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Scientists discover genetic errors that hamper sperm

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*DNA variants could aid new weight loss drugs
Scientists have found infertile male mice lack a crucial ‘repair gene’ – and they hope it could provide answers for drops in sperm counts and sperm quality being recorded across the world in humans.

The gene, XRCC1, is crucial for sperm development, to ensure a high sperm count, swift motility, normal shape, and solid concentration.

Previously, it wasn’t clear how important XRCC1 was to male fertility.

But a new study by Chinese researchers found it was the one thing that determined sperm quality in a batch of male mice.

Experts say the finding warrants research in humans as data show a concerning rise in male infertility.

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“Even modest Deoxy ribonucleic Acid (DNA)/ genetic material damage in human spermatozoa can reduce fertility and increase the risk of disease in offspring,” said Aihua Gu, a researcher at State Key Laboratory at the Ministry of Education School of Public Health in China.

“Now that we know XRCC1 plays a crucial role in maintaining normal spermatogenesis in mice, further study should explore potential treatments that could reverse male infertility caused by XRCC1 deficiency.”

Concerns about male infertility hit headlines globally in 2017, when researchers in Israel and the US published shocking data that sperm counts among men living in Western countries had fallen by 59.3 percent in the last 40 years. By reviewing the previous studies, the researchers found that, since 1973, sperm concentration for Western men had fallen by more than 52 percent, declining by 1.4 percent each year on average. Overall sperm count fell by 1.6 percent each year, resulting in a cumulative decline of nearly 60 percent in the last 40 years. Last year, another study by researchers in Spain and the US added weight to that warning, with data from two major fertility centers between 2002 and 2017. They found the number of men in their cohort went up seven-fold, from 8,000 to 60,000 in that time, with an increasing number diagnosed with oligospermia, a type of male infertility. Among those men with fertility issues, an increasing number had a sperm count so low they have a higher risk of needing In Vitro Fertilisation (IVF) to conceive, while the number of men with a ‘normal’ sperm count dropped.

Meanwhile, around four million people in the United Kingdom (UK) carry genetic variants that protect them from obesity, type 2 diabetes and heart disease, suggests new research from the University of Cambridge. The team said the discovery could lead to the development of new drugs that help people lose weight. Scientists have known for several years that genes can influence a person’s weight. One of the genes that are known to play a key role in regulating weight is MC4R, which codes for the melanocortin 4 receptor. This receptor acts like a switch in the brain to suppress appetite. People who have genetic variants that disrupt this receptor gain weight easily. Now, in a study published in the journal Cell, researchers have shown that other genetic variants in the MC4R gene that increase the activity of this brain receptor can protect people from becoming overweight, a finding that could lead to the development of new medicines that ‘copy’ the protective effect of these genetic variants to achieve or maintain weight-loss.

A team led by Professors Sadaf Farooqi and Nick Wareham and Dr. Claudia Langenberg at the Wellcome Trust-MRC Institute of Metabolic Science in Cambridge looked at the MC4R gene in half a million volunteers from the UK population who have taken part in the UK Biobank study, finding 61 distinct naturally-occurring genetic variants. While some of these genetic variants predisposed people to become obese, other variants provided protection against obesity and some of its major complications, such as type 2 diabetes and heart disease.

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