Tag: hibernation

Categories : GastrointestinalTags :

Probing the Gut’s Ability to Change Size According to Nutrient Intake

On By ModernMedia
Source: CC0

The gut has considerable plasticity among animals, shrinking as much 50% in cases of fasting such as hibernating and able to rapidly return to normal size on refeeding. Now, scientists from the University of Copenhagen used fruit flies to investigate the signalling mechanisms and cellular changes that regulate this rapidly renewable tissue, which could reveal insights into diseases such as colorectal cancer. Their results are published in Nature Communications.

“Taking advantage of the broad genetic toolbox available in the fruit fly, we have investigated the mechanisms underpinning nutrient-dependent gut resizing,” says Dr Ditte S. Andersen.

The results show that nutrient deprivation results in an accumulation of progenitor cells that fail to differentiate into the mature cells causing the gut to shrink.

Upon refeeding these stalled progenitor cells readily differentiate into mature cells to promote regrowth of the gut.

Ditte S. Andersen continues: “We have identified activins as critical regulators of this process. In nutrient restrictive conditions, activin signalling is strongly repressed, while it is reactivated and required for progenitor maturation and gut resizing in response to refeeding. Activin-dependent resizing of the gut is physiologically important as inhibition of activin signalling reduces survival of flies to intermittent fasting.”

Regulators of organ plasticity are essential for host adaptation to an ever-changing environment, however, the same signals are often deregulated in cancers. Indeed, mutations affecting activin signalling are frequent in cancer cells in a variety of tissues. This study provides a starting point for investigating the link between aberrant activin signalling and the development of colorectal cancers and sets the stage for exploring the efficiency of anti-activin therapeutic strategies in treating colorectal cancers.

Source: University of Copenhangen

Categories : Cardiovascular DiseaseTags :

Scientists ‘Poke the Bear’ to Gain a Better Understanding of Blood Clotting

On By ModernMedia
Photo by Mark Basarab on Unsplash

It’s generally good advice not to “poke the bear” as they say, but that’s exactly what a multinational team of scientists have been doing, to discover the secrets of blood clotting. Hibernating bears, paralysed humans, and pigs kept in small enclosures all avoid dangerous blood clots, despite being immobile for extremely long periods.

Their new study published in Science shows that reduction of a key protein inhibits the formation of blood clots in all three mammal species when they are immobile for days, months or even years.

Passengers on long haul flights run the risk of developing deep vein thrombosis if they do not take some time to walk around and use compression socks. Some people are predisposed to blood clots, due to genetic factors.

Yet, when humans – and other mammals such as bears – are immobilised for a much longer period than a flight, the researchers found that a protein known as Hsp47 is reduced by 55 times. This could lead to new medicines to help those who have inherited blood clotting disorders that put them at risk for pulmonary embolism, heart attack, and stroke.

Professor Jon Gibbins led the work at the University of Reading. He said: “It seems counterintuitive that people who have severe paralysis don’t appear to be at higher risk of blood clots. This tells us that something interesting is happening. And it turns out that reducing levels of Hsp47 plays a key role in preventing clots, not just in humans, but in other mammals, including bears and pigs.

“When we see something like this in multiple species, that reinforces its importance. Having Hsp47 must have been an evolutionary advantage.”

Hsp47 is released by platelets – the sticky blood cells that trigger blood clotting.  Usually clotting is an important response to an injury, to prevent blood loss, and Hsp47 is one of the necessary ingredients to enable platelets to do their job. Examining the role of Hsp47 in clotting function the team found that when released into the blood of bears, mice and humans that it promoted conditions that may give rise to deep vein thrombosis.

Professor Gibbins said, “We aren’t totally sure how, but it appears that there is something about movement that keeps Hsp47 at an appropriate level. It could be that the mechanical forces involved in moving around actually have an impact on gene expression, dramatically increasing the amount of Hsp47 that circulates in the blood.”

The team took blood samples from bears in winter, while hibernating, and in summer, while awake and moving around. They also compared people who were immobilised with those who can move and walk. And finally, pigs kept in small pens were compared with others that were free to move around in barns. In all three cases, proteomics experiments showed that the absence of movement was associated with having far less Hsp47.

Professor Gibbins continued: “Now we know that Hsp47 is so important, we can begin to look for new or existing medicines that might be able to inhibit the function of this protein in blood clotting and protect mobile people who are prone to clots.”

Source: University of Reading