Imaging Study On Brain Function And White Matter Integrity Regulated By Bariatric Surgery

With the rapid development of the domestic economy,people's living standards improved,eating habits changed,life and work pressure increased,hence Chinese obese population has been ranked first in the world,and obesity has become one of the important factors affecting human health.One of the main causes of obesity is the accumulation of fat in the body,which is due to excessive energy ingestion.Long-term obesity not only increases the prevalence of diabetes,cardiovascular disease,respiratory disease,high blood pressure,fatty liver and cancer,but also affects the mental health of obese people.Currently,there are many treatments for obesity,and weight loss surgery is considered to be the only long-term effective way to reduce and control weight.Obese imaging studies found that obesity caused brain functional and structural abnormalities in the prefrontal lobe,limbic system and other regions;but after weight loss surgery,changes in brain function and structure have rarely been studied.Did weight loss surgery cause changes in neural plasticity,reversing the abnormal function and structure of obesity? How does it cause this change? These are the scientific questions that need to be studied in this paper.Thus,the paper used magnetic resonance imaging(MRI),and adopted laparoscopic sleeve gastrectomy(LSG)and obesity-related models to study the changes of brain baseline activity and white matter fibrosis in obese patients before and after weight loss.In this study,we recruited obese subjects who were willing to accept weight loss surgery and normal weight subjects who were matched with obese subjects in gender and age.We collected the resting state functional magnetic resonance imaging,diffusion tensor imaging(DTI)and 3D structural images of the obese patients before and after surgery and normal weight people;then we collected behavioral data,and filled in their diet,mental state and other related scales.1)For the resting state functional image,the brain activity difference between the obese group before and after the operation and the normal weight group was studied by Amplitude of Low Frequency Fluctuation(ALFF).The results showed that obesity caused frontal lobe of the brain(dorsal lateral frontal lobe,anterior cingulate gyrus,orbital fissure,etc.)and limbic system(amygdala,hippocampus,insula,etc.)abnormalities,but after weight loss surgery,the above differences in the brain changed towards the trend of normal weight subjects.2)The regions with differences above were defined as regions of interest(ROIs),and the effective connectivity analysis based on Granger Causal Analysis(GCA)was used to describe the causal relationship between the regions.Studies showed that there was an enhanced effective connection between the orbital frontal cortex(OFC)and the reward system(caudate,thalamus,etc.)as well as the limbic system(amygdala,hippocampus,insula,etc.),resulting in an abnormal driving force.The effective connection between the DLPFC and midbrain margin system(amygdala,etc.)was weakened,indicating that the inhibitory ability decreased.The effective connectivity of the OFC and midbrain margin system was significantly decreased after surgery,thus the abnormal driving force was weakened.The DLPFC to the reward system(caudate nucleus)and the OFC had enhanced connectivity,which showed enhancement of their ability to suppress control.3)For DTI imaging,we mainly studied the changes of fibrous integrity of white matter in the brain before and after weight loss surgery.We found that the fractional anisotropy(FA)of obese patients was decreased,and post-surgery FA was increased showing a recovery.4)Then,fiber tracking was studied based on the regions where the above-mentioned function differed in explaining the change of the structural connection.The results showed that the connection of the DLPFC on the left and right sides and the hippocampus(HIPP),insula and thalamus,and the connection between the OFC and the caudate were enhanced,thus the connection between the DLPFC and the insula was weakened;post-surgery trend returned to the normal weight subjects' level.5)Finally,the fusion analysis of the functional and structural images was carried out,including the correlation analysis between brain activity level and white matter fiber integrity,the correlation analysis of functional and structural connection,and the relationship between functional and structural image data and behavioral data related to the analysis.It was found that the change of the OFC activity level was positively correlated with the change of body mass index(BMI).The change of the FA value in the GCC was positively correlated with waist circumference change,while the change of the OFC activity level and FA value of the GCC could be used as a target for evaluating the effect of weight loss surgery.In addition,the functional linkage between the OFC and DLPFC,OFC,and insula has a negative correlation and a positive correlation between postoperative and obese states respectively.In this paper,by studying obesity and weight loss surgery for the central nervous system function and structure impact,we can better reveal obesity and weight loss surgery mechanisms related to the central nervous system for clinical treatment.