Distinctive Roles of Sirtuins on Diabetes, Protective or Detrimental?

SIRT1 signaling pathways in sarcopenia: Novel mechanisms and potential therapeutic targets

Sarcopenia is an aging-related skeletal disease characterized by decreased muscle mass, strength, and physical function, severely affecting the quality of life (QoL) of the elderly population. Sirtuin 1 (SIRT1), as a nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylases, has been reported to participate in various aging-related signaling pathways and exert protective effect on many human diseases. SIRT1 functioned as an important role in the occurrence and progression of sarcopenia through regulating key pathways related to protein homeostasis, apoptosis, mitochondrial dysfunction, insulin resistance and autophagy in skeletal muscle, including SIRT1/Forkhead Box O (FoxO), AMP-activated protein kinase (AMPK)/SIRT1/nuclear factor κB (NF-κB), SIRT1/p53, AMPK/SIRT1/peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), and SIRT1/live kinase B1 (LKB1)/AMPK pathways. However, the specific mechanisms of these processes have not been fully illuminated. Currently, several SIRT1-mediated interventions on sarcopenia have been preliminarily developed, such as SIRT1 activator polyphenolic compounds, exercising and calorie restriction. In this review, we summarized the predominant mechanisms of SIRT1 involved in sarcopenia and therapeutic modalities targeting the SIRT1 signaling pathways for the prevention and prognosis of sarcopenia.

Histone deacetylases and inhibitors in diabetes mellitus and its complications

Diabetes mellitus (DM) is a metabolic disorder characterized by hyperglycemia, with its prevalence linked to both genetic predisposition and environmental factors. Epigenetic modifications, particularly through histone deacetylases (HDACs), have been recognized for their significant influence on DM pathogenesis. This review focuses on the classification of HDACs, their role in DM and its complications, and the potential therapeutic applications of HDAC inhibitors. HDACs, which modulate gene expression without altering DNA sequences, are categorized into four classes with distinct functions and tissue specificity. HDAC inhibitors (HDACi) have shown efficacy in various diseases, including DM, by targeting these enzymes. The review highlights how HDACs regulate β-cell function, insulin sensitivity, and hepatic gluconeogenesis in DM, as well as their impact on diabetic cardiomyopathy, nephropathy, and retinopathy. Finally, we suggest that targeted histone modification is expected to become a key method for the treatment of diabetes and its complications. The study of HDACi offers insights into new treatment strategies for DM and its associated complications.

Fatty infiltration in the musculoskeletal system: pathological mechanisms and clinical implications

Fatty infiltration denotes the anomalous accrual of adipocytes in non-adipose tissue, thereby generating toxic substances with the capacity to impede the ordinary physiological functions of various organs. With aging, the musculoskeletal system undergoes pronounced degenerative alterations, prompting heightened scrutiny regarding the contributory role of fatty infiltration in its pathophysiology. Several studies have demonstrated that fatty infiltration affects the normal metabolism of the musculoskeletal system, leading to substantial tissue damage. Nevertheless, a definitive and universally accepted generalization concerning the comprehensive effects of fatty infiltration on the musculoskeletal system remains elusive. As a result, this review summarizes the characteristics of different types of adipose tissue, the pathological mechanisms associated with fatty infiltration in bone, muscle, and the entirety of the musculoskeletal system, examines relevant clinical diseases, and explores potential therapeutic modalities. This review is intended to give researchers a better understanding of fatty infiltration and to contribute new ideas to the prevention and treatment of clinical musculoskeletal diseases.

Upregulation of α-ENaC induces pancreatic β-cell dysfunction, ER stress, and SIRT2 degradation

Islet beta cells (β-cells) produce insulin in response to high blood glucose levels, which is essential for preserving glucose homeostasis. Voltage-gated ion channels in β-cells, including Na +, K +, and Ca 2+ channels, aid in the release of insulin. The epithelial sodium channel alpha subunit (α-ENaC), a voltage-independent sodium ion channel, is also expressed in human pancreatic endocrine cells. However, there is no reported study on the function of ENaC in the β-cells. In the current study, we found that α-ENaC was expressed in human pancreatic glandule and pancreatic islet β-cells. In the pancreas of db/db mice and high-fat diet-induced mice, and in mouse islet β-cells (MIN6 cells) treated with palmitate, α-ENaC expression was increased. When α-ENaC was overexpressed in MIN6 cells, insulin content and glucose-induced insulin secretion were significantly reduced. On the other hand, palmitate injured islet β-cells and suppressed insulin synthesis and secretion, but increased α-ENaC expression in MIN6 cells. However, α-ENaC knockout ( Scnn1a -/-) in MIN6 cells attenuated β-cell disorder induced by palmitate. Furthermore, α-ENaC regulated the ubiquitylation and degradation of sirtuin 2 in β-cells. α-ENaC also modulated β-cell function in correlation with the inositol-requiring enzyme 1 alpha/X-box binding protein 1 (IRE1α/XBP1) and protein kinase RNA-like endoplasmic reticulum kinase/C/EBP homologous protein (PERK/CHOP) endoplasmic reticulum stress pathways. These results suggest that α-ENaC may play a novel role in insulin synthesis and secretion in the β-cells, and the upregulation of α-ENaC promotes islet β-cell dysfunction. In conclusion, α-ENaC may be a key regulator involved in islet β-cell damage and a potential therapeutic target for type 2 diabetes mellitus.

Effect of SIRT1 gene single-nucleotide polymorphisms on susceptibility to type 1 diabetes in a Han Chinese population

AIMS

SIRT1 deficiency has been associated with diabetes, and a variant of the SIRT1 gene has been found to be involved in human autoimmune diabetes; however, it is unclear whether this genetic variation exists in Han Chinese with type 1 diabetes (T1D) and whether it contributes to development of T1D. Therefore, we aimed to explore the association of the SIRT1 gene single-nucleotide polymorphisms (SNPs) rs10997866 and rs3818292 in a Han Chinese population with T1D.

METHODS

This study recruited 2653 unrelated Han Chinese individuals, of whom 1289 had T1D and 1364 were healthy controls. Allelic and genotypic distributions of SIRT1 polymorphisms (rs10997866 and rs3818292) were determined by MassARRAY. Basic characteristics, genotype and allele frequencies of selected SNPs were compared between the T1D patients and healthy controls. Further genotype-phenotype association analysis of the SNPs was performed on the T1D patients divided into three groups according to genotype. Statistical analyses included the chi-square test, Mann‒Whitney U test, Kruskal‒Wallis H test and logistic regression.

RESULTS

The allelic (G vs. A) and genotypic (GA vs. AA) distributions of SIRT1 rs10997866 were significantly different in T1D patients and healthy controls (P = 0.039, P = 0.027), and rs10997866 was associated with T1D susceptibility under dominant, overdominant and additive models (P = 0.026, P = 0.030 and P = 0.027, respectively). Moreover, genotype-phenotype association analysis showed the GG genotype of rs10997866 and the GG genotype of rs3818292 to be associated with higher titers of IA-2A (P = 0.013 and P = 0.038, respectively).

CONCLUSION

SIRT1 rs10997866 is significantly associated with T1D susceptibility, with the minor allele G conferring a higher risk of T1D. Moreover, SIRT1 gene rs10997866 and rs3818292 correlate with the titer of IA-2A in Han Chinese individuals with T1D.

Prediction of influential proteins and enzymes of certain diseases using a directed unimodular hypergraph

Protein-protein interaction (PPI) analysis based on mathematical modeling is an efficient means of identifying hub proteins, corresponding enzymes and many underlying structures. In this paper, a method for the analysis of PPI is introduced and used to analyze protein interactions of diseases such as Parkinson's, COVID-19 and diabetes melitus. A directed hypergraph is used to represent PPI interactions. A novel directed hypergraph depth-first search algorithm is introduced to find the longest paths. The minor hypergraph reduces the dimension of the directed hypergraph, representing the longest paths and results in the unimodular hypergraph. The property of unimodular hypergraph clusters influential proteins and enzymes that are related thereby providing potential avenues for disease treatment.

The role of sirtuins in the regulatin of oxidative stress during the progress and therapy of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by insulin resistance and impaired glucose homeostasis. Oxidative stress, arising from an imbalance between reactive oxygen species (ROS) production and antioxidant defense systems, plays a significant role in the development and progression of T2DM. The sirtuin family, particularly Sirt1, Sirt3, and Sirt6, have emerged as key regulators of oxidative stress in various cellular processes. This review aims to explore the role of the sirtuin family in oxidative stress during the progression of T2DM and their potential as therapeutic targets. We discussed the mechanisms through which sirtuins modulate oxidative stress, their impact on insulin sensitivity, and beta-cell function involved in T2DM. Furthermore, we highlight drugs targeting sirtuin activation and related complications in T2DM. This review summarizes the role as well as mechanism of sirtuins in the regulation of oxidative stress in T2DM and available drugs targeting sirtuins in clinic, which may provide novel insights into the mechanism and therapy of T2DM.

Impact of dietary interventions on pre-diabetic oral and gut microbiome, metabolites and cytokines

Diabetes and associated comorbidities are a global health threat on the rise. We conducted a six-month dietary intervention in pre-diabetic individuals (NCT03222791), to mitigate the hyperglycemia and enhance metabolic health. The current work explores early diabetes markers in the 200 individuals who completed the trial. We find 166 of 2,803 measured features, including oral and gut microbial species and pathways, serum metabolites and cytokines, show significant change in response to a personalized postprandial glucose-targeting diet or the standard of care Mediterranean diet. These changes include established markers of hyperglycemia as well as novel features that can now be investigated as potential therapeutic targets. Our results indicate the microbiome mediates the effect of diet on glycemic, metabolic and immune measurements, with gut microbiome compositional change explaining 12.25% of serum metabolites variance. Although the gut microbiome displays greater compositional changes compared to the oral microbiome, the oral microbiome demonstrates more changes at the genetic level, with trends dependent on environmental richness and species prevalence in the population. In conclusion, our study shows dietary interventions can affect the microbiome, cardiometabolic profile and immune response of the host, and that these factors are well associated with each other, and can be harnessed for new therapeutic modalities.

The role of microRNAs in pathophysiology and diagnostics of metabolic complications in obstructive sleep apnea patients

Obstructive sleep apnea (OSA) is one of the most common sleep disorders, which is characterized by recurrent apneas and/or hypopneas occurring during sleep due to upper airway obstruction. Among a variety of health consequences, OSA patients are particularly susceptible to developing metabolic complications, such as metabolic syndrome and diabetes mellitus type 2. MicroRNAs (miRNAs) as epigenetic modulators are promising particles in both understanding the pathophysiology of OSA and the prediction of OSA complications. This review describes the role of miRNAs in the development of OSA-associated metabolic complications. Moreover, it summarizes the usefulness of miRNAs as biomarkers in predicting the aforementioned OSA complications.

Identification of microRNAs implicated in modulating resveratrol-induced apoptosis in porcine granulosa cells

MicroRNAs (miRNAs) are small, noncoding RNAs that play a crucial role in the complex and dynamic network that regulates the apoptosis of porcine ovarian granulosa cells (POGCs). Resveratrol (RSV) is a nonflavonoid polyphenol compound that is involved in follicular development and ovulation. In previous study, we established a model of RSV treatment of POGCs, confirming the regulatory effect of RSV in POGCs. To investigate the miRNA-level effects of RSV on POGCs to reveal differentially expressed miRNAs, a control group (n = 3, 0 μM RSV group), a low RSV group (n = 3, 50 μM RSV group), and a high RSV group (n = 3, 100 μM RSV group) were created for small RNA-seq. In total, 113 differentially expressed miRNAs (DE-miRNAs) were identified, and a RT-qPCR analysis showed a correlation with the sequencing data. Functional annotation analysis revealed that DE-miRNAs in the LOW vs. CON group may be involved in cell development, proliferation, and apoptosis. In the HIGH vs. CON group, RSV functions were associated with metabolic processes and responses to stimuli, while the pathways were related to PI3K24, Akt, Wnt, and apoptosis. In addition, we constructed miRNA-mRNA networks related to Apoptosis and Metabolism. Then, ssc-miR-34a and ssc-miR-143-5p were selected as key miRNAs. In conclusion, this study provided an improved understanding of effects of RSV on POGCs apoptosis through the miRNA modulations. The results suggest that RSV may promote POGCs apoptosis by stimulating the miRNA expressions and provided a better understanding of the role of miRNAs combined with RSV in ovarian granulosa cell development in pigs.

Effect of Resveratrol on Markers of Oxidative Stress and Sirtuin 1 in Elderly Adults with Type 2 Diabetes

Type 2 diabetes (T2D) affects a large part of the adult population and impairs its quality of life. Because of this, natural compounds with antioxidant, anti-inflammatory and hypoglycemic properties have been used as adjuvants. Among these compounds, resveratrol (RV) stands out, a polyphenol that has been studied in several clinical trials, the results of which are controversial. We conducted a randomized clinical trial on 97 older adults with T2D to evaluate the effect of RV on oxidative stress markers and sirtuin 1, using doses of 1000 mg/day (EG1000, n = 37) and 500 mg/day (EG500, n = 32) compared with a placebo (PG, n = 28). Biochemical markers, oxidative stress and sirtuin 1 levels were measured at baseline and after six months. We observed a statistically significant increase (p < 0.05) in total antioxidant capacity, antioxidant gap, the percentage of subjects without oxidant stress and sirtuin 1 levels in EG1000. In the PG, we observed a significant increase (p < 0.05) in lipoperoxides, isoprostanes and C-reactive protein levels. An increase in the oxidative stress score and in the percentage of subjects with mild and moderate oxidative stress was observed too. Our findings suggest that 1000 mg/day of RV exerts a more efficient antioxidant effect than 500 mg/day.

Histone deacetylase functions and therapeutic implications for adult skeletal muscle metabolism

Skeletal muscle is a highly adaptive organ that sustains continuous metabolic changes in response to different functional demands. Healthy skeletal muscle can adjust fuel utilization to the intensity of muscle activity, the availability of nutrients and the intrinsic characteristics of muscle fibers. This property is defined as metabolic flexibility. Importantly, impaired metabolic flexibility has been associated with, and likely contributes to the onset and progression of numerous pathologies, including sarcopenia and type 2 diabetes. Numerous studies involving genetic and pharmacological manipulations of histone deacetylases (HDACs) in vitro and in vivo have elucidated their multiple functions in regulating adult skeletal muscle metabolism and adaptation. Here, we briefly review HDAC classification and skeletal muscle metabolism in physiological conditions and upon metabolic stimuli. We then discuss HDAC functions in regulating skeletal muscle metabolism at baseline and following exercise. Finally, we give an overview of the literature regarding the activity of HDACs in skeletal muscle aging and their potential as therapeutic targets for the treatment of insulin resistance.

Phytocannabinoids Stimulate Rejuvenation and Prevent Cellular Senescence in Human Dermal Fibroblasts

In light of the increased popularity of phytocannabinoids (pCBs) and their appearance in beauty products without rigorous research on their rejuvenation efficacy, we decided to investigate the potential role of pCBs in skin rejuvenation. Utilizing healthy and stress-induced premature senescent (SIPS) CCD-1064Sk skin fibroblasts, the effects of pCBs on cellular viability, functional activity, metabolic function, and nuclear architecture were tested. Both delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) within the range of 0.5 µM to 2.0 µM increased cell growth in a dose-dependent manner while significantly decreasing senescence as measured by beta-galactosidase activity. Utilizing a scratch assay, both THC and CBD (2.0 µM) significantly improved wound healing in both healthy and SIPS fibroblasts. THC and CBD altered nuclear architecture and mRNA levels of cell cycle regulators and genes involved in ECM production. Subsequently, we found ELN, Cyclin D1, PCNA, and BID protein levels altered by SIPS but ameliorated after pCBs exposure in human dermal fibroblasts. Lastly, we compared the efficacy of THC and CBD with common anti-aging nutrient signaling regulators in replicative senescent adult human dermal fibroblasts, CCD-1135Sk. Both THC and CBD were found to improve wound healing better than metformin, rapamycin, and triacetylresveratrol in replicative senescent CCD-1135Sk fibroblasts. Therefore, pCBs can be a valuable source of biologically active substances used in cosmetics, and more studies using clinical trials should be performed to confirm the efficacy of phytocannabinoids.

Sirtuins: Key players in obesity-associated adipose tissue remodeling

Obesity, a complex disease involving an excessive amount of body fat and a major threat to public health all over the world, is the determining factor of the onset and development of metabolic disorders, including type 2 diabetes, cardiovascular diseases, and non-alcoholic fatty liver disease. Long-term overnutrition results in excessive expansion and dysfunction of adipose tissue, inflammatory responses and over-accumulation of extracellular matrix in adipose tissue, and ectopic lipid deposit in other organs, termed adipose tissue remodeling. The mammalian Sirtuins (SIRT1-7) are a family of conserved NAD⁺-dependent protein deacetylases. Mounting evidence has disclosed that Sirtuins and their prominent substrates participate in a variety of physiological and pathological processes, including cell cycle regulation, mitochondrial biogenesis and function, glucose and lipid metabolism, insulin action, inflammatory responses, and energy homeostasis. In this review, we provided up-to-date and comprehensive knowledge about the roles of Sirtuins in adipose tissue remodeling, focusing on the fate of adipocytes, lipid mobilization, adipose tissue inflammation and fibrosis, and browning of adipose tissue, and we summarized the clinical trials of Sirtuin activators and inhibitors in treating metabolic diseases, which might shed light on new therapeutic strategies for obesity and its associated metabolic diseases.

Synergistic Beneficial Effects of Resveratrol and Diet on High-Fat Diet-Induced Obesity

Introduction: Despite decades of research, obesity and its related medical complications remain a major health concern globally. Therefore, novel therapeutic strategies are needed to combat obesity and its numerous debilitating complications. Resveratrol (RES) has a potential therapeutic effect in obesity and diabetes by improving oxidative metabolism and insulin signaling. Background and Objectives: The aim of this study was to investigate the effect of RES treatment on weight loss and glucose and fatty acid metabolism. Methods: Obesity was induced in 24 mice by exposure to a high-fat diet (HFD) for 8 weeks. Mice were randomly assigned to one group of either: group 1: control, non-treated low-fat diet (LFD) for 12 weeks (n = 8), group 2: non-treated high-fat diet (HFD) for 12 weeks (n = 8), group 3: RES-treated HFD (HFD + RES) (n = 8), or group 4: RES-treated and switched to LFD (HFD-LFD + RES) (n = 8). HFD + RES mice were first fed an HFD for 8 weeks followed by 4 weeks of RES. The HFD-LFD + RES group was first fed an HFD for 8 weeks and then treated with RES and switched to an LFD for 4 weeks. Results: After 12 weeks, group 2 mice had significantly higher body weights compared to group 1 (23.71 ± 1.95 vs. 47.83 ± 2.27; p < 0.05). Group 4 had a significant decrease in body weight and improvement in glucose tolerance compared to mice in group 2 (71.3 ± 1.17 vs. 46.1 ± 1.82 and 40.9 ± 1.75, respectively; p < 0.05). Skeletal muscles expression of SIRT1, SIRT3, and PGC1α were induced in group 3 and 4 mice compared to group 2 (p < 0.01), with no changes in AMP-activated protein kinase expression levels. Furthermore, combination of RES and diet ameliorated skeletal muscle intermediate lipid accumulation and significantly improved insulin sensitivity and secretion. Conclusions: The results of this study suggest a synergistic beneficial effect of LFD and RES to lower body weight and enhance glucose and fatty acid metabolism.

Virtual Screening in the Identification of Sirtuins’ Activity Modulators

Sirtuins are NAD⁺-dependent deac(et)ylases with different subcellular localization. The sirtuins’ family is composed of seven members, named SIRT-1 to SIRT-7. Their substrates include histones and also an increasing number of different proteins. Sirtuins regulate a wide range of different processes, ranging from transcription to metabolism to genome stability. Thus, their dysregulation has been related to the pathogenesis of different diseases. In this review, we discussed the pharmacological approaches based on sirtuins’ modulators (both inhibitors and activators) that have been attempted in in vitro and/or in in vivo experimental settings, to highlight the therapeutic potential of targeting one/more specific sirtuin isoform(s) in cancer, neurodegenerative disorders and type 2 diabetes. Extensive research has already been performed to identify SIRT-1 and -2 modulators, while compounds targeting the other sirtuins have been less studied so far. Beside sections dedicated to each sirtuin, in the present review we also included sections dedicated to pan-sirtuins’ and to parasitic sirtuins’ modulators. A special focus is dedicated to the sirtuins’ modulators identified by the use of virtual screening.

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.

Quantitative structure-activity relationship modeling reveals the minimal sequence requirement and amino acid preference of sirtuin-1's deacetylation substrates in diabetes mellitus

Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD[Formula: see text]-dependent deacetylase involved in multiple glucose metabolism pathways and plays an important role in the pathogenesis of diabetes mellitus (DM). The enzyme specifically recognizes its deacetylation substrates' peptide segments containing a central acetyl-lysine residue as well as a number of amino acids flanking the central residue. In this study, we attempted to ascertain the minimal sequence requirement (MSR) around the central acetyl-lysine residue of SIRT1 substrate-recognition sites as well as the amino acid preference (AAP) at different residues of the MSR window through quantitative structure-activity relationship (QSAR) strategy, which would benefit our understanding of SIRT1 substrate specificity at the molecular level and is also helpful to rationally design substrate-mimicking peptidic agents against DM by competitively targeting SIRT1 active site. In this procedure, a large-scale dataset containing 6801 13-mer acetyl-lysine peptides (and their SIRT1-catalyized deacetylation activities) were compiled to train 10 QSAR regression models developed by systematic combination of machine learning methods (PLS and SVM) and five amino acids descriptors (DPPS, T-scale, MolSurf, [Formula: see text]-score, and FASGAI). The two best QSAR models (PLS+FASGAI and SVM+DPPS) were then employed to statistically examine the contribution of residue positions to the deacetylation activity of acetyl-lysine peptide substrates, revealing that the MSR can be represented by 5-mer acetyl-lysine peptides that meet a consensus motif X[Formula: see text]X[Formula: see text]X[Formula: see text](AcK)₀X[Formula: see text]. Structural analysis found that the X[Formula: see text] and (AcK)₀ residues are tightly packed against the enzyme active site and confer both stability and specificity for the enzyme-substrate complex, whereas the X[Formula: see text], X[Formula: see text] and X[Formula: see text] residues are partially exposed to solvent but can also effectively stabilize the complex system. Subsequently, a systematic deacetylation activity change profile (SDACP) was created based on QSAR modeling, from which the AAP for each residue position of MSR was depicted. With the profile, we were able to rationally design an SDACP combinatorial library with promising deacetylation activity, from which nine MSR acetyl-lysine peptides as well as two known SIRT1 acetyl-lysine peptide substrates were tested by using SIRT1 deacetylation assay. It is revealed that the designed peptides exhibit a comparable or even higher activity than the controls, although the former is considerably shorter than the latter.

Sirtuin 5 is Dispensable for CD8+ T Cell Effector and Memory Differentiation

CD8⁺ T cell effector and memory differentiation is tightly controlled at multiple levels including transcriptional, metabolic, and epigenetic regulation. Sirtuin 5 (SIRT5) is a protein deacetylase mainly located at mitochondria, but it remains unclear whether SIRT5 plays key roles in regulating CD8⁺ T cell effector or memory formation. Herein, with adoptive transfer of Sirt5^+/+ or Sirt5^−/− OT-1 cells and acute Listeria monocytogenes infection model, we demonstrate that SIRT5 deficiency does not affect CD8⁺ T cell effector function and that SIRT5 is not required for CD8⁺ T cell memory formation. Moreover, the recall response of SIRT5 deficient memory CD8⁺ T cells is comparable with Sirt5^+/+ memory CD8⁺ T cells. Together, these observations suggest that SIRT5 is dispensable for the effector function and memory differentiation of CD8⁺ T cells.

Skeletal muscle energy metabolism in obesity

Comparing energy metabolism in human skeletal muscle and primary skeletal muscle cells in obesity, while focusing on glucose and fatty acid metabolism, shows many common changes. Insulin-mediated glucose uptake in skeletal muscle and primary myotubes is decreased by obesity, whereas differences in basal glucose metabolism are inconsistent among studies. With respect to fatty acid metabolism, there is an increased uptake and storage of fatty acids and a reduced complete lipolysis, suggesting alterations in lipid turnover. In addition, fatty acid oxidation is decreased, probably at the level of complete oxidation, as β -oxidation may be enhanced in obesity, which indicates mitochondrial dysfunction. Metabolic changes in skeletal muscle with obesity promote metabolic inflexibility, ectopic lipid accumulation, and formation of toxic lipid intermediates. Skeletal muscle also acts as an endocrine organ, secreting myokines that participate in interorgan cross talk. This review highlights interventions and some possible targets for treatment through action on skeletal muscle energy metabolism. Effects of exercise in vivo on obesity have been compared with simulation of endurance exercise in vitro on myotubes (electrical pulse stimulation). Possible pharmaceutical targets, including signaling pathways and drug candidates that could modify lipid storage and turnover or increase mitochondrial function or cellular energy expenditure through adaptive thermogenic mechanisms, are discussed.

Therapeutics for type-2 diabetes mellitus: a glance at the recent inclusions and novel agents under development for use in clinical practice

Diabetes mellitus (DM) is a chronic, progressive, and multifaceted illness resulting in significant physical and psychological detriment to patients. As of 2019, 463 million people are estimated to be living with DM worldwide, out of which 90% have type-2 diabetes mellitus (T2DM). Over the years, significant progress has been made in identifying the risk factors for developing T2DM, understanding its pathophysiology and uncovering various metabolic pathways implicated in the disease process. This has culminated in the implementation of robust prevention programmes and the development of effective pharmacological agents, which have had a favourable impact on the management of T2DM in recent times. Despite these advances, the incidence and prevalence of T2DM continue to rise. Continuing research in improving efficacy, potency, delivery and reducing the adverse effect profile of currently available formulations is required to keep pace with this growing health challenge. Moreover, new metabolic pathways need to be targeted to produce novel pharmacotherapy to restore glucose homeostasis and address metabolic sequelae in patients with T2DM. We searched PubMed, MEDLINE, and Google Scholar databases for recently included agents and novel medication under development for treatment of T2DM. We discuss the pathophysiology of T2DM and review how the emerging anti-diabetic agents target the metabolic pathways involved. We also look at some of the limiting factors to developing new medication and the introduction of unique methods, including facilitating drug delivery to bypass some of these obstacles. However, despite the advances in the therapeutic options for the treatment of T2DM in recent years, the industry still lacks a curative agent.

SIRT7 Acts as a Guardian of Cellular Integrity by Controlling Nucleolar and Extra-Nucleolar Functions

Sirtuins are key players for maintaining cellular homeostasis and are often deregulated in different human diseases. SIRT7 is the only member of mammalian sirtuins that principally resides in the nucleolus, a nuclear compartment involved in ribosomal biogenesis, senescence, and cellular stress responses. The ablation of SIRT7 induces global genomic instability, premature ageing, metabolic dysfunctions, and reduced stress tolerance, highlighting its critical role in counteracting ageing-associated processes. In this review, we describe the molecular mechanisms employed by SIRT7 to ensure cellular and organismal integrity with particular emphasis on SIRT7-dependent regulation of nucleolar functions.

The effect of daily intake of vitamin D-fortified yogurt drink, with and without added calcium, on serum adiponectin and sirtuins 1 and 6 in adult subjects with type 2 diabetes

BACKGROUND

Some evidence suggests indirect ameliorating effects of vitamin D in diabetes via adiponectin and sirtuins. This study aimed to evaluate the effects of daily intake of vitamin D-fortified yogurt drink, either with or without added calcium, on serum adiponectin, sirtuins (SIRT)1 and 6.

METHODS

Briefly, 75 adults aged 30-60 years from both sexes with type 2 diabetes were randomly allocated to one of the three groups: (i) D-fortified-yogurt drink (DY; containing 1000 IU vitamin D and 300 mg calcium), (ii) Ca+D-fortified-yogurt drink (CDY; containing 1000 IU vitamin D and 500 mg calcium) and (iii) plain yogurt drink (PY; containing no detectable vitamin D and 300 mg calcium). All assessments were performed initially and after 12 weeks.

RESULTS

A significant within-group increment in serum adiponectin concentrations was observed in both DY and CDY groups (+60.4 ± 8.6, +57.5 ± 6.4 µg/L, respectively; p < 0.001 for both). The concentrations of SIRT1 and SIRT6 had a significant within-group increment only in the CDY group (p = 0.003, p = 0.001 respectively). Being in CDY group was more favorable predictor of improvement in SIRT6 concentrations. Changes of 25(OH)D were a significant predictor of changes of adiponectin. However, this association disappeared following adjustment for changes of SIRT1. In contrast, the association between changes of 25(OH)D and HbA1c remained significant even after adjustment for SIRT1.

CONCLUSIONS

Daily consumption of vitamin D-fortified yogurt drink for 12 weeks resulted in an increase in circulating concentrations of SIRT1 and SIRT6 in T2D subjects and D+Ca-fortified yogurt drink was more in favor of SIRT6 increment.

The Emerging Role of HDACs: Pathology and Therapeutic Targets in Diabetes Mellitus

Diabetes mellitus (DM) is one of the principal manifestations of metabolic syndrome and its prevalence with modern lifestyle is increasing incessantly. Chronic hyperglycemia can induce several vascular complications that were referred to be the major cause of morbidity and mortality in DM. Although several therapeutic targets have been identified and accessed clinically, the imminent risk of DM and its prevalence are still ascending. Substantial pieces of evidence revealed that histone deacetylase (HDAC) isoforms can regulate various molecular activities in DM via epigenetic and post-translational regulation of several transcription factors. To date, 18 HDAC isoforms have been identified in mammals that were categorized into four different classes. Classes I, II, and IV are regarded as classical HDACs, which operate through a Zn-based mechanism. In contrast, class III HDACs or Sirtuins depend on nicotinamide adenine dinucleotide (NAD+) for their molecular activity. Functionally, most of the HDAC isoforms can regulate β cell fate, insulin release, insulin expression and signaling, and glucose metabolism. Moreover, the roles of HDAC members have been implicated in the regulation of oxidative stress, inflammation, apoptosis, fibrosis, and other pathological events, which substantially contribute to diabetes-related vascular dysfunctions. Therefore, HDACs could serve as the potential therapeutic target in DM towards developing novel intervention strategies. This review sheds light on the emerging role of HDACs/isoforms in diabetic pathophysiology and emphasized the scope of their targeting in DM for constituting novel interventional strategies for metabolic disorders/complications.

Resveratrol's Anti-Cancer Effects through the Modulation of Tumor Glucose Metabolism

Simple Summary

The prevention and treatment of cancer is an ongoing medical challenge. In the context of personalized medicine, the well-studied polyphenol resveratrol could complement classical tumor therapy. It may affect key processes such as inflammation, angiogenesis, proliferation, metastasis, glucose metabolism, and apoptosis in various cancers because resveratrol acts as a multi-targeting agent by modulating multiple signal transduction pathways. This review article focuses on resveratrol’s ability to modify tumor glucose metabolism and its associated therapeutic capacity. Resveratrol reduces glucose uptake and glycolysis by affecting Glut1, PFK1, HIF-1α, ROS, PDH, and the CamKKB/AMPK pathway. It also inhibits cell growth, invasion, and proliferation by targeting NF-kB, Sirt1, Sirt3, LDH, PI-3K, mTOR, PKM2, R5P, G6PD, TKT, talin, and PGAM. In addition, resveratrol induces apoptosis by targeting integrin, p53, LDH, and FAK. In conclusion, resveratrol has many potentials to intervene in tumor processes if bioavailability can be increased and this natural compound can be used selectively.

Abstract

Tumor cells develop several metabolic reprogramming strategies, such as increased glucose uptake and utilization via aerobic glycolysis and fermentation of glucose to lactate; these lead to a low pH environment in which the cancer cells thrive and evade apoptosis. These characteristics of tumor cells are known as the Warburg effect. Adaptive metabolic alterations in cancer cells can be attributed to mutations in key metabolic enzymes and transcription factors. The features of the Warburg phenotype may serve as promising markers for the early detection and treatment of tumors. Besides, the glycolytic process of tumors is reversible and could represent a therapeutic target. So-called mono-target therapies are often unsafe and ineffective, and have a high prevalence of recurrence. Their success is hindered by the ability of tumor cells to simultaneously develop multiple chemoresistance pathways. Therefore, agents that modify several cellular targets, such as energy restriction to target tumor cells specifically, have therapeutic potential. Resveratrol, a natural active polyphenol found in grapes and red wine and used in many traditional medicines, is known for its ability to target multiple components of signaling pathways in tumors, leading to the suppression of cell proliferation, activation of apoptosis, and regression in tumor growth. Here, we describe current knowledge on the various mechanisms by which resveratrol modulates glucose metabolism, its potential as an imitator of caloric restriction, and its therapeutic capacity in tumors.

The effect of tropisetron on oxidative stress, SIRT1, FOXO3a, and claudin-1 in the renal tissue of STZ-induced diabetic rats

Tropisetron is a 5-HT3 receptor antagonist that exerts protective effect against DN. The aim of this study was to investigate the possible molecular mechanisms associated with the renoprotective effects of tropisetron in STZ-induced diabetic rats. Animals were subdivided into 5 equal groups; control, tropisetron, diabetes, tropisetron + diabetes, and glibenclamide + diabetes (n = 7). For induction of type 1 diabetes, a single injection of STZ (55 mg/kg, i.p.) was administered to the animals. Diabetic rats were treated with tropisetron (3 mg/kg) and glibenclamide (1 mg/kg) for 2 weeks. According to the conducted analysis, diabetes led to renal dysfunction (reduction in glomerular filtration rate and urine urea and creatinine as well as elevation in plasma urea and creatinine) and abnormalities in antioxidant defense system (reduction in TAC and elevation in MDA), compared with the control group, which was prevented by tropisetron treatment. Reverse transcription-quantitative polymerase chain reaction and western blotting analysis demonstrated that SIRT1 gene expression decreased while FOXO3a and NF-κB gene expression as well as phosphorylated FOXO3a/total FOXO3a protein ratios and claudin-1 protein level increased in the kidney of diabetic rats compared with the control group. Herein, the results of this research showed that tropisetron treatment reversed these changes. Besides, all these changes were comparable with those produced by glibenclamide as a positive control. Hence, tropisetron ameliorated renal damage due to diabetic nephropathy possibly by suppressing oxidative stress and alteration of SIRT1, FOXO3a, and claudin-1 levels.

Isoliquiritigenin downregulates miR-195 and attenuates oxidative stress and inflammation in STZ-induced retinal injury

Diabetic retinopathy (DR) is a major microvascular complication of diabetes mellitus that leads to significant vision loss. Isoliquiritigenin (ISL) is a bioactive flavonoid found in the root of licorice with reported anti-oxidant and anti-inflammatory activities. In the present study, we evaluated the effect of ISL administration on diabetes-induced retinal injury. Diabetes was induced in male Sprague-Dawley rats using single intraperitoneal streptozotocin (STZ, 50 mg/kg) injection. Diabetic rats showed up-regulated retinal miR-195, reduced retinal levels of SIRT-1, and increased levels of oxidative stress, nuclear factor-κB (NF-κB), inflammatory cytokines, and endothelin-1. Moreover, histopathological and electron microscopy studies revealed distorted retinal layers and reduced number of ganglion cells. Oral administration of ISL (20 mg/kg/day) to diabetic rats for 8 weeks improved diabetes-induced retinal injury via down-regulation of miR-195, restoration of retinal SIRT-1 level, attenuation of oxidative stress, inflammation, and endothelial damage as well as preservation of retinal normal histology and ultrastructure. In conclusion, our results showed that ISL could be a promising therapeutic intervention to prevent the development and progression of DR. It also suggested that the miR-195/SIRT-1/NF-κB pathway may contribute to ISL treatment-induced beneficial effects.

SIRT1 Antagonizes Oxidative Stress in Diabetic Vascular Complication

Diabetic mellitus (DM) is a significant public health concern worldwide with an increased incidence of morbidity and mortality, which is particularly due to the diabetic vascular complications. Several pivotal underlying mechanisms are associated with vascular complications, including hyperglycemia, mitochondrial dysfunction, inflammation, and most importantly, oxidative stress. Oxidative stress triggers defective angiogenesis, activates pro-inflammatory pathways and causes long-lasting epigenetic changes to facilitate the development of vascular complications. Therefore, therapeutic interventions targeting oxidative stress are promising to manage diabetic vascular complications. Sirtuin1 (SIRT1), a class III histone deacetylase belonging to the sirtuin family, plays critical roles in regulating metabolism and ageing-related pathological conditions, such as vascular diseases. Growing evidence has indicated that SIRT1 acts as a sensing regulator in response to oxidative stress and attenuates vascular dysfunction via cooperating with adenosine-monophosphate-activated protein kinase (AMPK) to activate antioxidant signals through various downstream effectors, including peroxisome proliferator-activated receptor-gamma co-activator 1 (PGC-1α), forkhead transcription factors (FOXOs), and peroxisome proliferative-activated receptor α (PPARα). In addition, SIRT1 interacts with hydrogen sulfide (H2S), regulates NADPH oxidase, endothelial NO synthase, and mechanistic target of rapamycin (mTOR) to suppress oxidative stress. Furthermore, mRNA expression of sirt1 is affected by microRNAs in DM. In the current review, we summarize recent advances illustrating the importance of SIRT1 in antagonizing oxidative stress. We also discuss whether modulation of SIRT1 can serve as a therapeutic strategy to treat diabetic vascular complications.

Alternatives to Insulin for the Regulation of Blood Sugar Levels in Type 2 Diabetes

This short overview focuses on the causation and treatment of type 2 diabetes (T2D). Emphasis is given to the historical basis of understanding this disease and the background leading to emergence of the central role of insulin. The strengths of insulin administration in the treatment of diabetes are profound, but these need to be balanced against several serious shortcomings of its extended use. Some alternative approaches to T2D management are considered. Insulin is no longer considered as the first choice for type 2 diabetes, and an expanding range of new therapeutic possibilities is emerging. While these may lack the potency of insulin, at a minimum, they allow a major reduction in the intensity of insulin use. In view of the rising worldwide incidence of this disease, it is imperative to develop safe and inexpensive means of limiting its potential for impairment of normal functioning.

Protective effect of isoliquiritigenin on experimental diabetic nephropathy in rats: Impact on Sirt-1/NFκB balance and NLRP3 expression

The prevalence of diabetes mellitus (DM) drastically increases worldwide. Persistent hyperglycemia affects body microvasculature causing injuries to kidney producing diabetic nephropathy (DNE). Manifestation of these microvascular complications is associated with disturbed redox homeostasis. The current study evaluated the effect of isoliquiritigenin (ISLQ), a bioactive chalcone found in licorice which is known for its antioxidant effect, on diabetes-induced renal injury. DM was prompted in male rats by streptozotocin (STZ, 50 mg/kg, intraperitoneally). ISLQ was administrated by oral gavage for 8 weeks at a dose (20 mg/kg/day). Features of renal injury were observed in kidneys of diabetic rats including, albuminuria and deteriorated renal function. Renal dysfunction was associated with reduced sirtuin-1 (Sirt-1) expression, increased renal oxidative stress, nucleotide-binding domain and leucine-rich repeat containing protein-3 (NLRP3), nuclear factor-κB (NFκB) and inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). Moreover, there was significant downregulation of anti-inflammatory cytokine interleukin-10 (IL-10), glomerular and tubular injury and collagen accumulation. ISLQ administration preserved renal function and architecture, restored Sirt1 and renal oxidant-antioxidant balance, dampened inflammation and attenuated collagen accumulation. It can be inferred that ISLQ possess a protective effect and could have a potential as a food supplement to halt development and progression of DNE.

Impaired substrate-mediated cardiac mitochondrial complex I respiration with unaltered regulation of fatty acid metabolism and oxidative stress status in type 2 diabetic Asian Indians

BACKGROUND

The cardiovascular complications associated with type 2 diabetes mellitus could be attributed to changes in myocardial mitochondrial metabolism. Though it is a known fact that permeabilized cardiac muscle fibers and isolated mitochondria are metabolically compromised in the Caucasian population, studies of Asian Indian myocardial mitochondrial function are lacking. Thus, the objective of the present study is to analyze if there is altered cardiac mitochondrial substrate utilization in diabetic Asian Indians.

METHODS

Mitochondrial substrate utilization was measured using high-resolution respirometry in isolated mitochondria prepared from right atrial appendage tissues of diabetic and nondiabetic subjects undergoing coronary artery bypass graft surgery. Western blotting and densitometric analysis were also done to compare the levels of proteins involved in fatty acid metabolism and regulation.

RESULTS

The mitochondrial oxygen consumption rate for fatty acid substrate was shown to be decreased in diabetic subjects compared to nondiabetic subjects along with an unvaried mitochondrial DNA copy number and uniform levels of electron transport chain complex proteins and proteins involved in fatty acid metabolism and regulation. Decreased glutamate but unchanged pyruvate-mediated state 3 respiration were also observed in diabetic subjects.

CONCLUSION

The current study reports deranged cardiac mitochondrial fatty acid-mediated complex I respiration in type 2 diabetic Asian Indians with comparable levels of regulators of fatty acid oxidation to that of nondiabetic myocardium. Altered glutamate-mediated mitochondrial respiration also points toward possible alterations in mitochondrial complex I activity. When compared with previous reports on other ethnic populations, the current study suggests that Asian Indian population too have altered cardiac mitochondrial substrate utilization.

Haplotypes of the Mutated SIRT2 Promoter Contributing to Transcription Factor Binding and Type 2 Diabetes Susceptibility

Genetic variability is an important causative factor for susceptibility and pathogenesis of type 2 diabetes (T2D). Histone deacetylase, sirtuin 2 (SIRT2), plays regulatory roles in glucose metabolism and insulin sensitivity. However, whether the SIRT2 variants or haplotypes contribute to T2D risk remain to be elucidated. In this study, we first detected three novel polymorphisms (P-MU1, P-MU2, and P-MU3) in the promoter of SIRT2 in the Chinese population. All pairwise sets of the three loci were strongly in linkage disequilibrium. Next, we constructed the haplotype block structure, and found H1-GGC and H2-CCA accounted for the most (total 91.8%) in T2D. The haplotype combination H1-H1-GGGGCC displayed a high risk for T2D (OR = 2.03, 95% CI = 1.12-3.72). By association analysis, we found the individuals carrying H1-H1-GGGGCC had significantly higher fasting plasma glucose and glycated hemoglobin. The haplotype H1-GGC presented a 6.74-fold higher promoter activity than H2-CCA, which was consistent with the correlation results. Furthermore, we clarified the mechanism whereby the C allele of both the P-MU1 and P-MU2 loci disrupted the signal transducer and activator of transcription 1 (STAT1) binding sites, leading to the attenuation of the SIRT2 transcription. Together, these data suggest that the linked haplotype GGC could be considered as a promising marker for T2D diagnosis and therapy assessment.

Sirtuins and intervertebral disc degeneration: Roles in inflammation, oxidative stress, and mitochondrial function

Intervertebral disc degeneration (IDD) is one of the main causes of low back pain, which seriously reduces the quality of life of patients and places a heavy economic burden on their families. Cellular senescence is considered to be an important factor leading to IDD, and inflammatory response, oxidative stress, and mitochondrial dysfunction are closely related to intervertebral disc (IVD) senescence. Therefore, inhibition of the inflammatory response and oxidative stress, along with maintaining mitochondrial function, may be useful in treating IDD. The sirtuins are a family of evolutionarily conserved nicotinamide adenine dinucleotide (NAD⁺)-dependent histone deacetylases, which are the major molecules mediating life extension or delay of aging-related diseases. The sirtuin protein family consist of seven members (SIRT1 - 7), which are mainly involved in various aging-related diseases by regulating inflammation, oxidative stress, and mitochondrial function. Among them, SIRT1, SIRT2, SIRT3, and SIRT6 are closely related to IDD. In addition, some activators of sirtuin proteins, such as resveratrol, melatonin, magnolol, 1,4-dihydropyridine (DHP), SRT1720, and nicotinamide mononucleotide (NMN), have been evaluated in preclinical studies for their effects in preventing IDD. This review described the biological functions of sirtuins and the important roles of SIRT1, SIRT2, SIRT3, and SIRT6 in IDD by regulating oxidative stress, inflammatory response, and mitochondrial function. In addition, we introduce the status of some sirtuin activators in IDD preclinical studies. This review will provide a background for further clarification of the molecular mechanism underlying IDD and the development of potential therapeutic drugs.

SIRT3 deficiency delays diabetic skin wound healing via oxidative stress and necroptosis enhancement

Sirtuin 3 (SIRT3) plays a vital role in several dermatological diseases. However, the role and detailed mechanism of SIRT3 in diabetic wound healing are unknown well yet. To explore possible involvement of SIRT3 and necroptosis in diabetic skin wound healing, SIRT3 knockout (KO) mice and 129S1/SvImJ wild‐type (WT) mice were injected with streptozotocin (STZ), and mice skin fibroblasts were exposed to high glucose (HG). It was found that SIRT3 expression decreased in the skin of diabetic patients. SIRT3 deficiency delayed healing rate, reduced blood supply and vascular endothelial growth factor expression, promoted superoxide production, increased malondialdehyde (MDA) levels, decreased total antioxidant capacity (T‐AOC), reduced superoxide dismutase (SOD) activity and aggravated ultrastructure disorder in skin wound of diabetic mice. SIRT3 deficiency inhibited mice skin fibroblasts migration with HG stimulation, which was restored by SIRT3 overexpression. SIRT3 deficiency also suppressed α‐smooth muscle actin (α‐SMA) expression, enhanced superoxide production but decreased mitochondrial membrane potential with HG stimulation after scratch. SIRT3 deficiency further elevated receptor‐interacting protein kinase 3 (RIPK3), RIPK1 and caspase 3 expression both in vitro and in vivo. Collectively, SIRT3 deficiency delayed skin wound healing in diabetes, the mechanism might be related to impaired mitochondria function, enhanced oxidative stress and increased necroptosis. This may provide a novel therapeutic target to accelerate diabetic skin wound healing.

Protein Lysine Acetylation: Grease or Sand in the Gears of β-Cell Mitochondria?

Mitochondria carry out many essential functions in metabolism. A central task is the oxidation of nutrients and the generation of ATP by oxidative phosphorylation. Mitochondrial metabolism needs to be tightly regulated for the cell to respond to changes in ATP demand and nutrient supply. Here, we review how protein lysine acetylation contributes to the regulation of mitochondrial metabolism in insulin target tissues and the insulin-secreting pancreatic β-cell. We summarize recent evidence showing that in pancreatic β-cells, lysine acetylation occurs on a large number of proteins involved in metabolism. Furthermore, we give a brief overview of the molecular mechanism that controls lysine acetylation dynamics. We propose that protein lysine acetylation is an important mechanism for the fine-tuning of mitochondrial activity in β-cells during normal physiology. In contrast, nutrient oversupply, oxidative stress, or inhibition of the mitochondrial deacetylase SIRT3 leads to protein lysine hyperacetylation, which impairs mitochondrial function. By perturbing mitochondrial activity in β-cells and insulin target tissues, protein lysine hyperacetylation may contribute to the development of type 2 diabetes.

Glut 1 in Cancer Cells and the Inhibitory Action of Resveratrol as A Potential Therapeutic Strategy

An important hallmark in cancer cells is the increase in glucose uptake. GLUT1 is an important target in cancer treatment because cancer cells upregulate GLUT1, a membrane protein that facilitates the basal uptake of glucose in most cell types, to ensure the flux of sugar into metabolic pathways. The dysregulation of GLUT1 is associated with numerous disorders, including cancer and metabolic diseases. There are natural products emerging as a source for inhibitors of glucose uptake, and resveratrol is a molecule of natural origin with many properties that acts as antioxidant and antiproliferative in malignant cells. In the present review, we discuss how GLUT1 is involved in the general scheme of cancer cell metabolism, the mechanism of glucose transport, and the importance of GLUT1 structure to understand the inhibition process. Then, we review the current state-of-the-art of resveratrol and other natural products as GLUT1 inhibitors, focusing on those directed at treating different types of cancer. Targeting GLUT1 activity is a promising strategy for the development of drugs aimed at treating neoplastic growth.

Enhanced acetylation of ATP-citrate lyase promotes the progression of nonalcoholic fatty liver disease

Hepatic steatosis is a hallmark of nonalcoholic fatty liver disease (NAFLD) and is promoted by dysregulated de novo lipogenesis. ATP-citrate lyase (ACLY) is a crucial lipogenic enzyme that is up-regulated in individuals with NAFLD. A previous study has shown that acetylation of ACLY at Lys-540, Lys-546, and Lys-554 (ACLY-3K) increases ACLY protein stability by antagonizing its ubiquitylation, thereby promoting lipid synthesis and cell proliferation in lung cancer cells. But the functional importance of this regulatory mechanism in other cellular or tissue contexts or under other pathophysiological conditions awaits further investigation. Here, we show that ACLY-3K acetylation also promotes ACLY protein stability in AML12 cells, a mouse hepatocyte cell line, and found that the deacetylase sirtuin 2 (SIRT2) deacetylates ACLY-3K and destabilizes ACLY in these cells. Of note, the livers of mice and humans with NAFLD had increased ACLY protein and ACLY-3K acetylation levels and decreased SIRT2 protein levels. Mimicking ACLY-3K acetylation by replacing the three lysines with three glutamines (ACLY-3KQ variant) promoted lipid accumulation both in high glucose-treated AML12 cells and in the livers of high-fat/high-sucrose (HF/HS) diet-fed mice. Moreover, overexpressing SIRT2 in AML12 cells inhibited lipid accumulation, which was more efficiently reversed by overexpressing the ACLY-3KQ variant than by overexpressing WT ACLY. Additionally, hepatic SIRT2 overexpression decreased ACLY-3K acetylation and its protein level and alleviated hepatic steatosis in HF/HS diet-fed mice. Our findings reveal a posttranscriptional mechanism underlying the up-regulation of hepatic ACLY in NAFLD and suggest that the SIRT2/ACLY axis is involved in NAFLD progression.

Insulin/IGF-1R, SIRT1, and FOXOs Pathways-An Intriguing Interaction Platform for Bone and Osteosarcoma

Aging is a substantial risk factor for the development of osteoarthritis (OA) and, probably, an essential substrate for the development of neoplastic disease of the bone, such as osteosarcoma, which is the most common malignant mesenchymal primary bone tumor. Genetic studies have established that the insulin/insulin-like growth factor 1 (IGF-1)/phosphatidylinositol-3 kinase (PI3K)/AKT (Protein Kinase B) signal transduction pathway is involved across species, including nematodes, fruit flies, and mammals. SIRT1, a phylogenetically-conserved family of deacetylases, seems to play pleiotropic effects in epithelial malignancies of the liver and interact with the IGF-1/PI3K/AKT signal transduction pathway. Some of the most critical processes in degenerative conditions may indeed include the insulin/IGF1R and SIRT1 signaling pathways as well as some specific transcription factors. The Forkhead box O (FOXO) transcription factors (FOXOs) control diverse cellular functions, such as metabolism, longevity, and cell death. FOXOs play a critical role in the IGF-1/PI3K/AKT signal transduction pathway. FOXOs can indeed be modulated to reduce age-related diseases. FOXOs have advantageous inhibitory effects on fibroblast and myofibroblast activation, which are accompanied by a subsequent excessive production of extracellular matrix. FOXOs can block or decrease the fibrosis levels in numerous organs. Previously, we observed a correlation between nuclear FOXO3 and high caspase-8 expression, which induces cellular apoptosis in response to harmful external stimuli. In this perspective, we emphasize the current advances and interactions involving the insulin/IGF1R, SIRT1, and FOXOs pathways in the bone and osteosarcoma for a better understanding of the mechanisms potentially underpinning tissue degeneration and tumorigenesis.