Key result
Roux-en-Y gastric bypass surgery increased cerebral blood flow and decreased total brain FDG uptake during normoglycemia, with attenuated counterregulatory hormone responses during hypoglycemia.
Why the study?
Roux-en-Y gastric bypass frequently causes asymptomatic hypoglycemia with attenuated counterregulatory responses, but the underlying mechanisms and clinical consequences remain unclear.
Does Roux-en-Y gastric bypass surgery alter brain glucose uptake, blood flow, neural activity, and cognitive function during normo- and hypoglycemia in subjects without diabetes with severe obesity?
Observational (n=11)
Does Roux-en-Y gastric bypass surgery alter brain glucose uptake, blood flow, neural activity, and cognitive function during normo- and hypoglycemia in subjects without diabetes with severe obesity?
Roux-en-Y gastric bypass induces adaptive brain responses that may contribute to lowering glycemia and altering counterregulatory responses during hypoglycemia.
May indicate adaptive cerebral responses after bypass in obesity; leaves open effects on hypoglycemia risk or glycemic control.
While Roux-en-Y gastric bypass (RYGB) surgery in obese individuals typically improves glycemic control and prevents diabetes, it also frequently causes asymptomatic hypoglycemia. Previous work showed attenuated counterregulatory responses following RYGB. The underlying mechanisms as well as the clinical consequences are unclear. In this study, 11 subjects without diabetes with severe obesity were investigated pre- and post-RYGB during hyperinsulinemic normo-hypoglycemic clamps. Assessments were made of hormones, cognitive function, cerebral blood flow by arterial spin labeling, brain glucose metabolism by 18F-fluorodeoxyglucose (FDG) positron emission tomography, and activation of brain networks by functional MRI. Post- versus presurgery, we found a general increase of cerebral blood flow but a decrease of total brain FDG uptake during normoglycemia. During hypoglycemia, there was a marked increase in total brain FDG uptake, and this was similar for post- and presurgery, whereas hypothalamic FDG uptake was reduced during hypoglycemia. During hypoglycemia, attenuated responses of counterregulatory hormones and improvements in cognitive function were seen postsurgery. In early hypoglycemia, there was increased activation post- versus presurgery of neural networks in brain regions implicated in glucose regulation, such as the thalamus and hypothalamus. The results suggest adaptive responses of the brain that contribute to lowering of glycemia following RYGB, and the underlying mechanisms should be further elucidated.
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Almby et al. (2021) conducted an observational in Severe obesity without diabetes (n=11). Roux-en-Y gastric bypass (RYGB) surgery vs. Presurgery was evaluated on Cerebral blood flow, brain glucose metabolism, and activation of brain networks. Roux-en-Y gastric bypass surgery increased cerebral blood flow and decreased total brain FDG uptake during normoglycemia, with attenuated counterregulatory hormone responses during hypoglycemia.
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