96 6 ART for Antiaging
activator SIRT3. ARG leads to the highest Mn-SOD activity, suggesting a syner-
gistic manner of antioxidants located in different compartmental space. However,
ARG does not give rise to the highest SIRT3 activity although SIRT3 still shows
activation in a time-dependent manner. Accordingly, as an essential consequence
of ROS scavenging by coordinated antioxidation, a significant decline of ROS
was measured in mouse skeletal muscles treated by CR and mimetics (Wang et al.
2015b). These results indicated that all treatments exhibit the hormetic effects
through triggering antioxidative responses and in turn scavenging ROS thereafter.
6.3.2.2 Global Downregulation of Ubiquitylation Genes by a Low
Oxidative Stress Milieu
To make sure the plausible relevance of CR to autophagy, we set out to investigate
whether CR would affect autophagy-related ubiquitylation genes (Ubi) that are
involved in regulated protein degradation. Along with exposure of mice to CR, four
kinds of CR mimetics (ART, SNP, ARG, and H 2 O 2 ) were separately injected into
mouse skeletal muscles for expression profiling of Ubi pathway genes. Surprisingly,
almost all examined Ubi genes are notably downregulated among different treatment
groups. It could be observed that the ubiquitin-activating enzyme (E1)-encoding
gene, Atg7, and Ube2c gene that encodes a ubiquitin-conjugating enzyme (E2)
are downregulated much in CR but less in other treatments. It was also noticed the
upregulation of two ubiquitin-protein ligase (E3) genes, Hecw1 and Rnf148, in mice
treated by CR and H 2 O 2 , but not in other samples. These data demonstrated that E1
and E2 genes are downregulated by ART, SNP, or ARG, but E3 genes are upregu-
lated by CR or H 2 O 2 (Wang et al. 2015b). These results suggested that regulated
protein degradation is unlikely for mice treated by ART, SNP, or ARG, but likely for
mice treated by CR or H 2 O 2.
Among the expression profiles of Ubi genes, one of the most markedly down-
regulated genes is the well-known tumor suppressor gene Brca1, whose expres-
sion level declines down to approximately 25-folds in all samples of mouse skeletal
muscles treated by CR and mimetics. Another tumor suppressor gene, Bard1, which
encodes BARD1 interacting with BRCA1, is also downregulated much by ART,
SNP, or ARG, but less by CR. The famous tumor suppressor gene, Trp53, is slightly
downregulated in all treatment groups. BRCA1 is known to interact with other part-
ner proteins for DNA repair, so we further analyzed the expression levels of Brca2,
Rb, Myc, Rad50, and Rad51 in mouse skeletal muscles after treatment by CR per se
and mimetics. It is clear that all quantified DNA repair genes are either downregu-
lated or unchanged in the CR group. In other treatment groups, Brca2, Rad50, and
Rad51 are downregulated or unchanged, but Rb and Myc are mildly upregulated
(Wang et al. 2014 ). These results indicated that CR only allows the existence of
low-level DNA repair proteins, whereas CR mimetics partially mimic CR for down-
regulation of DNA repair genes. The global downregulation of tumor suppressor
genes and other DNA repair genes might reflect less DNA damage, higher chromo-
somal integrity, and thereby longer telomeres. If this deduction is correct, CR and
mimetics should increase the lengths of telomeres within treated cells.