ATR-FTIR Assessment of the Antioxidant and Anti-Inflammatory Effects of (−)-Epicatechin in MASLD

Lipid peroxidation is a contributor and a result of metabolic dysfunction-associated steatotic liver disease (MASLD), related to oxidative injury and inflammatory/fibrogenic signaling, which eventually results in disease progression. Early (conjugated dienes, CDs) and propagation (lipid hydroperoxides, LOOHs) products, along with attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy assessment, could possibly be used to quantify the extent of this process, while TNF-α and TGF-β1 reflect downstream inflammatory and profibrotic responses. (−)-Epicatechin (EC), a dietary polyphenol, shows antioxidant activity and could decrease the extent of lipid peroxidation and inflammation/fibrogenesis, thereby limiting MASLD progression. The aim of this study was to determine whether EC attenuates lipid peroxidation and pro-inflammatory/profibrotic signaling in an in vitro model of steatosis and whether ATR-FTIR could be used for such assessment in the context of steatosis and lipid peroxidation. Steatosis was induced in HepG2 cells with sodium oleate. EC (10–50 μM) was applied either as pretreatment before oleate exposure or as posttreatment during already established steatosis. Lipid peroxidation was quantified according to CDs, LOOHs, and the LOOH/CD ratio. ATR-FTIR band ratios and intensities related to lipid peroxidation (C═O and ═C–H bands) were evaluated alongside biochemical results. TNF-α and TGF-β1 concentrations were measured as they are potential indicators of inflammation and fibrogenesis in MASLD, respectively. Sodium oleate increased CDs, LOOHs, and the LOOH/CD ratio, consistent with enhanced lipid peroxidation, and elevated TNF-α and TGF-β1. EC pretreatment reduced CDs and LOOHs and lowered the LOOH/CD ratio and the TNF-α and TGF-β1 levels relative to sodium oleate control groups in a concentration-dependent manner. Although the posttreatment effects were less pronounced, EC posttreatment still decreased all these parameters in a concentration-dependent manner in steatotic HepG2 cells. ATR-FTIR spectra were consistent with the biochemical results where the ATR-FTIR carbonyl (C═O) band intensity showed a positive correlation with the LOOH/CD ratio, TNF-α, and TGF-β1 in the EC Pretreatment and Posttreatment models. Therefore, these results suggest that ATR-FTIR readings reflect quantitative changes in lipid peroxidation and associated inflammatory and fibrotic processes in steatosis.