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Diabetes. 2012 Mar;61(3):653-8. doi: 10.2337/db11-0944. Epub 2012 Feb 7.

miR-33a modulates ABCA1 expression, cholesterol accumulation, and insulin secretion in pancreatic islets.

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Department of Medical Genetics, Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada.


Changes in cellular cholesterol affect insulin secretion, and β-cell-specific deletion or loss-of-function mutations in the cholesterol efflux transporter ATP-binding cassette transporter A1 (ABCA1) result in impaired glucose tolerance and β-cell dysfunction. Upregulation of ABCA1 expression may therefore be beneficial for the maintenance of normal islet function in diabetes. Studies suggest that microRNA-33a (miR-33a) expression inversely correlates with ABCA1 expression in hepatocytes and macrophages. We examined whether miR-33a regulates ABCA1 expression in pancreatic islets, thereby affecting cholesterol accumulation and insulin secretion. Adenoviral miR-33a overexpression in human or mouse islets reduced ABCA1 expression, decreased glucose-stimulated insulin secretion, and increased cholesterol levels. The miR-33a-induced reduction in insulin secretion was rescued by cholesterol depletion by methyl-β-cyclodextrin or mevastatin. Inhibition of miR-33a expression in apolipoprotein E knockout islets and ABCA1 overexpression in β-cell-specific ABCA1 knockout islets rescued normal insulin secretion and reduced islet cholesterol. These findings confirm the critical role of β-cell ABCA1 in islet cholesterol homeostasis and β-cell function and highlight modulation of β-cell miR-33a expression as a means to influence insulin secretion.

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