Reduced insulin clearance contributes to the increased insulin levels after administration of glucagon-like peptide 1 in mice.
OBJECTIVE
Glucagon-like peptide-1 (GLP-1) is known to be a potent stimulator of insulin secretion. However, whether GLP-1 also affects insulin clearance is not known. To explore this, we developed a technique to determine prehepatic insulin secretion in mice, based on deconvolution of plasma C-peptide concentrations. The estimated beta cell secretion was then related to plasma insulin levels to allow determination of clearance rate of endogenously produced insulin.


METHODS
Kinetic parameters of C-peptide were estimated after i.v. injection of human C-peptide (0.8 or 3 nmol/kg) or glucose (1 g/kg), either alone or together with GLP-1 (10 nmol/kg), in anaesthetised NMRI mice.


RESULTS
C-peptide was distributed in two compartments (distribution volume 11.4+/-0.4 ml, 42+/-2% of which was in the accessible compartment). Fractional C-peptide clearance was 8.2+/-0.6% of the total distribution volume per minute. GLP-1 markedly enhanced prehepatic insulin secretion; more than 80% of prehepatic secretion occurred during the first minute after injection. Fractional clearance of endogenously released insulin after glucose was 0.66+/-0.11 min(-1) and this was reduced to 0.36+/-0.10 min(-1) by GLP-1 (p=0.04).


CONCLUSIONS
It is possible to perform C-peptide deconvolution for estimating prehepatic insulin secretion in mice. GLP-1 reduces the clearance of endogenously released insulin; therefore, it may affect insulin levels by increasing prehepatic insulin secretion and by reducing insulin clearance.
Ahrén
B
B
Department of Medicine, Lund University, Lund, Sweden. Bo.Ahren@med.lu.se
Thomaseth
K
K
Pacini
G
G
D000818:Animals; D019540:Area Under Curve; D002096:C-Peptide / Q000378:metabolism; D005260:Female; D052216:Glucagon-Like Peptide 1 / Q000008:administration & dosage / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism; D005951:Glucose Tolerance Test; D007275:Injections, Intravenous; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D051379:Mice
D002096:C-Peptide; D007328:Insulin; D052216:Glucagon-Like Peptide 1; D005947:Glucose