The probable role of insulin resistance and SIRT1 proteins in the Alzheimer's disease.

OBJECTIVE: Recent evidence suggests that insulin resistance may play an important role in the pathogenesis of Alzheimer's disease (AD). In this study, the probable role of insulin resistance in the pathogenesis of AD was investigated in patients with Type 2 Diabetes Mellitus (T2DM). METHODS: Serum amyloid beta (Aß) (1-42), insulin like growth factor-1 (IGF-1), sirtuin1 (SIRT1) and leptin protein levels were measured in serum samples of control (n = 26), probable AD (n = 26), and probable AD+T2DM patients (n = 12) using ELISA method. Mini mental state examination (MMSE) was performed to the patient and control groups. RESULT: Serum IGF-1 significantly increased in the probable AD+T2DM group as compared to the control and probable AD groups (p ˂ 0.05). The levels of serum leptin significantly decreased in the probable AD and AD+T2DM groups as compared to the control (p ˂ 0.05). There were no statistically significant differences in serum Aß (1-42) and SIRT1 levels among groups (p > 0.05). CONCLUSION: The significant decrease in serum leptin levels in AD patients may indicate that it may be a therapeutic marker in AD. The level of serum Aß peptide and SIRT1 proteins can vary depending on the stage of the disease. Therefore, this study should be supported by more comprehensive studies in terms of the number of patients in advanced stage (Tab. 1, Fig. 4, Ref. 29).

Thyroid hormones-mediated effects of insulin on antioxidant enzymes from diabetic rat hearts.

Free radicals, oxidative stress, and antioxidants have become commonly used terms in modern discussion of disease mechanisms. Accumulation of evidence suggests that toxic oxygen-derived reactive free radicals (superoxide, peroxide and hydroxyl radicals) play a crucial role in etiology of diabetes and its complication. Thus, it was aimed to determine the role of thyroid hormones in reversal of antioxidatant enzyme activities and lipid peroxidation alterations observed in experimentally induced diabetic rat hearts. The present study investigates the antioxidant enzyme activities such as SOD, CAT, GSH-Px and lipid peroxidation products in cardiac tissues of streptozotosin (STZ)-induced diabetic rats before and after thyroidectomy. Our results showed that CAT, GPx enzyme activities and FOX, MDA levels were increased (p<0.05) during diabetes, hypothyroidism and hypothyroidism with diabetes, which can be regulated in different percentages with treatment of insulin and various doses of thyroid hormone ((p<0.05). In conclusion, in this study, the possible contribution of thyroid hormones to the insulin effect of normalizing the induced diabetic changes in cardiac tissue and serum of rat has been seen (Tab. 5, Ref. 32).

Defective acidification in human breast tumor cells and implications for chemotherapy.

Multidrug resistance (MDR) is a significant problem in the treatment of cancer. Chemotherapeutic drugs distribute through the cyto- and nucleoplasm of drug-sensitive cells but are excluded from the nucleus in drug-resistant cells, concentrating in cytoplasmic organelles. Weak base chemotherapeutic drugs (e.g., anthracyclines and vinca alkaloids) should concentrate in acidic organelles. This report presents a quantification of the pH for identified compartments of the MCF-7 human breast tumor cell line and demonstrates that (a) the chemotherapeutic Adriamycin concentrates in acidified organelles of drug-resistant but not drug-sensitive cells; (b) the lysosomes and recycling endosomes are not acidified in drug-sensitive cells; (c) the cytosol of drug-sensitive cells is 0.4 pH units more acidic than the cytosol of resistant cells; and (d) disrupting the acidification of the organelles of resistant cells with monensin, bafilomycin A1, or concanamycin A is sufficient to change the Adriamycin distribution to that found in drug-sensitive cells, rendering the cell vulnerable once again to chemotherapy. These results suggest that acidification of organelles is causally related to drug resistance and is consistent with the hypothesis that sequestration of drugs in acidic organelles and subsequent extrusion from the cell through the secretory pathways contribute to chemotherapeutic resistance.

Evaluation of superoxide dismutase enzyme activity of polymorphonuclear leucocytes, erythrocytes and thrombocytes in patients with chronic myeloproliferative disorders.

This study aimed to investigate the activity of the antioxidant enzyme superoxide dismutase (SOD) in the three main cell types in chronic myeloproliferative disorders (CMPD) patients, i.e. polymorphonuclear leucocytes (PMNLs), erythrocytes and thrombocytes, prior to therapy. Patients with reactive neutrophilia (RN) and healthy volunteers were included as controls. The SOD activity of PMNLs was significantly decreased in CMPD and RN patients compared with healthy volunteers, whereas the SOD activity of erythrocytes was found to be significantly increased in patients with CMPD and RN compared with healthy volunteers. There were no significant differences in the SOD activity of thrombocytes between CMPD patients, RN patients or healthy volunteers. This study indicates that the activity of the SOD enzyme in two cell types is different in CMPD patients compared with healthy subjects. Thus, SOD activity may be altered dependent on cell type and due to specific cell function.

Multiple proteins interact with the fushi tarazu proximal enhancer.

The expression of the Drosophila segmentation gene fushi tarazu (ftz) is controlled at the level of transcription. The proximal enhancer, located approximately 3.4 kb upstream of the transcription start site, directs lacZ fusion gene expression in a ftz-like seven-stripe pattern in transgenic fly embryos. We have taken a biochemical approach to identify DNA-binding proteins that regulate ftz gene expression through the proximal enhancer. DNase I footprinting and methylation interference experiments with staged Drosophila embryo nuclear extracts identified nine protein binding sites in the proximal enhancer. Ten different sequence-specific DNA-binding complexes that interact with eight of these sites were identified. Some interact with multiple sites, while others bind to single sites in the enhancer. Two of the complexes that interact with multiple sites appear to contain the previously described ftz regulators, FTZ-F1 and TTK/FTZ-F2. These in vitro studies allowed us to narrow down the proximal enhancer to a 323-bp DNA fragment that contains all of the protein binding sites. Expression directed by this minimal enhancer element in seven ftz-like stripes in transgenic embryos is identical to that directed by the full-length enhancer. Internal deletions of several sites abolish reporter gene expression in vivo. Thus, the ftz proximal enhancer, like other cell-type-specific eukaryotic enhancers, interacts with an array of proteins that are expected to mediate the establishment, maintenance, and repression of transcription of the ftz gene in seven stripes in the developing embryo.

The effect of the sulfonylurea glyburide on glutathione-S-transferase and glucose-6-phosphate dehydrogenase in streptozotocin-induced diabetic rat liver.

Free radical-induced lipid peroxidation has been associated with numerous disease processes including diabetes mellitus. Glutathione-S-transferase (GST) catalyses the conjugation of glutathione with a variety of organic peroxides to form more water-soluble compounds. Glucose-6-phosphate dehydrogenase (G6PDH) is essential to control intracellular reductive potential by increasing glutathione intracellular levels, which in turn decrease the amount of reactive oxygen species. Glyburide decreases glucose production and enhances insulin action in liver. The aim of this study was to examine the effects of glyburide on the antioxidant enzyme activities in the liver tissue of diabetic rat. We investigated the activities of GST and G6PDH in the liver of both control and streptozotocin-induced diabetic rats. Forty male albino rats were included in this study. Liver GST and G6PDH activities decreased significantly in five-week diabetic rats (p<0.001 and p<0.001 respectively) compared to controls and glyburide therapy restored these activities (p<0.001 for GST and p<0.001 for G6PDH). Elevations of hepatic antioxidant enzymes with glyburide administration suggest that glyburide may directly alter hepatic enzyme activities.

Insulin-like and insulin-enhancing effects of the sulfonylurea glyburide on rat adipose glycogen synthase.

The effects of long-term exposure of cultured rat adipose tissue to glyburide were examined on glycogen synthase activity. Glyburide alone caused an increase in the activity ratio (low glucose-6-P/high glucose-6-P) of glycogen synthase, and enhanced insulin's activation of the enzyme. The glyburide effects were time dependent, requiring fat pieces to be exposed to the drug for at least 10-20 h. The glucose concentration in the culture medium was also important: optimal concentrations of glucose were 10-20 mM. Glyburide acted to shift the insulin dose-response curve to the left by a factor of 2.5, but did not enhance the effects of maximal concentrations of the hormone. The Ka of the glyburide effects was about 2.0 microM. If glucose was omitted during the 20-min incubation with or without insulin, the increase in the activity ratio of glycogen synthase by glyburide was unaffected, but the enhancement of insulin action was reduced. Because these data indicate that glyburide's actions are glucose dependent, we propose that the sulfonylurea is probably acting to increase glucose transport, thus allosterically increasing the activity of a synthase phosphatase by glucose-6-P. The net result of this would be increased dephosphorylation and activation of glycogen synthase.

Effect of the sulfonylurea glyburide on superoxide dismutase activity in alloxan-induced diabetic rat hepatocytes.

In the present study we administrated glyburide (glibenclamide) to type 2 (NIDDM) diabetic rats and determined the effect of such treatment on liver superoxide dismutase (SOD) activity. Hepatic SOD activity was significantly reduced in diabetic animals. Glyburide treatment of diabetic rats for 4 weeks corrected the changes observed in diabetic liver. In addition, blood glucose levels of untreated diabetic rats decreased following glyburide treatment. Administration of glyburide to diabetic rats reversed the diabetes-induced changes, suggesting that glyburide may directly increase liver SOD enzyme activity.

Temporal variation in hepatic superoxide dismutase activity in mice.

Circadian variations in superoxide dismutase (SOD) activity were determined in liver homogenates of Balb-C mice that were synchronized under controlled environmental conditions with 12 h light:12 h dark. The activity of hepatic SOD exhibited a significant circadian rhythm, with a minimum at 01:00 h and a maximum at 10:00-13:00 h. It is concluded that fluctuations in hepatic SOD activity render mice more susceptible to the toxic effects of reactive oxygen radicals at particular times of the day.

The effects of the sulfonylurea glyburide on glutathione peroxidase, superoxide dismutase and catalase activities in the heart tissue of streptozotocin-induced diabetic rat.

Oxygen free radicals have been suggested to be a contributory factor in diabetes complications. The aim of this study was to examine the effects of glyburide on the antioxidant enzyme activities in the heart tissue of diabetic rats. We investigated the activities of antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) in the hearts of both control and streptozotocin-induced diabetic rats. In the heart of diabetic rats, the activity of total superoxide dismutase decreased significantly (p < 0.005), whereas the activity of catalase and glutathione peroxidase increased to a large extent (p < 0.0001 and p = 0.05, respectively) at the end of the fourth week compared with the control group. Glyburide treatment of diabetic rats for 4 weeks corrected the changes observed in diabetic heart. In addition, blood glucose levels of untreated diabetic rats decreased following the glyburide treatment. These results demonstrate that the sulfonylurea glyburide is capable of exerting direct insulin-like effect on heart superoxide dismutase, catalase and glutathione peroxidase activities of diabetic rats in vivo.

Effects of obstructive jaundice on the antioxidative capacity of human red blood cells.

Transient haemolysis and shortened erythrocyte lifespan are reported in association with extrahepatic biliary tract obstruction. An increase in lipid peroxidation has been noted as evidence of oxidative damage in red cells due to cholestasis. The influence of surgical relief on the antioxidative capacity of the erythrocyte is less well defined. The ability of erythrocytes to regenerate the antioxidative capacity after side-to-side choledo-choduodenostomy was assessed by measuring the two principal antioxidant enzymes, namely superoxide dismutase (SOD) and catalase (CAT), as well as the glutathione (GSH) content in the red blood cells (RBC) taken from patients with obstructive jaundice. A comparison of patients and healthy volunteers revealed a consistent decrease in enzyme activities (pSOD = 0.01, pCAT = 0.0002) and glutathione concentrations (PGSH = 0.0000) in cholestatic patients. Statistical analysis proved a clear correlation between the surgical relief of common bile duct obstruction and restored antioxidative capacity of red cells. These observations suggest that the red cells from patients with multiple common bile duct stones almost completely regenerated their antioxidative capacity four weeks after side-to-side choledochoduodenostomy.

Liver glycogen in gangrenous intestinal obstruction.

Considerable drops in liver glycogen contents of guinea pigs suffering from gangrenous intestinal obstruction were recorded in regard to control values (P less than 0.001). An additional experiment was conducted by using carbontetrachloride (CT) to determine whether or not the shortening of survival related to liver glycogen content in animals with strangulation obstruction. The mean tissue glycogen content in the sham-operated group was 816.2 +/- 13.3 micrograms/g, w. wt., whereas in the CT-treated group it was 73.5 +/- 11.0 micrograms/g w. wt. This difference is highly significant (P less than 0.001). The mean survival was 54.4 +/- 5.8 h and 21.9 +/- 5.5 h in animals with gangrenous intestinal obstruction before and after CT treatment, respectively. These results suggested that the liver glycogen depletion was a significant factor in decreasing the survival time of guinea pigs with strangulation obstruction.

Effect of the sulfonylurea glyburide on glycogen synthase activity in alloxan-induced diabetic rat adipocytes.

1. The effect of glyburide (glibenclamide) treatment in vivo on the adipose tissue glycogen synthase activity of type II diabetic rats has been studied. 2. Three week treatment of diabetic animals with glyburide (5 mg/kg orally, in saline) increased adipose glycogen synthase activity and decreased blood glucose levels. 3. These results demonstrate that the sulfonylurea glyburide is capable of exerting direct insulin-like effect on adipose glycogen-synthase activity of type II diabetic rats in vivo.

Effect of the sulfonylurea glyburide on glycogen synthesis in alloxan-induced diabetic rat hepatocytes.

1. The effect of glyburide (glibenclamide) treatment on the liver glycogen levels of diabetic rats have been studied. 2. 3 weeks treatment with glyburide (5 mg/kg, orally) increased liver glycogen and decreased blood glucose levels. 3. The results of this study demonstrated that the sulfonylurea, glyburide is capable of exerting direct insulin-like effects on liver glycogen values in vivo.

An investigation into the effect of sulfonylurea glyburide on glutathione peroxidase activity in streptozotocin-induced diabetic rat muscle tissue.

1. Four weeks of glyburide (glibenclamide) treatment (5 mg/kg, orally) was administered in type II diabetic rats and the effect of such treatment was determined on muscle glutathione peroxidase (GPx) activity. 2. GPx activity was measured by a spectrophotometric method in which its activity was coupled to the oxidation of NADPH by glutathione reductase. 3. No statistically significant difference was found in muscle GPx activity between diabetic rats and controls. 4. There was a significant difference in GPx activity between glyburide-treated diabetic and nontreated diabetic groups and between glyburide-treated control and control groups. 5. The results of this study demonstrated that diabetes did not significantly alter skeletal muscle GPx activity in diabetic rats. However, glyburide may be an effective antioxidant agent in addition to its expected insulin-like effects.

Tamoxifen inhibits acidification in cells independent of the estrogen receptor.

Tamoxifen has been reported to have numerous physiological effects that are independent of the estrogen receptor, including sensitization of resistant tumor cells to many chemotherapeutic agents. Drug-resistant cells sequester weak base chemotherapeutics in acidic organelles away from their sites of action in the cytosol and nucleus. This work reports that tamoxifen causes redistribution of weak base chemotherapeutics from acidic organelles to the nucleus in drug-resistant cells. Agents that disrupt organelle acidification (e.g., monensin, bafilomycin A1) cause a similar redistribution. Measurement of cellular pH in several cell lines reveals that tamoxifen inhibits acidification of endosomes and lysosomes without affecting cytoplasmic pH. Similar to monensin, tamoxifen decreased the rate of vesicular transport though the recycling and secretory pathways. Organellar acidification is required for many cellular functions, and its disruption could account for many of the side effects of tamoxifen.

Effect of the sulfonylurea glyburide on glutathione and glutathione peroxidase activity in alloxan-induced diabetic rat hepatocytes.

1. The effect of glyburide treatment on glutathione peroxidase activity and glutathione levels of non-insulin diabetic rats has been studied. 2. Hepatic glutathione and glutathione peroxidase concentrations were significantly reduced in diabetic animals. 3. Glyburide treatment of diabetic rats for 4 weeks corrected the changes on the glutathione levels observed in diabetic liver. 4. High blood glucose levels of untreated diabetic rats were decreased following glyburide treatment as well. 5. Administration of glyburide to diabetic rats reversed the diabetes-induced changes suggesting that glyburide may directly increase liver glutathione concentrations.

The relationship between erythrocyte superoxide dismutase activity and plasma levels of some trace elements (Al, Cu, Zn) of dialysis patients.

1. The effect of erythropoietin and some trace elements on superoxide dismutase (SOD) activity of dialysis patients have been studied. 2. SOD activity of dialysis patients was found to be decreased. 3. The effect of erythropoietin on SOD activity was not found in vitro. 4. Plasma and erythrocyte aluminum increased in dialysis patients, but no significant change in plasma copper was found. 5. Plasma zinc levels of dialysis patients were found to be decreased. 6. These results suggest that inhibition of erythrocyte SOD activity of dialysis patients may contribute to their anemia.

The effect of short term lithium treatment on the leukocyte, liver and muscle carbohydrate metabolism of guinea-pigs.

1. The effect of lithium treatment on the leukocyte, liver and muscle glycogen levels of guinea-pigs has been studied. 2. A 4-week treatment with lithium chloride (5 mmol/l i.p. in saline) increased leukocyte, liver and muscle glycogen and decreased blood glucose levels. 3. These results strongly suggest that a lithium-induced insulin-like effect may be related to the long term effect.

Effect of lithium on gastro-intestinal complications in alloxan-diabetic rats.

1. Decreased beta-adrenergic and serotonergic responses have been reported in gastro-intestinal tract of experimentally diabetic rats. Effects of lithium on the decreased beta-adrenergic and serotonergic responsiveness of the gastro-intestinal tract due to diabetes were investigated using gastric fundus strips and proximal duodenum from alloxan diabetic rats. 2. A 6-day treatment with lithium chloride (2 mEq/kg i.p. in saline) normalized the decreased gastro-intestinal responses of the alloxan-diabetic rats, whereas the lithium treatment did not affect the elevated blood glucose levels due to experimental diabetes. 3. Furthermore, the lithium treatments of control and alloxan-diabetic rats did not alter the relaxing effect of manganese chloride on the isolated duodenum. 4. These results strongly suggest that the improving effect of lithium is not related to adenylate cyclase activation and may be as a consequence of its direct action on the diabetic gastro-intestinal smooth muscles.