Worldwide one of the most common inherited disease is hereditary haemochromatosis it is an autosomal recessive genetic disorder which is known for causing severe iron overload. It varies from type 1 up to type 4 the most common is type 1 which is caused by a mutation in the HFE gene responsible for encoding non classical MHC class 1 protein. The other types are not as common as type 1 and are usually caused by altered functions of different proteins which are important for regulating iron homeostasis. While they all differ in severity most patient with (HH) hereditary haemochromatosis are unable to regulate iron absorption effectively, the increase in iron builds up in the parenchymal organs until it exceeds the bodyâs storage capacity and then begins to cause damage to tissue and organs throughout the body such as the heart, liver and pancreas. These can lead to the development of liver fibrosis, arthritis, heart disease, diabetes, cirrhosis and premature death. This essay will discuss the mechanism involved in the development of hereditary haemochromatosis, pathways involved in iron absorption, and transport to the liver, mechanisms involved in liver Iron toxicity and current biochemical and molecular diagnostic tests.
Pathways involved in iron absorption, and transport to the liver
Iron is essential for life it is an important growth factor for the differentiation and proliferation of almost every living cell throughout the human body. Most eukaryotic cells need iron for metabolic pathways and are vital for enzyme functions (L.POWELL 2002). Iron is absorbed across the epithelial cells from the proximal small intestine also known as the duodenum in a heme or non heme form however most iron from food is ferric (Fe3+) which is not easily absorbed so needs to first be reduced to ferrous (Fe2+), a ferric reductase enzyme, (Dcytb) duodenal cytochrome b reduces (Fe3+) to (Fe2+) and then transported into the cells by DMT1 a protein also known as divalent metal transporter. Iron can then be stored in the cytoplasm of the villus as ferritin or transported through the basolateral membrane by IREG1 a membrane protein also known as ferroprotein, hephaestin (Heph) is also important in this process as it functions as a ferroxidase by oxidizing Fe2+ to Fe3+ (L. M. Fletcher and J. W. Halliday 2002).
Plasma transferrin can then bind to iron present on the surface of the basolateral body tissue primarily reticulocytes and also the liver with the help of TfR transferrin receptor. In the liver hepatocytes gain iron in a number of ways such as receptor mediated endocytosis through TfR transfrerrin receptors, iron is then released by acidification within the endosome and then transported by DMT1 throughout the endosomal membrane where it is stored as ferritin until it is needed or used in the metabolic process. Iron released from hepatocyte would usually involve cerplasmin and Ireg1 which oxidizes Fe2+ to Fe3+ (L. M. Fletcher and J. W. Halliday 2002).
Hereditary Haemochromatosis and the HFE Gene
Iron overload tends to occur when the regulatory process above begins to …
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