Plasma levels of SIRT1 associate with non-alcoholic fatty liver disease in obese patients

Two-year post-distraction cartilage-related structural improvement is accompanied by increased serum full-length SIRT1

BACKGROUND

Previously, fragments from Sirtuin 1 (SIRT1) were identified in preclinical and clinical samples to display an increase in serum levels for N-terminal (NT) SIRT1 vs. C-terminal (CT) SIRT1, indicative of early signs of OA. Here we tested NT/CT SIRT1 levels as well as a novel formulated sandwich assay to simultaneously detect both domains of SIRT1 in a manner that may inform us about the levels of full-length SIRT1 in the circulation (flSIRT1) of clinical cohorts undergoing knee joint distraction (KJD).

METHODS

We employed an indirect ELISA assay to test NT- and CT-SIRT1 levels and calculated their ratio. Further, to test flSIRT1 we utilized novel antibodies (Ab), which were validated for site specificity and used in a sandwich ELISA method, wherein the CT-reactive served as capture Ab, and its NT-reactive served as primary detection Ab. This method was employed in human serum samples derived from a two-year longitudinal study of KJD patients. Two-year clinical and structural outcomes were correlated with serum levels of flSIRT1 compared to baseline.

RESULTS

Assessing the cohort, exhibited a significant increase of NT/CT SIRT1 serum levels with increased osteophytes and PIIANP/CTX-II at baseline, while a contradictory increase in NT/CT SIRT1 was associated with less denuded bone, post-KJD. On the other hand, flSIRT1 exhibited an upward trend in serum level, accompanied by reduced denuded bone for 2-year adjusted values. Moreover, 2 year-adjusted flSIRT1 levels displayed a steeper linear regression for cartilage and bone-related structural improvement than those observed for NT/CT SIRT1.

CONCLUSIONS

Our data support that increased flSIRT1 serum levels are a potential molecular endotype for cartilage-related structural improvement post-KJD, while NT/CT SIRT1 appears to correlate with osteophyte and PIIANP/CTX-II reduction at baseline, to potentially indicate baseline OA severity.

SIRT1: Harnessing multiple pathways to hinder NAFLD

Non-alcoholic fatty liver disease (NAFLD) encompasses hepatic steatosis, non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma. It is the primary cause of chronic liver disorders, with a high prevalence but no approved treatment. Therefore, it is indispensable to find a trustworthy therapy for NAFLD. Recently, mounting evidence illustrates that Sirtuin 1 (SIRT1) is strongly associated with NAFLD. SIRT1 activation or overexpression attenuate NAFLD, while SIRT1 deficiency aggravates NAFLD. Besides, an array of therapeutic agents, including natural compounds, synthetic compounds, traditional Chinese medicine formula, and stem cell transplantation, alleviates NALFD via SIRT1 activation or upregulation. Mechanically, SIRT1 alleviates NAFLD by reestablishing autophagy, enhancing mitochondrial function, suppressing oxidative stress, and coordinating lipid metabolism, as well as reducing hepatocyte apoptosis and inflammation. In this review, we introduced the structure and function of SIRT1 briefly, and summarized the effect of SIRT1 on NAFLD and its mechanism, along with the application of SIRT1 agonists in treating NAFLD.

Chronic SIRT1 supplementation in diabetic mice improves endothelial function by suppressing oxidative stress

AIMS

Enhancing SIRT1 activity exerts beneficial cardiovascular effects. In diabetes, plasma SIRT1 levels are reduced. We aimed to investigate the therapeutic potential of chronic recombinant murine SIRT1 (rmSIRT1) supplementation to alleviate endothelial and vascular dysfunction in diabetic mice (db/db).

METHODS AND RESULTS

Left internal mammary arteries obtained from patients undergoing coronary artery bypass grafting with or without a diagnosis of diabetes were assayed for SIRT1 protein levels. Twelve-week-old male db/db mice and db/+ controls were treated with vehicle or rmSIRT1 intraperitoneally for 4 weeks, after which carotid artery pulse wave velocity (PWV) and energy expenditure/activity were assessed by ultrasound and metabolic cages, respectively. Aorta, carotid, and mesenteric arteries were isolated to determine endothelial and vascular function using the myograph system.Arteries obtained from diabetic patients had significantly lower levels of SIRT1 relative to non-diabetics. In line, aortic SIRT1 levels were reduced in db/db mice compared to db/+ mice, while rmSIRT1 supplementation restored SIRT1 levels. Mice receiving rmSIRT1 supplementation displayed increased physical activity and improved vascular compliance as reflected by reduced PWV and attenuated collagen deposition. Aorta of rmSIRT1-treated mice exhibited increased endothelial nitric oxide (eNOS) activity, while endothelium-dependent contractions of their carotid arteries were significantly decreased, with mesenteric resistance arteries showing preserved hyperpolarization. Ex vivo incubation with reactive oxygen species (ROS) scavenger Tiron and NADPH oxidase inhibitor apocynin revealed that rmSIRT1 leads to preserved vascular function by suppressing NADPH oxidase (NOX)-related ROS synthesis. Chronic rmSIRT1 treatment resulted in reduced expression of both NOX1 and NOX4, in line with a reduction in aortic protein carbonylation and plasma nitrotyrosine levels.

CONCLUSIONS

In diabetic conditions, arterial SIRT1 levels are significantly reduced. Chronic rmSIRT1 supplementation improves endothelial function and vascular compliance by enhancing eNOS activity and suppressing NOX-related oxidative stress. Thus, SIRT1 supplementation may represent novel therapeutic strategy to prevent diabetic vascular disease.

The Crosstalk between Mesenchymal Stromal/Stem Cells and Hepatocytes in Homeostasis and under Stress

Liver diseases, characterized by high morbidity and mortality, represent a substantial medical problem globally. The current therapeutic approaches are mainly aimed at reducing symptoms and slowing down the progression of the diseases. Organ transplantation remains the only effective treatment method in cases of severe liver pathology. In this regard, the development of new effective approaches aimed at stimulating liver regeneration, both by activation of the organ's own resources or by different therapeutic agents that trigger regeneration, does not cease to be relevant. To date, many systematic reviews and meta-analyses have been published confirming the effectiveness of mesenchymal stromal cell (MSC) transplantation in the treatment of liver diseases of various severities and etiologies. However, despite the successful use of MSCs in clinical practice and the promising therapeutic results in animal models of liver diseases, the mechanisms of their protective and regenerative action remain poorly understood. Specifically, data about the molecular agents produced by these cells and mediating their therapeutic action are fragmentary and often contradictory. Since MSCs or MSC-like cells are found in all tissues and organs, it is likely that many key intercellular interactions within the tissue niches are dependent on MSCs. In this context, it is essential to understand the mechanisms underlying communication between MSCs and differentiated parenchymal cells of each particular tissue. This is important both from the perspective of basic science and for the development of therapeutic approaches involving the modulation of the activity of resident MSCs. With regard to the liver, the research is concentrated on the intercommunication between MSCs and hepatocytes under normal conditions and during the development of the pathological process. The goals of this review were to identify the key factors mediating the crosstalk between MSCs and hepatocytes and determine the possible mechanisms of interaction of the two cell types under normal and stressful conditions. The analysis of the hepatocyte-MSC interaction showed that MSCs carry out chaperone-like functions, including the synthesis of the supportive extracellular matrix proteins; prevention of apoptosis, pyroptosis, and ferroptosis; support of regeneration; elimination of lipotoxicity and ER stress; promotion of antioxidant effects; and donation of mitochondria. The underlying mechanisms suggest very close interdependence, including even direct cytoplasm and organelle exchange.

The emerging significance of mitochondrial targeted strategies in NAFLD treatment

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease worldwide, ranging from liver steatosis to nonalcoholic steatohepatitis, which ultimately progresses to fibrosis, cirrhosis, and hepatocellular carcinoma. Individuals with NAFLD have a higher risk of developing cardiovascular and extrahepatic cancers. Despite the great progress being made in understanding the pathogenesis and the introduction of new pharmacological targets for NAFLD, no drug or intervention has been accepted for its management. Recent evidence suggests that NAFLD may be a mitochondrial disease, as mitochondrial dysfunction is involved in the pathological processes that lead to NAFLD. In this review, we describe the recent advances in our understanding of the mechanisms associated with mitochondrial dysfunction in NAFLD progression. Moreover, we discuss recent advances in the efficacy of mitochondria-targeted compounds (e.g., Mito-Q, MitoVit-E, MitoTEMPO, SS-31, mitochondrial uncouplers, and mitochondrial pyruvate carrier inhibitors) for treating NAFLD. Furthermore, we present some medications currently being tested in clinical trials for NAFLD treatment, such as exercise, mesenchymal stem cells, bile acids and their analogs, and antidiabetic drugs, with a focus on their efficacy in improving mitochondrial function. Based on this evidence, further investigations into the development of mitochondria-based agents may provide new and promising alternatives for NAFLD management.

SIRT1 Activator E1231 Alleviates Nonalcoholic Fatty Liver Disease by Regulating Lipid Metabolism

Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver diseases. Silencing information regulator 1 (SIRT1) was demonstrated to modulate cholesterol and lipid metabolism in NAFLD. Here, a novel SIRT1 activator, E1231, was studied for its potential improvement effects on NAFLD. C57BL/6J mice were fed a high-fat and high-cholesterol diet (HFHC) for 40 weeks to create a NAFLD mouse model, and E1231 was administered by oral gavage (50 mg/kg body weight, once/day) for 4 weeks. Liver-related plasma biochemistry parameter tests, Oil Red O staining, and hematoxylin-eosin staining results showed that E1231 treatment ameliorated plasma dyslipidemia, plasma marker levels of liver damage (alanine aminotransferase (ALT) and aspartate aminotransferase (AST)), liver total cholesterol (TC) and triglycerides (TG) contents, and obviously decreased hepatic steatosis score and NAFLD Activity Score (NAS) in the NAFLD mouse model. Western blot results showed that E1231 treatment significantly regulated lipid-metabolism-related protein expression. In particular, E1231 treatment increased SIRT1, PGC-1α, and p-AMPKα protein expression but decreased ACC and SCD-1 protein expression. Additionally, in vitro studies demonstrated that E1231 inhibited lipid accumulation and improved mitochondrial function in free-fatty-acid-challenged hepatocytes, and required SIRT1 activation. In conclusion, this study illustrated that the SIRT1 activator E1231 alleviated HFHC-induced NAFLD development and improved liver injury by regulating the SIRT1-AMPKα pathway, and might be a promising candidate compound for NAFLD treatment.

Investigating fatty liver disease-associated adverse outcome pathways of perfluorooctane sulfonate using a systems toxicology approach

Adverse outcome pathway (AOP) frameworks help elucidate toxic mechanisms and support chemical regulation. AOPs link a molecular initiating event (MIE), key events (KEs), and an adverse outcome by key event relationships (KERs), which assess the biological plausibility, essentiality, and empirical evidence involved. Perfluorooctane sulfonate (PFOS), a hazardous poly-fluoroalkyl substance, demonstrates hepatotoxicity in rodents. PFOS may induce fatty liver disease (FLD) in humans; however, the underlying mechanism remains unclear. In this study, we evaluated the toxic mechanisms of PFOS-associated FLD by developing an AOP using publicly available data. We identified MIE and KEs by performing GO enrichment analysis on PFOS- and FLD-associated target genes collected from public databases. The MIEs and KEs were then prioritized by PFOS-gene-phenotype-FLD networks, AOP-helpFinder, and KEGG pathway analyses. Following a comprehensive literature review, an AOP was then developed. Finally, six KEs for the AOP of FLD were identified. This AOP indicated that toxicological processes initiated by SIRT1 inhibition led to SREBP-1c activation, de novo fatty acid synthesis, and fatty acid and triglyceride accumulation, culminating in liver steatosis. Our study provides insights into the toxic mechanism of PFOS-induced FLD and suggests approaches to assessing the risk of toxic chemicals.

Peroxisome Proliferator-Activated Receptor-γ as a Target and Regulator of Epigenetic Mechanisms in Nonalcoholic Fatty Liver Disease

Peroxisome proliferator-activated receptor-γ (PPARγ) belongs to the superfamily of nuclear receptors that control the transcription of multiple genes. Although it is found in many cells and tissues, PPARγ is mostly expressed in the liver and adipose tissue. Preclinical and clinical studies show that PPARγ targets several genes implicated in various forms of chronic liver disease, including nonalcoholic fatty liver disease (NAFLD). Clinical trials are currently underway to investigate the beneficial effects of PPARγ agonists on NAFLD/nonalcoholic steatohepatitis. Understanding PPARγ regulators may therefore aid in unraveling the mechanisms governing the development and progression of NAFLD. Recent advances in high-throughput biology and genome sequencing have greatly facilitated the identification of epigenetic modifiers, including DNA methylation, histone modifiers, and non-coding RNAs as key factors that regulate PPARγ in NAFLD. In contrast, little is still known about the particular molecular mechanisms underlying the intricate relationships between these events. The paper that follows outlines our current understanding of the crosstalk between PPARγ and epigenetic regulators in NAFLD. Advances in this field are likely to aid in the development of early noninvasive diagnostics and future NAFLD treatment strategies based on PPARγ epigenetic circuit modification.

Protopanaxadiol ameliorates NAFLD by regulating hepatocyte lipid metabolism through AMPK/SIRT1 signaling pathway

Non-alcoholic fatty liver disease (NAFLD) has become one of the main chronic liver diseases worldwide. Protopanaxadiol (PPD), an active compound derived from Gynostemma pentaphyllum, has been found able to improve free fatty acid-induced lipid accumulation in hepatocytes. However, the efficacy of PPD on NAFLD and the underlying mechanism remains unknown. In this study, the mice were fed with a high-fat diet for 22 weeks to induce the NAFLD model, and then were treated with PPD by gavage for 8 weeks. Moreover, AML12 and HepG2 cells induced by free fatty acids for 24 h, were treated with different doses of PPD and/or AMPK or SIRT1 inhibitor to explore the pharmacological mechanism of PPD. The results showed that mice with PPD treatment had significantly reduced liver weight and serum aminotransferase levels, less severe hepatosteatosis, and inflammatory cell infiltration in liver tissues when compared with the model mice. PPD also reversed the down-regulated activation of AMPK and SIRT1 expression as well as the change of lipid metabolism-related molecules in the mice liver tissues. Consistently, the in vitro experiments showed the effect of PPD in ameliorating lipid accumulation in hepatocytes. The inhibitor of AMPK or SIRT1 suppressed the AMPK and SIRT1 signaling and markedly diminished the anti-steatosis effect of PPD. In conclusion, our results prove the ameliorating impact of PPD on NAFLD and also reveal the involvement of regulation of AMPK/SIRT1 signaling pathway-mediated lipid metabolism in the underlying mechanism, suggesting PPD as a potential natural compound for the treatment of NAFLD.

Increased SIRT1 Concentration Following Four Years of Selenium and Q10 Intervention Associated with Reduced Cardiovascular Mortality at 10-Year Follow-Up-Sub-Study of a Previous Prospective Double-Blind Placebo-Controlled Randomized Clinical Trial

Background: Selenium and coenzyme Q₁₀ (SeQ₁₀) possess antioxidant and anti-inflammatory properties, potentially mediated via Sirtuin1 (SIRT1). We aimed to investigate the influence of a SeQ₁₀ intervention on SIRT1 concentration, with potential interactions with microRNAs. Methods: In this sub-study of a prospective double-blind placebo-controlled clinical trial, healthy subjects (mean age 76 years) were randomized to receive an active treatment (n = 165, combined 200 µg/day of Se and 200 mg/day of Q₁₀) or a placebo (n = 161). SIRT1 concentration and microRNAs were measured with ELISA and PCR, respectively. Results: After four years, SIRT1 concentration was increased in the active treatment group, with mean (SD) ng/mL of 469 (436) vs. 252 (162), p < 0.001, and decreased in the placebo group, 190 (186) vs. 269 (172), p = 0.002, and the differences between the groups were significant (p = 0.006, adjusted). Those who suffered CV death during a 10-year follow-up (n = 25 and n = 52 in the active treatment and placebo groups, respectively) had significantly lower baseline SIRT1 concentrations compared to the survivors (p < 0.001). MiR-130a-3p was significantly downregulated during the intervention and correlated inversely with SIRT1 at baseline (r = -0.466, p = 0.007). Conclusion: The increased SIRT1 concentration after the SeQ₁₀ intervention associated with reduced CV mortality, partly mediated via miR-1303a-3p, suggests that SIRT1 is an additional mediator of the intervention, preventing vascular ageing.

The association of dietary inflammatory index (DII) and central obesity with non-alcoholic fatty liver disease (NAFLD) in people with diabetes (T2DM)

Background & Objective

High prevalence of non-alcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes mellitus results in deleterious complications and morbidities related to both diseases. Thus, we aimed to investigate dietary and anthropometric risk factors for progression of Non-alcoholic Fatty Liver Disease (NAFLD) in diabetic people.

Methods

Anthropometric, and dietary intakes, and hepatic steatosis and fibrosis were assessed in two hundred participants with type two diabetes (T2DM). Subjects with CAP score of more than 270 dB/m were considered to have NAFLD. Multivariable-adjusted ORs and 95% CIs were used to investigate the association between NAFLD and dietary inflammatory index (DII) score and anthropometric indices.

Results

Participants in the highest tertile of DII had 2.41 (95% CI:1.16-4.97), 2,53 (95% CI: 1.04-6.16), 2.78 (95% CI: 1.09-7.13) times higher odds of developing NAFLD in comparison to the lowest tertile in crude, adjusted model 1 and 2, respectively. Among those with the highest relative to the lowest tertile of trunk-to-leg fat ratio (TLR), ORs and 95% CI were OR = 1.88, 95% CI = 0.9-3.91, and OR = 7.99, 95% CI = 2.43-26.26 in crude and full-adjusted models. Odds of NAFLD in the third tertile of metabolic score for visceral fat (METS-VF) was higher than the first tertile in crude (OR = 9.5, 95% CI = 4.01-22.46) and full-adjusted models (OR = 4.55, 95% CI = 1.46-14.2).

Conclusions

In conclusion, this study highlighted an association between greater DII (pro-inflammatory diet) and higher NAFLD risk. Moreover, TLR and METS-VF are known as novel estimators of central obesity as a risk factor for NAFLD in diabetes.

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.

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.

The Benefit of Optimal Dietary Lipid Level for Black Seabream Acanthopagrus schlegelii Juveniles under Low-Salinity Environment

The present study was aimed at evaluating the regulatory effects of dietary lipid levels on growth performance, osmoregulation, fatty acid composition, lipid metabolism, and physiological response in Acanthopagrus schlegelii under low salinity (5 psu). An 8-week feeding trial was conducted in juvenile A. schlegelii with an initial weight of 2.27 ± 0.05 g, and six isonitrogenous experimental diets were formulated with graded levels of lipid: 68.7 g/kg (D1), 111.7 g/kg (D2), 143.5 g/kg (D3), 188.9 g/kg (D4), 239.3 g/kg (D5), and 269.4 g/kg (D6), respectively. Results indicated that fish fed with diet containing 188.9 g/kg lipid significantly improved growth performance. Dietary D4 improved ion reabsorption and osmoregulation by increasing the concentrations of Na⁺, K⁺, and cortisol in serum and activities of Na⁺/K⁺-ATPase as well as expression levels of osmoregulation related to gene expression levels in the gill and intestine. The expression levels of long chain polyunsaturated fatty acid biosynthesis-related genes were dramatically upregulated when dietary lipid levels increased from 68.7 g/kg to 189.9 g/kg with levels of docosahexaenoic (DHA), eicosapentaenoic (EPA), and DHA/EPA ratio being highest in the D4 group. When fish fed dietary lipid levels from 68.7 g/kg to 188.9 g/kg, lipid homeostasis could be maintained by upregulating sirt1 and pparα expression levels, whereas lipid accumulation was observed in dietary lipid levels of 239.3 g/kg and over. Fish fed with high dietary lipid levels resulted in physiological stress related to oxidative stress and endoplasmic reticulum stress. In conclusion, based on weight gain, the optimal dietary lipid requirement of juvenile A. schlegelii reared at low-salinity water is 196.0 g/kg. These findings indicate that the optimal dietary lipid level can improve growth performance, n-3 LC-PUFA accumulation, and osmoregulatory ability and maintain lipid homeostasis and normal physiological functions of juvenile A. schlegelii.

Salvia-Nelumbinis naturalis improves lipid metabolism of NAFLD by regulating the SIRT1/AMPK signaling pathway

Background

Salvia-Nelumbinis naturalis (SNN), the extract of Chinese herbal medicine, has shown effects on NAFLD. This study aims to explore the underlying mechanism of SNN for regulating the lipid metabolism disorder in NAFLD based on the SIRT1/AMPK signaling pathway.

Methods

Male C57BL/6J mice fed with a high-fat diet (HFD) were used to establish the NAFLD model. Dynamic changes of mice including body weight, liver weight, serological biochemical indexes, liver histopathological changes, and protein level of AMPK and SIRT1 were monitored. After18 weeks, SNN treatment was administrated to the NAFLD mice for another 4 weeks. Besides the aforementioned indices, TC and TG of liver tissues were also measured. Western blot and quantitative RT-PCR were used to detect the expression and/or activation of SIRT1 and AMPK, as well as the molecules associated with lipid synthesis and β-oxidation. Furthermore, AML12 cells with lipid accumulation induced by fatty acids were treated with LZG and EX527 (SIRT1 inhibitor) or Compound C (AMPK inhibitor ) to confirm the potential pharmacological mechanism.

Results

Dynamic observation found the mice induced by HFD with gradually increased body and liver weight, elevated serum cholesterol, hepatic lipid accumulation, and liver injury. After 16 weeks, these indicators have shown obvious changes. Additionally, the hepatic level of SIRT1 and AMPK activation was identified gradually decreased with NAFLD progress. The mice with SNN administration had lower body weight, liver weight, and serum level of LDL-c and ALT than those of the NAFLD model. Hepatosteatosis and hepatic TG content in the liver tissues of the SNN group were significantly reduced. When compared with control mice, the NAFLD mice had significantly decreased hepatic expression of SIRT1, p-AMPK, p-ACC, ACOX1, and increased total Acetylated-lysine, SUV39H2, and SREBP-1c. The administration of SNN reversed the expression of these molecules. In vitro experiments showed the effect of SNN in ameliorating hepatosteatosis and regulating the expression of lipid metabolism-related genes in AML12 cells, which were diminished by EX527 or Compound C co-incubation.

Conclusions

Taken together, the SIRT1/AMPK signaling pathway, involved in hepatic lipid synthesis and degradation, plays a pivotal role in the pathogenesis of NAFLD development. The regulation of SIRT1/AMPK signaling greatly contributes to the underlying therapeutic mechanism of SNN for NAFLD.

Progress in Nonalcoholic Fatty Liver Disease: SIRT Family Regulates Mitochondrial Biogenesis

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic steatosis, insulin resistance, mitochondrial dysfunction, inflammation, and oxidative stress. As a group of NAD+-dependent III deacetylases, the sirtuin (SIRT1-7) family plays a very important role in regulating mitochondrial biogenesis and participates in the progress of NAFLD. SIRT family members are distributed in the nucleus, cytoplasm, and mitochondria; regulate hepatic fatty acid oxidation metabolism through different metabolic pathways and mechanisms; and participate in the regulation of mitochondrial energy metabolism. SIRT1 may improve NAFLD by regulating ROS, PGC-1α, SREBP-1c, FoxO1/3, STAT3, and AMPK to restore mitochondrial function and reduce steatosis of the liver. Other SIRT family members also play a role in regulating mitochondrial biogenesis, fatty acid oxidative metabolism, inflammation, and insulin resistance. Therefore, this paper comprehensively introduces the role of SIRT family in regulating mitochondrial biogenesis in the liver in NAFLD, aiming to further explain the importance of SIRT family in regulating mitochondrial function in the occurrence and development of NAFLD, and to provide ideas for the research and development of targeted drugs. Relatively speaking, the role of some SIRT family members in NAFLD is still insufficiently clear, and further research is needed.

Ketone Bodies and SIRT1, Synergic Epigenetic Regulators for Metabolic Health: A Narrative Review

Ketone bodies (KBs) and Sirtuin-1 (SIRT1) have received increasing attention over the past two decades given their pivotal function in a variety of biological contexts, including transcriptional regulation, cell cycle progression, inflammation, metabolism, neurological and cardiovascular physiology, and cancer. As a consequence, the modulation of KBs and SIRT1 is considered a promising therapeutic option for many diseases. The direct regulation of gene expression can occur in vivo through histone modifications mediated by both SIRT1 and KBs during fasting or low-carbohydrate diets, and dietary metabolites may contribute to epigenetic regulation, leading to greater genomic plasticity. In this review, we provide an updated overview of the epigenetic interactions between KBs and SIRT1, with a particular glance at their central, synergistic roles for metabolic health.

NAFLD: Mechanisms, Treatments, and Biomarkers

Nonalcoholic fatty liver disease (NAFLD), recently renamed metabolic-associated fatty liver disease (MAFLD), is one of the most common causes of liver diseases worldwide. NAFLD is growing in parallel with the obesity epidemic. No pharmacological treatment is available to treat NAFLD, specifically. The reason might be that NAFLD is a multi-factorial disease with an incomplete understanding of the mechanisms involved, an absence of accurate and inexpensive imaging tools, and lack of adequate non-invasive biomarkers. NAFLD consists of the accumulation of excess lipids in the liver, causing lipotoxicity that might progress to metabolic-associated steatohepatitis (NASH), liver fibrosis, and hepatocellular carcinoma. The mechanisms for the pathogenesis of NAFLD, current interventions in the management of the disease, and the role of sirtuins as potential targets for treatment are discussed here. In addition, the current diagnostic tools, and the role of non-coding RNAs as emerging diagnostic biomarkers are summarized. The availability of non-invasive biomarkers, and accurate and inexpensive non-invasive diagnosis tools are crucial in the detection of the early signs in the progression of NAFLD. This will expedite clinical trials and the validation of the emerging therapeutic treatments.

The Clock-NAD+ -Sirtuin connection in nonalcoholic fatty liver disease

Nonalcoholic or metabolic associated fatty liver disease (NAFLD/MAFLD) is a hepatic reflection of metabolic derangements characterized by excess fat deposition in the hepatocytes. Identifying metabolic regulatory nodes in fatty liver pathology is essential for effective drug targeting. Fatty liver is often associated with circadian rhythm disturbances accompanied with alterations in physical and feeding activities. In this regard, both sirtuins and clock machinery genes have emerged as critical metabolic regulators in maintaining liver homeostasis. Knockouts of either sirtuins or clock genes result in obesity associated with the fatty liver phenotype. Sirtuins (SIRT1-SIRT7) are a highly conserved family of nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases, protecting cells from metabolic stress by deacetylating vital proteins associated with lipid metabolism. Circadian rhythm is orchestrated by oscillations in expression of master regulators (BMAL1 and CLOCK), which in turn regulate rhythmic expression of clock-controlled genes involved in lipid metabolism. The circadian metabolite, NAD+ , serves as a crucial link connecting clock genes to sirtuin activity. This is because, NAMPT which is a rate limiting enzyme in NAD+ biosynthesis is transcriptionally regulated by the clock genes and NAD+ in turn is a cofactor regulating the deacetylation activity of sirtuins. Intriguingly, on one hand the core circadian clock regulates the sirtuin activity and on the other hand the activated sirtuins regulate the acetylation status of clock proteins thereby affecting their transcriptional functions. Thus, the Clock-NAD+-Sirtuin connection represents a novel "feedback loop" circuit that regulates the metabolic machinery. The current review underpins the importance of NAD+ on the sirtuin and clock connection in preventing fatty liver disorder.

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.

Effect of Structured Diabetes Education on Diabetic Angiopathies Among Kidney Transplant Recipients With Posttransplant Diabetes: Kuwait Experience

OBJECTIVES

Diabetes knowledge among kidney transplant recipients with posttransplant diabetes has not been exhaustively assessed. Here, we evaluated the effects of structured diabetes education on development of diabetic micro- and macroangiopathies in kidney transplant patients with posttransplant diabetes.

MATERIALS AND METHODS

This prospective randomized controlled study categorized 210 renal transplant patients with posttransplant diabetes mellitus into 2:1 groups according to type of diabetes education. Group 1 (n = 140) received structured education, and group 2 (n = 70) received conventional education. Patient data were collected through patient identification and metabolic control parameter forms.

RESULTS

Most patients in groups 1 and 2, respectively, were Kuwaiti (60.7% vs 58.6%), men (57.9% vs 68.6%), and had high school-level education (43.6% vs 48.6%). Chronic glomerulonephritis was the original disease in 36.4% versus 35.4% of patients. Most patients (72.8% vs 78.6% in group 1 vs 2) received pretransplant hemodialysis. At study start, the rate of patients with diabetic neuropathy was comparable between groups (32.4% vs 27.9%). Moreover, after completion of 24 months of education, neurological evaluation by electromyograph and nerve conduction studies did not show any significant differences between the groups (P > .05). Similarly, the number of patients with fundus imaging showing retinopathy was comparable between groups at start and end of study (P > .05). Although macroangiopathic events were higher in group 1, this finding was not significant (P > .05). However, although the percentage of patients with nephropathy was comparable in both groups at start of study, the percentage decreased significantly in group 1 at 24 months after completion of education compared with group 2 and baseline value (P = .016).

CONCLUSIONS

Structured diabetes education was associated with reduced diabetic nephropathy but had no significant effects on other micro- or macroangiopathies. However, we recommend education for all kidney transplant recipients with diabetes.

Targeting Gut Microbiota With Natural Polysaccharides: Effective Interventions Against High-Fat Diet-Induced Metabolic Diseases

Unhealthy diet, in particular high-fat diet (HFD) intake, can cause the development of several metabolic disorders, including obesity, hyperlipidemia, type 2 diabetes mellitus (T2DM), non-alcoholic fatty liver disease (NAFLD), and metabolic syndrome (MetS). These popular metabolic diseases reduce the quality of life, and induce premature death worldwide. Evidence is accumulating that the gut microbiota is inextricably associated with HFD-induced metabolic disorders, and dietary intervention of gut microbiota is an effective therapeutic strategy for these metabolic dysfunctions. Polysaccharides are polymeric carbohydrate macromolecules and sources of fermentable dietary fiber that exhibit biological activities in the prevention and treatment of HFD-induced metabolic diseases. Of note, natural polysaccharides are among the most potent modulators of the gut microbiota composition. However, the prebiotics-like effects of polysaccharides in treating HFD-induced metabolic diseases remain elusive. In this review, we introduce the critical role of gut microbiota human health and HFD-induced metabolic disorders. Importantly, we review current knowledge about the role of natural polysaccharides in improving HFD-induced metabolic diseases by regulating gut microbiota.

Effect of Turmeric Supplementation on Blood Pressure and Serum Levels of Sirtuin 1 and Adiponectin in Patients with Nonalcoholic Fatty Liver Disease: A Double-Blind, Randomized, Placebo-Controlled Trial

Nonalcoholic fatty liver disease (NAFLD) is commonly associated with obesity. This randomized, double-blind, placebo-controlled trial aimed to evaluate the effects of turmeric on serum adiponectin and sirtuin 1 (SIRT1) levels, blood pressure, and body mass index (BMI) in patients with NAFLD. A total of 46 eligible patients with NAFLD (BMI, 25.0∼39.9 kg/m²) were randomly allocated to turmeric and placebo groups using block randomization. The turmeric group (n=23) was administered 3,000 mg/d turmeric powder in six 500-mg capsules for 12 weeks, whereas the placebo group (n=23) was administered six placebo capsules/d for 12 weeks. Body weight, BMI, serum SIRT1 and adiponectin levels, and systolic and diastolic blood pressures were measured at baseline and 12 weeks after intervention. Serum SIRT1 levels increased significantly in the turmeric group compared with the placebo group. Additionally, participants in the turmeric group exhibited lower weight, BMI, and systolic blood pressure after 12 weeks of intervention compared with the baseline. Turmeric effectively improved SIRT1 levels in patients with NAFLD compared with the placebo. The efficacy of turmeric might increase with long-term use at higher doses.

Factors That Predict the Progression of Non-alcoholic Fatty Liver Disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) refers to a spectrum of diseases involving the deposition of fat in the hepatocytes of people with little to no alcohol consumption. NAFLD is associated with hypertension, diabetes, obesity, etc. As their prevalence increases, the propensity and severity of NAFLD might increase. As per the recently developed multi-hit hypothesis, factors like oxidative stress, genetic predisposition, lipotoxicity, and insulin resistance have been found to play a key role in the development of NAFLD and its associated complications. This article focuses on NAFLD, its pathophysiology, risk factors, and the various genetic and epigenetic factors involved in its development along with possible treatment modalities.

We conducted an all-language literature search on Medline, Cochrane, Embase, and Google Scholar until October 2021. The following search strings and Medical Subject Heading (MeSH) terms were used: “NAFLD,” “NASH,” “Fibrosis,” and “Insulin Resistance.” We explored the literature on NAFLD for its epidemiology, pathophysiology, the role of various genes, and how they influence the disease and associated complications about the disease and its hepatic and extrahepatic complications. With its rapidly increasing prevalence rates across the world and serious complications like NASH and hepatocellular carcinoma, NAFLD is becoming a major public health issue and more research is needed to formulate better screening tools and treatment protocols.

Sirtuin 1 is involved in oleic acid-induced calf hepatocyte steatosis via alterations in lipid metabolism-related proteins

Sirtuin 1 (SIRT1), an NAD-dependent protein deacetylase, plays a central role in the control of lipid metabolism in nonruminants. However, the role of SIRT1 in hepatic lipid metabolism in dairy cows with fatty liver is not well known. Thus, we used isolated primary bovine hepatocytes to determine the role of SIRT1 in protecting cells against oleic acid (OA)-induced steatosis. Recombinant adenoviruses to overexpress (AD-GFP-SIRT1-E) or knockdown (AD-GFP-SIRT1-N) SIRT1 were used for transduction of hepatocytes. Calf hepatocytes isolated from five female calves (1 d old, 30 to 40 kg) were used to determine both time required and the lowest dose of OA that could induce triacylglycerol (TAG) accumulation. Analyses indicated that 0.25 mM OA for 24 h was suitable to induce TAG accumulation. In addition, OA not only led to an increase in TAG, but also upregulated mRNA and protein abundance of sterol regulatory element-binding transcription factor 1 (SREBF1) and downregulated SIRT1 and peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PPARGC1A). Thus, these in vitro conditions were deemed optimal for subsequent experiments. Calf hepatocytes were cultured and incubated with OA (0.25 mM) for 24 h, followed by adenoviral AD-GFP-SIRT1-E or AD-GFP-SIRT1-N transduction for 48 h. Overexpression of SIRT1 led to greater protein and mRNA abundance of SIRT1 along with fatty acid oxidation-related genes including PPARGC1A, peroxisome proliferator-activated receptor alpha (PPARA), retinoid X receptor α (RXRA), and ratio of phospho-acetyl-CoA carboxylase alpha (p-ACACA)/total acetyl-CoA carboxylase alpha (ACACA). In contrast, it resulted in lower protein and mRNA abundance of genes related to lipid synthesis including SREBF1, fatty acid synthase (FASN), apolipoprotein E (APOE), and low-density lipoprotein receptor (LDLR). The concentration of TAG decreased due to SIRT1 overexpression. In contrast, silencing SIRT1 led to lower protein and mRNA abundance of SIRT1, PPARGC1A, PPARA, RXRA, and greater protein and mRNA abundance of SREBF1, FASN, APOE, and LDLR. Further, those responses were accompanied by greater content of cellular TAG and total cholesterol (TC). Overall, data from these in vitro studies indicated that SIRT1 is involved in the regulation of lipid metabolism in calf hepatocytes subjected to an increase in the supply of OA. Thus, it is possible that alterations in SIRT1 abundance and activity in vivo contribute to development of fatty liver in dairy cows.

Dietary Patterns Influence Target Gene Expression through Emerging Epigenetic Mechanisms in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) refers to the pathologic buildup of extra fat in the form of triglycerides in liver cells without excessive alcohol intake. NAFLD became the most common cause of chronic liver disease that is tightly associated with key aspects of metabolic disorders, including insulin resistance, obesity, diabetes, and metabolic syndrome. It is generally accepted that multiple mechanisms and pathways are involved in the pathogenesis of NAFLD. Heredity, sedentary lifestyle, westernized high sugar saturated fat diet, metabolic derangements, and gut microbiota, all may interact on a on genetically susceptible individual to cause the disease initiation and progression. While there is an unquestionable role for gene-diet interaction in the etiopathogenesis of NAFLD, it is increasingly apparent that epigenetic processes can orchestrate many aspects of this interaction and provide additional mechanistic insight. Exciting research demonstrated that epigenetic alterations in chromatin can influence gene expression chiefly at the transcriptional level in response to unbalanced diet, and therefore predispose an individual to NAFLD. Thus, further discoveries into molecular epigenetic mechanisms underlying the link between nutrition and aberrant hepatic gene expression can yield new insights into the pathogenesis of NAFLD, and allow innovative epigenetic-based strategies for its early prevention and targeted therapies. Herein, we outline the current knowledge of the interactive role of a high-fat high-calories diet and gene expression through DNA methylation and histone modifications on the pathogenesis of NAFLD. We also provide perspectives on the advancement of the epigenomics in the field and possible shortcomings and limitations ahead.

A novel supplement with yeast β-glucan, prebiotic, minerals and Silybum marianum synergistically modulates metabolic and inflammatory pathways and improves steatosis in obese mice

OBJECTIVE

To evaluate the synergic effects of a novel oral supplement formulation, containing prebiotics, yeast β-glucans, minerals and silymarin (Silybum marianum), on lipid and glycidic metabolism, inflammatory and mitochondrial proteins of the liver, in control and high-fat diet-induced obese mice.

METHODS

After an acclimation period, 32 male C57BL/6 mice were divided into the following groups: nonfat diet (NFD) vehicle, NFD supplemented, high-fat diet (HFD) vehicle and HFD supplemented. The vehicle and experimental formulation were administered orally by gavage once a day during the last four weeks of the diet (28 consecutive days). We then evaluated energy homeostasis, inflammation, and mitochondrial protein expression in these groups of mice.

RESULTS

After four weeks of supplementation, study groups experienced reduced glycemia, dyslipidemia, fat, and hepatic fibrosis levels. Additionally, proliferator-activated receptor-α, AMP-activated protein kinase-1α, peroxisome proliferator-activated receptor γ co-activator-1α, and mitochondrial transcription factor A expression levels were augmented; however, levels of inhibitor of nuclear factor-κB kinase subunit α and p65 nuclear factor-κB expression, and oxidative markers were reduced. Notably, the cortisol/C-reactive protein ratio, a well-characterized marker of the hypothalamic-pituitary-adrenal axis immune interface status, was found to be modulated by the supplement.

CONCLUSION

We discovered that the novel supplement was able to modify different antioxidant, metabolic and inflammatory pathways, improving the energy homeostasis and inflammatory status, and consequently alleviated hepatic steatosis.

Role of Histone Deacetylases in Monocyte Function in Health and Chronic Inflammatory Diseases

Histone deacetylases (HDACs) are a family of 18 members that participate in the epigenetic regulation of gene expression. In addition to histones, some HDACs also deacetylate transcription factors and specific cytoplasmic proteins.Monocytes, as part of the innate immune system, maintain tissue homeostasis and help fight infections and cancer. In these cells, HDACs are involved in multiple processes including proliferation, migration, differentiation, inflammatory response, infections, and tumorigenesis. Here, a systematic description of the role that most HDACs play in these functions is reviewed. Specifically, some HDACs induce a pro-inflammatory response and play major roles in host defense. Conversely, other HDACs reprogram monocytes and macrophages towards an immunosuppressive phenotype. The right balance between both types helps monocytes to respond correctly to the different physiological/pathological stimuli. However, aberrant expressions or activities of specific HDACs are associated with autoimmune diseases along with other chronic inflammatory diseases, infections, or cancer.This paper critically reviews the interesting and extensive knowledge regarding the role of some HDACs in these pathologies. It also shows that as yet, very little progress has been made toward the goal of finding effective HDAC-targeted therapies. However, given their obvious potential, we conclude that it is worth the effort to develop monocyte-specific drugs that selectively target HDAC subtypes with the aim of finding effective treatments for diseases in which our innate immune system is involved.

Dietary Betaine Mitigates Hepatic Steatosis and Inflammation Induced by a High-Fat-Diet by Modulating the Sirt1/Srebp-1/Pparɑ Pathway in Juvenile Black Seabream (Acanthopagrus schlegelii)

The present study aimed to elucidate the mechanism of dietary betaine, as a lipid-lowering substance, on the regulation of lipid metabolism and inflammation in juvenile black seabream (Acanthopagrus schlegelii) fed a high fat diet. An 8-week feeding trial was conducted in black seabream with an initial weight of 8.39 ± 0.01g fed four isonitrogenous diets including Control, medium-fat diet (11%); HFD, high-fat diet (17%); and HFD supplemented with two levels (10 and 20 g/kg) of betaine, HFD+B1 and HFD+B2, respectively. SGR and FE in fish fed HFD+B2 were significantly higher than in fish fed HFD. Liver histology revealed that vacuolar fat droplets were smaller and fewer in bream fed HFD supplemented with betaine compared to fish fed HFD. Betaine promoted the mRNA and protein expression levels of silent information regulator 1 (Sirt1), up-regulated mRNA expression and protein content of lipid peroxisome proliferator-activated receptor alpha (pparα), and down-regulated mRNA expression and protein content of sterol regulatory element-binding protein-1(srebp-1). Furthermore, the mRNA expression levels of anti-inflammatory cytokines in liver and intestine were up-regulated, while nuclear factor kB (nf-kb) and pro-inflammatory cytokines were down-regulated by dietary betaine supplementation. Likewise, in fish that received lipopolysaccharide (LPS) to stimulate inflammatory responses, the expression levels of mRNAs of anti-inflammatory cytokines in liver, intestine and kidney were up-regulated in fish fed HFD supplemented with betaine compared with fish fed HFD, while nf-kb and pro-inflammatory cytokines were down-regulated. This is the first report to suggest that dietary betaine could be an effective feed additive to alleviate hepatic steatosis and attenuate inflammatory responses in black seabream fed a high fat diet by modulating the Sirt1/Srebp-1/Pparɑ pathway.

Non-Alcoholic Fatty Liver Disease: Metabolic, Genetic, Epigenetic and Environmental Risk Factors

Non-alcoholic fatty liver disease (NAFLD) is one of the most frequent causes of chronic liver disease in the Western world, probably due to the growing prevalence of obesity, metabolic diseases, and exposure to some environmental agents. In certain patients, simple hepatic steatosis can progress to non-alcoholic steatohepatitis (NASH), which can sometimes lead to liver cirrhosis and its complications including hepatocellular carcinoma. Understanding the mechanisms that cause the progression of NAFLD to NASH is crucial to be able to control the advancement of the disease. The main hypothesis considers that it is due to multiple factors that act together on genetically predisposed subjects to suffer from NAFLD including insulin resistance, nutritional factors, gut microbiota, and genetic and epigenetic factors. In this article, we will discuss the epidemiology of NAFLD, and we overview several topics that influence the development of the disease from simple steatosis to liver cirrhosis and its possible complications.

Role of histone deacetylase on nonalcoholic fatty liver disease

Introduction: Nonalcoholic fatty liver disease (NAFLD) is a group of diseases related to metabolic abnormalities, which severely impairs the life and health of patients, and brings great pressure to the society and medical resources. Currently, there is no specific treatment. Histone deacetylases (HDACs) have recently been reported to be involved in the pathogenesis of NAFLD and are considered as new targets for the treatment of NAFLD.Area covered: In this review, we summarized the role of HDACs in the pathogenesis of NAFLD and proposed possible therapeutic targets in order to provide new strategies for the treatment of NAFLD.Expert commentary: HDACs and related signal pathways are widely involved in the pathogenesis of NAFLD and have the potential to become therapeutic targets. However, based on current research alone, HDACs cannot be practical applied to the treatment of NAFLD. Therefore, more research on the pathogenesis of NAFLD and the mechanism of HDACs is what we need most now.

Echinacoside improves diabetic liver injury by regulating the AMPK/SIRT1 signaling pathway in db/db mice

AIMS

Echinacoside (ECH) is a natural compound extracted from the stem of the Cistanche deserticola plant, has significant biological properties, including antioxidant, anti-inflammatory, neuroprotective, anti-tumor, hepatoprotective, and immunomodulatory properties. In this study, we aimed to explore the protection effects and mechanisms of ECH on diabetic liver injury in db/db mice.

MAIN METHODS

Overall, 6-week-old db/db mice (n = 20) were randomly allocated to 2 groups: diabetic model group (db/db group, intragastric administration of normal saline, n = 10) and ECH-treated group (db/db + ECH group, n = 10). Additionally, the normal control group comprised 6-week-old db/m mice (db/m group, normal saline intragastric administration, n = 10). ECH was administered once a day for 10 weeks. Weight and fasting blood glucose (FBG) were measured biweekly. HE staining and Oil O staining were used to evaluate liver tissue pathological changes and lipid accumulation respectively. Immunofluorescence staining, Western blot and RT-PCR analysis were used to detect the expression of components of the AMPK/SIRT1 signaling axis.

KEY FINDINGS

The results showed that the administration of echinacoside for 10 weeks could significantly improve liver injury and insulin resistance in db/db mice (p < 0.01). Also, echinacoside treatment helped to reduce blood lipids and blood glucose (p < 0.01). Moreover, ECH actived AMPK/SIRT1 signaling, upregulated peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1α), proliferator-activated receptor-α (PPARα), carnitine palmitoyl transferase-1A (CPT1A) in db/db mice (p < 0.01).

SIGNIFICANCE

The effect of ECH may be elicited by the activation of the liver AMPK/SIRT1 pathway and its downstream factors to improve adiposity, insulin resistance, and dyslipidemia.

Mesenchymal stem cell-conditioned medium improved mitochondrial function and alleviated inflammation and apoptosis in non-alcoholic fatty liver disease by regulating SIRT1

Non-alcoholic fatty liver disease (NAFLD), an emerging risk factor for diabetes, is now recognized as the most common liver disease worldwide. Mesenchymal stem cells (MSCs), a promising tool in regenerative medicine, release abundant molecules into the conditioned medium (CM). Increasing evidence showed that MSC-CM is beneficial for diabetes-associated NAFLD. However, the mechanism of how MSC-CM improves NAFLD remains uncertain. In this study, to determine the effects of MSC-CM on NAFLD, streptozotocin (STZ) and high-fat diet (HFD) induced T2DM mice model and palmitic acid (PA)-stimulated L-O2 cells were used and treated with MSC-CM. Our results demonstrated that MSC-CM improved insulin resistance in diabetic mice, amended the pathological structure of the liver, enhanced the liver's total antioxidant capacity and mitochondrial function, reduced inflammation and cell apoptosis. We further verified that SIRT1 played a key role in mediating the protective effect of MSC-CM. These findings provide novel evidence that MSC-CM has the potential to treat T2DM patients with NAFLD clinically.

Dysregulation of intercellular signaling by MOF deletion leads to liver injury

Epigenetic mechanisms that alter heritable gene expression and chromatin structure play an essential role in many biological processes, including liver function. Human MOF (males absent on the first) is a histone acetyltransferase that is globally downregulated in human steatohepatitis. However, the function of MOF in the liver remains unclear. Here, we report that MOF plays an essential role in adult liver. Genetic deletion of Mof by Mx1-Cre in the liver leads to acute liver injury, with increase of lipid deposition and fibrosis akin to human steatohepatitis. Surprisingly, hepatocyte-specific Mof deletion had no overt liver abnormality. Using the in vitro coculturing experiment, we show that Mof deletion-induced liver injury requires coordinated changes and reciprocal signaling between hepatocytes and Kupffer cells, which enables feedforward regulation to augment inflammation and apoptotic responses. At the molecular level, Mof deletion induced characteristic changes in metabolic gene programs, which bore noticeable similarity to the molecular signature of human steatohepatitis. Simultaneous deletion of Mof in both hepatocytes and macrophages results in enhanced expression of inflammatory genes and NO signaling in vitro. These changes, in turn, lead to apoptosis of hepatocytes and lipotoxicity. Our work highlights the importance of histone acetyltransferase MOF in maintaining metabolic liver homeostasis and sheds light on the epigenetic dysregulation in liver pathogenesis.

Genetic and epigenetic disease modifiers: non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD)

Inter-individual and inter-ethnic differences and difference in the severity and progression of liver disease among patients with non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) suggests the involvement of genetic and epigenetic factors in their pathogenesis. This article reviews the genetic and epigenetic modifiers in patients with NAFLD and ALD. Evidence regarding the genetic and epigenetic disease modifiers of NAFLD and ALD was reviewed by searching the available literature. Both genome wide association studies (GWAS) and candidate gene studies pertaining to the pathogenesis in both diseases were included. Clinical implications of the available information are also discussed. Several studies have shown association of both NAFLD and ALD with I148M PNPLA3 variant. In addition to the higher prevalence of hepatic steatosis, the I148M PNPLA3 variant is also associated with severity of liver disease and risk of hepatocellular carcinoma (HCC). TM6SF2 is the other genetic variant shown to be significantly associated with hepatic steatosis and cirrhosis in patients with NAFLD and ALD. The Membrane bound O-acyltransferase domain-containing 7 (MBOAT7) genetic variant is also associated with both NAFLD and ALD. In addition to these mutations, several variants related to the genes involved in glucose metabolism, insulin resistance, lipid metabolism, oxidative stress, inflammatory pathways, fibrosis have also been shown to be the disease modifiers in patients with NAFLD and ALD. Epigenetics involving several micro RNAs and DNA methylation could also modify the disease course in NAFLD and ALD. In conclusion the available literature suggests that genetics and epigenetics are involved in the pathogenesis of NAFLD and ALD which may affect the disease prevalence, severity and response to treatment in these patients.

Ketogenesis and SIRT1 as a tool in managing obesity

Obesity is a serious chronic disease and a public health concern in both developing and developed countries. Managing obesity has been a great challenge for both health care professionals and patients alike. Among the various diet programs aimed at promoting weight loss, the ketogenic diet, a diet high in fat and low in carbohydrates, has been at the forefront recently and its mechanism in weight loss is much debated. Activation of Sirtuin 1 or SIRT1 is able to circumvent various diseases, including metabolic syndrome and obesity and is thought to be a potentially reliable treatment target for both of them. Augmentation of SIRT1 may be carried out using dietary means such as nicotinamide adenine dinucleotide (NAD) supplementation and/or ketogenic diet. Although ketogenic diet may augment SIRT1 activation in people affected by obesity, recent studies have indicated that the relationship between SIRT1 and ketogenesis is unpredictable. The exact circumstances and mechanisms of SIRT1, NAD and ketogenesis in the clinical setting as an intervention tool in managing obesity remained uncertain. Although several recent literatures have documented significant weight-loss following ketogenic diet interventions, there were limitations with regards to duration of trial, choice and the number of trial subjects. Studies investigating the safety of ketogenic diet in the long term, beyond 46 weeks and related mechanism and pathways are still lacking and the sustainability of this diet remains to be determined. This review explores the recent progress on ketogenic diet and its relationships with SIRT1 as a tool in managing obesity and relevant clinical implications.

Activation of the AMPK-SIRT1 pathway contributes to protective effects of Salvianolic acid A against lipotoxicity in hepatocytes and NAFLD in mice

Background: Salvianolic acid A (Sal A), a natural polyphenol compound extracted from Radix Salvia miltiorrhiza (known as Danshen in China), possesses a variety of potential pharmacological activities. The aim of this study is to determine mechanisms of hepatoprotective effects of Sal A against lipotoxicity both in cultured hepatocytes and in a mouse model of fatty liver disease. Methods: High-fat and high-carbohydrate diet (HFCD)-fed C57BL/6J mice were employed to establish hepatic lipotoxicity in a mouse model. Two doses of Sal A were administered every other day via intraperitoneal injection (20 and 40 mg/kg BW, respectively). After a 10-week intervention, liver injury was detected by immunohistochemical and biochemical analyses. For in vitro studies, we used HepG2, a human hepatoma cell line, and exposed them to palmitic acid to induce lipotoxicity. The protective effects of Sal A on palmitic acid-induced lipotoxicity were examined in Sal A-pretreated HepG2 cells. Results: Sal A treatments attenuated body weight gain, liver injury, and hepatic steatosis in mice exposed to HFCD. Sal A pretreatments ameliorated palmitic acid-induced cell death but did not reverse effects of HFCD- or palmitate-induced activations of JNK, ERK1/2, and PKA. Induction of p38 phosphorylation was significantly reversed by Sal A in HFCD-fed mice but not in palmitate-treated HepG2 cells. However, Sal A rescued hepatic AMP-activated protein kinase (AMPK) suppression and sirtuin 1 (SIRT1) downregulation by both HFCD feeding in mice and exposure to palmitate in HepG2 cells. Sal A dose-dependently up-regulated p-AMPK and SIRT1 protein levels. Importantly, siRNA silencing of either AMPK or SIRT1 gene expression abolished the protective effects of Sal A on lipotoxicity. Moreover, while AMPK silencing blocked Sal A-induced SIRT1, silencing of SIRT1 had no effect on Sal A-triggered AMPK activation, suggesting SIRT1 upregulation by Sal A is mediated by AMPK activation. Conclusion: Our data uncover a novel mechanism for hepatoprotective effects of Sal A against lipotoxicity both in livers from HFCD-fed mice and palmitic acid-treated hepatocytes.

Blood SIRT1 Shows a Coherent Association with Leptin and Adiponectin in Relation to the Degree and Distribution of Adiposity: A Study in Obesity, Normal Weight and Anorexia Nervosa

Sirtuin 1 (SIRT1) is a sensor of cell energy availability, and with leptin and adiponectin, it regulates metabolic homeostasis. Widely studied in tissues, SIRT1 is under evaluation as a plasmatic marker. We aimed at assessing whether circulating SIRT1 behaves consistently with leptin and adiponectin in conditions of deficiency, excess or normal fat content. Eighty subjects were evaluated: 27 with anorexia nervosa (AN), 26 normal-weight and 27 with obesity. Bloodstream SIRT1, leptin and adiponectin (ELISA), total and trunk fat mass (FM) %, abdominal visceral adipose tissue, liver steatosis and epicardial fat thickness (EFT) were assessed. For each fat store, the coefficient of determination (R²) was used to evaluate the prediction capability of SIRT1, leptin and adiponectin. Plasma SIRT1 and adiponectin coherently decreased with the increase of FM, while the opposite occurred with leptin. Mean levels of each analyte were different between groups (p < 0.005). A significant association between plasma variables and FM depots was observed. SIRT1 showed a good predictive strength for FM, particularly in the obesity group, where the best R² was recorded for EFT (R² = 0.7). Blood SIRT1, adiponectin and leptin behave coherently with FM and there is synchrony between them. The association of SIRT1 with FM is substantially superimposable to that of adiponectin and leptin. Given its homeostatic roles, SIRT1 may deserve to be considered as a plasma clinical/biochemical parameter of adiposity and metabolic health.

Understanding Dietary Intervention-Mediated Epigenetic Modifications in Metabolic Diseases

The global prevalence of metabolic disorders, such as obesity, diabetes and fatty liver disease, is dramatically increasing. Both genetic and environmental factors are well-known contributors to the development of these diseases and therefore, the study of epigenetics can provide additional mechanistic insight. Dietary interventions, including caloric restriction, intermittent fasting or time-restricted feeding, have shown promising improvements in patients' overall metabolic profiles (i.e., reduced body weight, improved glucose homeostasis), and an increasing number of studies have associated these beneficial effects with epigenetic alterations. In this article, we review epigenetic changes involved in both metabolic diseases and dietary interventions in primary metabolic tissues (i.e., adipose, liver, and pancreas) in hopes of elucidating potential biomarkers and therapeutic targets for disease prevention and treatment.

Reduced serum SIRT1 levels in patients with Parkinson's disease: a cross-sectional study in China

BACKGROUND

Parkinson's disease (PD) is a movement disorder lacking of validated biomarkers. Experimental studies support the potential value of silent information regulator 1 (SIRT1) in neurodegeneration including PD. We aim to detect the serum levels of SIRT1 in PD patients in order to assess its value as a potential biomarker of PD.

METHODS

Fifty-eight PD patients and 91 healthy controls were included. Serum SIRT1 was determined by enzyme-linked immunosorbent assay (ELISA) and compared between controls and PD patients. Spearman correlation coefficient was analyzed to study the relationship between serum SIRT1 and clinical parameters in PD patients. Receiver operating characteristic (ROC) analysis was conducted to assess the diagnostic value of serum SIRT1 in PD identification.

RESULTS

Serum SIRT1 was significantly reduced in PD patients compared with controls. According to the ROC curve, the optimal cut-off point was 0.47 ng/ml with the sensitivity of 71% and specificity of 71%. Serum SIRT1 level was related to age of onset, disease duration, Hoehn-Yahr staging scale (H-Y stage), Unified Parkinson's Disease Rating Scale III (UPDRS III), and Mini-Mental State Examination (MMSE). PD patients with cognitive impairment had lower serum SIRT1 than those with normal cognitive ability.

CONCLUSIONS

Serum SIRT1 was reduced in PD patients and associated with disease severity and cognitive function. Our results indicate that SIRT1 may be a potential biomarker for PD.

Serum NT/CT SIRT1 ratio reflects early osteoarthritis and chondrosenescence

Objective

Previous work has established that the deacetylase sirtuin-1 (SIRT1) is cleaved by cathepsin B in chondrocytes subjected to proinflammatory stress, yielding a stable but inactive N-terminal (NT) polypeptide (75SIRT1) and a C-terminal (CT) fragment. The present work examined if chondrocyte-derived NT-SIRT1 is detected in serum and may serve as an investigative and exploratory biomarker of osteoarthritis (OA).

Methods

We developed a novel ELISA assay to measure the ratio of NT to CT of SIRT1 in the serum of human individuals and mice subjected to post-traumatic OA (PTOA) or age-dependent OA (ADOA). We additionally monitored NT/CT SIRT1 in mice subject to ADOA/PTOA followed by senolytic clearance. Human chondrosenescent and non-senescent chondrocytes were exposed to cytokines and analysed for apoptosis and NT/CT SIRT1 ratio in conditioned medium.

Results

Wild-type mice with PTOA or ADOA of moderate severity exhibited increased serum NT/CT SIRT1 ratio. In contrast, this ratio remained low in cartilage-specific Sirt1 knockout mice despite similar or increased PTOA and ADOA severity. Local clearance of senescent chondrocytes from old mice with post-traumatic injury resulted in a lower NT/CT ratio and reduced OA severity. While primary chondrocytes exhibited NT/CT ratio increased in conditioned media after prolonged cytokine stimulation, this increase was not evident in cytokine-stimulated chondrosenescent cells. Finally, serum NT/CT ratio was elevated in humans with early-stage OA.

Conclusions

Increased levels of serum NT/CT SIRT1 ratio correlated with moderate OA in both mice and humans, stemming at least in part from non-senescent chondrocyte apoptosis, possibly a result of prolonged inflammatory insult.

Combined high-intensity interval training and green tea supplementation enhance metabolic and antioxidant status in response to acute exercise in overweight women

Thirty sedentary overweight women were randomly assigned to three groups (n = 10), including HIIT + green tea, HIIT + placebo and green tea. The training program included 3 sessions/week HIIT while the supplement consuming groups took 3 * 500 mg of green tea tablets/day for 10 weeks. Results indicated that 10 weeks of HIIT and green tea meaningfully pronounced baseline serum levels of SIRT1 (P ≤ 0.0001), PGC-1α (P ≤ 0.0001) and CAT (P ≤ 0.0001). In addition, significant increase was observed in three indicators in HIIT + green tea group in comparison with two other research groups. Further, the responses of SIRT1 (P ≤ 0.01) and CAT (P ≤ 0.002) increased significantly to second acute exercise in all three groups. The combination of HIIT and green tea consumption may induce increasing SIRT1 and CAT in response to acute exercise and can improve antioxidant system, body composition and VO2 max results rather than green tea and training alone, in young sedentary overweight women.

Relevance of SIRT1-NF-κB Axis as Therapeutic Target to Ameliorate Inflammation in Liver Disease

Inflammation is an adaptive response in pursuit of homeostasis reestablishment triggered by harmful conditions or stimuli, such as an infection or tissue damage. Liver diseases cause approximately 2 million deaths per year worldwide and hepatic inflammation is a common factor to all of them, being the main driver of hepatic tissue damage and causing progression from non-alcoholic fatty liver disease (NAFLD) to non-alcoholic steatohepatitis (NASH), cirrhosis and, ultimately, hepatocellular carcinoma (HCC). The metabolic sensor SIRT1, a class III histone deacetylase with strong expression in metabolic tissues such as the liver, and transcription factor NF-κB, a master regulator of inflammatory response, show an antagonistic relationship in controlling inflammation. For this reason, SIRT1 targeting is emerging as a potential strategy to improve different metabolic and/or inflammatory pathologies. In this review, we explore diverse upstream regulators and some natural/synthetic activators of SIRT1 as possible therapeutic treatment for liver diseases.

BDNF Val66Met polymorphism alters food intake and hypothalamic BDNF expression in mice

Obesity, a rising public health burden, is a multifactorial disease with an increased risk for patients to develop several pathological conditions including type 2 diabetes mellitus, hypertension, and cardiovascular disease. Increasing evidence suggests a relationship between the human brain-derived neurotrophic factor (BDNF) Val66Met single-nucleotide polymorphism (SNP) and obesity, although the underlying mechanisms of this connection are still not completely understood. In the present study, we found that homozygous knock-in BDNF^Met/Met mice were overweight and hyperphagic compared to wildtype BDNF^Val/Val mice. Increased food intake was associated with reduction of total BDNF and BDNF1, BDNF4 and BDNF6 transcripts in the hypothalamus of BDNF^Met/Met mice. In contrast, in the white adipose tissue total BDNF and Glut4 expression levels were augmented, while sirtuin 1 and leptin receptor (Ob-R) expression levels were reduced in BDNF^Met/Met mice. Moreover, plasmatic leptin levels were decreased in BDNF^Met/Met mice. However, BDNF^Val/Val and BDNF^Met/Met mice showed a similar response to the insulin tolerance test and glucose tolerance test. Altogether, these results suggest that BDNF Val66Met SNP strongly contributes to adipose tissue pathophysiology, resulting in reduced circulating leptin levels and hypothalamic expression of BDNF, which, in turn, promote increased food intake and overweight in BDNF^Met/Met mice.

EX-527 Prevents the Progression of High-Fat Diet-Induced Hepatic Steatosis and Fibrosis by Upregulating SIRT4 in Zucker Rats

Sirtuin (SIRT) is known to prevent nonalcoholic fatty liver disease (NAFLD); however, the role of SIRT4 in the progression of hepatic fibrosis remains unknown. We hypothesize that EX-527, a selective SIRT1 inhibitor, can inhibit the progression of high-fat diet (HFD)-induced hepatic fibrosis. We found that SIRT4 expression in the liver of NAFLD patients is significantly lower than that in normal subjects. In this study, EX-527 (5 µg/kg), administered to HFD rats twice a week for ten weeks, reduced the serum levels of triglyceride (TG), total cholesterol, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) and attenuated hepatic fibrosis evidenced by Masson’s trichrome and hepatic fat by oil red-O staining. EX-527 upregulated SIRT2, SIRT3, and SIRT4 expression in the liver of HFD fed rats but downregulated transforming growth factor-β1 (TGF-β1) and α-smooth muscle actin (α-SMA) expression. It decreased proinflammatory cytokine production and hydroxyproline levels in the serum and SMAD4 expression and restored apoptotic protein (Bcl-2, Bax, and cleaved caspase-3) expression. These data propose a critical role for the SIRT4/SMAD4 axis in hepatic fibrogenesis. SIRT4 upregulation has the potential to counter HFD-induced lipid accumulation, inflammation, and fibrogenesis. We demonstrate that EX-527 is a promising candidate in inhibiting the progression of HFD-induced liver fibrosis.

Analysis of SIRT1 Expression in Plasma and in an In Vitro Model of Preeclampsia

Preeclampsia (PE) is a pregnancy-specific disorder that affects 3–8% expecting mothers worldwide being one of the main causes of maternal and fetal morbidity and mortality. The search for altered circulating molecules in PE is an important target to better understand the pathophysiology of this disease. Therefore, we evaluated Sirtuin-1 (SIRT1) concentration in plasma from healthy pregnant (HP) women, gestational hypertensive women (GH), and preeclampsia women (PE) via enzyme-linked immunosorbent assay (ELISA). We also measured intracellular SIRT1 in HUVECs incubated with plasma from PE patients compared to HP and GH via Western Blot Assay. Statistical differences were considered when p < 0.05. SIRT1 was downregulated in PE compared to HP and GH, both in plasma and in in vitro assay. Similarly, SIRT1 was also reduced in pregnant women who subsequently developed PE (case) compared to women who had healthy pregnancies (control). This reduction may be indicative of possible underlying pathophysiology mechanisms in PE.

Sirt1 during childhood is associated with microvascular function later in life

Microvascular dysfunction often precedes other age-related macrovascular conditions and predicts future cardiovascular risk. Sirtuin 1 (Sirt1) has recently emerged as a protein that protects the vasculature and reduces the risk of cardiovascular diseases. We tested the hypothesis that lower Sirt1 during childhood is associated with a reduced microvascular function during adulthood. Thirty-four adults (34 ± 3 yr) from the Augusta Heart Study returned to participate in the present clinical observational study. Sirt1 was assessed in samples collected during both adulthood and participants' childhood (16 ± 3 yr), and data were divided based on childhood Sirt1 concentrations: <3 ng/dL (LowCS; n = 16) and ≥3 ng/dL (HighCS; n = 18). MVF was evaluated in all of the adults using laser-Doppler flowmetry coupled with three vascular reactivity tests: 1) local thermal hyperemia (LTH), 2) post-occlusive reactive hyperemia (PORH), and 3) iontophoresis of acetylcholine (ACh). The hyperemic response to LTH was significantly (P ≤ 0.044) lower in the LowCS than in the HighCS group. Similarly, the LowCS also exhibited an ameliorated (P ≤ 0.045) response to the PORH test and lower (P ≤ 0.008) vasodilation in response to iontophoresis of ACh when compared with the HighCS. Positive relationships were identified between childhood Sirt1 and all MVF reactivity tests (r≥0.367, P ≤ 0.004). Novel observations suggest that lower Sirt1 during childhood is associated with premature microvascular dysfunction in adulthood. These findings provide evidence that Sirt1 may play a critical role in microvascular function and have therapeutic potential for the prevention of age-associated vascular dysfunction in humans.NEW & NOTEWORTHY With a longitudinal cohort, novel observations from the present study demonstrate that individuals who had lower Sirt1 early in life exhibit premature microvascular dysfunction during adulthood and may be at higher risk to develop CVD. These results provide experimental evidence that Sirt1 may play an important role in microvascular function with age and represent a potential therapeutic target to prevent premature vascular dysfunction.