Discovery and translation of a target engagement marker for AMP-activated protein kinase (AMPK)

Hypoglycaemic stimulation of macrophage cytokine release is suppressed by AMP-activated protein kinase activation

AIMS

Acute hypoglycaemia promotes pro-inflammatory cytokine production, increasing the risk for cardiovascular events in diabetes. AMP-activated protein kinase (AMPK) is regulated by and influences the production of pro-inflammatory cytokines. We sought to examine the mechanistic role of AMPK in low glucose-induced changes in the pro-inflammatory cytokine macrophage migration inhibitory factor (MIF), which is elevated in people with diabetes.

METHODS

Macrophage cell line Raw264.7 cells, primary macrophage bone marrow-derived macrophages obtained from wild-type mice or AMPK γ1 gain-of-function mice, were used, as were AMPKα1/α2 knockout mouse embryonic fibroblasts (MEFs). Allosteric AMPK activators PF-06409577 and BI-9774 were used in conjunction with inhibitor SBI-0206965. We examined changes in protein phosphorylation/expression using western blotting and protein localisation using immunofluorescence. Metabolic function was assessed using extracellular flux analyses and luciferase-based ATP assay. Cytokine release was quantified by enzyme-linked immunosorbent assay (ELISA). Oxidative stress was detected using a fluorescence-based reactive oxygen species (ROS) assay, and cell viability was examined using flow cytometry.

RESULTS

Macrophages exposed to low glucose showed a transient and modest activation of AMPK and a metabolic shift towards increased oxidative phosphorylation. Moreover, low glucose increased oxidative stress and augmented the release of macrophage MIF. However, pharmacological activation of AMPK by PF-06409577 and BI-9774 attenuated low glucose-induced MIF release, with a similar trend noted with genetic activation using AMPKγ1 gain-of-function (D316A) mice, which produced a mild effect on low glucose-induced MIF release. Inhibition of NFĸB signalling diminished MIF release and AMPK activation modestly but significantly reduced low glucose-induced nuclear translocation of NFĸB.

CONCLUSIONS

Taken together, these data indicate that pharmacological AMPK activation suppresses the release of MIF from macrophages caused by energy stress, suggesting that AMPK activation could be a useful strategy for mitigating hypoglycaemia-induced inflammation.

Pan AMPK activation protects tubules in rat ischemic acute kidney injury

Acute kidney injury (AKI) is characterized by an abrupt decline in kidney function and has been associated with excess risks of death, kidney disease progression, and cardiovascular events. The kidney has a high energetic demand with mitochondrial health being essential to renal function, and damaged mitochondria have been reported across AKI subtypes. 5' Adenosine monophosphate-activated protein kinase (AMPK) activation preserves cellular energetics through improvement of mitochondrial function and biogenesis when ATP levels are low, such as under ischemia-induced AKI. We developed a selective potent small molecule pan AMPK activator, compound 1, and tested its ability to increase AMPK activity and preserve kidney function during ischemia/reperfusion injury in rats. A single administration of compound 1 caused sustained activation of AMPK for at least 24 hours, protected against acute tubular necrosis, and reduced clinical markers of tubular injury such as NephroCheck and fractional excretion of sodium. Reduction in plasma creatinine and increased glomerular filtration rate indicated preservation of kidney function. Surprisingly, we observed a strong diuretic effect of AMPK activation associated with natriuresis both with and without AKI. Our findings demonstrate that activation of AMPK leads to protection of tubular function under hypoxic/ischemic conditions which holds promise as a potential novel therapeutic approach for AKI. SIGNIFICANCE STATEMENT: No approved pharmacological therapies currently exist for acute kidney injury. We developed compound 1, which dose-dependently activated 5' adenosine monophosphate-activated protein kinase in the kidney and protected kidney function and tubules after ischemic renal injury in the rat. This was accompanied by natriuresis in injured as well as uninjured rats.

S100A8-CAMKK2-AMPK axis confers the protective effects of mild hypothermia against cerebral ischemia-reperfusion injury in rats

To investigate the neuroprotective mechanism of mild hypothermia (MH) in ameliorating cerebral ischemia reperfusion (IR) injury. The Pulsinelli's four-vessel ligation method was utilized to establish a rat model of global cerebral IR injury. To investigate the role of S100A8 in MH treatment of cerebral IR injury, hippocampus-specific S100A8 loss or gain of function was achieved using an adeno-associated virus system. We examined the effect of S100A8 over-expression or knock-down on the function of the SH-SY5Y cell line subjected to oxygen-glucose deprivation reoxygenation (OGDR) injury under MH treatment and delved into the underlying mechanisms. MH significantly ameliorates IR-induced neurological injury in the brain. Similarly to MH, knock-down of S100A8 significantly reduced neuronal oxidative stress, attenuated mitochondrial damage, inhibited apoptosis, and improved cognitive function in IR rats. Conversely, over-expression of S100A8 attenuated MH's protective effect and aggravated brain IR injury. In vitro, low expression of S100A8 significantly inhibited the decline in mitochondrial membrane potential induced by OGDR, reduced oxidative stress response, and decreased cell apoptosis, acting as a protective agent nearly equivalent to MH in SH-SY5Y cells. However, over-expression of S100A8 significantly inhibited these protective effects of MH. Mechanistically, MH down-regulated S100A8 expression, enhancing mitochondrial function via activation of the CAMKK2/AMPK signaling pathway. Moreover, with MH treatment, the administration of CAMKK2 and AMPK inhibitors STO-609 and Dorsomorphin significantly increased oxidative stress, mitochondrial damage, and cell apoptosis, thereby diminishing MH's neuroprotective effect against cerebral IR injury. Our study identified S100A8 as a master regulator that enables MH to ameliorate neurological injury during the early stage of cerebral IR injury by enhancing mitochondrial function. By targeting the S100A8-initiated CAMKK2/AMPK signaling pathway, we may unlock a novel therapeutic intervention or develop a refined MH therapeutic strategy against cerebral IR injury.

High-fat/high-fructose diet and Opisthorchis viverrini infection promote metabolic dysfunction-associated steatotic liver disease via inflammation, fibrogenesis, and metabolic dysfunction

Metabolic dysfunction-associated steatotic liver disease (MASLD) and opisthorchiasis, caused by Opisthorchis viverrini (O. viverrini) infection, frequently co-exist in Northeast Thailand. However, the underlying pathophysiology remains unknown. We aimed to investigate the effect of a high-fat/high-fructose (HFF) diet combined with O. viverrini infection on MASLD. Four groups each of ten male golden hamsters were established: normal controls (NC), O. viverrini-infected (OV), HFF-fed, and HFF-fed plus O. viverrini infection (HFF+OV). After four months of treatment, histopathological study indicated substantial hepatic damage in groups given the HFF diet. In particular, the HFF+OV group demonstrated marked lipid-droplet accumulation, hepatocyte ballooning, inflammatory-cell clustering, and widespread fibrosis. Biochemical tests indicated that the HFF+OV group had the highest concentrations of alanine aminotransferase and triglycerides, but cholesterol and low-density lipoprotein levels had increased in both HFF groups. Increased expression of Tgf-β1 and α-SMA, indicative of greater fibrosis, was demonstrated by picrosirius-red staining in the HFF+OV group. There was a significant increase in levels of inflammatory markers (HMGB-1, p65, and F4/80) and expression of genes related to the synthesis of fatty acids and glucose. FTIR microspectroscopy revealed distinct changes in fatty acids and proteins, associated with the more pronounced histopathology and impaired liver function in the HFF+OV group. The findings indicate that the interplay of a HFF diet and O. viverrini infection aggravates the progression of MASLD by augmenting liver damage, inflammation, fibrogenesis, and metabolic dysfunction. This study highlights the significance of incorporating both nutritional and infection factors into the management of liver disorders, especially in areas where opisthorchiasis is common.

The thienopyridine A-769662 and benzimidazole 991 inhibit human TASK-3 potassium channels in an AMPK-independent manner

Heteromeric Tandem pore domain Acid Sensitive (TASK)-1/3 channels are critical to oxygen-sensing by carotid body type 1 cells, where hypoxia-induced inhibition of TASK-3 and/or TASK-1/3 potassium currents leads to voltage-gated calcium entry, exocytotic transmitter release and increases in carotid body afferent input responses that initiate corrective changes in breathing patterns. It was proposed that, in response to hypoxia, the AMP-activated protein kinase (AMPK) might directly phosphorylate and inhibit TASK channels, in particular TASK-3, but studies on rat type I cells questioned this view. However, sequence alignment identified a putative AMPK recognition motif in human (h) TASK-3, but not hTASK-1, with Ser55 representing a potential phosphorylation site. We therefore studied the effects of five different AMPK activators on recombinant hTASK-3 potassium channels expressed in human embryonic kidney (HEK)-293 cells. Two structurally unrelated AMPK activators, the thienopyridine A-769662 (100-500 µM) and the benzimidazole 991 (3-30 µM) inhibited hTASK-3 currents in a concentration-dependent manner, while the 4-azabenzimidazole MK-8722 (3-30 µM) partially inhibited hTASK-3 at concentrations above those required for maximal AMPK activation. By contrast, the 4-azabenzimidazole, BI-9774 (10-100 µM; a closely related analogue of MK8722) and the pro-drug AICA-riboside (1 mM; metabolised to ZMP, an AMP-mimetic) had no significant effect on hTASK-3 currents at concentrations sufficient to maximally activate AMPK. Importantly, A-769662 (300 µM) also inhibited hTASK-3 channel currents in HEK-293 cells that stably over-expressed an AMPK-β1 subunit mutant (S108A) that renders AMPK insensitive to activators that bind to the Allosteric Drug and Metabolite site, such as A-769662. We therefore identify A-769662 and 991 as novel hTASK-3 channel inhibitors and provide conclusive evidence that AMPK does not regulate hTASK-3 channel currents.

Methyl Syringate Stimulates Glucose Uptake by Inhibiting Protein Tyrosine Phosphatases Relevant to Insulin Resistance

Several protein tyrosine phosphatases (PTPs), particularly PTPN1, PTPN2, PTPN6, PTPN9, PTPN11, PTPRS, and DUSP9, are involved in insulin resistance. Therefore, these PTPs could be promising targets for the treatment of type 2 diabetes. Our previous studies revealed that PTPN2 and PTPN6 are potential antidiabetic targets. Therefore, the identification of dual-targeting inhibitors of PTPN2 and PTPN6 could be a potential therapeutic strategy for the treatment or prevention of type 2 diabetes. In this study, we demonstrate that methyl syringate inhibits the catalytic activity of PTPN2 and PTPN6 in vitro, indicating that methyl syringate acts as a dual-targeting inhibitor of PTPN2 and PTPN6. Furthermore, methyl syringate treatment significantly increased glucose uptake in mature 3T3-L1 adipocytes. Additionally, methyl syringate markedly enhanced phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) in 3T3L1 adipocytes. Taken together, our results suggest that methyl syringate, a dual-targeting inhibitor of PTPN2 and PTPN6, is a promising therapeutic candidate for the treatment or prevention of type 2 diabetes.

Kinase Degraders, Activators, and Inhibitors: Highlights and Synthesis Routes to the Chemical Probes on opnMe.com, Part 1

Kinases are among the most important and successful drug targets. Chemical probe compounds have played a critical role in elucidating the role of kinases in many biological pathways. There are currently twelve well-validated chemical probes that target kinases available free-of-cost via the Molecules to Order (M2O) arm of Boehringer Ingelheim's open innovation platform, opnMe.com. Here we present a summary of the key data for each of these probe compounds and the synthesis routes to all twelve compounds. We hope this will aid researchers who use or plan to use these compounds in their research.

AMPK activation protects against prostate cancer by inducing a catabolic cellular state

Emerging evidence indicates that metabolic dysregulation drives prostate cancer (PCa) progression and metastasis. AMP-activated protein kinase (AMPK) is a master regulator of metabolism, although its role in PCa remains unclear. Here, we show that genetic and pharmacological activation of AMPK provides a protective effect on PCa progression in vivo. We show that AMPK activation induces PGC1α expression, leading to catabolic metabolic reprogramming of PCa cells. This catabolic state is characterized by increased mitochondrial gene expression, increased fatty acid oxidation, decreased lipogenic potential, decreased cell proliferation, and decreased cell invasiveness. Together, these changes inhibit PCa disease progression. Additionally, we identify a gene network involved in cell cycle regulation that is inhibited by AMPK activation. Strikingly, we show a correlation between this gene network and PGC1α gene expression in human PCa. Taken together, our findings support the use of AMPK activators for clinical treatment of PCa to improve patient outcome.

Protective Roles of Apigenin Against Cardiometabolic Diseases: A Systematic Review

Apigenin is a flavonoid with antioxidant, anti-inflammatory, and anti-apoptotic activity. In this study, the potential effects of apigenin on cardiometabolic diseases were investigated in vivo and in vitro. Potential signaling networks in different cell types induced by apigenin were identified, suggesting that the molecular mechanisms of apigenin in cardiometabolic diseases vary with cell types. Additionally, the mechanisms of apigenin-induced biological response in different cardiometabolic diseases were analyzed, including obesity, diabetes, hypertension and cardiovascular diseases. This review provides novel insights into the potential role of apigenin in cardiometabolic diseases.

Senolytic vaccination: a new mandate for cardiovascular health?

Senescent cell accumulation is increasingly associated with a number of age-related cardiovascular diseases. Now, a new manuscript in Nature Aging suggests that a novel vaccine-based strategy might provide a targeted method to eliminate the senescent cell population.

Rubusoside Reduces Blood Glucose and Inhibits Oxidative Stress by Activating the AMPK Signaling Pathway in Type 2 Diabetes Mellitus Mice

The current study aimed at investigating the therapeutic effects of rubusoside on type 2 diabetes mellitus (T2DM) mice models as an alternative hypoglycemic candidate drug. T2DM mice models were established with a combination of streptozotocin (STZ) intraperitoneal injection and high-fat diet. After 10 weeks of rubusoside intragastric administration (100, 200 mg/kg/day) to the mice, the body weight, fasting blood glucose, glucose tolerance, and blood lipids were measured. The liver protein expression levels of p-AMPK, GLUT2, GLUT4 and total antioxidant capacity were also investigated.

After 10 weeks of rubusoside administration, the levels of blood glucose and lipids were decreased in T2DM mice. Compared with the model group, rubusoside administration significantly decreased the liver mass-to-body weight ratio, upregulated p-AMPK and GLUT4, and downregulated GLUT2 expression levels in the liver. Activities of superoxide dismutase (SOD), catalase (CAT), and gluathione peroxidase (GSH-Px) were increased, and the concentration of malondialdehyde (MDA) was decreased to reduce oxidative stress in the liver. Liver hematoxylin and eosin (H&E) pathological analysis also showed that rubusoside had a protective effect on T2DM mice liver.

These results demonstrate that rubusoside could be used as an anti-diabetic candidate drug, and that its hypoglycemic mechanism might be related to the activation of adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) to modulate the expression of GLUT2 and GLUT4. Finally, rubusoside could also increase total antioxidant capacity to protect the liver from oxidative stress.

Nepetin Acts as a Multi-Targeting Inhibitor of Protein Tyrosine Phosphatases Relevant to Insulin Resistance

Protein tyrosine phosphatases (PTPs) are essential modulators of signal transduction pathways and has been implicated in many human diseases such as cancer, diabetes, obesity, autoimmune disorders, and neurological diseases, indicating that PTPs are next-generation drug targets. Since PTPN1, PTPN2, and PTPN11 have been reported to be negative regulators of insulin action, the identification of PTP inhibitors may be an effective strategy to develop therapeutic agents for the treatment of type 2 diabetes. In this study, we observed for the first time that nepetin inhibits the catalytic activity of PTPN1, PTPN2, and PTPN11 in vitro, indicating that nepetin acts as a multi-targeting inhibitor of PTPN1, PTPN2, and PTPN11. Furthermore, treatment of mature 3T3-L1 adipocytes with 20 μM nepetin stimulates glucose uptake through AMPK activation. Taken together, our findings provide evidence that nepetin, a multi-targeting inhibitor of PTPN1, PTPN2, and PTPN11, could be a promising therapeutic candidate for the treatment of type 2 diabetes.

GPNMB mitigates Alzheimer's disease and enhances autophagy via suppressing the mTOR signal

Alzheimer's disease (AD) is a common neurodegenerative disease which is characterized by amyloid beta (Aβ) accumulation. We found that glycoprotein NMB (GPNMB) was highly expressed in the brain of APP/PS1 mice, a mouse model of AD. However, its role in AD remains unclear. In this study, we aimed to explore the function of GPNMB in AD. The expression of GPNMB in the brain was detected by immunofluorescence and western blot. In addition, the role of GPNMB in AD was explored through gain-of-function. Autophagy, which is beneficial to Aβ clearance, was evaluated by transmission electron microscope and immunofluorescence with beclin-1. Furthermore, 3-MA, an autophagy inhibitor, was employed to evidence whether GPNMB reduced the level of Aβ through autophagy. We found that over-expression of GPNMB improved AD-like behaviors in APP/PS1 mice and reduced Aβ deposition. Further study showed that GPNMB enhanced autophagy, reduced microglial cells and inhibited the activation of the mTOR signal. Additionally, treatment with 3-MA abolished the beneficial effect of GPNMB on Aβ clearance. This study revealed that the high level of GPNMB in AD brain may help Aβ clearance and improve AD-like behaviors through enhancing autophagy via suppressing the mTOR signal. This beneficial role of GPNMB provides us novel strategies for the prevention and treatment of AD.

Maternal Undernutrition during Pregnancy Alters Amino Acid Metabolism and Gene Expression Associated with Energy Metabolism and Angiogenesis in Fetal Calf Muscle

To elucidate the mechanisms underlying maternal undernutrition (MUN)-induced fetal skeletal muscle growth impairment in cattle, the longissimus thoracis muscle of Japanese Black fetal calves at 8.5 months in utero was analyzed by an integrative approach with metabolomics and transcriptomics. The pregnant cows were fed on 60% (low-nutrition, LN) or 120% (high-nutrition, HN) of their overall nutritional requirement during gestation. MUN markedly decreased the bodyweight and muscle weight of the fetus. The levels of amino acids (AAs) and arginine-related metabolites including glutamine, gamma-aminobutyric acid (GABA), and putrescine were higher in the LN group than those in the HN group. Metabolite set enrichment analysis revealed that the highly different metabolites were associated with the metabolic pathways of pyrimidine, glutathione, and AAs such as arginine and glutamate, suggesting that MUN resulted in AA accumulation rather than protein accumulation. The mRNA expression levels of energy metabolism-associated genes, such as PRKAA1, ANGPTL4, APLNR, CPT1B, NOS2, NOS3, UCP2, and glycolytic genes were lower in the LN group than in the HN group. The gene ontology/pathway analysis revealed that the downregulated genes in the LN group were associated with glucose metabolism, angiogenesis, HIF-1 signaling, PI3K-Akt signaling, pentose phosphate, and insulin signaling pathways. Thus, MUN altered the levels of AAs and expression of genes associated with energy expenditure, glucose homeostasis, and angiogenesis in the fetal muscle.

Analysis of potential hub genes involved in the pathogenesis of Chinese type 1 diabetic patients

Background

Type 1 diabetes is an autoimmune disease strongly related to genetic factors. Although studies on T1D susceptibility genes have achieved great progress, the molecular mechanism of T1D remains to be explained.

Methods

To explore the underlying mechanisms of T1D, bioinformatic analysis based on a microarray database was used to determine the key biomarkers of T1D as well as their biofunctions and interactions. The microarray database GSE55100 was downloaded from the Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) were processed by packages in R Software. The database for Annotation, Visualization, and Integrated Discovery (DAVID, version 6.8) was used to conduct gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. The protein-protein interaction network was analyzed with the Search Tool for the Retrieval of Interacting Genes (STRING), and the module analysis was performed using Cytoscape.

Results

Seventy-eight DEGs and 13 hub genes were identified. The biofunctions and pathways of these DEGs were enriched in immune response, extracellular exosome, cytokine activity and antigen processing and presentation. Thirteen DEGs with MCODE score ≥2 were selected as hub genes including MMP9, ARG1, CAMP, CHI3L1, CRISP3, SLPI, LCN2, PGLYRP1, LTF, RETN, CEACAM1, CEACAM8 and MS4A3.

Conclusions

The identification and analyses of the DEGs and hub genes from database GSE55100 provide novel prospectives of the pathogenesis of T1D.

Pediatric Clinical Endpoint and Pharmacodynamic Biomarkers: Limitations and Opportunities

Medical research in children typically lags behind that of adult research in both quantity and quality. The conduct of rigorous clinical trials in children can raise ethical concerns because of children's status as a 'vulnerable' population. Moreover, carrying out studies in pediatrics also requires logistical considerations that rarely occur with adult clinical trials. Due to the relatively smaller number of pediatric studies to support evidence-based medicine, the practice of medicine in children is far more reliant upon expert opinion than in adult medicine. Children are at risk of not receiving the same level of benefits from precision medicine research, which has flourished with new technologies capable of generating large amounts of data quickly at an individual level. Although progress has been made in pediatric pharmacokinetics, which has led to safer and more effective dosing, gaps in knowledge still exists when it comes to characterization of pediatric disease and differences in pharmacodynamic response between children and adults. This review highlights three specific therapeutic areas where biomarker development can enhance precision medicine in children: asthma, type 2 diabetes mellitus, and pain. These 'case studies' are meant to update the reader on biomarkers used currently in the diagnosis and treatment of these conditions, and their shortcomings within a pediatric context. Current research on surrogate endpoints and pharmacodynamic biomarkers in the above therapeutic areas will also be described. These cases highlight the current lack in pediatric specific surrogate endpoints and pharmacodynamic biomarkers, as well as the research presently being conducted to address these deficiencies. We finally briefly highlight other therapeutic areas where further research in pediatric surrogate endpoints and pharmacodynamic biomarkers can be impactful to the care of children.