Islet amyloid polypeptide (IAPP): a second amyloid in Alzheimer's disease.
Amyloid formation is the pathological hallmark of type 2 diabetes (T2D) and Alzheimer's disease (AD). These diseases are marked by extracellular amyloid deposits of islet amyloid polypeptide (IAPP) in the pancreas and amyloid β (Aβ) in the brain. Since IAPP may enter the brain and disparate amyloids can cross-seed each other to augment amyloid formation, we hypothesized that pancreatic derived IAPP may enter the brain to augment misfolding of Aβ in AD. The corollaries for validity of this hypothesis are that IAPP [1] enters the brain, [2] augments Aβ misfolding, [3] associates with Aβ plaques, and most importantly [4] plasma levels correlate with AD diagnosis. We demonstrate the first 3 corollaries that: (1) IAPP is present in the brain in human cerebrospinal fluid (CSF), (2) synthetic IAPP promoted oligomerization of Aβ in vitro, and (3) endogenous IAPP localized to Aβ oligomers and plaques. For the 4th corollary, we did not observe correlation of peripheral IAPP levels with AD pathology in either an African American cohort or AD transgenic mice. In the African American cohort, with increased risk for both T2D and AD, peripheral IAPP levels were not significantly different in samples with no disease, T2D, AD, or both T2D and AD. In the Tg2576 AD mouse model, IAPP plasma levels were not significantly elevated at an age where the mice exhibit the glucose intolerance of pre-diabetes. Based on this negative data, it appears unlikely that peripheral IAPP cross-seeds or "infects" Aβ pathology in AD brain. However, we provide novel and additional data which demonstrate that IAPP protein is present in astrocytes in murine brain and secreted from primary cultured astrocytes. This preliminary report suggests a potential and novel association between brain derived IAPP and AD, however whether astrocytic derived IAPP cross-seeds Aβ in the brain requires further research.
Janelle N
JN
Fawver
Yonatan
Y
Ghiwot
Catherine
C
Koola
Wesley
W
Carrera
Jennifer
J
Rodriguez-Rivera
Caterina
C
Hernandez
Kelly T
KT
Dineley
Yu
Y
Kong
Jianrong
J
Li
Jack
J
Jhamandas
George
G
Perry
Department of Physiology and Neuroscience, PO-Box 7, St George's University, St Georges, Grenada, West Indies. IMurray@sgu.edu.
Ian V J
IV
Murray
D001741:Black or African American; D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000235:genetics; D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D002478:Cells, Cultured; D015331:Cohort Studies; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006801:Humans; D058228:Islet Amyloid Polypeptide / Q000008:administration & dosage / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009154:Mutation / Q000235:genetics; D058225:Plaque, Amyloid / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution / Q000187:drug effects
D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D005904:Glial Fibrillary Acidic Protein; D058228:Islet Amyloid Polypeptide