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The sixth “mass extinction” of global biodiversity is underway

Life on Earth has experienced five mass “extinction” events of biodiversity caused by extreme natural phenomena. Today, many experts warn that a sixth mass extinction crisis is underway, this time entirely caused by human activity.

Biologists at the University of Hawaii at Manoa and the National Museum of Natural History in Paris, France, recently published a comprehensive assessment of the evidence for this ongoing extinction event in the journal Biological Review.

Extrapolating from estimates of terrestrial snails and slugs, the researchers estimate that Earth may have lost 7.5 to 13 percent of its 2 million known species, or a staggering 150,000 to 260,000 species, since 1500. .

“The inclusion of invertebrates is key to confirming that we are witnessing the beginning of the sixth mass extinction in Earth’s history,” said lead author Professor Robert Cowie.

However, the situation is not the same around the world. Despite major threats to marine species, there is no evidence that the crisis is affecting the oceans to the same extent as land. On land, island species, such as those in the Hawaiian Islands, are much more affected than mainland species. Also, plants appear to be dying out at a slower rate than terrestrial animals.

Cowie stressed: “Humans are the only species capable of manipulating the biosphere on a large scale. We are not just another species that evolves in the face of external influences. By contrast, we are the only conscious choice for our future and for the planet’s biodiversity. species.”

Conservation initiatives have been successful for some charismatic animals in response to the crisis, but they do not target all species or reverse the general trend toward extinction. Nonetheless, humanity must continue to work hard and continue to do wonders for nature and document it before biodiversity disappears.

A collaborative study by German and British scientists found that deletion or mutation of the genes RNF43 and ZNRF3 triggers a regulatory signal of lipid metabolism, which in turn leads to lipid accumulation and inflammation in the liver. The results of this study may explain why some people are very thin, but still suffer from fatty liver. The related results were published in the journal Nature Communications.

Previous Cancer Genome studies have identified RNF43 and ZNRF3 as genes that are mutated in colon and liver cancer patients. A research team led by Dr. Merritt Schell Houch at the Max Planck Institute for Molecular Cell Biology and Genetics in Germany, together with scientists from the Gurdon Institute at the University of Cambridge, UK, investigated the mechanisms by which changes affect the development of liver disease. In non-obese mice fed a normal diet, deletion or mutation of the genes RNF43 and ZNRF3 resulted in lipid accumulation and inflammation in the liver. These genetic changes not only lead to an increase in fat accumulation, but also an increase in liver cells. In humans, these changes increase the risk of diseases such as fatty liver and liver cancer, and shorten the life expectancy of patients.

“With organoids, we were able to grow liver cells that were mutated only in these genes, and we saw that the loss of these genes triggered a lipid A regulatory signal for lipid metabolism. As a result, lipid metabolism is no longer under control, and lipids accumulate in the liver, which in turn leads to fatty liver. In addition, the activated signal leads to uncontrolled proliferation of liver cells. These two mechanisms work together to promote progression of fatty liver disease and cancer.”

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