Hormonal control of androgen receptor function through SIRT1

Inhibitory protein-protein interactions of the SIRT1 deacetylase are choreographed by post-translational modification

Regulation of SIRT1 activity is vital to energy homeostasis and plays important roles in many diseases. We previously showed that insulin triggers the epigenetic regulator DBC1 to prime SIRT1 for repression by the multifunctional trafficking protein PACS-2. Here, we show that liver DBC1/PACS-2 regulates the diurnal inhibition of SIRT1, which is critically important for insulin-dependent switch in fuel metabolism from fat to glucose oxidation. We present the x-ray structure of the DBC1 S1-like domain that binds SIRT1 and an NMR characterization of how the SIRT1 N-terminal region engages DBC1. This interaction is inhibited by acetylation of K112 of DBC1 and stimulated by the insulin-dependent phosphorylation of human SIRT1 at S162 and S172, catalyzed sequentially by CK2 and GSK3, resulting in the PACS-2-dependent inhibition of nuclear SIRT1 enzymatic activity and translocation of the deacetylase in the cytoplasm. Finally, we discuss how defects in the DBC1/PACS-2-controlled SIRT1 inhibitory pathway are associated with disease, including obesity and non-alcoholic fatty liver disease.

Regulating Androgen Receptor Function in Prostate Cancer: Exploring the Diversity of Post-Translational Modifications

Androgen receptor (AR) transcriptional activity significantly influences prostate cancer (PCa) progression. In addition to ligand stimulation, AR transcriptional activity is also influenced by a variety of post-translational modifications (PTMs). A number of oncogenes and tumor suppressors have been observed leveraging PTMs to influence AR activity. Subjectively targeting these post-translational modifiers based on their impact on PCa cell proliferation is a rapidly developing area of research. This review elucidates the modifiers, contextualizes the effects of these PTMs on AR activity, and connects these cellular interactions to the progression of PCa.

Acetylation of nuclear receptors in health and disease: an update

Lysine acetylation is a common reversible post-translational modification of proteins that plays a key role in regulating gene expression. Nuclear receptors (NRs) include ligand-inducible transcription factors and orphan receptors for which the ligand is undetermined, which together regulate the expression of genes involved in development, metabolism, homeostasis, reproduction and human diseases including cancer. Since the original finding that the ERα, AR and HNF4 are acetylated, we now understand that the vast majority of NRs are acetylated and that this modification has profound effects on NR function. Acetylation sites are often conserved and involve both ordered and disordered regions of NRs. The acetylated residues function as part of an intramolecular signalling platform intersecting phosphorylation, methylation and other modifications. Acetylation of NR has been shown to impact recruitment into chromatin, co-repressor and coactivator complex formation, sensitivity and specificity of regulation by ligand and ligand antagonists, DNA binding, subcellular distribution and transcriptional activity. A growing body of evidence in mice indicates a vital role for NR acetylation in metabolism. Additionally, mutations of the NR acetylation site occur in human disease. This review focuses on the role of NR acetylation in coordinating signalling in normal physiology and disease.

The Roles of Autophagy in the Genesis and Development of Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a common and frequent disease and always leads endocrine and metabolic disorder among women in reproductive age. Ovary is the main organ involved in polycystic ovary syndrome, and its function impairment will lead to reproductive dysfunction. Some recent studies have demonstrated that autophagy plays an important role in the pathogenesis of PCOS, and there are many different mechanisms that affect autophagy and the occurrence of PCOS, and they provide a new direction for us to predict the mechanism of PCOS. In this review, we discuss the role of autophagy in different ovarian cells: granulosa cells, oocytes, and theca cells, and introduce the important role that they play in the progress of PCOS. The main purpose of this review is to provide the research background and some relevant suggestions for our future work in autophagy and help us better explore the pathogenesis and autophagy mechanisms of PCOS. Furthermore, it will help us gain a new insight of the pathophysiology and treatment of PCOS.

Sirtuins and their influence on autophagy

Sirtuins and autophagy are well-characterized agents that can promote longevity and protect individual organisms from age-associated diseases like neurodegenerative disorders. In recent years, more and more data has been obtained that discerned potential overlaps and crosstalk between Sirtuin proteins and autophagic activity. This review aims to summarize the advances within the field for each individual Sirtuin in mammalian systems. In brief, most Sirtuins have been implicated in promoting autophagy, with Sirtuin 1 and Sirtuin 6 showing the highest immediate involvement, while Sirtuin 4 and Sirtuin 5 only demonstrate occasional influence. The way Sirtuins regulate autophagy, however, is very diverse, as they have been shown to regulate gene expression of autophagy-associated genes and posttranslational modifications of proteins, with consequences for the activity and cellular localization of these proteins. They have also been shown to determine specific proteins for autophagic degradation. Overall, much data has been accumulated over recent years, yet many open questions remain. Especially although the dynamic between Sirtuin proteins and the immediate regulation of autophagic players like Light Chain 3B has been confirmed, many of these proteins have various orthologues in mammalian systems, and research so far has not exceeded the bona fide components of autophagy.

The epigenetic function of androgen receptor in prostate cancer progression

Androgen and androgen deprivation (castration) therapies, including androgen receptor antagonists, are clinically used to treat patients with prostate cancer. However, most hormone-dependent prostate cancer patients progress into a malignant state with loss of hormone-dependency, known as castration (drug)-resistant prostate cancer (CRPC), after prolong androgen-based treatments. Even in the CRPC state with irreversible malignancy, androgen receptor (AR) expression is detectable. An epigenetic transition to CRPC induced by the action of AR-mediated androgen could be speculated in the patients with prostate cancer. Androgen receptors belongs to the nuclear receptor superfamily with 48 members in humans, and acts as a ligand-dependent transcriptional factor, leading to local chromatin reorganization for ligand-dependent gene regulation. In this review, we discussed the transcriptional/epigenetic regulatory functions of AR, with emphasis on the clinical applications of AR ligands, AR protein co-regulators, and AR RNA coregulator (enhancer RNA), especially in chromatin reorganization, in patients with prostate cancer.

Epigenetic (De)regulation in Prostate Cancer

Prostate cancer (PCa) is a heterogeneous disease exhibiting both genetic and epigenetic deregulations. Epigenetic alterations are defined as changes not based on DNA sequence, which include those of DNA methylation, histone modification, and chromatin remodeling. Androgen receptor (AR) is the main driver for PCa and androgen deprivation therapy (ADT) remains a backbone treatment for patients with PCa; however, ADT resistance almost inevitably occurs and advanced diseases develop termed castration-resistant PCa (CRPC), due to both genetic and epigenetic changes. Due to the reversible nature of epigenetic modifications, inhibitors targeting epigenetic factors have become promising anti-cancer agents. In this chapter, we focus on recent studies about the dysregulation of epigenetic regulators crucially involved in the initiation, development, and progression of PCa and discuss the potential use of inhibitors targeting epigenetic modifiers for treatment of advanced PCa.

The Mechanistic Roles of Sirtuins in Breast and Prostate Cancer

Simple Summary

There are diverse reports of the dual role of sirtuin genes and proteins in breast and prostate cancers. This review discusses the current information on the tumor promotion or suppression roles of SIRT1–7 in breast and prostate cancers. Precisely, we highlight that sirtuins regulate various proteins implicated in proliferation, apoptosis, autophagy, chemoresistance, invasion, migration, and metastasis of both breast and prostate cancer. We also provide evidence of the direct regulation of sirtuins by miRNAs, highlighting the consequences of this regulation in breast and prostate cancer. Overall, this review reveals the potential value of sirtuins as biomarkers and/or targets for improved treatment of breast and prostate cancers.

Abstract

Mammalian sirtuins (SIRT1–7) are involved in a myriad of cellular processes, including apoptosis, proliferation, differentiation, epithelial-mesenchymal transition, aging, DNA repair, senescence, viability, survival, and stress response. In this review, we discuss the current information on the mechanistic roles of SIRT1–7 and their downstream effects (tumor promotion or suppression) in cancers of the breast and prostate. Specifically, we highlight the involvement of sirtuins in the regulation of various proteins implicated in proliferation, apoptosis, autophagy, chemoresistance, invasion, migration, and metastasis of breast and prostate cancer. Additionally, we highlight the available information regarding SIRT1–7 regulation by miRNAs, laying much emphasis on the consequences in the progression of breast and prostate cancer.

Declining muscle NAD+ in a hyperandrogenism PCOS mouse model: Possible role in metabolic dysregulation

Polycystic ovary syndrome (PCOS) is a common endocrine disorder, defined by reproductive and endocrine abnormalities, with metabolic dysregulation including obesity, insulin resistance and hepatic steatosis. Recently, it was found that skeletal muscle insulin sensitivity could be improved in obese, post-menopausal, pre-diabetic women through treatment with nicotinamide mononucleotide (NMN), a precursor to the prominent redox cofactor nicotinamide adenine dinucleotide (NAD⁺). Given that PCOS patients have a similar endocrine profile to these patients, we hypothesised that declining NAD levels in muscle might play a role in the pathogenesis of the metabolic syndrome associated with PCOS, and that this could be normalized through NMN treatment. Here, we tested the impact of NMN treatment on the metabolic syndrome of the dihydrotestosterone (DHT) induced mouse model of PCOS. We observed lower NAD levels in the muscle of PCOS mice, which was normalized by NMN treatment. PCOS mice were hyperinsulinaemic, resulting in increased adiposity and hepatic lipid deposition. Strikingly, NMN treatment completely normalized these aspects of metabolic dysfunction. We propose that addressing the decline in skeletal muscle NAD levels associated with PCOS can normalize insulin sensitivity, preventing compensatory hyperinsulinaemia, which drives obesity and hepatic lipid deposition, though we cannot discount an impact of NMN on other tissues to mediate these effects. These findings support further investigation into NMN treatment as a new therapy for normalizing the aberrant metabolic features of PCOS.

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Polycystic ovarian syndrome (PCOS) leads to declining NAD⁺ levels in skeletal muscle tissue.

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Declining NAD⁺ in muscle can be rescued by treating with the metabolic precursor nicotinamide mononucleotide (NMN).

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NMN treatment corrects compensatory hyperinsulinemia in a mouse model of PCOS.

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Reductions in circulating insulin levels from NMN treatment moderates adipose expansion and hepatic lipid deposition.

Potential of histone deacetylase inhibitors in the control and regulation of prostate, breast and ovarian cancer

Histone deacetylases (HDACs) are enzymes that play a role in chromatin remodeling and epigenetics. They belong to a specific category of enzymes that eliminate the acetyl part of the histones’ -N-acetyl lysine, causing the histones to be wrapped compactly around DNA. Numerous biological processes rely on HDACs, including cell proliferation and differentiation, angiogenesis, metastasis, gene regulation, and transcription. Epigenetic changes, specifically increased expression and activity of HDACs, are commonly detected in cancer. As a result, HDACi could be used to develop anticancer drugs. Although preclinical outcomes with HDACs as monotherapy have been promising clinical trials have had mixed results and limited success. In both preclinical and clinical trials, however, combination therapy with different anticancer medicines has proved to have synergistic effects. Furthermore, these combinations improved efficacy, decreased tumor resistance to therapy, and decreased toxicity. In the present review, the detailed modes of action, classification of HDACs, and their correlation with different cancers like prostate, breast, and ovarian cancer were discussed. Further, the different cell signaling pathways and the structure-activity relationship and pharmaco-toxicological properties of the HDACi, and their synergistic effects with other anticancer drugs observed in recent preclinical and clinical studies used in combination therapy were discussed for prostate, breast, and ovarian cancer treatment.

The Role of Epigenetic Change in Therapy-Induced Neuroendocrine Prostate Cancer Lineage Plasticity

The androgen receptor (AR) signaling pathway is critical for growth and differentiation of prostate cancer cells. For that reason, androgen deprivation therapy with medical or surgical castration is the principal treatment for metastatic prostate cancer. More recently, new potent AR signaling inhibitors (ARSIs) have been developed. These drugs improve survival for men with metastatic castration-resistant prostate cancer (CRPC), the lethal form of the disease. However, ARSI resistance is nearly universal. One recently appreciated resistance mechanism is lineage plasticity or switch from an AR-driven, luminal differentiation program to an alternate differentiation program. Importantly, lineage plasticity appears to be increasing in incidence in the era of new ARSIs, strongly implicating AR suppression in this process. Lineage plasticity and shift from AR-driven tumors occur on a continuum, ranging from AR-expressing tumors with low AR activity to AR-null tumors that have activation of alternate differentiation programs versus the canonical luminal program found in AR-driven tumors. In many cases, AR loss coincides with the activation of a neuronal program, most commonly exemplified as therapy-induced neuroendocrine prostate cancer (t-NEPC). While genetic events clearly contribute to prostate cancer lineage plasticity, it is also clear that epigenetic events-including chromatin modifications and DNA methylation-play a major role. Many epigenetic factors are now targetable with drugs, establishing the importance of clarifying critical epigenetic factors that promote lineage plasticity. Furthermore, epigenetic marks are readily measurable, demonstrating the importance of clarifying which measurements will help to identify tumors that have undergone or are at risk of undergoing lineage plasticity. In this review, we discuss the role of AR pathway loss and activation of a neuronal differentiation program as key contributors to t-NEPC lineage plasticity. We also discuss new epigenetic therapeutic strategies to reverse lineage plasticity, including those that have recently entered clinical trials.

Exploring the Role of Posttranslational Modifications in Spinal and Bulbar Muscular Atrophy

Spinal and Bulbar Muscular Atrophy (SBMA) is an X-linked adult-onset progressive neuromuscular disease that affects the spinal and bulbar motor neurons and skeletal muscles. SBMA is caused by expansion of polymorphic CAG trinucleotide repeats in the Androgen Receptor (AR) gene, resulting in expanded glutamine tract in the AR protein. Polyglutamine (polyQ) expansion renders the mutant AR protein toxic, resulting in the formation of mutant protein aggregates and cell death. This classifies SBMA as one of the nine known polyQ diseases. Like other polyQ disorders, the expansion of the polyQ tract in the AR protein is the main genetic cause of the disease; however, multiple other mechanisms besides the polyQ tract expansion also contribute to the SBMA disease pathophysiology. Posttranslational modifications (PTMs), including phosphorylation, acetylation, methylation, ubiquitination, and SUMOylation are a category of mechanisms by which the functionality of AR has been found to be significantly modulated and can alter the neurotoxicity of SBMA. This review summarizes the different PTMs and their effects in regulating the AR function and discusses their pathogenic or protective roles in context of SBMA. This review also includes the therapeutic approaches that target the PTMs of AR in an effort to reduce the mutant AR-mediated toxicity in SBMA.

Association of sirtuins (SIRT1-7) with lung and intestinal diseases

"Exterior-interior correlation between the lung and large intestine" is one of the important contents of traditional Chinese medicine. This theory describes the role of the lung and the intestine in association with disease treatment. The "lung-gut" axis is a modern extension of the "exterior-interior correlation between lung and large intestine" theory in TCM. Sirtuin (SIRT) is a nicotinamide adenine dinucleotide (NAD⁺)-dependent enzyme family with deacetylase properties, which is highly conserved from bacteria to humans. The sirtuin defines seven silencing regulatory proteins (SIRT1-7) in human cells. It can regulate aging, metabolism, and certain diseases. Current studies have shown that sirtuins have dual characteristics, acting as both tumor promoters and tumor inhibitors in cancers. This paper provides a comparative summary of the roles of SIRT1-7 in the intestine and lung (both inflammatory diseases and tumors), and the promoter/suppressor effects of targeting SIRT family microRNAs and modulators of inflammation or tumors. Sirtuins have great potential as drug targets for the treatment of intestinal and respiratory diseases. Meanwhile, it may provide new ideas of future drug target research.

Patterns of indolence in prostate cancer (Review)

Although prostate cancer is a major cause of cancer-related mortality worldwide, most patients will have a relatively indolent clinical course. Contrary to most other types of cancer, even the diagnosis of locally advanced or metastatic disease is not always lethal. The present review aimed to summarize what is known regarding the underlying mechanisms related to the indolent course of subsets of prostate cancer, at various stages. The data suggested that no specific gene alteration by itself was responsible for carcinogenesis or disease aggressiveness. However, pathway analysis identified genetic aberrations in multiple critical pathways that tend to accumulate over the course of the disease. The progression from indolence into aggressive disease is associated with a complex interplay in which genetic and epigenetic factors are involved. The effect of the immune tumor microenvironment is also very important. Emerging evidence has suggested that the upregulation of pathways related to cellular aging and senescence can identify patients with indolent disease. In addition, a number of tumors enter a long-lasting quiescent state. Further research will determine whether halting tumor evolution is a feasible option, and whether the life of patients can be markedly prolonged by inducing tumor senescence or long-term dormancy.

Correlations between serum sirtuin levels and cardiovascular risk factors in women with polycystic ovary syndrome

PURPOSE

Polycystic ovary syndrome (PCOS) is associated with an increased risk of cardiovascular disease (CVD) and metabolic complications often related to obesity, such as insulin resistance and type 2 diabetes mellitus (T2DM). Sirtuins (SIRTs) are nicotinamide adenine dinucleotide NAD⁺-dependent histone deacetylases, which modulate protein post-translational modifications (PTMs), gene transcription, increase repairing activities of DNA, and regulate metabolic processes. The aim of our study was to measure the serum levels of SIRTs 1, 2, 3, 6 and 7, and evaluate correlations between SIRTs levels and cardiovascular risk factors in women with PCOS.

PATIENTS AND METHODS

The study included 54 women with PCOS and 33 healthy volunteers. Concentrations of SIRTs were measured by ELISA technique.

RESULTS

Mean serum levels of SIRTs did not differ significantly between PCOS and controls. SIRTs 1, 2, and 6 positively correlated with HDL, while SIRTs 2 and 6 negatively correlated with LDL cholesterol. Negative correlation between SIRT 3 and HOMA-IR and negative correlations of SIRT 1 and 2 with insulin 120' in oral glucose tolerance test (OGTT) were demonstrated. A positive correlation between BMI and SIRT 7 concentration, and a positive correlation between body weight and SIRT 7 concentration were verified in the study group. The observed correlations between concentrations of SIRTs and metabolic parameters may indicate the involvement of these factors in the development of cardiometabolic complications.

CONCLUSIONS

The results may indicate the involvement of SIRTs in the development of cardiometabolic complications. However, additional studies are required to validate this observation.

The neuroprotective effects of icariin on ageing, various neurological, neuropsychiatric disorders, and brain injury induced by radiation exposure

Epimedium brevicornum Maxim, a Traditional Chinese Medicine, has been used for the treatment of impotence, sinew and bone disorders, “painful impediment caused by wind-dampness,” numbness, spasms, hypertension, coronary heart disease, menopausal syndrome, bronchitis, and neurasthenia for many years in China. Recent animal experimental studies indicate that icariin, a major bioactive component of epimedium may effectively treat Alzheimer’s disease, cerebral ischemia, depression, Parkinson’s disease, multiple sclerosis, as well as delay ageing. Our recent study also suggested that epimedium extract could exhibit radio-neuro-protective effects and prevent ionizing radiation-induced impairment of neurogenesis. This paper reviewed the pharmacodynamics of icariin in treating different neurodegenerative and neuropsychiatric diseases, ageing, and radiation-induced brain damage. The relevant molecular mechanisms and its anti-neuroinflammatory, anti-apoptotic, anti-oxidant, as well as pro-neurogenesis roles were also discussed.

Metadichol®: A Novel Nanolipid Formulation That Inhibits SARS-CoV-2 and a Multitude of Pathological Viruses In Vitro

Increasing outbreaks of new pathogenic viruses have promoted the exploration of novel alternatives to time-consuming vaccines. Thus, it is necessary to develop a universal approach to halt the spread of new and unknown viruses as they are discovered. One such promising approach is to target lipid membranes, which are common to all viruses and bacteria. The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has reaffirmed the importance of interactions between the virus envelope and the host cell plasma membrane as a critical mechanism of infection. Metadichol®, a nanolipid emulsion of long-chain alcohols, has been demonstrated as a strong candidate that inhibits the proliferation of SARS-CoV-2. Naturally derived substances, such as long-chain saturated lipid alcohols, reduce viral infectivity, including that of coronaviruses (such as SARS-CoV-2) by modifying their lipid-dependent attachment mechanism to human host cells. The receptor ACE2 mediates the entry of SARS-CoV-2 into the host cells, whereas the serine protease TMPRSS2 primes the viral S protein. In this study, Metadichol® was found to be 270 times more potent an inhibitor of TMPRSS2 (EC50 = 96 ng/mL) than camostat mesylate (EC50 = 26000 ng/mL). Additionally, it inhibits ACE with an EC50 of 71 ng/mL, but it is a very weak inhibitor of ACE2 at an EC50 of 31 μg/mL. Furthermore, the live viral assay performed in Caco-2 cells revealed that Metadichol® inhibits SARS-CoV-2 replication at an EC90 of 0.16 μg/mL. Moreover, Metadichol® had an EC90 of 0.00037 μM, making it 2081 and 3371 times more potent than remdesivir (EC50 = 0.77 μM) and chloroquine (EC50 = 1.14 μM), respectively.

SIRT1 haplo-insufficiency results in reduced cortical bone thickness, increased porosity and decreased estrogen receptor alpha in bone in adult 129/Sv female mice

INTRODUCTION

Sirtuin 1 (SIRT1) is a key player in aging and metabolism and regulates bone mass and architecture. Sexual dimorphism in skeletal effects of SIRT1 has been reported, with an unfavorable phenotype primarily in female mice.

METHODS

To investigate the mechanisms of gender differences in SIRT1 skeletal effect, we investigated femoral and vertebral cortical and cancellous bone in global Sirt1 haplo-insufficient 129/Sv mice aged 2,7,12 months lacking Sirt1 exons 5,6,7 (Sirt1^+/Δ ) and their wild type (WT) counterparts.

RESULTS

In females, femoral bone mineral content, peak cortical thickness, and trabecular bone volume (BV/TV%), number and thickness were significantly lower in Sirt1^+/Δ compared to WT mice. Increased femoral cortical porosity was observed in 7-month-old Sirt1^+/Δ compared to WT female mice, accompanied by reduced biomechanical strength. No difference in vertebral indices was detected between Sirt1^+/Δ and WT female mice. SIRT1 decreased with aging in WT female mice and was lower in vertebrae and femur in 18- and 30- versus 3-month-old 129/Sv and C57BL/6J female mice, respectively. Decreased bone estrogen receptor alpha (ERα) was observed in Sirt1^+/Δ compared to WT female mice and was significantly higher in Sirt1 over-expressing C3HT101/2 murine mesenchymal stem cells. In males no difference in femoral indices was detected in Sirt1^+/Δ versus WT mice, however vertebral BV/TV%, trabecular number and thickness were higher in Sirt1^+/Δ vs. WT mice. No difference in androgen receptor (AR) was detected in bone in Sirt1^+/Δ vs. WT male mice. Bone SIRT1 was significantly lower in male compared to female WT mice, suggesting that SIRT1 maybe more significant in female than male skeleton.

DISCUSSION

These findings demonstrate that 50% reduction in SIRT1 is sufficient to induce the hallmarks of skeletal aging namely, decreased cortical thickness and increased porosity in female mice, highlighting the role of SIRT1 as a regulator of cortical bone quantity and quality. The effects of SIRT1 in cortical bone are likely mediated in part by its regulation of ERα. The age-associated decline in bone SIRT1 positions SIRT1 as a potential therapeutic target to ameliorate age-related cortical bone deterioration in females. The crosstalk between ERα, AR and SIRT1 in the bone microenvironment remains to be further investigated.

Roles of Key Epigenetic Regulators in the Gene Transcription and Progression of Prostate Cancer

Prostate cancer (PCa) is a top-incidence malignancy, and the second most common cause of death amongst American men and the fifth leading cause of cancer death in men around the world. Androgen receptor (AR), the key transcription factor, is critical for the progression of PCa by regulating a series of target genes by androgen stimulation. A number of co-regulators of AR, including co-activators or co-repressors, have been implicated in AR-mediated gene transcription and PCa progression. Epigenetic regulators, by modifying chromatin integrity and accessibility for transcription regulation without altering DNA sequences, influence the transcriptional activity of AR and further regulate the gene expression of AR target genes in determining cell fate, PCa progression and therapeutic response. In this review, we summarized the structural interaction of AR and epigenetic regulators including histone or DNA methylation, histone acetylation or non-coding RNA, and functional synergy in PCa progression. Importantly, epigenetic regulators have been validated as diagnostic markers and therapeutic targets. A series of epigenetic target drugs have been developed, and have demonstrated the potential to treat PCa alone or in combination with antiandrogens.

Sirtuin1 in vascular endothelial function, an overview

Sirtuin1 is a nutrient-sensitive class III histone deacetylase which is a well-known regulator of organismal lifespan. It has been extensively studied for its role in metabolic regulation as well. Along with its involvement in ageing and metabolism, Sirtuin1 directly deacetylates many critical proteins controlling cardiovascular pathophysiology. Studies using conditional expression and deletion of Sirtuin1 have revealed that it functions in a highly tissue/organ-specific manner. In the vasculature, Sirtuin1 controls endothelial homoeostasis by governing the expression of inflammatory mediators, oxidants and essential transcription factors. Adding to this complexity, Sirtuin1 expression and/or function is also governed by some of these target proteins. Therefore, the importance of better understanding the organ and tissue specificity of Sirtuin1 is highly desirable. Considering the huge volume of research done in this field, this review focuses on Sirtuin1 targets regulating vascular endothelial function. Here, we summarize the discovery of Sirtuin1 as a transcription controller and the further identification of direct target proteins involved in the vascular physiology. Overall, this review presents a holistic picture of the complex cross-talk involved in the molecular regulation of vascular physiology by Sirtuin1.

KAT2A-mediated AR translocation into nucleus promotes abiraterone-resistance in castration-resistant prostate cancer

Abiraterone, a novel androgen synthesis inhibitor, has been approved for castration-resistant prostate cancer (CRPC) treatment. However, most patients eventually acquire resistance to this agent, and the underlying mechanisms related to this resistance remain largely unelucidated. Lysine acetyltransferase 2 A (KAT2A) has been reported to enhance transcriptional activity for certain histone or non-histone proteins through the acetylation and post-translational modification of the androgen receptor (AR). Therefore, we hypothesised that KAT2A might play a critical role in the resistance of prostate tumours to hormonal treatment. In this study, we found that KAT2A expression was increased in abiraterone-resistant prostate cancer C4-2 cells (C4-2-AbiR). Consistently, elevated expression of KAT2A was observed in patients with prostate cancer exhibiting high-grade disease or biochemical recurrence following radical prostatectomy, as well as in those with poor clinical survival outcomes. Moreover, KAT2A knockdown partially re-sensitised C4-2-AbiR cells to abiraterone, whereas KAT2A overexpression promoted abiraterone resistance in parental C4-2 cells. Consistent with this finding, KAT2A knockdown rescued abiraterone sensitivity and inhibited the proliferation of C4-2-AbiR cells in a mouse model. Mechanistically, KAT2A directly acetylated the hinge region of the AR, and induced AR translocation from the cytoplasm to the nucleus, resulting in increased transcriptional activity of the AR-targeted gene prostate specific antigen (PSA) leading to resistance to the inhibitory effect of abiraterone on proliferation. Taken together, our findings demonstrate a substantial role for KAT2A in the regulation of post-translational modifications in AR affecting CRPC development, suggesting that targeting KAT2A might be a potential strategy for CRPC treatment.

Trending topics of SIRT1 in tumorigenicity

BACKGROUND

Carcinogenesis is governed by a series of genetic alterations and epigenetic changes that lead to aberrant patterns in neoplastic cells. Sirtuin-1(SIRT1), an NAD⁺-dependent protein deacetylase, is capable of deacetylating histones and non-histone substrates that regulate various physiological activities during tumorigenesis. Recent studies have identified the role of SIRT1 in different stages of cancer, including genome instability, tumor initiation, proliferation, metabolism, and therapeutic response. However, the action of SIRT1 has been reported to be both oncogenic and tumor suppressive during carcinogenesis. Consequently, the biological functions of SIRT1 in cancer remain controversial.

SCOPE OF REVIEW

We highlight the most recent findings on SIRT1 in different stages of tumorigenesis, and update the current status of SIRT1 small molecule modulators in clinical application of cancer treatment.

MAJOR CONCLUSION

By targeting both tumor suppressors and oncogenic proteins, SIRT1 has a bifunctional role at different stages of tumorigenesis. The impact of SIRT1 on tumorigenesis is also distinct at different stages and is dependent on its dosages. SIRT1 suppresses tumor initiation through its functions in promoting DNA repair, increasing genome stability, and inhibiting inflammation at the pre-cancer stage. However, SIRT1 enhances tumor proliferation, survival, and drug resistance through its roles in anti-apoptosis, pro-tumor metabolism, and anti-inflammation (inhibition of anti-tumor immunity) at the stages of tumor progression, metastasis, and relapse. Consequently, both SIRT1 inhibitors and activators have been explored for cancer treatment.

GENERAL SIGNIFICANCE

Better understanding the dose- and stage-dependent roles of SIRT1 in each cancer type can provide new avenues of exploration for therapy development.

Epigenetic Editing in Prostate Cancer: Challenges and Opportunities

Epigenome editing consists of fusing a predesigned DNA recognition unit to the catalytic domain of a chromatin modifying enzyme leading to the introduction or removal of an epigenetic mark at a specific locus. These platforms enabled the study of the mechanisms and roles of epigenetic changes in several research domains such as those addressing pathogenesis and progression of cancer. Despite the continued efforts required to overcome some limitations, which include specificity, off-target effects, efficacy, and longevity, these tools have been rapidly progressing and improving.Since prostate cancer is characterized by multiple genetic and epigenetic alterations that affect different signalling pathways, epigenetic editing constitutes a promising strategy to hamper cancer progression. Therefore, by modulating chromatin structure through epigenome editing, its conformation might be better understood and events that drive prostate carcinogenesis might be further unveiled.This review describes the different epigenome engineering tools, their mechanisms concerning gene's expression and regulation, highlighting the challenges and opportunities concerning prostate cancer research.

Proteostasis in the Male and Female Germline: A New Outlook on the Maintenance of Reproductive Health

For fully differentiated, long lived cells the maintenance of protein homeostasis (proteostasis) becomes a crucial determinant of cellular function and viability. Neurons are the most well-known example of this phenomenon where the majority of these cells must survive the entire course of life. However, male and female germ cells are also uniquely dependent on the maintenance of proteostasis to achieve successful fertilization. Oocytes, also long-lived cells, are subjected to prolonged periods of arrest and are largely reliant on the translation of stored mRNAs, accumulated during the growth period, to support meiotic maturation and subsequent embryogenesis. Conversely, sperm cells, while relatively ephemeral, are completely reliant on proteostasis due to the absence of both transcription and translation. Despite these remarkable, cell-specific features there has been little focus on understanding protein homeostasis in reproductive cells and how/whether proteostasis is "reset" during embryogenesis. Here, we seek to capture the momentum of this growing field by highlighting novel findings regarding germline proteostasis and how this knowledge can be used to promote reproductive health. In this review we capture proteostasis in the context of both somatic cell and germline aging and discuss the influence of oxidative stress on protein function. In particular, we highlight the contributions of proteostasis changes to oocyte aging and encourage a focus in this area that may complement the extensive analyses of DNA damage and aneuploidy that have long occupied the oocyte aging field. Moreover, we discuss the influence of common non-enzymatic protein modifications on the stability of proteins in the male germline, how these changes affect sperm function, and how they may be prevented to preserve fertility. Through this review we aim to bring to light a new trajectory for our field and highlight the potential to harness the germ cell's natural proteostasis mechanisms to improve reproductive health. This manuscript will be of interest to those in the fields of proteostasis, aging, male and female gamete reproductive biology, embryogenesis, and life course health.

Effects of androgens and estrogens on sirtuin 1 gene expression in human aortic endothelial cells

Objectives:

To investigate the effect of androgens and estrogens on surtuin 1 (SIRT1) expression in human aortic endothelial cells (HAECs).

Methods:

Real-time polymerase chain reaction analysis of SIRT-1 expression over 48 hours (h) was performed in HAECs treated with various concentrations of dehydroepiandrostendione (DHEA), androstenedione and testosterone (androgens), estrone (E1), estradiol (E2), and estriol (E3) (estrogens) to investigate the dose-dependency of time courses. The influence of high glucose on SIRT1 expression induced by the androgens and estrogens was also examined.

Results:

Dehydroepiandrostendione, androstenedione, and testosterone remarkably produced a dose-dependent increase in SIRT1 expression in the range of 10 to 20 μg/ml. High glucose (40mM) medium had significantly inhibitory effects on 10 μg/ml DHEA-induced SIRT1 expression (p=0.024). Estrone and E2, but not E3, caused a marked dose-dependent increase in SIRT1 expression from 10 to 20 μg/ml. Treatment with 20 mM or 40 mM glucose medium did not significantly inhibit E1- and E3-induced SIRT1 expression in control medium; however, both high glucose mediums significantly emphasized E2-induced SIRT1 expression in control medium (p=0.007, p=0.005).

Conclusion:

These results suggest that DHEA, androstenedione, testosterone, E1, and E2 definitely activate SIRT1 expression in HAECs. A high glucose medium is potent to inhibit the basal gene expression; however, it could not reduce powerful androgen- and estrogen-induced SIRT1 expression in HAECs.

The possible role of sirtuins in male reproduction

Global influence of male infertility is increasing in recent decades. Proper understanding of genetics, anatomy, physiology and the intricate interrelation of male reproductive system are much needed for explaining the etiology of male infertility; and a detailed study on the epigenetics, indeed, will reveal the molecular mechanism behind its etiology. Sirtuins, the molecular sensors, are NAD⁺ dependent histone deacetylases and ADP- ribosyl transferases, participate in the chief events of epigenetics. In mammals, sirtuin family comprises seven members (SIRT1-SIRT7), and they all possess a conserved NAD⁺ binding catalytic domain, termed the sirtuin core domain which is imperative for their activity. Sirtuins exert a pivotal role in cellular homeostasis, energy metabolism, apoptosis, age-related disorders and male reproductive system. However, their exact role in male reproduction is still obscure. This article specifically reviews the role of mammalian sirtuins in male reproductive function, thereby, prompting further research to discover the restorative methods and its implementation in reproductive medicine.

Androgen deprivation-induced elevated nuclear SIRT1 promotes prostate tumor cell survival by reactivation of AR signaling

The NAD⁺-dependent deacetylase, Sirtuin 1 (SIRT1) is involved in prostate cancer pathogenesis. However, the actual contribution is unclear as some reports propose a protective role while others suggest it is harmful. We provide evidence for a contextual role for SIRT1 in prostate cancer. Our data show that (i) mice orthotopically implanted with SIRT1-silenced LNCaP cells produced smaller tumors; (ii) SIRT1 suppression mimicked AR inhibitory effects in hormone responsive LNCaP cells; and (iii) caused significant reduction in gene signatures associated with E2F and MYC targets in AR-null PC-3 and E2F and mTORC1 signaling in castrate-resistant ARv7 positive 22Rv1 cells. Our findings further show increased nuclear SIRT1 (nSIRT1) protein under androgen-depleted relative to androgen-replete conditions in prostate cancer cell lines. Silencing SIRT1 resulted in decreased recruitment of AR to PSA enhancer selectively under androgen-deprivation conditions. Prostate cancer outcome data show that patients with higher levels of nSIRT1 progress to advanced disease relative to patients with low nSIRT1 levels. Collectively, we demonstrate that lowering SIRT1 levels potentially provides new avenues to effectively prevent prostate cancer recurrence.

Post-Translational Modifications That Drive Prostate Cancer Progression

While a protein primary structure is determined by genetic code, its specific functional form is mostly achieved in a dynamic interplay that includes actions of many enzymes involved in post-translational modifications. This versatile repertoire is widely used by cells to direct their response to external stimuli, regulate transcription and protein localization and to keep proteostasis. Herein, post-translational modifications with evident potency to drive prostate cancer are explored. A comprehensive list of proteome-wide and single protein post-translational modifications and their involvement in phenotypic outcomes is presented. Specifically, the data on phosphorylation, glycosylation, ubiquitination, SUMOylation, acetylation, and lipidation in prostate cancer and the enzymes involved are collected. This type of knowledge is especially valuable in cases when cancer cells do not differ in the expression or mutational status of a protein, but its differential activity is regulated on the level of post-translational modifications. Since their driving roles in prostate cancer, post-translational modifications are widely studied in attempts to advance prostate cancer treatment. Current strategies that exploit the potential of post-translational modifications in prostate cancer therapy are presented.

Leronlimab, a humanized monoclonal antibody to CCR5, blocks breast cancer cellular metastasis and enhances cell death induced by DNA damaging chemotherapy

Background

Triple-negative breast cancer (BCa) (TNBC) is a deadly form of human BCa with limited treatment options and poor prognosis. In our prior analysis of over 2200 breast cancer samples, the G protein-coupled receptor CCR5 was expressed in > 95% of TNBC samples. A humanized monoclonal antibody to CCR5 (leronlimab), used in the treatment of HIV-infected patients, has shown minimal side effects in large patient populations.

Methods

A humanized monoclonal antibody to CCR5, leronlimab, was used for the first time in tissue culture and in mice to determine binding characteristics to human breast cancer cells, intracellular signaling, and impact on (i) metastasis prevention and (ii) impact on established metastasis.

Results

Herein, leronlimab was shown to bind CCR5 in multiple breast cancer cell lines. Binding of leronlimab to CCR5 reduced ligand-induced Ca^+ 2 signaling, invasion of TNBC into Matrigel, and transwell migration. Leronlimab enhanced the BCa cell killing of the BCa chemotherapy reagent, doxorubicin. In xenografts conducted with Nu/Nu mice, leronlimab reduced lung metastasis of the TNBC cell line, MB-MDA-231, by > 98% at 6 weeks. Treatment with leronlimab reduced the metastatic tumor burden of established TNBC lung metastasis.

Conclusions

The safety profile of leronlimab, together with strong preclinical evidence to both prevent and reduce established breast cancer metastasis herein, suggests studies of clinical efficacy may be warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-021-01391-1.

The Regulatory Effect of SIRT1 on Extracellular Microenvironment Remodeling

The sirtuins family is well known by its unique nicotinamide adenine dinucleotide (NAD⁺)-dependent deacetylase function. The most-investigated member of the family, Sirtuin 1 (SIRT1), accounts for deacetylating a broad range of transcription factors and coregulators, such as p53, the Forkhead box O (FOXO), and so on. It serves as a pivotal regulator in various intracellular biological processes, including energy metabolism, DNA damage response, genome stability maintenance and tumorigenesis. Although the most attention has been focused on its intracellular functions, the regulatory effect on extracellular microenvironment remodeling of SIRT1 has been recognized by researchers recently. SIRT1 can regulate cell secretion process and participate in glucose metabolism, neuroendocrine function, inflammation and tumorigenesis. Here, we review the advances in the understanding of SIRT1 on remodeling the extracellular microenvironment, which may provide new ideas for pathogenesis investigation and guidance for clinical treatment.

Effects of curcumin supplementation on blood glucose, insulin resistance and androgens in patients with polycystic ovary syndrome: A randomized double-blind placebo-controlled clinical trial

BACKGROUND

Curcumin is a biologically active phytochemical ingredient found in turmeric. It has several pharmacologic effects that might benefit patients with polycystic ovary syndrome (PCOS).

OBJECTIVE

We hypothesized curcumin to be effective in improving blood sugar levels, insulin resistance and hyperandrogenism in individuals with PCOS.

METHODS

In a randomized double-blind placebo-controlled trial, individuals with PCOS were treated with curcumin (500 mg three times daily) or placebo for 12 weeks. Primary outcome measures were fasting plasma glucose (FPG), fasting insulin (FI), sex hormone levels, and hirsutism (Ferriman-Gallwey [mFG] score). Secondary outcomes included anthropometric measurements.

RESULTS

Of 72 randomized individuals, 67 completed the trial. The two groups were comparable at baseline. At the end of the study, FPG and Dehydroepiandrosterone levels had decreased significantly in the intervention group compared to control (difference of change (post-pre) between intervention and placebo groups: -4.11 mg/dL; 95% CI: -8.35, -0.35 mg/dL; p = 0.033 and -26.53 microg/dL; 95% CI: -47.99, -4.34 µg/dL; p = 0.035, respectively). We also observed a statistically non-significant increase (p = 0.082) in Estradiol levels in the intervention group compared to control. No serious adverse events were reported throughout the trial.

CONCLUSIONS

Curcumin might be a safe and useful supplement to ameliorate PCOS-associated hyperandrogenemia and hyperglycemia. However, longer trials investigating different dosages in longer durations are needed to underpin these findings.

The Versatility of Sirtuin-1 in Endocrinology and Immunology

Sirtuins belong to the class III family of NAD-dependent histone deacetylases (HDAC) and are involved in diverse physiological processes that range from regulation of metabolism and endocrine function to coordination of immunity and cellular responses to stress. Sirtuin-1 (SIRT1) is the most well-studied family member and has been shown to be critically involved in epigenetics, immunology, and endocrinology. The versatile roles of SIRT1 include regulation of energy sensing metabolic homeostasis, deacetylation of histone and non-histone proteins in numerous tissues, neuro-endocrine regulation via stimulation of hypothalamus-pituitary axes, synthesis and maintenance of reproductive hormones via steroidogenesis, maintenance of innate and adaptive immune system via regulation of T- and B-cell maturation, chronic inflammation and autoimmune diseases. Moreover, SIRT1 is an appealing target in various disease contexts due to the promise of pharmacological and/or natural modulators of SIRT1 activity within the context of endocrine and immune-related disease models. In this review we aim to provide a broad overview on the role of SIRT1 particularly within the context of endocrinology and immunology.

The SIRT3 and SIRT6 Promote Prostate Cancer Progression by Inhibiting Necroptosis-Mediated Innate Immune Response

The sirtuins (SIRTs), including seven family members, belong to class III histone deacetylase (HDAC) enzymes, which have been intensively investigated in cancers. Although the function of SIRTs in the cancer immunology is explored, SIRT-specific mechanisms regulating necroptosis-related innate immune response are not clear. In our present study, we found that both the mRNA and protein expression levels of SIRT3 and SIRT6 are significantly increased in the PCa tissues (HR, CI P = 3.30E - 03; HR, CI P = 2.35E - 08; and HR, CI P = 9.20E - 08) and were associated with patients' Gleason score and nodal metastasis. Furthermore, multivariate analysis showed that the PCa patients with higher expression levels of SIRT3 and SIRT6 had shorter overall survival (OS). Mechanistically, we found that SIRT3 and SIRT6 promote prostate cancer progress by inhibiting RIPK3-mediated necroptosis and innate immune response. Knockdown of both SIRT3 and SIRT6 not only activates TNF-induced necroptosis but also refreshes the corresponding recruitment of macrophages and neutrophils. Overall, our study identified that SIRT3 and SIRT6 are key regulators of necroptosis during prostate cancer progression.

Zinc, copper, sirtuin 1 concentration, and glucose metabolism parameters in the blood of women with polycystic ovary syndrome

The aim of this study was to assess concentration of zinc (Zn), copper (Cu), and sirtuin 1 (SIRT1) in serum of women with polycystic ovary syndrome (PCOS) and their relationships with glucose metabolism parameters. The study included 76 women with PCOS aged between 17 and 39 years old. The blood was collected according to the routine procedure during the follicular phase. Zn and Cu concentrations were performed by flame atomic absorption spectrometry (FAAS). Glucose concentration was estimated by colorimetric methods. Insulin (INs) concentration was determined by enzyme-linked immunosorbent assay. SIRT1 concentration was determined using commercial test. We found higher Cu concentration and Cu/Zn value in the serum of women with PCOS with overweight/obesity. Early stage of insulin resistance (IR) in the group of women with PCOS affected on higher Cu concentration and Cu/Zn value. However, increased value of body mass index, waist-hip ratio and homeostatic model assessment of insulin resistance (HOMA-IR) was not associated with changes in Zn and SIRT1 concentration. Further disturbances in glucose metabolic parameters in the blood of women with PCOS were intensified by overweight/obesity and IR. Overweight/obesity and IR in the women with PCOS increase disorders in Cu homeostasis and glucose metabolism parameters.

Metabolic Roles of Androgen Receptor and Tip60 in Androgen-Dependent Prostate Cancer

Androgen receptor (AR)-mediated signaling is essential for the growth and differentiation of the normal prostate and is the primary target for androgen deprivation therapy in prostate cancer. Tat interactive protein 60 kDa (Tip60) is a histone acetyltransferase that is critical for AR activation. It is well known that cancer cells rewire their metabolic pathways in order to sustain aberrant proliferation. Growing evidence demonstrates that the AR and Tip60 modulate key metabolic processes to promote the survival of prostate cancer cells, in addition to their classical roles. AR activation enhances glucose metabolism, including glycolysis, tricarboxylic acid cycle and oxidative phosphorylation, as well as lipid metabolism in prostate cancer. The AR also interacts with other metabolic regulators, including calcium/calmodulin-dependent kinase kinase 2 and mammalian target of rapamycin. Several studies have revealed the roles of Tip60 in determining cell fate indirectly by modulating metabolic regulators, such as c-Myc, hypoxia inducible factor 1α (HIF-1α) and p53 in various cancer types. Furthermore, Tip60 has been shown to regulate the activity of key enzymes in gluconeogenesis and glycolysis directly through acetylation. Overall, both the AR and Tip60 are master metabolic regulators that mediate cellular energy metabolism in prostate cancer, providing a framework for the development of novel therapeutic targets in androgen-dependent prostate cancer.

FSH, oxytocin and IGF-I regulate the expression of sirtuin 1 in porcine ovarian granulosa cells

The involvement of the mTOR system/enzyme sirtuin 1 (SIRT1) intracellular signaling system in the control of ovarian functions and its role in mediating hormonal action on the ovary has been proposed, but this hypothesis should be supported by a demonstrated influence of hormones on mTOR/SIRT1. Therefore, the aim of our in vitro experiments was to examine the effect of the known hormonal regulators of ovarian functions, such as follicle-stimulating hormone (FSH), oxytocin (OT) and insulin-like growth factor I (IGF-I), on mTOR/SIRT1. The accumulation of SIRT1 in porcine ovarian granulosa cells cultured with and without these hormones (at doses of 1, 10 or 100 ng.ml-1) was evaluated using immunocytochemistry. It was observed that the addition of FSH (at 10 ng.ml-1 but not at 1 or 100 ng/ml) and OT (at all tested doses) increased the expression of SIRT1 in ovarian cells. In addition, 100 ng.ml-1, but not at 1 or 10 ng.ml-1, of IGF-I decreased SIRT1 accumulation. Our observations are the first demonstration that hormones can directly regulate the ovarian mTOR/SIRT1 system and that this system could mediate the action of hormonal regulators on the ovary.

Posttranslational regulation of androgen dependent and independent androgen receptor activities in prostate cancer

Prostate cancer (PCa) is the most commonly diagnosed cancer among men in western countries. Androgen receptor (AR) signaling plays key roles in the development of PCa. Androgen deprivation therapy (ADT) remains the standard therapy for advanced PCa. In addition to its ligand androgen, accumulating evidence indicates that posttranscriptional modification is another important mechanism to regulate AR activities during the progression of PCa, especially in castration resistant prostate cancer (CRPC). To date, a number of posttranscriptional modifications of AR have been identified, including phosphorylation (e.g. by CDK1), acetylation (e.g. by p300 and recognized by BRD4), methylation (e.g. by EZH2), ubiquitination (e.g. by SPOP), and SUMOylation (e.g. by PIAS1). These modifications are essential for the maintenance of protein stability, nuclear localization and transcriptional activity of AR. This review summarizes posttranslational modifications that influence androgen-dependent and -independent activities of AR, PCa progression and therapy resistance. We further emphasize that in addition to androgen, posttranslational modification is another important way to regulate AR activity, suggesting that targeting AR posttranslational modifications, such as proteolysis targeting chimeras (PROTACs) of AR, represents a potential and promising alternate for effective treatment of CRPC. Potential areas to be investigated in the future in the field of AR posttranslational modifications are also discussed.

Biochemical insight into pseudouridine synthase 7 (PUS7) as a novel interactor of sirtuin, SIRT1

Sirtuin1 (SIRT1) forms a dynamic regulatory network with multiple proteins. The SIRT1 protein interactome comprises histone, non-histone substrates, and modulators of SIRT1 deacetylase. Proteomic studies have enlisted several proteins in SIRT1 network, but the structural and functional details of their interactions remain largely unexplored. In this study, we establish Pseudouridine synthase 7 (PUS7), a nuclear protein involved in stem cell development and intellectual disabilities, as a novel interactor of SIRT1. The binding regions are predicted and analyzed based on molecular docking studies. The direct interaction occurs between SIRT1 and PUS7, as evidenced by pull-down studies and surface plasmon resonance (SPR) assay. Furthermore, the truncation studies unambiguously suggested that the N-terminal region of PUS7 is essential for forming a stable complex with SIRT1. Overall, our results suggest that PUS7 may regulate the SIRT1 function when it directly interacts with SIRT1.

Diverse therapeutic efficacies and more diverse mechanisms of nicotinamide

BACKGROUND

Nicotinamide (NAM) is a form of vitamin B3 that, when administered at near-gram doses, has been shown or suggested to be therapeutically effective against many diseases and conditions. The target conditions are incredibly diverse ranging from skin disorders such as bullous pemphigoid to schizophrenia and depression and even AIDS. Similar diversity is expected for the underlying mechanisms. In a large portion of the conditions, NAM conversion to nicotinamide adenine dinucleotide (NAD⁺) may be a major factor in its efficacy. The augmentation of cellular NAD⁺ level not only modulates mitochondrial production of ATP and superoxide, but also activates many enzymes. Activated sirtuin proteins, a family of NAD⁺-dependent deacetylases, play important roles in many of NAM's effects such as an increase in mitochondrial quality and cell viability countering neuronal damages and metabolic diseases. Meanwhile, certain observed effects are mediated by NAM itself. However, our understanding on the mechanisms of NAM's effects is limited to those involving certain key proteins and may even be inaccurate in some proposed cases.

AIM OF REVIEW

This review details the conditions that NAM has been shown to or is expected to effectively treat in humans and animals and evaluates the proposed underlying molecular mechanisms, with the intention of promoting wider, safe therapeutic application of NAM.

KEY SCIENTIFIC CONCEPTS OF REVIEW

NAM, by itself or through altering metabolic balance of NAD⁺ and tryptophan, modulates mitochondrial function and activities of many molecules and thereby positively affects cell viability and metabolic functions. And, NAM administration appears to be quite safe with limited possibility of side effects which are related to NAM's metabolites.

Molecular Mechanisms and Therapeutics for SBMA/Kennedy's Disease

Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by a polyglutamine (polyQ) expansion in the androgen receptor (AR). Despite the fact that the monogenic cause of SBMA has been known for nearly 3 decades, there is no effective treatment for this disease, underscoring the complexity of the pathogenic mechanisms that lead to a loss of motor neurons and muscle in SBMA patients. In the current review, we provide an overview of the system-wide clinical features of SBMA, summarize the structure and function of the AR, discuss both gain-of-function and loss-of-function mechanisms of toxicity caused by polyQ-expanded AR, and describe the cell and animal models utilized in the study of SBMA. Additionally, we summarize previously conducted clinical trials which, despite being based on positive results from preclinical studies, proved to be largely ineffective in the treatment of SBMA; nonetheless, these studies provide important insights as researchers develop the next generation of therapies.

SIRT1 in the Development and Treatment of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death worldwide. Current treatment options for inoperable HCCs have decreased therapeutic efficacy and are associated with systemic toxicity and chemoresistance. Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide–dependent enzyme that is frequently overexpressed in HCC, where it promotes tumorigenicity, metastasis, and chemoresistance. SIRT1 also maintains the tumorigenic and self-renewal proprieties of liver cancer stem cells. Multiple tumor-suppressive microRNAs (miRNAs) are downregulated in HCC and, as a consequence, permit SIRT1-induced tumorigenicity. However, either directly targeting SIRT1, combining conventional chemotherapy with SIRT1 inhibitors, or upregulating tumor-suppressive miRNAs may improve therapeutic efficacy and patient outcomes. Here, we present the interaction between SIRT1, miRNAs, and liver cancer stem cells and discuss the consequences of their interplay for the development and treatment of HCC.

MicroRNA‑506 regulates apoptosis in retinoblastoma cells by targeting sirtuin 1

BACKGROUND

MicroRNAs have been reported to participate in the initiation and progression of retinoblastoma (RB), most common malignancy in children. The refractory mechanisms of chemoresistance and the toxicity of chemotherapies hindered the treatment especially on young children. Novel RB therapies are urgently required. MiR-506 is probed to be associated with the tumorigenesis of various cancers whilst the role of this miR in RB remains unclear.

METHODS

Here, the impact of miR-506 on RB cell survival in vitro and tumorigenesis in vivo was examined. MiR-506 expression was examined in human RB samples and cell lines as compared with healthy tissues and non-RB cells. EdU staining and colony formation assay were performed to determine the effect of miR-506 on RB cell growth. TdT-mediated dUTP nick end labeling (TUNEL) staining and flow cytometry analysis were applied to detect the apoptotic cell number after miR-506 was downregulated in RB cells. Furthermore, dual-luciferase reporter assay was utilized to confirm the direct interaction between miR-506 and SIRT1 gene.

RESULTS

MiR-506 expression was upregulated in 20 human RB samples from patients as well as in human RB cell lines, WERI-Rb1 and Y79, as compared to that in healthy tissues and non-RB cells. In contrast, the expression of sirtuin 1 (SIRT1), known as NAD-dependent deacetylase, was downregulated in RB samples and cell lines. Aberrant reduced miR-506 expression impaired survival and proliferation of WERI-Rb1 and Y79 cells. The depletion of miR-506 expression promoted apoptosis of the two RB cell lines. The results of bioinformatics analysis and dual-luciferase assay exhibited that miR-506 targeted the 3'-untranslated region of SIRT1 on silencing purpose. The SIRT1 silencing lessened the miR-506 inhibition on RB cell proliferation and undermined apoptosis.

CONCLUSION

The results provided an insight into the role of miR-506 during RB development and offered potential pharmaceutical strategy for RB diagnosis.

Gender effect of hyperuricemia on the development of nonalcoholic fatty liver disease (NAFLD): A clinical analysis and mechanistic study

BACKGROUND AND AIMS

Hyperuricemia is a risk factor for nonalcoholic fatty liver disease (NAFLD), however, the effect of gender on the hyperuricemia-related NAFLD development remains unclear. Here, we evaluated the clinical characteristics of NAFLD patients with hyperuricemia, and experimentally recapitulated this condition in male rats in order to gain insights on the possible impact of gender on the development of NAFLD in patients with hyperuricemia.

METHODS

The clinical characteristics of 238 NAFLD patients, together with the impacts of hyperuricemia on the major parameters related to the development of NALFD were analysed. In animal studies, NAFLD with hyperuricemia was induced in male SD rats using high-yeast high-fat diet containing potassium oxonate. The impact of uric acids on liver pathology, and the expression patterns of key molecules involved in the development of NAFLD, including silent information regulator 1 (SIRT1), nuclear factor kappa B subunit p65 (NF-κB p65), fork-head box class O-3a (FOXO3a), androgen receptor (AR), and xanthine oxidase (XO) were analysed.

RESULTS

Male NAFLD patients with hyperuricemia displayed more frequent and extensive liver injury than those in female patients. In male rats, hyperuricemia was associated with increased levels of insulin, alanine aminotransferase (ALT) and triglyceride (TG). At the molecular level, hyperuricemia was associated with decreased expression of SIRT1 and its phosphorylation, phosphorylation of FOXO3a, increased expression of AR and XO, and deacetylation of NF-κB P65.

CONCLUSIONS

Hyperuricemia is a compounding factor for NAFLD, particularly in males. The severer hepatic injury observed in male NAFLD patients may be attributed to the suppression of SIRT1 signalling induced by hyperuricemia.

Spironolactone-induced degradation of the TFIIH core complex XPB subunit suppresses NF-κB and AP-1 signalling

Aims

Spironolactone (SPL) improves endothelial dysfunction and survival in heart failure. Immune modulation, including poorly understood mineralocorticoid receptor (MR)-independent effects of SPL might contribute to these benefits and possibly be useful in other inflammatory cardiovascular diseases such as pulmonary arterial hypertension.

Methods and results

Using human embryonic kidney cells (HEK 293) expressing specific nuclear receptors, SPL suppressed NF-κB and AP-1 reporter activity independent of MR and other recognized nuclear receptor partners. NF-κB and AP-1 DNA binding were not affected by SPL and protein synthesis blockade did not interfere with SPL-induced suppression of inflammatory signalling. In contrast, proteasome blockade to inhibit degradation of xeroderma pigmentosum group B complementing protein (XPB), a subunit of the general transcription factor TFIIH, or XPB overexpression both prevented SPL-mediated suppression of inflammation. Similar to HEK 293 cells, a proteasome inhibitor blocked XPB loss and SPL suppression of AP-1 induced target genes in human pulmonary artery endothelial cells (PAECs). Unlike SPL, eplerenone (EPL) did not cause XPB degradation and failed to similarly suppress inflammatory signalling. SPL combined with siRNA XPB knockdown further reduced XPB protein levels and had the greatest effect on PAEC inflammatory gene transcription. Using chromatin-immunoprecipitation, PAEC target gene susceptibility to SPL was associated with low basal RNA polymerase II (RNAPII) occupancy and TNFα-induced RNAPII and XPB recruitment. XP patient-derived fibroblasts carrying an N-terminal but not C-terminal XPB mutations were insensitive to both SPL-mediated XPB degradation and TNFα-induced target gene suppression. Importantly, SPL treatment decreased whole lung XPB protein levels in a monocrotaline rat model of pulmonary hypertension and reduced inflammatory markers in an observational cohort of PAH patients.

Conclusion

SPL has important anti-inflammatory effects independent of aldosterone and MR, not shared with EPL. Drug-induced, proteasome-dependent XPB degradation may be a useful therapeutic approach in cardiovascular diseases driven by inflammation.

Molecular Mechanisms Related to Hormone Inhibition Resistance in Prostate Cancer

Management of metastatic or advanced prostate cancer has acquired several therapeutic approaches that have drastically changed the course of the disease. In particular due to the high sensitivity of prostate cancer cells to hormone depletion, several agents able to inhibit hormone production or binding to nuclear receptor have been evaluated and adopted in clinical practice. However, despite several hormonal treatments being available nowadays for the management of advanced or metastatic prostate cancer, the natural history of the disease leads inexorably to the development of resistance to hormone inhibition. Findings regarding the mechanisms that drive this process are of particular and increasing interest as these are potentially related to the identification of new targetable pathways and to the development of new drugs able to improve our patients' clinical outcomes.

Regulatory Effects of NAD+ Metabolic Pathways on Sirtuin Activity

NAD⁺ acts as a crucial regulator of cell physiology and as an integral participant in cellular metabolism. By virtue of a variety of signaling activities this central metabolite can exert profound effects on organism health status. Thus, while it serves as a well-known metabolic cofactor functioning as a redox-active substrate, it can also function as a substrate for signaling enzymes, such as sirtuins, poly (ADP-ribosyl) polymerases, mono (ADP-ribosyl) transferases, and CD38. Sirtuins function as NAD⁺-dependent protein deacetylases (deacylases) and catalyze the reaction of NAD⁺ with acyllysine groups to remove the acyl modification from substrate proteins. This deacetylation provides a regulatory function and integrates cellular NAD⁺ metabolism into a large spectrum of cellular processes and outcomes, such as cell metabolism, cell survival, cell cycle, apoptosis, DNA repair, mitochondrial homeostasis and mitochondrial biogenesis, and even lifespan. Increased attention to how regulated and pharmacologic changes in NAD⁺ concentrations can impact sirtuin activities has motivated openings of new areas of research, including investigations of how NAD⁺ levels are regulated at the subcellular level, and searches for more potent NAD⁺ precursors typified by nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN). This review describes current results and thinking of how NAD⁺ metabolic pathways regulate sirtuin activities and how regulated NAD⁺ levels can impact cell physiology. In addition, NAD⁺ precursors are discussed, with attention to how these might be harnessed to generate novel therapeutic options to treat the diseases of aging.

Neuronal SIRT1 Regulates Metabolic and Reproductive Function and the Response to Caloric Restriction

Sirt1 is an NAD-dependent, class III deacetylase that functions as a cellular energy sensor. In addition to its well-characterized effects in peripheral tissues, emerging evidence suggests that neuronal Sirt1 activity plays a role in the central regulation of energy balance and glucose metabolism. In this study, we generated mice expressing an enzymatically inactive form (N-MUT) or wild-type (WT) SIRT1 (N-OX) in mature neurons. N-OX male and female mice had impaired glucose tolerance, and N-MUT female, but not male, mice had improved glucose tolerance compared with that of WT littermates. Furthermore, glucose tolerance was improved in all mice with caloric restriction (CR) but was greater in the N-OX mice, who had better glucose tolerance than their littermates. At the reproductive level, N-OX females had impaired estrous cycles, with increased cycle length and more time in estrus. LH and progesterone surges were absent on the evening of proestrus in the N-OX mice, suggesting a defect in spontaneous ovulation, which was confirmed by the ovarian histology revealing fewer corpora lutea. Despite this defect, the mice were still fertile when mated to WT mice on the day of proestrus, indicating that the mice could respond to normal pheromonal or environmental cues. When subjected to CR, the N-OX mice went into diestrus arrest earlier than their littermates. Together, these results suggested that the overexpression of SIRT1 rendered the mice more sensitive to the metabolic improvements and suppression of reproductive cycles by CR, which was independent of circadian rhythms.

The Wonder Years: What Can Primary School Children Teach Us About Immunity to Mycobacterium tuberculosis?

In high burden settings, the risk of infection with Mycobacterium tuberculosis increases throughout childhood due to cumulative exposure. However, the risk of progressing from tuberculosis (TB) infection to disease varies by age. Young children (<5 years) have high risk of disease progression following infection. The risk falls in primary school children (5 to <10 years), but rises again during puberty. TB disease phenotype also varies by age: generally, young children have intrathoracic lymph node disease or disseminated disease, while adolescents (10 to <20 years) have adult-type pulmonary disease. TB risk also exhibits a gender difference: compared to adolescent boys, adolescent girls have an earlier rise in disease progression risk and higher TB incidence until early adulthood. Understanding why primary school children, during what we term the "Wonder Years," have low TB risk has implications for vaccine development, therapeutic interventions, and diagnostics. To understand why this group is at low risk, we need a better comprehension of why younger children and adolescents have higher risks, and why risk varies by gender. Immunological response to M. tuberculosis is central to these issues. Host response at key stages in the immunopathological interaction with M. tuberculosis influences risk and disease phenotype. Cell numbers and function change dramatically with age and sexual maturation. Young children have poorly functioning innate cells and a Th2 skew. During the "Wonder Years," there is a lymphocyte predominance and a Th1 skew. During puberty, neutrophils become more central to host response, and CD4+ T cells increase in number. Sex hormones (dehydroepiandrosterone, adiponectin, leptin, oestradiol, progesterone, and testosterone) profoundly affect immunity. Compared to girls, boys have a stronger Th1 profile and increased numbers of CD8+ T cells and NK cells. Girls are more Th2-skewed and elicit more enhanced inflammatory responses. Non-immunological factors (including exposure intensity, behavior, and co-infections) may impact disease. However, given the consistent patterns seen across time and geography, these factors likely are less central. Strategies to protect children and adolescents from TB may need to differ by age and sex. Further work is required to better understand the contribution of age and sex to M. tuberculosis immunity.