Vyacheslav Buko

Background and purpose: Cardiac mitochondria dysfunction plays a central pathophysiological role in the abnormal glucose metabolism in the heart and in diabetic cardiomyopathy. The present study evaluated the effects of flavonoid glycoside naringin treatment on the interconnection between changes in cardiac mitochondria oxygen consumption, membrane potential and mitochondrial Ca2+ sensitivity during type 1 diabetes. Experimental approach: Type 1 diabetes was induced by an intraperitoneal injection of streptozotocin (40 mg/kg) in rats and islet morphology, glucose and insulin levels, changes in heart mitochondria respiration, membrane potential, spontaneous and Ca2+ - induced mitochondrial permeability transition (MPT) pore opening were evaluated. Key results: Diabetes resulted in typical signs of hyperglycemia, which were accompanied by a rat cardiac mitochondria dysfunction, manifested by decreased V2 and V3 rates of oxygen consumption, while the initial membrane potential value remained unchanged. The rates of Ca2+-induced MPT pore opening and Ca2+-induced membrane potential dissipation in isolated mitochondria decreased under type 1 diabetes. The naringin treatment (40 mg/kg of the body weight, 4 weeks) partially recovered impaired cardiac mitochondria respiration, decreased spontaneous and increased Ca2+-induced MPT pore opening, improved pancreatic islets morphology and dystrophic changes, lowered glycated hemoglobin and blood plasma urea, and decreased the oxidative stress level with glucose or insulin concentrations remaining unchanged in diabetic animals. Conclusions: Naringin administration demonstrated beneficial effects during type 1 diabetes and represents a promising therapeutic (or nutriceutical) approach for diabetes treatment.

Betulin, a pentacyclic triterpene, possesses antioxidant, anti-inflammatory and hepatoprotective properties. The aim of this study was to evaluate the impact of liver mitochondria in hepatoprotection of betulin using a rat model of alcoholic steatohepatitis induced by ethanol administration (4 g/kg, intragastric) for 8 weeks. The treatment with betulin (50 and 100 mg/kg b.w., intragastric) during this period attenuated the histological signs of steatohepatitis and lowered the serum and liver triglyceride contents, as well as the serum activities of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase. Betulin (100 mg/kg) decreased the liver/body weight ratio and inhibited the increase in the serum levels of TNFα, IL-1β, TGFβ, and hyaluronic acid, demonstrating hepatoprotective, anti-inflammatory, and antifibrotic potential. Betulin also inhibited the formation of superoxide anions in mitochondria and the end-products of lipid peroxidation in liver tissue, the amount of which was significantly increased in ethanol-treated rats. The disturbances in mitochondrial respiration, uncoupling of oxidative phosphorylation and decreasing of mitochondrial complex I, II, and IV activities in rats with steatohepatitis, were reverted by betulin administration. The increased susceptibility of mitochondria to Ca²⁺-induced permeability transition pore formation in the hepatitis group was improved in rats treated with betulin. In conclusion, betulin, having antioxidant properties, exerts a beneficial effect in the rat model of alcoholic steatohepatitis via prevention of liver mitochondria dysfunction, which may be attributed to the inhibition of mitochondrial permeability transition.

Cytochrome P450 2E1 (CYP2E1) and its production of ROS play an essential role in the development and progression of inflammatory liver diseases such as alcoholic steatohepatitis. For this isoenzyme we have developed two new inhibitors - 12-imidazolyl-1-dodecanol (I-ol) and 1-imidazolyldodecane (I-an) - and wanted to test their effect on the related disease of non-alcoholic steatohepatitis (NASH). The fat-rich Lieber-DeCarli diet, which was administered over the entire experimental period of 16 weeks, was used for disease induction in the rat model, while the experimental substances were administered in parallel over the last four weeks. This high-calorie diet pathologically altered the ROS balance, the amount of adipocytokines, TNF-α and lipids as well as the activities of liver enzymes. Together with the histological examinations, the conclusion could be drawn that the diet led to the formation of NASH. I-ol and to a lesser extent I-an were able to shift the pathological values towards the normal range - despite continued administration of the noxious agent. I-ol, in particular, showed an extremely good tolerability in the acute toxicity study in rats. Thus, CYP2E1 appears to be a suitable drug target as well as I-ol and I-an promising drug candidates for the treatment of NASH.

Quercetin (3,3ʹ,4ʹ,5,7-pentahydroxyflavon), one of the most common and studied flavonoids, possesses the antioxidant activity and demonstrates the pronounced therapeutic potential under a number of pathological conditions. The purpose of this work is to estimate the electronic structure of the quercetin and its semi-quinone radical molecules and to compare the antioxidant activities of quercetin and its inclusion complex with hydroxypropyl-β-cyclodextrin. Generation of maps of the electron density distribution in quercetin and quercetin semi-quinone radical molecules showed that the active electron orbitals (HOMO and LUMO) are delocalized over all phenolic rings providing the radical stabilization. We have showed that quercetin prevents the tert-butyl hydroperoxide-induced lipid peroxidation of erythrocytes (IC₅₀= 25 ± 3 μM) and mitochondrial membranes (IC₅₀= 31 ± 4 μM). The efficiency of quercetin inhibition the reduced glutathione oxidation in erythrocytes and mitochondria is much lower reflecting the lipophilicity of polyphenol. Quercetin also prevented the hypochlorite-induced lysis of red blood cells (IC₅₀= 3 ± 0.5 μM). Our data revealed that the quercetin-hydroxypropyl-β-cyclodex-trin complex is more effective inhibitor of the membrane lipids peroxidation and glutathione oxidation processes.

The protective effect of red cabbage extract (RCE) was evaluated in rats with streptozotocin-induced diabetes, assessing a probable role of this extract in the prevention of erythrocyte impairments associated with a high risk of vascular complications in diabetes. RCE was analyzed by ultrahigh performance liquid chromatography and mass spectrometry, and 11 anthocyanins, 3 hydroxybenzoic acids and 9 hydroxycinnamic acids were identified. Type 1 diabetes was induced by streptozotocin (60 mg kg⁻¹) in Wistar male rats (n = 8 per group). After 7 days of acclimatization, streptozotocin-treated rats were given RCE (800 mg kg⁻¹) or vehicle by intragastric administration for 4 weeks. The RCE treatment lowered blood glucose, and glycated and fetal hemoglobin concentrations and improved glucose tolerance as well as considerably raised serum insulin, proinsulin and C-peptide levels in streptozotocin-treated rats. Simultaneously, RCE improved pancreatic islet morphology, increasing the amount of pancreatic β-cells in diabetic animals. The RCE administration prevented anemia in rats with streptozotocin-induced diabetes, enhanced erythrocyte resistance to acid hemolysis, and normalized reticulocyte production as well as sialic acid content in erythrocyte membranes. The enhanced lectin-induced erythrocyte aggregation in diabetic rats was significantly lowered after the RCE treatment. RCE demonstrated a significant antioxidant effect, decreasing MDA and protein carbonyl contents and increasing catalase and glutathione peroxidase activities in erythrocytes. These results indicate that RCE can be considered as a promising candidate for use as a drug or a food supplement to alleviate diabetes and its vascular complications.