Long-acting insulin analogues elicit atypical signalling events mediated by the insulin receptor and insulin-like growth factor-I receptor.
OBJECTIVE
Insulin analogues were developed to improve the pharmacological properties of injected insulin and to better mimic endogenous insulin output. However, certain insulin analogues have been suggested to display IGF-I-like biological activities. Furthermore, several recent epidemiological studies have suggested a potential increase in cancer risk for treatment of diabetes patients with long-acting analogue insulin glargine (A21Gly,B31Arg,B32Arg human insulin). Additional studies, however, reported no increased cancer risk. The purpose of the present study was to identify the receptor(s) and signal transduction pathways responsible for the biological actions of insulin glargine and insulin detemir (B29Lys[ε-tetradecanoyl],desB30 human insulin).


METHODS
The colon cancer-derived cell line HCT116 was treated with increasing doses of insulin glargine, insulin detemir, regular insulin or IGF-I, and receptor activation was evaluated by immunoprecipitation assays. IGF-I receptor (IGF-IR) internalisation following insulin glargine treatment was assessed by confocal microscopy. Activation of the Akt and extracellular signal-regulated kinase pathways was evaluated by western blots. The anti-apoptotic effect of the analogues was measured by poly-(ADP ribose) polymerase antibody and annexin assays.


RESULTS
We found evidence for dual activation of the insulin receptor and IGF-IR by the analogues. Dose-dependency experiments showed that insulin glargine was able to phosphorylate the IGF-IR at fivefold lower doses than those required to activate the insulin receptor. We also showed that insulin glargine can lead to prolonged activation of the receptors and therefore promote abnormal signalling. Confocal imaging experiments showed that insulin glargine, but not regular insulin induced IGF-IR internalisation similarly to IGF-I. Finally, both analogues displayed IGF-I-like anti-apoptotic activities and stimulated cell cycle progression.


CONCLUSIONS
Our data indicate that insulin glargine and insulin detemir display atypical signalling activities that differ from those elicited by regular insulin and involve activation of the anti-apoptotic IGF-IR.
Yehezkel
E
E
Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
Weinstein
D
D
Simon
M
M
Sarfstein
R
R
Laron
Z
Z
Werner
H
H
D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D045325:HCT116 Cells; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000031:analogs & derivatives / Q000494:pharmacology; D000069057:Insulin Detemir; D000069036:Insulin Glargine; D049528:Insulin, Long-Acting / Q000031:analogs & derivatives* / Q000494:pharmacology*; D017526:Receptor, IGF Type 1 / Q000819:agonists* / Q000378:metabolism / Q000502:physiology; D011972:Receptor, Insulin / Q000819:agonists* / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors
D007004:Hypoglycemic Agents; D007328:Insulin; D049528:Insulin, Long-Acting; D000069036:Insulin Glargine; D000069057:Insulin Detemir; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin