The effect of glucose-dependent insulinotropic polypeptide infused at physiological concentrations on the release of insulin in man.
Blood glucose and the responses of insulin and glucose-dependent insulinotropic polypeptide (GIP) were measured in 12 healthy, normal weight subjects after drinking 50 g glucose. On a subsequent occasion each subject was given  a simultaneous infusion of GIP and glucose to mimic the plasma concentrations observed in the first test. The peak GIP concentration after oral glucose was 22.3 +/- 1.9 pmol/l (mean +/- SEM), but was higher after GIP infusion at 36.3 +/- 4.6 pmol/l, (p less than 0.005). The blood glucose levels following oral glucose peaked at 6.3 +/- 0.5 mmol/l which was the same as seen after intravenous glucose. The insulin response to oral glucose was, however, far higher (431.3 +/- 58.2 pmol/l) than that obtained after GIP and glucose infusion (191.6 +/- 30.9 pmol/l, p less than 0.001). Thus it has not proved possible to explain completely the oral enhancement of insulin release by the action of GIP alone.
D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D005260:Female; D005749:Gastric Inhibitory Polypeptide / Q000378:metabolism / Q000494:pharmacology* / Q000502:physiology; D005768:Gastrointestinal Hormones / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D007275:Injections, Intravenous; D007328:Insulin / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D013997:Time Factors
D001786:Blood Glucose; D005768:Gastrointestinal Hormones; D007328:Insulin; D005749:Gastric Inhibitory Polypeptide; D005947:Glucose