Effects of glucose intolerance on myocardial function and collagen-linked glycation

In experimental diabetes, diastolic dysfunction of the left ventricle has been associated with collagen-linked glycation. To determine whether less severe hyperglycemia may have similar effects, we gave alloxan to mongrel dogs (group 2) to induce impaired glucose tolerance (IGT) for comparison with normal subjects (group 1). After 6 months, hemodynamic studies were performed in the anesthetized animals. Basal heart rate, aortic pressure, and ejection fraction were comparable in the two groups, but calculated chamber stiffness was increased in group 2, associated with a reduced end diastolic volume and increased pressure. During infusion of dextran, the volume and pressure responses were similarly abnormal in group 2. In the myocardium, the collagen concentration rose with an increased interstitial distribution histologically. To assess glycation, collagen was extracted, digested with collagenase, and measured for fluorescence. Advanced glycation end products were increased in group 2 to 10.6 +/- 1.6 vs. 6.9 +/- 0.7 fluorescent units (FU)/mg collagen in group 1 (P < 0.01). To assess whether this could be pharmacologically prevented, we administered enalapril to inhibit ACE during the 6 months of glucose intolerance to group 3. This resulted in normal glycation and significant reduction in chamber stiffness increment. We gave group 4 animals aminoguanidine daily for 6 months, which prevented abnormal collagen glycation and chamber stiffness. Thus, in animals with IGT, collagen-linked glycosylation appeared to be a major factor affecting diastolic function and was shown to be amenable to pharmacological intervention.