Modulation of SIRT1 expression in different neurodegenerative models and human pathologies

Mitochondrial targeted antioxidants as potential therapy for huntington's disease

Huntington's disease (HD) is an inherited neurodegenerative disorder caused by an expansion in CAG repeat on huntington (Htt) gene, leading to a degeneration of GABAergic medium spiny neurons (MSNs) in the striatum, resulting in the generation of reactive oxygen species, and decrease antioxidant activity. These pathophysiological alterations impair mitochondrial functions, leading to an increase in involuntary hyperkinetic movement. However, researchers investigated the neuroprotective effect of antioxidants using various animal models. Still, their impact is strictly limited to curtailing oxidative stress and increasing the antioxidant enzyme in the brain, which is less effective in HD. Meanwhile, researchers discovered Mitochondria-targeted antioxidants (MTAXs) that can improve mitochondrial functions and antioxidant activity through the modulation of mitochondrial signaling pathways, including peroxisome proliferator-activated receptor (PPAR)-coactivator 1 (PGC-1α), dynamin-related protein 1 (Drp1), mitochondrial fission protein 1 (Fis1), and Silent mating type information regulation 2 homolog 1 (SIRT-1), showing neuroprotective effects in HD. The present review discusses the clinical and preclinical studies that investigate the neuroprotective effect of MTAXs (SS31, XJB-5-131, MitoQ, bezafibrate, rosiglitazone, meldonium, coenzyme Q10, etc.) in HD. This brief literature review will help to understand the relevance of MTAXs in HD and enlighten the importance of MTAXs in future drug discovery and development.

Dietary fasting and time-restricted eating in Huntington's disease: therapeutic potential and underlying mechanisms

Huntington's disease (HD) is a devastating neurodegenerative disorder caused by aggregation of the mutant huntingtin (mHTT) protein, resulting from a CAG repeat expansion in the huntingtin gene HTT. HD is characterized by a variety of debilitating symptoms including involuntary movements, cognitive impairment, and psychiatric disturbances. Despite considerable efforts, effective disease-modifying treatments for HD remain elusive, necessitating exploration of novel therapeutic approaches, including lifestyle modifications that could delay symptom onset and disease progression. Recent studies suggest that time-restricted eating (TRE), a form of intermittent fasting involving daily caloric intake within a limited time window, may hold promise in the treatment of neurodegenerative diseases, including HD. TRE has been shown to improve mitochondrial function, upregulate autophagy, reduce oxidative stress, regulate the sleep-wake cycle, and enhance cognitive function. In this review, we explore the potential therapeutic role of TRE in HD, focusing on its underlying physiological mechanisms. We discuss how TRE might enhance the clearance of mHTT, recover striatal brain-derived neurotrophic factor levels, improve mitochondrial function and stress-response pathways, and synchronize circadian rhythm activity. Understanding these mechanisms is critical for the development of targeted lifestyle interventions to mitigate HD pathology and improve patient outcomes. While the potential benefits of TRE in HD animal models are encouraging, future comprehensive clinical trials will be necessary to evaluate its safety, feasibility, and efficacy in persons with HD.

Phosphodiesterase-4 Inhibition in Parkinson's Disease: Molecular Insights and Therapeutic Potential

Clinicians and researchers are exploring safer and novel treatment strategies for treating the ever-prevalent Parkinson's disease (PD) across the globe. Several therapeutic strategies are used clinically for PD, including dopamine replacement therapy, DA agonists, MAO-B blockers, COMT blockers, and anticholinergics. Surgical interventions such as pallidotomy, particularly deep brain stimulation (DBS), are also employed. However, they only provide temporal and symptomatic relief. Cyclic adenosine monophosphate (cAMP) is one of the secondary messengers involved in dopaminergic neurotransmission. Phosphodiesterase (PDE) regulates cAMP and cGMP intracellular levels. PDE enzymes are subdivided into families and subtypes which are expressed throughout the human body. PDE4 isoenzyme- PDE4B subtype is overexpressed in the substantia nigra of the brain. Various studies have implicated multiple cAMP-mediated signaling cascades in PD, and PDE4 is a common link that can emerge as a neuroprotective and/or disease-modifying target. Furthermore, a mechanistic understanding of the PDE4 subtypes has provided perceptivity into the molecular mechanisms underlying the adverse effects of phosphodiesterase-4 inhibitors (PDE4Is). The repositioning and development of efficacious PDE4Is for PD have gained much attention. This review critically assesses the existing literature on PDE4 and its expression. Specifically, this review provides insights into the interrelated neurological cAMP-mediated signaling cascades involving PDE4s and the potential role of PDE4Is in PD. In addition, we discuss existing challenges and possible strategies for overcoming them.

SIRT1 pathway in Parkinson's disease: a faraway snapshot but so close

Silent information regulator (SIRT) has distinctive enzymatic activities and physiological functions to control cell-cycle progression, gene expression, and DNA stability by targeting histone and non-histone proteins. SIRT1 enhances synaptic formation and synaptic activity, and therefore, can reduce the progression of various degenerative brain diseases including Parkinson's disease (PD). SIRT1 activity is decreased by aging with a subsequent increased risk for the development of degenerative brain diseases. Inhibition of SIRT1 promotes inflammatory reactions since SIRT1 inhibits transcription of nuclear factor kappa B (NF-κB) which also inhibits SIRT1 activation via activation of microRNA and miR-34a which reduce NAD synthesis. SIRT1 is highly expressed in microglia as well as neurons, and has antioxidant and anti-inflammatory effects. Therefore, this review aimed to find the possible role of SIRT1 in PD neuropathology. SIRT1 has neuroprotective effects; therefore, downregulation of SIRT1 during aging promotes p53 expression and may increase the vulnerability of neuronal cell deaths. PD neuropathology is linked with the sequence of inflammatory changes and the release of pro-inflammatory cytokines due to the activation of inflammatory signaling pathways. In addition, oxidative stress, inflammatory disorders, mitochondrial dysfunction, and apoptosis contribute mutually to PD neuropathology. Thus, SIRT1 and SIRT1 activators play a crucial role in the mitigation of PD neuropathology through the amelioration of oxidative stress, inflammatory disorders, mitochondrial dysfunction, apoptosis, and inflammatory signaling pathways.

HIV-Associated Insults Modulate ADAM10 and Its Regulator Sirtuin1 in an NMDA Receptor-Dependent Manner

Neurologic deficits associated with human immunodeficiency virus (HIV) infection impact about 50% of persons with HIV (PWH). These disorders, termed HIV-associated neurocognitive disorders (HAND), possess neuropathologic similarities to Alzheimer’s disease (AD), including intra- and extracellular amyloid-beta (Aβ) peptide aggregates. Aβ peptide is produced through cleavage of the amyloid precursor protein (APP) by the beta secretase BACE1. However, this is precluded by cleavage of APP by the non-amyloidogenic alpha secretase, ADAM10. Previous studies have found that BACE1 expression was increased in the CNS of PWH with HAND as well as animal models of HAND. Further, BACE1 contributed to neurotoxicity. Yet in in vitro models, the role of ADAM10 and its potential regulatory mechanisms had not been examined. To address this, primary rat cortical neurons were treated with supernatants from HIV-infected human macrophages (HIV/MDMs). We found that HIV/MDMs decreased levels of both ADAM10 and Sirtuin1 (SIRT1), a regulator of ADAM10 that is implicated in aging and in AD. Both decreases were blocked with NMDA receptor antagonists, and treatment with NMDA was sufficient to induce reduction in ADAM10 and SIRT1 protein levels. Furthermore, decreases in SIRT1 protein levels were observed at an earlier time point than the decreases in ADAM10 protein levels, and the reduction in SIRT1 was reversed by proteasome inhibitor MG132. This study indicates that HIV-associated insults, particularly excitotoxicity, contribute to changes of APP secretases by downregulating levels of ADAM10 and its regulator.

Brain Region and Sex-specific Changes in Mitochondrial Biogenesis Induced by Acute Trimethyltin Exposure

Objective

In this study, we investigated sex- and region-specific effects of acute trimethyltin (TMT) exposure on mitochondrial biogenesis.

Methods

We treated TMT to primary neuronal cultures and 4-week-old male and female mice. We measured the mitochondrial DNA copy numbers using the quantitative polymerase chain reaction method. We also measured mitochondrial biogenesis related genes (sirtuin-1, estrogen-related receptor alpha, cytochrome C oxidase subunit IV) by western blotting.

Results

The mitochondrial DNA copy number increased in the primary hippocampal neuron; however, it decreased in the primary cortical neuron. The mitochondrial copy number increased in the hippocampus and decreased in the cortex in the TMT treated female mice, though the mitochondrial copy number increased in both cortex and hippocampus in the TMT treated male mice. TMT treatment increased sirtuin-1 expression in the male hippocampus but did not in the female brain. In the female brain, estrogen-related receptor alpha expression decreased in the cortex though there is no significant change in the male brain. The protein level of mitochondrial protein, cytochrome C oxidase subunit IV, increased in both cortex and hippocampus after TMT injection in male mice brain, but not in female mice brain.

Conclusion

Our data suggest that acute TMT exposure induces distinct sex-specific metabolic characteristics in the brain before significant sexual maturation.

Exposure to a mixture of heavy metals induces cognitive impairment: Genes and microRNAs involved

Converging evidence demonstrates that microRNAs (miRNAs) play an important role in the etiology of cognitive impairment. Thus, we aim to: (i) identify the molecular mechanisms of heavy metals, particularly miRNAs involved in the development of cognitive impairment; and (ii) generate miRNA sponges to prevent them from binding with their target messenger RNAs. The Comparative Toxicogenomics Database (CTD; http://ctd.mdibl.org), MicroRNA ENrichment TURned NETwork (MIENTURNET, http://userver.bio.uniroma1.it/apps/mienturnet/) and the microRNA sponge generator and tester (miRNAsong, http://www.med.muni.cz/histology/miRNAsong) were used as the core data-mining approaches in the current study. We observed that lead acetate, arsenic, gold, copper, iron, and aluminum, as well as their mixtures, had significant effects on the development of cognitive impairment. Although prevalent genes obtained from investigated heavy metals of cognitive impairment were different, the "PI3K-Akt signaling pathway", "pathways of neurodegeneration-multiple diseases", "apoptosis", "apoptosis-multiple species", "p53 signaling pathway", "NF-kappa B signaling pathway", and "Alzheimer's disease pathway" were highlighted. The mixed heavy metals altered the genes BAX, CASP3, BCL2, TNF, and IL-1B, indicating the significance of apoptosis and pro-inflammatory cytokines in the pathogenesis of cognitive impairment and the possibility of targeting these genes in future neuroprotective therapy. In addition, we used a network-based approach to identify key genes, miRNAs, pathways, and diseases related to the development of cognitive impairment. We also found 16 significant miRNAs related to cognitive impairment (hsa-miR-1-3p, hsa-let-7a-5p, hsa-miR-9-5p, hsa-miR-16-5p, hsa-miR-17-5p, hsa-miR-20a-5p, hsa-miR-26a-5p, hsa-miR-26b-5p, hsa-miR-34a-5p, hsa-miR-101-3p, hsa-miR-106a-5p, hsa-miR-128-3p, hsa-miR-144-3p, hsa-miR-199a-3p, hsa-miR-204-5p, and hsa-miR-335-5p). Finally, we created and evaluated miRNA sponge sequences for these miRNAs in silico. Further studies, including in vivo and in vitro, are needed to assess the link between these genes, miRNAs, pathways, and cognitive impairment.

Roflupram protects against rotenone-induced neurotoxicity and facilitates α-synuclein degradation in Parkinson's disease models

We have previously shown that roflupram (ROF) protects against MPP+-induced neuronal damage in models of Parkinson's disease (PD). Since impaired degradation of α-synuclein (α-syn) is one of the key factors that lead to PD, here we investigated whether and how ROF affects the degradation of α-syn in rotenone (ROT)-induced PD models in vivo and in vitro. We showed that pretreatment with ROF (10 μM) significantly attenuated cell apoptosis and reduced the level of α-syn in ROT-treated SH-SY5Y cells. Furthermore, ROF significantly enhanced the lysosomal function, as evidenced by the increased levels of mature cathepsin D (CTSD) and lysosomal-associated membrane protein 1 (LAMP1) through increasing NAD+/NADH and the expression of sirtuin 1 (SIRT1). Pretreatment with an SIRT1 inhibitor selisistat (SELI, 10 μM) attenuated the neuroprotection of ROF, ROF-reduced expression of α-syn, and ROF-increased expression levels of LAMP1 and mature CTSD. Moreover, inhibition of CTSD by pepstatin A (20 μM) attenuated ROF-reduced expression of α-syn. In vivo study was conducted in mice exposed to ROT (10 mg·kg-1·d-1, i.g.) for 6 weeks; then, ROT-treated mice received ROF (0.5, 1, or 2 mg·kg-1·d-1; i.g.) for four weeks. ROF significantly ameliorated motor deficits, which was accompanied by increased expression levels of tyrosine hydroxylase, SIRT1, mature CTSD, and LAMP1, and a reduced level of α-syn in the substantia nigra pars compacta. Taken together, these results demonstrate that ROF exerts a neuroprotective action and reduces the α-syn level in PD models. The mechanisms underlying ROF neuroprotective effects appear to be associated with NAD+/SIRT1-dependent activation of lysosomal function.

Physical Work and Exercise Reduce the Risk of Cognitive Impairment in Older Adults: A Population-based Longitudinal Study

BACKGROUND

The independent effect of physical work on the risk of cognitive impairment in older Chinese older adults living in rural areas remains to be elucidated.

OBJECTIVE

We aimed to determine whether physical work and physical exercise can reduce the risk of cognitive impairment.

METHODS

We collected data from 7,000 permanent residents without cognitive impairment (age ≥60 years) over a follow-up period of 2 years. We used the Chinese version of the Mini-Mental State Examination (MMSE) to assess cognitive function. We performed multivariate Cox regression analyses to calculate adjusted Hazard Ratios (HRs) and 95% Confidence Intervals (%95 CIs) as measures of the association between physical work/exercise and cognitive impairment while controlling for potential confounders.

RESULTS

Over a median follow-up period of 1.93 years, 1,224 (17.5%) of 7,000 participants developed cognitive impairment, with a total incidence of 97.69 per 1,000 person-years. After adjustment for potential confounders, participating in physical work (HR: 0.51; 95% CI: 0.43-0.60) or physical exercise (HR: 0.53; 95% CI: 0.44-0.65) was associated with a reduced risk of cognitive impairment. Stratified analyses suggested additive and multiplicative interactions between physical work and exercise. Agricultural work (HR: 0.46; 95% CI: 0.38-0.55), walking/tai chi (HR: 0.54; 95% CI: 0.44-0.67), and brisk walking/yangko (HR: 0.57; 95% CI: 0.33-0.97) exerted significant protective effects against cognitive impairment.

CONCLUSION

Both physical work and exercise can reduce the risk of cognitive impairment in older adults. Reasonable types and appropriate intensities of physical activity are recommended to prevent or delay the progression of cognitive impairment.

Tau Protein Interaction Partners and Their Roles in Alzheimer's Disease and Other Tauopathies

Tau protein plays a critical role in the assembly, stabilization, and modulation of microtubules, which are important for the normal function of neurons and the brain. In diseased conditions, several pathological modifications of tau protein manifest. These changes lead to tau protein aggregation and the formation of paired helical filaments (PHF) and neurofibrillary tangles (NFT), which are common hallmarks of Alzheimer's disease and other tauopathies. The accumulation of PHFs and NFTs results in impairment of physiological functions, apoptosis, and neuronal loss, which is reflected as cognitive impairment, and in the late stages of the disease, leads to death. The causes of this pathological transformation of tau protein haven't been fully understood yet. In both physiological and pathological conditions, tau interacts with several proteins which maintain their proper function or can participate in their pathological modifications. Interaction partners of tau protein and associated molecular pathways can either initiate and drive the tau pathology or can act neuroprotective, by reducing pathological tau proteins or inflammation. In this review, we focus on the tau as a multifunctional protein and its known interacting partners active in regulations of different processes and the roles of these proteins in Alzheimer's disease and tauopathies.

Melatonin Attenuates Neuroinflammation by Down-Regulating NLRP3 Inflammasome via a SIRT1-Dependent Pathway in MPTP-Induced Models of Parkinson's Disease

Background

Inflammasome-induced neuroinflammation is a key contributor to the pathology of Parkinson's disease (PD). NLR family pyrin domain-containing 3 (NLRP3) inflammasome activation has been implicated in PD in postmortem human PD brains, indicating it as a potential target for PD treatment. Melatonin, a multitasking molecule, has been found to have anti-inflammatory activities, mediated by silence information regulator 1 (SIRT1). However, whether and how melatonin is involved in inflammasome-induced neuroinflammation in PD pathogenesis remains unclear.

Methods

We investigated the potential anti-inflammatory effects of melatonin in vitro and in vivo, using 1-methyl-4-phenylpyridinium (MPP⁺)-simulated BV2 and primary microglia cell models, and a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced murine PD model, with or without melatonin treatment. Rotarod, grip strength, and open-field tests were performed to measure the effects of melatonin on MPTP-induced motor disorders. Degeneration of dopaminergic neurons was evaluated by immunofluorescence. Changes in microglia were examined by immunofluorescence and Western blotting, and the expression levels of the involved signaling molecules were assessed by Western blotting and enzyme-linked immunosorbent assay (ELISA). Intracellular reactive oxygen species (ROS) was detected using fluorescent probes via flow cytometry.

Results

We found that melatonin significantly alleviated motor dysfunction and prevented MPTP-induced neurotoxicity in dopaminergic neurons. Additionally, melatonin reduced MPTP-induced microglial activation and suppressed NLRP3 inflammasome activity, and also inhibited IL-1β secretion. Moreover, in MPP⁺-primed BV2 cells, melatonin markedly restored the downregulation of SIRT1 and attenuated the activation of the NLRP3 inflammasome. This was reversed by SIRT1 inhibitor treatment.

Conclusion

In conclusion, our data demonstrated that melatonin attenuates neuroinflammation by negatively regulating NLRP3 inflammasome activation via a SIRT1-dependent pathway in MPTP-induced PD models. These findings provide novel insights into the mechanism underlying the anti-inflammatory effects of melatonin in PD.

Beneficial Effects of Exogenous Ketogenic Supplements on Aging Processes and Age-Related Neurodegenerative Diseases

Life expectancy of humans has increased continuously up to the present days, but their health status (healthspan) was not enhanced by similar extent. To decrease enormous medical, economical and psychological burden that arise from this discrepancy, improvement of healthspan is needed that leads to delaying both aging processes and development of age-related diseases, thereby extending lifespan. Thus, development of new therapeutic tools to alleviate aging processes and related diseases and to increase life expectancy is a topic of increasing interest. It is widely accepted that ketosis (increased blood ketone body levels, e.g., β-hydroxybutyrate) can generate neuroprotective effects. Ketosis-evoked neuroprotective effects may lead to improvement in health status and delay both aging and the development of related diseases through improving mitochondrial function, antioxidant and anti-inflammatory effects, histone and non-histone acetylation, β-hydroxybutyrylation of histones, modulation of neurotransmitter systems and RNA functions. Administration of exogenous ketogenic supplements was proven to be an effective method to induce and maintain a healthy state of nutritional ketosis. Consequently, exogenous ketogenic supplements, such as ketone salts and ketone esters, may mitigate aging processes, delay the onset of age-associated diseases and extend lifespan through ketosis. The aim of this review is to summarize the main hallmarks of aging processes and certain signaling pathways in association with (putative) beneficial influences of exogenous ketogenic supplements-evoked ketosis on lifespan, aging processes, the most common age-related neurodegenerative diseases (Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis), as well as impaired learning and memory functions.

Role of SIRT1 in Isoflurane Conditioning-Induced Neurovascular Protection against Delayed Cerebral Ischemia Secondary to Subarachnoid Hemorrhage

We recently reported that isoflurane conditioning provided multifaceted protection against subarachnoid hemorrhage (SAH)-induced delayed cerebral ischemia (DCI), and this protection was through the upregulation of endothelial nitric oxide synthase (eNOS). SIRT1, an NAD-dependent deacetylase, was shown to be one of the critical regulators of eNOS. The aim of our current study is to examine the role of SIRT1 in isoflurane conditioning-induced neurovascular protection against SAH-induced DCI. Mice were divided into four groups: sham, SAH, or SAH with isoflurane conditioning (with and without EX-527). Experimental SAH via endovascular perforation was performed. Anesthetic conditioning was performed with isoflurane 2% for 1 h, 1 h after SAH. EX-527, a selective SIRT1 inhibitor, 10 mg/kg was injected intraperitoneally immediately after SAH in the EX-527 group. SIRT1 mRNA expression and activity levels were measured. Vasospasm, microvessel thrombosis, and neurological outcome were assessed. SIRT1 mRNA expression was downregulated, and no difference in SIRT1 activity was noted after isoflurane exposure. Isoflurane conditioning with and without EX-527 attenuated vasospasm, microvessel thrombosis and improved neurological outcomes. Our data validate our previous findings that isoflurane conditioning provides strong protection against both the macro and micro vascular deficits induced by SAH, but this protection is likely not mediated through the SIRT1 pathway.

Differential role of melatonin in healthy brain aging: a systematic review and meta-analysis of the SAMP8 model

The relationship between oxidative stress (OS) and cellular senescence (CS) is an important research topic because of the rapidly aging global population. Melatonin (MT) is associated with aging and plays a pivotal role in redox homeostasis, but its role in maintaining physiological stability in the brain (especially in OS-induced senescence) remains elusive. Here, we systematically reviewed the differential role of MT on OS-induced senescence in the SAMP8 mouse model. Major electronic databases were searched for relevant studies. Pooled mean differences (MDs)/standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated to estimate the effect size. Overall, 10 studies met the inclusion criteria. MT treatment was associated with the reduction of lipid peroxidation (SMD = -2.00, 95% CI [-2.91, -1.10]; p < 0.0001) and carbonylated protein (MD = -5.74, 95% CI [-11.03, -0.44]; p = 0.03), and with enhancement of the reduced-glutathione/oxidized-glutathione ratio (MD = 1.12, 95% CI [0.77, 1.47]; p < 0.00001). No differences were found in catalase and superoxide dismutase activities between MT-treated and vehicle-treated groups. Furthermore, nuclear-factor-κB, cyclin-dependent kinase-5, and p53 were regulated by MT administration. MT may improve physiological stability during aging by regulating interactions in brain senescence, but acts differentially on the antioxidant system.

Sirtuins and Their Implications in Neurodegenerative Diseases from a Drug Discovery Perspective

Sirtuins are class III histone deacetylase (HDAC) enzymes that target both histone and non-histone substrates. They are linked to different brain functions and the regulation of different isoforms of these enzymes is touted to be an emerging therapy for the treatment of neurodegenerative diseases (NDs), including Parkinson's disease (PD), Alzheimer's disease (AD), and amyotrophic lateral sclerosis (ALS). The level of sirtuins affects brain health as many sirtuin-regulated pathways are responsible for the progression of NDs. Certain sirtuins are also implicated in aging, which is a risk factor for many NDs. In addition to SIRT1-3, it has been suggested that the less studied sirtuins (SIRT4-7) also play critical roles in brain health. This review delineates the role of each sirtuin isoform in NDs from a disease centric perspective and provides an up-to-date overview of sirtuin modulators and their potential use as therapeutics in these diseases. Furthermore, the future perspectives for sirtuin modulator development and their therapeutic application in neurodegeneration are outlined in detail, hence providing a research direction for future studies.

Elucidating the Neuroprotective Role of Formulated Camel α-Lactalbumin-Oleic Acid Complex by Curating the SIRT1 Pathway in Parkinson's Disease Model

Parkinson's Disease (PD) is characterized by increased oxidative stress and decreased level of dopamine. At present, the therapeutic interventions of PD are associated with undesirable adverse effects. To overcome these side effects, a new candidate bioinspired molecule is needed for the management of PD. Camel α-lactalbumin (α-LA) is the most abundant protein in camel's milk and has a potential to act as a nutraceutical supplement for neurological functions. Oleic acid, a monounsaturated fatty acid, has been widely associated with a reduced risk of PD. The present study aimed to formulate the camel α-LA and oleic acid (CLOA) complex under specific conditions and to evaluate its efficacy as a neuroprotective in rotenone induced PC12 cell model of PD. Our results demonstrated that removal of Ca++ ions from camel α-LA by EDTA enhances its binding efficiency with oleic acid, and the complex was characterized by UV-CD, ANS fluorescence spectroscopy, and NMR spectroscopy. Moreover, CLOA complex treatment reduced the oxidative stress and increased the cell viability by enhancing the level of dopamine and the expression of SIRT1, FOXO3a, HIF-1α, and HSF-1. We also validated the neuroprotective role of the complex by incubating the cells with CLOA complex prior to rotenone treatment. We inferred from the outcome of the results that the individual entity, i.e., α-LA or OA, is not as effective as the complex. Taken together, our study indicates that CLOA complex might be a potential candidate for the development of future therapeutic drugs for PD.

The Critical Role of SIRT1 in Parkinson's Disease: Mechanism and Therapeutic Considerations

Silence information regulator 1 (SIRT1), a member of the sirtuin family, targets histones and many non-histone proteins and participates in various physiological functions. The enzymatic activity of SIRT1 is decreased in patients with Parkinson’s disease (PD), which may reduce their ability to resist neuronal damage caused by various neurotoxins. As far as we know, SIRT1 can induce autophagy by regulating autophagy related proteins such as AMP-activated protein kinase, light chain 3, mammalian target of rapamycin, and forkhead transcription factor 1. Furthermore, SIRT1 can regulate mitochondrial function and inhibit oxidative stress mainly by maintaining peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) in a deacetylated state and thus maintaining a constant level of PGC-1α. Other studies have demonstrated that SIRT1 may play a role in the pathophysiology of PD by regulating neuroinflammation. SIRT1 deacetylases nuclear factor-kappa B and thus reduces its transcriptional activity, inhibits inducible nitric oxide synthase expression, and decreases tumor necrosis factor-alpha and interleukin-6 levels. SIRT1 can also upregulate heat shock protein 70 by deacetylating heat shock factor 1 to increase the degradation of α-synuclein oligomers. Few studies have focused on the relationship between SIRT1 single nucleotide polymorphisms and PD risk, so this topic requires further research. Based on the neuroprotective effects of SIRT1 on PD, many in vitro and in vivo experiments have demonstrated that some SIRT1 activators, notably resveratrol, have potential neuroprotective effects against dopaminergic neuronal damage caused by various neurotoxins. Thus, SIRT1 plays a critical role in PD development and might be a potential target for PD therapy.

Sirt1/FoxO1-Associated MAO-A Upregulation Promotes Depressive-Like Behavior in Transgenic Mice Expressing Human A53T α-Synuclein

Nonmotor symptoms are of pivotal importance in Parkinson's disease (PD), among which depressive disorder occurs in more than 45% of PD cases. Decreased levels of noradrenaline (NA) and serotonin (5-HT) in the central nervous system are relevant to it; however, the underlying mechanism is largely unknown. To this end, we conducted behavioral assays to analyze the depressive phenotype in transgenic mice with overexpressed A53T human α-synuclein (A53T mice) and examined alterations of NAergic and 5-HTergic systems in the neuron degeneration, neurotransmitter production, and degradation aspects of the mouse. As compared to controls, A53T mice displayed elevated depressive-like behavior at 6 months, which presents earlier than motor deficits do at 12 months. We detected reduced levels of NA and 5-HT in the hippocampus and NA in the locus coeruleus of 6-month A53T mice. There was no loss of NAergic and 5-HTergic neurons or decreased neurotransmitter synthesis in the brain. However, the expression of MAO-A, an enzyme responsible for NA and 5-HT degradation, was upregulated in A53T mice. Mechanistically, Sirt1 was downregulated which lead to an increase in FoxO1 acetylation, which subsequently increased the transcription of MAO-A. Activation of Sirt1 by resveratrol or inhibition of MAO-A by moclobemide administration could restore brain NA and 5-HT levels and attenuate the depressive-like behavior of A53T mice. Taken together, our results provided a novel correlation between Sirt1 and MAO-A, and compounds targeting on these molecules are beneficial for improving depression in the A53T mouse model of PD.

Aβ-Induced Damage Memory in hCMEC/D3 Cells Mediated by Sirtuin-1

It is well accepted by the scientific community that the accumulation of beta-amyloid (Aβ) may be involved in endothelial dysfunction during Alzheimer’s disease (AD) progression; however, anti-Aβ anti-bodies, which remove Aβ plaques, do not improve cerebrovascular function in AD animal models. The reasons for these paradoxical results require investigation. We hypothesized that Aβ exposure may cause persistent damage to cerebral endothelial cells even after Aβ is removed (referred to as cerebrovascular endothelial damage memory). In this study, we aimed to investigate whether cerebrovascular endothelial damage memory exists in endothelial cells. hCMEC/D3 cells were treated with Aβ_1–42 for 12 h and then Aβ_1–42 was withdrawn for another 12 h incubation to investigate whether cerebrovascular endothelial damage memory exists in endothelial cells. A mechanism-based kinetics progression model was developed to investigate the dynamic characters of the cerebrovascular endothelial damage. After Aβ_1–42 was removed, the sirt-1 levels returned to normal but the cell vitality did not improve, which suggests that cerebrovascular endothelial damage memory may exist in endothelial cells. Sirt-1 activator SRT2104 and NAD⁺ (Nicotinamide Adenine Dinucleotide) supplement may dose-dependently relieve the cerebrovascular endothelial damage memory. sirt-1 inhibitor EX527 may exacerbate the cerebrovascular endothelial damage memory. Kinetics analysis suggested that sirt-1 is involved in initiating the cerebrovascular endothelial damage memory; otherwise, NAD⁺ exhaustion plays a vital role in maintaining the cerebrovascular endothelial damage memory. This study provides a novel feature of cerebrovascular endothelial damage induced by Aβ.

SIRT1 mediates hypoxic preconditioning induced attenuation of neurovascular dysfunction following subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Vasospasm and delayed cerebral ischemia (DCI) contribute significantly to the morbidity/mortality associated with aneurysmal subarachnoid hemorrhage (SAH). While considerable research effort has focused on preventing or reversing vasospasm, SAH-induced brain injury occurs in response to a multitude of concomitantly acting pathophysiologic mechanisms. In this regard, the pleiotropic epigenetic responses to conditioning-based therapeutics may provide an ideal SAH therapeutic strategy. We previously documented the ability of hypoxic preconditioning (PC) to attenuate vasospasm and neurological deficits after SAH, in a manner that depends on the activity of endothelial nitric oxide synthase. The present study was undertaken to elucidate whether the NAD-dependent protein deacetylase sirtuin isoform SIRT1 is an upstream mediator of hypoxic PC-induced protection, and to assess the efficacy of the SIRT1-activating polyphenol Resveratrol as a pharmacologic preconditioning therapy.

METHODS

Wild-type C57BL/6J mice were utilized in the study and subjected to normoxia or hypoxic PC. Surgical procedures included induction of SAH via endovascular perforation or sham surgery. Multiple endpoints were assessed including cerebral vasospasm, neurobehavioral deficits, SIRT1 expression via quantitative real-time PCR for mRNA, and western blot for protein quantification. Pharmacological agents utilized in the study include EX-527 (SIRT1 inhibitor), and Resveratrol (SIRT1 activator).

RESULTS

Hypoxic PC leads to rapid and sustained increase in cerebral SIRT1 mRNA and protein expression. SIRT1 inhibition blocks the protective effects of hypoxic PC on vasospasm and neurological deficits. Resveratrol pretreatment dose-dependently abrogates vasospasm and attenuates neurological deficits following SAH - beneficial effects that were similarly blocked by pharmacologic inhibition of SIRT1.

CONCLUSION

SIRT1 mediates hypoxic preconditioning-induced protection against neurovascular dysfunction after SAH. Resveratrol mimics this neurovascular protection, at least in part, via SIRT1. Activation of SIRT1 is a promising, novel, pleiotropic therapeutic strategy to combat DCI after SAH.

Targeting Multiple Mitochondrial Processes by a Metabolic Modulator Prevents Sarcopenia and Cognitive Decline in SAMP8 Mice

The age-dependent declines of skeletal muscle and cognitive functions often coexist in elderly subjects. The underlying pathophysiological mechanisms share common features of mitochondrial dysfunction, which plays a central role in the development of overt sarcopenia and/or dementia. Dietary supplementation with formulations of essential and branched-chain amino acids (EAA-BCAA) is a promising preventive strategy because it can preserve mitochondrial biogenesis and function. The senescence-accelerated mouse prone 8 (SAMP8) is considered an accurate model of age-related muscular and cognitive alterations. Hence, we aimed to investigate the progression of mitochondrial dysfunctions during muscular and cognitive aging of SAMP8 mice and to study the effects of a novel EAA-BCAA-based metabolic modulator on these changes. We evaluated body condition, motor endurance, and working memory of SAMP8 mice at 5, 9, 12, and 15 months of age. Parallel changes in protein levels of mitochondrial respiratory chain subunits, regulators of mitochondrial biogenesis and dynamics, and the antioxidant response, as well as respiratory complex activities, were measured in the quadriceps femoris and the hippocampus. The same variables were assessed in 12-month-old SAMP8 mice that had received dietary supplementation with the novel EAA-BCAA formulation, containing tricarboxylic acid cycle intermediates and co-factors (PD-0E7, 1.5 mg/kg/body weight/day in drinking water) for 3 months. Contrary to untreated mice, which had a significant molecular and phenotypic impairment, PD-0E7-treated mice showed preserved healthy body condition, muscle weight to body weight ratio, motor endurance, and working memory at 12 months of age. The PD-0E7 mixture increased the protein levels and the enzymatic activities of mitochondrial complex I, II, and IV and the expression of proliferator-activated receptor γ coactivator-1α, optic atrophy protein 1, and nuclear factor, erythroid 2 like 2 in muscles and hippocampi. The mitochondrial amyloid-β-degrading pitrilysin metallopeptidase 1 was upregulated, while amyloid precursor protein was reduced in the hippocampi of PD-0E7 treated mice. In conclusion, we show that a dietary supplement tailored to boost mitochondrial respiration preserves skeletal muscle and hippocampal mitochondrial quality control and health. When administered at the early onset of age-related physical and cognitive decline, this novel metabolic inducer counteracts the deleterious effects of precocious aging in both domains.

Intrathecal administration of SRT1720 relieves bone cancer pain by inhibiting the CREB/CRTC1 signalling pathway

Bone cancer pain (BCP) caused by primary or metastatic bone tumours significantly interferes with the quality of life of patients. However, the relief of BCP remains a major challenge. Our previous study demonstrated that intrathecal administration of the Sirtuin 1 (SIRT1) activator SRT1720 attenuated BCP in a murine model. Nevertheless, the underlying mechanisms have not been fully clarified. Previous studies demonstrated that the activation of the cAMP response element binding (CREB) protein played a critical role in BCP. Furthermore, SIRT1 can also regulate the balance between glucose and lipid metabolism through CREB deacetylation. In this study, we measured the analgesic effects of different intrathecal doses of SRT1720 on BCP in a murine model and further examined whether SRT1720 attenuated BCP by suppressing CREB/CREB-regulated transcription coactivator 1 (CRTC1) signalling pathway. Our results demonstrated that the BCP mice developed significant mechanical allodynia and spontaneous flinching, which were accompanied by the upregulation of phospho-Ser133 CREB (p-CREB) and CRTC1 expression in the spinal cord. SRT1720 treatment produced a dose-dependent analgesic effect on the BCP mice and downregulated the expression of p-CREB and CRTC1. These results suggest that intrathecal administration of SRT1720 reverses BCP likely by inhibiting the CREB/CRTC1 signalling pathway.

Biological Aging and the Cellular Pathogenesis of Huntington's Disease

Huntington's disease (HD) is a fatal, inherited neurodegenerative disorder caused by a mutation in the huntingtin gene (HTT). While mutant HTT is present ubiquitously throughout life, HD onset typically occurs in mid-life, suggesting that aging may play an active role in pathogenesis. Cellular aging is defined as the slow decline in stress resistance and accumulation of damage over time. While different cells and tissues can age at different rates, 9 hallmarks of aging have emerged to better define the cellular aging process. Strikingly, many of the hallmarks of aging are also hallmarks of HD pathology. Models of HD and HD patients possess markers of accelerated aging, and processes that decline during aging also decline at a more rapid rate in HD, further implicating the role of aging in HD pathogenesis. Furthermore, accelerating aging in HD mouse and patient-derived neurons unmasks HD-specific phenotypes, suggesting an active role for the aging process in the onset and progression of HD. Here, we review the overlap between the hallmarks of aging and HD and discuss how aging may contribute to pathogenesis in HD.

PGC-1α, Sirtuins and PARPs in Huntington's Disease and Other Neurodegenerative Conditions: NAD+ to Rule Them All

In this review, we summarize the available published information on the neuroprotective effects of increasing nicotinamide adenine dinucleotide (NAD+) levels in Huntington's disease models. We discuss the rationale of potential therapeutic benefit of administering nicotinamide riboside (NR), a safe and effective NAD+ precursor. We discuss the agonistic effect on the Sirtuin1-PGC-1α-PPAR pathway as well as Sirtuin 3, which converge in improving mitochondrial function, decreasing ROS production and ameliorating bioenergetics deficits. Also, we discuss the potential synergistic effect of increasing NAD+ combined with PARPs inhibitors, as a clinical therapeutic option not only in HD, but other neurodegenerative conditions.

Integration of the Deacetylase SIRT1 in the Response to Nucleolar Stress: Metabolic Implications for Neurodegenerative Diseases

Understanding underlying mechanisms of neurodegenerative diseases is fundamental to develop effective therapeutic intervention. Yet they remain largely elusive, but metabolic, and transcriptional dysregulation are common events. Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD⁺)-dependent lysine deacetylase, regulating transcription, and critical for the cellular adaptations to metabolic stress. SIRT1 regulates the transcription of ribosomal RNA (rRNA), connecting the energetic state with cell growth and function. The activity of the transcription initiation factor-IA (TIF-IA) is important for the transcriptional regulation of ribosomal DNA (rDNA) genes in the nucleolus, and is also sensitive to changes in the cellular energetic state. Moreover, TIF-IA is responsive to nutrient-deprivation, neurotrophic stimulation, and oxidative stress. Hence, both SIRT1 and TIF-IA connect changes in cellular stress with transcriptional regulation and metabolic adaptation. Moreover, they finely tune the activity of the transcription factor p53, maintain mitochondrial function, and oxidative stress responses. Here we reviewed and discussed evidence that SIRT1 and TIF-IA are regulated by shared pathways and their activities preserve neuronal homeostasis in response to metabolic stressors. We provide evidence that loss of rDNA transcription due to altered TIF-IA function alters SIRT1 expression and propose a model of interdependent feedback mechanisms. An imbalance of this signaling might be a critical common event in neurodegenerative diseases. In conclusion, we provide a novel perspective for the prediction of the therapeutic benefits of the modulation of SIRT1- and nucleolar-dependent pathways in metabolic and neurodegenerative diseases.

Eriodictyol alleviates lipopolysaccharide-triggered oxidative stress and synaptic dysfunctions in BV-2 microglial cells and mouse brain

Oxidative stress takes part in the development of the neurodegenerative disease. Eriodictyol, a flavonoid, commonly presents in citrus fruits, which was well-known for its various bioactivities. The purpose of this study was to investigate the neuroprotective effects of eriodictyol on lipopolysaccharide (LPS)-induced neuroinflammation, oxidative stress, synaptic dysfunctions, and the potential mechanisms involved. We found that eriodictyol explicitly restored LPS-triggered the decrease of cell viability and the mitochondrial potential as well as inflammation responses via mitogen-activated protein kinases (MAPKs) and nuclear factor κB (NF-κB) pathways regulated by reactive oxygen species (ROS). Besides, eriodictyol alleviated LPS-induced oxidative stress via NF-E2-Related factor2/Kelch-like ECH-associated protein 1 (Nrf2/Keap1) pathway in vivo and in vitro. Furthermore, eriodictyol reduced LPS-elicited synaptic dysfunctions via increasing the expression of silent information regulator 1 (Sirt1). Overall, eriodictyol protects LPS-triggered oxidative stress, neuroinflammation, and synaptic dysfunctions partially through MAPKs, NF-κB mediated by ROS, Sirt1, and Nrf2/Keap1 signal pathways, which further supports that eriodictyol is a potentially nutritional preventive strategy for oxidative stress-related neurodegenerative diseases.

Upregulation of miR-200a and miR-204 in MPP+ -treated differentiated PC12 cells as a model of Parkinson's disease

Background

Parkinson's disease (PD) is ranked as the second most common neurodegenerative disorder caused by loss of dopaminergic neurons in the substantia nigra. Micro(mi)RNAs are a class of small noncoding RNAs that regulate gene expression and aberrant expression of them is closely correlated with many neurodegenerative conditions including PD. Silent information regulator 1 (SIRT1) as a known deacetylase and B‐cell lymphoma‐2 (BCL2) as an antiapoptotic factor play vital roles in neural protection and survival.

Methods

Differentiated PC12 cells exposed to MPP⁺ were served here as a known PD model. Cell viability was determined by MTS assay. Apoptotic cells and ROS levels were detected using flow cytometry. Gene selection and miRNA–mRNA interaction analysis were performed through in silico methods. Relative expression of miRNAs and genes was examined by RT‐qPCR.

Results

MPP⁺ exposure markedly reduced cell viability, enhanced oxidative stress, and induced apoptosis in differentiated PC12 cells. Sirt1 and BCL2were shown to be markedly declined in response to MPP⁺, while miR‐200a and miR‐204 were significantly upregulated.

Conclusion

The first novel finding of the current study is altered expression of miR‐200a and miR‐204 in differentiated PC12 cells in response to MPP⁺, suggesting that deregulation of them participate in MPP⁺ neurotoxicity mechanisms, possibly via affecting the expression of Sirt1 and BCL2 as potential targets.

Brain SIRT1 Mediates Metabolic Homeostasis and Neuroprotection

Sirtuins are evolutionarily conserved proteins that use nicotinamide adenine dinucleotide (NAD+) as a co-substrate in their enzymatic reactions. There are seven proteins (SIRT1-7) in the human sirtuin family, among which SIRT1 is the most conserved and characterized. SIRT1 in the brain, in particular, within the hypothalamus, plays crucial roles in regulating systemic energy homeostasis and circadian rhythm. Apart from this, SIRT1 has also been found to mediate beneficial effects in neurological diseases. In this review, we will first summarize how SIRT1 in the brain relates to obesity, type 2 diabetes, and circadian synchronization, and then we discuss the neuroprotective roles of brain SIRT1 in the context of cerebral ischemia and neurodegenerative disorders.

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.

SIRT1 activation by butein attenuates sepsis-induced brain injury in mice subjected to cecal ligation and puncture via alleviating inflammatory and oxidative stress

Sepsis-induced brain injury is frequently encountered in critically ill patients with severe systemic infection. Butein (3,4,2',4'-tetrahydroxychalcone) has been demonstrated as the neuro-protective agent via reducing inflammation and oxidative stress on neurons. Moreover, activation of silent information regulator 1 (SIRT1) inhibits apoptosis, oxidation and inflammation thus alleviating sepsis-induced multiorgan injuries. In present study, we show that butein administrated intraperitoneally (10 mg/kg) saved mice from sepsis-induced lethality by increasing 7-day survival rate after cecal ligation and puncture (CLP) surgery. Additionally, butein treatment enhanced SIRT1 signaling thus decreasing the Ac-NF-κB, Ac-FOXO1 and Ac-p53 levels, thus attenuating the brain injury of mice after CLP surgery by decreasing cerebral edema, maintaining the blood-brain barrier integrity, inhibiting neuronal apoptosis, and decreasing pro-inflammatory cytokines production (IL-6, TNF-α and IL-1β) and oxidative stress (downregulation of MDA, and upregulation of SOD and CAT) in both serum and cerebral cortex tissues. Moreover, butein treatment attenuated LPS induced neurological function loss. However, all above mentioned neuro-protective actions of butein were partially inhibited by EX527 co-treatment, one standard SIRT1 inhibitor. Collectively, butein attenuates sepsis-induced brain injury through alleviation of cerebral inflammation, oxidative stress and apoptosis by SIRT1 signaling activation.

Peripheral blood SIRT1 mRNA levels in depression and treatment with electroconvulsive therapy

Sirtuins are a family of nicotinamide adenine dinucleotide (NAD+) dependent enzymes that regulate cellular functions through deacetylation of protein targets. They have roles in both the periphery and central nervous system and have been implicated in depression biology. A recent genome-wide association study has identified a locus for major depression in the Sirtuin1 gene (SIRT1) and lower blood levels of SIRT1 mRNA in patients with depression have also been observed in two studies. To our knowledge, no studies have examined the effect of treatment on SIRT1 levels in patients with depression. We therefore examined SIRT1 mRNA levels in a well characterised group of patients with depression, compared to healthy controls, and characterised the effects of a course of electroconvulsive therapy (ECT) on peripheral blood SIRT1 mRNA. Depressed patients (n = 91) were matched to healthy controls (n = 85) on the basis of age and sex. In line with previous studies, blood SIRT1 mRNA levels were lower in depressed patients in comparison to controls (p = 0.005). However, ECT had no effect on SIRT1 levels (p = 0.67). There was no relationship between baseline pre-ECT SIRT1 levels and depression severity, change in mood scores, suicidality, depression polarity, presence of psychosis, or response to treatment. There was a trend for a negative association between an increase in SIRT1 mRNA and a decrease in HAM-D24 scores in ECT responders and remitters. These results indicate that reduced peripheral blood SIRT1 mRNA could be a trait feature of depression.

Evidence supporting a mechanistic role of sirtuins in mood and metabolic disorders

Sirtuins are NAD⁺-dependent histone deacetylases that play essential roles in cell survival, energy metabolism, inflammation, and aging; therefore, sirtuins are potential therapeutic targets in the treatment of type 2 diabetes, cancer, inflammatory and metabolic disorders, and neurodegenerative diseases. Available evidence provides the basis for hypothesizing that sirtuins 1, 2, and 3 (SIRT1, SIRT2, and SIRT3) may have a mechanistic role subserving mood disorders (i.e. downregulation) and associated co-morbidity (e.g. metabolic disorders). Specifically, the domains of general cognitive processes, as well as cognitive emotional processing may be particularly relevant to sirtuin physiology. Given the role of sirtuins in the perpetuation of circadian rhythmicity, and evidence of dysfunctional circadian cycling in mood disorders, sirtuins may be an underlying etiological factor that links circadian rhythm functionality with mood disorders. Caloric restriction, and caloric restriction mimetics (e.g. resveratrol) are all capable of upregulating sirtuin isoforms implicated in stress response syndromes. Repurposing existing treatments and/or discovery of novel agents capable of modulating sirtuin physiology may represent genuinely novel approaches for trans-diagnostic domains affected in mood disorders and other brain-based illnesses.

Chia Seed Supplementation Reduces Senescence Markers in Epididymal Adipose Tissue of High-Fat Diet-Fed SAMP8 Mice

Adipose tissue is a key organ with substantial senescent cell accumulation under both obesity and aging conditions. Chia seed is an ancient seed and is the richest plant source of α-linolenic acid. We aimed to determine how cellular senescence markers will be altered in adipose tissue of senescence-accelerated mouse-prone 8 (SAMP8) mice fed with high-fat diets (HFDs); and how chia seed can affect the above markers. SAMP8 mice and their control senescence-accelerated mouse-resistant 1 (SAMR1) were divided into four groups, that is, SAMR1 low-fat diet group (R1LF), SAMP8LF group (P8LF), SAMP8 high-fat group (P8HF), and SAMP8HF group supplemented with 10% chia seed (P8HC). At the end of the intervention, body composition was measured through T₁-weighted magnetic resonance imaging, and epididymal (EPI) and subcutaneous (SC) adipose tissues were dissected for further analysis. Compared with the R1LF group, the P8HF and P8HC groups had significantly increased body fat mass. In EPI fat, p16, CD68 and PAI-1 mRNA expression from P8HF group were significantly increased; chia seed partially reduced p16 and CD68 mRNA expression. The P8LF group has increased p16 and CD68, and the P8HF group has increased p16, p21, and CD68; and P8HC group has increased p16 mRNA expression. The protein expression of p-AMPK in EPI and SC fat from the P8HF group was reduced. In conclusion, reductions in AMPK activity might be partially responsible for elevation in HFD-induced senescence markers in both EPI and SC fat, and chia seed supplementation is able to reduce senescence-associated markers at least in EPI adipose tissue.

Down-regulated miR-448 relieves spinal cord ischemia/reperfusion injury by up-regulating SIRT1

MicroRNAs play a crucial role in the progression of spinal cord ischemia/reperfusion injury (SCII). The role of miR-448 and SIRT1 in SCII was investigated in this study, to provide further insights into prevention and improvement of this disorder. In this study, expressions of miR-448 and SIRT1 protein were determined by qRT-PCR and western blot, respectively. Flow cytometry was used to analyze cell apoptosis. The endogenous expression of genes was modulated by recombinant plasmids and cell transfection. Dual-luciferase reporter assay was performed to determine the interaction between miR-448 and SIRT1. The Basso, Beattie, and Bresnahan score was used to measure the hind-limb function of rat. The spinal cord ischemia reperfusion injury model of adult rats was developed by abdominal aorta clamping, and the nerve function evaluation was completed by motor deficit index score. In SCII tissues and cells treated with hypoxia, miR-448 was up-regulated while SIRT1 was down-regulated. Hypoxia treatment reduced the expression of SIRT1 through up-regulating miR-448 in nerve cells. Up-regulation of miR-448 induced by hypoxia promoted apoptosis of nerve cells through down-regulating SIRT1. Down-regulated miR-448 improved neurological function and hind-limb motor function of rats with SCII by up-regulating SIRT1. Down-regulated miR-448 inhibited apoptosis of nerve cells and improved neurological function by up-regulating SIRT1, which contributes to relieving SCII.

The potential role of epigenetic modulations in BPPV maneuver exercises

Benign paroxysmal positional vertigo (BPPV) is one of the most common complaints encountered in clinics and is strongly correlated with advanced age or, possibly, degeneration. Redistribution exercises are the most effective approaches to treat BPPV, and canalith repositioning procedure (CRP) cure most BPPV cases. However, the mechanisms through which the treatment modulates systemic molecules in BPPV patients remain largely unknown. In this study, we report that the miR-34a and Sirtuin 1 (SIRT1) genes correlated with the treatment effects of CRP in BPPV subjects. We found that miR-34a expression was largely inhibited and SIRT1 expression was significantly reversed after BPPV maneuver treatment. We also confirmed that the PPAR-γ, PGC-1 and FoxO gene expressions were decreased immediately after canalith repositioning procedure (CRP) for BPPV, and were largely increased after a complete cure of BPPV. Moreover, we observed that after a complete recovery of BPPV, the ROS concentrations, pro-inflammatory cytokine concentrations and p53 expression levels were attenuated. We conclude that BPPV treatment might involve some epigenetic regulations through the mediation of miR-34a, SIRT1 functions and repression of redox status.

SIRT1 as a therapeutic target for Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent cause of dementia in the aging population worldwide. SIRT1 deacetylation of histones and transcription factors impinge on multiple neuronal and non-neuronal targets, and modulates stress response, energy metabolism and cellular senescence/death pathways. Collectively, SIRT1 activity could potentially affect multiple aspects of hippocampal and cortical neuron function and survival, thus modifying disease onset and progression. In this review, the known and potential mechanisms of action of SIRT1 with regard to AD, and its potential as a therapeutic target, are discussed.

High Levels of SIRT1 Expression as a Protective Mechanism Against Disease-Related Conditions

SIRT1 protein, a member of Silent Information Regulator 2 (Sir2) protein family, have gained considerable attention as epigenetic regulators for a great area in the human physiology. Changes in sirtuin expression are critical in several diseases, including metabolic syndrome, cardiovascular diseases, cancer and neurodegeneration. Here, we provide an overview of the association of the increasing level of SIRT1 protein for regulating some disease related conditions such as obesity, cardiovascular diseases and neurodegeneration. This review also provides a detailed molecular understanding of the interaction of the some basic molecules with increasing SIRT1 levels rather than reduction of the SIRT1 expression. In this context, the current approaches to enhancing the expression of SIRT1 points the importance of epigenetics in several age-related diseases to provide a healthy aging by developing novel therapies which can prevent or damp the progression of some diseases.

Perturbations in the p53/miR-34a/SIRT1 pathway in the R6/2 Huntington's disease model

The three factors, p53, the microRNA-34 family and Sirtuin 1 (SIRT1), interact in a positive feedback loop involved in cell cycle progression, cellular senescence and apoptosis. Each factor in this triad has roles in metabolic regulation, maintenance of mitochondrial function, and regulation of brain-derived neurotrophic factor (BDNF). Thus, this regulatory network holds potential importance for the pathophysiology of Huntington's disease (HD), an inherited neurodegenerative disorder in which both mitochondrial dysfunction and impaired neurotrophic signalling are observed. We investigated expression of the three members of this regulatory triad in the R6/2 HD mouse model. Compared to wild-type littermates, we found decreased levels of miR-34a-5p, increased SIRT1 mRNA and protein levels, and increased levels of p53 protein in brain tissue from R6/2 mice. The upregulation of SIRT1 did not appear to lead to an increased activity of the enzyme, as based on measures of p53 acetylation. In other words, the observed changes did not reflect the known interactions between these factors, indicating a general perturbation of the p53, miR-34a and SIRT1 pathway in HD. This is the first study investigating the entire triad during disease progression in an HD model. Given the importance of these three factors alone and within the triad, our results indicate that outside factors are regulating - or dysregulating - this pathway in HD.

Hydrogen sulfide attenuates chronic restrain stress-induced cognitive impairment by upreglulation of Sirt1 in hippocampus

Chronic restraint stress (CRS) has detrimental effects on cognitive function. Hydrogen sulfide (H₂S), as a neuromodulator, regulates learning and memory. Hippocampus is a key structure in learning and memory. Sirt1 (silence signal regulating factor 1) plays an important role in modulating cognitive function. Therefore, our present work was to investigate whether H₂S meliorates CRS-induced damage in hippocampus and impairment in cognition, and further to explore whether the underlying mechanism is via upreglulating Sirt1. In our present work, the behavior experiments [Y-maze test, Novel object recognition (NOR) test, Morris water maze (MWM) test] showed that sodium hydrosulfide (NaHS, a donor of H₂S) blocked CRS-induced cognitive impairments in rats. NaHS inhibited CRS-induced hippocampal oxidative stress as evidenced by decrease in MDA level as well as increases in GSH content and SOD activity. NaHS rescued CRS-generated ER stress as evidenced by downregulations of CPR78, CHOP, and cleaved caspase-12. NaHS reduced CRS-exerted apoptosis as evidenced by decreases in the number of TUNEL-positive cells and Bax expression as well as increase in Bcl-2 expression. NaHS upregulated the expression of Sirt1 in the hippocampus of CRS-exposed rats. Furthermore, inhibited Sirt1 by Sirtinol reversed the protective effects of NaHS against CRS-produced cognitive dysfunction and oxidative stress, ER stress as well as apoptosis in hippocampus. Together, these results suggest that H₂S meliorates CRS-induced hippocampal damage and cognitive impairment by upregulation of hippocampal Sirt1.

SIRT1 mediates salidroside-elicited protective effects against MPP+ -induced apoptosis and oxidative stress in SH-SY5Y cells: involvement in suppressing MAPK pathways

Parkinson's disease (PD) is a progressive neurodegenerative disease, leading to tremor, rigidity, bradykinesia, and gait impairment. Salidroside has been reported to exhibit antioxidative and neuroprotective properties in PD. However, the underlying neuroprotective mechanisms effects of salidroside are poorly understood. Recently, a growing body of evidences suggest that silent information regulator 1 (SIRT1) plays important roles in the pathophysiology of PD. Hence, the present study investigated the roles of SIRT1 in neuroprotective effect of salidroside against N-methyl-4-phenylpyridinium (MPP⁺ )-induced SH-SY5Y cell injury. Our findings revealed that salidroside attenuates MPP⁺ -induced neurotoxicity as evidenced by the increase in cell viability, and the decreases in the caspase-3 activity and apoptosis ratio. Simultaneously, salidroside pretreatment remarkably increased SIRT1 activity, SIRT1 mRNA and protein levels in MPP⁺ -treated SH-SY5Y cell. However, sirtinol, a SIRT1 activation inhibitor, significantly blocked the inhibitory effects of salidroside on MPP⁺ -induced cytotoxicity and apoptosis. In addition, salidroside abolished MPP⁺ -induced the production of reactive oxygen species (ROS), the up-regulation of NADPH oxidase 2 (NOX2) expression, the down-regulations of superoxide dismutase (SOD) activity and glutathione (GSH) level in SH-SY5Y cells, while these effects were also blocked by sirtinol. Finally, we found that the inhibition of salidroside on MPP⁺ -induced phosphorylation of p38, extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) were also reversed by sirtinol in SH-SY5Y cells. Taken together, these results indicated that SIRT1 contributes to the neuroprotection of salidroside against MPP⁺ -induced apoptosis and oxidative stress, in part through suppressing of mitogen-activated protein kinase (MAPK) pathways.

Nutritional biomarkers: Current view and future perspectives

There is a poor relationship between nutrient intake and existing nutritional biomarkers due to variety of factors affecting their sensitivity and specificity. To explore the impact of nutrients at molecular level and devising a sensitive biomarker, proteomics is a central technology with sirtuins as one of the most promising nutritional biomarker. Sirtuins (seven mammalian sirtuins reported so far) have been reported to perform protein deacetylases and ADP-ribosyltransferases activity. It is distributed in different cellular compartments thereby controlling several metabolic processes. Sirtuins are oxidized nicotinamide adenine dinucleotide dependent, which implicates a direct effect of the metabolic state of the cell on its activity. Calorie restriction upregulates the mammalian sirtuin protein levels in variety of tissues and organs where it acts upon both histone and nonhistone substrates. Sirtuin senses nutrient availability and impacts gluconeogenesis, glycolysis, and insulin sensitivity. It deacetylates and inhibits the nuclear receptor that activates fat synthesis and adipogenesis in the body, leading to fat loss and bringing favorable cellular and health changes. Sirtuins mediates intracellular response that promotes cell survival, DNA damage repair thereby increasing the cell longitivity. The activation of sirtuins brings a wide spectrum of other health benefits and its activity levels are indicative of nutritional status as well as disease progression in cancer, inflammation, obesity, cardiovascular diseases, and viral infections. There are several foods that activate sirtuin activity and offer significant health benefits by their consumption.

SIRT1 ameliorates oxidative stress induced neural cell death and is down-regulated in Parkinson's disease

Background

Sirtuins (SIRTs) are NAD⁺ dependent lysine deacetylases which are conserved from bacteria to humans and have been associated with longevity and lifespan extension. SIRT1, the best studied mammalian SIRT is involved in many physiological and pathological processes and changes in SIRT1 have been implicated in neurodegenerative disorders, with SIRT1 having a suggested protective role in Parkinson’s disease. In this study, we determined the effect of SIRT1 on cell survival and α-synuclein aggregate formation in SH-SY5Y cells following oxidative stress.

Results

Over-expression of SIRT1 protected SH-SY5Y cells from toxin induced cell death and the protection conferred by SIRT1 was partially independent of its deacetylase activity, which was associated with the repression of NF-кB and cPARP expression. SIRT1 reduced the formation of α-synuclein aggregates but showed minimal co-localisation with α-synuclein. In post-mortem brain tissue obtained from patients with Parkinson’s disease, Parkinson’s disease with dementia, dementia with Lewy bodies and Alzheimer’s disease, the activity of SIRT1 was observed to be down-regulated.

Conclusions

These findings suggests a negative effect of oxidative stress in neurodegenerative disorders and possibly explain the reduced activity of SIRT1 in neurodegenerative disorders. Our study shows that SIRT1 is a pro-survival protein that is downregulated under cellular stress.

Electronic supplementary material

The online version of this article (doi:10.1186/s12868-017-0364-1) contains supplementary material, which is available to authorized users.

Resveratrol ameliorates hyperglycemia-induced renal tubular oxidative stress damage via modulating the SIRT1/FOXO3a pathway

AIMS

Oxidative stress plays an important role in the development and progression of diabetic nephropathy (DN). We aimed to investigate if resveratrol (RSV) could ameliorate hyperglycemia-induced oxidative stress in renal tubules via modulating the SIRT1/FOXO3a pathway.

METHODS

The effects of RSV on diabetes rats were assessed by periodic acid-Schiff, Masson staining, immunohistochemistry, and western blot analyses. Additionally, oxidative indicators (such as catalase, superoxide dismutase, reactive oxygen species, and malondialdehyde), the deacetylase activity of SIRT1 and protein expressions of SIRT1, FOXO3a, and acetylated-FOXO3a were measured. These indicators were similarly evaluated in an in vitro study. Furthermore, the silencing of SIRT1 was used to confirm its role in the resistance to oxidative stress and the relationship between SIRT1 and FOXO3a in vitro.

RESULTS

After 16weeks of RSV treatment, the renal function and glomerulosclerosis of rats with DN was dramatically ameliorated. RSV treatment increased SIRT1 deacetylase activity, subsequently decreasing the expression of acetylated-FOXO3a and inhibiting the oxidative stress caused by hyperglycemia both in vivo and in vitro. The silencing of SIRT1 in HK-2 cells aggravated the high glucose-induced oxidative stress and overexpression of acetylated-FOXO3a; RSV treatment failed to protect against these effects.

CONCLUSIONS

RSV modulates the SIRT1/FOXO3a pathway by increasing SIRT1 deacetylase activity, subsequently ameliorating hyperglycemia-induced renal tubular oxidative stress damage. This mechanism provides the basis for a new approach to developing an effective DN treatment, which is of great clinical significance for reducing the morbidity and mortality associated with DN.