Horm Metab Res 1987; 19(1): 1-5
DOI: 10.1055/s-2007-1011722
ORIGINALS
Basic
© Georg Thieme Verlag, Stuttgart · New York

Immunoreactive C-Peptide in Spontaneous Syndromes of Obesity and Diabetes in Mice

P. R. Flatt1 , C. J. Bailey2 , S. M. Hampton1 , S. K. Swanston-Flatt1 , V. Marks1
  • 1Department of Biochemistry, Divisions of Nutrition and Food Science, and Clinical Biochemistry, University of Surrey, Guildford, United Kingdom
  • 2Department of Molecular Sciences, Division of Biology, Aston University, Birmingham, United Kingdom
Weitere Informationen

Publikationsverlauf

1985

1986

Publikationsdatum:
14. März 2008 (online)

Summary

Immunoreactive C-peptide was evaluated in the plasma and pancreas of Aston ob/ob and C57BL/KsJ db/db mice in relation to disturbances in pancreatic B-cell function. At 18-24 weeks of age, ob/ob and db/db mice displayed hyperglycaemia (1.6 and 3.8 fold increases respectively) and hyperinsulinaemia (10.8 and 5.1 fold increases respectively) despite a similar pancreatic insulin content to their respective non-diabetic lean control mice. Immunoreactive C-peptide concentrations in the plasma and pancreas of the mutants corresponded with the degree of hyperinsulinaemia and pancreatic insulin content, and the insulin: C-peptide molar ratios in both mutants were similar to lean controls. In ob/ob mice parenteral glucose administration decreased plasma insulin and C-peptide concentrations, despite markedly raised glucose concentrations. However, administration of a low dose of insulin (5 U/kg) to lean mice and much higher doses of insulin (50 and 120 U/kg) to ob/ob mice markedly decreased plasma glucose and C-peptide concentrations. When the rate and extent of insulin-induced glucose suppression observed in ob/ob mice was mimicked in lean mice, an almost complete (95%) inhibition of C-peptide was achieved compared with a 57% decrease in the ob/ob mutant. Injection of ob/ob mice with glucose to counter the insulin-induced hypoglycaemia failed to affect the fall of C-peptide concentrations. The data suggest that the metabolic processing of insulin and C-peptide are undisturbed in obese-diabetic mice, and that the impaired suppression of circulating C-peptide by insulin-hypoglycaemia in ob/ob mice predominantly reflects impaired feedback inhibition by insulin.