TY - JOUR
T1 - Circulating insulin-like growth factors may contribute substantially to insulin receptor isoform A and insulin receptor isoform B signalling
AU - Varewijck, Aimee
AU - Brugts, Michel
AU - Frystyk, J
AU - Goudzwaard, Jeannette
AU - Uitterlinden, Piet
AU - Waaijers, Marlijn
AU - Feng, Yan
AU - Dimitrov, DS
AU - Lamberts, S.W.J.
AU - Hofland, Leo
AU - Janssen, J.A.M.J.L.
PY - 2013
Y1 - 2013
N2 - Background: Only a fraction of circulating insulin-like activity is due to insulin itself. The aim of this study was to determine total serum insulin-like activity mediated via the insulin receptor isoform A (IR-A) and isoform B (IR-B) by using kinase receptor activation (KIRA) assays specific for the IR-A and IR-B. Methods: The IR-A and IR-B KIRA assays use human embryonic kidney cells which have been transfected with the human IR-A or IR-B gene and quantify serum-mediated phosphorylation of the IR. Results: Both IR KIRA assays were sensitive (detection limit 32 pmol/L) and precise (intra- and inter assay CV: <12% and <15%). The EC(50)s of insulin, IGF-1 and IGF-II were 1.4, 11.2 and 6.7 nmol/L for the IR-A KIRA assay, and 1.3, 31.0 and 15.7 nmol/L for the IR-B KIRA assay. Results: The operational range of both assays allowed for determination of total insulin-like activity in human serum. Analysis of serum samples showed that there was a significant positive correlation between serum insulin-like and immunoreactive insulin concentrations (IR-A: r=0.56, p=0.01, IR-B: r=0.68, p=0.001). Importantly, addition of IGF-I or IGF-II antibodies to human serum samples could substantially decrease the endpoint signal in both KIRA assays. Conclusions: We showed that serum IGF-1 and IGF-Il may substantially contribute to IR signalling. Since IR isoform specific KIRA assays also take into account the contribution of IGFs present in serum on IR signalling, they may help to gain more insight into the roles of IGF mediated IR-A and IR-B activation in health and disease. (C) 2012 Elsevier Ireland Ltd. All rights reserved.
AB - Background: Only a fraction of circulating insulin-like activity is due to insulin itself. The aim of this study was to determine total serum insulin-like activity mediated via the insulin receptor isoform A (IR-A) and isoform B (IR-B) by using kinase receptor activation (KIRA) assays specific for the IR-A and IR-B. Methods: The IR-A and IR-B KIRA assays use human embryonic kidney cells which have been transfected with the human IR-A or IR-B gene and quantify serum-mediated phosphorylation of the IR. Results: Both IR KIRA assays were sensitive (detection limit 32 pmol/L) and precise (intra- and inter assay CV: <12% and <15%). The EC(50)s of insulin, IGF-1 and IGF-II were 1.4, 11.2 and 6.7 nmol/L for the IR-A KIRA assay, and 1.3, 31.0 and 15.7 nmol/L for the IR-B KIRA assay. Results: The operational range of both assays allowed for determination of total insulin-like activity in human serum. Analysis of serum samples showed that there was a significant positive correlation between serum insulin-like and immunoreactive insulin concentrations (IR-A: r=0.56, p=0.01, IR-B: r=0.68, p=0.001). Importantly, addition of IGF-I or IGF-II antibodies to human serum samples could substantially decrease the endpoint signal in both KIRA assays. Conclusions: We showed that serum IGF-1 and IGF-Il may substantially contribute to IR signalling. Since IR isoform specific KIRA assays also take into account the contribution of IGFs present in serum on IR signalling, they may help to gain more insight into the roles of IGF mediated IR-A and IR-B activation in health and disease. (C) 2012 Elsevier Ireland Ltd. All rights reserved.
U2 - 10.1016/j.mce.2012.08.021
DO - 10.1016/j.mce.2012.08.021
M3 - Article
SN - 0303-7207
VL - 365
SP - 17
EP - 24
JO - Molecular and Cellular Endocrinology
JF - Molecular and Cellular Endocrinology
IS - 1
ER -