Background/Aims: We previously reported that increase in plasma homocysteine (Hcys) levels by a 6-week methionine treatment produced remarkable glomerular injury. However, the mechanism by which hyperhomocysteinemia (hHcys) produces glomerular injury remains unknown. The present study was to observe when glomerular injury happens during hHcys and to explore the possible role of podocyte injury in the progression of glomerulosclerosis associated with hHcys. Methods: Uninephrectomized Sprague-Dawley rats treated with methionine were used to examine the time course of glomerular injury induced by hHcys. Results: Creatinine clearance was not different until rats were treated with methionine for 6 weeks, although plasma Hcys levels significantly increased at the 1st week of methionine treatment. However, urinary albumin excretion increased at the 2nd week of methionine treatment. Morphological examinations showed that mesangial expansion occurred at the 2nd week and podocyte effacement was also observed as processed glomerular damage during hHcys. Immunofluorescence analyses demonstrated that podocin and nephrin expressions were reduced, while α-actinin-4 increased during hHcys. Conclusions: Increased plasma Hcys level is an important pathogenic factor resulting in glomerular injury even in the very early time of hHcys. These pathogenic effects of Hcys are associated with podocyte injury and changed expression and distribution of podocyte-associated proteins.

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