Preclinical and clinical evaluation of a new method to assess cardiac insulin resistance using nuclear imaging

Myocardial insulin resistance (IR) could be a predictive factor of cardiovascular events. This study aimed to introduce a new method using ¹²³I-6-deoxy-6-iodo-D-glucose (6DIG), a pure tracer of glucose transport, for the assessment of IR using cardiac dynamic nuclear imaging.

The protocol evaluated first in rat-models consisted in two 6DIG injections and one of insulin associated with planar imaging and blood sampling. Compartmental modeling was used to analyze 6DIG kinetics in basal and insulin conditions and to obtain an index of IR. As a part of a translational approach, a clinical study was then performed in 5 healthy and 6 diabetic volunteers.

In rodent models, the method revealed reproducible when performed twice at 7 days apart in the same animal. Rosiglitazone, an insulin-sensitizing drug, induced a significant increase of myocardial IR index in obese Zucker rats from 0.96 ± 0.18 to 2.26 ± 0.44 (P<.05) after 7 days of an oral treatment, and 6DIG IR indexes correlated with the gold standard IR index obtained through the hyperinsulinemic-euglycemic clamp (r=.68, P<.02). In human, a factorial analysis was applied on images to obtain vascular and myocardial kinetics before compartmental modeling. 1.5-fold to 2.2-fold decreases in mean cardiac IR indexes from healthy to diabetic volunteers were observed without reaching statistical significance.

These preclinical results demonstrate the reproducibility and sensibility of this novel imaging methodology. Although this first in-human study showed that this new method could be rapidly performed, larger studies need to be planned in order to confirm its performance.