Effects of cold exposure on energy metabolism and oxidative stress in two plateau rodents

Low temperature is a major environmental constraint for animals inhabiting cold plateau regions because it increases thermoregulatory energy demand and can disrupt oxidative balance. We examined physiological responses of two sympatric plateau rodents, Eothenomys miletus and Apodemus chevrieri, during 28 d of cold exposure (5 °C ± 1 °C) relative to control conditions (25 °C ± 1 °C). Both species increased resting metabolic rate (RMR) and food intake and showed lower body mass under cold conditions. Cold exposure also increased liver mass and induced digestive-tract remodeling, with more extensive changes in E. miletus than A. chevrieri. Activities of the antioxidant enzyme superoxide dismutase (SOD) and catalase (CAT), together with the oxidative stress markers malondialdehyde (MDA) and hydrogen peroxide (H2O2), changed in a tissue- and species-specific manner. Correlation and principal component analyses further indicated different patterns of oxidative regulation in the two species. E. miletus showed a comparatively dense inter-organ correlation structure centered on CAT, whereas A. chevrieri showed fewer significant inter-organ associations. Thus, the two rodents share a broad metabolic response to sustained cold exposure but differ in the organ-level organization of oxidative balance.