Estradiol-induced regulation of GLUT4 in 3T3-L1 cells: involvement of ESR1 and AKT activation

Abstract

Impaired insulin-stimulated glucose uptake involves reduced expression of the GLUT4 (solute carrier family 2 facilitated glucose transporter member 4, gene). 17β-estradiol (E) modulates /GLUT4 expression, but the involved mechanisms are unclear. Although E exerts biological effects by binding to estrogen receptors 1/2 (ESR1/2), which are nuclear transcriptional factors; extranuclear effects have also been proposed. We hypothesize that E regulates GLUT4 through an extranuclear ESR1 mechanism. Thus, we investigated the effects of E upon (1) subcellular distribution of ESRs and the proto-oncogene tyrosine-protein kinases (SRC) involvement; (2) serine/threonine-protein kinase (AKT) activation; (3) /GLUT4 expression and (4) GLUT4 subcellular distribution and glucose uptake in 3T3-L1 adipocytes. Differentiated 3T3-L1 adipocytes were cultivated or not with E for 24 h, and additionally treated or not with ESR1-selective agonist (PPT), ESR1-selective antagonist (MPP) or selective SRC inhibitor (PP2). Subcellular distribution of ESR1, ESR2 and GLUT4 was analyzed by immunocytochemistry; mRNA and GLUT4 were quantified by qPCR and Western blotting, respectively; plasma membrane GLUT4 translocation and glucose uptake were analyzed under insulin stimulus for 20 min or not. E induced (1) translocation of ESR1, but not of ESR2, from nucleus to plasma membrane and AKT phosphorylation, effects mimicked by PPT and blocked by MPP and PP2; (2) increased /GLUT4 expression and (3) increased insulin-stimulated GLUT4 translocation and glucose uptake. In conclusion, E treatment promoted a SRC-mediated nucleus-plasma membrane shuttle of ESR1, and increased AKT phosphorylation, /GLUT4 expression and plasma membrane GLUT4 translocation; consequently, improving insulin-stimulated glucose uptake. These results unravel mechanisms through which estrogen improves insulin sensitivity.

Estrogen Receptor 1 (ESR1) Enhances Slc2a4/GLUT4 Expression by a SP1 Cooperative Mechanism

“…Although only PPT+E2 increased the Sp1 mRNA expression, the nuclear content of SP1 protein was increased by both PPT and DPN, added or not with E2. Similar discrepancies between Sp1 mRNA expression and SP1 protein content were already described in HepG2 cell and related to a PI3K/AKT-mediated stabilization of SP1 protein 36, highlighting that activation of this pathway has already been observed in 3T3-L1 adipocytes in response to ESR1 activation 29. That could explain the PPT effect here observed in nuclear content of SP1; however, the absence of E2 effect and the positive effect of DPN lack appropriate explanation at present.…”

Study on the Mechanism of Periplaneta americana Extract to Accelerate Wound Healing after Diabetic Anal Fistula Operation Based on Network Pharmacology

“…Estrogen has anti-inflammatory activity and can antagonize the stimulation of the lipopolysaccharide component (LPS) of the cell wall of Gram-negative bacteria. Studies have confirmed that estrogen can accelerate wound healing, by reducing wound macrophage infiltration, inhibiting LPS-induced inflammatory signals, promoting the migration of mouse keratinocytes in vitro, promoting wound formation in diabetic mice, improving insulin sensitivity, and stimulating glucose to ingest [30][31][32][33]. Estrogen may become a new therapeutic target for diabetic anal fistula wounds.…”

Estrogen receptor 1 (ESR1) regulates VEGFA in adipose tissue

“…Moreover, in the uterus, it has been demonstrated that E2 induced VEGFA expression via membrane ER and activation of PI3K/Akt pathway, which is required for the recruitment of HIF1 to the VEGFA gene promoter 28 . Indeed, our group has previously observed that treatments with E2 and ER-agonist PPT induced AKT phosphorylation in adipocytes 58 . Together, these data support the notion that E2/ESR1 can activate HIF1A in adipocytes to induce VEGFA expression.…”