Increased myocardial fatty acid metabolism in patients with type 1 diabetes mellitus

OBJECTIVES The purpose of this study was to determine if myocardial fatty acid utilization (MFAU) and myocardial fatty acid oxidation (MFAO) are increased in diabetic patients. BACKGROUND Experimental models of diabetes mellitus demonstrate that MFAU and MFAO are increased, and that this dependence on myocardial fatty acid metabolism may be detrimental to cardiac function. Whether similar metabolic changes occur in humans with diabetes mellitus is unclear. METHODS Eleven healthy non-diabetic control patients (5 women, ages 25 +/- 5 years) and 11 otherwise healthy patients with type 1 diabetes mellitus (T1DM) (8 women, ages 36 +/- 10 years, HbA1c 8.4 +/- 1.9%) underwent positron emission tomography for the determination of myocardial blood flow (MBF); myocardial oxygen consumption (MVO2); myocardial glucose utilization (MGU); and MFAU, MFAO, and %MFAO. RESULTS Plasma lactate, insulin, and MBF levels were similar between the two groups. However, plasma glucose (5.71 +/- 0.98 mu mol/ml vs. 5.28 +/- 0.65 mu mol/ml, p = 0.04), free fatty acid levels (0.60 +/- 0.24 mu mol/ml vs. 0.19 +/- 0.07 mu mol/ml, p < 0.0001), and MVO2 (6.64 +/- 2.21 vs. 4.51 +/- 1.39 mu mol/g/min, p = 0.007) levels were higher in the T1DM subjects. Furthermore, compared with control patients, T1DM subjects exhibited higher MFAU (213 +/- 135 nmol/g/min vs. 57 +/- 28 nmol/g/min, p = 0.0004), MFAO (206 +/- 131 nmol/g/min s. 50 +/- 26 nmol/g/min, p = 0.0002), and %MFAO (94 +/- 6% vs. 81 +/- 19%, respectively, p = 0.04). In contrast, MGU was lower in T1DM subjects than in controls (207 +/- 108 nmol/g/min vs. 403 +/- 191 nmol/g/min, p = 0.0008). CONCLUSIONS Humans with diabetes mellitus exhibit increased MFAU and MFAO and reduced MGU consistent with observations obtained in experimental models of diabetes.