Mechanism Research Of Simvastatin Improving Kidney Damages Caused By High-fat Diet

Objective: 1.To observe whether high fat diet(HFD)induced pathological changes such as endoplasmic reticulum stress(ERS)in rat kidney,and whether the effects of simvastatin(SIM)were related with improved ERS by altering the expression of adiponectin and its receptors in rat kidney.2.To study whether palmitic acid(PA)could induce ERS in human embryonic kidney epithelial cells(HEK293T)and whether SIM played a protective role by up-regulation of expression of adiponectin,adiponectin receptors and activation of AMPK and PPAR? pathway.Methods: 3.In vivo studies: According to the principle of random assignment,the rats were randomly divided into normal diet group(SCD),HFD group(HFD)and HFD plus simvastatin treatment group(HFD+ST),by high-fat diet for five months to establish hyperlipidemic model of SD rat,then by gavage of simvastatin for two months.The rat weights were weighed per week,serum biochemical indexes of TG,TC,HDL-C,LDL-C were measured;HE staining was used to observe the pathological changes of renal tissue,Masson staining was used to detect the changes of renal collagen fiber,oil red O staining of renal lipid deposition;Quantitative RT-PCR was used to analyze gene expression of CHOP,GRP78 and adiponectin expression in kidney.RT-PCR was used to analyze expression of inflammatory factors IL-6 and TNF? in kidney;protein expression of CHOP,GRP78 and IRE1-a(markers of ERS),Adipo R1,Adipo R2,PPAR?,AMPK and p-AMPK were analyzed by Western blot;immunohistochemistry was used to assay the expression and distribution of CHOP,GRP78,Adipo R1,Adipo R2.4.In vitro studies: The cultured HEK293 T were divided into normal control group(CON),palmitic acid(PA),palmitic acid + simvastatin group(PA+ST),normal control +AMPK agonist(CON+AICAR),palmitic acid +AMPK agonist group(PA+AICAR),normal control +PPAR? agonist(CON+FF),palmitic acid +PPAR? agonist(PA+FF).Methyl thiazolyl tetrazolium(MTT)was used to assay cell proliferation;Western blot was used to analyze the marker protein expression changes of CHOP,GRP78,IRE1?in ERS and the expression of AMPK,p-AMPK,PPAR?,Adipo R1,Adipo R2;HE staining was used to analyze morphological changes of cells;immunocytochemistry was used to analyze expression and distribution of CHOP,GRP78,IRE1?,Adipo R1 and Adipo R2.Results: 1.In vivo studies: Compared with the control group,body weight in HFD group were significantly higher than that of SCD group;serum TC,TG and LDL-C were significantly increased,HDL-C decreased significantly in HFD group;the HE and Masson staining showed that glomerular cell number was increased,mesangial cells and mesangial matrix was increased,and renal tubular epithelial cells appeared edema and vacuolar degeneration,glomerular volume was increased,a large number of blue collagen fibers were emerged in HFD group;oil red-O staining showed that renal lipid deposition was significantly increased in HFD group;the protein expression of CHOP,GRP78,IRE1? was significantly higher than that of SCD group,CHOP,GRP78 gene expression was significantly higher than that of SCD group,P-AMPK and PPAR? expression decreased significantly in the model group.The expression of Adipo R1 and Adipo R2 were decreased and positively correlated with gene expression of adiponectin in HFD group;SIM treatment significantlyreduced the body weight of the rats,reversed blood lipid levels,improved renal pathological changes,reduced gene expression of CHOP and GRP78,significantly decreased the protein expression of CHOP,GRP78,IRE1 and increased the protein expression of p-AMPK,PPAR?,Adipo R1 and Adipo R2.SIM treatment also decreased the expression of inflammatory factors IL-6 and TNF?.2.In vitro studies: Compared with the CON group,different concentration of PA decreased significantly the activity of HEK293 T,with the effect of 0.5 mmol/L PA for 24 h treatment was the most obvious;PA induced expression of CHOP,GRP78 IRE1,PPAR?,P-AMPK and reduced expression of adiponectin,Adipo R1 and Adipo R2 significantly;the AMPK agonist AICAR and PPAR? agonist FA pretreatment in PA group increased the expression of AMPK and PPAR? respectively compared with PA group.HE staining showed that HEK293 T cells shrinked by PA treatment;Expression of CHOP,GRP78,IRE1? were also increased by immunocytochemical assay,meanwhile the expression of Adipo R1 and Adipo R2 were decreased.SIM treatment decreased expression of CHOP,GRP78,IRE1? and thus relieved endoplasmic reticulum stress.SIM treatment also increased the expression of adiponectin,Adipo R1 and Adipo R2.Conclusion: 1.5 months of HFD diet successfully induced the model of hyperlipemia and endoplasmic reticulum stress in rat kidney.Simvastatin significantly alleviated the above symptoms,the mechanism may be related with activated AMPK and PPAR? pathways by upregulating the expression of adiponectin and its receptors R1 and R2,reducing the expression of inflammatory cytokines.2.Palmitic acid treatment could inhibit the proliferation of HEK293 T and induce endoplasmic reticulum stress.Simvastatin may play a protective role by inhibiting the endoplasmic reticulum stress through the activation of AMPK and PPAR? pathwayby increasing the expression of adiponectin receptor R1 and R2.