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Medin-amyloid: a recently characterized age-associated arterial amyloid form affects mainly arteries in the upper part of the body
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology.
2005 (English)In: Amyloid: Journal of Protein Folding Disorders, ISSN 1350-6129, Vol. 12, no 2, 96-102 p.Article in journal (Refereed) Published
Abstract [en]

Amyloid deposition occurs commonly in the aging aortic media. We recently found that a 50 amino acid amyloid fibril protein, which we called medin, forms the fibrils of this amyloid form. Medin is an internal fragment of the 364 long precursor lactadherin, which is expressed by several kinds of cells including vascular smooth muscle cells. With the use of specific antibodies we have now studied the vascular distribution of medin (AMed) amyloid in a series of 18 individuals, 57 years of age and older. All individuals had widely spread AMed amyloid in the media of the thoracic aorta while this type of amyloid occurred less commonly in the abdominal aorta. In 8 of the 18 individuals, AMed-amyloid was also found in the basilar artery while the frequency was lower in other studied arteries. Amyloid was usually seen in close association with the internal elastic lamina. Analysis of proteins extracted from amyloid-rich aortic media showed presence of both lactadherin and medin. This study shows that AMed amyloid is not restricted to the aorta and the temporal artery but also occurs in other arteries, mainly in the upper part of the body. AMed amyloid has to be added to the forms of amyloid that may be seen in intracranial vessels.

Place, publisher, year, edition, pages
2005. Vol. 12, no 2, 96-102 p.
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-94209DOI: 10.1080/13506120500107006PubMedID: 16011985OAI: oai:DiVA.org:uu-94209DiVA: diva2:167983
Available from: 2006-04-06 Created: 2006-04-06 Last updated: 2010-11-11Bibliographically approved
In thesis
1. Medin Amyloid in Human Arteries and its Association with Arterial Diseases
Open this publication in new window or tab >>Medin Amyloid in Human Arteries and its Association with Arterial Diseases
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Amyloid is a form of abnormal protein aggregation within the living body. Massive deposits can lead to organ failure. There is also increasing evidence that smaller pre-amyloid aggregates exert direct toxic effects to cells. To date 25 different proteins are known to occur as amyloid deposition in human tissues, although not all of these conditions are known to be associated with clinical diseases.

This thesis deals with the very common form of amyloid localized to the arterial media. The fibril protein called ‘medin’ was identified in 1999. Medin is a 50 amino acid residue internal fragment of the precursor protein lactadherin. Lactadherin, first found in human milk, is expressed in various tissues such as breast epithelium (including carcinomas), macrophages and aorta. The function of the protein is not known but it has several functional domains. There is an EFG like domain, including an RGD-sequence, in the N-terminal part of the molecule. The C-terminal part consists of C1 and C2 coagulation factor V and VIII like domains. Medin is from within the C2 domain. This region is suggested to be involved in phosphatidyl serine binding, important in phagocytosis of apoptotic cells.

Medin amyloid was originally described from studies of the aorta. It is shown here that deposits are more widely spread and can be found in many large arteries, particularly within the upper part of the body. The prevalence of medin amyloid increases with age and deposits are found, to a certain degree, in virtually everyone above the age of 60 years. The amyloid is not only found extracellularly but intracellular deposits may also occur. Amyloid is usually associated with elastic lamina or lamellae which often show signs of fragmentation.

Given the localization of amyloid to elastic structures of the arterial media, three different vascular diseases were studied: temporal (giant cell) arteritis, thoracic aortic aneurysm and thoracic aortic dissection. Medin amyloid was found in temporal arteries with and without inflammation. In inflamed arteries, amyloid was mainly located along the broken internal elastic lamina. Medin was also demonstrated within giant cells. It is suggested that medin may be an antigen triggering autoimmune giant cell arteritis. In the study of thoracic aortic aneurysms and dissections, we found significant less medin amyloid in diseased aortic tissues compared with a control material. On the other hand, immunoreactive medin, probably in the state of oligomeric aggregates, was regularly found in association with aneurysms and dissections but not in the control material. It is suggested that medin oligomers exert toxic effects on smooth muscle cells which may lead to weakening of the arterial wall with aneurysm or dissection as a consequence.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 40 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 129
Pathology, Amyloid, Medin, Lactadherin, Aneurysm, Aortic dissection, Temporal artery, Arteritis, Giant cell, Pre-aggregation., Patologi
National Category
Cell and Molecular Biology
urn:nbn:se:uu:diva-6700 (URN)91-554-6507-2 (ISBN)
Public defence
2006-04-27, Rudbeck Hall, C11, Rudbeck Laboratory, Uppsala, 09:15 (English)
Available from: 2006-04-06 Created: 2006-04-06 Last updated: 2009-05-28Bibliographically approved

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