1,25-Dihydroxyvitamin D(3) inhibits the proliferation of rat mesangial cells induced by high glucose via DDIT4

1,25-Dihydroxyvitamin D(3)(1,25(OH)(2) D(3)) is a secosteroid with antiproliferative property. It also plays a pivotal renoprotective role in diabetic nephropathy. We investigated whether 1,25(OH)(2)D(3) could inhibit the proliferation of rat mesangial cells exposed to high glucose via the DNA-damage-inducible transcript 4/mammalian target of rapamycin(DDIT4/mTOR) pathway. The cell proliferation rate and cell cycle duration were measured using cell counting kit-8 assay and flow cytometry. Protein expression was assayed by Western blot. Glucose acted as a growth factor in rat mesangial cells, promoted cell proliferation. In parallel, the protein expression of DDIT4, TSC1/TSC2, and 4E-BP1 were decreased, and Rheb, mTOR, and p70S6K were increased. Acting via the DDIT4/mTOR signaling, 1,25(OH)(2) D(3) treatment reversed these pathological changes, upregulated DDIT4, TSC1/TSC2, and 4E-BP1, downregulated Rheb, mTOR, and p70S6K. The short-term overexpression of DDIT4 inhibited the proliferation of rat mesangial cells, similar to 1,25(OH)(2) D(3) treatment. siRNA knockdown of DDIT4 suppressed antiproliferative responses to 1,25(OH)(2) D(3). These results suggest that 1,25(OH)(2) D(3) inhibits the proliferation of rat mesangial cells induced by high glucose via the DDIT4/mTOR signaling pathway.