Molecular Sciences II.
Kinga Tibori 1, Veronika Zámbó 1, Miklós Csala 1, Éva Kereszturi 1
1 Department of Molecular Biology, Semmelweis University, Budapest, Hungary
Introduction: Syndromes associated with excessive food intake and sedentary lifestyle may be due to systemic disturbances in lipid metabolism. A crucial enzyme in the defense against lipotoxicity is the Stearoyl-CoA desaturase-1 (SCD1), catalyzing the unsaturated fatty acid synthesis. On the other hand, increased activity or overexpression of the enzyme is a potential risk factor for type II diabetes mellitus (T2DM) as it favors fat storage and obesity.
Aims: In this study we sought to investigate the influence of different types of fatty acids (FAs), including saturated and monounsaturated cis or trans fatty acids, on the expression of SCD1 containing the most common promoter polymorphisms. On the other hand, we examined whether these polymorphisms affect any transcription factor (TF) binding sites of the promoter region.
Methods: Impact of FAs on the endogenous and transiently transfected SCD1 in HEK293T and HepG2 cells was monitored by immunoblotting and qPCR. Four promoter variants were generated by site-directed mutagenesis. The effect of SCD1 promoter polymorphisms on the TF binding site was investigated in silico with the JASPAR program and in vitro with a luciferase reporter system.
Results: We demonstrated that both the protein and mRNA level of the SCD1 significantly increases in response to elaidate (18:1 trans Δ9) compared to vaccinate (18:1 trans Δ11). This effect was also confirmed in the luciferase reporter system. The four most common promoter polymorphisms alone did not affect the promoter activity of SCD1, however, rs1054411 enhanced it in the presence of FAs, especially in the case of the two trans FA, elaidate and vacccenate. Based on our in silico analysis, in the presence of the minor allele of this polymorphism, the probability of ETS1 TF binding to the SCD1 promoter is reduced by 20%. Co-transfection with SCD1 promoter constructions with different alleles and ETS1 expression vector confirmed the reduced affinity of ETS1 to rs1054411_G variant.
Conclusions: From our results we conclude that the rs1054411 polymorphism may influence the protective role of SCD1 by modifying its promoter sensitivity to different fatty acids and altering its expression through the reduction of ETS1 promoter binding affinity.
Funding: This work was supported by the Hungarian National Research, Development and Innovation Office (NKFIH grant number: FK138115).