Mikrostrukturelle Hirnveränderung bei adipösen Patienten nach Gewichtsreduktion durch interdisziplinär betreute Diät oder Roux-en-Y Magenbypass. Eine Diffusion Tensor Imaging-Studie.

Obesity is a chronical disease, which is associated with a variety of comorbidities. An increased body mass index (BMI) has been linked with structural brain changes and lower cognitive performance. Moreover, an enhancement of cerebral microstructure after sleeve gastrectomy has already been proven. In our study we aimed to determine the effect of different ways of weight loss on various dimensions of cognitive functions. Therefore, obese participants, who successfully underwent either a dieting program (OPTIFAST®52) or a surgical Roux-en-Y gastric bypass (RYGB), were analyzed by neuropsychological testing and magnetic resonance imaging (MRI). Subject of this particular dissertation was a longitudinal analysis of brain microstructure by diffusion tensor imaging (DTI). We assessed, whether changes in brain structure could be detected by DTI after the different methods of weight loss, and if one of the methods could be shown to be more effective. In total 36 obese participants with a BMI > 25 kg/m² and an age of 18-75 years were involved (OPTIFAST®52 n=17, RYGB n=11, control group n=8). The examination included an anamnesis, neuropsychological tests and brain MRI at two times – before the beginning of weight loss intervention (T0) and at least three months thereafter (T1). In MRI, T1-weighted images using 3D MPRAGE sequences were taken as well as diffusion-weighted images using singleshot echoplanar imaging (EPI). Subsequently the scans were analyzed to determine changes in brain structure within the study groups as well as differences between the groups. Fractional anisotropy (FA), axial diffusivity (AD) and radial diffusivity (RD) were adduced as verifiable parameters for axonal integrity and myelination. We also calculated white and gray matter volumes. Results of DTI-measurements showed a significant increase of FA in the brain stem and the cerebellum as well as a decrease of RD in the brain stem of patients after RYGB. Furthermore, there were significant findings in white and gray matter changes in RYGB-group. An increase in white matter in the left pericalcarine cortex as well as an increase in gray matter in the left inferior parietal lobule was determined. A decrease of grey matter was registered in the rostral middle frontal gyrus. Regarding to the anatomical functional brain correlate, we could find an advantage of weight loss by surgical RYGB over an interdisciplinary coached dieting program. Participants undergoing RYGB showed higher fiber integrity, density and myelination in central brain structures playing a role in motion sequence and food intake. There were greater volumes of gray and white matter in brain areas, which take part in cognitive functions such as speech, calculating, writing and processing of visual stimuli. A decrease of gray matter in the rostral middle frontal gyrus could be related to a lowered occurrence of depression and to a reduced stress level. Participants, who took part in the dieting program, didn’t show significant changes in brain structure in DTI-measurements. By volume calculation there could be found a reduction of grey matter in the nucleus accumbens, which is associated with an increased incidence of neuropsychiatric disorders such as depression and Alzheimer’s disease. This disadvantageous effect should be investigated in a further study including a longer observation period. The control group provided a large number of false positive results due to a very small group size. Additional research should incorporate a larger number of participants, to achieve a greater comparability between the groups by enhanced matching e. g. to sex and age.