The Differential Effect of Treadmill Exercise Intensity on Hippocampal Soluble Aβ and Lipid Metabolism in APP/PS1 Mice

The Intersection of cerebral cholesterol metabolism and Alzheimer's disease: Mechanisms and therapeutic prospects

Alzheimer's disease (AD) is a common neurodegenerative disease in the elderly, the exact pathogenesis of which remains incompletely understood, and effective preventive and therapeutic drugs are currently lacking. Cholesterol plays a vital role in cell membrane formation and neurotransmitter synthesis, and its abnormal metabolism is associated with the onset of AD. With the continuous advancement of imaging techniques and molecular biology methods, researchers can more accurately explore the relationship between cholesterol metabolism and AD. Elevated cholesterol levels may lead to vascular dysfunction, thereby affecting neuronal function. Additionally, abnormal cholesterol metabolism may affect the metabolism of β-amyloid protein, thereby promoting the onset of AD. Brain cholesterol levels are regulated by multiple factors. This review aims to deepen the understanding of the subtle relationship between cholesterol homeostasis and AD, and to introduce the latest advances in cholesterol-regulating AD treatment strategies, thereby inspiring readers to contemplate deeply on this complex relationship. Although there are still many unresolved important issues regarding the risk of brain cholesterol and AD, and some studies may have opposite conclusions, further research is needed to enrich our understanding. However, these findings are expected to deepen our understanding of the pathogenesis of AD and provide important insights for the future development of AD treatment strategies targeting brain cholesterol homeostasis.

Exercise Intervention for Alzheimer's Disease: Unraveling Neurobiological Mechanisms and Assessing Effects

Alzheimer's disease (AD) is a progressive neurodegenerative disease and a major cause of age-related dementia, characterized by cognitive dysfunction and memory impairment. The underlying causes include the accumulation of beta-amyloid protein (Aβ) in the brain, abnormal phosphorylation, and aggregation of tau protein within nerve cells, as well as neuronal damage and death. Currently, there is no cure for AD with drug therapy. Non-pharmacological interventions such as exercise have been widely used to treat AD, but the specific molecular and biological mechanisms are not well understood. In this narrative review, we integrate the biology of AD and summarize the knowledge of the molecular, neural, and physiological mechanisms underlying exercise-induced improvements in AD progression. We discuss various exercise interventions used in AD and show that exercise directly or indirectly affects the brain by regulating crosstalk mechanisms between peripheral organs and the brain, including "bone-brain crosstalk", "muscle-brain crosstalk", and "gut-brain crosstalk". We also summarize the potential role of artificial intelligence and neuroimaging technologies in exercise interventions for AD. We emphasize that moderate-intensity, regular, long-term exercise may improve the progression of Alzheimer's disease through various molecular and biological pathways, with multimodal exercise providing greater benefits. Through in-depth exploration of the molecular and biological mechanisms and effects of exercise interventions in improving AD progression, this review aims to contribute to the existing knowledge base and provide insights into new therapeutic strategies for managing AD.

Dietary Supplementation with Lauric Acid Improves Aerobic Endurance in Sedentary Mice via Enhancing Fat Mobilization and Glyconeogenesis

BACKGROUND

Lauric acid (LA), a major, natural, medium-chain fatty acid, is considered an efficient energy substrate for intense exercise and in patients with long-chain fatty acid β-oxidation disorders. However, few studies have focused on the role of LA in exercise performance and related glucolipid metabolism in vivo.

OBJECTIVES

We aimed to investigate the effect of dietary supplementation with LA on exercise performance and related metabolic mechanisms.

METHODS

Male C57BL/6N mice (14 wk old) were fed a basal diet or a diet containing 1% LA, and a series of exercise tests, including a high-speed treadmill test, aerobic endurance exercises, a 4-limb hanging test, and acute aerobic exercises, were performed.

RESULTS

Dietary supplementation with 1.0% LA accelerated the recovery from fatigue after explosive exercise (P < 0.05) and improved aerobic endurance and muscle strength in sedentary mice (P = 0.039). Lauric acid intake not only changed muscle fatty acid profiles, including increases in C12:0 and n-6/n-3 PUFAs (P < 0.001) and reductions in C18:0, C20:4n-6, C22:6n-3, and n-3 PUFAs (P < 0.05) but also enhanced fat mobilization from adipose tissue and fatty acid oxidation in the liver, at least partly via the AMP-activated protein kinase-acetyl CoA carboxylase pathway (P < 0.05). Likewise, LA supplementation promoted liver glyconeogenesis and conserved muscular glycogen during acute aerobic exercise (P < 0.05), which was accompanied by an increase in the mitochondrial DNA copy number and Krebs cycle activity in skeletal muscle (P < 0.05).

CONCLUSIONS

Dietary supplemental LA serves as an efficient energy substrate for sedentary mice to improve aerobic exercise endurance and muscle strength through regulation of glucolipid metabolism. These findings imply that LA supplementation might be a promising nutritional strategy to improve aerobic exercise performance in sedentary people.

Brain metabolism in Alzheimer's disease: biological mechanisms of exercise

Alzheimer's disease (AD) is a major subtype of neurodegenerative dementia caused by long-term interactions and accumulation of multiple adverse factors, accompanied by dysregulation of numerous intracellular signaling and molecular pathways in the brain. At the cellular and molecular levels, the neuronal cellular milieu of the AD brain exhibits metabolic abnormalities, compromised bioenergetics, impaired lipid metabolism, and reduced overall metabolic capacity, which lead to abnormal neural network activity and impaired neuroplasticity, thus accelerating the formation of extracellular senile plaques and intracellular neurofibrillary tangles. The current absence of effective pharmacological therapies for AD points to the urgent need to investigate the benefits of non-pharmacological approaches such as physical exercise. Despite the evidence that regular physical activity can improve metabolic dysfunction in the AD state, inhibit different pathophysiological molecular pathways associated with AD, influence the pathological process of AD, and exert a protective effect, there is no clear consensus on the specific biological and molecular mechanisms underlying the advantages of physical exercise. Here, we review how physical exercise improves crucial molecular pathways and biological processes associated with metabolic disorders in AD, including glucose metabolism, lipid metabolism, Aβ metabolism and transport, iron metabolism and tau pathology. How metabolic states influence brain health is also presented. A better knowledge on the neurophysiological mechanisms by which exercise improves AD metabolism can contribute to the development of novel drugs and improvement of non-pharmacological interventions.

Effects of exercise intensity on spatial memory performance and hippocampal synaptic function in SAMP8 mice

Learning and memory impairment is commonly noted in Alzheimer's disease (AD), which is regarded as a progressive synaptic failure disease. Exercise is a nonpharmacological strategy that may help prevent cognitive decline and reduce the risk of AD, which is usually thought to be related to synaptic damage in the hippocampus. However, the effects of exercise intensity on hippocampal memory and synaptic function in AD remain unclear. In this study, senescence-accelerated mouse prone-8 (SAMP8) mice were randomly assigned to the control group (Con), low-intensity exercise group (Low), and moderate-intensity exercise group (Mid). Here, we showed that eight weeks of treadmill exercise beginning in four-month-old mice improved spatial memory and recognition memory in six-month-old SAMP8 mice, while the Con group exhibited impaired spatial memory and recognition memory. Treadmill exercise also improved hippocampal neuron morphology in SAMP8 mice. Furthermore, dendritic spine density and the levels of postsynaptic density protein-95 (PSD95) and Synaptophysin (SYN) increased significantly in the Low and Mid groups as compared with the Con group. We further showed that moderate-intensity exercise (60% of maximum speed) was more efficacious in increasing dendritic spine density、PSD95 and SYN, than low-intensity exercise (40% of maximum speed). In conclusion, the positive effect of treadmill exercise is closely related to exercise intensity, with moderate-intensity exercise showing the most optimal effects.

Systematic review of brain and blood lipidomics in Alzheimer's disease mouse models

Alzheimer's disease (AD) diagnosis is based on invasive and expensive biomarkers. Regarding AD pathophysiological mechanisms, there is evidence of a link between AD and aberrant lipid homeostasis. Alterations in lipid composition have been observed in blood and brain samples, and transgenic mouse models represent a promising approach. Nevertheless, there is great variability among studies in mice for the determination of different types of lipids in targeted and untargeted methods. It could be explained by the different variables (model, age, sex, analytical technique), and experimental conditions used. The aim of this work is to review the studies on lipid alteration in brain tissue and blood samples from AD mouse models, focusing on different experimental parameters. As result, great disparity has been observed among the reviewed studies. Brain studies showed an increase in gangliosides, sphingomyelins, lysophospholipids and monounsaturated fatty acids and a decrease in sulfatides. In contrast, blood studies showed an increase in phosphoglycerides, sterols, diacylglycerols, triacylglycerols and polyunsaturated fatty acids, and a decrease in phospholipids, lysophospholipids and monounsaturated fatty acids. Thus, lipids are closely related to AD, and a consensus on lipidomics studies could be used as a diagnostic tool and providing insight into the mechanisms involved in AD.

Effects of enriched environment on the expression of β-amyloid and transport-related proteins LRP1 and RAGE in chronic sleep-deprived mice

Sleep plays an important role in the learning process and memory consolidation, and sleep deprivation (SD) leads to inadequate memory consolidation and plays an important role in brain development and plasticity. SD increases β-amyloid levels while impairing cognitive function. We explored the effect of enriched environment (EE) on β-amyloid and transporter protein LRP1 and receptor for advanced glycosylation end-products (RAGE) expression in chronic sleep deprived mice. We randomly divided mice into four groups (n = 10), the standard environment group (Ctrl group), the sleep deprivation group (SD group), the enriched environment intervention group (EE group), and the sleep deprivation plus environmental enrichment intervention group (SD + EE group). A modified multi-platform SD model was used to sleep deprive the mice for 19 h per day. Five hours of EE intervention was performed daily in the EE group and the SD + EE group, respectively. The behavioral measurements of mice were performed by Y-maze method and new object recognition; the expression levels of Aβ1-42, LRP1, and RAGE in prefrontal cortex and hippocampus of mice were measured by immunofluorescence; the expression levels of LRP1 and RAGE in prefrontal cortex and hippocampus were detected by Western blot. The results showed that EE could effectively ameliorate the effects of SD on cognitive impairment, reduce SD induced Aβ deposition, and decrease the expression of RAGE, while increase the expression of LRP1.

The gut microbiome and Alzheimer's disease: Complex and bidirectional interactions

Structural and functional alterations to the gut microbiome, referred to as gut dysbiosis, have emerged as potential key mediators of neurodegeneration and Alzheimer disease (AD) pathogenesis through the "gut -brain" axis. Emerging data from animal and clinical studies support an important role for gut dysbiosis in mediating neuroinflammation, central and peripheral immune dysregulation, abnormal brain protein aggregation, and impaired intestinal and brain barrier permeability, leading to neuronal loss and cognitive impairment. Gut dysbiosis has also been shown to directly influence various mechanisms involved in neuronal growth and repair, synaptic plasticity, and memory and learning functions. Aging and lifestyle factors including diet, exercise, sleep, and stress influence AD risk through gut dysbiosis. Furthermore, AD is associated with characteristic gut microbial signatures which offer value as potential markers of disease severity and progression. Together, these findings suggest the presence of a complex bidirectional relationship between AD and the gut microbiome and highlight the utility of gut modulation strategies as potential preventative or therapeutic strategies in AD. We here review the current literature regarding the role of the gut-brain axis in AD pathogenesis and its potential role as a future therapeutic target in AD treatment and/or prevention.

Aquaporin 4 deficiency eliminates the beneficial effects of voluntary exercise in a mouse model of Alzheimer's disease

Regular exercise has been shown to reduce the risk of Alzheimer's disease (AD). Our previous study showed that the protein aquaporin 4 (AQP4), which is specifically expressed on the paravascular processes of astrocytes, is necessary for glymphatic clearance of extracellular amyloid beta (Aβ) from the brain, which can delay the progression of Alzheimer's disease. However, it is not known whether AQP4-regulated glymphatic clearance of extracellular Aβ is involved in beneficial effects of exercise in AD patients. Our results showed that after 2 months of voluntary wheel exercise, APP/PS1 mice that were 3 months old at the start of the intervention exhibited a decrease in Aβ burden, glial activation, perivascular AQP4 mislocalization, impaired glymphatic transport, synapse protein loss, and learning and memory defects compared with mice not subjected to the exercise intervention. In contrast, APP/PS1 mice that were 7 months old at the start of the intervention exhibited impaired AQP4 polarity and reduced glymphatic clearance of extracellular Aβ, and the above-mentioned impairments were not alleviated after the 2-month exercise intervention. Compared with age-matched APP/PS1 mice, AQP4 knockout APP/PS1 mice had more serious defects in glymphatic function, Aβ plaque deposition, and cognitive impairment, which could not be alleviated after the exercise intervention. These findings suggest that AQP4-dependent glymphatic transport is the neurobiological basis for the beneficial effects of voluntary exercises that protect against the onset of AD.

Recent Neurotherapeutic Strategies to Promote Healthy Brain Aging: Are we there yet?

Owing to the global exponential increase in population ageing, there is an urgent unmet need to develop reliable strategies to slow down and delay the ageing process. Age-related neurodegenerative diseases are among the main causes of morbidity and mortality in our contemporary society and represent a major socio-economic burden. There are several controversial factors that are thought to play a causal role in brain ageing which are continuously being examined in experimental models. Among them are oxidative stress and brain inflammation which are empirical to brain ageing. Although some candidate drugs have been developed which reduce the ageing phenotype, their clinical translation is limited. There are several strategies currently in development to improve brain ageing. These include strategies such as caloric restriction, ketogenic diet, promotion of cellular nicotinamide adenine dinucleotide (NAD+) levels, removal of senescent cells, 'young blood' transfusions, enhancement of adult neurogenesis, stem cell therapy, vascular risk reduction, and non-pharmacological lifestyle strategies. Several studies have shown that these strategies can not only improve brain ageing by attenuating age-related neurodegenerative disease mechanisms, but also maintain cognitive function in a variety of pre-clinical experimental murine models. However, clinical evidence is limited and many of these strategies are awaiting findings from large-scale clinical trials which are nascent in the current literature. Further studies are needed to determine their long-term efficacy and lack of adverse effects in various tissues and organs to gain a greater understanding of their potential beneficial effects on brain ageing and health span in humans.

Potential Value of Serum Lipid in the Identication of Postoperative Delirium Undergoing Knee/Hip Arthroplasty: The Perioperative Neurocognitive Disorder and Biomarker Lifestyle Study

OBJECTIVE

We aimed to investigate the relationship between preoperative lipid level and postoperative delirium (POD) and explore whether lipid's effect on POD is mediated by POD core protein.

METHODS

A total of 635 patients who were planned to undergo knee/hip arthroplasty under combined spinal-epidural anesthesia, regardless of gender, were selected. The patients were aged 40-90 years with American Society of Anesthesiologists physical status I II. The Mini-Mental State Examination (MMSE) was completed 1 day before the operation. Five milliliter elbow venous blood was taken from the patients before anesthesia, and serum levels of total cholesterol (TG), triglyceride (TC), low-density lipoprotein (LDL-C), and high-density lipoprotein (HDL-C) were detected. Cerebrospinal fluid (CSF) was extracted after successful spinal-epidural combined puncture, and amyloid beta₄₀ (Aβ₄₀), amyloid beta₄₂ (Aβ₄₂), total Tau (t-Tau), and phosphorylated Tau (p-Tau) in the CSF were measured by enzyme-linked immunosorbent assays (ELISA). After the operation, the occurrence and severity of POD were assessed using the Confusion Assessment Method and the Memorial Delirium Assessment Scale (MDAS), respectively. Patients were categorized into POD group and NPOD group. Logistic regression was used to analyze the relationship between POD and TC, TG, LDL-C, and HDL-C, and the mediating effect was used to analyze the role of POD core proteins in the relationship between lipid and MDAS. We used the receiver operating characteristic (ROC) and the precision-recall curve (PRC) analysis to assess the ability of TC, TG, LDL-C, and HDL-C ability to predict POD. Finally, we performed a sensitivity analysis to assess the stability of the results.

RESULTS

A total of 562 patients were finally enrolled in this study, and 66 patients developed POD, with an incidence of 11.7%. Logistic regression analysis showed that high concentration of TC (OR = 3.148, 95%CI 1.858∼5.333, P < 0.001), TG (OR = 2.483, 95%CI 1.573∼3.918, P < 0.001), and LDL-C (OR = 2.469, 95%CI 1.310∼4.656, P = 0.005) in serum were risk factors for POD. A high concentration of HDL-C (OR = 0.258, 95%CI 0.112∼0.594, P = 0.001) was a protective factor for POD after adjusted for age, sex, education, and MMSE score. ROC curves showed that HDL-C have the highest sensitivity and specificity in predicting POD. For these four lipid markers, the PRC range from 0.602 to 0.731, respectively. The mediating analysis showed that POD core proteins could partially mediate the relationship between lipid and POD (effect value: 16.19∼91.04%). The results were barely changed in the sensitivity analysis, and the sensitivity analysis has shown that the results were stable.

CONCLUSION

The increase of serum TG, TC, and LDL-C concentration is a risk factor for POD development, while high HDL-C concentration is a protective factor for POD, and the occurrence of POD is caused by hyperlipidemia may be caused by POD core proteins.

CLINICAL TRIAL REGISTRATION

[www.ClinicalTrials.gov], identifier [Chictr200033439].

The Beneficial Role of Exercise on Treating Alzheimer's Disease by Inhibiting β-Amyloid Peptide

Alzheimer's disease (AD) is associated with a very large burden on global healthcare systems. Thus, it is imperative to find effective treatments of the disease. One feature of AD is the accumulation of neurotoxic β-amyloid peptide (Aβ). Aβ induces multiple pathological processes that are deleterious to nerve cells. Despite the development of medications that target the reduction of Aβ to treat AD, none has proven to be effective to date. Non-pharmacological interventions, such as physical exercise, are also being studied. The benefits of exercise on AD are widely recognized. Experimental and clinical studies have been performed to verify the role that exercise plays in reducing Aβ deposition to alleviate AD. This paper reviewed the various mechanisms involved in the exercise-induced reduction of Aβ, including the regulation of amyloid precursor protein cleaved proteases, the glymphatic system, brain-blood transport proteins, degrading enzymes and autophagy, which is beneficial to promote exercise therapy as a means of prevention and treatment of AD and indicates that exercise may provide new therapeutic targets for the treatment of AD.

Effect of involuntary chronic physical exercise on beta-amyloid protein in experimental models of Alzheimer's disease: Systematic review and meta-analysis

The excessive deposition of β-amyloid proteins (Aβ) is directly correlated with the establishment and development of Alzheimer's Disease (AD). Current treatments for AD only reduce symptoms instead of acting on Aβ, the primary etiological agent. Hence, the anti-amyloid effect of regular exercise has been widely investigated as an alternative therapy. This systematic review and meta-analysis examined the anti-amyloid effect of regular physical exercise in animal models of AD. The search was conducted on the electronic databases Pubmed, Embase, Scopus and Web of Science without data limitation and using the following describers: "amyloid beta" (OR senile plaque OR amyloid plaque) and "exercise" (OR physical activity OR training). The risk of bias was evaluated using the SYRCLE's tool. Meta-analyses were conducted using models of random continuous effects. A total of 36 studies were selected and most used: transgenic mice (n = 29), treadmill training, duration of 12 weeks (interval of 4 to 28 weeks), rate of 60 min/day (interval of 30 min and up until free access) and speed of 12 m/min (interval of 3.2 to 32 m/min). The hippocampus and cortex were the most frequently investigated regions. Meta-analysis demonstrated a decrease in Aβ with greater effect in unspecified isoforms Meta-analysis demonstrated a decrease in Aβ with greater effect in unspecified isoforms (N = 4; SMD = -2.71, IC 95%: -3.59, -1.84, p < 0.00001, Q2 = 3.38, I2 = 11%) and Aβ_1-42 (N = 21; SMD = -1.94, IC 95%: -2.37, -1.51, p < 0.00001, Q2 = 33,37, I2 = 40%). Concerning training, greater effect was found with: 1) swimming (N = 4; SMD = -1.98, IC 95%: -3,28 - -0,68, p = 0.003, Q2 = 9.74, I2 = 69%), 2) moderate intensity (N = 4; SMD = -2.03, IC 95%: -3.31 - -0.75, p < 0.005, Q² = 12.68, I² = 76%); 3) duration up to six weeks (N = 6; N = 6; SMD = -2.35, IC 95%: -3.15 - -1.55, p < 0.00001, Q² = 8.38, I² = 40%); 4) young animals (SMD = -2.00, IC 95%: -2.59 - -1.42, p < 0.00001, Q² = 24.90, I² = 52%); 5) in the amygdala region (N = 1; SMD = -8.56, IC 95%: -12.88 - -4.23, p = 0.0001) and females (N = 4; SMD = -2.14, IC 95%: -3.48 - -0.79, p = 0.002, Q² = 10.31, I² = 71%). However, the reduction of Aβ was associated with decrease of amyloidogenic pathway and increase of non-amyloidogenic. Hence, regular physical exercise demonstrated anti-amyloid effect in experimental models of AD through positive alterations in APP processing through different signaling pathways.

Neuroprotective mechanisms of chronic physical exercise via reduction of β-amyloid protein in experimental models of Alzheimer's disease: A systematic review

AIMS

Alzheimer's disease (AD) is the most common irreversible chronic neurodegenerative disease. It is characterized by the abnormal accumulation of β-amyloid protein (Aβ), which triggers homeostatic breakage in several physiological systems. However, the effect of chronic exercise on the formation of Aβ as an alternative therapy has been investigated. This systematic review examines the antiamyloid effect of different types and intensities of exercise, seeking to elucidate its neuroprotective mechanisms.

MAIN METHODS

The research was conducted in the electronic databases Pubmed, Embase, Scopus and Web of Science, using the following descriptors: "amyloid beta" (OR senile plaque OR amyloid plaque) and "exercise" (OR physical activity OR training). The risk of bias was evaluated through SYRCLE's Risk of Bias for experimental studies.

KEY FINDINGS

2268 articles were found, being 36 included in the study. A higher frequency of use of mice with genetic alterations was identified for the Alzheimer's disease (AD) model (n = 29). It was used as chronic training: treadmill running (n = 24), voluntary running wheel (n = 7), swimming (n = 4) and climbing (n = 2). The hippocampus and the cortex were the most investigated regions. However, physiological changes accompanied by the reduction of Aβ and associated with AD progression were verified. It is concluded that exercise reduces the production of Aβ in models of animals with AD.

SIGNIFICANCE

Nevertheless, this effect contributes to the improvement of several physiological aspects related to Aβ and that contribute to neurological impairment in AD.

Thyroid hormone treatment improved the response to maximum exercise test and preserved the ventricular geometry in myocardial infarcted rats

NEW FINDINGS

What is the central question of this study? Does thyroid hormone treatment given after myocardial infarction preserve left ventricular function and treadmill exercise performance, and improve parameters of oxidative stress in the right ventricle and lungs of Wistar rats? What is the main finding and its importance? Thyroid hormone treatment improved the performance of the maximum exercise test in infarcted rats and induced effects in the heart and lungs that were similar to those observed with exercise training. This suggests there is a significant value of thyroid hormones for preserving exercise tolerance after myocardial infarction.

ABSTRACT

Left ventricular myocardial infarction (MI) provokes damage in the heart and in other tissues, such as right ventricle and lungs. The present study elucidated whether thyroid hormone treatment (THT) may present positive effects in heart and lungs after MI, and whether or not these effects are similar to those of exercise training (ET). Male Wistar rats were divided into four groups: sham operated (SHAM), infarcted (MI), infarcted + exercise training (MIE), and infarcted + thyroid hormones (MIH). A maximum exercise test, left ventricle echocardiography, pulmonary histology, and oxidative stress in the right ventricle and lung were evaluated. THT and ET both reduced left ventricular dilatation and end-diastolic wall stress indexes to a similar extent. MI accentuated the content of macrophages and inflammatory infiltrate in the lungs, which was partially prevented in the MIH and MIE groups. THT and ET presented similar effects in the heart and lungs, and both improved the performance of the maximum exercise test in infarcted animals.