Abstract
Daily endogenous insulin secretion was assessed by measuring the modified urinary C-peptide (UCP) in 40 non-insulin-dependent diabetic patients (DM), 14 nondiabetic patients with liver diseases (LD), 20 patients with DM+LD and 15 normal controls (N). The ratio of the urinary C-peptide (CP) clearance to the creatinine clearance (CCP/CCR) was determined in the early morning after an overnight fast, and the 24-hour urinary C-peptide output was measured (24h-UCP). The corrected value of the fasting UCP or the 24h-UCP was calculated as the fasting UCP/(CCP/CCR×10) or the 24h-UCP/(CCP/CCR×10). Using a rate of 5 ml/kg/min as the metabolic clearance rate of CP, the proportion of the C-peptide excreted in the urine was calculated to be 7.1%(2.2-21.3) based on the measured value of the UCP, and 3.5%(2.4-5.3) based on its corrected value in the fasting state. Since a good correlation (r=0.93) was obtained between the corrected value of the 24h-UCP and the sum of the day-10ng serum CP levels, the corrected value of the 24h-UCP was also presumed to be approximately 3.5% of the secreted C-peptide during a whole day. The insulin secretion was calculated to be 54±20U/day in N, 38±23U/day in DM, 77±38U/day in DM+LD and 115±54U/day in LD when the amount of Gpeptide was simply converted into that of insulin. It was suggested that some LD patients whose insulin secretory capacity could not overcome the increased insulin requirement showed hyperglycemia.
