Osmotin reduced amyloid beta (Aβ) burden by inhibiting SREBP2 expression in APP/PS1 mice

Gut microbiota-host lipid crosstalk in Alzheimer's disease: implications for disease progression and therapeutics

Trillions of intestinal bacteria in the human body undergo dynamic transformations in response to physiological and pathological changes. Alterations in their composition and metabolites collectively contribute to the progression of Alzheimer's disease. The role of gut microbiota in Alzheimer's disease is diverse and complex, evidence suggests lipid metabolism may be one of the potential pathways. However, the mechanisms that gut microbiota mediate lipid metabolism in Alzheimer's disease pathology remain unclear, necessitating further investigation for clarification. This review highlights the current understanding of how gut microbiota disrupts lipid metabolism and discusses the implications of these discoveries in guiding strategies for the prevention or treatment of Alzheimer's disease based on existing data.

Reexamining the Causes and Effects of Cholesterol Deposition in the Brains of Patients with Alzheimer's Disease

Alzheimer's disease (AD) is a degenerative disease of the central nervous system. Numerous studies have shown that imbalances in cholesterol homeostasis in the brains of AD patients precede the onset of clinical symptoms. In addition, cholesterol deposition has been observed in the brains of AD patients even though peripheral cholesterol does not enter the brain through the blood‒brain barrier (BBB). Studies have demonstrated that cholesterol metabolism in the brain is associated with many pathological conditions, such as amyloid beta (Aβ) production, Tau protein phosphorylation, oxidative stress, and inflammation. In 2022, some scholars put forward a new hypothesis of AD: the disease involves lipid invasion and its exacerbation of the abnormal metabolism of cholesterol in the brain. In this review, by discussing the latest research progress, the causes and effects of cholesterol retention in the brains of AD patients are analyzed and discussed. Additionally, the possible mechanism through which AD may be improved by targeting cholesterol is described. Finally, we propose that improving the impairments in cholesterol removal observed in the brains of AD patients, instead of further reducing the already impaired cholesterol synthesis in the brain, may be the key to preventing cholesterol deposition and improving the corresponding pathological symptoms.

Aerobic Exercise Facilitates the Nuclear Translocation of SREBP2 by Activating AKT/SEC24D to Contribute Cholesterol Homeostasis for Improving Cognition in APP/PS1 Mice

Impaired cholesterol synthesizing ability is considered a risk factor for the development of Alzheimer's disease (AD), as evidenced by reduced levels of key proteases in the brain that mediate cholesterol synthesis; however, cholesterol deposition has been found in neurons in tangles in the brains of AD patients. Although it has been shown that statins, which inhibit cholesterol synthesis, reduce the incidence of AD, this seems paradoxical for AD patients whose cholesterol synthesizing capacity is already impaired. In this study, we aimed to investigate the effects of aerobic exercise on cholesterol metabolism in the brains of APP/PS1 mice and to reveal the mechanisms by which aerobic exercise improves cognitive function in APP/PS1 mice. Our study demonstrates that the reduction of SEC24D protein, a component of coat protein complex II (COPII), is a key factor in the reduction of cholesterol synthesis in the brain of APP/PS1 mice. 12 weeks of aerobic exercise was able to promote the recovery of SEC24D protein levels in the brain through activation of protein kinase B (AKT), which in turn promoted the expression of mem-brane-bound sterol regulatory element-binding protein 2 (SREBP2) nuclear translocation and the expression of key proteases mediating cholesterol synthesis. Simultaneous aerobic exercise restored cholesterol transport capacity in the brain of APP/PS1 mice with the ability to efflux excess cholesterol from neurons and reduced neuronal lipid rafts, thereby reducing cleavage of the APP amyloid pathway. Our study emphasizes the potential of restoring intracerebral cholesterol homeostasis as a therapeutic strategy to alleviate cognitive impairment in AD patients.

Progress in the development of naturally derived active metabolites-based drugs: Potential therapeutics for Alzheimer's disease

Alzheimer's disease (AD) is an extensive age-associated neurodegenerative disorder. In spite of wide-ranging progress in understanding the AD pathology for the past 50 years, clinical trials based on the hypothesis of amyloid-beta (Aβ) have reserved worsening particularly at late-stage human trials. Consequently, very few old drugs are presently used for AD with inadequate clinical consequences and various side effects. We focus on widespread pharmacological and beneficial principles for existing as well as future drugs. Multitargeting approaches by means of general antioxidant and anti-inflammatory mechanisms allied with particular receptor and/or enzyme-mediated actions in neuroprotection and neurodegeneration. The plant kingdom comprises a vast range of species with an incredible diversity of bioactive metabolites with diverse chemical scaffolds. In recent times, an increasing body of facts recommended the use of phytochemicals to decelerate AD's onset and progression. The definitive goal of AD investigation is to avert the onset of neurodegeneration, thereby allowing successful aging devoid of cognitive decline. At this point, we discussed the neurological protective role of natural products and naturally derived therapeutic agents for AD from various natural polyphenolic compounds and medicinal plants. In conclusion, medicinal plants act as a chief source of different bioactive constituents.

Paricalcitol accelerates BACE1 lysosomal degradation and inhibits calpain-1 dependent neuronal loss in APP/PS1 transgenic mice

BACKGROUND

Recent studies have revealed that vitamin D deficiency may increase the risk of Alzheimer's disease, and vitamin D supplementation may be effective strategy to ameliorate the neurodegenerative process in Alzheimer's disease patients. Paricalcitol (PAL), a low-calcemic vitamin D receptor agonist, is clinically used to treat secondary hyperparathyroidism. However, the potential application of PAL for treating neurodegenerative disorders remains unexplored.

METHODS

The APP/PS1 mice were intraperitoneally injected with PAL or vehicle every other day for 15 weeks. The β-amyloid (Aβ) production was confirmed using immunostaining and enzyme linked immunosorbent assay. The underlying mechanism was verified by western blot and immunostaining in vivo and in vitro.

FINDINGS

Long-term PAL treatment clearly reduced β-amyloid (Aβ) generation and neuronal loss in APP/PS1 transgenic mouse brains. PAL stimulated the expression of low-density lipoprotein receptor-related protein 1 (LRP1) possibly through inhibiting sterol regulatory element binding protein-2 (SREBP2); PAL also promoted LRP1-mediated β-site APP cleavage enzyme 1 (BACE1) transport to late endosomes, thus increasing the lysosomal degradation of BACE1. Furthermore, PAL diminished 8-hydroxyguanosine (8-OHdG) generation in neuronal mitochondria via enhancing base excision repair (BER), resulting in the attenuation of calpain-1-mediated neuronal loss.

INTERPRETATION

The present data demonstrate that PAL can reduce Aβ generation through accelerating BACE1 lysosomal degradation and can inhibit neuronal loss through suppressing mitochondrial 8-OHdG generation. Hence, PAL might be a promising agent for treating Alzheimer's disease. FUND: This study was financially supported by the Natural Science Foundation of China (U1608282).

The sterol regulatory element-binding protein 2 is dysregulated by tau alterations in Alzheimer disease

Disturbed neuronal cholesterol homeostasis has been observed in Alzheimer disease (AD) and contributes to the pathogenesis of AD. As the master switch of cholesterol biosynthesis, the sterol regulatory element-binding protein 2 (SREBP-2) translocates to the nucleus after cleavage/activation, but its expression and activation have not been studied in AD which is the focus of the current study. We found both a significant decrease in the nuclear translocation of N-terminal SREBP-2 accompanied by a significant accumulation of C-terminal SREBP-2 in NFT-containing pyramidal neurons in AD. N-terminal- SREBP-2 is also found in dystrophic neurites around plaques in AD brain. Western blot confirmed a significantly reduced nuclear translocation of mature SREBP-2 (mSREBP-2) in AD brain. Interestingly, reduced nuclear mSREBP-2 was only found in animal models of tauopathies such as 3XTg AD mice and P301L Tau Tg mice but not in CRND8 APP transgenic mice, suggesting that tau alterations likely are involved in the changes of mSREBP-2 distribution and activation in AD. Altogether, our study demonstrated disturbed SREBP-2 signaling in AD and related models, and proved for the first time that tau alterations contribute to disturbed cholesterol homeostasis in AD likely through modulation of nuclear mSREBP-2 translocation.

Examining the Potential of Developing and Implementing Use of Adiponectin-Targeted Therapeutics for Metabolic and Cardiovascular Diseases

Cardiometabolic diseases encompass those affecting the heart and vasculature as well as other metabolic problems, such as insulin resistance, diabetes, and non-alcoholic fatty liver disease. These diseases tend to have common risk factors, one of which is impaired adiponectin action. This may be due to reduced bioavailability of the hormone or resistance to its effects on target tissues. A strong negative correlation between adiponectin levels and cardiometabolic diseases has been well-documented and research shown that adiponectin has cardioprotective, insulin sensitizing and direct beneficial metabolic effects. Thus, therapeutic approaches to enhance adiponectin action are widely considered to be desirable. The complexity of adiponectin structure and function has so far made progress in this area less than ideal. In this article we will review the effects and mechanism of action of adiponectin on cardiometabolic tissues, identify scenarios where enhancing adiponectin action would be of clinical value and finally discuss approaches via which this can be achieved.

Resilience Against Traumatic Stress: Current Developments and Future Directions

Given the high prevalence of stress-related mental disorders, their impact on person, family, and society and the paucity of treatment options for most of these disorders, there is currently a pressing need for innovative approaches to deal with these issues and enhance well-being. One approach which has received increasing attention over the last decade is to shift our scientific and clinical focus from risk factors for psychopathology to factors promoting resilience and mental well-being. In order to summarize and evaluate the current state of scientific affairs on the biological basis of resilience, we provide an overview of the literature on animal and human studies of resilience. Because resilience can only truly be operationalized through longitudinal data collection and analyses, we focus primarily on longitudinal studies. This review shows that the concept of resilience is currently being operationalized, measured and even defined in widely variable manners, both within animal and human studies. We further provide an overview of existing and new strategies that could help promote resilience and which are proposed to be implemented more often in clinical situations. Finally, we summarize the challenges the field is facing and provide recommendations for future research.

Sirtuins in Neuroendocrine Regulation and Neurological Diseases

Silent information regulator 1 (SIRT1) is a mammalian homolog of the nicotinamide adenine dinucleotide (NAD)-dependent deacetylase sirtuin family. Sirtuin was originally studied as the lifespan-extending gene, silent information regulator 2 (SIRT2) in budding yeast. There are seven mammalian homologs of sirtuin (SIRT1–7), and SIRT1 is the closest homolog to SIRT2. SIRT1 modulates various key targets via deacetylation. In addition to histones, these targets include transcription factors, such as forkhead box O (FOXO), Ku70, p53, NF-κB, PPAR-gamma co-activator 1-alpha (PGC-1α), and peroxisome proliferator-activated receptor γ (PPARγ). SIRT1 has many biological functions, including aging, cell survival, differentiation, and metabolism. Genetic and physiological analyses in animal models have shown beneficial roles for SIRT1 in the brain during both development and adulthood. Evidence from in vivo and in vitro studies have revealed that SIRT1 regulates the cellular fate of neural progenitors, axon elongation, dendritic branching, synaptic plasticity, and endocrine function. In addition to its importance in physiological processes, SIRT1 has also been implicated in protection of neurons from degeneration in models of neurological diseases, such as traumatic brain injury and Alzheimer’s disease. In this review, we focus on the role of SIRT1 in the neuroendocrine system and neurodegenerative diseases. We also discuss the potential therapeutic implications of targeting the sirtuin pathway.