Effects of Gastric Bypass Surgery on the Brain: Simultaneous Assessment of Glucose Uptake,Blood Flow,Neural Activity,and Cognitive Function During Normo- and Hypoglycemia |
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Authors: | Kristina E Almby Martin H Lundqvist Niclas Abrahamsson Sofia Kvernby Markus Fahlstrm Maria J Pereira Malin Gingnell F Anders Karlsson Giovanni Fanni Magnus Sundbom Urban Wiklund Sven Haller Mark Lubberink Johan Wikstrm Jan W Eriksson |
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Institution: | 1.Department of Medical Sciences, Clinical Diabetes and Metabolism, Uppsala University, Uppsala, Sweden;2.Department of Surgical Sciences, Uppsala University, Uppsala, Sweden;3.Department of Neurosciences and Department of Psychology, Uppsala University, Uppsala, Sweden;4.Department of Radiation Sciences, Umeå University, Umeå, Sweden;5.Faculty of Medicine, University of Geneva, Geneva, Switzerland |
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Abstract: | 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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