A High-sugar High-fat Diet Induced Metabolic Syndrome Shows some Symptoms of Alzheimer's Disease in Rats

Ceramides may Play a Central Role in the Pathogenesis of Alzheimer's Disease: a Review of Evidence and Horizons for Discovery

While several hypotheses have been proposed to explain the underlying mechanisms of Alzheimer's disease, none have been entirely satisfactory. Both genetic and non-genetic risk factors, such as infections, metabolic disorders and psychological stress, contribute to this debilitating disease. Multiple lines of evidence indicate that ceramides may be central to the pathogenesis of Alzheimer's disease. Tumor necrosis factor-α, saturated fatty acids and cortisol elevate the brain levels of ceramides, while genetic risk factors, such as mutations in APP, presenilin, TREM2 and APOE ε4, also elevate ceramide synthesis. Importantly, ceramides displace sphingomyelin and cholesterol from lipid raft-like membrane patches that connect the endoplasmic reticulum and mitochondria, disturbing mitochondrial oxidative phosphorylation and energy production. As a consequence, the flattening of lipid rafts alters the function of γ-secretase, leading to increased production of Aβ42. Moreover, ceramides inhibit the insulin-signaling cascade via at least three mechanisms, resulting in the activation of glycogen synthase kinase-3 β. Activation of this kinase has multiple consequences, as it further deteriorates insulin resistance, promotes the transcription of BACE1, causes hyperphosphorylation of tau and inhibits the transcription factor Nrf2. Functional Nrf2 prevents apoptosis, mediates anti-inflammatory activity and improves blood-brain barrier function. Thus, various seemingly unrelated Alzheimer's disease risk factors converge on ceramide production, whereas the elevated levels of ceramides give rise to the well-known pathological features of Alzheimer's disease. Understanding and targeting these mechanisms may provide a promising foundation for the development of novel preventive and therapeutic strategies.

Murine Non-Transgenic Models of Alzheimer's Disease Pathology: Focus on Risk Factors

Alzheimer's disease (AD) represents a significant challenge among neurodegenerative disorders, as effective treatments and therapies remain largely undeveloped. Despite extensive research efforts employing various methodologies and diverse genetic models focused on amyloid-β (Aβ) pathology, the research for effective therapeutic strategies remains inconclusive. The key pathological features of AD include Aβ senile plaques, neurofibrillary tangles (NFTs), and the activation of neuroinflammatory pathways. Presently, investigations into AD and assessing potential treatments predominantly utilize Aβ transgenic models. Conversely, non-transgenic models may provide valuable insights into the multifaceted pathological states associated with AD. Thus, these models may serve as practical complementary tools for evaluating therapeutic and intervention strategies, since the primary AD risk factors are most frequently modeled. This review aims to critically assess the existing literature on AD non-transgenic models induced by streptozotocin, scopolamine, aging, mechanical stress, metals, and dietary patterns to enhance their application in AD research.

APOE4 rat model of Alzheimer's disease: sex differences, genetic risk and diet

The strongest genetic risk factor for Alzheimer's disease (AD) is the ε4 allele of apolipoprotein E (ApoE ε4). A high fat diet also adds to the risk of dementia and AD. In addition, there are sex differences as women carriers have a higher risk of an earlier onset and rapid decline in memory than men. The present study looked at the effect of the genetic risk of ApoE ε4 together with a high fat/high sucrose diet (HFD/HSD) on brain function in male and female rats using magnetic resonance imaging. We hypothesized female carriers would present with deficits in cognitive behavior together with changes in functional connectivity as compared to male carriers. Four-month-old wildtype and human ApoE ε4 knock-in (TGRA8960), male and female Sprague Dawley rats were put on a HFD/HSD for four months. Afterwards they were imaged for changes in function using resting state BOLD functional connectivity. Images were registered to, and analyzed, using a 3D MRI rat atlas providing site-specific data on 173 different brain areas. Resting state functional connectivity showed male wildtype had greater connectivity between areas involved in feeding and metabolism while there were no differences between female and male carriers and wildtype females. The data were unexpected. The genetic risk was overshadowed by the diet. Male wildtype rats were most sensitive to the HFD/HSD presenting with a deficit in cognitive performance with enhanced functional connectivity in neural circuitry associated with food consumption and metabolism.

Mechanisms Underlying Obesity-induced Aβ Accumulation in Alzheimer's Disease: A Qualitative Review

Epidemiological studies show that individuals with obesity are more likely to develop Alzheimer's disease (AD) than those who do not have obesity. However, the mechanisms underlying the relationship between obesity and AD are not entirely unclear. Here, we have reviewed and analyzed relevant articles published in the literature and found that obesity has correlation or potential increase in the levels of β-amyloid (Aβ) protein, which may explain why people with obesity are more likely to suffer from AD. Additionally, the published findings point to the roles of obesity-related metabolic disorders, such as diabetes, inflammation, oxidative stress, and imbalance in gut microbiota in Aβ accumulation caused by obesity. Therefore, in-depth experimental and clinical studies on these mechanisms in the future may help shed light on appropriate prevention and treatment strategies for AD, such as dietary changes and regular exercise to reverse or prevent obesity and related metabolic disorders.

Aloe polysaccharides ameliorate obesity-associated cognitive dysfunction in high-fat diet-fed mice by targeting the gut microbiota and intestinal barrier integrity

Aloe polysaccharides (APs) display cognition-improving properties, but the underlying mechanisms remain unclear. Herein, AP supplementation for 24 weeks significantly improved cognitive behavioral disturbances caused by a high-fat diet. Moreover, APs notably reshaped the structure of the gut microbiota, which was manifested by increasing the relative abundance of Alloprevotella, Alistipes, Romboutsia, Turicibacter, Prevotellaceae_UCG-001, and Akkermansia while reducing the abundance of Parasutterella, Staphylococcus, Helicobacter, Enterococcus, and Erysipelatoclostridium. Notably, the gut barrier damage and LPS leakage caused by HF were recovered by APs. Additionally, with the improvement of intestinal barrier integrity, oxidative stress and inflammation in the brain and jejunum were significantly ameliorated. Furthermore, the expression of genes associated with cognitive impairment and the intestinal tract barrier was up-regulated (CREB, BDNF, TrkB, ZO-1 and occludin), while the expression of genes associated with inflammatory factors was down-regulated (IL-1β, IL-6, and TNF-α). Finally, we observed a significant correlation among cognition-related genes, gut microbiota, oxidative stress, and inflammation in the HF-AP group. Together, our findings suggest that altered gut microbiota composition and improved gut barrier integrity may be important targets for potentially improving high-fat diet-induced cognitive impairment.

In Vivo Anti-Alzheimer and Antioxidant Properties of Avocado (Persea americana Mill.) Honey from Southern Spain

There is growing evidence that Alzheimer's disease (AD) can be prevented by reducing risk factors involved in its pathophysiology. Food-derived bioactive molecules can help in the prevention and reduction of the progression of AD. Honey, a good source of antioxidants and bioactive molecules, has been tied to many health benefits, including those from neurological origin. Monofloral avocado honey (AH) has recently been characterized but its biomedical properties are still unknown. The aim of this study is to further its characterization, focusing on the phenolic profile. Moreover, its antioxidant capacity was assayed both in vitro and in vivo. Finally, a deep analysis on the pathophysiological features of AD such as oxidative stress, amyloid-β aggregation, and protein-tau-induced neurotoxicity were evaluated by using the experimental model C. elegans. AH exerted a high antioxidant capacity in vitro and in vivo. No toxicity was found in C. elegans at the dosages used. AH prevented ROS accumulation under AAPH-induced oxidative stress. Additionally, AH exerted a great anti-amyloidogenic capacity, which is relevant from the point of view of AD prevention. AH exacerbated the locomotive impairment in a C. elegans model of tauopathy, although the real contribution of AH remains unclear. The mechanisms under the observed effects might be attributed to an upregulation of daf-16 as well as to a strong ROS scavenging activity. These results increase the interest to study the biomedical applications of AH; however, more research is needed to deepen the mechanisms under the observed effects.

Prevalence and Mechanisms of Skeletal Muscle Atrophy in Metabolic Conditions

Skeletal muscle atrophy is prevalent in a myriad of pathological conditions, such as diabetes, denervation, long-term immobility, malnutrition, sarcopenia, obesity, Alzheimer's disease, and cachexia. This is a critically important topic that has significance in the health of the current society, particularly older adults. The most damaging effect of muscle atrophy is the decreased quality of life from functional disability, increased risk of fractures, decreased basal metabolic rate, and reduced bone mineral density. Most skeletal muscle in humans contains slow oxidative, fast oxidative, and fast glycolytic muscle fiber types. Depending on the pathological condition, either oxidative or glycolytic muscle type may be affected to a greater extent. This review article discusses the prevalence of skeletal muscle atrophy and several mechanisms, with an emphasis on high-fat, high-sugar diet patterns, obesity, and diabetes, but including other conditions such as sarcopenia, Alzheimer's disease, cancer cachexia, and heart failure.

Polyphenols from Conyza dioscoridis (L.) ameliorate Alzheimer’s disease- like alterations through multi-targeting activities in two animal models

Background

Recent investigations suggested that anticancer agents may inhibit the progression of Alzheimer's disease (AD) pathology. Conyza dioscoridis (L.) was demonstrated to have anticancer, antioxidant, anti-inflammatory and antidiabetic effects. This study was carried out to investigate the efficacy of polyphenols from Conyza dioscoridis (L.) extract (PCDE) on AD.

Methods

Impacts of 3 doses of PCDE and donepezil, a reference drug, on the features of Alzheimer's disease in two animal models were investigated.

Results

PCDE ameliorated the memory and learning impairment shown in rats following a single dose of scopolamine (scopolamine model) or 17 weeks of high-fat/high-fructose(HF/Hfr) diet coupled with a single dose of streptozotocin, (25 mg/kg) (T2D model). They reduced significantly the high hippocampal cholinesterase activity in the two models of rats. Administration of PCDE for 8 weeks in the T2D model showed a significant reduction in hippocampal GSK-3β, caspase-3 activity and increase in the inhibited glutamate receptor expression (AMPA GluR1 subunit and NMDA receptor subunits NR1, NR2A, NR2B). A significant reduction of HOMA-insulin resistance and serum hypercholesterolemia was observed. The Tau hyperphosphorylation and Aβ 1–42 generation in the hippocampal of T2D rats were significantly decreased by PCDE. Modulation of the oxidative stress markers, (rise in GH and SOD; decrease in MDA levels) and a significant reduction of TNF-α and IL-1β in the hippocampus of T2D rats treated by PCDE extract were important findings in this study. The highest dose tested was 4% of the highest safe dose.

Conclusion

Our study suggests that PCDE is multi-targeting agent with multiple beneficial activities in combating features of AD. This study may provide a novel therapeutic strategy for AD treatment that warrants clinical studies.

Nutrients and amyloid β status in the brain: A narrative review

Amyloid beta (Aβ) is a peptide and a hallmark of Alzheimer's disease (AD). Emerging evidence suggests that Aβ levels could be influenced by diet. However, the evidence is sparse and for some nutrients, controversial. The aim of this narrative review is to gather the findings of observational and clinical trials involving human participants on the relationships between nutrients and brain Aβ status. Some dietary patterns are associated to reduced levels of Aβ in the brain, such as the Mediterranean diet, ketogenic diet as well as low intake of saturated fat, high-glycemic-index food, sodium, and junk/fast food. Low Aβ status in the brain was also associated with higher density lipoproteins (HDL) cholesterol and polyunsaturated fatty acids consumption. Data on alcohol intake is not conclusive. On the contrary, high Aβ levels in the brain were related to a higher intake of total cholesterol, triglycerides, low-density lipoproteins (LDL) cholesterol, saturated fat, sucrose, and fructose. Folic acid, cobalamin, vitamin E, and vitamin D were not associated to Aβ status, while high blood concentrations of Calcium, Aluminum, Zinc, Copper, and Manganese were associated with decreased Aβ blood levels but were not associated with Aβ cerebral spinal fluid (CSF) concentrations. In conclusion, certain dietary patterns and nutrients are associated to brain Aβ status. Further research on the association between nutrients and brain Aβ status is needed in order to pave the way to use nutritional interventions as efficacious strategies to prevent Aβ disturbance and potentially AD.

Meta-analysis of sugar-sweetened beverage intake and the risk of cognitive disorders

BACKGROUND

Previous epidemiological studies revealed inconsistent associations between sugar-sweetened beverage (SSB) consumption and cognitive disorders, but there have been no meta-analyses of the pooled results. Thus, a meta-analysis was performed to determine the association between SSB consumption and cognitive disorders.

METHODS

A systematic search of the literature prior to May 20, 2022 was performed using the PubMed and Web of Science databases. Random effects models were used to calculate and combine odds ratios (ORs) depending on the degree of heterogeneity.

RESULTS

13 studies met the inclusion criteria. A total of 242,014 participants (2752 in three cross-sectional studies and 239,262 in ten cohort studies) were included. A random effects meta-analysis, according to the comprehensive analysis of SSB consumption, was associated with a greater prevalence of cognitive disorders (OR = 1.17, 95 % CI = 1.05-1.29; I² = 90.1 %). Subgroup analyses of study design, type of SSB, or cognitive disorders outcome was performed. In subgroup analyses, we found that SSB intake was associated with a higher prevalence of cognitive disorders in cohort studies, middle-aged and elderly population, and participants with sugar-sweetened soft drinks. However, no significant association was found in other subgroups.

CONCLUSION

Our results indicate that SSB intake is positively associated with the prevalence of cognitive disorders. Therefore, attention should be paid to reducing SSB intake as an early intervention for cognitive disorders.

Effects of Genistein and Exercise Training on Brain Damage Induced by a High-Fat High-Sucrose Diet in Female C57BL/6 Mice

In recent decades, a shift in the nutritional landscape to the Western-style diet has led to an unprecedented rise in the prevalence of obesity and neurodegenerative diseases. Consumption of a healthy diet and engaging in regular physical activity represents safe and affordable approaches known to mitigate the adverse consequences of the Western diet. We examined whether genistein treatment, exercise training, and a combination treatment (genistein and exercise training) mitigated the effects of a Western diet-induced by high-fat, high-sugar (HFHS) in brain of female mice. HFHS increased the amyloid-beta (Aβ) load and phosphorylation of tau, apoptosis, and decreased brain-derived neurotrophic factor (BDNF) levels. Exercise training and genistein each afforded modest protection on Aβ accumulation and apoptosis, and both increased BDNF. The greatest neuroprotective effect occurred with combination treatment. BDNF and all markers of Aβ accumulation, phosphorylation of tau, and apoptosis were improved with combined treatment. In a separate series of experiments, PC12 cells were exposed to high glucose (HG) and palmitate (PA) to determine cell viability with genistein as well as in the presence of tamoxifen, an estrogen receptor antagonist, to assess a mechanism of action of genistein on cell apoptosis. Genistein prevented the neurotoxic effects of HG and PA in PC12 cells and tamoxifen blocked the beneficial effects of genistein on apoptosis. Our results indicate the beneficial effects of genistein and exercise training on HFHS-induced brain damage. The benefits of genistein may occur via estrogen receptor-mediated pathways.

Western diet as a trigger of Alzheimer's disease: From metabolic syndrome and systemic inflammation to neuroinflammation and neurodegeneration

An excess of saturated fatty acids and simple sugars in the diet is a known environmental risk factor of Alzheimer's disease (AD) but the holistic view of the interacting processes through which such diet may contribute to AD pathogenesis is missing. We addressed this need through extensive analysis of published studies investigating the effects of western diet (WD) on AD development in humans and laboratory animals. We reviewed WD-induced systemic alterations comprising metabolic changes, induction of obesity and adipose tissue inflammation, gut microbiota dysbiosis and acceleration of systemic low-grade inflammation. Next we provide an overview of the evidence demonstrating that WD-associated systemic alterations drive impairment of the blood-brain barrier (BBB) and development of neuroinflammation paralleled by accumulation of toxic amyloid. Later these changes are followed by dysfunction of synaptic transmission, neurodegeneration and finally memory and cognitive impairment. We conclude that WD can trigger AD by acceleration of inflammaging, and that BBB impairment induced by metabolic and systemic inflammation play the central role in this process. Moreover, the concurrence of neuroinflammation and Aβ dyshomeostasis, which by reciprocal interactions drive the vicious cycle of neurodegeneration, contradicts Aβ as the primary trigger of AD. Given that in 2019 the World Health Organization recommended focusing on modifiable risk factors in AD prevention, this overview of the sequential, complex pathomechanisms initiated by WD, which can lead from peripheral disturbances to neurodegeneration, can support future prevention strategies.

Cerebrovascular insufficiency and amyloidogenic signaling in Ossabaw swine with cardiometabolic heart failure

Individuals with heart failure (HF) frequently present with comorbidities, including obesity, insulin resistance, hypertension, and dyslipidemia. Many patients with HF experience cardiogenic dementia, yet the pathophysiology of this disease remains poorly understood. Using a swine model of cardiometabolic HF (Western diet+aortic banding; WD-AB), we tested the hypothesis that WD-AB would promote a multidementia phenotype involving cerebrovascular dysfunction alongside evidence of Alzheimer’s disease (AD) pathology. The results provide evidence of cerebrovascular insufficiency coupled with neuroinflammation and amyloidosis in swine with experimental cardiometabolic HF. Although cardiac ejection fraction was normal, indices of arterial compliance and cerebral blood flow were reduced, and cerebrovascular regulation was impaired in the WD-AB group. Cerebrovascular dysfunction occurred concomitantly with increased MAPK signaling and amyloidogenic processing (i.e., increased APP, BACE1, CTF, and Aβ40 in the prefrontal cortex and hippocampus) in the WD-AB group. Transcriptomic profiles of the stellate ganglia revealed the WD-AB group displayed an enrichment of gene networks associated with MAPK/ERK signaling, AD, frontotemporal dementia, and a number of behavioral phenotypes implicated in cognitive impairment. These provide potentially novel evidence from a swine model that cerebrovascular and neuronal pathologies likely both contribute to the dementia profile in a setting of cardiometabolic HF.

Western Diet Induces Impairment of Liver-Brain Axis Accelerating Neuroinflammation and Amyloid Pathology in Alzheimer's Disease

Alzheimer's disease (AD) is an aging-dependent, irreversible neurodegenerative disorder and the most common cause of dementia. The prevailing AD hypothesis points to the central role of altered cleavage of amyloid precursor protein (APP) and formation of toxic amyloid-β (Aβ) deposits in the brain. The lack of efficient AD treatments stems from incomplete knowledge on AD causes and environmental risk factors. The role of lifestyle factors, including diet, in neurological diseases is now beginning to attract considerable attention. One of them is western diet (WD), which can lead to many serious diseases that develop with age. The aim of the study was to investigate whether WD-derived systemic disturbances may accelerate the brain neuroinflammation and amyloidogenesis at the early stages of AD development. To verify this hypothesis, transgenic mice expressing human APP with AD-causing mutations (APPswe) were fed with WD from the 3rd month of age. These mice were compared to APPswe mice, in which short-term high-grade inflammation was induced by injection of lipopolysaccharide (LPS) and to untreated APPswe mice. All experimental subgroups of animals were subsequently analyzed at 4-, 8-, and 12-months of age. APPswe mice at 4- and 8-months-old represent earlier pre-plaque stages of AD, while 12-month-old animals represent later stages of AD, with visible amyloid pathology. Already short time of WD feeding induced in 4-month-old animals such brain neuroinflammation events as enhanced astrogliosis, to a level comparable to that induced by the administration of pro-inflammatory LPS, and microglia activation in 8-month-old mice. Also, WD feeding accelerated increased Aβ production, observed already in 8-month-old animals. These brain changes corresponded to diet-induced metabolic disorders, including increased cholesterol level in 4-months of age, and advanced hypercholesterolemia and fatty liver disease in 8-month-old mice. These results indicate that the westernized pattern of nourishment is an important modifiable risk factor of AD development, and that a healthy, balanced, diet may be one of the most efficient AD prevention methods.

Insulin resistance: a connecting link between Alzheimer's disease and metabolic disorder

Recent evidence suggests that Alzheimer's disease (AD) is closely linked with insulin resistance, as seen in type 2 diabetes mellitus (T2DM). Insulin signaling is impaired in AD brains due to insulin resistance, ultimately resulting in the formation of neurofibrillary tangles (NFTs). AD and T2DM are connected at molecular, clinical, and epidemiological levels making it imperative to understand the contribution of T2DM, and other metabolic disorders, to AD pathogenesis. In this review, we have discussed various modalities involved in the pathogenesis of these two diseases and explained the contributing parameters. Insulin is vital for maintaining glucose homeostasis and it plays an important role in regulating inflammation. Here, we have discussed the roles of various contributing factors like miRNA, leptin hormone, neuroinflammation, metabolic dysfunction, and gangliosides in insulin impairment both in AD and T2DM. Understanding these mechanisms will be a big step forward for making molecular therapies that may help maintain or prevent both AD and T2DM, thus reducing the burden of both these diseases.

Date seeds alleviate behavioural and neuronal complications of metabolic syndrome in rats

Unhealthy dietary habits can play a crucial role in metabolic damages, promoting alteration of neural functions through the lifespan. Recently, dietary change has been perceived as the first line intervention in prevention and/or treatment of metabolic damages and related diseases. In this context, our study was designed to assess the eventual therapeutic effect of date seeds administration on memory and learning and on neuronal markers in a rat Metabolic Syndrome model. For this purpose, 32 adult male Wistar rats were fed with standard diet or high-fat high-sugar diet during ten weeks. After this, 16 rats were sacrified and the remaining rats received an oral administration of 300 mg of date seeds/kg of body weight during four supplementary weeks. Before sacrifice, we evaluate cognitive performances by the Barnes maze test. Afterwards, neuronal, astrocytic, microtubular and oxidative markers were investigated by immunoblotting methods. In Metabolic syndrome rats, results showed impairment of spatial memory and histological alterations. We identified neuronal damages in hippocampus, marked by a decrease of NeuN and an increase of GFAP and pTau396. Finally, we recorded an increase in protein oxidation and lipid peroxidation, respectively identified by an up-regulation of protein carbonyls and 4-HNe. Interestingly, date seeds administration improved these behavioural, histological, neuronal and oxidative damages highlighting the neuroprotective effect of this natural compound. Liquid Chromatography-Mass Spectrometry (LC-MS) identified, in date seeds, protocatechuic acid, caffeoylshikimic acid and vanillic acid, that could potentially prevent the progression of neurodegenerative diseases, acting through their antioxidant properties.

Critical Review of the Alzheimer's Disease Non-Transgenic Models: Can They Contribute to Disease Treatment?

Alzheimer's disease (AD) is a growing neurodegenerative disease without effective treatments or therapies. Despite the use of different approaches and an extensive variety of genetic amyloid based models, therapeutic strategies remain elusive. AD is characterized by three main pathological hallmarks that include amyloid-β plaques, neurofibrillary tangles, and neuroinflammatory processes; however, many other pathological mechanisms have been described in the literature. Nonetheless, the study of the disease and the screening of potential therapies is heavily weighted toward the study of amyloid-β transgenic models. Non-transgenic models may aid in the study of complex pathological states and provide a suitable complementary alternative to evaluating therapeutic biomedical and intervention strategies. In this review, we evaluate the literature on non-transgenic alternatives, focusing on the use of these models for testing therapeutic strategies, and assess their contribution to understanding AD. This review aims to underscore the need for a shift in preclinical research on intervention strategies for AD from amyloid-based to alternative, complementary non-amyloid approaches.

Resveratrol and Metformin Recover Prefrontal Cortex AMPK Activation in Diet-Induced Obese Mice but Reduce BDNF and Synaptophysin Protein Content

BACKGROUND

Obesity, insulin resistance, and type 2 diabetes are established risk factors for the development of Alzheimer's disease (AD). Given this connection, two drugs, metformin (MET) and resveratrol (RESV), are considered for the clearance of amyloid-β peptides through AMPK-mediated activation of autophagy. However, overactivation of AMPK observed in late-stage AD brains and relationships between AMPK and neurogenesis (through mTORC1 inhibition), questions treatment with these drugs.

OBJECTIVE

To examine if MET and/or RESV supplementation activates brain AMPK, regulates markers of autophagy, and affects markers of neuronal health/neurogenesis.

METHODS

8-week-old male C57BL/6J mice were fed a low (N = 12; 10% kcal fat; LFD) or high fat diet (N = 40; 60% kcal fat; HFD) for 9 weeks to induce insulin resistance and obesity. HFD mice were then treated with/without MET (250 mg/kg/day), RESV (100 mg/kg/day), or COMBO (MET: 250 mg/kg/day, RESV: 100 mg/kg/day) for 5 weeks. Hippocampus and prefrontal cortex were extracted for western blotting analysis.

RESULTS

Cortex AMPK (T172) and raptor (S792, the regulatory subunit of mTORC1) phosphorylation were upregulated following RESV, COMBO treatments. mTOR (S2448) and ULK1 (S555) activation was seen following MET, COMBO and RESV, COMBO treatments, respectively, in the cortex and hippocampus. p62 content was decreased following RESV, COMBO, with LC3 content being increased following RESV treatment in the cortex. Brain derived neurotropic factor (BDNF) was significantly decreased following RESV, COMBO, and synaptophysin following all treatment in the cortex.

CONCLUSION

These results demonstrate that while treatments upregulated markers of autophagy in the prefrontal cortex, reductions in neuronal health markers question the efficacy of AMPK as a therapy for AD.

Detection of presymptomatic Alzheimer's disease through breath biomarkers

Introduction

Novel sensors were developed to detect exhaled volatile organic compounds to aid in the diagnosis of mild cognitive impairment associated with early stage Alzheimer's disease (AD). The sensors were sensitive to a rat model that combined the human apolipoprotein E (APOE)4 gene with aging and the Western diet.

Methods

Gas sensors fabricated from molecularly imprinted polymer-graphene were engineered to react with alkanes and small fatty acids associated with lipid peroxidation. With a detection sensitivity in parts per trillion the sensors were tested against the breath of wild-type and APOE4 male rats. Resting state BOLD functional connectivity was used to assess hippocampal function.

Results

Only APOE4 rats, and not wild-type controls, tested positive to several small hydrocarbons and presented with reduced functional coupling in hippocampal circuitry.

Discussion

These results are proof-of-concept toward the development of sensors that can be used as breath detectors in the diagnosis, prognosis, and treatment of presymptomatic AD.

Adiponectin: The Potential Regulator and Therapeutic Target of Obesity and Alzheimer's Disease

Animal and human mechanistic studies have consistently shown an association between obesity and Alzheimer's disease (AD). AD, a degenerative brain disease, is the most common cause of dementia and is characterized by the presence of extracellular amyloid beta (Aβ) plaques and intracellular neurofibrillary tangles disposition. Some studies have recently demonstrated that Aβ and tau cannot fully explain the pathophysiological development of AD and that metabolic disease factors, such as insulin, adiponectin, and antioxidants, are important for the sporadic onset of nongenetic AD. Obesity prevention and treatment can be an efficacious and safe approach to AD prevention. Adiponectin is a benign adipokine that sensitizes the insulin receptor signaling pathway and suppresses inflammation. It has been shown to be inversely correlated with adipose tissue dysfunction and may enhance the risk of AD because a range of neuroprotection adiponectin mechanisms is related to AD pathology alleviation. In this study, we summarize the recent progress that addresses the beneficial effects and potential mechanisms of adiponectin in AD. Furthermore, we review recent studies on the diverse medications of adiponectin that could possibly be related to AD treatment, with a focus on their association with adiponectin. A better understanding of the neuroprotection roles of adiponectin will help clarify the precise underlying mechanism of AD development and progression.

Ovariectomized rodents as a menopausal metabolic syndrome model. A minireview

Bilateral ovariectomy is the best characterized and the most reported animal model of human menopause. Ovariectomized rodents develop insulin resistance (IR) and visceral obesity, the main risk factors in the pathophysiology of metabolic syndrome (MS). These alterations are a consequence of hypoestrogenic status, which produces an augment of visceral fat, high testosterone levels (hyperandrogenism), as well as inflammation, oxidative stress, and metabolic complications, such as dyslipidemia, hepatic steatosis, and endothelial dysfunction, among others. Clinical trials have reported that menopause per se increases the severity and incidence of MS, and causes the highest mortality due to cardiovascular disease in women. Despite all the evidence, there are no reports that clarify the influence of estrogenic deficiency as a cause of MS. In this review, we provide evidence that ovariectomized rodents can be used as a menopausal metabolic syndrome model for evaluating and discovering new, safe, and effective therapeutic approaches in the treatment of cardiometabolic complications associated to MS during menopause.

Evaluation of the neuroprotective effect of donepezil in type 2 diabetic rats

Recent studies raise the possibility that donepezil can delay the progression of Alzheimer's disease (AD). This research evaluated the efficacy of donepezil in an animal model with brain insulin resistance and AD-like alterations. Rats were fed with high-fat/high-fructose (HF/Hfr) diet during the study period (17 weeks) and received one injection of streptozotocin (STZ) (25 mg/kg) after 8 weeks of starting the study. Diabetic (T2D) rats were treated with donepezil (4 mg/kg; p.o.) or vehicle for 8 weeks after STZ injection. The influence of donepezil on AD-related behavioral, biochemical, and neuropathological changes was investigated in T2D rats. Treatment of diabetic rats with donepezil led to a significant decrease in both amyloid-β deposition and the raised hippocampal activity of cholinesterase (ChE). It significantly increased the suppressed glutamate receptor expression (AMPA GluR1 subunit and NMDA receptor subunits NR1, NR2A, NR2B). It also improved cognitive dysfunction in the passive avoidance and the Morris water maze tests. However, donepezil treatment did not significantly decrease the elevated levels of P-tau, caspase-3, GSK-3β, MDA, TNF-α, and IL-1β in the hippocampus of diabetic rats. Also, it did not restore the suppressed levels of glutathione and superoxide dismutase in the brain of these rats. Moreover, donepezil did not alter the elevated serum level of glucose, insulin, and total cholesterol. These findings suggest that donepezil treatment could ameliorate learning and memory impairment in T2D rats through reversal of some of the AD-related alterations, including reduction of amyloid-β burden and ChE activity as well as restoration of glutamate receptor expression. However, lack of any significant effect on P-tau load, oxidative stress, neuroinflammation, and insulin resistance raises the question about the ability of donepezil to delay the development or arrest the progression of T2D-induced AD and it is still a matter of debate that requires further studies.

Perindopril ameliorates experimental Alzheimer's disease progression: role of amyloid β degradation, central estrogen receptor and hyperlipidemic-lipid raft signaling

Accumulating evidence indicates that over-stimulation of angiotensin-converting enzyme 1 (ACE1) activity is associated with β-amyloid (Aβ) and phosphorylated tau (p-tau)-induced apoptosis, oxido-nitrosative neuroinflammatory stress and neurodegeneration in Alzheimer's disease (AD). Alternatively, activation of the ACE2, the metalloprotease neprilysin (Neutral Endopeptidase; NEP) and the insulin-degrading enzyme (IDE) could oppose the effects of ACE1 activation. We aim to investigate the relationship between ACE1/ACE2/NEP/IDE and amyloidogenic/hyperlipidemic-lipid raft signaling in hyperlipidemic AD model. Induction of AD was performed in ovariectomized female rats with high-fat high fructose diet (HFFD) feeding after 4 weeks following D-galactose injection (150 mg/kg). The brain-penetrating ACE1 inhibitor perindopril (0.5 mg/kg/day, p.o.) was administered on a daily basis for 30 days. Perindopril significantly decreased hippocampal expression of ACE1 and increased expression of ACE2, NEP and IDE. Perindopril markedly decreased Aβ_1-42, improved lipid profile and ameliorated the lipid raft protein markers caveolin1 (CAV1) and flotillin 1 (FLOT1). This was accompanied by decreased expression of p-tau and enhancement of cholinergic neurotransmission, coupled with decreased oxido-nitrosative neuroinflammatory stress, enhancement of blood-brain barrier (BBB) functioning and lower expression of the apoptotic markers glial fibrillary acidic protein (GFAP), Bax and β-tubulin. In addition, perindopril ameliorated histopathological damage and improved learning, cognitive and recognition impairment as well as depressive behavior in Morris water maze, Y maze, novel object recognition and forced swimming tests, respectively. Conclusively, perindopril could improve cognitive defects in AD rats, at least through activation of ACE2/NEP/IDE and inhibition of ACE1 and subsequent modulation of amyloidogenic/hyperlipidemic-lipid raft signaling and oxido-nitrosative stress.

Resolvin D1 Prevents the Impairment in the Retention Memory and Hippocampal Damage in Rats Fed a Corn Oil-Based High Fat Diet by Upregulation of Nrf2 and Downregulation and Inactivation of p66Shc

This study investigated the effect of a high-fat diet rich in corn oil (CO-HFD) on the memory retention and hippocampal oxidative stress, inflammation, and apoptosis in rats, and examined if the underlying mechanisms involve modulating Resolvin D1 (RvD1) levels and activation of p⁶⁶Shc. Also, we tested if co-administration of RvD1 could prevent these neural adverse effects induced by CO-HFD. Adult male Wistar rats were divided into 4 groups (n = 18/each) as control fed standard diet (STD) (3.82 kcal/g), STD + RvD1 (0.2 µg/Kg, i.p/twice/week), CO-HFD (5.4 kcal/g), and CO-HFD + RvD1. All treatments were conducted for 8 weeks. With normal fasting glucose levels, CO-HFD induced hyperlipidemia, hyperinsulinemia, increased HOMA-IRI and reduced the rats' memory retention. In parallel, CO-HFD increased levels of reactive oxygen species (ROS), malondialdehyde (MDA), cytoplasmic cytochrome-c, and cleaved caspase-3 and significantly decreased levels of glutathione (GSH), Bcl-2, and manganese superoxide dismutase (MnSOD) in rats' hippocampi. Besides, CO-HFD significantly reduced hippocampal levels of docosahexaenoic acid (DHA) and RvD1, as well as total protein levels of Nrf2 and significantly increased nuclear protein levels of p-NF-κB. Concomitantly, CO-HFD increased hippocampal protein levels of p-JNK, p53, p⁶⁶Shc, p-p⁶⁶Shc, and NADPH oxidase. However, without altering plasma and serum levels of glucose, insulin, and lipids, co-administration of RvD1 to CO-HFD completely reversed all these events. It also resulted in similar effects in the STD fed-rats. In conclusion, CO-HFD impairs memory function and induces hippocampal damage by reducing levels of RvD1 and activation of JNK/p53/p⁶⁶Shc/NADPH oxidase, effects that are prevented by co-administration of RvD1.

γ-Aminobutyric Acid Attenuates High-Fat Diet-Induced Cerebral Oxidative Impairment via Enhanced Synthesis of Hippocampal Sulfatides

Long-term high-fat diet (HFD) in rats triggered cerebral oxidative stress, reflected by reactive oxygen species accumulation and antioxidant decline in peripheral and cerebral tissues, together with hippocampal lipid disturbance, particularly for triglyceride accumulation and sulfatide deficiency. Hippocampal formation and cerebral cortex also exhibited pathological changes, characterized by neurofibrillary tangle and reduced Nissl bodies. Sulfatides were noted to protect hippocampal neurons from oxidative damage through the clearance of β-amyloid protein, with apolipoprotein E transporting and low-density lipoprotein receptor binding. Delightedly, we found γ-aminobutyric acid (GABA) supplement delivered by rice bran to rats significantly promoted hippocampal sulfatide synthesis and reversed the HFD-induced sulfatide deficiency and oxidative-triggered cerebral impairment. Elevated GABA concentration in hippocampus and the activation of GABA B-type receptors might be the primary contributors. This study demonstrated the potential of GABA-enriched rice bran as a novel dietary supplement to enhance a sulfatide-based therapeutic approach for neurodegenerative diseases in the early stages.

Evaluation of neuropathological effects of a high-fat high-sucrose diet in middle-aged male C57BL6/J mice

Metabolic dysfunction related to diet-induced obesity has recently been linked to the pathogenesis of sporadic Alzheimer's disease (AD). However, the underlying mechanisms linking obesity and AD remain unclear. The purpose of this study was to examine early alterations in brain insulin signaling, inflammatory/stress markers, and energetic stress in a model of diet-induced obesity during middle age. Male C57BL/6J mice were randomized to either a control diet (AGE n = 12) or high-fat and sucrose diet (AGE-HFS n = 12) for 13-weeks from 20-weeks of age. Prefrontal cortex and hippocampal samples were collected at 20-weeks of age (BSL n = 11) and at 33-weeks of age (AGE and AGE-HFS). The HFS diet resulted in increased body weight (30%; P = 0.0001), increased %fat mass (28%; P = 0.0001), and decreased %lean mass (33%; P = 0.0001) compared to aged controls. In the prefrontal cortex, AGE-HFS resulted in increased 5' adenosine monophosphate - activated protein kinase (AMPK) phosphorylation (P = 0.045). In the hippocampus, AGE-HFS resulted in increased extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) phosphorylation and protein kinase B (Akt) serine473 and glycogen synthase kinase (GSK) phosphorylation (P < 0.05). Results from this study demonstrate that aging combined with a HFS diet results in increased inflammation (pERK and pJNK) and energetic stress (pAMPK) in the hippocampus and prefrontal cortex, respectively. Together these novel results provide important information for future targets in early AD pathogenesis.

Western diet induces endogen oxidative deoxyribonucleic acid damage and infl ammation in Wistar rats

ABSTRACT Objective Nutritional diseases such as metabolic syndrome, cardiovascular disorder, chronic inflammation or even cancer are observed in people who sustain their lifestyle by Western diet due to high calorie intake. The origin of these diseases are the degraded deoxyribonucleic acid structure. In this study, we investigated whether Western diet produced endogenous oxidative deoxyribonucleic acid damage, apoptosis or inflammation. Methods Twenty-eight male Wistar rats, aged 10-12 weeks, were divided into four groups. The rats in control group received the standard diet and the remaining rats were given one of the following three diets for four weeks: a high-fat diet containing 35% fat, a high-sucrose diet containing 69% sucrose and Western diet comprising both two types of diets. After treatment the serum 8-hydroxy-2-deoxyguanosine, poly (adenosine diphosphate ribose) polymerase-1, chitinase-3-like protein 1, soluble urokinase-type plasminogen activator receptor, Fas ligand and cytochrome c levels were measured. Results It was observed no changes in the serum soluble urokinase-type plasminogen activator receptor, Fas ligand and cytochrome c levels whereas a statistically significant increase in the serum 8-hydroxy-2-deoxyguanosine, poly (adenosine diphosphate ribose) polymerase-1 and chitinase-3-like protein 1 levels were found only in rats that were given Western diet. Conclusion The findings show that Western diet produced endogenous oxidative deoxyribonucleic acid damage, which then increased serum poly (adenosine diphosphate ribose) polymerase-1 levels, eventually leading to inflammation.

Metabolism-Centric Overview of the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is a degenerative brain disease and the most common cause of dementia. AD is characterized by the extracellular amyloid beta (Aβ) plaques and intraneuronal deposits of neurofibrillary tangles (NFTs). Recently, as aging has become a familiar phenomenon around the world, patients with AD are increasing in number. Thus, many researchers are working toward finding effective therapeutics for AD focused on Aβ hypothesis, although there has been no success yet. In this review paper, we suggest that AD is a metabolic disease and that we should focus on metabolites that are affected by metabolic alterations to find effective therapeutics for AD. Aging is associated with not only AD but also obesity and type 2 diabetes (T2DM). AD, obesity, and T2DM share demographic profiles, risk factors, and clinical and biochemical features in common. Considering AD as a kind of metabolic disease, we suggest insulin, adiponectin, and antioxidants as mechanistic links among these diseases and targets for AD therapeutics. Patients with AD show reduced insulin signal transductions in the brain, and intranasal injection of insulin has been found to have an effect on AD treatment. In addition, adiponectin is decreased in the patients with obesity and T2DM. This reduction induces metabolic dysfunction both in the body and the brain, leading to AD pathogenesis. Oxidative stress is known to be induced by Aβ and NFTs, and we suggest that oxidative stress caused by metabolic alterations in the body induce brain metabolic alterations, resulting in AD.

Sugary beverage intake and preclinical Alzheimer's disease in the community

INTRODUCTION

Excess sugar consumption has been linked with Alzheimer's disease (AD) pathology in animal models.

METHODS

We examined the cross-sectional association of sugary beverage consumption with neuropsychological (N = 4276) and magnetic resonance imaging (N = 3846) markers of preclinical Alzheimer's disease and vascular brain injury (VBI) in the community-based Framingham Heart Study. Intake of sugary beverages was estimated using a food frequency questionnaire.

RESULTS

Relative to consuming less than one sugary beverage per day, higher intake of sugary beverages was associated with lower total brain volume (1-2/day, β ± standard error [SE] = -0.55 ± 0.14 mean percent difference, P = .0002; >2/day, β ± SE = -0.68 ± 0.18, P < .0001), and poorer performance on tests of episodic memory (all P < .01). Daily fruit juice intake was associated with lower total brain volume, hippocampal volume, and poorer episodic memory (all P < .05). Sugary beverage intake was not associated with VBI in a consistent manner across outcomes.

DISCUSSION

Higher intake of sugary beverages was associated cross-sectionally with markers of preclinical AD.