Changes in hypothalamic subunits volume and their association with metabolic parameters and gastrointestinal appetite-regulating hormones following bariatric surgery

BackgroundSome nuclei of the hypothalamus are known for their important roles in maintaining energy homeostasis and regulating food intake. Moreover, obesity has been associated with hypothalamic inflammation and morphological alterations, as indicated by increased volume. However, the reversibility of these changes after bariatric surgery-induced weight loss remains underexplored. ObjectiveThe aim of this study was to characterize volume changes in hypothalamic subunits up to two years following bariatric surgery and to determine whether these differences were associated with changes in metabolic parameters and levels of gastrointestinal appetite-regulating hormone levels. MethodsParticipants with severe obesity undergoing bariatric surgery were recruited. They completed high-resolution T1-weighted brain magnetic resonance imaging (MRI) before bariatric surgery and at 4, 12 and 24 months post-surgery. Blood samples collected during the fasting and postprandial states were analyzed for glucagon-like peptide 1 (GLP-1), peptide YY (PYY), and ghrelin concentrations. The hypothalamus was segmented into 5 subunits per hemisphere using a publicly available automated tool. Linear mixed-effects models were employed to examine volume changes between visits and their associations with variables of interest. ResultsA total of 73 participants (mean age 44.5 {+/-} 9.1 years, mean BMI 43.5 {+/-} 4.1 kg/m2) were included at baseline. Significant volume reductions were observed in the whole left hypothalamus 24 months post-surgery. More specifically, decreases were noted in both the left anterior-superior and left posterior subunits at 12 and 24 months post-surgery (all p<0.05, after FDR correction). These reductions were significantly associated with the percentage of total weight loss (both subunits p<0.001), improvements in systolic blood pressure (both subunits p<0.05), and an increase in postprandial PYY (both subunits p<0.05). ConclusionThese results suggest that some hypothalamic morphological alterations observed in the context of obesity could potentially be reversed with bariatric surgery induced-weight loss.