Influence of small increments of epinephrine on glucose tolerance in normal humans

To ascertain whether small elevations of epinephrine alter glucose tolerance, we infused epinephrine or saline into seven healthy volunteers for 5 hours. Two hours after starting the infusions, subjects ingested 100 g of glucose. Plasma epinephrine (basal 23 +/- 4 pg/mL) rose during epinephrine infusion to levels (75 to 80 pg/mL) similar to those observed in nine outpatients presenting with mild viral illnesses (66 +/- 8 pg/mL). Although epinephrine produced only a small (5 mg/dL) increase n plasma glucose before glucose ingestion, after oral glucose the levels of glucose increased by 30 to 60 mg/dL above saline control values (163 +/- 14 mg/dL versus 108 +/- 15 at 2 h, p < 0.005). This diabetogenic effect occurred despite two-fold higher insulin levels and normal suppression of plasma glucagon. We conclude that small physiologic increments of epinephrine, which cause minimal changes in fasting plasma glucose, produce a marked reduction in glucose tolerance. Our data suggest marked sensitivity to the insulin antagonistic effects of epinephrine and may provide a mechanism for stress-induced glucose intolerance.