Uric acid correlates with the severity of histopathological parameters in IgA nephropathy

Immunoglobulin-A nephropathy (IgAN) is the most common chronic glomerulonephritis worldwide. Many clinical and histopathological risk factors for progression have been found previously. Recently, metabolic risk factors, such as hyperuricaemia and hypertriglyceridaemia, also have been associated with the progression of IgAN.

In the present study we correlated clinical and metabolic risk factors with histopathological parameters in 202 patients with IgAN. Morphological changes in glomerular, tubulointerstitial and vascular tissue were semiquantitatively graded into three classes. Mesangial proliferation activity and the amount of inflammatory cells were also evaluated by immunohistochemical staining of Ki-67 (MIB-1), CD45 (LCA) and CD68 stainings. Serum uric acid, triglycerides and cholesterol, urine protein excretion (UPE), blood pressure and body mass index (BMI) were measured. Smoking habits and occurrence of diabetes mellitus also were evaluated. The independent role of serum uric acid in the development of renal morphological changes was evaluated in multivariate analysis.

Serum uric acid and UPE level correlated with several histological parameters. Uric acid level showed the strongest correlation with tubulointerstitial changes and UPE with glomerulosclerosis. The level of serum triglycerides correlated with interstitial fibrosis and hyaline arteriolosclerosis. Blood pressure correlated with hyaline arteriolosclerosis, glomerulosclerosis and tubulointerstitial changes. BMI and diabetes mellitus correlated with both tubulointerstitial and vascular changes. We found no significant correlations between histopathological parameters and smoking habits or serum cholesterol level. Serum uric acid had independent associations with the presence of tubular atrophy and interstitial fibrosis and inflammation.

We conclude that many metabolic factors are univariately associated with renal morphological findings in IgAN. These same factors are central in the metabolic or insulin resistance syndrome and may have a pathogenetic role in the progression of IgAN. Serum uric acid may have an independent role in development of tubulointerstitial lesions as well as being associated with inflammation in renal tissue of patients with IgAN.