sábado, 21 de dezembro de 2019

Ancient 'chewing gum' yields insights into people and bacteria of the past

Date: December 17, 2019 Source: University of Copenhagen The Faculty of Health and Medical Sciences Summary: Researchers have succeeded in extracting a complete human genome from a thousands-of-years old 'chewing gum.' According to the researchers, it is a new untapped source of ancient DNA.


Researchers from the University of Copenhagen have succeeded in extracting a complete human genome from a thousands-of-years old "chewing gum." According to the researchers, it is a new untapped source of ancient DNA.

During excavations on Lolland, archaeologists have found a 5,700-year-old type of "chewing gum" made from birch pitch. In a new study, researchers from the University of Copenhagen succeeded in extracting a complete ancient human genome from the pitch.

It is the first time that an entire ancient human genome has been extracted from anything other than human bones. The new research results have been published in the scientific journal Nature Communications.

'It is amazing to have gotten a complete ancient human genome from anything other than bone,'' says Associate Professor Hannes Schroeder from the Globe Institute, University of Copenhagen, who led the research.

'What is more, we also retrieved DNA from oral microbes and several important human pathogens, which makes this a very valuable source of ancient DNA, especially for time periods where we have no human remains,' Hannes Schroeder adds.

Based on the ancient human genome, the researchers could tell that the birch pitch was chewed by a female. She was genetically more closely related to hunter-gatherers from the mainland Europe than to those who lived in central Scandinavia at the time. They also found that she probably had dark skin, dark hair and blue eyes.

Sealed in mud

The birch pitch was found during archaeological excavations at Syltholm, east of Rødbyhavn in southern Denmark. The excavations are being carried out by the Museum Lolland-Falster in connection with the construction of the Fehmarn tunnel.

'Syltholm is completely unique. Almost everything is sealed in mud, which means that the preservation of organic remains is absolutely phenomenal,' says Theis Jensen, Postdoc at the Globe Institute, who worked on the study for his PhD and also participated in the excavations at Syltholm.

'It is the biggest Stone Age site in Denmark and the archaeological finds suggest that the people who occupied the site were heavily exploiting wild resources well into the Neolithic, which is the period when farming and domesticated animals were first introduced into southern Scandinavia,' Theis Jensen adds.

This is reflected in the DNA results, as the researchers also identified traces of plant and animal DNA in the pitch -- specifically hazelnuts and duck -- which may have been part of the individual's diet.

Bacterial evolution

In addition, the researchers succeeded in extracting DNA from several oral microbiota from the pitch, including many commensal species and opportunistic pathogens.

'The preservation is incredibly good, and we managed to extract many different bacterial species that are characteristic of an oral microbiome. Our ancestors lived in a different environment and had a different lifestyle and diet, and it is therefore interesting to find out how this is reflected in their microbiome,' says Hannes Schroeder.

The researchers also found DNA that could be assigned to Epstein-Barr Virus, which is known to cause infectious mononucleosis or glandular fever. According to Hannes Schroeder, ancient "chewing gums" bear great potential in researching the composition of our ancestral microbiome and the evolution of important human pathogens.

'It can help us understand how pathogens have evolved and spread over time, and what makes them particularly virulent in a given environment. At the same time, it may help predict how a pathogen will behave in the future, and how it might be contained or eradicated,' says Hannes Schroeder.

Chewing gum, all-purpose glue or medicine?
Birch pitch is a black-brown substance that is produced by heating birch bark. It was commonly used in prehistory for hafting stone tools as an all-purpose glue. The earliest known use of birch pitch dates back to the Palaeolithic.
Pieces of birch pitch are often found with tooth imprints suggesting that they were chewed. As the pitch solidifies on cooling, it has been suggested that it was chewed to make it malleable again before using it for hafting etc.
Other uses for birch pitch have also been suggested. For example, one theory suggests that birch pitch could have been used to relieve toothache or other ailments as it is mildly antiseptic. Other theories suggest, people may have used it as a kind of prehistoric tooth brush, to suppress hunger, or just for fun as a chewing gum.

Story Source:

Materials provided by University of Copenhagen The Faculty of Health and Medical Sciences. Note: Content may be edited for style and length.

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Journal Reference:
Theis Z. T. Jensen, Jonas Niemann, Katrine Højholt Iversen, Anna K. Fotakis, Shyam Gopalakrishnan, Åshild J. Vågene, Mikkel Winther Pedersen, Mikkel-Holger S. Sinding, Martin R. Ellegaard, Morten E. Allentoft, Liam T. Lanigan, Alberto J. Taurozzi, Sofie Holtsmark Nielsen, Michael W. Dee, Martin N. Mortensen, Mads C. Christensen, Søren A. Sørensen, Matthew J. Collins, M. Thomas P. Gilbert, Martin Sikora, Simon Rasmussen, Hannes Schroeder. A 5700 year-old human genome and oral microbiome from chewed birch pitch. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-019-13549-9


Cite This Page:
University of Copenhagen The Faculty of Health and Medical Sciences. "Ancient 'chewing gum' yields insights into people and bacteria of the past." ScienceDaily. ScienceDaily, 17 December 2019. <www.sciencedaily.com/releases/2019/12/191217141549.htm>.

Fatty meal interrupts gut's communication with the body, but why?

If that second helping of prime rib stuns your gut into silence, is that good or bad?

Date: December 17, 2019 Source: Duke University Summary: Gut cells that normally tell the brain and the rest of the body what's going on after a meal shut down completely for a few hours after a high-fat meal, a team of researchers discovered in zebrafish. Enteroendocrine cells normally produce at least 15 different hormones to send signals to the rest of the body. The finding could be a clue to insulin resistance that leads to Type 2 diabetes.

A high-fat meal can silence communication between the intestine and the rest of the body, according to a new Duke University study in zebrafish.

While using the fish to examine cells that normally tell the brain and the rest of the body what's going on inside the gut after a meal, a team of Duke researchers discovered that a high-fat meal completely shuts down that communication for a few hours.

The cells they were looking at are the enteroendocrine cells, which occur sparsely throughout the lining of the gut, but play a key role in signaling the body about the all-important alimentary canal. In addition to releasing hormones, the cells also have a recently-discovered direct connection to the nervous system and the brain.

These cells produce at least 15 different hormones to send signals to the rest of the body about gut movement, feelings of fullness, digestion, nutrient absorption, insulin sensitivity and energy storage.

"But they fall asleep on the job for a few hours after a high-fat meal, and we don't yet know if that's good or bad," said John Rawls, an associate professor of molecular genetics and microbiology in the Duke School of Medicine.

Since enteroendocrine cells are key players in digestion, the feeling of being full and subsequent feeding behavior, this silencing may be a mechanism that somehow causes people eating a high-fat diet to eat even more.

"This is a previously unappreciated part of the postprandial (after-meal) cycle," Rawls said. "If this happens every time we eat an unhealthy, high-fat meal, it might cause a change in insulin signaling, which could in turn contribute to the development of insulin resistance and Type 2 diabetes."

To understand the silencing better, the researchers tried to break the process down step by step in zebrafish.

After they first sense a meal, the enteroendocrine cells trigger a calcium burst within seconds, initiating the signaling process. But after that initial signal there's a delayed effect later in the after-meal period. It's during this later response that the silencing occurs, said Rawls, who also directs Duke's Microbiome Center.

The silenced cells change shape and experience stress in their endoplasmic reticulum, a structure that assembles new proteins. It seems that these enteroendocrine cells, which are specialized to synthesize and secrete proteins like hormones and neurotransmitters, become overstimulated and exhausted for a while.

The team tried the high-fat diet on a line of germ-free zebrafish raised in the absence of any microbes, and found they didn't experience the same silencing effect. So they began looking for gut microbes that might be involved in the process.

After screening through all the kinds of bacteria found in the gut, they saw that the silencing appeared to be the work of a single type of gut bacteria, called Acinetobacter. These bugs are normally less than 0.1 percent of the total gut microbiome, but they increased 100-fold after a high-fat meal and were the only bacteria able to induce the silencing effect.

"Next we want to understand how Acinetobacter evokes this interesting response," said Lihua Ye, a postdoctoral fellow and lead author on this paper. "We also suspect other bacteria might also have this capability."

Rawls said they aren't sure why silencing occurs, nor whether it has any positive effect on the fish. It might be a way to prevent excessive signaling about the fat, but by being silenced completely like this, the cells won't be communicating anything else either.

"We don't understand yet what the long-term impact of enteroendocrine silencing would be on metabolic health," Rawls said. "This may be a maladaptive response to high-fat feeding that impairs the normal regulatory functions of these cells, leading to metabolic disorders like insulin resistance. But it's also possible that the silencing is a beneficial adaptation to protect the animal from over-stimulation of the gut cells."

Story Source:

Materials provided by Duke University. Note: Content may be edited for style and length.

Journal Reference:
Lihua Ye, Olaf Mueller, Jennifer Bagwell, Michel Bagnat, Rodger A Liddle, John F Rawls. High fat diet induces microbiota-dependent silencing of enteroendocrine cells. eLife, 2019; 8 DOI: 10.7554/eLife.48479

Cite This Page:
Duke University. "Fatty meal interrupts gut's communication with the body, but why? If that second helping of prime rib stuns your gut into silence, is that good or bad?." ScienceDaily. ScienceDaily, 17 December 2019. <www.sciencedaily.com/releases/2019/12/191217141551.htm>.

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