Isolation rearing reduces brain glucose metabolism after burn injury

Objectives We Previously identified brain regions with decreased immediate early gene (IEG) expression in isolation reared (IR) rats ( Levine et al., 2008). In the current study, effects of burn injury on brain FDG uptake were evaluated in Group reared (GR) and Isolation reared (IR) rats. If FDG PET findings correlate with the genetic changes, they could serve as a biomarker in translational studies aimed at linking findings in isolation reared animals to clinical studies of patients presenting with symptoms due to early psychosocial deprivation.

Methods A total of 12 male rats were obtained on post natal day (PN) 17 with lactating dams and were housed as in our prior studies (Levine et al., 2008). On PN 21, 1/2 of the animals were subjected to 20% dorsal burn in 90 degree water for 8 sec or sham treatment. The IR rats were then housed individually and the GR rats were housed in groups (Levine et al., 2007). On PN 49 the rats were fasted for 24 h, anaesthetized with isoflurane/N2O2, positioned in to a custom fabricated head holder, injected with FDG (1.0 mCi via tail vein) and brain images of 5 min. duration were acquired with a Siemens focus 220 (PET/CT. Images were reconstructed using the OSEM 3D/MAP algorithm with zoom 6 (256 x 256 matrix) and ROIs (SUV) were constructed for whole brain and multiple regions.

Results The FDG PET results are summarized in the Table. For whole brain, FDG uptake in sham rats was neatly identical for IR and GR animals (p=NS). In contrast, whole brain FDG PET SUV was reduced by ~53% and IR ~ 68% for GR (p<0.001) and IR (p<0.001) animals at 28 days after burn injury . Similar reduction in FDG PET SUV were observed for thalamus, cerebellum, frontal cortex, parietal cortex and putamen.

Conclusions The finding of FDG SUV differences, suggest the possibility that metabolic changes that can be measured in vivo using PET can be used as a biomarker of molecular changes that have previously only been accessible by ex-vivo measurements.

Research Support Shriners Hospital Boston