Beta-cell sensitivity to glucose is impaired after gastric bypass surgery.

AIMS Patients who have undergone Roux-en-Y gastric bypass surgery (GB) have exaggerated postprandial insulin secretion, which has been attributed to increased meal glucose appearance and enhanced incretin effect. Here, we sought to determine β-cell glucose sensitivity in the absence of meal stimulation and insulinotropic gut factors. MATERIALS AND METHODS A total of 12 non-diabetic subjects with prior GB, and 7 matched non-surgical control subjects with normal glucose tolerance were studied. Blood glucose and insulin secretion rates were measured during a graded glucose infusion at increasing and then decreasing rates. Insulin sensitivity (SI ) and glucose effectiveness (SG ) were determined by the minimal model. RESULTS GB subjects had SI comparable to that of control subjects. GB subjects had relative hyperglycaemia during the highest dose of glucose infusion associated with significantly reduced β-cell glucose sensitivity throughout both step-up (GB: 34 ± 6, CN: 82 ± 9 pmol min-1 mM-1 L, P < .0001) and step-down (GB: 31 ± 6, CN: 74 ± 9 pmol min-1 mM-1 L, P < .0001) phases of the glucose infusion. GB subjects also had reduced SG (GB: 0.04 ± 0.00, CN: 0.07 ± 0.01 min-1 , P = .004). CONCLUSION In the absence of enteric stimuli, β-cell sensitivity to changes in glycaemia is blunted among individuals with GB, indicating a significant shift in a fundamental property of β-cell function several years after surgery.