Small molecule adenosine 5'-monophosphate activated protein kinase (AMPK) modulators and human diseases

Immunometabolism in cancer: basic mechanisms and new targeting strategy

Maturing immunometabolic research empowers immune regulation novel approaches. Progressive metabolic adaptation of tumor cells permits a thriving tumor microenvironment (TME) in which immune cells always lose the initial killing capacity, which remains an unsolved dilemma even with the development of immune checkpoint therapies. In recent years, many studies on tumor immunometabolism have been reported. The development of immunometabolism may facilitate anti-tumor immunotherapy from the recurrent crosstalk between metabolism and immunity. Here, we discuss clinical studies of the core signaling pathways of immunometabolism and their inhibitors or agonists, as well as the specific functions of these pathways in regulating immunity and metabolism, and discuss some of the identified immunometabolic checkpoints. Understanding the comprehensive advances in immunometabolism helps to revise the status quo of cancer treatment. An overview of the new landscape of immunometabolism. The PI3K pathway promotes anabolism and inhibits catabolism. The LKB1 pathway inhibits anabolism and promotes catabolism. Overactivation of PI3K/AKT/mTOR pathway and IDO, IL4I1, ACAT, Sirt2, and MTHFD2 promote immunosuppression of TME formation, as evidenced by increased Treg and decreased T-cell proliferation. The LKBI-AMPK pathway promotes the differentiation of naive T cells to effector T cells and memory T cells and promotes anti-tumor immunity in DCs.

Extract of Isatidis Radix Inhibits Lipid Accumulation in In Vitro and In Vivo by Regulating Oxidative Stress

Isatidis Radix (IR), the root of Isatis tinctoria L. belonging to Brassicaceae, has been traditionally used as a fever reducer. Although some pharmacological effects, such as anti-diabetes, anti-virus, and anti-inflammatory, have been reported, there is no study on the anti-obesity effect of IR. This study used 3T3-L1 cells, human mesenchymal adipose stem cells (hAMSCs), and a high-fat diet (HFD)-induced obese mouse model to confirm the anti-adipogenic effect of IR. Intracellular lipid accumulation in 3T3-L1 cells and hAMSCs was decreased by IR treatment.IR extract especially suppressed reactive oxygen species (ROS) production through a cluster of differentiation 36 (CD36)-AMP-activated protein kinase (AMPK) pathway. Consequently, the expressions of peroxisome proliferator-activated receptor gamma (PPARγ), CCAAT-enhancer-binding proteins alpha (C/EBPα), and fatty acid synthesis (FAS) were inhibited by IR extract. In addition, β-oxidation-related genes were also decreased by treatment of IR extract. IR inhibited weight gain through this cascade in the HFD-induced obese mouse model. IR significantly suppressed lipid accumulation in epididymal white adipose tissue (eWAT). Furthermore, the administration of IR extract decreased serum free fatty acid (FFA), total cholesterol (TC), and LDL cholesterol, suggesting that it could be a potential drug for obesity by inhibiting lipid accumulation.

AMPK activation by AICAR reduces diet induced fatty liver in C57BL/6 mice

Dysregulation of 5'-adenosine monophosphate-activated protein kinase (AMPK) occurs in metabolic disorders including non-alcoholic fatty liver disease (NAFLD) which makes it a molecular target for treatment. An AMPK activator, 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) alleviates NAFLD in experimental rats, however the specific mechanism remains to be explored. We aimed to study the effect of AICAR on lipid levels, oxidant-antioxidant balance, AMPK and mTOR activation and FOXO3 gene expression in liver of mice model. Fatty liver was induced in two groups of C57BL/6 mice (groups 2 and 3) by providing a high fat high fructose diet (HFFD) for 10 weeks while groups 1 and 4 animals were fed normal pellet. For the last two weeks, groups 3 and 4 were administered AICAR (150 mg/kg bw/day, i.p.) while groups 1 and 2 were administered saline. AICAR decreased fatty liver, decreased glucose and insulin in circulation, prevented the accumulation of triglycerides and collagen and ameliorated oxidative stress in HFFD fed mice. At the molecular level, AICAR upregulated FOXO3 and p-AMPK expression and reduced p-mTOR expression. AMPK activation may involve FOXO3 in protection against NAFLD. The role of AMPK, mTOR and FOXO3 crosstalk in NAFLD needs to be characterised in future.

Identification of novel benzimidazole derivatives as highly potent AMPK activators with anti-diabetic profiles

Diabetes is a global healthcare problem that affects more than 400 million people worldwide. Treatment for type 1 and 2 diabetes is expected by targeting adenosine monophosphate activated protein kinase, AMPK, a well-known master regulator of glucose. Many pharmaceutical companies have tried to identify AMPK activators but few direct AMPK activators with high potency for the β2-AMPK isoform, which is important for glucose homeostasis, have been found. In addition, their chemical structure is limited to benzimidazole or indole derivatives bearing an aromatic substituent at the C5 position of the core structure. We describe herein our efforts to identify novel benzimidazole derivatives that directly activate the β2-AMPK isoform. Our newly designed activator 14d bearing a 1-amino indanyl moiety at the C5 position of the core exhibited high in vitro potency and good pharmacokinetic profiles. A single oral dosing of 14d showed dose-dependent activation of AMPK and blood-glucose-lowering effects was observed in a diabetic animal model. In addition, chronic AMPK activation with 14d led to dose-dependent reduction in HbA1c of the animal model.

Identification of novel indole derivatives as highly potent AMPK activators with anti-diabetic profiles

AMP-activated protein kinase (AMPK) has been shown to play an important role in the beneficial effects of exercise on glucose and lipid metabolism in skeletal muscle and liver. Therefore, activation of AMPK has been proposed as an attractive strategy for the treatment of metabolic disorders, such as type 2 diabetes. Many of existing AMPK activators bearing diverse chemical structure were reported. However, there have been few reports of direct AMPK activator with high potency for β2-AMPK isoform, which is thought to be important for glucose homeostasis, and their chemical structure is limited to benzimidazole core. We describe herein our efforts for identification of novel AMPK activator. Our newly designed 4-azaindole derivative 16g exhibited single-digit nM in vitro activity, and chronic treatment with 16g led to dose-dependent improvement in HbA1c as well as decrease in hepatic lipid accumulation in diabetic animal model.

Characterization and Comparison of the Divergent Metabolic Consequences of High-Sugar and High-Fat Diets in Male Wistar Rats

Diet-induced obesity (DIO) in laboratory rodents can serve as a model with which to study the pathophysiology of obesity, but obesogenic diets (high-sugar and/or high-fat) are often poorly characterised and simplistically aimed at inducing metabolic derangements for the purpose of testing the therapeutic capacity of natural products and other bioactive compounds. Consequently, our understanding of the divergent metabolic responses to different obesogenic diet formulations is limited. The aim of the present study was to characterise and compare differences in the metabolic responses induced by low-fat, medium-fat/high-sugar and high-fat diets in rats through multivariate statistical modelling. Young male Wistar rats were randomly assigned to CON (laboratory chow, low-fat), OB1 (high-sugar, medium-fat) or OB2 (high-fat) dietary groups (n = 24 each) for 17 weeks, after which metabolic responses were characterised. Projection-based multivariate analyses (principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA)) were used to explore the associations between measures of body composition and metabolism. Furthermore, we conducted a systematic literature survey to examine reporting trends in rat dietary intervention studies, and to determine how the metabolic responses observed in the present study compared to other recently published studies. The OB1 and OB2 dietary regimens resulted in distinct metabolic profiles, with OB1 characterised by perturbations in insulin homeostasis and adipose tissue secretory function, while OB2 was characterised by altered lipid and liver metabolism. This work therefore confirms, by means of direct comparison, that differences in dietary composition have a profound impact on metabolic and pathophysiological outcomes in rodent models of DIO. However, through our literature survey we demonstrate that dietary composition is not reported in the majority of rat dietary intervention studies, suggesting that the impact of dietary composition is often not considered during study design or data interpretation. This hampers the usefulness of such studies to provide enhanced mechanistic insights into DIO, and also limits the translatability of such studies within the context of human obesity.

The importance of AMPK in obesity and chronic diseases and the relationship of AMPK with nutrition: a literature review

This review will examine the role of 5'-adenosine monophosphate-activated protein kinase (AMPK) in the treatment of obesity, medical nutrition and chronic diseases, and its relationship with nutrition. In the literature, the number of studies examining the direct relationship of AMPK with nutrition is negligible. For this reason, information on the subject has been compiled from all the studies that can be accessed by searching the terms AMPK and disease, AMPK and health, AMPK and exercise, AMPK and nutrition. It can be stated that AMPK is inhibited in many pathological conditions such as inflammation, diabetes, aging and cancer, and AMPK activation has positive effects in many diseases such as insulin resistance, diabetes, obesity, cancer and Alzheimer's. When the relationship between nutrition and AMPK is examined, it is seen that food intake inhibits AMPK, but especially high-carbohydrate and fatty diets are more effective at this point. In addition, high fructose corn sirup and long chain saturated fatty acids increased by consumption of industrial foods and frequent meals appear to be an inactivator for AMPK. For AMPK activation in medical nutrition therapy, it is recommended to use methods such as evening fasting and intermittent fasting, taking into account the human circadian rhythm.

Novel pyrazolo[3,4-b]pyridine derivatives: Synthesis, structure-activity relationship studies, and regulation of the AMPK/70S6K pathway

A series of novel pyrazolo[3,4-b]pyridine derivatives were designed, synthesized, and biologically evaluated for anti-lung cancer activity. Structure-activity relationship and AutoGPA models were constructed based on the in vitro antiproliferative potency of the compounds against a human lung adenocarcinoma cell line (A549). Compound 9d exhibits improved potency for A549 cell growth inhibition (3.06 ± 0.05 μM) compared with A-769662 (45.29 ± 2.14 μM). Compound 9d can elevate the phosphorylation levels of adenosine monophosphate-activated protein kinase (AMPK) and its substrate acetyl-CoA carboxylase and reduce the level of phosphorylated ribosomal S6 kinase (p-70S6K) at 1 μM, which is comparable to the activity of A-769662 at 20 μM. 9d induced G2/M cell cycle arrest, which was rescued when co-incubated with "Compound C," a potent AMPK inhibitor. Taken together, compound 9d showed potential anti-lung cancer activity via inducing cell cycle arrest by regulation of the AMPK/70S6K pathway in A549 cells, which could provide a new lead for the discovery of anti-lung cancer agents.

The Role of AMP-activated Protein Kinase in Oxytosis/Ferroptosis: Protector or Potentiator?

Significance: Evidence for a role for the oxytosis/ferroptosis regulated cell death pathway in aging and neurodegenerative diseases has been growing over the past few years. Because of this, there is an increasing necessity to identify endogenous signaling pathways that can be modulated to protect cells from this form of cell death. Recent Advances: Recently, several studies have identified a protective role for the AMP-activated protein kinase (AMPK)/acetyl CoA carboxylase 1 (ACC1) pathway in oxytosis/ferroptosis. However, there are also a number of studies suggesting that this pathway contributes to cell death initiated by various inducers of oxytosis/ferroptosis. Critical Issues: The goals of this review are to provide an overview and analysis of the published studies and highlight specific areas where more research is needed. Future Directions: Much remains to be learned about AMPK signaling in oxytosis/ferroptosis, especially the conditions where it is protective. Furthermore, the role of AMPK signaling in the brain and especially the aging brain needs further investigation.

Research Progress on Oxidative Stress and Its Nutritional Regulation Strategies in Pigs

Oxidative stress refers to the dramatic increase in the production of free radicals in human and animal bodies or the decrease in the ability to scavenging free radicals, thus breaking the antioxidation-oxidation balance. Various factors can induce oxidative stress in pig production. Oxidative stress has an important effect on pig performance and healthy growth, and has become one of the important factors restricting pig production. Based on the overview of the generation of oxidative stress, its effects on pigs, and signal transduction pathways, this paper discussed the nutritional measures to alleviate oxidative stress in pigs, in order to provide ideas for the nutritional research of anti-oxidative stress in pigs.

Multifunctional agents based on benzoxazolone as promising therapeutic drugs for diabetic nephropathy

Diabetic nephropathy (DN) is resulted from activations of polyol pathway and oxidative stress by abnormal metabolism of glucose, and no specific medication is available. We designed a novel class of benzoxazolone derivatives, and a number of individuals were found to have significant antioxidant activity and inhibition of aldose reductase of the key enzyme in the polyol pathway. The outstanding compound (E)-2-(7-(4-hydroxy-3-methoxystyryl)-2-oxobenzo[d]oxazol-3(2H)-yl)acetic acid was identified to reduce urinary proteins in diabetic mice suggesting an alleviation in the diabetic nephropathy, and this was confirmed by kidney hematoxylin-eosin staining. Further investigations showed blood glucose normalization, declined in the polyol pathway and lipid peroxides, and raised glutathione and superoxide dismutase activity. Thus, we suggest a therapeutic function of the compound for DN which could be attributed to the combination of hypoglycemic, aldose reductase inhibition and antioxidant.

Superior hypoglycemic activity of mulberry lacking monosaccharides is accompanied by better activation of the PI3K/Akt and AMPK signaling pathways

Mulberry has been used as a functional food to treat type 2 diabetes mellitus (T2DM). However, it contains relatively high levels of fructose and glucose, which are not suitable for excess consumption by diabetic patients. In this study we used microbial fermentation to remove fructose and glucose from mulberry fruit, and then determined the effects on glycemia, the phosphatidylinositol 3-hydroxykinase/Akt (PI3K/Akt) and adenosine monophosphate-activated protein kinase (AMPK) signaling pathways and their downstream effectors in T2DM mice. After 5 weeks of administration, fermented mulberry (FM) significantly reduced fasting blood glucose, and also improved insulin sensitivity and glucose tolerance, more effectively than unfermented mulberry (MP). Moreover, compared with MP, FM had a more marked effect on the protein expression of intermediates in the PI3K/Akt and AMPK signaling pathways and their effectors: insulin receptor, phosphorylated Akt (Ser 308), phosphorylated glycogen synthase kinase-3β (Ser 9), glycogen synthetase, phosphorylated forkhead transcription factor 1 (Ser 256), pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose-1, 6-bisphosphatase, glucose-6-phosphatase, lipoprotein lipase, and phosphorylated AMPK (Thr 172), glucose transporter 4 and pyruvate kinase. These findings indicate that mulberry fruit modified to remove fructose and glucose may be more promising than whole mulberry as a treatment for diabetes.

Modulation of Glucose Metabolism by Leaf Tea Constituents: A Systematic Review of Recent Clinical and Pre-clinical Findings

Leaf teas are widely used as a purported treatment for dysregulated glucose homeostasis. The objective of this study was to systematically evaluate the clinical and cellular-metabolic evidence, published between January 2013 and May 2019, and indexed on PubMed, ScienceDirect, and Web of Science, supporting the use of leaf teas for this purpose. Fourteen randomized controlled trials (RCTs) (13 on Camellia sinensis teas) were included, with mixed results, and providing scant mechanistic information. In contrast, 74 animal and cell culture studies focusing on the pancreas, liver, muscle, and adipose tissue yielded mostly positive results and highlighted enhanced insulin signaling as a recurring target associated with the effects of teas on glucose metabolism. We conclude that more studies, including RCTs and pre-clinical studies examining teas from a wider variety of species beyond C. sinensis, are required to establish a stronger evidence base on the use of leaf teas to normalize glucose metabolism.

The Race to Bash NASH: Emerging Targets and Drug Development in a Complex Liver Disease

Nonalcoholic steatohepatitis (NASH) is a severe form of nonalcoholic fatty liver disease (NAFLD) characterized by liver steatosis, inflammation, and hepatocellular damage. NASH is a serious condition that can progress to cirrhosis, liver failure, and hepatocellular carcinoma. The association of NASH with obesity, type 2 diabetes mellitus, and dyslipidemia has led to an emerging picture of NASH as the liver manifestation of metabolic syndrome. Although diet and exercise can dramatically improve NASH outcomes, significant lifestyle changes can be challenging to sustain. Pharmaceutical therapies could be an important addition to care, but currently none are approved for NASH. Here, we review the most promising targets for NASH treatment, along with the most advanced therapeutics in development. These include targets involved in metabolism (e.g., sugar, lipid, and cholesterol metabolism), inflammation, and fibrosis. Ultimately, combination therapies addressing multiple aspects of NASH pathogenesis are expected to provide benefit for patients.

Oxidative stress mediates heat-induced changes of tight junction proteins in porcine sertoli cells via inhibiting CaMKKβ-AMPK pathway

Heat stress causes reversible changes in tight junction proteins in immature Sertoli cells via inhibition of the AMPK signaling pathway; these effects are accompanied by an increase in the early apoptotic rate and decrease in the cell viability of Sertoli cells. Since heat stress is known to also cause oxidative damage, in the present study, we investigated whether the earlier mentioned effects of heat stress were brought about via the induction of oxidative stress in boar Sertoli cells. Immature Sertoli cells obtained from 3-week-old piglets were subjected to heat treatment (43 °C, 30 min), and the percentage of ROS-positive cells, the malonaldehyde (MDA) concentration, and the activity of the antioxidases, including superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) were measured. Next, the Sertoli cells were treated with N-acetyl-l-cysteine (NAC) (1 mmol/L, 2 h), an antioxidant agent, before they were exposed to heat stress. The effects of NAC on ROS accumulation, MDA levels, antioxidase activity, the CaMKKβ-AMPK signaling pathway and expression of tight junction proteins were assessed. The results showed that heat stress reversibly increased the percentage of ROS-positive cells and MDA levels, and decreased the activity of SOD, GSH-Px, and CAT. Pretreatment with NAC abrogated these effects of heat stress. Additionally, NAC reversed the heat stress-induced decrease in the expression of CaMKKβ and dephosphorylation of AMPK. NAC also obviously rescued the heat stress-induced downregulation of tight junction proteins (claudin-11, JAM-A, occludin, and ZO-1) both at the mRNA and protein level. In conclusion, the findings indicate that oxidative damage participates in heat stress-induced downregulation of tight junction proteins in Sertoli cells by inhibiting the CaMKKβ-AMPK axis. Further, NAC reversed the effects of heat stress on tight junction proteins; this means that it has potential as a protective agent that can prevent reproductive dysfunction in boars under conditions of heat stress.

JAZF1, a relevant metabolic regulator in type 2 diabetes

Excessive adiposity and metabolic inflammation are the key risk factors of type 2 diabetes mellitus (T2DM). Juxtaposed with another zinc finger gene 1 (JAZF1) has been identified as a novel transcriptional cofactor, with function of regulating glucose and lipid homeostasis and inflammation. JAZF1 is involved in metabolic process of T2DM via interaction with several nuclear receptors and protein kinases. Additionally, increasing evidence from genome-wide association studies (GWAS) has shown that JAZF1 polymorphisms are closely associated with T2DM. In this review, we have updated the latest research advances on JAZF1 and discussed its regulatory network in T2DM. The association between JAZF1 polymorphisms and T2DM is discussed as well. The information provided is of importance for guiding future studies as well as for the design of JAZF1-based T2DM therapy.

Crystal structure of methyl 2-(4-(pyrazolo[1,5-a]pyrimidin-6-yl)phenyl)acetate, C15H13N3O2

C15H13N3O2, triclinic, P1̄ (no. 2), a = 4.6502(18) Å, b = 11.937(3) Å, c = 13.1822(19) Å, α = 115.26(4)°, β = 94.81(5)°, γ = 96.49(5)°, V = 650.4(4) Å3, Z = 2, R gt(F) = 0.0762, wR ref(F 2) = 0.1794, T = 296(2) K.

AMPK activation by AICAR sensitizes prostate cancer cells to radiotherapy

Although radiotherapy is often used to treat localized disease and for palliative care in prostate cancer patients, novel methods are required to improve the sensitivity of aggressive disease to ionizing radiation. AMP-activated protein kinase (AMPK) is an energy sensor which regulates proliferation, aggressiveness and survival of cancer cells. We assessed the ability of the AMPK activator 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) to sensitize prostate cancer cells to radiation. Prostate cancer cell lines LNCaP and PC3 were treated with X-rays and AICAR then assessed for clonogenic survival, spheroid growth delay, cell cycle progression, and AMPK and p53 activity. AICAR synergistically enhanced the clonogenic killing capacity, spheroid growth inhibition and pro-apoptotic effect of X-rays. The mechanism of radiosensitization appeared to involve cell cycle regulation, but not oxidative stress. Moreover, it was not dependent on p53 status. Treatment of PC3 cells with a fatty acid synthase inhibitor further enhanced clonogenic killing of the combination of X-rays and AICAR, whereas mTOR inhibition caused no additional enhancement. These results indicate that interference with metabolic signalling pathways which protect cells against irradiation have the potential to enhance radiotherapy. Activation of AMPK in combination with radiotherapy has the potential to target metabolically active and aggressive tumors which are currently untreatable.

Effects of interleukin-6 and IL-6/AMPK signaling pathway on mitochondrial biogenesis and astrocytes viability under experimental septic condition

OBJECTIVE

Interleukin-6 (IL-6) is a neuromodulation factor with extensive and complex biological activities. IL-6 has been reported to activate AMPK, while AMPK regulates mitochondrial biogenesis and autophagy. The aim of this study was to investigate the role of IL-6 in mitochondrial biogenesis using astrocytes under experimental septic condition and examined how IL-6/AMPK signaling pathway affected this process.

METHODS

The primary cultures of cerebral cortical astrocytes were randomly allocated into six groups: control group, LPS+IFN-γ group, IL-6 group (LPS+IFN-γ+IL-6), C group (LPS+IFN-γ+IL-6+Compound C), siRNA group (LPS+IFN-γ+IL-6+IL-6R siRNA) and siRNA+C group (LPS+IFN-γ+IL-6+IL-6R siRNA+ Compound C). All groups were stimulated for 6 h. Cytokines and reactive oxygen species (ROS) analyses, detection of adenosine triphosphate (ATP), mtDNA content and cell viability, evaluation of the mitochondrial ultrastructure and volume density, western blots of proteins associated with mitochondrial biogenesis and phospho-adenosine monophosphate activated protein kinase (p-AMPK) were performed respectively.

RESULTS

Compared with LPS+IFN-γ group, IL-6 group had milder ultrastructural damage of mitochondria, higher mtDNA content and mitochondrial volume density, higher expression of proteins associated with mitochondrial biogenesis (PGC-1α, NRF-1 and TFAM) and p-AMPK, and thus higher cell viability, whereas blocking IL-6/AMPK signaling pathway, the protective effect of IL-6 has been diminished, compared with IL-6 group.

CONCLUSION

IL-6 enhances mitochondrial biogenesis in astrocytes under experimental septic condition through IL-6/AMPK signaling pathway.

Identification of a novel 2-oxindole fluorinated derivative as in vivo antitumor agent for prostate cancer acting via AMPK activation

The key metabolic sensor adenosine monophosphate-dependent kinase (AMPK) has emerged as a promising therapeutic target for cancer prevention and treatment. Besides its role in energy homeostasis, AMPK blocks cell cycle, regulates autophagy and suppresses the anabolic processes required for rapid cell growth. AMPK is especially relevant in prostate cancer in which activation of lipogenic pathways correlate with tumor progression and aggressiveness. This study reports the discovery of a new series of 2-oxindole derivatives whose AMPK modulatory ability, as well as the antitumoral profile in prostate cancer cells, was evaluated. One of the assayed compounds, compound 8c, notably activated AMPK in cultured PC-3, DU145 and LNCaP prostate cancer cells. Likewise, compound 8c caused PC-3, DU145 and LNCaP cells viability inhibition. Selective knocking down of α1 or α2 isoforms as well as in vitro assays using human recombinant α1β1γ1 or α2β1γ1 AMPK isoforms revealed that compound 8c exhibit preference for AMPKα1. Consistent with efficacy at the cellular level, compound 8c was potent in suppressing the growth of PC-3 xenograft tumors. In conclusion, our results show that a new 2-oxindole fluorinated derivative exerts potent in vivo antitumor actions against prostate cancer cells, indicating a promising clinical therapeutic strategy for the treatment of androgen-independent prostate cancer.

Discovery of MK-8722: A Systemic, Direct Pan-Activator of AMP-Activated Protein Kinase

5'-Adenosine monophosphate-activated protein kinase (AMPK) is a key regulator of mammalian energy homeostasis and has been implicated in mediating many of the beneficial effects of exercise and weight loss including lipid and glucose trafficking. As such, the enzyme has long been of interest as a target for the treatment of Type 2 Diabetes Mellitus. We describe the optimization of β1-selective, liver-targeted AMPK activators and their evolution into systemic pan-activators capable of acutely lowering glucose in mouse models. Identifying surrogates for the key acid moiety in early generation compounds proved essential in improving β2-activation and in balancing improvements in plasma unbound fraction while avoiding liver sequestration.

Systemic pan-AMPK activator MK-8722 improves glucose homeostasis but induces cardiac hypertrophy

5'-Adenosine monophosphate-activated protein kinase (AMPK) is a master regulator of energy homeostasis in eukaryotes. Despite three decades of investigation, the biological roles of AMPK and its potential as a drug target remain incompletely understood, largely because of a lack of optimized pharmacological tools. We developed MK-8722, a potent, direct, allosteric activator of all 12 mammalian AMPK complexes. In rodents and rhesus monkeys, MK-8722-mediated AMPK activation in skeletal muscle induced robust, durable, insulin-independent glucose uptake and glycogen synthesis, with resultant improvements in glycemia and no evidence of hypoglycemia. These effects translated across species, including diabetic rhesus monkeys, but manifested with concomitant cardiac hypertrophy and increased cardiac glycogen without apparent functional sequelae.

Identification of Direct Activator of Adenosine Monophosphate-Activated Protein Kinase (AMPK) by Structure-Based Virtual Screening and Molecular Docking Approach

Adenosine monophosphate-activated protein kinase (AMPK) plays a critical role in the regulation of energy metabolism and has been targeted for drug development of therapeutic intervention in Type II diabetes and related diseases. Recently, there has been renewed interest in the development of direct β1-selective AMPK activators to treat patients with diabetic nephropathy. To investigate the details of AMPK domain structure, sequence alignment and structural comparison were used to identify the key amino acids involved in the interaction with activators and the structure difference between β1 and β2 subunits. Additionally, a series of potential β1-selective AMPK activators were identified by virtual screening using molecular docking. The retrieved hits were filtered on the basis of Lipinski’s rule of five and drug-likeness. Finally, 12 novel compounds with diverse scaffolds were obtained as potential starting points for the design of direct β1-selective AMPK activators.

Targeting AMPK: From Ancient Drugs to New Small-Molecule Activators

The AMP-activated protein kinase (AMPK) is an evolutionary conserved and ubiquitously expressed serine/threonine kinase mainly acting as a key regulator of cellular energy homeostasis. AMPK is a heterotrimeric protein complex, consisting of a catalytic α subunit and two regulatory β and γ subunits, whose activity is tightly regulated by changes in adenine nucleotides and several posttranslational modifications. Once activated in response to energy deficit, AMPK concomitantly inhibits ATP-consuming anabolic processes and promotes ATP-generating catabolic pathways via direct phosphorylation of multiple downstream effectors, leading to restoration of cellular energy balance. A growing number of energy/nutrient-independent functions of AMPK are also regularly reported, progressively expanding its role to regulation of non-metabolic cellular processes. Historically, AMPK as a therapeutic target has attracted much of interest due to its potential impact on metabolic disorders, such as obesity and type 2 diabetes, but has also recently received considerable renewed attention in the framework of cancer studies, highlighting the persistent need for selective, reversible, potent, and tissue-specific activators. In this chapter, we review the most recent advances in the understanding of the mechanism(s) of action of the current portfolio of AMPK activators, including plant-derived natural compounds and newly discovered small-molecule agonists directly targeting various AMPK subunits.

Hypoglycemic and hypolipidemic effects of a polysaccharide from Lachnum YM240 and its derivatives in mice, induced by a high fat diet and low dose STZ

Carboxymethylated and sulfated polysaccharides (CLEP and SLEP) were prepared from an exopolysaccharide previously obtained from Lachnum YM240 (LEP) by chemical modifications. Two doses (50 mg kg-1 and 200 mg kg-1 b. w.) of LEP, CLEP and SLEP were orally administered to normal mice and type 2 diabetic mice (T2DM) that were induced by streptozotocin (STZ) and a high fat diet, respectively. The hypoglycemic effect was evaluated by testing the oral glucose tolerance, fasting blood glucose (FBG) levels, fasting serum insulin (FINS), glycosylated hemoglobin A1c (HbA1c), and the hypolipidemic effect was evaluated by the body, spleen, pancreas, liver and kidney weights, as well as serum triglycerides (TG), cholesterol (TC) and free fatty acids (FFA). After four weeks of administration, LEP, CLEP and SLEP showed a marked FBG fall rate of 11.2%, 44.0% and 42.5% for the high-dose and 7.43%, 38.5% and 33.1% for the low-dose, respectively, as compared to the DC group. Moreover, compared with DC mice, TC concentrations in the high-dose groups of LEP, CLEP and SLEP were significantly decreased by 29.6%, 38.7% (P < 0.05), 33.0% (P < 0.05), and TG concentrations decreased by 18.9%, 43.9% (P < 0.01), 29.0% (P < 0.05), respectively. In addition, LEP and the derivatives significantly upregulated the expression of glucokinase (GK) and adenosine monophosphate-activated protein kinase (AMPK) in the liver, AMPK and glucose transporter 4 (Glut4) in skeletal muscle and peroxysome proliferator-activated receptor (PPAR-γ) in adipose tissue, whereas downregulated the expression of glucose-6-phosphatase (G6P) in the liver; these were examined using ELISA detection kits. These results for FBG and serum lipids indicate that LEP and its derivatives possess significant hypoglycemic and hypolipidemic effects and carboxymethylation improved the hypoglycemic and hypolipidemic effects more effectively than sulfation. Therefore, the carboxymethylated and sulfated modifications were effective ways to enhance the hypoglycemic and hypolipidemic activities of polysaccharides.

Allosteric Modulation of AMPK Enzymatic Activity: In Vitro Characterization

AMP-activated protein kinase (AMPK) is a heterotrimeric serine/threonine protein kinase found in nearly all eukaryotes that functions as a master energy sensor in cells. During times of cell stress and changes in the AMP/ATP ratio, AMPK becomes activated and phosphorylates a multitude of protein substrates involved in various cellular processes such as metabolism, cell growth and autophagy. The endogenous ligand AMP is known to bind to the γ-subunit and activates the enzyme via three distinct mechanisms (1) enhancing phosphorylation by upstream kinases of Thr172 in the activation loop (a site critical for AMPK activity), (2) protecting Thr172 from dephosphorylation by phosphatases, and (3) allosteric activation of the kinase activity. Given the important regulatory role for AMPK in various cellular processes and the multiple known modes of activation, there is great interest in identifying small-molecule activators of this kinase and a need for assays to identify and characterize compounds. Here we describe several assay formats that have been used for identifying and characterizing small-molecule AMPK activators.

A concise review on advances in development of small molecule anti-inflammatory therapeutics emphasising AMPK: An emerging target

Inflammatory diseases are complex, multi-factorial outcomes of evolutionarily conserved tissue repair processes. For decades, non-steroidal anti-inflammatory drugs and cyclooxygenase inhibitors, the primary drugs of choice for the management of inflammatory diseases, addressed individual targets in the arachidonic acid pathway. Unsatisfactory safety and efficacy profiles of the above have necessitated the development of multi-target agents to treat complex inflammatory diseases. Current anti-inflammatory therapies still fall short of clinical needs and the clinical trial results of multi-target therapeutics are anticipated. Additionally, new drug targets are emerging with improved understanding of molecular mechanisms controlling the pathophysiology of inflammation. This review presents an outline of small molecules and drug targets in anti-inflammatory therapeutics with a summary of a newly identified target AMP-activated protein kinase, which constitutes a novel therapeutic pathway in inflammatory pathology.

Recent progress in the identification of adenosine monophosphate-activated protein kinase (AMPK) activators

Adenosine monophosphate-activated protein kinase (AMPK), a serine/threonine heterotrimeric protein kinase, is a critical regulator of cellular and whole body energy homeostasis. There are twelve known AMPK isoforms that are differentially expressed in tissues and species. Dysregulation of AMPK signaling is associated with a multitude of human pathologies. Hence isoform-selective activators of AMPK are actively being sought for the treatment of cardiovascular and metabolic diseases. The present review summarizes the status of direct AMPK activators from the patent and published literature.

Antidiabetic activity of perylenequinonoid-rich extract from Shiraia bambusicola in KK-Ay mice with spontaneous type 2 diabetes mellitus

ETHNOPHARMACOLOGICAL RELEVANCE

Bitter and cold traditional Chinese medicines (TCMs) have been long used to treat diabetes mellitus (DM) based on unique medical theory system since ancient China. As one of bitter and cold TCMs, the stromatas of Shiraia bambusicola have been used for the treatment of DM and exerted clinical effects to a certain extent. However, the corresponding active principles and antidiabetic mechanism of the TCM still remain unknown. Therefore, the aim of the present investigation was to evaluate the potential antidiabetic effect of the active Shiraia bambusicola EtOAc extract (SB-EtOAc) in vitro and in vivo, and elucidate its probable antidiabetic mechanism.

MATERIALS AND METHODS

A LC-PDA-ESIMS protocol was developed to determine the chemical principles of the active EtOAc extract rapidly and unambiguously. The effect of SB-EtOAc on the glucose transporter type 4 (GLUT4) translocation and glucose uptake in L6 cells was examined. SB-EtOAc was orally administration at the dose of 30, 60 and 120mg/kg/d in KK-Ay mice, for 21 days. Body weight, plasma glucose, oral glucose tolerance test, fasted blood glucose levels, oral glucose tolerance test and insulin tolerance test, serum insulin and blood-lipid indexes were measured. GLUT4 on L6 cells membrane and phosphorylation of the AMP-activated protein kinase (p-AMPK) expression in L6 cells were measured. The GLUT4 and p-AMPK expression in KK-Ay mice skeletal muscle were measured. Phosphorylation of the acetyl-CoA carboxylase (p-ACC) and p-AMPK were measured.

RESULTS

In vitro, SB-EtOAc exhibited a strong effect of stimulation on GLUT4 translocation by 3.2 fold in L6 cells compared with basal group, however, the selective AMPK inhibitor compound C can completely inhibit the AMPK pathway and prevent the GLUT4 translocation caused by SB-EtOAc. The further western blotting experiments showed that SB-EtOAc can stimulate AMPK phosphorylation in L6 cells and improve the expression of GLUT4. In vivo, SB-EtOAc can improve the KK-Ay mice insulin resistant and oral glucose tolerance to a certain extent. And the body weight, blood glucose levels and the serum TC, TG, FFA, AST, ALT and LDL-C were significantly reduced and HDL-C were increased after 3 weeks treatment. Mechanistically, phosphorylation of the AMPK and ACC had been improved obviously and the levels of AMPK phosphorylation and GLUT4 had been also enhanced.

CONCLUSION

In vitro, SB-EtOAc exhibited a strong effect of stimulation on GLUT4 translocation and improved significantly the glucose uptake. In vivo, SB-EtOAc significantly improved oral glucose tolerance and the insulin resistant as well as glucolipid metabolism. In this study, SB-EtOAc displayed promising positive antidiabetic activity in vitro and in vivo, partly by modulating AMPK-GLUT4 and AMPK-ACC signaling pathways.

Hypoglycemic Activity and the Potential Mechanism of the Flavonoid Rich Extract from Sophora tonkinensis Gagnep. in KK-Ay Mice

This study investigated the active principles, hypoglycemic activity and potential mechanisms of the flavonoid rich extract from Sophora tonkinensis Gagnep. (ST-EtOAc) in KK-Ay diabetic mice. An off-line semipreparative liquid chromatography-nuclear magnetic resonance (LC-NMR) and liquid chromatography-ultraviolet-electrospray ionization mass spectrometry (LC-UV–ESIMS) protocol was performed to determine 13 flavonoids from ST-EtOAc. ST-EtOAc administrated orally to the KK-Ay mice significantly increased their sensibility to insulin, reduced fasting blood-glucose levels and blood lipid indexes such as triglyceride and cholesterol. Moreover, ST-EtOAc exhibited a strong effect of stimulation on glucose transporter 4 (GLUT4) translocation by 2.7-fold in L6 cells. However, the selective AMP-activated protein kinase (AMPK) inhibitor compound C can completely inhibit the activation of the AMPK pathway and prevent the GLUT4 translocation caused by ST-EtOAc. In vivo, phosphorylation of the AMPK expression in the liver and skeletal muscle was measured. The results showed phosphorylation of the AMPK had been improved and GLUT4 expression had been also enhanced. In this paper, we conclude that, ST-EtOAc seems to have potential beneficial effects on the treatment of type 2 diabetes mellitus with the probable mechanism of stimulating GLUT4 translocation modulated by the AMPK pathway.

Pharmacological Targeting of AMP-Activated Protein Kinase and Opportunities for Computer-Aided Drug Design

As a central regulator of metabolism, the AMP-activated protein kinase (AMPK) is an established therapeutic target for metabolic diseases. Beyond the metabolic area, the number of medical fields that involve AMPK grows continuously, expanding the potential applications for AMPK modulators. Even though indirect AMPK activators are used in the clinics for their beneficial metabolic outcome, the few described direct agonists all failed to reach the market to date, which leaves options open for novel targeting methods. As AMPK is not actually a single molecule and has different roles depending on its isoform composition, the opportunity for isoform-specific targeting has notably come forward, but the currently available modulators fall short of expectations. In this review, we argue that with the amount of available structural and ligand data, computer-based drug design offers a number of opportunities to undertake novel and isoform-specific targeting of AMPK.

New synthetic AICAR derivatives with enhanced AMPK and ACC activation

5-Aminoimidazole-4-carboxamide riboside (AICAR) has an important role in the regulation of the cellular metabolism showing a broad spectrum of therapeutic activities against different metabolic processes. Due to these proven AICAR properties, we have designed, synthesized and tested the biological activity of two ribose-modified AICAR derivatives, named A3 and A4, in comparison to native AICAR and its 5'-phosphorylated counterpart ZMP. Our findings have shown that A3 and A4 derivatives induce the phosphorylation of 5'-AMP activated protein kinase α (AMPKα), which leads to the inhibition of acetyl-CoA carboxylase (ACC), and down-regulate the activity of the extracellular signal-regulated kinases (ERK1/2). Cytotoxicity tests demonstrated that A3 and A4 do not significantly reduce cell viability up to 24 h. Taken together our results indicate that A3 and A4 have a comparable activity to AICAR and ZMP at 0.5 and 1 mM suggesting their potential use in future pharmacological strategies relating to metabolic diseases.

Development of Potent Adenosine Monophosphate Activated Protein Kinase (AMPK) Activators

Previously, we reported the identification of a thiazolidinedione-based adenosine monophosphate activated protein kinase (AMPK) activator, compound 1 (N-[4-({3-[(1-methylcyclohexyl)methyl]-2,4-dioxothiazolidin-5-ylidene}methyl)phenyl]-4-nitro-3-(trifluoromethyl)benzenesulfonamide), which provided a proof of concept to delineate the intricate role of AMPK in regulating oncogenic signaling pathways associated with cell proliferation and epithelial-mesenchymal transition (EMT) in cancer cells. In this study, we used 1 as a scaffold to conduct lead optimization, which generated a series of derivatives. Analysis of the antiproliferative and AMPK-activating activities of individual derivatives revealed a distinct structure-activity relationship and identified 59 (N-(3-nitrophenyl)-N'-{4-[(3-{[3,5-bis(trifluoromethyl)phenyl]methyl}-2,4-dioxothiazolidin-5-ylidene)methyl]phenyl}urea) as the optimal agent. Relative to 1, compound 59 exhibits multifold higher potency in upregulating AMPK phosphorylation in various cell lines irrespective of their liver kinase B1 (LKB1) functional status, accompanied by parallel changes in the phosphorylation/expression levels of p70S6K, Akt, Foxo3a, and EMT-associated markers. Consistent with its predicted activity against tumors with activated Akt status, orally administered 59 was efficacious in suppressing the growth of phosphatase and tensin homologue (PTEN)-null PC-3 xenograft tumors in nude mice. Together, these findings suggest that 59 has clinical value in therapeutic strategies for PTEN-negative cancer and warrants continued investigation in this regard.

JAZF1 promotes proliferation of C2C12 cells, but retards their myogenic differentiation through transcriptional repression of MEF2C and MRF4-Implications for the role of Jazf1 variants in oncogenesis and type 2 diabetes

Single-nucleotide polymorphisms associated with type 2 diabetes (T2D) have been identified in Jazf1, which is also involved in the oncogenesis of endometrial stromal tumors. To understand how Jazf1 variants confer a risk of tumorigenesis and T2D, we explored the functional roles of JAZF1 and searched for JAZF1 target genes in myogenic C2C12 cells. Consistent with an increase of Jazf1 transcripts during myoblast proliferation and their decrease during myogenic differentiation in regenerating skeletal muscle, JAZF1 overexpression promoted cell proliferation, whereas it retarded myogenic differentiation. Examination of myogenic genes revealed that JAZF1 overexpression transcriptionally repressed MEF2C and MRF4 and their downstream genes. AMP deaminase1 (AMPD1) was identified as a candidate for JAZF1 target by gene array analysis. However, promoter assays of Ampd1 demonstrated that mutation of the putative binding site for the TR4/JAZF1 complex did not alleviate the repressive effects of JAZF1 on promoter activity. Instead, JAZF1-mediated repression of Ampd1 occurred through the MEF2-binding site and E-box within the Ampd1 proximal regulatory elements. Consistently, MEF2C and MRF4 expression enhanced Ampd1 promoter activity. AMPD1 overexpression and JAZF1 downregulation impaired AMPK phosphorylation, while JAZF1 overexpression also reduced it. Collectively, these results suggest that aberrant JAZF1 expression contributes to the oncogenesis and T2D pathogenesis.

Inhibition of AMP Kinase by the Protein Phosphatase 2A Heterotrimer, PP2APpp2r2d

AMP kinase is a heterotrimeric serine/threonine protein kinase that regulates a number of metabolic processes, including lipid biosynthesis and metabolism. AMP kinase activity is regulated by phosphorylation, and the kinases involved have been uncovered. The particular phosphatases counteracting these kinases remain elusive. Here we discovered that the protein phosphatase 2A heterotrimer, PP2A(Ppp2r2d), regulates the phosphorylation state of AMP kinase by dephosphorylating Thr-172, a residue that activates kinase activity when phosphorylated. Co-immunoprecipitation and co-localization studies indicated that PP2A(Ppp2r2d) directly interacted with AMP kinase. PP2A(Ppp2r2d) dephosphorylated Thr-172 in rat aortic and human vascular smooth muscle cells. A positive correlation existed between decreased phosphorylation, decreased acetyl-CoA carboxylase Acc1 phosphorylation, and sterol response element-binding protein 1c-dependent gene expression. PP2A(Ppp2r2d) protein expression was up-regulated in the aortas of mice fed a high fat diet, and the increased expression correlated with increased blood lipid levels. Finally, we found that the aortas of mice fed a high fat diet had decreased AMP kinase Thr-172 phosphorylation, and contained an Ampk-PP2A(Ppp2r2d) complex. Thus, PP2A(Ppp2r2d) may antagonize the aortic AMP kinase activity necessary for maintaining normal aortic lipid metabolism. Inhibiting PP2A(Ppp2r2d) or activating AMP kinase represents a potential pharmacological treatment for many lipid-related diseases.

Activation of AMPK in human fetal membranes alleviates infection-induced expression of pro-inflammatory and pro-labour mediators

INTRODUCTION

In non-gestational tissues, the activation of adenosine monophosphate (AMP)-activated kinase (AMPK) is associated with potent anti-inflammatory actions. Infection and/or inflammation, by stimulating pro-inflammatory cytokines and matrix metalloproteinase (MMP)-9, play a central role in the rupture of fetal membranes. However, no studies have examined the role of AMPK in human labour.

METHODS

Fetal membranes, from term and preterm, were obtained from non-labouring and labouring women, and after preterm pre-labour rupture of membranes (PPROM). AMPK activity was assessed by Western blotting of phosphorylated AMPK expression. To determine the effect of AMPK activators on pro-inflammatory cytokines, fetal membranes were pre-treated with AMPK activators then stimulated with bacterial products LPS and flagellin or viral dsDNA analogue poly(I:C). Primary amnion cells were used to determine the effect of AMPK activators on IL-1β-stimulated MMP-9 expression.

RESULTS

AMPK activity was decreased with term labour. There was no effect of preterm labour. AMPK activity was also decreased in preterm fetal membranes, in the absence of labour, with PROM compared to intact membranes. AMPK activators AICAR, phenformin and A769662 significantly decreased IL-6 and IL-8 stimulated by LPS, flagellin and poly(I:C). Primary amnion cells treated with AMPK activators significantly decreased IL-1β-induced MMP-9 expression.

DISCUSSION

The decrease in AMPK activity in fetal membranes after spontaneous term labour and PPROM indicates an anti-inflammatory role for AMPK in human labour and delivery. The use of AMPK activators as possible therapeutics for threatened preterm labour would be an exciting future avenue of research.