The Protective Effect Of Polydatin On High Fat Diets-induced Fatty Liver Injury In Gift Tilapia (Oreochromis Niloticus)

Fatty liver is a common injury in fish;it has many predisposing factors,such as nutritional imbalance,environmental factor stress,and abnormal physiological function,which can lead to excessive accumulation of liver fat,disorder of lipid metabolism,and liver lesions.High fat diet(HFD)is emerging as one of the most common causes,for the increasing incidence of fatty liver injury in most aquaculture.Thus HFD-induced fatty liver model was often used to study pathogenesis of fatty liver and screen liver protection drugs.In mammal,this model has been used to examine the protective effect of polydatin in mice,rats and many other experimental animals including humans but this has not been tried in the GIFT tilapia(Oreochromis niloticus)yet.Many Chinese herbal medicines(CHMs)have displayed beneficial liver protection effects which have been used as a folk medicine for several chronic liver injuries.They have been shown abilities in protecting the liver compared to conventional therapies,as effective anti-inflammatory and anti-oxidative agents.Polydatin(PD),one of the main compound derived from the root and rhizome of Polygonum cuspidatum(Chinese name:Hu Zhang),has previously been demonstrated to possess hepatoprotective effects,and treat several diseases,such as cardiovascular diseases,hepatic diseases and various cancers.In this study,we aimed to investigate the protective effects of PD on fatty liver injury(FLI)using a HFD-induced tilapia model.Establishment of liver injury model in GIFT tilapia:The fishes were randomly arranged in-to three groups as the liver injury model at the different level of 6%,11%and 21%fat diet.After 8 weeks feeding,the blood and liver samples were collected from these fish,and then the biochemical parameters were determined for evaluating the liver injury.The results clearly showed that the levels of serum triglyceride(TG),total cholesterol(TC),high-density lipoprotein cholesterol(HDL-c),low-density lipoprotein cholesterol(LDL-c),glutamic pyruvic transaminase(GPT),glutamic oxaloacetic transaminase(GOT)and malondialdehyde(MDA)were significantly increased(P<0.05)at fishes fed 21%of high fat diet,whereas the levels of liver superoxide dismutase(SOD)and glutathione(GSH)in fishes given at 21%fat diet were significantly decreased(P<0.05).Protective effect of polydatin on high fat diet induced fatty liver injury in GIFT tilapia:Based on the establishment of the liver injury,fishes were randomly divided into normal control(NC)group,HFD model group,and polydatin-treated group.The experimental fish were fed with feed mixed with polydatin(0.1,0.5,and lg/kg)for 8 weeks,and then collected the blood and liver to detect liver injury,antioxidative parameters and changes of genes expression.The results showed that GPT,GOT,TC,TG,HDL-c and LDL-c levels in the serum were reduced at normal control(NC)and plydatin supplemented groups,while the levels of GPT,TC,TG,HDL and LDL at high level of polydatin(1g/kg)and GOT,TP at low level of polydatin(0.1g/kg)groups were significantly lower than those in the HFD model group.Whereas the levels of SOD,catalase(CAT)and GSH in liver were significantly increased at NC&polydatin treated groups as compared to HFD model group,the MDA level at NC&polydatin supplemented groups were reduced when compared to HFD model.Level of total antioxidant capacities(T-AOC)in the liver was also found significantly increased at NC&polydatin treated at high levels(1 g/kg)groups.In this study polydatin also increased the gene expressions of peroxisome proliferator-activated receptor(PPAR-α)and aminocyclopropane-1(ACO-1)in the liver were significantly increased at the NC and polydatin supplemented with medium(0.5 g/kg)and high(1 g/kg)level groups as compared to HFD model group.The gene expression of carnitine palmitoyl transferase(CPT-1)was also found significantly higher at NC and high level of polydatin(1g/kg)treated groups when compared to HFD model group.In this study also,we found that the mRNA expression levels of proinflammatory mediator Interleukin 1 beta(IL-1β)was decreased significantly in the liver tissue of tilapia fed high fat diet with polydatin for 8 week and NC groups as compared with HFD model group.In current study result showed that,surprisingly at the NC and polydatin treated with low and medium groups the expression of ACC1 was significantly higher than that of HFD model group.The expression of SREBP-1c mRNA and FAS were also increased at NC and polydatin supplemented groups when compared to HFD model group,but there were no found significant change at any groups.The present results showed that excess fat deposition in the liver altered serum biochemical and antioxidant enzyme activities in the experimental tilapia.On the basis of these data and considerations,the tilapia fatty liver injury model was established successfully by means of feeding a high fat diet(21%fat)for 8 weeks.Polydatin has therapeutic effects on HFD-induced fatty liver injury in GIFT tilapia by lowering lipid levels,reducing oxidative damage and inflammation in the blood and liver.Therefore,polydatin has a marked effect on the improvement of blood and liver lipid levels in the tilapia.Polydatin also has favorable potency to regulate the gene PPAR-α,CPT-1,ACO-1 and IL-1β expression of hepatic fatty acid biosynthesis on fatty liver injury in GIFT tilapia.These finding provide evidence that polydatin might be an effective hepatoprotective agent and a promising herb candidate for the prevention of fatty liver injury in tilapia.