Post-Prandial Carbohydrate Metabolism in Individuals With and Without Post-Bariatric Surgery Hypoglycemia (PBH)

Summary

In this study, the investigators will determine (a) whether metabolism (secretion and turnover) of glucagon is altered in patients with PBH, (b) whether this is affected by a meal, (c) whether PBH affects the ability of the body to produce glucose (endogenous glucose production), and (d) whether PBH affects the amount of glycogen in the liver (storage form of glucose) when fasting and after a meal. The investigators will determine the effect of glucagon to raise glucose levels after a meal. To answer these questions, participants will receive an infusion of a stable (nonradioactive) isotope of glucose and glucagon, and a meal containing a stable isotope of glucose. Glycogen will be measured by magnetic resonance imaging (MRI) of the liver before and after the meal. This information will be used to develop computer models for the glucagon pump system.

Detailed Description

The purpose of this study is to assess post-prandial carbohydrate, hormone, and hepatic glycogen metabolism comparing individuals with post-bariatric surgery hypoglycemia (PBH+) to individuals post-bariatric surgery without hypoglycemia (PBH-). There will be 3 visits to the study center in total. In this study, the investigators will determine (a) whether metabolism (secretion and turnover) of glucagon is altered in patients with PBH, (b) whether this is affected by a meal, (c) whether PBH affects the ability of the body to produce glucose (endogenous glucose production), and (d) whether PBH affects the amount of glycogen in the liver (storage form of glucose) when fasting and after a meal. The investigators will determine the effect of glucagon to raise glucose levels after a meal. To answer these questions, participants will receive an infusion of a stable (nonradioactive) isotope of glucose and glucagon, and a meal containing a stable isotope of glucose. Glycogen will be measured by magnetic resonance imaging (MRI) of the liver before and after the meal. This information will be used to develop computer models for the glucagon pump system. During Visit 1, the participants will undergo a medical history, physical examination, vital signs, and ECG; inclusion/exclusion criteria will be assessed. Participants will also be advised to complete food log entries and to follow a low glycemic index diet. At Visit 2, a continuous glucose monitor (CGM sensor) in masked mode will be placed on the participant. During Visit 3, participants will undergo infusions of glucose, glucagon, and their respective isotope tracers, and will consume a triple tracer mixed meal containing labeled glucose. The participants will complete C13 MRS scans to estimate liver glycogen content. Participants at Joslin Diabetes Center will not have MRS; response to an exogenous subcutaneous glucagon injection in the post-prandial state will be assessed instead. Blood samples will be processed and stored for subsequent analysis.

Eligibility Criteria

Interventions