IR ELISA Kit

Insulin resistance is associated with an increased risk of several metabolic disorders including type 2 diabetes, hypertension and cardiovascular diseases. Advances over the last decade have expanded our understanding of the molecular mechanisms underlying insulin resistance; however, many details of the mechanisms causing insulin resistance remain unknown. Recently, attention has shifted toward the role of epigenetics in insulin resistance. In this regard, acetylation of the histone tails has been widely investigated for its role in influencing both metabolic and mitogenic cascades of insulin signaling. More specifically, histone acetyltransferases and histone deacetylases, as major modulators of chromatin accessibility and gene expression, have been studied to determine a possible interconnectivity between the special effects of lysine acetylation status and tyrosine phosphorylation networks on the target proteins of downstream pathways involved in both metabolic and mitogenic cascades of insulin signaling. There is accumulating evidence for the post-translational modification effects of IGFR, InsR, IRS1/2, PI3K, Akt, GLUT4, FoxO, PGC-1 alpha, PPAR, AMPK and MAPKs on insulin resistance and glucose homeostasis. In this paper, we review the importance of acetylation of these factors in the regulation of insulin signaling and glucose metabolism, with a primary focus on the target proteins of downstream signaling of insulin. We also provide an update on the interplay between epigenetic modification and the cellular genome in the context of insulin signaling and describe the possible effect of the environment on this epigenetic regulation.

Preclinical studies indicate that activated IGF-1R can drive endocrine resistance in ER-positive (ER+) breast cancer, but its clinical relevance is unknown. We studied the effect of IGF-1R signaling on tamoxifen benefit in patients and we searched for approaches to overcome IGF-1R-mediated tamoxifen failure in cell lines. Primary tumor blocks from postmenopausal ER+ breast cancer patients randomized between adjuvant tamoxifen versus nil were recollected. Immunohistochemistry for IGF-1R, p-IGF-1R/InsR, p-ER alpha(Ser118), p-ER alpha(Ser167) and PI3K/MAPK pathway proteins was performed. Multivariate Cox models were employed to assess tamoxifen efficacy. The association between p-IGF-1R/InsR and PI3K/MAPK pathway activation in MCF-7 and T47D cells was analyzed with Western blots. Cell proliferation experiments were performed under various growth-stimulating and -inhibiting conditions. Patients with ER+, IGF-1R-positive breast cancer without p-IGF-1R/InsR staining (n = 242) had tamoxifen benefit (HR 0.41, p = 0.0038), while the results for p-IGF-1R/InsR-positive patients (n = 125) were not significant (HR 0.95, p = 0.3). High p-ER alpha(Ser118) or p-ER alpha(Ser167) expression was associated with less tamoxifen benefit. In MCF-7 cells, IGF-1R stimulation increased phosphorylation of PI3K/MAPK proteins and ER alpha(Ser167) regardless of IGF-1R overexpression. This could be abrogated by the dual IGF-1R/InsR inhibitor linsitinib, but not by the IGF-IR-selective antibody 1H7. In MCF-7 and T47D cells, stimulation of the IGF-1R/InsR pathway resulted in cell proliferation regardless of tamoxifen. Abrogation of cell growth was regained by addition of linsitinib. In conclusion, p-IGF-1R/InsR positivity in ER+ breast cancer is associated with reduced benefit from adjuvant tamoxifen in postmenopausal patients. In cell lines, stimulation rather than overexpression of IGF-1R is driving tamoxifen resistance to be abrogated by linsitinib.