BioGilbert – Biomarker for Patients with Gilbert Disease
Gilbert syndrome is a mild genetic liver disorder in which the body cannot properly process bilirubin, a yellowish waste product that is formed when old or worn out red blood cells are broken down (hemolysis). Individuals with Gilbert syndrome have elevated levels of bilirubin (hyperbilirubinemia), because they have a reduced level of a specific liver enzyme required for elimination of bilirubin. Most affected individuals have no symptoms (asymptomatic) or may only exhibit mild yellowing of the skin, mucous membranes, and whites of the eyes (jaundice). Jaundice may not be apparent until adolescence. Bilirubin levels may increase following stress, exertion, dehydration alcohol consumption, fasting, and/or infection. In some individuals, jaundice may only be apparent when triggered by one of these conditions. Gilbert syndrome is inherited as an autosomal recessive trait.
Although Gilbert syndrome may become apparent shortly after birth, it may not be recognized for many years. Episodes of mild jaundice may appear in young adults and is more common in males than females. Frequently, episodes of jaundice are overlooked. Gilbert syndrome is associated with fluctuating levels of bilirubin in the blood (hyperbilirubinemia). Bilirubin levels may increase with stress, strain, dehydration, fasting, infection or exposure to cold. In many individuals, jaundice is only evident when one of these triggers raises the bilirubin levels.
Some affected individuals have reported vague, unspecific symptoms including fatigue, weakness and gastrointestinal symptoms such as nausea, abdominal discomfort, and diarrhea.
Gilbert syndrome is inherited as an autosomal recessive trait. Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.
Gilbert syndrome is caused by mutations to the UGT1A1 gene located on the long arm (q) of chromosome 2 (2q37). Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual.
The UGT1A1 gene contains instructions for creating (encoding) a liver enzyme known as uridine disphosphate-glucuronosyltransferase-1A1 (UGT1A1). This enzyme is required for the conversion (conjugation) and subsequent excretion of bilirubin from the body. Mild jaundice associated with Gilbert syndrome occurs due to reduced amounts of this enzyme, which results in the accumulation of unconjugated bilirubin in the body. Bilirubin is an orange-yellow bile pigment that is mainly a byproduct of the natural breakdown (degeneration) of red blood cells (hemolysis). Bilirubin circulates in the liquid portion of the blood (plasma) bound to a protein called albumin; this is called unconjugated bilirubin, which does not dissolve in water (water-insoluble). Normally, this unconjugated bilirubin is taken up by the liver cells and, with the help of the UGT1A1 enzyme, is converted to form water-soluble bilirubin glucuronides (conjugated bilirubin), which are then excreted in the bile. The bile is stored in the gall bladder and, when called upon, passes into the common bile duct and then into the upper portion of the small intestine (duodenum) and aids in digestion. Most bilirubin is eliminated from the body in the feces.
Individuals with Gilbert syndrome retain approximately one third of the normal UGT1A1 enzyme activity and are able to conjugate enough bilirubin to prevent symptoms from developing. However, in some cases, especially when an affected individual is fasting, dehydrated or not feeling well, mild jaundice may develop.
Gilbert syndrome is diagnosed more often in males than females. New methods, like mass-spectrometry give a good chance to characterize specific metabolic alterations in the blood (plasma) of affected patients that allow diagnosing in the future the disease earlier, with a higher sensitivity and specificity.
Therefore it is the goal of the study to identify and validate a new biochemical marker from the plasma of the affected patients helping to benefit other patients by an early diagnose and thereby with an earlier treatment.