Early glycemic control and incretin improvement after gastric bypass: the role of oral and gastrostomy route

Background: Patients with obesity have a suppressed incretin effect and a consequent imbalance of glycemic homeostasis. Several studies have shown improved type 2 diabetes after Roux-en-Y gastric bypass (RYGB). The mechanisms of early action are linked to caloric restriction, improvement of insulin resistance, pancreatic beta cell function, and the incretin effect of glycogen-like protein 1 and gastric inhibitory polypeptide, but reported data are conflicting.

Objective: The objective of this study was to evaluate glycemic metabolism, including the oral glucose tolerance test and enterohormonal profile in the early postoperative period in severely obese patients who underwent RYGB with gastrostomy, comparing the preoperative supply of a standard bolus of nutrient against the postoperative administration through an oral and a gastrostomy route.

Setting: Clinics Hospital of University of São Paulo, Brazil.

Methods: Eleven patients with obesity and diabetes underwent RYGB with a gastrostomy performed in the excluded gastric remnant. Patients were given preoperative assessments of glycemic and enterohormone profiles and an oral glucose tolerance test; these were compared with early postoperative assessments after oral and gastrostomy route administrations.

Results: The mean preoperative body mass index of the group was 44.1 ± 6.6 kg/m², mean fasting blood glucose of 194.5 ± 62.4 mg/dL, and glycated hemoglobin 8.7 ± 1.6%. In 77.7% of the patients, there was normalization of the glycemic curve in the early postoperative period as evaluated by the oral glucose tolerance test. Significant decreases in glycemia, insulinemia, and homeostatic model assessment-insulin resistance were also observed, regardless of the route of administration. There was significant increase in glycogen-like protein 1 by the postoperative oral route and reduction of gastric inhibitory polypeptide in both routes. Ghrelin did not change.

Conclusion: Glycemia and peripheral insulin resistance reductions were observed in early-postoperative RYGB, independent of the oral or gastrostomy route. Incretin improvement, mediated by glycogen-like protein 1 increased was observed only in the postoperative oral route, while GIP reduced for both routes.