Insulin secretion and plasma levels of glucose-dependent insulinotropic peptide and glucagon-like peptide 1 [7-36 amide] after oral glucose in cirrhosis.

A blunted initial insulin secretory response may contribute to oral glucose intolerance in cirrhosis. Oral glucose is a better stimulant to insulin secretion than intravenous (IV) glucose in part because of release of gut peptides, notably glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide 1 [7-36 amide] (GLP-1 [7-36 amide]). Because impaired release of or resistance to these gut peptides could explain impaired insulin secretion after oral glucose, we measured insulin secretion, plasma GIP, and GLP-1 [7-36 amide] levels, basally and after 75 g oral glucose, in 10 cirrhotics and 10 controls. Insulin secretion was calculated from a two-compartment analysis of serum C-peptide levels using kinetic parameters derived from IV injection of recombinant human C-peptide. C-peptide metabolic clearance rate, and the fractional rate constants for C-peptide (using the two-compartment model) were not significantly different, but the volume of the central compartment was 15% greater in cirrhotics (P < .01). Fasting blood glucose levels were similar (cirrhotics, 4.9 +/- 0.2; controls, 4.6 +/- 0.1 mmol/L) but serum insulin was six times higher in cirrhotics (P < .001). Cirrhotics had higher fasting GIP (215 +/- 72 vs. 42 +/- 18 pmol/L) and GLP-1 [7-36 amide] levels (25 +/- 3 vs. 16 +/- 1 pmol/L) (both P < .05). After oral glucose, blood glucose levels were significantly higher in cirrhotics. The timing of the gut peptide response to oral glucose was similar in the two groups, but peak levels of both peptides were approximately x2 higher in the cirrhotics.(ABSTRACT TRUNCATED AT 250 WORDS)