MIAMI.- For many decades, the color of the urine, which is usually a transparent or yellowish liquid, was a mystery that until now had no scientific explanation. Recently, a study carried out by a team of American scientists from the University of Maryland discovered that an enzyme called bilirubin reductaseis the cause of this yellowish coloration.
Urine is a watery liquid with a characteristic odor, which is secreted by the kidneys and eliminated through the urinary system. Through which the human being eliminates toxins and excess fluid.
Professor Brantley Hall, an assistant in the department of Cellular Biology and Molecular Genetics at the University of Maryland, who led the study, said: “The discovery of this enzyme finally unravels the mystery of the yellow color of urine. “It is incredible that an everyday biological phenomenon went unexplained for so long and our team is delighted to be able to explain it.”
What makes urine yellow?
In the article about the study, published on December 3, 2023 in the journal Nature Microbiologythe researchers explained that when red blood cells break down after about six months of existence, a yellow-orange bile pigment called bilirubin.
Bilirubin is a yellowish substance that is formed during the body’s normal process of breaking down old red blood cells. It is found in bile, a liquid secreted by the liver that helps digest food.
They explained that according to the findings, in the intestine the microbes create the enzyme bilirubin reductase to convert bilirubin into a colorless compound called urobilinogen that spontaneously degrades into a molecule called urobilin, which is ultimately responsible for the yellow color of urine that we all know.
They highlighted that although urobilin was identified more than 125 years ago as the yellow pigment in urine, the role played by the enzyme that produces it and that gives it its characteristics and color was unknown.
How does the study was realized?
To identify intestinal microbial species that were capable of reducing bilirubin, the experts used a fluorescence assay on extracts of bacteria cultured with bilirubin.
They cultured several bacteria from the human gut microbiome, prioritizing previously reported bilirubin-reducing species and their taxonomic relatives.
They identified bilirubin-lowering activity in nine strains, including three species not previously known to be able to lower bilirubin: Clostridium symbiosum, Clostridium and Ruminococcus gnavus.
Bacterial strains were obtained from the National Institutes of Health (NIH) Biodefense and Emerging Infections (BEI) Research Resource Repository.
Facilitates disease research
They highlighted that this discovery, beyond answering an enigma that has intrigued generations, may facilitate research into diseases related to the gut microbiome such as jaundice and inflammation.
They added that when bilirubin, which is secreted in the intestine for subsequent excretion, is absorbed in excess into the bloodstream, it can cause jaundice, a disease that causes the eyes and skin to appear yellowish.
“After identifying the enzyme bilirubin reductase, we can begin to investigate how intestinal bacteria affect bilirubin levels and diseases such as jaundice and gallstone formation,” said co-author of the research, Xiaofang Jiang.
Hall’s team also found that although bilirubin reductase is present in almost all healthy adults, Newborns and individuals with inflammatory bowel disease often lack this enzyme.
To examine the relationship of bilirubin reductase with age and health, they conducted a large-scale analysis of human intestinal metagenomes, examining the presence and absence of bilirubin reductase in 4,296 infant intestinal metagenomes from the first year. of life.
Additionally, the gut microbiome has also been linked to other diseases including allergies, arthritis and psoriasis, a chronic inflammatory skin diseaseso the impact of discovering the origin of the yellow color of urine may go beyond simply having found the answer.
@Lydr05
Source: With information from the journal Nature Microbiology and Health Day
