Genetic and Environmental Influences on Regional Brain Uptake of 18F-FDG: A PET Study on Monozygotic and Dizygotic Twins.

UNLABELLED Genetic or environmental influences on cerebral glucose metabolism are unknown. We attempted to reveal these influences in elderly twins by means of (18)F-FDG PET. METHODS (18)F-FDG uptake was studied in 40 monozygotic and 18 dizygotic volunteer twin pairs aged 30 y or over. We also created 18 control pairs by pairing age- and sex-matched genetically unrelated subjects from dizygotic and monozygotic pairs. SUV images of the brain were reconstructed and analyzed by voxel-based statistical analysis with automated region-of-interest setting. The (18)F-FDG uptake in each cerebral lobe was semiquantified by taking a ratio of SUVmean in each region of interest to whole-brain SUVaverage. We calculated an intraclass correlation coefficient of SUV ratio in each region of interest for monozygotic and dizygotic pairs. By comparing differences in coefficients between monozygotic and dizygotic pairs, genetic and environmental contributions were estimated. RESULTS The intraclass correlation coefficient in monozygotic pairs was significantly higher than that in dizygotic pairs in the parietal lobes bilaterally (P < 0.001) and in the left temporal lobe (P < 0.05) but was not significantly different in other lobes. CONCLUSION The present study indicated that in the right and left parietal lobes and left temporal lobe, cerebral glucose metabolism is influenced more by genetics than by environment, whereas in other brain regions the influence of environment is dominant.