Abnormal retinal vascular reactivity in individuals with impaired glucose tolerance: a preliminary study.

Purpose: To investigate the relationship between vascular function parameters measured at the retinal and systemic level and known markers for cardiovascular risk in patients with impaired glucose tolerance (IGT).

Methods: Sixty age- and sex-matched white European adults (30 with IGT and 30 with normal glucose tolerance [NGT]) were recruited for the study. Fasting plasma glucose, lipids, and 24-hour blood pressure (BP) were measured in all subjects. Systemic vascular and endothelial function was assessed by using carotid-artery intimal media thickness (cIMT) and flow-mediated dilation (FMD). Retinal vascular reactivity was assessed by the dynamic retinal vessel analyzer. Additionally, blood glutathione (reduced glutathione [GSH], glutathione disulfide [GSSG], and total glutathione [tGSH]) and plasma von Willebrand (vWF) factor levels were also measured.

Results: Individuals with IGT demonstrated higher BP values (P < 0.001), fasting triglyceride (TG) levels and TG:high-density lipoprotein (HDL) ratios (P < 0.001) than NGT subjects. Furthermore, total:HDL-cholesterol (HDL-C) ratios and Framingham scores were raised (P = 0.010 and P < 0.001, respectively). Blood glutathione levels (GSH, GSSG, and tGSH) were lower (P < 0.001, P = 0.039, and P < 0.001, respectively) while plasma vWF was increased (P = 0.014) in IGT subjects compared to controls. IGT individuals also demonstrated higher IMT in right and left carotid arteries (P = 0.017 and P = 0.005, respectively) alongside larger brachial artery diameter (P = 0.015) and lower FMD percentage (P = 0.026) and glyceryl trinitrate-induced dilation (P = 0.012) than healthy controls. At the retinal arterial level, the IGT subjects showed higher baseline diameter fluctuations (BDFs) (P = 0.026), longer reaction time (RT) (P = 0.032), and reduced baseline-corrected flicker response (bFR) (P = 0.045). In IGT subjects, retinal BDF correlated with total:HDL (P = 0.003) and HDL-C (P = 0.004). Arterial RT also correlated with FMD (P = 0.017) in IGT but not NGT subjects.

Conclusions: In IGT individuals there is a relationship between macro- and microvascular function, as well as a direct correlation between the observed retinal microcirculatory changes and established plasma markers for cardiovascular diseases. Multifactorial preventive interventions to decrease vascular risk in these individuals should be considered.