Figure 3

Insulin receptor binding, activation and biological activities of cis- and trans isomers. (a) Competition binding of insulin (squares), cis- (triangles) and trans- (circles) isomers with europium-labelled insulin. Results are expressed as a percentage of binding in the absence of competing ligand (%B/B0). (b) Activation of IR-B by increasing concentrations of dicarba insulins (10 min stimulation) is expressed as receptor phosphorylation as a percentage of the maximal phosphorylation induced by insulin. Insulin vs cis isomer (non significant); insulin vs trans isomer ****(P ≤ 0.0001) (2-way ANOVA; Dunnett’s multiple comparison) (c) Glucose uptake stimulated by increasing concentrations of insulin or cis isomer is expressed as fold glucose uptake (pmol/min/mg) above basal. Insulin vs cis isomer (ns) (paired T-test). (d) DNA synthesis in response to increasing concentrations of dicarba insulins is shown as percentage incorporation of ³H-thymidine (³H-Thy) above basal. All data in (a–d) are the mean ± S.E.M. n = at least 3 independent experiments. (e) Insulin tolerance test in mice fed on a normal diet (chow), or (f) on a high fat diet were administered through intraperitoneal injection (ip) with 0.75 IU/kg insulin (squares; solid lines) or cis isomer (triangles; dotted lines) under non-fasting conditions and tail vein blood glucose was measured via glucose meter at indicated times²⁷. n = 5–6 per group. Blood glucose levels are expressed as change over basal levels (mmol/L). Chow diet, insulin vs cis isomer ** (P ≤ 0.01); high fat diet, insulin vs cis isomer **(P ≤ 0.01) (paired T-test).