ABCA1 and type 2 diabetes mellitus: However, while ABCA1 knockout mice do not develop T2D, pancreatic beta-cell specific ABCA1 knockout mice (Abca1-P/-P) showed a gene-dose dependent and age-related accumulation of cellular cholesterol in β-cells, marked reduction in insulin secretion in vivo and progressive impairment in glucose tolerance that was independent of islet development or β-cell mass [5], and disruption of insulin granule exocytosis [6].