Hyperglycemia and Hyperlipidemia Act Synergistically to Induce Renal Disease in LDL Receptor-Deficient BALB Mice

Diabetic nephropathy is the leading cause of end-stage renal disease in Western countries, but only a portion of diabetic patients develop diabetic nephropathy. Dyslipidemia represents an important aspect of the metabolic imbalance in diabetic patients. In this study, we addressed the impact of combined hyperlipidemia and hyperglycemia on renal pathology. Kidneys from wildtype (WT) or LDL receptor-deficient BALB/cBy mice (BALB. LDLR -/-) were examined at 22 weeks of age. Diabetes was induced by administration of streptozotocin and mice were randomly assigned to either standard chow or Western diet. Chow fed BALB. LDLR -/- mice did not demonstrate renal abnormalities, whereas BALB. LDLR -/- mice fed a Western diet showed occasional glomerular and tubulointerstitial foam cells. Diabetic WT mice had modestly increased glomerular cellularity and extracellular matrix. Hyperlipidemic and diabetic BALB. LDLR -/- mice exhibited an increase in glomerular cellularity and extracellular matrix, accumulation of glomerular and tubulointerstitial foam cells and mesangial lipid deposits. The tubular epithelium demonstrated pronounced lipid induced tubular degeneration with increased tubular epithelial cell turnover. Hyperlipidemia and hyperglycemia seem to act synergistically in inducing renal injury in the BALB. LDLR-/- mouse. This model of diabetic nephropathy is unique in its development of tubular lesions and may represent a good model for hyperlipidemia-exacerbated diabetic nephropathy. Copyright (C) 2004 S. Karger AG, Basel

Protease Nexin-1, tPA, and PAI-1 are Upregulated in Cryoglobulinemic Membranoproliferative Glomerulonephritis

Thymic stromal lymphopoietin (TSLP) transgenic mice develop cryoglobulin-associated membranoproliferative glomerulonephritis, characterized by renal monocyte/macrophage infiltration, marked expansion of extracellular matrix, and variable intraluminal and mesangial deposits of cryoglobulins. A microarray approach was used to study global gene expression in glomerular RNA obtained from these mice, as well as from combined TSLP transgenic and Fcγ receptor IIb null mice (TSLP/FcIIb−/−), which develop aggravated membranoproliferative glomerulonephritis. Protease nexin-1 (PN-1) and tissue plasminogen activator (tPA), two potential regulators of fibrosis that are involved in the fibrinolytic and coagulation pathways, were dramatically upregulated in TSLP mice compared with wild-type controls. In situ hybridization revealed minimal expression of PN-1 mRNA in the glomeruli of wild-type mice, increased expression in TSLP mice, and the greatest expression in the mesangial cells of TSLP/FcIIb−/− mice. Immunohistochemistry demonstrated greater expression of PN-1, tPA, and PAI-1 in the mesangial cells of TSLP mice compared with wild-type and the greatest in TSLP/FcIIb−/− mice. In cultured mesangial cells, incubation with cryoglobulins induced an upregulation of PN-1 mRNA; increased expression of PN-1, tPA, and PAI-1 proteins; and stimulated secretion of TGF-β1. It is concluded that PN-1, tPA, PAI-1, and TGF-β1 are likely important mediators of murine cryoglobulinemic glomerulonephritis and that the cryoglobulins may directly upregulate their expression

Exosomal gene expression of cystatin C mRNA.

<p>mRNA expression analysis in urinary exosomes isolated from the urine of rats during the course of PAN (day 0 before disease induction, day 5 after injection of puromycin and day 10 after disease induction). Cyclophilin A was used as reference gene. A: Cystatin C mRNA expression in gene array analysis from urinary exosomes relative to exosomes isolated from day 0, n = 3 animals. Bars represent mean ± SD. Significance level was assessed by Affymetrix Power Tools, using constitutive probe sets with detection above background p-values <0.01 and a raw expression threshold of 50. Threefold changes with a p-value of ≤0.01 were used as cut-off for up/down regulation. B: cystatin C mRNA from urinary exosomes relative to exosomes isolated from day 0 measured by RT-qPCR in separate animals, n = 3 animals. Bars represent mean ± SD. Statistical significant differences: *p<0.05.</p

Urinary cystatin C expression.

<p>Cystatin C excretion in the urine (mg/l) of rats with PAN on the different days after induction of PAN. Bars represent mean ± SD. Statistical significant differences: ** p<0.01.</p

Sequences of primers used for real-time reverse transcriptase PCR.

<p>Sequences of primers used for real-time reverse transcriptase PCR.</p

Kidney function during the course of PAN.

<p>A: Development of massive proteinuria 5 days after induction of PAN as indicated by an increase in protein/creatinine ratio. B: Decrease in urine output 5 days after the induction of PAN. C: Urea and creatinine on days 0, 5 and 10 after induction of PAN. Values represent mean ± SD. Statistical significant differences: *** p<0.001.</p