Lipid Biosynthesis as a Biomarker of Metformin Treatment in Renal Tumor Cells Using Stable Isotope Resolved Metabolomics and High Field NMR

Motivation: NMR-based analyses of lipids can reveal the sources and pathways contributing to lipid biosynthesis in cells grown in the presence of 13C-labeled tracers. Goal(s): Our goal was to determine whether treatment of FLCN-deficient renal cell carcinoma (RCC) cells with the Complex I inhibitor metformin modulated cellular biosynthesis of lipids. Approach: We utilized 1H-13C HSQC NMR analysis of cellular lipids in FLCN-deficient tumor cells to assess incorporation of acetyl groups derived 13C6-glucose or 13C515N2-L-glutamine into cellular lipids during treatment with metformin. Results: We observed a sharp decrease in incorporation of 13C-glucose-derived carbon into lipid acyl chains and cholesterol methyl groups following metformin treatment. Impact: We found that metformin decreased synthesis of lipids from glucose while enhancing lipid synthesis from glutamine in renal tumor cells. These findings demonstrate that targeting Complex I may be a promising therapeutic avenue for treatment and prevention of FLCN-deficient RCC.