Hepatic ABCA1 Expression Improves b-Cell Function and Glucose Tolerance

Low HDL is a risk factor for the development of type 2 diabetes. Hepatic ABCA1 is the rate-limiting protein in HDL biogenesis, and mice lacking hepatic ABCA1 (ABCA1) have very low plasma HDL concentrations. To investigate the role of hepatic ABCA1 in glucose tolerance and b-cell function, we used ABCA1 mice, which showed impaired glucose tolerance without changes in insulin sensitivity. Insulin secretion was reduced following glucose gavage. Ex vivo, glucose stimulated insulin secretion from b-cells from wild-type (WT) and ABCA1 mice was similar. Insulin secretion was, however, reduced upon addition of ABCA1 serum to the medium compared with WT serum, whereas islets lacking b-cell ABCA1 were not affected differently by ABCA1 or WT serum. After high-fat feeding, WT and ABCA1 mice showed no difference in glucose tolerance or insulin secretion, and serum from ABCA1 and WT mice fed a high-fat diet did not affect insulin secretion differently. We conclude that hepatic ABCA1 improves glucose tolerance by improving b-cell function through both HDL production and interaction with b-cell ABCA1. The beneficial effect of hepatic ABCA1 is decreased under metabolic stress. Increasing hepatic ABCA1 may represent a novel therapeutic strategy for improving glucose homeostasis in diabetes.