Hepatocyte growth factor is a novel stimulator of glucose uptake and metabolism in skeletal muscle cells

Pathway and Network Analyses Identify Growth Factor Signaling and MMP9 as Potential Mediators of Mitochondrial Dysfunction in Severe COVID-19

Patients with preexisting metabolic disorders such as diabetes are at a higher risk of developing severe coronavirus disease 2019 (COVID-19). Mitochondrion, the very organelle that controls cellular metabolism, holds the key to understanding disease progression at the cellular level. Our current study aimed to understand how cellular metabolism contributes to COVID-19 outcomes. Metacore pathway enrichment analyses on differentially expressed genes (encoded by both mitochondrial and nuclear deoxyribonucleic acid (DNA)) involved in cellular metabolism, regulation of mitochondrial respiration and organization, and apoptosis, was performed on RNA sequencing (RNASeq) data from blood samples collected from healthy controls and patients with mild/moderate or severe COVID-19. Genes from the enriched pathways were analyzed by network analysis to uncover interactions among them and up- or downstream genes within each pathway. Compared to the mild/moderate COVID-19, the upregulation of a myriad of growth factor and cell cycle signaling pathways, with concomitant downregulation of interferon signaling pathways, were observed in the severe group. Matrix metallopeptidase 9 (MMP9) was found in five of the top 10 upregulated pathways, indicating its potential as therapeutic target against COVID-19. In summary, our data demonstrates aberrant activation of endocrine signaling in severe COVID-19, and its implication in immune and metabolic dysfunction.

The Efficacy of HGF/VEGF Gene Therapy for Limb Ischemia in Mice with Impaired Glucose Tolerance: Shift from Angiogenesis to Axonal Growth and Oxidative Potential in Skeletal Muscle

BACKGROUND

Combined non-viral gene therapy (GT) of ischemia and cardiovascular disease is a promising tool for potential clinical translation. In previous studies our group has developed combined gene therapy by vascular endothelial growth factor 165 (VEGF165) + hepatocyte growth factor (HGF). Our recent works have demonstrated that a bicistronic pDNA that carries both human HGF and VEGF165 coding sequences has a potential for clinical application in peripheral artery disease (PAD). The present study aimed to test HGF/VEGF combined plasmid efficacy in ischemic skeletal muscle comorbid with predominant complications of PAD-impaired glucose tolerance and type 2 diabetes mellitus (T2DM).

METHODS

Male C57BL mice were housed on low-fat (LFD) or high-fat diet (HFD) for 10 weeks and metabolic parameters including FBG level, ITT, and GTT were evaluated. Hindlimb ischemia induction and plasmid administration were performed at 10 weeks with 3 weeks for post-surgical follow-up. Limb blood flow was assessed by laser Doppler scanning at 7, 14, and 21 days after ischemia induction. The necrotic area of m.tibialis anterior, macrophage infiltration, angio- and neuritogenesis were evaluated in tissue sections. The mitochondrial status of skeletal muscle (total mitochondria content, ETC proteins content) was assessed by Western blotting of muscle lysates.

RESULTS

At 10 weeks, the HFD group demonstrated impaired glucose tolerance in comparison with the LFD group. HGF/VEGF plasmid injection aggravated glucose intolerance in HFD conditions. Blood flow recovery was not changed by HGF/VEGF plasmid injection either in LFD or HFD conditions. GT in LFD, but not in HFD conditions, enlarged the necrotic area and CD68+ cells infiltration. However, HGF/VEGF plasmid enhanced neuritogenesis and enlarged NF200+ area on muscle sections. In HFD conditions, HGF/VEGF plasmid injection significantly increased mitochondria content and ETC proteins content.

CONCLUSIONS

The current study demonstrated a significant role of dietary conditions in pre-clinical testing of non-viral GT drugs. HGF/VEGF combined plasmid demonstrated a novel aspect of potential participation in ischemic skeletal muscle regeneration, through regulation of innervation and bioenergetics of muscle. The obtained results made HGF/VEGF combined plasmid a very promising tool for PAD therapy in impaired glucose tolerance conditions.

The mechanism of action of a novel neuroprotective low molecular weight dextran sulphate: New platform therapy for neurodegenerative diseases like Amyotrophic Lateral Sclerosis

Background: Acute and chronic neurodegenerative diseases represent an immense socioeconomic burden that drives the need for new disease modifying drugs. Common pathogenic mechanisms in these diseases are evident, suggesting that a platform neuroprotective therapy may offer effective treatments. Here we present evidence for the mode of pharmacological action of a novel neuroprotective low molecular weight dextran sulphate drug called ILB^®. The working hypothesis was that ILB^® acts via the activation of heparin-binding growth factors (HBGF).

Methods: Pre-clinical and clinical (healthy people and patients with ALS) in vitro and in vivo studies evaluated the mode of action of ILB^®. In vitro binding studies, functional assays and gene expression analyses were followed by the assessment of the drug effects in an animal model of severe traumatic brain injury (sTBI) using gene expression studies followed by functional analysis. Clinical data, to assess the hypothesized mode of action, are also presented from early phase clinical trials.

Results: ILB^® lengthened APTT time, acted as a competitive inhibitor for HGF-Glypican-3 binding, effected pulse release of heparin-binding growth factors (HBGF) into the circulation and modulated growth factor signaling pathways. Gene expression analysis demonstrated substantial similarities in the functional dysregulation induced by sTBI and various human neurodegenerative conditions and supported a cascading effect of ILB^® on growth factor activation, followed by gene expression changes with profound beneficial effect on molecular and cellular functions affected by these diseases. The transcriptional signature of ILB^® relevant to cell survival, inflammation, glutamate signaling, metabolism and synaptogenesis, are consistent with the activation of neuroprotective growth factors as was the ability of ILB^® to elevate circulating levels of HGF in animal models and humans.

Conclusion: ILB^® releases, redistributes and modulates the bioactivity of HBGF that target disease compromised nervous tissues to initiate a cascade of transcriptional, metabolic and immunological effects that control glutamate toxicity, normalize tissue bioenergetics, and resolve inflammation to improve tissue function. This unique mechanism of action mobilizes and modulates naturally occurring tissue repair mechanisms to restore cellular homeostasis and function. The identified pharmacological impact of ILB^® supports the potential to treat various acute and chronic neurodegenerative disease, including sTBI and ALS.

Quantifying the inflammatory secretome of human intermuscular adipose tissue

Adipose tissue secretes an abundance of lipid and protein mediators, and this secretome is depot-specific, with local and systemic effects on metabolic regulation. Intermuscular adipose tissue (IMAT) accumulates within the skeletal muscle compartment in obesity, and is associated with insulin resistance and metabolic disease. While the human IMAT secretome decreases insulin sensitivity in vitro, its composition is entirely unknown. The current study was conducted to investigate the composition of the human IMAT secretome, compared to that of the subcutaneous (SAT) and visceral adipose tissue (VAT) depots. IMAT, SAT, and VAT explants from individuals with obesity were used to generate conditioned media. Proteomics analysis of conditioned media was performed using multiplex proximity extension assays, and eicosanoid analysis using liquid chromatography-tandem mass spectrometry. Compared to SAT and/or VAT, IMAT secreted significantly more cytokines (IL2, IL5, IL10, IL13, IL27, FGF23, IFNγ and CSF1) and chemokines (MCP1, IL8, CCL11, CCL20, CCL25 and CCL27). Adipokines hepatocyte growth factor and resistin were secreted significantly more by IMAT than SAT or VAT. IMAT secreted significantly more eicosanoids (PGE2, TXB2 , 5-HETE, and 12-HETE) compared to SAT and/or VAT. In the context of obesity, IMAT is a distinct adipose tissue with a highly immunogenic and inflammatory secretome, and given its proximity to skeletal muscle, may be critical to glucose regulation and insulin resistance.

Mesenchymal Stem Cells Promote IL-6 Secretion and Suppress the Gene Expression of Proinflammatory Cytokines in Contractile C2C12 Myotubes

Sarcopenia is not only a major cause of disability but also a risk factor for obesity and diabetes in elderly persons. Exercise is an effective method for improving the sarcopenic condition by inducing the secretion of interleukin (IL)-6, which has the capacities to both promote muscle hypertrophy and regulate lipid metabolism and glucose homeostasis, by skeletal muscle. We previously showed that mesenchymal stem cells (MSCs) promote IL-6 secretion by lipopolysaccharide-stimulated C2C12 mouse skeletal muscle myotubes via paracrine mechanisms. Therefore, in this study, we investigated the effect of paracrine actions of MSCs on IL-6 and proinflammatory cytokine expression in contractile C2C12 myotubes by applying electrical stimulation. IL-6 secretion by C2C12 myotubes was increased by electrical stimulation, and a more significant increase in IL-6 secretion was observed in electrically stimulated C2C12 myotubes cultured in conditioned medium from MSCs. The activation of nuclear factor-κB in C2C12 myotubes was also promoted by the combination of conditioned medium from MSCs and electrical stimulation. Moreover, the increases in tumor necrosis factor-α and IL-1β mRNA expression in C2C12 myotubes induced by electrical stimulation were suppressed by culture in conditioned medium from MSCs. The present findings suggest that MSCs transplantation or injection of their extracellular vesicles improve the therapeutic effect of exercise against sarcopenia without exacerbating inflammation.

A phase II open label clinical study of the safety, tolerability and efficacy of ILB® for Amyotrophic Lateral Sclerosis

Introduction

Amyotrophic lateral sclerosis (ALS) is an invariably lethal progressive disease, causing degeneration of neurons and muscle. No current treatment halts or reverses disease advance. This single arm, open label, clinical trial in patients with ALS investigated the safety and tolerability of a novel modified low molecular weight dextran sulphate (LMW-DS, named ILB^®) previously proven safe for use in healthy volunteers and shown to exert potent neurotrophic effects in pre-clinical studies. Secondary endpoints relate to efficacy and exploratory biomarkers.

Methods

Thirteen patients with ALS were treated with 5 weekly subcutaneous injections of ILB^®. Safety and efficacy outcome measures were recorded weekly during treatment and at regular intervals for a further 70 days. Functional and laboratory biomarkers were assessed before, during and after treatment.

Results

No deaths, serious adverse events or participant withdrawals occurred during or after ILB^® treatment and no significant drug-related changes in blood safety markers were evident, demonstrating safety and tolerability of the drug in this cohort of patients with ALS. The PK of ILB^® in patients with ALS was similar to that seen in healthy controls. The ILB^® injection elicited a transient elevation of plasma Hepatocyte Growth Factor, a neurotrophic and myogenic growth factor. Following the ILB^® injections patients reported increased vitality, decreased spasticity and increased mobility. The ALSFRS-R rating improved from 36.31 ± 6.66 to 38.77 ± 6.44 and the Norris rating also improved from 70.61 ± 13.91 to 77.85 ± 14.24 by Day 36. The improvement of functions was associated with a decrease in muscle atrophy biomarkers. These therapeutic benefits decreased 3–4 weeks after the last dosage.

Conclusions

This pilot clinical study demonstrates safety and tolerability of ILB^® in patients with ALS. The exploratory biomarker and functional measures must be cautiously interpreted but suggest clinical benefit and have a bearing on the mechanism of action of ILB^®. The results support the drug’s potential as the first disease modifying treatment for patients with ALS.

Trial registration

EudraCT 2017-005065-47.

Lack of Tgfbr1 and Acvr1b synergistically stimulates myofibre hypertrophy and accelerates muscle regeneration

In skeletal muscle, transforming growth factor-β (TGF-β) family growth factors, TGF-β1 and myostatin, are involved in atrophy and muscle wasting disorders. Simultaneous interference with their signalling pathways may improve muscle function; however, little is known about their individual and combined receptor signalling. Here, we show that inhibition of TGF-β signalling by simultaneous muscle-specific knockout of TGF-β type I receptors Tgfbr1 and Acvr1b in mice, induces substantial hypertrophy, while such effect does not occur by single receptor knockout. Hypertrophy is induced by increased phosphorylation of Akt and p70S6K and reduced E3 ligases expression, while myonuclear number remains unaltered. Combined knockout of both TGF-β type I receptors increases the number of satellite cells, macrophages and improves regeneration post cardiotoxin-induced injury by stimulating myogenic differentiation. Extra cellular matrix gene expression is exclusively elevated in muscle with combined receptor knockout. Tgfbr1 and Acvr1b are synergistically involved in regulation of myofibre size, regeneration, and collagen deposition.

Enhanced Wild-Type MET Receptor Levels in Mouse Hepatocytes Attenuates Insulin-Mediated Signaling

Compelling evidence points to the MET receptor tyrosine kinase as a key player during liver development and regeneration. Recently, a role of MET in the pathophysiology of insulin resistance and obesity is emerging. Herein, we aimed to determine whether MET regulates hepatic insulin sensitivity. To achieve this, mice in which the expression of wild-type MET in hepatocytes is slightly enhanced above endogenous levels (Alb-R26^Met mice) were analyzed to document glucose homeostasis, energy balance, and insulin signaling in hepatocytes. We found that Alb-R26^Met mice exhibited higher body weight and food intake when compared to R26^stopMet control mice. Metabolic analyses revealed that Alb-R26^Met mice presented age-related glucose and pyruvate intolerance in comparison to R26^stopMet controls. Additionally, in Alb-R26^Met mice, high MET levels decreased insulin-induced insulin receptor (IR) and AKT phosphorylation compared to control mice. These results were corroborated in vitro by analyzing IR and AKT phosphorylation in primary mouse hepatocytes from Alb-R26^Met and R26^stopMet mice upon insulin stimulation. Moreover, co-immunoprecipitation assays revealed MET-IR interaction under both basal and insulin stimulation conditions; this effect was enhanced in Alb-R26^Met hepatocytes. Altogether, our results indicate that enhanced MET levels alter hepatic glucose homeostasis, which can be an early event for subsequent liver pathologies.

Proteomic and phosphoproteomic analyses identify liver-related signaling in retinal pigment epithelial cells during EMT

Epithelial-mesenchymal transition (EMT) of the retinal pigment epithelium (RPE) is associated with several blinding retinal diseases. Using proteomics and phosphoproteomics studies of human induced pluripotent stem cell-derived RPE monolayers with induced EMT, we capture kinase/phosphatase signaling cascades 1 h and 12 h after induction to better understand the pathways mediating RPE EMT. Induction by co-treatment with transforming growth factor β and tumor necrosis factor alpha (TGNF) or enzymatic dissociation perturbs signaling in many of the same pathways, with striking similarity in the respective phosphoproteomes at 1 h. Liver hyperplasia and hepatocyte growth factor (HGF)-MET signaling exhibit the highest overall enrichment. We also observe that HGF and epidermal growth factor signaling, two cooperative pathways inhibited by EMT induction, regulate the RPE transcriptional profile.

HGF can reduce accumulation of inflammation and regulate glucose homeostasis in T2D mice

Hepatocyte growth factor (HGF) has been studied as a protective factor for the survival of islet β cells and regulatory glucose transport and metabolism in many studies. The addition of exogenous HGF to cells or mice is the most common way to study HGF, but the persistence and stability of the administered HGF are unclear. In this experiment, wild-type C57BL6 (WT) mice and HGF-overexpressing transgenic (HGF-Tg) mice were divided into a normal diet (ND) group and an HFD group. The HGF protein level in the liver, kidney, spleen, pancreas, and VAT of HGF-Tg-ND mice was upregulated compared to that of WT-ND mice, and it was also upregulated in HGF-Tg-HFD mice compared to that in WT-HFD mice. In the ND group, though the HGF-Tg-ND mice showed higher fasted blood glucose levels and larger integrated density (IOD) of glucagon-positive cells than WT-ND mice, we found that HGF-Tg-ND mice can still maintain normal glucose tolerance based on an intraperitoneal glucose tolerance test (IPGTT) and an intraperitoneal insulin tolerance test (IPITT). In the HFD group, the HGF-Tg-HFD mice showed insulin sensitivity in IPGTT and IPITT and had larger areas and higher IOD values of islet β cells and smaller areas and IOD values of islet α cells than the WT-HFD mice. HGF-Tg-HFD mice had lower level of serum insulin than WT-HFD mice. The HGF-Tg-HFD mice showed inhibited accumulation of CD4+ T cells, CD8+ T cells, Ly6G+ neutrophils, and F4/80+ macrophages in the blood and tissues and protected liver and kidney functions. Oil Red O-stained liver sections revealed that WT-HFD mice had larger areas and higher IOD values of Oil Red O-positive cells than HGF-Tg-HFD mice, and WT-HFD mice had higher score of NASH. PAS-stained kidney sections found WT-HFD has higher mesangial area/glomerular area × 100% than HGF-Tg-HFD mice. Comparative analyses demonstrated that HGF reduces the proportions of inflammatory cells in the blood and tissues, and protects liver and kidney tissues by regulating glucose homeostasis of type 2 diabetic mice.

HGF/c-Met Signalling in the Tumor Microenvironment

Recently, it has become clearer that tumor plasticity increases the chance that cancer cells could acquire new mechanisms to escape immune surveillance, become resistant to conventional drugs, and spread to distant sites.Effectively, tumor plasticity drives adaptive response of cancer cells to hypoxia and nutrient deprivation leading to stimulation of neoangionesis or tumor escape. Therefore, tumor plasticity is believed to be a great contributor in recurrence and metastatic dissemination of cancer cells. Importantly, it could be an Achilles' heel of cancer if we could identify molecular mechanisms dictating this phenotype.The reactivation of stem-like signalling pathways is considered a great determinant of tumor plasticity; in addition, a key role has been also attributed to tumor microenvironment (TME). Indeed, it has been proved that cancer cells interact with different cells in the surrounding extracellular matrix (ECM). Interestingly, well-established communication represents a potential allied in maintenance of a plastic phenotype in cancer cells supporting tumor growth and spread. An important signalling pathway mediating cancer cell-TME crosstalk is represented by the HGF/c-Met signalling.Here, we review the role of the HGF/c-Met signalling in tumor-stroma crosstalk focusing on novel findings underlying its role in tumor plasticity, immune escape, and development of adaptive mechanisms.

The tyrosine kinase inhibitor crizotinib influences blood glucose and mRNA expression of GLUT4 and PPARs in the heart of rats with experimental diabetes

Tyrosine kinases inhibitors (TKIs) may alter glycaemia and may be cardiotoxic with importance in the diabetic heart. We investigated the effect of multi-TKI crizotinib after short-term administration on metabolic modulators of the heart of diabetic rats. Experimental diabetes mellitus (DM) was induced by streptozotocin (STZ; 80 mg·kg^-1, i.p.), and controls (C) received vehicle. Three days after STZ, crizotinib (STZ+CRI; 25 mg·kg^-1 per day p.o.) or vehicle was administered for 7 days. Blood glucose, C-peptide, and glucagon were assessed in plasma samples. Receptor tyrosine kinases (RTKs), cardiac glucose transporters, and peroxisome proliferator-activated receptors (PPARs) were determined in rat left ventricle by RT-qPCR method. Crizotinib moderately reduced blood glucose (by 25%, P < 0.05) when compared to STZ rats. The drug did not affect levels of C-peptide, an indicator of insulin secretion, suggesting altered tissue glucose utilization. Crizotinib had no impact on cardiac RTKs. However, an mRNA downregulation of insulin-dependent glucose transporter Glut4 in the hearts of STZ rats was attenuated after crizotinib treatment. Moreover, crizotinib normalized Ppard and reduced Pparg mRNA expression in diabetic hearts. Crizotinib decreased blood glucose independently of insulin and glucagon. This could be related to changes in regulators of cardiac metabolism such as GLUT4 and PPARs.

Low Molecular Weight Dextran Sulfate (ILB®) Administration Restores Brain Energy Metabolism Following Severe Traumatic Brain Injury in the Rat

Traumatic brain injury (TBI) is the leading cause of death and disability in people less than 40 years of age in Western countries. Currently, there are no satisfying pharmacological treatments for TBI patients. In this study, we subjected rats to severe TBI (sTBI), testing the effects of a single subcutaneous administration, 30 min post-impact, of a new low molecular weight dextran sulfate, named ILB^®, at three different dose levels (1, 5, and 15 mg/kg body weight). A group of control sham-operated animals and one of untreated sTBI rats were used for comparison (each group n = 12). On day 2 or 7 post-sTBI animals were sacrificed and the simultaneous HPLC analysis of energy metabolites, N-acetylaspartate (NAA), oxidized and reduced nicotinic coenzymes, water-soluble antioxidants, and biomarkers of oxidative/nitrosative stress was carried out on deproteinized cerebral homogenates. Compared to untreated sTBI rats, ILB^® improved energy metabolism by increasing ATP, ATP/ adenosine diphosphate ratio (ATP/ADP ratio), and triphosphate nucleosides, dose-dependently increased NAA concentrations, protected nicotinic coenzyme levels and their oxidized over reduced ratios, prevented depletion of ascorbate and reduced glutathione (GSH), and decreased oxidative (malondialdehyde formation) and nitrosative stress (nitrite + nitrate production). Although needing further experiments, these data provide the first evidence that a single post-injury injection of a new low molecular weight dextran sulfate (ILB^®) has beneficial effects on sTBI metabolic damages. Due to the absence of adverse effects in humans, ILB^® represents a promising therapeutic agent for the treatment of sTBI patients.

Therapeutic Angiogenesis Using HGF Plasmid

Hepatocyte growth factor (HGF) is secreted from stromal and mesenchymal cells, and its receptor cMet is expressed on various types of cells such as smooth muscle cells, fibroblast, and endothelial cells. HGF stimulates epithelial and endothelial cell proliferation, motility, and morphogenesis in a paracrine and autocrine manner, organizing multistep of angiogenesis in many organs. In addition, HGF is recognized as a potent anti-inflammatory and anti-fibrotic growth factor, which has been proved in several animal studies, including neointimal hyperplasia and acute myocardial infarction model in rodent. Thus, as compared to other angiogenic growth factors, HGF exerts multiple effects on ischemic tissues, accompanied by the regression of tissue inflammation and fibrosis. These data suggest the therapeutic potential of the HGF for peripheral artery disease as it being accompanied with chronic tissue inflammation and fibrosis. In the present narrative review, the pleiotropic action of the HGF that differentiates it from other angiogenic growth factors is discussed first, and later, outcomes of the human clinical study with gene therapy are overviewed.

Regulation of Energy Metabolism by Receptor Tyrosine Kinase Ligands

Metabolic diseases, such as diabetes, obesity, and fatty liver disease, have now reached epidemic proportions. Receptor tyrosine kinases (RTKs) are a family of cell surface receptors responding to growth factors, hormones, and cytokines to mediate a diverse set of fundamental cellular and metabolic signaling pathways. These ligands signal by endocrine, paracrine, or autocrine means in peripheral organs and in the central nervous system to control cellular and tissue-specific metabolic processes. Interestingly, the expression of many RTKs and their ligands are controlled by changes in metabolic demand, for example, during starvation, feeding, or obesity. In addition, studies of RTKs and their ligands in regulating energy homeostasis have revealed unexpected diversity in the mechanisms of action and their specific metabolic functions. Our current understanding of the molecular, biochemical and genetic control of energy homeostasis by the endocrine RTK ligands insulin, FGF21 and FGF19 are now relatively well understood. In addition to these classical endocrine signals, non-endocrine ligands can govern local energy regulation, and the intriguing crosstalk between the RTK family and the TGFβ receptor family demonstrates a signaling network that diversifies metabolic process between tissues. Thus, there is a need to increase our molecular and mechanistic understanding of signal diversification of RTK actions in metabolic disease. Here we review the known and emerging molecular mechanisms of RTK signaling that regulate systemic glucose and lipid metabolism, as well as highlighting unexpected roles of non-classical RTK ligands that crosstalk with other receptor pathways.

The impact of maternal obesity in pregnancy on placental glucocorticoid and macronutrient transport and metabolism

Maternal obesity is the most common metabolic disturbance in pregnancy affecting >1 in 5 women in some countries. Babies born to obese women are heavier with more adiposity at birth, and are vulnerable to obesity and metabolic disease across the lifespan suggesting offspring health is 'programmed' by fetal exposure to an obese intra-uterine environment. The placenta plays a major role in dictating the impact of maternal health on prenatal development. Maternal obesity impacts the function of integral placental receptors and transporters for glucocorticoids and nutrients, key drivers of fetal growth, though mechanisms remain poorly understood. This review aims to summarise current knowledge in this area, and considers the impact of obesity on the epigenetic machinery of the placenta at this vital juncture in offspring development. Further research is required to advance understanding of these areas in the hope that the trans-generational cycle of obesity can be alleviated.

The Influence of Met Receptor Level on HGF-Induced Glycolytic Reprogramming in Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) is known to overexpress a variety of receptor tyrosine kinases, such as the HGF receptor Met. Like other malignancies, HNSCC involves a mutual interaction between the tumor cells and surrounding tissues and cells. We hypothesized that activation of HGF/Met signaling in HNSCC influences glucose metabolism and therefore substantially changes the tumor microenvironment. To determine the effect of HGF, we submitted three established HNSCC cell lines to mRNA sequencing. Dynamic changes in glucose metabolism were measured in real time by an extracellular flux analyzer. As expected, the cell lines exhibited different levels of Met and responded differently to HGF stimulation. As confirmed by mRNA sequencing, the level of Met expression was associated with the number of upregulated HGF-dependent genes. Overall, Met stimulation by HGF leads to increased glycolysis, presumably mediated by higher expression of three key enzymes of glycolysis. These effects appear to be stronger in Met^high-expressing HNSCC cells. Collectively, our data support the hypothesized role of HGF/Met signaling in metabolic reprogramming of HNSCC.

Hepatocyte growth factor alleviates hepatic insulin resistance and lipid accumulation in high-fat diet-fed mice

AIMS/INTRODUCTION

Type 2 diabetes mellitus is frequently accompanied by fatty liver disease. Lipid accumulation within the liver is considered as one of the risk factors for insulin resistance. Hepatocyte growth factor (HGF) is used to treat liver dysfunction; however, the effect and mechanism of HGF on hepatic lipid metabolism are still not fully understood.

MATERIALS AND METHODS

Male C57BL/6 mice were induced with a high-fat diet for 12 weeks, followed by a 4-week treatment of HGF or vehicle saline. The levels of fasting blood glucose, fasting insulin and homeostatic model assessment of insulin resistance were calculated for insulin sensitivity. Biochemical plasma parameters were also measured to assess the effect of HGF on lipid accumulation. Additionally, genes in the lipid metabolism pathway were evaluated in palmitic acid-treated HepG2 cells and high-fat diet mice.

RESULTS

HGF treatment significantly decreased the levels of fasting blood glucose, hepatic triglyceride and cholesterol contents. Additionally, HGF-regulated expression levels of sterol regulatory element-binding protein-1c/fatty acid synthase, peroxidase proliferator-activated receptor-α, and upstream nuclear receptors, such as farnesoid X receptor and small heterodimer partner. Furthermore, c-Met inhibitor could partially reverse the effects of HGF.

CONCLUSIONS

HGF treatment can ameliorate hepatic insulin resistance and steatosis through regulation of lipid metabolism. These effects might occur through farnesoid X receptor-small heterodimer partner axis-dependent transcriptional activity.

Human placental glucose transport in fetoplacental growth and metabolism

While efficient glucose transport is essential for all cells, in the case of the human placenta, glucose transport requirements are two-fold; provision of glucose for the growing fetus in addition to the supply of glucose required the changing metabolic needs of the placenta itself. The rapidly evolving environment of placental cells over gestation has significant consequences for the development of glucose transport systems. The two-fold transport requirement of the placenta means also that changes in expression will have effects not only for the placenta but also for fetal growth and metabolism. This review will examine the localization, function and evolution of placental glucose transport systems as they are altered with fetal development and the transport and metabolic changes observed in pregnancy pathologies.

Excess Hydrocortisone Hampers Placental Nutrient Uptake Disrupting Cellular Metabolism

Low birth weight increases neonatal morbidity and mortality, and surviving infants have increased risk of metabolic and cardiovascular disturbances later in life, as well as other neurological, psychiatric, and immune complications. A gestational excess of glucocorticoids (GCs) is a well-known cause for fetal growth retardation, but the biological basis for this association remains elusive. Placental growth is closely related to fetal growth. The placenta is the main regulator of nutrient transport to the fetus, resulting from the difference between placental nutrient uptake and the placenta's own metabolism. The aim of this study was to analyze how excess hydrocortisone affects placental glucose and lipid metabolism. Human placenta explants from term physiological pregnancies were cultured for 18 hours under different hydrocortisone concentrations (2.75, 5.5, and 55 mM; 1, 2, and 20 mg/ml). Placental glucose and lipid uptake and the metabolic partitioning of fatty acids were quantified by isotopic techniques, and expression of specific glucose transporter GLUT1 was quantified by western blot. Cell viability was assessed by MTT, immunohistochemistry and caspase activity. We found that excess hydrocortisone impairs glucose uptake and lipoprotein lipase (LPL) activity, coincident with a GC-dose dependent inhibition of fatty acid oxidation and esterification. None of the experimental conditions showed an increased cell death. In conclusion, our results show that GC overexposure exerts a dysfunctional effect on lipid transport and metabolism and glucose uptake in human placental explants. These findings could well be directly related to a reduced placental growth and possibly to a reduced supply of nutrients to the fetus and the consequent fetal growth retardation and metabolic programming.

Stroma-derived HGF drives metabolic adaptation of colorectal cancer to angiogenesis inhibitors

The role of paracrine Hepatocyte Growth Factor (HGF) in the resistance to angiogenesis inhibitors (AIs) is hidden in xenograft models because mouse HGF fails to fully activate human MET. To uncover it, we compared the efficacy of AIs in wild-type and human HGF knock-in SCID mice bearing orthotopic human colorectal tumors. Species-specific HGF/MET signaling dramatically impaired the response to anti-angiogenic agents and boosted metastatic dissemination. In cell-based assays mimicking the consequences of anti-angiogenic therapy, colorectal cancer cells were completely resistant to hypoxia but extremely sensitive to nutrient deprivation. Starvation-induced apoptosis could be prevented by HGF, which promoted GLUT1-mediated glucose uptake, sustained glycolysis and activated autophagy. Pharmacological inhibition of GLUT1 in the presence of glucose killed tumor cells as effectively as glucose deprivation, and this effect was antagonized by HGF. Concomitant targeting of GLUT1 and HGF potently suppressed growth and dissemination of AI-resistant human tumors in human HGF knock-in SCID mice without exacerbating tumor hypoxia. These data suggest that stroma-derived HGF protects CRC cells against glucose starvation-induced apoptosis, promoting resistance to both AIs and anti-glycolytic agents. Combined inhibition of glucose metabolism and HGF/MET signaling (‘anti-METabolic therapy’) may represent a more effective CRC treatment compared to utterly blocking tumor blood supply.

The Role of Hepatocyte Growth Factor (HGF) in Insulin Resistance and Diabetes

In obesity, insulin resistance (IR) and diabetes, there are proteins and hormones that may lead to the discovery of promising biomarkers and treatments for these metabolic disorders. For example, these molecules may impair the insulin signaling pathway or provide protection against IR. Thus, identifying proteins that are upregulated in IR states is relevant to the diagnosis and treatment of the associated disorders. It is becoming clear that hepatocyte growth factor (HGF) is an important component of the pathophysiology of IR, with increased levels in most common IR conditions, including obesity. HGF has a role in the metabolic flux of glucose in different insulin sensitive cell types; plays a key role in β-cell homeostasis; and is capable of modulating the inflammatory response. In this review, we discuss how, and to what extent HGF contributes to IR and diabetes pathophysiology, as well as its role in cancer which is more prevalent in obesity and diabetes. Based on the current literature and knowledge, it is clear that HGF plays a central role in these metabolic disorders. Thus, HGF levels could be employed as a biomarker for disease status/progression, and HGF/c-Met signaling pathway modulators could effectively regulate IR and treat diabetes.

18F-fluorodeoxyglucose uptake predicts MET expression in lung adenocarcinoma

Objective

MET is a member of the receptor tyrosine kinases. Several MET-targeting inhibitors and antagonistic antibodies have shown promising data in clinical trials of lung adenocarcinoma. Finding noninvasive diagnostic tools to estimate the status of MET is helpful in clinical practice. ¹⁸F-fluorodeoxyglucose positron emission tomography/computerized tomography (¹⁸F-FDG PET/CT) has been used routinely for the diagnosis and staging of tumors. However, the relationship between MET expression and ¹⁸F-FDG uptake has not been investigated yet. This study aimed to determine the correlation of MET expression with ¹⁸F-FDG uptake on PET-CT scan and whether or not ¹⁸F-FDG PET/CT can be used to predict the MET status of lung adenocarcinoma patients.

Patients and methods

Fifty-seven lung adenocarcinoma patients were analyzed in our study. Maximum standardized uptake value (SUV_max) was calculated in all PET/CT images. The expression levels of MET and two important glycolysis-related markers, glucose transporter 1 (GLUT1) and pyruvate kinase M2, were analyzed by immunohistochemistry of tissues. Spearman rank correlation was used to analyze the association between MET expression and SUV_max. In vitro MET knockdown in lung adenocarcinoma cells was used to examine the role of MET in tumor metabolism. The effect of MET on GLUT1 expression was investigated using Western blot assay and quantitative polymerase chain reaction.

Results

SUV_max was positively correlated with the expression levels of MET (r=0.458; P<0.001) and GLUT1 (r=0.551; P<0.001). SUV_max was significantly higher in patients with positive MET expression than in those with negative MET expression (9.92±6.62 vs 4.60±3.00; P=0.002). MET knockdown in lung adenocarcinoma cells led to a significant decrease in GLUT1 expression and ¹⁸F-FDG uptake.

Conclusion

MET could increase ¹⁸F-FDG uptake by upregulating GLUT1 expression. ¹⁸F-FDG PET/CT could be used to predict the MET status of lung adenocarcinoma patients and to supply valuable information to guide targeted therapy.

Hepatocyte Growth Factor Prevented High-Fat Diet-Induced Obesity and Improved Insulin Resistance in Mice

Obesity and its associated chronic inflammation in adipose tissue initiate insulin resistance, which is related to several pathologies including hypertension and atherosclerosis. Previous reports demonstrated that circulating hepatocyte growth factor (HGF) level was associated with obesity and type 2 diabetes. However, its precise role in obesity and related-pathology is unclear. In this experiment, cardiac-specific over-expression of human HGF in mice (HGF-Tg mice) which showed 4–5 times higher serum HGF levels than wild-type mice were used. While body weight in wild-type mice fed with high fat diet (HFD) for 14 weeks was significantly increased accompanied with insulin resistance, HGF-Tg mice prevented body weight gain and insulin resistance. The accumulation of macrophages and elevated levels of inflammatory mediators in adipose tissue were significantly inhibited in HGF-Tg mice as compared to wild-type mice. The HFD-induced obesity in wild-type mice treated with HGF-neutralizing antibody showed an exacerbated response to the glucose tolerance test. These gain-of-function and loss-of-function studies demonstrated that the elevated HGF level induced by HFD have protective role against obesity and insulin resistance.

HGF/Met Signaling in Head and Neck Cancer: Impact on the Tumor Microenvironment

Studies to date have revealed several major molecular alterations that contribute to head and neck squamous cell carcinoma (HNSCC) initiation, progression, metastatic spread, and therapeutic failure. The EGFR is the only FDA-approved therapeutic target, yet responses to cetuximab have been limited. Activation and cross-talk of cellular receptors and consequent activation of different signaling pathways contribute to limited activity of blockade of a single pathway. The hepatocyte growth factor (HGF) receptor, Met, has been implicated in HNSCC tumorigenesis and EGFR inhibitor resistance. HGF, the sole ligand of Met, is overexpressed in the tumor microenvironment. The role of HGF/Met signaling in proliferation, metastasis, and angiogenesis has been investigated in HNSCC, leading to clinical trials with various Met inhibitors and HGF antibodies. However, the role of the HGF/Met signaling axis in mediating the tumor microenvironment has been relatively understudied in HNSCC. In this review, we discuss the functional roles of Met and HGF in HNSCC with a focus on the tumor microenvironment and the immune system. Clin Cancer Res; 22(16); 4005-13. ©2016 AACR.

Circulating level of hepatocyte growth factor predicts incidence of type 2 diabetes mellitus: The Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND

Hepatocyte growth factor (HGF) is a pleotropic factor posited to have metabolic homeostatic properties. The purpose of this study is to examine whether level of HGF is associated with the development of type 2 diabetes.

METHODS

Data from the Multi-Ethnic Study of Atherosclerosis (MESA) were used to examine the prospective association between serum level of HGF and incident diabetes. Fasting HGF was measured at Exam 1 (2000-2002) in 5395 participants free from diabetes (61.5±10.2 years old) and incidence of diabetes was determined at four subsequent follow-up exams over 12 years. Hazard ratios (HR) for incident diabetes were estimated according to 1 standard deviation (SD) unit increment of HGF (1 SD=26 μg/l), before and after adjustment for age, sex, race/ethnicity, education, study center, smoking status, alcohol consumption, body mass index, waist circumference, fasting glucose and insulin, C-reactive protein, and interleukin-6 levels.

RESULTS

A 1 SD increment of baseline HGF was associated with a 46% (95% CI=1.37, 1.56) increased risk of diabetes before adjustment. After adjustment, diabetes risk per 1 SD increment of HGF was attenuated but remained significantly increased (HR=1.21; 95% CI=1.12, 1.32). Men had a significantly greater HR compared to women per equivalent increase of HGF (p-value for sex interaction=0.04). There was no evidence of effect modification by race/ethnicity.

CONCLUSIONS

This study advances understanding from cross-sectional studies and investigation of incident insulin resistance, demonstrating higher level of HGF is associated with incident diabetes and may reflect a unique type of impaired metabolism.

Targeted delivery of HGF to the skeletal muscle improves glucose homeostasis in diet-induced obese mice

Hepatocyte growth factor (HGF) is a cytokine that increases glucose transport ex vivo in skeletal muscle. The aim of this work was to decipher the impact of whether conditional overexpression of HGF in vivo could improve glucose homeostasis and insulin sensitivity in mouse skeletal muscle. Following tetracyclin administration, muscle HGF levels were augmented threefold in transgenic mice (SK-HGF) compared to control mice without altering plasma HGF levels. In conditions of normal diet, SK-HGF mice showed no differences in body weight, plasma triglycerides, blood glucose, plasma insulin and glucose tolerance compared to control mice. Importantly, obese SK-HGF mice exhibited improved whole-body glucose tolerance independently of changes in body weight or plasma triglyceride levels compared to control mice. This effect on glucose homeostasis was associated with significantly higher (∼80%) levels of phosphorylated protein kinase B in muscles from SK-HGF mice compared to control mice. In conclusion, muscle expression of HGF counteracts obesity-mediated muscle insulin resistance and improves glucose tolerance in mice.

Hepatocyte growth factor ameliorates hyperglycemia and corrects β-cell mass in IRS2-deficient mice

Insulin resistance, when combined with decreased β-cell mass and relative insufficient insulin secretion, leads to type 2 diabetes. Mice lacking the IRS2 gene (IRS2(-/-) mice) develop diabetes due to uncompensated insulin resistance and β-cell failure. Hepatocyte growth factor (HGF) activates the phosphatidylinositol 3-kinase/Akt signaling pathway in β-cells without recruitment of IRS1 or IRS2 and increases β-cell proliferation, survival, mass, and function when overexpressed in β-cells of transgenic (TG) mice. We therefore hypothesized that HGF may protect against β-cell failure in IRS2 deficiency. For that purpose, we cross-bred TG mice overexpressing HGF in β-cells with IRS2 knockout (KO) mice. Glucose homeostasis analysis revealed significantly reduced hyperglycemia, compensatory hyperinsulinemia, and improved glucose tolerance in TG/KO mice compared with those in KO mice in the context of similar insulin resistance. HGF overexpression also increased glucose-stimulated insulin secretion in IRS2(-/-) islets. To determine whether this glucose homeostasis improvement correlated with alterations in β-cells, we measured β-cell mass, proliferation, and death in these mice. β-Cell proliferation was increased and death was decreased in TG/KO mice compared with those in KO mice. As a result, β-cell mass was significantly increased in TG/KO mice compared with that in KO mice, reaching levels similar to those in wild-type mice. Analysis of the intracellular targets involved in β-cell failure in IRS2 deficiency showed Pdx-1 up-regulation, Akt/FoxO1 phosphorylation, and p27 down-regulation in TG/KO mouse islets. Taken together, these results indicate that HGF can compensate for IRS2 deficiency and subsequent insulin resistance by normalizing β-cell mass and increasing circulating insulin. HGF may be of value as a therapeutic agent against β-cell failure.

Diet-induced obesity impairs muscle satellite cell activation and muscle repair through alterations in hepatocyte growth factor signaling

A healthy skeletal muscle mass is essential in attenuating the complications of obesity. Importantly, healthy muscle function is maintained through adequate repair following overuse and injury. The purpose of this study was to investigate the impact of diet-induced obesity (DIO) on skeletal muscle repair and the functionality of the muscle satellite cell (SC) population. Male C57BL/6J mice were fed a standard chow or high-fat diet (60% kcal fat; DIO) for 8 weeks. Muscles from DIO mice subjected to cardiotoxin injury displayed attenuated muscle regeneration, as indicated by prolonged necrosis, delayed expression of MyoD and Myogenin, elevated collagen content, and persistent embryonic myosin heavy chain expression. While no significant differences in SC content were observed, SCs from DIO muscles did not activate normally nor did they respond to exogenous hepatocyte growth factor (HGF) despite similar receptor (cMet) density. Furthermore, HGF release from crushed muscle was significantly less than that from muscles of chow fed mice. This study demonstrates that deficits in muscle repair are present in DIO, and the impairments in the functionality of the muscle SC population as a result of altered HGF/c-met signaling are contributors to the delayed regeneration.

Hepatocyte growth factor is elevated in amniotic fluid from obese women and regulates placental glucose and fatty acid metabolism

INTRODUCTION

To evaluate the impact of the pro-inflammatory cytokine hepatocyte growth factor (HGF) on the regulation of glucose and lipid placental metabolism.

METHODS

HGF levels were quantified in amniotic fluid and placenta from control and obese women. 2-deoxy-glucose (2-DOG) uptake, glycolysis, fatty acid oxidation (FAO), fatty acid esterification, de novo fatty acid synthesis, triglyceride levels and carnitine palmitoyltransferase activities (CPT) were measured in placental explants upon addition of pathophysiological HGF levels.

RESULTS

In obese women, total- and -activated-HGF levels in amniotic fluid were elevated ∼24%, and placental HGF levels were ∼3-fold higher than in control women. At a similar dose to that present in amniotic fluid of obese women, HGF (30 ng/mL) increased Glut-1 levels and 2-DOG uptake by ∼25-30% in placental explants. HGF-mediated effect on 2-DOG uptake was dependent on the activation of phosphatidylinositol 3-kinase signaling pathway. In addition, HGF decreased ∼20% FAO, whereas esterification and de novo fatty acid synthesis increased ∼15% and ∼25% respectively, leading to 2-fold triglyceride accumulation in placental explants. In parallel, HGF reduced CPT-I activity ∼70%.

DISCUSSION

HGF is a cytokine elevated in amniotic fluid and placental tissue of obese women, which through its ability to stimulate 2-DOG uptake and metabolism impairs FAO and enhances esterification and de novo fatty acid synthesis, leading to accumulation of placental triglycerides.

Physiological Signaling and Structure of the HGF Receptor MET

The "hepatocyte growth factor" also known as "scatter factor", is a multifunctional cytokine with the peculiar ability of simultaneously triggering epithelial cell proliferation, movement and survival. The combination of those proprieties results in the induction of an epithelial to mesenchymal transition in target cells, fundamental for embryogenesis but also exploited by tumor cells during metastatization. The hepatocyte growth factor receptor, MET, is a proto-oncogene and a prototypical transmembrane tyrosine kinase receptor. Inhere we discuss the MET molecular structure and the hepatocyte growth factor driven physiological signaling which coordinates epithelial proliferation, motility and morphogenesis.

Glucose and Fatty Acid Metabolism in Placental Explants From Pregnancies Complicated With Gestational Diabetes Mellitus

Placental metabolism is an important mechanism for the regulation of fetal growth and long-term health of the newborns. In this study, we investigated the effects of maternal metabolic environment on human placental fatty acid and glucose metabolism. We used placental explants from uncomplicated pregnancies or pregnancies complicated with gestational diabetes mellitus (GDM), undergoing vaginal delivery (VD) or cesarean section (CS). Fatty acid oxidation (FAO) and glucose uptake (2-DOG) were similar in both modes of delivery in normal and GDM pregnancies. However, placental explants from GDM exhibited 40% to 50% reduced FAO capacity compared to control placentas in women undergoing VD or CS. In contrast, 2-DOG uptake was 2- to 3-fold higher in placental explants from GDM compared to control placentas in women undergoing VD or CS, respectively. In conclusion, ex vivo placental fuel selection is influenced by maternal GDM, but placental metabolic characteristics are not altered by the mode of delivery.

MSP: an emerging player in metabolic syndrome

MSP (Macrophage Stimulating Protein; also known as Hepatocyte Growth Factor-like protein (HGFL) and MST1) is a secreted protein and the ligand for transmembrane receptor tyrosine kinase Recepteur d'Origine Nantais (RON; also known as MST1R). Since its discovery, MSP has been demonstrated to play a key role in regulating inflammation in the peripheral tissues of multiple disease models. Recent evidences also point toward a beneficial role of MSP in the regulation of hepatic lipid and glucose metabolism, thereby implicating MSP as a crucial regulator in maintaining metabolic homeostasis while simultaneously suppressing inflammatory processes. In this review, we discuss the recent advances that demonstrate the significance of MSP in metabolic syndrome and build a strong case supporting its therapeutic potential.

A link between hepatic glucose production and peripheral energy metabolism via hepatokines

Type 2 diabetes is characterized by a deterioration of glucose tolerance, which associates insulin resistance of glucose uptake by peripheral tissues and increased endogenous glucose production. Here we report that the specific suppression of hepatic glucose production positively modulates whole-body glucose and energy metabolism. We used mice deficient in liver glucose-6 phosphatase that is mandatory for endogenous glucose production. When they were fed a high fat/high sucrose diet, they resisted the development of diabetes and obesity due to the activation of peripheral glucose metabolism and thermogenesis. This was linked to the secretion of hepatic hormones like fibroblast growth factor 21 and angiopoietin-like factor 6. Interestingly, the deletion of hepatic glucose-6 phosphatase in previously obese and insulin-resistant mice resulted in the rapid restoration of glucose and body weight controls. Therefore, hepatic glucose production is an essential lever for the control of whole-body energy metabolism during the development of obesity and diabetes.

Decorin induces mitophagy in breast carcinoma cells via peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) and mitostatin

Tumor cell mitochondria are key biosynthetic hubs that provide macromolecules for cancer progression and angiogenesis. Soluble decorin protein core, hereafter referred to as decorin, potently attenuated mitochondrial respiratory complexes and mitochondrial DNA (mtDNA) in MDA-MB-231 breast carcinoma cells. We found a rapid and dynamic interplay between peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) and the decorin-induced tumor suppressor gene, mitostatin. This interaction stabilized mitostatin mRNA with concurrent accumulation of mitostatin protein. In contrast, siRNA-mediated abrogation of PGC-1α-blocked decorin-evoked stabilization of mitostatin. Mechanistically, PGC-1α bound MITOSTATIN mRNA to achieve rapid stabilization. These processes were orchestrated by the decorin/Met axis, as blocking the Met-tyrosine kinase or knockdown of Met abrogated these responses. Furthermore, depletion of mitostatin blocked decorin- or rapamycin-evoked mitophagy, increased vascular endothelial growth factor A (VEGFA) production, and compromised decorin-evoked VEGFA suppression. Collectively, our findings underscore the complexity of PGC-1α-mediated mitochondrial homeostasis and establish mitostatin as a key regulator of tumor cell mitophagy and angiostasis.

Independent association of elevated serum hepatocyte growth factor levels with development of insulin resistance in a 10-year prospective study

OBJECTIVE

Hepatocyte growth factor (HGF) receptors form a hybrid complex with insulin receptors in the liver of mice, which lead to robust signalling to regulate glucose metabolism. Serum HGF levels are high in subjects with metabolic syndrome and/or obesity. Accordingly, we prospectively investigated the relationship between HGF and the development of insulin resistance (IR) in a general population without IR at baseline.

METHODS

A total of 1492 subjects received health examinations. After excluding subjects with diabetes and/or IR (n = 402) at baseline, the remaining subjects (n = 1090) were followed-up 10 years later. Complete data sets were available from 716 subjects for prospective analysis. Logistic regression was performed to determine factors associated with the development of IR after 10 years.

RESULTS

In subjects without diabetes at baseline, serum HGF levels were higher (0·26 ± 0·10 ng/ml, n = 259) in subjects with IR than without it (0·22 ± 0·09 ng/ml, n = 1090). After deleting subjects who developed liver disease during follow-up, 188 were found to have developed IR at 10 years after the original screening. HGF (P < 0·05), age (P < 0·001), homoeostasis model assessment index (P < 0·001), HDL-c (P < 0·05; inversely) and hypertensive medication (P < 0·05) were significantly associated with the development of IR by multivariate stepwise logistic regression analysis. A significant (P < 0·05) relative risk [1·75 (95%CI: 1·01-3·12)] for the development of IR was observed in the highest (≥0·30 ng/ml) vs the lowest categories (<0·15 ng/ml) of HGF after adjustments for confounders.

CONCLUSIONS

Our 10-year prospective study suggests that elevated serum HGF levels were significantly associated with the development of IR.

Impact of tumor microenvironment and epithelial phenotypes on metabolism in breast cancer

PURPOSE

Cancer cells have altered metabolism, with increased glucose uptake, glycolysis, and biomass production. This study conducted genomic and metabolomic analyses to elucidate how tumor and stromal genomic characteristics influence tumor metabolism.

EXPERIMENTAL DESIGN

Thirty-three breast tumors and six normal breast tissues were analyzed by gene expression microarray and by mass spectrometry for metabolites. Gene expression data and clinical characteristics were evaluated in association with metabolic phenotype. To evaluate the role of stromal interactions in altered metabolism, cocultures were conducted using breast cancer cells and primary cancer-associated fibroblasts (CAF).

RESULTS

Across all metabolites, unsupervised clustering resulted in two main sample clusters. Normal breast tissue and a subset of tumors with less aggressive clinical characteristics had lower levels of nucleic and amino acids and glycolysis byproducts, whereas more aggressive tumors had higher levels of these Warburg-associated metabolites. While tumor-intrinsic subtype did not predict metabolic phenotype, metabolic cluster was significantly associated with expression of a wound response signature. In cocultures, CAFs from basal-like breast cancers increased glucose uptake and basal-like epithelial cells increased glucose oxidation and glycogen synthesis, suggesting interplay of stromal and epithelial phenotypes on metabolism. Cytokine arrays identified hepatocyte growth factor (HGF) as a potential mediator of stromal-epithelial interaction and antibody neutralization of HGF resulted in reduced expression of glucose transporter 1 (GLUT1) and decreased glucose uptake by epithelium.

CONCLUSIONS

Both tumor/epithelial and stromal characteristics play important roles in metabolism. Warburg-like metabolism is influenced by changes in stromal-epithelial interactions, including altered expression of HGF/Met pathway and GLUT1 expression.

The metabolic profile of tumors depends on both the responsible genetic lesion and tissue type

The altered metabolism of tumors has been considered a target for anticancer therapy. However, the relationship between distinct tumor-initiating lesions and anomalies of tumor metabolism in vivo has not been addressed. We report that MYC-induced mouse liver tumors significantly increase both glucose and glutamine catabolism, whereas MET-induced liver tumors use glucose to produce glutamine. Increased glutamine catabolism in MYC-induced liver tumors is associated with decreased levels of glutamine synthetase (Glul) and the switch from Gls2 to Gls1 glutaminase. In contrast to liver tumors, MYC-induced lung tumors display increased expression of both Glul and Gls1 and accumulate glutamine. We also show that inhibition of Gls1 kills cells that overexpress MYC and catabolize glutamine. Our results suggest that the metabolic profiles of tumors are likely to depend on both the genotype and tissue of origin and have implications regarding the design of therapies targeting tumor metabolism.

Insulin receptor-independent upregulation of cellular glucose uptake

BACKGROUND

Cellular glucose uptake can be enhanced by up-regulating Ras signaling in either insulin dependent or independent manner. In presence of insulin and intact insulin signaling, Ras plays a negligible role in glucose uptake. Conversely, when insulin signaling is impaired in obesity or diabetes, the insulin-independent Ras pathway may be valuable for enhancing glucose disposal. We previously reported that Ad36, a human adenovirus, enhances cellular glucose uptake by up-regulating the Ras/Glut4 pathway. Here, we investigated if Ad36-up-regulated Ras via the insulin-independent pathway, to enhance glucose uptake. Furthermore, uncontrolled up-regulation of Ras is linked with oncogenic cell transformation, if the tumor suppressor gene p53 is also down regulated. Hence, we determined if up-regulation of Ras by Ad36 would induce oncogenic cell transformation. Finally, we determined the relevance of Ad36 to insulin resistance in humans.

METHODS

Insulin receptor (IR) was knocked down with siRNA in 3T3-L1 adipocytes, to determine if Ad36 increases the Ras/Glut4 pathway and glucose uptake without IR-signaling. Next, the effects of Ad36 on cell transformation and p53 abundance were determined. Finally, overweight or obese women were screened for seropositivty to Ad36, as an indicator of natural Ad36 infection. Associations of Ad36 infection with adiposity and C-Reactive proteins (CRP) –two key markers of insulin resistance, and with glucose disposal, were determined.

RESULTS

Unaffected by IR knock-down, Ad36 significantly increased the Ras pathway, Glut4 translocation, and glucose uptake in 3T3-L1 adipocytes. Despite Ras up-regulation, Ad36 did not transform 3T3-L1 cells. This may be because Ad36 significantly increased p53 protein in 3T3-L1 cells or mice adipose tissue. Ad36 seropositivity was associated with greater adiposity and CRP levels, yet a significantly higher systemic glucose disposal rate.

CONCLUSIONS

Overall, the study offers Ras/Glut4 pathway as an alternate to enhance glucose disposal when insulin signaling is impaired, and, importantly, provides Ad36 as a tool to understand the modulation of that pathway.

A hepatocyte growth factor receptor (Met)-insulin receptor hybrid governs hepatic glucose metabolism

Met is the transmembrane tyrosine kinase cell surface receptor for hepatocyte growth factor (HGF) and is structurally related to the insulin receptor (INSR) tyrosine kinase. Here we report that the HGF-Met axis regulates metabolism by stimulating hepatic glucose uptake and suppressing hepatic glucose output. We show that Met is essential for an optimal hepatic insulin response by directly engaging INSR to form a Met-INSR hybrid complex, which culminates in a robust signal output. We also found that the HGF-Met system restores insulin responsiveness in a mouse model of insulin refractoriness. These results provide new insights into the molecular basis of hepatic insulin resistance and suggest that HGF may have therapeutic potential for type 2 diabetes in the clinical setting.

Peripheral leptin and ghrelin receptors are regulated in a tissue-specific manner in activity-based anorexia

The aim of this research was to investigate the effect of long-term exposure to low leptin and high ghrelin levels, inherent to activity-based anorexia (ABA), on peripheral metabolism-implicated tissues such as muscle and fat depots. For this purpose, rats under ABA were submitted to a global study which included the characterization of body weight and composition change, the evaluation of leptin and ghrelin levels as well as their receptors expression at peripheral level. Our results confirm that feeding restriction to 1 h per day, and particularly the combination of this fasting regime with exercise (ABA), significantly reduces fat mass, decreases leptin circulating levels, increases ghrelin levels strikingly and enhances insulin sensitivity. By direct in vitro assays, we show that visceral and gonadal fat participate more than subcutaneous fat in the hypoleptinemia of these animals. The study of ghrelin (GHS-R1a) and leptin (LEPR) receptors at peripheral level exhibits a tissue-specific expression pattern. Concretely, oxidative-soleus type of muscle appears to be more susceptible to ghrelin and leptin circulating levels than glycolytic-gastrocnemius type under exercise and food restriction situations. In relation to adipose tissue, chronic hyperghrelinemia induces GHS-R1a expression on visceral and subcutaneous fat which might suggest the prevention of lipid loss. On the other hand, only subcutaneous fat express the active long form of LEPR compared to visceral and gonadal fat under low leptin levels in ABA animals. All together, these findings indicate tissue-specific mechanisms for the control of energy homeostasis in response to nutrient and energy availability.

Novel proapoptotic effect of hepatocyte growth factor: synergy with palmitate to cause pancreatic {beta}-cell apoptosis

Increasing evidence suggests that elevation of plasma fatty acids that often accompanies insulin resistance contributes to beta-cell insufficiency in obesity-related type 2 diabetes. Circulating levels of hepatocyte growth factor (HGF) are increased in humans with metabolic syndrome and obesity. HGF is known to protect beta-cells against streptozotocin and during islet engraftment. However, whether HGF is a beta-cell prosurvival factor in situations of excessive lipid supply has not been deciphered. Mice overexpressing HGF in the beta-cell [rat insulin type II promoter (RIP)-HGF transgenic mice] fed with standard chow display improved glucose homeostasis and increased beta-cell mass and proliferation compared with normal littermates. However, after 15 wk of high-fat feeding, glucose homeostasis and beta-cell expansion and proliferation are indistinguishable between normal and transgenic mice. Interestingly, RIP-HGF transgenic mouse beta-cells and normal beta-cells treated with HGF display increased sensitivity to palmitate-mediated apoptosis in vitro. Palmitate completely eliminates Akt and Bad phosphorylation in RIP-HGF transgenic mouse islets. HGF-overexpressing islets also show significantly decreased AMP-activated protein kinase-alpha and acetyl-coenzyme A carboxylase phosphorylation, diminished fatty acid oxidation, increased serine palmitoyltransferase expression, and enhanced ceramide formation compared with normal islets. Importantly, human islets overexpressing HGF also display increased beta-cell apoptosis in the presence of palmitate. Treatment of both mouse and human islet cells with the de novo ceramide synthesis inhibitors myriocin and fumonisin B1 abrogates beta-cell apoptosis induced by HGF and palmitate. Collectively, these studies indicate that HGF can be detrimental for beta-cell survival in an environment with excessive fatty acid supply.

HGF-induced invasion by prostate tumor cells requires anterograde lysosome trafficking and activity of Na+-H+ exchangers

Hepatocyte growth factor (HGF) is found in tumor microenvironments, and interaction with its tyrosine kinase receptor Met triggers cell invasion and metastasis. It was previously shown that acidic extracellular pH stimulated peripheral lysosome trafficking, resulting in increased cathepsin B secretion and tumor cell invasion, which was dependent upon sodium-proton exchanger (NHE) activity. We now demonstrate that HGF induced the trafficking of lysosomes to the cell periphery, independent of HGF-induced epithelial-mesenchymal transition. HGF-induced anterograde lysosome trafficking depended upon the PI3K pathway, microtubules and RhoA, resulting in increased cathepsin B secretion and invasion by the cells. HGF-induced NHE activity via increased net acid production, and inhibition of NHE activity with 5-(N-ethyl-N-isopropyl)-amiloride (EIPA), or a combination of the NHE1-specific drug cariporide and the NHE3-specific drug s3226 prevented HGF-induced anterograde trafficking and induced retrograde trafficking in HGF-overexpressing cells. EIPA treatment reduced cathepsin B secretion and HGF-induced invasion by the tumor cells. Lysosomes were located more peripherally in Rab7-shRNA-expressing cells and these cells were more invasive than control cells. Overexpression of the Rab7 effector protein, RILP, resulted in a juxtanuclear location of lysosomes and reduced HGF-induced invasion. Together, these results suggest that the location of lysosomes is an inherently important aspect of invasion by tumor cells.

Mechanisms for increased expression of cholesterol 7alpha-hydroxylase (Cyp7a1) in lactating rats

Cholesterol 7alpha-hydroxylase (Cyp7a1) and the bile acid pool size are increased 2 to 3-fold in lactating postpartum rats. We investigated the interaction of nuclear receptors with the Cyp7a1 proximal promoter and the expression of regulatory signaling pathways in postpartum rats at day 10 (PPd10) versus female controls to identify the mechanisms of increased expression of Cyp7a1, which is maximal at 16 hours. Liver X receptor (LXRalpha) and RNA polymerase II (RNA Pol II) recruitment to Cyp7a1 chromatin were increased 1.5- and 2.5-fold, respectively, at 16 hours on PPd10. Expression of nuclear receptors farnesoid X receptor (FXR), LXRalpha, liver receptor homolog (LRH-1), hepatocyte nuclear factor 4alpha (HNF4alpha), and short heterodimer partner (SHP) messenger RNA (mRNA) and coactivator peroxisome proliferators-activated receptor gamma coactivator-1alpha (PGC-1alpha) mRNA was unchanged in PPd10 versus controls at 16 hours, whereas chicken ovalbumin upstream transcription factor II (COUP-TFII) was decreased 40% at 16 hours. Investigation of a repressive signaling pathway, the c-Jun-N-terminal kinase (JNK) signaling pathway in PPd10 versus controls, showed decreased mRNA expression of hepatocyte growth factor (HGF; decreased 60% at 16 hours) and tyrosine kinase receptor c-Met (decreased 44%-50% at 16 hours), but these were not accompanied by decreased expression of phosphorylated c-Jun. Importantly, expression of fibroblast growth factor 15 (FGF15) mRNA in the ileum was decreased 70% in PPd10 versus controls, whereas phosphorylated mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2 (Erk1/2) protein expression in liver was decreased 88% at 16 hours.

CONCLUSION

The increased recruitment of LXRalpha, a Cyp7a1 stimulatory pathway, and decreased expression of FGF15 and phosphorylated Erk1/2, a Cyp7a1 repressive pathway, combined to increase Cyp7a1 expression during lactation.