Exposure to an acute stress impaired the metabolic plasticity of resilient rats by enhancing fatty acid β-oxidation in the ventral hippocampus

The concept of resilience has changed over time and nowadays it refers to the positive adaptation to life adversities, rather than to the absence of a pathological response normally occurring in susceptible people. Based on our previous data showing that the exposure to the chronic mild stress (CMS) paradigm differently affected bioenergetics in the ventral hippocampus of vulnerable and resilient animals, here we investigated whether resilience is a stable trait or if the energetic strategy set in motion to sustain resilience unveils a vulnerability feature in a more dynamic situation. To this aim, vulnerable and resilient rats after 6 weeks of CMS were subjected to a further acute, unfamiliar restraint stress (ARS) and metabolomic studies were conducted in the ventral hippocampus. We observed that exposure to a single novel challenge negatively affects the fuel utilization of resilient animals. Indeed, while they increase glycolysis to sustain the non-hedonic phenotype when exposed to CMS, they shift to fatty acid β-oxidation after ARS, as vulnerable animals following CMS, suggesting that the energy strategy that guarantees resilience is fragile and can be negatively modified by a different environmental condition. These results suggest that strengthening resilience to foster individuals to bounce back from stressful life events may represent a strategy to decrease vulnerability or prevent the risk of relapsing to a pathological state.