Assessment of myocardial metabolism in diabetic rats using small-animal PET: A feasibility study

This feasibility study was undertaken to determine whether kinetic modeling in conjunction with small-animal PET could noninvasively quantify alterations in myocardial perfusion and substrate metabolism in rats. Methods: All small-animal PET was performed on either of 2 tomographs. Myocardia blood flow and substrate metabolism were measured in 10 male Zucker diabetic fatty rats (ZDF, fa/fa) and 10 lean littermates (Lean, Fa/+) using O-15-water, 1-C-11-glucose, 1-C-11-acetate, and 1-C-11-palmitate. Animals were 12.0 +/- 1.4-wk old. Results: Consistent with a type 2 diabetic phenotype, the ZDF animals showed higher plasma hemoglobin A,., insulin, glucose, and free fatty acid (FFA) levels than their lean controls. Myocardial glucose uptake (mL/g/ min) was not significantly different between the 2 groups. However, higher glucose plasma levels in the ZDF rats resulted in higher myocardial glucose utilization (nmol/g/min) (Lean, 629 +/- 785, vs. ZDF, 1,737 +/- 1,406; P = 0.06). Similarly, myocardial FFA uptake (mL/g/min) was not significantly different between the 2 groups, (Lean, 0.51 +/- 28, vs. ZDF, 0.72 +/- 0.19; P = not significant) However, due to higher FFA plasma levels, utilization and oxidation (nmol/g/min) were significantly higher in the ZDF group (Lean, 519 +/- 462, vs. ZDF, 1,623 +/- 712, P < .001; and Lean, 453 +/- 478, vs. ZDF, 1,636 +/- 730, P < .01). Conclusion: Noninvasive measurements of myocardial substrate metabolism in ZDF rats using small-animal PET are consistent with the expected early metabolic abnormalities that occur in this well-characterized model of type 2 diabetes mellitus. Thus, small-animal PET demonstrates significant promise in providing a means to link the myocardial metabolic abnormalities that occur in rat of disease with the human condition.