Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis of (A) IRS-1, (B) IRS-2, (C) FAS and (D) PPAR-α expression in the liver tissue of the control, IR and metformin-administered rats. RNA (1 mg) was extracted, reverse transcribed and RT-PCR analysis was conducted to assess IRS-1, IRS-2, FAS and PPAR-α expression, as described in the materials and methods. Densitometric analysis was conducted for three independent experiments, and data are presented as the mean ± standard error for the three independent experiments. *P<0.05, vs. control; #P<0.05, vs. IR group. IR, insulin resistance; IRS, insulin receptor substrate; FAS, fatty acid synthetase; PPAR-, peroxisome proliferator activated receptor; G3PDH, glyceraldehyde-3-phosphate dehydrogenase.