GDF15 promotes weight loss by enhancing energy expenditure in muscle.

Caloric restriction that promotes weight loss is an effective strategy for treating non-alcoholic fatty liver disease and improving insulin sensitivity in people with type 2 diabetes1. Despite its effectiveness, in most individuals, weight loss is usually not maintained partly due to physiological adaptations that suppress energy expenditure, a process known as adaptive thermogenesis, the mechanistic underpinnings of which are unclear2,3. Treatment of rodents fed a high-fat diet with recombinant growth differentiating factor 15 (GDF15) reduces obesity and improves glycaemic control through glial-cell-derived neurotrophic factor family receptor α-like (GFRAL)-dependent suppression of food intake4-7. Here we find that, in addition to suppressing appetite, GDF15 counteracts compensatory reductions in energy expenditure, eliciting greater weight loss and reductions in non-alcoholic fatty liver disease (NAFLD) compared to caloric restriction alone. This effect of GDF15 to maintain energy expenditure during calorie restriction requires a GFRAL-ß-adrenergic-dependent signalling axis that increases fatty acid oxidation and calcium futile cycling in the skeletal muscle of mice. These data indicate that therapeutic targeting of the GDF15-GFRAL pathway may be useful for maintaining energy expenditure in skeletal muscle during caloric restriction.

Inhibition of tumor migration and invasion by fenofibrate via suppressing epithelial-mesenchymal transition in breast cancers.

The recurrence and metastasis in breast cancer within 3 years after the chemotherapies or surgery leads to poor prognosis with approximately 1-year overall survival. Large-scale scanning research studies have shown that taking lipid-lowering drugs may assist to reduce the risk of death from many cancers, since cholesterol in lipid rafts are essential for maintain integral membrane structure and functional signaling regulation. In this study, we examined five lipid-lowering drugs: swertiamarin, gemfibrozil, clofibrate, bezafibrate, and fenofibrate in triple-negative breast cancer, which is the most migration-prone subtype. Using human and murine triple-negative breast cancer cell lines (Hs 578 t and 4 T1), we found that fenofibrate displays the highest potential in inhibiting the colony formation, wound healing, and transwell migration. We further discovered that fenofibrate reduces the activity of pro-metastatic enzymes, matrix metalloproteinases (MMP)-9 and MMP-2. In addition, epithelial markers including E-cadherin and Zonula occludens-1 are increased, whereas mesenchymal markers including Snail, Twist and α-smooth muscle actin are attenuated. Furthermore, we found that fenofibrate downregulates ubiquitin-dependent GDF-15 degradation, which leads to enhanced GDF-15 expression that inhibits cell migration. Besides, nuclear translocation of FOXO1 is also upregulated by fenofibrate, which may responsible for GDF-15 expression. In summary, fenofibrate with anti-cancer ability hinders TNBC from migration and invasion, and may be beneficial to repurposing use of fenofibrate.

GFRAL-expressing neurons suppress food intake via aversive pathways.

The TGFß cytokine family member, GDF-15, reduces food intake and body weight and represents a potential treatment for obesity. Because the brainstem-restricted expression pattern of its receptor, GDNF Family Receptor α-like (GFRAL), presents an exciting opportunity to understand mechanisms of action for area postrema neurons in food intake; we generated GfralCre and conditional GfralCreERT mice to visualize and manipulate GFRAL neurons. We found infection or pathophysiologic states (rather than meal ingestion) stimulate GFRAL neurons. TRAP-Seq analysis of GFRAL neurons revealed their expression of a wide range of neurotransmitters and neuropeptides. Artificially activating GfralCre -expressing neurons inhibited feeding, decreased gastric emptying, and promoted a conditioned taste aversion (CTA). GFRAL neurons most strongly innervate the parabrachial nucleus (PBN), where they target CGRP-expressing (CGRPPBN) neurons. Silencing CGRPPBN neurons abrogated the aversive and anorexic effects of GDF-15. These findings suggest that GFRAL neurons link non-meal-associated pathophysiologic signals to suppress nutrient uptake and absorption.

Growth differentiation factor 15 is required for triple-negative breast cancer cell growth and chemoresistance.

Growth differentiation factor 15 (GDF15) is a pleiotropic cytokine, which is involved in the cellular stress response following acute damage. However, the functional role of GDF15 in triple-negative breast cancer (TNBC) has not been fully elucidated. ELISA, Western blot, and PCR assays as well as bioinformatics analyses were conducted to observe the expression of GDF15. Cell Counting Kit-8, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and crystal violet staining assays were conducted to evaluate paclitaxel resistance and cell viability. Cell apoptosis was analyzed by Western blotting. Murine xenograft model assay was employed to evaluate tumor growth in vivo . Our data indicate that GDF15 is markedly elevated in paclitaxel-resistant TNBC cells, which is significantly associated with unfavorable prognosis. Silencing of GDF15 robustly inhibits the proliferation of tumor cells and increases their sensitivity to paclitaxel in vitro and in vivo , whereas the treatment of purified GDF15 protein confers breast cancer cells with chemoresistance ability. Moreover, GDF15 activates protein kinase B (AKT) /mammalian target of rapamycin (mTOR) signaling, inhibition of AKT or mTOR reverses the prosurvival effect of GDF15 and enhances the antitumor efficacy of paclitaxel in TNBC cells. Altogether, our study uncovers the role of GDF15 in tumor growth and paclitaxel resistance, implicating a potential therapeutic target for TNBC.

Non-homeostatic body weight regulation through a brainstem-restricted receptor for GDF15.

Under homeostatic conditions, animals use well-defined hypothalamic neural circuits to help maintain stable body weight, by integrating metabolic and hormonal signals from the periphery to balance food consumption and energy expenditure. In stressed or disease conditions, however, animals use alternative neuronal pathways to adapt to the metabolic challenges of altered energy demand. Recent studies have identified brain areas outside the hypothalamus that are activated under these 'non-homeostatic' conditions, but the molecular nature of the peripheral signals and brain-localized receptors that activate these circuits remains elusive. Here we identify glial cell-derived neurotrophic factor (GDNF) receptor alpha-like (GFRAL) as a brainstem-restricted receptor for growth and differentiation factor 15 (GDF15). GDF15 regulates food intake, energy expenditure and body weight in response to metabolic and toxin-induced stresses; we show that Gfral knockout mice are hyperphagic under stressed conditions and are resistant to chemotherapy-induced anorexia and body weight loss. GDF15 activates GFRAL-expressing neurons localized exclusively in the area postrema and nucleus tractus solitarius of the mouse brainstem. It then triggers the activation of neurons localized within the parabrachial nucleus and central amygdala, which constitute part of the 'emergency circuit' that shapes feeding responses to stressful conditions. GDF15 levels increase in response to tissue stress and injury, and elevated levels are associated with body weight loss in numerous chronic human diseases. By isolating GFRAL as the receptor for GDF15-induced anorexia and weight loss, we identify a mechanistic basis for the non-homeostatic regulation of neural circuitry by a peripheral signal associated with tissue damage and stress. These findings provide opportunities to develop therapeutic agents for the treatment of disorders with altered energy demand.

Growth differentiation factor 15 (GDF15) and semaglutide inhibit food intake and body weight through largely distinct, additive mechanisms.

AIMS: To evaluate whether the potent hypophagic and weight-suppressive effects of growth differentiation factor-15 (GDF15) and semaglutide combined would be a more efficacious antiobesity treatment than either treatment alone by examining whether the neural and behavioural mechanisms contributing to their anorectic effects were common or disparate. MATERIALS/METHODS: Three mechanisms were investigated to determine how GDF15 and semaglutide induce anorexia: the potentiation of the intake suppression by gastrointestinal satiation signals; the reduction in motivation to feed; and the induction of visceral malaise. We then compared the effects of short-term, combined GDF15 and semaglutide treatment on weight loss to the individual treatments. Rat pharmaco-behavioural experiments assessed whether GDF15 or semaglutide added to the satiating effects of orally gavaged food and exogenous cholecystokinin (CCK). A progressive ratio operant paradigm was used to examine whether GDF15 or semaglutide reduced feeding motivation. Pica behaviour (ie, kaolin intake) and conditioned affective food aversion testing were used to evaluate visceral malaise. Additionally, fibre photometry studies were conducted in agouti-related protein (AgRP)-Cre mice to examine whether GDF15 or semaglutide, alone or in combination with CCK, modulate calcium signalling in hypothalamic AgRP neurons. RESULTS: Semaglutide reduced food intake by amplifying the feeding-inhibitory effect of CCK or ingested food, inhibited the activity of AgRP neurons when combined with CCK, reduced feeding motivation and induced malaise. GDF15 induced visceral malaise but, strikingly, did not affect feeding motivation, the satiating effect of ingested food or CCK signal processing. Combined GDF15 and semaglutide treatment produced greater food intake and body weight suppression than did either treatment alone, without enhancing malaise. CONCLUSIONS: GDF15 and semaglutide reduce food intake and body weight through largely distinct processes that produce greater weight loss and feeding suppression when combined.

GDF15 Contributes to Radioresistance by Mediating the EMT and Stemness of Breast Cancer Cells.

Radiotherapy is one of the conventional methods for the clinical treatment of breast cancer. However, radioresistance has an adverse effect on the prognosis of breast cancer patients after radiotherapy. In this study, using bioinformatic analysis of GSE59732 and GSE59733 datasets in the Gene Expression Omnibus (GEO) database together with the prognosis database of breast cancer patients after radiotherapy, the GDF15 gene was screened out to be related to the poor prognosis of breast cancer after radiotherapy. Compared with radiosensitive parental breast cancer cells, breast cancer cells with acquired radioresistance exhibited a high level of GDF15 expression and enhanced epithelial-to-mesenchymal transition (EMT) properties of migration and invasion, as well as obvious stem-like traits, including the increases of mammosphere formation ability, the proportion of stem cells (CD44+ CD24- cells), and the expressions of stem cell-related markers (SOX2, NANOG). Moreover, knockdown of GDF15 sensitized the radioresistance cells to irradiation and significantly inhibited their EMT and stem-like traits, indicating that GDF15 promoted the radioresistance of breast cancer by enhancing the properties of EMT and stemness. Conclusively, GDF15 may be applicable as a novel prognosis-related biomarker and a potential therapeutic target for breast cancer radiotherapy.

Treatment with GDF15, a TGFß superfamily protein, induces protective effect on retinal ganglion cells.

Growth differentiation factor 15 (GDF15) is a protein belonging to the transforming growth factor beta (TGF-ß) superfamily. The precursor GDF15 is cleaved and activated as a mature GDF15 by protease. GDF15 has been detected in the aqueous humor of the primary open angle glaucoma patients, however the localization and the effect on the retinal ganglion cells (RGCs) are still unknown. Thus, the purpose of this study was to elucidate the effect of GDF15 on mouse optic nerve crush (ONC) model and primary culture of rat RGCs. Immunostaining showed that the GDF15 was in the ganglion cell layer (GCL), and colocalized with GFAP-positive cells in the GCL and the optic nerve. Western blotting analysis showed that the mature GDF15 was upregulated in the retina and the optic nerve after the ONC. Intravitreal injection of GDF15 suppressed RGCs loss of the ONC model mice in vivo. The neurites length of the primary culture of rat RGCs were increased by mature GDF15 treatment. In addition, the neurotrophic effect of GDF15 was canceled by RET inhibitor treatment. These findings indicate that GDF15 has neuroprotective effect on RGCs via GFRAL-RET pathway. Therefore, GDF15 may be one of novel therapeutic targets in RGC degenerative diseases.

GDF15 promotes simultaneous astrocyte remodeling and tight junction strengthening at the blood-brain barrier.

Perivascular astrocyte processes (PAP) surround cerebral endothelial cells (ECs) and modulate the strengthening of tight junctions to influence blood-brain barrier (BBB) permeability. Morphologically altered astrocytes may affect barrier properties and trigger the onset of brain pathologies. However, astrocyte-dependent mediators of these events remain poorly studied. Here, we show a pharmacologically driven elevated expression and release of growth/differentiation factor 15 (GDF15) in rat primary astrocytes and cerebral PAP. GDF15 has been shown to possess trophic properties for motor neurons, prompting us to hypothesize similar effects on astrocytes. Indeed, its increased expression and release occurred simultaneously to morphological changes of astrocytes in vitro and PAP, suggesting modulatory effects of GDF15 on these cells, but also neighboring EC. Administration of recombinant GDF15 was sufficient to promote astrocyte remodeling and enhance barrier properties between ECs in vitro, whereas its pharmacogenetic abrogation prevented these effects. We validated our findings in male high anxiety-related behavior rats, an animal model of depressive-like behavior, with shrunk PAP associated with reduced expression of the junctional protein claudin-5, which were both restored by a pharmacologically induced increase in GDF15 expression. Thus, we identified GDF15 as an astrocyte-derived trigger of astrocyte process remodeling linked to enhanced tight junction strengthening at the BBB.

Growth Differentiation Factor 15 Promotes Progression of Esophageal Squamous Cell Carcinoma via TGF-ß Type II Receptor Activation.

OBJECTIVES: Growth differentiation factor 15 (GDF15), which is derived from tumor-associated macrophages (TAM) and cancer cells, promotes progression of esophageal squamous cell carcinomas (ESCC). However, its role in the ESCC microenvironment remains unclear. Here, we examined the effects of GDF15 on ESCC cell lines and tissues. METHODS: Western blotting, MTS, and Transwell migration/invasion assays were used to evaluate cell signaling, proliferation, and migration/invasion, respectively, in ESCC cell lines treated with recombinant human GDF15 (rhGDF15). ESCC cell lines were administered a TGF-ßRI/II inhibitor (LY2109761), small interfering RNA against TGF-ß type II receptor (TGF-ßRII), or neutralizing antibody against TGF-ßRII to study the role of TGF-ßRII in mediating the effects of rhGDF15. The localization of GDF15 and TGF-ßRII in ESCC cell lines was observed by immunofluorescence. TGF-ßRII expression in ESCC tissues was analyzed by immunohistochemistry, and the relationship between clinicopathological factors and prognosis in ESCC patients was evaluated. RESULTS: rhGDF15 increased levels of phosphorylated Akt, Erk1/2, and TGF-ßRII in ESCC cell lines. Inhibition/knockdown of TGF-ßRII suppressed rhGDF15-induced activation of Akt and Erk1/2 and enhancement of cellular proliferation, migration, and invasion. Immunofluorescence revealed that TGF-ßRII and GDF15 were colocalized in ESCC cell lines. High TGF-ßRII expression in ESCC tissues, as determined by immunohistochemistry, correlated with depth of invasion and increased number of infiltrating TAMs. ESCC patients with high TGF-ßRII expression showed a tendency toward poor prognosis. CONCLUSIONS: GDF15 promotes ESCC progression by increasing cellular proliferation, migration, and invasion via TGF-ßRII signaling.

GDF15 induced apoptosis and cytotoxicity in A549 cells depends on TGFBR2 expression.

GDF15 plays a paradoxical role during carcinogenesis; it inhibits tumour growth in the early stages and promotes tumour cell proliferation in the late stages of cancer. Besides, GDF15 can induce apoptosis in some cancer cells including A549 but not in some others. Moreover, as a potential receptor for GDF15, TGFBR2 is inactivated during carcinogenesis in many types of cancers, and it is not present in cells with no GDF15 induced apoptosis. Thus, we tested whether GDF15 overexpression and/or TGFBR2 silencing can affect the GDF15 induced apoptosis in A549 cells. The full and mature forms of GDF15 were cloned and overexpressed in A549 cells. The TGFBR2 was silenced using specific siRNA and confirmed by real-time PCR. Results indicated that overexpression of full and mature forms of GDF15 as well as TGFBR2 knocked down reduced A549 cell viability in 24 and 48 hours. Flow cytometric analysis of annexin V/PI indicated induction of apoptosis in A549 cells by overexpression of GDF15 or silencing TGFBR2. Interestingly, the silencing of TGFBR2 inhibited the GDF15 induced cytotoxicity and apoptosis in A549 cells. Overexpression of GDF15 activated caspase-9 and caspase-3 and inhibited ERK1/2 and p38 phosphorylation in A549 cells. TGFBR2 knocked down inhibited GDF15 effects on caspases, ERK1/2, and p38MAPK activation. Our results indicated that the effect of GDF15 on apoptosis and activation of MAPK in A549 cells depends on TGFBR2 expression. These findings may point to mechanisms in which GDF15 exerts dual effect during carcinogenesis with regard to TGFBR2 expression. SIGNIFICANCE OF THE STUDY: GDF15 plays a tumour suppressor or promotor roles during carcinogenesis. The expression of GDF15 induced cytotoxicity, apoptosis, and inhibition of MAPK in A549 cells. All these effects were blocked by silencing TGFBR2 expression. These findings may point to mechanisms in which GDF15 exerts dual effect during carcinogenesis with regard to TGFBR2 expression.

Inhibition of Breast Cancer Cell Invasion by Ras Suppressor-1 (RSU-1) Silencing Is Reversed by Growth Differentiation Factor-15 (GDF-15).

Extracellular matrix (ECM)-related adhesion proteins are important in metastasis. Ras suppressor-1 (RSU-1), a suppressor of Ras-transformation, is localized to cell⁻ECM adhesions where it interacts with the Particularly Interesting New Cysteine-Histidine rich protein (PINCH-1), being connected to Integrin Linked Kinase (ILK) and alpha-parvin (PARVA), a direct actin-binding protein. RSU-1 was also found upregulated in metastatic breast cancer (BC) samples and was recently demonstrated to have metastasis-promoting properties. In the present study, we transiently silenced RSU-1 in BC cells, MCF-7 and MDA-MB-231. We found that RSU-1 silencing leads to downregulation of Growth Differentiation Factor-15 (GDF-15), which has been associated with both actin cytoskeleton reorganization and metastasis. RSU-1 silencing also reduced the mRNA expression of PINCH-1 and cell division control protein-42 (Cdc42), while increasing that of ILK and Rac regardless of the presence of GDF-15. However, the downregulation of actin-modulating genes PARVA, RhoA, Rho associated kinase-1 (ROCK-1), and Fascin-1 following RSU-1 depletion was completely reversed by GDF-15 treatment in both cell lines. Moreover, complete rescue of the inhibitory effect of RSU-1 silencing on cell invasion was achieved by GDF-15 treatment, which also correlated with matrix metalloproteinase-2 expression. Finally, using a graph clustering approach, we corroborated our findings. This is the first study providing evidence of a functional association between RSU-1 and GDF-15 with regard to cancer cell invasion.

Effect of growth differentiation factor-15 secreted by human umbilical cord blood-derived mesenchymal stem cells on amyloid beta levels in in vitro and in vivo models of Alzheimer's disease.

Alzheimer's disease (AD), which is the most common progressive neurodegenerative disease, causes learning and memory impairment. The pathological progress of AD can derive from imbalanced homeostasis of amyloid beta (Aß) in the brain. In such cases, microglia play important roles in regulating the brain Aß levels. In the present study, we found that human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) can increase, through paracrine action, the ability of microglial cells to clear Aß. In order to identify the associated paracrine factors, a secretome of hUCB-MSCs co-cultured with Aß-treated BV2 microglial cells was analyzed using a human cytokine protein array. As a result, growth differentiation factor-15 (GDF-15) was identified as a predominant candidate, and its association with Aß clearance by microglial cells was investigated in vitro and in a 5XFAD mouse model. When Aß-treated BV2 cells were treated with exogenous recombinant GDF-15, the Aß levels in the culture medium decreased. Moreover, GDF-15 injection in the brain parenchyma of 5XFAD mice also led to decrease in Aß plaques. In contrast, co-culture of BV2 cells and hUCB-MSCs treated with GDF-15-specific siRNA did not influence the Aß levels in the culture medium. To elucidate how these phenomena are related, we confirmed that GDF-15 specifically increases insulin-degrading enzyme (IDE) expression in microglial cells through TGFß receptor type II (TGFßRII), both in vitro and in vivo. These findings suggest that hUCB-MSCs promote the Aß clearance ability of microglial cells through regulation of GDF-15 secretion, thus elucidating a therapeutic mechanism for AD.

CST3 and GDF15 ameliorate renal fibrosis by inhibiting fibroblast growth and activation.

The final strategies to care patients with end-stage renal fibrosis rely on dialysis and kidney transplantation. Because such treatments are invasive and cause health problems eventually, it is necessary to develop new therapeutic strategies for delaying the disease progress. We here searched for cytokines showing an anti-fibrotic activity in cell-based experiments. Cystatin C (CST3) and Growth differentiation factor 15 (GDF15) were identified to have anti-fibrotic activities in a cytokine array screening. In primary fibroblasts isolated from the mouse kidneys subjected to ureteral obstruction-induced fibrosis, each cytokine induced apoptotic cell death and reduced collagen production. These anti-fibrotic effects were further augmented by co-administration of both cytokines. Mechanistically, CST3 and GDF15 were found to block the TGF-ß receptor and the N-Myc signaling pathways, respectively. In mice with unilateral ureter obstruction, each cytokine and the combination of two cytokines effectively reduced the fibrotic burden in the subjected kidneys. Therefore, we propose that CST3 and GDF15 could be potential candidates for biopharmaceutics to ameliorate renal fibrosis.

Treatment with the TGF-b superfamily cytokine MIC-1/GDF15 reduces the adiposity and corrects the metabolic dysfunction of mice with diet-induced obesity.

OBJECTIVES: To test the potential efficacy of recombinant macrophage inhibitory cytokine-1 (MIC-1/GDF15) as an obesity therapeutic. METHODS: Male C57BL/6 J mice, either fed on normal chow or high-fat diet for 16 weeks to induce diet-induced obesity, were infused with either recombinant MIC-1/GDF15 or vehicle for 34 days by osmotic minipump. During the experimental period metabolic parameters were measured. Blood and tissue were collected for analysis of inflammatory markers. RESULTS: MIC-1/GDF15 decreased food intake and body weight of high-fat-fed and chow-fed mice compared with their vehicle-treated control mice. MIC-1/GDF15 reduced body weight, accompanied by greater reduction in fat mass in high-fat-fed mice compared to its effect on chow-fed mice. Further, whilst MIC-1/GDF15-treated chow-fed mice lost lean as well as fat mass, MIC-1/GDF15-treated high-fat-fed mice lost fat mass alone. This reduction in body weight and adiposity was due largely to reduced food intake, but MIC-1/GDF15-treated high-fat-fed mice also displayed increased energy expenditure that may be due to increased thermogenesis. MIC-1/GDF15-treated high-fat-fed mice also had higher circulating level of adiponectin and lower tissue expression, and circulating levels of leptin and inflammatory mediators associated with insulin resistance. Peripheral insulin and glucose intolerance were improved in both MIC-1/GDF15-treated high-fat-fed and chow-fed mice compared to that of their vehicle-treated control mice. CONCLUSIONS: MIC-1/GDF15 is highly effective in reducing adiposity and correcting the metabolic dysfunction of mice with high-fat fed. These studies suggest that MIC-1/GDF15 may be a candidate anti-obesity therapeutic.

GDF-15 enhances intracellular Ca2+ by increasing Cav1.3 expression in rat cerebellar granule neurons.

GDF-15 (growth/differentiation factor 15) is a novel member of the TGF (transforming growth factor)-ß superfamily that has critical roles in the central and peripheral nervous systems. We reported previously that GDF-15 increased delayed rectifier outward K(+) currents and Kv2.1 α subunit expression through TßRII (TGF-ß receptor II) to activate Src kinase and Akt/mTOR (mammalian target of rapamycin) signalling in rat CGNs (cerebellar granule neurons). In the present study, we found that treatment of CGNs with GDF-15 for 24 h increased the intracellular Ca(2+) concentration ([Ca(2+)]i) in response to membrane depolarization, as determined by Ca(2+) imaging. Whole-cell current recordings indicated that GDF-15 increased the inward Ca(2+) current (ICa) without altering steady-state activation of Ca(2+) channels. Treatment with nifedipine, an inhibitor of L-type Ca(2+) channels, abrogated GDF-15-induced increases in [Ca(2+)]i and ICa The GDF-15-induced increase in ICa was mediated via up-regulation of the Cav1.3 α subunit, which was attenuated by inhibiting Akt/mTOR and ERK (extracellular-signal-regulated kinase) pathways and by pharmacological inhibition of Src-mediated TßRII phosphorylation. Given that Cav1.3 is not only a channel for Ca(2+) influx, but also a transcriptional regulator, our data confirm that GDF-15 induces protein expression via TßRII and activation of a non-Smad pathway, and provide novel insight into the mechanism of GDF-15 function in neurons.

GDF15 derived from both tumor-associated macrophages and esophageal squamous cell carcinomas contributes to tumor progression via Akt and Erk pathways.

Tumor-associated macrophages (TAMs) are known to be involved in the progression, angiogenesis, and motility of various cancers. We previously reported the association between an increased number of infiltrating TAMs with tumor progression and poor prognosis in esophageal squamous cell carcinomas (ESCCs). To study the roles of TAMs in ESCC, we first exposed peripheral blood monocyte (PBMo)-derived macrophages from healthy volunteers to conditioned media of TE series human ESCC cell line (TECM) and confirmed the induction of the expression of the M2 macrophage marker CD204 and the protumorigenic factors interleukin (IL)-10, VEGFA, and MMPs. Next, we compared gene expression profiles between PBMo-derived macrophages stimulated with or without TECM by cDNA microarray and focused on growth differentiation factor 15 (GDF15) among the highly expressed genes including IL-6, IL-8, and CXCL1. Our immunohistochemical study of 70 surgically resected ESCCs revealed that GDF15 was present not only in cancer cells but also in macrophages. The high expression of GDF15 in the ESCCs was significantly correlated with several more malignant phenotypes including vessel invasion, lymph node metastasis, and clinical stages. Patients with high GDF15 expression showed significantly poorer disease-free survival (P=0.011) and overall survival (P=0.041). We also found that recombinant human GDF15 promotes cell proliferation and the phosphorylation of both Akt and Erk1/2 in ESCC cell lines in vitro. These results indicate that GDF15 is secreted by both TAMs and cancer cells in the tumor microenvironment and is associated with aberrant growth and a poor prognosis in human ESCC.

Increased expression of GDF-15 may mediate ICU-acquired weakness by down-regulating muscle microRNAs.

RATIONALE: The molecular mechanisms underlying the muscle atrophy of intensive care unit-acquired weakness (ICUAW) are poorly understood. We hypothesised that increased circulating and muscle growth and differentiation factor-15 (GDF-15) causes atrophy in ICUAW by changing expression of key microRNAs. OBJECTIVES: To investigate GDF-15 and microRNA expression in patients with ICUAW and to elucidate possible mechanisms by which they cause muscle atrophy in vivo and in vitro. METHODS: In an observational study, 20 patients with ICUAW and seven elective surgical patients (controls) underwent rectus femoris muscle biopsy and blood sampling. mRNA and microRNA expression of target genes were examined in muscle specimens and GDF-15 protein concentration quantified in plasma. The effects of GDF-15 on C2C12 myotubes in vitro were examined. MEASUREMENTS AND MAIN RESULTS: Compared with controls, GDF-15 protein was elevated in plasma (median 7239 vs 2454 pg/mL, p=0.001) and GDF-15 mRNA in the muscle (median twofold increase p=0.006) of patients with ICUAW. The expression of microRNAs involved in muscle homeostasis was significantly lower in the muscle of patients with ICUAW. GDF-15 treatment of C2C12 myotubes significantly elevated expression of muscle atrophy-related genes and down-regulated the expression of muscle microRNAs. miR-181a suppressed transforming growth factor-ß (TGF-ß) responses in C2C12 cells, suggesting increased sensitivity to TGF-ß in ICUAW muscle. Consistent with this suggestion, nuclear phospho-small mothers against decapentaplegic (SMAD) 2/3 was increased in ICUAW muscle. CONCLUSIONS: GDF-15 may increase sensitivity to TGF-ß signalling by suppressing the expression of muscle microRNAs, thereby promoting muscle atrophy in ICUAW. This study identifies both GDF-15 and associated microRNA as potential therapeutic targets.

Research Progress on the Role and Mechanism of GDF15 in Body Weight Regulation.

BACKGROUND: Growth differentiation factor-15 (GDF15) is a member of the growth differentiation factor subfamily in the transforming growth factor beta superfamily. GDF15 has multiple functions and can regulate biological processes. High levels of GDF15 in the circulation can affect metabolic processes. Studies have shown that GDF15 is associated with changes in body weight. SUMMARY: This review reviews the current knowledge on the relationship between GDF15 and body weight change, focusing on the role and mechanism of GDF15 in body weight regulation. GDF15 plays an important role in reducing food intake, improving insulin resistance, and breaking down fat, suggesting that GDF15 has an important regulatory effect on body weight. The mechanism by which GDF15 causes reduced food intake may be related to changes in food preference, delayed gastric emptying, and conditioned taste aversion. GDF15 can combat insulin resistance induced by inflammation or protect ß cell from apoptosis. GDF15 probably promotes lipolysis through a brain-somatic tissue circuit. Several factors and related signaling pathways are also mentioned that can contribute to the effects of GDF15 on reducing weight. KEY MESSAGE: GDF15 plays an important role in weight regulation and provides a new direction for the treatment of obesity. Its effects on resisting obesity are of great significance to inhibiting the progression of metabolic diseases. It is expected to become a new target for regulating body weight, improving obesity, and treating metabolic diseases such as diabetes.

Growth Differentiation Factor-15 Orchestrates Inflammation-Related Diseases via Macrophage Polarization.

Macrophage polarization is a critical determinant of disease progression and regression. Studies on macrophage plasticity and polarization can provide a theoretical basis for the tactics of diagnosis and treatment for macrophage-related diseases. These include inflammation-related diseases, such as sepsis, tumors, and metabolic disorders. Growth differentiation factor-15 (GDF-15) or macrophage inhibitory cytokine-1, a 25 kDa secreted homodimeric protein, is a member of the transforming growth factor-ß (TGF-ß) superfamily that is released in response to external stressors. GDF-15 regulates biological effects such as tumor occurrence, inflammatory response, tissue damage, angiogenesis, and bone metabolism. It has been shown to exert anti-inflammatory and pro-inflammatory effects in inflammation-related diseases. Moreover, inflammatory stimuli can induce GDF-15 expression in immune and parenchymal cells. GDF-15 exhibits a feedback inhibitory effect by inhibiting tumor necrosis factor-α secretion during the macrophage activation anaphase, suggesting that there may be a close association between the two. GDF-15 directly induces CD14+ monocytes to produce the M2-like macrophage phenotype, inhibits monocyte-derived macrophage for M1-like polarization, and induces monocyte-derived Mφ for M2-like polarization. This review summarizes the macrophage polarization mechanism of GDF-15 under the conditions of sepsis, colon cancer, atherosclerosis, and obesity. An improved understanding of the role and molecular mechanisms of action of GDF-15 could greatly elucidate the mechanism of disease occurrence and development and provide new ideas for targeted disease prevention and treatment. An advanced understanding of the function and molecular mechanisms of action of GDF-15 may be helpful in the assessment of its potential value as a therapeutic and diagnostic target.