Sirtuins as Important Factors in Pathological States and the Role of Their Molecular Activity Modulators

Type 1 diabetes impairs the activity of rat testicular somatic and germ cells through NRF2/NLRP3 pathway-mediated oxidative stress

Background

It is well known that metabolic disorders, including type 1 diabetes (T1D), are often associated with reduced male fertility, mainly increasing oxidative stress and impairing the hypothalamus-pituitary-testis (HPT) axis, with consequently altered spermatogenesis and reduced sperm parameters. Herein, using a rat model of T1D obtained by treatment with streptozotocin (STZ), we analyzed several parameters of testicular activity.

Methods

A total of 10 adult male Wistar rats were divided into two groups of five: control and T1D, obtained with a single intraperitoneal injection of STZ. After 3 months, the rats were anesthetized and sacrificed; one testis was stored at -80°C for biochemical analysis, and the other was fixed for histological and immunofluorescence analysis.

Results

The data confirmed that T1D induced oxidative stress and, consequently, alterations in both testicular somatic and germ cells. This aspect was highlighted by enhanced apoptosis, altered steroidogenesis and Leydig cell maturity, and impaired spermatogenesis. In addition, the blood-testis barrier integrity was compromised, as shown by the reduced levels of structural proteins (N-cadherin, ZO-1, occludin, connexin 43, and VANGL2) and the phosphorylation status of regulative kinases (Src and FAK). Mechanistically, the dysregulation of the SIRT1/NRF2/MAPKs signaling pathways was proven, particularly the reduced nuclear translocation of NRF2, affecting its ability to induce the transcription of genes encoding for antioxidant enzymes. Finally, the stimulation of testicular inflammation and pyroptosis was also confirmed, as highlighted by the increased levels of some markers, such as NF-κB and NLRP3.

Conclusion

The combined data allowed us to confirm that T1D has detrimental effects on rat testicular activity. Moreover, a better comprehension of the molecular mechanisms underlying the association between metabolic disorders and male fertility could help to identify novel targets to prevent and treat fertility disorders related to T1D.

Yiqigubiao pill treatment regulates Sirtuin 5 expression and mitochondrial function in chronic obstructive pulmonary disease

Background

Chronic obstructive pulmonary disease (COPD) is a heterogeneous group of pathophysiological bases of airway inflammation and its anti-inflammatory response. Aberrant mitochondrial signaling and mitochondrial dysfunction underlie the pathomechanisms leading to COPD. This study aims to investigate the effects of the Yiqigubiao (YQGB) pill, a traditional Chinese medicine (TCM), on Sirtuin 5 (SIRT5) and mitochondrial function in patients with COPD.

Methods

Thirty-four patients with COPD were randomized into oral YQGB or placebo groups concurrent with a 24-week routine treatment. The pulmonary function was assessed by examining the levels of forced expiratory volume in one second (FEV1)/forced vital capacity (FVC), FEV1, and FVC. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot were used to detect SIRT5 expression in mitochondria isolated from peripheral blood. Flow cytometry was used to detect changes in mitochondrial membrane potential and reactive oxygen species (ROS) in peripheral blood lymphocytes. Human bronchial epithelial (HBE) cells stimulated by cigarette smoke extract (CSE) were treated with YQGB. After SIRT5 was knocked down in cells, the changes in mitochondrial membrane potential, levels of adenosine triphosphate (ATP), and ROS were detected.

Results

YQGB treatment significantly improved lung function in patients with COPD. The expression of SIRT5 and the mitochondrial membrane potential significantly increased and ROS decreased in patients with COPD after YQGB treatment. The CSE decreased cell proliferation and SIRT5 expression, which was alleviated after YQGB treatment. Furthermore, SIRT5 was knocked down in CSE-stimulated HBE cells, and its expression was elevated upon YQGB treatment. The knockdown of SIRT5 significantly altered the CSE-stimulation-induced dysregulation of mitochondrial membrane potential, ATP levels, and ROS. This was also restored after YQGB treatment.

Conclusions

YQGB treatment can elevate SIRT5 expression, restore mitochondrial function in COPD, and exert protective effects.

Novel xanthone derivatives as potent sirtuin 2 inhibitors

Six amino derivatives of xanthone were obtained via chemical synthesis. Biochemical studies revealed their SIRT2 inhibitory activity ranging from 48.5 % (compound 4, 5-chloro-2-((4-(3-methoxyphenyl)piperazin-1-yl)methyl)-9H-xanthen-9-one hydrochloride) to 93.2 % (compound 3, 5-chloro-2-(((2-methoxyphenethyl)amino)methyl)-9H-xanthen-9-one hydrochloride). The structure-activity analysis showed favourable properties of secondary amines relative to tertiary piperazine derivatives. The tested compounds do not possess additional SIRT1 activating activity and no antioxidant activity (DPPH in vitro assay). Comprehensive analysis of the lipophilicity of the obtained compounds was also performed. For compound 3 potential molecular targets and similar active compounds were predicted in order to facilitate further research in this group of compounds.

Sirtuins as Players in the Signal Transduction of Citrus Flavonoids

Sirtuins (SIRTs) belong to the family of nicotine adenine dinucleotide (NAD+)-dependent class III histone deacetylases, which come into play in the regulation of epigenetic processes through the deacetylation of histones and other substrates. The human genome encodes for seven homologs (SIRT1-7), which are localized into the nucleus, cytoplasm, and mitochondria, with different enzymatic activities and regulatory mechanisms. Indeed, SIRTs are involved in different physio-pathological processes responsible for the onset of several human illnesses, such as cardiovascular and neurodegenerative diseases, obesity and diabetes, age-related disorders, and cancer. Nowadays, it is well-known that Citrus fruits, typical of the Mediterranean diet, are an important source of bioactive compounds, such as polyphenols. Among these, flavonoids are recognized as potential agents endowed with a wide range of beneficial properties, including antioxidant, anti-inflammatory, hypolipidemic, and antitumoral ones. On these bases, we offer a comprehensive overview on biological effects exerted by Citrus flavonoids via targeting SIRTs, which acted as modulator of several signaling pathways. According to the reported studies, Citrus flavonoids appear to be promising SIRT modulators in many different pathologies, a role which might be potentially evaluated in future therapies, along with encouraging the study of those SIRT members which still lack proper evidence on their support.

Genetic insights into bladder cancer: the impact of SIRT1 gene polymorphism

Bladder cancer (BC) has shown a significant global health concern with distinct pathological, genetic, and epigenetic characteristics. Its prevalence is influenced by various risk factors, including age, gender, and genetic predisposition. This study investigates the association between BC and the Sirtuin 1 (SIRT1) gene polymorphism rs369274325 in the Turkish population. Genomic DNA was isolated from peripheral blood samples and genotyping of rs369274325 polymorphism in SIRT 1 was investigated in 200 individuals (in 100 Turkish bladder cancer patients and 100 healthy individuals as the control group.) by real-time PCR. Demographic information, smoking and alcohol consumption status was analyzed by statistical analysis. Statistical analysis was performed by Pearson's Chi-square test. Smoking and alcohol consumption were significantly higher in BC patients compared to controls (p < 0.00018 and p < 0.0001, respectively). The genotypic distribution of SIRT1 rs369274325 did not show a significant difference between BC patients and controls (p = 0.5550). BC, influenced by genetic and environmental factors, has been linked to various gene mutations. SIRT1, involved in diverse physiological processes, is proposed to play a role in BC. However, our study did not find a significant association between SIRT1 rs369274325 polymorphism and BC in the Turkish population.

Multiple omics analysis reveals the regulation of SIRT5 on mitochondrial function and lipid metabolism during the differentiation of bovine preadipocytes

Preadipocyte differentiation represents a critical stage in adipogenesis, with mitochondria playing an undeniable pivotal role. Given the intricate interplay between transcription and metabolic signaling during adipogenesis, the regulation of sirtuin 5 (SIRT5) on mitochondrial function and lipid metabolism was revealed via multiple omics analysis. The findings suggest that SIRT5 plays a crucial role in promoting mitochondrial biosynthesis and maintaining mitochondrial function during preadipocyte differentiation. Moreover, SIRT5 modulates the metabolic levels of numerous bioactive substances by extensively regulating genes expression associated with differentiation, energy metabolism, lipid synthesis, and mitochondrial function. Finally, SIRT5 was found to suppress triacylglycerols (TAG) accumulation while enhancing the proportion and diversity of unsaturated fatty acids, and providing conditions for the expansion and stability of membrane structure during mitochondrial biosynthesis through numerous gene regulations. Our findings provide a foundation for the identification of crucial functional genes, signaling pathways, and metabolic substances associated with adipose tissue differentiation and metabolism.

Cyclovirobuxine D alleviates aldosterone-induced myocardial hypertrophy by protecting mitochondrial function depending on the mutual regulation of Nrf2-SIRT3

BACKGROUND

Cyclovirobuxine D (CVB-D) is a natural alkaloid that exhibits multiple pharmacological activities, such as anti-inflammatory, anti-oxidative stress, and anti-cancer properties. However, its specific protective mechanism of action for myocardial hypertrophy remains unresolved.

PURPOSE

This work was to investigate the ameliorative impact of CVB-D in myocardial hypertrophy, and to elucidate aldosterone (ALD)-induced myocardial hypertrophy by inhibiting the SIRT3 mediated Nrf2 activation.

METHODS

The myocardial hypertrophy model was reproduced by ALD both in vitro and in vivo, and the protective effect of CVB-D on myocardium and mitochondria was evaluated by TEM, H&E, qPCR, Western blot and ChIP. An immunoprecipitation experiment was adopted to evaluate the acetylation level of Nrf2 and the binding between SIRT3 and Nrf2. Additionally, bardoxolone-methyl (BAR, an Nrf2 agonist), ML385 (an Nrf2 inhibitor), resveratrol (RES, a SIRT3 agonist), and 3-TYP (a SIRT3 inhibitor) were used to confirm the molecular mechanism of CVB-D. Lastly, a molecular docking technique was employed to predict the binding site of SIRT3 and Nrf2 proteins.

RESULTS

Our findings suggested that CVB-D improved mitochondrial function, leading to a reduction in ALD-induced cardiomyocyte hypertrophy. By CVB-D treatment, there was an activation of mutual regulation between Nrf2 and SIRT3. Specifically, CVB-D resulted in the increase of Nrf2 protein in the nucleus and activated Nrf2 signaling pathway, thus up-regulating SIRT3. The activation of SIRT3 and the protective action of mitochondrion disappeared because of the intervention of ML385. After CVB-D activated SIRT3, the acetylation level of Nrf2 decreased, followed by activating the Nrf2 pathway. The activation of Nrf2 and mitochondrial protection by CVB-D were reversed by 3-TYP. Our results are also supported by Co-IP and molecular docking analysis, revealing that CVB-D promotes SIRT3-mediated Nrf2 activation.

CONCLUSION

Thus, CVB-D ameliorates ALD-induced myocardial hypertrophy by recovering mitochondrial function by activating the mutual regulation of Nrf2 and SIRT3. Thus, CVB-D could be a beneficial drug for myocardial hypertrophy.

Sirtuin 1 Expression in Canine Mammary Tumors: A Pilot Study

Sirtuin 1 (SIRT1) is a protein involved in aging, cell protection, and energy metabolism in mammals. Recently, SIRT1 has been intensively studied in medical oncology, but the role of SIRT1 is still controversial, as it has been proposed as both an oncogene and a tumor suppressor. The aim of this study is to investigate the expression of SIRT1 by immunohistochemistry in canine mammary tissues, and by Western blot and immunofluorescence analysis in different canine mammary cell lines. Our results showed a decrease in SIRT1 expression from normal mammary gland tissue, and from benign and well-differentiated malignant tumors (G1) to less differentiated ones (G2-G3). Furthermore, a shift in the subcellular localization of SIRT1 from the nucleus to the cytoplasm was observed in less differentiated malignant tumors. However, further studies are needed to investigate the subcellular localization of SIRT1 in canine cancer cells and the role it may play in oncogenesis in animals.

Therapeutic application of natural products: NAD+ metabolism as potential target

BACKGROUND

Nicotinamide adenine dinucleotide (NAD⁺) metabolism is involved in the entire physiopathological process and is critical to human health. Long-term imbalance in NAD⁺ homeostasis is associated with various diseases, including non-alcoholic fatty liver disease, diabetes mellitus, cardiovascular diseases, neurodegenerative disorders, aging, and cancer, making it a potential target for effective therapeutic strategies. Currently, several natural products that target NAD⁺ metabolism have been widely reported to have significant therapeutic effects, but systematic summaries are lacking.

PURPOSE

To summarize the latest findings on the prevention and treatment of various diseases through the regulation of NAD⁺ metabolism by various natural products in vivo and in vitro models, and evaluate the toxicities of the natural products.

METHODS

PubMed, Web of Science, and ScienceDirect were searched using the keywords "natural products sources," "toxicology," "NAD⁺ clinical trials," and "NAD⁺," and/or paired with "natural products" and "diseases" for studies published within the last decade until January 2023.

RESULTS

We found that the natural products mainly include phenols (curcumin, cyclocurcumin, 4-hydroxybenzyl alcohol, salvianolic acid B, pterostilbene, EGCG), flavonoids (pinostrobin, apigenin, acacetin, tilianin, kaempferol, quercetin, isoliquiritigenin, luteolin, silybin, hydroxysafflor yellow A, scutellarin), glycosides (salidroside), quinones (emodin, embelin, β-LAPachone, shikonin), terpenoids (notoginsenoside R1, ginsenoside F2, ginsenoside Rd, ginsenoside Rb1, ginsenoside Rg3, thymoquinone, genipin), pyrazines (tetramethylpyrazine), alkaloids (evodiamine, berberine), and phenylpropanoids (ferulic acid). These natural products have antioxidant, energy-producing, anti-inflammatory, anti-apoptotic and anti-aging effects, which mainly influence the NAMPT/NAD⁺/SIRT, AMPK/SIRT1/PGC-1α, Nrf2/HO-1, PKCs/PARPs/NF-κB, and AMPK/Nrf2/mTOR signaling pathways, thereby regulating NAD⁺ metabolism to prevent and treat various diseases. These natural products have been shown to be safe, tolerable and have fewer adverse effects in various in vivo and in vitro studies and clinical trials.

CONCLUSION

We evaluated the toxic effects of natural products and summarized the available clinical trials on NAD⁺ metabolism, as well as the recent advances in the therapeutic application of natural products targeting NAD⁺ metabolism, with the aim to provide new insights into the treatment of multiple disorders.

Role of sirtuins in hepatocellular carcinoma progression and multidrug resistance: Mechanistical and pharmacological perspectives

Hepatocellular carcinoma (HCC) is the third most common cause of death from cancer worldwide. Therapeutic strategies are still challenging due to the high relapse rate after surgery and multidrug resistance (MDR). It is essential to better understand the mechanisms for HCC progression and MDR for the development of new therapeutic strategies. Mammalian sirtuins (SIRTs), a family of seven members, are related to tumor progression, MDR and prognosis and were proposed as potential prognostic markers, as well as therapeutic targets for treating cancer. SIRT1 is the most studied member and is overexpressed in HCC, playing an oncogenic role and predicting poor prognosis. Several manuscripts describe the role of SIRTs2-7 in HCC; most of them report an oncogenic role for SIRT2 and -7 and a suppressive role for SIRT3 and -4. The scenario is more confusing for SIRT5 and -6, since information is contradictory and scarce. For SIRT1 many inhibitors are available and they seem to hold therapeutic promise in HCC. For the other members the development of specific modulators has just started. This review is aimed to describe the features of SIRTs1-7 in HCC, and the role they play in the onset and progression of the disease. Also, when possible, we will depict the information related to the SIRTs modulators that have been tested in HCC and their possible implication in MDR. With this, we hope to clarify the role of each member in HCC and to shed some light on the most successful strategies to overcome MDR.

Ellagic acid ameliorates aging-induced renal oxidative damage through upregulating SIRT1 and NRF2

BACKGROUND

Aging is associated with impaired renal function and structural alterations. Oxidative stress plays a vital role in renal senescence and damage. Sirtuin 1 (SIRT1) is thought to protect cells from oxidative stress through nuclear factor erythroid 2-related factor 2 (NRF2). Ellagic acid (EA), a natural antioxidant, has been demonstrated to have renoprotective roles in vitro and in vivo. This study investigated if SIRT1 and NRF2 mediate the protective effects of EA in aged kidneys.

METHODS

Male Wistar rats were divided into three groups including young (4 months), old, and old + EA (25 months). Young and old groups received EA solvent, while the old + EA group was treated with EA (30 mg/kg) by gavage for 30 days. Then, the level of renal oxidative stress, SIRT1 and NRF2 expression, kidney function parameters, and histopathological indices were measured.

RESULTS

Treatment with EA significantly increased the level of antioxidant enzymes and reduced malondialdehyde concentration (P < 0.01). Moreover, EA administration remarkably upregulated mRNA and protein levels of SIRT1 and NRF2 as well as deacetylated NRF2 protein (P < 0.05). Additionally, EA treated rats improved kidney function and histopathological scores (P < 0.05).

CONCLUSIONS

These findings suggest that ellagic acid exerts protective effects on aged kidneys by activating SIRT1 and NRF2 signaling.

SIRT6 regulates endothelium-dependent relaxation by modulating nitric oxide synthase 3 (NOS3)

BACKGROUND AND OBJECTIVE

SIRT6, an NAD⁺-dependent protein deacetylase, is a key modulator of various biological functions. However, the precise role of SIRT6 in the regulation of endothelial function is still not fully understood. The current study sought to determine whether SIRT6 modulates NOS3 activity to regulate endothelium-dependent relaxations in the arterial wall and, if so, to investigate the potential underlying mechanism (s).

METHODS

ApoE^-/- mice and Sprague-Dawley rats had their aortic rings isolated for a vascular reactivity assay. Endothelial cells were cultured before qRT-PCR, western blot, immunoprecipitation, NO bioavailability, and acetylation/deacetylation assays were performed.

RESULTS

SIRT6 expression was significantly reduced in the aorta of ApoE^-/- mice fed a high-cholesterol diet, as was endothelium-dependent relaxation. Endothelial dysfunction could be corrected by delivering a SIRT6 overexpression construct via an adenovirus. In cultured endothelial cells, siRNA knockdown of SIRT6 decreased NOS3 catalytic activity, whereas adenoviral overexpression of SIRT6 increased NOS3-derived nitric oxide (NO) generation. SIRT6 interacted with and deacetylated human NOS3 at lysines 494, 497, and 504 of the calmodulin-binding domain, allowing calmodulin to bind to NOS3 and stimulate NOS3 activity. SIRT6 knockdown also reduced NOS3 expression by inhibiting Kruppel-Like Factor 2 (KLF2).

CONCLUSIONS

We identified SIRT6 as a new regulator of the activity of NOS3, with functional implications for endothelial-dependent relaxation.

Implications of altered sirtuins in metabolic regulation and oral cancer

Sirtuins (SIRTs 1-7) are a group of histone deacetylase enzymes with a wide range of enzyme activities that target a range of cellular proteins in the nucleus, cytoplasm, and mitochondria for posttranslational modifications by acetylation (SIRT1, 2, 3, and 5) or ADP ribosylation (SIRT4, 6, and 7). A variety of cellular functions, including mitochondrial functions and functions in energy homeostasis, metabolism, cancer, longevity and ageing, are regulated by sirtuins. Compromised sirtuin functions and/or alterations in the expression levels of sirtuins may lead to several pathological conditions and contribute significantly to alterations in metabolic phenotypes as well as oral carcinogenesis. Here, we describe the basic characteristics of seven mammalian sirtuins. This review also emphasizes the key molecular mechanisms of sirtuins in metabolic regulation and discusses the possible relationships of sirtuins with oral cancers. This review will provide novel insight into new therapeutic approaches targeting sirtuins that may potentially lead to effective strategies for combating oral malignancies.

Sex-divergent effects on the NAD+-dependent deacetylase sirtuin signaling across the olfactory-entorhinal-amygdaloid axis in Alzheimer's and Parkinson's diseases

BACKGROUND

Smell impairment is one of the earliest features in Alzheimer's (AD) and Parkinson's diseases (PD). Due to sex differences exist in terms of smell and olfactory structures as well as in the prevalence and manifestation of both neurological syndromes, we have applied olfactory proteomics to favor the discovery of novel sex-biased physio-pathological mechanisms and potential therapeutic targets associated with olfactory dysfunction.

METHODS

SWATH-MS (sequential window acquisition of all theoretical fragment ion spectra mass spectrometry) and bioinformatic workflows were applied in 57 post-mortem olfactory tracts (OT) derived from controls with no known neurological history (n = 6F/11M), AD (n = 4F/13M) and PD (n = 7F/16M) subjects. Complementary molecular analyses by Western-blotting were performed in the olfactory bulb (OB), entorhinal cortex (EC) and amygdala areas.

RESULTS

327 and 151 OT differentially expressed proteins (DEPs) were observed in AD women and AD men, respectively (35 DEPs in common). With respect to PD, 198 DEPs were identified in PD women, whereas 95 DEPs were detected in PD men (20 DEPs in common). This proteome dyshomeostasis induced a disruption in OT protein interaction networks and widespread sex-dependent pathway perturbations in a disease-specific manner, among them Sirtuin (SIRT) signaling. SIRT1, SIRT2, SIRT3 and SIRT5 protein levels unveiled a tangled expression profile across the olfactory-entorhinal-amygdaloid axis, evidencing disease-, sex- and brain structure-dependent changes in olfactory protein acetylation.

CONCLUSIONS

Alteration in the OT proteostasis was more severe in AD than in PD. Moreover, protein expression changes were more abundant in women than men independent of the neurological syndrome. Mechanistically, the tangled SIRT profile observed across the olfactory pathway-associated brain regions in AD and PD indicates differential NAD (+)-dependent deacetylase mechanisms between women and men. All these data shed new light on differential olfactory mechanisms across AD and PD, pointing out that the evaluation of the feasibility of emerging sirtuin-based therapies against neurodegenerative diseases should be considered with caution, including further sex dimension analyses in vivo and in clinical studies.

Dietary restriction in senolysis and prevention and treatment of disease

Aging represents a key risk factor for a plethora of diseases. Targeting detrimental processes which occur during aging, especially before onset of age-related disease, could provide drastic improvements in healthspan. There is increasing evidence that dietary restriction (DR), including caloric restriction, fasting, or fasting-mimicking diets, extend both lifespan and healthspan. This has sparked interest in the use of dietary regimens as a non-pharmacological means to slow aging and prevent disease. Here, we review the current evidence on the molecular mechanisms underlying DR-induced health improvements, including removal of senescent cells, metabolic reprogramming, and epigenetic rejuvenation.

Cardioprotective Properties of Phenolic Compounds: A Role for Biological Rhythms

Cardiovascular diseases (CVD) are the leading cause of deaths worldwide and their prevalence is continuously increasing. Available treatments may present several side effects and therefore the development of new safer therapeutics is of interest. Phenolic compounds have shown several cardioprotective properties helpful in reducing different CVD risk factors such as inflammation, elevated blood pressure, hyperlipidemia, or endothelial dysfunction. These factors are significantly influenced by biological rhythms which are in fact emerging as key modulators of important metabolic and physiological processes. Thus, increased events of CVD have been observed under circadian rhythm disruption or in winter versus other seasons. These rhythms can also affect the functionality of phenolic compounds. Indeed, different effects have been observed depending on the administration time or under different photoperiods. Therefore, in this review the focus will be on the potential of phenolic compounds as therapeutics to prevent CVD via biological rhythm modulation.

Silencing SIRT5 induces the senescence of UCB-MSCs exposed to TNF-α by reduction of fatty acid β-oxidation and anti-oxidation

Tumor necrosis factor-α (TNF-α) is an inflammatory cytokine involved in cell survival, apoptosis, and homeostasis. However, the regulatory effect of TNF-α on mesenchymal stem cell (MSC) redox regulation remains unknown. The process of delaying the senescence of MSCs and maintaining antioxidation mechanism is important in transplantation therapy to treat inflammatory diseases that result from restricted immunomodulatory effects of senescent MSCs. Thus, we examined the role of TNF-α-mediated signaling and its regulatory mechanisms on the senescence of umbilical cord blood-derived MSCs (UCB-MSCs) and identified its therapeutic efficacy in a collagen-induced arthritis (CIA) mouse model. We found that TNF-α increased fatty acid synthesis and lipid droplet (LD) formation through NF-κB/SREBP1-mediated FASN, SCD1, and DGAT2 expression, which protects UCB-MSCs from oxidative stress against accumulated toxic lipids. Additionally, DGAT2-mediated LD formation was regulated by TNF-α-activated TNF receptor (TNFR)1 signaling. We also found that storage of unsaturated FAs in LDs is regulated by SIRT5-dependent β-oxidation of FAs, which reduces mitochondrial ROS (mtROS) accumulation. Particularly, mtROS homeostasis was maintained by superoxide dismutase 2 (SOD2) upregulation through TNFR2-mediated SIRT5/Nrf2 signaling. In a CIA mouse model, UCB-MSCs transfected with SIRT5 siRNA exhibited reduced therapeutic effects compared with UCB-MSCs transfected with NT siRNA. Overall, the results indicated that SIRT5 plays a central role in protecting TNF-α-induced UCB-MSC senescence through FA β-oxidation and SOD2-mediated antioxidation.

HIGHER SIRT1 IS ASSOCIATED WITH A BETTER BODY COMPOSITION IN MASTER SPRINTERS AND UNTRAINED PEERS

Sirt1 is an enzyme involved in several anti-aging pathways. Associations between Sirt1, age, and body fat (BF) were assessed in master sprinters (MS; n = 35; 50.25 ±5.93 yr.), untrained young non-athletes (UY; n = 32; 23.78 ±3.98 yr.), and untrained middle-aged (UMA; n = 24; 47.29 ±8.04 yr.). BF was assessed using a skinfold protocol, and Sirt1 was measured in plasma by using commercial kits. Sirt1 of MS (17.18 ±4.77 ng/mL) was higher than UMA (6.36 ±2.29 ng/mL; p<0.0001) and did not differ from UY (20.26 ±6.20 ng/mL). Relative BF of MS was lower than UMA (12.71 ±4.07% vs. 22.13 ±4.18%; p<0.0001). Sirt1 was negatively correlated with chronological age (r =-0.735; p<0.0001) when combining UY and UMA in the analysis. However, when Sirt1 of MS and UY were analyzed together, no significant relationship between Sirt1 and chronological age was observed (r= -0.243; p=0.083). Sirt1 correlated inversely with BF (r= -0.743; p<0.0001) for UY and UMA. Stepwise multiple regression revealed that being either a young or master athlete, as well as body adiposity, are possible predictors of Sirt1 levels. MS and UY were associated with higher levels of Sirt1, while UMA and increased BF were associated with lower levels of this enzyme. The relationships among Sirt1, BF, and chronological age of young and middle-aged non-athletes were not statistically significant when the middle-aged participants were MS. These findings suggest possible links between Sirt1 and body composition, which may play roles in the rate of biological aging.Highlights Lower levels of Sirt1 are associated with higher body fat.Master Athlete lifestyle seems to promote higher Sirt1 Levels.

Role of Sirtuins in Physiology and Diseases of the Central Nervous System

Silent information regulators, sirtuins (SIRTs), are a family of enzymes which take part in major posttranslational modifications of proteins and contribute to multiple cellular processes, including metabolic and energetic transformations, as well as regulation of the cell cycle. Recently, SIRTs have gained increased attention as the object of research because of their multidirectional activity and possible role in the complex pathomechanisms underlying human diseases. The aim of this study was to review a current literature evidence of SIRTs' role in the physiology and pathology of the central nervous system (CNS). SIRTs have been demonstrated to be crucial players in the crosstalk between neuroinflammation, neurodegeneration, and metabolic alterations. The elucidation of SIRTs' role in the background of various CNS diseases offers a chance to define relevant markers of their progression and promising candidates for novel therapeutic targets. Possible diagnostic and therapeutic implications from SIRTs-related investigations are discussed, as well as their future directions and associated challenges.

Recent two-year advances in anti-dengue small-molecule inhibitors

Dengue is an acute tropical infectious disease transmitted by mosquitoes, which has posed a major challenge to global public health. Unfortunately, there is a lack of clinically proven dengue-specific drugs for its prevention and treatment. As the pathogenesis of dengue has not been fully elucidated, the development of specific drugs is seriously hindered. This article briefly describes the pathogenesis of dengue fever, the molecular characteristics, and epidemiology of dengue virus, and focuses on the potential small-molecule inhibitors of dengue virus, including on-target and multi-targeted inhibitors, which have been reported in the past two years.

The Association between Clusterin Sialylation Degree and Levels of Oxidative–Antioxidant Balance Markers in Seminal Plasmas and Blood Sera of Male Partners with Abnormal Sperm Parameters

Nearly 30% of infertility cases are caused by male factor. This study aimed at checking the associations between the sialylation degree of glycoprotein clusterin (CLU) and levels of oxidative–antioxidant balance markers in infertile men. Using lectin-ELISA with biotinylated lectins specific to α2,6-linked (Sambucus nigra agglutinin, SNA) and α2,3-linked (Maackia amurensis agglutinin, MAA) sialic acid (SA), the CLU sialylation in 132 seminal plasmas (SP) and 91 blood sera (BS) were analyzed. Oxidative–antioxidant status was measured by determining Sirtuin-3 (SIRT3), Sirtuin-5 (SIRT5), total antioxidant status (TAS), and ferric reducing antioxidant power (FRAP) levels. We indicate that multiple sperm disorders are associated with decreased expression of MAA-reactive SA in SP. Decreased SP SIRT3 concentrations may be associated with teratozoospermia and oligoasthenoteratozoospermia. ROC curve and cluster analysis revealed that SP relative reactivity of CLU glycans with MAA, the value of MAA/SNA ratio, and SIRT3 and SIRT5 concentrations may constitute an additional set of markers differentiating infertile oligoasthenoteratozoospermic patients (OAT) from normozoospermic (N), asthenoteratozoospermic (AT) and teratozoospermic (T). The multinomial logistic regression analysis confirmed the potential utility of SIRT3 determinations for differentiation between N and OAT groups as well as between N and T groups for SIRT3 and SIRT5. For BS, based on ROC curve and cluster analysis, relative reactivities of CLU glycans with SNA, MAA, SIRT3 and FRAP concentrations may be useful in the differentiation of normozoospermic patients from those with sperm disorders. The multinomial logistic regression analysis showed that the SNA relative reactivity with CLU glycans significantly differentiated the N group from AT, OAT and T groups, and FRAP concentrations significantly differed between N and AT groups, which additionally confirms the potential utility of these biomarkers in the differentiation of infertile patients with abnormal sperm parameters. The knowledge about associations between examined parameters may also influence future research aimed at seeking new male infertility therapies.

Obesity, the other pandemic: linking diet and carcinogenesis by epigenetic mechanisms

Both obesity and cancer are complex medical conditions that are considered public health problems. The influence of obesity on the predisposition to develop various types of cancer has been observed in a wide variety of studies. Due to their importance as public health problems, and the close relationship between both conditions, it is important to be able to understand and associate them mechanistically. In this review article, we intend to go a little further, by finding relationships between lifestyle, which can lead a person to develop obesity, and how it influences at the cellular and molecular level, affecting gene expression to favor signaling pathways or transcriptional programs involved in cancer. We describe how products of metabolism and intermediate metabolism can affect chromatin structure, participating in the regulation (or dysregulation) of gene expression, and we show an analysis of genes that are responsive to diets high in sugar and fat, and how their epigenetic landscape is altered.

Obesity II: Establishing causal links between chemical exposures and obesity

Obesity is a multifactorial disease with both genetic and environmental components. The prevailing view is that obesity results from an imbalance between energy intake and expenditure caused by overeating and insufficient exercise. We describe another environmental element that can alter the balance between energy intake and energy expenditure: obesogens. Obesogens are a subset of environmental chemicals that act as endocrine disruptors affecting metabolic endpoints. The obesogen hypothesis posits that exposure to endocrine disruptors and other chemicals can alter the development and function of the adipose tissue, liver, pancreas, gastrointestinal tract, and brain, thus changing the set point for control of metabolism. Obesogens can determine how much food is needed to maintain homeostasis and thereby increase the susceptibility to obesity. The most sensitive time for obesogen action is in utero and early childhood, in part via epigenetic programming that can be transmitted to future generations. This review explores the evidence supporting the obesogen hypothesis and highlights knowledge gaps that have prevented widespread acceptance as a contributor to the obesity pandemic. Critically, the obesogen hypothesis changes the narrative from curing obesity to preventing obesity.

Mitochondrial Sirtuins in Chronic Degenerative Diseases: New Metabolic Targets in Colorectal Cancer

Sirtuins (SIRTs) are a family of class III histone deacetylases (HDACs) consisting of seven members, widely expressed in mammals. SIRTs mainly participate in metabolic homeostasis, DNA damage repair, cell survival, and differentiation, as well as other cancer-related biological processes. Growing evidence shows that SIRTs have pivotal roles in chronic degenerative diseases, including colorectal cancer (CRC), the third most frequent malignant disease worldwide. Metabolic alterations are gaining attention in the context of CRC development and progression, with mitochondrion representing a crucial point of complex and intricate molecular mechanisms. Mitochondrial SIRTs, SIRT2, SIRT3, SIRT4 and SIRT5, control mitochondrial homeostasis and dynamics. Here, we provide a comprehensive review on the latest advances on the role of mitochondrial SIRTs in the initiation, promotion and progression of CRC. A deeper understanding of the pathways by which mitochondrial SIRTs control CRC metabolism may provide new molecular targets for future innovative strategies for CRC prevention and therapy.

Lingonberry Improves Hepatic Lipid Metabolism by Targeting Notch1 Signaling

Impaired hepatic lipid metabolism is a hallmark of non-alcoholic fatty liver disease (NAFLD), which has no effective treatment option. Recently, Notch signaling has been identified as an important mediator of hepatic lipid metabolism. Lingonberry (Vaccinium vitis-idaea L.) is an anthocyanin-rich fruit with significant lipid-lowering properties. In this study, we examined how lingonberry influenced Notch signaling and fatty acid metabolism in a mouse model of NAFLD. Mice (C57BL/6J) fed a high-fat diet (HFD) for 12 weeks developed fatty liver and activated hepatic Notch1 signaling. Lingonberry supplementation inhibited hepatic Notch1 signaling and improved lipid profile by improving the expression of the genes involved in hepatic lipid metabolism. The results were verified using a palmitic-acid-challenged cell model. Similar to the animal data, palmitic acid impaired cellular lipid metabolism and induced Notch1 in HepG2 cells. Lingonberry extract or cyanidin-3-glucoside attenuated Notch1 signaling and decreased intracellular triglyceride accumulation. The inhibition of Notch in the hepatocytes attenuated sterol-regulatory-element-binding-transcription-factor-1 (SREBP-1c)-mediated lipogenesis and increased the expression of carnitine palmitoyltransferase-I-alpha (CPTIα) and acyl-CoA oxidase1 (ACOX1). Taken together, lingonberry’s hepatoprotective effect is mediated by, in part, improving hepatic lipid metabolism via inhibiting Notch1 signaling in HFD-induced fatty liver.

SIRT1: A Key Player in Male Reproduction

Reproduction is the way to immortality for an individual, and it is essential to the continuation of the species. Sirtuins are involved in cellular homeostasis, energy metabolism, apoptosis, age-related problems, and sexual reproduction. Sirtuin 1 (SIRT1) belongs to the sirtuin family of deacetylases, and it is a nicotinamide adenine dinucleotide (NAD)-dependent deacetylase. It removes the acetyl group from a variety of substrates. SIRT1 regulates endocrine/metabolic, reproductive, and placental development by deacetylating histone, different transcription factors, and signal transduction molecules in a variety of cellular processes. It also plays a very important role in the synthesis and secretion of sex hormones via regulating the hypothalamus-pituitary-gonadal (HPG) axis. Moreover, SIRT1 participates in several key stages of spermatogenesis and sperm maturation. The current review will give a thorough overview of SIRT1’s functions in male reproductive processes, thus paving the way for more research on restorative techniques and their uses in reproductive medicine.

The Effect of Antiretroviral Therapy on SIRT1, SIRT3 and SIRT6 Expression in HIV-Infected Patients

Human Immunodeficiency Virus (HIV) infection and the chronic use of combined antiretroviral therapy (cART) may affect the occurrence of certain disturbances in the body. There is growing interest in sirtuins–enzymes involved in the regulation of many metabolic processes in the organism and in the pathogenesis of many diseases which also exhibit potential antiviral activity. The aim of the study was to investigate the connection of cART to the expression of Sirtuin 1 (SIRT1), Sirtuin 3 (SIRT3) and Sirtuin 6 (SIRT6) in HIV-infected men. The plasma levels of sirtuins were measured before and one year after cART, and related to HIV viral load, lymphocytes T CD4+ and CD8+ count as well as the applied cART. The levels of sirtuins in plasma were measured in HIV-infected patients (n = 53) and the control group (n = 35) by immunoassay methods. There were statistically significant (p < 0.05) differences between SIRT6 in the HIV-infected patients before therapy and in the subgroups, depending on the count of lymphocytes T CD8+. There were significant differences in the levels of SIRT1 depending on the applied treatment regimen. The obtained results indicate the most significant changes in the expression of SIRT6 in the course of HIV infection and suggest an influence of the type of cART on the level of SIRT1, which indicates its important role in the course of HIV.

Transcription Factor ChREBP Mediates High Glucose-Evoked Increase in HIF-1α Content in Epithelial Cells of Renal Proximal Tubules

Hyperglycemia/diabetes appears to be accompanied by the state of hypoxia, which especially affects kidneys. The aim of the study was to elucidate the mechanism of high glucose action on HIF-1α expression in renal proximal tubule epithelial cells. The research hypotheses included: (1) the participation of transcription factor ChREBP; and (2) the involvement of the effects resulting from pseudohypoxia, i.e., lowered intracellular NAD+/NADH ratio. The experiments were performed on HK-2 cells and primary cells: D-RPTEC (Diseased Human Renal Proximal Tubule Epithelial Cells—Diabetes Type II) and RPTEC (Renal Proximal Tubule Epithelial Cells). Protein and mRNA contents were determined by Western blot and RT-qPCR, respectively. ChREBP binding to DNA was detected applying chromatin immunoprecipitation, followed by RT-qPCR. Gene knockdown was performed using siRNA. Sirtuin activity and NAD⁺/NADH ratio were measured with commercially available kits. It was found that high glucose in HK-2 cells incubated under normoxic conditions: (1) activated transcription of HIF-1 target genes, elevated HIF-1α and ChREBP content, and increased the efficacy of ChREBP binding to promoter region of HIF1A gene; and (2), although it lowered NAD⁺/NADH ratio, it affected neither sirtuin activity nor HIF-1α acetylation level. The stimulatory effect of high glucose on HIF-1α expression was not observed upon the knockdown of ChREBP encoding gene. Experiments on RPTEC and D-RPTEC cells demonstrated that HIF-1α content in diabetic proximal tubular cells was lower than that in normal ones but remained high glucose-sensitive, and the latter phenomenon was mediated by ChREBP. Thus, it is concluded that the mechanism of high glucose-evoked increase in HIF-1α content in renal proximal tubule endothelial cells involves activation of ChREBP, indirectly capable of HIF1A gene up-regulation.

Profiling sirtuin activity using Copper-free click chemistry

The mammalian sirtuins are a group of posttranslational modification enzymes that remove acyl modifications from lysine residues in an NAD⁺-dependent manner. Although initially proposed as histone deacetylases (HDACs), they are now known to target other cellular enzymes and proteins as well. Sirtuin-catalyzed simple amide hydrolysis has profound biological consequences including suppression of gene expression, promotion of DNA damage repair, and regulation of glucose and lipid metabolism. Human sirtuins have been intensively pursued by both academia and industry as potential therapeutic targets for the treatment of diseases such as cancer and neurodegeneration. To gain a better understanding of their roles in various cellular events, innovative chemical probes are highly sought after. This current study focuses on the development of activity-based chemical probes (ABPs) for the profiling of sirtuin activity in biological samples. Cyclooctyne-containing and azido-containing probes were synthesized to enable the subsequent copper-free "click" conjugation to either a fluorophore or biotin. The two groups of structurally related ABPs demonstrated different labeling efficiency and selectivity: the cyclooctyne-containing probes failed to label recombinant sirtuins to any appreciable level, while the azido-containing ABPs showed good isoform selectivity. The azido-containing ABPs were further analyzed for their ability to label an individual sirtuin isoform in protein mixtures and cell lysates. These biocompatible ABPs allow the study of dynamic cellular protein activity change to become possible.

Sirtuins as Interesting Players in the Course of HIV Infection and Comorbidities

The sirtuins (SIRTs) are a family of enzymes from the group of NAD⁺-dependent deacetylases. Through the reaction of splitting the acetyl group of various transcription factors and histones they regulate many processes in the organism. The activity of sirtuins is linked to metabolic control, oxidative stress, inflammation and apoptosis, and they also affect the course of viral infections. For this reason, they may participate in the pathogenesis and development of many diseases, but little is known about their role in the course of human immunodeficiency virus (HIV) infection, which is the subject of this review. In the course of HIV infection, comorbidities such as: neurodegenerative disorders, obesity, insulin resistance and diabetes, lipid disorders and cardiovascular diseases, renal and bone diseases developed more frequently and faster compared to the general population. The role of sirtuins in the development of accompanying diseases in the course of HIV infection may also be interesting. There is still a lack of detailed information on this subject. The role of sirtuins, especially SIRT1, SIRT3, SIRT6, are indicated to be of great importance in the course of HIV infection and the development of the abovementioned comorbidities.

Is There a Balance in Oxidative-Antioxidant Status in Blood Serum of Patients with Advanced Endometriosis?

Can redox homeostasis indicators be potential non-invasive markers, crucial in the diagnosis and treatment of endometriosis? We checked if the differences in levels of serum oxidative-antioxidant balance parameters (TAS, FRAP, albumin, total bilirubin, uric acid, iron, SIRT3, SIRT5, SIRT6, telomerase, AOPP) are significant between patients with advanced endometriosis (E), healthy women (control group, C) and non-endometriosis women, but with other gynecological disorders (NE). The FRAP concentrations were significantly higher in E and NE group than in the control group (p = 0.015 and p = 0.017, respectively). The telomerase concentrations were significantly higher in the endometriosis group than in the control group (p = 0.004). Significantly higher concentrations of AOPP were observed in E (p < 0.001) and NE groups (p = 0.028) in comparison to the control subjects. Between stages III and IV of endometriosis, a significant difference existed only in concentration of iron (p = 0.013). There were no significant differences between the studied groups in the values of the remaining parameters. Based on the results of ROC curve analysis, we can conclude that the levels of serum FRAP, telomerase and AOPP may be taken into account as promising diagnostics markers that reflect the degree of oxidative stress accompanying advanced endometriosis.

Blood Pressure-Lowering Effect of Wine Lees Phenolic Compounds Is Mediated by Endothelial-Derived Factors: Role of Sirtuin 1

The antihypertensive effect of wine lees powder (WLPW) from a Cabernet grape variety was related to its high content in flavanols and anthocyanins compounds. This study investigates the involvement of endothelial-derived factors and SIRT1 in its bioactivity. Spontaneously hypertensive rats (SHR) were orally administered water or WLPW (125 mg/kg bw). Posteriorly, both groups were intraperitoneally administered saline, Nω-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthesis inhibitor, indomethacin, a prostacyclin synthesis inhibitor, or sirtinol, an inhibitor of sirtuins. Blood pressure (BP) was recorded before and 6 h after WLPW administration. In an additional experiment, SHR were administered water or WLPW and endothelial expressions of eNos, Sirt1, Nox4, and Et1 were determined. The BP-lowering properties of WLPW were abolished by L-NAME and partially reduced by indomethacin, demonstrating that WLPW antihypertensive effect was mediated by changes in NO availability, although prostacyclin also contributed to this activity. Moreover, BP-lowering effect was reduced by sirtinol, indicating that WLPW decreased BP in a SIRT1-dependent manner. Furthermore, WLPW upregulated eNos and Sirt1 and downregulated Nox4 and Et1 endothelial gene expression. These results evidence the vasoprotective effect of WLPW and show that its antihypertensive effect in SHR is endothelium dependent and mediated by SIRT1.

The study of sirtuins in breast cancer patients before and after radiotherapy

Background/aim

Targeting the new and unique proteins is an important medical strategy for treating breast cancer. It is quite important to find out proteins that have a role in the development of cancer. Sirtuins (SIRT) are well related in different physiological activities and connected with cancer. We aimed to determine the effect of radiotherapy on SIRT1 and SIRT2, which have not been yet been clarified as a tumor suppressor or promoter.

Materials and methods

Twenty-two women with nonmetastatic breast cancer enrolled in the study. Blood samples were taken before and after radiotherapy, soluble SIRT1 and SIRT2 levels were determined with ELISA kits.

Results

There was no difference in SIRT1 levels before and after radiotherapy (p = 0.548). SIRT2 levels were significantly found to be decreased after radiotherapy (p = 0.042). There was a strong and positive correlation before radiotherapy (p < 0.001), and a moderate and positive correlation after radiotherapy (p = 0.007) between SIRT1 and SIRT2.

Conclusion

These results suggest that SIRT2 may provide a new strategy for follow-up of breast cancer treatment. Additionally, by emphasizing the importance of SIRT2 in breast cancer, it opens ways to provide grounds for the development of the next generation of SIRT2-specific radiotracers. Finally, the most important thing, in fact, the positive correlation between SIRT1 and SIRT2 both before and after radiotherapy, appears to be clear evidence suggesting more oncogenic roles of sirtuins.

Advances in the role of silence information regulator family in pathological pregnancy

Aberrant maternal inflammation and oxidative stress are the two main mechanisms of pathological pregnancy. The silence information regulator (sirtuin) family is a highly conserved family of nicotinamide adenine dinucleotide (NAD)-dependent deacylases. By regulating the post-translational modification of proteins, sirtuin is involved in various biological processes including oxidative stress and inflammation. Nowadays, emerging evidence indicates that sirtuin may be closely related to the occurrence and development of pathological pregnancy. The down-regulation of sirtuin can cause spontaneous preterm delivery by promoting uterine contraction and rupture of fetal membranes, cause gestational diabetes mellitus through promoting oxidative stress and affecting the activity of key enzymes in glucose metabolism, cause preeclampsia by reducing the proliferation and invasion ability of trophoblasts, cause intrahepatic cholestasis of pregnancy by promoting the production of bile acids and T helper 1 cell (Th1) cytokines, and cause intrauterine growth restriction through inducing mitochondrial dysfunction. Moreover, the expression and activation of sirtuin can be modulated through dietary interventions, thus sirtuin is expected to become a new target for the prevention and treatment of pregnancy complications. This article reviews the role of the sirtuin family in the occurrence and development of pathological pregnancy and its influence on the development of the offspring.