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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: ATP Binding Cassette Transporter 1, Amyloid, Amyloidosis, Animals, Cholesterol, Humans, Insulin-Secreting Cells, Islet Amyloid Polypeptide, Islets of Langerhans, Lovastatin, Male, Mice, MicroRNAs, Palmitates, Rats.
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Does aBCA1 deficiency and cellular cholesterol accumulation increase islet amyloidogenesis in mice? Context: 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. 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. 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.
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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. Final Decision: yes