An increase in the accumulation of adipose tissue in growing male mice caused by disturbances in the sleep-wake cycle following night-shifts

The aim of this study was to assess the effects of circadian rhythm disturbances induced by night-shift activities on the accumulation of abdominal adipose tissue and the morphological characteristics and bone mineral density (BMD) of the trabecular bone in the fourth lumbar vertebrae (L4). Fourteen 6-week-old C57BL/6 male mice were assigned to 2 groups, namely, the normal group (NOR; n = 7) and the night-shift group (NS; n = 7). Mice in the NS group were kept under a light/dark cycle that changed every 3 days. The area of the visceral, subcutaneous, and entire abdominal adipose tissue and the structural parameters and BMD of the trabecular bone in the L4 were measured at 0 weeks and 4 weeks from images acquired by in vivo micro-computed tomography. At 4 weeks, the area of the visceral abdominal adipose tissue was significantly higher in the NOR group than in the NS group (p <0.06). However, there were no significant differences in the accumulation of other adipose tissue or in the structural parameters and BMD of the trabecular bone in the L4 (p>0.05). These results implied that the circadian rhythm disturbances induced by night-shift activities increased the accumulation of abdominal adipose tissue, particularly in the visceral region, and led to an increased risk of obesity in the growing mice.