Summary： Abnormal cholesterol metabolism is associated with an elevated risk of developing athero- sclerosis, hypertension, and diabetes etc. Na＋/K＋-ATPase was found to regulate cholesterol synthesis, distribution ...Summary： Abnormal cholesterol metabolism is associated with an elevated risk of developing athero- sclerosis, hypertension, and diabetes etc. Na＋/K＋-ATPase was found to regulate cholesterol synthesis, distribution and trafficking. This study aimed to examine the effect of high-fat diet on cholesterol me- tabolism in rats and the role of Na＋/K＋-ATPase/Src/ERK signaling pathway in the process. Forty male SD rats were evenly divided into high-fat diet group and control group at random. Animals in the former group were fed on high-fat diet for 12 weeks, and those fed on basic diet served as control. Blood lipids, including total cholesterol （TC）, triglyceride （TG）, high density lipoprotein-cholesterol （HDL-C）, and low density lipoprotein-cholesteral （LDL-C） levels, were detected at 3, 6 and 12 weeks. The ratio of cholesterol content in cytoplasm to that in cell membrane was detected in liver tissues. RT-PCR and Western blotting were used to measure the expression of lipid metabolism-associated genes （HMG-CoA reductase and SREBP-2） after 12-week high-fat diet. Na＋/K＋-ATPase/Src/ERK signaling path- way-related components （Na＋/K＋-ATPase ctl, Src-PY418 and pERK1/2） were also measured by West- ern blotting. The results showed that the serum TC, TG, and LDL-C levels were significantly higher in high-fat diet group than those in control group, while the HDL-C level was significantly lower in high-fat diet group at 6 weeks （P〈0.01）. High-fat diet led to an increase in the cholesterol content in the cytoplasm and cell membrane. The ratio of cholesterol content in cytoplasm to that in cell membrane was elevated over time. The expression of HMG-CoA reductase and SREBP-2 was significantly sup- pressed at mRNA and protein levels after 12-week high-fat diet （P〈0.05）. Moreover, high-fat diet pro- moted the expression of Na＋/K＋-ATPase α1 but suppressed the phosphorylation of Src-PY418 and ERK1/2 at 12 weeks （P〈0.05）. It was concluded that high-fat diet regulates cholesterol metabolism, and Na＋/K＋-ATPase signaling pathway is involved in the process possibly by regulating the expression of lipid metabolism-associated proteins HMG-CoA reductase and SREBP-2.展开更多
AIM: Peroxynitrite (ONOO-) is a powerful oxidant shown to damage membranes. In the present study, the effect of taurine on changes of liver plasma membrane Na+, K+-ATPase induced by ONOO- was investigated. METHODS: Li...AIM: Peroxynitrite (ONOO-) is a powerful oxidant shown to damage membranes. In the present study, the effect of taurine on changes of liver plasma membrane Na+, K+-ATPase induced by ONOO- was investigated. METHODS: Liver plasma membrane was exposed toONOO-with or without taurine. Na+, K+-ATPase activity and lipid peroxidation as thiobarbituric acid reactive substances (TBARS) levels were measured.RESULTS: Different concentrations of ONOO- (100, 200,500, and 1 000 μmol/L) were found to decrease liver plasma membrane Na+, K+-ATPase activity significantly. The depletion of enzyme activity was not concentration dependent. Effects of different concentrations of taurine on liver plasma membrane Na+, K+-ATPase activity were also measured. Taurine did not cause any increase in enzyme activity. When plasma membranes were treated with 200 μmol/L ONOO- with different concentrations of taurine, a restoring effect of taurine on enzyme activity was observed. TBARS levels were also measured and taurine was found to decrease the elevated values. CONCLUSION: Taurine is observed to act as an antioxidant of ONOO-to decrease lipid peroxidation and thus affect liver plasma membrane Na+, K+-ATPase by restoring its activity.展开更多
基金supported by a grant from the National Natural Science Foundation of China(No.81200637)
文摘Summary： Abnormal cholesterol metabolism is associated with an elevated risk of developing athero- sclerosis, hypertension, and diabetes etc. Na＋/K＋-ATPase was found to regulate cholesterol synthesis, distribution and trafficking. This study aimed to examine the effect of high-fat diet on cholesterol me- tabolism in rats and the role of Na＋/K＋-ATPase/Src/ERK signaling pathway in the process. Forty male SD rats were evenly divided into high-fat diet group and control group at random. Animals in the former group were fed on high-fat diet for 12 weeks, and those fed on basic diet served as control. Blood lipids, including total cholesterol （TC）, triglyceride （TG）, high density lipoprotein-cholesterol （HDL-C）, and low density lipoprotein-cholesteral （LDL-C） levels, were detected at 3, 6 and 12 weeks. The ratio of cholesterol content in cytoplasm to that in cell membrane was detected in liver tissues. RT-PCR and Western blotting were used to measure the expression of lipid metabolism-associated genes （HMG-CoA reductase and SREBP-2） after 12-week high-fat diet. Na＋/K＋-ATPase/Src/ERK signaling path- way-related components （Na＋/K＋-ATPase ctl, Src-PY418 and pERK1/2） were also measured by West- ern blotting. The results showed that the serum TC, TG, and LDL-C levels were significantly higher in high-fat diet group than those in control group, while the HDL-C level was significantly lower in high-fat diet group at 6 weeks （P〈0.01）. High-fat diet led to an increase in the cholesterol content in the cytoplasm and cell membrane. The ratio of cholesterol content in cytoplasm to that in cell membrane was elevated over time. The expression of HMG-CoA reductase and SREBP-2 was significantly sup- pressed at mRNA and protein levels after 12-week high-fat diet （P〈0.05）. Moreover, high-fat diet pro- moted the expression of Na＋/K＋-ATPase α1 but suppressed the phosphorylation of Src-PY418 and ERK1/2 at 12 weeks （P〈0.05）. It was concluded that high-fat diet regulates cholesterol metabolism, and Na＋/K＋-ATPase signaling pathway is involved in the process possibly by regulating the expression of lipid metabolism-associated proteins HMG-CoA reductase and SREBP-2.
基金Supported by the Istanbul University Research Foundation,No.BYP-247/20082003
文摘AIM: Peroxynitrite (ONOO-) is a powerful oxidant shown to damage membranes. In the present study, the effect of taurine on changes of liver plasma membrane Na+, K+-ATPase induced by ONOO- was investigated. METHODS: Liver plasma membrane was exposed toONOO-with or without taurine. Na+, K+-ATPase activity and lipid peroxidation as thiobarbituric acid reactive substances (TBARS) levels were measured.RESULTS: Different concentrations of ONOO- (100, 200,500, and 1 000 μmol/L) were found to decrease liver plasma membrane Na+, K+-ATPase activity significantly. The depletion of enzyme activity was not concentration dependent. Effects of different concentrations of taurine on liver plasma membrane Na+, K+-ATPase activity were also measured. Taurine did not cause any increase in enzyme activity. When plasma membranes were treated with 200 μmol/L ONOO- with different concentrations of taurine, a restoring effect of taurine on enzyme activity was observed. TBARS levels were also measured and taurine was found to decrease the elevated values. CONCLUSION: Taurine is observed to act as an antioxidant of ONOO-to decrease lipid peroxidation and thus affect liver plasma membrane Na+, K+-ATPase by restoring its activity.
