To investigate the physiological mechanisms leading to rapid improvement in diabetes after Roux-en-Y Gastric Bypass (RYGB). In particular, the roles of concurrent peri-operative dietary restrictions, which may also alter glucose metabolism, have not been completely elucidated.
Materials and Methods
To assess the differential contributions of diet and surgery to the mechanisms leading to the rapid improvement in diabetes after RYGB we enrolled ten patients with type 2 diabetes scheduled to undergo RYGB. All patients underwent a 10-day inpatient supervised dietary intervention equivalent with the peri-operative diet (Diet only Period), followed by, after a re-equilibration (washout) period, an identical period of pair matched-diet in conjunction with RYGB (Diet and RYGB Period). We conducted extensive metabolic assessments during a 6 hours Mixed Meal Challenge Test with stable isotope glucose tracer infusion performed before and after each intervention.
Similar improvements in glucose levels, β-cell function, insulin sensitivity, and post-meal hepatic insulin resistance were observed with both interventions. Both interventions led to significant reductions in fasting and postprandial acyl-ghrelin. The Diet only intervention induced greater improvements in basal hepatic glucose output and post-meal GIP secretion. The Diet and RYGB intervention induced significantly greater increases in post-meal GLP-1, PYY, and glucagon.
The strict peri-operative dietary restriction is a main contributor to the rapid improvement in glucose metabolism following RYGB. The RYGB-induced changes in the incretin hormones (GLP-1 and PYY) likely exert a major role in the long-term compliance with such major dietary restrictions through central and peripheral mechanisms.