17-iodoheptadecanoic-acid and Diabetes-Mellitus--Type-2

Increased triglyceride accumulation has been observed in the diabetic heart, but it is not known whether the abnormalities in myocardial fatty acid metabolism differ between insulin-dependent (IDDM) and non-insulin-dependent (NIDDM) diabetic patients or whether they are present even prior to overt diabetes. Therefore, we studied myocardial fatty acid kinetics with single-photon emission tomography using 123I-heptadecanoic acid (HDA) in four groups of men: impaired glucose tolerance (IGT) (n = 13, age 53 +/- 2 years, mean +/- SEM), IDDM (n = 8, age 43 +/- 3 years), NIDDM (n = 10, age 51 +/- 2 years) and control subjects (n = 8, age 45 +/- 4 years). Echocardiography and myocardial perfusion scintigraphy (IGT and NIDDM groups) were performed to study cardiac function and flow. In the IGT subjects, myocardial HDA beta-oxidation index was reduced by 53% (4.6 +/- 0.4 vs 9.7 +/- 1.0 mumol .min-1.100 g-1, p < 0.01) and HDA uptake by 34% (3.7 +/- 0.2 vs 5.6 +/- 0.3% of injected dose 100g, p < 0.01) compared with the control subjects. The fractional HDA amount used for beta-oxidation was lower in the IGT compared with the control subjects (43 +/- 4 vs 61 +/- 4%, p < 0.05). NIDDM patients also tended to have a lowered HDA beta-oxidation index, whereas IDDM patients had similar myocardial HDA kinetics compared to the control subjects. Myocardial perfusion imaging during the dipyridamole-handgrip stress was normal both in the IGT and NIDDM groups, indicating that abnormal myocardial perfusion could not explain abnormal fatty acid kinetics. In conclusion, even before clinical diabetes, IGT subjects show abnormalities in myocardial fatty acid uptake and kinetics. These abnormalities may be related to disturbed plasma and cellular lipid metabolism.

Topics: Adult; Analysis of Variance; C-Peptide; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Echocardiography; Fatty Acids; Fatty Acids, Nonesterified; Glucagon; Glucose Intolerance; Heart; Humans; Iodine Radioisotopes; Male; Middle Aged; Models, Cardiovascular; Myocardium; Reference Values; Tissue Distribution; Tomography, Emission-Computed; Ventricular Function, Left

Myocardial free fatty acid metabolism and left ventricular function were evaluated in 15 middle-aged patients with non-insulin-dependent diabetes mellitus (NIDDM) and in 8 healthy control subjects. The study subjects had no evidence of coronary heart disease on the basis of clinical history, exercise ECG or myocardial perfusion scintigraphy. During peak exercise, iodine-123 hepatadecanoic acid (HDA) was intravenously injected. Myocardial activity distribution of 123I-HDA was measured 10, 30, and 50 min after exercise using single-photon emission tomography (SPET); and then further corrected by free 123I-iodine. Venous blood samples were drawn for detecting the plasma activity of 123I. The net extraction of 123I-HDA into the myocardium was obtained by dividing the corrected tissue 123I concentration by the integral of the plasma time activity curve. The net extraction was 0.40 +/- 0.06 min-1 (mean +/- SD) patients with NIDDM and 0.38 +/- 0.06 min-1 in control subjects (P greater than 0.1), respectively. The faster elimination rate of 123I-HDA was found in patients with NIDDM (0.029 +/- 0.008 min-1) than in control subjects (0.022 +/- 0.004 min-1; P less than 0.01). There was no statistically significant difference in left ventricular ejection fraction (LVEF) at rest between patients with NIDDM (53 +/- 9%) and control subjects (56 +/- 2%), whereas the increase of LVEF during exercise remained lower in patients with NIDDM (3.4 +/- 8.2%) than in control subjects (11.8 +/- 5.8%; P less than 0.025).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Diabetes Mellitus, Type 2; Fatty Acids; Fatty Acids, Nonesterified; Humans; Iodine Radioisotopes; Middle Aged; Myocardium; Tomography, Emission-Computed, Single-Photon; Ventricular Function, Left