Reduction of Hepatic Injury and Improvement of Cardiac Function and Increased Survival in a Rat Model of Combined Burn Injury and Polymicrobial Sepsis

Joseph L. Messina, Ph.D.; University of Alabama at Birmingham; PRMRP Investigator-Initiated Research Award

What we’re trying to determine is if there are ways in far-forward situations, in a battlefield situation, where someone is injured, when there is a trauma of some sort, whether there are ways to treat them on site that would help them recover later on. So, can we stabilize them, are there relatively simple treatments that can be performed at the site of the injury that might help them later on. A few years ago we started doing work looking at injury research and found that one of the problems in injuries was glucose metabolism. And specifically there was an increase in blood glucose levels in some types of injuries and the body would no longer respond to insulin, which is the primary regulator of metabolism. We hypothesized that there might be some treatments with something called thiazolidinediones. They’re a class of drugs that are used in type 2 diabetics. They have two interesting properties, one is they make cells more responsive – they respond better to insulin. And the second is they’re anti-inflammatory. I hypothesized that this class of drugs might be really useful after various types of injuries. And so we started treating with these drugs in experimental animals trying to mimic at least some of the different types of injuries that would occur on the battlefield. This is a combination of a burn injury that would occur in many different ways in the field with sepsis, which is an infection. And this is just survival curves. For instance, if you just have the burn injury alone – this top curve is about 90-95 percent survivable so it’s a very survivable injury. And then we do what’s a relatively severe form of CLP, but it’s also quite survivable about 60-70 percent of the animals will survive after 10 days. But if you combine the two you can see that by two days, none of them survive. So you combine these injuries and it’s much, much worse than either injury alone. But if we gave this drug, rosiglitazone, about half the animals survived. So that’s a really large difference in survival. So we knew we were on the right track, that giving this drug could result in greater survival. OK, so then we said, “why do those animals survive?” And we started looking at two different organ systems. The first one here in figure 3 is the liver. When the liver is damaged they release some of their contents into the blood and you can measure those. And a couple of enzymes called ALT and AST, that are normally very low. These dotted lines, it’s very low in the blood. But upon injury they are released and you can measure them. The combined injury is the black bars and you can see at 6 hours and 24 hours there’s quite a large increase in the combined injury in the larger than single injury alone. And this is the important point, if we administer this drug one time right after the injury, so something that is very easy to do, that the damage that takes place at 6 hours wasn’t affected by the drug. But that the greater damage that occurred between 6 and 24 hours was prevented. So there was some liver damage, but it sort of stopped from continuing to get worse. The other thing was that we looked at blood glucose. Again there is a complex reaction to these injuries. At first there was an increase in blood glucose called hyperglycemia. But after 24 hours and 48 hours, there is a decrease in blood glucose the hypo metabolic state that’s sort of well known in the literature. If we look at that hypo metabolic state at 24 hours where the blood glucose goes down treated with rosiglitazone, we were able to normalize the blood glucose. So then we asked, what would happen to the heart? We found that the time constant decrease and the ability to change the pressure over time was increased. Both of these indicate that heart was actually functioning better due to rosiglitazone, due to the drug. So we not only had an effect on the liver, but also an effect on the heart. And then because there was a change in glucose metabolism, we wanted to look at whether there was an effect on insulin signaling. And we found that by 6 hours or 24 hours after the injury, insulin did not function as well, it did not signal. It looks like it might have been going up a little bit by 48 hours, but in fact by 48 hours a number of the animals had already died. So it was the ones that survived that were actually a little bit better at responding. And we think that actually might be key and something we want to pursue in the future is that the ability to respond to insulin we think is correlated with survival. But in any case if we give rosiglitazone, we were able to recapture the response so that the animals would recover and at the same time that they’re recovering their insulin signaling their heart is working better and their overall glucose metabolism is better and their liver is not as damaged. So, we feel that all these together are helping to increase the survival of the animal. These drugs have been used for decades in type 2 diabetics so they may be useful in the battlefield situation.