Relationship Between Glycemic Control and Gastric Emptying in Poorly Controlled Type 2 Diabetes

BACKGROUND & AIMS: Acute hyperglycemia delays gastric emptying in patients with diabetes. However, it is not clear whether improved control of glycemia affects gastric emptying in these patients. We investigated whether overnight and short-term (6 mo) improvements in control of glycemia affect gastric emptying. METHODS: We studied 30 patients with poorly controlled type 2 diabetes (level of glycosylated hemoglobin, >9%). We measured gastric emptying using the [C-13]-Spirulina platensis breath test on the patients' first visit (visit 1), after overnight administration of insulin or saline, 1 week later (visit 2), and 6 months after intensive therapy for diabetes. We also measured fasting and postprandial plasma levels of C-peptide, glucagon-like peptide 1, and amylin, as well as autonomic functions. RESULTS: At visit 1, gastric emptying was normal in 10 patients, delayed in 14, and accelerated in 6; 6 patients had gastrointestinal symptoms; vagal dysfunction was associated with delayed gastric emptying (P <.05). Higher fasting blood levels of glucose were associated with shorter half-times of gastric emptying (t(half)) at visits 1 (r = -0.46; P = .01) and 2 (r = -0.43; P = .02). Although blood levels of glucose were lower after administration of insulin (132 +/- 7 mg/dL) than saline (211 +/- 15 mg/dL; P = .0002), gastric emptying t(half) was not lower after administration of insulin, compared with saline. After 6 months of intensive therapy, levels of glycosylated hemoglobin decreased from 10.6% +/- 0.3% to 9% +/- 0.4% (P = .0003), but gastric emptying t(half) did not change (92 +/- 8 min before, 92 +/- 7 min after). Gastric emptying did not correlate with plasma levels of glucagon-like peptide 1 and amylin. CONCLUSIONS: Two-thirds of patients with poorly controlled type 2 diabetes have mostly asymptomatic yet abnormal gastric emptying. Higher fasting blood levels of glucose are associated with faster gastric emptying. Overnight and sustained (6 mo) improvements in glycemic control do not affect gastric emptying.