Plasma hepatic glutathione S-transferase concentrations after insulin-induced hypoglycaemia in normal subjects and diabetic patients

Characterization of metabolic alterations in the lean metabolically unhealthy alpha defensin transgenic mice

Inflammation is consistently linked to dysmetabolism. In transgenic mice (Def+/+) model the neutrophilic peptide, alpha defensin, proved atherogenic. This phenotype occurred despite favorable cholesterol and glucose levels, and lower body weight and blood pressure. In this study, integration of metabolic&behavioral phenotyping system, endocrine, biochemical and mitochondrial assessment, pathological and immunohistochemical tests, and multiple challenge tests was established to explore the metabolic impact of alpha defensin. Compared to the control group, Def+/+ mice exhibited lower total energy expenditure and carbohydrate utilization, and higher fat oxidation. Their ACTH-cortisol and thyroid profiles were intact. Intriguingly, they had low levels of glucagon, with high ammonia, uric acid, triglyceride, and lactate. Mitochondrial evaluations were normal. Overall, defensin-induced hypoglucagonemia is associated with lipolysis, restricted glucose oxidation, and enhanced wasting. Def+/+ mice may be a useful model for studying the category of lean, apparently metabolically healthy, and atherosclerotic phenotype, with insight into a potential inflammatory-metabolic link.

Glutathione suppresses increase of serum creatine kinase in experimental hypoglycemia

Inhibitory effects of reduced glutathione (GSH) on serum enzymes including alanine aminotransferase (AST), lactate dehydrogenase (LDH) and creatine kinase (CK) were investigated in the hypoglycemic rabbits. Hypoglycemia lasting for 60 min was induced by intravenous injection of insulin (10U/kg) and then recovered by intravenous glucose injection. Serum levels of ALT, AST, LDH and CK increased significantly (p<0.05) at 6h after the induction of hypoglycemia. Plasma GSH, oxidized glutathione (GSSG) and total glutathione (TGSH) began to increase significantly (p<0.05) at 1h after the insulin injection, and GSSG/TGSH ratio rose significantly (p<0.05) at 6h after the induction of hypoglycemia. GSSG contents and GSSG/TGSH ratio in quadriceps significantly increased during hypoglycemia. Administration of GSH significantly decreased plasma GSSG levels, GSSG/TGSH ratio (p<0.05) and suppressed the rise of serum enzymes induced by hypoglycemia. These results suggest that GSH administration may play a preventive role for increases of serum enzymes by experimental hypoglycemia.

Comparative study on glutathione transferases of rat brain and testis under the stress of phenobarbitol and beta-methylcholanthrene

A comparative study was made on the tissue specific expression of glutathione transferases (GST) in brain and testis after exposure of rat to phenobarbitol (PB) and b-methylcholanthrene (MC). Glutathione transferases, a family of multifunctional proteins are involved in intracellular transport processes and in detoxication of electrophilic xenobiotics by catalyzing reactions such as conjugation, isomerization, reduction and thiolysis. On purification, the yield of GST proteins by affinity chromatography was 39% in testis and 32% in brain. The affinity purified testis GSTs were resolved by chromatofocusing into six anionic and four cationic isozymes, and in brain glutathione transferases were resolved into four anionic and three cationic isozymes, suggesting the presence of multiple isozymes with Yc, Yb, Ybeta and Ydelta in both of them. In testis and brain, these isozymes at identical pI values showed variable functions with a battery of substrates and the cationic isozymes of brain and testis showed identical properties in CHP (cumene hydroperoxide) at pH values of above 7.0. Substrate specificity studies and immunoblot analysis of testis and brain proteins revealed that they play a predominant role in the detoxication of phenobarbitol or beta-methylcholanthrene. Expression of the isozymes in testis and brain on exposure to PB and MC indicated elevated subunit variation. In both testis and brain, Ydelta of pi class was expressed on PB treatment and Yc of alpha class and Ybeta of mu class was expressed in MC treated testis and only Yc was predominantly expressed in MC treated brain. Thus these subunits expression is considered as markers for carcinogenesis and specific to chemical toxicity under phenobarbitol and beta-methylcholanthrene stress.

Muscle damage induced by experimental hypoglycemia

To determine organ damage due to hypoglycemia, we studied the effects of insulin dose and hypoglycemia duration on serum enzyme activity in rabbits. Thirty rabbits were randomly divided into five groups according to hypoglycemia duration and insulin dose: A2, hypoglycemia for 30 minutes with 2 U/kg insulin; A10, hypoglycemia for 30 minutes with 10 U/kg insulin; B2, hypoglycemia for 60 minutes with 2 U/kg insulin; B10, hypoglycemia for 60 minutes with 10 U/kg insulin; and C, no hypoglycemia with 10 U/kg insulin and 50% glucose. Insulin-induced hypoglycemia was reversed by intravenous injection of glucose. Alterations in serum enzyme activity and creatine kinase (CK) isoenzyme distribution were determined before and after insulin injection. Serum CK activity increased significantly in all hypoglycemic groups compared with preinjection values, and tended to remain high for 24 hours in both groups A10 and B10. Serum activity of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) increased only in group B10. In addition, the level of band 4 of serum CK isoenzymes, which exists predominantly in skeletal muscle and myocardium, increased significantly in group B10. These results suggest that the increase in both serum enzyme and CK band 4 isoenzyme activities during hypoglycemia is primarily due to damage in muscle rather than liver, and that the hypoglycemia duration and insulin dosage may influence the extent of organ damage.

Plasma enzymic changes in insulin-induced hypoglycemia in experimental rabbits

In order to elucidate the effects of hypoglycemia on cardiac and skeletal muscle, plasma activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and creatine kinase (CK) were assessed in rabbits with hypoglycemia induced by i.v. injection of insulin. After hypoglycemia lasting for more than 30 min, the plasma levels of ALT, AST and LDH rose significantly in 4 out of 5 rabbits reaching a peak at 24 hr. The plasma activity of CK rose remarkably and reached a peak at 6 hr after insulin injection in all rabbits. These results suggest prolonged hypoglycemia may cause myocardial and/or skeletal muscle damage, which can be ascertained by measuring plasma activities of the related enzymes.

Evaluation of an enzyme-immunometric assay for serum alpha-glutathione S-transferase

A commercially available enzyme-immunometric assay for serum alpha-glutathione S-transferase (GST) was evaluated. Endogenous serum alpha-GST diluted linearly within the calibration range. However, we recommend that the sample and second antibody reagent are always added sequentially in the assay to avoid hook effect. Between-assay variability was below 7% across the calibration range and the upper limit of the reference range in adults (n = 219) was 11.4 micrograms/L. Within-individual variability in serum alpha-GST concentrations measured over a 4-6 week period in 4 healthy adults was small. Serum alpha-GST concentrations did not change significantly 6 h after a therapeutic dose of paracetamol. Studies in two patients after liver transplantation showed that serum alpha-GST is a better discriminant of acute changes in liver function than conventional tests. Serum alpha-GST concentrations were unaffected by gross muscle damage, extrahepatic inflammation, or haemolysis and thus appear to be more liver specific than transaminase activities. The effect of renal impairment on serum alpha-GST concentrations requires further investigation.

Glutathione S-transferases in neonatal liver disease

AIMS

To investigate the distribution of alpha and pi class glutathione S-transferases (GST) in normal fetal, neonatal, and adult liver; and to examine changes in GST expression in neonatal liver disease.

METHODS

alpha and pi class GST were immunolocalised in sections of formalin fixed liver tissue obtained from human fetuses (n = 21), neonates (n = 8), young children (n = 9) and adults (n = 10), and from neonates with extrahepatic biliary atresia (n = 15) and neonatal hepatitis (n = 12). Monospecific rabbit polyclonal antibodies were used with a peroxidase-antiperoxidase method.

RESULTS

Expression of pi GST was localised predominantly within biliary epithelial cells of developing and mature bile ducts of all sizes from 16 weeks' gestation until term and in neonatal and adult liver. Coexpression of pi and alpha GST was seen in hepatocytes of developing fetal liver between 16 and 34 weeks' gestation. Although pi GST was seen in occasional hepatocytes up to six months of life, this isoenzyme was not expressed by hepatocytes in adult liver. By contrast, alpha GST continued to be expressed by hepatocytes in adult liver; this isoenzyme was also seen in some epithelial cells of large bile ducts in adult liver. No change was observed in the distribution of alpha GST in either neonatal hepatitis or extrahepatic biliary atresia. However, aberrant expression of pi GST was identified in hepatocytes of all but one case of extrahepatic biliary atresia but in only two cases of neonatal hepatitis.

CONCLUSIONS

The phenotypic alterations noted in extrahepatic biliary atresia may result from the effect of cholate stasis. Evaluation of the pattern of pi and alpha GST distribution by immunohistochemical staining may provide valuable information in distinguishing between these two forms of neonatal liver disease.

Intravenous N-acetylcysteine, hepatotoxicity and plasma glutathione S-transferase in patients with paracetamol overdosage

The concentration of glutathione S-transferase B1 (GST B1) subunits was measured in sequential plasma samples taken at frequent intervals for 48 h from ten patients with severe paracetamol poisoning who were treated with intravenous N-acetylcysteine. No significant increase in plasma GST B1 concentration was observed over the study period and with 4 h of starting treatment with N-acetylcysteine there were significant decreases in plasma GST B1 concentrations. None of the patients subsequently developed significant liver damage. At the dose used for the treatment of paracetamol poisoning, N-acetylcysteine has no hepatotoxic effects.