Insulin and C-peptide plasma levels in patients with severe chronic pancreatitis and fasting normoglycemia

The aim of the present study was to evaluate insulin secretion by the pancreatic B cell in a group of patients with severe chronic pancreatitis and without overt diabetes. For this purpose we have measured plasma insulin and C-peptide peripheral levels in the fasting state and after a 100-g oral glucose load in 10 patients with severe chronic pancreatitis and fasting normoglycemia, and in 10 sex-, age-, and weight-matched healthy controls. As compared to normal subjects, patients with chronic pancreatitis showed: (1) significantly higher plasma glucose levels after oral glucose load (area under the plasma glucose curve 1708±142 vs 1208±47 mmol/liter × 240 min, P < 0.005); (2) plasma insulin levels significantly higher at fasting (0.11±0.008 vs 0.08±0.005 nmol/liter, P < 0.01) but not after oral glucose administration (area under the plasma insulin curve 79±12 vs 88 ±16 nmol/liter × 240 min); (3) significantly lower plasma C-peptide concentrations both in the fasting state (0.15±0.01 vs 0.54±0.05 nmol/liter, P<0.001) and after oral glucose load (area under the plasma C-peptide curve 211±30 vs 325±37 nmol/liter × 240 min, P<0.05). The finding of diminished plasma C-peptide levels suggests that chronic pancreatitis is associated with an impaired B-cell function even in the absence of overt diabetes. The increased or unchanged plasma insulin levels in spite of decreased plasma C-peptide concentrations indicate that in chronic pancreatitis insulin metabolism is reduced, most likely within the liver.