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Renal accumulation of biglycan and lipid retention accelerates diabetic nephropathy.

ABSTRACT: Hyperlipidemia worsens diabetic nephropathy, although the mechanism by which renal lipids accumulate is unknown. We previously demonstrated that renal proteoglycans have high low-density lipoprotein (LDL) binding affinity, suggesting that proteoglycan-mediated LDL retention may contribute to renal lipid accumulation. The aim of this study was to determine the relative effect of diabetes and hyperlipidemia on renal proteoglycan content. Diabetic and non-diabetic LDL receptor-deficient mice were fed diets containing 0% or 0.12% cholesterol for 26 weeks, and then kidneys were analyzed for renal lipid and proteoglycan content. Diabetic mice on the high-cholesterol diet had accelerated development of diabetic nephropathy with elevations in urine albumin excretion, glomerular and renal hypertrophy, and mesangial matrix expansion. Renal lipid accumulation was significantly increased by consumption of the 0.12% cholesterol diet, diabetes, and especially by both. The renal proteoglycans biglycan and decorin were detectable in glomeruli, with a significant increase in renal biglycan content in diabetic mice on the high-cholesterol diet. Renal biglycan and renal apolipoprotein B were colocalized, and regression analyses showed a significant relation between renal biglycan and renal apolipoprotein B content. The increased renal biglycan content in diabetic nephropathy probably contributes to renal lipid accumulation and the development of diabetic nephropathy.

SUBMITTER: Thompson J

PROVIDER: S-EPMC3157166 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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Renal accumulation of biglycan and lipid retention accelerates diabetic nephropathy.

Thompson Joel J Wilson Patricia P Brandewie Katie K Taneja Deepa D Schaefer Liliana L Mitchell Bonnie B Tannock Lisa R LR

The American journal of pathology 20110630 3

Hyperlipidemia worsens diabetic nephropathy, although the mechanism by which renal lipids accumulate is unknown. We previously demonstrated that renal proteoglycans have high low-density lipoprotein (LDL) binding affinity, suggesting that proteoglycan-mediated LDL retention may contribute to renal lipid accumulation. The aim of this study was to determine the relative effect of diabetes and hyperlipidemia on renal proteoglycan content. Diabetic and non-diabetic LDL receptor-deficient mice were f ...[more]

PMID: 21723246

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Project description:Background: Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease worldwide with limited treatment options. The intricate pathogenesis of dysregulated lipid metabolism leading to the development of DKD remains obscure. Lipophagy, which refers to the autophagic degradation of intracellular lipid droplets, has been found to be impaired in DKD, resulting in renal tubule dysfunction and ectopic lipid deposition (ELD). The lipotoxity in renal tubules is closely related to the pathogenesis of DKD. Therefore, it is crucial to develop effective and safe agents that can restore autophagic flux and lipophagy in renal tubules for potential preventive interventions. Purpose: This study seeks to investigate the preventive effect of sodium butyrate (NaB) on ELD in the progression of DKD and elucidate the underlying mechanisms involved.Methods: The beneficial effects of NaB were investigated in glucolipotoxicity (GLT)-stimulated HK-2 cells and the streptozotocin (STZ) injection combined with a high-fat diet induced DKD model mice. Additionally, we managed to silence transcription factor EB (TFEB) in HK-2 cells and establish the renal specific silence model by retrograde ureteral infusion of AAV9-shTFEB in mice. We investigated the expression profile of RNAs in HK-2 cells through. The mechanism of NaB is demonstrated by RNA sequencing (RNA-seq), pulldown MS assay, SPR experiments etc.Results: Our findings revealed that serum butyrate level is reduced in DKD patients and is statistically correlated with urinary protein excretion and eGFR. Sodium butyrate (NaB) dose-dependently improved lipid deposition in HK-2 cells and renal tubular epithelial cells of DKD model mice. This effect may be attributed to the promotion of TFEB dephosphorylation, as NaB can directly interact with PPP2R1A to activate PP2A phosphorylation activity. Therefore, NaB may play a role in improving renal lipid deposition in DKD through the PP2A-TFEB pathway. Conclusion: NaB acts as a PP2A-TFEB axis activator that restores lipophagy to ameliorate ELD and renal dysfunction in DKD.

Project description:Background/aims:Liver lipid accumulation induced by high-fat diet (HFD) is an early onset process of non-alcoholic fatty liver diseases (NAFLD). Protein kinase A (PKA) is known to be involved in hepatic lipid metabolism. However, the role of PKA in NAFLD has not been well tested in vivo due to the lack of optimal PKA deficient mouse model. Methods:A novel PKA-specific inhibitor gene was conditionally overexpressed in mouse (PKAi mouse) liver using LoxP/Cre system. PKA activity in the liver extract was measured with a commercial assay kit. The PKAi and control mice of 8-week age, were subjected to HFD or chow diet (CD) for 2 months. Body weight, liver index, and triglyceride in the liver were measured. RNA sequencing was performed for the liver tissues and analyzed with Gene Ontology (GO) and pathway enrichment. Results:PKAi-GFP protein was overexpressed in the liver and the PKA activation was significantly inhibited in the liver of PKAi mouse. When fed with CD, RNA sequencing revealed 56 up-regulated and 51 down-regulated genes in PKAi mice compared with control mice, which were mainly involved in lipid metabolism though no significant differences in the body weight, liver index, triglyceride accumulation were observed between PKAi and control mice. However, when fed with HFD for 2 months, the liver was enlarged more, and the accumulation of triglyceride in the liver was more severe in PKAi mice. When comparing the transcriptomes of CD-fed and HFD-fed control mice, GO enrichment showed that the genes down-regulated by HFD were mainly enriched in immune-related GO terms, and up-regulated genes were enriched in metabolism. When comparing the transcriptomes of CD-fed and HFD-fed PKAi mice, GO analysis showed that the down-regulated genes were enriched in metabolism, while the up-regulated genes were clustered in ER stress-related pathways. When comparing HFD-fed PKAi and HFD-fed control mice, the genes with lower expression level in PKAi mice were enriched in the lipoprotein synthesis, which might explain that more TG is accumulated in PKAi liver after HFD feeding. Conclusions:Reduced PKA activity could be a factor promoting the TG accumulation in the liver and the development of NAFLD.

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Renal accumulation of biglycan and lipid retention accelerates diabetic nephropathy.

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Renal accumulation of biglycan and lipid retention accelerates diabetic nephropathy.

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