Anti­adipogenic effect and underlying mechanism of lignan­enriched nutmeg extract on 3T3­L1 preadipocytes.

Nutmeg is the seed derived from Myristica fragrans. Nutmeg seeds contain alkylbenzene derivatives such as myristicin, which are toxic to the human organism, and lignan compounds such as nectandrin B, which possess anti-aging and anti-diabetic properties. However, the anti-adipogenic, prolipolytic and anti-inflammatory effects of lignan-enriched nutmeg extract (LNX) on preadipocytes remain unclear. In the present study, the effects of LNX on lipid accumulation, glycerol release and inflammatory cyclooxygenase-2 (COX-2) expression in differentiated 3T3-L1 preadipocytes were investigated. Oil red O staining demonstrated that treatment with LNX resulted in a concentration-dependent reduction in lipid accumulation in differentiating 3T3-L1 preadipocytes without affecting cell growth. Mechanistically, LNX treatment at 6 µg/ml led to a reduction in phosphorylation levels of signal transducer and activator of transcription 3 (STAT3), whereas it did not influence the peroxisome proliferator-activated receptor gamma (PPAR-γ) and CCAAT enhancer binding protein alpha (C/EBP-α) expression levels during 3T3-L1 preadipocyte differentiation. In addition, LNX treatment at 6 µg/ml led to a decrease in fatty acid synthase (FAS) expression levels on day (D) 2, but not D5 and D8, during preadipocyte differentiation. Treatment with LNX at 6 µg/ml did not affect the expression levels of perilipin A during preadipocyte differentiation. In differentiated 3T3-L1 adipocytes, LNX treatment at 6 µg/ml did not stimulate glycerol release and hormone-sensitive lipase phosphorylation, which are known lipolysis hallmarks. Furthermore, LNX treatment at the doses tested had no effect on tumor necrosis factor alpha-induced COX-2 expression in 3T3-L1 preadipocytes. Collectively, these results demonstrated that LNX has an anti-adipogenic effect on differentiating 3T3-L1 preadipocytes, which is mediated by the downregulation of STAT3 phosphorylation and FAS expression.

Suppression of Lipid Accumulation in the Differentiation of 3T3-L1 Preadipocytes and Human Adipose Stem Cells into Adipocytes by TAK-715, a Specific Inhibitor of p38 MAPK.

Excessive preadipocyte differentiation is linked with obesity. Although previous studies have shown that p38 MAPK is associated with adipogenesis, the regulation of preadipocyte differentiation by TAK-715, an inhibitor of p38 mitogen-activated protein kinase (MAPK), remains unclear. Interestingly, TAK-715 at 10 µM vastly suppressed the accumulation of lipid and intracellular triglyceride (TG) content with no cytotoxicity during 3T3-L1 preadipocyte differentiation. On mechanistic levels, TAK-715 significantly decreased the expressions of the CCAAT/enhancer-binding protein-α (C/EBP-α), peroxisome proliferator-activated receptor gamma (PPAR-γ), fatty acid synthase (FAS), and perilipin A. Similarly, the phosphorylation of the signal transducer and activator of transcription-3 (STAT-3) in differentiating 3T3-L1 cells was also reduced with TAK-715 treatment. Moreover, TAK-715 significantly blocked the phosphorylation of activating transcription factor-2 (ATF-2), a p38 MAPK downstream molecule, during 3T3-L1 preadipocyte differentiation. Of importance, TAK-715 also markedly impeded the phosphorylation of p38 MAPK and suppressed lipid accumulation during the adipocyte differentiation of human adipose stem cells (hASCs). Concisely, this is the first report that TAK-715 (10 µM) has potent anti-adipogenic effects on the adipogenesis process of 3T3-L1 cells and hASCs through the regulation of the expression and phosphorylation of p38 MAPK, C/EBP-α, PPAR-γ, STAT-3, FAS, and perilipin A.