Glucose depletion reduces cholesterol intracellular accumulation in ABCB1-dependent mechanism.

Abstract

Lipids and glucose are important components of energy metabolism closely linked to each other. Glucose regulates cholesterol uptake via regulating the expression of different membrane transport proteins including NPC1L1, SR-B1 and ATP-binding cassette (ABC) transporters. Here, we explored further the mechanism underlying glucose-mediated regulation of cholesterol absorption and secretion. Caco-2 cells were cultivated in glucose-repletion versus glucose-depletion conditions. Quantitative real-time PCR and western blot were performed to assess mRNA and protein levels of different transporters. The amount of 25-NBD cholesterol uptake and the activity of P-gp (ABCB1) protein were measured by direct fluorometry and Rhodamine 123 efflux assay, respectively. Glucose-depleted Caco-2 cells showed lower NPC1L1 expression accompanied by reduced cholesterol uptake when compared to glucose-repleted cells. This effect was associated with an increase in the apical secretion of cholesterol compared with the basal secretion. In addition, glucose depletion upregulated both the expression level and activity of ABCB1, an apical pole transporter. However, the expression levels of ABCG5/G8, an apical sterol dimer transporter as well as ABCA1, a basal cholesterol transporter, were unchanged. The knockdown of ABCB1 in Caco-2 cells increased the intracellular accumulation of cholesterol. Glucose depletion reduces cholesterol accumulation in intestinal cells upon inducing its apical removal via ABCB1-dependent mechanism.