Fibrosis is a major complication of diabetes mellitus, largely driven by chronic hyperglycemia that promotes fibroblasts activation into pro-fibrotic myofibroblasts. Both green tea and green coffee have many health benefits, but the effects of their combination on hyperglycemia-induced fibroblast activation remain unclear. This study investigated the efficacy of a combined decaffeinated green coffee and green tea extract (GCGTE) in attenuating high-glucose–induced fibroblast activation in NIH-3T3 mouse embryonic fibroblast (NIH-3T3) cells. NIH-3T3 fibroblasts were assigned to six experimental conditions: a normal glucose control group (NG); a high-glucose (HG, 30 mM) group; a metformin (M) group (50 µM); and two treatment groups receiving GCGTE at two concentrations (160/160 and 320/320 µg/mL). Cells were pretreated for 2 h prior to exposure to high-glucose concentrations (30 mM) for 24 h. Cell viability was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, collagen type I secretion in the conditioned medium was measured using ELISA, and the expression of α-smooth muscle actin (αSMA), matrix metalloproteinase-9 (MMP-9), and phosphorylated AKT (pAKT) protein were analyzed using immunofluorescence staining, and cell size was assessed by flowcytometer. High glucose significantly increased collagen type I secretion, downregulated pAKT expression, upregulated αSMA and MMP-9 expression, and increased cell size, indicating fibroblast activation into the myofibroblast phenotype. Pretreatment with GCGTE at both concentrations did not reduce cell viability and effectively attenuated these effects with comparable efficacy compared to conventional oral antidiabetes drug−metformin, although no dose-dependent effect was observed. These findings suggest that GCGTE suppresses fibroblast activation and extracellular matrix accumulation, which is associated with the modulation of the MMP-9/transforming growth factor beta (TGF-β)/mothers against decapentaplegic homolog (Smad) and phosphoinositide 3-Kinase (PI3K)/AKT signaling pathways. In conclusion, GCGTE exhibits promising antifibrotic properties in vitro and may represent a potential plant-based therapeutic strategy for preventing fibrosis in diabetes. Further studies are warranted to validate these effects in vivo and to elucidate the precise molecular mechanisms involved.
Fukata et al. (Sat,) studied this question.