Development Of Diabetic Encephalopathy Research Articles

Liraglutide reduces oxidative stress and improves energy metabolism in methylglyoxal-induced SH-SY5Y cells

Diabetes mellitus can result in severe complications, such as neurodegenerative diseases including cognitive impairment and dementia. The glucagon-like peptide-1 (GLP-1) receptor agonist, liraglutide, is a novel antidiabetic drug with neuroprotective effects against neurodegenerative diseases. In this study, we explored the protective effect of liraglutide on SH-SY5Y cells exposed to methylglyoxal (MG), a byproduct of glucose metabolism that plays a key role in the development of diabetic encephalopathy. We found that liraglutide reduced the MG-induced oxidative stress, increased the activity of superoxide dismutase (SOD) and expression levels of P22phox, Gp91phox, and Xdh genes, and reduced reactive oxygen species (ROS) content. Metabolomics analysis based on 1H nuclear magnetic resonance showed that liraglutide induced alterations in metabolites involved in energy metabolism，including promotion of gluconeogenesis. Moreover, we found that liraglutide promoted oxidative phosphorylation and inhibited glycolysis in SH-SY5Y cells. This study revealed that liraglutide improved diabetes-related neuropathy damage by reducing the level of oxidative stress and maintaining the balance of energy metabolism, thus offering new insights into the potential mechanism of liraglutide in neuronal protection.

The circRNA circ-Nbea participates in regulating diabetic encephalopathy

Circular RNAs (circRNAs) play key roles in various pathogenic and biological processes in human disease. However, the effect of circRNAs on the development of diabetic encephalopathy (DE) remains largely unknown. Therefore, the aim of this study was to investigate changes in the expression of circRNAs and their potential mechanism in DE formation. Compared with db/m mice, spatial learning/memory, dendritic spines, and synaptic plasticity were all impaired in the hippocampus of the db/db mice. In addition, the dendritic spine density of neurons was significantly decreased after treatment with advanced glycation end-products (AGEs). We used high-throughput RNA sequencing (RNA-Seq) to detect circRNA expression in DE, and the results revealed that 183 circRNAs were significantly altered in primary hippocampal neurons treated with AGEs. Three circRNAs were chosen for detection using quantitative real-time polymerase chain reaction (qRT–PCR), including circ-Smox (chr2: 131511984–131516443), circ-Nbea (mmu-chr3: 56079859–56091120), and circ-Setbp1 (chr18: 79086551–79087180), and circ-Nbea expression was significantly decreased. According to the bioinformatics prediction and detection using qRT–PCR and double luciferase assays, circ-Nbea sponges miR-128-3p. Based on these results, we speculated that a newly identified circRNA, circ-Nbea, may play an important role in the development of DE, and the mechanism is mediated by sponging miR-128-3p. This study provides new insight into the treatment of DE.

ВЛИЯНИЕ ИНТРАНАЗАЛЬНО ВВОДИМЫХ ИНСУЛИНА И С-ПЕПТИДА НА АКТИВНОСТЬ АМФ-АКТИВИРУЕМОЙ ПРОТЕИНКИНАЗЫ, МИТОХОНДРИАЛЬНУЮ ДИНАМИКУ И МАРКЕРЫ АПОПТОЗА В ГИПОТАЛАМУСЕ КРЫС СО СТРЕПТОЗОТОЦИНОВЫМ ДИАБЕТОМ

Most important factors leading to the development of diabetic encephalopathy in type 1 diabetes mellitus (T1DM) are impaired energy metabolism and mitochondrial dynamics, as well as activation of apoptosis in brain neurons, which is largely due to insulin and C-peptide deficiency in the CNS. In T1DM, hypothalamic neuronal dysfunctions lead to disturb both feeding behavior and central regulation of energy metabolism. One of the approaches to compensate for insulin and C-peptide deficiency in the brain is their intranasal administration, how- ever its influence on the functional state of hypothalamic neurons has not yet been studied. The aim of the work was to study the effect of intranasally administered insulin and C-peptide on the activity of AMP-activated protein kinase (AMPK) and expression of Drp-1 and mitofusins (Mfn-1 and -2) responsible for the biogenesis of mitochondria, pro- and anti-apoptotic proteins Bax and Bcl-2, autophagy-associated protein Beclin-1, and melanocortin receptors (MCR) in the hypothalamus of male rats with T1DM induced by 50 mg/kg of streptozotocin. We studied a 7-day intranasal administration to diabetic rats (D) of insulin (20 μ g/rat/day, DI), C-peptide (36 μ g/rat/day, DC), and insulin combined with C-peptide at two doses of 12 and 36 μ g/rat/day (DIC12, DIC36). In the hypothalamus of DI and DIC36 rat groups, there were observed normalization of AMPK activity and the Bax/Bcl-2 ratio (typically increased in T1DM), restoration of Drp-1, Mfn-2 and Beclin-1 expression, and enhancement of type 4 MCR expression responsible for transduction of anorexigenic signals, with all changes being associated with attenuated hyperphagia in these groups. In the DIС12 and DС rat groups, the restorative effects of the intranasal treatment were less pronounced. Thus, intranasal administration of insulin and C-pep- tide, to the greatest extent at a 1:3 molar ratio, restores energetic balance and mitochondrial dynamics, as well as suppresses pro-apoptotic processes in the hypothalamus of rats with severe T1DM. These effects appear to underlie their neuroprotective action.

Gastrodin Alleviates Cognitive Dysfunction and Depressive-Like Behaviors by Inhibiting ER Stress and NLRP3 Inflammasome Activation in db/db Mice.

Patients with diabetes mellitus (DM) suffer more risks from diabetic encephalopathy such as cognitive dysfunction and depressive-like behaviors. Numerous studies show that ER (endoplasmic reticulum) stress and inflammation play important roles in the development of diabetic encephalopathy. Gastrodin (Gas), one major component of Gastrodia elata, is traditionally used in central nervous system disorders and is believed to possess anti-inflammatory, anti-apoptotic, and other neuroprotective effects. This present study aims to explore the protective effects of Gas on diabetic encephalopathy. Gas was administrated daily (70 and 140 mg/Kg) for 12 weeks. Meanwhile, the fasting blood glucose and body weight of db/db mice were measured every two weeks. After Gas treatment, the Morris water maze (MWM) test and novel object recognition (NOR) test were performed to assess the learning and memory functions of db/db mice, and the forced swim test was performed to evaluate depressive-like behaviors of db/db mice. Additionally, the expression of ER stress and Nucleotide binding and oligomerization domain-like (Nod) receptor family pyrin domain-containing 3 (NLRP3) inflammasome related proteins were evaluated by using Western blot. Our study suggested that Gas attenuated blood glucose levels and dyslipidemia of db/db mice. It has been shown that Gas could improve learning and memory function and depressive-like behaviors of db/db mice. Moreover, Gas inhibited ER stress and NLRP3 inflammasome activation in the hippocampus. Taken together, this study demonstrates that Gas attenuates the diabetic encephalopathy by inhibiting ER stress and NLRP3 inflammasome activation.

Autophagy of macrophages is regulated by PI3k/Akt/mTOR signalling in the development of diabetic encephalopathy.

The development of diabetic encephalopathy (DE) is enhanced by inflammatory macrophages, and is suppressed by macrophage autophagy. However, the molecular signaling that controls macrophage autophagy in DE remains ill-defined. Here, DE is induced in rats that received intraperitoneal injection of streptozotocin (STZ). In macrophages isolated from the brain of the rats, we detected downregulated autophagy activity and enhanced PI3k/Akt/mTOR/S6K1 signaling. In order to examine the role of autophagy and PI3k/Akt/mTOR signaling in DE development, an mTOR inhibitor, rapamycin, or an autophagy inhibitor, chloroquine (CQ), were administered to the rats that that received STZ. We found that rapamycin significantly enhanced DE development through mTOR suppression-induced augmentation of macrophage autophagy, while CQ significantly decreased DE development through suppression of macrophage autophagy. Together, our data suggest that PI3k/Akt/mTOR signaling may promote the development of DE through suppression of macrophage autophagy.

Inhibiting the NLRP3 Inflammasome Activation with MCC950 Ameliorates Diabetic Encephalopathy in db/db Mice

Diabetes is associated with a high risk of developing cognitive dysfunction and neuropsychiatric disabilities, and these disease symptomsare termed diabetic encephalopathy (DEP). Inflammation is involved in the development of DEP. The cleavage and maturation of the proinflammatory cytokine interleukin (IL)-1β is regulated by the NLRP3 inflammasome. Obese and type 2 diabetic db/db mice show anxiety- and depression-like behaviors and cognitive disorders associated with hippocampal inflammation. The purpose of this study was to explore the role of NLRP3 inflammasome in DEP. Results showed that expression levels of inflammasome components including NLRP3, apoptosis-associated speck-like protein (ASC), and caspase-1, as well as IL-1β in the hippocampus of diabetic db/db mice were higher than those of non-diabetic db/m mice. Treatment of db/db mice with NLRP3 inflammasome inhibitor MCC950 ameliorated anxiety- and depression-like behaviors as well as cognitive dysfunction, and reversed increased NLRP3, ASC, and IL-1βexpression levels and caspase-1 activity in hippocampus. Moreover, MCC950 treatment significantly improved insulin sensitivity in db/db mice. These results demonstrate that inhibition of NLRP3 inflammasome activation may prove to be a potential therapeutic approach for DEP treatment.

Notoginsenoside R1 ameliorates diabetic encephalopathy by activating the Nrf2 pathway and inhibiting NLRP3 inflammasome activation.

Numerous researches supported that oxidative stress and inflammation play important roles in the development of diabetic encephalopathy (DEP). Notoginsenoside R1 (NGR1), one major component of Panax notoginseng, is believed to have anti-oxidative, anti-inflammatory and neuroprotective properties. However, its neuroprotective effects against DEP and underlying mechanisms are still unknown. In this study, db/db mice as well as high-glucose (HG)-treated HT22 hippocampal neurons were used as in vivo and in vitro models to estimate NGR1 neuroprotection. NGR1 administration for 10 weeks could ameliorate cognitive dysfunction, depression-like behaviors, insulin resistance, hyperinsulinemia, dyslipidemia, and inflammation in db/db mice. NGR1 markedly decreased the oxidative stress induced by hyperglycemia in hippocampal neurons. NGR1 significantly activated the protein kinase B (Akt)/nuclear factor-erythroid 2-related factor2 (Nrf2) pathway, and inhibited NLRP3 inflammasome activation in hippocampal neurons, which might be essential for the neuroprotective effects of NGR1. Further supporting these results, we observed that pretreatment with the phosphatidylinositol 3-kinase inhibitor LY294002 abolished NGR1-mediated neuroprotective effects against oxidative stress and NLRP3 inflammasome activation in HG-treated HT22 hippocampal neurons. In conclusion, the present study demonstrates the neuroprotective effects of NGR1 on DEP by activating the Akt/Nrf2 pathway and inhibiting NLRP3 inflammasome activation. This study also provides a novel strategy for the application of NGR1 as a therapeutic agent for patients with DEP.

Когнитивные нарушения при сахарном диабете

Background. Diabetes mellitus is one of the most frequent chronic diseases, affecting up to 10% of the population. The risk of dementia in patients with diabetes increases by an average of 1,6 times, with the risk of vascular dementia 2–2,6 times, and the risk of Alzheimer’s disease (AD) — about 1,5 times, regardless of age diabetes onset. The aim was to review scientifc publications on the role of hyperglycemia in the development of cognitive dysfunction. Results: on shown that only a moderate, predominantly neurodynamic cognitive defcit can be associated with it. Apparently cerebrovascular or neurodegenerative pathology, accelerated by metabolic disorders in diabetes, and hypoglycemic episodes, can play a more important role in the development of cognitive decline. A parallelism in the development of diabetes and AD is largely explained by insulin dysfunction. The decrease with age of insulin concentration and the number of insulin receptors in the brain partially explains the age-related cognitive dysfunction. Therapy, simultaneously directed to several key pathophysiological links in the development of diabetic encephalopathy, appears to be the most promising. It can include a combination of drugs acting on different therapeutic targets, or those few multicomponent drugs that can directly affect several targets. Conclusion: current conceptions of diabetes pathogenesis determine complex therapeutical intervention.

Endoplasmic reticulum stress-induced neuronal inflammatory response and apoptosis likely plays a key role in the development of diabetic encephalopathy.

We assumed that diabetic encephalopathy (DEP) may be induced by endoplasmic reticulum (ER)-mediated inflammation and apoptosis in central nervous system. To test this notion, here we investigated the neuronal ER stress and associated inflammation and apoptosis in a type 2 diabetes model induced with high-fat diet/streptozotocin in Sprague-Dawley rats. Elevated expressions of ER stress markers, including glucose-regulated protein 78 (GRP78), activating transcription factor-6 (ATF-6), X-box binding protein-1 (XBP-1), and C/EBP homologous protein, and phosphor-Jun N-terminal kinase (p-JNK) were evident in the hippocampus CA1 of diabetic rats. These changes were also accompanied with the activation of NF-κB and the increased levels of inflammatory cytokines, tumor necrosis factor-α (TNF-α) and Interleukin-6 (IL-6). Mechanistic study with in vitro cultured hippocampus neurons exposed to high glucose (HG), which induced a diabetes-like effects, shown by increased ER stress, JNK and NF-κB activation, and inflammatory response. Inhibition of ER stress by 4-phenylbutyrate (4-PBA) or blockade of JNK activity by specific inhibitor or transfection of DN-JNK attenuated HG-induced inflammation and associated apoptosis. To validate the in vitro finding, in vivo application of 4-PBA resulted in a significant reduction of diabetes-induced neuronal ER stress, inflammation and cell death, leading to the prevention of DEP. These results suggest that diabetes-induced neuronal ER stress plays the critical role for diabetes-induced neuronal inflammation and cell death, leading to the development of DEP.

ClC-3 Expression and Its Association with Hyperglycemia Induced HT22 Hippocampal Neuronal Cell Apoptosis.

Although apoptosis plays an important role in the development of Diabetic Encephalopathy (DE), the underlying molecular mechanisms remain unclear. With respect to this, the present work aims to study the variation in chloride/proton exchanger ClC-3 expression and its association with HT22 hippocampal neuronal apoptosis under hyperglycemic condition in vitro. The cells were stimulated with added 0, 5, or 25 mM glucose or mannitol for up to 72 hours before assessing the rate of ClC-3 expression, cell viability, and apoptosis. In a consecutive experiment, cells received chloride channel blocker in addition to glucose. The rate of cellular death/apoptosis and viability was measured using Flow Cytometry and MTT assay, respectively. Changes in ClC-3 expression were assessed using immunofluorescence staining and western blot analysis. The results revealed a significant increase in cellular apoptosis and reduction in viability, associated with increased ClC-3 expression in high glucose group. Osmolarity had no role to play. Addition of chloride channel blocker completely abolished this effect. Thus we conclude that, with its increased expression, ClC-3 plays a major role in hyperglycemia induced hippocampal neuronal apoptosis. To strengthen our understanding of this aforesaid association, we conducted an extensive literature search which is presented in this paper.

Dynamics of the Initial Signs of Experimental Diabetic Encephalopathy

Modeling of alloxan diabetes leads to the early development of diabetic encephalopathy on the background of suppression of exploratory-orientational activity in animals and decreases their ability to achieve conditioned reflex learning. The initial signs of experimental diabetic encephalopathy were linked with rapidly progressing losses of neurons and glial cells in structures of the primary somatosensory cortex (field Par 1) and hippocampus (field CA1) during the period from day 4 of the day 17 after administration of alloxan. This was accompanied by accumulation of lipofuscin in neocortical neurons. The occurrence of diabetic encephalopathy at the diencephalic level was seen only 10 days after alloxan administration. This applied to the paraventricular nucleus, where decreases in the number of neurocytes were seen in the period from day 10 to day 17 of induction of diabetes. The initial signs of experimental diabetic encephalopathy were linked with progressive suppression of the animals’ exploratory-orientational activity and decreases in their ability to achieve conditioned reflex learning.

Effects of avocado oil in brain mitochondrial ETC function and ROS generation in diabetic rats (960.5)

Diabetes mellitus is associated with functional and structural changes in the brain leading to neurodegeneration, with oxidative stress playing a role in the development of diabetic brain complications. In some cases, it has been reported that impaired function of the electron transport chain (ETC) may be involved in the development of diabetic encephalopathy and oxidative stress. Recently, we have reported that avocado oil supplementation has beneficial effects in kidney mitochondria during diabetes by increasing the resistance of the ETC to oxidative stress and decreasing ROS production in the complex III. Thus, the main goals of this work were to identify alterations in ETC function of brain mitochondria leading to ROS production in rats with 90‐days of STZ‐induced diabetes and the evaluation of the effects of avocado oil intake in these alterations. No alterations were found in the activity of any of the ETC complexes of diabetic rats. Avocado oil supplementation increases 1.2‐fold the activity of the complex III from diabetic rats and 3.5 times the activity of the complex II of normoglycemic rats. Despite no net changes in ROS generation were detected, a decrease in this parameter was identified in diabetic rats when ROS generation was normalized against complex III activity, with avocado oil further decreasing ROS production in the same group. These data suggest that 90 days of diabetes do not exert important changes in mitochondrial function of brain. However, early avocado supplementation may prevent further development of mitochondrial dysfunction in late stages of diabetes by improving the electron flow in the complex III and decreasing ROS generation.Grant Funding Source: Suuported by CONACYT (130638 to CCR) and CIC‐UMSNH (16.12 to CCR) grants

Protective effect of N-acetylcysteine supplementation on mitochondrial oxidative stress and mitochondrial enzymes in cerebral cortex of streptozotocin-treated diabetic rats

Diabetic encephalopathy, characterized by cognitive deficits involves hyperglycemia-induced oxidative stress. Impaired mitochondrial functions might play an important role in accelerated oxidative damage observed in diabetic brain. The aim of the present study was to examine the role of mitochondrial oxidative stress and dysfunctions in the development of diabetic encephalopathy along with the neuroprotective potential of N-acetylcysteine (NAC). Chronic hyperglycemia accentuated mitochondrial oxidative stress in terms of increased ROS production and lipid peroxidation. Significant decrease in Mn-SOD activity along with protein and non-protein thiols was observed in the mitochondria from diabetic brain. The activities of mitochondrial enzymes; NADH dehydrogenase, succinate dehydrogenase and cytochrome oxidase were decreased in the diabetic brain. Increased mitochondrial oxidative stress and dysfunctions were associated with increased cytochrome c and active caspase-3 levels in cytosol. Electron microscopy revealed mitochondrial swelling and chromatin condensation in neurons of diabetic animals. NAC administration, on the other hand was found to significantly improve diabetes-induced biochemical and morphological changes, bringing them closer to the controls. The results from the study provide evidence for the role of mitochondrial oxidative stress and dysfunctions in the development of diabetic encephalopathy and point towards the clinical potential of NAC as an adjuvant therapy to conventional anti-hyperglycemic regimens for the prevention and/or delaying the progression of CNS complications.

Increased Expression of Phosphorylated Smad2 and Smad3 in the Hippocampus of Streptozotocin-induced Diabetic Rats

Activation of the Smad signalling pathway has been implicated in the pathological process of diabetic associated complications. The current study was designed to see whether Smad signalling was activated in the hippocampus of streptozotocin-induced diabetic rats. Compared with vehicle-treated controls, immunoblot analysis of hippocampal extracts showed that phosphorylated Smad2 was upregulated at 8 weeks post streptozotocin induction (p<0.01), and phosphorylated Smad3 protein was upregulated at 4 and 8 weeks post streptozotocin induction (p<0.01) in streptozotocin-induced diabetic rats. In addition, immunofluorescence labelling assay showed that the percentage of pSmad2 immunoreactive astrocytes increased significantly in CA1, CA3 and dentate gyrus region (p<0.01), and pSmad3 immunoreactive astrocytes increased significantly in CA1 region (p<0.01) and in CA3 and dentate gyrus region (p<0.05) of the hippocampus in diabetic rats. These data indicate that Smad signalling is enhanced in hippocampal astrocytes of diabetic rats, and may thereby represent a clue to explore its exact role in the development of diabetic encephalopathy.

Hyperglycemia-induced alterations in synaptosomal membrane fluidity and activity of membrane bound enzymes: beneficial effect of N-acetylcysteine supplementation

Diabetic encephalopathy is characterized by impaired cognitive functions that appear to underlie neuronal damage triggered by glucose driven oxidative stress. Hyperglycemia-induced oxidative stress in diabetic brain may initiate structural and functional changes in synaptosomal membranes. The objective of the present study was to examine the neuroprotective role of N-acetylcysteine (NAC) in hyperglycemia-induced alterations in lipid composition and activity of membrane bound enzymes (Na +,K +-ATPase and Ca 2+-ATPase) in the rodent model of type 1 diabetes. Male Wistar rats weighing between 180 and 200 g were rendered diabetic by a single injection of streptozotocin (50 mg/kg body weight, i.p.). The diabetic animals were administered NAC (1.4–1.5 g/kg body weight) for eight weeks and lipid composition along with membrane fluidity were determined. A significant increase in lipid peroxidation was observed in cerebral cortex of diabetic rats. NAC administration on the other hand lowered the hyperglycemia-induced lipid peroxidation to near control levels. The increased lipid peroxidation following chronic hyperglycemia was accompanied by a significant increase in the total lipids which can be attributed to increase in the levels of cholesterol, triglycerides and glycolipids. On the contrary phospholipid and ganglioside levels were decreased. Hyperglycemia-induced increase in cholesterol to phospholipid ratio reflected decrease in membrane fluidity. Fluorescence polarization (p) with DPH also confirmed decrease in synaptosomal membrane fluidity that influenced the activity of membrane bound enzymes. An inverse correlation was found between fluorescence polarization with the activities of Na +,K +-ATPase ( r 2=0.416, P<0.05) and Ca 2+ ATPase ( r 2=0.604, P<0.05). NAC was found to significantly improve lipid composition, restore membrane fluidity and activity of membrane bound enzymes. Our results clearly suggest perturbations in lipid composition and membrane fluidity as a major factor in the development of diabetic encephalopathy. Furthermore, NAC administration ameliorated the effect of hyperglycemia on oxidative stress and alterations in lipid composition thereby restoring membrane fluidity and activity of membrane bound enzymes.

Neuroprotective effect of N-acetylcysteine in the development of diabetic encephalopathy in streptozotocin-induced diabetes

Diabetic encephalopathy is characterized by impaired cognitive functions that involve neuronal damage triggered by glucose driven oxidative stress. The objective of the present study was to determine whether N-acetylcysteine (NAC) supplementation ameliorates learning and memory deficits caused by hyperglycemia-induced oxidative stress in experimental diabetes. Male Wistar rats (200-250 g) were rendered diabetic by a single intraperitoneal injection of streptozotocin (50 mg/kg). Cognitive deficits were observed in diabetic animals assessed using elevated plus maze test after 8 weeks of induction of diabetes. Acetylcholinesterase activity, a marker of cholinergic function, was decreased by 15.6% in the cerebral cortex, 20.9% in cerebellum and 14.9% in brain stem of diabetic rats compared to control rats. There was an increase in lipid peroxidation in cerebral cortex (21.97%), cerebellum (20.4%) and brain stem (25.5%) of diabetic rats. This was accompanied by decrease in glutathione and total thiol content along with decrease in the activities of superoxide dismutase, catalase and glutathione reductase. However, glutathione peroxidase activity increased by 11.2%, 13.6% and 23.1% in cerebral cortex, cerebellum and brain stem respectively, while the activity of glutathione-s-transferase decreased only in cerebral cortex (21.7%). Supplementation with NAC (1.4 g/kg/day in drinking water) significantly attenuated cognitive deficits and oxidative stress in diabetic rats. Our results emphasize the involvement of increased oxidative stress in cognitive impairment in diabetic animals and point towards the potential beneficial role of NAC as an adjuvant therapy to conventional anti-hyperglycemic regimens for the prevention and treatment of diabetic encephalopathy.

Neurodegenerative changes in the hippocampus within the early period of experimental diabetes mellitus

We studied the dynamics of modifications of the structure and architectonics in different zones of the pyramidal layer of the rat hippocampus within the early periods (3, 7, and 14 days) after induction of diabetes mellitus by streptozotocin. Using confocal immunofluorescence microscopy, we found neurons containing a specific protein, NeuN; a fluorescence dye, Hoechst 33258, allowed us to visualize the cell nuclei. The density of localization of neurons in the CA2 area decreased significantly on the 3rd day of development of diabetes. In the CA1 and CA3 areas, a significant decrease in this index was observed beginning from the 7th day. Within this time interval, we observed neurons with clear condensation of chromatin in the nuclei of these cells. The obtained data indicate that formation of appreciable neurodegenerative changes in the hippocampus occurs within the initial stages of development of experimental diabetes mellitus; this phenomenon can be a factor in the development of diabetic encephalopathy.