Alliin inhibits adipocyte differentiation by downregulating Akt expression: Implications for metabolic disease.

Obesity is currently an important health problem and is associated with an increased likelihood of various diseases. The efficacies of various natural treatments have been assessed for their utility in treating obesity. Alliin (S-allyl-L-cysteine sulfoxides) is considered the major component of garlic and has a wide range of natural antioxidant properties. However, the direct effects of alliin on obesity have not been well clarified. The present study investigated the effects and possible mechanisms of alliin on adipocyte differentiation. The 3T3-L1 cells were treated with alliin (0-40 µg/ml) during adipogenic differentiation. The effect of alliin on lipid accumulation was evaluated by Oil red O staining. Reverse transcription-quantitative PCR was performed to investigate the expression levels of adipogenic differentiation-related genes. The accumulation of lipid droplets was markedly inhibited following alliin treatment. The expression levels of multiple adipogenic transcription markers, such as CCAAT/enhancer-binding protein (C/EBP) β, C/EBP α and peroxisome proliferation-activity receptor γ, were markedly decreased following treatment with alliin during adipogenic differentiation. Expression levels of several adipocyte-related genes were subsequently suppressed. Additionally, alliin suppressed PKB/Akt and PI3K expression. These results suggested that alliin exhibits anti-adipogenic activity by downregulating major adipogenic differentiation-related genes and Akt/PI3K expression. Alliin may have a potential therapeutic effect on metabolic disease.