Biomedical subjects

E T Shapiro

Publications and source records attributed to E T Shapiro.

35 records · Page 2Linked to original sources

PubMed1988

Peripheral insulin parallels changes in insulin secretion more closely than C-peptide after bolus intravenous glucose administration.

The changes in peripheral serum insulin and plasma C-peptide levels and in the insulin secretory rate in response to iv glucose (0.5 g/kg BW) administration were studied in seven normal subjects. Insulin secretory rates were calculated according to a two-compartment model of distribution for C-peptide, using individual C-peptide kinetics calculated from iv bolus injections of biosynthetic human C-peptide. The mean plasma glucose level increased from a fasting level of 5.1 +/- 0.1 (+/- SE) to a peak of 24.0 +/- 1.0 mmol/L at 3 min and reached basal levels 101 +/- 6 min after glucose administration. The mean serum insulin value increased from 50 +/- 12 to a peak of 405 +/- 58 pmol/L at 3 min and then declined to fasting levels 139 +/- 14 min after the stimulus. In contrast, the mean plasma C-peptide level increased from 390 +/- 50 to a peak of 1460 +/- 210 pmol/L at 3 min and only began declining 45 min after glucose administration, reaching fasting levels 191 +/- 15 min after the stimulus. The mean insulin secretory rate increased from 69.8 +/- 19.9 to a peak of 1412.7 +/- 159.1 pmol/min at 3 min (15.3 +/- 2.5-fold elevation over baseline) and reached basal levels 135 +/- 12 min after the stimulus. The clearance of endogenous insulin during the basal period (2.505 +/- 0.365 L/min) and that during the 4 h after the stimulus (2.319 +/- 0.230 L/min) were similar. In conclusion, after bolus iv glucose administration: 1) the insulin secretory rate is more closely represented by changes in peripheral serum insulin than in plasma C-peptide levels; and 2) no change in endogenous insulin clearance occurs.

Adult↗

PubMed1988

Reduction of insulin clearance during hyperglycemic clamp. Dose-response study in normal humans.

Insulin secretion and clearance were studied in eight normal subjects who underwent hyperglycemic clamp studies at plasma glucose levels of 120, 225, and 300 mg/dl on three occasions. Insulin secretion rates were calculated during a 1-h baseline period and during 3 h of glucose clamping from a two-compartmental analysis of peripheral C-peptide concentrations with individual kinetic parameters derived after intravenous bolus injections of biosynthetic human C-peptide. At the 300-mg/dl clamp level, the insulin secretion rate increased to a value 9.9 +/- 0.7 times that of basal at the end of the clamp (mean +/- SE), whereas over the same period, the peripheral insulin concentrations increased to a greater extent, reaching a value 15.4 +/- 1.2 times that of basal (P = .002). This greater relative increase in the insulin concentration in comparison with the corresponding insulin secretion rate suggests a reduction in the clearance of endogenous insulin. A similar trend was seen at the 225-mg/dl clamp level, but the relative increase in the insulin concentration (9.9 +/- 1.5 times that of basal) was not significantly higher than the relative increase in the insulin secretion rate (8.1 +/- 0.5 times that of basal, P = .17). At the 120-mg/dl clamp level, the relative increases in the insulin secretion rate (2.7 +/- 0.2 times that of basal) and the insulin concentration (2.4 +/- 0.2 times that of basal) were similar (P = .26), indicating no reduction in endogenous insulin clearance during moderate stimulation of insulin secretion. In conclusion, a reduction in endogenous insulin clearance occurs during greater stimulation of insulin secretion at higher glucose-clamp levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

Reevaluation of urine C-peptide as measure of insulin secretion.

Urine C-peptide (UCP) has been proposed as a measure of insulin secretion, because insulin and C-peptide are consecreted in equimolar concentrations by the pancreatic beta-cell. The validity of this approach was tested by comparing insulin secretion rates, calculated by application of a two-compartmental analysis of peripheral C-peptide concentrations, with UCP excretion rates. Insulin secretion and UCP excretion with subjects on a mixed diet were simultaneously measured over a 24-h period in 13 patients with noninsulin-dependent diabetes mellitus and in 14 matched nondiabetic control subjects. The fraction of secreted C-peptide that was excreted in the urine (fractional C-peptide excretion) showed considerable intersubject variability in the diabetic (11.3 +/- 1.6%, range 3.9-20.8) and control (8.0 +/- 1.7%, range 1.1-27.9, P = .07) subjects (means +/- SE). UCP clearance demonstrated a similar degree of variability and was not significantly different (P = .07) between diabetic (23.8 +/- 3.0 ml/min) and control (16.5 +/- 2.7 ml/min) subjects. In control subjects, the 24-h insulin secretion rate correlated more closely with the fasting insulin secretion rate (r = .97, P = .0001), fasting C-peptide (r = .81, P = .0005), and fasting insulin (r = .80, P = .0005) concentrations than with the 24-h UCP excretion rate (r = .62, P = .02). Similar results were obtained in the diabetic patients.(ABSTRACT TRUNCATED AT 250 WORDS)

C-Peptide↗

PubMed1987

Insulin secretion and clearance. Comparison after oral and intravenous glucose.

Insulin secretion and clearance in response to the administration of oral and intravenous glucose was investigated in nine normal men. C-peptide metabolic kinetics were calculated by analysis of individual C-peptide decay curves after the bolus injection of biosynthetic human C-peptide. Glucose was administered to the subjects on three occasions: as a 75-g oral dose, a 75-g i.v. infusion, and an intravenous glucose infusion at a variable rate adjusted to mimic the peripheral glucose levels obtained after the oral glucose load (matching experiment). Glucose, insulin, and C-peptide concentrations were measured for the subsequent 5 h. The glucose level after the oral glucose load (115.9 +/- 2.6 mg/dl, mean +/- SE) closely approximated that after the matching experiment (120.5 +/- 2.5 mg/dl) but was significantly lower than after 75 g i.v. glucose (127.7 +/- 3.4 mg/dl, P less than .05). Analysis of the areas under the peripheral concentration curves (60-360 min) showed that the responses of both insulin (52.7 +/- 5.6 and 46.5 +/- 4.5 pmol.ml-1.300 min-1) and C-peptide (252.7 +/- 27.5 and 267.0 +/- 21.6 pmol.ml-1.300 min-1) were not significantly different after the oral and 75-g i.v. glucose studies, respectively, whereas in the matching experiment, both the insulin (26.1 +/- 3.9 pmol.ml-1.300 min-1) and C-peptide (178.0 +/- 18.9 pmol.ml-1.300 min-1) responses were lower (P less than .05) than in the other two studies. Insulin secretory rates were derived from peripheral C-peptide concentrations with an open two-compartment model and individually derived model parameters. (ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1987