Oxidative Inactivation of Liver Mitochondria in High Fructose Diet-Induced Metabolic Syndrome in Rats: Effect of Glycyrrhizin Treatment.

Metabolic syndrome is a serious health problem in the present world. Glycyrrhizin, a triterpenoid saponin of licorice (Glycyrrhiza glabra) root, has been reported to ameliorate the primary complications and hepatocellular damage in rats with the syndrome. In this study, we have explored metabolic syndrome-induced changes in liver mitochondrial function and effect of glycyrrhizin against the changes. Metabolic syndrome was induced in rats by high fructose (60%) diet for 6 weeks. The rats were then treated with glycyrrhizin (50 mg/kg body weight) by single intra-peritoneal injection. After 2 weeks of the treatment, the rats were sacrificed to collect liver tissue. Elevated mitochondrial ROS, lipid peroxidation and protein carbonyl, and decreased reduced glutathione content indicated oxidative stress in metabolic syndrome. Loss of mitochondrial inner membrane cardiolipin was observed. Mitochondrial complex I activity did not change but complex IV activity decreased significantly. Mitochondrial MTT reduction ability, membrane potential, phosphate utilisation and oxygen consumption decreased in metabolic syndrome. Reduced mitochondrial aconitase activity and increased aconitase carbonyl content suggested oxidative damage of the enzyme. Elevated Fe(2+) ion level in mitochondria might be associated with increased ROS generation in metabolic syndrome. Glycyrrhizin effectively attenuated mitochondrial oxidative stress and aconitase degradation, and improved electron transport chain activity. Copyright © 2016 John Wiley & Sons, Ltd.

Glycyrrhizin ameliorates metabolic syndrome-induced liver damage in experimental rat model.

Glycyrrhizin, a major constituent of licorice (Glycyrrhiza glabra) root, has been reported to ameliorate insulin resistance, hyperglycemia, dyslipidemia, and obesity in rats with metabolic syndrome. Liver dysfunction is associated with this syndrome. The objective of this study is to investigate the effect of glycyrrhizin treatment on metabolic syndrome-induced liver damage. After induction of metabolic syndrome in rats by high fructose (60%) diet for 6 weeks, the rats were treated with glycyrrhizin (50 mg/kg body weight, single intra-peritoneal injection). After 2 weeks of treatment, rats were sacrificed to collect blood samples and liver tissues. Compared to normal, elevated activities of serum alanine transaminase, alkaline phosphatase and aspartate transaminase, increased levels of liver advanced glycation end products, reactive oxygen species, lipid peroxidation, protein carbonyl, protein kinase Cα, NADPH oxidase-2, and decreased glutathione cycle components established liver damage and oxidative stress in fructose-fed rats. Activation of nuclear factor κB, mitogen-activated protein kinase pathways as well as signals from mitochondria were found to be involved in liver cell apoptosis. Increased levels of cyclooxygenase-2, tumor necrosis factor, and interleukin-12 proteins suggested hepatic inflammation. Metabolic syndrome caused hepatic DNA damage and poly-ADP ribose polymerase cleavage. Fluorescence-activated cell sorting using annexin V/propidium iodide staining confirmed the apoptotic hepatic cell death. Histology of liver tissue also supported the experimental findings. Treatment with glycyrrhizin reduced oxidative stress, hepatic inflammation, and apoptotic cell death in fructose-fed rats. The results suggest that glycyrrhizin possesses therapeutic potential against hepatocellular damage in metabolic syndrome.

Isolation and characterisation of methanol-soluble fraction of Alternanthera philoxeroides (Mart.) - evaluation of their antioxidant, α-glucosidase inhibitory and antimicrobial activity in in vitro systems.

Alternanthera philoxeroides (Mart.) is a tropical weed commonly known as alligator weed. It grows rapidly within a small span of time and easily available all over the world. The objective of this work was to isolate and characterise the major phenolic components present in the methanol-soluble fraction (fraction X) of A. philoxeroides leaves and to explore the biological activity (antioxidant, α-glucosidase inhibition and antimicrobial) of the fraction in in vitro system. Chromatographic (HPLC) and spectroscopic (MALDI-TOF, ¹H NMR) techniques were used to purify and characterise the phenolics present in fraction X. Five major phenolics (kaempferol, ferulic acid, salicylic acid, syringic acid and chlorogenic acid) were found in fraction X. The fraction showed anti-oxidant property, dose-dependent inhibition of α-glucosidase activity and anti-microbial activity. Hence fraction X from the weed has therapeutic potential in pathophysiological condition.

Glycyrrhizin ameliorates insulin resistance, hyperglycemia, dyslipidemia and oxidative stress in fructose-induced metabolic syndrome-X in rat model.

This study investigates if glycyrrhizin, a constituent of licorice (Glycyrrhiza glabra) root, is able to treat the complications (insulin resistance, hyperglycemia, dyslipidemia and oxidative stress) of metabolic syndrome. Metabolic syndrome was induced in rats by feeding a fructose-enriched (60%) diet for six weeks, after which single dose of glycyrrhizin (50 mg/kg body weight) was administered intraperitoneally. Different biochemical parameters from blood were estimated during three weeks after treatment. Then the rats were sacrificed to collect skeletal muscle tissue. Glycyrrhizin reduced the enhanced levels of blood glucose, insulin and lipids in metabolic syndrome group. Increased advanced glycation end products of hemoglobin, glycohemoglobin, hemoglobin-mediated iron release and iron-mediated free radical reactions (arachidonic acid and deoxyribose degradation) in metabolic syndrome were inhibited by glycyrrhizin treatment. Reduced activities of enzymatic antioxidants (superoxide dismutase and catalase) and elevated oxidative stress markers (malonaldehyde, fructosamine, hemoglobin carbonyl content and DNA damage) in metabolic syndrome were reversed to almost normal levels by glycyrrhizin. The decreased levels of peroxisome proliferator activated receptor gamma (PPARgamma) and glucose transporter 4 (GLUT4) proteins in skeletal muscle of metabolic syndrome group were elevated by glycyrrhizin, indicating improved fatty acid oxidation and glucose homeostasis.

Non-enzymatic glycation induces structural modifications of myoglobin.

Increased glucose concentration in diabetes mellitus causes glycation of several proteins, leading to changes in their properties. Although glycation-induced functional modification of myoglobin is known, structural modification of the protein has not yet been reported. Here, we have studied glucose-modified structural changes of the heme protein. After in vitro glycation of metmyoglobin (Mb) by glucose at 25 degrees C for 6 days, glycated myoglobin (GMb) and unchanged Mb have been separated by ion exchange (BioRex 70) chromatography, and their properties have been compared. Compared to Mb, GMb exhibits increased absorbance around 280 nm and enhanced fluorescence emission with excitation at 285 nm. Fluorescence quenching experiments of the proteins by acrylamide and KI indicate that more surface accessible tryptophan residues are exposed in GMb. CD spectroscopic study reveals a change in the secondary structure of GMb with decreased alpha-helix content. 1-anilino-naphthaline-8-sulfonate (ANS) binding with Mb and GMb indicates that glycation increases hydrophobicity of the heme protein. GMb appears to be less stable with respect to thermal denaturation and differential calorimetry experiments. Heme-globin linkage becomes weaker in GMb, as shown by spectroscopic and gel electrophoresis experiments. A correlation between glycation-induced structural and functional modifications of the heme protein has been suggested.