Myocardial fatty acid oxidation in patients with impaired glucose tolerance

Fatty acids are an important source of energy in the myocardium. Abnormal myocardial fatty acid metabolism could contribute to the deterioration of cardiac function frequently observed in patients with Type II (non-insulin-dependent) diabetes mellitus. In our previous study, myocardial total uptake of non-esterified fatty acid (NEFA) was measured in patients with impaired glucose tolerance and found to be normal. This study aimed to investigate the subsequent metabolic steps and beta-oxidation of NEFA.

A total of 6 men with impaired fasting glucose (age 50 +/- 2 years, BMI 29 +/- 1 kg/m2, means +/- SEM) and 6 healthy men (50 +/- 1 years, 25 +/- 1 kg/ m2) were studied in the fasting state. Myocardial blood flow was measured with [15O]H2O and positron emission tomography and myocardial NEFA metabolism with [11C]palmitic acid.

Myocardial blood flow was normal and not different between the impaired glucose tolerance and the control group (78 +/- 6 vs 73 +/- 13 ml/100 g/ min, NS). The [11C]palmitic acid uptake indices were similar between the groups (10.4 +/- 0.5 vs 11.2 +/- 0.8 ml/100 g/min, respectively, NS). The clearance of [11C]-palmitate from the myocardium, an index of NEFA beta-oxidation, was similar between the groups (half-times of activity 17.6 +/- 1.6 vs 19.5 +/- 2.3 min, respectively, NS) CONCLUSION/INTERPRETATION: The results indicate that myocardial NEFA uptake and beta-oxidation are not altered in patients with IGT. Thus, it is not likely that altered NEFA metabolism contributes to the deterioration of the cardiac function in patients with IGT or Type II diabetes.