The Effect Of Aerobic Exercise On Lipid Metabolism And The Expression Of Perilipin1 Protein In The Liver Tissue In Rats With Non-alcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease(NAFLD) is a clinicopathological change characterized by the accumulation of triglycerides in hepatocytes without excessive alcohol intake which is conventionally considered by not less than 20 g perday and other causes that could damage liver.Triacyglycerols are a major energy reserve of the body and are normally stored in adipose tissue as lipid droplets(LDs). The pathological features of NAFLD is that excessive neutral lipid stored in the liver cell. Notably, research in recent years has shown LD as highly dynamic organelles for maintaining lipid homeostasis through fat storage, protein sorting and other molecular events studied in adipocytes and other cells of living organisms. LDs are comprised of a neutral lipid [TAG and/or cholesterylester(CE)] core surrounded by a single phospholipid layer and much functional protein on the surface of it. These LD coat proteins modulate LD dynamics and lipid metabolism. PAT protein family is a notable kind of LD coat proteins. In recent years many research data on LD coat proteins indicate there are five kinds of proteins comprised PAT family: Plin1(perilipin, Plin1, Plin2 or ADRP, Plin3 or TIP47, Plin4 or S3-12 and Plin5. Plin1 is expressed in WAT, brown adipose tissue(BAT), steroidogenic tissue, fatty liver cells and normal liver cells. Unphos-phorylated Plin1 serves a barrier to lipases, phorylated Plin1 interacts with other proteins to balance lipid storage and hydrolysis. Plin1 can shape the structure of LDs by turn multilocular adipose cells into unilocular adipose cells and change the size of LDs. Plin1 plays an important role on lipid metabolism in liver tissue and even on the preventing of NAFLD.Fatty liver disease has become a major health burden with more than 90% of obese, nearly 70% of overweight and about 25% of normal weight patients being affected.Along with the change of life style and dietary structure, daily dietary represented by fat obviously increase the proportion of high quantity of heat food ingredients. This increase the incidence of NAFLD. There are more and more focus on the NAFLD in medical and research fields. Among the many treatment of NAFLD, as an effective,individual, lower expense and less side effect treatment, aerobic exercise is attracting more and more attention.Objective: In this research, we studied the changes of the shape and the number of LDs in the liver tissue,and the changes of lipid metabolism in the liver tissue and the changes in expression of perilipin1 protein in the liver tissue in rats with non-alcoholic fatty liver disease. Meanwhile, we demonstrated the preventing effects of aerobic exercise on lipid metabolism, the changes of the shape and the number of LDs and the expression of perilipin1 protein in the liver tissue in rats with non-alcoholic fatty liver disease. This research is in order to provide new ideas for study the pathogenesis and preventing of NAFLD.Methods: Twenty Sprague-Dawley(SD)male rats, with body weight of 180-220 grams were randomly divided into 3 groups:rats in group N were fed by standard diet without exercise training, rats in group H were fed by high-fat diet(standard diet supplemented with 10% lard oil, 5% egg white power, 2% cholesterol and 0.5% sodium cholate) without exercise training, rats in group HE were exercised by swimming training and fed by high-fat diet. Swimming training proceed only from Monday to Saturday.In the first to fourth week,swimming training proceed twice in the morning,and in fifth to eigth week,swimming training proceed once in the morning or afternoon.In the first week,swimming training proceed 15 min at a time.In the second week, swimming training proceed 20 min at a time. In the third week, swimming training proceed 25 min at a time.In the fourth week, swimming training proceed 30 min at a time. In the fifth week, swimming training proceed 40 min at a time in the first two days,50 min in the later days. From sixth to eigth week, swimming training proceed 60 min at a time. By the end of eigth week, all rats were killed and serum and liver parameters were evaluated after weighing body weight. After the anesthesia by intraperitoneal injection of 8% 3ml/kg weight chloral hydrate, collected blood from inferior vena cava,and made that standing in the 4℃ice water.Then separated serum and kept it in-20 ℃for later use.Then opened the abdominal cavity, stripped liver completely, flushed it by brine ice, then blotted them up by flitter paper, weighed them by electronic balance. Under the condition of ice bath, cut out about 100 g of right liver lobe in paraformaldehyde fixed fluid for pathological and immunohistochemical experiment. Cut out about 200 g of right liver lobe and kept them in the low temperature of-80 ℃for making tissue homogenate to detect the FFA in liver and serum and the expression of perilipin1 by western-blot.Results:1 Comparison of the general condition of rats in three groupsResults showed: rats in normal control group had steady increase in weight. They were in good health spiritually,fur lustrous, quick response. The rats in group H had significant increase in weight. They were in general health spiritually, fur lustrous, quick response. The rats in group C were better than the rats in group H. During the whole experiment there were no adverse reactions and without death.2 Changes of body weight,liver weight and liver index of rats in each groupResults showed: in the eigth week,compared with the normal control group, the body weight in group H and group C were obviously higher(P<0.01). The body weight in group C were obviously higher than group N(P<0.01). Compared with the normal control group, the liver weight in group H and group C were obviously higher(P<0.01). The liver weight in group C were obviously higher than group N(P<0.01). Compared with the normal control group, the liver index in group H and group C were obviously higher(P<0.01). No significant differences were found in liver index of the group C and group H(P>0.05). At the beginning of the experiment,there were no significant differences in the body weight of the three groups.3 Comparison of hepatohistological examination in three groupsResults showed: under light microscope,group H showed severe steatosis and steatosis severity was higher than group C and group N(P<0.01). The steatosis severity of group C was higher than group N.4 Comparison of serum biochemical in three groupsResults showed: the serum TG, ALT, AST, TC, LDL content in group H were all higher than that in group N(P<0.01). Compared with group H, the serum TG, ALT, AST content in group HE were lower than group H(P<0.01). But there were no significant differences in the serum TC and LDL of the group C and group H(P>0.05). There were no significant differences in the serum HDL of the three groups.5 Comparison of the FFA in the liver and serum in the three groupsResults showed: the FFA of liver and serum in group H was higer than group N and group C(P<0.01). Compared with group N, the serum FFA was no significant difference of the group C(P>0.05). Compared with group H, the serum and liver of FFA in group C were lower(P<0.01).6 The immunohistochemistry of perilipin1 proteinResults showed: perilipin1 protein was expressed more in the lipid droplets of larger diameter and single room and in multilocular and small diameter lipid droplets,perilipin1 protein was expressed less. Perilipin1 protein is not only expressed in the lipid droplets and cell membrane of fatty liver tissue,but also expressed a little in the normal liver cell.7 Comparison of the expression of perilipin1 proteinResults showed: The level of perilipin1 protein was increased in group H in comparison with group N and group C(P<0.01). Compared with the group H, the content of perilipin1 protein markedly decreased in group C(P<0.01). And in the group N,there was only a little of expression of perilipin1.Conclusions:1 Rats NAFLD model can be copied successful by eight week high-fat diet(standard diet supplemented with 10% lard oil, 5% egg white power, 2% cholesterol and 0.5% sodium cholate).2 Aerobic exercise(swimming training) can alleviate steatosis severity of liver tissue of rats in NAFLD.It indicate swimming training can prevent the NAFLD.3 The probable pathogenesy of the prevention effect of the swimming training on NAFLD are as follows: by decreasing serum TG, TC, FFA, ALT, AST and liver FFA to alleviate steatosis severity of liver tissue; by affecting the expression of perilipin1 protein to affect the lipid metabolism and lipid droplets metabolism and then to prevent the NAFLD.4 As an important protein affecting lipid droplets metabolism, Perilipin1 may provide a new prevention and treatment target for NAFLD.