The CCR2 promoter polymorphism T-960A, but not the serum MCP-1 level, is associated with endothelial function in prediabetic individuals

Abstract

Monocyte-chemoattractant-protein (MCP)-1 and its receptor CCR2 have been shown to play a pivotal role in vascular inflammation and atherosclerotic plaque formation. However, it is currently unclear whether MCP-1/CCR2 triggered inflammation affects nitric oxide (NO)-bioavailability, hence influencing vascular function, a sign of early atherosclerosis. Therefore, we sought to investigate the association between serum levels of MCP-1 and NO-bioavailability, expressed as flow mediated dilation (FMD) in vivo, and the impact of CCR2 gene variations on FMD. We studied a German population of 242 prediabetic individuals (144 women, 98 men; mean age 45 ± 0.8 years) via FMD by high-resolution ultrasound (13 MHz). In order to replicate our findings, a second, independent population ( n = 115; 44 women, 77 men; mean age 48 ± 1.0 years) (total = 357 individuals) from Italy was studied. Vascular function in the Italian population was studied via intra-arterial application of acetylcholine. MCP-1 serum-levels were assessed by ELISA and CCR2 polymorphisms were determined by sequencing. MCP-1 serum levels showed no association with FMD ( p = 0.90), whereas the CCR2 promoter polymorphism was associated with elevated FMD (T/T: 5.6 ± 0.3%; T/A: 6.7 ± 0.4%; A/A: 8.3 ± 0.8%; p = 0.01) after adjusting for possible confounders. These results were confirmed in the independent Italian population (A/A: 97.1 ± 20.3 vs. T/T: 60.5 ± 5.6% forearm blood-flow increase; p < 0.05). When testing for the functional relevance of the T-960A (rs3918359) polymorphism, we found that the A/A-genotype was associated with moderately increased protein binding in EMSA, increased promoter activity in luciferase assays and reduced transendothelial monocyte migration. In conclusion, MCP-1 serum levels do not reflect endothelial function in vivo in prediabetic individuals. However, the functionally relevant CCR2 promoter polymorphism T-960A (rs3918359) is associated with elevated vascular function. This might be due to reduced subendothelial inflammation, mediated by reduced transendothelial monocyte-migration ability.