Hepatocyte growth factor induces glucose uptake in 3T3-L1 adipocytes through A Gab1/phosphatidylinositol 3-kinase/Glut4 pathway

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.

Investigation of the Repairing Effect and Mechanism of Oral Degraded Sericin on Liver Injury in Type II Diabetic Rats

In the sericulture and silk production industry, sericin is discharged in the degumming wastewater, resulting in a large amount of wasted natural protein and environmental pollution. This study investigated the effect of degraded sericin recovered by the Ca(OH)₂–ultrasound degumming method (a green process) on liver injury in T2D rats. After 4 weeks of dietary sericin supplementation, the liver masses and organ coefficients of the T2D rats improved compared with those of the model rats that were not fed sericin. Oral sericin activated the damaged PI3K/AKT/AMPK pathway to enhance glycogen synthesis, accelerate glycolysis, and inhibit gluconeogenesis. The protein expression levels of the inflammatory factors NF-κB, IL-6, and TNF-α in the T2D model group were up to two times higher than in the normal group. However, all three T2D groups that received oral sericin showed significant decreases in these factors to the level found in the normal group, indicating that inflammation in the body was significantly reduced. These results show that the sericin protein might improve glycogen synthesis, accelerate glycolysis, and inhibit gluconeogenesis by enhancing the anti-oxidation capability and reducing inflammatory reactions. Therefore, sericin recovered by Ca(OH)₂ degradation has potential use in the development of functional health foods that can lower blood sugar.

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.

The Lifestyle Modifications and Endometrial Proteome Changes of Women With Polycystic Ovary Syndrome and Obesity

Polycystic ovary syndrome (PCOS) is a polyendocrine disorder and the most common endocrinopathy in women of reproductive age. Affected women have an elevated prevalence of being overweight and obese. Our study sought to determine how weight loss associated with lifestyle changes affects the endometrium specific proteome, endocrine-metabolic characteristics, and motor capabilities of obese women with PCOS and infertility. A group of 12 infertile women under the age of 38 with PCOS and BMI ≥30 kg/m² were included in the study. An evaluation was performed by a gynecologist and an endocrinologist. The weight-loss program lasted 8 weeks under the guidance of a professional trainer. Endometrial sampling during a period of implantation window for proteome determination was performed before and after weight loss. In endometrial samples at the end of the study increased protein abundance was recorded for Legumain, Insulin-like growth factor-binding protein 7, Hepatocyte growth factor receptor, Keratin, type II cytoskeletal 7, and Cystatin-B, while the B-lymphocyte antigen CD20 protein abundance decreased. Our results also indicate significantly lowered fasting blood glucose level and free testosterone concentration and significant improvements in body composition and physical capacity. This study may open up the venues for investigating important biomarkers that may affect endometrial receptivity.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT04989244?term=NCT04989244&draw=2&rank=1, identifier: NCT04989244.

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.

miR-93-5p promotes insulin resistance to regulate type 2 diabetes progression in HepG2 cells by targeting HGF

Insulin resistance is a common feature of type 2 diabetes mellitus (T2DM). However, the mechanisms underlying insulin resistance are not completely understood. The present study aimed to investigate the effect of microRNA (miR)-93-5p on insulin resistance in T2DM cells. Human hepatocellular carcinoma (HCC; HepG2) cells were cultured in medium with high glucose content (30 mM glucose) to establish an in vitro insulin-resistant cell model (IR group). Glucose consumption and glycogen synthesis assays were performed to assess glucose consumption and glycogen synthesis, respectively. By performing immunoprecipitation assays, the abundance of the Met-insulin receptor complex was detected in HepG2 cells. miR-93-5p and hepatocyte growth factor (HGF) mRNA expression levels were measured via reverse transcription-quantitative PCR, and HGF protein expression levels were measured via western blotting. A dual-luciferase reporter assay was conducted to investigate the interaction between miR-93-5p and HGF. Cell Counting Kit-8, BrdU and caspase-3 activity assays were performed to evaluate cell viability, proliferation and apoptosis, respectively, in insulin-resistant HepG2 cells following transfection with small interfering RNA-HGF, HGF overexpression vector, miR-93-5p mimic or miR-93-5p inhibitor. The results demonstrated that miR-93-5p expression was significantly increased and HGF expression was significantly decreased in HCC tissues isolated from patients with or without T2DM compared with adjacent healthy tissues isolated from patients without T2DM. Compared with the IR group, miR-93-5p overexpression significantly increased cell proliferation, glucose consumption and glycogen synthesis, but significantly inhibited apoptosis in insulin-resistant HepG2 cells. By contrast, compared with the IR group, HGF overexpression significantly inhibited cell proliferation, glucose consumption and glycogen synthesis, but significantly enhanced cell apoptosis in insulin-resistant HepG2 cells. Following co-transfection with HGF overexpression vector and miR-93-5p mimic, miR-93-5p mimic-mediated induction of HepG2 cell proliferation, glucose consumption and glycogen synthesis in insulin-resistant HepG2 cells was inhibited. Collectively, the results of the present study indicated that miR-93-5p enhanced insulin resistance to regulate T2DM progression in HepG2 cells by targeting HGF.

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.

Metabolic Profiling Reveals Aggravated Non-Alcoholic Steatohepatitis in High-Fat High-Cholesterol Diet-Fed Apolipoprotein E-Deficient Mice Lacking Ron Receptor Signaling

Non-alcoholic steatohepatitis (NASH) represents the progressive sub-disease of non-alcoholic fatty liver disease that causes chronic liver injury initiated and sustained by steatosis and necroinflammation. The Ron receptor is a tyrosine kinase of the Met proto-oncogene family that potentially has a beneficial role in adipose and liver-specific inflammatory responses, as well as glucose and lipid metabolism. Since its discovery two decades ago, the Ron receptor has been extensively investigated for its differential roles on inflammation and cancer. Previously, we showed that Ron expression on tissue-resident macrophages limits inflammatory macrophage activation and promotes a repair phenotype, which can retard the progression of NASH in a diet-induced mouse model. However, the metabolic consequences of Ron activation have not previously been investigated. Here, we explored the effects of Ron receptor activation on major metabolic pathways that underlie the development and progression of NASH. Mice lacking apolipoprotein E (ApoE KO) and double knockout (DKO) mice that lack ApoE and Ron were maintained on a high-fat high-cholesterol diet for 18 weeks. We observed that, in DKO mice, the loss of ligand-dependent Ron signaling aggravated key pathological features in steatohepatitis, including steatosis, inflammation, oxidation stress, and hepatocyte damage. Transcriptional programs positively regulating fatty acid (FA) synthesis and uptake were upregulated in the absence of Ron receptor signaling, whereas lipid disposal pathways were downregulated. Consistent with the deregulation of lipid metabolism pathways, the DKO animals exhibited increased accumulation of FAs in the liver and decreased level of bile acids. Altogether, ligand-dependent Ron receptor activation provides protection from the deregulation of major metabolic pathways that initiate and aggravate non-alcoholic steatohepatitis.

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.

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.

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.

miR-206-3p Inhibits 3T3-L1 Cell Adipogenesis via the c-Met/PI3K/Akt Pathway

MicroRNAs (miRNAs) are important post-transcriptional regulators during adipocyte adipogenesis. MiR-206-3p, a tissue-specific miRNA, is absent in white adipocytes. In this study, we examined the roles of mmu-miR-206-3p in the adipogenic differentiation of 3T3-L1 preadipocytes. The miR-206-3p expression has shown an apparent decreasing trend after induction, and sustained low expression throughout the differentiation of 3T3-L1 cells. miR-206-3p blocked the adipogenic differentiation of 3T3-L1 cells by attenuating c-Met expression; the inhibition effect of miR-206 to the adipogenic differentiation can be counteracted by restoring c-Met expression. In addition, miR-206-3p decreased the phosphorylation of Akt, which is the downstream effector of c-Met in the PI3K/Akt signaling pathway. These data indicate that miR-206-3p inhibits adipocyte adipogenesis through silencing c-Met and subsequently inactivating the PI3K/Akt signaling pathway.

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.

The epigenetic signature of systemic insulin resistance in obese women

AIMS/HYPOTHESIS

Insulin resistance (IR) links obesity to type 2 diabetes. The aim of this study was to explore whether white adipose tissue (WAT) epigenetic dysregulation is associated with systemic IR by genome-wide CG dinucleotide (CpG) methylation and gene expression profiling in WAT from insulin-resistant and insulin-sensitive women. A secondary aim was to determine whether the DNA methylation signature in peripheral blood mononuclear cells (PBMCs) reflects WAT methylation and, if so, can be used as a marker for systemic IR.

METHODS

From 220 obese women, we selected a total of 80 individuals from either of the extreme ends of the distribution curve of HOMA-IR, an indirect measure of systemic insulin sensitivity. Genome-wide transcriptome and DNA CpG methylation profiling by array was performed on subcutaneous (SAT) and visceral (omental) adipose tissue (VAT). CpG methylation in PBMCs was assayed in the same cohort.

RESULTS

There were 647 differentially expressed genes (false discovery rate [FDR] 10%) in SAT, all of which displayed directionally consistent associations in VAT. This suggests that IR is associated with dysregulated expression of a common set of genes in SAT and VAT. The average degree of DNA methylation did not differ between the insulin-resistant and insulin-sensitive group in any of the analysed tissues/cells. There were 223 IR-associated genes in SAT containing a total of 336 nominally significant differentially methylated sites (DMS). The 223 IR-associated genes were over-represented in pathways related to integrin cell surface interactions and insulin signalling and included COL5A1, GAB1, IRS2, PFKFB3 and PTPRJ. In VAT there were a total of 51 differentially expressed genes (FDR 10%); 18 IR-associated genes contained a total of 29 DMS.

CONCLUSIONS/INTERPRETATION

In individuals discordant for insulin sensitivity, the average DNA CpG methylation in SAT and VAT is similar, although specific genes, particularly in SAT, display significantly altered expression and DMS in IR, possibly indicating that epigenetic regulation of these genes influences 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.

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.

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.

Hepatocyte growth factor regulates neovascularization in developing fat pads

In this study, we used lentiviral-delivered shRNA to generate a clonal line of 3T3-F442A preadipocytes with stable silencing of hepatocyte growth factor (HGF) expression and examined the long-term consequence of this modification on fat pad development. HGF mRNA expression was reduced 94%, and HGF secretion 79% (P < 0.01), compared with preadipocytes treated with nontargeting shRNA. Fat pads derived from HGF knockdown preadipocytes were significantly smaller (P < 0.01) than control pads beginning at 3 days postinjection (0.022 ± 0.003 vs. 0.037 ± 0.004 g), and further decreased in size at day 7 (0.015 ± 0.004 vs. 0.037 ± 0.003 g) and day 14 (0.008 ± 0.002 vs. 0.045 ± 0.007 g). Expression of the endothelial cell genes TIE1 and PECAM1 increased over time in control fat pads (1.6 ± 0.4 vs. 11.4 ± 1.7 relative units at day 3 and 14, respectively; P < 0.05) but not in HGF knockdown fat pads (1.1 ± 0.5 vs. 5.9 ± 2.2 relative units at day 3 and 14). Contiguous vascular structures were observed in control fat pads but were much less developed in HGF knockdown fat pads. Differentiation of preadipocytes to mature adipocytes was significantly attenuated in HGF knockdown fat pads. Fat pads derived from preadipocytes with knockdown of the HGF receptor c-MET were smaller than control pads at day 3 postinjection (0.034 ± 0.002 vs. 0.049 ± 0.004 g; P < 0.05), and remained the same size through day 14. c-MET knockdown fat pads developed a robust vasculature, and preadipocytes differentiated to mature adipocytes. Overall these data suggest that preadipocyte-secreted HGF is an important regulator of neovascularization in developing fat pads.

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.

Circulating hepatocyte growth factor (HGF) in patients with comorbidity of chronic heart failure, type 2 diabetes mellitus and impaired lipid metabolism

AIM: To evaluate the plasma level of circulating heptocyte growth factor (HGF) in patients with comorbidity of post-infarction chronic heart failure (CHF), type 2 diabetes mellitus (T2DM) and obesity. We also aimed to assess possible correlations between HGF levels and parameters of carbohydrate and lipid metabolism, as well as myocardial functional characteristics and classic biochemical severity markers for CHF.17Сахар ный диабет КардиологияСахарный диабет. 2013;(2):17-25 MATERIALS AND METHODS: We enrolled 100 patients for participation in this study, including the following subgroups: 20 individuals with- out cardiovascular and glycemic disorders, 30 patients with CHF, 25 patients with CHF/T2DM comorbidity and 25 diabetic patients with no signs of heart failure. Quantitative plasma HGF analysis was performed with enzyme-linked immunosorbent assay (ELISA). RESULTS: Plasma HGF was elevated both in patients with CHF and T2DM as measured against healthy control group. The elevation was most prominent in patients with CHF/T2DM comorbidity and was found to correlate with HbA1c level (r=0.52, p=0.03). Plasma HGF also correlated with BMI (r=0.42, p=0007) in a unified study group, though we observed no statistically significant difference between subgroups with a trend toward higher HGF in obese patients with CHF/T2DM comorbidity (626.1?254.1 pg/ml vs 742.0?210.7 pg/ml respectively; p 0.05). Interestingly, plasma HGF was also significantly higher in controls with BMI 30 km/m2 (324.1?107.7 pg/ml vs 436.9?112.3 pg/ml, p=0.03).Circulating HGF correlated with plasma levels of N-terminal fragment of B-type natriuretic peptide (NT-proBNP) and such structural and functional myocardial characteristics as left atrial size and maximum volume along with left ventricular ejection fraction (EF), end-diastolic volume (EDV) and end-diastolic dimension (EDD). CONCLUSION: These findings suggest that HGF may potentially serve as a prediction marker for unfavorable myocardial remodeling and poor prognosis in CHF patients with T2DM and obesity, though this possibility should be further investigated in follow-up studies.

Hepatocyte growth factor and interferon-γ inducible protein-10 are related to visceral adiposity

BACKGROUND

Increased production of chemokines by adipose tissue and defective adipose tissue oxygenation as a result of obesity may induce leucocyte infiltration and subsequent systemic inflammation.

OBJECTIVES

1-To determine the relation between the amount of visceral and subcutaneous adipose tissue and the chemokine interferon-γ-inducible protein 10 (IP-10) and angiogenic factor hepatocyte growth factor (HGF). 2-To determine the relation between the metabolic syndrome and IP-10 as well as HGF.

METHODS

Patients originated from the Secondary Manifestations of ARTerial disease (SMART) cohort. In this study, a cohort of 1251 patients with manifest vascular disease was included. Subcutaneous and visceral adipose tissue thickness (SAT and VAT respectively) were measured ultrasonographically. IP-10 and HGF concentrations were measured with Luminex multiplex immuno assay in addition to fasting metabolic parameters. Linear regression analyses with adjustments for age, gender, smoking, estimated glomerular filtration rate, type 2 diabetes mellitus and medication use were applied to quantify the relations between adiposity or metabolic syndrome and IP-10 and HGF concentrations.

RESULTS

VAT was significantly associated with (log)IP-10 and (log)HGF, reflected by significant higher β-values in VAT quartile 4 compared with VAT quartile 1 (reference): β0.155 (95%CI:0.073-0.237) for IP-10 and β0.147 (95%CI:0.076-0.218) for HGF. Per standard deviation increase in VAT, (log)IP-10 levels increased with 0.057 pg/mL (95%CI:0.027-0.087) and (log)HGF increased with 0.051 pg/mL (95%CI:0.025-0.077). Effect estimates were not affected by including body mass index(BMI) in the model. In contrast, SAT was not associated with IP-10 and HGF. Furthermore, the presence of the metabolic syndrome was associated with IP-10 and HGF.

CONCLUSIONS

Visceral adipose tissue but not subcutaneous adipose tissue is significantly associated with circulating levels of IP-10 and HGF, irrespective of BMI.

Alpha-synuclein elicits glucose uptake and utilization in adipocytes through the Gab1/PI3K/Akt transduction pathway

Insulin is the main glucoregulator that promotes the uptake of glucose by tissues and the subsequent utilization of glucose as an energy source. In this paper, we describe a novel glucoregulator, the alpha-synuclein (SNCA) protein, that has previously been linked to Parkinson's disease. Treatment with recombinant SNCA promotes glucose uptake in vitro in preadipocytes and in vivo in the adipose tissues and skeletal muscles of mice through the LPAR2/Gab1/PI3K/Akt pathway; these effects occur independently of the insulin receptor. This function of SNCA represents a new mechanistic insight that creates novel avenues of research with respect to the process of glucose regulation.

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.

A serum factor induces insulin-independent translocation of GLUT4 to the cell surface which is maintained in insulin resistance

In response to insulin, glucose transporter GLUT4 translocates from intracellular compartments towards the plasma membrane where it enhances cellular glucose uptake. Here, we show that sera from various species contain a factor that dose-dependently induces GLUT4 translocation and glucose uptake in 3T3-L1 adipocytes, human adipocytes, myoblasts and myotubes. Notably, the effect of this factor on GLUT4 is fully maintained in insulin-resistant cells. Our studies demonstrate that the serum-induced increase in cell surface GLUT4 levels is not due to inhibition of its internalization and is not mediated by insulin, PDGF, IGF-1, or HGF. Similarly to insulin, serum also augments cell surface levels of GLUT1 and TfR. Remarkably, the acute effect of serum on GLUT4 is largely additive to that of insulin, while it also sensitizes the cells to insulin. In accordance with these findings, serum does not appear to activate the same repertoire of downstream signaling molecules that are implicated in insulin-induced GLUT4 translocation. We conclude that in addition to insulin, at least one other biological proteinaceous factor exists that contributes to GLUT4 regulation and still functions in insulin resistance. The challenge now is to identify this factor.

Hepatocyte growth factor and clinical diabetes in postmenopausal women

OBJECTIVE

To investigate the association between circulating levels of hepatocyte growth factor (HGF), a mesenchymal-derived pleiotrophic factor that is elevated in obesity, and the prevalence of type 2 diabetes.

RESEARCH DESIGN AND METHODS

A cross-sectional analysis among 892 postmenopausal women within the Women's Health Initiative Observational Study (WHI-OS).

RESULTS

HGF levels positively correlated with BMI and homeostasis model assessment for insulin resistance. In the multivariable analysis comparing the highest tertile with the lowest tertile of HGF, the odds ratio for prevalent diabetes was 2.47 (95% CI [1.12-5.47], P for trend = 0.014) after accounting for age, race, BMI, and other risk factors for diabetes.

CONCLUSIONS

HGF levels are associated with the presence of type 2 diabetes in postmenopausal women. Future studies should consider the prospective evaluation of the association of HGF with the development of type 2 diabetes.

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.

Ciliary neurotrophic factor stimulates muscle glucose uptake by a PI3-kinase-dependent pathway that is impaired with obesity

OBJECTIVE

Ciliary neurotrophic factor (CNTF) reverses muscle insulin resistance by increasing fatty acid oxidation through gp130-LIF receptor signaling to the AMP-activated protein kinase (AMPK). CNTF also increases Akt signaling in neurons and adipocytes. Because both Akt and AMPK regulate glucose uptake, we investigated muscle glucose uptake in response to CNTF signaling in lean and obese mice.

RESEARCH DESIGN AND METHODS

Mice were injected intraperitoneally with saline or CNTF, and blood glucose was monitored. The effects of CNTF on skeletal muscle glucose uptake and AMPK/Akt signaling were investigated in incubated soleus and extensor digitorum longus (EDL) muscles from muscle-specific AMPKalpha2 kinase-dead, gp130(DeltaSTAT), and lean and obese ob/ob and high-fat-fed mice. The effect of C2-ceramide on glucose uptake and gp130 signaling was also examined.

RESULTS

CNTF reduced blood glucose and increased glucose uptake in isolated muscles in a time- and dose-dependent manner with maximal effects after 30 min with 100 ng/ml. CNTF increased Akt-S473 phosphorylation in soleus and EDL; however, AMPK-T172 phosphorylation was only increased in soleus. Incubation of muscles from AMPK kinase dead (KD) and wild-type littermates with the PI3-kinase inhibitor LY-294002 demonstrated that PI3-kinase, but not AMPK, was essential for CNTF-stimulated glucose uptake. CNTF-stimulated glucose uptake and Akt phosphorylation were substantially reduced in obesity (high-fat diet and ob/ob) despite normal induction of gp130/AMPK signaling--effects also observed when treating myotubes with C2-ceramide.

CONCLUSIONS

CNTF acutely increases muscle glucose uptake by a mechanism involving the PI3-kinase/Akt pathway that does not require AMPK. CNTF-stimulated glucose uptake is impaired in obesity-induced insulin resistance and by ceramide.

Elevated expression of osteopontin may be related to adipose tissue macrophage accumulation and liver steatosis in morbid obesity

OBJECTIVE

Osteopontin (OPN) plays an important role in the development of insulin resistance and liver complications in dietary murine models. We aimed to determine the expression pattern of OPN and its receptor CD44 in obese patients and mice according to insulin resistance and liver steatosis.

RESEARCH DESIGN AND METHODS

OPN and CD44 expressions were studied in 52 morbidly obese patients and in mice. Cellular studies were performed in HepG2 cells.

RESULTS

Hepatic OPN and CD44 expressions were strongly correlated with liver steatosis and insulin resistance in obese patients and mice. This increased OPN expression could be due to the accumulation of triglycerides, since fat loading in HepG2 promotes OPN expression. In contrast, OPN expression in adipose tissue (AT) was enhanced independently of insulin resistance and hepatic steatosis in obese patients. The elevated OPN expression in AT was paralleled with the AT macrophage infiltration, and both phenomena were reversed after weight loss. The circulating OPN level was slightly elevated in obese patients and was not related to liver steatosis. Further, AT did not appear to secrete OPN. In contrast, bariatric surgery-induced weight loss induced a strong increase in circulating OPN.

CONCLUSIONS

The modestly elevated circulating OPN levels in morbidly obese patients were not related to liver steatosis and did not appear to result from adipose tissue secretion. In subcutaneous AT, expression of OPN was directly related to macrophage accumulation independently from liver complications. In contrast, hepatic OPN and CD44 expressions were related to insulin resistance and steatosis, suggesting their local implication in the progression of liver injury.

Screening of genes differentially expressed in HepG2 cells transfected with human hepatocyte growth factor

AIM: To construct the eukaryotic expression vector of pcDNA3.1(-)-hHGF, and to screen the differentially expressed genes in HepG2 cells transfected with the vector.

METHODS: We constructed the expression vector of pcDNA3.1(-)-hHGF, which was confirmed by restriction enzyme digestion and DNA sequencing, and then transfected it into HepG2 cell line. The expression of HGF protein was observed by Western blotting. At last, we compared the differentially expressed genes between HepG2 cells transfected with pcDNA3.1(-)-hHGF and pcDNA3.1(-) respectively by cDNA microarray technique.

RESULTS: The expression vector was constructed successfully and confirmed by restriction enzyme digestion and DNA sequencing analysis. The expression of hHGF protein was confirmed by Western blotting. High quality mRNA and cDNA had been prepared and successful microarray screening had been conducted. From the scanning results, we found 430 genes that were up-regulated and 88 genes down-regulated in HepG2 cells transfected with hHGF.

CONCLUSION: cDNA microarray technology is successfully used to screen the genes differentially expressed in HepG2 cells transfected with hHGF, which brings some new clues for studying the regulatory mechanism of hHGF in liver cells.

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

Skeletal muscle plays a major role in glucose and lipid metabolism. Active hepatocyte growth factor (HGF) is present in the extracellular matrix in skeletal muscle. However, the effects of HGF on glucose and lipid metabolism in skeletal muscle are completely unknown. We therefore examined the effects of HGF on deoxyglucose uptake (DOGU), glucose utilization, and fatty acid oxidation (FAO) in skeletal muscle cells. HGF significantly enhanced DOGU in mouse soleus muscles in vitro. Furthermore, HGF significantly increased: (i) DOGU in a time- and dose-dependent manner; (ii) glucose utilization; and (iii) plasma membrane expression of Glut-1 and Glut-4 in the rat skeletal muscle model of L6 myotubes. HGF-mediated effect on DOGU was dependent on the activation of phosphatidylinositol 3-kinase signaling pathway. On the other hand, HGF markedly and significantly decreased FAO in L6 myotubes without affecting the activities of carnitine palmitoyltransferase I and II. Collectively, these results indicate that HGF is a potent activator of glucose transport and metabolism and also a strong inhibitor of FAO in rodent myotubes. HGF, through its ability to stimulate glucose transport and metabolism and to impair FAO, may participate in the regulation of glucose disposal in skeletal muscle.

Glucose transport in fibroblasts is unaffected by polyamines

OBJECTIVE

Wound healing is characterized by a net increase in glucose utilization in wound tissues. The mediators involved in this process remain largely unknown. Because polyamines are known to stimulate d-glucose uptake in brush-border membrane vesicles, we investigated whether or not they stimulated sugar uptake in confluent cultured fibroblasts.

METHODS

Cells (at a quiescent or growing state) were incubated for 1 h with various concentrations (0.5-4 mM) of putrescine, spermine, or spermidine or for a range of times (30 min to 3 h) with 2 mM of these same polyamines. Cultures were then incubated for 5 min at +37 degrees C with 2-deoxy-d-[1-(3)H] glucose.

RESULTS

Polyamines were found to have no action on sugar uptake in any of the experimental configurations.

CONCLUSION

These data suggest that polyamines have no effect in cell types in which glucose uptake is mediated by a passive facilitated diffusion process (energy independent). This contrasts with results obtained with cells in which sugar uptake is dependent on adenosine triphosphate. Even if this model does not reflect the complexity of wound healing, these negative results are nevertheless important because they suggest that the arginine- and ornithine-mediated effects on wound healing are not related to a polyamine-mediated increase in glucose transport in fibroblasts.