Abstract
Aging and diseases related to aging, such as cancer, have been linked to oxidative stress. On the other hand, calorie restriction (CR) is one of the most effective interventions to slow down aging and prevent a variety of diseases such as cancer in preclinical models. CR has also been reported to modify oxidative stress. The aim of this study was to investigate the effects of different CR protocols and aging on oxidative stress parameters in the MMTV-TGF-α breast cancer mouse model in a cross-sectional study. Female mice were randomly enrolled in three groups: ad libitum (AL), chronic calorie restriction (CCR, 15% CR) or intermittent calorie restriction (ICR, three weeks AL followed by one week 60% CR in cyclic periods) starting at the age of 10 weeks until 81/82 weeks of age. Liver samples were analyzed for malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD), glutathione (GSH), and glutathione peroxidase (GSH-Px) levels. At week 49/50, the GSH level increased significantly in the CCR group compared to the AL and ICR-R groups which had higher mammary tumor (MT) incidence rates. Additionally, liver MDA levels in ICR groups were significantly increased, while aging led to decreased CAT and SOD activities in all CR groups. The application of different CR protocols did not have any significant effect on MDA, CAT, and SOD parameters in the liver at week 81/82. These results suggest that although GSH may interfere with MT development at the systemic level, many of the oxidative stress parameters may have more local effects on tumor development than the systemic effects.