Increased SIRT1 expression improves telomere length maintenance with increasing age in SIRT1^super mice. (A and D, left) Telomere fluorescence frequency distribution as determined by Q-FISH on liver sections from mice of the indicated genotypes. (C and F) Representative images of telomere Q-FISH on liver sections from SIRT1^super and SIRT1^+/+ mice, where DAPI nuclear staining is shown in blue and telomere signal in red. (B) Mean telomere length in auf, percentage of short telomeres (<60 auf), and percentage of long telomeres (>80 auf) are shown. (E) Mean telomere length in auf, percentage of short telomeres (<100 auf), and percentage of long telomeres (>120 auf) are shown. (G) Telomere fluorescence frequency distribution (Q-FISH) of glomeruli and tubules in kidney sections from mice of the indicated age and genotype. (H) Mean telomere fluorescence, percentage of short telomeres (<100 auf), and percentage of long telomeres (>120 auf) are shown. Note that telomere fluorescence decreases with age in kidney glomeruli and tubules indicative of telomere shortening, whereas this shortening does not occur in SIRT1^super mice. SEM, the number of animals, and telomere signals used for the analysis are shown for each genotype. Student’s t test was used in the case of the mean telomere intensity; otherwise, the Fisher exact test was used for statistical calculations. P-values are indicated. Bars, 100 µm.