AMPK signalling in health and disease

doi:10.1016/j.ceb.2017.01.005

Current Opinion in Cell Biology

Volume 45, April 2017, Pages 31-37

https://doi.org/10.1016/j.ceb.2017.01.005 Get rights and content

In eukaryotic cells AMP-activated protein kinase (AMPK) plays a major role in regulating cellular energy balance. AMPK responds to changes in intracellular adenine nucleotide levels, being activated by an increase in AMP/ADP relative to ATP. Activation of AMPK increases the rate of catabolic (ATP-generating) pathways and decreases the rate of anabolic (ATP-utilising) pathways. In addition to its role in maintaining intracellular energy balance, AMPK regulates whole body energy metabolism. Given its key role in controlling energy homeostasis, AMPK has attracted widespread interest as a potential therapeutic target for metabolic diseases, including type 2 diabetes and, more recently, cancer. Here I review the regulation of AMPK and its potential as a target for therapeutic intervention in human disease.

Introduction

The hydrolysis of ATP to ADP provides the energy for driving virtually all of the processes associated with living cells. Maintaining an adequate supply of energy is an essential requirement for survival [1]. At a single cell level this means keeping ATP, the immediate source of energy, at a relatively high concentration — in the millimolar range in most eukaryotic cells. The concentration of ATP within most eukaryotic cells is kept at a remarkably constant level, despite wide fluctuations in the demand for ATP [2]. In order to achieve this, cells require systems to monitor changes in ATP levels, and to couple these changes to a transponder that leads to functional outputs to restore ATP levels. One such system that has been identified is the AMP-activated protein kinase (AMPK) and orthologues of AMPK are found in virtually all eukaryotes. A major function of AMPK is to monitor changes in the level of ATP and to couple this to phosphorylation of downstream substrates leading to an increase in the rate of ATP-producing pathways and/or a decrease in the rate of ATP-utilising pathways. Dysregulation of energy homeostasis is thought to be an important factor in driving changes in a wide range of human diseases, such as type 2 diabetes, obesity and cancer. The central role of AMPK in maintaining energy homeostasis has made it an attractive target for drugs aimed at preventing and/or treating metabolic diseases, including cancer [3, 4, 5]. In this review, I will focus on recent developments regarding the regulation of AMPK that directly impact on its therapeutic utility. I will also discuss some potential caveats arising from studies examining the role of AMPK in vivo using mouse models.

Section snippets

AMPK subunits

Mammalian AMPK is a heterotrimeric complex [2, 6, 7, 8]. The α subunit encodes an N-terminal protein kinase domain (KD) linked to a C-terminal regulatory domain. The C-terminal region of the β subunit acts as a scaffold, interacting with the γ subunit and the C-terminal region of the α subunit. The β subunit also contains a region termed the carbohydrate binding module (CBM), sometimes referred to as the glycogen binding domain (GDB). The γ subunit contains four cystathionine-β-synthase (CBS)

Species specific roles

In the case of AMPK, this is exemplified by two recent studies examining mouse models harbouring knock-in mutations of the Prkag2 gene encoding γ2 [15••, 16••]. Three mouse lines were generated harbouring different mutations identified in patients with Wolff–Parkinson–White Syndrome: R302Q, N4881 and R531G. As well as observing differences in the phenotypes between the three mouse lines [15••, 16••], the phenotypes reported in the mouse models failed to recapitulate the symptoms associated with

AMPK regulation

AMPK is activated by phosphorylation of threonine 172 (T172) within the activation segment of the KD of the α subunit [22]. In mammals, calcium/calmodulin dependent protein kinase kinase (CaMKK) β and liver kinase B1 (LKB1) have been identified as the two upstream kinases in the cascade [23, 24, 25, 26]. Phosphorylation of T172 increases AMPK activity by 2–3 orders of magnitude [27, 28]. The rate of dephosphorylation of T172 is decreased by AMP/ADP [27, 29]. In addition, a number of small

Pharmacological AMPK activators

As is the case with AMP, the degree of allosteric activation by 991 depends on the isoform composition of the AMPK complex, ranging from about 3-fold for α1β2γ1 to over 10-fold for α2β1γ1 [5]. Moreover, where it has been reported, the pharmacological activators that have been identified to date bind significantly tighter to AMPK complexes containing the β1 isoform relative to β2. An important point to note here, however, is that although there is clearly isoform selectivity between binding to

Role of AMPK phosphorylation

A recent study examined the requirement for T172 and S108 phosphorylation on AMPK activity [49]. In the absence of T172 phosphorylation, A769662 activated AMPK to a level similar to that of AMPK phosphorylated on T172. Phosphorylation of S108 on β1 was required for optimal activation of the non-T172 phosphorylated AMPK by A769662, and mutation of S108 to an alanine significantly reduced the ability of A769662 to stimulate AMPK. However, the presence of both AMP and A769662 was sufficient to

Conclusions and perspectives

AMPK plays an important role in maintaining energy homeostasis in eukaryotic cells. In multicellular organisms, the role of AMPK has been adapted to play a role in integrating energy metabolism at an organismal level. There has been a significant development over the last few years in identifying small molecule direct AMPK activators, and we now understand the mechanism by which a major class of these drugs work to activate the kinase. A key challenge for the future is to translate findings

References and recommended reading

Papers of particular interest, published within the period of review, have been highlighted as:

•
of special interest
•
of outstanding interest

Acknowledgements

Studies in the author’s laboratory are funded by the Medical Research Council and a BBSRC/CASE PhD studentship award in collaboration with AstraZeneca. I would like to thank members of my group for many helpful discussions whilst preparing this manuscript.

References (51)

B. Cool et al.
Identification and characterization of a small molecule AMPK activator that treats key components of type 2 diabetes and the metabolic syndrome
Cell Metab
(2006)
D.G. Hardie et al.
AMPK: an energy-sensing pathway with multiple inputs and outputs
Trends Cell Biol
(2016)
A. Yavari et al.
Chronic activation of gamma2 AMPK induces obesity and reduces beta cell function
Cell Metab
(2016)
M. Mahlapuu et al.
Expression profiling of the gamma-subunit isoforms of AMP-activated protein kinase suggests a major role for gamma3 in white skeletal muscle
Am J Physiol Endocrinol Metab
(2004)
S.A. Hawley et al.
Calmodulin-dependent protein kinase kinase-beta is an alternative upstream kinase for AMP-activated protein kinase
Cell Metab
(2005)
A. Woods et al.
LKB1 is the upstream kinase in the AMP-activated protein kinase cascade
Curr Biol
(2003)
M.J. Sanders et al.
Investigating the mechanism for AMP activation of the AMP-activated protein kinase cascade
Biochem J
(2007)
M. Suter et al.
Dissecting the role of AMP for allosteric stimulation, activation and deactivation of AMP-activated protein kinase
J Biol Chem
(2006)
G. Zadra et al.
A novel direct activator of AMPK inhibits prostate cancer growth by blocking lipogenesis
EMBO Mol Med
(2014)
O. Goransson et al.
Mechanism of action of A-769662, a valuable tool for activation of AMP-activated protein kinase
J Biol Chem
(2007)

F. Rajamohan et al.

Probing the enzyme kinetics, allosteric modulation and activation of α1- and α2-subunit-containing AMP-activated protein kinase (AMPK) heterotrimeric complexes by pharmacological and physiological activators

Biochem J

(2016)

F.A. Ross et al.

Differential regulation by AMP and ADP of AMPK complexes containing different gamma subunit isoforms

Biochem J

(2016)

N. Stahmann et al.

Thrombin activates AMP-activated protein kinase in endothelial cells via a pathway involving Ca2+/calmodulin-dependent protein kinase kinase beta

Mol Cell Biol

(2006)

J.W. Scott et al.

Thienopyridone drugs are selective activators of AMP-activated protin kinase beta1-containing complexes

Chem Biol

(2008)

Y.C. Lai et al.

A small-molecule benzimidazole derivative that potently activates AMPK to increase glucose transport in skeletal muscle: comparison with effects of contraction and other AMPK activators

Biochem J

(2014)

M.F. Calabrese et al.

Structural basis for AMPK activation: natural and synthetic ligands regulate kinase activity from opposite poles by different molecular mechanisms

Structure

(2014)

A. Woods et al.

Identification of phosphorylation sites in AMP-activated protein kinase (AMPK) for upstream AMPK kinases and study of their roles by site-directed mutagenesis

J Biol Chem

(2003)

P.D. Boyer et al.

Oxidative phosphorylation and photophosphorylation

Annu Rev Biochem

(1977)

D. Carling et al.

AMP-activated protein kinase: new regulation, new roles?

Biochem J

(2012)

F. Giordanetto et al.

Direct AMP-activated protein kinase activators: a review of evidence from the patent literature

Exprt Opin Ther Pat

(2012)

B. Xiao et al.

Structural basis of AMPK regulation by small molecule activators

Nat Commun

(2013)

D. Carling et al.

AMP-activated protein kinase: nature’s energy sensor

Nat Chem Biol

(2011)

G.R. Steinberg et al.

AMPK in health and disease

Physiol Rev

(2009)

M. Arad et al.

Constitutively active AMP kinase mutations cause glycogen storage disease mimicking hypertrophic cardiomyopathy

J Clin Invest

(2002)

E. Blair et al.

Mutations in the g2 subunit of AMP-activated protein kinase cause familial hypertrophic cardiomyopathy: evidence for the central role of energy compromise in disease pathogenesis

Hum Mol Genet

(2001)

Cited by (562)

Protective effect of alizarin on vascular endothelial dysfunction via inhibiting the type 2 diabetes-induced synthesis of THBS1 and activating the AMPK signaling pathway
2024, Phytomedicine
In this study, we investigated the protective effects of alizarin (AZ) on endothelial dysfunction (ED). AZ has inhibition of the type 2 diabetes mellitus (T2DM)-induced synthesis of thrombospondin 1 (THBS1). Adenosine 5‘-monophosphate- activated protein kinase (AMPK), particularly AMPKα2 isoform, plays a critical role in maintaining cardiac homeostasis.
The aim of this study was to investigate the ameliorative effect of AZ on vascular injury caused by T2DM and to reveal the potential mechanism of AZ in high glucose (HG)-stimulated human umbilical vein endothelial cells (HUVECs) and diabetic model rats.
HUVECs, rats and AMPK^-/- transgenic mice were used to investigate the mitigating effects of AZ on vascular endothelial dysfunction caused by T2DM and its in vitro and in vivo molecular mechanisms.
In type 2 diabetes mellitus rats and HUVECs, the inhibitory effect of alizarin on THBS1 synthesis was verified by immunohistochemistry (IHC), immunofluorescence (IF) and Western blot (WB) so that increase endothelial nitric oxide synthase (eNOS) content in vitro and in vivo. In addition, we verified protein interactions with immunoprecipitation (IP). To probe the mechanism, we also performed AMPKα2 transfection. AMPK's pivotal role in AZ-mediated prevention against T2DM-induced vascular endothelial dysfunction was tested using AMPKα2^-/- mice.
We first demonstrated that THBS1 and AMPK are targets of AZ. In T2DM, THBS1 was robustly induced by high glucose and inhibited by AZ. Furthermore, AZ activates the AMPK signaling pathway, and recoupled eNOS in stressed endothelial cells which plays a protective role in vascular endothelial dysfunction.
The main finding of this study is that AZ can play a role in different pathways of vascular injury due to T2DM. Mechanistically, alizarin inhibits the increase in THBS1 protein synthesis after high glucose induction and activates AMPKα2, which increases NO release from eNOS, which is essential in the prevention of vascular endothelial dysfunction caused by T2DM.
Abnormal expression of PRKAG2-AS1 in endothelial cells induced inflammation and apoptosis by reducing PRKAG2 expression
2024, Non-coding RNA Research
PRKAG2 is required for the maintenance of cellular energy balance. PRKAG2-AS1, a long non-coding RNA (lncRNA), was found within the promoter region of PRKAG2. Despite the extensive expression of PRKAG2-AS1 in endothelial cells, the precise function and mechanism of this gene in endothelial cells have yet to be elucidated. The localization of PRKAG2-AS1 was predominantly observed in the nucleus, as revealed using nuclear and cytoplasmic fractionation and fluorescence in situ hybridization. The manipulation of PRKAG2-AS1 by knockdown and overexpression within the nucleus significantly altered PRKAG2 expression in a cis-regulatory manner. The expression of PRKAG2-AS1 and its target genes, PRKAG2b and PRKAG2d, was down-regulated in endothelial cells subjected to oxLDL and Hcy-induced injury. This finding suggests that PRKAG2-AS1 may be involved in the mechanism behind endothelial injury. The suppression of PRKAG2-AS1 specifically in the nucleus led to an upregulation of inflammatory molecules such as cytokines, adhesion molecules, and chemokines in endothelial cells. Additionally, this nuclear suppression of PRKAG2-AS1 facilitated the adherence of THP1 cells to endothelial cells. We confirmed the role of nuclear knockdown PRKAG2-AS1 in the induction of apoptosis and inhibition of cell proliferation, migration, and lumen formation through flow cytometry, TUNEL test, CCK8 assay, and cell scratching. Finally, it was determined that PRKAG2-AS1 exerts direct control over the transcription of PRKAG2 by its binding to their promoters. In conclusion, downregulation of PRKAG2-AS1 suppressed the proliferation and migration, promoted inflammation and apoptosis of endothelial cells, and thus contributed to the development of atherosclerosis resulting from endothelial cell injury.
Hypoxia-associated autophagy flux dysregulation in human cancers
2024, Cancer Letters
A general feature of cancer is hypoxia, determined as low oxygen levels. Low oxygen levels may cause cells to alter in ways that contribute to tumor growth and resistance to treatment. Hypoxia leads to variations in cancer cell metabolism, angiogenesis and metastasis. Furthermore, a hypoxic tumor microenvironment might induce immunosuppression. Moreover, hypoxia has the potential to impact cellular processes, such as autophagy. Autophagy refers to the catabolic process by which damaged organelles and toxic macromolecules are broken down. The abnormal activation of autophagy has been extensively recorded in human tumors and it serves as a regulator of cell growth, spread to other parts of the body, and resistance to treatment. There is a correlation between hypoxia and autophagy in human malignancies. Hypoxia can regulate the activity of AMPK, mTOR, Beclin-1, and ATGs to govern autophagy in human malignancies. Furthermore, HIF-1α, serving as an indicator of low oxygen levels, controls the process of autophagy. Hypoxia-induced autophagy has a crucial role in regulating the growth, spread, and resistance to treatment in human malignancies. Hypoxia-induced regulation of autophagy can impact other mechanisms of cell death, such as apoptosis. Chemoresistance and radioresistance have become significant challenges in recent years. Hypoxia-mediated autophagy plays a crucial role in determining the response to these therapeutic treatments.
Human neural stem cells promote mitochondrial genesis to alleviate neuronal damage in MPTP-induced cynomolgus monkey models
2024, Neurochemistry International
Currently, there is no effective treatment for Parkinson's disease (PD), and the regenerative treatment of neural stem cells (NSCs) is considered the most promising method. This study aimed to investigate the protective effect and mechanism of NSCs on neurons in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induced cynomolgus monkey (Macaca fascicularis) model of PD. We first found that injecting NSCs into the subarachnoid space relieved motor dysfunction in PD cynomolgus monkeys, as well as reduced dopaminergic neuron loss and neuronal damage in the substantia nigra (SN) and striatum. Besides, NSCs decreased 17-estradiol (E2) level, an estrogen, in the cerebrospinal fluid (CSF) of PD cynomolgus monkeys, which shows NSCs may provide neuro-protection by controlling estrogen levels in the CSF. Furthermore, NSCs elevated proliferator-activated receptor gamma coactivator-1 alpha (PGC-1a), mitofusin 2 (MFN2), and optic atrophy 1 (OPA1) expression, three genes mediating mitochondrial biogenesis, in the SN and striatum of PD monkeys. In addition, NSCs suppress reactive oxygen species (ROS) production caused by MPTP, as well as mitochondrial autophagy, therefore preserving dopaminergic neurons. In summary, our findings show that NSCs may preserve dopaminergic and neuronal cells in an MPTP-induced PD cynomolgus monkey model. These protective benefits might be attributed to NSCs' ability of modulating estrogen balance, increasing mitochondrial biogenesis, and limiting oxidative stress and mitochondrial autophagy. These findings add to our understanding of the mechanism of NSC treatment and shed light on further clinical treatment options.
Artesunate improves glucose and lipid metabolism in db/db mice by regulating the metabolic profile and the MAPK/PI3K/Akt signalling pathway
2024, Phytomedicine
Diabetes is a metabolic disorder characterized by chronic hyperglycaemia. Chronic metabolic abnormalities and long-term hyperglycaemia may result in a wide range of acute and chronic consequences. Previous studies have demonstrated that artesunate(ART) has antidiabetic, anti-inflammatory, antiatherosclerotic, and other beneficial effects, but the specific regulatory mechanism is not completely clear.
This study investigated the effects of ART on metabolic disorders in type 2 diabetes mellitus (T2DM) model db/db mice and explored the underlying mechanisms involved.
C57BL/KsJ-db/db mice were used to identify the targets and molecular mechanism of ART. Metabolomic methods were used to evaluate the efficacy of ART in improving T2DM-related metabolic disorders. Network pharmacology and transcriptomic sequencing were used to analyse the targets and pathways of ART in T2DM. Finally, molecular biology experiments were performed to verify the key targets and pathways selected by network pharmacology and transcriptomic analyses.
After a 7-week ART intervention (160 mg/kg), the glucose and lipid metabolism levels of the db/db mice improved. Additionally, the oxidative stress indices, namely, the MDA and SOD levels, significantly improved (p<0.01). Linoleic acid and glycerophospholipid metabolism, amino acid metabolism, bile acid synthesis, and purine metabolism disorders in db/db mice were partially corrected after ART treatment. Network pharmacology analysis identified important targets of ART for the treatment of metabolic disorders in T2DM . These targets are involved in key signalling pathways, including the highest scores observed for the PI3K/Akt signalling pathway. Transcriptomic analysis revealed that ART could activate the MAPK signalling pathway and two key gene targets, HGK and GADD45. Immunoblotting revealed that ART increases p-PI3K, p-AKT, Glut2, and IRS1 protein expression and suppresses the phosphorylation of p38, ERK1/2, and JNK, returning HGK and GADD45 to their preartesunate levels.
Treatment of db/db mice with 160 mg/kg ART for 7 weeks significantly reduced fasting blood glucose and lipid levels. It also improved metabolic imbalances in amino acids, lipids, purines, and bile acids, thereby improving metabolic disorders. These effects are achieved by activating the PI3K/AKT pathway and inhibiting the MAPK pathway, thus demonstrating the efficacy of the drug.
Dietary creatine promotes creatine reserves, protein deposition, and myofiber hyperplasia in muscle of juvenile largemouth bass (Micropterus salmoides)
2024, Aquaculture
Creatine can increase muscle mass, enhance performance, prevent disease-induced muscle atrophy, and improve overall cellular energy. This study investigated the effects of creatine as a feed additive on muscle growth and intrinsic molecular regulation mechanism in largemouth bass (Micropterus salmoides). Seven diets supplemented with different concentrations of creatine (0%, 0.1%, 0.25%, 0.5%, 1%, 2%, and 4%) were fed to juvenile largemouth bass (4.5–5.1 g) for eight weeks. Dietary creatine significantly increased body weight and body length, and reduced feed conversion ratio. High-performance liquid chromatography analysis revealed that dietary creatine addition notably increased creatine and phosphocreatine levels by 19.94% and 16.54% in the muscle of largemouth bass, respectively. Histological observation showed that dietary creatine significantly increased the total muscle fiber number and decreased the mean muscle fiber diameter. The Western blot results indicated that creatine ingestion significantly increased the protein level of MyoD1 in the muscle and promoted muscle fiber hyperplasia. In addition, dietary creatine also contributed to mTOR-S6K/4EBP1-mediated protein synthesis by maintaining AMPKα Thr172 dephosphorylation and AKT Thr308 phosphorylation. Moreover, the protein levels of the muscle-specific E3 ligases Atrogin1 and Murf1 responsible for ubiquitination degradation exhibited no significant change after feeding with creatine in largemouth bass. Overall, our data showed that creatine as a feed additive increased creatine and phosphocreatine contents, thus promoting muscle protein deposition and myofiber hyperplasia, eventually elevating growth performance and feed utilization efficiency in juvenile largemouth bass. The regression analysis of weight gain rate, specific growth rate, and feed conversion ratio determined 0.46%–0.54% creatine concentration range as optimal supplementation concentration for the culture of juvenile largemouth bass.

View all citing articles on Scopus

View full text

AMPK signalling in health and disease

Introduction

Section snippets

AMPK subunits

Species specific roles

AMPK regulation

Pharmacological AMPK activators

Role of AMPK phosphorylation

Conclusions and perspectives

References and recommended reading

Acknowledgements

Cell Metab

Trends Cell Biol

Cell Metab

Am J Physiol Endocrinol Metab

Cell Metab

Curr Biol

Biochem J

J Biol Chem

EMBO Mol Med

J Biol Chem

Biochem J

Biochem J

Mol Cell Biol

Chem Biol

Biochem J

Structure

J Biol Chem

Oxidative phosphorylation and photophosphorylation

Annu Rev Biochem

AMP-activated protein kinase: new regulation, new roles?

Biochem J

Direct AMP-activated protein kinase activators: a review of evidence from the patent literature

Exprt Opin Ther Pat

Structural basis of AMPK regulation by small molecule activators

Nat Commun

AMP-activated protein kinase: nature’s energy sensor

Nat Chem Biol

AMPK in health and disease

Physiol Rev

Constitutively active AMP kinase mutations cause glycogen storage disease mimicking hypertrophic cardiomyopathy

J Clin Invest

Mutations in the g2 subunit of AMP-activated protein kinase cause familial hypertrophic cardiomyopathy: evidence for the central role of energy compromise in disease pathogenesis

Hum Mol Genet