard control conditions or 5-day heat wave temperatures, which were 5°C to 7°C above the standard temperature. The researchers then evaluated, via different experiments, the damage of heat on reproduction, sperm function and the quality of the offspring.

 

Heat waves kill sperm , this is the first observation of the team which notes a reduction by half of the number of offspring with a first exposure of males, then a virtual absence of offspring after a second heat wave. Females, on the other hand, do not seem to be affected by heat waves. After several heat waves, all sperm have difficulty migrating through the female tract and are likely to die before fertilization.

Heat waves halve the reproductive abilities of males, say researchers who suggest different causes for this vulnerability:

• heat waves have an initial impact on the sexual behavior of males, which mate approximately twice as often as controls;
• heat waves cause "damage" to sperm over several generations;
• 2 heat waves, 10 days apart, are enough to reduce the sperm production of exposed males to less than 1% of that of the control group;
• finally, heat waves shorten - always in these insects - the lifespan of the offspring, by the equivalent of a few months;
• the reproductive performance of first-generation males descended from males exposed to heat wave conditions is also affected: these sons have reduced fertility and produce fewer offspring.

 

Additional pressure on populations already affected by climate change? This is the hypothesis of researchers who believe that "thermal shock" can also harm male reproduction in warm-blooded animals and lead mammals to sterility...

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