Fasting hyperglycemia impairs glucose- but not insulin-mediated suppression of glucagon secretion

Muhammad Abdul-Ghani, Ralph A. DeFronzo

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

Aim: Our aim was to assess the effect of chronic hyperglycemia on glucose- and insulin-mediated suppression of glucagon secretion by the α-cell. Methods: Thirty subjects with normal glucose tolerance, 27 with impaired fasting glucose and/or impaired glucose tolerance, and 32 type 2 diabetic subjects were studied with oral glucose tolerance test (OGTT) and euglycemic hyperinsulinemic clamp. Fasting plasma glucagon concentration and plasma glucagon concentration during the OGTT and insulin clamp were measured. Results: During the OGTT, the decrement in the plasma glucagon concentration (area under the curve) was correlated inversely with the fasting plasma glucose concentration (r = -0.35; P < 0.001). As the fasting glucose level increased, the suppression of plasma glucagon progressively diminished. In contrast, during the euglycemic insulin clamp, the suppression of plasma glucagon was not correlated with the fasting plasma glucose concentration and was similar in subjects with normal glucose tolerance, subjects with impaired fasting glucose/impaired glucose tolerance, and diabetic subjects: 18, 23, and 18%, respectively. Conclusion: Insulin-mediated suppression of glucagon secretion is unrelated to the fasting plasma glucose concentration and is not impaired by chronic hyperglycemia. Thus, the defect in plasma glucagon suppression during the OGTT most likely results from impaired glucose-mediated glucagon suppression. The close correlation between fasting plasma glucose concentration and reduced glucagon suppression suggests a glucotoxic effect on α-cell function.

Original languageEnglish (US)
Pages (from-to)1778-1784
Number of pages7
JournalJournal of Clinical Endocrinology and Metabolism
Volume92
Issue number5
DOIs
StatePublished - May 2007

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Endocrinology
  • Clinical Biochemistry
  • Biochemistry, medical

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