Recent studies have frequently employed small-cage housing as a method to induce sedentary behavior (SED) in animal models. However, no research has been conducted to prove that the small cage can limit energy expenditure (EE) below the established SED threshold of 1.5 METs. This study demonstrated the EE of small-cage animals across 24 h and detected alterations in glucose uptake after sedentariness in young male rats. After an 8-weeks period, energy consumption of the animals housed in small-cage environments (S group) stayed below 1.5 METs in 24-h. In contrast, the rats in control group had significant variance in energy expenditure throughout 24-h, with energy consumption exceeding 1.5 METs in over half of the cases. Besides, a significant reduction in body weight was observed in rats in S group compared to controls after 2 weeks. Metabolic assessments demonstrated persistent elevations in fasting blood glucose (FBG) and glycated hemoglobin (HbA1c) levels in the S group throughout the study duration. Relatively muscle weight (wet muscle weight/ body weight) of gastrocnemius and soleus in S group was also decreased. The biochemical analysis indicated reduced muscle glycogen content in the gastrocnemius after both 4-week and 8-week time points. Histopathological examination through HE staining demonstrated disorganized arrangement of muscle fibers in the gastrocnemius of S group animals. Oral glucose tolerance test (OGTT) revealed a significant divergence in glucose levels between groups at 8 weeks, with control animals demonstrating improved glucose clearance, particularly reaching statistical significance at 15 min. Similarly, the area under the curve (AUC) value for the S group was significantly higher than that in the control group. Overall, our findings provide empirical evidence that small-cage housing effectively reduces EE below the established SED threshold of 1.5 METs. Furthermore, our results suggest that prolonged sedentariness induced by small-cage confinement may significantly impair glucose metabolism in rats.
Liang et al. (Sat,) studied this question.