Continuous glucose monitoring reveals glycemic variability and hypoglycemia after vertical sleeve gastrectomy in rats

Simon S. Evers, Ki-Suk Kim, Nadejda Bozadjieva, Alfor G. Lewis, Diana Farris, Matthew J. Sorensen, Youngsoo Kim, Steven E. Whitesall, Robert T. Kennedy, Daniel E. Michele, Randy J. Seeley, Darleen A. Sandoval

With the rising use of bariatric surgery, there is also greater awareness of associated complications, one of which is post-bariatric surgery hypoglycemia (PBH). Episodes of hypoglycemia impair cognition and increase the risk for syncope, cardiac arrhythmias, seizures, coma, and even death. While medication or lifestyle modifications can be used effectively to reduce recurrence in diabetic patients, this is not the case for bariatric surgery patients. Evers, Kim, and colleagues propose that rat models of VSG replicate many aspects of PBH in humans. They found that VSG increases glycemic variability, and in response to a mixed-meal liquid gavage, hypoglycemia is readily detectable. Blockade of GLP-1R signaling prevents falls in the glucose nadir but does not improve glycemic variability.

Objective: Post–bariatric surgery hypoglycemia (PBH) is defined as the presence of neuroglycopenic symptoms accompanied by postprandial hypoglycemia in bariatric surgery patients. Recent clinical studies using continuous glucose monitoring (CGM) technology revealed that PBH is more frequently observed in vertical sleeve gastrectomy (VSG) patients than previously recognized. PBH cannot be alleviated by current medication. Therefore, a model system to investigate the mechanism and treatment is required.

Methods: We used CGM in a rat model of VSG and monitored the occurrence of glycemic variability and hypoglycemia in various meal conditions for 4 weeks after surgery. Another cohort of VSG rats with CGM was used to investigate whether the blockade of glucagon-like peptide-1 receptor (GLP-1R) signaling alleviates these symptoms. A mouse VSG model was used to investigate whether the impaired glucose counterregulatory system causes postprandial hypoglycemia.

Results: Like in humans, rats have increased glycemic variability and hypoglycemia after VSG. Postprandial hypoglycemia was specifically detected after liquid versus solid meals. Further, the blockade of GLP-1R signaling raises the glucose nadir but does not affect glycemic variability.

Conclusions: Rat bariatric surgery duplicates many features of human post–bariatric surgery hypoglycemia including postprandial hypoglycemia and glycemic variability, while blockade of GLP-1R signaling prevents hypoglycemia but not the variability.