OBJECTIVES: To observe the effect of acupuncture on the expressions of transforming growth factor β(TGF-β)/Smad homolog 3(Smad 3)signaling pathway and autophagy-related factors in obese rats induced by a high-fat diet, so as to explore its possible mechanisms in improving obesity.
METHODS: Male SD rats were randomly divided into normal, model, medication and acupuncture groups, with 10 rats in each group.The obesity model was established by feeding the rats with a high-fat diet.Rats of the acupuncture group received acupuncture at "Guanyuan"(CV4) "Zhongwan"(CV12) and bilateral "Tianshu"(ST25) etc., for 30 min, once daily for 4 weeks. Rats in the medication group received gavage of orlistat solution (32.4 mg·kg·d), once daily for 4 weeks.The rat's body weight was measured for calculating the Lee's index.The weights of epididymal fat and perirenal fat were measured.The fasting blood glucose (FBG) and insulin levels were measured, and the homeostasis model assessment of insulin resistance (HOMA-IR) index was calculated. Additionally, intraperitoneal glucose tolerance and insulin tolerance tests were performed.The serum levels of triglyceride (TG), total cholesterol (TC), low-density lipoprotein (LDL) and high-density lipoprotein (HDL) were measured. HE staining was used to observe the morphology and structure of liver and epididymal adipose tissue, and oil red O staining was used to observe the lipid droplets in liver tissue.The mRNA and protein expression levels of TGF-β, TGF-β receptor 1 (TGF-βR1), Smad3, autophagy related protein Beclin-1, ubiquitin binding protein p62, and microtubule-associated protein 1 light chain 3(LC3) in epididymal adipose tissue were detected by real-time fluorescence quantitative PCR and Western blot, respectively. -1 -1
RESULTS: Compared with the normal group, the body weight, Lee's index, perirenal and epididymal fat mass, serum TC, TG and LDL content, fasting insulin level, and HOMA-IR of rats in the model group were increased (<0.01), the blood glucose levels were also increased at 30, 60, and 120 min after glucose and insulin injection (<0.01,<0.05), while the HDL content was decreased (<0.01). Compared with the model group, the body weight, Lee's index, perirenal and epididymal fat mass, serum TC, TG and LDL content, and HOMA-IR of the medication and acupuncture groups were decreased (<0.01,<0.05), and the serum HDL content of the acupuncture group was increased (<0.01). Compared with the normal group, the mRNA expression levels of TGF-β, TGF-βR1, Smad3, LC3, and Beclin-1, the protein expression levels of TGF-β, TGF-βR1, p-Smad3/Smad3, LC3-Ⅱ/LC3- Ⅰ, and Beclin-1 in the epididymal adipose tissue of rats in the model group were significantly increased (<0.01,<0.05), while the mRNA and protein expression levels of p62 were decreased (<0.01). Compared with the model group, the mRNA expression levels of TGF-β, LC3, and Beclin-1, the protein expression levels of TGF-β, p-Smad3/Smad3, and Beclin-1 in the medication and acupuncture groups were decreased (<0.01), while the mRNA and protein expression levels of p62 were increased (<0.01). Additionally, the mRNA expression of TGF-βR1, the protein expression of TGF-βR1 and LC3-Ⅱ/LC3- Ⅰ in the acupuncture group was decreased (<0.05,<0.01). Compared with the medication group, the serum HDL content and the expression of p62 protein in adipose tissue were significantly increased in the acupuncture group (<0.01), while the protein expression level of TGF-βR1, the ratio of p-Smad3/Smad3, and the expression of Beclin-1 protein in adipose tissue were significantly decreased (<0.01). Compared with the normal group, the adipocytes in the model group exhibited significantly enlarged lipid droplets with disordered arrangement, and hepatic lipid deposition was markedly increased;whereas compared with the model group, both the acupuncture and medication groups showed reduced lipid droplet size. P P P P P P P P P P P P P P P P
CONCLUSIONS: Acupuncture may induce weight loss by inhibiting the TGF-β/Smad3 signaling pathway and excessive autophagy of adipose tissue, thereby improving the metabolic state of obese rats and reducing the volume of adipocytes.
