Effects Of Carotenoids On 3T3-L1 Preadipocyte Viability And Differentiation

Carotenoids are a kind of natural pigments which are synthesized by plants and microorganisms. They are aliphatic or alicyclic compounds with numerous conjugated carbon-carbon double bonds as chromophore skeleton. Carotenoids are lipid-soluble yellow-orange-red pigments widely distributed among a great variety of fruits and vegetables. Carotenoids as important micronutrients have also been paid more and more attention to.It is well known that carotenoids are a kind of excellent biological antioxidants. A large number of research results show that carotenoids can reduce the risk of some chronic diseases, such as coronary artery disease and cancer. The increases in adipocyte number and the expansion of adipocyte size may lead to excess accumulation of adipose tissues, which causes obesity. Adipocytes not only store triacylglycerols, but also secrete a variety of adipokines. They can regulate metabolism processes in adipocytes and the cells of other tissues, and even in the whole body. The incidence of obesity may be reduced via suppressing the proliferation and differentiation of adipocytes. Some animal and cellular experiments show that many carotenoids, such as neoxanthin, fucoxanthin and β-cryptoxanthin, can effectively suppress the proliferation and differentiation of adipocytes and lead to the change in adipose tissue mass. The proliferation and differentiation of adipocytes which involve the synthesis of triacylglycerols are a rigorous and complex process, in which a variety of genes are involved. Until now, more than 600 genes are found to be associated with obesity. Peroxisome proliferator activated receptor gamma(PPARγ) is one of the key factors in the differentiation of adipocytes and plays important roles in numerous physiological and pathological processes, such as glucose and lipid metabolism and the incidence of several diseases including hypertension and diabetes. Leptin(lep), adipocyte fatty acid binding protein(FABP4) and acetyl-CoA carboxylase(ACACA) are the specific proteins expressed in adipocytes and take part in fatty acid metabolism. Previous studies indicated that the suppression of proliferation and differentiation of adipocytes is associated not onlywith repression of PPARγ expression, but also with the regulation of lep, FABP4, and ACACA expression. It is helpful for making nutritional intervention – based strategie for preventing obesity and putting them into effect to investigate the effect of carotenoids on the proliferation and differentiation of 3T3-L1 preadipocyte, measure the expression of PPARγ, lep, FABP4 and ACACA, and explore their relationship.3T3-L1 preadipocytes were used as the target cells in the present study. This experiment studied the effects of carotenoids on 3T3-L1 preadipocyte viability and differentiation and further explored the roles of the PPARγ, FABP4, lep and ACACA in the process. The methods used in the present study are as follows,(1) predipocytes were cultivated in DMEM cell culture medium containing 10% FBS in 5% CO2 incubator under 37 °C, the model of 3T3-L1 preadipocyte differentiation was established at the same time;(2) the viability of the predipocytes treated with carotenoids for three days was evaluated by MTT assay;(3) differentiation of the preadipocytes was induced to by typical hormone “cock tail” method, and carotenoids were added at the third day;(4) Oil red O staining was used to observe the differentiation of 3T3-L1 preadipocyte;(5) the changes of PPARγ, FABP4, lep and ACACA expression were measured by Western blot.The experimentations expressed that bixin, lycopene and β-carotene obviously decreased and suppressed the viability and differentiation of 3T3-L1 preadipocytes, respectively. Bixin and lycopene had weaker suppressive effects than β-carotene on adipocyte differentiation in 3T3-L1 cells. Moreover, the carotenoids down-regulated PPARγ, FABP4 and lep expression. they up-regulated ACACA expression at the same time. It presents that bixin, lycopene and β-carotene bated the adipocyte differentiation of 3T3-L1 cells via PPARγ-dependent signaling pathway and affected the synthesis and accumulation of fatty acid as well as the functions of the cells through regulating the expression of FABP4, lep and ACACA. It may provide the basis and reference for prevention and treatment of obesity to suppress the proliferation and differentiation of adipocytes and regulate metabolism in adipocytes by the compounds among functional food.