'Self-eating' enzymes key to organ failure, research suggests
Digestive juices normally used to break down food can turn against the body and start damaging it when people are critically unwell, research suggests.
The study undertaken in rats looks closely at why the body starts to shut down when facing overwhelming illness.
And this research could help explain why vital organs often fail during sepsis and shock, University of California researchers say.
But more work is needed before firm conclusions can be drawn, experts say.
Shock, overwhelming infections and multi-organ failure are terminal conditions that are commonly seen in intensive care.
But why the body starts to shut down in these ways, or how best to treat it when it does, are not fully understood.
Previous research has shown that the intestine plays an important role in these often lethal scenarios.
But scientists at the University of California, San Diego, say they are the first to consider how the enzymes in the gut, which normally digest our food, could play a key role in this process.
In the study the researchers infused chemicals which block digestive enzymes into the intestines of seriously ill rats.
They found these rodents were more quick to recover from shock and less likely to die than rats that did not receive this treatment.
The rats were also quicker to return to their everyday behaviours than the ones that did not get the enzyme-blocking drugs, shows the study, published in the journal Science Translational Medicine.
Dr Geert Schmid-Schonbein, co-author of the study, said: "Many of the events that typically occur in shock - organ injury and increased chance of death - were totally turned around when we blocked these enzymes."
The enzymes the researchers worked on are normally made in the pancreas and most organs are shielded from their corrosive effects by tough membrane walls.
"The digestive enzymes are powerful - they have an amazing ability to digest most biological material," Dr Schmid-Schonbein said.
But when a person is in shock, their organ walls become more permeable, letting harmful substances in and out more indiscriminately, researchers say.
High death rate
The scientists think once the rats were in a state of shock, the walls of the intestines become leaky, allowing the "self-eating" enzymes to flow into them more freely.
In the rats, the enzymes then appear to eat through the intestinal walls and can travel in the blood to the lungs, liver and kidneys, Dr Schmid-Schonbein said.
"No organ is spared," he says.
The researchers think the high death rate from sepsis and shock may have its origin in the digestive system and that using enzyme-blocking drugs may help reduce the harmful effects.
But Dr Bob Winter, president of the Intensive Care Society, is more cautious. "This is very early work in a rat model. Lots of treatments have shown positive results in a rat model and then failed in human trials of sepsis," he said.
"Having said that we know there are reductions in gut blood flow in all forms of shock and blocking digestive enzymes does have some biological plausibility."