Label-free study of intracellular glycogen level in metformin and resveratrol-treated insulin-resistant HepG2 by live-cell FTIR spectroscopy

Conventional in vitro study often involves the destruction of the cells followed by purification and dilution steps before applying enzymatic assay or metabolomic analysis. It is a costly and laborious process, and it cannot monitor changes as a function of time. Recently, we have developed a new label-free live-cell FTIR approach that can directly measure biochemical compositional changes within living cells in situ and the spectral changes are shown to be highly specific to the drug applied. In this work, we have demonstrated for the first time the effect of two anti-diabetic drugs, metformin and Resveratrol, on insulin-resistant liver cells (HepG2). Using live-cell FTIR with principal component analysis, we have shown the differences in the biochemical profiles between normal and insulin-resistant cells (p < 0.05), the lack of response/difference from the insulin-resistant cell to insulin (p > 0.05) and the restoration of the biochemical profile and sensitivity to insulin from the insulin-resistant cells after the drug treatment (p < 0.05). Particularly, a rise in the glycogen level, marked by three distinctive peaks at 1150, 1080 and 1020 cm(-1), within the living cells after the anti-diabetic drug treatments is observed. The livecell FTIR results are confirmed by a parallel gold-standard biochemical assay, demonstrating the restoration of insulin sensitivity of the insulin-resistance cells. Live-cell FTIR can be a complementary tool for drug efficacy screening, especially for insulin sensitizers.

Automated summary

Conventional in vitro study often involves destructive methods and cannot monitor changes over time. This research presents a label-free live-cell FTIR method that directly measures biochemical changes within living cells. The study investigates the effects of two anti-diabetic drugs on insulin-resistant liver cells and demonstrates the differences in biochemical profiles between normal and insulin-resistant cells, lack of response from insulin-resistant cells to insulin, and restoration of biochemical profile after drug treatment.