Impaired insulin secretion in four Tangier disease patients with ABCA1 mutations

Tangier disease (TD), caused by deficiency of ATP-binding cassette transporter A1, is characterized by the absence of high density lipoprotein and the accumulation of cholesteryl esters in many tissues. Recently, it has been reported that ABCA1 is expressed in pancreatic beta cells and mice with specific inactivation of ABCA1 in beta cells showed markedly impaired insulin secretion, suggesting that ABCA1 deficiency may be involved in diabetes. The aim of the current study was to confirm these findings by the oral glucose tolerance test (OGTT) in human subjects with ABCA1 deficiency.

Four Japanese patients with TD were investigated by OGTT with 75 g glucose. In all TD patients, the plasma glucose concentration after 30 min progressively increased, indicating a type 2 diabetic pattern; however the plasma insulin concentration did not respond well to glucose increase. The calculated insulinogenic index was significantly lower in TD patients than in non-diabetic controls (0.055+/-0.034 vs 0.775+/-0.538, mean+/-SD, p<0.05, respectively).

Although the number of TD patients was very small in the current study, these observations indicated a possible mechanism that glucose-stimulated insulin secretion might be impaired in human TD patients with ABCA1 mutations. Taken together, ABCA1 may be involved in insulin secretion from pancreatic beta-cells.