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The Vanishing Y Chromosome: A Potential Contributor to Heart Disease in Men

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Human Y (right) and X chromosomes observed via scanning electron microscopy

Human Y (right) and X chromosomes observed with scanning electron microscopy

Power and Syred/Science Photo Library

A recent study involving over 30,000 individuals has revealed that men who experience a loss of Y chromosomes in a substantial number of immune cells are at a higher risk for narrower blood vessels, a significant factor in the development of heart disease.

“The loss of Y chromosomes greatly impacts men,” states Kenneth Walsh from the University of Virginia, who was not involved in the research. “Men’s lifespan averages six years shorter than women’s, primarily due to the instability of sex chromosomes.”

Loss of the Y chromosome is one of the most prevalent mutations following conception in men. This phenomenon typically occurs in leukocytes, the immune cells responsible for attacking and eliminating pathogens, as the rapidly multiplying stem cells that generate white blood cells undergo division. The cells without Y chromosomes accumulate and become more frequent as individuals age; approximately 40% of 70-year-old men show detectable losses.

This issue gained traction in 2014 when Lars Forsberg from Uppsala University in Sweden and his colleagues noted that elderly men with significant Y chromosome loss in their blood typically had a lifespan that was five years shorter than those without it. Walsh later linked this loss to heart disease.

Forsberg and his research team have now uncovered further connections between Y chromosome loss and specific cardiovascular issues. They analyzed data from Swedish cardiopulmonary bioimaging studies, which provided detailed vascular scans of 30,150 volunteers aged between 65 and 64. None of the participants exhibited symptoms of cardiovascular disease; however, they were assessed for vascular stenosis or atherosclerosis.

Among the male participants, 12,400 possessed the necessary genetic information to evaluate their Y chromosome loss. They were categorized into three groups: those with no detectable Y loss in leukocytes, those with less than 10% loss, and those with over 10% loss. Atherosclerosis scores for these groups were then compared with each other and with a female cohort in the study.

The researchers discovered that approximately 75% of men who had the highest Y chromosome loss exhibited narrowed blood vessels, while around 60% of those with less than 10% loss showed similar findings.

Despite some atherosclerosis being observed even in those with undetectable Y loss, about 55% of men and roughly 30% of women in this category had been affected. “Clearly,” Forsberg noted, “[loss of Y] involves other factors.”

In the coming months, Thimoteus Speer and colleagues from the University of Goethe in Frankfurt studied men undergoing angiography, an X-ray technique for examining blood vessels due to suspected cardiovascular disease. They found that over the next decade, individuals who lost Y chromosomes in more than 17% of their immune cells were more than twice as likely to die from a heart attack compared to those with less affected cells.

“The findings of Lars Forsberg and our study are quite consistent,” Speer remarked. “He observes increased coronary atherosclerosis, correlating it with a higher risk of mortality from myocardial infarction [heart attack], emphasizing the relationship with coronary atherosclerosis.”

Walsh acknowledges that neither study definitively proves that Y chromosome loss directly causes these outcomes. However, statistical analyses suggest its independent effect aside from smoking or aging— the primary risk factors for mutations.

The pressing question remains: how does Y chromosome loss impact health? Previous research by Walsh indicated that removing chromosomes from mouse immune cells adversely affects the cardiovascular system by driving fibrosis, which is the formation of scar tissue. However, heart attacks and atherosclerosis are typically more associated with inflammation and lipid metabolism defects than fibrosis. Both Speer and Walsh assert that more research is essential to unravel this relationship.

With a deeper understanding of the underlying processes, Speer hopes that future blood tests for Y chromosome loss will guide proactive interventions. “[These tests] may help in identifying patients who could particularly benefit from specific treatments,” he concludes.

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Source: www.newscientist.com

Seabed trawling is a significant contributor to global CO2 emissions

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In bottom trawling, a weighted net is dragged across the ocean floor.

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Bottom trawling releases about 340 million tons of carbon dioxide into the atmosphere each year, according to the first study to estimate these emissions. This represents almost 1% of the world's CO2 emissions, but is a major contribution that has been overlooked until now.

Trawling involves dragging a weighted net across the ocean floor to capture bottom-dwelling fish, crustaceans, and shellfish. Although this method of fishing is widely used around the world, it is controversial because the fishing gear damages undersea environments such as cold-water reefs. Some corals are thousands of years old.

“Trawling is a highly destructive fishing method as the nets and weights dragged along the bottom destroy marine habitat, which can take years to rebuild and recover.” he says. Micah Peck from the University of Sussex, UK, was not involved in the study.

It also stirs up sediment, releasing the oxygen needed by microorganisms to break down organic matter into carbon dioxide. Otherwise, these deposits could continue to accumulate for thousands of years, with the organic matter within them preserved by low-oxygen conditions. This means that carbon is effectively trapped.

In 2021, trisha atwood Researchers at Utah State University in Logan combined a study that looked at the amount of carbon dioxide released during trawling with data on the global scale of trawling. global fishing watch.The team concluded that released in large quantities into the seawater.

But the big unanswered question was how much of the CO2 released from the sediments would be emitted into the atmosphere.

“A lot of countries and different institutions started contacting us about that research,” Atwood says. “But they basically said, as long as it just stays in the ocean, we don't really care.”

So the team teamed up with researchers who had developed computer models of ocean circulation. According to these models, about 55 percent of the CO2 released into the water by trawling will be released into the atmosphere after nine years.

“I was surprised that more than half of them came out,” Atwood said. “And it shows up very quickly.”

According to the global carbon budget, the total amount of CO is2 emissions from human activities Increased to 40.9 billion tons Therefore, if the team's estimates are correct, trawling accounts for about 0.8 percent of global emissions. Air and maritime transport: 2.8%.

Conservationists say the discovery strengthens the case for reducing trawling. “Many marine habitats are trawled at least once a year, resuspending sediment and releasing carbon into the atmosphere,” Peck said. “Banning destructive fishing practices is key to the future of healthy marine ecosystems and the marine ecosystems that depend on them.”

“Measures to reduce the carbon impact of trawling gear are urgently needed, but they must be done as part of a just transition,” said Gareth Cunningham. marine conservation association, is calling for a ban on trawling in so-called marine reserves around the UK. “There is no one-size-fits-all model and solutions will vary by location.”

However, not all researchers are satisfied with this number. “I'm very skeptical of their estimates,” he says. Jan Gerd Hiddink At Bangor University, UK.

Hiddink believes that much of the carbon that reaches the ocean floor is in forms that are difficult to decompose, such as bones, and that carbon is not released even when sediments are disturbed.Atwood's team is probably overestimate emissions Up to 1000x, he claims.

Atwood said this estimate is based on actual measurements. “We conducted a study to measure the amount of carbon dioxide emitted from the ocean floor in areas where trawling takes place,” she says.

She says that the amount of carbon dioxide emitted could be more or less than these studies suggest, although there is a lot of uncertainty because so few such studies have been done. says.

Mr Atwood says the government needs to start calculating the carbon footprint of trawling. “This allows us to decide whether emissions should be regulated,” she says.

What is clear is that Global Fishing Watch's trawling data is based on boats sending automatic signals to satellites, and many trawlers do not have such systems, so the extent of trawling remains under-studied. That means it's bigger than expected.

“We know that we underestimate the global scale and perhaps the intensity of trawling,” Atwood says.

The trawling industry also has an opportunity to sell carbon credits in exchange for reduced emissions, she says. “If you were to put a price on it in today's independent market, it's a $100 million market.”

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Source: www.newscientist.com