bis(1-hydroxy-2-2-6-6-tetramethyl-4-piperidinyl)decandioate and 3-nitrotyrosine

We previously reported that in a diabetes mouse model, characterised by moderate hyperglycaemia and reduced beta-cell mass, the radical scavenger bis(1-hydroxy-2,2,6,6-tetramethyl-4-piperidinyl)decandioate di-hydrochloride (IAC), a non-conventional cyclic hydroxylamine derivative, improves metabolic alterations by counteracting beta-cell dysfunction associated with oxidative stress. The aims of this study were to ascertain whether the beneficial effects of IAC treatment could be maintained after its discontinuation and further elucidate the underlying mechanisms. Diabetes was induced in C57Bl/6J mice by streptozotocin (STZ) and nicotinamide (NA) administration. Diabetic mice were treated for 7 weeks with various doses of IAC (7.5, 15, or 30 mg/kg b.w./die i.p.) and monitored for additional 8 weeks after suspension of IAC. Then, pancreatic tissue was used for determination of beta-cell mass by immunohistochemistry and beta-cell ultrastructural analysis. STZ-NA mice showed moderate hyperglycaemia, glucose intolerance and reduced beta-cell mass (25% of controls). IAC-treated STZ-NA mice (at both doses of 15 and 30 mg/kg b.w.) showed long-term reduction of hyperglycaemia even after discontinuation of treatment, attenuation of glucose intolerance and partial preservation of beta-cell mass. The lowest IAC dose was much less effective. Plasma nitrotyrosine levels (an oxidative stress index) significantly increased in untreated diabetic mice and were lowered upon IAC treatment. At ultrastructural level, beta cells of IAC-treated diabetic mice were protected against degranulation and mitochondrial alterations. In the STZ-NA diabetic mouse model, the radical scavenger IAC induces a prolonged reduction of hyperglycaemia associated with partial restoration of beta-cell mass and function, likely dependent on blockade of oxidative stress-induced damaging mechanisms.

Topics: Animals; Blood Glucose; Diabetes Mellitus, Experimental; Free Radical Scavengers; Glucose Tolerance Test; Hyperglycemia; Immunohistochemistry; Insulin; Insulin-Secreting Cells; Male; Mice; Mice, Inbred C57BL; Microscopy, Electron; Molecular Structure; Niacinamide; Piperidines; Streptozocin; Tyrosine

Chronic exposure to high free fatty acids (FFA) can lead to irreversible damage of beta-cell accounting for impaired insulin secretion. Multiple mechanisms concur in generating the damage, but activation of oxidative stress may contribute to the final toxic effect. To better understand the phenomenon of lipotoxicity in human beta-cells, we evaluated the effects of 24-h pre-culture with 1.0 mmol/l FFA on the function, survival and mRNA expression of several enzymes involved in the generation and scavenging of reactive oxygen species (ROS).. Human islets, prepared by collagenase digestion and density gradient purification from 9 pancreases of multiorgan donors, were incubated for 24-h in the presence 1.0 mmol/l long-chain mixture (oleate:palmitate, 2:1) FFA, with or without 100 micromol/l IAC, a non-peptidyl low molecular weight radical scavenger. At the end of incubation period, insulin secretion was measured by static incubation, and mRNA expression of insulin, Cu/Zn-SOD, Mn-SOD, Catalase, Glutathione peroxidase (GSH-px) and HO-1 by quantitative Real-Time RT-PCR. Nitrotyrosine levels were determined by an ELISA technique.. As compared to control incubation (Ctrl, no FFA), exposure to FFA was associated with impaired insulin release and reduced insulin mRNA expression. The presence of IAC in the incubation medium increased insulin release significantly and prevented changes in mRNA expression. Exposure to FFA was associated with oxidative stress as indicated by a significant accumulation of nitrotyrosine and IAC restrained such an increase. mRNA expression of Cu/Zn-SOD, Mn-SOD, Catalase, GSH-Px, and HO-1 were all modified after FFA exposure. These changes were partially prevented in the presence of IAC.. In human islets 24-h exposure to high FFA causes oxidative stress associated with changes of several enzymes involved in ROS scavenging. These effects were prevented by the use of an antioxidant molecule.

Topics: Antioxidants; Apoptosis; bcl-2-Associated X Protein; Catalase; Cell Survival; Cytoprotection; Fatty Acids; Free Radical Scavengers; Gene Expression Regulation; Glucokinase; Glucose Transporter Type 2; Glutathione Peroxidase; Humans; Insulin; Islets of Langerhans; Molecular Weight; Oxidative Stress; Peptides; Piperidines; RNA, Messenger; Superoxide Dismutase; Tyrosine

We examined a possible protective effect of the nonpeptidyl low molecular weight radical scavenger IAC [bis(1-hydroxy-2,2,6,6-tetramethyl-4-piperidinyl)decanedioate di-hydrochloride] on isolated human islet cells against isolation and culture oxidative stress. Islets isolated from pancreases of nondiabetic multiorgan donors by collagenase digestion were purified by density gradient centrifugation. After the isolation, islets were either exposed or not exposed for 7 days to 10 micromol/L IAC. We found that IAC markedly reduced oxidative stress and ameliorated islets function. These results suggest that the use of IAC could be an interesting pharmacological approach for the treatment of the islets before transplantation.

Topics: Adult; Aged; Antioxidants; Catalase; Cell Culture Techniques; Cells, Cultured; Esters; Female; Free Radical Scavengers; Gene Expression Regulation, Enzymologic; Humans; Hypoglycemic Agents; Islets of Langerhans; Male; Middle Aged; Molecular Weight; Oxidative Stress; Piperidines; Superoxide Dismutase; Tyrosine

We have previously established a nonobese diabetes mouse model characterized by moderate hyperglycemic levels, like those usually occurring in human type 2 diabetes. As oxidative stress is considered a major mechanism of progressive beta-cell damage in diabetes, we tested in this model the protective effects of a new low-molecular-weight antioxidant, namely, bis(1-hydroxy-2,2,6,6-tetramethyl-4-piperidinyl)decandioate dihydrochloride (IAC).. Diabetes was induced in C57Bl/6J mice by streptozotocin (STZ) and nicotinamide (NA) administration. Two weeks later, STZ-NA mice were treated for 5 weeks with different doses of IAC (15 or 30 mg/kg per day intraperitoneally) and monitored for glycemia, insulinemia, glucose tolerance, and pancreatic insulin content.. Streptozotocin-NA mice showed moderate hyperglycemia, hypoinsulinemia, glucose intolerance, growth impairment, and markedly reduced pancreatic insulin content (22% of controls). IAC-treated STZ-NA mice showed clear-cut reduction of hyperglycemia and attenuation of glucose intolerance, associated to higher residual pancreatic insulin content with respect to untreated diabetic animals. Plasma nitrotyrosine levels (an index of oxidative stress), enhanced 3-fold in diabetic mice, were significantly reduced by IAC treatment. Significant correlations were found between plasma nitrotyrosine values and either blood glucose levels or pancreatic insulin content.. In the STZ-NA diabetic mouse model, the new antioxidant, IAC, improves diabetic metabolic alterations, likely by counteracting beta-cell dysfunction and loss associated with oxidative stress.

Topics: Animals; Antioxidants; Blood Glucose; Body Weight; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Dose-Response Relationship, Drug; Esters; Fatty Acids, Nonesterified; Glucose Intolerance; Glucose Tolerance Test; Hyperglycemia; Hypoglycemic Agents; Insulin; Male; Mice; Mice, Inbred C57BL; Molecular Weight; Niacinamide; Oxidative Stress; Pancreas; Piperidines; Streptozocin; Time Factors; Tyrosine