Figure 3.

SIRT6 overexpression blocks the cardiac hypertrophic response. (a) [³H]-leucine incorporation into total cellular protein normalized to the DNA content of neonatal rat cardiomyocytes infected with WT SIRT6 adenovirus (Ad.SIRT6) or control adenovirus (Ad.GFP) and then treated with phenylephrine (PE) (20 µm) for 48 h. Data are presented as the mean ± s.d. n = 5 independent experiments. C.p.m. counts per minute. (b) Sarcomere organization, as determined by immunostaining cells for sarcomeric α-actinin (green), and ANF release (red), as determined by staining cells with an ANF-specific antibody, in cardiomyocytes infected with the indicated adenoviruses (Ad.mock indicates empty vector) and stimulated with phenylephrine. DAPI stain marks the position of nuclei. Scale bars, 10 µm. (c) HW/TL ratios in nontransgenic (NTg) and SIRT6 transgenic (SIRT6-Tg) mice subjected to sham or to TAC treatment for 4 weeks. Data are presented as the mean ± s.d. n = 8 mice per group. (d,e) Left ventricular wall thickness and fractional shortening, as measured by echocardiography, of the same hearts as in c. n = 6 mice per group. For c–e, one-way analysis of variance (ANOVA) was applied to calculate the P value. (f) Heart sections of nontransgenic and SIRT6 transgenic mice subjected to sham or TAC treatment and stained with WGA to demarcate cell boundaries (top; scale bars, 10 µm) or Masson’s trichrome to detect fibrosis (bottom; scale bars, 40 µm). (g) Quantification of myocyte cross-sectional area in nontransgenic and SIRT6 transgenic mice subjected to sham or to TAC treatment. Data are presented as the mean ± s.d. n = 5 mice per group. Student’s t test was used to calculate the P value. NS, not significant.