Is Bariatric Surgery Brain Surgery?

Roux-en-Y gastric bypass (RYGB) reliably produces sustained weight losses, reduces circulating blood glucose, and lowers risk of type 2 diabetes (1). Accompanying these benefits, however, is symptomatic hypoglycemia, reported by up to one-third of post–bariatric surgery patients (2,3). In an estimated <1% of RYGB patients (4), postprandial hyperinsulinemic hypoglycemia causes severe symptoms including neuroglycopenia with significant morbidity. New mechanistic insights and treatment options for these patients are needed. Potential contributors include rapid glucose delivery into the bloodstream, improved β-cell function, and gut adaptations, but the role of the central nervous system (CNS) is an important and underdeveloped area of research (3). In their article in this issue of Diabetes , Almby et al. (5) investigate whether RYGB alters the brain response to hypoglycemia in humans—a topic with further relevance to the CNS contribution to RYGB’s modification of overall glucose homeostasis. Human neuroimaging studies document RYGB-induced changes in brain function and suggest reversibility of obesity-associated findings (6–8). Studies of cerebral metabolism measuring [18F]-fluorodeoxyglucose uptake by positron emission tomography (FDG-PET) show that brain glucose uptake is elevated in participants with obesity and partially reversed post-RYGB (6,7), but controlled studies of the cerebral metabolic response to insulin-induced hypoglycemia are lacking. Cerebral blood flow response to insulin-induced hypoglycemia assessed by arterial spin labeling (ASL) showed increased regional blood flow (vs. euglycemia) in the cortex, thalamus (9), and hypothalamus (10) in healthy adults. Almby et al. provide novel data on the effect of RYGB on brain response to hypoglycemia (5). Almby et al. included 11 participants that underwent, before and …