Caucasian patients with type 2 diabetes mellitus have elevated levels of monocyte chemoattractant protein-1 that are not influenced by the-2518 A→G promoter polymorphism

Aim: To investigate the association of serum levels and the -2518 A -> G promoter polymorphism of the gene for chemokine monocyte chemoattractant protein-1 (MCP-1), a major chemoattractant of monocytes and activated lymphocytes, with metabolic parameters as well as insulin, leptin and the cytokines tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in 534 Caucasian patients with type 2 diabetes mellitus. Methods: MCP-1 concentrations were measured by enzyme-linked immunosorbent assay. MCP-1 genotyping was performed by RFLP analysis in a subset of 426 patients. Results: Two hundred and thirty-one (54.2%) patients were homozygous for the wildtype allele (AA), 156 (36.6%) were heterozygous (AG) and 39 (9.2%) were homozygous for the mutated allele (GG). Allelic frequency was similar to non-diabetic populations (wildtype allele A: 0.73; mutated allele G: 0.27). MCP-1 mean concentrations and percentiles were substantially higher in non-diabetic populations but were not influenced by the genotype (AA: 662.0 +/- 323.0 pg/ml; AG: 730.6 +/- 491.4 pg/ml; GG: 641.2 +/- 323.8 pg/ml). MCP-1 serum levels and genotypes were only marginally related to hormones (insulin and leptin) and cytokines (TNF-alpha and IL-6). Conclusions: This is the first study providing MCP-1 levels, percentiles and genotype frequency in a large and representative cohort of patients with type 2 diabetes mellitus. Compared to the literature, MCP-1 levels were found to be substantially higher in patients with type 2 diabetes mellitus. In contrast, genotype frequencies were similar compared to those in non-diabetic patients and were not related to MCP-1 levels. The mechanisms behind these elevated MCP-1 serum levels in type 2 diabetes are not to be explained by simple associations with hormones, cytokines or genotypes.