Pancreatic glucagon response to glucose in obesity with normal and impaired carbohydrate tolerance

Pancreatic glucagon (IRG) and insulin (IRI) secretion patterns were studied in obese subjects with normal (n = 7), borderline (n = 5) and pathological carbohydrate tolerance (n = 11), as well as in 19 non-obese healthy controls without a family history of diabetes, by means of a 2-h glucose infusion (12 mg/kg/min), primed by an initial injection of 0.33 g/kg glucose. With regard to the insulin secretion all obese groups were characterized by a significant hyperinsulinaemia during the late secretion phase, whereas the early insulin response ( delta IRI-area 0-5 min) was significantly reduced in obesity with pathological carbohydrate tolerance. There was no significant differences in fasting IRG levels among controls (29.7 +/- 6.1 pmol/l) and pathological glucose tolerance (31.2 +/- 4.6 pmol/l). In addition, absolute IRG levels and the IRG concentration pattern during glucose infusion were comparable in all groups confirming no alpha-cell resistance to glucose suppression in obesity, irrespective of normal or impaired carbohydrate tolerance. The molar IRI-IRG ratio was significantly increased during glucose infusion in all obese groups reflecting a relative anabolic state. There were no correlations between IRG secretion and relative body weight, glucose tolerance or insulin response to glucose.