Chennam Srinivasulu Shyamaladevi

GREEN TEA EXTRACT IMPEDES DYSLIPIDAEMIA AND DEVELOPMENT OF CARDIAC DYSFUNCTION IN STREPTOZOTOCIN-DIABETIC RATS

1 The efficacy of green tea extract (GTE) on serum and cardiac lipids was investigated in streptozotocin (STZ)‐diabetic rats. 2 Diabetes was induced in rats by a single intraperitoneal injection of STZ (60 mg/kg bodyweight). Six weeks after the induction of diabetes, GTE was administered orally for 4 weeks (300 mg/kg bodyweight daily). Bodyweight, heart weight, heart weight : bodyweight ratio, blood glucose, serum and cardiac lipids were determined in experimental rats. 3 In diabetic rats, there was a significant decrease in bodyweight with an increase in heart weight : bodyweight ratio and blood glucose. Diabetic rats had significantly increased serum levels of cholesterol, triglycerides, free fatty acids and low‐density lipoprotein–cholesterol (LDL‐C) and decreased levels of high‐density lipoprotein–cholesterol (HDL‐C). In the hearts of diabetic rats, there was a significant increase in cholesterol, triglycerides and free fatty acids levels, with an increase in lipoprotein lipase activity. 4 The administration of GTE to diabetic rats resulted in significant recovery in bodyweight, heart weight : bodyweight ratio and blood glucose levels. The administration of GTE reduced cholesterol, triglyceride, free fatty acid and LDL‐C levels, and increased HDL‐C levels, in the serum of diabetic rats. In addition, GTE decreased cholesterol, triglyceride, free fatty acids levels and lipoprotein lipase activity in the myocardium of diabetic rats. These beneficial effects of GTE are ascribed to its antihyperglycaemic and hypolipidaemic activity. In conclusion, green tea can reduce the risk of cardiovascular disease in diabetes with a significant improvement in lipid metabolism.

Therapeutic effect of green tea extract on advanced glycation and cross-linking of collagen in the aorta of streptozotocin diabetic rats.

1 The therapeutic effect of green tea extract (GTE) on the aortic collagen content and its characteristics were investigated in streptozotocin diabetic rats. 2 Diabetes was induced in rats by a single intra peritoneal injection of streptozotocin (60 mg/kg bodyweight). Six weeks after diabetes induction, GTE was administered orally for four weeks (300 mg/kg bodyweight daily). Systolic blood pressure, blood glucose, anti‐oxidant status, collagen content, extent of glycation, collagen linked fluorescence and aortic collagen solubility pattern were determined in experimental rats. 3 At the end of the experimental period, there was a significant increase in the systolic blood pressure and blood glucose in diabetic rats. The lipid peroxides increased whereas glutathione and vitamin C levels were decreased in the serum of diabetic rats. The collagen content, extent of glycation, the advanced glycation end products (AGEs) and degree of cross‐linking were increased in the aorta of diabetic rats. 4 The oral administration of GTE to diabetic rats significantly reduced the systolic blood pressure and blood glucose. The level of lipid peroxides reduced and the content of glutathione and vitamin C increased in the serum of GTE treated diabetic rats. Green tea extract also impede the accumulation of aortic collagen, extent of glycation, formation of AGEs and cross‐linking of collagen in diabetic rats. The antihyperglycemic, anti‐oxidant and antiglycating effects of GTE ascribed for these beneficial effects. In conclusion, green tea may have therapeutic effect in the treatment of cardiovascular complications characterized by increased AGE accumulation and protein cross‐linking associated with diabetes.

Protective effect of aspartate and glutamate on cardiac mitochondrial function during myocardial infarction in experimental rats

The present study investigates the effect of aspartate and glutamate on mitochondrial function during myocardial infarction (MI) in wistar rats. Male albino wistar rats were pretreated with aspartate [100 mg(kgbody weight)(-1) day(-1)] or glutamate [100 mg(kg body weight)(-1) day(-1)] intraperitoneally for a period of 7 days. Following amino acid treatment, MI was induced in rats by subcutaneous injection of isoproterenol [200 mg(kg body weight)(-1) day(-1)] for 2 days at an interval of 24 h. Isoproterenol (ISO) induction resulting in significant (P<0.05) increase in the levels of cardiac mitochondrial lipid peroxidation with a decrease in reduced glutathione level. The activities of glutathione peroxidase and glutathione reductase were significantly (P<0.05) decreased by ISO. ISO-induction also caused significant (P<0.05) decrease in the activities of mitochondrial tricarboxylic acid cycle enzymes (malate dehydrogenase, isocitrate dehydrogenase, succinate dehydrogenase, alpha-ketoglutarate dehydrogenase) and respiratory chain enzymes (NADH dehydrogenase and cytochrome-c-oxidase). ISO significantly (P<0.05) reduced the cytochrome contents, ATP production, ADP/O ratio and oxidation of succinate in state 3/state 4 whereas significantly (P<0.05) increased NADH oxidation. Pretreatment with aspartate or glutamate significantly (P<0.05) reduced the alterations induced by ISO and maintained normal mitochondrial function. The present findings reveal the protective effect of aspartate and glutamate on cardiac mitochondrial function in myocardial infarction-induced rats.

Aspartate and glutamate prevents isoproterenol-induced cardiac toxicity by alleviating oxidative stress in rats

The protective effect of aspartate and glutamate in isoproterenol induced myocardial infarction (MI) was investigated in experimental animals. Male albino wistar rats were pretreated with aspartate [100mg (kg body weight)-1 day-1] or glutamate [100mg (kg body weight)-1 day-1] intraperitoneally for a period of 7 days. Following amino acid treatment, MI was induced in rats by subcutaneous injection of isoproterenol [200mg (kg body weight)-1 day-1] for 2 days. After 24h following the last injection, the animals were sacrificed and the biochemical analysis was carried out. The activities of cardiac marker enzymes (alanine transaminase, aspartate transaminase, lactate dehydrogenase and creatine phosphokinase) were increased significantly (P<0.05) in the serum of MI induced rats as compared to control rats. The levels of glutathione and mitochondrial ATP and the activities of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione transferase and glutathione reductase) were decreased whereas lipid peroxides increased significantly (P<0.05) in the heart of MI induced rats as compared to control rats. However, pretreatment with aspartate or glutamate to MI induced rats significantly (P<0.05) reduced the activities of cardiac marker enzymes and increased the activities of antioxidant enzymes as compared to MI induced rats. Aspartate or glutamate pretreatment also increased the levels of glutathione and mitochondrial ATP while decreased the level of lipid peroxides in the cardiac tissue. The overall effects of aspartate and glutamate in reducing the oxidative stress in MI induced rats are similar. There was no significant difference between the control rats and aspartate or glutamate treated control rats. The present study shows that aspartate and glutamate could reduce oxidative stress in MI induced rats.

Regulation of Intracellular Calcium Levels and Urokinase Activity in MDA MB 231 Cells by Quercetin

Background: The common plant bioflavonoid, quercetin, is cytotoxic to various tumor cell lines, particularly breast cancer, by affecting the protein-kinase-C-dependent signal pathways and by cell cycle regulation. However, its role in breast cancer metastasis has not been studied so far. Increased uPA activity is evident in highly metastatic breast cancer, which is calcium dependent. Methods: MDA MB 231 cells were treated with various concentrations of quercetin (15–45 µg/ml). The cytotoxic effect of quercetin was assessed by MTT assay and DNA fragmentation analysis. Intracellular calcium levels were measured using Fura-2, a specific Ca2+ fluorescence indicator. Calcium uptake and release in cells treated with quercetin were measured using radioactive 45Ca2+. Urokinase enzyme activity was assayed by a casein zymogram. Results: Quercetin elicited dose- and time-dependent cytotoxicity as evidenced by the MTT assay. The maximum effect was observed at 48 h with a quercetin concentration of (45 µg/ml). DNA agarose gel electrophoresis showed dose-dependent DNA fragmentation on quercetin treatment. Quercetin caused significant depletion of cytosolic calcium levels and decreased calcium uptake from the intracellular stores. Casein zymogram showed a marked reduction of urokinase activity as evident by clear lysis bands on a dark background on treatment with quercetin. Conclusion: Quercetin was found to exhibit cytotoxicity in the highly invasive breast cancer cell line MDA MB 231 in a dose- and time-dependent manner. Quercetin inhibited calcium dependent urokinase activity and hence may prove to be an effective antimetastatic agent.

Histone H1 modulates immune status in experimental breast cancer.

Background: Breast cancer chemotherapy aims at employing cytotoxic agents that swing the balance between tumor cell invasion and host immune cells in favor of the latter. This study aimed at assessing the effect of exogenous histone H1 in maintaining the immune status of animals in experimental breast cancer taking advantage of its tumor-suppressive activity. Methods: Histone H1 was injected intratumorally as a single injection in tumor-bearing animals. Tumor response was assessed from changes in tumor volume, survival time and the immune status of animals from total and differential blood cell counts, levels of circulating immune complexes, thromboxane B2 and IgA in serum. Immune response was assessed from the macrophage count in the tumor and peritoneal exudates after activation. Results: Histone H1 treatment significantly inhibited tumor growth, enhanced mean survival time and significantly improved the immune response and status. Conclusion: These results indicate that histone H1 plays a vital role in maintaining the immune status.

Effect of Solanum trilobatum on hepatic drug metabolising enzymes during diethylnitrosamine-induced hepatocarcinogenesis promoted by Phenobarbital in rat.

The present study was aimed to investigate the chemopreventive effects of Solanum trilobatum (ST) extract against diethylnitrosamine (DEN)‐induced hepatocarcinogenesis promoted by Phenobarbital (PB) in Wistar rats. Hepatocarcinogenesis was initiated by a single intraperitoneal injection of DEN (200 mg/kg b.w.) and promoted with PB (0.05%) in basal diet. The experimental study extended for periods of 13 and 26 weeks. Alcoholic extract of ST was orally administered for the entire experimental period after initiation along with commencement of promotion. The chemopreventive effect of ST was assessed from the incidence of nodules, drug metabolizing phase I components such as contents of cytochrome P450, cytochrome b5, activities of NADPH cytochrome c reductase, NADH – cytochrome b5 reductase and phase II components such as levels of glutathione, activities of UDP‐glucuronyl transferase, glutathione S‐transferase and γ‐glutamyl transpeptidase in the liver. Lipid peroxidation at basal and prooxidants‐induced (NADPH + ADP + Fe and Ascorbate + Fe) states was assessed in the microsomes. Animals administered with ST extract evidenced significant inhibition of tumor nodular incidence in DEN + PB + ST animals compared to DEN + PB animals, with favorable alterations in the hepatic drug‐metabolizing phase I and phase II components. Administration of ST inhibited basal and pro‐oxidant‐induced lipid peroxidation. The present result suggests the probable mediation of chemoprevention by ST against DEN‐induced carcinogenesis by the modulation of drug metabolizing components in the liver of treated animals.

Modulatory Action of α-Tocopherol on Erythrocyte Membrane Adenosine Triphosphatase against Radiation Damage in Oral Cancer

To investigate the possible effects of α-tocopherol on erythrocyte membrane adenosine triphosphatases against radiation damage in oral cancer patients. Adenosine triphosphatase activities were analysed in oral cancer patients before and after radiotherapy (at a dosage of 6000 cGY in five fractions per week for a period of six weeks) and after supplemented with α-tocopherol (400 IU per day for entire period of radiotherapy). The membrane bound enzymes such as Na+/K+-ATPase, Ca2+-ATPase, Mg2+-ATPase and some trace elements were altered in oral cancer patients before and after radiotherapy. Supplemented with α-tocopherol modulates the erythrocyte membrane which is damaged by radiotherapy which suggests that α-tocopherol protects the erythrocyte membrane from radiation damage in oral cancer patients.