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Erschienen in:
12.03.2016 | Short Communication
ABCA1 deficiency and cellular cholesterol accumulation increases islet amyloidogenesis in mice
Erschienen in: Diabetologia | Ausgabe 6/2016
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Aims/hypothesis
Islet amyloid, a pathological feature of type 2 diabetes, forms from the aggregation of islet amyloid polypeptide (IAPP), a beta cell peptide that is produced and co-secreted with insulin. Cholesterol regulates amyloid-β processing, deposition and clearance, promoting amyloidogenesis in the brain. ATP-binding cassette transporter 1 (ABCA1) is a cholesterol efflux transporter that when absent increases and when overexpressed reduces brain amyloid-β deposition in mouse models of Alzheimer’s disease. We examined whether alterations in ABCA1 expression and islet cholesterol content could also modulate islet amyloidogenesis.
Methods
Thioflavin S staining for amyloid was performed in islets isolated from mice with beta cell expression of human IAPP (hIAPP
Tg/o) and cultured for 8 days following cholesterol loading, microRNA-33 overexpression (to reduce ABCA1 expression) or palmitate treatment in the presence or absence of ABCA1 overexpression or mevastatin treatment (to reduce cholesterol synthesis). hIAPP
Tg/o mice were crossed with beta cell-specific Abca1-knockout mice (hIAPP
Tg/o
Abca1
βKO) and glucose tolerance and amyloid formation were assessed.
Results
Cholesterol loading and microRNA-33-induced reduction in islet ABCA1 expression increased Thioflavin S-positive amyloid in hIAPP
Tg/o islets. Palmitate treatment also increased amyloid formation and this was reduced by both ABCA1 overexpression and mevastatin treatment. hIAPP
Tg/o
Abca1
βKO mice had increased islet cholesterol, accompanied by fasting hyperglycaemia, glucose intolerance, impaired in vivo insulin secretion and an increased islet proinsulin:insulin ratio. Amyloid area was increased in cultured hIAPP
Tg/o
Abca1
βKO islets compared with hIAPP
Tg/o controls.
Conclusions/interpretation
These data suggest that elevations in islet cholesterol may lead to increases in IAPP aggregation and islet amyloid formation, further worsening beta cell function and glucose homeostasis.