Research Paper Volume 7, Issue 3 pp 152—166

Figure 4. SIRT1 protein levels in normal human diploid fibroblasts decrease with increasing passage number and CR treatment retards this effect. (A) Representative immunoblots for SIRT1 (upper panels) and β-actin (lower panels) proteins from IMR-90 cells (left panel) and WI-38 cells (right panel) at different passage number. (B) Quantification of SIRT1 protein levels shown in (A), after correction for β-actin loading controls. Data represent the average -/+ SEM from three independent experiments; *= statistically significant (p<0.05). (C) Representative immunoblots of SIRT1 (upper panels) and β-actin (lower panels) proteins from IMR-90 cells at PDL 32 and PDL 45 (left panels) and WI-38 cells at PDL 37 (right panels) cultured for one week in media containing 10% CR or AL serum. (D) Quantification of SIRT1 protein levels shown in (C), after correction for β-actin loading control. Data represent the average -/+ SEM from three independent experiments (*and #= statistically significant (p<0.05) for PDL effect and CR vs. AL effect, respectively).