People with higher but normal blood levels of bilirubin, a component of bile, are less likely to suffer from serious lung disease and death from a variety of causes, according to a study published in the Journal of the American Medical Association.
Scientists from the University Collegium in London came to such conclusions after analyzing the data collected in a group of over 500 people. adult primary care patients in the UK. They concerned lung cancer, chronic obstructive pulmonary disease (COPD) and deaths from various causes.
Measurements of bilirubin in blood serum were performed in the examined persons in the years 1988-2008.
Bilirubin is a breakdown product of hemoglobin that is present in red blood cells. After binding to proteins (albumin), it is transported from the blood to the liver, where it undergoes further changes and passes into the bile, and then is further broken down in the intestines and is excreted together with the faeces (which gives it color).
Elevated levels of bilirubin in the blood lead to jaundice and may indicate increased destruction of red blood cells, leading to anemia, or that the liver is unable to clear it quickly due to conditions such as cirrhosis, inflammation or obstruction of the bile ducts. In newborns, an excess of non-protein bound bilirubin can lead to brain damage. In this form, it is toxic to the nervous tissue.
The researchers led by Laura J. Horsfall made sure that none of the people in the study had a condition that was causing the blood bilirubin to rise.
After taking into account various health indicators, it turned out that people with higher – albeit within normal – serum bilirubin levels were less likely to develop lung cancer, COPD, and death from various causes.
The researchers calculated that for each 0,1 milligram per deciliter (i.e. 100 milliliter) increase in bilirubin, the risk of lung cancer was reduced by 8%. for men and 11 percent. for women, while the risk of COPD decreased by 6% and the risk of death by 3%. in both groups.
The mean blood bilirubin concentration was 0,64 milligrams per deciliter (mg / dL) for men and 0,53 mg / dL for women. In total, 1 cases of lung cancer were diagnosed, 341 cases of COPD and over 5 deaths were reported.
As emphasized by the authors of the study, there is currently no known mechanism that would explain the relationship between bilirubin and the risk of respiratory diseases. Previous animal studies have shown that elevated bilirubin may protect against external damage to the respiratory system.
Perhaps it has something to do with the fact that bilirubin can act as an antioxidant, neutralizing free radicals that damage cells, and also has anti-inflammatory effects.
Better understanding of bilirubin’s influence on susceptibility to respiratory diseases could lead to the development of a treatment for these conditions by gently blocking a liver enzyme called UDP-glucuronyl transferase, which binds bilirubin to glucuronic acid, according to the researchers. In this form, bilirubin is found in the blood only in small amounts. (PAP)