Cardiac ischemia and reperfusion in spontaneously diabetic rats with and without application of EGb 761, I. cardiomyocytes

Diabetic cardiomyopathy is known to result in increased mortality after ischemic events. Permanently increased oxidative stress with formation of oxygen-free radicals plays a key role in the development of specific heart muscle disease. Associated lesions include structural alterations to cardiomyocytes. Antioxidative treatment in addition to the usual insulin substitution would seem sensible in preventing or delaying long-term diabetic complications and protecting the myocardium against acute ischemic events. We investigated the effects of radical scavenger Ginkgo biloba extract EGb 761 against diabetes-induced damage to cardiomyocytes and additional ischemia/ reperfusion injury in spontaneously diabetic BioBreeding/Ottawa Karlsburg (BB/OK) rats, as a model of diabetic myocardium infarction. Morphological and morphometric parameters of heart muscles were analyzed by light and electron-microscopic techniques. We used immunohistochemistry to evaluate parameters of oxidative stress (superoxide dismutase [SOD]) and inducible nitric oxide synthase (iNOS) protein expression. Our results indicated that A) Diabetic myocardium appears more vulnerable to ischemia/ reperfusion damage concerning ultrastructure of cardiomyocytes (sarcomeres, vacuoles, mitochondria), expression of antioxidative enzymes (CuZnSOD, MnSOD), and iNOS than normal myocardium; B) Pretreatment of diabetic myocardium with EGb and additional ischemia/reperfusion leads to a relative improvement in myocardial ultrastructure compared to unprotected myocardium. In summary, EGb appears to be promising as an adjuvant therapeutic drug in diabetics with respect to ischemic myocardium injury. It may contribute to the prevention of late diabetic complications in diabetic cardiomyopathy

Cardiac ischemia and reperfusion in spontaneously diabetic rats with and without application of EGb 761: II. Interstitium and microvasculature

Besides alterations in cardiomyocytes themselves, diabetic cardiopathy is characterized by interstitial and microvascular disorders. On the assumption that a specific heart muscle disease develops due to permanently increased oxidative stress on liberation of oxygen-free radicals, adjuvant application of antioxidative therapeutics appears promising in preventing or delaying long-term diabetic complications and protecting the myocardium against acute ischemia. We have investigated the effects of Ginkgo biloba extract (EGb 761), a radical scavenger, against diabetesinduced myocardial interstitium and microvasculature damage, and against additional ischemia/reperfusion injury in spontaneously diabetic BioBreeding/Ottawa Karlsburg (BB/OK) rats modelling diabetic cardiac infarction. Morphological and morphometric parameters in the heart muscle were evaluated by light and electron microscope. We used immunohistochemistry to investigate collagen protein expression as a marker for tissue remodelling together with endothelial nitric oxide synthase (eNOS) protein expression as a marker for endothelial-dependent vasodilation. We also evaluated inflammation response caused by neuropeptide Substance P and interacting mast cells in the diabetic heart. Our results revealed that A) Diabetic myocardium appears more vulnerable to ischemia/reperfusion injury than normal myocardium with regard to myocardial interstitium and microvessel ultrastructure, as well as eNOS protein expression; B) Inflammation response increases in diabetic animals exposed to ischemia/reperfusion injury compared to controls; C) Pre-treatment of diabetic myocardium with EGb results in an improvement of impaired endothelial-dependent vasodilation in diabetes and additional ischemia/ reperfusion, diminished mast cell and substance P accumulation, and better preserved myocardial ultrastructure compared to unprotected myocardium. In conclusion, EGb may act as a potent therapeutic adjuvant in diabetics with respect to ischemic myocardial injury, and may contribute to preventing late complications in diabetic cardiopathy

Cardiovascular autonomic neuropathy in spontaneously diabetic rats with and without application of EGb 761

Cardiovascular autonomic neuropathy causes abnormalities in the diabetic heart with various clinical sequelae, including exercise intolerance, arrhythmias and painless myocardial infarction. Little is known about (ultra)structural alterations of the myocardial nervous network. On the assumption that this diabetes-specific neuropathy develops due to permanently increased oxidative stress by liberation of oxygen-free radicals, adjuvant application of antioxidative therapeutics appears promising in preventing or delaying long-term diabetic complications. We have investigated the effects of Ginkgo biloba extract (EGb 761), a radical scavenger, against diabetes-induced myocardial nervous damage in spontaneously diabetic BioBreeding/Ottawa Karlsburg (BB/OK) rats. Morphological and morphometric parameters were evaluated by electron microscopy. We used immunohistochemistry to investigate protein expression of protein gene product 9.5, S100 protein, and thyroxin hydroxylase as a neuronal marker. Alterations of cardiac sympathetic activity were measured using the in vivo 123I-metaiodobenzylguanidine imaging, and the immunofluorescent labeling of beta1-adrenergic receptors and adenylate cyclase. Our results revealed that A) Diabetes results in slight to moderate ultrastructural alterations (hydrops, disintegration of substructure) of autonomic nerve fibers and related Schwann cells in untreated BB diabetic rats; B) Cardiac sympathetic integrity and activity is impaired due to alterations in the presynaptic nerve terminals and the postsynaptic ß1-AR-AC coupling system; C) Pretreatment of diabetic myocardium with EGb results in an improvement of most of these parameters compared to unprotected myocardium. In conclusion, EGb may act as a potent therapeutic adjuvant in diabetics with respect to cardiovascular autonomic neuropathy, which may contribute to the prevention of late complications in diabetes