Influence Of Hypothyroidism On Liver Lipid Metabolism In Rat

Objective: To observe the change of hepatic lipid metabolism and explore the molecular mechanisms in hypothyroidism rat.Methods: Wistar male rats were randomly assigned into three groups: control group,hypothyroidism group and L-thyroxine treatment group.The ¹³¹? diluted with saline to obtain a mixture,hypothyroidism group and Levothyoxine treatment group were intraperitoneally injected with 500?Ci equal volume ¹³¹? mixture and the control group received an equal volume of saline.L-thyroxine 5?g/100 g were given orally in treatment group and Equal amount nomal saline was given orally to control group and hypothyroidism group.The weight of rats were measured per week.TG,alanine aminotransferase?ALT?,aspartate aminotransferase?AST?were observed at the end of 4 weeks.Animals were put to death at the end of 8 weeks.Blood samples and liver tissues were collected for detection of TG,alanine aminotransferase?ALT?,aspartate aminotransferase?AST?.Western Blot was performed to evaluate the protein expressiom level of SREBP-1c?ACC?FAS?SCD1?CD36?PPAR? in liver.Results:1 The results of thyroid functionAt end of 4 weeks and 8weeks,the level of TT₃,TT₄ were decreased in the hypothyroidism group Compared with control group?P<0.05?.Compared with control group,the level of TSH was significantly increased in hypothyroidism group?P<0.05?.And there were no significant difference between control group and treatment group.2 Body weight and liver indexThere were no significant difference between the three groups in body weight at the end of the experiment?P > 0.05?.Compared with the control group,the liver index was significantly increased in hypothyroidism group?P < 0.05?.3 Blood biochemical assaysAt the end of the 4 week and 8 week,the serum TG levels of hypothyroidism group were significantly higher than those of control group and treatment group.Compared with 4th weeks,hypothyroidism group TC levels increased significantly at week 8,the difference is statistically significant?P < 0.05?.4 Liver lipidAt the end of the 8 week,hypothyroidism group liver tissue triglyceride levels were increased compared with the control group and the treatment group?P < 0.05?.5 Pathological resultsCompared with the normal control group and treatment group,hepatocytes were swollen,fat and cells infiltration in hypothyroidism group by hematoxylin and Eosin staining.6 The expression protein of liver lipid metabolismWestern blot results showed that SREBP-1c,ACC,FAS,PPAR? protein expression level in hypothyroid group decreased significantly?P < 0.05?,and CD36,SCD1 protein expression increased in the hypothyroid group compared with the control group and the treatment group?P < 0.05?.Conclusion:1.Hypothyroidism can lead to the disorder of lipid metabolism,and can increase triglyceride deposition in liver and promote liver steatosis and Levothyroxine can obviously improve hepatic triglyceride deposition.2.The role of hypothyroidism on triglyceride metabolism in the liver Through various ways which decreased triglyceride de novo synthesiss and fatty acid oxidation,but increased fatty acid transport.