Coronavirus infects fat cells, immune cells in body fat, research finds

Host Amber Smith: Upstate Medical University in Syracuse, New York, invites you to be "The Informed Patient" with the podcast that features experts from Central New York's only academic medical center. I'm your host, Amber Smith.

Starting early in the pandemic, one thing that stood out was that the coronavirus seemed to be more severe in people who were overweight or obese. Recent research shows that the virus actually infects fat cells and certain immune cells within body fat.

I've asked Dr. Timothy Shope for help understanding this research. Dr. Shope is the chief of bariatric surgery at Upstate. Thank you for making time for this interview, Dr Shope.

Timothy Shope, MD: Thank you for having me, Amber.

Host Amber Smith: Now, didn't most medical experts assume that people who were overweight or obese got sicker from COVID-19 because of other health conditions that they had, such as diabetes?

Timothy Shope, MD: That's generally true. We weren't certain exactly if it was the virus itself or the comorbid (simultaneously existing) conditions that come along with being obese that was the most important.

Host Amber Smith: So were you surprised about this research that was showing that the virus infects fat cells and immune cells?

Timothy Shope, MD: Somewhat. We've known for many years that viruses can certainly live in adipose tissue.

The virus that causes HIV, for example, and the standard flu virus, both of these can live in fatty tissue. This virus in particular, however, also appears to be able to evade some of the body's innate defenses a little bit better, and it probably directly infects some of the immune cells that are in the fatty tissue.

Host Amber Smith: Now, you use the word "adipose" tissue. Is that fatty tissue, another word for fatty tissue?

Timothy Shope, MD: It is. And it's the medical or scientific word for fatty tissue.

Host Amber Smith: Does this adipose tissue do anything in the body, or what do we know about it? Does it have a role?

Timothy Shope, MD: It does have a role. Generally speaking, it's historically been considered a place where we can store energy. It's a place where we can essentially insulate ourselves. But more recently we've started to think about this as essentially an endocrine organ, in that it generates substances called cytokines that sends a signal to other cells and causes other cells to respond. Most of these signals that it sends out cause a low-grade, chronic inflammatory state in the body.

Host Amber Smith: I've heard that the fat that surrounds internal organs, the visceral fat, I guess it's called, is the most dangerous. Is that still the case? Is that still the belief?

Timothy Shope, MD: This is called visceral adiposity, and yes, it is considered to becertainly much more of a risk factor for multiple medical problems, such as diabetes, high blood pressure, problems with cholesterol and lipids.

We think that it has an especially high capacity for creating that inflammatory state that I mentioned earlier.

Host Amber Smith: OK. And in terms of where the fat accumulates in the body, there's no rhyme or reason, sometimes it feels like weight is going on in different areas of the body. Do we have any control over where it ends up?

Timothy Shope, MD: Largely, no. Some of that is genetically based. This visceral adiposity that we're talking about is largely the fat that you can't see on a person. It's the fat that's in and around the organs, particularly in the abdominal cavity, but also in the chest, as well.

Host Amber Smith: Well, the research that made headlines recently came from scientists at Stanford University School of Medicine, and it helped confirm some similar findings of researchers at Weill Cornell Medicine in New York and elsewhere.

You were not part of these studies, but can you explain how this research was done?

Timothy Shope, MD: Sure. And I was not part of the studies, and I think it's also important to mention that this has not yet been published in a peer-reviewed journal, but the data does seem compelling. Basically, these scientists took some fat cells that they obtained from human surgical specimens, patients that were undergoing weight-loss surgery, undergoing cardiac surgery,and they were able to take those cells, culture them in a lab and then directly infect them with the coronavirus.They then were able to identify that the macrophages, those immune cells in that adipose tissue, were also able to become infected and that that led to a substantial inflammatory response, which we believe likely creates a systemic response.

They've identified an increase in the markers that are present in patients that have severe disease, patients that are in the ICU for other reasons, patients that have progressive disease, for example, and then subsequently they were able to find evidence of the virus in the adipose tissue from autopsy specimens, from patients that were known to have died with COVID.

They then felt that this adipose tissue was basically a relatively safe harbor for the virus and that it allowed for it to increase the negative effects of that inflammatory response. If this is all true, then we could usethat adipose tissue and those immune cells in the adipose tissue as a target for treatment.

That's why it's important.

Host Amber Smith: Now, the immune cells, the macrophages, if they develop a robust inflammatory response to a coronavirus infection, does that mean that the person's got an immune system that's working well?

Timothy Shope, MD: Maybe. The inflammatory response is certainly needed to fight off a normal infection and to promote healing, and just to maintain a healthy individual.

The problem is when this becomes unregulated or responds too vigorously, it can then damage normal cells and tissue, and that's going to then promote more inflammation, and it's going to set off this dangerous sort of self-propagating cycle.

Host Amber Smith: Can you help us understand why someone who's overweight and has a strong immune response to COVID-19 is at risk for dying or for a lengthy and severe illness?

You mentioned cytokine storm earlier, and that has something to do with the fat cells. Can you explain that again?

Timothy Shope, MD: So these cytokines are, again, inflammatory mediators that send a signal from one cell to another, and if that signal then causes more inflammation, that's going to again be this self-propagating cycle.It seems that those folks that are overweight or classified as obese will have, additionally, those medical troubles you're talking about earlier: diabetes, high blood pressure, primary problems with their lungs and other organs.

Host Amber Smith: So does this research, and I understand it hasn't been published in a peer-reviewed journal yet, but does this research, is it leading to a consensus for why patients with excess pounds are more vulnerable?

Timothy Shope, MD: I think we're all understanding that obesity is a risk factor for a lot of medical problems, including new ones or ones that we haven't yet experienced, unfortunately, and I think that controlling that obesity prior to experiencing some of these other troubles is really the key to this.

Host Amber Smith: This is Upstate's "The Informed Patient" podcast. I'm your host, Amber Smith. I'm talking with Dr. Timothy Shope. He's the chief of bariatric surgery at Upstate, and we're talking about research showing that the coronavirus infects fat cells and certain immune cells in the body fat.

I'd like to ask you about bariatric surgery patients and COVID-19. I wanted to ask you to tell us about research that compares people who had bariatric surgery with those who qualified for it but did not have the surgery.

Timothy Shope, MD: Sure. There were some actually recently published studies, just within the past few months, from New York City and also from the Cleveland Clinic. Patients that had bariatric surgery compared to a group of patients that were eligible for bariatric surgery but did not have the procedure were less likely to be admitted to the hospital, less likely to require ICU (intensive care unit) care.

They had shorter ICU care length of stay. If they were in the ICU, they all had shorter overall lengths of stay. The Cleveland Clinic study also found that they were less likely to need dialysis, and both studies show that they were less likely to have a death occur as a result of being infected with the virus.

Host Amber Smith: So what about bariatric surgery seems to be protective, or what do you think it is?

Timothy Shope, MD: Well, I think it's probably both the loss of weight and the control of the comorbid conditions. Again, we know that even non-obese patients with advanced diabetes, non-obese patients with underlying medical troubles, were more likely to die from this virus.

So clearly, the control of those medical troubles is part of it, but also I think that this newer research showing that the virus can maybe have a safe harbor in excess adipose tissue. Losing that extra tissue probably helped as well.

Host Amber Smith: What about vaccines? Do you think that the vaccines are as protective in people who are obese or overweight as in people who are at normal weight?

Timothy Shope, MD: Well, we've got no reason to believe that they're not; they appear to be protective, and it doesn't appear that obesity is a reason to not become vaccinated. There is some question out there about the dosages, but there's still no data to support that. I think that the dosage data may be more important regarding medications to treat the disease, not to prevent disease.

Host Amber Smith: Are people who are obese considered at high risk? Would they be one of those categories that maybe would need additional doses?

Timothy Shope, MD: Hard to know yet. They're certainly at high risk, but again, it's hard to know just exactly what that right dose is just yet.

Host Amber Smith: Well, let me ask you what you would say to people who have had bariatric surgery, as well as people who are overweight, in terms of how best to protect themselves during the pandemic.

Timothy Shope, MD: Same thing that (I would say to) the rest of us, you know, the counsel that I would give to the rest of us: Make sure that you use appropriate hand hygiene, practice social distancing, it's appropriate in most cases for people to be vaccinated. I think that for the obese patients, they also need to do whatever they can to lose weight and to control those underlying medical conditions.

Most people are probably aware that there's largely a pause on surgical procedures at this time based on the need to provide care for the COVID-positive patients across the country, so right now we're not performing as many of these procedures as we'd like to. But that doesn't mean that the patients can't pursue other weight-loss methods in the meantime, it doesn't mean that they can't do their best to control their other underlying medical problems.

Host Amber Smith: Well, thank you again for your time, Dr. Shope.

Timothy Shope, MD: Sure. Thank you for having me.

Host Amber Smith: My guest has been Dr. Timothy Shope, the chief of bariatric surgery at Upstate. "The Informed Patient" is a podcast covering health, science and medicine, brought to you by Upstate Medical University in Syracuse, New York. I'm your host, Amber Smith, thanking you for listening.