Metformin suppresses hepatic gluconeogenesis through induction of SIRT1 and GCN5

Metformin: From Diabetes to Cancer-Unveiling Molecular Mechanisms and Therapeutic Strategies

Metformin, a widely used anti-diabetic drug, has garnered attention for its potential in cancer management, particularly in breast and colorectal cancer. It is established that metformin reduces mitochondrial respiration, but its specific molecular targets within mitochondria vary. Proposed mechanisms include inhibiting mitochondrial respiratory chain Complex I and/or Complex IV, and mitochondrial glycerophosphate dehydrogenase, among others. These actions lead to cellular energy deficits, redox state changes, and several molecular changes that reduce hyperglycemia in type 2 diabetic patients. Clinical evidence supports metformin's role in cancer prevention in type 2 diabetes mellitus patients. Moreover, in these patients with breast and colorectal cancer, metformin consumption leads to an improvement in survival outcomes and prognosis. The synergistic effects of metformin with chemotherapy and immunotherapy highlights its potential as an adjunctive therapy for breast and colorectal cancer. However, nuanced findings underscore the need for further research and stratification by molecular subtype, particularly for breast cancer. This comprehensive review integrates metformin-related findings from epidemiological, clinical, and preclinical studies in breast and colorectal cancer. Here, we discuss current research addressed to define metformin's bioavailability and efficacy, exploring novel metformin-based compounds and drug delivery systems, including derivatives targeting mitochondria, combination therapies, and novel nanoformulations, showing enhanced anticancer effects.

The significance of caloric restriction mimetics as anti-aging drugs

Aging is an intricate process characterized by the gradual deterioration of the physiological integrity of a living organism. This unfortunate phenomenon inevitably leads to a decline in functionality and a heightened susceptibility to the ultimate fate of mortality. Therefore, it is of utmost importance to implement interventions that possess the capability to reverse or preempt age-related pathology. Caloric restriction mimetics (CRMs) refer to a class of molecules that have been observed to elicit advantageous outcomes on both health and longevity in various model organisms and human subjects. Notably, these compounds offer a promising alternative to the arduous task of adhering to a caloric restriction diet and mitigate the progression of the aging process and extend the duration of life in laboratory animals and human population. A plethora of molecular signals have been linked to the practice of caloric restriction, encompassing Insulin-like Growth Factor 1 (IGF1), Mammalian Target of Rapamycin (mTOR), the Adenosine Monophosphate-Activated Protein Kinase (AMPK) pathway, and Sirtuins, with particular emphasis on SIRT1. Therefore, this review will center its focus on several compounds that act as CRMs, highlighting their molecular targets, chemical structures, and mechanisms of action. Moreover, this review serves to underscore the significant relationship between post COVID-19 syndrome, antiaging, and importance of utilizing CRMs. This particular endeavor will serve as a comprehensive guide for medicinal chemists and other esteemed researchers, enabling them to meticulously conceive and cultivate novel molecular entities with the potential to function as efficacious antiaging pharmaceutical agents.

The Roles of Caloric Restriction Mimetics in Central Nervous System Demyelination and Remyelination

The dysfunction of myelinating glial cells, the oligodendrocytes, within the central nervous system (CNS) can result in the disruption of myelin, the lipid-rich multi-layered membrane structure that surrounds most vertebrate axons. This leads to axonal degeneration and motor/cognitive impairments. In response to demyelination in the CNS, the formation of new myelin sheaths occurs through the homeostatic process of remyelination, facilitated by the differentiation of newly formed oligodendrocytes. Apart from oligodendrocytes, the two other main glial cell types of the CNS, microglia and astrocytes, play a pivotal role in remyelination. Following a demyelination insult, microglia can phagocytose myelin debris, thus permitting remyelination, while the developing neuroinflammation in the demyelinated region triggers the activation of astrocytes. Modulating the profile of glial cells can enhance the likelihood of successful remyelination. In this context, recent studies have implicated autophagy as a pivotal pathway in glial cells, playing a significant role in both their maturation and the maintenance of myelin. In this Review, we examine the role of substances capable of modulating the autophagic machinery within the myelinating glial cells of the CNS. Such substances, called caloric restriction mimetics, have been shown to decelerate the aging process by mitigating age-related ailments, with their mechanisms of action intricately linked to the induction of autophagic processes.

Histone Modifications in NAFLD: Mechanisms and Potential Therapy

Nonalcoholic fatty liver disease (NAFLD) is a progressive condition that encompasses a spectrum of liver disorders, beginning with the simple steatosis, progressing to nonalcoholic steatohepatitis (NASH), and possibly leading to more severe diseases, including liver cirrhosis and hepatocellular carcinoma (HCC). In recent years, the prevalence of NAFLD has increased due to a shift towards energy-dense dietary patterns and a sedentary lifestyle. NAFLD is also strongly associated with metabolic disorders such as obesity and hyperlipidemia. The progression of NAFLD could be influenced by a variety of factors, such as diet, genetic factors, and even epigenetic factors. In contrast to genetic factors, epigenetic factors, including histone modifications, exhibit dynamic and reversible features. Therefore, the epigenetic regulation of the initiation and progression of NAFLD is one of the directions under intensive investigation in terms of pathogenic mechanisms and possible therapeutic interventions. This review aims to discuss the possible mechanisms and the crucial role of histone modifications in the framework of epigenetic regulation in NAFLD, which may provide potential therapeutic targets and a scientific basis for the treatment of NAFLD.

Exploring the mechanism of metformin action in Alzheimer's disease and type 2 diabetes based on network pharmacology, molecular docking, and molecular dynamic simulation

Background

Metformin, which has been shown to be highly effective in treating type 2 diabetes (T2D), is also believed to be valuable for Alzheimer's disease (AD). Computer simulation techniques have emerged as an innovative approach to explore mechanisms.

Objective

To study the potential mechanism of metformin action in AD and T2D.

Methods

The chemical structure of metformin was obtained from PubChem. The targets of metformin were obtained from PubChem, Pharm Mapper, Batman, SwissTargetPrediction, DrugBank, and PubMed. The pathogenic genes of AD and T2D were retrieved from the GeneCards, OMIM, TTD, Drugbank, PharmGKB, and DisGeNET. The intersection of metformin with the targets of AD and T2D is represented by a Venn diagram. The protein-protein interaction (PPI) and core targets networks of intersected targets were constructed by Cytoscape 3.7.1. The enrichment information of GO and Kyoto Encyclopedia of Gene and Genomics (KEGG) pathways obtained by the Metascape was made into a bar chart and a bubble diagram. AutoDockTools, Pymol, and Chem3D were used for the molecular docking. Gromacs software was used to perform molecular dynamics (MD) simulation of the best binding target protein.

Results

A total of 115 key targets of metformin for AD and T2D were obtained. GO analysis showed that biological process mainly involved response to hormones and the regulation of ion transport. Cellular component was enriched in the cell body and axon. Molecular function mainly involved kinase binding and signal receptor regulator activity. The KEGG pathway was mainly enriched in pathways of cancer, neurodegeneration, and endocrine resistance. Core targets mainly included TP53, TNF, VEGFA, HIF1A, IL1B, IGF1, ESR1, SIRT1, CAT, and CXCL8. The molecular docking results showed best binding of metformin to CAT. MD simulation further indicated that the CAT-metformin complex could bind well and converge relatively stable at 30 ns.

Conclusion

Metformin exerts its effects on regulating oxidative stress, gluconeogenesis and inflammation, which may be the mechanism of action of metformin to improve the common pathological features of T2D and AD.

Emerging role of GCN5 in human diseases and its therapeutic potential

As the first histone acetyltransferase to be cloned and identified in yeast, general control non-depressible 5 (GCN5) plays a crucial role in epigenetic and chromatin modifications. It has been extensively studied for its essential role in regulating and causing various diseases. There is mounting evidence to suggest that GCN5 plays an emerging role in human diseases and its therapeutic potential is promising. In this paper, we begin by providing an introduction GCN5 including its structure, catalytic mechanism, and regulation, followed by a review of the current research progress on the role of GCN5 in regulating various diseases, such as cancer, diabetes, osteoporosis. Thus, we delve into the various aspects of GCN5 inhibitors, including their types, characteristics, means of discovery, activities, and limitations from a medicinal chemistry perspective. Our analysis highlights the importance of identifying and creating inhibitors that are both highly selective and effective inhibitors, for the future development of novel therapeutic agents aimed at treating GCN5-related diseases.

The development and benefits of metformin in various diseases

Metformin has been used for the treatment of type II diabetes mellitus for decades due to its safety, low cost, and outstanding hypoglycemic effect clinically. The mechanisms underlying these benefits are complex and still not fully understood. Inhibition of mitochondrial respiratory-chain complex I is the most described downstream mechanism of metformin, leading to reduced ATP production and activation of AMP-activated protein kinase (AMPK). Meanwhile, many novel targets of metformin have been gradually discovered. In recent years, multiple pre-clinical and clinical studies are committed to extend the indications of metformin in addition to diabetes. Herein, we summarized the benefits of metformin in four types of diseases, including metabolic associated diseases, cancer, aging and age-related diseases, neurological disorders. We comprehensively discussed the pharmacokinetic properties and the mechanisms of action, treatment strategies, the clinical application, the potential risk of metformin in various diseases. This review provides a brief summary of the benefits and concerns of metformin, aiming to interest scientists to consider and explore the common and specific mechanisms and guiding for the further research. Although there have been countless studies of metformin, longitudinal research in each field is still much warranted.

Metformin-induced TTP mediates communication between Kupffer cells and hepatocytes to alleviate hepatic steatosis by regulating lipophagy and necroptosis

OBJECTIVE

Emerging evidence suggests that crosstalk between Kupffer cells (KCs) and hepatocytes protects against non-alcoholic fatty liver disease (NAFLD). However, the underlying mechanisms that lead to the reduction of steatosis in NAFLD remain obscure.

METHODS

Ttp^+/+ and Ttp^-/- mice were fed with a high-fat diet. Hepatic steatosis was analyzed by Nile Red staining and measurement of inflammatory cytokines. Lipid accumulation and cell death were evaluated in co-culture systems with primary hepatocytes and KCs derived from either Ttp^+/+ or Ttp^-/- mice.

RESULTS

Tristetraprolin (TTP), an mRNA binding protein, was essential for the protective effects of metformin in NAFLD. Metformin activated TTP via the AMPK-Sirt1 pathway in hepatocytes and KCs. TTP inhibited TNF-α production in KCs, which in turn decreased hepatocyte necroptosis. Downregulation of Rheb expression by TTP promoted hepatocyte lipophagy via mTORC1 inhibition and increased nuclear translocation of transcription factor-EB (TFEB). Consistently, TTP-deficient NAFLD mice failed to respond to metformin with respect to alleviation of hepatic steatosis, protection of hepatocyte necroptosis, or induction of lipophagy.

CONCLUSIONS

TTP, which is essential for the protective effects of metformin, may represent a novel primary therapeutic target in NAFLD.

Differentiated modulation of signaling molecules AMPK and SIRT1 in experimentally drug-induced hepatocyte injury

AIM

Currently available medicines have little to offer in terms of supporting the regeneration of injured hepatic cells. Previous experimental studies have shown that resveratrol and metformin, less specific activators of AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1), can effectively attenuate acute liver injury. The aim of this experimental study was to elucidate whether modulation of AMPK and SIRT1 activity can modify drug/paracetamol (APAP)-induced hepatocyte damage in vitro.

METHODS

Primary rat hepatocytes were pretreated with mutual combinations of specific synthetic activators and inhibitors of SIRT1 and AMPK and followed by a toxic dose of APAP. At the end of cultivation, medium samples were collected for biochemical analysis of alanine-aminotransferase and nitrite levels. Hepatocyte viability, thiobarbituric reactive substances, SIRT1 and AMPK activity and protein expression were also assessed.

RESULTS

The harmful effect of APAP was associated with decreased AMPK and SIRT1 activity and protein expression alongside enhanced oxidative stress in hepatocytes. The addition of AMPK activator (AICAR) or SIRT1 activator (CAY10591) significantly attenuated the deleterious effects of AMPK inhibitor (Compound C) on the hepatotoxicity of APAP. Furthermore, CAY10591 but not AICAR markedly decreased the deleterious effect of APAP in combination with SIRT1 inhibitor (EX-527).

CONCLUSION

Our findings demonstrate that decreased AMPK activity is associated with the hepatotoxic effect of APAP which can be significantly attenuated by the administration of a SIRT1 activator. These findings suggest that differentiated modulation of AMPK and SIRT1 activity could therefore provide an interesting and novel therapeutic opportunity in the future to combat hepatocyte injury.

Inflammaging as a target for healthy ageing

Life expectancy has been on the rise for the past few decades, but healthy life expectancy has not kept pace, leading to a global burden of age-associated disorders. Advancing age is accompanied by a chronic increase in basal systemic inflammation, termed inflammaging, contributing towards an increased risk of developing chronic diseases in old age. This article reviews the recent literature to formulate hypotheses regarding how age-associated inflammaging plays a crucial role in driving chronic diseases and ill health in older adults. Here, we discuss how non-pharmacological intervention strategies (diet, nutraceutical supplements, phytochemicals, physical activity, microbiome-based therapies) targeting inflammaging restore health in older adults. We also consider alternative existing pharmacological interventions (Caloric restriction mimetics, p38 mitogen-activated protein kinase inhibitors) and explore novel targets (senolytics) aimed at combating inflammaging and optimising the ageing process to increase healthy lifespan.

Effects of dietary inclusion of Bambara groundnut and sweet orange peels on streptozotocin/HFD type-2 induced diabetes mellitus complications and related biochemical parameters

The effects of dietary inclusion of Bambara groundnut and sweet orange peels composite bread on low-dose streptozotocin and high-fat diet (HFD)-induced type-2 diabetes mellitus (T2D) complications was evaluated in the present study. Male experimental rats-induced T2D were administered with acarbose (standard) and fed with Bambara groundnut and sweet orange peels composite bread for a period of 14 days while monitoring their blood glucose levels. More so, the activities of angiotensin-I-converting enzyme (ACE), serum aspartate aminotransferase, alkaline phosphatase, and alanine aminotransferase activities, as well as nitric oxide (NO), reactive oxygen species (ROS), albumin, total bilirubin, creatinine, urea, and uric acid serum concentrations were assayed for. Diabetic untreated rats showed disorders in ACE, AST, ALT, and ALP activities, and NO, ROS, glucose, albumin, bilirubin, creatinine, urea, uric acid levels, as well as lipid profiles. Interestingly, these disorders were significantly ameliorated in composite bread diet-fed rats in comparison to the diabetic untreated rats. Meanwhile, the presence of polyphenols in the Bambara groundnut and sweet orange peels composite bread diet could have aided the amelioration of these metabolic disorders after the 14th day of administration. Finally, it was proposed that the ability of Bambara groundnut-wheat and sweet orange peel composite bread to treat T2D and its complications makes it a more successful therapy than medications that just target one of the diseased states. PRACTICAL APPLICATIONS: Diabetes mellitus is a global and chronic disease that presently affects 536.6 million people alongside 1.5 million deaths directly attributed to it yearly. Several drug and medicinal agents have been employed for the management of diabetes but those drugs are mostly limited to the management of diabetes while the associated complications are most untreated, while drugs that can manage diabetes and its related complications mostly come at high prices. Therefore, there is an urgent need to evaluate legumes, such as Bambara groundnut, with proven therapeutic potential in the management of diabetes and its complications. However, the Bambara groundnut takes a long period to prepare for a meal, therefore including it in a ready-to-eat product will not only improve its acceptability but also add to economic improvement. Furthermore, adding a waste product, sweet orange peels, will both add flavor and source of additional antioxidant attributes.

Effects of single-nucleotide polymorphism on the pharmacokinetics and pharmacodynamics of metformin

INTRODUCTION

Metformin has been recognized as the first-choice drug for type 2 diabetes mellitus (T2DM). The potency of metformin in the treatment of type 2 diabetes has always been in the spotlight and shown significant individual differences. Based on previous studies, the efficacy of metformin is related to the single-nucleotide polymorphisms of transporter genes carried by patients, amongst which a variety of gene polymorphisms of transporter and target protein genes affect the effectiveness and adverse repercussion of metformin.

AREAS COVERED

Here, we reviewed the current knowledge about gene polymorphisms impacting metformin efficacy based on transporter and drug target proteins.

EXPERT OPINION

The reason for the difference in clinical drug potency of metformin can be attributed to the gene polymorphism of drug transporters and drug target proteins in the human body. Substantial evidence shows that genetic polymorphisms in transporters such as organic cation transporter 1 (OCT1) and organic cation transporter 2 (OCT2) affect the glucose-lowering effectiveness of metformin. However, optimization of individualized dosing regimens of metformin is necessary to clarify the role of several polymorphisms.

Advances in metformin for the treatment of non-alcoholic fatty liver disease in children

INTRODUCTION

The increased economic and social burdens for NAFLD worldwide make treating such a disease a significant public health issue. Metformin, a kind of insulin sensitizer generally used to treat type 2 diabetes, has been recently found to have efficacy on children's NAFLD in various areas such as glucolipid metabolism, intestinal bacterial metabolism, oxidative stress, and anti-inflammatory response. This article aims to provide an overview of the possible mechanisms of NAFLD in children and the potential therapeutic application of metformin.

AREAS COVERED

The Cochrane Library, PubMed, Scopus, and EMBASE database was systematically searched on 12 April 2022, using the keywords metformin; non-alcoholic fatty liver disease; and children to identify similar studies. An additional search for recently published research was performed in June 2020.

EXPERT OPINION

Although metformin has been proved to have an excellent therapeutic effect on children's NAFLD; we can still explore its potential impacts and mechanisms from different angles, such as combined medication. At the same time, we should also pay attention to its side effects.

Epigenetics of type 2 diabetes mellitus and weight change - a tool for precision medicine?

Pioneering studies performed over the past few decades demonstrate links between epigenetics and type 2 diabetes mellitus (T2DM), the metabolic disorder with the most rapidly increasing prevalence in the world. Importantly, these studies identified epigenetic modifications, including altered DNA methylation, in pancreatic islets, adipose tissue, skeletal muscle and the liver from individuals with T2DM. As non-genetic factors that affect the risk of T2DM, such as obesity, unhealthy diet, physical inactivity, ageing and the intrauterine environment, have been associated with epigenetic modifications in healthy individuals, epigenetics probably also contributes to T2DM development. In addition, genetic factors associated with T2DM and obesity affect the epigenome in human tissues. Notably, causal mediation analyses found DNA methylation to be a potential mediator of genetic associations with metabolic traits and disease. In the past few years, translational studies have identified blood-based epigenetic markers that might be further developed and used for precision medicine to help patients with T2DM receive optimal therapy and to identify patients at risk of complications. This Review focuses on epigenetic mechanisms in the development of T2DM and the regulation of body weight in humans, with a special focus on precision medicine.

The effects of metformin monotherapy and combination of metformin and glibenclamide therapy on the expression of RAGE, Sirt1, and Nrf2 genes in peripheral blood mononuclear cells of type 2 diabetic patients

Purpose

Although metformin is the first-line treatment of type 2 diabetes mellitus (T2DM), a few studies have evaluated the benefits of monotherapies (metformin) versus combination therapy (metformin and glibenclamide) for treatment of T2DM patients. The present study aimed to evaluate the effect of monotherapy with metformin compared to combination therapy with metformin and glibenclamide on the expression of RAGE, Nrf 2, and Sirt1genes.

Methods

EightyT2DM patients and 40 healthy individuals participated in this case-control study. The patients in the treatment group were divided into two groups who received either metformin alone (n = 40) or metformin in combination with glibenclamide (n = 40). FBS, HbA1c, and fructosamine were measured. The expression of RAGE, Nrf 2, and Sirt 1 genes in PBMC of all subjects were assessed using real-time PCR.

Results

RAGE gene expression in both treatment groups was significantly lower than the control (P < 0.05). RAGE gene expression was significantly reduced in the combination of metformin and glibenclamide treated group compared to metformin group (P < 0.05). Additionally, the expression of Sirt 1 and Nrf 2 genes in both treatment groups was higher than that of the control group (P < 0.05). The expression of Sirt 1 and Nrf 2 genes in metformin and glibenclamide treated group were higher than the metformin group (P < 0.05).

Conclusion

Combination therapy (metformin and glibenclamide) showed stronger effect on repression of the RAGE gene and activation of Nrf 2 and Sirt 1 genes compared to monotherapy (metformin); therefore, it can be concluded that combination therapy may have more protective effects on the T2DM patients. No significant correlation was observed between HbA1c and RAGE, Sirt 1, and Nrf 2 genes expression.

Calorie Restriction for Cancer Prevention and Therapy: Mechanisms, Expectations, and Efficacy

Cancer is one of the most frequently diagnosed diseases, and despite the continuous efforts in searching for new and more effective treatments, its morbidity and mortality remain a significant health problem worldwide. Calorie restriction, a dietary manipulation that consists in a reduction of the calorie intake, is gaining attention as a potential adjuvant intervention for preventing and/or fighting cancer. Several forms of energy reduction intake, which includes caloric restriction tout-court, dietary restrictions, and intermittent fasting, are being explored for their ability to prevent or slow down cancer progression. Additionally, another anti-cancer approach being under investigation relies on the use of nutraceuticals known as “Caloric Restriction Mimetics” that can provide caloric restriction-mediated benefits without subjecting the patients to a strict diet. Preclinical in vitro and in vivo studies consistently show that diet modifiers reducing the calorie have impact on tumor microenvironment and cancer metabolism, resulting in reduced growth and progression of cancer. Preliminary clinical studies show that patients subjected to a reduced nutrient/energy intake experience improved outcomes from chemo- and radiotherapy while better tolerating the side effects. Here, we review the state of the art on the therapeutic potential of calorie restriction and of caloric restriction mimetics in preventing or retarding tumor development by modulating a subset of cellular processes. The most recent clinical progresses with caloric restriction mimetics in the clinical practice are also discussed.

Targeting Cardiovascular Risk Factors Through Dietary Adaptations and Caloric Restriction Mimetics

The average human life expectancy continues to rise globally and so does the prevalence and absolute burden of cardiovascular disease. Dietary restriction promotes longevity and improves various cardiovascular risk factors, including hypertension, obesity, diabetes mellitus, and metabolic syndrome. However, low adherence to caloric restriction renders this stringent dietary intervention challenging to adopt as a standard practice for cardiovascular disease prevention. Hence, alternative eating patterns and strategies that recapitulate the salutary benefits of caloric restriction are under intense investigation. Here, we first provide an overview of alternative interventions, including intermittent fasting, alternate-day fasting and the Mediterranean diet, along with their cardiometabolic effects in animal models and humans. We then present emerging pharmacological alternatives, including spermidine, NAD+ precursors, resveratrol, and metformin, as promising caloric restriction mimetics, and briefly touch on the mechanisms underpinning their cardiometabolic and health-promoting effects. We conclude that implementation of feasible dietary approaches holds the promise to attenuate the burden of cardiovascular disease and facilitate healthy aging in humans.

Metformin Alleviates Steatohepatitis in Diet-Induced Obese Mice in a SIRT1-Dependent Way

Metformin is the first-line anti-diabetic drug for type 2 diabetes. It has been found to significantly reduce liver aminotransferase in nonalcoholic fatty liver disease (NAFLD). However, whether metformin improves NAFLD progression remains controversial. Sirtuin 1 (SIRT1), an NAD⁺-dependent deacetylase, plays a vital role in hepatic steatosis and inflammation. Here, we investigated the effect of metformin on steatohepatitis and the role of SIRT1 in diet-induced obese (DIO) mice. The results showed that metformin significantly reduced body weight and fat mass of DIO mice. In addition, metformin also alleviated adiposity and hepatic steatosis, and greatly upregulated uncoupling protein 1 (UCP1) expression in adipose tissues of DIO mice. Unexpectedly, the effects of metformin on reducing body weight and alleviating hepatic steatosis were not impaired in Sirt1 heterozygous knockout (Sirt1^+/−) mice. However, SIRT1-deficiency remarkably impaired the effects of metformin on lowering serum transaminases levels, downregulating the mRNA expression of proinflammatory factors, and increasing the protein level of hepatic Cholesterol 25-Hydroxylase (CH25H), a cholesterol hydroxylase in cholesterol catabolism. In summary, we demonstrated that metformin alleviates steatohepatitis in a SIRT1-dependent manner, and modulation of M1 polarization and cholesterol metabolism may be the underlying mechanism.

The GCN5: its biological functions and therapeutic potentials

General control non-depressible 5 (GCN5) or lysine acetyltransferase 2A (KAT2A) is one of the most highly studied histone acetyltransferases. It acts as both histone acetyltransferase (HAT) and lysine acetyltransferase (KAT). As an HAT it plays a pivotal role in the epigenetic landscape and chromatin modification. Besides, GCN5 regulates a wide range of biological events such as gene regulation, cellular proliferation, metabolism and inflammation. Imbalance in the GCN5 activity has been reported in many disorders such as cancer, metabolic disorders, autoimmune disorders and neurological disorders. Therefore, unravelling the role of GCN5 in different diseases progression is a prerequisite for both understanding and developing novel therapeutic agents of these diseases. In this review, we have discussed the structural features, the biological function of GCN5 and the mechanical link with the diseases associated with its imbalance. Moreover, the present GCN5 modulators and their limitations will be presented in a medicinal chemistry perspective.

Nigella sativa as a promising intervention for metabolic and inflammatory disorders in obese prediabetic subjects: A comparative study of Nigella sativa versus both lifestyle modification and metformin

AIM

This study aimed at evaluating the effect of Nigella sativa (NS) on anthropometric, metabolic and inflammatory parameters and examining its related molecular mechanisms in obese prediabetic individuals as compared to both lifestyle modification (LM) and Metformin (Met).

METHODS

This study included 117 obese prediabetic subjects who were randomized into LM group which followed controlled diet and exercise regimen, metformin group received metformin 500 mg tablets twice daily and NS group received NS oil soft gelatin capsules 450 mg twice daily. Anthropometric (weight, BMI), glycemic, lipid, inflammatory parameters and genetic expressions of Sirtuin-1 (SIRT1) and p53 genes were assessed before and six months after interventions.

RESULTS

Post-intervention pairwise comparison revealed that, NS was statistically similar to metformin in improving anthropometric, glycemic parameters and SIRT1 gene expression. There was non-significant difference between LM and NS regarding their effects on anthropometric and most of glycemic parameters. Lifestyle modification group showed significantly higher HOMA-B and SIRT1 expression than NS and metformin. Nigella sativa improved lipid panel and significantly reduced TNF-α level and Castelli risk index-I as compared to other interventions.

CONCLUSION

Nigella sativa uniquely improved lipid panel and significantly suppressed inflammation. Therefore, Nigella sativa may represent a promising intervention for obese prediabetic subjects. Clinicaltrial.gov ID: NCT03925714.

Sirtuin 1 as the mechanism of action of agents used in the diabetes mellitus pharmacotherapy

SIRT1 (sirtuin 1, a member of histone deacetylase III family) is responsible for deacetylation of lysine in histones and the conservation of DNA in the state of transcriptionally inactive heterochromatin. SIRT1 is also capable of deacetylation of transcription factors, as well as other regulatory proteins. The SIRT1 activity plays a unique role in the prevention of metabolic memory, reducing many pathways leading to chronic diabetic complications or diseases concomitant with diabetes. Factors modifying expression and/or activity of SIRT1 may be especially helpful for patients with diabetes. This article attempts to sum up the current state of knowledge about agents commonly used in the treatment of type 2 diabetes which might have an impact on the SIRT1 expression and activity. It is the review of several studies regarding drug-induced pleiotropic activity and the way in which their interference with cellular pathways gives us better understanding of this activity, as well as the influence of therapy on the course of the disease.

Bioinformatics Analysis of ceRNA Network Related to Polycystic Ovarian Syndrome

Introduction

Polycystic ovary syndrome (PCOS) is caused by the hormonal environment in utero, abnormal metabolism, and genetics, and it is common in women of childbearing age. A large number of studies have reported that lncRNA is important to the biological process of cancer and can be used as a potential prognostic biomarker. Thus, we studied lncRNAs' roles in PCOS in this article.

Methods

We obtained mRNAs', miRNAs', and lncRNAs' expression profiles in PCOS specimens and normal specimens from the National Biotechnology Information Gene Expression Comprehensive Center database. The EdgeR software package is used to distinguish the differentially expressed lncRNAs, miRNAs, and mRNAs. Functional enrichment analysis was carried out by the clusterProfiler R Package, and the lncRNA-miRNA-mRNA interaction ceRNA network was built in Cytoscape plug-in BiNGO and Database for Annotation, Visualization, and Integration Discovery (DAVID), respectively.

Results

We distinguished differentially expressed RNAs, including 1087 lncRNAs, 14 miRNAs, and 566 mRNAs in PCOS. Among them, 410 lncRNAs, 11 miRNAs, and 185 mRNAs were contained in the ceRNA regulatory network. The outcomes from Gene Ontology (GO) analysis showed that the differentially expressed mRNAs (DEMs) were mainly enriched in response to the maternal process involved in female pregnancy, morphogenesis of embryonic epithelium, and the intracellular steroid hormone receptor signaling pathway. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis data showed that DEMs were primarily enriched in pathways related to the TGF-β signaling pathway, Type I diabetes mellitus, and glycolysis/gluconeogenesis. In addition, we chose NONHSAT123397, ENST00000564619, and NONHSAT077997 as key lncRNAs due to their high bearing on PCOS.

Conclusion

ceRNA networks play an important role in PCOS. The research indicated that specific lncRNAs were related to PCOS development. NONHSAT123397, ENST00000564619, and NONHSAT077997 could be regarded as potential diagnostic mechanisms and biomarkers for PCOS. This discovery might provide more effective and more novel insights into the mechanisms of PCOS worthy of further exploration.

Metformin Improves Biochemical and Pathophysiological Changes in Hepatocellular Carcinoma with Pre-Existed Diabetes Mellitus Rats

Hepatocellular carcinoma (HCC) is one of the world’s most widely recognized malignant tumors that accounts for 90% of all the primary liver cancers and is a major cause of death from cancer, representing half a million deaths per year. Obesity and associated metabolic irregularities, particularly diabetes mellitus (DM) and insulin resistance, are important risk factors for the advancement of HCC. Recently, retrospective studies showed that metformin (MET) could protect the hepatic tissues in pre-existing diabetes mellitus from HCC. The purpose of this study was to assess the role of MET treatment in the pre-existing diabetic rats before and after HCC induction by diethylnitrosamine (DEN). Thirty-five male Sprague Dawley albino rats were partitioned into the following groups: Group 1 (Gp1) was the control. Gp2 was injected intraperitoneally (i.p) with streptozotocin (STZ) (80 mg/kg) and DEN (50 mg/kg/7 weeks). Gp3, Gp4, and Gp5 were injected as in Gp2 and treated with MET (150 mg/kg) before and/or after HCC induction. Biochemical parameters including liver functions, lipid profile, and oxidative stress biomarkers were determined. Furthermore, histological and immunohistochemical changes were assessed in all groups. Our results illustrated that the group of rats that were treated with STZ and DEN had significant changes in both liver functions and were associated with alterations in the liver histopathological architectures. Treatment with MET before or after HCC induction ameliorated the cellular changes in the liver tissues; however, the utmost protection was found in a group of rats, which were treated with MET before and after HCC induction.

Liver Phosphoenolpyruvate Carboxykinase-1 Downregulation via siRNA-Functionalized Graphene Oxide Nanosheets Restores Glucose Homeostasis in a Type 2 Diabetes Mellitus In Vivo Model

Metabolic disorders have been increasing at an alarming rate, and one such example of metabolic disorder is type 2 diabetes mellitus (T2DM). Unregulated gluconeogenesis in T2DM results in increased hepatic glucose output that causes fasting and postprandial hyperglycaemia. Extensive proofs have shown that the downregulation of the key rate-limiting enzyme phosphoenolpyruvate carboxykinase-1 (PCK-1) of gluconeogenesis improved glucose homeostasis in vivo. In the present study, we have synthesized and characterized liver-specific stearic acid conjugated octaarginine (StA-R8) functionalized 4arm-2K-PEGamineylated graphene oxide nanosheets (GPR8) for the delivery of siRNA against PCK-1 in T2DM C57BL/6 mice. We found that a single intravenous administration of siRNA (3 mg/kg BW) conjugated to GPR8 (GPR8:PCK-1_{siRNA(3 mg/kg BW)} conjugate) in an optimized N/P ratio exploited as a therapeutic nanoformulation maintained glucose homeostasis for nearly 4 weeks in the T2DM mice. Efficient silencing of PCK-1 in T2DM liver tissue increased the phosphorylation of serine-256 of FOXO-1, thus showing a marked decrease in hepatic gluconeogenesis. Gluconeogenesis control and consequently glucose output from the liver furthermore partially enhanced liver and muscle insulin sensitivity results in the stimulation of the insulin/AKT-2 signaling pathway which indirectly restored glucose homeostasis in the treated T2DM group. Our therapeutic nanoformulation also improved glycogen storage in the liver and membrane translocation of GLUT4 in the muscle of the treated T2DM group. In conclusion, GPR8:PCK-1_{siRNA (3 mg/Kg BW)} restored glucose homeostasis by controlling the hepatic glucose production and improved peripheral insulin sensitivity as a consequence of reduced hyperglycemia. Thus, the current approach offered an alternative strategy for the therapeutics for T2DM.

SIRTI and cortisol in unexplained infertile females; a cross sectional study, in Karachi Pakistan

OBJECTIVE

To explore a disparity in anti-oxidants (SIRT1) and pro-oxidants (cortisol) levels as a plausible cause of unexplained infertility in females.

METHODOLOGY

It was a cross sectional study in which 342 females with unexplained infertility were recruited from ACIMC outpatient clinic: 135 infertile cases and 207 fertile controls. Biochemical estimation of serum cortisol and SIRT1 was performed using Enzyme Linked Immuno Sorbent Assay. Statistical comparisons were performed using Student-t test and Mann-Whitney U test. Associations between circulating hormone levels and infertility were determined using Spearman's rank correlation. Associations were considered significant where value of p was less than 0.05.

RESULTS

The stress hormones profile of case and control demonstrated that the antioxidant SIRT1 was significantly lower in infertile females when compared with the fertile (p =< 0.001) while (the oxidant) Cortisol showed a contrast of results with higher values of in infertile females when compared with fertile counterparts (p =< 0.01). There was a strong negative association observed between SIRT1 and cortisol serum level (r = 0.244, p < 0.001).

CONCLUSION

Chronic stress causes oxidative stress that is depicted by a decrease in antioxidant levels in infertile females.

Metformin ameliorates skeletal muscle atrophy in Grx1 KO mice by regulating intramuscular lipid accumulation and glucose utilization

Skeletal muscle is the largest tissue in the body, and plays a remarkable role in energy and metabolic homeostasis. Disorder in lipid metabolism and glucose utilization could impair the quality and function of skeletal muscle. Glutaredoxin-1 (Grx1) acts as a vital metabolic regulator of redox homeostasis. Recent studies have shown that Grx1 regulates hepatic lipid metabolism. The skeletal muscle also contains abundant Grx1, but the role of Grx1 in skeletal muscle remains unknown. Therefore, we investigated the effect of Grx1 on skeletal muscle. In this study, we found that Grx1-deficient mice (Grx1^-/-) spontaneously developed muscle atrophy by 3 months of age. And the p-AMPK activity and Sirt1 activity were inhibited in Grx1^-/- mice, which led to intramuscular lipid deposition and glucose utilization disorder in skeletal muscle. However, intraperitoneal injection of metformin for 15 consecutive days ameliorated skeletal muscle atrophy caused by Grx1 deficiency to a certain extent. Taken together, these findings indicate that Grx1 deficiency might induce skeletal muscle atrophy by regulating the intramuscular lipid deposition and glucose utilization, which could be attenuated by metformin. Therefore, the expression or activity of Grx1 may be a pharmacological approach to ameliorate muscle atrophy diseases, such as sarcopenia.

Sirt1-PPARS Cross-Talk in Complex Metabolic Diseases and Inherited Disorders of the One Carbon Metabolism

Sirtuin1 (Sirt1) has a NAD (+) binding domain and modulates the acetylation status of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α) and Fork Head Box O1 transcription factor (Foxo1) according to the nutritional status. Sirt1 is decreased in obese patients and increased in weight loss. Its decreased expression explains part of the pathomechanisms of the metabolic syndrome, diabetes mellitus type 2 (DT2), cardiovascular diseases and nonalcoholic liver disease. Sirt1 plays an important role in the differentiation of adipocytes and in insulin signaling regulated by Foxo1 and phosphatidylinositol 3′-kinase (PI3K) signaling. Its overexpression attenuates inflammation and macrophage infiltration induced by a high fat diet. Its decreased expression plays a prominent role in the heart, liver and brain of rat as manifestations of fetal programming produced by deficit in vitamin B12 and folate during pregnancy and lactation through imbalanced methylation/acetylation of PGC1α and altered expression and methylation of nuclear receptors. The decreased expression of Sirt1 produced by impaired cellular availability of vitamin B12 results from endoplasmic reticulum stress through subcellular mislocalization of ELAVL1/HuR protein that shuttles Sirt1 mRNA between the nucleus and cytoplasm. Preclinical and clinical studies of Sirt1 agonists have produced contrasted results in the treatment of the metabolic syndrome. A preclinical study has produced promising results in the treatment of inherited disorders of vitamin B12 metabolism.

Metformin Mitigates Cartilage Degradation by Activating AMPK/SIRT1-Mediated Autophagy in a Mouse Osteoarthritis Model

Chondrocyte dysfunction is a key mechanism underlying osteoarthritis. Metformin has shown protective effects in many diseases. The present study aimed to investigate the effects of metformin on autophagy and apoptosis in the process of osteoarthritis. A mouse osteoarthritis model was set up by surgically destabilizing medial meniscus in the knee. Intraarticular injection of metformin or vehicle was applied in the right knee for eight weeks. Mouse articular chondrocytes were isolated and passaged for in vitro experiments. Small interfering RNA (siRNA) transfection was used to silence target genes. Western blotting, immunohistochemistry, transmission electron microscopy were used. After eight weeks, metformin restored surgery-induced upregulation of MMP13 and downregulation of type II collagen in the joint cartilage. In cultured primary murine chondrocytes, IL-1β aggravated apoptosis and catabolic response in a dose-dependent manner. In the presence of IL-1β, metformin increased phosphorylated levels of AMPKα and upregulated SIRT1 protein expression, leading to an increase in autophagy as well as a decrease in catabolism and apoptosis. Inactivating AMPKα or inhibiting SIRT1 prevented the augmented autophagy in the presence of metformin. Silencing AMPKα2, but not AMPKα1, reduced SIRT1 expression and downregulated autophagy in cultured chondrocytes. Metformin protects against IL-1β-induced extracellular matrix (ECM) degradation in cultured chondrocytes and in mouse osteoarthritis model through activating AMPKα/SIRT1 signaling. Metformin shed light on the treatment of osteoarthritis.

LC-Q-TOF-MS Characterization of Polyphenols from White Bayberry Fruit and Its Antidiabetic Effect in KK-Ay Mice

The present study is to investigate the polyphenolic composition and in vivo antidiabetic effect of white-fleshed Chinese bayberry cultivar "Shui Jing". By liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS), 38 polyphenols were identified in the Shui Jing fruit extract (SJE), where proanthocyanidins (PAs), including epigallocatechin gallate (EGCG), as well as flavonols, including myricitrin and quercetrin, were the predominant ingredients. After a 5-week experiment, the SJE (200 mg/kg bodyweight) significantly reduced fasting blood glucose, elevated glucose tolerance, and insulin sensitivity in diabetic KK-A^y mice. It markedly attenuated bodyweight gain and decreased glycolipid metabolism-related markers including insulin, leptin, glucagon, triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c) and alanine aminotransferase (ALT) levels in mice. Liver weight and hepatic lipid accumulation were also significantly reduced by the SJE. Gene expressions of insulin 1 (INS1) and glycogen synthase kinase 3 β (GSK3b) were markedly inhibited while the hepatic phosphorylation of AMPKα was significantly increased in the liver of SJE-treated mice, indicating that the SJE may exert an antidiabetic effect through an AMPK-dependent pathway. In conclusion, white bayberry rich in PAs and flavonols may have great potential in the regulation of diabetes mellitus.

Metformin and 2-Deoxyglucose Collaboratively Suppress Human CD4+ T Cell Effector Functions and Activation-Induced Metabolic Reprogramming

Metabolic reprogramming plays a central role in T cell activation and differentiation, and the inhibition of key metabolic pathways in activated T cells represents a logical approach for the development of new therapeutic agents for treating autoimmune diseases. The widely prescribed antidiabetic drug metformin and the glycolytic inhibitor 2-deoxyglucose (2-DG) have been used to study the inhibition of oxidative phosphorylation and glycolysis, respectively, in murine immune cells. Published studies have demonstrated that combination treatment with metformin and 2-DG was efficacious in dampening mouse T cell activation-induced effector processes, relative to treatments with either metformin or 2-DG alone. In this study, we report that metformin + 2-DG treatment more potently suppressed IFN-γ production and cell proliferation in activated primary human CD4⁺ T cells than either metformin or 2-DG treatment alone. The effects of metformin + 2-DG on human T cells were accompanied by significant remodeling of activation-induced metabolic transcriptional programs, in part because of suppression of key transcriptional regulators MYC and HIF-1A. Accordingly, metformin + 2-DG treatment significantly suppressed MYC-dependent metabolic genes and processes, but this effect was found to be independent of mTORC1 signaling. These findings reveal significant insights into the effects of metabolic inhibition by metformin + 2-DG treatment on primary human T cells and provide a basis for future work aimed at developing new combination therapy regimens that target multiple pathways within the metabolic networks of activated human T cells.

Mechanisms of action of metformin in type 2 diabetes: Effects on mitochondria and leukocyte-endothelium interactions

Type 2 diabetes (T2D) is a very prevalent, multisystemic, chronic metabolic disorder closely related to atherosclerosis and cardiovascular diseases. It is characterised by mitochondrial dysfunction and the presence of oxidative stress. Metformin is one of the safest and most effective anti-hyperglycaemic agents currently employed as first-line oral therapy for T2D. It has demonstrated additional beneficial effects, unrelated to its hypoglycaemic action, on weight loss and several diseases, such as cancer, cardiovascular disorders and metabolic diseases, including thyroid diseases. Despite the vast clinical experience gained over several decades of use, the mechanism of action of metformin is still not fully understood. This review provides an overview of the existing literature concerning the beneficial mitochondrial and vascular effects of metformin, which it exerts by diminishing oxidative stress and reducing leukocyte-endothelium interactions. Specifically, we describe the molecular mechanisms involved in metformin's effect on gluconeogenesis, its capacity to interfere with major metabolic pathways (AMPK and mTORC1), its action on mitochondria and its antioxidant effects. We also discuss potential targets for therapeutic intervention based on these molecular actions.

The Effect of Metformin on Thyroid-Associated Serum Hormone Levels and Physiological Indexes: A Meta-Analysis

BACKGROUND

Many diseases can be treated with metformin. People with serum thyrotropin (TSH) levels higher than 10 mIU/L are at a risk of cardiovascular events. Some studies have suggested that metformin can lower serum TSH levels to a subnormal level in patients with hyperthyrotropinaemia or hypothyroidism.

OBJECTIVE

The objective of this analysis is to evaluate the effect of metformin treatment on serum TSH, free triiodothyronine (FT3), and free thyroxine (FT4) levels and other associated physiological indices.

METHODS

A comprehensive search using the PubMed, EMBASE, Web of Science and Cochrane Central databases was undertaken for controlled trials on the effect of metformin on serum TSH, FT3, and FT4 levels and associated physiological indices. The primary outcome measures were serum TSH, FT3 and FT4 levels, thyroid size, thyroid nodule size, blood pressure, heart rate, body weight, and body mass index (BMI). The final search was conducted in April 2019.

RESULTS

Six RCTs were included. A total of 494 patients met the inclusion criteria. Metformin treatment did not significantly lower the serum TSH levels at 3 or 6 months but did at 12 months. Moreover, forest plots also suggested that metformin can significantly lower the serum TSH levels in patients with normal thyroid function but cannot statistically change the serum TSH levels in patients with abnormal thyroid function. In addition, metformin treatment clearly lowered the serum FT3 levels and had no significant effect on serum FT4 levels. Lastly, metformin cannot significantly change the systolic blood pressure (SBP) or BMI but can clearly increase the diastolic blood pressure (DBP).

CONCLUSION

Metformin treatment can significantly lower the serum TSH levels, and this effect was much clearer after a 12-month treatment duration and in people with normal thyroid function. However, metformin cannot significantly change the serum FT4 levels or lower serum FT3 levels in people with non-thyroid cancer diseases. In addition, metformin can significantly increase DBP, but it has no clear effect on SBP or BMI.

Murine remote ischemic preconditioning suppresses diabetic ketoacidosis by enhancing glycolysis and entry into tricarboxylic acid cycle in the liver

AIMS

Hindlimb ischemia-reperfusion (IR) was previously demonstrated by our group to decrease blood sugar levels by suppressing hepatic gluconeogenesis and enhancing glucose uptake using activation of the parasympathetic nervous system. While IR attenuated hyperglycemia in diabetic mice, it was unclear whether IR regulated energy metabolism in the liver. We investigated the mechanisms by which IR regulates energy metabolism in the liver from type1 diabetic mice.

MAIN METHODS

Streptozotocin-induced diabetic male C57BL/6J mice were used to determine the effect of IR on the factors involved in energy metabolism in the liver (i.e., activation levels of AMP-activated protein kinase, aconitase and pyruvate dehydrogenase; adenosine triphosphate and fumarate concentrations; sirtuin (Sirt) 1 expression). These various signaling pathways and key enzyme activities were examined using western blot analysis and a biochemical technique including a colorimetric assay.

KEY FINDINGS

Under feeding conditions (free access to normal murine chow and water), blood glucose levels and serum ketone body levels were significantly suppressed by IR, whereas phospho-AMP-activated protein kinase and its activity, pyruvate dehydrogenase, aconitase activity, and Sirt 1expression were upregulated. In contrast, peroxisome proliferator-activated receptor γ coactivator-1, which accelerated fatty acid use, was suppressed by IR.

SIGNIFICANCE

These results indicated that in the IR-treated diabetic liver, energy production was promoted through acceleration of the tricarboxylic acid cycle linked with increased glucose preference rather than fatty acid under feeding conditions. Therefore, IR may be beneficial against diabetic hyperglycemia, but also ketoacidosis.

SIRT1 Regulation in Ageing and Obesity

Ageing and obesity have common hallmarks: altered glucose and lipid metabolism, chronic inflammation and oxidative stress are some examples. The downstream effects of SIRT1 activity have been thoroughly explored, and their research is still in expanse. SIRT1 activation has been shown to regulate pathways with beneficiary effects on 1) ageing and obesity-associated metabolic disorders such as metabolic syndrome, insulin resistance and type-II diabetes with, 2) chronic inflammatory processes such as arthritis, atherosclerosis and emphysema, 3) DNA damage and oxidative stress with impact on neurodegenerative diseases, cardiovascular health and some cancers. This knowledge intensified the interest in uncovering the mechanisms regulating the expression and activity of SIRT1. This review focuses on the upstream regulatory mechanisms controlling SIRT1, and how this knowledge could potentially contribute to the development of therapeutic interventions.

Effect of dapagliflozin, a sodium-glucose co-transporter-2 inhibitor, on gluconeogenesis in proximal renal tubules

AIMS

To investigate the effect of dapagliflozin, a sodium-glucose co-transporter-2 (SGLT2) inhibitor, on renal gluconeogenesis in vitro, ex vivo and in vivo.

MATERIALS AND METHODS

We treated HK-2 cells (human renal proximal tubule cells) and mouse primary renal proximal tubule cells with dapagliflozin, and evaluated the process of renal gluconeogenesis. We also examined the effect of dapagliflozin on renal gluconeogenesis in normoglycaemic and hyperglycaemic mice.

RESULTS

Dapagliflozin enhanced renal gluconeogenesis in vitro, ex vivo and in vivo. It increased phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (G6Pase), peroxisome proliferative activated receptor-gamma co-activator 1α (PGC-1α) and phosphorylated cyclic-AMP response element binding protein (CREB) expression and decreased phosphorylated Forkhead Box O1 (FOXO1) expression in HK-2 cells, mouse primary renal proximal tubule cells, and the mouse renal cortex. Glutamine enhanced the gluconeogenic effect of dapagliflozin in HK-2 cells. Also, dapagliflozin increased ¹⁴ C-glutamine utilization in HK-2 cells. Glucagon did not affect dapagliflozin-induced enhancement in renal gluconeogenesis in HK-2 cells. SGLT2 gene knockdown with siRNA resulted in an increase of gluconeogenic gene expression and associated transcription factors in HK-2 cells. Dapagliflozin reduced fasting plasma glucose levels and improved oral glucose tolerance and insulin tolerance in high-fat diet-fed hyperglycaemic mice, although renal gluconeogenesis was enhanced.

CONCLUSIONS

Dapagliflozin increased levels of gluconeogenic enzyme in the renal cortex and consequently increased renal gluconeogenesis, which is mediated by SGLT2 inhibition.

Structure-functional changes in eNAMPT at high concentrations mediate mouse and human beta cell dysfunction in type 2 diabetes

AIMS/HYPOTHESIS

Progressive decline in functional beta cell mass is central to the development of type 2 diabetes. Elevated serum levels of extracellular nicotinamide phosphoribosyltransferase (eNAMPT) are associated with beta cell failure in type 2 diabetes and eNAMPT immuno-neutralisation improves glucose tolerance in mouse models of diabetes. Despite this, the effects of eNAMPT on functional beta cell mass are poorly elucidated, with some studies having separately reported beta cell-protective effects of eNAMPT. eNAMPT exists in structurally and functionally distinct monomeric and dimeric forms. Dimerisation is essential for the NAD-biosynthetic capacity of NAMPT. Monomeric eNAMPT does not possess NAD-biosynthetic capacity and may exert distinct NAD-independent effects. This study aimed to fully characterise the structure-functional effects of eNAMPT on pancreatic beta cell functional mass and to relate these to beta cell failure in type 2 diabetes.

METHODS

CD-1 mice and serum from obese humans who were without diabetes, with impaired fasting glucose (IFG) or with type 2 diabetes (from the Body Fat, Surgery and Hormone [BodyFatS&H] study) or with or at risk of developing type 2 diabetes (from the VaSera trial) were used in this study. We generated recombinant wild-type and monomeric eNAMPT to explore the effects of eNAMPT on functional beta cell mass in isolated mouse and human islets. Beta cell function was determined by static and dynamic insulin secretion and intracellular calcium microfluorimetry. NAD-biosynthetic capacity of eNAMPT was assessed by colorimetric and fluorescent assays and by native mass spectrometry. Islet cell number was determined by immunohistochemical staining for insulin, glucagon and somatostatin, with islet apoptosis determined by caspase 3/7 activity. Markers of inflammation and beta cell identity were determined by quantitative reverse transcription PCR. Total, monomeric and dimeric eNAMPT and nicotinamide mononucleotide (NMN) were evaluated by ELISA, western blot and fluorometric assay using serum from non-diabetic, glucose intolerant and type 2 diabetic individuals.

RESULTS

eNAMPT exerts bimodal and concentration- and structure-functional-dependent effects on beta cell functional mass. At low physiological concentrations (~1 ng/ml), as seen in serum from humans without diabetes, eNAMPT enhances beta cell function through NAD-dependent mechanisms, consistent with eNAMPT being present as a dimer. However, as eNAMPT concentrations rise to ~5 ng/ml, as in type 2 diabetes, eNAMPT begins to adopt a monomeric form and mediates beta cell dysfunction, reduced beta cell identity and number, increased alpha cell number and increased apoptosis, through NAD-independent proinflammatory mechanisms.

CONCLUSIONS/INTERPRETATION

We have characterised a novel mechanism of beta cell dysfunction in type 2 diabetes. At low physiological levels, eNAMPT exists in dimer form and maintains beta cell function and identity through NAD-dependent mechanisms. However, as eNAMPT levels rise, as in type 2 diabetes, structure-functional changes occur resulting in marked elevation of monomeric eNAMPT, which induces a diabetic phenotype in pancreatic islets. Strategies to selectively target monomeric eNAMPT could represent promising therapeutic strategies for the treatment of type 2 diabetes.

Anti-hyperglycemic and ameliorative effect of concentrated hot water-infusion of Phragmanthera incana leaves on type 2 diabetes and indices of complications in diabetic rats

Objectives

This study investigated the anti-hyperglycemic effects of concentrated hot water infusion of Phragmanthra incana leaves as well as its ameliorative effect on indices related to diabetic complications in a type 2 diabetes model of rats.

Methods

Type 2 diabetes was induced by feeding 10% fructose solution ad libitum for two weeks followed by an intraperitoneal injection of streptozotocin (40 mg/kg body weight (b.w.)). Concentrated plant infusion was administered orally at a dose of 150 and 300 mg/kg b.w. to two type 2 diabetes rat groups. Diabetic rats without treatment served as a negative control while the group administered with metformin was served as a positive control. The intervention lasted for 4 weeks when a single oral dose was given daily for 5 days a week. Body weight and blood glucose were determined every week. An oral glucose tolerance test was performed in the last week of treatment. The rats were sacrificed after 4 weeks of intervention, and the blood and organs were harvested for further analysis.

Results

Both dosages of the plant infusion significantly improved body weight, pancreatic β-cell function (HOMA-β), insulin secretion and reduced blood glucose, insulin resistance (HOMA-IR) with concomitant reduction in the elevated level of serum α-amylase activity, fructosamine, uric acid, urea, and liver function enzymes. The liver glycogen content was significantly improved while the activity of liver glucose-6-phosphatase was significantly reduced.

Conclusion

The results demonstrate the anti-hyperglycemic ability of P. incana and its ability to delay the onset of diabetic complications which can be exploited for the anti-diabetic drug discovery.

Molecular Mechanism of Autophagy: Its Role in the Therapy of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder of progressive dementia that is characterized by the accumulation of beta-amyloid (Aβ)-containing neuritic plaques and intracellular Tau protein tangles. This distinctive pathology indicates that the protein quality control is compromised in AD. Autophagy functions as a "neuronal housekeeper" that eliminates aberrant protein aggregates by wrapping then into autophagosomes and delivering them to lysosomes for degradation. Several studies have suggested that autophagy deficits in autophagy participate in the accumulation and propagation of misfolded proteins (including Aβ and Tau). In this review, we summarize current knowledge of autophagy in the pathogenesis of AD, as well as some pathways targeting the restoration of autophagy. Moreover, we discuss how these aspects can contribute to the development of disease-modifying therapies in AD.

A review on the cardioprotective mechanisms of metformin against doxorubicin

Doxorubicin (DOX) is an antineoplastic agent obtained from Streptomyces peucetius. It is utilized in treating different kinds of cancers, such as leukemia, lymphoma, and lung, and breast cancers. The main side effect of DOX is cardiotoxicity. Metformin (MET) is an antihyperglycemic drug used for type 2 diabetes treatment. It is proposed that MET has a protective effect against DOX cardiotoxicity. Our review demonstrated that MET has several possible mechanisms of action, which can prevent or at least reduce DOX cardiotoxicity including a decrease of free radical generation and oxidative stress, 5′ adenosine monophosphate-activated protein kinase activation, and ferritin heavy chain expression in cardiomyocytes cells. The combination of MET and DOX has been shown to enhance the anticancer activity of DOX by a number of authors. The literature reviewed in the present report supports the hypothesis that MET can reduce the cardiotoxicity that often occurs with DOX treatment.

Understanding the glucoregulatory mechanisms of metformin in type 2 diabetes mellitus

Despite its position as the first-line drug for treatment of type 2 diabetes mellitus, the mechanisms underlying the plasma glucose level-lowering effects of metformin (1,1-dimethylbiguanide) still remain incompletely understood. Metformin is thought to exert its primary antidiabetic action through the suppression of hepatic glucose production. In addition, the discovery that metformin inhibits the mitochondrial respiratory chain complex 1 has placed energy metabolism and activation of AMP-activated protein kinase (AMPK) at the centre of its proposed mechanism of action. However, the role of AMPK has been challenged and might only account for indirect changes in hepatic insulin sensitivity. Various mechanisms involving alterations in cellular energy charge, AMP-mediated inhibition of adenylate cyclase or fructose-1,6-bisphosphatase 1 and modulation of the cellular redox state through direct inhibition of mitochondrial glycerol-3-phosphate dehydrogenase have been proposed for the acute inhibition of gluconeogenesis by metformin. Emerging evidence suggests that metformin could improve obesity-induced meta-inflammation via direct and indirect effects on tissue-resident immune cells in metabolic organs (that is, adipose tissue, the gastrointestinal tract and the liver). Furthermore, the gastrointestinal tract also has a major role in metformin action through modulation of glucose-lowering hormone glucagon-like peptide 1 and the intestinal bile acid pool and alterations in gut microbiota composition.

SIRT1 in the Development and Treatment of Hepatocellular Carcinoma

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

Dual peroxisome-proliferator-activated-receptor-α/γ activation inhibits SIRT1-PGC1α axis and causes cardiac dysfunction

Dual peroxisome proliferator-activated receptor (PPAR)α/γ agonists that were developed to target hyperlipidemia and hyperglycemia in type 2 diabetes patients, caused cardiac dysfunction or other adverse effects. We studied the mechanisms that underlie the cardiotoxic effects of a dual PPARα/γ agonist, tesaglitazar, in wild type and diabetic (leptin receptor deficient - db/db) mice. Mice treated with tesaglitazar-containing chow or high fat diet developed cardiac dysfunction despite lower plasma triglycerides and glucose levels. Expression of cardiac peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), which promotes mitochondrial biogenesis, had the most profound reduction among various fatty acid metabolism genes. Furthermore, we observed increased acetylation of PGC1α, which suggests PGC1α inhibition and lowered sirtuin 1 (SIRT1) expression. This change was associated with lower mitochondrial abundance. Combined pharmacological activation of PPARα and PPARγ in C57BL/6 mice reproduced the reduction of PGC1α expression and mitochondrial abundance. Resveratrol-mediated SIRT1 activation attenuated tesaglitazar-induced cardiac dysfunction and corrected myocardial mitochondrial respiration in C57BL/6 and diabetic mice but not in cardiomyocyte-specific Sirt1-/- mice. Our data shows that drugs, which activate both PPARα and PPARγ lead to cardiac dysfunction associated with PGC1α suppression and lower mitochondrial abundance likely due to competition between these two transcription factors.

Enzymatic and nonenzymatic protein acetylations control glycolysis process in liver diseases

Impaired glycolysis has pathologic effects on the occurrence and progression of liver diseases, and it appears that glycolysis is increased to different degrees in different liver diseases. As an important post-translational modification, reversible lysine acetylation regulates almost all cellular processes, including glycolysis. Lysine acetylation can occur enzymatically with acetyltransferases or nonenzymatically with acetyl-coenzyme A. Accompanied by the progression of liver diseases, there seems to be a temporal and spatial variation between enzymatic and nonenzymatic acetylations in the regulation of glycolysis. Here, we summarize the most recent findings on the functions and targets of acetylation in controlling glycolysis in the different stages of liver diseases. In addition, we discuss the differences and causes between enzymatic and nonenzymatic acetylations in regulating glycolysis throughout the progression of liver diseases. Then, we review these new discoveries to provide the potential implications of these findings for therapeutic interventions in liver diseases.-Li, J., Wang, T., Xia, J., Yao, W., Huang, F. Enzymatic and nonenzymatic protein acetylations control glycolysis process in liver diseases.

AMPK-SIRT1-independent inhibition of ANGPTL3 gene expression is a potential lipid-lowering mechanism of metformin

Objectives

Hypertriglyceridaemia enhances cardiovascular disease risk in patients with diabetes. Lipoprotein lipase (LPL) regulates plasma triglyceride levels by hydrolysing chylomicrons and very-low-density lipoprotein (VLDL). Metformin, an antidiabetic drug, improves plasma lipids including triglycerides. We examined metformin's regulation of angiopoietin-like 3 (ANGPTL3), a liver-derived secretory protein with LPL inhibitory property.

Methods

Using HepG2 cells, a human hepatocyte cell line, the effects of metformin on ANGPTL3 gene and protein expression were determined. The role of AMPK-SIRT1 pathway in metformin regulation of ANGPTL3 was determined using pharmacological, RNAi and reporter assays. Metformin regulation of ANGPTL3 expression was also examined in sodium palmitate-induced insulin resistance.

Key findings

Metformin and pharmacological activators of AMPK and SIRT1 inhibited the expression of ANGPTL3 in HepG2 cells. Pharmacological or RNAi-based antagonism of AMPK or SIRT1 failed to affect metformin inhibition of ANGPTL3. AMPK-SIRT1 activators and metformin exhibited distinct effects on the expression of ANGPTL3 gene luciferase reporter. Sodium palmitate-induced insulin resistance in cells resulted in increased ANGPTL3 gene expression which was suppressed by pretreatment with metformin.

Conclusions

Metformin inhibits ANGPTL3 expression in the liver in an AMPK-SIRT1-independent manner as a potential mechanism to regulate LPL and lower plasma lipids.

Water-soluble polyphenol-rich clove extract lowers pre- and post-prandial blood glucose levels in healthy and prediabetic volunteers: an open label pilot study

BACKGROUND/OBJECTIVES

Type 2 diabetes (T2D) is a global pandemic, and contributes significantly to the increasing incidence of conditions such as cardiovascular disease (CVD). Postprandial plasma glucose measured 2-h after the start of a meal is a good indicator of the overall status of glucose homeostasis. Clove (Syzygium aromaticum L.) and its essential oils (eugenol and acetyl eugenol) have been shown in preclinical studies to modulate pathways involved in glucose homeostasis. In addition, a water-soluble polyphenolic extract of unopened clove buds was recently shown to benefit liver function and redox status. Therefore, we conducted an open-label pilot study to test whether this polyphenolic clove extract (PCE) could influence glucose metabolism.

METHODS

We evaluated the effect of PCE supplementation (250 mg once daily for 30 days) on preprandial glucose levels and 2-h postprandial glucose levels in 13 otherwise healthy volunteers who were stratified into two groups according to their initial preprandial glucose levels: Group I (n = 7) ≤100 mg/dL, Group II (n = 6) - between 101 and 125 mg/dL. In an effort to elucidate the molecular mechanisms of PCE action, we tested in vitro the effects of PCE on glucose uptake, hepatocyte glucose production, and carbohydrate hydrolyzing enzymes.

RESULTS

At day 12 of supplementation, we observed statistically significant reductions in mean postprandial glucose levels in both groups [(Group I: Initial - Day 12 PPG = 13.29 mg/dL, 95% CI: 3.329-23.24) (Group II: Initial - Day 12 PPG = 16.67 mg/dL, 95% CI: 4.687-28.65, P = 0.0159)], which continued through study completion at day 30. PCE supplementation significantly decreased mean preprandial glucose levels only in Group II at Days 24 (Initial - Day 24 = 13.00 mg/dL, 95% CI: 1.407-24.59, P = 0.0345) and 30 (Initial - Day 30 = 13.67 mg/dL, 95% CI: 5.766-21.57, P = 0.0067). In cell-based assays, PCE enhanced glucose uptake in L6 myocytes and inhibited hepatocyte glucose production HepG2 cells. In cell-free assays, PCE inhibited α-amylase activity and α-glucosidase activity.

CONCLUSIONS

These findings underscore the therapeutic utility of PCE for maintaining healthy glucose metabolism and warrant further larger-scale clinical trials.

TRIAL REGISTRATION

This trial was retrospectively registered in the ISRCTN registry on September 29, 2018 ( ISRCTN15680985 ).

Loss of growth hormone-mediated signal transducer and activator of transcription 5 (STAT5) signaling in mice results in insulin sensitivity with obesity

Growth hormone (GH) has an important function as an insulin antagonist with elevated insulin sensitivity evident in humans and mice lacking a functional GH receptor (GHR). We sought the molecular basis for this sensitivity by utilizing a panel of mice possessing specific deletions of GHR signaling pathways. Metabolic clamps and glucose homeostasis tests were undertaken in these obese adult C57BL/6 male mice, which indicated impaired hepatic gluconeogenesis. Insulin sensitivity and glucose disappearance rate were enhanced in muscle and adipose of mice lacking the ability to activate the signal transducer and activator of transcription (STAT)5 via the GHR (Ghr-391^-/-) as for GHR-null (GHR^-/-) mice. These changes were associated with a striking inhibition of hepatic glucose output associated with altered glycogen metabolism and elevated hepatic glycogen content during unfed state. The enhanced hepatic insulin sensitivity was associated with increased insulin receptor β and insulin receptor substrate 1 activation along with activated downstream protein kinase B signaling cascades. Although phosphoenolpyruvate carboxykinase (Pck)-1 expression was unchanged, its inhibitory acetylation was elevated because of decreased sirtuin-2 expression, thereby promoting loss of PCK1. Loss of STAT5 signaling to defined chromatin immunoprecipitation targets would further increase lipogenesis, supporting hepatosteatosis while lowering glucose output. Finally, up-regulation of IL-15 expression in muscle, with increased secretion of adiponectin and fibroblast growth factor 1 from adipose tissue, is expected to promote insulin sensitivity.-Chhabra, Y., Nelson, C. N., Plescher, M., Barclay, J. L., Smith, A. G., Andrikopoulos, S., Mangiafico, S., Waxman, D. J., Brooks, A. J., Waters, M. J. Loss of growth hormone-mediated signal transducer and activator of transcription 5 (STAT5) signaling in mice results in insulin sensitivity with obesity.

Independent effect of alanine transaminase on the incidence of type 2 diabetes mellitus, stratified by age and gender: A secondary analysis based on a large cohort study in China

BACKGROUND

Previous studies have revealed that alanine aminotransferase (ALT) may be one of the risk factors of developing diabetes. We aimed to demonstrate the independent effect of ALT on incident diabetes and to investigate whether the association between ALT and incident diabetes is modified by age and gender in the general Chinese population.

METHODS

The present study was a retrospective cohort study, including 210,051 Chinese adult participants. The primary outcome was developing diabetes. The serum ALT activities were stratified by quintiles. We obtained data from 'DATADRYAD' website and used the data for secondary analysis.

RESULTS

At a median follow-up of 3.0 y, 4144 of 210,051 (1.97%) participants developed diabetes. After adjustment for potential confounders, a significantly higher risk of the incident diabetes (HR: 1.43, 95% CI: 1.25-1.63) was found in participants in the fifth quintile (Q5, ≥31 U/L) compared to those in the first to fourth quintiles (Q1-4) for ALT activities. Among males aged 30 to 40 and 40 to 50 y with the fifth quintile of ALT activity had 2.4- and 1.5-fold increased odds of developing diabetes, respectively, in comparison with those in the lower ALT activities. Among females with age 30 to 40 and ≥ 70 y, the fifth quintile of ALT activity had 4.9- and 2.2-fold increased odds for incident diabetes.

CONCLUSION

Our result indicated that the ALT activity was positively associated with the incident diabetes among Chinese persons. Moreover, 30-40 y individuals, whether male or female, with elevated ALT activities had the greatest increased risk for diabetes compared with persons with lower ALT activities in the same age group.

Caloric Restriction Mimetics against Age-Associated Disease: Targets, Mechanisms, and Therapeutic Potential

The increase in life expectancy has boosted the incidence of age-related pathologies beyond social and economic sustainability. Consequently, there is an urgent need for interventions that revert or at least prevent the pathogenic age-associated deterioration. The permanent or periodic reduction of calorie intake without malnutrition (caloric restriction and fasting) is the only strategy that reliably extends healthspan in mammals including non-human primates. However, the strict and life-long compliance with these regimens is difficult, which has promoted the emergence of caloric restriction mimetics (CRMs). We define CRMs as compounds that ignite the protective pathways of caloric restriction by promoting autophagy, a cytoplasmic recycling mechanism, via a reduction in protein acetylation. Here, we describe the current knowledge on molecular, cellular, and organismal effects of known and putative CRMs in mice and humans. We anticipate that CRMs will become part of the pharmacological armamentarium against aging and age-related cardiovascular, neurodegenerative, and malignant diseases.