Retinal vessel abnormalities are associated with elevated fasting insulin levels and cerebral atrophy in nondiabetic individuals

Abstract

Objective: To determine the impact of insulin resistance short of diabetes on the arteriolar-to-venular ratio (AVR) and whether AVR is related to cerebral atrophy.

Design: Cross-sectional study.

Participants: Forty-six nondiabetic subjects with normal glucose tolerance and varying degrees of insulin resistance ranging in age from 43 to 77 years.

Methods: Insulin resistance was assessed by fasting insulin and the homeostasis model assessment. Arteriolar-to-venular ratio was determined using digital retinal photography with a nonmydriatic camera, and retinal data were analyzed using a reliable semiautomated method. Cerebral atrophy was derived by means of manual tracing and thresholding procedures on structural magnetic resonance images.

Main outcome measures: Arteriolar-to-venular ratio and cerebral atrophy.

Results: Hyperinsulinemia negatively impacted AVR. Furthermore, AVR was associated with cerebral atrophy. Both of these findings were independent of the effects of age and hypertension.

Conclusions: These novel findings indicate that insulin resistance short of diabetes and independent of age and hypertension has a negative impact on retinal vessel health. Moreover, impaired retinal vessel health related to brain atrophy also was independent of hypertension and white matter hyperintensities. Given the connections between retinal and cerebral vasculature, this may offer a partial explanation for the presence of cognitive and brain abnormalities among individuals with insulin resistance.

Financial disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Figure 1

Cropped and red-free retinal photograph showing the outline of the optic disc (blue) and circles at 0.5 and 1.0 disc diameters (yellow and green respectively) out from the disc margin, thus creating zone A and zone B. The red arrow points from the 5 equidistant lines sampling the artery segment to the corresponding profile generated by one of those lines.

Figure 2

Plot of correspondence between two independent raters (AT and SR) in the measurement of arteriolar-to-venular-ratio (AVR) in 27 subjects. The inter-rater reliability was excellent with an intra-class correlations coefficient (ICC) of 0.89.