Effects of fasting and re-feeding on energy metabolism and thermogenesis in the tree shrew (Tupaia belangeri)

Abstract

To investigate the effect of fasting and re-feeding on energy metabolism and thermogenesis in the tree shrew (Tupaia belangeri), the changes in body mass and body fat mass, resting metabolic rate (RMR), non-shivering thermogenesis (NST), body composition, mitochondrial cytochrome c oxidase (COX) activity in liver and brown adipose tissue (BAT), uncoupling protein-1 (UCP1) content of BAT, serum leptin level and post-fasting food intake were monitored and measured. The results showed that fasting induced a significant reduction in body mass and body fat mass. Body mass was restored to the control level in re-feeding tree shrew except for the body fat. RMR and NST decreased significantly in response to fasting, and returned to the control level after re-feeding. Fasting induced significant reduction in total, but not specific, COX activity (nmol O2/min/total tissue) in liver and BAT, and UCP1 content in BAT, which was reversed after re-feeding 48 h. Fasting of 12 h induced a rapid reduction in serum leptin content. There were no post-fasting compensatory increases in food intake. Interestingly, the tree shrew did not recover adipose tissue mass, nor serum leptin levels, upon re-feeding. These results suggest that T. belangeri can adjust the status of its physiology integratively to cope with the lack of food by means of decreasing body mass, adaptive thermogenesis and serum leptin levels, and serum leptin level acted as a starvation signal to mediate predominantly the reduction in body mass and energy expenditure.