Osis and left ventricular function in type 2 diabeticFigure 1. Mean blood glucose concentrations (mg/dl) (a), daily insulin dose (international unit [IU]) (b), systolic and diastolic blood pressure (mmHg) (c) at baseline and during the first 10 days of IT. Empty bars indicate systolic and gray bars diastolic blood pressure values; error bars delineate SEM. doi:10.1371/journal.pone.0050077.gInsulin Alters Myocardial Lipids and MorphologyTable 2. Results of MR imaging studies.Left ventricular variable Heart rate (min1) Ejection fraction ( ) End-diastolic volume (ml/m2) End-systolic volume (ml/m2) Stroke volume (ml/m2) Cardiac index (l/min/m2) Myocardial mass (g/m2) Thickness in ED (mm/m2) Concentricity 
(g/ml) E/A ratioBaseline N = 8 (oral CASIN web medication, OT) (mean ?SEM) 7562.8 7162.8 5963.5 1861.9 4262.6 3.160.2 5863.9 8.160.7 0.8860.08 1.0660.Baseline 
N = 10 (standardized IT) (mean ?SEM) 7664.1 7162.5 5565.0 1762.5 3862.8 2.960.2 5464.0 8.660.5 0.9660.08 0.9360.Day 10 N = 10 (standardized IT) (mean ?SEM) 7364.6 7363.3 4964.8 1462.5 3663.4 2.660.3 6264.3* 9.760.6* 1.2360.11* 0.9260.Follow up N = 7 (standardized IT) (mean ?SEM) 7263.1 7363.5 5265.3 1462.4 3864.3 2.760.2 6264.5{ 9.560.6 1.1560.12 0.8760.Values are mean6SEM. ED, end-diastole. *p,0.05 baseline IT vs. 10th day of IT, { p,0.05 baseline IT vs. follow up IT. doi:10.1371/journal.pone.0050077.tpatients [9]. In contrast, a study performed in individuals with uncomplicated T2DM indicates that MYCL content is an indirect predictor of myocardial dysfunction [7]. Previous cross-sectional investigations applying cardiac MRS [7,9,35] or histology [6] have confirmed elevated MYCLs in metabolic diseases including T2DM, obesity and impaired glucose tolerance. In order to elucidate the underlying mechanisms causative for the development of myocardial steatosis we have recently performed a standardized hyperglycemic clamp test in healthy subjects. We could demonstrate that endogenous hyperinsulinemia in response to hyperglycemia induces an acute increase in MYCL content. [14]. In the present study, we observed a strong correlation between glucose concentrations at day 1 and MYCL at day 10 of IT. 23727046 Insulin forcefully stimulates myocardial glucose uptake via increased GLUT 4 translocation to the cellular membrane fostering substrate competition between fatty acids and glucose [36,37]. The resulting switch in mitochon-drial substrate utilization from fatty acid- to glucose utilization is mediated mainly by malonyl-CoA. Malonyl-CoA is generated by acetyl-CoA carboxylase (ACC 2) and inhibits CPT I (carnitine palmitoyltransferase) [36], which controls the rate limiting step of mitochondrial FFA-uptake and in turn xidation. Insulin also exerts a direct stimulatory effect on ACC, thereby potently suppressing mitochondrial lipid oxidation in the presence of hyperglycemia [38]. In addition increased insulin-mediated uptake of circulating FFA and stimulation of intracellular triglyceride synthesis likely contributed to myocardial lipid accumulation [26]. Our results confirm myocardial steatosis in the expected range in patients with T2DM (OT-group) [21]. However, in subjects with secondary failure of oral glucose lowering therapy MYCL content was in the normal range at baseline. Relative insulin deficiency due to progressive Gracillin web b-cell dysfunction [39] in the ITgroup likely contributed to unexpectedly normal (low) MYCL stores in patients with longstanding T2DM.Figure 2. Intramyocardial lipid- (MYCL, given in of.Osis and left ventricular function in type 2 diabeticFigure 1. Mean blood glucose concentrations (mg/dl) (a), daily insulin dose (international unit [IU]) (b), systolic and diastolic blood pressure (mmHg) (c) at baseline and during the first 10 days of IT. Empty bars indicate systolic and gray bars diastolic blood pressure values; error bars delineate SEM. doi:10.1371/journal.pone.0050077.gInsulin Alters Myocardial Lipids and MorphologyTable 2. Results of MR imaging studies.Left ventricular variable Heart rate (min1) Ejection fraction ( ) End-diastolic volume (ml/m2) End-systolic volume (ml/m2) Stroke volume (ml/m2) Cardiac index (l/min/m2) Myocardial mass (g/m2) Thickness in ED (mm/m2) Concentricity (g/ml) E/A ratioBaseline N = 8 (oral medication, OT) (mean ?SEM) 7562.8 7162.8 5963.5 1861.9 4262.6 3.160.2 5863.9 8.160.7 0.8860.08 1.0660.Baseline N = 10 (standardized IT) (mean ?SEM) 7664.1 7162.5 5565.0 1762.5 3862.8 2.960.2 5464.0 8.660.5 0.9660.08 0.9360.Day 10 N = 10 (standardized IT) (mean ?SEM) 7364.6 7363.3 4964.8 1462.5 3663.4 2.660.3 6264.3* 9.760.6* 1.2360.11* 0.9260.Follow up N = 7 (standardized IT) (mean ?SEM) 7263.1 7363.5 5265.3 1462.4 3864.3 2.760.2 6264.5{ 9.560.6 1.1560.12 0.8760.Values are mean6SEM. ED, end-diastole. *p,0.05 baseline IT vs. 10th day of IT, { p,0.05 baseline IT vs. follow up IT. doi:10.1371/journal.pone.0050077.tpatients [9]. In contrast, a study performed in individuals with uncomplicated T2DM indicates that MYCL content is an indirect predictor of myocardial dysfunction [7]. Previous cross-sectional investigations applying cardiac MRS [7,9,35] or histology [6] have confirmed elevated MYCLs in metabolic diseases including T2DM, obesity and impaired glucose tolerance. In order to elucidate the underlying mechanisms causative for the development of myocardial steatosis we have recently performed a standardized hyperglycemic clamp test in healthy subjects. We could demonstrate that endogenous hyperinsulinemia in response to hyperglycemia induces an acute increase in MYCL content. [14]. In the present study, we observed a strong correlation between glucose concentrations at day 1 and MYCL at day 10 of IT. 23727046 Insulin forcefully stimulates myocardial glucose uptake via increased GLUT 4 translocation to the cellular membrane fostering substrate competition between fatty acids and glucose [36,37]. The resulting switch in mitochon-drial substrate utilization from fatty acid- to glucose utilization is mediated mainly by malonyl-CoA. Malonyl-CoA is generated by acetyl-CoA carboxylase (ACC 2) and inhibits CPT I (carnitine palmitoyltransferase) [36], which controls the rate limiting step of mitochondrial FFA-uptake and in turn xidation. Insulin also exerts a direct stimulatory effect on ACC, thereby potently suppressing mitochondrial lipid oxidation in the presence of hyperglycemia [38]. In addition increased insulin-mediated uptake of circulating FFA and stimulation of intracellular triglyceride synthesis likely contributed to myocardial lipid accumulation [26]. Our results confirm myocardial steatosis in the expected range in patients with T2DM (OT-group) [21]. However, in subjects with secondary failure of oral glucose lowering therapy MYCL content was in the normal range at baseline. Relative insulin deficiency due to progressive b-cell dysfunction [39] in the ITgroup likely contributed to unexpectedly normal (low) MYCL stores in patients with longstanding T2DM.Figure 2. Intramyocardial lipid- (MYCL, given in of.
