| Part 1. Effects of Fenofibrate and Pioglitazone on Adipose Triglyceride Lipase in High Fat Diet RatsObjective: Adipose triglyceride lipase is an essential TG lipase. Previous study shows that enhancing TG metabolism may ameliorate insulin resistance. However, the regulation of ATGL in the majoy metabolic tissues remains poorly defined. Both fenofibrate and pioglitazone have positive effects on lipid hydrolysis as well as increasing insulin sensitivity. The study aims to analyze the changing of ATGL level in adipose tissue, liver and muscle of high fat diet rats, and to elucidate the regulation of fenofibrate and pioglitazone on ATGL.Methods: 32 male SD rats were randomly divided into 2 groups, normal diet group (NC, n = 8), high fat diet group (HFD, n = 24). After 8 weeks, rats in the HFD group were divided into untreated(HFD-UT), fenofibrate treatment(HFD-FT) and pioglitazone treatment group(HF-PT). Insulin sensitivity was detected by oral glucose tolerance (OGTT) and insulin tolerance (ITT) ; Blood glucose, lipid profiles and surum insulin were measured; Weight of liver and epididymal adipose were also measured; TG content in adipose tissue, liver and muscle were detected; Western blot was used to assay ATGL protein in epididymal adipose, liver and muscle.Results: 1. The levels of blood glucose, lipid profiles and fasting insulin in HFD-UT group were higher than those in NC group. HFD-UT group had higher triglyceride content in adipose tissue, liver and muscle than NC group(P<0.01, respectively). 2. ATGL in adipose tissue, liver and muscle were decreased by 50%, 70%, 51% in HFD-UT group than NC group.3. These metabolic changes were almost completely improved by fenofibrate or pioglitazone treatment(P<0.05). 4.ATGL levels in adipose tissue, liver and muscle were increased by 40%, 40%, 90% after fenobrate treatment and increased by 90%, 50%, 48% after pioglitazone treatment.Conclusion: High fat diet contributed to the development of obesity and its associated disorders such as glucose intolerance, insulin resistance, diabetes. Fenofibrate or pioglitazone improved the expression of ATGL in adipose tissue, liver and muscle as well as decreasing the TG level in these tissues.Part 2. Effects of Fenofibrate and Pioglitazone on Adipose Triglyceride Lipase in VitroObjective: The study aims to analyze the effects of fenofibrate or pioglitazone on adipose triglyceride lipase in HepG2 and C2C12 cells.Methods: HepG2 cells as well as C2C12 myoblasts were cultured in DMEM supplemented with 10 % FBS, 1% penicillin-streptomycin. C2C12 was developed into myotubes. Cells were stimulated in serum free media in the presence or absence of palmitate, fenofibrate, pioglitazone for 24h. RT-PCR and western blot were used to detect ATGL level in these cells.Results: After treatment of palmitate, ATGL protein was decreased by 40% in HepG2 cells and 60% in C2C12 cells. ATGL mRNA was decreased by 60% in C2C12 cells. Fenofibrate and pioglitazone respectively increased ATGL protein by 120%, 70% in HepG2 and 100%, 80% in C2C12 cells, and also increased ATGL mRNA in C2C12 cells.Conclusion: Fenofibrate and pioglitazone reversed the effects of palmitate on adipose triglyceride lipase in HepG2 and C2C12 cells.Part 3. APPL1 is a Key Mediator on the Regulation of Adipose Triglyceride Lipase by PalmitateObjective: APPL1 mediates adiponectin signalling and insulin signalling. We do this study in order to detect the effect of APPL1 on adipose triglyceride lipase in C2C12 cells that treated with palmitate, fenofibrate or pioglitazone.Methods: 1.Establishment of APPL1-suppressed C2C12 cells and Scrambled control C2C12 cells. 2. C2C12 cells were cultured in DMEM supplemented with 10 % FBS, 1% penicillin-streptomycin, developed into myotubes. 3. Treating cells with palmitate, fenofibrate or pioglitazone in serum free medium, collect cells after 24h. 4. RT-PCR and western blot were used to detect ATGL level.Results: In scrambled control C2C12 cells, both ATGL protein and ATGL mRNA were ruduced by palmitate when compared with CON(P<0.01). Fenofibrate or pioglitazone improved the expression of ATGL(P<0.01, P<0.05, respectively). Whereas, in APPL1-suppressed C2C12 cells, ATGL level did not change after palmitate, fenofibrate or pioglitazone treatment.Conclusion: APPL1 mediates the regulation of palmitate on ATGL level.Conclusion1. High fat diets leading to insulin resistance.2. TG accumulation in adipose tissue, liver and muscle in obese rats.3. Decreased the levels of ATGL in the adipose tissue, liver and muscle in obese rats.4. Palmitate decreased the expression of ATGL in C2C12 and HepG2 cells.5. Fenofibrate or pioglitazone ameliorated insulin resistance, improved TG accumulation and ATGL level in adipose, liver and muscle.6. APPL1 mediates the regulation of palmitate on ATGL level. |
