Mice with specific inactivation of ABCA1 (ATP-binding cassette transporter subfamily A member 1), a transporter that mediates reverse cholesterol efflux in β-cells [10], and mice with LXR-β (liver X receptor beta) deficiency [11], a nuclear hormone receptor that increases ABCA1 expression in response to cholesterol, show impaired glucose tolerance and insulin secretion. Here, ABCA1 is linked to hyperinsulinemic hypoglycemia, familial, 4.