Tissue-specific changes in antioxidant defence during ageing: the effect of chronic cold exposure

Ageing is a multifactorial process characterised by the progressive dysregulation of redox homeostasis in different organs. Although various endogenous and exogenous factors influencing ageing have been identified, limited evidence exists regarding the effects of chronic cold exposure on aged rats. To address this, we investigated interscapular brown (iBAT) and retroperitoneal white (rWAT) adipose tissue, skeletal muscle, and liver in rats (3-, 6- and 24-month-old) at 22 ± 1 °C, alongside a cohort of 24-month-old rats kept at 4 ± 1 °C from 6 to 24 months of age. We measured antioxidant defence (AD) components: the activity of copper zinc (CuZnSOD) and manganese (MnSOD) superoxide dismutase, catalase, glutathione peroxidase (GSH-Px), glutathione reductase (GR), thioredoxin reductase (TR), glutathione S-transferase (GST), and total glutathione (GSH) content. With chronological ageing, enzyme activity decreased in rWAT (catalase, GSH-Px, GR, TR, GST) and iBAT (GSH-Px). Conversely, aged rats exposed to 4 ± 1 °C showed an upregulation of AD components in rWAT (catalase, GSH-Px, GR, TR, GST; GSH), iBAT (catalase, GSH-Px, TR; GSH), and muscle (GSH-Px, GR, TR, GST), compared to age-matched group. However, CuZnSOD and MnSOD activities remained unchanged across all experimental groups and tissues. In addition, none of the measured AD components in the liver changed significantly across groups. Collectively, these results reveal a distinct modulation of the AD profiles in different organs, both during chronological ageing and after long-term exposure to cold, underscoring an integrated systemic responsiveness. This is most evident in the preserved AD response to prolonged cold exposure in the key thermogenic tissue, iBAT, of aged rats.