Background: Monocyte chemoattractant protein-1 (MCP-1) is a specific chemokine to recruit and activate monocytes from the circulation to inflammatory site. In diabetic nephropathy, similar to other glomerulonephropathies, infiltration and activation of monocytes/macrophages in glomerulus have been implicated in the development of glomerular injury. The aim of the present study was to examine a possible relationship of MCP-1 with diabetic nephropathy and to investigate the role of glycated albumin (Gly-Alb) as well as high concentration of glucose (HG) on MCP-1 production by cultured human mesangial cells.
Methods: MCP-1 in serum or urine and urinary albumin (Alb) as well as several clinical parameters such as plasma glucose, serum Gly-Alb, and hemoglobin A1c (HbA1c) were measured after overnight fasting in 16 control subjects and 54 diabetic patients. The relationships between the levels of urinary Alb and urinary or serum MCP-1 and also between the values of respective clinical parameter and urinary MCP-1 levels were analyzed. Next, using cultured human mesangial cells, we investigated the role of Gly-Alb and/or HG on the gene and protein expression of MCP-1.
Results: Urinary levels (ng/g creatinine), but not serum levels, of MCP-1 increased in accordance with the extent of albuminuria. In all subjects, there were significant correlations between the urinary levels of Alb and MCP-1 (r = 0.746, P < 0.0001) and between the levels of serum Gly-Alb and urinary MCP-1 (r = 0.475, P < 0.0001). In cultured human mesangial cells, the gene and protein expression of MCP-1 was dose and time dependently up-regulated by Gly-Alb. HG slightly but significantly stimulated MCP-1 expression. The combination of Gly-Alb and HG showed the greatest stimulation in more than an additive manner on MCP-1 production.
Conclusions: This study suggests that facilitated MCP-1 production by mesangial cells in diabetic milieu contributes to the initiation and progression of diabetic nephropathy.