Metabolic consequences of chronic social stress
Male rats in mixed-gender rat colonies quickly form dominance hierarchies when housed in a visible burrow system (VBS), an animal model of chronic social stress. Subordinate (SUB) males consistently lose 10-15% of their original body weight over 14 days in the VBS, while dominant (DOM) males maintain their body weight. Body composition analysis revealed that DOM and SUB lost adipose tissue; SUB also lost lean tissue as well. SUB had elevated plasma corticosterone and reduced plasma testosterone compared to DOM and control males, suggesting that SUB weight gain during recovery would be predominantly adipose tissue. When allowed to recover from VBS stress for 21 days, SUB quickly regained lost weight and were hyperphagic throughout the recovery period. SUB had a higher % body fat after the 21-day recovery period than DOM and this effect was further enhanced when rats were exposed to a second cycle of VBS stress and recovery. Consistent with increased % fat, SUB had elevated plasma leptin and insulin levels suggesting that SUB were glucose intolerant. However, after 21 days recovery, both SUB and DOM were more efficient at clearing an oral glucose load suggesting that there may be differences if glucose trafficking. The data also suggest that neurochemical changes associated with chronic social stress influence systems involved in food intake and body weight regulation and may result in metabolic disorders over long-term, repeated exposures to stress.