BackgroundThe naphthoquinone pigment, shikonin, is a major component of Lithospermum erythrorhizon and has been shown to have various biological functions, including antimicrobial, anti-inflammatory, and antitumor effects. In this study, we investigated the effect of shikonin on adipocyte differentiation and its mechanism of action in 3T3-L1 cells.MethodsTo investigate the effects of shikonin on adipocyte differentiation, 3T3-L1 cells were induced to differentiate using 3-isobutyl-1-methylzanthine, dexamethasone, and insulin (MDI) for 8 days in the presence of 0–2 μM shikonin. Oil Red O staining was performed to determine the lipid accumulation in 3T3-L1 cells. To elucidate the anti-adipogenic mechanism of shikonin, adipogenic transcription factors, the phosphorylation levels of ERK, and adipogenic gene expression were analyzed by Western blotting and quantitative real-time PCR. To further confirm that shikonin inhibits adipogenic differentiation through downregulation of ERK 1/2 activity, 3T3-L1 cells were treated with shikonin in the presence of FGF-2, an activator, or PD98059, an inhibitor, of the ERK1/2 signaling pathway.ResultsShikonin effectively suppressed adipogenesis and downregulated the protein levels of 2 major transcription factors, PPARγ and C/EBPα, as well as the adipocyte specific gene aP2 in a dose-dependent manner. qRT-PCR analysis revealed that shikonin inhibited mRNA expression of adipogenesis-related genes, such as PPARγ, C/EBPα, and aP2. Adipocyte differentiation was mediated by ERK 1/2 phosphorylation, which was confirmed by pretreatment with PD98059 (an ERK 1/2 inhibitor) or FGF-2 (an ERK 1/2 activator). The phosphorylation of ERK1/2 during the early stages of adipogenesis in 3T3-L1 cells was inhibited by shikonin. We also confirmed that FGF-2-stimulated ERK 1/2 activity was attenuated by shikonin.ConclusionsThese results demonstrate that shikonin inhibits adipogenic differentiation via suppression of the ERK signaling pathway during the early stages of adipogenesis.

Lithospermum erythrorhizon, which has traditionally been used as a vegetable and to make the liquor Jindo Hongju, contains several naphthoquinone pigments, including shikonin. This study aimed to evaluate the antiobesity effects of Lithospermum erythrorhizon ethanol extract (LE) and elucidate the underlying mechanism. C57BL/6J mice were fed a normal or high-fat diet with or without LE supplementation for 8 weeks. LE reduced high-fat diet-induced increases in body weight, white adipose tissue mass, serum triglyceride and total cholesterol levels, and hepatic lipid levels while decreasing lipogenic and adipogenic gene expression. Furthermore, acetylshikonin suppressed adipocyte differentiation in a dose-dependent manner and significantly attenuated adipogenic transcription factor expression in 3T3-L1 cells. These findings suggest that Lithospermum erythrorhizon prevents obesity by inhibiting adipogenesis through downregulation of genes involved in the adipogenesis pathway and may be a useful dietary supplement for the prevention of obesity.

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