Urinary mitochondrial DNA level is an indicator of intra-renal mitochondrial depletion and renal scarring in diabetic nephropathy

Background

Mitochondrial dysfunction plays an important role in the pathogenesis and progression of diabetic nephropathy (DN). We study the relation between urinary and intra-renal mitochondrial deoxyribonucleic acid (mtDNA) levels and renal dysfunction in DN.

Methods

We recruited 92 patients with biopsy-proven DN. Urinary sediment, urinary supernatant and intra-renal mtDNA levels were measured and compared with baseline renal biopsy, kidney scarring and renal function decline in the subsequent 24 months.

Results

mtDNA could be detected in all urine supernatant, urine sediment and renal biopsy specimens. There was a modest but statistically significant inverse correlation between urinary supernatant and intra-renal mtDNA levels (r = -0.453, P = 0.012). Urinary supernatant mtDNA level had modest but statistically significant correlations, inversely with estimated glomerular filtration rate (r = -0.214, P = 0.04), and positively with interstitial fibrosis (r = 0.300, P = 0.005). Intra-renal mtDNA had significant inverse correlation with interstitial fibrosis (r = -0.537, P = 0.003). However, there was no significant relation between renal function decline and urinary supernatant, urinary sediment or intra-renal mtDNA levels.

Conclusions

mtDNA is readily detectable in urinary supernatant and kidney tissue, and their levels correlate with renal function and scarring in DN. Further studies are needed to determine the accuracy of urinary supernatant mtDNA level as a prognostic indicator of DN, as well as its role in other kidney diseases.

Urinary mitochondrial DNA level in non-diabetic chronic kidney diseases

BACKGROUND

Mitochondrial dysfunction plays an important role in the pathogenesis and progression of chronic kidney disease (CKD). We study the relation between urinary mitochondrial DNA (mtDNA) levels and renal dysfunction in non-diabetic CKD.

METHODS

We recruited 32 CKD patients (20 had hypertensive nephrosclerosis, 12 had IgA nephropathy). Urinary supernatant mtDNA level was measured and compared to baseline clinical and pathological parameters. The patients were followed 57.8 ± 30.5 months for renal function decline.

RESULTS

The average urinary supernatant mtDNA level was 222.0 ± 210.3 copy/μL. There was a modest but significant correlation between urinary mtDNA level and proteinuria (Spearman's r = 0.387, p = 0.035), but not any other baseline clinical or pathological parameter. Urinary mtDNA level had a significant inverse correlation with the slope of GFR decline (r = -0.402, p = 0.023). Urinary mtDNA level is a predictor of renal survival even after adjusting for baseline proteinuria with multivariate Cox analysis. In this model, every increase in urinary mtDNA by 100 copy/μL confers a 25.0% increase in risk of doubling of serum creatinine or need of dialysis (95%CI, 0.7% to 55.1%).

CONCLUSION

Mitochondrial DNA is readily detectable in the urinary supernatant of non-diabetic CKD, and its level correlates with the rate of renal function decline and predicts the risk of doubling of serum creatinine or need of dialysis. Further studies are needed to determine the value of urinary supernatant mtDNA level as a prognostic indicator of non-diabetic CKD.