Effects of the 2-ethylthiobenzimidazole hydrobromide (bemithyl) on carbohydrate metabolism in cirrhotic rat liver

Characterization of Metal-Bound Benzimidazole Derivatives, Effects on Tumor Cells of Lung Cancer

Four new ligands and four new copper (II) coordination compounds were prepared and characterized by chemical, elemental analysis, cytotoxicity, and FTIR spectroscopy (Fourier transform infrared spectroscopy). The nature of metal-ligand coordination was investigated. The thermal properties of complexes in the solid state were studied using TG-MS techniques (thermogravimetric analysis coupled with mass spectrometry) under dynamic flowing air atmosphere to analyze the principal volatile thermal decomposition and fragmentation products that evolved during thermolysis. The intermediate and final solid thermolysis products were also determined. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide) assay was used to evaluate active metabolic cells as an IC50 (half maximal inhibitory concentration). The relationship between antitumor activity and the position of nitrogen atoms in the organic ligand has been shown.

Spatial Structure of Glycogen Molecules in Cells

Glycogen is a strongly branched polymer of α-D-glucose, with glucose residues in the linear chains linked by 1→4-bonds (~93% of the total number of bonds) and with branching after every 4-8 residues formed by 1→6-glycosidic bonds (~7% of the total number of bonds). It is thought currently that a fully formed glycogen molecule (β-particle) with the self-glycosylating protein glycogenin in the center has a spherical shape with diameter of ~42 nm and contains ~ 55,000 glucose residues. The glycogen molecule also includes numerous proteins involved in its synthesis and degradation, as well as proteins performing a carcass function. However, the type and force of bonds connecting these proteins to the polysaccharide moiety of glycogen are significantly different. This review presents the available data on the spatial structure of the glycogen molecule and its changes under various physiological and pathological conditions.

Metformin normalizes the structural changes in glycogen preceding prediabetes in mice overexpressing neuropeptide Y in noradrenergic neurons

Hepatic insulin resistance and increased gluconeogenesis are known therapeutic targets of metformin, but the role of hepatic glycogen in the pathogenesis of diabetes is less clear. Mouse model of neuropeptide Y (NPY) overexpression in noradrenergic neurons (OE-NPY^DβH) with a phenotype of late onset obesity, hepatosteatosis, and prediabetes was used to study early changes in glycogen structure and metabolism preceding prediabetes. Furthermore, the effect of the anti-hyperglycemic agent, metformin (300 mg/kg/day/4 weeks in drinking water), was assessed on changes in glycogen metabolism, body weight, fat mass, and glucose tolerance. Glycogen structure was characterized by cytofluorometric analysis in isolated hepatocytes and mRNA expression of key enzymes by qPCR. OE-NPY^DβH mice displayed decreased labile glycogen fraction relative to stabile fraction (the intermediate form of glycogen) suggesting enhanced glycogen cycling. This was supported by decreased filling of glucose residues in the 10th outer tier of the glycogen molecule, which suggests accelerated glycogen phosphorylation. Metformin reduced fat mass gain in both genotypes, but glucose tolerance was improved mostly in wild-type mice. However, metformin inhibited glycogen accumulation and normalized the ratio between glycogen structures in OE-NPY^DβH mice indicating decreased glycogen synthesis. Furthermore, the presence of glucose residues in the 11th tier together with decreased glycogen phosphorylase expression suggested inhibition of glycogen degradation. In conclusion, structural changes in glycogen of OE-NPY^DβH mice point to increased glycogen metabolism, which may predispose them to prediabetes. Metformin treatment normalizes these changes and suppresses both glycogen synthesis and phosphorylation, which may contribute to its preventive effect on the onset of diabetes.

Activity of glycogen synthase and glycogen phosphorylase in normal and cirrhotic rat liver during glycogen synthesis from glucose or fructose

Cirrhotic patients often demonstrate glucose intolerance, one of the possible causes being a decreased glycogen-synthesizing capacity of the liver. At the same time, information about the rates of glycogen synthesis in the cirrhotic liver is scanty and contradictory. We studied the dynamics of glycogen accumulation and the activity of glycogen synthase (GS) and glycogen phosphorylase (GP) in the course of 120min after per os administration of glucose or fructose to fasted rats with CCl4-cirrhosis or fasted normal rats. Blood serum and liver pieces were sampled for examinations. In the normal rat liver administration of glucose/fructose initiated a fast accumulation of glycogen, while in the cirrhotic liver glycogen was accumulated with a 20min delay and at a lower rate. In the normal liver GS activity rose sharply and GPa activity dropped in the beginning of glycogen synthesis, but 60min later a high synthesis rate was sustained at the background of a high GS and GPa activity. Contrariwise, in the cirrhotic liver glycogen was accumulated at the background of a decreased GS activity and a low GPa activity. Refeeding with fructose resulted in a faster increase in the GS activity in both the normal and the cirrhotic liver than refeeding with glucose. To conclude, the rate of glycogen synthesis in the cirrhotic liver is lower than in the normal one, the difference being probably associated with a low GS activity.

Hepatocytes of cirrhotic rat liver accumulate glycogen more slowly than normal ones

PURPOSE

To investigate the accumulation of glycogen in cirrhotic rat liver at several time intervals after per os administration of glucose to fasted animals.

METHODS

Liver cirrhosis was produced by inhalation of the hepatotropic poison CCl4. Glycogen concentration in the liver was determined biochemically. Glycogen content in hepatocytes was measured cytofluorimetrically in the smears stained with a fluorescent PAS reaction. Glycogen content in the hepatocytes of the portal and the central zone of the liver lobule was determined by absorption cytophotometry.

RESULTS

Rats poisoned with CCl4 for 6 months developed typical liver cirrhosis characterized by a fourfold (p < 0.001) increase in the proportion of the connective tissue. In the cirrhotic rats fasted for 48 h, glycogen concentration in the liver and glycogen content in hepatocytes were lower as compared with the control by 36 and 27 % (p < 0.01), respectively. According to data obtained by different methods, the control animals accumulated glycogen at a high rate. In particular, the glycogen content in hepatocytes increased by 34 % after 10 min (p < 0.01). In the cirrhotic rats, glycogen content remained at the same level for 20 min. In both groups of animals, hepatocytes of the portal zone accumulated more glycogen than those of the central zone.

CONCLUSIONS

Glycogen accumulation in cirrhotic rats starts after a delay and proceeds at a lower rate than in the norm.