mRNA levels of TGF-β1 and CTGF in the sitagliptin-treated mesangial cells at 36 h. (A) Agarose electrophoresis of RT-PCR products amplified from the total RNA extracts of mesangial cells, where β-actin was used as the internal standard in each sample. (B and C) RT-PCR data for the mRNA relative quantity of TGF-β1 and CTGF performed by densitometric analysis. Data are expressed as the mean ± standard error of the mean, n=3. *P<0.05 and **P<0.01 vs. the NG group; #P<0.05 and ##P<0.01 vs. the HG group; @P<0.05 vs. SITL. TGF-β1, transforming growth factor-β1; CTGF, connective tissue growth factor; NG, normal glucose; MA, mannitol; HG, high glucose; DMSO, high glucose with 1% dimethyl sulfoxide; SITL, high glucose with 0.1 µmol/ml sitagliptin; SITM, high glucose with 1 µmol/ml sitagliptin; SITH, high glucose with 10 µmol/ml sitagliptin.