Effects of long-term intermittent versus chronic calorie restriction on oxidative stress in a mouse cancer model.

Calorie restriction (CR) is one of the most effective methods to prevent many diseases including cancer in preclinical models. However, the molecular mechanism of how CR prevents cancer is unclear. The aim of this study was to understand the role of oxidative stress (OS) in the preventive effects of different types of CR in aging mouse mammary tumor virus-transforming growth factor-alpha (MMTV-TGF-α) female mice. Mice were enrolled in ad libitum (AL), chronic CR (CCR, 15% CR) or intermittent CR [ICR, 3 weeks AL (ICR-Refeed, ICR-RF) and 1 week 60% CR (ICR-Restriction, ICR-R) in cyclic periods] groups started at the age of 10 weeks and continued until 81/82 weeks of age. Blood samples were collected to measure malondialdehyde (MDA), glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD) levels. There was no significant difference for MDA levels among the dietary groups although the chronic calorie restriction (CCR) group had lower MDA levels compared to intermittent calorie restriction (ICR) and AL group at different time points. There was also no change in MDA levels of CCR group with aging. On the other hand, the CCR group had higher CAT and SOD activity compared to ICR-R, ICR-RF, and AL groups. Moreover, GSH level was higher in CCR compared to ICR group at week 49/50 (p < .05). CAT and SOD activities were also positively correlated (p < .05). Here, for the first time, the long-term (72 weeks) effects of different types of CR on OS parameters were reported. In conclusion, moderate that is, 15%, CCR is more likely to be protective compared to the same overall calorie deficit implemented by ICR against OS that may play role in the preventive effects of CR.