Inhibitors of Poly(ADP-Ribose)Polymerase-1 as Agents Providing Correction of Brain Dysfunctions Induced by Experimental Diabetes

Nicotinamide prevention in diabetes-induced alterations in the rat liver

Objective. The study was performed to elucidate whether nicotinamide (NAm) can attenuate the diabetes-induced liver damage by correction of ammonia detoxifying function and disbalance of NAD-dependent processes in diabetic rats. Methods. After four weeks of streptozotocin-induced diabetes, Wistar male rats were treated for two weeks with or without NAm. Urea concentration, arginase, and glutamine synthetase activities, NAD+ levels, and NAD+/NADH ratio were measured in cytosolic liver extracts. Expression of parp-1 gene in the liver was estimated by quantitative polymerase chain reaction and PARP-1 cleavage evaluated by Western blotting. Results. Despite the blood plasma lipid peroxidation products in diabetic rats were increased by 60%, the activity of superoxide dismutase (SOD) was reduced. NAm attenuated the oxidative stress, but did not affect the enzyme activity in diabetic rats. In liver of the diabetic rats, urea concentration and arginase activity were significantly higher than in the controls. The glutamine synthetase activity was decreased. Decline in NAD+ level and cytosolic NAD+/NADH ratio in the liver of diabetic rats was observed. Western blot analysis demonstrated a significant up-regulation of PARP-1 expression accompanied by the enzyme cleavage in the diabetic rat liver. However, no correlation was seen between mRNA expression of parp-1 gene and PARP-1 protein in the liver of diabetic rats. NAm markedly attenuated PARP-1 cleavage induced by diabetes, but did not affect the parp-1 gene expression. Conclusions. NAm counteracts diabetes-induced impairments in the rat liver through improvement of its detoxifying function, partial restoration of oxidative stress, NAD+ level, normalization of redox state of free cytosolic NAD+/NADH-couples, and prevention of PARP-1 cleavage.

Modulatory effects of vitamin B3 and its derivative on the levels of apoptotic and vascular regulators and cytoskeletal proteins in diabetic rat brain as signs of neuroprotection

BACKGROUND

Beneficial effects of nicotinamide (NAm) and its derivates have been earlier shown in animal models of diabetes mellitus (DM), but the mechanisms of their neuroprotective activities are still largely unknown. The aim of the present study was to investigate if NAm and conjugate of nicotinic acid with gamma-aminobutyric acid (N-GABA) are able to modulate expression levels of apoptosis regulators, angiogenesis-related molecules, and specific cytoskeletal proteins in diabetic rat brain.

METHODS

After six weeks of streptozotocin induced type 1 DM, rats were daily administered either by NAm (100 mg/kg) or N-GABA (55 mg/kg) intraperitoneally for two weeks. Protein levels were assessed by western blot and immunohistochemistry.

RESULTS

Both NAm and N-GABA down-regulated NF-κB and Bax levels in diabetic rat brain, suggesting their anti-apoptotic activities. Tested compounds normalized VEGF and nNOS contents improving pro-angiogenic signaling reduced by hyperglycemia. Western blot showed marked up-regulation of astroglial marker GFAP and lowering neurofilament protein levels in DM group, confirmed immunohistochemically, indicating the development of reactive astrogliosis as a major response to diabetes-induced neurodegeneration. NAm had no effects on GFAP and Nf-L levels in the diabetic brain, while N-GABA increased their expression. Inversely, NAm and N-GABA dramatically reduced enhanced levels of GFAP and Nf-L found in the blood serum of diabetic rats, providing for the first time strong evidence for preserving blood-brain barrier integrity by studied compounds.

CONCLUSION

Thus, NAm and N-GABA may exert neuroprotective effects by decreasing pro-apoptotic regulators levels and improving expression of angiogenic and cytoskeletal proteins impaired by hyperglycemia in rat brain.

Alterations in tanycytes and related cell populations of arcuate nucleus in streptozotocin-induced Alzheimer disease model

It is assumed that dysfunction of tanycytes could be one of the components of pathogenesis of both Alzheimer disease and type 2 diabetes mellitus. The study was aimed to assess alterations in the tanycyte morphology in the Alzheimer disease model. The 3 mg/kg streptozotocin dose was injected in the lateral ventricles of Wistar rats in order to model the Alzheimer disease. Alterations in hypothalamic tanycytes were assessed 2 weeks, 4 weeks, 3 months and 6 months after administration of the toxin. Immunohistochemistry was used to identify the protein markers of tanycytes (vimentin, nestin), astrocytes (GFAP, glutamine synthetase) and neurons (HuC/D), as well as to assess cell proliferation (with the use of Ki67 protein) and mitochondrial alterations (mitochondrial complex IV, PGC1a). Administration of streptozotocin lead to β-amyloid accumulation in hypothalamus and ventricular enlargement (p < 0.001). Streptozotocin damaged both α1/α2 tanycytes and β1 tanycytes. The intensity of vimentin staining in α1/α2 tanycytes decreased by week 4 (p = 0.003), and in β1 tanycytes it decreased in three months (p < 0.001). The same trend was observed for nestin. The number of Ki67+ nuclei decreased (p < 0.05), and the expression of proteins associated with mitochondria changed. The density of hypothalamic tanycytes decreased by week 4 after administration of the toxin. Moreover, astrocyte activation was revealed. However, no prominent damage to both astrocytes and neurons was observed within four weeks after administration of streptozotocin. The revealed high tanycyte vulnerability to streptozotocin is in line with the hypothesis of the role of damage to hypothalamic structures in both local and systemic metabolic disorders occurring in the Alzheimer disease models.

Changes in the transcriptional activity of the entero-insular axis genes in streptozotocin-induced diabetes and after the administration of TNF-α non-selective blockers

OBJECTIVE

The aim of the present study was to investigate the transcriptional activity of the GLP-1R, DPP-4, SGLT-1, INSR, and IGF-1R genes in GALT cells of rats with streptozotocin-induced diabetes in both untreated and treated with pentoxifylline, as a non-specific blocker of TNF-α.

METHODS

The expression of GLP-1R, DPP-4, SGLT-1, INSR, and IGF-1R genes in GALT cells of rats was studied by real time quantitative polymerase chain reaction.

RESULTS

It was shown that the development of diabetes was accompanied by the decrease of GLP-1R and an increase of DPP-4 genes expression in rat ileum. The administration of pentoxifyl-line to diabetic animals led to an increase in the transcriptional activity of GLP-1R on the 4th week and decrease in transcriptional activity of DPP-4 on the 2nd and 4th weeks of the experiment. An increase in the normalized expression of SGLT-1 on the 4th week of the experimental diabetes was also noted, while the administration of pentoxifylline to diabetic animals did not lead to significant changes in this index. The transcriptional activity of the INSR and IGF-1R genes was reduced in diabetic rats and the administration of the non-specific TNF-α blocker - pentoxifylline led to a significant increase only for INSR gene in animals on the 4th week of the experimental diabetes.

CONCLUSIONS

The expression of incretins, glucose transporters, and pro-inflammatory cytokines (e.g. TNF-α) in immune cells may be used as markers of several autoimmune pathologies progression such as type 1 diabetes due to their effect on the balance of pro- and anti-inflammatory factors.

The parp-1 and bax genes as potential targets for treatment of the heart functioning impairments induced by type 1 diabetes mellitus

Objectives. The present study was designed to assess whether apoptosis-related genes as parp-1 and bax could be targets for treatment of diabetes mellitus and whether vitamin D may exert beneficial effects. Methods. Vitamin D₃ treatment for 4 weeks, starting after 4 weeks of the diabetes duration. The expression of parp-1 and bax genes was estimated on mRNA levels using real time quantitative polymerase chain reaction. Results. After 8 weeks, diabetic rats had weight loss, while blood glucose was increased about 4.9-fold compared to control group. Vitamin D₃ administration to diabetic animals had no effect on these parameters. It was found that total serum alkaline phosphatase activity was significantly elevated in diabetic rats as compared to control animals and was restored by vitamin D₃. Diabetes was accompanied by reduction of nicotinamidadenindinucleotide, a substrate of poly-ADP-ribosylation, level by 31.7% as compared to control rats, which was not reversed in response to vitamin D₃ treatment. In diabetic hearts, the mRNA expression level of parp-1 gene was 2.8-fold higher compared to control rats and partially decreased by vitamin D3 treatment. Less significant alterations were observed in diabetic hearts for the mRNA expression level of bax gene that was 2.0-fold higher compared to control animals and vitamin D₃ normalized it. These results indicate that cardiomyocytes have a tendency to apoptosis. Conclusions. The findings suggest that investigated genes can be targets at the transcriptional level for vitamin D action that may be contributed to the improving metabolic/signaling pathways induced by diabetes mellitus.

The Relationship Between Lipid Metabolism and The Level of Albuminuria with Single Nucleotide Polymorphism -204A>C [rs 3808607] CYP7A1 Gene in Patients with Type 2 Diabetes Mellitus and Diabetic Nephropathy

Background and aims. The purpose of our study was to determine the features of diabetic nephropathy, to identify the relationship between the level of albumin excretion, urine and lipid profile, genotype variants of the CYP7A1 gene in people with type 2 diabetes and diabetic nephropathy.

Material and methods. Patients were divided into three groups. Normoalbinuria was detected in group I, and II - microalbuminuria, and III -macroalbuminuria. Determination of albumin to creatinine ratio was more accurate, although more expensive method. We examined single nucleotide polymorphism -204A> C [rs 3808607] of the promoter region of the CYP7A1 gene.

Results. It was established that homozygotes by the major allele with genotype AA had lower values of albuminuria, atherogenic lipoproteins, total cholesterol, triglycerides and higher levels of anti-atherogenic lipoproteins than patients with AС and СС genotypes.

Conclusion. The СС genotype was most unfavorable in the prognostic plan, since homozygotes for this minor allele were characterized by higher values of albuminuria, total cholesterol, triglycerides, and lower values of high-density lipoprotein

Mitigating effect of biotin against irradiation-induced cerebral cortical and hippocampal damage in the rat brain tissue

Radiation-induced brain injury is common and mainly occurs in patients receiving radiotherapy for malignant head and neck tumors. The brain is oversensitive to oxidant injury induced by radiation. Biotin is a member of the vitamin B complex family and its deficiency has been associated with neurogenesis impairment in animals and humans. The present study was undertaken to investigate the mitigating effect of biotin on the cerebral cortical and hippocampal damage induced by radiation exposure. Animals were exposed to radiation in the presence or absence of biotin and sacrificed on day 10. The results demonstrated that the administration of biotin 2 mg to irradiated rats had no significant effect on the radiation-induced damage of the cerebral cortex and the hippocampus, while the administration of biotin 6 mg has significantly attenuated oxidative stress in the hippocampus, manifested by a reduction of 4-hydroxynonenal (4HNE), total nitrate/nitrite (NOx), and xanthine oxidase (XO) levels associated with an elevation of glutathione (GSH) content as well as superoxide dismutase (SOD) and catalase (CAT) activities. In addition, biotin decreased the pro-inflammatory cytokines (interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrotic factor alpha (TNF-α)), caspase-3, poly(ADP-ribose) polymerase 1 (PARP1) level, and PARP1 gene expression. Moreover, biotin 6 mg treatment diminished serum S100 protein (S100B) and neuron-specific enolase (NSE) levels. In conclusion, biotin treatment at high dose post-irradiation has efficiently neutralized the effect of free radicals in the hippocampal region of rats. Thus, it could be applicable as a radio-mitigator for reducing or delayed radiation-induced brain injury in patients post-radiotherapy.

Comparative Study of the Effect of Various Forms of Quercetin on Experimental Diabetes

Background and aims: Diabetes mellitus (DM) is a multifactorial metabolic disorder characterized by hyperglycaemia caused by insulin deficiency or insulin resistance. It is a global public health problem. This study aimed to determine specific pharmacological effect of quercetin in water soluble and liposomal preparations in experimental diabetes mellitus. Material and methods: We examined the effect of Corvitin and Lipoflavone (at the dose of 10 mg / kg body weight) in a comparative study in white rats with type 1 diabetes and type 2 diabetes coupled with obesity. To simulate the forms of diabetes mellitus most analogous to those in humans we used Streptozotocin at the doses of 30 mg / kg and 50 mg / kg. We tested the levels of glucose, glycosylated hemoglobin, C-reactive protein, and interleukins 6 and 4 in the blood. Results: In animals with type 1 and type 2 diabetes Lipoflavone significantly reduces glucose and glycosylated hemoglobin levels compared to the rats treated with Corvitin. When administered to animals with diabetes, the effect of quercetin in liposomal form on the concentrations of IL-6, IL-4 and Creactive protein is also larger compared to the water-soluble form. Conclusions: Water soluble quercetin preparation Corvitin and to a larger extent liposomal preparation of this flavonoid, Lipoflavone, show anti-inflammatory effect and restore key parameters of carbohydrate metabolism in experimental type 1 diabetes mellitus and type 2 diabetes coupled with obesity, reducing blood glucose and glycosylated hemoglobin levels.

Markers of Endogenous Intoxication in Rats with Diabetes Mellitus Combined with Carrageenan-Induced Enterocolitis

Background and aims: Diabetes mellitus (DM) is a significant public health issue, being one of the major contributors to morbidity and mortality in the modern societies. Chronic hyperglycemia produces significant physiological, biochemical, and histological changes in the affected organisms. This study aims to evaluate the markers of endogenous intoxication in rats with diabetes mellitus combined with carrageenan-induced enterocolitis. Materials and methods: Diabetes mellitus was induced by a single intraperitoneal administration of streptozotocin (Sigma Aldrich, USA, at a dose of 60 mg/kg body weight). Carrageenan-induced enterocolitis was modeled by giving the animals free access to 1.0 % solution of carrageenan in drinking water for 1 month. The syndrome of endogenous intoxication was assessed by quantification of low and medium molecular weight substances in blood plasma, red blood cell suspension and urine using extraction-spectrophotometric method. Results: The increase in endogenous intoxication in streptozotocin-induced diabetes combined with chronic enterocolitis can mainly be attributed to the catabolic pool of blood plasma substances of low and medium molecular weight. The index of distribution of low- and medium-molecular-weight substances between blood plasma proteins and glycocalyx of erythrocytes in the experimental groups increased simultaneously with the quantities of investigated fractions in the erythrocyte suspension measured at the wavelengths of 242, 254 and 280 nm. Conclusions: We observed upsurge of endogenous intoxication markers in the rats with diabetes mellitus. Endotoxicosis became even more evident in the rats with diabetes mellitus combined with carrageenan-induced enterocolitis.

The Indices of Nitric Oxide System in Rats with Carrageenan-Induced Enterocolitis Combined with Diabetes Mellitus

Background and aims: Diabetes mellitus (DM) represents a considerable public health issue, being one of the major causes of morbidity and mortality in the modern societies. Chronic hyperglycemia is accompanied by significant physiological, biochemical, and histological changes, e.g. development of oxidative stress that affects the motor activity of the intestine. This study aimed to evaluate the indices of nitric oxide (NO) system in blood serum and colon tissue supernatant of rats with carrageenan-induced enterocolitis combined with streptozotocin-induced diabetes.

Material and methods: The total NOS activity was determined by monitoring the rate of conversion of L-arginine into citrulline. The total quantity of NO metabolites was assessed by evaluating their amount, which included nitrite ions that were initially present in the sample (NO2 −) and nitrate ions reducted to nitrites (NO3 −).

Results: We found a significant increase in total NOS activity in colon tissue of all experimental groups vs. control animals (54.8, 30.6 and 79.2 % respectively). The total content of NO metabolites in colon tissue of all experimental groups also significantly increased (2.8, 1.9 and 3.4 times respectively) compared to the control animals.

Conclusions: We observed activation of nitroxydergic process in blood serum and colon tissue of rats with carrageenan-induced enterocolitis. Nitroxydergic processes markedly intensified in rats with carrageenan-induced enterocolitis combined with diabetes mellitus.