In newborns, jaundice is something so common that it is considered physiological, affecting about 60% of full-term babies and 80% of premature babies during the first week of life. It is something that doctors have to watch carefully and even treat, since it can cause diseases such as acute bilirubin encephalopathy or the kernícterus that can damage the baby's brain and cause developmental problems.
But now it turns out that this jaundice is not only one of the dangers that comes to reach the world: a new research recently published in the journal Scientific Reports and in which we have been part suggests that it is one of the gifts of evolution. Humans can develop jaundice at birth to protect us from something even more serious: sepsis.
Bilirubin molecule. Molekuul_b
When most people think of jaundice, they probably think of yellow skin, an effect caused by an excess of a yellow-orange pigment in the blood known as bilirubin. Bilirubin is released when old red blood cells break down.
Normally bilirubin reaches the liver where it becomes soluble in water before being excreted in both feces and urine, but this process can go wrong when there has been some alteration in the liver that prevents it from functioning properly. In adults, this may be a sign of underlying conditions6 ranging from hepatitis to alcoholic cirrhosis.
In Babies and more Jaundice: a very common condition in newborns that keeps Beyoncé's twins inIn the case of newborns, the situation is slightly different: the body needs to make a transition from the blood of the fetus to the adult blood, but the liver does not yet have the ability to cope with the bilirubin released in the production of red blood cells. The resulting jaundice generally has no consequences.
The risk of complications such as encephalopathy and the kernícterus occurs when bilirubin circulates at high levels for prolonged periods, allowing it to cross the blood brain barrier and deposit deep in the brain. As a result, neonatologists treat high bilirubin levels with blue and white light phototherapy lamps, which convert bilirubin into a more water soluble form (temporarily doing the job that corresponds to the liver). Today, complications are fortunately extremely rare, at least in rich countries.
The inexplicable motive
Here is the mystery: Why have humans not evolved to overcome this temporary bilirubin problem? Richard asked himself this question when he was doing his doctorate in intestinal microbiology at the University of Aberdeen while working as a guard in the neonatology unit as the person in charge of registration at the maternity hospital in the city.
One night I was taking care of a baby with sepsis8 (when the immune system starts up to protect against infections, which can lead to severe inflammation, organ failure and death). The baby was very ill in intensive care, with inflammation and surprisingly high bilirubin levels that were only being controlled with three phototherapy lamps. Usually, this type of severe jaundice is caused by an immune reaction between the mother's and baby's blood groups, but not in this case.
In Babies and moreBililuces: treatment for jaundiceRichard began to wonder if bilirubin was directly related to the infection and if it was part of the baby's body's attempt to eliminate sepsis (in this case, the baby survived). It was there that he began to think about the problem in evolutionary terms: If jaundice can harm the baby, what benefits does it offer us?
According to research to date, most scientists talked about antioxidant effects of bilirubin as a way to counteract the oxidative stress caused by birth. However, what I did not quite convince was the moment in which it occurred: when jaundice develops in most babies, the process of oxidation linked to childbirth has already occurred at least 24 hours ago.
Thinking about prehistoric babies born in caves without medical attention and without antibiotics, Richard realized that the greatest threat to his life after surviving childbirth would probably be an overwhelming sepsis in the early days, exactly when the level of Bilirubin increases naturally. Could jaundice be an evolutionary mechanism to protect us against this?
Starting the search
Richard worked with a team of 11 people from the University of Aberdeen and the National Health Service of Scotland, recruiting a medical student willing to spend their summer vacations working with blood plates, bilirubin and bacteria originally grown from blood cultures Neonatals taken in septic babies.
Some of the first signs that support this hypothesis first emerged in 2009 when the team discovered that bilirubin seemed to affect the growth of the most common cause of early sepsis in infants: the gram-positive bacteria streptococcus agalactiae. When there were more bacteria involved in sepsis, the results were mixed: bilirubin also affected some types of staphylococci, but not to gram-negative bacteria Escherichia coli.
Colonies of streptococcus agalactiae. angellodeco
The research earned Sophie Gibnos to obtain a doctoral scholarship from the Medical Research Council of the United Kingdom and continue researching these ideas. Sophie developed a new liquid culture system to test the hypothesis further and observe the direct impact on bacteria.
The results of this project have just been published and our team has shown that even modest concentrations of bilirubin reduce the growth of gram-positive bacteria by one third. streptococcus agalactiae. We also show that bilirubin can alter substrate metabolism in bacteria.
In summary, it seems that the hypothesis is being confirmed. Now what is necessary is to work more thoroughly, probably in experiments on sepsis with animals, which will allow us to reflect on if doctors should raise the threshold of accepted bilirubin for babies at risk of sepsis, such as premature babies.
It seems that we are discovering something new about the physiology of newborns and clinical science can be something exciting: taking an idea based on a real patient to the laboratory and testing it, to later develop it and help future patients.When newborns develop jaundice in the future, we will still have to treat it carefully, but it is very possible that we are grateful that it is protecting babies from a life-threatening cause.
Authors: Richard Hansen, Honorary Clinical Associate Professor, University of Glasgow; Elaina Collie-duguid, Manager, Center for Biology and Medicine Enabled by Genome, University of Aberdeen; and Georgina Hold, Professor of intestinal microbiology, UNSW.
This article has originally been published in The Conversation. You can read the original article here.
Translated by Silvestre Urbón
