Kaempferol이 3T3-L1 지방세포의 lipogenesis에 미치는 영향

Abstract

Kaempferol은 phytochemical중에서 flavonoid의 일종으로 브로콜리, 은행나무, 과일, 야채 등에 많이 함유되어 있다. Kaempferol은 벤젠고리 B에 수산화기를 함유하고 있으며 이로 인해 항산화, 항암에 효과가 있다는 연구가 많이 되어 있지만 비만에 관련된 연구는 많이 되어 있지 않다. Kaempferol을 전구지방세포 3T3-L1에 독성확인을 위해 5 ug/ml, 10 ug/ml, 20 ug/ml의 농도로 kaempferol을 처리한 결과 세포에 미치는 독성이 없음을 확인하였다. 3T3-L1세포에 1.25-20 ug/ml 농도로 kaempferol을 3-isobutyl-1-methylxanthine, dexamethasone, insulin (MDI)과 함께 처리한 후 triglycerol (TG) 양을 측정한 결과 농도의존적으로 TG의 축적이 억제되었으며 20 ug/ml의 경우 70% 가량의 억제효과가 나타났다. 분화 후 7 일동안 kaempferol을 처리한 후 7 일째부터 세포에 kaempferol을 처리하지 않은 경우 TG축적은 무처리구에 상응하는 양을 나타내었다. Kaempferol 처리에 의하여 지방세포의 분화에 영향을 미치는 전사인자인 CCAAT/enhancer-binding protein a (C/EBPa), peroxisome pro-liferators activated receptor γ (PPARγ)의 급격한 발현억제가 농도의존적으로 나타났다. Sterol regulatory element binding protein-1c (SREBP-1c) 또한 kaempferol의 모든 농도범위에서 발현이 억제되었으며, SREBP-1c의 down-stream에 존재하는 fatty acid synthase (FAS), stearoyl-CoA desaturase-1 (SCD-1)의 발현 억제 또한 농도의존적으로 나타났다. PPARγ의 발현억제는 세포내 포도당 유입과 관련된 glucose transporter 4 (GLUT4)의 발현에도 영향을 미쳤다. 단백질 발현 수준에서도 지방세포 분화와 지방합성에 관련된 전사인자인 PPARγ, C/EBPα의 합성이 억제되었으며, 이들 전사인자들의 조절을 받는 FAS, SCD-1의 발현억제가 나타났다. 따라서 kaempferol의 비만억제 효과는 LXRα-SREBP-1c-C/EBPα 경로를 통한 전사인자의 발현억제와 이들 전사인자의 downstream에 존재하는 FAS와 SCD-1의 발현억제로 인한 것으로 판단된다.

Obesity is both an individual clinical condition and is increasingly viewed as a serious public health problem. Excessive body weight has been shown to predispose to various diseases, particularly cardiovascular disease, diabetes mellitus type 2, sleep apnea, Coronary heart disease, and osteoarthritis. Kaempferol are polyphenolic bioflabonoids and water-soluble pigments of the red to blue range of the visible spectrum that provide color in many fruits, vegetables, cereal grains and flowers. Previous work has focused on antioxidant and anti-inflammatory properties in relation to cardiovascular disease and maintenance of brain function with ageing. Recent studies have demonstrated that kaempferol show promise in preventing obesity and ameliorating hyperglycemia in mice. The results showed kaempferol suppressed the development of obesity through down-regulation of the genes involved in the lipogenesis, and kaempferol were non-cytotoxic activity up to 40 μg/ml in undifferentiated 3T3-L1 preadipocytes. When induced to differentiate in the presence of kaempferol (1.0-40 μg/ml), 3T3-L1 preadipocytes reduced accumulation of cytoplasmic triglycerides by dose- and time-dependent manner. This phenomenon was rapidly reversible. In addition, when applied to mature 3T3-L1 adipocytes, kaempferol induced a moderate reduction in cellular triglyceride content. Furthermore, mRNA or protein expression levels of peroxisome proliferators-activated receptor γ (PPARγ), sterol regulatory element-binding protein-1c (SREBP-1c) and liver X receptor α (LXRα), which act as key transcription factors of lipogenesis, were decreased by kaempferol treatment. Kaempferol also decreased mRNA or protein expression of CCAAT enhancer-binding protein α (C/EBPα) and SREBP-1c target genes such as fatty acid synthase (FAS), stearoyl-CoA desaturase-1 (SCD-1) and acetyl CoA carboxylase α (ACCα). When considered together, these results suggest that the inhibitory effect of kaempferol on lipogenesis might be mediated through down-regulation of the SREBP-1c-dependent lipogenic pathway including SREBP-1c target genes such as SCD-1, FAS and ACCα, and through down-regulation of other genes involved in lipogenesis such as LXRα, adiponectin, PPARγ, GLUT4 and C/EBPα. These results suggest that kaempferol might be an important natural functional compound in the prevention of obesity.