Myocardial sympathetic innervation in patients with impaired glucose tolerance: relationship to subclinical inflammation

Aim: This study was designed to assess cardiac adrenergic nerve activity, using iodine (I)-123-labeled metaiodobenzylguanidine (MIBG), in patients with impaired glucose tolerance (IGT) and to investigate its relation to circulating levels of proinflammatory cytokines. Methods: We studied 22 patients with IGT (aged 34-68 years) and 18 age-matched healthy controls, using I-123 MIBG cardiac imaging. The early (10 min) and late (4 h) heart to mediastinum MIBG uptake (H/M) ratio and washout were calculated. Levels of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-a), and its soluble receptor [soluble TNF receptor II (sTNFRII)] were measured by immunoassay of blood samples from patients and controls. Results: The early and late MIBG uptake was lower (both P<.001) and the WR was higher (P<.001) in patients than in controls. The analysis showed innervation defects in 20 of the 22 patients. Nearly half (45.4%) showed severe adrenergic innervation defects in both the inferior wall and the apex. Regarding cytokines, patients showed significantly elevated TNF-a (P=.005), sTNFRII (P<.001), and IL-6 (P<.001) levels compared to controls. IL-6 and sTNFRII were found to correlate with the WR (r=0.468, P=.028 and r=0.455, P=.034, respectively). Conclusion: Patients with IGT show reduced MIBG cardiac uptake with a segmental pattern. The reduced cardiac sympathetic innervation was related to the elevated proinflammatory cytokine levels and could be considered an index of early atherosclerotic process in these patients. (C) 2008 Elsevier Inc. All rights reserved.