The Skinny on Fat and Covid-19
Obesity is a risk factor for worse outcomes for a variety of medical conditions ranging from cancer to Covid-19. Most experts attribute it simply to underlying low-grade inflammation and added weight that make breathing more difficult.
Now researchers have found a more direct reason: SARS-CoV-2, the virus that causes Covid-19, can infect adipocytes, more commonly known as fat cells, and macrophages, immune cells that are part of the broader matrix of cells that support fat tissue. Stanford University researchers Catherine Blish and Tracey McLaughlin are senior authors of the study.
Most of us think of fat as the spare tire that can accumulate around the middle as we age, but fat also is present closer to most internal organs. McLaughlin's research has focused on epicardial fat, “which sits right on top of the heart with no physical barrier at all,” she says. So if that fat got infected and inflamed, it might directly affect the heart.” That could help explain cardiovascular problems associated with Covid-19 infections.
Looking at tissue taken from autopsy, there was evidence of SARS-CoV-2 virus inside the fat cells as well as surrounding inflammation. In fat cells and immune cells harvested from health humans, infection in the laboratory drove "an inflammatory response, particularly in the macrophages…They secreted proteins that are typically seen in a cytokine storm” where the immune response runs amok with potential life-threatening consequences. This suggests to McLaughlin “that there could be a regional and even a systemic inflammatory response following infection in fat.”
It is easy to see how the airborne SARS-CoV-2 virus infects the nose and lungs, but how does it get into fat tissue? That is a mystery and the source of ample speculation.
The macrophages studied by McLaughlin and Blish were spewing out inflammatory proteins, While the the virus within them was replicating, the new viral particles were not able to replicate within those cells. It was a different story in the fat cells. “When [the virus] gets into the fat cells, it not only replicates, it's a productive infection, which means the resulting viral particles can infect another cell,” including microphages, McLaughlin explains. It seems to be a symbiotic tango of the virus between the two cell types that keeps the cycle going.
It is easy to see how the airborne SARS-CoV-2 virus infects the nose and lungs, but how does it get into fat tissue? That is a mystery and the source of ample speculation.
Macrophages are mobile; they engulf and carry invading pathogens to lymphoid tissue in the lymph nodes, tonsils and elsewhere in the body to alert T cells of the immune system to the pathogen. Perhaps some of them also carry the virus through the bloodstream to more distant tissue.
ACE2 receptors are the means by which SARS-CoV-2 latches on to and enters most cells. They are not thought to be common on fat cells, so initially most researchers thought it unlikely they would become infected.
However, while some cell receptors always sit on the surface of the cell, other receptors are expressed on the surface only under certain conditions. Philipp Scherer, a professor of internal medicine and director of the Touchstone Diabetes Center at the University of Texas Southwestern Medical Center, suggests that, in people who have obesity, “There might be higher levels of dysfunctional [fat cells] that facilitate entry of the virus,” either through transiently expressed ACE2 or other receptors. Inflammatory proteins generated by macrophages might contribute to this process.
Another hypothesis is that viral RNA might be smuggled into fat cells as cargo in small bits of material called extracellular vesicles, or EVs, that can travel between cells. Other researchers have shown that when EVs express ACE2 receptors, they can act as decoys for SARS-CoV-2, where the virus binds to them rather than a cell. These scientists are working to create drugs that mimic this decoy effect as an approach to therapy.
Do fat cells play a role in Long Covid? “Fat cells are a great place to hide. You have all the energy you need and fat cells turn over very slowly; they have a half-life of ten years,” says Scherer. Observational studies suggest that acute Covid-19 can trigger the onset of diabetes especially in people who are overweight, and that patients taking medicines to regulate their diabetes “were actually quite protective” against acute Covid-19. Scherer has funding to study the risks and benefits of those drugs in animal models of Long Covid.
McLaughlin says there are two areas of potential concern with fat tissue and Long Covid. One is that this tissue might serve as a “big reservoir where the virus continues to replicate and is sent out” to other parts of the body. The second is that inflammation due to infected fat cells and macrophages can result in fibrosis or scar tissue forming around organs, inhibiting their function. Once scar tissue forms, the tissue damage becomes more difficult to repair.
Current Covid-19 treatments work by stopping the virus from entering cells through the ACE2 receptor, so they likely would have no effect on virus that uses a different mechanism. That means another approach will have to be developed to complement the treatments we already have. So the best advice McLaughlin can offer today is to keep current on vaccinations and boosters and lose weight to reduce the risk associated with obesity.
Story by Big Think
In rare cases, a woman’s heart can start to fail in the months before or after giving birth. The all-important muscle weakens as its chambers enlarge, reducing the amount of blood pumped with each beat. Peripartum cardiomyopathy can threaten the lives of both mother and child. Viral illness, nutritional deficiency, the bodily stress of pregnancy, or an abnormal immune response could all play a role, but the causes aren’t concretely known.
If there is a silver lining to peripartum cardiomyopathy, it’s that it is perhaps the most survivable form of heart failure. A remarkable 50% of women recover spontaneously. And there’s an even more remarkable explanation for that glowing statistic: The fetus‘ stem cells migrate to the heart and regenerate the beleaguered muscle. In essence, the developing or recently born child saves its mother’s life.
Saving mama
While this process has not been observed directly in humans, it has been witnessed in mice. In a 2015 study, researchers tracked stem cells from fetal mice as they traveled to mothers’ damaged cardiac cells and integrated themselves into hearts.
Evolutionarily, this function makes sense: It is in the fetus’ best interest that its mother remains healthy.
Scientists also have spotted cells from the fetus within the hearts of human mothers, as well as countless other places inside the body, including the skin, spleen, liver, brain, lung, kidney, thyroid, lymph nodes, salivary glands, gallbladder, and intestine. These cells essentially get everywhere. While most are eliminated by the immune system during pregnancy, some can persist for an incredibly long time — up to three decades after childbirth.
This integration of the fetus’ cells into the mother’s body has been given a name: fetal microchimerism. The process appears to start between the fourth and sixth week of gestation in humans. Scientists are actively trying to suss out its purpose. Fetal stem cells, which can differentiate into all sorts of specialized cells, appear to target areas of injury. So their role in healing seems apparent. Evolutionarily, this function makes sense: It is in the fetus’ best interest that its mother remains healthy.
Sending cells into the mother’s body may also prime her immune system to grow more tolerant of the developing fetus. Successful pregnancy requires that the immune system not see the fetus as an interloper and thus dispatch cells to attack it.
Fetal microchimerism
But fetal microchimerism might not be entirely beneficial. Greater concentrations of the cells have been associated with various autoimmune diseases such as lupus, Sjogren’s syndrome, and even multiple sclerosis. After all, they are foreign cells living in the mother’s body, so it’s possible that they might trigger subtle, yet constant inflammation. Fetal cells also have been linked to cancer, although it isn’t clear whether they abet or hinder the disease.
A team of Spanish scientists summarized the apparent give and take of fetal microchimerism in a 2022 review article. “On the one hand, fetal microchimerism could be a source of progenitor cells with a beneficial effect on the mother’s health by intervening in tissue repair, angiogenesis, or neurogenesis. On the other hand, fetal microchimerism might have a detrimental function by activating the immune response and contributing to autoimmune diseases,” they wrote.
Regardless of a fetus’ cells net effect, their existence alone is intriguing. In a paper published earlier this year, University of London biologist Francisco Úbeda and University of Western Ontario mathematical biologist Geoff Wild noted that these cells might very well persist within mothers for life.
“Therefore, throughout their reproductive lives, mothers accumulate fetal cells from each of their past pregnancies including those resulting in miscarriages. Furthermore, mothers inherit, from their own mothers, a pool of cells contributed by all fetuses carried by their mothers, often referred to as grandmaternal microchimerism.”
So every mother may carry within her literal pieces of her ancestors.
New implants let paraplegics surf the web and play computer games
When I greeted Rodney Gorham, age 63, in an online chat session, he replied within seconds: “My pleasure.”
“Are you moving parts of your body as you type?” I asked.
This time, his response came about five minutes later: “I position the cursor with the eye tracking and select the same with moving my ankles.” Gorham, a former sales representative from Melbourne, Australia, living with amyotrophic lateral sclerosis, or ALS, a rare form of Lou Gehrig’s disease that impairs the brain’s nerve cells and the spinal cord, limiting the ability to move. ALS essentially “locks” a person inside their own body. Gorham is conversing with me by typing with his mind only–no fingers in between his brain and his computer.
The brain-computer interface enabling this feat is called the Stentrode. It's the brainchild of Synchron, a company backed by Amazon’s Jeff Bezos and Microsoft cofounder Bill Gates. After Gorham’s neurologist recommended that he try it, he became one of the first volunteers to have an 8mm stent, laced with small electrodes, implanted into his jugular vein and guided by a surgeon into a blood vessel near the part of his brain that controls movement.
After arriving at their destination, these tiny sensors can detect neural activity. They relay these messages through a small receiver implanted under the skin to a computer, which then translates the information into words. This minimally invasive surgery takes a day and is painless, according to Gorham. Recovery time is typically short, about two days.
When a paralyzed patient thinks about trying to move their arms or legs, the motor cortex will fire patterns that are specific to the patient’s thoughts.
When a paralyzed patient such as Gorham thinks about trying to move their arms or legs, the motor cortex will fire patterns that are specific to the patient’s thoughts. This pattern is detected by the Stentrode and relayed to a computer that learns to associate this pattern with the patient’s physical movements. The computer recognizes thoughts about kicking, making a fist and other movements as signals for clicking a mouse or pushing certain letters on a keyboard. An additional eye-tracking device controls the movement of the computer cursor.
The process works on a letter by letter basis. That’s why longer and more nuanced responses often involve some trial and error. “I have been using this for about two years, and I enjoy the sessions,” Gorham typed during our chat session. Zafar Faraz, field clinical engineer at Synchron, sat next to Gorham, providing help when required. Gorham had suffered without internet access, but now he looks forward to surfing the web and playing video games.
Gorham, age 63, has been enjoying Stentrode sessions for about two years.
Rodeny Dekker
The BCI revolution
In the summer of 2021, Synchron became the first company to receive the FDA’s Investigational Device Exemption, which allows research trials on the Stentrode in human patients. This past summer, the company, together with scientists from Icahn School of Medicine at Mount Sinai and the Neurology and Neurosurgery Department at Utrecht University, published a paper offering a framework for how to develop BCIs for patients with severe paralysis – those who can't use their upper limbs to type or use digital devices.
Three months ago, Synchron announced the enrollment of six patients in a study called COMMAND based in the U.S. The company will seek approval next year from the FDA to make the Stentrode available for sale commercially. Meanwhile, other companies are making progress in the field of BCIs. In August, Neuralink announced a $280 million financing round, the biggest fundraiser yet in the field. Last December, Synchron announced a $75 million financing round. “One thing I can promise you, in five years from now, we’re not going to be where we are today. We're going to be in a very different place,” says Elad I. Levy, professor of neurosurgery and radiology at State University of New York in Buffalo.
The risk of hacking exists, always. Cybercriminals, for example, might steal sensitive personal data for financial reasons, blackmailing, or to spread malware to other connected devices while extremist groups could potentially hack BCIs to manipulate individuals into supporting their causes or carrying out actions on their behalf.
“The prospect of bestowing individuals with paralysis a renewed avenue for communication and motor functionality is a step forward in neurotech,” says Hayley Nelson, a neuroscientist and founder of The Academy of Cognitive and Behavioral Neuroscience. “It is an exciting breakthrough in a world of devastating, scary diseases,” says Neil McArthur, a professor of philosophy and director of the Centre for Professional and Applied Ethics at the University of Manitoba. “To connect with the world when you are trapped inside your body is incredible.”
While the benefits for the paraplegic community are promising, the Stentrode’s long-term effectiveness and overall impact needs more research on safety. “Potential risks like inflammation, damage to neural tissue, or unexpected shifts in synaptic transmission due to the implant warrant thorough exploration,” Nelson says.
There are also concens about data privacy concerns and the policies of companies to safeguard information processed through BCIs. “Often, Big Tech is ahead of the regulators because the latter didn’t envisage such a turn of events...and companies take advantage of the lack of legal framework to push forward,” McArthur says. Hacking is another risk. Cybercriminals could steal sensitive personal data for financial reasons, blackmailing, or to spread malware to other connected devices. Extremist groups could potentially hack BCIs to manipulate individuals into supporting their causes or carrying out actions on their behalf.
“We have to protect patient identity, patient safety and patient integrity,” Levy says. “In the same way that we protect our phones or computers from hackers, we have to stay ahead with anti-hacking software.” Even so, Levy thinks the anticipated benefits for the quadriplegic community outweigh the potential risks. “We are on the precipice of an amazing technology. In the future, we would be able to connect patients to peripheral devices that enhance their quality of life.”
In the near future, the Stentrode could enable patients to use the Stentrode to activate their wheelchairs, iPods or voice modulators. Synchron's focus is on using its BCI to help patients with significant mobility restrictions—not to enhance the lives of healthy people without any illnesses. Levy says we are not prepared for the implications of endowing people with superpowers.
I wondered what Gorham thought about that. “Pardon my question, but do you feel like you have sort of transcended human nature, being the first in a big line of cybernetic people doing marvelous things with their mind only?” was my last question to Gorham.
A slight smile formed on his lips. In less than a minute, he typed: “I do a little.”