BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: metabolism

Sea Otters: Tiny and Toasty

Weighing in at anywhere from 30 to just under 100 lbs, sea otters are the smallest ocean mammal. Scientists have long wondered how such small animals can withstand the cold waters in which they live. Unlike other sea mammals like whales who can have hundreds of pounds of blubber to insulate themselves, sea otters have rather trim, muscular builds. Although their fur is the densest out of any creature on the planet, scientists have concluded that their fur alone is not enough to insulate their bodies from harsh coastal climates. Scientists were puzzled for years as to how these petite mammals could endure water temperatures approaching and below 0 degrees Celsius. Finally, in the summer of 2021, a group of scientists revealed they found the answer to how sea otters stay warm: mitochondrial leaking.

On July 9 2021, Traver Wright and his colleagues at Texas A&M University published their research that solved the long standing mystery of sea otter survival. For their research, the team took muscular tissue samples from 21 different otters, varying in age and habitat. The team chose to study muscle tissue as this is predominantly where metabolic reactions occur in mammals. Utilizing a tool called a respirator, the researchers measured the oxygen flow and respiratory capacity of the otters’ cells as an indicator for the amount of heat their cells are producing.

The mitochondria is an organelle found in all living cells. Often cited as “the powerhouse of the cell”, the mitochondria is responsible for many important processes within a cell, most notably the generation of ATP through the process known as the Krebs Cycle. The mitochondria also has a special process of generating heat. Peter Mitchell’s 1961 chemiosmotic theory explains how electrons being passed through the mitochondrial electron transport chain creates a proton gradient, or gradual change in concentration within an area, that drives the production of ATP. Sometimes, the protons escape the mitochondria’s inner membrane, leading to energy being released as heat. This process is called “non-shivering thermogenesis” and it is precisely what happens in the muscles of sea otters.

Because a lot of energy is lost in this process of generating heat, sea otters have a high metabolism and need to consume a lot of food to maintain homeostasis. This explains the studies of oxygen flow in and out of the otters’ muscles! The research shows that over 40 percent of the cell respiratory capacity is due to these proton leaks, showing the major significance of this phenomenon on the metabolisms of otters and how hard their bodies work to keep them warm.

The scientists’ next steps are to find whether otters are born with such traits or if they develop them when they live in cold water as a means to survive. While baby otters don’t generate heat well due to their low muscle mass, the study showed that proton leak was still heavily occurring in the babies’ cells. While the Texas A&M team made significant contributions to our scientific understanding of otters, they have also opened the door to a many new research opportunities to further our understanding and answer the new questions that their research posed.

Small But Mighty: Sea Otters And Their Leaky Mitochondria

Sea otters: they bob up and down in the water, hold hands when they are sleeping, poop together at social events, stay warm by their fur and leaky mitochondria… wait, what?

Let’s rewind.

Sea-otter-morro-bay 13

A Cute Sea Otter Floating On Its Back

Warm-blooded marine mammals have a thick layer of fat and oils, known as blubber, as their skin layer to insulate their body. In cold waters, blubber helps retain heat and maintain homeostasis.

But what if warm-blooded marine mammals lack blubber? Sea otters are a prime example (and the only example) of a marine mammal without a layer of blubber. Instead, they have a thick coat of dense hairs, 1000x denser than human hair–the thickest on earth. This enables sea otters to trap large amounts of air within their fur coat, acting as insulation. (This is the same reason why sea otters float: the air trapped in their fur coat makes them buoyant).

But with that said, can you stay warm in a fleece jacket? Possibly. What if you were wearing it while in the ocean? That might be somewhat difficult. Similarly, fur can’t solely protect these animals from losing too much heat. These mammals are still living in water, which transfers heat 23 times as efficiently as air. Since sea otters are the smallest aquatic mammals, they have a lot of surface area relative to their volume, making it even harder for these animals to maintain homeostasis.

So how do they do it? Researchers have already understood that sea otters have an extreme metabolism, how food gets converted to energy in cells, eating about twenty-five percent of their body mass in food every day. But the pieces were still not adding up, which prompted researcher T. Wright to investigate this question on a cellular level. He and his colleagues searched for the source of heat in otters’ muscles. Playing a pivotal role in the body’s metabolism, the skeletal muscle makes up 40 to 50 percent of the sea otters’ entire body mass. His study required the collection of tissue from 21 sea otters of different ages and then measured the muscle cells’ respiratory capacity compared to that of other animals. The sea otters’ oxygen flow rate would roughly indicate the measurement of the cells’ heat production.

Mitochondria pump protons across their cell membranes to store energy in the form of ATP, like we learned in AP Biology’s diffusion unit. From this study, T. Wright concluded that the protons are diffusing back through the membrane before being used for work, resulting in excess heat. Since some of the energy is lost as heat, sea otters need to eat more food to compensate for the lost energy. This “leak in energy” is what contributes to the sea otters’ speedy metabolism.

It’s unknown if sea otters develop leaky mitochondria by living in cold water or simply inherit it. Future research into the fascinating design of sea otters may potentially reveal intriguing insight into their evolution, behavior, and maybe someday, their cuteness.

 

 

Microbiome Genes have Macro-significance

Ever been told that the little things matter in life? This same proclamation that you’ve been told by your elders rings true in your gut: one small modification to your human gut microbiome (a batch of bacteria that call your digestive tract home) can have drastic effects on your metabolism.

A. Sloan Devlin, assistant professor at Harvard medical school, carried out a study that proved the importance of the gut microbiome. She first located the gene in “an abundant gut bacterium” for an enzyme that processes bile acids. She then removed that gene from the bacterium. Next, she “colonized” “germ-free” mice with one of two types of the gut bacterium: either with the bile-processing enzyme or without the bile-processing enzyme. The results were surprising.

Credit: mcmurryjulie on pixabay

After both mice were fed the same high-fat, high-sugar diet, the mice without the bile-processing enzyme “had more fat in the liver and gained weight much more slowly than the other group. They also used proportionately less fat and more carbohydrate for energy.” Changing one single enzyme in a gut bacterium appears to change “whether the host is using [primarily] fats versus carbohydrates” for energy.

Even more staggering was the “correlation of lean body mass to energy expenditure.” Typically, in humans and mice, the more lean body mass an organism has, the more energy it expends. However, for the mice without the bile-processing enzyme, this relationship “broke down.” Devlin hypothesizes that this change could be due to a “signaling,” a process in which “physical states in the body trigger a cascade of genes to switch on or off.” Researchers can use this knowledge to treat diseases: figure out which microbiome bacteria activate which genetic switches, and better treatment for genetic problems such as, acid imbalances, metabolic disorders and obesity, may become a reality.

Devlin is sure to stress that this groundbreaking microbiome research is just her “first step.” Although this study was carried out on “germ-free” mice, Devlin dreams that one day she may use her research to improve the health of her own species: as Devlin states, her research brings her “one step closer to humans.”

 

Does Immigration Alter the Microbiome?

Each human has our own microbiome; one that is unique to us. However, recent research has shown that the microbiome of someone’s body is not static, but highly subject to alteration. Microbiomes change depending on the atmosphere you are in- and they change very quickly, taking only nine months in the U.S. The University of Minnesota has found that, in people emigrating to the US, microbiomes “rapidly westernize”; aka, their native microbes are replaced with new ones. However, this shift in microbes is not equal- there aren’t enough new microbes to replace the old, resulting in a harsh decline in diversity; diversity that stimulates metabolism, digestion, and immune system development.

Dan Knights, a computational microbiologist at the University of Minnesota, states that in moving to another country, you pick up new microbes native to that country, and new disease risks as well. In this case, the shift in the microbiome makeup can be beneficial, as the new microbes may aid in defense against new disease. However, it has also been found that “Obesity rates among many of the study immigrants increased sixfold. Those who became obese also lost an additional 10 percent of their diversity.” This fact links diet shifts to microbiome shifts, yet Knights states that “diet alone wasn’t enough to explain the rapid Westernization of the microbiome,” and that other things such as water and antibiotic use factor in as well. However, diet is still an important part in microbiome health and diversity. Knights studied microbiota of Hmong and Karen women who had immigrated to the U.S., these immigrants’ American-born children, and white American controls. Their microbiomes shifted to Prevotella to Bacteroides, coming to resemble those of the white Americans who acted as the control. The immigrants’ children were even more susceptible to changes in and loss of microbial diversity.

Obesity statistics worldwide from the years 1996-2003.

We as Americans are highly aware of our obesity epidemic and are doing all we can to find a way to fix it. Research that links it to a cause relieves people- it provides hope that there is a way to change it. Knights remarks that “we do see that Westernization of the microbiome is associated with obesity in immigrants, so this could an interesting avenue for future research into treatment of obesity, both in immigrants and potentially in the broader population.” However, it cannot be used as an excuse for our problem as Americans- it is simply a breakthrough in a long journey that may help us in the long run.

Fish might be shrinking!

To all the seafood lovers, you are being warned here first! The tiny piece of tuna on your plate will soon become even smaller due to climate change. Fish in the ocean will struggle to breathe due to the increasing water temperature, and many species of fish will likely shrink. According to a study published in Global Change Biology, the author predicts a decrease in sizes of the fish by as much as 30 percent. As Nexus Media explains, fish are cold-blooded animals, which means that they cannot regulate their own body temperature. Daniel Pauly, the study’s lead author and a University of British Columbia research initiative, say that due to the increase in ocean temperature, fish will have a higher metabolic rate and have to consume more oxygen. The whole metabolisms in the fish’s body, all the chemical reactions, are accelerated.

Credit:  Attribution license: Taras Kalapun,

Source

So if the fish need to have more oxygen intake, why not just grow bigger gills? In Pauly’s research, he suggests that growing bigger gills won’t help. According to the article, the gills being mostly two-dimensional, just cannot keep up with the three-dimensional growth in the rest of the fish’s body. When a fish grows 100 percent larger, its gill could only grow about 80 percent or less, according to the study. When a gill can no longer supply enough oxygen for a fish’s larger body, the fish will just stop growing larger all together, according to William Cheung, a director of science for the Nippon Foundation. In order to match the decreased supply of oxygen, fish will have to lower their demand, which means that fish of all kinds will shrink as a result of climate change.

There is already evidence to the phenomena of fish shrinking due to climate change, researchers in the North Sea have found that fish stocks like haddock and sole had decreased in body size over the past couple decades, and it is primarily due to climate change since commercial fishing and other factors have been corrected. Furthermore, the entire ecosystem will be affected since the larger fish eat the smaller ones, and a change in body size would alter food web interactions and structure.

To read more about other impacts of climate change on marine species.

Sources:
https://www.scientificamerican.com/podcast/episode/climate-change-might-shrink-fish/

Overload of Calories

You may not realize this, but we lose a significant amount of calories while we are asleep. Now imagine if the calories we burned while resting or sleeping did not get burned. If those calories did not burn while we were asleep it could cause us to become obese much more easily. The process of our metabolism rates getting slower does not occur until later on in most people’s lives. Unfortunately, those who have to take antipsychotic drugs may approach this problem sooner than expected.

Risperidone2D.svg

 

 

Image Link

New research has been found by the University of Iowa Health care that an antipsychotic drug, risperidone, effects people’s metabolism rates. The reason why is due to the gut microbiome going through an alteration through it’s bacterial anatomy. Kirby Carlarge, University of Iowa pediatrician,  and Justin Grobe, University of Iowa professor in pharmacology, worked together to test mice on risperidone. After two months the mice on risperidone gained an extra 2.5 grams compared to the control group of mice. Carlarge and Grobe used the total calorimetry machine to understand whether aerobic-resting states or non-aerobic resting states in terms of metabolism have been affected. The total calorimetry machine is able to give the exact measurement of the total energy change by inputting exact amounts of oxygen into the mice, outputting exact amounts of carbon dioxide, and the reaction of heat production. The results were the aerobic-resting metabolic rate to remain the same, but the anaerobic-resting metabolic rate had decreased . Therefore, the shift in the mice’s microbiomes does not affect the aerobic-resting metabolic rate, but instead affects the anaerobic-resting metabolic rate.

180px-Risperdal_tablets

Image Link

Risperidone draws a connection to weight gain due to the alteration in the bacterial anatomy of the microbiome. However, despite this understanding of risperidone there are no definite ways of preventing this situation occurring. Therefore, it is very likely for patients undergoing this treatment to become obese. Do you think there are other variables that could change and prevent risperidone creating this effect?

Throw Away Those Old Dinosaur Toys, Theres A New Kind of Dino in Town

Macronaria_scrubbed_enh

 

Growing up, dinosaurs were always cold-blooded, reptile-like creatures, right? Well recent research has put that theory to rest. Dinosaurs may have been much more warm blooded, than we previously thought.

Originally, scientists thought that dinosaurs were slow, low-energy creatures that only required heat from sunlight to go about their daily lives. This thought changed drastically in the 1960s when research showed that dinosaurs were much more like birds in the sense that they actually use lots of energy and internally regulate their body temperature. These theories created our super fast Jurassic Park dinosaurs.

Recently, though, paleoecologist John Grady stated that it isn’t quite so black and white for these animals. Grady got together with a team of colleagues and calculated the growth rate of an animal in relation to it’s energy use and put it on a scale ranging from animals such as crocodiles, slow-moving and low metabolism, to ostriches, fast moving and high metabolism. From there, the research team was able to estimate where on the scale dinosaurs fell, and to their surprise, it was right in the middle.

It turns out that dinosaurs may have had metabolisms similar to that of a great white shark or tuna. And while it may be hard to believe that dinosaurs are similar to tuna, these findings will help scientists better understand dinosaurs especially things such as how they hunted and why they grew to such large sizes!

Our view of what kind of creatures dinosaurs were could change completely in the next few years! Discoveries like these will help us understand how they lived on the planet so long, and possibly help us understand how to better the longevity of the human race.

 

Artificial Sweeteners: Not So Sweet After All?

425555319_86d3866d4b_o

Amy van der Hiel

A recent study conducted at the Weizmann Science Institute suggests that artificial sweeteners may trigger health problems instead of benefiting people. This is important because not only is saccharin in artificial sweeteners, but it is also found in salad dressings, vitamins, and in low/zero calorie items we often eat.

Previously, sweeteners were known to pass through the gut undigested, therefore allowing people with health issues to use the sugar substitute. Recent tests on mice and humans found that saccharin actually interferes and alters microbiota bacteria found in the gut and small intestines, leading to serious conditions such as obesity and diabetes.

Mice were monitored for 11 consecutive weeks when given drinking water doped with saccharin and the results showed they had abnormally high levels of glucose in their bloodstream. When food is digested it is broken down into glucose, the most common carbohydrate, and then enters the bloodstream to either be used as fuel or stored. When glucose metabolism is blocked, the blood glucose level is high. The test was repeated with mice on high-fat diet and the results were the same, showing that the saccharin had the same effect irrespective of the animal’s weight. Four of seven humans that ate a high-saccharin diet were also found to have an impaired glucose metabolism.

Why the microbiota are affected is still unknown as the test is preliminary, but the conclusion has been made that certain saccharin sugar substitutes are not simply passing through the intestines.

Original Article: https://www.sciencenews.org/article/artificial-sweeteners-may-tip-scales-toward-metabolic-problems

Photo Credit: https://www.flickr.com/photos/amyvdh/425555319

More Links:

http://www.biologynews.net/archives/2014/09/17/gut_bacteria_artificial_sweeteners_and_glucose_intolerance.html

http://well.blogs.nytimes.com/2014/09/17/artificial-sweeteners-may-disrupt-bodys-blood-sugar-controls/

http://wis-wander.weizmann.ac.il/gut-bacteria-artificial-sweeteners-and-glucose-intolerance#.VB48n4ARD1h

Cuts, Scrapes, and Hair Loss a Thing of the Past!

images

Can adults repair their tissues as easily as children can? A study currently conducted at Boston Children’s hospital is attempting to find the answer to this question. Researchers have found that by activating a gene called Lin28a, they were able to “regrow hair and repair cartilage, bone, skin and other soft tissues in a mouse model.”  The scientists found that Lin28a works by enhancing metabolism in mitochondria—which, as we learned in class, are the “powerhouses” of the cells. This in turn helps generate the energy needed to stimulate and grow new tissues.
This discovery is a very exciting one for the field of medicine. The study’s senior investigator George Daley said, “[Previous] efforts to improve wound healing and tissue repair have mostly failed, but altering metabolism provides a new strategy which we hope will prove successful.” Scientists were even able to bypass Lin28a and directly activate the mitochondrial metabolism with a small compound and still enhance healing. Researcher Shyh-Chang says of this, “Since Lin28 itself is difficult to introduce into cells, the fact that we were able to activate mitochondrial metabolism pharmacologically gives us hope.” Since it is difficult for scientist to actually introduce Lin28a into a cell, it might be easier to simply synthetically create a substitute and introduce that. Either way, I think this is a very promising discovery! What other uses can you think of for this discovery?

 

Source:

http://www.sciencedaily.com/releases/2013/11/131107123144.htm

Powered by WordPress & Theme by Anders Norén

Skip to toolbar