Glucagon-stimulated and postprandial plasma C-peptide values as measures of insulin secretory capacity.
Basal, postprandial (2 h after breakfast), and glucagon-stimulated plasma C-peptide concentrations were determined in a group of 36 adult diabetic patients. Basal and postprandial C-peptide values were measured on consecutive days to estimate the degree of variation of C-peptide secretion. In a subgroup of 15 diabetic patients treated chronically with diet and oral hypoglycemic agents (sulfonylureas or a combination of sulfonylureas and metformin), we studied whether administration of sulfonylureas immediately before breakfast had any effect on postprandial C-peptide values. Absolute differences between two consecutive fasting C-peptide concentrations in insulin-requiring patients were less than 0.1 nM in all but 1 patient, in whom the difference was 0.18 nM. In subjects treated with oral hypoglycemic agents the median difference was 0.12 nM (range 0-0.38 nM). Absolute differences between two consecutive postprandial C-peptide concentrations were all less than 0.1 nM in insulin-requiring patients. No significant difference was found between postprandial C-peptide concentrations with or without preceding administration of oral hypoglycemic agents (medians 1.35 and 1.30 nM, respectively). Glucagon-stimulated C-peptide concentrations were somewhat higher than the postprandial values. However, equal discrimination between insulin-requiring and non-insulin-requiring diabetic patients was found by measuring postprandial or glucagon-stimulated C-peptide concentrations.
D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000032:analysis; D002096:C-Peptide / Q000097:blood*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000503:physiopathology*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000503:physiopathology*; D004435:Eating; D005215:Fasting; D005934:Glucagon; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D008875:Middle Aged
D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin; D005934:Glucagon