Neuroanatomical Changes in White and Grey Matter after Sleeve Gastrectomy

Abstract

Background: MRI studies show that obese adults have reduced grey (GM) and white matter (WM) tissue density as well as altered WM integrity. It remains to be examined if bariatric surgery induces structural brain changes. The aim of this study is to characterize GM and WM density changes in a longitudinal setting, comparing pre-and post-operation and to determine whether these changes are related to inflammation and cardiometabolic markers. Methods: 29 severely obese participants (age: 45.9±7.8 years) scheduled to undergo sleeve gastrectomy (SG) were recruited. High-resolution T1-weighted anatomical images were acquired 1 month prior to as well as 4 and 12 months after surgery. GM and WM densities were quantified using voxel-based morphometry (VBM). Circulating lipid profile, glucose, insulin and inflammatory markers (interleukin (IL)-6, C-reactive protein (CRP) and lipopolysaccharide-binding protein (LBP) were measured at each time point.A linear mixed effect model was used to compare brain changes before and after SG, controlling for age, gender, initial BMI and diabetic status. To assess the associations between changes in adiposity, metabolism and inflammation and changes in GM or WM density, the mean GM and WM densities were extracted across all the participants using atlas, and linear mixed-effect models were used. Results: As expected, weight, BMI, waist circumference and neck circumference significantly decreased after SG compared with baseline (p<0.001 for all). A widespread increase in WM density was observed after surgery, particularly in the cerebellum, brain stem, cerebellar peduncle, cingulum, corpus callosum and corona radiata (p<0.05, after FDR correction). Significant increases in GM density were observed 4 months after SG compared to baseline in several brain regions such as the bilateral occipital cortex, temporal cortex, precentral gyrus and cerebellum as Michaud et al. 2019, page 3 well as right fusiform gyrus, right hippocampus and right insula. These GM and WM increases were more pronounced and widespread after 12 months and were significantly associated with post-operative weight loss and the improvement of metabolic alterations.Our linear mixed-effect models also showed strong associations between post-operative reductions in LBP, a marker of inflammation, and increased WM density. To confirm our results, we tested whether the peak of each significant region showed BMI-related differences in an independent dataset (Human Connectome Project). We matched a group of severely obese individuals with a group of lean individuals for age, gender and ethnicity.Severe obesity was associated with reduced WM density in the brain stem and cerebellar peduncle as well as reduced GM density in cerebellum, regions that significantly changed after surgery (p<0.01 for all clusters). Conclusions: Bariatric surgery-induced weight loss and improvement in metabolic alterations is associated with widespread increases in WM and GM densities. These post-operative changes overlapped with baseline brain difference...

Spontaneous Neural Activity Changes after Bariatric Surgery: a resting-state fMRI study

“…To support the idea that the effects of bariatric surgery represent a resolution of adiposity-related brain abnormalities, we previously investigated whether the brain regions that show improvements after bariatric surgery are also different between individuals who are severely obese and those who are lean. Using an independent dataset from the Human Connectome Project (HCP), we found that changes in brain morphometry observed following surgery overlapped with brain differences between the obese and normal weight states, in line with the hypothesis that weight loss and/or concomitant improvement of metabolic/inflammatory alterations could be responsible for the post-operative changes in the areas previously impacted by obesity (29). Previous studies have also suggested that post-operative changes in WM and GM densities could be attributed to neural plasticity (30), recovery of brain integrity (31,32), or changes in the composition of fiber tracts (30).…”

“…Our recent findings (29) confirmed the results of three studies showing an increase in WM and GM densities following bariatric surgery (30)(31)(32). These GM and WM increases were most pronounced and widespread 12 months after the surgery, and were significantly associated with post-operative weight loss and improvement of metabolic/inflammatory variables (29). To support the idea that the effects of bariatric surgery represent a resolution of adiposity-related brain abnormalities, we previously investigated whether the brain regions that show improvements after bariatric surgery are also different between individuals who are severely obese and those who are lean.…”

“…As in our previous study (29), GM densities were measured from T1-weighted anatomical MRIs of each participant using a standard voxel-based morphometry (VBM) pipeline (10). The preprocessing steps included: 1) image denoising (50); 2) intensity non-uniformity correction (51); and 3) image intensity normalization into range (0-100) using histogram matching.…”

“…We tested the hypothesis that bariatric surgery induces significant changes in spontaneous neural activity (ReHo and fALFF), and these changes are related to changes in GM density as well as improvements in cardiometabolic variables. As in our previous study (29), we used an independent dataset from HCP to test whether the change in rsfMRI signals observed following bariatric surgery is similar to that seen in individuals with normal body weight versus severe obesity.…”

Association between Visceral Adiposity Index, Binge Eating Behavior, and Grey Matter Density in Caudal Anterior Cingulate Cortex in Severe Obesity

“…Grey matter density was assessed from each T1-weighted MRI using a standard voxel-based morphometry pipeline [ 28 , 52 ]. The preprocessing steps were the following: (1) image denoising [ 53 ]; (2) intensity non-uniformity correction [ 54 ]; and (3) image intensity normalization into range (0–100) using histogram matching.…”