Salah Abdel-aleem

Depletion of total antioxidant capacity in type 2 diabetes

The purpose of the study was to examine the relationship between antioxidant depletion, glycemic control, and development of chronic complications in a controlled population of type 2 diabetic patients. Fifty age-matched type 2 diabetic patients receiving sulfonylureas but not insulin treatment were screened and assigned to two groups based on the presence or absence of proteinuria. A third group of normal subjects without diabetes were also enrolled in the study. All subjects in the three groups were Egyptians who were matched for body weight, and the two diabetic groups were also age-matched. Plasma glucose and fructosamine levels were higher in the two groups of diabetic patients versus the control group, but lipid peroxide levels were higher only in the patients with proteinuria. Compared with the control group, the total antioxidant capacity was depleted in the two diabetic groups, but the depletion was more severe in patients with proteinuria. Thus, the mean Trolox equivalent antioxidant capacity (TEAC) of the control group was 2.7+/-0.45, versus 1.7+/-0.5 (P < .001) in the patients without proteinuria. Furthermore, the TEAC measured in patients with proteinuria, who also had more diabetic complications, was lower (1.4+/-0.5, P < .001) than the TEAC in patients without urinary protein. In conclusion, a depletion of the total antioxidant capacity is associated with a higher incidence of diabetic complications.

Free fatty acid metabolism during myocardial ischemia and reperfusion.

Long chain free fatty acids (FFA) are the preferred metabolic substrates of myocardium under aerobic conditions. However, under ischemic conditions long chain FFA have been shown to be harmful both clinically and experimentally. Serum levels of free fatty acids frequently are elevated in patients with myocardial ischemia. The proposed mechanisms of the detrimental effects of free fatty acids include: (1) accumulation of toxic intermediates of fatty acid metabolism, such as long chain acyl-CoA thioesters and long chain acylcarnitines, (2) inhibition of glucose utilization, particularly glycolysis, during ischemia and/or reperfusion, and (3) uncoupling of oxidative metabolism from electron transfer. The relative importance of these mechanisms remains controversial. The primary site of FFA-induced injury appears to be the sarcolemmal and intracellular membranes and their associated enzymes. Inhibitors of free fatty acid metabolism have been shown experimentally to decrease the size of myocardial infarction and lessen postischemic cardiac dysfunction in animal models of regional and global ischemia. The mechanism by which FFA inhibitors improve cardiac function in the postischemic heart is controversial. Whether the effects are dependent on decreased levels of long chain intermediates and/or enhancement of glucose utilization is under investigation. Manipulation of myocardial fatty acid metabolism may prove beneficial in the treatment of myocardial ischemia, particularly during situations of controlled ischemia and reperfusion, such as percutaneous transluminal coronary angioplasty and coronary artery bypass grafting. (Mol Cell Biochem 166: 85-94, 1997)

Pulsatile versus nonpulsatile reperfusion improves cerebral blood flow after cardiac arrest

Cardiopulmonary bypass using nonpulsatile flow (NF) is currently advocated for treating refractory cardiac arrest. Although the heart can be revived using cardiopulmonary bypass support, the brain must recover if such therapy is to be considered successful. Previous studies have demonstrated that pulsatile flow (PF) reperfusion can improve neurologic outcome compared with NF reperfusion after cardiac arrest. The purpose of this study was to assess cerebral perfusion and oxygen consumption during either PF or NF reperfusion after cardiac arrest. Dogs (n = 22) underwent a 15-minute cardiac arrest followed by 1 hour of either PF or NF reperfusion. Microsphere techniques were used to assess cerebral perfusion and oxygen consumption at 3, 15, and 60 minutes of reperfusion. Mean arteriovenous gradients and total brain flows were similar in both groups. However, cerebral oxygen consumption was significantly improved at 3 minutes of reperfusion with PF versus NF (1.8 +/- 0.3 versus 0.9 +/- 0.3 mL O2.dL-1.min-1, respectively; p < 0.05). These results were coincident with improved gray-to-white flow ratios at 3 minutes of PF versus NF reperfusion (5.2 +/- 1.0 versus 2.0 +/- 0.3, respectively; p < 0.05). There were no statistically significant differences in brain perfusion variables by 15 minutes of reperfusion. However, a relative hyperemia was exhibited at 15 minutes of NF versus PF reperfusion, which suggests nutrient flow was insufficient during early NF versus PF reperfusion. In conclusion, PF reperfusion can better restore cerebral blood flow and oxygen consumption than can NF reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic Changes in the Normal and Hypoxic Neonatal Myocardium

Abstract: Hypoxia is characterized by inadequate oxygen delivery to the myocardium with a resulting imbalance between oxygen demand and energy supply. Several adaptive mechanisms occur to preserve myocardial survival during hypoxia. These include both short‐ and long‐term mechanisms, which serve to achieve a new balance between myocardial oxygen demand and energy production. Short‐term adaptation includes downregulation of myocardial function along with upregulation of energy production via anaerobic glycolysis following an increase in glucose uptake and glycogen breakdown. Long‐term adaptation includes genetic reprogramming of key glycolytic enzymes. Thus, the initial decline in high‐energy phosphates following hypoxia is accompanied by a decrease in myocardial contractility and myocardial energy requirements are subsequently met by ATP supplied from anaerobic glycolysis. Thus, a downregulation in cardiac function and/or enhanced energy production via anaerobic glycolysis are the major mechanisms promoting myocardial survival during hypoxia. In contrast to the aforementioned metabolic changes occurring in adult myocardium, the effects of chronic hypoxia on neonatal myocardial metabolism remain undefined. Studies from our laboratory using a novel neonatal piglet model of chronic hypoxia have shown a shift in cardiac myocyte substrate utilization towards the newborn state with a preference for glucose utilization. We have also shown, using this same model, that chronically hypoxic neonatal hearts were more tolerant to ischemia than non‐hypoxic hearts. This ischemic tolerance is likely due to adaptive metabolic changes in the chronically hypoxic hearts, such as increased anaerobic glycolysis and glycogen breakdown.

Regulation of carbohydrate and fatty acid utilization by L-carnitine during cardiac development and hypoxia

This study is designed to investigate whether substrate preference in the myocardium during the neonatal period and hypoxia-induced stress is controlled intracellularly or by extracellular substrate availability. To determine this, the effect of exogenous L-carnitine on the regulation of carbohydrate and fatty acid metabolism was determined during cardiac stress (hypoxia) and during the postnatal period. The effect of L-carnitine on long chain (palmitate) and medium chain (octonoate) fatty acid oxidation was studied in cardiac myocytes isolated from less than 24 h old (new born; NB), 2 week old (2 week) and hypoxic 4 week old (HY) piglets. Palmitate oxidation was severely decreased in NB cells compared to those from 2 week animals (0.456 ± 0.04 vs. 1.207 ± 0.52 nmol/mg protein/30 min); surprisingly, cells from even older hypoxic animals appeared shifted toward the new born state (0.695 ± 0.038 nmol/mg protein/30 min). Addition of L-carnitine to the incubation medium, which stimulates carnitine palmitoyl-transferase I (CPTI) accelerated palmitate oxidation 3 fold in NB and approximately 2 fold in HY and 2 week cells. In contrast, octanoate oxidation which was greater in new born myocytes than in 2 week cells, was decreased by L-carnitine suggesting a compensatory response. Furthermore, oxidation of carbohydrates (glucose, pyruvate, and lactate) was greatly increased in new born myocytes compared to 2 week and HY cells and was accompanied by a parallel increase in pyruvate dehydrogenase (PDH) activity. The concentration of malonyl-CoA, a potent inhibitor of CPTI was significantly higher in new born heart than at 2 weeks. These metabolic data taken together suggest that intracellular metabolic signals interact to shift from carbohydrate to fatty acid utilization during development of the myocardium. The decreased oxidation of palmitate in NB hearts probably reflects decreased intracellular L-carnitine and increased malonyl-CoA concentrations. Interestingly, these data further suggest that the cells remain compliant so that under stressful conditions, such as hypoxia, they can revert toward the neonatal state of increased glucose utilization.

Myocardial tolerance to mechanical actuation is affected by biomaterial characteristics

Direct mechanical ventricular actuation (DMVA) uses a pressure regulated heart cup, fabricated from silicone rubber (SR) for mechanical massage of the heart. Because DMVA has demonstrated potential for long-term circulatory support, investigations are currently exploring the use of more durable materials for fabricating DMVA heart cups. This study assessed the acute effects of heart cups fabricated from SR versus polyurethane (PU) on the myocardium. Dogs (n - 18) received DMVA for 4 hr of ventricular fibrillation (VF) using either SR (n = 10) or PU (n = 8) cups. Microspheres were used to determine perfusion during sinus rhythm (control) and at 2 and 4 hr of support. After support, myocardial biopsies were assayed for high energy phosphate content. Results demonstrated that PU cups required relatively frequent adjustments in drive line parameters that were likely due to material softening during PU cup support. Both PU and SR cups achieved similar hemodynamics during 4 hr of support. Myocardial perfusion, however, demonstrated a marked hyperemia at 4 hr of PU versus SR cup support. Regional high energy phosphate content was significantly decreased in hearts supported by PU versus SR cups. These results suggest that the relatively compliant characteristics of SR materials are important for achieving effective DMVA support without injuring the myocardium.

Effects of phosphodiesterase inhibitors on glucose utilization in isolated cardiac myocytes

The phosphodiesterase (PDE) inhibitor, enoximone, enhances the oxidation of fatty acids in cardiac myocytes. Since carbohydrate oxidation is tightly coupled and inversely related in cardiac tissue to fatty acid oxidation, this study was designed to investigate enoximones effects on glucose metabolism in the heart. To determine if enoximone alters this reciprocal relationship, the effects of enoximone on [U-14C]glucose and [2-14C]pyruvate oxidation were determined in isolated cardiac myocytes. The effect of PDE inhibitors was also examined on pyruvate dehydrogenase complex (PDH) activity, a key component of oxidative glucose metabolism. Two PDE inhibitors, enoximone and milrinone, decreased PDH activity by 69 and 64%, respectively at 0.5 mM. This inhibition of PDH activity by enoximone was completely reversed after removing enoximone from the myocyte medium. PDH activity was unaffected by agents which alter cyclic nucleotide signaling: cGMP, dibutyryl cyclic AMP, and AMP. The effect of enoximone on [2-14C]pyruvate oxidation was similar to that on PDH. Interestingly, the oxidation of glucose was decreased 35% by 0.5 mM enoximone. In isolated rat heart mitochondria (RHM), enoximone decreased PDH activity by 37%. These studies suggest that PDE inhibitors decrease carbohydrate utilization by inhibiting the PDH complex in the heart. The inhibition of PDH by PDE inhibitors appears unrelated to their effects on cAMP or cGMP. This inhibition of PDH by PDE inhibitors may occur, at least in part, secondary to stimulating fatty acid oxidation.

Experimental aortocoronary saphenous vein graft function after mechanical cardiac massage with the Anstadt Cup

Direct mechanical ventricular actuation (DMVA) using the Anstadt Cup can achieve total circulatory support by massaging the fibrillating, asystolic, or failing heart. The device does not contact the blood or cause significant myocardial trauma. The purpose of this study was to assess the functional integrity of saphenous vein grafts (SVGs) subjected to DMVA vs cardiopulmonary bypass (CPB). Human SVGs were used to bypass the ligated left anterior descending coronary artery in 11 dogs. Animals then received 2 hrs of either DMVA (n=5) or CPB (n=6) during sustained ventricular fibrillation. Grafted and non grafted (control) SVG segments were then studied in vitro. SVG patency was confirmed by radiolabeled microspheres and pathologic evaluation. Matched SVG specimens (control) were not exposed to circulatory support. All SVGs were subjected to isometric tension studies. SVG contractile responses to norepinephrine, bradykinin, serotonin, and histamine were assessed. Maximal response to all agonists were similar between control SVG segments compared to either CPB or DMVA support (p=NS, ANOVA). All cumulative dose response curves were similar after DMVA vs CPB support. In conclusion, the smooth muscle function of SVGs in this study was not significantly altered by DMVA support. Therefore, short-term DMVA support does not impair patency or adversely effect the functional integrity of smooth muscle within SVGs.

Regulation of glucose utilization by inhibition of mitochondrial fatty acid uptake in cardiac cells.

In order to investigate the mechanism by which fatty acid oxidation inhibitors regulate cardiac metabolism, the effects of 2-tetradecylglycidic acid (2-TDGA), and 2-bromopalmitic acid (2-BPA) on the oxidation of [1-14C]palmitate, [1-14C]octanoate and [U-14C]glucose were studied in isolated rat myocytes. Fifty per cent inhibition of palmitate oxidation was achieved at 20 microM 2-TDGA and 60 microM 2-BPA. Octanoate oxidation was also inhibited by 2-BPA. In contrast to their effect on palmitate oxidation, fatty acid inhibitors significantly stimulated the oxidation of glucose in a concentration-dependent manner. Moreover, the oxidation of [2-14C]pyruvate was increased two-fold by these compounds. The rate of uptake of [U-14C]-2-deoxyglucose was also stimulated two-fold by these inhibitors. These studies suggest that the stimulation of glucose utilization via the inhibition of fatty acid oxidation may be mediated through the stimulation of both glucose transport and the oxidation of pyruvate by the pyruvate dehydrogenase complex.

Cardiac Metabolism in Health and Disease

Preface S. Abdel-aleem, J.E. Lowe. 1. Glucose and Glycogen Utilisation in Myocardial Ischemia - Changes in Metabolism and Consequences for the Myocyte L.M. King, L.H. Opie. 2. Differential Regulation in the Heart of Mitochondrial Carnitine Palmitoyltransferase-I Muscle and Liver Isoforms E.A. Park, G.A. Cook. 3. Carnitine Deficiency-Induced Cardiomyopathy D.J. Paulson. 4. Fatty Acid-binding Proteins in the Heart F.G. Schaap, et al. 5. Metabolic Disturbances in Diabetic Cardiomyopathy B. Rodrigues, et al. 6. Diabetes Mellitus and Cardiac Function M.A. Mahgoub, A.S. Abd-Elfattah. 7. Phospholipase A2-mediated Hydrolysis of Cardiac Phospholipids. The Use of Molecular and Transgenic Techniques L.J. De Windt, et al. 8. The Role of Glucose Metabolism in a Pig Heart Model of Short-Term Hibernation T.A. Hacker, et al. 9. Glucose Metabolism, H+ Production and Na+/H+-Exchanger mRNA Levels in Ischemic Hearts from Diabetic Rats J.R.B. Dyck, G.D. Lopaschuk. 10. Regulation of Carbohydrate and Fatty Acid Utilization by L-Carnitine During Cardiac Development and Hypoxia S. Abdel-aleem, et al. 11. Identification of Nucleoside Transport Binding Sites in the Human Myocardium A.-S.A. Abd-Elfattah, et al. 12. Mutagenesis and Characterization of Specific Residues in Fatty Acid Ethyl Ester Synthase: A Gene for Alcohol Induced Cardiomyopathy P.S. Bora, et al. 13. Palmitate Oxidation by the Mitochondria From Volume-Overloaded Rat Hearts B. Christian, et al. 14. Effects of Phosphodiesterase Inhibitors on Glucose Utilization in Isolated Cardiac Myocytes S. Abdel-aleem, et al. 15. Energy Metabolism and Mechanical Recovery after Cardioplegia in Moderately Hypertrophied Hearts R.T. Smolenski, et al. 16. Role of Nucleoside Transport and Purine Release in a Rabbit Model of Myocardial Stunning A.-S.A. Abd-Elfattah, et al. 17. Ischemic Preconditioning in Rat Heart: No Correlation Between Glycogen Content and Return of Function T. Doenst, et al. 18. The Liver Isoform of Carnitine Palmitoyltransferase I is Activated in Neonatal Rat Cardiac Myocytes by Hypoxia Dachun Wang, et al. 19. Human Myocardial ATP Content and In Vivo Contractile Function R.C. Starling, et al. 20. Differential Cardioprotection with Selective Inhibitors of Adenosine Metabolism and Transport: Role of Purine Release in Ischemic and Reperfusion Injury A.-S. Abd-Elfattah, et al. 21. Effects of Nucleoside Transport Inhibitors and Adenine/Ribose Supply on ATP Concentration and Adenosine Production in Cardiac Myocytes K.K. Kalsi, et al.