| Background:With the improving people’s living standards, the incidence of lipidmetabolism also increased gradually. Lipid metabolism disorders induce avariety of cardiovascular and cerebrovascular disease, and high-fat diet canaggravate kidney damage in patients with kidney disease or lead to healthkidney damage. Animal experiments demonstrated that the renal damagecaused by primary disorders of lipid metabolism may result in clinicalproteinuria and multi-focal segmental glomerular sclerosis.Podocyte is one type of the intrinsic glomerular cells. Relying on itsfeet sudden and hiatus between films, podocytes constitute the outermostlayer of the glomerular filtration barrier, which is the last barrier to preventfrom the formation of proteinuria and blood plasma protein loss. Previousstudies found that the early period of podocyte injury is characterized bythe foot process fusion, the disappearance of the main morphologicaldamage, and the glomerular basement membrane adhesion dysfunction, and may be associated with abnormal expression of the slit diaphragm,which may result in proteinuria as the renal glomerular filtration membraneintegrity is destructed. In late period, the loss, apoptosis, and reduction ofnumber density of podocyte appeared. The activated podocytes secretinflammatory mediators and extracellular matrix, and participateglomerulosclerosis together with the mesangial cells. Some recent studiesdemonstrated that the early lipid metabolism disorders mostly injurypodocyte, but not mesangial cell. This foot process fusion of podocyte andits corresponding dysfunction may be the earliest part of lipid metabolismdisorder.However, the pathological mechanisms including damage andactivation of mesangial cells occur in the late period of lipid metabolismdisorders and kidney damage.Pdlim2is a new type of regulatory protein for actin expression in theglomerular podocyte foot processes, and mainly expresses in the secondarypodocyte foot. Pdlim2protein is one member of superfamily of the actininassociated protein LIM protein (ALP), and exists in many cell nuclei,containing a PDZ domain at the N-terminus and a LIM domain at theC-terminus. LIM domain is the domain of protein-protein interactions andplays an important role in the signal transduction and regulation of celldifferentiation in the actin cytoskeleton. Recent studies have found that theexpress Pdlim2decreased in the podocytes of nephrotic syndrome patients,such as minimal change nephrotic syndrome (MCNS) and membranous nephropathy (MN). Significant retraction and disappear of podocyte footprocesses, and increase in urinary protein also appeared. However, fewstudies focused in Pdlim2expression in the glomerular podocytes ofhyperlipidemic rat.Objective: This study aimed to establish the rat model ofhyperlipidemia, to observe the24h urine protein, serum cholesterol (TC),low density lipoprotein cholesterol (LDL-C) levels and other biochemicalparameters of the simvastatin treated rats, to observe the podocyte damageby electron microscopy, to detect changes and mechanism of proteindistribution and expression of rat kidney Pdlim2by usingimmunofluorescence staining and immunoblotting (Western blot).Thisstudy will provide a theoretical basis for understanding and intervention ofearly kidney hyperlipidemia impact.Methods:30individuals of SD rats were divided randomly into3groups (n=10in each group). The control group was fed with normal diet.The high fat group was fed with high fat diet. The simvastatin group wasfed with high fat diet plus with simvastatin gavage (10mg/kg.d).5ratswere sampled randomly from each group at week4and10and the urinaryprotein excretion, the concentration of serum cholesterol, and theconcentration of low density lipoprotein were determined. The glomerularpodocyte damage in rats was detected by electron microscope, theexpression of Pdlim2protein was determined by immunohistochemistry and Western blotting.Results:(1) Rats’ lipids, urine protein changes: The level of serumTC and LDL-C increased significantly in HG group and SG group at week4which compared to the NG group, and the level in SG group wassignificantly decreased in HG group(P＜0.05). At10weeks,the urineprotein levels in HG and SG group than at4weeks was significantly higher(P <0.05); SG and HG group compared with NG group were significantlyhigher, while the rat protein levels in urine SG group was significantlylower than the same period in HG group, the difference was statisticallysignificant by pairwise comparison (P <0.05).(2) Rats for kidney damagein podocyte: TEM observation showed that glomerular podocyte footprocess fusion in a mild part in HG group at4weeks, podocyte footprocesses are widely seen fusion and bending and thickening and podocyteedema at10weeks. The damage of podocyte in SG Group are lighter thanin the HG group.(3) The expression of immunofluorescent staining of ratglomerular Pdlim2: There Pdlim2protein express in glomeruli in NG ratsat4weeks and10weeks,but the Pdlim2protein expression decrease in HGrats at4weeks. The Pdlim2protein expression decrease in HG rats at10weeks obviously, then the simvastatin group were higher than the NGgroup and were lower than the NG group at10weeks.(4) Western blotting:The expression of Pdlim2protein of HG group compared with the sameperiod in NG group rats decreased by27%at4weeks, the difference wassignificant sex (P <0.05); SG group and the NG group difference was notstatistically significant. The expression of Pdlim2protein of HG comparedwith the same period in NG group rats decreased by49at10weeks,SGgroup than in the HG group rats were higher by24%;every two groups,the difference was significant (P <0.05). Conclusions:(1) Hyperlipidemia may lead to a reduction in glomerular Pdlim2regulate this cytoskeletal protein, leading to podocyte foot process fusion,which may be an important mechanism of lipid metabolism kidneydamage;(2) Simvastatin may be through the inhibition of the expression ofglomerular Pdlim2hyperlipidemia reduction, reducing fat caused bypodocyte foot process fusion. |
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