Diabetes augments cognitive dysfunction in chronic cerebral hypoperfusion by increasing neuronal cell death: implication of cilostazol for diabetes mellitus-induced dementia

Combination treatment with cilostazol and isosorbide mononitrate attenuates microemboli-mediated vascular cognitive impairment and improves imaging and plasma biomarkers in diabetic rats

Diabetes is a major risk factor for all types of dementia. The underlying reasons are not fully understood, and preventive therapeutic strategies are lacking. Previously we have shown that diabetic but not control rats developed a progressive cognitive decline in a microemboli (ME) model of vascular contributions to cognitive impairment & dementia (VCID). Given the cerebrovascular dysfunction is a mutual pathological change between diabetes and VCID, we hypothesized that the cognitive impairment in this ME model can be prevented by improving the endothelial function in diabetes. Our treatment paradigm was based on the LACI-2 Trial which assessed the efficacy of isosorbide mononitrate (ISMN) and cilostazol (Cil) treatments in small vessel disease progression. Control and diabetic rats were treated with ISMN/Cil or vehicle for 4 weeks, then injected with cholesterol crystal ME and the behavioral outcomes were monitored. Brain microstructure integrity was assessed by diffusion MRI. Plasma biomarkers were assessed using angiogenesis, neurology and amyloid β 42/40 panels recommended by the MarkVCID consortium. Behavioral deficits and the loss of tissue integrity previously observed in untreated diabetic rats were not noted in the treated animals in this study. Treatment improved tissue perfusion but there were no differences in plasma biomarkers. These results suggest that restoration of endothelial function with ISMN/Cil before ME injection prevented the possible deleterious effects of ME in diabetic rats by improving the endothelial integrity and it is a practical preventive and therapeutic strategy for VCID.

Intra-cisterna-magna bevacizumab injection (ICM-BI) reproduces pathological alterations of cerebral small vessel diseases

General modeling strategies for sporadic cerebral small blood vessel diseases (CSVDs) include limiting blood stream in large blood vessels and inducing systemic hypertension, in which small blood vessel deficit is either a secondary or concomitant pathology. In the current study, we introduce that intra-cisterna-magna Bevacizumab injection (ICM-BI) directly causes cerebral small blood vessel injury by neutralizing VEGF-A, the indispensable growth factor for angiogenesis. ICM-BI reproduces neuro-functional impairment, tight junction loss, cerebral micro-bleeds (CMBs), amyloid peptide accumulation, neuronal injury, white matter loss, and glial cell activation, which are common manifestations of sporadic CSVDs. Compared with existing CSVD models, small blood vessel injury is more prominent in the ICM-BI brain. Moreover, no significant alteration in large blood vessels or peripheral organs after ICM-BI is recorded. We thus propose that ICM-BI is a neat, economic and applicable methodology to establish murine sporadic CSVD model.

Insulin resistance as the molecular link between diabetes and Alzheimer's disease

Diabetes mellitus (DM) and Alzheimer's disease (AD) are two major health concerns that have seen a rising prevalence worldwide. Recent studies have indicated a possible link between DM and an increased risk of developing AD. Insulin, while primarily known for its role in regulating blood sugar, also plays a vital role in protecting brain functions. Insulin resistance (IR), especially prevalent in type 2 diabetes, is believed to play a significant role in AD's development. When insulin signalling becomes dysfunctional, it can negatively affect various brain functions, making individuals more susceptible to AD's defining features, such as the buildup of beta-amyloid plaques and tau protein tangles. Emerging research suggests that addressing insulin-related issues might help reduce or even reverse the brain changes linked to AD. This review aims to explore the rela-tionship between DM and AD, with a focus on the role of IR. It also explores the molecular mechanisms by which IR might lead to brain changes and assesses current treatments that target IR. Understanding IR's role in the connection between DM and AD offers new possibilities for treatments and highlights the importance of continued research in this interdisciplinary field.

Brain-derived endothelial cells are neuroprotective in a chronic cerebral hypoperfusion mouse model

Whether organ-specific regeneration is induced by organ-specific endothelial cells (ECs) remains unelucidated. The formation of white matter lesions due to chronic cerebral hypoperfusion causes cognitive decline, depression, motor dysfunction, and even acute ischemic stroke. Vascular ECs are an important target for treating chronic cerebral hypoperfusion. Brain-derived ECs transplanted into a mouse chronic cerebral hypoperfusion model showed excellent angiogenic potential. They were also associated with reducing both white matter lesions and brain dysfunction possibly due to the high expression of neuroprotective humoral factors. The in vitro coculture of brain cells with ECs from several diverse organs suggested the function of brain-derived endothelium is affected within a brain environment due to netrin-1 and Unc 5B systems. We found brain CD157-positive ECs were more proliferative and beneficial in a mouse model of chronic cerebral hypoperfusion than CD157-negative ECs upon inoculation. We propose novel methods to improve the symptoms of chronic cerebral hypoperfusion using CD157-positive ECs.

The Tao Hong Si Wu Decoction ameliorates diabetes-associated cognitive dysfunction by inhibiting the formation of amyloid plaques

OBJECTIVES

The herbs in Tao Hong Si Wu Decoction (THSWD) are beneficial in the treatment of cognitive impairment. However, the underlying mechanisms of THSWD in treating diabetes-associated cognitive dysfunction (DACD) are not entirely explored. This study is aimed to investigate the therapeutic effects of THSWD in DACD model rats and the underlying mechanism.

METHODS

Ultra-high-phase liquid chromatography was employed to identify the main compounds contained in the THSWD extract. DACD rat model was induced by feeding with a high-sugar and high-fat diet and injecting streptozotocin (35 mg/kg). DACD rats were gavaged with THSWD for 1 week. The learning and memory abilities of the rats were measured by using the Morris water maze. Western blotting was used to detect the changes in DACD rat targets. Statistical methods were used to evaluate the correlation between proteins.

RESULTS

The results show that THSWD effectively reduced the escape latency, hippocampal neuron damage, glycosylated hemoglobin, type A1C, and blood lipid levels in DACD rats. Furthermore, DACD rats showed significantly increased amyloid precursor protein, β-secretase, Aβ1-40 , Aβ1-42 , Tau phosphorylation, and advanced glycation end products (AGEs) expression. However, THSWD treatment can reverse this phenomenon.

CONCLUSIONS

THSWD can improve the learning and memory abilities of DACD rats by inhibiting the expression of AEGs-AGE receptors pathway, which provides an experimental basis for the clinical application of THSWD. In addition, the experiment combines pharmacological and statistical methods, which offers a new perspective for the study of Chinese herbal medicine.

Intermittent fasting alleviates type 1 diabetes-induced cognitive dysfunction by improving the frontal cortical metabolic disorder

Intermittent fasting (IF) is an ecological strategy to control various metabolic disorder symptoms, but its protective effect on type 1 diabetes (T1D)-induced cognitive dysfunction and the underlying mechanisms remain poorly defined. Herein, we examined the efficacy of IF in altering the behaviors and brain metabolome in T1D mice and investigated the potential molecular mechanisms. We demonstrated that IF remarkably improved frontal cortical-dependent memory in T1D mice and reduced the loss of neuronal cells. Metabolomics and targeted mass spectrometry assay showed that IF reprogrammed the frontal cortical metabolome composition, including activated the aspartate and glutamate pathway and reversed glycerophospholipid and sphingolipid depositions in T1D mice. Mechanistically, IF attenuated the levels of oxidative stress proteins, such as NOX2, NOX4, 8-OHdG, 4-HNE, and inhibited the levels of pro-apoptotic factors Bax and cleaved Caspase-3, finally improved the memory ability of T1D mice. In vitro studies confirmed the protective effect of the supplemented N-acetylaspartate, a pivotal metabolite involved in IF-regulated T1D-induced cognitive dysfunction, in high glucose-stimulated SH-SY5Y cells by eliminating toxic lipids accumulation, oxidative stress and apoptosis. To conclude, the frontal cortical metabolites mediated the protective effects of IF against T1D-induced cognitive dysfunction by attenuating oxidative stress and apoptotic signaling. Thus, IF can be a potential therapeutic strategy for T1D-induced cognitive dysfunction.

Effects of Diabetes and Voluntary Exercise on IgA Concentration and Polymeric Immunoglobulin Receptor Expression in the Submandibular Gland of Rats

Background and Objectives: Patients with diabetes are more susceptible to upper respiratory tract infections (URTIs) because they are easily infected. Salivary IgA (sali-IgA) levels play a major role in transmitting URTIs. Sali-IgA levels are determined by salivary gland IgA production and polymeric immunoglobulin receptor (poly-IgR) expression. However, it is unknown whether salivary gland IgA production and poly-IgR expression are decreased in patients with diabetes. While exercise is reported to increase or decrease the sali-IgA levels, it is unclear how exercise affects the salivary glands of patients with diabetes. This study aimed to determine the effects of diabetes and voluntary exercise on IgA production and poly-IgR expression in the salivary glands of diabetic rats. Materials and Methods: Ten spontaneously diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats (eight-week-old) were divided into two groups of five rats each: a non-exercise group (OLETF-C) and a voluntary wheel-running group (OLETF-E). Five Long-Evans Tokushima Otsuka (LETO) rats without diabetes were bred under the same conditions as the OLETF-C. Sixteen weeks after the study began, the submandibular glands (SGs) were collected and analyzed for IgA and poly-IgR expression levels. Results: IgA concentrations and poly-IgR expression levels in SGs were lower in OLETF-C and OLETF-E than in LETO (p < 0.05). These values did not differ between the OLETF-C and OLETF-E. Conclusions: Diabetes decreases IgA production and poly-IgR expression in the salivary glands of rats. Moreover, voluntary exercise increases sali-IgA levels but does not increase IgA production and poly-IgR expression in the salivary glands of diabetic rats. Increasing IgA production and poly-IgR expression in the salivary glands, which is reduced in diabetes, might require slightly higher-intensity exercise than voluntary exercise under the supervision of a doctor.

Effect of Huangdisan grain on improving cognitive impairment in VD rats and its mechanism in immune inflammatory response

BACKGROUND

Vascular dementia (VD) is the second most common type of dementia after Alzheimer's disease (AD). Although the incidence rate is very high, there is no definitive treatment for VD. And it has serious impact on the quality of life of VD patients. In recent years, more and more studies about the clinical efficacy and pharmacological effects of traditional Chinese medicine (TCM) in the treatment of VD have been conducted. And Huangdisan grain has been used to treat VD patients with a good curative effect in clinic.

OBJECTIVE

This study was designed to investigate the effect of Huangdisan grain on the inflammatory response and cognitive function of VD rats modeled by bilateral common carotid artery occlusion (BCCAO), that aimed to improve the treatment methods for VD.

METHODS

8-week-old healthy SPF male Wistar rats (280 ± 20 g) were randomly divided into the normal group (Gn, n = 10), sham operated group (Gs, n = 10), and operated group (Go, n = 35). The VD rat models in Go group were established by BCCAO. 8 weeks after surgery, the operated rats were screened by the hidden platform trail of Morris Water Maze (MWM), and the rats with cognitive dysfunction were further randomly divided into the impaired group (Gi, n = 10) and TCM group (Gm, n = 10). The VD rats in Gm group were given the intragastric administration of Huangdisan grain decoction once a day for 8 weeks, and the other groups were given intragastric administration of normal saline. Then the cognitive ability of rats in each group was detected by the MWM Test. The lymphocyte subsets in peripheral blood and hippocampus of rats were measured by flow cytometry. The levels of cytokines (IL-1β, IL-2, IL-4, IL-10, TNF-α, INF-γ, MIP-2, COX-2, iNOS) in peripheral blood and hippocampus were measured by ELISA (enzyme linked immunosorbent assay). The number of Iba-1⁺ CD68⁺ co-positive cells in the CA1 region of hippocampus was measured by immunofluorescence.

RESULTS

Compared with the Gn group, the escape latencies of the Gi group were prolonged (P < 0.01), the time spent in the former platform quadrant was shortened (P < 0.01), and the number of times of crossing over the former platform location was reduced (P < 0.05). But compared with the Gi group, the escape latencies of Gm group were shortened (P < 0.01), the time spent in the former platform quadrant was prolonged (P < 0.05), and the number of times of crossing over the former platform location was increased (P < 0.05). The number of Iba-1⁺ CD68⁺ co-positive cells in the CA1 region of hippocampus of VD rats in Gi group was increased (P < 0.01) compared with the Gn group. And the proportions of T Cells, CD4⁺ T Cells, CD8⁺ T Cells in the hippocampus were increased (P < 0.01). The level of pro-inflammatory cytokines in the hippocampus was increased significantly, such as IL-1β (P < 0.01), IL-2 (P < 0.01), TNF-α (P < 0.05), IFN-γ (P < 0.01), COX-2 (P < 0.01), MIP-2 (P < 0.01) and iNOS (P < 0.05). And the level of IL-10 (P < 0.01), a kind of anti-inflammatory cytokine, was decreased. The proportions of T Cells (P < 0.05), CD4⁺ T Cells (P < 0.01) and NK Cells (P < 0.05) in the peripheral blood of the VD rats in Gi group were decreased, and the level of IL-1β, IL-2, TNF-α, IFN-γ, COX-2, MIP-2 and iNOS was increased significantly (P < 0.01) compared with the Gn group. Meanwhile, the level of IL-4 and IL-10 was decreased (P < 0.01). Huangdisan grain could reduce the number of Iba-1⁺ CD68⁺ co-positive cells in the CA1 region of hippocampus (P < 0.01), decrease the proportions of T Cells, CD4⁺ T Cells, CD8⁺ T Cells and the level of IL-1β, MIP-2 in hippocampus (P < 0.01) of VD rats. Moreover, it could rise the proportion of NK Cells (P < 0.01) and the level of IL-4 (P < 0.05), IL-10 (P < 0.05), and decrease the level of IL-1β (P < 0.01), IL-2 (P < 0.05), TNF-α (P < 0.01), IFN-γ (P < 0.01), COX-2 (P < 0.01) and MIP-2 (P < 0.01) in peripheral blood of VD rats.

CONCLUSION

This study indicated that Huangdisan grain could decrease the activation of microglia/macrophages, regulate the proportions of lymphocyte subsets and the level of cytokines, which could adjust the immunologic abnormalities of VD rats, and ultimately improve cognitive function.

Novel Targets and Interventions for Cognitive Complications of Diabetes

Diabetes and cognitive dysfunction, ranging from mild cognitive impairment to dementia, often coexist in individuals over 65 years of age. Vascular contributions to cognitive impairment/dementia (VCID) are the second leading cause of dementias under the umbrella of Alzheimer's disease and related dementias (ADRD). Over half of dementia patients have VCID either as a single pathology or a mixed dementia with AD. While the prevalence of type 2 diabetes in individuals with dementia can be as high as 39% and diabetes increases the risk of cerebrovascular disease and stroke, VCID remains to be one of the less understood and less studied complications of diabetes. We have identified cerebrovascular dysfunction and compromised endothelial integrity leading to decreased cerebral blood flow and iron deposition into the brain, respectively, as targets for intervention for the prevention of VCID in diabetes. This review will focus on targeted therapies that improve endothelial function or remove iron without systemic effects, such as agents delivered intranasally, that may result in actionable and disease-modifying novel treatments in the high-risk diabetic population.

Double-blind, randomized, placebo-controlled pilot study of the phosphodiesterase-3 inhibitor cilostazol as an adjunctive to antidepressants in patients with major depressive disorder

AIMS

Cilostazol (CLS) has shown antidepressant effect in cardiovascular patients, post-stroke depression, and animal models through its neurotrophic and antiinflammatory activities. Consequently, we aimed to investigate its safety and efficacy in patients with MDD by conducting double-blind, randomized, placebo-controlled pilot study.

METHODS

80 participants with MDD (DSM-IV criteria) and Hamilton Depression Rating Scale (HDRS) score >20 were treated with CLS 50 mg or placebo twice daily plus escitalopram (ESC) 20 mg once daily for six weeks. Patients were evaluated by HDRS scores (weeks 0, 2, 4, and 6). Serum levels of CREB1, BDNF, 5-HT, TNF-α, NF- κB, and FAM19A5 were assessed pre- and post-treatment.

RESULTS

Co-administration of CLS had markedly decreased HDRS score at all-time points compared to the placebo group (p < 0.001). Early improvement, response, and remission rates after 6 weeks were significantly higher in the CLS group (90%, 90%, 80%, respectively) than in the placebo group (25%, 65%, 50% respectively) (p < 0.001). Moreover, the CLS group was superior to the placebo group in modulation of the measured neurotrophic and inflammatory biomarkers.

CONCLUSION

CLS is safe and effective short-term adjunctive therapy in patients with MDD with no other comorbid conditions. Trial registration ID:NCT04069819.

Legumain knockout improved cognitive impairment via reducing neuroinflammation in right unilateral common carotid artery occlusion mice

AIMS

Chronic cerebral hypoperfusion (CCH) is a state of chronic cerebral blood flow reduction, and it is the main cause of cognitive impairment and neurodegenerative diseases. The abnormal upregulation of legumain, a lysosomal cysteine protease, trigger synaptic plasticity impairment and neuroinflammation, which are involved in the underlying pathophysiology of CCH. At present, few studies have reported the role of legumain in cognitive impairment caused by CCH. In our study, we aimed to investigate the involvement of legumain knockout in cognitive function and neuroinflammation in a CCH mouse model.

MAIN METHODS

In this study, right unilateral common carotid artery occlusion (rUCCAO) was used to simulate the pathological state of cerebral ischemic injury. Various behavioural tests were executed to assess cognitive performance. In vivo electrophysiological recordings were used to measure synaptic functions. Western blotting, Golgi staining, haematoxylin/eosin staining, and immunofluorescence assays were conducted to examine pathological changes and molecular mechanisms.

KEY FINDINGS

The data showed that the level of legumain was significantly increased in the hippocampus of mice subjected to rUCCAO. Legumain knockout significantly improved cognitive function and synaptic plasticity induced by rUCCAO, suggesting that legumain knockout-regulation effectively protected against CCH-induced behavioural dysfunctions. Moreover, legumain knockout suppressed rUCCAO-induced microglial activation, reduced the abnormal expression of inflammatory cytokines and the inflammasome complex, and impeded the activation of P65 and pyroptosis.

SIGNIFICANCE

These findings suggest that legumain is an effective regulator of CCH, and may be an ideal target for the development of cerebral ischemia treatments in the future.

Physical exercise modulates the astrocytes polarization, promotes myelin debris clearance and remyelination in chronic cerebral hypoperfusion rats

AIMS

White matter damage is the main pathological feature of chronic cerebral hypoperfusion (CCH) and glial activation is crucial in this process. Physical exercise has protective effects on CCH, but the mechanism is unclear. Therefore, this study focuses on investigating the influence of physical exercise on activated astrocytes polarization and its role in CCH.

MAIN METHODS

Rats were given wheel running 48 h after 2VO (2 vessel occlusion) surgery. The cognitive function was evaluated by Morris water maze and novel object recognition test. Inflammatory cytokines expressions were detected by ELISA. Astrocytes polarization was analyzed by immunofluorescence. Myelin debris clearance and remyelination were detected by immunofluorescence and transmission electron microscopy.

KEY FINDINGS

Astrocytes were activated and mainly switched to A1 phenotype in rats 2 and 3 months after 2VO. Myelin debris deposition and limited remyelination can be observed at the corresponding time. Whereas physical exercise can improve the cognitive function of 2VO rats, downregulate the expression of inflammatory factors IL-1α, C1q and TNF, upregulate the release of TGFβ, and promote activated astrocytes transformation from A1 to A2 phenotype. In addition, it can also enhance myelin debris removal and remyelination.

SIGNIFICANCE

These findings suggest that the benefits of physical exercise on white matter repair and cognition improvement may be related to its regulation of astrocytes polarization, which contributes to myelin debris clearance and effective remyelination in CCH.

Ameliorative effects of endurance training and Matricaria chamomilla flowers hydroethanolic extract on cognitive deficit in type 2 diabetes rats

Diabetes mellitus is mainly associated with degeneration of the central nervous system, which eventually leads to cognitive deficit. Although some studies suggest that exercise can improve the cognitive decline associated with diabetes, the potential effects of endurance training (ET) accompanied by Matricaria chamomilla (M.ch) flowers extract on cognitive impairment in type 2 diabetes has been poorly understood. Forty male Wistar rats were randomized into 5 equal groups of 8: healthy-sedentary (H-sed), diabetes-sedentary (D-sed), diabetes-endurance training (D-ET), diabetes-Matricaria chamomilla. (D-M.ch), and diabetes-endurance training-Matricaria chamomilla. (D-ET-M.ch). Nicotinamide (110 mg/kg, i.p.) and Streptozotocin (65 mg/kg, i.p.) were utilized to initiate type 2 diabetes. Then, ET (5 days/week) and M.ch (200 mg/kg body weight/daily) were administered for 12 weeks. After 12 weeks of the experiment, cognitive functions were assessed using the Morris Water Maze (MWM) test and a passive avoidance paradigm using a shuttle box device. Subsequently, using crystal violet staining, neuron necrosis was examined in the CA3 area of the hippocampus. Diabetic rats showed cognitive impairment following an increase in the number of necrotic cells in region CA3 of the hippocampal tissue. Also, diabetes increased serum levels of lipid peroxidation and decreased total antioxidant capacity in serum and hippocampal tissue. ET + M.ch treatment prevented the necrosis of neurons in the hippocampal tissue. Following positive changes in hippocampal tissue and serum antioxidant enzyme levels, an improvement was observed in the cognitive impairment of the diabetic rats receiving ET + M.ch. Therefore the results showed that treatment with ET + M.ch could ameliorate memory and inactive avoidance in diabetic rats. Hence, the use of ET + M.ch interventions is proposed as a new therapeutic perspective on the death of hippocampal neurons and cognitive deficit caused by diabetes.

Curcumin protects against cognitive impairments in a rat model of chronic cerebral hypoperfusion combined with diabetes mellitus by suppressing neuroinflammation, apoptosis, and pyroptosis

BACKGROUND

Chronic cerebral hypoperfusion (CCH) is regarded as a high-risk factor for cognitive decline in vascular dementia (VaD). We have previously shown that diabetes mellitus (DM) synergistically promotes CCH-induced cognitive dysfunction via exacerbating neuroinflammation. Furthermore, curcumin has been shown to exhibit anti-inflammatory and neuroprotective activities. However, the effects of curcumin on CCH-induced cognitive impairments in DM have remained unknown.

METHODS

Rats were fed with a high-fat diet (HFD) and injected with low-dose streptozotocin (STZ), followed by bilateral common carotid artery occlusion (BCCAO), to model DM and CCH in vivo. After BCCAO, curcumin (50 mg/kg) was administered intraperitoneally every two days for eight weeks to evaluate its therapeutic effects. Additionally, mouse BV2 microglial cells were exposed to hypoxia and high glucose to model CCH and DM pathologies in vitro.

RESULTS

Curcumin treatment significantly improved DM/CCH-induced cognitive deficits and attenuated neuronal cell death. Molecular analysis revealed that curcumin exerted protective effects via suppressing neuroinflammation induced by microglial activation, regulating the triggering receptor expressed on myeloid cells 2 (TREM2)/toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) pathway, alleviating apoptosis, and reducing nod-like receptor protein 3 (NLRP3)-dependent pyroptosis.

CONCLUSIONS

Taken together, our findings suggest that curcumin represents a promising therapy for DM/CCH-induced cognitive impairments.

Preservation of spatial memory and neuroprotection by the fatty acid amide hydrolase inhibitor URB597 in a rat model of vascular dementia

Background

Chronic cerebral hypoperfusion (CCH) is a major risk factor for vascular dementia (VaD). There are currently no broadly effective prevention or treatment strategies for VaD, but recent studies have reported promising results following vascular bypass surgery and pharmacomodulation of the brain endocannabinoid system (ECS). In this study, early effects of encephalomyosynangiosis (EMS) bypass surgery and augmented endocannabinoid signaling on CCH-induced cognitive dysfunction and neuronal damage were investigated.

Methods

An animal model of VaD was established by bilateral common carotid artery occlusion (BCCAO). Cannabinoid signaling was upregulated by treatment with the fatty acid amide hydrolase inhibitor URB597 (URB). Spatial learning and memory, cerebral blood flow (CBF), revascularization, brain-derived neurotrophic factor (BDNF)-tropomyosin receptor kinase B (TrkB) signaling, and apoptosis were compared among Sham, BCCAO, BCCAO + EMS, BCCAO + URB, and BCCAO + URB + EMS groups. Spatial learning and memory were evaluated using the Morris water maze (MWM). The CBF in cortex and hippocampus was evaluated by 3-dimensional arterial spin labeling. The neovascularization was visualized by CD34 immunofluorescence staining, and BDNF-TrkB signaling protein expression levels were assessed by Western blotting.

Results

Treatment with URB597 but not EMS alone reversed the spatial learning and memory deficits induced by BCCAO. Neovascularization was enhanced after EMS surgery but not by URB597. Alternatively, there were no significant differences in CBF among treatment groups. Expression levels of BDNF and TrkB were significantly reduced by CCH compared to Sham treatment, and downregulation of both proteins was reversed by URB597 treatment but not EMS. BCCAO enhanced neuronal apoptosis, which was also reversed by URB597.

Conclusions

Augmentation of endogenous cannabinoid signaling but not EMS protects against CCH-induced neurodegeneration and preserves spatial learning and memory, possibly by activating BDNF-TrkB signaling.

Clinical and Pathological Benefits of Edaravone for Alzheimer's Disease with Chronic Cerebral Hypoperfusion in a Novel Mouse Model

Alzheimer's disease (AD) and chronic cerebral hypoperfusion (CCH) often coexist in dementia patients in aging societies. The hallmarks of AD including amyloid-β (Aβ)/phosphorylated tau (pTau) and pathology-related events such as neural oxidative stress and neuroinflammation play critical roles in pathogenesis of AD with CCH. A large number of lessons from failures of drugs targeting a single target or pathway on this so complicated disease indicate that disease-modifying therapies targeting multiple key pathways hold potent potential in therapy of the disease. In the present study, we used a novel mouse model of AD with CCH to investigate a potential therapeutic effect of a free radical scavenger, Edaravone (EDA) on AD with CCH via examining motor and cognitive capacity, AD hallmarks, neural oxidative stress, and neuroinflammation. Compared with AD with CCH mice at 12 months of age, EDA significantly improved motor and cognitive deficits, attenuated neuronal loss, reduced Aβ/pTau accumulation, and alleviated neural oxidative stress and neuroinflammation. These findings suggest that EDA possesses clinical and pathological benefits for AD with CCH in the present mouse model and has a potential as a therapeutic agent for AD with CCH via targeting multiple key pathways of the disease pathogenesis.

Atorvastatin ameliorates depressive behaviors and neuroinflammatory in streptozotocin-induced diabetic mice

Depression is a chronic and progressive syndrome and commonly associated with several neuropsychiatric comorbidities, of which depression is the most studied. It has been demonstrated that statins also have anti-inflammatory and immunomodulatory properties, which being explored for potential benefits in depression. However, the role of statins in the treatment of diabetes-related depression has not been well examined. Herein, we investigated the effects of atorvastatin on depressive behaviors and neuroinflammation in streptozotocin-induced diabetic mice. Our data indicated that oral administration of atorvastatin at 10 or 20 mg/kg for 3 weeks markedly ameliorated diabetes-associated depressive behaviors reflected by better performance in sucrose preference test (SPT), tail suspension test (TST), and novelty-suppressed feeding test (NSFT). The study further showed that atrovastatin decreased the expression of nucleus NF-κB p65 expression and ameliorated neuroinflammatory responses in prefrontal cortex as evidenced by less Iba-1-positive cells and lower inflammatory mediators including IL-1β and TNF-α. As expected, atorvastatin-treated diabetic mice exhibited significant improvement of hyperlipidemia rather than hyperglycemia. These results suggest that atorvastatin has the potential to be employed as a therapy for diabetes-related depression.

Effect of amyloid toxicity or chronic cerebral hypoperfusion on brain insulin resistance in a rat model with intracerebroventricular streptozotocin

Sporadic Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder affected by amyloid and vascular pathogenesis. Brain insulin resistance (BIR) has been suggested as one of the pathomechanisms of sporadic AD. We investigated how the amyloid and vascular pathogenesis of AD interacts with BIR. We examined experimental groups mimicking amyloid pathogenesis following intracerebroventriculr (icv) injection of amyloid β or vascular pathogenesis following permanent ligation of the bilateral common carotid arteries in Wistar rats that had undergone icv injection of streptozotocin. Behavioral tests and pathologic studies were performed. Cognitive impairments were induced by BIR superimposed by amyloid or vascular pathogenesis. Neuroinflammation in the white matter and hippocampus was aggravated by an interaction between BIR and vascular pathogenesis. Amyloid-associated pathology in the white matter was enhanced by BIR and vascular pathogenesis. Tau-associated pathology in the hippocampus was altered by BIR in a relation with amyloid or vascular pathogenesis. Our study may provide useful experimental insights based on an integrated approach to the influence of amyloid and vascular pathogenesis on BIR, permitting better understanding of the heterogeneous pathogenesis of sporadic AD. Pathologic responses in sporadic AD may differ depending on amyloid and vascular pathogenesis and may sometimes be synergistically aggravated when combined with BIR.

Progress in the Mechanism and Clinical Application of Cilostazol

Cilostazol is a unique platelet inhibitor that has been used clinically for more than 20 years. As a phosphodiesterase type III inhibitor, cilostazol is capable of reversible inhibition of platelet aggregation and vasodilation, has antiproliferative effects, and is widely used in the treatment of peripheral arterial disease, cerebrovascular disease, percutaneous coronary intervention, etc. This article briefly reviews the pharmacological mechanisms and clinical application of cilostazol.

Influence of metabolic syndrome on cerebral perfusion and cognition

Vascular cognitive impairment (VCI) is associated with chronic cerebral hypoperfusion (CCH) and memory deficits, and often occurs concurrently with metabolic syndrome (MetS). Despite their common occurrence, it is unknown whether CCH and MetS act synergistically to exacerbate VCI-associated pathology. Here, using male Sprague-Dawley rats, we examined the effects of a clinically relevant model of adolescent-onset MetS and adult-onset CCH on neuro-vascular outcomes, combining a cafeteria diet with a 2-vessel occlusion (2VO) model. Using longitudinal imaging, histology, and behavioural assessments, we identified several features of MetS and CCH including reduced cerebral blood volume, white matter atrophy, alterations in hippocampal cell density, and memory impairment. Furthermore, we identified a number of significant associations, potentially predictive of MetS and pathophysiological outcomes. White matter volume was positively correlated to HDL cholesterol; hippocampal cell density was negatively correlated to fasted blood glucose; cerebral blood flow and volume was negatively predicted by the combination of 2VO surgery and increased fasted blood glucose. These results emphasize the importance of including comorbid conditions when modeling VCI, and they outline a highly translational preclinical model that could be used to investigate potential interventions to mitigate VCI-associated pathology and cognitive decline.

Thioredoxin-Interacting Protein (TXNIP) Regulates Parkin/PINK1-mediated Mitophagy in Dopaminergic Neurons Under High-glucose Conditions: Implications for Molecular Links Between Parkinson's Disease and Diabetes

Patients with diabetes mellitus have a higher risk of developing Parkinson's disease (PD). However, the molecular links between PD and diabetes remain unclear. In this study, we investigated the roles of thioredoxin-interacting protein (TXNIP) in Parkin/PINK1-mediated mitophagy in dopaminergic (DA) cells under high-glucose (HG) conditions. In streptozotocin-induced diabetic mice, TXNIP was upregulated and autophagy was inhibited in the midbrain, while the loss of DA neurons was accelerated by hyperglycemia. In cultured PC12 cells under HG, TXNIP expression was upregulated and the intracellular reactive oxygen species (ROS) levels increased, leading to cell death. Autophagic flux was further blocked and PINK1 expression was decreased under HG conditions. Parkin expression in the mitochondrial fraction and carbonyl cyanide 3-chlorophenylhydrazone (CCCP)-induced co-localization of COX IV (marker for mitochondria) and LAMP1 (marker for lysosomes) were also significantly decreased by HG. Overexpression of TXNIP was sufficient to decrease the expression of both PINK1 and Parkin in PC12 cells, while knockdown of the expression of TXNIP by siRNA decreased intracellular ROS and attenuated cellular injury under HG. Moreover, inhibition of TXNIP improved the CCCP-induced co-localization of COX IV and LAMP1 in PC12 cells under HG. Together, these results suggest that TXNIP regulates Parkin/PINK1-mediated mitophagy under HG conditions, and targeting TXNIP may be a promising therapeutic strategy for reducing the risk of PD under hyperglycemic conditions.

Cerebral Small Vessel Disease (CSVD) - Lessons From the Animal Models

Cerebral small vessel disease (CSVD) refers to a spectrum of clinical and imaging findings resulting from pathological processes of various etiologies affecting cerebral arterioles, perforating arteries, capillaries, and venules. Unlike large vessels, it is a challenge to visualize small vessels in vivo, hence the difficulty to directly monitor the natural progression of the disease. CSVD might progress for many years during the early stage of the disease as it remains asymptomatic. Prevalent among elderly individuals, CSVD has been alarmingly reported as an important precursor of full-blown stroke and vascular dementia. Growing evidence has also shown a significant association between CSVD's radiological manifestation with dementia and Alzheimer's disease (AD) pathology. Although it remains contentious as to whether CSVD is a cause or sequelae of AD, it is not far-fetched to posit that effective therapeutic measures of CSVD would mitigate the overall burden of dementia. Nevertheless, the unifying theory on the pathomechanism of the disease remains elusive, hence the lack of effective therapeutic approaches. Thus, this chapter consolidates the contemporary insights from numerous experimental animal models of CSVD, to date: from the available experimental animal models of CSVD and its translational research value; the pathomechanical aspects of the disease; relevant aspects on systems biology; opportunities for early disease biomarkers; and finally, converging approaches for future therapeutic directions of CSVD.

Phosphodiesterase inhibitors say NO to Alzheimer's disease

Phosphodiesterases (PDEs) consisted of 11 subtypes (PDE1 to PDE11) and over 40 isoforms that regulate levels of cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP), the second messengers in cell functions. PDE inhibitors (PDEIs) have been attractive therapeutic targets due to their involvement in diverse medical conditions, e.g. cardiovascular diseases, autoimmune diseases, Alzheimer's disease (AD), etc. Among them; AD with a complex pathology is a progressive neurodegenerative disorder which affect mostly senile people in the world and only symptomatic treatment particularly using cholinesterase inhibitors in clinic is available at the moment for AD. Consequently, novel treatment strategies towards AD are still searched extensively. Since PDEs are broadly expressed in the brain, PDEIs are considered to modulate neurodegenerative conditions through regulating cAMP and cGMP in the brain. In this sense, several synthetic or natural molecules inhibiting various PDE subtypes such as rolipram and roflumilast (PDE4 inhibitors), vinpocetine (PDE1 inhibitor), cilostazol and milrinone (PDE3 inhibitors), sildenafil and tadalafil (PDE5 inhibitors), etc have been reported showing encouraging results for the treatment of AD. In this review, PDE superfamily will be scrutinized from the view point of structural features, isoforms, functions and pharmacology particularly attributed to PDEs as target for AD therapy.

Triptolide Improves Cognitive Dysfunction in Rats with Vascular Dementia by Activating the SIRT1/PGC-1α Signaling Pathway

Tripterygium Wilfordii Hook F has been exploited as a treatment for several diseases due to its neuroprotective, anti-tumor, and anti-inflammatory effects. Triptolide is one of its key bioactive compounds. Currently, the role of triptolide in cognitive dysfunction remains unclear. Here, the role of triptolide on cognitive dysfunction was investigated using chronic cerebral hypoperfusion-induced vascular dementia (VD) rat model. SD rats were administrated with Triptolide (5 μg/kg) for 6 weeks after undergoing permanent bilateral common carotid artery occlusion. The results show that triptolide treatment conferred neuroprotective effects in VD rats. Intraperitoneal injection of triptolide attenuated oxidative stress, learning and memory deficits, and neuronal apoptosis in the hippocampi. Moreover, triptolide enhanced the expression of SIRT1, PGC-1α, ZO-1, Claudin-5, and decreased the serum levels of NSE and S100B significantly. It also improved CCH-induced learning and memory deficits, and this is attributed to its capacity to promote SIRT1/PGC-1α signaling, confer antioxidant effects, and inhibit neuronal apoptosis. These findings indicate that triptolide may be an effective therapeutic agent for vascular cognitive dysfunction.

Insights into the potential antidepressant mechanisms of cilostazol in chronically restraint rats: impact on the Nrf2 pathway

Ample evidence has pointed to a close link between oxidative stress, mitochondrial dysfunction, and depression. Nuclear factor-erythroid 2-related factor-2 (Nrf2) is a master regulator of cellular redox homeostasis and affects mitochondrial function. Nrf2 holds promise for depression prevention and treatment. This study aimed to investigate the potential prophylactic antidepressant effect of cilostazol and the contribution of the Nrf2 pathway toward the putative neuroprotection. The behavioral and neurochemical effects of concomitant treatment of oral cilostazol at doses of 7.5, 15, and 30 mg/kg/day in Wistar rats exposed to chronic restraint stress (CRS) for 4 weeks were assayed. Cilostazol prevented CRS-induced depressive-like behavior shown in sucrose-preference, forced-swimming, and open-field tests, and hypothalamus-pituitary-adrenal axis hyperactivity (adrenal gland weight and serum corticosterone). Cilostazol prevented CRS-induced increase in hippocampal lipid peroxidation and 8-hydroxy-2'-deoxyguanosine, and a decrease in antioxidant activities (glutathione level, superoxide dismutase, and catalase). Western blot and PCR showed that cilostazol favorably modulated the Nrf2 protein and heme oxygenase-1 and NAD(P)H: quinone oxidoreductase-1 gene expression in the hippocampus of CRS rats. Cilostazol also prevented the decrease in the hippocampal activities of mitochondrial respiratory enzyme complexes I-IV. These behavioral and biochemical findings indicated the potential prophylactic antidepressant effect and mechanism of cilostazol by preventing oxidative stress by activation of redox defense mechanisms mediated through the Nrf2 pathway and restoring mitochondrial dysfunction.

Neuregulin1 attenuates cognitive deficits and hippocampal CA1 neuronal apoptosis partly via ErbB4 receptor in a rat model of chronic cerebral hypoperfusion

Neuregulin1 (NRG1) is an effective neuroprotectant. Previously we demonstrated that the expression of hippocampal NRG1/ErbB4 gradually decreased and correlates with neuronal apoptosis during chronic cerebral hypoperfusion (CCH). Here we aimed to further investigate the protective role of NRG1 in CCH. AG1478, an ErbB4 inhibitor, was used to explore the involvement of ErbB4 receptors in NRG1's action. Permanent bilateral common carotid artery occlusion (2VO) or sham operation was performed in Sprague-Dawley rats. NRG1 (100 μM) and AG1478 (50 mM) was administered intraventricularly. Eight weeks post-surgery, cognitive impairment was analyzed using Morris water maze (MWM) and radial arm water maze (RAWM) tests, followed by histological assessment of the survival and apoptosis of hippocampal CA1 neurons using NeuN and TUNEL immunostaining respectively. Expression of apoptosis-related proteins and ErbB4 activation (pErbB4/ErbB4) was evaluated by Western blotting. The results showed that NRG1 significantly improved the performances in MWM (spatial learning and memory) and RAWM (spatial working and reference memory), attenuated hippocampal CA1 neuronal loss and apoptosis, upregulated the expression of pErbB4/ErbB4 and the anti-apoptotic protein Bcl-2, and downregulated the expression of pro-apoptotic proteins of Cleaved (Cl)-caspase3 and Bax. In addition, the protective effects of NRG1 could be partly abolished by AG1478. Taken together, our study suggested that NRG1 ameliorates cognitive impairment and neuronal apoptosis partly via ErbB4 receptors in rats with CCH.

The Expression of Hippocampal NRG1/ErbB4 Correlates With Neuronal Apoptosis, but Not With Glial Activation During Chronic Cerebral Hypoperfusion

Permanent bilateral common carotid occlusion (2VO) is well-established to investigate the chronic cerebral hypoperfusion (CCH)-induced cognitive deficits. Besides, previous studies suggested that disturbance of Neuregulin1 (NRG1)/ErbB4 signaling is associated with cognitive impairments, as well as neuronal apoptosis and neuroinflammation in CNS. However, the expression pattern of hippocampal NRG1/ErbB4 has not been systematically investigated during CCH. Here, we aim to investigate the temporal changes of hippocampal NRG1/ErbB4 during CCH and their possible relationship with neuronal apoptosis and glial activation. Morris water maze (MWM) and Radial arm water maze (RAWM) tests were used to analyze cognitive impairment in 2VO rats at 28 days post-surgery, and Enzyme-Linked Immunosorbent Assay (ELISA), western blotting and immunostaining were performed at different time points (24 h, 7 days, 14 days, 28 days) to detect the expression pattern of NRG1/ErbB4 and the distribution of ErbB4. Neuronal nuclei (NeuN), NeuN/TUNEL, Iba1 and GFAP immunostaining and caspase activity in hippocampal CA1 subarea were assessed during CCH as well. We found that the expression of NRG1 and phosphorylated ErbB4 (pErbB4)/ErbB4 changed in a time-dependent manner (up-regulated in the acute phase and then decreased in the chronic phase of CCH). Besides, ErbB4-expressed neurons and selective types of GABAergic cells decreased after CCH, but the distribution pattern of ErbB4 remained unchanged. In addition, the expression of hippocampal NRG1/ErbB4 positively correlated with the level of neuronal apoptosis (both NeuN/TUNEL immunostaining and caspase-3 activity), but not with glial activation according to Pearson’s correlation. These findings indicated that hippocampal NRG1/ErbB4 may be involved in the pathogenesis of CCH, especially neuronal apoptosis during CCH.

Betulinic acid, a natural PDE inhibitor restores hippocampal cAMP/cGMP and BDNF, improve cerebral blood flow and recover memory deficits in permanent BCCAO induced vascular dementia in rats

Vascular dementia (VaD) is the second most common form of senile dementia, embraces memory deficits, neuroinflammation, executive function damage, mood and behavioral changes and abnormal cerebral blood flow. The purpose of the study was to explore the therapeutic potential of betulinic acid in bilateral common carotid artery occlusion (BCCAO) induced VaD in experimental rats. VaD was induced by BCCAO in rats and betulinic acid (10 and 15 mg/kg/day po) was administered 1 week after surgery. The cerebral blood pressure of the animal was recorded before and after the treatment using Laser Doppler flow meter. Object recognition task for non-spatial, Morris water maze for spatial and locomotor activity was performed to evaluate behavioral changes in rats. At the end of the study, animals were decapitated and hippocampus was separated to perform biochemical, neuroinflammatory and second messengers cAMP/cGMP analysis. Histology was done to study the brain pathophysiology. BCCAO surgery was able to significantly impaired memory in rats as observed behavioral and biochemical parameters. Moreover, BA demonstrated a neuroprotective effect in a dose-dependent manner. BA was able to re-establish cerebral blood flow, restore behavioral parameters and showed significant improvements in the as cAMP,cGMP and BDNF levels, restrain the oxidative stress and inflammatory parameters. In histopathology, betulinic acid treated groups showed a decrease in microgliosis and less pathological abnormalities comparable to diseased rat's brain. The observed effect might be attributed to the neuroprotective potential of betulinic acid and its ability to restore cognitive impairment and hippocampal neurochemistry in VaD.

Dihydromyricetin improves type 2 diabetes-induced cognitive impairment via suppressing oxidative stress and enhancing brain-derived neurotrophic factor-mediated neuroprotection in mice

Type 2 diabetes mellitus (T2DM) leads to cognitive impairment (CI), but there have been no effective pharmacotherapies or drugs for cognitive dysfunction in T2DM. Dihydromyricetin (DHM) is a natural flavonoid compound extracted from the leaves of Ampelopsis grossedentata and has various pharmacological effects including anti-oxidant and anti-diabetes. Thus, we investigated the effects of DHM on CI in T2DM mouse model and its possible mechanism. To induce T2DM, mice were fed with high-sugar and high-fat diet for 8 weeks, followed by a low dose streptozotocin (STZ) administration. After the successful induction of T2DM mouse model, mice were treated respectively with equal volume of saline (T2DM group), 125 mg/kg/d DHM (L-DHM group), or 250 mg/kg/d DHM (H-DHM group). After 16 weeks of DHM administration, the body weight (BW), fasting blood glucose, blood lipids, intraperitoneal glucose tolerance (IPGT), and cognitive function were determined. Then, alterations in the expressions of oxidative stress markers and brain-derived neurotrophic factor (BDNF) in the hippocampus were investigated. Our findings demonstrated that DHM could significantly ameliorate CI and reverse aberrant glucose and lipid metabolism in T2DM mice, likely through the suppression of oxidative stress and enhancement of BDNF-mediated neuroprotection. In conclusion, our results suggest that DHM is a promising candidate for the treatment of T2DM-induced cognitive dysfunction.

Involvement of impaired autophagy and mitophagy in Neuro-2a cell damage under hypoxic and/or high-glucose conditions

Chronic cerebral hypoperfusion (CCH) plays an insidious role in the development of cognitive impairment. Considerable evidence suggests that Diabetes Mellitus (DM) as a vascular risk factor may exacerbate CCH and is closely related to cognitive decline. Dysregulation of autophagy is known to be associated with the pathogenesis of neurodegenerative diseases such as Alzheimer's disease. To elucidate the role of autophagy in CCH- and/or DM-related pathogenesis, mouse neuroblastoma Neuro-2a cells were exposed to hypoxia and/or high glucose for 48 h, mimicking CCH complicated with DM pathologies. Chronic hypoxia reduced cell proliferation and increased levels of cleaved caspase-3, whereas high glucose had no obvious synergistic toxic effect. Accumulation of autophagic vacuoles under hypoxia may be due to both autophagy impairment and induction, with the former accounting for Neuro-2a cell death. Additionally, aberrant accumulation of mitochondria in Neuro-2a cells may be attributed to insufficient BNIP3-mediated mitophagy due to poor interaction between BNIP3 and LC3-II. Despite the lack of a significant cytotoxic effect of high glucose under our experimental conditions, our data indicated for the first time that impaired autophagy degradation and inefficient BNIP3-mediated mitophagy may constitute mechanisms underlying neuronal cell damage during chronic hypoxia.

Potential benefits of mesenchymal stem cells and electroacupuncture on the trophic factors associated with neurogenesis in mice with ischemic stroke

The beneficial effects of mesenchymal stem cells (MSCs) and electroacupuncture (EA) on neurogenesis and related trophic factors remain unclear. Bone marrow MSCs (mBMSC) were transplanted into the striatum of mice with middle cerebral artery occlusion (MCAO), and EA stimulation was applied at two acupoints, Baihui and Dazhui. EA treatment significantly improved motor function, and a synergistic effect of combined mBMSC and EA treatment was observed. Combined mBMSC and EA treatment reduced prominent atrophic changes in the striatum and led to proliferation of neural progenitor cells in the subventricular zone (SVZ) and the surrounding areas of the striatum (SVZ + striatum) of MCAO mice. The mBMSC and EA treatment markedly enhanced mature brain-derived neurotrophic factor (mBDNF) expression in the SVZ + striatum and hippocampus of mice with MCAO, and combined treatment enhanced neurotrophin-4 (NT4) expression. The number of mBDNF- and NT4-positive neurons in the SVZ + striatum and hippocampus increased following EA treatment. Combined treatment led to an increase in the expression levels of phosphorylated cAMP response element binding protein in the neuroblasts of the striatum. Our results indicate that combined MSC and EA treatment may lead to a better therapeutic effect via co-regulation of neurotrophic factors in the brain, by regulating neurogenesis more than single therapy.

Endoplasmic reticulum stress/autophagy pathway is involved in diabetes-induced neuronal apoptosis and cognitive decline in mice

Diabetes mellitus is a significant global public health problem depicting a rising prevalence worldwide. As a serious complication of diabetes, diabetes-associated cognitive decline is attracting increasing attention. However, the underlying mechanisms are yet to be fully determined. Both endoplasmic reticulum (ER) stress and autophagy have been reported to modulate neuronal survival and death and be associated with several neurodegenerative diseases. Here, a streptozotocin-induced diabetic mouse model and primary cultured mouse hippocampal neurons were employed to investigate the possible role of ER stress and autophagy in diabetes-induced neuronal apoptosis and cognitive impairments, and further explore the potential molecular mechanisms. ER stress markers GRP78 and CHOP were both enhanced in diabetic mice, as was phosphorylation of PERK, IRE1α, and JNK. In addition, the results indicated an elevated level of autophagy in diabetic mice, as demonstrated by up-regulated expressions of autophagy markers LC3-II, beclin 1 and down-regulated level of p62, and increased formation of autophagic vacuoles and LC3-II aggregates. Meanwhile, we found that these effects could be abolished by ER stress inhibitor 4-phenylbutyrate or JNK inhibitor SP600125 in vitro. Furthermore, neuronal apoptosis of diabetic mice was attenuated by pretreatment with 4-phenylbutyrate, while aggravated by application of inhibitor of autophagy bafilomycin A1 in vitro. These results suggest that ER stress pathway may be involved in diabetes-mediated neurotoxicity and promote the following cognitive impairments. More important, autophagy was induced by diabetes possibly through ER stress-mediated JNK pathway, which may protect neurons against ER stress-associated cell damages.

Liraglutide ameliorates cognitive decline by promoting autophagy via the AMP-activated protein kinase/mammalian target of rapamycin pathway in a streptozotocin-induced mouse model of diabetes

Diabetic cognitive dysfunction has gained widespread attention for its deleterious impact on individuals with diabetes. However, few clinical interventions are available to prevent the disorder. The glucagon-like peptide-1 analog liraglutide exerts neuroprotective effects in several models of neurodegenerative diseases. We investigated the effect of liraglutide pretreatment on diabetes-induced cognitive decline and explored the underlying mechanisms in vivo and in vitro. Liraglutide pretreatment prevented diabetes-induced cognitive impairment as assessed by the Morris Water Maze test, and alleviated neuronal injuries and ultrastructural damage to synapses in the hippocampal CA1 region. Furthermore, liraglutide promoted autophagy as indicated by enhanced expression of the autophagy markers Microtubule-associated protein 1 light chain 3 (LC3)-II and Beclin 1, decreased expression of p62, and increased formation of autophagic vacuoles and LC3-II aggregates. In vitro, liraglutide treatment elevated phosphorylated (p)-AMP-activated protein kinase (AMPK) levels and reduced p-mammalian target of rapamycin (p-mTOR) expression. Additionally, the AMPK inhibitor Compound C exhibited an inhibitory effect on liraglutide-induced increased LC3-II expression and p62 degradation. Liraglutide exhibits neuroprotective effects against diabetes-induced hippocampal neuronal injuries and cognitive impairment by promoting autophagy via the AMPK/mTOR pathway.

The Giant Geriatric Syndromes Are Intensified by Diabetic Complications

By 2015, diabetes has affected more than 415 million people over the world. It is anticipated that 640 million adults will suffer from diabetes in 2040. The elongation of the life expectancy, as the result of better general health care, extends also the time when diabetic complications may develop together with other senility-specific problems. The Giant Geriatric Syndromes (Geriatric Giants) have been qualified by the original Nascher's criteria defined more than 100 years ago, but they are becoming more and more relevant in connection with the aging of societies. The criteria comprise the older age, commonness of the health problem, multifactorial etiology, functional or cognitive impairment, worsened outcome, and increased morbidity and mortality. We described the impact of diabetes on Geriatric Giants including cognitive dysfunction, depression, malnutrition, incontinence, falls and fractures, chronic pain, and the loss of senses. The association of diabetes with Geriatric Giants reveals as a vicious circle with the background of neurovascular complications. However, diabetes influence on the incidence of cancer in elderly was also discussed, since neoplastic diseases associate with Geriatric Giants, for example, chronic pain and depression. The knowledge about these aspects of functional decline in geriatric population is crucial to improve patient care.

Advances in chronic cerebral circulation insufficiency

Chronic cerebral circulation insufficiency (CCCI) may not be an independent disease; rather, it is a pervasive state of long-term cerebral blood flow insufficiency caused by a variety of etiologies, and considered to be associated with either occurrence or recurrence of ischemic stroke, vascular cognitive impairment, and development of vascular dementia, resulting in disability and mortality worldwide. This review summarizes the features and recent progress of CCCI, mainly focusing on epidemiology, experimental research, pathophysiology, etiology, clinical manifestations, imaging presentation, diagnosis, and potential therapeutic regimens. Some research directions are briefly discussed as well.

Dl-3-n-Butylphthalide Treatment Enhances Hemodynamics and Ameliorates Memory Deficits in Rats with Chronic Cerebral Hypoperfusion

Our previous study has revealed that chronic cerebral hypoperfusion (CCH) activates a compensatory vascular mechanism attempting to maintain an optimal cerebral blood flow (CBF). However, this compensation fails to prevent neuronal death and cognitive impairment because neurons die prior to the restoration of normal CBF. Therefore, pharmacological invention may be critical to enhance the CBF for reducing neurodegeneration and memory deficit. Dl-3-n-butylphthalide (NBP) is a compound isolated from the seeds of Chinese celery and has been proven to be able to prevent neuronal loss, reduce inflammation and ameliorate memory deficits in acute ischemic animal models and stroke patients. In the present study, we used magnetic resonance imaging (MRI) techniques, immunohistochemistry and Morris water maze (MWM) to investigate whether NBP can accelerate CBF recovery, reduce neuronal death and improve cognitive deficits in CCH rats after permanent bilateral common carotid artery occlusion (BCCAO). Rats were intravenously injected with NBP (5 mg/kg) daily for 14 days beginning the first day after BCCAO. The results showed that NBP shortened recovery time of CBF to pre-occlusion levels at 2 weeks following BCCAO, compared to 4 weeks in the vehicle group, and enhanced hemodynamic compensation through dilation of the vertebral arteries (VAs) and increase in angiogenesis. NBP treatment also markedly reduced reactive astrogliosis and cell apoptosis and protected hippocampal neurons against ischemic injury. The escape latency of CCH rats in the MWM was also reduced in response to NBP treatment. These findings demonstrate that NBP can accelerate the recovery of CBF and improve cognitive function in a rat model of CCH, suggesting that NBP is a promising therapy for CCH patients or vascular dementia.

Bridging Type 2 Diabetes and Alzheimer's Disease: Assembling the Puzzle Pieces in the Quest for the Molecules With Therapeutic and Preventive Potential

Type 2 diabetes (T2D) and Alzheimer's disease (AD) are two age-related amyloid diseases that affect millions of people worldwide. Broadly supported by epidemiological data, the higher incidence of AD among type 2 diabetic patients led to the recognition of T2D as a tangible risk factor for the development of AD. Indeed, there is now growing evidence on brain structural and functional abnormalities arising from brain insulin resistance and deficiency, ultimately highlighting the need for new approaches capable of preventing the development of AD in type 2 diabetic patients. This review provides an update on overlapping pathophysiological mechanisms and pathways in T2D and AD, such as amyloidogenic events, oxidative stress, endothelial dysfunction, aberrant enzymatic activity, and even shared genetic background. These events will be presented as puzzle pieces put together, thus establishing potential therapeutic targets for drug discovery and development against T2D and diabetes-induced cognitive decline-a heavyweight contributor to the increasing incidence of dementia in developed countries. Hoping to pave the way in this direction, we will present some of the most promising and well-studied drug leads with potential against both pathologies, including their respective bioactivity reports, mechanisms of action, and structure-activity relationships.

Inter-day reliability of blood pressure and cerebral blood flow velocities in persons with spinal cord injury and intact controls

BACKGROUND

Due to interruption of cardiovascular autonomic control unstable blood pressure (BP) is common in individuals with spinal cord injury (SCI) above the sixth thoracic vertebral level. The impact of unstable BP on cerebral blood flow (CBF) is not well appreciated, but symptoms associated with altered cerebral perfusion are reported, which can negatively impact daily life activities.

METHODS

We measured seated BP and CBF in participants with SCI and able-bodied (AB) controls on three laboratory visits to determine the inter-day reliability (intraclass correlation coefficient: ICC). BP was assessed at the finger using photoplethysmography and at the brachial artery with manual sphygmomanometry. CBF velocities (CBFv) were assessed at the middle cerebral artery using transcranial Doppler (TCD) ultrasound.

RESULTS

Data were collected in 15 participants with chronic SCI (C3-T4) and 10 AB controls, the groups did not differ for age, height, weight or BMI; however, brachial BP (P < 0.001), finger BP (P < 0.01) and CBFv (P < 0.05) were significantly lower in the SCI group compared to the controls. The inter-day ICC for brachial BP ranged from 0.51 to 0.79, whereas the ICC for finger BP was not as high (0.17 to 0.47). The inter-day ICC for CBFv ranged from 0.45 to 0.96, indicating fair to substantial reliability.

CONCLUSIONS

These data indicate good inter-day reliability of brachial BP and TCD recording of CBFv; however, the assessment of finger BP appears to be somewhat less reliable. In addition, these data confirm reduced resting CBFv in association with hypotension in individuals with SCI compared to matched controls with low BP.

Moderate exercise ameliorates dysregulated hippocampal glycometabolism and memory function in a rat model of type 2 diabetes

AIMS/HYPOTHESIS

Type 2 diabetes is likely to be an independent risk factor for hippocampal-based memory dysfunction, although this complication has yet to be investigated in detail. As dysregulated glycometabolism in peripheral tissues is a key symptom of type 2 diabetes, it is hypothesised that diabetes-mediated memory dysfunction is also caused by hippocampal glycometabolic dysfunction. If so, such dysfunction should also be ameliorated with moderate exercise by normalising hippocampal glycometabolism, since 4 weeks of moderate exercise enhances memory function and local hippocampal glycogen levels in normal animals.

METHODS

The hippocampal glycometabolism in OLETF rats (model of human type 2 diabetes) was assessed and, subsequently, the effects of exercise on memory function and hippocampal glycometabolism were investigated.

RESULTS

OLETF rats, which have memory dysfunction, exhibited higher levels of glycogen in the hippocampus than did control rats, and breakdown of hippocampal glycogen with a single bout of exercise remained unimpaired. However, OLETF rats expressed lower levels of hippocampal monocarboxylate transporter 2 (MCT2, a transporter for lactate to neurons). Four weeks of moderate exercise improved spatial memory accompanied by further increase in hippocampal glycogen levels and restoration of MCT2 expression independent of neurotrophic factor and clinical symptoms in OLETF rats.

CONCLUSIONS/INTERPRETATION

Our findings are the first to describe detailed profiles of glycometabolism in the type 2 diabetic hippocampus and to show that 4 weeks of moderate exercise improves memory dysfunction in type 2 diabetes via amelioration of dysregulated hippocampal glycometabolism. Dysregulated hippocampal lactate-transport-related glycometabolism is a possible aetiology of type-2-diabetes-mediated memory dysfunction.

Antidepressant Effects of Aripiprazole Augmentation for Cilostazol-Treated Mice Exposed to Chronic Mild Stress after Ischemic Stroke

The aim of this study was to determine the effects and underlying mechanism of aripiprazole (APZ) augmentation for cilostazol (CLS)-treated post-ischemic stroke mice that were exposed to chronic mild stress (CMS). Compared to treatment with either APZ or CLS alone, the combined treatment resulted in a greater reduction in depressive behaviors, including anhedonia, despair-like behaviors, and memory impairments. This treatment also significantly reduced atrophic changes in the striatum, cortex, and midbrain of CMS-treated ischemic mice, and inhibited neuronal cell apoptosis, particularly in the striatum and the dentate gyrus of the hippocampus. Greater proliferation of neuronal progenitor cells was also observed in the ipsilateral striatum of the mice receiving combined treatment compared to mice receiving either drug alone. Phosphorylation of the cyclic adenosine monophosphate response element binding protein (CREB) was increased in the striatum, hippocampus, and midbrain of mice receiving combined treatment compared to treatment with either drug alone, particularly in the neurons of the striatum and hippocampus, and dopaminergic neurons of the midbrain. Our results suggest that APZ may augment the antidepressant effects of CLS via co-regulation of the CREB signaling pathway, resulting in the synergistic enhancement of their neuroprotective effects.

Cerebrovascular complications of diabetes: focus on cognitive dysfunction

The incidence of diabetes has more than doubled in the United States in the last 30 years and the global disease rate is projected to double by 2030. Cognitive impairment has been associated with diabetes, worsening quality of life in patients. The structural and functional interaction of neurons with the surrounding vasculature is critical for proper function of the central nervous system including domains involved in learning and memory. Thus, in this review we explore cognitive impairment in patients and experimental models, focusing on links to vascular dysfunction and structural changes. Lastly, we propose a role for the innate immunity-mediated inflammation in neurovascular changes in diabetes.

Anti-photoaging properties of the phosphodiesterase 3 inhibitor cilostazol in ultraviolet B-irradiated hairless mice

We investigated whether cilostazol, an activator of cyclic adenosine monophosphate (cAMP)-dependent intracellular signaling, could inhibit ultraviolet B (UVB) irradiation-induced photoaging in HR-1 hairless mice. Cilostazol decreased wrinkle formation and skin thickness in UVB-irradiated mice, as well as increased staining of collagen fibers and inhibition of reactive oxygen species (ROS) formation in the skin. Moreover, the proteolytic activities of gelatinase matrix metalloproteinase (MMP)-9 and collagenase MMP-3 were significantly decreased in UVB-irradiated mice treated with cilostazol. Western blotting showed that UVB-induced activation of p38 mitogen-activated protein kinases (MAPK) and nuclear factor (NF)-κB was significantly inhibited by cilostazol, whereas the activation of Akt was significantly enhanced by cilostazol. Confirmation of localized protein expression in the skin revealed marked p38 MAPK and NF-κB activation that was mainly detected in the dermis. Marked Akt activation was mainly detected in the epidermis. Our results suggest that cilostazol may have anti-photoaging effects on UVB-induced wrinkle formation by maintaining the extracellular matrix density in the dermis, which occurs via regulation of ROS and related p38 MAPK and NF-κB signaling, and subsequent down-regulation of MMPs. Therefore, cilostazol may protect against photoaging-induced wrinkle formation.

High fat diet-induced diabetes in mice exacerbates cognitive deficit due to chronic hypoperfusion

Diabetes causes endothelial dysfunction and increases the risk of vascular cognitive impairment. However, it is unknown whether diabetes causes cognitive impairment due to reductions in cerebral blood flow or through independent effects on neuronal function and cognition. We addressed this using right unilateral common carotid artery occlusion to model vascular cognitive impairment and long-term high-fat diet to model type 2 diabetes in mice. Cognition was assessed using novel object recognition task, Morris water maze, and contextual and cued fear conditioning. Cerebral blood flow was assessed using arterial spin labeling magnetic resonance imaging. Vascular cognitive impairment mice showed cognitive deficit in the novel object recognition task, decreased cerebral blood flow in the right hemisphere, and increased glial activation in white matter and hippocampus. Mice fed a high-fat diet displayed deficits in the novel object recognition task, Morris water maze and fear conditioning tasks and neuronal loss, but no impairments in cerebral blood flow. Compared to vascular cognitive impairment mice fed a low fat diet, vascular cognitive impairment mice fed a high-fat diet exhibited reduced cued fear memory, increased deficit in the Morris water maze, neuronal loss, glial activation, and global decrease in cerebral blood flow. We conclude that high-fat diet and chronic hypoperfusion impair cognitive function by different mechanisms, although they share commons features, and that high-fat diet exacerbates vascular cognitive impairment pathology.

Cerebral hypoperfusion and glucose hypometabolism: Key pathophysiological modulators promote neurodegeneration, cognitive impairment, and Alzheimer's disease

Aging, hypertension, diabetes, hypoxia/obstructive sleep apnea (OSA), obesity, vitamin B12/folate deficiency, depression, and traumatic brain injury synergistically promote diverse pathological mechanisms including cerebral hypoperfusion and glucose hypometabolism. These risk factors trigger neuroinflammation and oxidative-nitrosative stress that in turn decrease nitric oxide and enhance endothelin, Amyloid-β deposition, cerebral amyloid angiopathy, and blood-brain barrier disruption. Proinflammatory cytokines, endothelin-1, and oxidative-nitrosative stress trigger several pathological feedforward and feedback loops. These upstream factors persist in the brain for decades, upregulating amyloid and tau, before the cognitive decline. These cascades lead to neuronal Ca²⁺ increase, neurodegeneration, cognitive/memory decline, and Alzheimer's disease (AD). However, strategies are available to attenuate cerebral hypoperfusion and glucose hypometabolism and ameliorate cognitive decline. AD is the leading cause of dementia among the elderly. There is significant evidence that pathways involving inflammation and oxidative-nitrosative stress (ONS) play a key pathophysiological role in promoting cognitive dysfunction. Aging and several comorbid conditions mentioned above promote diverse pathologies. These include inflammation, ONS, hypoperfusion, and hypometabolism in the brain. In AD, chronic cerebral hypoperfusion and glucose hypometabolism precede decades before the cognitive decline. These comorbid disease conditions may share and synergistically activate these pathophysiological pathways. Inflammation upregulates cerebrovascular pathology through proinflammatory cytokines, endothelin-1, and nitric oxide (NO). Inflammation-triggered ONS promotes long-term damage involving fatty acids, proteins, DNA, and mitochondria; these amplify and perpetuate several feedforward and feedback pathological loops. The latter includes dysfunctional energy metabolism (compromised mitochondrial ATP production), amyloid-β generation, endothelial dysfunction, and blood-brain-barrier disruption. These lead to decreased cerebral blood flow and chronic cerebral hypoperfusion- that would modulate metabolic dysfunction and neurodegeneration. In essence, hypoperfusion deprives the brain from its two paramount trophic substances, viz., oxygen and nutrients. Consequently, the brain suffers from synaptic dysfunction and neuronal degeneration/loss, leading to both gray and white matter atrophy, cognitive dysfunction, and AD. This Review underscores the importance of treating the above-mentioned comorbid disease conditions to attenuate inflammation and ONS and ameliorate decreased cerebral blood flow and hypometabolism. Additionally, several strategies are described here to control chronic hypoperfusion of the brain and enhance cognition. © 2016 Wiley Periodicals, Inc.