Discrepancy between intrarenal messenger RNA and protein expression of ACE and ACE2 in human diabetic nephropathy

BACKGROUND

The intrarenal angiotensin-converting enzyme (ACE) and type 2 ACE (ACE2) play important roles in the pathogenesis of diabetic nephropathy, but human data are limited. We studied glomerular and tubulointerstitial mRNA and the protein expression of ACE and ACE2 in patients with diabetic nephropathy.

METHODS

We studied renal biopsy specimens of 22 patients with diabetic nephropathy and 11 transplant donors as normal controls. Intrarenal mRNA expression of ACE and ACE2 was measured by laser microdissection and real-time quantitative polymerase chain reaction; expression at the protein level was determined by immunostaining.

RESULTS

Glomerular and tubulointerstitial mRNA expression levels of ACE and ACE2 were significantly higher in patients with diabetic nephropathy than in normal controls (p < 0.001 for all comparisons). Glomerular ACE and ACE2 protein levels of patients with diabetic nephropathy were significantly higher than those of kidney donors (4.90 +/- 2.55% vs. 2.64 +/- 0.98%, p = 0.022, and 7.40 +/- 3.36% vs. 4.37 +/- 2.36%, p = 0.017, respectively). The tubulointerstitial ACE at the protein level, however, was similar between diabetic patients and controls (8.76 +/- 4.18% vs. 10.44 +/- 6.61%, p = 0.453), and the tubulointerstitial ACE2 at the protein level was significantly lower in diabetic nephropathy (16.48 +/- 7.68% vs. 23.23 +/- 7.65%, p = 0.025).

CONCLUSION

The mRNA expression of ACE and ACE2 increased in both the glomerular and tubulointerstitial area of diabetic nephropathy. However, the tubulointerstitial ACE expression at the protein level remained unchanged, while that of ACE2 actually decreased. Our results suggest a posttranscriptional modulation of tubulointerstitial ACE and ACE2 expression. Experimental data of intrarenal mRNA expression of ACE and ACE2 should be interpreted with caution.

Messenger RNA expression of podocyte-associated molecules in urinary sediment of patients with lupus nephritis

OBJECTIVE

To examine urinary expression of podocyte-associated molecules in patients with lupus nephritis (LN).

METHODS

We studied 32 patients with active LN (Active group) and 17 patients with inactive lupus (Silent group). Messenger RNA expression of nephrin, podocin, and synaptopodin in urinary sediment was quantified by real-time polymerase chain reaction and compared to other clinical measures.

RESULTS

The urinary concentrations of nephrin, podocin, and synaptopodin were significantly higher in the Active than the Silent group (p < 0.05 for all comparisons). There was no relation between urinary gene expression and the histological class of LN, but urinary nephrin expression correlated with proteinuria (r = 0.480, p < 0.01) and the score of the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI; r = 0.578, p < 0.01). Urinary podocin expression also correlated with SLEDAI score (r = 0.389, p = 0.006). After initiation of immunosuppressive treatment, all patients were followed for an average of 13.7 +/- 2.4 months. The decline of the glomerular filtration rate (GFR) correlated with urinary expression of podocin (r = 0.406, p = 0.005) and synaptopodin (r = 0.337, p = 0.021). In a multiple linear regression model, urinary podocin expression and baseline GFR were independent predictors of GFR decline.

CONCLUSION

The concentration of podocyte-associated molecules in urinary sediment correlated with lupus activity and GFR decline. The clinical utility of quantifying urinary expression of podocyte-associated molecules for risk stratification of patients with LN deserves further study.

Messenger RNA expression of podocyte-associated molecules in the urinary sediment of patients with diabetic nephropathy

BACKGROUND

Podocyte loss plays an important role in the pathogenesis of diabetic nephropathy. We hypothesize that messenger RNA expression of podocyte-associated molecules in urinary sediment may provide important clinical information in patients with diabetic nephropathy.

METHOD

We studied 21 patients with biopsy-proven diabetic nephropathy and 9 healthy controls. The mRNA expression of nephrin, podocin, synaptopodin, Wilms' tumor-1 (WT-1) and alpha-actinin-4 in urinary sediment were measured by real-time quantitative polymerase chain reaction. The degree of histological damage was quantified by morphometric analysis. Patients were then followed for an average of 25.63 +/- 10.76 months. The rate of glomerular filtration rate (GFR) decline was calculated by the least-square regression.

RESULTS

There were significant differences in nephrin, podocin, synaptopodin, alpha-actinin-4 (p < 0.01 for all comparisons) and WT-1 (p = 0.028) expression between patients and normal controls. Urinary nephrin expression was significantly correlated with proteinuria (r = 0.502, p = 0.020); urinary synaptopodin was significantly correlated with proteinuria (r = 0.585, p = 0.005), serum creatinine (r = 0.516, p = 0.017) and estimated GFR (r = -0.560, p = 0.008), and urinary WT-1 expression was significantly correlated with the degree of tubulointerstitial fibrosis (r = 0.558, p = 0.009). There was no significant correlation between GFR decline and urinary expression of target genes.

CONCLUSION

Urinary mRNA expressions of nephrin, podocin, synaptopodin, WT-1 and alpha-actinin-4 are higher in patients with diabetic nephropathy than in normal controls. Urinary nephrin and synaptopodin expressions are correlated with baseline clinical parameters such as proteinuria or renal function, while WT-1 expression is related to the degree of histological damage. Our results suggest that urinary mRNA expression of podocyte-associated molecules may be used for risk stratification of diabetic nephropathy.