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Developmental Biology - Sperm Motility
A Man's Diet Quickly Effects His Sperm Quality
Sperm are influenced by diet and the effects are rapid...
Sperm are influenced by diet with effects being fast. This is the conclusion of a study by researchers at Linköping University, Sweden. The study of healthy young men fed a diet rich in sugar, is published in PLOS and gives new insight into the function of sperm.
In the long term, it may contribute to new methods measuring sperm quality.
"We see that diet influences the motility of the sperm, and we can link the changes to specific molecules. Our study revealed rapid effects that are noticeable after one to two weeks."
Anita Öst PhD, Senior Lecturer, Department of Clinical and Experimental Medicine, Linköping University Hospital, Sweden; and head of the study.
Sperm quality can be harmed by several environmental and lifestyle factors, of which obesity and related diseases, such as type 2 diabetes, are well-known risk factors for poor sperm quality.
Researchers are interested in epigenetic effects on levels of gene expression change, even if genetic material - the DNA sequence - is not changed. Such epigenetic changes can lead to properties being transferred from a parent to offspring via the sperm or the egg.
In a previous study, scientists showed that male fruit flies consumming excess sugar shortly before mating more often produce offspring who became overweight. Similar studies on mice suggest that small fragments of RNA known as tsRNA play a role in this epigenetic phenomena — which appears in the next generation.
tsRN fragments are present in unusually large amounts in the sperm of many species, including humans, fruit flies and mice. But, their function has not been examined in detail.
Scientists speculated that tsRNA fragments in sperm may be involved in epigenetic phenomena — but it's too early to say whether this is the case in humans.
This new study was initiated by investigation into whether high consumption of sugar affects RNA fragments in human sperm.
Researchers examined 15 normal, non-smoking young men, who followed a diet given to them from the scientists for two weeks. The diet was based on the Nordic Nutrition Recommendations for healthy eating with one exception! During the second week researchers added sugar, corresponding to around 3.5 litres of fizzy drinks, or 450 grams [90 tsp] of confectionary sugar, every day. [Another away to visualize this is that 450 grams of sugar is equal to about 10 cans of 12 oz soda per day.]
Sperm quality and other indicators of participants' health were investigated at the start of the study, after the first week (during which they ate a healthy diet), and after the second week (when they had consumed large amounts of sugar).
At the beginning of the study, one third of the participants had low sperm motility — motility being one of several factors influencing sperm quality. The fraction of people with low sperm motility in the study corresponded to what is found in the general population. Researchers were surprised to discover that sperm motility in all participants became normal during the study!
"The study shows that sperm motility can be changed in a short period, and seems to be closely coupled to diet. This has important clinical implications. But we can't say whether it was the sugar that caused the effect, as it may be a component of a basic healthly diet that has a positive effect on sperm."
Anita Öst PhD.
Researchers also found that the small RNA fragments, which are linked to sperm motility, also changed. They are now planning to continue the work and investigate whether there is a link between male fertility and these RNA fragments found in sperm. They also want to determine if the RNA code can be used as a new diagnostic way to measure sperm quality during in vitro fertilisation.
Abstract
The global rise in obesity and steady decline in sperm quality are two alarming trends that have emerged during recent decades. In parallel, evidence from model organisms shows that paternal diet can affect offspring metabolic health in a process involving sperm tRNA-derived small RNA (tsRNA). Here, we report that human sperm are acutely sensitive to nutrient flux, both in terms of sperm motility and changes in sperm tsRNA. Over the course of a 2-week diet intervention, in which we first introduced a healthy diet followed by a diet rich in sugar, sperm motility increased and stabilized at high levels. Small RNA-seq on repeatedly sampled sperm from the same individuals revealed that tsRNAs were up-regulated by eating a high-sugar diet for just 1 week. Unsupervised clustering identified two independent pathways for the biogenesis of these tsRNAs: one involving a novel class of fragments with specific cleavage in the T-loop of mature nuclear tRNAs and the other exclusively involving mitochondrial tsRNAs. Mitochondrial involvement was further supported by a similar up-regulation of mitochondrial rRNA-derived small RNA (rsRNA). Notably, the changes in sugar-sensitive tsRNA were positively associated with simultaneous changes in sperm motility and negatively associated with obesity in an independent clinical cohort. This rapid response to a dietary intervention on tsRNA in human sperm is attuned with the paternal intergenerational metabolic responses found in model organisms. More importantly, our findings suggest shared diet-sensitive mechanisms between sperm motility and the biogenesis of tsRNA, which provide novel insights about the interplay between nutrition and male reproductive health.
Authors
Daniel Nätt, Unn Kugelberg, Eduard Casas, Elizabeth Nedstrand, Stefan Zalavary, Pontus Henriksson, Carola Nijm, Julia Jäderquist, Johanna Sandborg, Eva Flinke, Rashmi Ramesh, Lovisa Örkenby, Filip Appelkvist, Thomas Lingg, Nicola Guzzi, Cristian Bellodi, Marie Löf, Tanya Vavouri and Anita Öst.
Acknowledgments
The study has been carried out in collaboration with the Reproductive Medicine Center at Linköping University Hospital, with financial support from the Swedish Research Council, the Knut and Alice Wallenberg Foundation, and the Ragnar Söderberg Foundation.
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Jan 8 2020 Fetal Timeline Maternal Timeline News
 Sperm motility can be changed in a short period of time and is closely coupled to diet. Small tsRNAs sampled from sperm reveal they are up-regulated by eating a high-sugar diet for just 1 week. CREDIT Coka Cola.
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