PhD Scientific Days 2024

Molecular Medicine I.

Functional analysis of common SCD1 gene variants

Text of the abstract

Stearoyl-CoA desaturase-1 (SCD1), which catalyzes the synthesis of unsaturated fatty acids (FAs), is a key regulator of defense against lipotoxicity. However, altered activity or expression of SCD1 is a potential risk factor for metabolic disorders such as type II diabetes mellitus (T2DM) through its effect on fat storage.
The aim of the present study was to determine the nutritional and genetic factors that influence SCD1 enzyme levels, separately and in combination.
The impact of different saturated and cis or trans monounsaturated FAs on the endogenous and transiently transfected SCD1 was monitored in HEK293T and HepG2 cells. Four promoter variants and the single missense polymorphism in the coding region (M224L) were generated by site-directed mutagenesis. The effect of SCD1 promoter variants on the TF binding site was investigated in silico using the JASPAR database and in vitro with a luciferase reporter system. Intracellular mRNA and protein levels were determined by qPCR and immunoblotting, respectively. Desaturase functions were measured by GC-FID.
SCD1 responds differently to different types of FAs at both mRNA and protein levels. The four most common promoter polymorphisms were found to be ineffective alone, but in the presence of FAs, they already modulated SCD1 promoter activity. Both in silico and in vitro analyses revealed that in the presence of the minor allele of the rs1054411 promoter variant, the probability of ETS1 TF binding to the SCD1 promoter was reduced by 20%. The Leu224 polymorphic enzyme was more abundant in cells due to slower protein degradation and more stable mRNA structure, which could be further enhanced by FAs. Significantly increased intracellular amounts of the SCD1 enzyme products (C18:1 and C16:1) proved the functionality of the highly expressed Leu224 variant.
Our results suggest that the levels of SCD1, a key regulator of lipid metabolism, may be influenced by a combination of common polymorphisms and available FAs. This highlights the need to map gene-environment interactions to understand both the normal function and the pathomechanism of lipid metabolism-related diseases.
This work was supported by FK_138115 and ÚNKP_2023-1 grants.