Postprandial GLP-1, norepinephrine, and reactive hypoglycemia in dumping syndrome

Rapid gastric emptying and exaggerated plasma concentrations of the insulin otropic hormone GLP-1 precede reactive hypoglycemia after oral glucose in g astrectomy patients. We suspected that the plasma volume drop associated wi th rapid gastric emptying (early dumping) would be accompanied by elevated plasma concentrations of norepinephrine. In order to study any relationship between postprandial norepinephrine, the enteroinsular axis, and plasma gl ucose, twelve patients with dumping syndrome and nine controls were studied . The plasma concentrations of norepinephrine, GLP-1, GIP, glucagon, insuli n, and glucose were measured following a 1.5 g/kg lean body mass glucose me al. The early (0-30 min) integrated norepinephrine concentration was signif icantly higher in dumpers (22.1 +/- 3.8 nmol/ml/min) compared to controls ( 14.7 +/- 3.1 nmol/ml/min; P < 0.001) and correlated closely with the postpr andial hematocrit increment (r = 0.71; P < 0.05). Early immunoreactivities of GLP-1, GIP, and glucagon peaked 30 min after glucose ingestion and were significantly higher in dumpers. Insulin peaked after 60 min and correlated with early GLP-1. In 11 of the patients glucose fell below baseline after a median interval of 120 min. Glucose at 120 min, when most of the nadirs o ccurred was lowest in patients with high early GLP-1 concentrations (r = 0. 78; P < 0.001). Gel filtration chromatography of the dumpers' plasma reveal ed that pancreatic glucagon was detectable at time 0 and after 20 min, but not after 120 min. It is concluded that in dumpers pancreatic glucagon is a ugmented in the early postprandial period, probably through stimulation by catecholamines. At 120 min, when most of the hypoglycemias are encountered, pancreatic glucagon is no longer detectable, probably through inhibition b y GLP-1.