Plasma total homocysteine concentration in nephrotic patients with idiopathic membranous nephropathy.

BACKGROUND: The atherothrombotic risk pattern of the nephrotic syndrome resembles that of hyperhomocysteinemia. However, the effect of nephrotic range proteinuria on homocysteine metabolism has never been studied. METHODS: The study included 11 male nephrotic patients with idiopathic membranous nephropathy who underwent a treatment trial with adrenocorticotrophic hormone and 11 male non-nephrotic, renal function-matched control subjects. The nephrotic patients were studied before and after the treatment, which induced a marked reduction in urinary protein excretion and a moderate improvement in renal function in all cases. RESULTS: Plasma total homocysteine (tHcy) concentration did not change significantly during treatment, whereas the nephrotic patients had significantly lower tHcy than the non-nephrotic patients (14.2 +/- 3.4 micromol/l vs 19.0 +/- 5.4 micromol/l). tHcy correlated significantly with serum concentrations of creatinine (r = 0.53, P < 0.05) and albumin (r = 0.43, P < 0.05), glomerular filtration rates (GFRs) (iohexol clearances) (r = -0.42, P < 0.05) and urinary albumin excretion (r = -0.47, P < 0.05). CONCLUSION: The expected tHcy-lowering effect of improved renal function may have masked a tHcy-elevating effect due to reduced proteinuria leading to no net change in tHcy during treatment. The notion of an increase in tHcy associated with remission of the nephrotic syndrome is in accordance with the significantly lower tHcy in the nephrotic renal patients compared with the non-nephrotic renal function-matched patients, and the relationships between tHcy and serum albumin concentrations as well as urinary albumin excretion. Thus, the results of this small study suggest that nephrotic range proteinuria directs homocysteine metabolism towards a decrease in tHcy. However, the findings need to be confirmed in larger patient populations and in different varieties of the nephrotic syndrome.