Glycated albumin modulates the expression of Slc2a4/GLUT4 in adipose cells in a hormetic manner with potential participation of the NFKB pathway.

Author(s)

Maria Luiza Estimo Michalani

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI)
• Defense date: 2019-02-20

Examining board members

Ubiratan Fabres Machado; Gisele Giannocco; Rodrigo Tallada Iborra; Raphael de Souza Pinto

• Advisor: Ubiratan Fabres Machado

Abstract

One of the main pathogenic factors of the insulin resistance is the deficiency in the expression of Slc2a4/GLUT4, which in the long term causes impaired glucose homeostasis. In addition, constant hyperglycemia leads to a glycotoxicity that also contributes to the pathogenesis of this condition. Increased circulating glucose leads to the formation of advanced glycated end products (AGEs) which, when interacting with RAGE receptor, trigger inflammatory processes and oxidative and reticulum stress in the cell, culminating in the activation of the NFKB pathway. This transcriptional factor is a known repressor of the Slc2a4 gene. In this sense, the objective of the present study was to investigate the effects of AGEs on the expression of Slc2a4/GLUT4 and whether this effect is mediated by the activation of the NFKB pathway. For this, we used 3T3-L1 adipocytes treated with bovine serum albumin without modification or conjugated with glycolaldehyde and verified the expression of the genes Slc2a4, Nfkb1 and Rela, abundance of GLUT4, p65 and p50 proteins, the degree of phosphorylation of IKK alpha and IKK beta proteins and p65 subunit binding activity in the Slc2a4 gene promoter. The results indicated that glycated albumin is able to modulate the expression of Slc2a4/GLUT4 in a hormetic manner, i.e. at low concentration (0.4 mg/mL) and short time (24 hours), there was an increase in gene expression and protein. However, there is a reduction of the gene and the protein expression when in high concentration (5.4 mg/mL) and prolonged time (72 hours). In addition, glycated albumin induces proinflammatory activity in the adipocyte and increases the amount of p65 and p50 in the nucleus in high concentration and prolonged time. Nonetheless, the activation of the NFKB pathway does not occur through canonical pathway, since no IKK activation was observed. Finally, despite being a preliminary finding, glycated albumin induces increased NFKB binding in the promoter region of the Slc2a4 gene. In summary, the present study demonstrates that AGEs participate not only in the genesis of the degenerative complications present in diabetes mellitus, but also contributes actively to the loss of glycemic homeostasis. (AU)

• FAPESP's process: 16/17002-4 - Effect of glycated albumin in the expression of glucose transporter GLUT4 in adipose cell: potencial participation of transcription factor NFKB
• Grantee: Maria Luiza Estimo Michalani Toledo
• Support Opportunities: Scholarships in Brazil - Master