Sirt1 protects against high-fat diet-induced metabolic damage

NAD+ supplementation limits triple-negative breast cancer metastasis via SIRT1-P66Shc signaling

NAD⁺ levels decline with age and in certain disease conditions. NAD⁺ precursors have been shown to stimulate NAD⁺ biosynthesis and ameliorate various age-associated diseases in mouse models. However, NAD⁺ metabolism is complicated in cancer and its role in triple-negative breast cancer (TNBC) remains elusive. Here, we show that NAD⁺ supplement suppresses tumor metastasis in a TNBC orthotopic patient-derived xenograft (PDX) model. Sirtuin1 lysine deacetylase (SIRT1) is required for the effects since SIRT1 knockdown blocks NAD⁺-suppressed tumor metastasis. Overexpression of SIRT1 effectively impairs the metastatic potential of TNBC. Importantly, the interaction between SIRT1 and p66Shc causes the deacetylation and functional inactivation of p66Shc, which inhibits epithelial-mesenchymal transition (EMT). Overall, we demonstrate that NAD⁺ supplementation executes its anti-tumor function via activating the SIRT1-p66Shc axis, which highlights the preventive and therapeutic potential of SIRT1 activators as effective interventions for TNBC.

Selenium-Enriched Probiotic Alleviates Western Diet-Induced Non-alcoholic Fatty Liver Disease in Rats via Modulation of Autophagy Through AMPK/SIRT-1 Pathway

Current study was aimed to investigate the ability of L.acidophilus SNZ 86 to biotransform inorganic selenium to a more active organic form, resulting in trace element enrichment. Selenium-enriched L. acidophilus SNZ 86 has been shown to be effective in the treatment of a variety of gastrointestinal illnesses, indicating the need for additional research to determine the full potential of this therapeutic strategy in the treatment of metabolic disorders. Herein, we employed the western style diet-induced model of non-alcoholic fatty liver disease (NAFLD) to explore the therapeutic effect of selenium-enriched probiotic (SP). Male Sprague Dawley rats (160-180 g) were fed a high-fat (58% Kcal of fat) and high-fructose (30% w/v) diet for 12 weeks to develop an animal model mimicking NAFLD. High-fat and High-fructose diet-fed rats exhibited hyperglycemia, hyperlipidemia, insulin resistance, abnormal liver function test, increased hepatic oxidative stress, and steatosis. SP was then administered orally (L acidophilus 1 × 10⁹ CFU/ml containing 0.4 g Se/day; p.o.) for 8 weeks. The selenium enrichment within L. acidophilus SNZ 86 was validated by TEM, which allowed for visualisation of the selenium deposition and size distribution in the probiotic. In NAFLD control rats, the expression of autophagy proteins (LC-3 A/B and Beclin), AMPK, and SIRT-1 was significantly reduced indicating downregulation of autophagy. However, supplementation of SP ameliorates hepatic steatosis as evidenced by improved biochemical markers and autophagic activation via upregulation of the AMPK and SIRT-1 pathway showing the relevance of autophagy in the disease aetiology. Collectively, these findings provide us with a better understanding of the role of SP in the treatment of hepatic steatosis and establish a therapeutic basis for potential clinical application of SP in the prevention of NAFLD and associated pathological conditions.

Multifaceted Influence of Histone Deacetylases on DNA Damage Repair: Implications for Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most commonly diagnosed cancers and a leading cause of cancer-related mortality worldwide, but its pathogenesis remains largely unknown. Nevertheless, genomic instability has been recognized as one of the facilitating characteristics of cancer hallmarks that expedites the acquisition of genetic diversity. Genomic instability is associated with a greater tendency to accumulate DNA damage and tumor-specific DNA repair defects, which gives rise to gene mutations and chromosomal damage and causes oncogenic transformation and tumor progression. Histone deacetylases (HDACs) have been shown to impair a variety of cellular processes of genome stability, including the regulation of DNA damage and repair, reactive oxygen species generation and elimination, and progression to mitosis. In this review, we provide an overview of the role of HDAC in the different aspects of DNA repair and genome instability in HCC as well as the current progress on the development of HDAC-specific inhibitors as new cancer therapies.

Histone lysine methyltransferase-related neurodevelopmental disorders: current knowledge and saRNA future therapies

Neurodevelopmental disorders encompass a group of debilitating diseases presenting with motor and cognitive dysfunction, with variable age of onset and disease severity. Advances in genetic diagnostic tools have facilitated the identification of several monogenic chromatin remodeling diseases that cause Neurodevelopmental disorders. Chromatin remodelers play a key role in the neuro-epigenetic landscape and regulation of brain development; it is therefore not surprising that mutations, leading to loss of protein function, result in aberrant neurodevelopment. Heterozygous, usually de novo mutations in histone lysine methyltransferases have been described in patients leading to haploinsufficiency, dysregulated protein levels and impaired protein function. Studies in animal models and patient-derived cell lines, have highlighted the role of histone lysine methyltransferases in the regulation of cell self-renewal, cell fate specification and apoptosis. To date, in depth studies of histone lysine methyltransferases in oncology have provided strong evidence of histone lysine methyltransferase dysregulation as a determinant of cancer progression and drug resistance. As a result, histone lysine methyltransferases have become an important therapeutic target for the treatment of different cancer forms. Despite recent advances, we still lack knowledge about the role of histone lysine methyltransferases in neuronal development. This has hampered both the study and development of precision therapies for histone lysine methyltransferases-related Neurodevelopmental disorders. In this review, we will discuss the current knowledge of the role of histone lysine methyltransferases in neuronal development and disease progression. We will also discuss how RNA-based technologies using small-activating RNAs could potentially provide a novel therapeutic approach for the future treatment of histone lysine methyltransferase haploinsufficiency in these Neurodevelopmental disorders, and how they could be first tested in state-of-the-art patient-derived neuronal models.

A Therapeutically Targetable NOTCH1-SIRT1-KAT7 Axis in T-cell Leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is a NOTCH1-driven disease in need of novel therapies. Here, we identify a NOTCH1-SIRT1-KAT7 link as a therapeutic vulnerability in T-ALL, in which the histone deacetylase SIRT1 is overexpressed downstream of a NOTCH1-bound enhancer. SIRT1 loss impaired leukemia generation, whereas SIRT1 overexpression accelerated leukemia and conferred resistance to NOTCH1 inhibition in a deacetylase-dependent manner. Moreover, pharmacologic or genetic inhibition of SIRT1 resulted in significant antileukemic effects. Global acetyl proteomics upon SIRT1 loss uncovered hyperacetylation of KAT7 and BRD1, subunits of a histone acetyltransferase complex targeting H4K12. Metabolic and gene-expression profiling revealed metabolic changes together with a transcriptional signature resembling KAT7 deletion. Consistently, SIRT1 loss resulted in reduced H4K12ac, and overexpression of a nonacetylatable KAT7-mutant partly rescued SIRT1 loss-induced proliferation defects. Overall, our results uncover therapeutic targets in T-ALL and reveal a circular feedback mechanism balancing deacetylase/acetyltransferase activation with potentially broad relevance in cancer.

SIGNIFICANCE

We identify a T-ALL axis whereby NOTCH1 activates SIRT1 through an enhancer region, and SIRT1 deacetylates and activates KAT7. Targeting SIRT1 shows antileukemic effects, partly mediated by KAT7 inactivation. Our results reveal T-ALL therapeutic targets and uncover a rheostat mechanism between deacetylase/acetyltransferase activities with potentially broader cancer relevance. This article is highlighted in the In This Issue feature, p. 1.

Raphanus sativus L. var. caudatus Extract Alleviates Impairment of Lipid and Glucose Homeostasis in Liver of High-Fat Diet-Induced Obesity and Insulin Resistance in Mice

The present study investigated the activities of Raphanus sativus L. var. caudatus extract (RS) on abnormal lipid and glucose homeostasis in a high-fat diet (HFD)-induced obesity and insulin resistance in a mouse model. Institute of Cancer Research mice were rendered obese by 16-week HFD feeding. Obese mice were administered with 100 or 200 mg/kg/d RS orally during the last 8 weeks of diet feeding. Then, the biochemical parameters were determined. The gene and protein expressions regulating lipid and glucose homeostasis in the liver were measured. This study revealed that the state of hyperglycemia, hyperleptinemia, hyperinsulinemia, and hyperlipidemia was reduced after 8 weeks of RS treatment (100 or 200 mg/kg). Administration of RS also improved insulin sensitivity and increased serum adiponectin. The liver total cholesterol and triglyceride concentrations were decreased by both doses of RS. Notably, a decrease in the expression of liver-specific genes, including sterol regulatory element-binding protein 1c, fatty acid synthase, and acetyl-CoA carboxylase, was found in the RS-treated groups. Moreover, administration of RS showed a significant increase in the expression of adenosine monophosphate-activated protein kinase (AMPK) phosphorylation and sirtuin1 (Sirt1) proteins. These findings indicated that RS improved abnormal lipid and glucose homeostasis in the liver of obesity-associated insulin resistance mouse model, possibly through the stimulation of the AMPK/Sirt1 pathway.

The sirtuin family in health and disease

Sirtuins (SIRTs) are nicotine adenine dinucleotide(+)-dependent histone deacetylases regulating critical signaling pathways in prokaryotes and eukaryotes, and are involved in numerous biological processes. Currently, seven mammalian homologs of yeast Sir2 named SIRT1 to SIRT7 have been identified. Increasing evidence has suggested the vital roles of seven members of the SIRT family in health and disease conditions. Notably, this protein family plays a variety of important roles in cellular biology such as inflammation, metabolism, oxidative stress, and apoptosis, etc., thus, it is considered a potential therapeutic target for different kinds of pathologies including cancer, cardiovascular disease, respiratory disease, and other conditions. Moreover, identification of SIRT modulators and exploring the functions of these different modulators have prompted increased efforts to discover new small molecules, which can modify SIRT activity. Furthermore, several randomized controlled trials have indicated that different interventions might affect the expression of SIRT protein in human samples, and supplementation of SIRT modulators might have diverse impact on physiological function in different participants. In this review, we introduce the history and structure of the SIRT protein family, discuss the molecular mechanisms and biological functions of seven members of the SIRT protein family, elaborate on the regulatory roles of SIRTs in human disease, summarize SIRT inhibitors and activators, and review related clinical studies.

The Ethanolic Extract of Lindera aggregata Modulates Gut Microbiota Dysbiosis and Alleviates Ethanol-Induced Acute Liver Inflammation and Oxidative Stress SIRT1/Nrf2/NF-κB Pathway

This study is an attempt to evaluate the therapeutic effect of the ethanolic extract of Lindera aggregata on the liver and intestinal microbiota in rats with alcohol-induced liver injury (ALI). Rats were treated with 70 mg probiotics, 1 g/kg, 2 g/kg, and 3 g/kg ethanolic extract of Lindera aggregata, respectively, for 10 days. We found that Lindera aggregata could significantly reduce the biochemical parameters in the serum of ALD rats. Lindera aggregata alleviates oxidative stress and inflammation by upregulating SIRT1 and Nrf2 and downregulating COX2 and NF-κB. The results of 16S rRNA gene sequencing showed that the medium dose of Lindera aggregata had the best effect on the growth of beneficial bacteria. Diversity analysis and LEfSe analysis showed that beneficial bacteria gradually occupied the dominant niche. The relative abundance of potential pathogens in the gut decreased significantly. We demonstrated that the ethanolic extract of Lindera aggregata can alleviate the oxidative stress and inflammation induced by alcohol through the SIRT1/Nrf2/NF-κB pathway and can modulate the disturbance of gut microbiota induced by alcohol intake.

Ketogenic Diet Increases Serum and White Adipose Tissue SIRT1 Expression in Mice

Overnutrition and its sequelae have become a global concern due to the increasing incidence of obesity and insulin resistance. A ketogenic diet (KD) is widely used as a dietary treatment for metabolic disorders. Sirtuin1 (SIRT1), a metabolic sensor which regulates fat homeostasis, is modulated by dietary interventions. However, the influence of nutritional ketosis on SIRT1 is still debated. We examined the effect of KD on adipose tissue, liver, and serum levels of SIRT1 in mice. Adult C57BL/6J male mice were randomly assigned to two isocaloric dietary groups and fed with either high-fat KD or normal chow (NC) for 4 weeks. Serum SIRT1, beta-hydroxybutyrate (βHB), glucose, and triglyceride levels, as well as SIRT1 expression in visceral (VAT), subcutaneous (SAT), and brown (BAT) adipose tissues, and in the liver, were measured. KD-fed mice showed an increase in serum βHB in parallel with serum SIRT1 (r = 0.732, p = 0.0156), and increased SIRT1 protein expression in SAT and VAT. SIRT1 levels remained unchanged in BAT and in the liver, which developed steatosis. Normal glycemia and triglycerides were observed. Under a KD, serum and white fat phenotypes show higher SIRT1, suggesting that one of the molecular mechanisms underlying a KD's potential benefits on metabolic health involves a synergistic interaction with SIRT1.

Enhancing SIRT1 Gene Expression Using Small Activating RNAs: A Novel Approach for Reversing Metabolic Syndrome

Metabolic syndrome (MetS) is a pathological condition characterized by abdominal obesity, insulin resistance, hypertension, and hyperlipidemia. Sirtuin 1 (SIRT1), a highly conserved histone deacetylase, is characterized as a key metabolic regulator and protector against aging-associated pathologies, including MetS. In this study, we investigate the therapeutic potential of activating SIRT1 using small activating RNAs (saRNA), thereby reducing inflammatory-like responses and re-establishing normal lipid metabolism. SIRT1 saRNA significantly increased SIRT1 messenger RNA (mRNA) and protein levels in both lipopolysaccharide-stimulated and nonstimulated macrophages. SIRT1 saRNA significantly decreased inflammatory-like responses, by reducing mRNA levels of key inflammatory cytokines, such as Tumor Necrosis Factor alpha, Interleukin 1 beta (IL-1β), Interleukin 6 (IL-6), and chemokines Monocyte Chemoattractant Protein-1 and keratinocyte chemoattractant. SIRT1 overexpression also significantly reduced phosphorylation of nuclear factor-κB and c-Jun N-terminal kinase, both key signaling molecules for the inflammatory pathway. To investigate the therapeutic effect of SIRT1 upregulation, we treated a high-fat diet model with SIRT1 saRNA conjugated to a transferrin receptor aptamer for delivery to the liver and cellular internalization. Animals in the SIRT1 saRNA treatment arm demonstrated significantly decreased weight gain with a significant reduction in white adipose tissue, triglycerides, fasting glucose levels, and intracellular lipid accumulation. These suggest treatment-induced changes to lipid and glucose metabolism in the animals. The results of this study demonstrate that targeted activation of SIRT1 by saRNAs is a potential strategy to reverse MetS.

Mouse promyelocytic leukemia zinc finger protein (PLZF) regulates hepatic lipid and glucose homeostasis dependent on SIRT1

Previous studies have demonstrated that promyelocytic leukemia zinc finger protein (PLZF) promotes the expression of gluconeogenic genes and hepatic glucose output, which leads to hyperglycemia. However, the role played by PLZF in regulating lipid metabolism is not known. In this study, we aimed to examine the function of PLZF in regulating hepatic lipid and glucose homeostasis and the underlying mechanisms. The expression of PLZF was determined in different mouse models with regard to non-alcoholic fatty liver disease (NAFLD). In the next step, adenoviruses that express PLZF (Ad-PLZF) or PLZF-specific shRNA (Ad-shPLZF) were utilized to alter PLZF expression in mouse livers and in primary hepatocytes. For the phenotype of the fatty liver, histologic and biochemical analyses of hepatic triglyceride (TG), serum TG and cholesterol levels were carried out. The underlying molecular mechanism for the regulation of lipid metabolism by PLZF was further explored using luciferase reporter gene assay and ChIP analysis. The results demonstrated that PLZF expression was upregulated in livers derived from ob/ob, db/db and diet-induced obesity (DIO) mice. Liver PLZF-overexpressing C57BL/6J mice showed fatty liver phenotype, liver inflammation, impaired glucose tolerance and insulin sensitivity. On the other hand, hepatic PLZF knockdown in db/db and DIO mice alleviated hepatic steatosis. Of note, we found that PLZF activates SREBP-1c gene transcription through binding directly to the promoter fragment of this gene, which would induce a repressor-to-activator conversion depending on its interaction with SIRT1 in the role played by PLZF in the transcription process through deacetylation. Thus, PLZF is identified as an essential regulator of hepatic lipid and glucose metabolism, where the modulation of its liver expression could open up a therapeutic path for treating NAFLD.

Gastric Bypass Resolves Metabolic Dysfunction-Associated Fatty Liver Disease (MAFLD) in Low-BMI Patients: A Prospective Cohort Study

OBJECTIVE

Metabolic dysfunction-associated fatty liver disease (MAFLD) reflects the multifactorial pathogenesis of fatty liver disease in metabolically sick patients. The effects of metabolic surgery on MAFLD have not been investigated. This study assesses the impact of Roux-en-Y gastric bypass (RYGB) on MAFLD in a prototypical cohort outside the guidelines for obesity surgery.

METHODS

Twenty patients were enrolled in this prospective, single-arm trial investigating the effects of RYGB on advanced metabolic disease (DRKS00004605). Inclusion criteria were an insulin-dependent type 2 diabetes, body mass index of 25 to 35 kg/m 2 , glucagon-stimulated C-peptide of >1.5 ng/mL, glycated hemoglobin >7%, and age 18 to 70 years. A RYGB with intraoperative liver biopsies and follow-up liver biopsies 3 years later was performed. Steatohepatitis was assessed by expert liver pathologists. Data were analyzed using the Wilcoxon rank sum test and a P value <0.05 was defined as significant.

RESULTS

MAFLD completely resolved in all patients 3 years after RYGB while fibrosis improved as well. Fifty-five percent were off insulin therapy with a significant reduction in glycated hemoglobin (8.45±0.27% to 7.09±0.26%, P =0.0014). RYGB reduced systemic and hepatic nitrotyrosine levels likely through upregulation of NRF1 and its dependent antioxidative and mitochondrial genes. In addition, central metabolic regulators such as SIRT1 and FOXO1 were upregulated while de novo lipogenesis was reduced and β-oxidation was improved in line with an improvement of insulin resistance. Lastly, gastrointestinal hormones and adipokines secretion were changed favorably.

CONCLUSIONS

RYGB is a promising therapy for MAFLD even in low-body mass index patients with insulin-treated type 2 diabetes with complete histologic resolution. RYGB restores the oxidative balance, adipose tissue function, and gastrointestinal hormones.

Crosstalk between Sirtuins and Nrf2: SIRT1 activators as emerging treatment for diabetic neuropathy

About 50% of the diabetic patients worldwide suffer from Diabetic peripheral neuropathy (DPN) which is characterized by chronic pain and loss of sensation, frequent foot ulcerations, and risk for amputation. Numerous factors like hyperglycemia, oxidative stress (OS), impaired glucose signaling, inflammatory responses, neuronal cell death are known to be the various mechanisms underlying DACD and DPN. Development of tolerance, insufficient and inadequate relief and potential toxicity of classical antinociceptives still remains a challenge in the clinical setting. Therefore, there is an emerging need for novel treatments which are both without any potential side effects as well as which focus more on the pathophysiological mechanisms underlying the disease. Also, sirtuins are known to deacetylate Nrf2 and contribute to its action of reducing ROS by generation of anti-oxidant enzymes. Therefore, targeting sirtuins could be a favourable therapeutic strategy to treat diabetic neuropathy by reducing ROS and thereby alleviating OS in DPN. In the present review, we outline the potential use of SIRT1 activators as therapeutic alternatives in treating DPN. We have tried to highlight how sirtuins are interlinked with Nrf2 and NF-κB and put forth how SIRT activators could serve as potential therapy for DPN.

Sirtuins are Not Conserved Longevity Genes

It is central to biology that sequence conservation suggests functional conservation. Animal longevity is an emergent property of selected traits that integrates capacities to perform physical and mental functions after reproductive maturity. Though the yeast SIR2 gene was nominated as a longevity gene based on extended replicative longevity of old mother cells, this is not a selected trait: SIR2 is selected against in chronological aging and the direct targets of SIR2 in replicative lifespan are not conserved. Though it would be difficult to imagine how a gene that advantages 1 in 5 million yeast cells could have anticipated causes of aging in animals, overexpression of SIR2 homologs was tested in invertebrates for longevity. Because artifactual positive results were reported years before they were sorted out and because it was not known that SIR2 functions as a pro-aging gene in yeast chronological aging and in flies subject to amino acid deprivation, a global pursuit of longevity phenotypes was driven by a mixture of framing bias, confirmation bias and hype. Review articles that propagate these biases are so rampant that few investigators have considered how weak the case ever was for sirtuins as longevity genes. Acknowledging that a few positive associations between sirtuins and longevity have been identified after thousands of person-years and billions of dollars of effort, we review the data and suggest rejection of the notions that sirtuins 1) have any specific connection to lifespan in animals and 2) are primary mediators of the beneficial effects of NAD repletion.

Nicotinamide riboside kinase 1 protects against diet and age-induced pancreatic β-cell failure

OBJECTIVE

Disturbances in NAD⁺ metabolism have been described as a hallmark for multiple metabolic and age-related diseases, including type 2 diabetes. While alterations in pancreatic β-cell function are critical determinants of whole-body glucose homeostasis, the role of NAD⁺ metabolism in the endocrine pancreas remains poorly explored. Here, we aimed to evaluate the role of nicotinamide riboside (NR) metabolism in maintaining NAD⁺ levels and pancreatic β-cell function in pathophysiological conditions.

METHODS

Whole body and pancreatic β-cell-specific NRK1 knockout (KO) mice were metabolically phenotyped in situations of high-fat feeding and aging. We also analyzed pancreatic β-cell function, β-cell mass and gene expression.

RESULTS

We first demonstrate that NRK1, the essential enzyme for the utilization of NR, is abundantly expressed in pancreatic β-cells. While NR treatment did not alter glucose-stimulated insulin secretion in pancreatic islets from young healthy mice, NRK1 knockout mice displayed glucose intolerance and compromised β-cells response to a glucose challenge upon high-fat feeding or aging. Interestingly, β cell dysfunction stemmed from the functional failure of other organs, such as liver and kidney, and the associated changes in circulating peptides and hormones, as mice lacking NRK1 exclusively in β-cells did not show altered glucose homeostasis.

CONCLUSIONS

This work unveils a new physiological role for NR metabolism in the maintenance of glucose tolerance and pancreatic β-cell function in high-fat feeding or aging conditions.

Daytime restriction of feeding prevents illuminated night-induced impairment of metabolism and sleep in diurnal zebra finches

We investigated whether nocturnal eating was causal to the impairment of metabolism and sleep disruption in diurnal animals exposed to illuminated nights. Adult zebra finches hatched and raised in 12 h light: 12 h darkness (LD) were exposed to 5-lux dim light at night (dLAN, two groups), with a control group maintained on LD. For the next 3 weeks, the food availability to one of the dLAN groups was restricted to the 12 h light period (dLAN -F); the other dLAN (dLAN +F) and LD groups were continued on ad lib feeding. In spite of similar food intakes, dLAN +F condition led to the fat accumulation and weight gain. These birds showed concurrent changes in hepatic expression of genes associated with carbohydrate and lipid metabolism, suggesting an enhanced gluconeogenesis and impaired fatty acids synthesis. Increased sirt1 mRNA levels indicated the activation of molecular mechanisms to counter-balance the metabolic damage under dLAN +F. Furthermore, reduced bout length and total duration of the nocturnal sleep suggested a poorer sleep in dLAN +F condition. Negative sleep effects of dLAN were supported by the lower hypothalamic expression of sleep promoting sik3 and camkii genes, and higher mRNA expression of awake promoting achm3 gene in dLAN +F, compared to the LD condition. Importantly, dLAN-induced negative effects in metabolism and sleep were alleviated in the dLAN -F group. These results suggest the role of timed feeding in alleviating the negative impact of illuminated nights in metabolism and sleep in diurnal zebra finches.

Stress-Induced Premature Senescence Related to Oxidative Stress in the Developmental Programming of Nonalcoholic Fatty Liver Disease in a Rat Model of Intrauterine Growth Restriction

Metabolic syndrome (MetS) refers to cardiometabolic risk factors, such as visceral obesity, dyslipidemia, hyperglycemia/insulin resistance, arterial hypertension and non-alcoholic fatty liver disease (NAFLD). Individuals born after intrauterine growth restriction (IUGR) are particularly at risk of developing metabolic/hepatic disorders later in life. Oxidative stress and cellular senescence have been associated with MetS and are observed in infants born following IUGR. However, whether these mechanisms could be particularly associated with the development of NAFLD in these individuals is still unknown. IUGR was induced in rats by a maternal low-protein diet during gestation versus. a control (CTRL) diet. In six-month-old offspring, we observed an increased visceral fat mass, glucose intolerance, and hepatic alterations (increased transaminase levels, triglyceride and neutral lipid deposit) in male rats with induced IUGR compared with the CTRL males; no differences were found in females. In IUGR male livers, we identified some markers of stress-induced premature senescence (SIPS) (lipofuscin deposit, increased protein expression of p21WAF, p16INK4a and Acp53, but decreased pRb/Rb ratio, foxo-1 and sirtuin-1 protein and mRNA expression) associated with oxidative stress (higher superoxide anion levels, DNA damages, decreased Cu/Zn SOD, increased catalase protein expression, increased nfe2 and decreased keap1 mRNA expression). Impaired lipogenesis pathways (decreased pAMPK/AMPK ratio, increased pAKT/AKT ratio, SREBP1 and PPARγ protein expression) were also observed in IUGR male livers. At birth, no differences were observed in liver histology, markers of SIPS and oxidative stress between CTRL and IUGR males. These data demonstrate that the livers of IUGR males at adulthood display SIPS and impaired liver structure and function related to oxidative stress and allow the identification of specific therapeutic strategies to limit or prevent adverse consequences of IUGR, particularly metabolic and hepatic disorders.

Nucleolar protein NOC4L inhibits tumorigenesis and progression by attenuating SIRT1-mediated p53 deacetylation

SIRT1 is an NAD⁺-dependent deacetylase and plays an important role in the deacetylation of both histone and non-histone proteins. Many studies revealed that SIRT1 is upregulated in a variety of tumors and tightly associated with tumorigenesis and cancer progression, but the detailed underlying mechanism of the biological processes remains unclarified. In the present study, we found a nucleolar protein NOC4L, human ortholog of yeast Noc4p, which is essential for the nuclear export of the ribosomal 40S subunit and could bind to SIRT1 to inhibit SIRT1 mediated deacetylation of p53. NOC4L interacts with SIRT1 in variety of cells under nucleolar stress and directly interacts with SIRT1 in vitro. Furthermore, we determined the C-terminal of NOC4L and the catalytic domain of SIRT1 were required for their interaction. Overexpression of NOC4L did not change the protein levels of SIRT1 or p53, but increased the acetylation of p53 and promoted cell apoptosis. Additionally, NOC4L inhibited tumor cell proliferation in a p53-dependent manner and restrained tumor growth in a nude mice xenograft model. Clinically, colorectal cancer patients with the high expression of NOC4L had a better prognosis as TP53 was normally expressed, but no significant difference was observed in survival with mutant TP53. Taken together, our results identified a novel SIRT1 regulatory protein and broaden our understanding of the molecular mechanism of how nucleolar protein NOC4L regulates p53 under nucleolar stress. This research provides an insight into tumorigenesis and cell self-protection in the early stage of DNA damage.

Gut-Flora-Dependent Metabolite Trimethylamine-N-Oxide Promotes Atherosclerosis-Associated Inflammation Responses by Indirect ROS Stimulation and Signaling Involving AMPK and SIRT1

Trimethylamine-N-oxide (TMAO), a gut-microbiota-dependent metabolite after ingesting dietary choline, has been identified as a novel risk factor for atherosclerosis through inducing vascular inflammation. However, the underlying molecular mechanism is poorly understood. Using an in vitro vascular cellular model, we found that the TMAO-induced inflammation responses were correlated with an elevation of ROS levels and downregulation of SIRT1 expression in VSMCs and HUVECs. The overexpression of SIRT1 could abrogate both the stimulation of ROS and inflammation. Further studies revealed that AMPK was also suppressed by TMAO and was a mediator upstream of SIRT1. Activation of AMPK by AICAR could reduce TMAO-induced ROS and inflammation. Moreover, the GSH precursor NAC could attenuate TMAO-induced inflammation. In vivo studies with mice models also showed that choline-induced production of TMAO and the associated glycolipid metabolic changes leading to atherosclerosis could be relieved by NAC and a probiotic LP8198. Collectively, the present study revealed an unrecognized mechanistic link between TMAO and atherosclerosis risk, and probiotics ameliorated TMAO-induced atherosclerosis through affecting the gut microbiota. Consistent with previous studies, our data confirmed that TMAO could stimulate inflammation by modulating cellular ROS levels. However, this was not due to direct cytotoxicity but through complex signaling pathways involving AMPK and SIRT1.

Balancing NAD+ deficits with nicotinamide riboside: therapeutic possibilities and limitations

Alterations in cellular nicotinamide adenine dinucleotide (NAD+) levels have been observed in multiple lifestyle and age-related medical conditions. This has led to the hypothesis that dietary supplementation with NAD+ precursors, or vitamin B3s, could exert health benefits. Among the different molecules that can act as NAD+ precursors, Nicotinamide Riboside (NR) has gained most attention due to its success in alleviating and treating disease conditions at the pre-clinical level. However, the clinical outcomes for NR supplementation strategies have not yet met the expectations generated in mouse models. In this review we aim to provide a comprehensive view on NAD+ biology, what causes NAD+ deficits and the journey of NR from its discovery to its clinical development. We also discuss what are the current limitations in NR-based therapies and potential ways to overcome them. Overall, this review will not only provide tools to understand NAD+ biology and assess its changes in disease situations, but also to decide which NAD+ precursor could have the best therapeutic potential.

Notch-activated mesenchymal stromal/stem cells enhance the protective effect against acetaminophen-induced acute liver injury by activating AMPK/SIRT1 pathway

Background

Notch signaling plays important roles in regulating innate immunity. However, little is known about the role of Notch in mesenchymal stromal/stem cell (MSC)-mediated immunomodulation during liver inflammatory response.

Methods

Notch activation in human umbilical cord-derived MSCs was performed by a tissue culture plate coated with Notch ligand, recombinant human Jagged1 (JAG1). Mice were given intravenous injection of Notch-activated MSCs after acetaminophen (APAP)-induced acute liver injury. Liver tissues were collected and analyzed by histology and immunohistochemistry.

Results

MSC administration reduced APAP-induced hepatocellular damage, as manifested by decreased serum ALT levels, intrahepatic macrophage/neutrophil infiltration, hepatocellular apoptosis and proinflammatory mediators. The anti-inflammatory activity and therapeutic effects of MSCs were greatly enhanced by Notch activation via its ligand JAG1. However, Notch2 disruption in MSCs markedly diminished the protective effect of MSCs against APAP-induced acute liver injury, even in the presence of JAG1 pretreatment. Strikingly, Notch-activated MSCs promoted AMP-activated protein kinase (AMPKα) phosphorylation, increased the sirtuins 1 (SIRT1) deacetylase expression, but downregulated spliced X-box-binding protein 1 (XBP1s) expression and consequently reduced NLR family pyrin domain-containing 3 (NLRP3) inflammasome activation. Furthermore, SIRT1 disruption or XBP1s overexpression in macrophages exacerbated APAP-triggered liver inflammation and augmented NLRP3/caspase-1 activity in MSC-administrated mice. Mechanistic studies further demonstrated that JAG1-pretreated MSCs activated Notch2/COX2/PGE2 signaling, which in turn induced macrophage AMPK/SIRT1 activation, leading to XBP1s deacetylation and inhibition of NLRP3 activity.

Conclusions

Activation of Notch2 is required for the ability of MSCs to reduce the severity of APAP-induced liver damage in mice. Our findings underscore a novel molecular insights into MSCs-mediated immunomodulation by activating Notch2/COX2/AMPK/SIRT1 pathway and thus provide a new strategy for the treatment of liver inflammatory diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02999-6.

Implications of Resveratrol in Obesity and Insulin Resistance: A State-of-the-Art Review

Background: Resveratrol is a polyphenol chemical that naturally occurs in many plant-based dietary products, most notably, red wine. Discovered in 1939, widespread interest in the potential health benefits of resveratrol emerged in the 1970s in response to epidemiological data on the cardioprotective effects of wine. Objective: To explore the background of resveratrol (including its origins, stability, and metabolism), the metabolic effects of resveratrol and its mechanisms of action, and a potential future role of dietary resveratrol in the lifestyle management of obesity. Data sources: We performed a narrative review, based on relevant articles written in English from a Pubmed search, using the following search terms: “resveratrol”, “obesity”, “Diabetes Mellitus”, and “insulin sensitivity”. Results: Following its ingestion, resveratrol undergoes extensive metabolism. This includes conjugation (with sulfate and glucuronate) within enterocytes, hydrolyzation and reduction within the gut through the action of the microbiota (with the formation of metabolites such as dihydroresveratrol), and enterohepatic circulation via the bile. Ex vivo studies on adipose tissue reveal that resveratrol inhibits adipogenesis and prevents the accumulation of triglycerides through effects on the expression of Peroxisome Proliferator-activated Receptor γ (PPARγ) and sirtuin 1, respectively. Furthermore, resveratrol induces anti-inflammatory effects, supported by data from animal-based studies. Limited data from human-based studies reveal that resveratrol improves insulin sensitivity and fasting glucose levels in patients with Type 2 Diabetes Mellitus and may improve inflammatory status in human obesity. Although numerous mechanisms may underlie the metabolic benefits of resveratrol, evidence supports a role in its interaction with the gut microbiota and modulation of protein targets, including sirtuins and proteins related to nitric oxide, insulin, and nuclear hormone receptors (such as PPARγ). Conclusions: Despite much interest, there remain important unanswered questions regarding its optimal dosage (and how this may differ between and within individuals), and possible benefits within the general population, including the potential for weight-loss and improved metabolic function. Future studies should properly address these important questions before we can advocate the widespread adoption of dietary resveratrol supplementation.

Atherosclerosis Plaque Reduction by Lycopene Is Mediated by Increased Energy Expenditure through AMPK and PPARα in ApoE KO Mice Fed with a High Fat Diet

Lycopene is a carotenoid found in tomatoes that has potent antioxidant activity. The Mediterranean diet is particularly rich in lycopene, which has well-known beneficial effects on cardiovascular health. We tested the effects of lycopene extract in a group of 20 ApoE knockout mice, fed with a high fat western diet for 14 weeks. Starting from week 3 and up to week 14, the mice were randomly divided into two groups that received lycopene (n = 10) by oral suspension every day at the human equivalent dose of 60 mg/day (0.246 mg/mouse/day), or the vehicle solution (n = 10). The lycopene administration reduced triglycerides and cholesterol blood levels starting from week 6 and continuing through to the end of the experiment (p < 0.001). This reduction was mediated by an enhanced liver expression of PPAR-α and AMPK-α and reduced SREBP levels (p < 0.0001). As a histological red-out, the extent of atherosclerotic plaques and the intima−media thickness in the aorta were significantly reduced by lycopene. In this context, lycopene augmented the Nrf-2 positivity staining in the endothelium, thereby confirming that its antioxidant activity was mediated by this nuclear factor. The positive results obtained in this pre-clinical model further support the use of lycopene extracts to reduce atherosclerosis.

Non-alcoholic Fatty Liver Disease and Liver Fibrosis during Aging

Non-alcoholic fatty liver disease (NAFLD) and its progressive form non-alcoholic steatohepatitis (NASH) have emerged as the leading causes of chronic liver disease-related mortality. The prevalence of NAFLD/NASH is expected to increase given the epidemics of obesity and type 2 diabetes mellitus. Older patients are disproportionally affected by NASH and related complications such as progressive fibrosis, cirrhosis and hepatocellular carcinoma; however, they are often ineligible for liver transplantation due to their frailty and comorbidities, and effective medical treatments are still lacking. In this review we focused on pathways that are key to the aging process in the liver and perpetuate NAFLD/NASH, leading to fibrosis. In addition, we highlighted recent findings and cross-talks of normal and/or senescent liver cells, dysregulated nutrient sensing, proteostasis and mitochondrial dysfunction in the framework of changing metabolic milieu. Better understanding these pathways during preclinical and clinical studies will be essential to design novel and specific therapeutic strategies to treat NASH in the elderly.

Sirtuins as therapeutic targets for improving delayed wound healing in diabetes

Sirtuins are a vast family of histone deacetylases, which are NAD⁺ dependent enzymes, consisting of seven members, namely SIRT 1, SIRT 6 and SIRT 7 located within the nucleus, SIRT 2 in the cytoplasm and SIRT 3, SIRT 4, and SIRT 5 in the mitochondria. They have vital roles in regulating various biological functions such as age-related metabolic disorders, inflammation, stress response, cardiovascular and neuronal functions. Delayed wound healing is one of the complication of diabetes, which can lead to lower limb amputation if not treated timely. SIRT 1, 3 and 6 are potent targets for diabetic wound healing. SIRT 1 deficiency reduces recruitment of fibroblasts, macrophages, mast cells, neutrophils to wound site and delays wound healing; negatively expressing MMP-9. The SIRT 1 mediated signalling pathway in diabetic wound healing is the SIRT 1-foxo-C-Myc pathway. On the contrary SIRT 3 deficiency, impairs proliferation and migration of fibroblasts and SIRT 6 deficiency impairs wound closure rate and interrupts the vascular remodelling. This review focuses on the role of sirtuins in improving delayed wound healing in diabetes and its natural modulators with their specific functions towards healing diabetic wounds.

Mitochondrial Dysfunction Plays Central Role in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a global pandemic that affects one-quarter of the world’s population. NAFLD includes a spectrum of progressive liver disease from steatosis to nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis and can be complicated by hepatocellular carcinoma. It is strongly associated with metabolic syndromes, obesity, and type 2 diabetes, and it has been shown that metabolic dysregulation is central to its pathogenesis. Recently, it has been suggested that metabolic- (dysfunction) associated fatty liver disease (MAFLD) is a more appropriate term to describe the disease than NAFLD, which puts increased emphasis on the important role of metabolic dysfunction in its pathogenesis. There is strong evidence that mitochondrial dysfunction plays a significant role in the development and progression of NAFLD. Impaired mitochondrial fatty acid oxidation and, more recently, a reduction in mitochondrial quality, have been suggested to play a major role in NAFLD development and progression. In this review, we provide an overview of our current understanding of NAFLD and highlight how mitochondrial dysfunction contributes to its pathogenesis in both animal models and human subjects. Further we discuss evidence that the modification of mitochondrial function modulates NAFLD and that targeting mitochondria is a promising new avenue for drug development to treat NAFLD/NASH.

Biochemical Mechanisms of Sirtuin-Directed Protein Acylation in Hepatic Pathologies of Mitochondrial Dysfunction

Mitochondrial protein acetylation is associated with a host of diseases including cancer, Alzheimer’s, and metabolic syndrome. Deciphering the mechanisms regarding how protein acetylation contributes to disease pathologies remains difficult due to the complex diversity of pathways targeted by lysine acetylation. Specifically, protein acetylation is thought to direct feedback from metabolism, whereby nutritional status influences mitochondrial pathways including beta-oxidation, the citric acid cycle, and the electron transport chain. Acetylation provides a crucial connection between hepatic metabolism and mitochondrial function. Dysregulation of protein acetylation throughout the cell can alter mitochondrial function and is associated with numerous liver diseases, including non-alcoholic and alcoholic fatty liver disease, steatohepatitis, and hepatocellular carcinoma. This review introduces biochemical mechanisms of protein acetylation in the regulation of mitochondrial function and hepatic diseases and offers a viewpoint on the potential for targeted therapies.

Remission of obesity and insulin resistance is not sufficient to restore mitochondrial homeostasis in visceral adipose tissue

Metabolic plasticity is the ability of a biological system to adapt its metabolic phenotype to different environmental stressors. We used a whole-body and tissue-specific phenotypic, functional, proteomic, metabolomic and transcriptomic approach to systematically assess metabolic plasticity in diet-induced obese mice after a combined nutritional and exercise intervention. Although most obesity and overnutrition-related pathological features were successfully reverted, we observed a high degree of metabolic dysfunction in visceral white adipose tissue, characterized by abnormal mitochondrial morphology and functionality. Despite two sequential therapeutic interventions and an apparent global healthy phenotype, obesity triggered a cascade of events in visceral adipose tissue progressing from mitochondrial metabolic and proteostatic alterations to widespread cellular stress, which compromises its biosynthetic and recycling capacity. In humans, weight loss after bariatric surgery showed a transcriptional signature in visceral adipose tissue similar to our mouse model of obesity reversion. Overall, our data indicate that obesity prompts a lasting metabolic fingerprint that leads to a progressive breakdown of metabolic plasticity in visceral adipose tissue.

SIRT1 plays an important role in implantation and decidualization during mouse early pregnancy

Sirtuin 1 (SIRT1) is a member of the sirtuin family that functions to deacetylate both histones and non-histone proteins. Previous studies have identified significant SIRT1 upregulation in eutopic endometrium from infertile women with endometriosis. However, SIRT1 function in the uterus has not been directly studied. Using immunochemistry analysis, we found SIRT1 to be most strongly expressed at GD4.5 and GD5.5 in decidualized cells and at GD7.5 in secondary decidual cells in mouse. To assess the role of SIRT1 in uterine function, we generated uterine Sirt1 conditional knockout mice (Pgrcre/+Sirt1f/f; Sirt1d/d). A 6-month fertility trial revealed that Sirt1d/d females were subfertile. Implantation site numbers were significantly decreased in Sirt1d/d mice compared with controls at GD5.5. Sirt1d/d implantation sites at GD4.5 could be divided into two groups, Group #1 with luminal closure and nonspecific COX2 expression compared with controls (14/20) and Group #2 with an open lumen and no COX2 (6/20). In Sirt1d/d Group #1, nuclear FOXO1 expression in luminal epithelial cells was significantly decreased. In Sirt1d/d Group #2, nuclear FOXO1 expression was almost completely absent, and there was strong PGR expression in epithelial cells. At GD5.5, stromal PGR and COX2 were significantly decreased in Sirt1d/d uterine in the areas surrounding the embryo compared with controls, indicating defective decidualization. An artificially induced decidualization test revealed that Sirt1d/d females showed defects in decidualization response. All together, these data suggest that SIRT1 is important for decidualization and contributes to preparing a receptive endometrium for successful implantation.

11β-HSD1 Inhibitor Alleviates Non-Alcoholic Fatty Liver Disease by Activating the AMPK/SIRT1 Signaling Pathway

We investigated the effect of an 11β-HSD1 inhibitor (H8) on hepatic steatosis and its mechanism of action. Although H8, a curcumin derivative, has been shown to alleviate insulin resistance, its effect on non-alcoholic fatty liver disease (NAFLD) remains unknown. Rats were fed a high-fat diet (HFD) for 8 weeks, intraperitoneally injected with streptozotocin (STZ) to induce NAFLD, and, then, treated with H8 (3 or 6 mg/kg/day) or curcumin (6 mg/kg/day) for 4 weeks, to evaluate the effects of H8 on NAFLD. H8 significantly alleviated HFD+STZ-induced lipid accumulation, fibrosis, and inflammation as well as improved liver function. Moreover, 11β-HSD1 overexpression was established by transfecting animals and HepG2 cells with lentivirus, carrying the 11β-HSD1 gene, to confirm that H8 improved NAFLD, by reducing 11β-HSD1. An AMP-activated protein kinase (AMPK) inhibitor (Compound C, 10 μM for 2 h) was used to confirm that H8 increased AMPK, by inhibiting 11β-HSD1, thereby restoring lipid metabolic homeostasis. A silencing-related enzyme 1 (SIRT1) inhibitor (EX572, 10 μM for 4 h) and a SIRT1 activator (SRT1720, 1 μM for 4 h) were used to confirm that H8 exerted anti-inflammatory effects, by elevating SIRT1 expression. Our findings demonstrate that H8 alleviates hepatic steatosis, by inhibiting 11β-HSD1, which activates the AMPK/SIRT1 signaling pathway.

Paeoniflorin ameliorates lipopolysaccharide-induced acute liver injury by inhibiting oxidative stress and inflammation via SIRT1/FOXO1a/SOD2 signaling in rats

Acute liver injury (ALI) is a poor prognosis and high mortality complication of sepsis. Paeoniflorin (PF) has remarkable anti-inflammatory effects in different disease models. Here, we explored the protective effect and underlying molecular mechanisms of PF against lipopolysaccharide (LPS)-induced ALI. Sprague-Dawley rats received intraperitoneal (i.p.) injection of PF for 7 days, 1 h after the last administration, and rats were injected i.p. 10 mg/kg LPS. PF improved liver structure and function, reduced hepatic reactive oxygen species (ROS) and methane dicarboxylic aldehyde (MDA) levels, and increased superoxide dismutase (SOD) activity. Western blot analysis suggested that PF significantly inhibited expression of inflammatory cytokines (TNF-α, IL-1β, and IL-18) and inhibited activation of the NLRP3 inflammasome. PF or mitochondrial ROS scavenger (mito-TEMPO) significantly improved liver mitochondrial function by scavenging mitochondrial ROS (mROS), restoring mitochondrial membrane potential loss and increasing level of ATP and enzyme activity of complex I and III. In addition, PF increased expression of sirtuin-1 (SIRT1), forkhead box O1 (FOXO1a) and manganese superoxide dismutase (SOD2), and increased FOXO1a nuclear retention. However, the inhibitor of SIRT1 (EX527) abolished the protective effect of PF. Taken together, PF promotes mROS clearance to inhibit mitochondrial damage and activation of the NLRP3 inflammasome via SIRT1/FOXO1a/SOD2 signaling.

Sirtuin deficiency and the adverse effects of fructose and uric acid synthesis

Fructose metabolism and hyperuricemia have been shown to drive insulin resistance, metabolic syndrome, hepatic steatosis, hypertension, inflammation, and innate immune reactivity in experimental studies. We suggest that these adverse effects are at least in part the result of suppressed activity of sirtuins, particularly Sirtuin1. Deficiency of sirtuin deacetylations is a consequence of reduced bioavailability of its cofactor nicotinamide adenine dinucleotide (NAD+). Uric acid-induced inflammation and oxidative stress consume NAD+ and activation of the polyol pathway of fructose and uric acid synthesis also reduces the NAD+-to-NADH ratio. Variability in the compensatory regeneration of NAD+ could result in variable recovery of sirtuin activity that may explain the inconsistent benefits of treatments directed to reduce uric acid in clinical trials. Here, we review the pathogenesis of the metabolic dysregulation driven by hyperuricemia and their potential relationship with sirtuin deficiency. In addition, we discuss therapeutic options directed to increase NAD+ and sirtuins activity that may improve the adverse effects resulting from fructose and uric acid synthesis.

Biochemical Functions and Clinical Characterizations of the Sirtuins in Diabetes-Induced Retinal Pathologies

Diabetic retinopathy (DR) is undoubtedly one of the most prominent causes of blindness worldwide. This pathology is the most frequent microvascular complication arising from diabetes, and its incidence is increasing at a constant pace. To date, the insurgence of DR is thought to be the consequence of the intricate complex of relations connecting inflammation, the generation of free oxygen species, and the consequent oxidative stress determined by protracted hyperglycemia. The sirtuin (SIRT) family comprises 7 histone and non-histone protein deacetylases and mono (ADP-ribosyl) transferases regulating different processes, including metabolism, senescence, DNA maintenance, and cell cycle regulation. These enzymes are involved in the development of various diseases such as neurodegeneration, cardiovascular pathologies, metabolic disorders, and cancer. SIRT1, 3, 5, and 6 are key enzymes in DR since they modulate glucose metabolism, insulin sensitivity, and inflammation. Currently, indirect and direct activators of SIRTs (such as antagomir, glycyrrhizin, and resveratrol) are being developed to modulate the inflammation response arising during DR. In this review, we aim to illustrate the most important inflammatory and metabolic pathways connecting SIRT activity to DR, and to describe the most relevant SIRT activators that might be proposed as new therapeutics to treat DR.

Can Epigenetics Help Solve the Puzzle Between Concomitant Cardiovascular Injury and Severity of Coronavirus Disease 2019?

ABSTRACT

The ongoing coronavirus disease 2019 (COVID-19) pandemic caused by SARS-CoV-2 has significant implications in patients with concomitant cardiovascular disease (CVD) because they are the population at the greatest risk of death. The treatment of such patients and complications may represent a new challenge for the fields of cardiology and pharmacology. Thus, understanding the involvement of this viral infection in CVD might help to reduce the aggressiveness of SARS-CoV-2 in causing multiorgan infection and damage. SARS-CoV-2 disturbs the host epigenome and several epigenetic processes involved in the pathophysiology of COVID-19 that can directly affect the function and structure of the cardiovascular system (CVS). Hence, it would be relevant to identify epigenetic alterations that directly impact CVS physiology after SARS-CoV-2 infection. This could contribute to the view of this virus-induced CVS injury and direct forthcoming tackles for COVID-19 treatment to reduce mortality in patients with CVD. Targeting epigenetic marks could offer strong evidence for the development of novel antiviral therapies, especially in the context of COVID-19-related CVS damage. In this review, we address some of the main signaling pathways that are currently known as being involved in COVID-19 pathophysiology and the importance of this glint on epigenetics and some of its modifiers (epidrugs) to control the unregulated epitope activity in the context of SARS-CoV-2 infection, COVID-19, and underlying CVD.

Versatile role of sirtuins in metabolic disorders: From modulation of mitochondrial function to therapeutic interventions

Sirtuins (SIRT1-7) are distinct histone deacetylases (HDACs) whose activity is determined by cellular metabolic status andnicotinamide adenine dinucleotide (NAD⁺ ) levels. HDACs of class III are the members of the SIRT's protein family. SIRTs are the enzymes that modulate mitochondrial activity and energy metabolism. SIRTs have been linked to a number of clinical and physiological operations, such as energy responses to low-calorie availability, aging, stress resistance, inflammation, and apoptosis. Mammalian SIRT2 orthologs have been identified as SIRT1-7 that are found in several subcellular sections, including the cytoplasm (SIRT1, 2), mitochondrial matrix (SIRT3, 4, 5), and the core (SIRT1, 2, 6, 7). For their deacetylase or ADP-ribosyl transferase action, all SIRTs require NAD⁺ and are linked to cellular energy levels. Evolutionarily, SIRT1 is related to yeast's SIRT2 as well as received primary attention in the circulatory system. An endogenous protein, SIRT1 is involved in the development of heart failure and plays a key role in cell death and survival. SIRT2 downregulation protects against ischemic-reperfusion damage. Increase in human longevity is caused by an increase in SIRT3 expression. Cardiomyocytes are also protected by SIRT3 from oxidative damage and aging, as well as suppressing cardiac hypertrophy. SIRT4 and SIRT5 perform their roles in the heart. SIRT6 has also been linked to a reduction in heart hypertrophy. SIRT7 is known to be involved in the regulation of stress responses and apoptosis in the heart.

SIRT1 selectively exerts the metabolic protective effects of hepatocyte nicotinamide phosphoribosyltransferase

Calorie restriction abates aging and cardiometabolic disease by activating metabolic signaling pathways, including nicotinamide adenine dinucleotide (NAD⁺) biosynthesis and salvage. Nicotinamide phosphoribosyltransferase (NAMPT) is rate-limiting in NAD⁺ salvage, yet hepatocyte NAMPT actions during fasting and metabolic duress remain unclear. We demonstrate that hepatocyte NAMPT is upregulated in fasting mice, and in isolated hepatocytes subjected to nutrient withdrawal. Mice lacking hepatocyte NAMPT exhibit defective FGF21 activation and thermal regulation during fasting, and are sensitized to diet-induced glucose intolerance. Hepatocyte NAMPT overexpression induced FGF21 and adipose browning, improved glucose homeostasis, and attenuated dyslipidemia in obese mice. Hepatocyte SIRT1 deletion reversed hepatocyte NAMPT effects on dark-cycle thermogenesis, and hepatic FGF21 expression, but SIRT1 was dispensable for NAMPT insulin-sensitizing, anti-dyslipidemic, and light-cycle thermogenic effects. Hepatocyte NAMPT thus conveys key aspects of the fasting response, which selectively dissociate through hepatocyte SIRT1. Modulating hepatocyte NAD⁺ is thus a potential mechanism through which to attenuate fasting-responsive disease.

High-fat diet intake ameliorates the expression of hedgehog signaling pathway in adult rat liver

BACKGROUND

Disproportionate fatty diet intake provokes hepatic lipid accumulation that causes non-alcoholic fatty liver disease, triggering the embryonically conserved Hedgehog (Hh) pathway in the adult liver. The present study incorporates exploring the impact of chronically administered unsaturated (D-1) and saturated (D-2) fat-enriched diets on hematological parameters, liver functioning, and lipid profile in the rat model. Besides, hepatohistology and real time gene expression analysis of Hh signaling pathway genes i.e., Shh, Ihh, Hhip, Ptch1, Smo, Gli1, Gli2, and Gli3 were carried out.

METHODS AND RESULTS

Fifteen Rattus norvegicus (♂) of 200 ± 25 g weight were grouped into control, D-1, and D-2. Animals were fed on their respective diets for 16 weeks. Fatty diet intake resulted in neutropenia, lymphocytosis, monocytosis, polycythemia, and macrocytosis in both experimental groups. Altered liver injury biomarkers, hypertriglyceridemia, and significantly increased very-low-density lipoprotein VLDL were also noted in both high-fat diet (HFD) groups as compared to control. Hepatohistological examination showed disrupted microarchitecture, infiltration of inflammatory cells, cellular necrosis, widened sinusoidal spaces, and microvesicular steatotic hepatocytes in D-1 and D-2. Collagen deposition in both HFD groups marks the extent of fibrosis. Significant upregulation of hedgehog pathway genes was found in fatty diet groups. In comparison with the control group, Shh Ihh, Hhip, Ptch1, Smo, Gli1, Gli2, and Gli3 were upregulated in D-1. In D-2 Shh, Hhip, and Smo expressions were upregulated, Ihh exhibited downregulation as compared to control.

CONCLUSION

Excess fat deposits in liver due to chronic consumption of high-fat diet results in anomalous architecture and functioning. High-fat diet induced significant variations in Hh pathway genes expression; especially Shh, Ihh, Hhip, Ptch1, Smo, Gli1, Gli2, and Gli3 were upregulated. Infiltration of inflammatory cells ( ), widened sinusoidal spaces (▲), cellular necrosis, and micro vesicular steatotic hepatocytes (*) were shown in the liver. Significant collagen deposition in both HFD groups i.e. D-1 and D-2 confirmed liver fibrosis. Excessive intake of dietary fats impaired normal liver functioning and liver inflammation triggered Hh signaling in adult rats.

Obesity and Male Reproduction: Do Sirtuins Play a Role?

Obesity is a major current public health problem of global significance. A progressive sperm quality decline, and a decline in male fertility, have been reported in recent decades. Several studies have reported a strict relationship between obesity and male reproductive dysfunction. Among the many mechanisms by which obesity impairs male gonadal function, sirtuins (SIRTs) have an emerging role. SIRTs are highly conserved nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases that play a role in gene regulation, metabolism, aging, and cancer. SIRTs regulate the energy balance, the lipid balance, glucose metabolism, and adipogenesis, but current evidence also indicates a role for SIRTs in male reproduction. However, the majority of the studies have been conducted in animal models and very few have been conducted with humans. This review shows that SIRTs play an important role among the molecular mechanisms by which obesity interferes with male fertility. This highlights the need to deepen this relationship. It will be of particular interest to evaluate whether synthetic and/or natural compounds capable of modifying the activity of SIRTs may also be useful for the treatment of obesity and its effects on gonadal function. Although few studies have explored the role of SIRT activators in obesity-induced male infertility, some molecules, such as resveratrol, appear to be effective in modulating SIRT activity, as well as counteracting the negative effects of obesity on male fertility. The search for strategies to improve male reproductive function in overweight/obese patients is a challenge and understanding the role of SIRTs and their activators may open new interesting scenarios in the coming years.

Common pathways in dementia and diabetic retinopathy: understanding the mechanisms of diabetes-related cognitive decline

Type 2 diabetes (T2D) is associated with multiple comorbidities, including diabetic retinopathy (DR) and cognitive decline, and T2D patients have a significantly higher risk of developing Alzheimer's disease (AD). Both DR and AD are characterized by a number of pathological mechanisms that coalesce around the neurovascular unit, including neuroinflammation and degeneration, vascular degeneration, and glial activation. Chronic hyperglycemia and insulin resistance also play a significant role, leading to activation of pathological mechanisms such as increased oxidative stress and the accumulation of advanced glycation end-products (AGEs). Understanding these common pathways and the degree to which they occur simultaneously in the brain and retina during diabetes will provide avenues to identify T2D patients at risk of cognitive decline.

Grafting Resveratrol onto Mesoporous Silica Nanoparticles towards Efficient Sustainable Immunoregulation and Insulin Resistance Alleviation for Diabetic Periodontitis Therapy

The treatment of diabetic periodontitis (DP) has become a tough challenge in dental clinic mainly due to the intrinsic drawbacks of conventional therapy strategy and currently unclear mechanisms to elucidate...

Comparative proteomic profiling reveals a pathogenic role for the O-GlcNAcylated AIMP2-PARP1 complex in aging-related hepatic steatosis in mice

The prevalence of non-alcoholic fatty liver disease (NAFLD) increases with aging. However, the mechanism of aging-related NAFLD remains unclear. Herein, we constructed an aging-related hepatic steatosis model and analyzed the differentially expressed proteins (DEPs) in livers from young and old mice using liquid chromatography-mass spectrometry. Five hundred and eighty-eight aging-related DEPs and novel pathways were identified. Aminoacyl tRNA synthetase complex-interacting multifunctional protein 2 (AIMP2), the most significantly upregulated protein, promoted poly(ADP-ribose) polymerase 1 (PARP1) activation in aging-related hepatic steatosis. Additionally, mice liver-specific O-GlcNAcase knockout promoted AIMP2 and PARP1 expression. O-GlcNAc transferase (OGT) overexpression and O-GlcNAcase inhibition by genetic or pharmaceutical manipulations increased AIMP2 and PARP1 levels in vitro. Mechanistically, O-GlcNAcylation increased AIMP2 protein stability, leading to its aggregation. Our study reveals O-GlcNAcylated AIMP2 as a novel pathogenic regulator of aging-related hepatic steatosis.

Metabolic Regulation of Macrophages by SIRT1 Determines Activation During Cholestatic Liver Disease in Mice

BACKGROUND & AIMS

Inflammation is the hallmark of chronic liver disease. Metabolism is a key determinant to regulate the activation of immune cells. Here, we define the role of sirtuin 1 (SIRT1), a main metabolic regulator, in controlling the activation of macrophages during cholestatic liver disease and in response to endotoxin.

METHODS

We have used mice overexpressing SIRT1, which we treated with intraperitoneal lipopolysaccharides or induced cholestasis by bile duct ligation. Bone marrow-derived macrophages were used for mechanistic in vitro studies. Finally, PEPC-Boy mice were used for adoptive transfer experiments to elucidate the impact of SIRT1-overexpressing macrophages in contributing to cholestatic liver disease.

RESULTS

We found that SIRT1 overexpression promotes increased liver inflammation and liver injury after lipopolysaccharide/GalN and bile duct ligation; this was associated with an increased activation of the inflammasome in macrophages. Mechanistically, SIRT1 overexpression associated with the activation of the mammalian target of rapamycin (mTOR) pathway that led to increased activation of macrophages, which showed metabolic rewiring with increased glycolysis and broken tricarboxylic acid cycle in response to endotoxin in vitro. Activation of the SIRT1/mTOR axis in macrophages associated with the activation of the inflammasome and the attenuation of autophagy. Ultimately, in an in vivo model of cholestatic disease, the transplantation of SIRT1-overexpressing myeloid cells contributed to liver injury and fibrosis.

CONCLUSIONS

Our study provides novel mechanistic insights into the regulation of macrophages during cholestatic disease and the response to endotoxin, in which the SIRT1/mTOR crosstalk regulates macrophage activation controlling the inflammasome, autophagy and metabolic rewiring.

Two novel InDels within the Promoter of SIRT1 are associated with growth traits in chickens

1. The objectives of the present study were to elucidate the relationship between novel variations of the SIRT1 gene and chicken growth traits. In total, 1,429 chickens, including six breeds and a Gushi ×Anka F2 resource population, were genotyped using PCR-RFLP.

2. Two novel InDels (c.-1552_-1553insCG and c.-450_-451delCG) in the promoter of the chicken SIRT1 gene were identified. An association study showed that c.-1552_-1553insCG was significantly correlated with growth traits and serum lipid indicators.

3. The insertion genotype was most highly associated with body weight at day old, two- and four-week-old chickens, and with shank circumference at four and eight weeks of age. The wild type genotype at this site was most highly associated with serum lipid indicators.

4. In contrast, c.-450_-451delCG was significantly correlated with muscle fibre diameter. The SIRT1 gene expression in chickens with different InDel genotypes was analysed and was significantly higher with heterozygous genotypes at both sites in muscle and fat tissue, relative to expression in chickens with the corresponding homozygous genotypes.

5. The effects of different haplotypes on SIRT1 promoter activity showed that promoter activity depends on haplotype, with haplotype HapII exhibiting the highest activity.

6. It was concluded that the SIRT1 gene is associated with chicken growth traits and that the two InDels influence SIRT1 promoter activity in chickens.

Retinol binding protein 4 antagonists and protein synthesis inhibitors: Potential for therapeutic development

Retinol-binding protein 4 (RBP4) is a serum protein that transports Vitamin A. RBP4 is correlated with numerous diseases and metabolic syndromes, including insulin resistance in type 2 diabetes, cardiovascular diseases, obesity, and macular degeneration. Recently, RBP4 antagonists and protein synthesis inhibitors are under development to regulate the effect of RBP4. Several RBP4 antagonists, especially BPN-14136, have demonstrated promising safety profiles and potential therapeutic benefits in animal studies. Two RBP4 antagonists, specifically tinlarebant (Belite Bio) and STG-001 (Stargazer) are currently undergoing clinical trials. Some antidiabetic drugs and nutraceuticals have been reported to reduce RBP4 expression, but more clinical data is needed to evaluate their therapeutical benefits. As regulating RBP4 levels or its activities would benefit a wide range of patients, further research is highly recommended to develop clinically useful RBP4 antagonists or protein synthesis inhibitors.

Hypoglycemic effect of astragaloside IV via modulating gut microbiota and regulating AMPK/SIRT1 and PI3K/AKT pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Radix Astragali, the dried root of Astragalus mongholicus Bunge, has long been used in traditional Chinese Medicine to treat diabetes. Astragaloside IV (AS-IV), one of the most active ingredients in the root, has been shown to have anti-diabetes ability; however, its underlying mechanism is still unclear.

MATERIALS AND METHODS

In this study, we evaluated the hypoglycemic effect and possible mechanisms of AS-IV in diabetic mice and insulin resistance-HepG2 cells. The components of the intestinal microflora in mice with type 2 diabetes mellitus (T2DM) were determined using high-throughput 16S rRNA gene sequencing. Moreover, the molecular mechanisms of specific members of insulin signaling pathways were analyzed.

RESULTS

AS-IV significantly reversed the abnormalities in blood lipids, glucose, insulin resistance, as well as oxidative stress levels in T2DM mice. Histological finding showed that AS-IV could protect the cellular architecture of the liver and pancreas. AS-IV also regulated the abundance and diversity of intestinal flora of T2DM mice in a positive direction and increased butyric acid levels. The active role of AS-IV as an anti-diabetic compound by regulating the AMPK/SIRT1 and PI3K/AKT signaling pathways was revealed using a T2DM model and verified through the intervention of inhibitors using insulin-resistance HepG2 cells.

CONCLUSION

Our results suggested that AS-IV may be used as an anti-diabetic drug candidate owing to its effects of regulating gut microbiota and AMPK/SIRT1 and PI3K/AKT signaling pathways.