Acute metabolic actions of des-(B27–B30)-insulin and related analogues in adult rats

Abstract

Metabolic potencies of the destetrapeptide insulin analogues des-(B27-B30)-insulin, des-(B27-B30)-insulin-B26-amide, [ThrB26] des-(B27-B30)-insulin-B26-amide and [GluB26] des-(B27-B30)-insulin-B26-amide were studied in anaesthetized adult rats and in primary cultures of rat hepatocytes and compared with that of the native hormone. Hypoglycaemic effects following intravenous bolus injection of insulin or analogues were similar, as were the stimulatory actions on total body glucose disposal during euglycaemic clamping. In these latter studies a maximal stimulation in the range 16-20 mg glucose/kg per hour was observed and identical half-maximally effective serum concentrations for all peptides of about 1 pmol/ml were obtained. Analogue actions on individual peripheral tissues estimated by the uptake of 2-deoxyglucose were not different from those of insulin. In hepatocyte cultures the stimulatory action of destetrapeptide analogues on glycogenesis and on aminoisobutyric acid transport was indistinguishable from that of native insulin, with identical half-maximally effective concentrations. These data demonstrate that des-(B27-B30)-insulin and related destetrapeptide analogues have high biological activity. Since the truncated non-amidated analogue appeared to be monomeric in solution, this peptide could be a candidate for an insulin preparation potentially showing rapid absorption from subcutaneous tissue.

Poly(ethylene glycol)-Mediated Conformational Alteration of α-Chymotrypsin Prevents Inactivation of Insulin by Stabilizing Active Intermediates

“…For example, cleavage at B29-Lys by trypsin does not inactivate insulin, and sequential shortening of the B-chain from both termini gradually reduces the activity. It has also been reported that both des-pentapeptide (B26–30)-insulin (DPI) and des-tetrapeptide (B27–B30)-insulin (DTI) retain insulin-like activities. − We wonder whether the digested products of insulin by α-CT in the presence of PEG 400 would also preserve some biological activities of insulin. As such, the ability of the digested products to reduce blood glucose level was tested in normal male BABL/c mice via subcutaneous injection.…”

“…Unlike existing approaches to overcome proteolytic enzymes in the GI tract by using protease inhibitors or particles coated with chelating materials, PEG 400 protects degradation of insulin by altering the conformation of α-CT to produce active intermediate products (DPI and DTI). Des-insulin retains comparable bioactivity to native insulin while having decreased molecular size, which thereby facilitates its intestinal absorption via paracellular transport across epithelial tight junctions. , PEG 400 is a safe polymer which has negligible effect on the microscopic changes in the kidney or urinary bladder following 13-week gavage in Fischer-334 rats . With its desired biocompatibility and capability as crowding agents, PEG 400 serves as a promising candidate for modulating enzymatic reaction in vivo and would thus provide an important addition to existing strategies in oral delivery of therapeutic proteins.…”