Connectome-Based Prediction of Optimal Weight Loss Six Months After Bariatric Surgery.

Despite bariatric surgery being the most effective treatment for obesity, a proportion of subjects have suboptimal weight loss post-surgery. Therefore, it is necessary to understand the mechanisms behind the variance in weight loss and identify specific baseline biomarkers to predict optimal weight loss. Here, we employed functional magnetic resonance imaging (fMRI) with baseline whole-brain resting-state functional connectivity (RSFC) and a multivariate prediction framework integrating feature selection, feature transformation, and classification to prospectively identify obese patients that exhibited optimal weight loss at 6 months post-surgery. Siamese network, which is a multivariate machine learning method suitable for small sample analysis, and K-nearest neighbor (KNN) were cascaded as the classifier (Siamese-KNN). In the leave-one-out cross-validation, the Siamese-KNN achieved an accuracy of 83.78%, which was substantially higher than results from traditional classifiers. RSFC patterns contributing to the prediction consisted of brain networks related to salience, reward, self-referential, and cognitive processing. Further RSFC feature analysis indicated that the connection strength between frontal and parietal cortices was stronger in the optimal versus the suboptimal weight loss group. These findings show that specific RSFC patterns could be used as neuroimaging biomarkers to predict individual weight loss post-surgery and assist in personalized diagnosis for treatment of obesity.

Brain Connectivity, and Hormonal and Behavioral Correlates of Sustained Weight Loss in Obese Patients after Laparoscopic Sleeve Gastrectomy.

The biological mediators that support cognitive-control and long-term weight-loss after laparoscopic sleeve gastrectomy (LSG) remain unclear. We measured peripheral appetitive hormones and brain functional-connectivity (FC) using magnetic-resonance-imaging with food cue-reactivity task in 25 obese participants at pre, 1 month, and 6 month after LSG, and compared with 30 normal weight controls. We also used diffusion-tensor-imaging to explore whether LSG increases brain structural-connectivity (SC) of regions involved in food cue-reactivity. LSG significantly decreased BMI, craving for high-calorie food cues, ghrelin, insulin, and leptin levels, and increased self-reported cognitive-control of eating behavior. LSG increased FC between the right dorsolateral prefrontal cortex (DLPFC) and the pregenual anterior cingulate cortex (pgACC) and increased SC between DLPFC and ACC at 1 month and 6 month after LSG. Reduction in BMI correlated negatively with increased FC of right DLPFC-pgACC at 1 month and with increased SC of DLPFC-ACC at 1 month and 6 month after LSG. Reduction in craving for high-calorie food cues correlated negatively with increased FC of DLPFC-pgACC at 6 month after LSG. Additionally, SC of DLPFC-ACC mediated the relationship between lower ghrelin levels and greater cognitive control. These findings provide evidence that LSG improved functional and structural connectivity in prefrontal regions, which contribute to enhanced cognitive-control and sustained weight-loss following surgery.

Laparoscopic sleeve gastrectomy improves brain connectivity in obese patients.

OBJECTIVE: Obese individuals have shown functional abnormalities in frontal-limbic regions, and bariatric surgery is an effective treatment for morbid obesity. The aim of the study was to investigate how bariatric surgery modulates brain regional activation and functional connectivity (FC) to food cues, and whether the underlying structural connectivity (SC) alterations contribute to these functional changes as well as behavioral changes. METHODS: A functional magnetic resonance imaging cue-reactivity task with high- (HiCal) and low-calorie (LoCal) food pictures and diffusion tensor imaging (DTI) with deterministic tractography were used to investigate brain reactivity, FC and SC in 28 obese participants tested before and 1 month after laparoscopic sleeve gastrectomy (LSG). Twenty-two obese controls (Ctr) without surgery were also tested at baseline and 1 month later. RESULTS: LSG significantly decreased right dorsolateral prefrontal cortex (DLPFC) activation to HiCal versus LoCal cues and increased FC between DLPFC and ventral anterior cingulate cortex (vACC), which are regions involved in self-regulation of feeding behaviors. LSG also increased SC between DLPFC and ACC as quantified by fractional anisotropy. Increases in SC and FC between DLPFC and ACC were associated with greater reductions in BMI, and SC changes were positively correlated with FC changes. Increased SC between right DLPFC and ACC mediated the relationship between reduced BMI and increased right DLPFC-vACC FC; likewise, increases in right DLPFC-vACC FC mediated the relationship between increased right DLPFC-ACC SC and reduced BMI. CONCLUSION: LSG might induce weight loss in part by increasing SC and FC between DLPFC and ACC, and thus strengthening top-down control over food intake.