High glucose increases mesangial lipid accumulation via impaired cholesterol transporters

Diabetes, whether it occurs before or after transplantation, plays an important role to decrease graft function and survival. In addition renal lipid accumulation has been suggested to play a role in the development and progression of chronic renal allograft rejection. Intracellular lipid accumulation is governed by a balance between the influx and efflux of lipid. Cholesterol transporters, such as scavenger receptor (SR)-A1, CD36, and ATP binding cassette (ABC) A1 and G1 (ABCG1), coordinate to regulate cellular lipid status. Therefore, in the present study, we examined whether high glucose caused lipid accumulation in mesangial cells as a result of altered cholesterol transporters. Mouse mesangial cells were stimulated with 30 mmol/L D-glucose (high glucose); 100 μmol/L oleic acid (OA) used as a positive control. Cellular lipid accumulation was measured by Oil Red O staining. Protein and mRNA expression of cholesterol influx (SR-A1 and CD36) and efflux (ABCA1 and ABCG1) transporters were evaluated using Western blot analysis and real-time quantitative polymerase chain reaction, respectively. High glucose was shown to significantly increase lipid accumulation in mesangial cells at 24 hours as was observed for OA. SR-A1 and CD36 mRNA expression levels were 1.5-fold and 3.5-fold higher, respectively, in high glucose-stimulated than control mesangial cell, whereas ABCG1 mRNA expression decreased to 60% of controls; however, there was no decrease in ABCA1 mRNA. Altered protein expression of each transporter in mesangial cells cultured under conditions of high glucose concentrations was consistent with mRNA expression. Osmotic control using mannitol did not significantly affect any of the measured parameters in the present study. These results demonstrated that high glucose, in itself, can induce mesangial lipid accumulation; this effect may be associated with an impaired balance between the influx and efflux of cholesterol.