The impact of type I diabetes on rat liver gamma-glutamyltranspeptidase

Plasma Levels of Cell-Free Apoptotic DNA Ladders and Gamma-Glutamyltranspeptidase (GGT) in Diabetic Children

The plasma levels of apoptotic DNA ladders (i.e., apoptosemia) and γ-glutamyltranspeptidase (GGT) in diabetic outpatients and rats were investigated. Apoptotic DNA ladders were detected in plasma from 26.8% of type 1 (T1) and 18.5% of type 2 (T2) diabetic children 1–20 years of age, 25.7% of hospitalized children and 35.7% of adult RA outpatients, but in only 3.5% of adult pre-op patients. Plasma from 7.7% of young streptozotocin-induced diabetic but not control rats contained apoptotic DNA ladders. Apoptosemia was detected more often in male T1 (31%) and T2 (30.8%) diabetic outpatients than in female T1 (20.8%) and T2 (15.4%) diabetic outpatients. GGT in apoptosemic plasma was significantly higher than in nonapoptosemic plasma from T1 ( P = 0.001) but not T2 diabetic children. The highest amounts of apoptotic DNA were detected most often in diabetic children ≥14 years of age. In vitro study results suggest that cell-free apoptotic DNA ladders appear prior to an increase in GGT activity in serum from human blood incubated at 37°C. The results suggest that 24.7% of plasma samples from diabetic children contained apoptotic DNA ladders, the incidence and amounts of apoptotic DNA ladders were higher in the older diabetic children, and GGT was elevated in apoptosemic T1 diabetic children ( P = 0.01). The results indicate that “silent” apoptosemia occurs in T1 and T2 diabetic children and suggest elevated GGT in diabetic children could be due to release from apoptotic cells.

Combined therapy with metformin and insulin attenuates systemic and hepatic alterations in a model of high-fat diet-/streptozotocin-induced diabetes

In this study we have explored the pathogenesis of the hepatic alterations which occur in diabetes and the modulation of these complications by the combination of metformin adjunct treatment and insulin monotherapy. For this purpose, diabetic rats were treated with insulin (DM + Ins) or metformin plus insulin (DM + Met + Ins). Biochemical and cardiometabolic parameters were analysed by spectrophotometry. Intravital microscopy was used to study the hepatic microcirculation. In the liver tissue, real-time PCR was used to analyse oxidative stress enzymes, inflammatory markers and receptors for advanced glycation end products (AGE) (RAGE) gene expression. Lipid peroxidation was assessed by thiobarbituric acid reactive species (TBARs) analyses. AGE deposition and RAGE protein expression were studied by fluorescence spectrophotometry and Western blot respectively. Body weight, %HbA1c , urea, total proteins and oxidative stress parameters were found to be similarly improved by insulin or Met + Ins treatments. On the other hand, Met + Ins treatment showed a more pronounced effect on fasting blood glucose level than insulin monotherapy. Fructosamine, uric acid, creatinine, albumin and amylase levels and daily insulin dose requirements were found to be only improved by the combined Met + Ins treatment. Liver, renal and pancreatic dysfunction markers were found to be more positively affected by metformin adjunct therapy when compared to insulin treatment. Liver microcirculation damage was found to be completely protected by Met + Ins treatment, while insulin monotherapy showed no effect. Our results suggest that oxidative stress, microcirculatory damage and glycated proteins could be involved in the aetiology of liver disease due to diabetes. Additionally, metformin adjunct treatment improved systemic and liver injury in induced diabetes and showed a more pronounced effect than insulin monotherapy.

Zebularine induces long-term survival of pancreatic islet allotransplants in streptozotocin treated diabetic rats

BACKGROUND

Coping with the immune rejection of allotransplants or autologous cells in patients with an active sensitization towards their autoantigens and autoimmunity presently necessitates life-long immune suppressive therapy acting on the immune system as a whole, which makes the patients vulnerable to infections and increases their risk of developing cancer. New technologies to induce antigen selective long-lasting immunosuppression or immune tolerance are therefore much needed.

METHODOLOGY/PRINCIPAL FINDINGS

The DNA demethylating agent Zebularine, previously demonstrated to induce expression of the genes for the immunosuppressive enzymes indolamine-2,3-deoxygenase-1 (IDO1) and kynureninase of the kynurenine pathway, is tested for capacity to suppress rejection of allotransplants. Allogeneic pancreatic islets from Lewis rats were transplanted under the kidney capsule of Fischer rats previously made diabetic by a streptozotocin injection (40 mg/kg). One group was treated with Zebularine (225 mg/kg) daily for 14 days from day 6 or 8 after transplantation, and a control group received no further treatment. Survival of the transplants was monitored by blood sugar measurements. Rats, normoglycemic for 90 days after allografting, were subjected to transplant removal by nephrectomy to confirm whether normoglycemia was indeed due to a surviving insulin producing transplant, or alternatively was a result of recovery of pancreatic insulin production in some toxin-treated rats. Of 9 Zebularine treated rats, 4 were still normoglycemic after 90 days and became hyperglycemic after nephrectomy. The mean length of normoglycemia in the Zebularine group was 67±8 days as compared to 14±3 days in 9 controls. Seven rats (2 controls and 5 Zebularine treated) were normoglycemic at 90 days due to pancreatic recovery as demonstrated by failure of nephrectomy to induce hyperglycemia.

CONCLUSIONS/SIGNIFICANCE

Zebularine treatment in vivo induces a long-lasting suppression of the immune destruction of allogeneic pancreatic islets resulting in protection of allograft function for more than 10 weeks after end of treatment.

Therapeutic potential of some plant extracts used in Turkish traditional medicine on streptozocin-induced type 1 diabetes mellitus in rats

Diabetes mellitus (DM) is known to impair many physiological functions. Some reports claim that medicinal plants can reduce these alterations caused by DM. The aim of this study was to investigate the therapeutic potential of aqueous-methanol extracts of Urtica dioica, Thymus vulgaris (TV), Myrtus communis (MC), Scolymus hispanicus (SH) and Cinnamomun zeylanicum (CZ) on streptozotocin (STZ)-induced type 1 DM in rats. Diabetes was induced via a single i.p. injection of STZ (65 mg/kg body weight). After 1 week to allow for development of diabetes, each plant extract was administered to diabetic rats separately at a dose of 100 mg/kg body weight daily for 28 days. The results showed that only SH extract significantly (P < 0.05) amended fasting blood glucose level. The lipid profile was ameliorated especially by supplementations of TV, MC and CZ extracts. Almost all plant extract treatments markedly (P < 0.05) increased reduced glutathione content and decreased lipid peroxidation levels of erythrocyte, plasma, retina and lens tissues. They also significantly (P < 0.05) amended erythrocyte catalase activity, levels of marker serum enzymes (except amylase), urea and blood urea nitrogen when compared to diabetic rats treated with nothing. Furthermore, none of the plant extracts counteracted body weight loss of diabetic rats. Our data revealed that the aforementioned plant extracts have remarkable potential to counteract DM-caused alterations, probably through their antioxidant and free radical-defusing effects.

Brown alga Ecklonia cava attenuates type 1 diabetes by activating AMPK and Akt signaling pathways

The antidiabetic therapeutic effect of Ecklonia cava, a brown alga, was investigated using streptozotocin-induced type 1 diabetes mellitus rats and C2C12 myoblasts. The methanol extract of E. cava (ECM), having a strong radical scavenging activity, significantly reduced plasma glucose level and increased insulin concentration in type 1 diabetes mellitus rats. Moreover, the elevation of plasma ALT in diabetic rats was dramatically restored near to normal range by the treatment of ECM, whereas AST level was not meaningfully altered in any group throughout the experiment. The characteristic indications of diabetes, such as polyphagia and polydipsia, were greatly improved by ECM treatment as well. The mechanism of action of ECM appears to be, at least partially, mediated by the activation of both AMP-activated protein kinase/ACC and PI-3 kinase/Akt signal pathways. Taken together, the present results suggest that E. cava has both in vivo and in vitro antidiabetic effects.

Diabetes, oxidative stress, and antioxidants: a review

Increasing evidence in both experimental and clinical studies suggests that oxidative stress plays a major role in the pathogenesis of both types of diabetes mellitus. Free radicals are formed disproportionately in diabetes by glucose oxidation, nonenzymatic glycation of proteins, and the subsequent oxidative degradation of glycated proteins. Abnormally high levels of free radicals and the simultaneous decline of antioxidant defense mechanisms can lead to damage of cellular organelles and enzymes, increased lipid peroxidation, and development of insulin resistance. These consequences of oxidative stress can promote the development of complications of diabetes mellitus. Changes in oxidative stress biomarkers, including superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, glutathione levels, vitamins, lipid peroxidation, nitrite concentration, nonenzymatic glycosylated proteins, and hyperglycemia in diabetes, and their consequences, are discussed in this review. In vivo studies of the effects of various conventional and alternative drugs on these biomarkers are surveyed. There is a need to continue to explore the relationship between free radicals, diabetes, and its complications, and to elucidate the mechanisms by which increased oxidative stress accelerates the development of diabetic complications, in an effort to expand treatment options.

Sucrose feeding effects inhibition of gamma-glutamyltranspeptidase in the liver of the rat: possible mediation by thyroid hormone

The effect of sucrose on Fischer 344 rat liver gamma-glutamyltranspeptidase (gammaGT) was studied: in adults fed sucrose for 3 weeks; and rats exposed to sucrose from the 18th day of gestation to the 40th day after birth. Rats fed regular rodent chow served as controls. Sucrose caused mild lipemia; and in the liver an increase in size and fat build-up without damage. In adult sucrose-fed rats, compared to controls, plasma glucose levels were increased: 1.12-, 1.40- and 1.13-fold after 24, 48h and 3 week consumption of sucrose, respectively. Insulin levels were unaltered for the first week of sucrose consumption but increased from control levels: 16% at 1 week, and 2.0-fold at 3 weeks. The T3 levels were comparable to control levels 24h after the sucrose was started and were increased: 1.22-, 1.13- and 1.12-fold at 48h, 1 and 3 weeks, respectively. The T4 levels were comparable at all time points between sucrose-fed and control rats. Liver gammaGT activity exhibited a steady decrease from control levels: after 24, 48h, 1 and 3 weeks of sucrose feeding the decrease was 5, 8, 21 and 37%, respectively in homogenates; and 10, 17, 24 and 41%, respectively in plasma membranes. Perinatal sucrose exposure effected in 40-day-old rats, compared controls: a 1.09-fold increase in plasma glucose; no change in plasma insulin; an increase of 1.15- and 1.39-fold in plasma levels of total and free T3, respectively; a decrease of 20 and 14% in plasma levels of total and free T4, respectively. gammaGT activity was decreased in liver plasma membranes isolated from sucrose-exposed rats relative to those of control: 80% in the male; 82% in the female. Relative specific activities of gammaGT were the same in both males: 15.4 and 16.1 in control and sucrose-exposed male rats, respectively; and females: 14.1 and 15.4 in control and sucrose-exposed female rats, respectively. gammaGT was 2-fold higher in the livers of female relative to male rats in sucrose-exposed and control groups. Kidney gammaGT activities were the same in control and sucrose-exposed rats. The involvement of T3 in the sucrose-induced decrease in liver gammaGT is discussed.

Gamma glutamyl transferase

Serum gamma-glutamyl transferase (GGT) has been widely used as an index of liver dysfunction and marker of alcohol intake. The last few years have seen improvements in these areas and advances in understanding of its physiological role in counteracting oxidative stress by breaking down extracellular glutathione and making its component amino acids available to the cells. Conditions that increase serum GGT, such as obstructive liver disease, high alcohol consumption, and use of enzyme-inducing drugs, lead to increased free radical production and the threat of glutathione depletion. However, the products of the GGT reaction may themselves lead to increased free radical production, particularly in the presence of iron. There have also been important advances in the definition of the associations between serum GGT and risk of coronary heart disease, Type 2 diabetes, and stroke. People with high serum GGT have higher mortality, partly because of the association between GGT and other risk factors and partly because GGT is an independent predictor of risk. This review aims to summarize the knowledge about GGT's clinical applications, to present information on its physiological roles, consider the results of epidemiological studies, and assess how far these separate areas can be combined into an integrated view.

Characterization of gamma-glutamyltranspeptidase in the liver of the frog: 3. Response to freezing and thawing in the freeze-tolerant wood frog Rana sylvatica

The freeze tolerant wood frog Rana sylvatica was studied to determine the impact of the freezing and thawing of this frog on the activity of gamma-glutamyltranspeptidase in the liver. On exposure to -2.5 degrees C, for 1, 12 and 24 h, frogs were found to be cool, covered with ice crystals and frozen, respectively. Thawing for 24 h at 4 degrees C recovered the frogs completely. A 45 per cent decrease in the liver weight: body weight ratio was notable after 1 h at -2.5 degrees C, suggestive of an early hepatic capacitance response. A glycemic response to freezing was observed: blood glucose levels exhibited a 55 per cent decrease after 1 h at -2.5 degrees C on cooling; a 10.5-fold increase after 12 h at -2.5 degrees C on the initiation of freezing; and a 22-fold increase after 24 h at -2.5 degrees C in the fully frozen state. Blood glucose levels remained elevated four-fold in the thawed state. Plasma insulin levels were increased twofold in the frozen state and 1.8-fold in the thawed state, while plasma ketone levels were increased 1.8-fold in the frozen state and 1.5-fold in the thawed state. Plasma total T3 levels were decreased by 22 per cent in the frozen state and normalized on thawing. In homogenates and plasma membranes isolated from the livers of Rana sylvatica, the activity of gamma-glutamyltrans-peptidase was found to be elevated at all stages of the freeze-thaw process. After 1, 12 and 24 h at -2.5 degrees C, activities were increased 2.5-, 2.3-, 2.4-fold respectively in the homogenates and 2.5-, 2.2-, 2.4-fold respectively in the plasma membranes. After thawing, activities were still increased 1.9-fold in both homogenates and plasma membranes. In homogenates prepared from the kidneys of Rana sylvatica, the activity of gamma-glutamyltranspeptidase was increased 1.4-fold after 1 h at -2.5 degrees C after which it returned to normal. The role of thyroid hormone in producing the increase in gamma-glutamyltranspeptidase in the liver of Rana sylvatica in response to freezing is discussed as is the significance of the enzyme increase in terms of hepatic cytoprotection and freeze tolerance.