PI3K/Akt pathway mediates high glucose-induced lipid accumulation in human renal proximal tubular cells via spliced XBP-1

In the present study, we investigated the effect of X‐box‐binding protein‐1 (XBP‐1) splicing on lipogenesis in high glucose‐stimulated human renal proximal tubular cell line (HKC). The results revealed that high glucose promoted the splicing of XBP‐1, concomitant with up‐regulation of lipogenic genes including fatty acid synthase, acetyl‐CoA carboxylase, adipocyte differentiation‐related protein, and cellular triglyceride. Again, silence of XBP‐1 with shRNA vector inhibited high glucose‐caused increased lipogenesis. Furthermore, we confirmed that the inhibition of phosphotidyl inositol 3‐kinase (PI3K)/Akt pathway with LY294002 or Akt shRNA vector blocked the effect of high glucose on XBP‐1 splicing and cellular triglyceride. These above data suggest that spliced XBP‐1 mediates high glucose‐induced lipid accumulation in HKC cells and PI3K/Akt pathway may be involved in high glucose‐caused XBP‐1 splicing. J. Cell. Biochem. 113: 3288–3298, 2012. © 2012 Wiley Periodicals, Inc.