This study aimed to investigate the impact of yeast hydrolysate (YH) on lipogenesis, elucidate its mechanistic action, and identify the active compounds responsible for its anti-adipogenic effects. YH (2 mg/mL) significantly reduced Oil Red O-stained lipids. YH (2 mg/mL) also downregulated C/EBPβ and upregulated KLF2, both of which are early adipogenic factors. Moreover, YH (2 mg/mL) decreased C/EBPα, PPARγ, FABP4, FAS, ACC, and HMGCR mRNA expression. Additionally, YH significantly downregulated SEBP1c and SREBP2 and their target genes, which govern fatty acid and cholesterol metabolism; however, 2 mg/mL YH had a greater suppressive effect on SREBP1c than on SREBP2. YH (2 mg/mL) also significantly reduced the mRNA level of G6PD and malic enzyme, which are enzymes that synthesize NADPH for lipid synthesis, compared with the control. Furthermore, 1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (MTCA) was identified as the active compound with anti-adipogenic effects using solvent fractionation and chromatographic analysis of YH, and 1.1 μg/mL MTCA significantly downregulated SREBP1c/SREBP2 mRNAs by 47.8% and 69.2%, respectively, along with the target genes FAS, ACC, and HMGCR by 79.0%, 77.0%, and 40.9%, respectively. Collectively, YH effectively suppressed adipogenic lipid storage by downregulating SREBP- and NADPH-synthesizing genes. These findings suggest that YH containing MTCA has the potential to act as an anti-obesity agent.

Obesity is well-known as a major risk factor for metabolic disorders, and natural compounds are being explored as alternatives to conventional therapies. While Centella asiatica is well known for its medicinal and dietary benefits, the biological activities of Giant Centella asiatica (GCA), especially when extracted with mineral-rich lava seawater, remain poorly characterized. This study aimed to evaluate the anti-adipogenic and lipid-metabolism-regulating effects of a novel GCA extract (GCA-LS-90) and its ability to stimulate GLP-1 secretion in vitro. GCA-LS-90 significantly inhibited lipid accumulation in 3T3-L1 adipocytes by up to 24.3% at 200 µg/mL (p < 0.001). It downregulated adipogenic transcription factors (C/EBPβ, C/EBPα, PPARγ) and lipogenic regulators (SREBP1c, FAS, G6PD, ME), while upregulating KLF2 (all p < 0.001). Western blotting confirmed reduced SREBP1c and SREBP2 protein expression, increased phosphorylation of AMPKα/ACC, and enhanced HSL activity (p < 0.05–0.001). In STC-1 cells, GCA-LS-90 increased GLP-1 secretion (53.5 pmol/L at 90 µg/mL vs. 41.3 pmol/L in control, p < 0.001). The major compounds, 3,5- and 4,5-di-O-caffeoylquinic acids, reproduced these effects. In conclusion, GCA-LS-90 modulated adipogenesis-, lipid-metabolism-, and GLP-1 secretion-related pathways in vitro, suggesting its potential as a functional ingredient for obesity management. Further in vivo studies are needed to confirm efficacy and translational relevance.