AMPK activation by metformin inhibits local innate immune responses in the isolated rat heart by suppression of TLR 4-related pathway

Targeting Immune Cell Metabolism: A Promising Therapeutic Approach for Cardiovascular Disease

Cardiovascular disease (CVD) is a leading cause of morbidity and mortality globally. Recent groundbreaking preclinical and clinical research underscores the pivotal role of metabolite remodelling in the pathology of CVD. This metabolic transformation not only directly fuels the progression of CVD but also profoundly influences the immune response within the cardiovascular system. In this review, we focused on the complex interactions between cardiovascular metabolic alterations and immune responses during the course of CVD. Furthermore, we explore the potential therapeutic interventions that could be developed based on the understanding of metabolic alterations and immune dysregulation in CVD. By targeting these metabolic and immunological pathways, novel strategies for the prevention and treatment of CVDs might be developed to improve patient outcomes and reduce the global burden of this disease.

Tetrahedral Framework Nucleic Acid (tFNA)-Loaded Metformin (Met) Modulates Cellular Pyroptosis and AMPK to Ameliorate Type II Diabetic Periodontitis

Diabetic periodontitis presents a unique therapeutic challenge, primarily due to its chronic inflammatory profile and the associated bone loss driven by immune dysregulation. Metformin (Met) is recognized for its potent anti-inflammatory properties, yet its limited cellular uptake has hindered its clinical effectiveness in diabetic periodontitis. A tetrahedral framework nucleic acid (tFNA)-based delivery system is developed to enhance Met cellular uptake and investigate its effects on diabetic periodontitis in this study. The tFNA-loaded Met complex (TMC) demonstrates efficient Met loading efficiency and rapid cellular internalization. These results show that in vitro, TMC significantly inhibited pro-inflammatory cytokines and matrix metalloproteinaseat both mRNA and protein levels under high glucose conditions. Mechanistically, TMC suppresses NLRP3-mediated pyroptosis by downregulating NLRP3, Caspase-1, Caspase-11, and GSDMD, ultimately reducing Mature-IL-1β and Mature-IL-18 production. Furthermore, TMC activates AMPK while inhibiting NF-κB signaling, thus mitigating the inflammatory response in diabetic periodontitis. In vivo, intraperitoneal administration of TMC in a diabetic periodontitis mouse model significantly reduces inflammatory cell infiltration, collagen degradation, and osteoclast formation, thus alleviating alveolar bone loss. These findings highlight the therapeutic potential of tFNA as an efficient Met delivery vehicle to tackle diabetic periodontitis-associated inflammation and bone resorption, providing a promising strategy for managing diabetic complications.

Novel applications of metformin in the treatment of septic myocardial injury based on metabolomics and network pharmacology

BACKGROUND

While metformin has shown promise in treating septic myocardial injury (SMI), its underlying mechanisms and impact on metabolic disturbances remain poorly understood.

METHODS

This study employed an integrated approach of metabolomics and network pharmacology to identify key targets and pathways through which metformin may act against SMI. Findings were validated using a lipopolysaccharide (LPS)-induced mouse model.

RESULTS

Metformin was found to counter myocardial metabolic disruptions, indicated by the reversal of 49 metabolites primarily involved in purine metabolism, pantothenate and CoA biosynthesis, and histidine metabolism. In vivo, metformin significantly improved survival rates and cardiac function, reduced cardiomyocyte apoptosis, and inhibited inflammation and oxidative stress in LPS-induced mice. Integrated analyses identified 27 potential targets for metformin in SMI treatment. KEGG pathway analysis revealed significant enrichment in TNF, HIF-1, IL-17, and PI3K/AKT signaling pathways, while protein-protein interaction analysis pinpointed ten core targets, including IL6, IL1B, CCL2, CASP3, MMP9, HIF1A, IGF1, NOS3, MMP2, and LEP. Molecular docking and dynamics simulations demonstrated metformin's high affinity for these core targets. Further, RT-qPCR and Western blot analyses confirmed that metformin modulates core target expression to mitigate SMI. Notably, our data underscore the importance of PI3K/AKT and MMP2/MMP9 signaling pathways in SMI therapy.

CONCLUSION

This study elucidates the metabolic and molecular mechanisms of metformin in SMI treatment, supporting its potential repurposing for SMI.

Metformin's cardioprotective role in isoprenaline-induced myocardial infarction: Unveiling insights into the AMPK, NF-κB, JAK2/STAT3 pathways, and cholinergic regulation

AIM

Despite advancements in treatment modalities, myocardial infarction (MI) remains a significant global cause of mortality and morbidity. Metformin (MET), a commonly used antidiabetic medication, has demonstrated potential in various cardioprotective mechanisms. This study investigated whether MET could alleviate the histopathological, electrocardiographic, and molecular consequences of MI in rats.

MATERIALS AND METHODS

The study hypothesis was tested using an isoprenaline (ISOP)-induced MI model, where male Wistar rats were injected with ISOP (85 mg/kg/day, s.c., for 2 days) and treated with MET at the doses of 500 and 1000 mg/kg/day for 18 days or left untreated.

KEY FINDINGS

ISOP-treated rats exhibited several indicators of MI, including significant ST-segment depression and prolonged QT-intervals on ECGs, worsened left ventricular histopathology with increased inflammatory cell infiltration, reduced expression of cardiac CHRM2, a cardioprotective cholinergic receptor, adaptive increases in AMPK and α7nAchR levels, and elevated levels of iNOS, NO, STAT3, JAK2, IL-6, TNF-α, and NF-κB. These effects were attenuated in rats treated with either low or high doses of MET. MET administration restored normal ECG recordings, diminished oxidative stress and inflammatory mediators, and downregulated NF-κB expression. Moreover, MET improved CHRM2 expression and normalized α7nAchR levels. Additionally, MET influenced the expression of key signaling molecules such as Akt, STAT3, and JAK2.

SIGNIFICANCE

These findings might suggest that MET exerts cardioprotective effects in ISOP-induced MI in rats by mitigating critical inflammatory signaling pathways and regulating protective cholinergic mechanisms in the heart.

AMPK activation modulates IL-36-induced inflammatory responses by regulating IκBζ expression in the skin

BACKGROUND AND PURPOSE

The interleukin (IL)-36 pathway is a critical player in the pathogenesis of pustular psoriasis. However, therapies targeting this pathway are limited or unaffordable (e.g. the anti-IL-36 receptor antibody). AMP-activated protein kinase (AMPK), a regulator of cellular energy and metabolism, is known to participate in inflammatory diseases. However, its role in IL-36-induced skin inflammation remains unclear. Therefore, we sought to investigate the role of AMPK signals in regulating IL-36-induced responses in the skin.

EXPERIMENTAL APPROACH

IL-36-stimulated primary normal human epidermal keratinocytes (NHEKs) and IL-36-injected (intradermally) BALB/c mice served as the cell and animal models, respectively. Additionally, 5-aminoimidazole-4-carboxamide riboside (AICAR) and A769662 served as AMPK activators.

KEY RESULTS

AICAR and A769662 significantly suppressed the IL-36-induced IL-8 (CXCL8) and CCL20 production from NHEKs. IL-36-induced IκBζ protein expression was prominently reduced and IKK/IκBα phosphorylation was attenuated by AICAR and A769662. Conversely, AMPKα knockdown increased IκBζ protein expression and IKK/IκBα phosphorylation in IL-36-treated NHEKs. Furthermore, AICAR and A769662 enhanced IL-36-induced-IκBζ protein degradation via the proteasome-dependent but not the lysosome-dependent pathway. Pretreatment of NHEKs with IL-36 slightly suppressed the AICAR- and A769662-triggered phosphorylation of AMPK and acetyl-CoA carboxylase. In the mouse model, topical application of AICAR significantly reduced ear swelling, redness, epidermal thickening, neutrophil infiltration and inflammatory and antimicrobial peptide gene expression.

CONCLUSION AND IMPLICATIONS

AMPK activation suppresses IL-36-induced IL-8 and CCL20 release by regulating IκBζ expression in keratinocytes and reduces IL-36-induced skin inflammation in mice, suggesting that AMPK activation is a potential strategy for treating patients with IL-36-mediated inflammatory skin disorders.

Toll-Like Receptor 4 (TLR4) and AMPK Relevance in Cardiovascular Disease

Toll-like receptors (TLRs) are essential receptors of the innate immune system, playing a significant role in cardiovascular diseases. TLR4, with the highest expression among TLRs in the heart, has been investigated extensively for its critical role in different myocardial inflammatory conditions. Studies suggest that inhibition of TLR4 signaling pathways reduces inflammatory responses and even prevents additional injuries to the already damaged myocardium. Recent research results have led to a hypothesis that there may be a relation between TLR4 expression and 5' adenosine monophosphate-activated protein kinase (AMPK) signaling in various inflammatory conditions, including cardiovascular diseases. AMPK, as a cellular energy sensor, has been reported to show anti-inflammatory effects in various models of inflammatory diseases. AMPK, in addition to its physiological acts in the heart, plays an essential role in myocardial ischemia and hypoxia by activating various energy production pathways. Herein we will discuss the role of TLR4 and AMPK in cardiovascular diseases and a possible relation between TLRs and AMPK as a novel therapeutic target. In our opinion, AMPK-related TLR modulators will find application in treating different immune-mediated inflammatory disorders, especially inflammatory cardiac diseases, and present an option that will be widely used in clinical practice in the future.

5'AMP-activated protein kinase: an emerging target of phytochemicals to treat chronic inflammatory diseases

Inflammation is a defensive response of the organism to traumatic, infectious, toxic, ischemic, and autoimmune injury. Inflammatory mediators are released to effectively eliminate the inflammatory trigger and restore homeostasis. However, failure of these processes can lead to chronic inflammatory conditions and diseases such as inflammatory bowel diseases, rheumatoid arthritis, inflammatory lung diseases, atherosclerosis, and neurodegenerative diseases. The cure of chronic inflammatory diseases remains challenging as current therapies have various limitations, such as pronounced side effects, progressive loss of efficacy, and high cost especially for biologics. In this context, phytochemicals (such as alkaloids, flavonoids, lignans, phenolic acids, saponins, terpenoids, and other classes) are considered as an interesting alternative approach. Among the numerous targets of phytochemicals, AMP-activated protein kinase (AMPK) can be considered as an interesting target in the context of inflammation. AMPK regulates inflammatory response by inhibiting inflammatory pathways (NF-κB, JAK/STAT, and MAPK) and regulating several other processes of the inflammatory response (oxidative stress, autophagy, and apoptosis). In this review, we summarize and discuss the studies focusing on phytochemicals that showed beneficial effects by blocking different inflammatory pathways implicating AMPK activation in chronic inflammatory disease models. We also highlight elements to consider when investigating AMPK in the context of phytochemicals.

Anti-Hyperglycemic Agents in the Adjuvant Treatment of Sepsis: Improving Intestinal Barrier Function

Intestinal barrier injury and hyperglycemia are common in patients with sepsis. Bacteria translocation and systemic inflammatory response caused by intestinal barrier injury play a significant role in sepsis occurrence and deterioration, while hyperglycemia is linked to adverse outcomes in sepsis. Previous studies have shown that hyperglycemia is an independent risk factor for intestinal barrier injury. Concurrently, increasing evidence has indicated that some anti-hyperglycemic agents not only improve intestinal barrier function but are also beneficial in managing sepsis-induced organ dysfunction. Therefore, we assume that these agents can block or reduce the severity of sepsis by improving intestinal barrier function. Accordingly, we explicated the connection between sepsis, intestinal barrier, and hyperglycemia, overviewed the evidence on improving intestinal barrier function and alleviating sepsis-induced organ dysfunction by anti-hyperglycemic agents (eg, metformin, peroxisome proliferators activated receptor-γ agonists, berberine, and curcumin), and summarized some common characteristics of these agents to provide a new perspective in the adjuvant treatment of sepsis.

Alisol B 23-Acetate Ameliorates Lipopolysaccharide-Induced Intestinal Barrier Dysfunction by Inhibiting TLR4-NOX1/ROS Signaling Pathway in Caco-2 Cells

Alisol B 23-Acetate (AB23A) is a naturally occurring triterpenoid, which can be indicated in the rhizome of medicinal and dietary plants from Alisma species. Previous studies have demonstrated that AB23A could inhibit intestinal permeability by regulating tight junction (TJ)-related proteins. Even so, the AB23A protective mechanism against intestinal barrier dysfunction remains poorly understood. This investigation seeks to evaluate the AB23A protective effects on intestinal barrier dysfunction and determine the mechanisms for restoring intestinal barrier dysfunction in LPS-stimulated Caco-2 monolayers. According to our findings, AB23A attenuated the inflammation by reducing pro-inflammatory cytokines production like IL-6, TNF-α, IL-1β, and prevented the paracellular permeability by inhibiting the disruption of TJ in LPS-induced Caco-2 monolayers after treated with LPS. AB23A also inhibited LPS-induced TLR4, NOX1 overexpression and subsequent ROS generation in Caco-2 monolayers. Transfected with NOX1-specific shRNA diminished the up-regulating AB23A effect on ZO-1 and occludin expression. Moreover, transfected with shRNA of TLR4 not only enhanced ZO-1 and occludin expression but attenuated NOX1 expression and ROS generation. Therefore, AB23A ameliorates LPS-induced intestinal barrier dysfunction by inhibiting TLR4-NOX1/ROS signaling pathway in Caco-2 monolayers, suggesting that AB23A may have positive impact on maintaining the intestinal barrier’s integrity.

Metformin for Cardiovascular Protection, Inflammatory Bowel Disease, Osteoporosis, Periodontitis, Polycystic Ovarian Syndrome, Neurodegeneration, Cancer, Inflammation and Senescence: What Is Next?

Diabetes is accompanied by several complications. Higher prevalence of cancers, cardiovascular diseases, chronic kidney disease (CKD), obesity, osteoporosis, and neurodegenerative diseases has been reported among patients with diabetes. Metformin is the oldest oral antidiabetic drug and can improve coexisting complications of diabetes. Clinical trials and observational studies uncovered that metformin can remarkably prevent or alleviate cardiovascular diseases, obesity, polycystic ovarian syndrome (PCOS), osteoporosis, cancer, periodontitis, neuronal damage and neurodegenerative diseases, inflammation, inflammatory bowel disease (IBD), tuberculosis, and COVID-19. In addition, metformin has been proposed as an antiaging agent. Numerous mechanisms were shown to be involved in the protective effects of metformin. Metformin activates the LKB1/AMPK pathway to interact with several intracellular signaling pathways and molecular mechanisms. The drug modifies the biologic function of NF-κB, PI3K/AKT/mTOR, SIRT1/PGC-1α, NLRP3, ERK, P38 MAPK, Wnt/β-catenin, Nrf2, JNK, and other major molecules in the intracellular signaling network. It also regulates the expression of noncoding RNAs. Thereby, metformin can regulate metabolism, growth, proliferation, inflammation, tumorigenesis, and senescence. Additionally, metformin modulates immune response, autophagy, mitophagy, endoplasmic reticulum (ER) stress, and apoptosis and exerts epigenetic effects. Furthermore, metformin protects against oxidative stress and genomic instability, preserves telomere length, and prevents stem cell exhaustion. In this review, the protective effects of metformin on each disease will be discussed using the results of recent meta-analyses, clinical trials, and observational studies. Thereafter, it will be meticulously explained how metformin reprograms intracellular signaling pathways and alters molecular and cellular interactions to modify the clinical presentations of several diseases.

Metformin inhibition of mitochondrial ATP and DNA synthesis abrogates NLRP3 inflammasome activation and pulmonary inflammation

Acute respiratory distress syndrome (ARDS), an inflammatory condition with high mortality rates, is common in severe COVID-19, whose risk is reduced by metformin rather than other anti-diabetic medications. Detecting of inflammasome assembly in post-mortem COVID-19 lungs, we asked whether and how metformin inhibits inflammasome activation while exerting its anti-inflammatory effect. We show that metformin inhibited NLRP3 inflammasome activation and interleukin (IL)-1β production in cultured and alveolar macrophages along with inflammasome-independent IL-6 secretion, thus attenuating lipopolysaccharide (LPS)- and SARS-CoV-2-induced ARDS. By targeting electron transport chain complex 1 and independently of AMP-activated protein kinase (AMPK) or NF-κB, metformin blocked LPS-induced and ATP-dependent mitochondrial (mt) DNA synthesis and generation of oxidized mtDNA, an NLRP3 ligand. Myeloid-specific ablation of LPS-induced cytidine monophosphate kinase 2 (CMPK2), which is rate limiting for mtDNA synthesis, reduced ARDS severity without a direct effect on IL-6. Thus, inhibition of ATP and mtDNA synthesis is sufficient for ARDS amelioration.

TLR4-Associated IRF-7 and NFκB Signaling Act as a Molecular Link Between Androgen and Metformin Activities and Cytokine Synthesis in the PCOS Endometrium

CONTEXT

Low-grade chronic inflammation is commonly seen in polycystic ovary syndrome (PCOS) patients with elevated levels of inflammatory cytokines in the endometrium.

OBJECTIVE

This work aimed to increase the limited understanding of the mechanisms underlying cytokine synthesis and increased endometrial inflammation in PCOS patients.

METHODS

Endometrial biopsy samples were collected from non-PCOS (n = 17) and PCOS (n = 22) patients either during the proliferative phase of the menstrual cycle or with hyperplasia. Endometrial explants were prepared from PCOS patients and underwent pharmacological manipulation in vitro. The expression and localization of toll-like receptor 2 (TLR2)/4, key elements of innate immune signal transduction and nuclear factor κB (NFκB) signaling pathways, and multiple cytokines were comprehensively evaluated by Western blotting, immunohistochemistry, and immunofluorescence in endometrial tissues.

RESULTS

We demonstrated the distribution of protein expression and localization associated with the significantly increased androgen receptor, TLR2, and TLR4-mediated activation of interferon regulatory factor-7 (IRF-7) and NFκB signaling, cytokine production, and endometrial inflammation in PCOS patients compared to non-PCOS patients with and without endometrial hyperplasia. In vitro experiments showed that 5-dihydrotestosterone (DHT) enhanced androgen receptor, TLR4, IRF-7, and p-NFκB p65 protein expression along with increased interferon α (IFNα) and IFNɣ abundance. The effects of DHT on IRF-7, p-NFκB p65, and IFN abundance were abolished by flutamide, an antiandrogen. Although 17β-estradiol (E2) decreased p-IRF-7 expression with little effect on TLR-mediated IRF7 and NFκB signaling or on cytokine protein levels, exposure to metformin alone or in combination with E2 suppressed interleukin-1 receptor-associated kinase 4 (IRAK4), p-IRF-7, IRF-7, IκB kinase α (IKKα), p-NFκB p65, IFNɣ, and tumor necrosis factor α protein expression.

CONCLUSION

Cytokine synthesis and increased endometrial inflammation in PCOS patients are coupled to androgen-induced TLR4/IRF-7/NFκB signaling, which is inhibited by metformin treatment.

Immunotherapy Targeting Myeloid-Derived Suppressor Cells (MDSCs) in Tumor Microenvironment

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells that accumulate in tumor-bearing hosts to reduce T cells activity and promote tumor immune escape in the tumor microenvironment (TME). The immune system in the TME can be stimulated to elicit an anti-tumor immune response through immunotherapy. The main theory of immunotherapy resides on the plasticity of the immune system and its capacity to be re-educated into a potent anti-tumor response. Thus, MDSCs within the TME became one of the major targets to improve the efficacy of tumor immunotherapy, and therapeutic strategies for tumor MDSCs were developed in the last few years. In the article, we analyzed the function of tumor MDSCs and the regulatory mechanisms of agents targeting MDSCs in tumor immunotherapy, and reviewed their therapeutic effects in MDSCs within the TME. Those data focused on discussing how to promote the differentiation and maturation of MDSCs, reduce the accumulation and expansion of MDSCs, and inhibit the function, migration and recruitment of MDSCs, further preventing the growth, invasion and metastasis of tumor. Those investigations may provide new directions for cancer therapy.

Role of gut microbiome in regulating the effectiveness of metformin in reducing colorectal cancer in type 2 diabetes

The prevalence of colorectal cancer (CRC) and type 2 diabetes mellitus (T2DM) is increasing globally. It is rarely noticed that the incidence of CRC is higher in patients with T2DM. What needs to be mentioned is that metformin, a commonly used clinical drug for T2DM, attracts scholars’ attention because of its benefits in lowering the risk of developing CRC. Hence, we try to find the common grounds of initiation of T2DM and CRC and the reason why metformin reduces the risk of CRC in patients with T2DM. We noticed consistent changes of gut microbiota, such as elevated Bacteroides, Prevotella and Bifidobacterium and depressed Firmicutes and Lactobacillus. Furthermore, many studies in recent years have proved that the efficacy of metformin, such as improving blood glucose, depends on the gut microbiota. Coincidentally, the progression of CRC is inseparable from the contributions of gut microbiota. Therefore, we first proposed the concept of the metformin-gut microbiota–CRC (in T2DM) axis to explain the effect of metformin in reducing CRC in patients with T2DM. In this review, we elaborated the new concept and its potential clinical application value.

Short-term Effects of Metformin on Cardiac and Peripheral Blood Cells Following Cecal Ligation and Puncture-induced Sepsis

AIM OF THE STUDY

Sepsis has well-documented inflammatory effects on cardiovascular and blood cells. This study is designed to investigate potential anti-inflammatory effects of metformin on cardiac and blood cells 12 and 24 h following cecal ligation and puncture (CLP)-induced sepsis.

METHODS

For the purpose of this study, 36 male Wistar rats were divided into six groups: two groups underwent CLP, two groups underwent CLP and received metformin, and two groups only received sham operations. 12 h later, 18 rats (half of rats in each of the three aforementioned groups) were sacrificed and cardiac and blood cells were harvested. Subsequently, 12 h later, the rest of the rats were euthanatized. In all harvested blood and cardiac cells, oxidative stress indicators, antioxidant properties, count of blood cells, neutrophil infiltration, percentage of weight loss and pathological assessment were conducted.

RESULTS

In our experiment, metformin elevated antioxidant levels, improved function of blood cells and percentage of weight loss. Moreover, in the groups which received metformin, oxidative stress and neutrophil infiltration markers were decreased significantly. Moreover, pathological investigations of cardiac cell injury were reduced in the metformin group.

CONCLUSIONS

Our findings suggest that in CLP induced sepsis model, metformin can improve the function of blood and cardiac cells through alleviating inflammation, improvement of anti-inflammation properties, and enhancement of blood profile, and all these effects are more pronounced after 24 h in comparison with 12 h after induction of sepsis.

Anti-inflammatory effects of vinpocetine in LPS-stimulated microglia via activation of AMPK

Microglia are the resident immune cells in the central nervous system (CNS), which play important roles in the repair of neuroinflammatory injury. The present study investigated the anti-neuroinflammatory effects of vinpocetine induced by lipopolysaccharide (LPS) in BV2 microglia. BV2 microglia were pretreated with vinpocetine, and then stimulated with LPS (100 ng/mL). The cytotoxicity of BV2 microglia was assessed by MTT assay. The expression levels of nitrite oxide were measured by Griess assay. Proinflammatory cytokines and mediators were determined by Western blot, ELISA, or quantitative real-time PCR. Vinpocetine significantly decreased the generation of nitric oxide-inducible nitric oxide synthase (iNOS), cyclooxygenase- (COX-) 2 in a dose-dependent manner. In addition, vinpocetine decreased the production of pro-inflammatory cytokines such as tumor necrosis factor alpha (TNF-α), interleukin (IL)-6 and IL-1β. Furthermore, it was observed that phosphorylation levels of AMPK (Thr-172) decreased in LPS-stimulated BV2 microglia. Vinpocetine treatment increased AMPK phosphorylation in LPS-stimulated BV2 microglia. AMPK inhibition by siRNA blocked the anti-inflammatory effects of vinpocetine induced by LPS in BV2 microglia. The overall results demonstrate that vinpocetine has anti-inflammatory effects on LPS-stimulated BV2 microglia via inducing phosphorylation of AMPK, suggesting that vinpocetine is a potential therapeutic agent in neuroinflammatory injury.

Metformin reduces saturated fatty acid-induced lipid accumulation and inflammatory response by restoration of autophagic flux in endothelial cells

Autophagy, an integral part of the waste recycling process, plays an important role in cellular physiology and pathophysiology. Impaired autophagic flux causes ectopic lipid deposition, which is defined as the accumulation of lipids in non-adipose tissue. Ectopic lipid accumulation is observed in patients with cardiometabolic syndrome, including obesity, diabetes, insulin resistance, and cardiovascular complications. Metformin is the first line of treatment for type 2 diabetes, and one of the underlying mechanisms for the anti-diabetic effect of metformin is mediated by the stimulation of AMP-activated protein kinase (AMPK). Because the activation of AMPK is crucial for the initiation of autophagy, we hypothesize that metformin reduces the accumulation of lipid droplets by increasing autophagic flux in vascular endothelial cells. Incubation of vascular endothelial cells with saturated fatty acid (SFA) increased the accumulation of lipid droplets and impaired autophagic flux. We observed that the accumulation of lipid droplets was reduced, and the autophagic flux was enhanced by treatment with metformin. The knock-down of AMPKα by using siRNA blunted the effect of metformin. Furthermore, treatment with SFA or inhibition of autophagy increased leukocyte adhesion, whereas treatment with metformin decreased the SFA-induced leukocyte adhesion. The results suggest a novel mechanism by which metformin protects vascular endothelium from SFA-induced ectopic lipid accumulation and pro-inflammatory responses. In conclusion, improving autophagic flux may be a therapeutic strategy to protect endothelial function from dyslipidemia and diabetic complications.

Metformin Had Potential to Increase Endocan Levels in STZ-Induced Diabetic Mice

Background: Type 2 diabetes mellitus is a chronic metabolic disorder with prominent vascular injuries. In this condition, the levels of multiple pro- and anti-angiogenic factors have been shown to change. This study aimed to investigate the possible effect of metformin on pro-angiogenic factor, endocan levels, via the modulation of p-AMPK/AMPK axis in diabetic mice. Methods: Mice were randomly assigned to one of 4 groups (n=6): Control (normal saline) and the diabetic group was injected streptozotocin and two groups were given 50 and 100 mg/kg metformin orally, once daily for two weeks after diabetes induction. Endocan protein levels were detected in the liver and kidneys by ELISA and immunofluorescence analysis. Phosphorylation of AMPK was assessed using western blotting. Histological examination was performed to follow the metformin effect on Von Willebrand factor expression and diabetes-related pathologies. Results: ELISA assay showed an elevated levels of endocan in the renal and hepatic tissues of diabetic mice following treatment with metformin (p<0.05). Immunofluorescence and immunohistochemistry examination of kidneys showed that the increase of endocan protein coincided with the promotion of vWF factors in mice treated with metformin (p<0.05). We did not find endocan factor in hepatic tissue of diabetic mice pre- and post-treatment with metformin. Western blotting confirmed the phosphorylation of AMPK by metformin in kidneys (p<0.05), but these changes did not reach statistically significant levels in hepatic tissues (p>0.05). Conclusion: Metformin could change the endocan levels during diabetic condition possibly by the modulation of p-AMPK/AMPK axis.

The Metabolic Basis of Immune Dysfunction Following Sepsis and Trauma

Critically ill, severely injured and high-risk surgical patients are vulnerable to secondary infections during hospitalization and after hospital discharge. Studies show that the mitochondrial function and oxidative metabolism of monocytes and macrophages are impaired during sepsis. Alternatively, treatment with microbe-derived ligands, such as monophosphoryl lipid A (MPLA), peptidoglycan, or β-glucan, that interact with toll-like receptors and other pattern recognition receptors on leukocytes induces a state of innate immune memory that confers broad-spectrum resistance to infection with common hospital-acquired pathogens. Priming of macrophages with MPLA, CPG oligodeoxynucleotides (CpG ODN), or β-glucan induces a macrophage metabolic phenotype characterized by mitochondrial biogenesis and increased oxidative metabolism in parallel with increased glycolysis, cell size and granularity, augmented phagocytosis, heightened respiratory burst functions, and more effective killing of microbes. The mitochondrion is a bioenergetic organelle that not only contributes to energy supply, biosynthesis, and cellular redox functions but serves as a platform for regulating innate immunological functions such as production of reactive oxygen species (ROS) and regulatory intermediates. This review will define current knowledge of leukocyte metabolic dysfunction during and after sepsis and trauma. We will further discuss therapeutic strategies that target leukocyte mitochondrial function and might have value in preventing or reversing sepsis- and trauma-induced immune dysfunction.

A Review on The Protective Effects of Metformin in Sepsis-Induced Organ Failure

Despite advances in sepsis management, it remains a major intensive-care-unit (ICU) concern. From new prospective, positive effects of metformin, such as anti-oxidant and anti-inflammatory properties are considered potentially beneficial properties for management of septic patients. This article reviewed the potential ameliorative effects of metformin in sepsis-induced organ failure. Information were retrieved from PubMed, Scopus, Embase, and Google Scholar. Multi-organ damage, oxidative stress, inflammatory cytokine stimulation, and altered circulation are hallmarks of sepsis. Metformin exerts its effect via adenosine monophosphate-activated protein kinase (AMPK) activation. It improves sepsis-induced organ failure by inhibiting the production of reactive oxygen species (ROS) and pro-inflammatory cytokines, preventing the activation of transcription factors related to inflammation, decreasing neutrophil accumulation/infiltration, and also maintaining mitochondrial membrane potential. Studies reported the safety of metformin therapeutic doses, with no evidence of lactic acidosis, in septic patients.

Anti-inflammatory Property of AMP-activated Protein Kinase

BACKGROUND

One of the many debated topics in inflammation research is whether this scenario is really an accelerated form of human wound healing and immunityboosting or a push towards autoimmune diseases. The answer requires a better understanding of the normal inflammatory process, including the molecular pathology underlying the possible outcomes. Exciting recent investigations regarding severe human inflammatory disorders and autoimmune conditions have implicated molecular changes that are also linked to normal immunity, such as triggering factors, switching on and off, the influence of other diseases and faulty stem cell homeostasis, in disease progression and development.

METHODS

We gathered around and collected recent online researches on immunity, inflammation, inflammatory disorders and AMPK. We basically searched PubMed, Scopus and Google Scholar to assemble the studies which were published since 2010.

RESULTS

Our findings suggested that inflammation and related disorders are on the verge and interfere in the treatment of other diseases. AMPK serves as a key component that prevents various kinds of inflammatory signaling. In addition, our table and hypothetical figures may open a new door in inflammation research, which could be a greater therapeutic target for controlling diabetes, obesity, insulin resistance and preventing autoimmune diseases.

CONCLUSION

The relationship between immunity and inflammation becomes easily apparent. Yet, the essence of inflammation turns out to be so startling that the theory may not be instantly established and many possible arguments are raised for its clearance. However, this study might be able to reveal some possible approaches where AMPK can reduce or prevent inflammatory disorders.

Alisol B 23-Acetate Ameliorates Lipopolysaccharide-Induced Cardiac Dysfunction by Suppressing Toll-Like Receptor 4 (TLR4)/NADPH Oxidase 2 (NOX2) Signaling Pathway

Background

Cardiac dysfunction during endotoxemia is a major cause of cardiovascular disease with high morbidity and mortality. Alisol B 23-acetate (AB23A) is a triterpenoid extracted from the Rhizoma Alismatis, a kind of traditional Chinese medicine, exhibits anti-inflammatory activity on endotoxemia. This investigation aimed to uncover the protective effects of AB23A against sepsis-induced cardiac dysfunction.

Material/Methods

Adult male C57BL/6 mice received lipopolysaccharide (LPS) (20 mg/kg intravenous) stimulation, with or without pre-treatment of AB23A (10 mg/kg, 20 mg/kg, or 40 mg/kg). Histopathological staining and cardiac function were performed 4 hours after LPS stimulation. Then the levels of interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α were monitored with enzyme-linked immunosorbent assay (ELISA). In addition, H9C2 cells were treated with LPS (5 μg/mL) with or without pre-treated with AB23A (0.1 μM, 1 μM, or 10 μM), and the production of reactive oxygen species (ROS) was detected by DCFH-DA combined with flow cytometry. The expression of Toll-like receptor 4 (TLR4), NADPH oxidase 2 (NOX2), NOX4, P38, p-P38, extracellular-signal-regulated kinase (ERK), and p-ERK were assessed by western blotting.

Results

AB23A improved the survival rate and ameliorated myocardial injury, decreased inflammatory infiltration and the level of IL-6, IL-1β, and TNF-α in the LPS-stimulated mouse model. Moreover, AB23A inhibited the ROS production in LPS-treated H9C2 cells. In addition, AB23A suppressed the levels of TLR4 and NOX2 as well as the activation levels of P38 and ERK both in vivo and in vitro.

Conclusions

AB23A reduced LPS-induced myocardial dysfunction by inhibiting inflammation and ROS production through the TLR4/NOX2 pathway.

The AMPK system of salmonid fishes was expanded through genome duplication and is regulated by growth and immune status in muscle

5′adenosine monophosphate-activated protein kinase (AMPK) is a master regulator of energy homeostasis in eukaryotes. This study identified expansions in the AMPK-α, -β and -γ families of salmonid fishes due to a history of genome duplication events, including five novel salmonid-specific AMPK subunit gene paralogue pairs. We tested the hypothesis that the expanded AMPK gene system of salmonids is transcriptionally regulated by growth and immunological status. As a model, we studied immune-stimulated coho salmon (Oncorhynchus kisutch) from three experiment groups sharing the same genetic background, but showing highly-divergent growth rates and nutritional status. Specifically, we compared wild-type and GH-transgenic fish, the latter achieving either enhanced or wild-type growth rate via ration manipulation. Transcript levels for the fifteen unique salmonid AMPK subunit genes were quantified in skeletal muscle after stimulation with bacterial or viral mimics to alter immune status. These analyses revealed a constitutive up-regulation of several AMPK-α and -γ subunit-encoding genes in GH-transgenic fish achieving accelerated growth. Further, immune stimulation caused a decrease in the expression of several AMPK subunit-encoding genes in GH-transgenic fish specifically. The dynamic expression responses observed suggest a role for the AMPK system in balancing energetic investment into muscle growth according to immunological status in salmonid fishes.

AMPK activation inhibits the functions of myeloid-derived suppressor cells (MDSC): impact on cancer and aging

AMP-activated protein kinase (AMPK) has a crucial role not only in the regulation of tissue energy metabolism but it can also control immune responses through its cooperation with immune signaling pathways, thus affecting immunometabolism and the functions of immune cells. It is known that AMPK signaling inhibits the activity of the NF-κB system and thus suppresses pro-inflammatory responses. Interestingly, AMPK activation can inhibit several major immune signaling pathways, e.g., the JAK-STAT, NF-κB, C/EBPβ, CHOP, and HIF-1α pathways, which induce the expansion and activation of myeloid-derived suppressor cells (MDSC). MDSCs induce an immunosuppressive microenvironment in tumors and thus allow the escape of tumor cells from immune surveillance. Chronic inflammation has a key role in the expansion and activation of MDSCs in both tumors and inflammatory disorders. The numbers of MDSCs also significantly increase during the aging process concurrently with the immunosenescence associated with chronic low-grade inflammation. Increased fatty acid oxidation and lactate produced by aerobic glycolysis are important immunometabolic enhancers of MDSC functions. However, it seems that AMPK signaling regulates the functions of MDSCs in a context-dependent manner. Currently, the activators of AMPK signaling are promising drug candidates for cancer therapy and possibly for the extension of healthspan and lifespan. We will describe in detail the AMPK-mediated regulation of the signaling pathways controlling the expansion and activation of immunosuppressive MDSCs. We will propose that the beneficial effects mediated by AMPK activation, e.g., in cancers and the aging process, could be induced by the inhibition of MDSC functions.

Ginsenoside Rg1 Ameliorates Palmitic Acid-Induced Hepatic Steatosis and Inflammation in HepG2 Cells via the AMPK/NF-κB Pathway

Nonalcoholic fatty liver disease (NAFLD) is one of the common diseases in the world, and it can progress from simple lipid accumulation to sustained inflammation. The present study was designed to investigate the effects and underlying mechanisms of ginsenoside Rg1 (G-Rg1) treatment on NAFLD in vitro. HepG2 cells were treated with palmitic acid (PA) to induce steatosis and inflammation and then successively incubated with G-Rg1. Lipids accumulation was analyzed by Oil Red O staining and intracellular triglyceride (TG) quantification. Inflammatory conditions were examined by quantifying the levels of cell supernatant alanine transaminase/aspartate aminotransferase (ALT/AST) and secretory proinflammatory cytokines, including IL-1β, IL-6, and TNF-α in the cell supernatants. Quantitative RT-PCR and western blotting were used to measure the expressions of genes and proteins associated with lipogenic synthesis and inflammation, including AMP-activated protein kinase (AMPK) and nuclear factor-kappa B (NF-κB) pathways. HepG2 cells were pretreated with an AMPK inhibitor; then, Oil Red O staining and TG quantification were performed to study the lipid deposition. Phospho-AMPK (Thr172) (p-AMPK) and phospho-acetyl-CoA carboxylase (Ser79) (p-ACCα) were quantified by immunoblotting. Immunofluorescence was performed to demonstrate the nuclear translocation of NF-κB P65. The present study showed that PA markedly increased the intracellular lipid droplets accumulation and TG levels, but decreased AMPK phosphorylation and the expressions of its downstream lipogenic genes. However, G-Rg1 alleviated hepatic steatosis and reduced the intracellular TG content; these changes were accompanied by the activation of the AMPK pathway. In addition, blocking AMPK by using the AMPK inhibitor markedly abolished the G-Rg1-mediated protection against PA-induced lipid deposition in HepG2 cells. Furthermore, G-Rg1 reduced the ALT/AST levels and proinflammatory cytokines release, which were all enhanced by PA. These effects were correlated with the inactivation of the NF-κB pathway and translocation of P65 from the cytoplasm to the nucleus. Overall, these results suggest that G-Rg1 effectively ameliorates hepatic steatosis and inflammation, which might be associated with the AMPK/NF-κB pathway.

Isoquercitrin Attenuated Cardiac Dysfunction Via AMPKα-Dependent Pathways in LPS-Treated Mice

SCOPE

Isoquercitrin (IQC) has been reported to play a protective role in many pathological conditions. Here, the effects of IQC on lipopolysaccharide (LPS)-induced cardiac dysfunction are investigated, exploring its potential molecular mechanisms.

METHODS AND RESULTS

C57BL/6 mice or H9c2 cardiomyoblasts are subjected to LPS challenge for 12 h. Pretreatment with IQC attenuates LPS-induced cardiac dysfunction. IQC remarkably reduces LPS-mediated inflammatory responses by inhibiting the mRNA levels of TNF-α, IL6, and MCP1 as well as the protein levels of p-IKKβ, p-IκBα, and p-p65 in vivo and in vitro. Interestingly, IQC administration also improves energy deficiencies caused by LPS, manifesting as significant increases in cardiac and cellular ATP levels. Furthermore, ATP levels increase due to the upregulation of PGC1β and PPAR-α, which enhances fatty acid oxidation in vivo and in vitro. However, the protective roles of IQC against LPS-mediated increased inflammatory responses and decreased acid fatty oxidation are partially blunted by inhibiting AMPKα in vitro, and suppressing AMPKα partially blocks the increased cardiac function elicited by IQC in LPS-treated mice.

CONCLUSION

IQC attenuates LPS-induced cardiac dysfunction by inhibiting inflammatory responses and by enhancing fatty acid oxidation, partially by activating AMPKα. IQC might be a potential drug for sepsis-induced cardiac dysfunction.

Metformin Mediates Protection against Legionella Pneumonia through Activation of AMPK and Mitochondrial Reactive Oxygen Species

In Legionella pneumophila infection, macrophages play a critical role in the host defense response. Metformin, an oral drug for type 2 diabetes, is attracting attention as a new supportive therapy against a variety of diseases, such as cancer and infectious diseases. The novel mechanisms for metformin actions include modulation of the effector functions of macrophages and other host immune cells. In this study, we have examined the effects of metformin on L. pneumophila infection in vitro and in vivo. Metformin treatment suppressed growth of L. pneumophila in a time- and concentration-dependent fashion in bone marrow-derived macrophages, RAW cells (mouse), and U937 cells (human). Metformin induced phosphorylation of AMP-activated protein kinase (AMPK) in L. pneumophila-infected bone marrow-derived macrophages, and the AMPK inhibitor Compound C negated metformin-mediated growth suppression. Also, metformin induced mitochondrial reactive oxygen species but not phagosomal NADPH oxidase-derived reactive oxygen species. Metformin-mediated growth suppression was mitigated in the presence of the reactive oxygen species scavenger glutathione. In a murine L. pneumophila pneumonia model, metformin treatment improved survival of mice, which was associated with a significant reduction in bacterial number in the lung. Similar to in vitro observations, induction of AMPK phosphorylation and mitochondrial ROS was demonstrated in the infected lungs of mice treated with metformin. Finally, glutathione treatment abolished metformin effects on lung bacterial clearance. Collectively, these data suggest that metformin promotes mitochondrial ROS production and AMPK signaling and enhances the bactericidal activity of macrophages, which may contribute to improved survival in L. pneumophila pneumonia.

AMPK and cardiac remodelling

Cardiac remodelling is generally accepted as a critical process in the progression of heart failure. Myocyte hypertrophy, inflammatory responses and cardiac fibrosis are the main pathological changes associated with cardiac remodelling. AMP-activated protein kinase (AMPK) is known as an energy sensor and a regulator of cardiac metabolism under normal and ischaemic conditions. Additionally, AMPK has been shown to play roles in cardiac remodelling extending well beyond metabolic regulation. In this review, we discuss the currently defined roles of AMPK in cardiac remodelling and summarize the effects of AMPK on cardiac hypertrophy, inflammatory responses and fibrosis and the molecular mechanisms underlying these effects. In addition, we discuss some pharmacological activators of AMPK that are promising treatments for cardiac remodelling.

Ablation of toll-like receptor 4 mitigates cardiac mitochondrial dysfunction in hyperhomocysteinemia

Hyperhomocysteinemia (HHcy) is a risk factor for adverse cardiovascular events; however, the mechanism for development of this disease is still unknown. Toll-like receptor 4 (TRL4) is a molecule involved in the immune response pathway and is quickly becoming a receptor of interest in the field of hypertension. In this study, we hypothesized that ablation of TLR4 mitigates cardiac mitochondrial dysfunction in a model of HHcy. Five strains of mice (C57BL/6J, CBS+/−, C3H, CBS+/−/C3H, and C3H/HeOuJ) 10–12 weeks old were utilized. We found that HHcy causes heart hypertrophy and promotes oxidative stress while mice with HHcy and inactivated TLR4 showed significant improvement in examined parameters. A dominance of endothelial cell mitochondrial fission over mitochondrial fusion in HHcy and oxidative stress was observed, which may explain the endothelial cell loss and dysfunction that contributes to inward cardiac remodeling.

Glutamine ameliorates lipopolysaccharide-induced cardiac dysfunction by regulating the toll-like receptor 4/mitogen-activated protein kinase/nuclear factor-kB signaling pathway

The inflammatory response of sepsis induced by lipopolysaccharide (LPS) may result in irreversible cardiac dysfunction. Glutamine (GLN) has a multitude of pharmacological effects, including anti-inflammatory abilities. Previous studies have reported that GLN attenuated LPS-induced acute lung injury and intestinal mucosal injury. The present study investigated whether GLN exerts potential protective effects on LPS-induced cardiac dysfunction. Male Sprague-Dawley rats were divided into three groups (15 rats per group), including the control (saline-treated), LPS and LPS+GLN groups. Pretreatment with 1 g/kg GLN was provided via gavage for 5 days in the LPS+GLN group, while the control and LPS groups received the same volume of normal saline. On day 6, a cardiac dysfunction model was induced by administration of LPS (10 mg/kg). After 24 h, the cardiac functions of the rats that survived were detected by echocardiography and catheter-based measurements. The serum levels of tumor necrosis factor α (TNF-α), interleukin (IL)-1β and IL-6 were detected by enzyme-linked immunosorbent assay, while the mRNA levels of toll-like receptor (TLR)4, TNF-α, IL-1β and IL-6 were examined by reverse transcription-quantitative polymerase chain reaction. The protein expression of TLR4, mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) were also determined by western blot analysis. The results of echocardiography and catheter-based measurements revealed that GLN treatment attenuated cardiac dysfunction. GLN treatment also attenuated the serum and mRNA levels of the pro-inflammatory cytokines. In addition, the protein levels of TLR4, phosphorylated (p-)extracellular signal-regulated kinase, p-c-Jun N-terminal kinase and p-P38 were reduced upon GLN pretreatment. Furthermore, GLN pretreatment resulted in decreased activation of the NF-κB signaling pathway. In conclusion, GLN has a potential therapeutic effect in the protection against cardiac dysfunction mediated by sepsis through regulating the TLR4/MAPK/NF-κB signaling pathway.

Aged garlic extract suppresses inflammation in apolipoprotein E-knockout mice

SCOPE

Chronic inflammation plays a major role in the formation and progression of atherosclerotic plaques. To clarify the mode of action of aged garlic extract (AGE) to retard atherosclerosis, we investigated whether AGE suppresses the inflammation in apolipoprotein E-knockout (ApoE-KO) mice.

METHODS AND RESULTS

ApoE-KO mice were fed standard diet with or without 3% AGE for 12 wk. AGE feeding inhibited the progression of atherosclerotic lesion by 27% and reduced the level of C-reactive protein (CRP) and thromboxane B₂ (TXB₂ ), a marker of platelet activation, in serum by 39 and 33%, respectively, compared to ApoE-KO mice without AGE treatment. AGE treatment also decreased the level of tumor necrosis factor alpha (TNF-α), a major stimulus inducing CRP production, in the liver by 35%. AGE decreased the level of interleukin-1 receptor-associated kinase 4 (IRAK4) by 60% and almost doubled the level of phospho-AMP-activated protein kinase (p-AMPK) in the liver.

CONCLUSION

The anti-atherosclerotic effect of AGE involves the suppression of inflammation by reducing the serum level of CRP and TXB₂ , and the protein level of TNF-α and IRAK4, and increasing AMPK activity in liver.

High doses of baicalin induces kidney injury and fibrosis through regulating TGF-β/Smad signaling pathway

Baicalin is a major flavonoid compound purified from Scutellariae radix, which has been described as an herb in the Chinese Pharmacopoeia. Previous studies have suggested baicalin possessed extensive anti-inflammatory, anti-cancer, anti-viral properties. However, up to known, there have been no reports of safety and toxicity in the rats following oral administration of baicalin. In this present study, we showed the first evidence that treatment of baicalin (400, 800 and 1600mg/kg/day) induced significantly kidney injury and fibrosis. The collagen synthesis and fibrosis-related protein expression were increased in the kidney of Sprague-Dawley (SD) rats after treatment with high doses of baicalin. We further investigated the potential molecular mechanism of baicalin-mediated renal fibrosis and revealed that baicalin activated the transforming growth factor-β (TGF-β)/Smad signaling pathway in a dose-dependent manner. Moreover, we also observed that baicalin induced Smad3 interaction with transcriptional coactivator p300 accompanying with increment of Smad3 acetylation. Our results may contribute to better understanding of the future pharmacological and toxicological studies of Scutellaria baicalensis Georgi and its active compounds on the human disease.