Comparative study on the difference of obesity model induced by two kinds of high fat diet in Sprague-Dawley rats

Objective: To explore the differences of obese Sprague-Dawley(SD)rats model induced by lard oil high-fat(HF)diet or purified HF diet. Methods: SD weanling rats were randomly divided into three groups: D1 group,where rats were fed by lard oil HF diet;D2 group,where rats were fed by purified HF diet;C group,where rats were fed on chow. After 12 weeks,diet-induced obesity rat(stop 33% based on weight)were selected for further study,and the rest rats from group D1 and D2 were excluded. The food intake and weight were weighted daily and weekly,respectively. The subcutaneous,visceral and total fat contents of rats was measured by 256-row CT scan and the Lee index was calculated accordingly. The kidney,liver,testis,spleen and heart were weighted respectively. Serum leptin and insulin levels were quantified. The pathology in liver and adipose tissues were analyzed by HE staining. Oral glucose tolerance test(OGTT)was used to compare the glucose tolerance ability. Serum total cholestero(lT-CHO),high density lipoprotein(HDL-C),low density lipoprotein(LDL-C),triglyceride(TG)and inflammatory cytokines IL-6,TNF-α were detected as well. Results: After 12 weeks,the body weight,subcutaneous fat,visceral fat,total fat mass,wet weight of liver,kidney and heart,area under blood glucose curve and the levels of serum insulin,leptin,T-CHO,LDL-C,TG,IL-6 and TNF-α in group D2 were significantly increased compared to those of group C and group D1. HDL-C of group D2 was markedly lower than that in group C(P<0. 05). The visceral fat,total fat content and HDL-C in group D1 were significantly different from those of group C(P<0. 05). Steatosis and enlarged adipocyte were found in the livers of rats in group D1 and D2,and the lesions were more significant in group D2. Conclusion: Purified HF diet was more effective in inducing metabolic abnormalities,steatosis,peripheral chronic inflammation in obese SD rat models. But lard oil HF diet was more economical when only inducing visceral steatosis was required.

TRAF6 Affects RAC1 Expression and Apoptosis in SK-Hep1 Cells

RAC1 is a small-molecule G protein that regulates multiple cell cycle, cytoskeletal reorganization, cell migration, and apoptosis. FADD-dependent TRAIL can promote tumor metastasis through RAC1 and PI3K, and down-regulating RAC1 expression can reduce FasL-induced apoptosis. In addition, RIP1 bound to GTP acts as an activating protein for RAC1 and is involved in cytoskeletal reorganization. TRAF6 promotes migration and metastasis by regulating the RAS pathway in tumors. Thus, it is necessary to understand the interaction between RAC1 and TRAF6 as well as FADD and RIP1. In this study, we cultured hepatoma SK-Hep1 cells in vitro, specifically blocked the necroptosis pathway with Nec-1, and silenced FADD, RIP1 and TRAF6 gene expression using RNAi technology. At the same time, the expression of RAC1 was evaluated separately using RT-PCR and Western blot. The hepatoma SK-Hep1 cells survival rate was highest when the concentration of Nec-1 was 60 μM and the concentration of Z-vad-fmk was 20 μM. And the apoptosis rate of the transfected RAC1 siRNA cells was 3.59% compared with transfected siRNA cells 10.01% which was significantly decreased (P < 0.01). RAC1 could promote the occurrence of apoptosis in SK-Hep1 cells. RAC1 expression was suppressed in both protein and gene level in SK-Hep1 cells when the TRAF6 gene was silenced, but there was no significant change in RAC1 gene and protein expression when FADD and RIP1 genes were silenced. TRAF6 affects RAC1 expression and apoptosis in SK-Hep1 cells, while the FADD and RIP1 genes do not affect the role of RAC1. The TRAF6 gene is an important target in liver cancer cells.