The Function Of Cideb In Renal Tubular Lipoprotein Metabolism

Cell death-inducing DFF45-like effector b(Cideb) is found in the late20thcentury and caninduce apoptosis. However, recent studies have also addressed the role of CIDE familymember in lipid metabolism. Apolipoprotein B(apoB) is known to have a particularlycritical role in the assembly of the triglycerde-rich chylomicron (CM) and VLDL. Cideb islocalized to the lipid droplet(LD) and endoplasmic reticulum(ER) and facilitates very lowdensity lipoprotein(VLDL) lipidation and maturation, possibly through its interaction withapolipoprotein B (apoB). Mice with Cideb deficiency also exhibited increase eneryexpenditure and improved insulin sensitivity and were resistant to high-fat diet(HFD)induced obesity and diabetes. Now, the main studies reported Cideb was expressed at highlevels in the kidney, but little information is available regarding the physiological role ofCideb in the kidney. From those studies, involved in the metabolism of lipid storage droplets. We hypothesized that Cideb may also be involved in the renal tubularreabsorption of lipid droplets, while the exact function and the possible molecularmechanisms were called for more and deep study.The kidney is usually regarded as an important organ in lipid metabolism.Hyperlipidaemia have been common found in primary and secondary glomerular disease,such as nephrotic syndrome(NS), diabetic nephropathy, dialysis patient, after kidneytransplantation, especially those who are treated with nephrotic syndrome. Many studieshave shown that glomerular filtration increased in nephrotic syndrome, nearly two-thirdsof lipid was reabsorbed in the renal proximal tubule, thereby increasing the renal tubularreabsorption of burden. Renal tubular reabsorption of urine lipids, and these lipids in renaltubules in the form of lipoproteins secreted into the blood. Therefore, NS has become animportant model for the study of renal tubule fatty metabolism. In this study, we used theCideb knockout mice to determine the effect of Cideb on kidney fat content. We detectedthe expression of Cideb and apoB in human membranous nephropathy(MN) of renalspecimens and mice. Furthermore, the role and possible mechanism of Cideb in kidneywere investigated by Cideb overexpression and Cideb silencing. This research is not onlyhelps to elucidate the Cideb specific function in the kidney, but also has an importantsignificance for understanding of the process of renal lipid metabolism.[Objectives]1to investigate the relationship between renal tubule and lipoprotein;2to analysis Cidebexpression on the membranous nephropathy of renal biopsy specimens and mouse models,to make sure the relationship between Cideb and hyperlipidemia;3using transwellsimulation of renal tubular epithelial cell secrete lipoprotein, to identify the possiblefunction of Cideb in renal tubular epithelial, to study the function of Cideb on the renaltubular epithelial cell lipoprotein metabolism.[methods]1.using transmission electron micrograph, we detected the localization of lipoprotein; theexpression of apoB and Cideb in human renal tubuletissues was detected by immunohistochemical staining (IHC).2. in order to study the function of Cideb, lipid droplet changes in Cideb knockoutmicerenal were observed.3. animals in the experimental group received cationic bovine serum albumin (C-BSA) viatail vein. the establishment of models were verified by serum, urine tests and pathologicalexaminations(PASM staining, IgG immunofluorescence and transmission electronmicroscopy).4. to evaluate the expression of Cideb protein in membranous nephropathy patients, wecollected58renal biopsy specimens. To investigate the expression of apoB inmembranous nephropathy patients, we evaluated30MN patient plasma.5. to detect the effects of palmitic acid(PA) under different concentration on HK-2cell bywestern blot, bodipy493/503and TG content methods.6.using ad-Cideb or ad-si-Cideb infected HK-2cell line, the biological functions of Cidebon renal tubular epithelial lipid changes were observed by western blot, bodipy493/503and TG content methods.7.after human renal proximal tubular epithelial cells HK-2were cultured on the transwell,using3H labeled fatty acids, the lipoprotein level was detected by TG content. The cellmonolayer compactness and integrity were measured by the cell membrane resistance andfluorescein sodium methods.[results]1the expression of Cideb in renal tubular epithelial was detected by IHC, and Cidebdeficient mice exhibited the accumulation of LDs.First of all, we observed lipoprotein-like particles in renal tubular epithelial cells byelectron microscopy. By IHC, Cideb was abundantly expression in renal tubular epithelialand mainly localized in the proximal tubules, was negative expression in the glomerular.Oil Red O analysis demonstrated that the kidney of Cideb deficiency mice led to theincreased accumulation of lipid obviously. TG quantitative analysis further confirmed thatCideb-/-mice have increased lipid accumulation. These results suggest that Cideb isinvolved in the process of lipid metabolism in kidney. 2Cideb expression in the mouse model and membrane nephropathy patientsThe biopsy specimens from membrane nephropathy and mouse model, we foundexpression of Cideb and apoB were all increased. Many studies have shown thatglomerular filtration increased in nephrotic syndrome, nearly two-thirds of lipid wasreabsorbed in the renal proximal tubule, thereby increasing the renal tubular reabsorptionof burden. Renal tubular reabsorption of urine lipids, and these lipids in renal tubules inthe form of lipoproteins secreted into the blood. Therefore, NS has become an importantmodel for the study of renal tubulefatty metabolism. Animals in the experimental groupwhose received C-BSA via tail vein developed hypoalbuminemia, hypercholesterolemiaand severe proteinuria. The expression of Cideb and apoB both were increased in mousemodel and membrane nephropathy.3Cideb can inhibit lipid accumulation in renal tubular epithelial cells, and promotethe secretion of TG.After different concentration of PA induce lipid accumulation in the renal tubularepithelial cells, the expression of Cideb was significantly increased. Overexpression ofCideb in HK-2cells, which can reduce the synthesis of intracellular triglyceride, inhibitTG accumulation. We found that the depletion of Cideb resulted in the formation ofnumber small lipid droplets and the content of TG was significantly higher. All the datademonstrated that Cideb could play an important role in lipid droplet morphology andnumbers. Using transwell board simulation of the renal tubular secretion of lipoproteins.Overexpression of Cideb could promote the renal tubular secretion of lipoproteins.moreover, knock-down of Cideb significantly decreased secretion of lipoproteins in therenal tubular epithelial cells.[Conclusion]:This study first identified that Cideb mainly expressed in renal tubular epithelial cells, andthe highest expression in the epithelial cells of the proximal tubule, and the apoBexpression levels had consistent with renal tubular reabsorption, however, Oil Red Oanalysis demonstrated that the kidney of Cideb deficiency mice led to the increasedaccumulation of lipid obviously. TG quantitative analysis further confirmed that Cideb-/- mice have increased lipid accumulation. The biopsy specimens from membranenephropathy and mouse model, we found expression of Cideb and apoB were all increased.Furthermore, the role and possible mechanism of Cideb in kidney were investigated byCideb overexpression and Cideb silencing. Overexpression of Cideb in HK-2cells, whichcan reduce the synthesis of intracellular triglyceride, inhibit TG accumulation. We foundthat the depletion of Cideb resulted in the formation of number small lipid droplets and thecontent of TG was significantly higher.In summary, we have observed that Cideb was highly expressed in the renal proximaltubule. Cideb was associated with renal tubular reabsorption function. Cideb is localizedto the lipid droplet(LD) and endoplasmic reticulum(ER). In vitro studies showed thatCideb could promote the secretion of triglyceride in renal tubular epithelial cells, andinhibit the lipid accumulation. we speculated that the function of Cideb in kidney couldplay a similar role in liver,which was involved in lipoprotein formation and secretionprocess, but the specific mechanism needed further study.