Uniting GDF15 and GFRAL: Therapeutic Opportunities in Obesity and Beyond

GDF15 Analogues Acting as GFRAL Ligands

Growth differentiation factor 15 (GDF15) is a TGF-β superfamily member involved in diverse physiological and pathological processes. It is expressed in various tissues and its circulating levels rise during exercise, aging, pregnancy, and conditions such as cancer, cardiovascular disease, and infections. The biological activities of GDF15, including anorexia and cachexia, are primarily mediated through the GFRAL receptor, localized in the brainstem and functioning via RET co-receptor recruitment. This signaling is crucial for energy homeostasis and nausea induction. Recent studies suggest a broader GFRAL distribution, potentially explaining GDF15's distinct roles. These findings sparked interest in leveraging GDF15-GFRAL pathways for therapeutic development. Two primary strategies include GDF15 analogues as GFRAL agonists for obesity treatment and GDF15-derived peptides as antagonists to counteract cancer-induced cachexia and related disorders. This review highlights advancements in understanding GDF15-GFRAL signaling and its implications, summarizing bioactive GDF15-derived molecules, their pharmacological applications, and offering insights into novel treatment avenues for GDF15-associated conditions.

The association between serum growth differentiation factor 15 and insulin resistance in women diagnosed with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is strongly associated with metabolic abnormalities, with 50-70% of patients exhibiting insulin resistance (IR), which significantly impacts the reproductive health of women in their reproductive years. Growth differentiation factor 15 (GDF15), a hormone responsive to nutritional stress, has been implicated in several diseases. This study sought to clarify the relationship between GDF15 levels and IR condition in PCOS patients. Based on the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), patients were categorized into an IR-PCOS group (n = 124) and a non-insulin-resistant group (non-IR-PCOS group, n = 109). Fasting blood samples were collected to measure GDF15 concentrations. To assess metabolic complications in relation to GDF15 levels, patients were also classified into high and normal GDF15 groups. Serum GDF15 levels were significantly higher in IR-PCOS patients (median 772.94 pg/ml) compared to non-IR-PCOS patients (median 575.80 pg/ml, P < 0.05). The high GDF15 group showed more severe metabolic and lipid abnormalities than the normal GDF15 group. Spearman correlation analysis revealed a correlation between increased GDF15 levels and impaired glucose metabolism. Logistic regression analysis identified GDF15, HDL-C, and prolactin as risk factors for IR in PCOS, and the fully adjusted regression coefficient for GDF15 levels and IR prevalence was 4.490 (95% CI 1.541 to 13.088). Restricted cubic spline analysis confirmed a positive association between GDF15 levels and IR within a specific range. The combined predictive probability of GDF15, prolactin, and HDL-C for IR was 0.763 (95% CI 0.701 to 0.826) according to ROC analysis. Elevated GDF15 levels may be associated with IR in PCOS patients, suggesting a potential role for GDF15 in the pathophysiology of IR in this condition.

The clinical utility in hospital-wide use of growth differentiation factor 15 as a biomarker for mitochondrial DNA-related disorders

Clinical recognition of primary mitochondrial disorders (PMD) is difficult due to the clinical and genetic heterogeneity. Whereas lactate has low sensitivity and specificity, in structured clinical studies growth differentiation factor 15 (GDF15) has shown promise with elevations in mitochondrial DNA (mtDNA)-related PMD, but its specificity has been questioned. In a tertiary care hospital-wide study, medical records were retrospectively reviewed from 418 cases where GDF15 levels were obtained by clinicians. Patients were classified into patients with PMD due to mtDNA-related defects (mtDNA maintenance, mtDNA deletions, and mtDNA-encoded tRNA variants), PMD due to structural defects or other nuclear causes, and in non-mitochondrial disease. Patients with liver disease or systemic critical illness were excluded. GDF15 was assayed in a clinical laboratory with a cutoff of 750 ng/L. There were 38 mtDNA-related PMD (GDF15 >750 pg/mL in 76%), 35 other nuclear DNA-encoded PMD or structural subunits (31% elevated GDF15), 309 non-mitochondrial disorders (13% elevated GDF15). Based on the highest Youden J-index, the optimal cut-off value to identify these target mtDNA-related disorders was 815 pg/mL, with sensitivity 76%, specificity 88%, positive predictive value of 41% and negative predictive value of 97%. At this optimized cutoff level, mtDNA-encoded PMD patients had elevated GDF15 in 76%, nuclear DNA-encoded PMD in 26%, and non-mitochondrial disorders in 11% of patients. Thus, in a real-life clinical setting, after excluding abnormal liver function and critical illness, GDF15 had good clinical utility increasing the odds at predicting mtDNA-related primary mitochondrial disorders 14-fold, but not for structural or other nuclear-encoded primary mitochondrial disorders.

Alterations in Biomarkers Associated with Cardiovascular Health and Obesity with Short-Term Lifestyle Changes in Overweight Women: The Role of Exercise and Diet

Background and Objectives: In this study, the effects of an eight-week exercise and nutrition program on blood lipids, glucose, insulin, insulin resistance (HOMA-IR), leptin, ghrelin, irisin, malondialdehyde (MDA), and Growth Differentiation Factor 15 (GDF15) in overweight women were investigated. Materials and Methods: A total of 48 women volunteers participated in this study. The participants were randomly divided into four groups: control (C), exercise (E), nutrition (N), exercise + nutrition (E + N). While no intervention was applied to group C, the other groups participated in the predetermined programs for 8 weeks. At the beginning and end of this study, body composition was measured and blood samples were taken. Results: It was determined that the body composition components, lipid profile indicators, insulin, glucose, insulin resistance, leptin, ghrelin, irisin, and MDA parameters examined in this study showed positive changes in the intervention groups. Group E had a greater effect on body muscle percentage, MDA, and irisin levels, while group N had a greater effect on blood lipids and ghrelin levels. Conclusions: As a result, it is thought that lifestyle changes are important to improve cardiovascular health and combat obesity, and that maintaining a healthy diet together with exercise may be more effective.

Overview of growth differentiation factor 15 (GDF15) in metabolic diseases

GDF15 is a stress response cytokine and a distant member of the transforming growth factor beta (TGFβ) superfamily, its levels increase in response to cell stress and certain diseases in the serum. To exert its effects, GDF15 binds to glial-derived neurotrophic factor (GDNF) receptor alpha-like (GFRAL), which was firstly identified in 2017 and highly expressed in the brain stem. Many studies have demonstrated that elevated serum GDF15 is associated with anorexia and weight loss. Herein, we focus on the biology of GDF15, specifically how this circulating protein regulates appetite and metabolism in influencing energy homeostasis through its actions on hindbrain neurons to shed light on its impact on diseases such as obesity and anorexia/cachexia syndromes. It works as an endocrine factor and transmits metabolic signals leading to weight reduction effects by directly reducing appetite and indirectly affecting food intake through complex mechanisms, which could be a promising target for the treatment of energy-intake disorders.

Different roles of circulating and intramuscular GDF15 as markers of skeletal muscle health

Introduction

Growth Differentiation Factor 15 (GDF15) is a mitokine expressed in response to various stresses whose circulating levels increase with age and are associated with numerous pathological conditions, including muscle wasting and sarcopenia. However, the use of circulating GDF15 (c-GDF15) as a biomarker of sarcopenia is still debated. Moreover, the role of GDF15 intracellular precursor, pro-GDF15, in human skeletal muscle (SM-GDF15) is not totally understood. In order to clarify these points, the association of both forms of GDF15 with parameters of muscle strength, body composition, metabolism and inflammation was investigated.

Methods

the levels of c-GDF15 and SM-GDF15 were evaluated in plasma and muscle biopsies, respectively, of healthy subjects (HS) and patients with lower limb mobility impairment (LLMI), either young (<40 years-old) or old (>70 years-old). Other parameters included in the analysis were Isometric Quadriceps Strength (IQS), BMI, lean and fat mass percentage, Vastus lateralis thickness, as well as circulating levels of Adiponectin, Leptin, Resistin, IGF-1, Insulin, IL6, IL15 and c-PLIN2. Principal Component Analysis (PCA), Canonical Discriminant Analysis (CDA) and Receiving Operating Characteristics (ROC) analysis were performed.

Results

c-GDF15 but not SM-GDF15 levels resulted associated with decreased IQS and IGF-1 levels in both HS and LLMI, while only in LLMI associated with increased levels of Resistin. Moreover, in LLMI both c-GDF15 and SM-GDF15 levels were associated with IL-6 levels, but interestingly SM-GDF15 is lower in LLMI with respect to HS. Furthermore, a discrimination of the four groups of subjects based on these parameters was possible with PCA and CDA. In particular HS, LLMI over 70 years or under 40 years of age were discriminated based on SM-GDF15, c-GDF15 and Insulin levels, respectively.

Conclusion

our data support the idea that c-GDF15 level could be used as a biomarker of decreased muscle mass and strength. Moreover, it is suggested that c-GDF15 has a different diagnostic significance with respect to SM-GDF15, which is likely linked to a healthy and active state.

Analysis of the Associations of Measurements of Body Composition and Inflammatory Factors with Cardiovascular Disease and Its Comorbidities in a Community-Based Study

The associations of cardiovascular disease (CVD) with comorbidities and biochemical and body composition measurements are repeatedly described but have not been studied simultaneously. In the present cross-sectional study, information on CVD and comorbidities [type 2 diabetes mellitus (T2DM), hypertension (HTN), and hyperlipidemia (HDL)], body composition, levels of soluble markers, and other measures were collected from 1079 individuals. When we examined the association of each comorbidity and CVD, controlling for other comorbidities, we observed a clear pattern of the comorbidity-related specific associations with tested covariates. For example, T2DM was significantly associated with GDF-15 levels and the leptin/adiponectin (L/A) ratio independently of two other comorbidities; HTN, similarly, was independently associated with extracellular water (ECW) levels, L/A ratio, and age; and HDL was independently related to age only. CVD showed very strong independent associations with each of the comorbidities, being associated most strongly with HTN (OR = 10.89, 6.46-18.38) but also with HDL (2.49, 1.43-4.33) and T2DM (1.93, 1.12-3.33). An additive Bayesian network analysis suggests that all three comorbidities, particularly HTN, GDF-15 levels, and ECW content, likely have a main role in the risk of CVD development. Other factors, L/A ratio, lymphocyte count, and the systemic inflammation response index, are likely indirectly related to CVD, acting through the comorbidities and ECW.

Growth Differentiation Factor 15 and Diet Quality Trajectory Interact to Determine Frailty Incidence among Middle-Aged Urban Adults

BACKGROUND

Elevated plasma growth differentiation factor 15 (GDF15) and poor diet quality may be associated with increased frailty incidence, although their interactive associations have not been assessed in urban middle-aged adults.

OBJECTIVES

We aimed to examine GDF15 and its interactive association with diet quality in relation to frailty incidence among a sample of middle-aged urban adults.

METHODS

The relationship between GDF15 and diet quality trajectories in relation to incident frailty was examined in a longitudinal study of participants in the Healthy Aging in Neighborhoods of Diversity across the Life Span (2004-2017). Serum GDF15 concentration and frailty incidence were primary exposure and outcome, respectively. Group-based trajectory models were used to assess diet quality trajectories (≤3 visits/participant, N = 945, N' = 2247 observations) using the Healthy Eating Index 2010 version (HEI-2010), Dietary Inflammatory Index, and mean adequacy ratio (MAR). Cox proportional hazards models were used, testing interactive associations of GDF15 and diet quality trajectories with frail/prefrail incidence (N = 400 frailty-free at first visit, N' = 604 observations, n = 168 incident frail/prefrail).

RESULTS

Both elevated GDF15 and lower diet quality trajectories were associated with a lower probability of remaining nonfrail (≤13 y follow-up). Among females, the "high diet quality" HEI-2010 trajectory had a hazard ratio (HR) of 0.15 [95% confidence interval (CI): 0.04, 0.54; P = 0.004; fully adjusted model] when compared with the "low diet quality" trajectory group. Among males only, there was an antagonistic interaction between lower HEI-2010 trajectory and elevated GDF15. Specifically, the HR for GDF15-frailty in the higher diet quality trajectory group (high/medium combined), and among males, was 2.69 (95% CI: 1.06, 6.62; P = 0.032), whereas among the lower diet quality trajectory group, the HR was 0.94 (95% CI: 0.49, 1.80; P = 0.86). Elevated GDF15 was independently associated with frailty among African American adults.

CONCLUSIONS

Pending replication, we found an antagonistic interaction between GDF15 and HEI-2010 trajectory in relation to frailty incidence among males.

The association between growth differentiation factor-15, erythroferrone, and iron status in thalassemic patients

BACKGROUND

Iron overload can result in grave consequences in thalassemic patients, despite the availability of iron chelators. Therefore, alternative pathways aiming to reduce iron toxicity are currently investigated. Among which, reduction of iron absorption through control of hepcidin production appears to be promising. In this study, we investigated growth differentiation factor-15 (GDF15) and erythroferrone (ERFE) as potential suppressors of hepcidin.

METHODS

This cross-sectional study was conducted on 61 thalassemic patients and 60 healthy controls. The frequency of GDF15 gene polymorphism (rs4808793) (-3148C/G), serum level of GDF15 and erythroferrone were measured and correlated with those of hepcidin and serum ferritin.

RESULTS

The presence of GDF15 gene mutations were significantly higher in the patients' group compared to controls (P value 0.035). Also, thalassemia patients had significantly higher levels of GDF15 and ERFE and lower hepcidin levels than controls (P value < 0.001). Serum hepcidin level showed significantly negative correlations with GDF15, ERFE, reticulocyte count, LDH level, and serum ferritin. Contrarily, it had highly significant positive correlation with hemoglobin.

CONCLUSIONS

High level of GDF15 and/or ERFE may inhibit hepcidin production and increase iron load in patients with thalassemia; therefore, medications that suppress their actions may provide new therapeutic potentials for iron toxicity.

IMPACT

Iron overload continues to be a major contributor to high morbidity and mortality in patients with thalassemia. New strategies together with proper chelation, need to be developed to minimize the effect of iron toxicity. Growth differentiation factor-15 (GDF15) and erythroferrone (ERFE) inhibit hepcidin production and increase iron levels in conditions with ineffective erythropoiesis. Medications that suppress the production or interfere with the action of GDF15 or ERFE may represent new therapeutic potentials for iron toxicity. Prevention of iron toxicity will significantly reduce morbidity and mortality and improve the quality of life of thalassemia patients.

GDF15 is a major determinant of ketogenic diet-induced weight loss

A ketogenic diet (KD) has been promoted as an obesity management diet, yet its underlying mechanism remains elusive. Here we show that KD reduces energy intake and body weight in humans, pigs, and mice, accompanied by elevated circulating growth differentiation factor 15 (GDF15). In GDF15- or its receptor GFRAL-deficient mice, these effects of KD disappeared, demonstrating an essential role of GDF15-GFRAL signaling in KD-mediated weight loss. Gdf15 mRNA level increases in hepatocytes upon KD feeding, and knockdown of Gdf15 by AAV8 abrogated the obesity management effect of KD in mice, corroborating a hepatic origin of GDF15 production. We show that KD activates hepatic PPARγ, which directly binds to the regulatory region of Gdf15, increasing its transcription and production. Hepatic Pparγ-knockout mice show low levels of plasma GDF15 and significantly diminished obesity management effects of KD, which could be restored by either hepatic Gdf15 overexpression or recombinant GDF15 administration. Collectively, our study reveals a previously unexplored GDF15-dependent mechanism underlying KD-mediated obesity management.

Growth differentiation factor-15 stimulates the synthesis of corticotropin-releasing factor in hypothalamic 4B cells

Growth differentiation factor-15 (GDF15) is a stress-activated cytokine that regulates cell growth and inflammatory and stress responses. We previously reported the role and regulation of GDF15 in pituitary corticotrophs. Dexamethasone increases Gdf15 gene expression levels and production. GDF15 suppresses adrenocorticotropic hormone synthesis in pituitary corticotrophs and subsequently mediates the negative feedback effect of glucocorticoids. Here, we analyzed corticotropin-releasing factor (Crf) promoter activity in hypothalamic 4B cells transfected with promoter-driven luciferase reporter constructs. The effects of time and GDF15 concentration on Crf mRNA levels were analyzed using quantitative real-time polymerase chain reaction. Glial cell-derived neurotrophic factor family receptor α-like (GFRAL) protein is expressed in 4B cells. GDF15 increased Crf promoter activity and Crf mRNA levels in 4B cells. The protein kinase A and C pathways also contributed to the GDF15-induced increase in Crf gene expression. GDF15 stimulates GFRAL, subsequently increasing the phosphorylation of AKT, an extracellular signal-related kinase, and the cAMP response element-binding protein. Therefore, GDF15-dependent pathways may be involved in regulating Crf expression under stressful conditions in hypothalamic cells.

Alteration of BDNF, SPARC, FGF-21, and GDF-15 circulating levels after 1 year of anti-obesity treatments and their association with 1-year weight loss

PURPOSE

Emerging evidence revealed that brain-derived neurotrophic factor (BDNF), secreted protein acidic and rich in cysteine (SPARC), fibroblast growth factor 21(FGF-21) and growth differentiation factor 15 (GDF-15) are involved in energy metabolism and body weight regulation. Our study aimed at examining their association with BMI, their alterations after anti-obesity treatments, and their association with 1-year weight loss.

METHODS

A prospective observational study of 171 participants with overweight and obesity and 46 lean controls was established. All participants received lifestyle educational intervention (LEI) with or without anti-obesity treatments (LEI + bariatric/metabolic surgery, n = 41; LEI + topiramate, n = 46; LEI + liraglutide, n = 31; LEI + orlistat, n = 12; and LEI alone, n = 41). Anthropometric and metabolic parameters, insulin sensitivity, C-reactive protein (CRP), fasting plasma levels of BDNF, SPARC, GDF-15, and FGF-21 were measured at baseline and 1 year.

RESULTS

Multiple linear regression showed that fasting levels of SPARC, FGF-21, and GDF-15 were significantly associated with baseline BMI after adjustment for age and sex. At 1 year, the average weight loss was 4.8% in the entire cohort with a significant improvement in glycemia, insulin sensitivity, and CRP. Multiple linear regression adjusted for age, sex, baseline BMI, type of treatment, and presence of T2DM revealed that the decrease in log10FGF-21 and log10GDF-15 at 1 year from baseline was significantly associated with a greater percentage of weight loss at 1 year.

CONCLUSIONS

This study highlights the association of SPARC, FGF-21, and GDF-15 levels with BMI. Decreased circulating levels of GDF-15 and FGF-21 were associated with greater weight loss at 1 year, regardless of the types of anti-obesity modalities.

The roles of FGF21 and GDF15 in mediating the mitochondrial integrated stress response

Various models of mitochondrial stress result in induction of the stress-responsive cytokines fibroblast growth factor 21 (FGF21) and growth differentiation factor 15 (GDF15). This is an adaptive mechanism downstream of the mitochondrial integrated stress response frequently associated with improvements in systemic metabolic health. Both FGF21 and GDF15 have been shown to modulate energy balance and glucose homeostasis, and their pharmacological administration leads to promising beneficial effects against obesity and associated metabolic diseases in pre-clinical models. Furthermore, endogenous upregulation of FGF21 and GDF15 is associated with resistance to diet-induced obesity (DIO), improved glucose homeostasis and increased insulin sensitivity. In this review, we highlight several studies on transgenic mouse models of mitochondrial stress and will compare the specific roles played by FGF21 and GDF15 on the systemic metabolic adaptations reported in these models.

Creation of a Peptide Antagonist of the GFRAL-RET Receptor Complex for the Treatment of GDF15-Induced Malaise

Growth differentiation factor 15 (GDF15) is a contributor to nausea, emesis, and anorexia following chemotherapy via binding to the GFRAL-RET receptor complex expressed in hindbrain neurons. Therefore, GDF15-mediated GFRAL-RET signaling is a promising target for improving treatment outcomes for chemotherapy patients. We developed peptide-based antagonists of GFRAL that block GDF15-mediated RET recruitment. Our initial library screen led to five novel peptides. Surface plasmon resonance and flow cytometric analyses of the most efficacious of this group, termed GRASP, revealed its capacity to bind to GFRAL. In vivo studies in rats revealed that GRASP could attenuate GDF15-induced nausea and anorexia resulting from cisplatin. Combined with Ondansetron, GRASP led to an even greater attenuation of the anorectic effects of cisplatin compared to either agent alone. Our results highlight the beneficial effects of GRASP as an agent to combat chemotherapy-induced malaise. GRASP may also be effective in other conditions associated with elevated levels of GDF15.

GDF15 enhances body weight and adiposity reduction in obese mice by leveraging the leptin pathway

GDF15 regulates its anorexic effects through the hindbrain area postrema (AP) and nucleus of the solitary tract (NTS) neurons where its receptor, glial-derived neurotrophic factor receptor alpha-like (GFRAL), is expressed. The actions of GDF15 may interact with other appetite regulators elevated in obesity, such as leptin. Here, we report that in mice with high-fat-diet-induced obesity (HFD), the combined infusion of GDF15 and leptin causes significantly greater weight and adiposity loss than either treatment alone, indicating potentiation between GDF15 and leptin. Furthermore, obese, leptin-deficient ob/ob mice are less responsive to GDF15, as are normal mice treated with a competitive leptin antagonist. GDF15 and leptin induce more hindbrain neuronal activation in HFD mice than either treatment alone does. We report extensive connections between GFRAL- and LepR-expressing neurons and find LepR knockdown in the NTS to reduce the GDF15-mediated activation of AP neurons. Overall, these findings suggest that leptin signaling pathways in the hindbrain increase GDF15's metabolic actions.

Screening study of anti-emetics to improve GDF15-induced malaise and anorexia: Implications for emesis control

Considerable preclinical and clinical attention has focused on the food intake and body weight suppressive effects of growth differentiation factor 15 (GDF15) and its elevated blood levels as a consequence of disease states and disease treatment therapeutics. We have previously reported that exogenous administration of GDF15 induces anorexia through nausea and emesis in multiple species. Importantly, GDF15 signaling as a meditator of chemotherapy-induced anorexia and emesis has recently been demonstrated in both murine and nonhuman primate models. The mechanism, however, by which GDF15 induces malaise and the utility of existing therapeutic targets to counteract its effects remain largely unknown. Using a dose of GDF15 that mimics stimulated levels following chemotherapy administration and reliably induces malaise, we sought to screen anti-emetics that represent distinct pharmacotherapeutic classes hypothesized to reduce GDF15-induced effects in rats. Strikingly, our results showed that none of the tested compounds were effective at preventing GDF15-induced malaise. These results illustrate the complexity of GDF15 signaling mechanism and may have important implications for medical conditions characterized by elevated GDF15 levels and incomplete symptom control, such as chemotherapy-induced nausea and vomiting.

GDF-15 Is Associated with Poor Physical Function in Prefrail Older Adults with Diabetes

Introduction

Growth differentiation factor 15 (GDF-15) has been shown to be a metabolic and appetite regulator in diabetes mellitus (DM) and obesity. We aimed to investigate (i) the association between GDF-15 and DM with and without poor physical function independent of inflammation and (ii) the prediction model for poor physical function in prefrail older adults.

Methods

A cross-sectional study of 108-prefrail participants ≥60 years recruited for multidomain interventions. Data was collected for demographics, cognition, function, frailty, nutrition, handgrip strength (HGS), short physical performance battery (SPPB), and gait speed. Serum concentrations of GDF-15, IL-6, and TNF-α were measured. GDF-15 was classified into tertiles (T1, T2, and T3), and its association was studied with DM and physical function (DM poor physical function, DM no poor physical function, no DM poor physical function, and no DM no poor physical function).

Results

Compared with T1, participants in T3 were significantly older, had a lower education level, had almost three times higher prevalence of DM, slower gait speed, longer chair-stand time, and lower SPPB scores. On multivariate analysis, the odds of having both DM and poor physical performance compared to having no DM and no poor physical performance were significantly higher in GDF-15 T3 vs. GDF-15 T1 (aOR 9.7, 95% CI 1.4-67.7; p = 0.021), and the odds of having DM no poor physical function compared to having no DM and no poor physical performance were significantly higher in GDF-15 T2 (aOR 12.7, 95% CI 1.1-143.7; p = 0.040) independent of BMI, IL-6, TNF-α, nutrition, physical function, education, age, and gender.

Conclusion

The association of GDF-15 with DM-associated poor physical function is independent of inflammation in prefrail older adults. Its causal-association link needs to be determined in longitudinal studies.

Discovery, development, and clinical proof of mechanism of LY3463251, a long-acting GDF15 receptor agonist

GDF15 and its receptor GFRAL/RET form a non-homeostatic system that regulates food intake and body weight in preclinical species. Here, we describe a GDF15 analog, LY3463251, a potent agonist at the GFRAL/RET receptor with prolonged pharmacokinetics. In rodents and obese non-human primates, LY3463251 decreased food intake and body weight with no signs of malaise or emesis. In a first-in-human study in healthy participants, single subcutaneous LY3463251 injections showed a safety and pharmacokinetic profile supporting further clinical development with dose-dependent nausea and emesis in a subset of individuals. A subsequent 12-week multiple ascending dose study in overweight and obese participants showed that LY3463251 induced significant decreases in food intake and appetite scores associated with modest body weight reduction independent of nausea and emesis (clinicaltrials.gov: NCT03764774). These observations demonstrate that agonism of the GFRAL/RET system can modulate energy balance in humans, though the decrease in body weight is surprisingly modest, suggesting challenges in leveraging the GDF15 system for clinical weight-loss applications.

GDF15 and its association with cognitive performance over time in a longitudinal study of middle-aged urban adults

Serum GDF15 levels are correlated with multiple neurodegenerative diseases. Few studies have tested this marker's association with middle-aged cognitive performance over time, and whether race affects this association is unknown. We examined associations of initial serum GDF15 concentrations with longitudinal cognitive performance, spanning domains of global mental status, visual and verbal memory, attention, fluency, and executive function in a sub-sample of adults participating in the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study (n = 776, Agev1:30-66y, 45.6 % male, 57.0 % African American, 43.0 % below poverty). This analysis consisted of mixed-effects regression models applied to the total selected sample, while also stratifying the analyses by race in the main analyses and further stratifying by sex, age group and poverty status in an exploratory analysis. Our main findings, which passed multiple testing and covariate-adjustment, indicated that GDF15 was associated with poorer baseline performance on several cognitive tests, including animal fluency [overall sample: (Model 1: γ0 ± SE: -0.664 ± 0.208, P < 0.001; Model 2, γ0 ± SE: -0.498 ± 0.217, P < 0.05)]. Among White adults, GDF15 was linked to poorer performance on a brief test of attention (Model 1: γ0 ± SE: -0.426 ± 0.126, P < 0.001; Model 2, γ0 ± SE: -0.281 ± 0.139, P < 0.05); and Trailmaking test, part B (Model 1: γ0 ± SE: +0.129 ± 0.040, P < 0.001; Model 2, γ0 ± SE: +0.089 ± 0.041, P < 0.05), the latter being also linked to higher GDF15 among individuals living below poverty. Among women, GDF15 was associated with poor global mental status (Normalized MMSE: Model 1: γ0 ± SE: -2.617 ± 0.746, P < 0.001; Model 2: γ0 ± SE: -1.729 ± 0.709, P < 0.05). GDF15 was not associated with decline on any of the 11 cognitive test scores considered in ∼ 4 years of follow-up. In sum, we detected cross-sectional associations between GDF15 and cognition, although GDF15 did not predict rate of change in cognitive performance over time among a sample of middle-aged adults. More longitudinal studies are needed to address the clinical utility of this biomarker for early cognitive defects.

Association between physical activity, growth differentiation factor 15 and bodyweight in older adults: A longitudinal mediation analysis

BACKGROUND

Late-life aging is often associated with appetite reduction and weight loss. Physical activity (PA) may prevent these processes, but the molecular mechanisms involved remain elusive. The present study investigated the putative mediating aspect of growth differentiation factor 15 (GDF-15), a stress signalling protein involved in aging, exercise and appetite control, on the association between PA and late-life-associated weight loss.

METHODS

One thousand eighty-three healthy adults (63.8% women) aged 70 years and over who participated in the Multidomain Alzheimer Preventive Trial were included. Bodyweight (kg) and PA levels (square root of metabolic equivalent of task-min/week) were assessed repeatedly from baseline to the 3-year visit, whereas plasma GDF-15 (pg/mL) was measured at the 1-year visit. Multiple linear regressions were performed to test the association between first-year mean PA level, 1-year visit GDF-15 concentration and subsequent bodyweight changes. Mediation analyses were used to investigate whether GDF-15 mediated the association between first-year mean PA levels and consecutive bodyweight changes.

RESULTS

Multiple regression analyses demonstrated that higher first-year mean PA levels significantly predicted lower GDF-15 and bodyweight at 1 year (B = -2.22; SE = 0.79; P = 0.005). In addition, higher 1-year visit GDF-15 levels were associated with faster subsequent bodyweight loss (Time × GDF-15 interaction B = -0.0004; SE = 0.0001; P = 0.003). Mediation analyses confirmed that GDF-15 mediated the association between first-year mean PA levels and subsequent bodyweight changes (mediated effect ab = 0.0018; bootstrap SE = 0.001; P < 0.05) and revealed that mean PA had no direct effect on subsequent bodyweight changes (c' = 0.006; SE = 0.008; P > 0.05).

CONCLUSIONS

This study suggests that GDF-15 may be one of the molecules mediating the link between PA and late-life weight loss, but mechanistic studies are necessary to further support the present findings.

Growth differentiation factor-15 is independently associated with metabolic syndrome and hyperglycemia in non-elderly subjects

Metabolic syndrome (MetS) is a major health issue worldwide accompanied by cardiovascular comorbidities. Growth differentiation factor-15 (GDF-15) is a stress-responsive cytokine expressed in cardiomyocytes, adipocytes, macrophages, and endothelial cells. Previous research in elderly subjects revealed that GDF-15 levels were associated with the MetS. However, the association between GDF-15 levels and MetS or its components in the non-elderly subjects remains unclear. In this study, a total of 279 subjects younger than 65-year-old with (n = 84) or without (n = 195) MetS were recruited. MetS was defined according to modified NCEP/ATP III criteria. The GDF-15 levels were measured by an enzyme-linked immunosorbent assay. A multiple linear regression analysis was conducted to identify factors independently associated with GDF-15 levels. Subjects with MetS had higher GDF-15 levels than those without MetS (median (interquartile range), 1.72 ng/mL (1.38, 2.26) vs. 1.63 ng/mL (1.27, 2.07), P = 0.037). With the number of MetS components increased, the GDF-15 levels increased significantly (P for trend = 0.005). Multiple linear regression analysis revealed that the presence of MetS was positively associated with the GDF-15 levels (β = 0.132, P = 0.037). When substituting MetS with its components, only the presence of hyperglycemia was positively associated with the GDF-15 levels after adjustment for covariates (β = 0.193, P = 0.003). Taken together, the presence of the MetS in non-elderly was associated with higher GDF-15 levels. Among the MetS components, only hyperglycemia was significantly associated with the GDF-15 levels. Future longitudinal studies will be needed to explore whether GDF-15 has the potential to be a biomarker of gluco-metabolic dysfunction in non-elderly subjects.

Knocking on GDF15's door for the treatment of type 2 diabetes mellitus

Although a large number of drugs are available for the treatment of type 2 diabetes mellitus (T2DM), many patients do not achieve adequate disease control despite adhering to medication. Recent findings indicate that the pharmacological modulation of the stress-induced cytokine growth differentiation factor 15 (GDF15) shows promise for the treatment of T2DM. GDF15 suppresses appetite and reduces inflammation, increases thermogenesis and lipid catabolism, sustains AMP-activated protein kinase (AMPK) activity, and ameliorates insulin resistance and hepatic steatosis. In addition, circulating GDF15 levels are elevated in response to several antidiabetic drugs, including metformin, with GDF15 mediating some of their effects. Here, we review the mechanistic insights into the beneficial effects of recently explored therapeutic approaches that target GDF15 for the treatment of T2DM.

Diltiazem inhibits breast cancer metastasis via mediating growth differentiation factor 15 and epithelial-mesenchymal transition

Migration and metastasis commonly happen to triple-negative breast cancer (TNBC) patients with advanced diseases. In many studies, it has been suggested that epithelial-mesenchymal transition (EMT) is one of the key mechanisms triggering cancer metastasis. Accumulating evidence has proven that calcium channel blockers mediate cell motility. Therefore, we attempt to investigate the effects of diltiazem, which has been selected from several FDA-approved clinical calcium channel blockers, on EMT in TNBC. By using both mouse and human TNBC cell lines, we found that diltiazem decreases colony formation and cell migration in breast cancer cells. The expression of epithelial markers such as E-cadherin and ZO-1 were increased dose-dependently by diltiazem, while mesenchymal markers such as Snail and Twist were decreased. In addition, we found that the expression of growth differentiation factor-15 (GDF-15) was also increased by diltiazem. Administering recombinant GDF-15 also reverses EMT, inhibits colony formation and migration in breast cancer cells. Moreover, treatment with diltiazem in tumor-bearing mice also decreases cancer metastasis and nodule formation, with more GDF-15 expression in diltiazem-treated mice than saline-treated mice, respectively. These findings suggest that diltiazem regulates EMT and cell motility through elevating GDF-15 expression in breast cancers in vitro and in vivo.

GDF15 and Cortisol Response to Meal Tolerance Test in Post-Sleeve Gastrectomy Patients with Weight Regain

BACKGROUND

Hormonal factors behind weight regain (WR) after surgical weight loss remain inadequately understood. Growth/differentiation factor 15 (GDF15) has emerged as a potential therapeutic target in obesity treatment. Cortisol, another stress hormone, has also been associated with weight gain at both low and high circulating concentrations. We aimed to compare meal-stimulated GDF15 and cortisol response in adults with and without WR after sleeve gastrectomy (SG). We hypothesized that GDF15 and cortisol response to meal tolerance test (MTT) will be lower in those with versus without WR after SG.

METHODS

Cross-sectional study comprised 21 adults without diabetes, who underwent SG. WR was defined as 100 × (current weight - nadir)/(preoperative weight - nadir) > 10%. GDF15, cortisol, insulin, glucose, and incretins (total glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic polypeptide (GIP) circulating concentrations) were measured during MTT (0-240 min) after 3-6 years post-bariatric surgery.

RESULTS

All participants were 48% White, 85% female, with mean (SD) age: 43(10) years, and BMI: 36.2(7.6) kg/m². Compared to the non-WR group (n = 6), the WR group (n = 15) had significantly higher BMI (WR: 38.6 ± 7.6 kg/m², non-WR: 30.3 ± 3.5 kg/m², p = 0.02) and showed lower GDF15 response (WR AUC vs non-WR AUC (116143 ± 13973 vs 185798 ± 38884 ng*min/L, p = 0.047)) and lower cortisol response (WR AUC vs non-WR AUC (3492 ± 210 vs 4880 ± 655 µg*min/dL, p = 0.015)). Incretin response did not differ between the groups.

CONCLUSIONS

GDF15 and cortisol responses to MTT were lower in those who regained the weight after SG compared to those who did not, suggesting that dysregulation in GDF15 and cortisol response following bariatric surgery.

Hindbrain circuits in the control of eating behaviour and energy balance

Body weight and adiposity represent biologically controlled parameters that are influenced by a combination of genetic, developmental and environmental variables. Although the hypothalamus plays a crucial role in matching caloric intake with energy expenditure to achieve a stable body weight, it is now recognized that neuronal circuits in the hindbrain not only serve to produce nausea and to terminate feeding in response to food consumption or during pathological states, but also contribute to the long-term control of body weight. Additionally, recent work has identified hindbrain neurons that are capable of suppressing food intake without producing aversive responses like those associated with nausea. Here we review recent advances in our understanding of the hindbrain neurons that control feeding, particularly those located in the area postrema and the nucleus tractus solitarius. We frame this information in the context of new atlases of hindbrain neuronal populations and develop a model of the hindbrain circuits that control food intake and energy balance, suggesting important areas for additional research.

Region-Specific Characteristics of Astrocytes and Microglia: A Possible Involvement in Aging and Diseases

Although different regions of the brain are dedicated to specific functions, the intra- and inter-regional heterogeneity of astrocytes and microglia in these regions has not yet been fully understood. Recently, an advancement in various technologies, such as single-cell RNA sequencing, has allowed for the discovery of astrocytes and microglia with distinct molecular fingerprints and varying functions in the brain. In addition, the regional heterogeneity of astrocytes and microglia exhibits different functions in several situations, such as aging and neurodegenerative diseases. Therefore, investigating the region-specific astrocytes and microglia is important in understanding the overall function of the brain. In this review, we summarize up-to-date research on various intra- and inter-regional heterogeneities of astrocytes and microglia, and provide information on how they can be applied to aging and neurodegenerative diseases.

Novel Noninvasive Approaches to the Treatment of Obesity: From Pharmacotherapy to Gene Therapy

Recent insights into the pathophysiologic underlying mechanisms of obesity have led to the discovery of several promising drug targets and novel therapeutic strategies to address the global obesity epidemic and its comorbidities. Current pharmacologic options for obesity management are largely limited in number and of modest efficacy/safety profile. Therefore, the need for safe and more efficacious new agents is urgent. Drugs that are currently under investigation modulate targets across a broad range of systems and tissues, including the central nervous system, gastrointestinal hormones, adipose tissue, kidney, liver, and skeletal muscle. Beyond pharmacotherapeutics, other potential antiobesity strategies are being explored, including novel drug delivery systems, vaccines, modulation of the gut microbiome, and gene therapy. The present review summarizes the pathophysiology of energy homeostasis and highlights pathways being explored in the effort to develop novel antiobesity medications and interventions but does not cover devices and bariatric methods. Emerging pharmacologic agents and alternative approaches targeting these pathways and relevant research in both animals and humans are presented in detail. Special emphasis is given to treatment options at the end of the development pipeline and closer to the clinic (ie, compounds that have a higher chance to be added to our therapeutic armamentarium in the near future). Ultimately, advancements in our understanding of the pathophysiology and interindividual variation of obesity may lead to multimodal and personalized approaches to obesity treatment that will result in safe, effective, and sustainable weight loss until the root causes of the problem are identified and addressed.

Increased Complement-Associated Inflammation in Cytomegalovirus-Positive Hypertensive Anterior Uveitis Patients Based on the Aqueous Humor Proteomics Analysis

Herpetic anterior uveitis-associated ocular inflammation is commonly manifested with ocular hypertension and glaucoma. Relative to other viruses, cytomegalovirus (CMV) positive hypertensive anterior uveitis is associated with high recurrences of uveitis, as well as with uncontrolled intraocular pressure (IOP) and a subsequent higher requirement for future glaucoma surgery. To gain novel insights into the pathogenesis of ocular hypertension in these patients, we investigated the proteome changes of the aqueous humor (AH) derived from the CMV hypertensive anterior uveitis (CMV-HAU; n = 10) patients and non-glaucoma (cataract; n = 10) patients using liquid chromatography with tandem mass spectrometry. Among a total of 562 proteins identified, fifty and fifteen proteins were significantly elevated and decreased, respectively, in the AH of CMV-HAU patients compared to the control subjects by ≥2 fold. Gene ontology (GO) enrichment and network analyses of elevated proteins revealed that the enrichment of protein was involved in the complement activation, the humoral immune response mediated by the circulating immunoglobulins, proteolysis, and platelet degranulation. In the AH of CMV-HAU, GDF (growth/differentiation factor)-15, the inflammatory marker belonging to the TGF-β superfamily proteins, was significantly increased, while vasorin, an anti-TGF-β protein, levels were decreased. The trabecular meshwork cells infected with CMV exhibited a significantly increased expression of inflammatory markers. Collectively, these data indicate increased complement factor associated inflammation and humoral immunity in CMV-HAU associated ocular hypertension.

Navigating Between Right, Wrong, and Relevant: The Use of Mathematical Modeling in Preclinical Decision Making

The goal of this mini-review is to summarize the collective experience of the authors for how modeling and simulation approaches have been used to inform various decision points from discovery to First-In-Human clinical trials. The article is divided into a high-level overview of the types of problems that are being aided by modeling and simulation approaches, followed by detailed case studies around drug design (Nektar Therapeutics, Genentech), feasibility analysis (Novartis Pharmaceuticals), improvement of preclinical drug design (Pfizer), and preclinical to clinical extrapolation (Merck, Takeda, and Amgen).

Deadenylase-dependent mRNA decay of GDF15 and FGF21 orchestrates food intake and energy expenditure

Hepatokines, secretory proteins from the liver, mediate inter-organ communication to maintain a metabolic balance between food intake and energy expenditure. However, molecular mechanisms by which hepatokine levels are rapidly adjusted following stimuli are largely unknown. Here, we unravel how CNOT6L deadenylase switches off hepatokine expression after responding to stimuli (e.g., exercise and food) to orchestrate energy intake and expenditure. Mechanistically, CNOT6L inhibition stabilizes hepatic Gdf15 and Fgf21 mRNAs, increasing corresponding serum protein levels. The resulting upregulation of GDF15 stimulates the hindbrain to suppress appetite, while increased FGF21 affects the liver and adipose tissues to induce energy expenditure and lipid consumption. Despite the potential of hepatokines to treat metabolic disorders, their administration therapies have been challenging. Using small-molecule screening, we identified a CNOT6L inhibitor enhancing GDF15 and FGF21 hepatokine levels, which dramatically improves diet-induced metabolic syndrome. Our discovery, therefore, lays the foundation for an unprecedented strategy to treat metabolic syndrome.

Growth differentiation factor-15 prevents glucotoxicity and connexin-36 downregulation in pancreatic beta-cells

Pancreatic beta cell dysfunction is a hallmark of type 2 diabetes. Growth differentiation factor 15 (GDF15), which is an energy homeostasis regulator, has been shown to improve several metabolic parameters in the context of diabetes. However, its effects on pancreatic beta-cell remain to be identified. We, therefore, performed experiments using cell models and histological sectioning of wild-type and knock-out GDF15 mice to determine the effect of GDF15 on insulin secretion and cell viability. A bioinformatics analysis was performed to identify GDF15-correlated genes. GDF15 prevents glucotoxicity-mediated altered glucose-stimulated insulin secretion (GSIS) and connexin-36 downregulation. Inhibition of endogenous GDF15 reduced GSIS in cultured mouse beta-cells under standard conditions while it had no impact on GSIS in cells exposed to glucolipotoxicity, which is a diabetogenic condition. Furthermore, this inhibition exacerbated glucolipotoxicity-reduced cell survival. This suggests that endogenous GDF15 in beta-cell is required for cell survival but not GSIS in the context of glucolipotoxicity.

Camptothecin effectively treats obesity in mice through GDF15 induction

Elevated circulating levels of growth differentiation factor 15 (GDF15) have been shown to reduce food intake and lower body weight through activation of hindbrain receptor glial-derived neurotrophic factor (GDNF) receptor alpha-like (GFRAL) in rodents and nonhuman primates, thus endogenous induction of this peptide holds promise for obesity treatment. Here, through in silico drug-screening methods, we found that small molecule Camptothecin (CPT), a previously identified drug with potential antitumor activity, is a GDF15 inducer. Oral CPT administration increases circulating GDF15 levels in diet-induced obese (DIO) mice and genetic ob/ob mice, with elevated Gdf15 expression predominantly in the liver through activation of integrated stress response. In line with GDF15's anorectic effect, CPT suppresses food intake, thereby reducing body weight, blood glucose, and hepatic fat content in obese mice. Conversely, CPT loses these beneficial effects when Gdf15 is inhibited by a neutralizing antibody or AAV8-mediated liver-specific knockdown. Similarly, CPT failed to reduce food intake and body weight in GDF15's specific receptor GFRAL-deficient mice despite high levels of GDF15. Together, these results indicate that CPT is a promising anti-obesity agent through activation of GDF15-GFRAL pathway.

Elevated Levels of Growth/Differentiation Factor-15 in the Aqueous Humor and Serum of Glaucoma Patients

Dysregulated levels of growth/differentiation factor-15 (GDF15), a divergent member of the transforming growth factor-beta super family, have been found to be associated with the pathology of various diseases. In this study, we evaluated the levels of GDF15 in aqueous humor (AH) and serum samples derived from primary open-angle glaucoma (POAG) and age- and gender-matched non-glaucoma (cataract) patients to assess the plausible association between GDF15 and POAG. GDF15 levels were determined using an enzyme-linked immunosorbent assay, and data analysis was performed using the Wilcoxon rank sum test, or the Kruskal–Wallis test and linear regression. GDF15 levels in the AH (n = 105) of POAG patients were significantly elevated (by 7.4-fold) compared to cataract patients (n = 117). Serum samples obtained from a subgroup of POAG patients (n = 41) also showed a significant increase in GDF15 levels (by 50%) compared to cataract patients. GDF15 levels were elevated in male, female, African American, and Caucasian POAG patients. This study reveals a significant and marked elevation of GDF15 levels in the AH of POAG patients compared to non-glaucoma cataract control patients. Although serum GDF15 levels were also elevated in POAG patients, the magnitude of difference was much smaller relative to that found in the AH.

Increased Circulating Levels of Growth Differentiation Factor 15 in Association with Metabolic Disorders in People Living with HIV Receiving Combined Antiretroviral Therapy

Objective: People living with HIV (PLWH) have an increased cardiovascular risk (CVR) owing to dyslipidemia, insulin resistance, metabolic syndrome, and HIV/combination antiretroviral therapy (cART)-associated lipodystrophy (HALS). Atherosclerosis and inflammation are related to growth differentiation factor-15 (GDF15). The relationship between metabolic disturbances, HALS, and CVR with GDF15 in PLWH is not known. Research design and methods: Circulating GDF15 levels in 152 PLWH (with HALS = 60, without HALS = 43, cART-naïve = 49) and 34 healthy controls were assessed in a cross-sectional study. Correlations with lipids, glucose homeostasis, fat distribution, and CVR were explored. Results: PLWH had increased circulating GDF15 levels relative to controls. The increase was the largest in cART-treated PLWH. Age, homeostatic model assessment of insulin resistance 1 (HOMA1-IR), HALS, dyslipidemia, C-reactive protein, and CVR estimated with the Framingham score correlated with GDF15 levels. The GDF15-Framingham correlation was lost after age adjustment. No correlation was found between GDF15 and the D:A:D Data Collection on Adverse Effects of Anti-HIV Drugs (D:A:D) score estimated CVR. CVR independent predictors were patient group (naïve, HALS−, and HALS+) and cumulated protease inhibitor or nucleoside reverse transcriptase inhibitor exposure. Conclusions: PLWH, especially when cART-treated, has increased GDF15 levels—this increase is associated with dyslipidemia, insulin resistance, metabolic syndrome, HALS, and inflammation-related parameters. GDF15 is unassociated with CVR when age-adjusted.

The effect of bariatric surgery on the expression of Growth Differentiation Factor-15/Macrophage-Inhibitory Cytokine-1 (GDF-15/MIC-1) in rat

BACKGROUND

Reduced appetite and loss of preference to nutrition dense high-fat diet are present after bariatric surgery. But the mechanism responsible for these changes in biological activities remains unclear. Similar changes in biological activities have been observed with growth/differentiation factor-15/macrophage-inhibitory cytokine-1 (GDF-15/MIC-1) treatment alone.

AIM OF STUDY

To assess the effect of bariatric surgery on GDF-15/MIC-1expression and circulating level in rodent model.

SETTING

The Affiliated Hospital of Xuzhou Medical University, Xuzhou Jiangsu 221,006, P. R. China.

METHODS

Among 40 fatty Sprague-dawley (SD) rats, 30 randomly receive low-dose STZ to induced diabetes and were randomly assigned to Roux en Y gastric bypass (RYGB, n = 10), Sleeve gastrectomy (SG, n = 10), and SHAM (n = 10). The remaining fatty SD rats were assigned to Normal control (NC, n = 10). Rats were followed for 8 weeks postoperatively. Circulating levels of GDF15 and tissue (gastrointestinal and liver) expression were assessed after surgery. Preoperative oral glucose tolerance test (OGTT), and Insulin tolerance test (ITT) were reassessed postoperatively. Changes in bodyweight and food intake were also recorded.

RESULTS

Bariatric surgery significantly increased circulating plasma level of GDF15 (p < 0.05). Postoperatively, tissue expression of GDF15 was significantly higher in the stomach pouch, jejunum, and ileum of rats in the RYGB group as well as ileum of rats in the SG group compared to Sham and NC (p < 0.05). Higher Expression of GDF15 in the stomach pouch of the SG group was not statistically significant compared to the stomach of Sham and NC group. GDF15 expression in the liver was significantly less in the RYGB group (p < 0.05).

CONCLUSION

Bariatric surgery significantly increases circulating levels and gastrointestinal tissue expression of GDF15. Given that GDF15 is an important regulator of energy homeostasis, further studies are needed to ascertain the relevance in bariatric surgery.

GDF15 in Appetite and Exercise: Essential Player or Coincidental Bystander?

Growth differentiation factor 15 (GDF15) has recently moved to the forefront of metabolism research. When administered pharmacologically, GDF15 reduces food intake and lowers body weight via the hindbrain-situated receptor GFRAL (glial cell-derived neurotrophic factor family receptor alpha-like). Endogenous GDF15 is a ubiquitous cellular stress signal that can be produced and secreted by a variety of cell types. Circulating levels are elevated in a series of disease states, but also in response to exogenous agents such as metformin, colchicine, AICAR, and cisplatin. Recently, exercise has emerged as a relevant intervention to interrogate GDF15 physiology. Prolonged endurance exercise increases circulating GDF15 to levels otherwise associated with certain pathological states and in response to metformin treatment. The jury is still out on whether GDF15 is a functional "exerkine" mediating organ-to-brain crosstalk or whether it is a coincidental bystander. In this review, we discuss the putative physiological implication of exercise-induced GDF15, focusing on the potential impact on appetite and metabolism.

Cell non-autonomous effect of hepatic growth differentiation factor 15 on the thyroid gland

The thyroid gland plays an essential role in the regulation of body energy expenditure to maintain metabolic homeostasis. However, to date, there are no studies investigating the morphological and functional changes of the thyroid gland due to mitochondrial stress in metabolic organs such as the liver. We used data from the Genotype-Tissue Expression portal to investigate RNA expression patterns of the thyroid gland according to the expression of growth differentiation factor 15 (GDF15) such as the muscles and liver. To verify the effect of hepatic GDF15 on the thyroid gland, we compared the morphological findings of the thyroid gland from liver-specific GDF15 transgenic mice to that of wild type mice. High GDF15 expression in the muscles and liver was associated with the upregulation of genes related to hypoxia, inflammation (TGF-α via NFκB), apoptosis, and p53 pathway in thyroid glands. In addition, high hepatic GDF15 was related to epithelial mesenchymal transition and mTORC1 signaling. Electron microscopy for liver-specific GDF15 transgenic mice revealed short mitochondrial cristae length and small mitochondrial area, indicating reduced mitochondrial function. However, serum thyroid stimulating hormone (TSH) level was not significantly different. In our human cohort, those with a high serum GDF15 level showed high fasting glucose, alanine transaminase, and alkaline phosphatase but no difference in TSH, similar to the data from our mice model. Additionally, high serum GDF15 increased the risk of lymph node metastasis to lateral neck. The hepatic GDF15 affected thyroid morphogenesis via a TSH-independent mechanism, affecting aggressive features of thyroid cancers.

Network Analyses Reveal Negative Link Between Changes in Adipose Tissue GDF15 and BMI During Dietary-induced Weight Loss

CONTEXT

Adipose tissue (AT) transcriptome studies provide holistic pictures of adaptation to weight and related bioclinical settings changes.

OBJECTIVE

To implement AT gene expression profiling and investigate the link between changes in bioclinical parameters and AT gene expression during 3 steps of a 2-phase dietary intervention (DI).

METHODS

AT transcriptome profiling was obtained from sequencing 1051 samples, corresponding to 556 distinct individuals enrolled in a weight loss intervention (8-week low-calorie diet (LCD) at 800 kcal/day) followed with a 6-month ad libitum randomized DI. Transcriptome profiles obtained with QuantSeq sequencing were benchmarked against Illumina RNAseq. Reverse transcription quantitative polymerase chain reaction was used to further confirm associations. Cell specificity was assessed using freshly isolated cells and THP-1 cell line.

RESULTS

During LCD, 5 modules were found, of which 3 included at least 1 bioclinical variable. Change in body mass index (BMI) connected with changes in mRNA level of genes with inflammatory response signature. In this module, change in BMI was negatively associated with changes in expression of genes encoding secreted protein (GDF15, CCL3, and SPP1). Through all phases of the DI, change in GDF15 was connected to changes in SPP1, CCL3, LIPA and CD68. Further characterization showed that these genes were specific to macrophages (with LIPA, CD68 and GDF15 expressed in anti-inflammatory macrophages) and GDF15 also expressed in preadipocytes.

CONCLUSION

Network analyses identified a novel AT feature with GDF15 upregulated with calorie restriction induced weight loss, concomitantly to macrophage markers. In AT, GDF15 was expressed in preadipocytes and macrophages where it was a hallmark of anti-inflammatory cells.

GDF15: a potential therapeutic target for type 1 diabetes

INTRODUCTION

Current treatment for type 1 diabetes (T1D) is centered around insulin supplementation to manage the effects of pancreatic β cell loss. GDF15 is a potential preventative therapy against T1D progression that could work to curb increasing disease incidence.

AREAS COVERED

This paper discusses the known actions of GDF15, a pleiotropic protein with metabolic, feeding, and immunomodulatory effects, connecting them to highlight the open opportunities for future research. The role of GDF15 in the prevention of insulitis and protection of pancreatic β cells against pro-inflammatory cytokine-mediated cellular stress are examined and the pharmacological promise of GDF15 and critical areas of future research are discussed.

EXPERT OPINION

GDF15 shows promise as a potential intervention but requires further development. Preclinical studies have shown poor efficacy, but this result may be confounded by the measurement of gross GDF15 instead of the active form. Additionally, the effect of GDF15 in the induction of anorexia and nausea-like behavior and short-half-life present significant challenges to its deployment, but a systems pharmacology approach paired with chronotherapy may provide a possible solution to therapy for this currently unpreventable disease.

GDF-15, a future therapeutic target of glucolipid metabolic disorders and cardiovascular disease

Growth and differentiation factor 15 (GDF-15) was discovered as a member of the transforming growth factor β (TGF-β) superfamily and the serum level of GDF-15 was significantly correlated with glucolipid metabolic disorders (GLMD) and cardiovascular diseases. In 2017, a novel identified receptor of GDF-15-glial-derived neurotrophic factor receptor alpha-like (GFRAL) was found to regulate energy homeostasis (such as obesity, diabetes and non-alcoholic fatty liver disease (NAFLD)). The function of GDF-15/GFRAL in suppressing appetite, enhancing glucose/lipid metabolism and vascular remodeling has been gradually revealed. These effects make it a potential therapeutic target for GLMD and vascular diseases. In this narrative review, we included and reviewed 121 articles by screening 524 articles from literature database. We primarily focused on the function of GDF-15 and its role in GLMD/cardiovascular diseases and discuss its potential clinical application.

Single nuclei RNA sequencing of the rat AP and NTS following GDF15 treatment

Objective

Growth differentiation factor 15 (GDF15) is known to play a role in feeding, nausea, and body weight, with action through the GFRAL-RET receptor complex in the area postrema (AP) and nucleus tractus solitarius (NTS). To further elucidate the underlying cell type-specific molecular mechanisms downstream of GDF15 signaling, we used a single nuclei RNA sequencing (snRNAseq) approach to profile AP and NTS cellular subtype-specific transcriptomes after systemic GDF15 treatment.

Methods

AP and NTS micropunches were used for snRNAseq from Sprague Dawley rats 6 h following GDF15 or saline injection, and Seurat was used to identify cellular subtypes and cell type-specific alterations in gene expression that were due to the direct and secondary effects of systemic GDF15 treatment.

Results

Using the transcriptome profile of ∼35,000 individual AP/NTS nuclei, we identified 19 transcriptomically distinct cellular subtypes, including a single population Gfral and Ret positive excitatory neurons, representing the primary site of action for GDF15. A total of ∼600 cell type-specific differential expression events were identified in neurons and glia, including the identification of transcriptome alterations specific to the direct effects of GDF15 in the Gfral-Ret positive excitatory neurons and shared transcriptome alterations across neuronal and glial cell types. Downstream analyses identified shared and cell type-specific alterations in signaling pathways and upstream regulatory mechanisms of the observed transcriptome alterations.

Conclusions

These data provide a considerable advance in our understanding of AP and NTS cell type-specific molecular mechanisms associated with GDF15 signaling. The identified cellular subtype-specific regulatory mechanism and signaling pathways likely represent important targets for future pharmacotherapies.

•

GDF15 directly alters transcription in Gfral- and Ret-positive excitatory neurons.

•

GDF15 indirectly alters transcription in other neuronal and glial populations.

•

Cell type-specific expression changes identify regulatory and signaling mechanisms.

Clinical and Tumor Characteristics of Patients with High Serum Levels of Growth Differentiation Factor 15 in Advanced Pancreatic Cancer

Simple Summary

Growth differentiation factor 15 (GDF-15) is a stress responsive cytokine that mediates food intake, energy consumption, and body weight. We aimed to evaluate whether circulating GDF-15 level could be associated with cachexia symptoms, which include loss of skeletal muscle mass, systemic inflammatory reaction, poor performance status, anorexia, shortened survival time and biological tumor activity in advanced pancreatic cancer (APC). The cut-off for serum GDF-15 was 3356.6 pg/mL, as the mean plus two standard deviations in patients with benign pancreatic disease. APC patients with high serum GDF-15 showed worsened performance, anorexia and elevations of inflammatory and tumor burden, signatures of cachexia, and activation of Akt and JNK in tumor GDF-15-producing pathways. This study identified tumor-driven GDF-15 as a potential cause of cachexia symptoms in APC.

Abstract

We aimed to evaluate the association of circulating growth differentiation factor 15 (GDF-15) with cachexia symptoms and the biological activity of advanced pancreatic cancer (APC). Treatment-naïve patients with liver metastasis of APC or with benign pancreatic disease were retrospectively analyzed. Clinical data, blood samples, and biopsy specimens of liver metastasis were collected prior to anti-cancer treatment. Serum GDF-15 levels and multiple protein expressions in lysates extracted from liver metastasis were measured by enzyme-linked immuno-sorbent assay and reverse-phase protein array, respectively. The cut-off for serum GDF-15 was determined as 3356.6 pg/mL, the mean plus two standard deviations for benign pancreatic disease. The high-GDF-15 group was characterized as showing low Karnofsky performance status (KPS) (p = 0.037), poor Eastern Cooperative Oncology Group performance status (ECOG-PS) (p = 0.049), severe appetite loss (p = 0.011), and high serum levels of carbohydrate antigen 19-9 (p = 0.019) and C-reactive protein (p = 0.009). Tumors of the high-GDF-15 group expressed high levels of phosphorylated (p)JNK (p = 0.007) and pAkt (p = 0.040). APC patients with high serum GDF-15 showed signatures of cachexia and activation of the signaling pathways involving Akt and JNK in the tumor. This study indicated circulating GDF-15 could be associated with cachectic symptoms in APC.

The effect of sleeve ablation of gastric mucosa on body weight and glucose homeostasis in Sprague-Dawley rat model

BACKGROUND

The gastric mucosa is an important endocrine organ, most of which is resected in sleeve gastrectomy (SG). The effect of removing most of the gastric mucosa has not been studied.

OBJECTIVE

To assess the effect of ablating the gastric mucosa (an area proportional to that in SG), on obesity and diabetes in a rat model.

SETTING

The Affiliated Hospital of Xuzhou Medical University in Xuzhou Jiangsu, P. R. China.

METHODS

Among 34 fatty Sprague-Dawley rats, 26 randomly received low-dose streptozotocin (STZ) to induce diabetes and then were randomly assigned to gastric mucosa ablation (GMA, n = 10), sleeve gastrectomy (SG, n = 8), and sham (n = 8) groups. The remaining normal fatty rats were assigned to the non-diabetic gastric mucosa ablation (nGMA, n = 8) group. In the GMA groups, the gastric mucosa was thermally ablated using electrocautery. Rats were followed for 8 weeks postoperatively. Preoperative oral glucose tolerance test (OGTT), insulin tolerance test (ITT), and mixed meal tolerance test (MMTT) were repeated at designated time points postoperatively. Changes in body weight, food intake, and fasting blood glucose were also recorded.

RESULTS

Fasting ghrelin concentration and area under curve (AUC) decreased significantly (P < .05) in the GMA groups and the SG group after surgery. Gastrin concentration remained unchanged in SG but decreased significantly in the GMA groups after surgery. Significantly increased GLP-1 AUC was found in the GMA groups and the SG group postoperatively. The decrease in fasting blood glucose did not differ significantly between the diabetic GMA and SG groups after surgery. Glucose AUC during OGTT in both SG and diabetic GMA groups was decreased significantly from the preoperative level, but the decreased glucose AUC in the SG group was significantly greater (P < .05). The decrease in body weight and food intake in the SG group was significantly greater than in the GMA groups.

CONCLUSION

Ablation of most of the gastric mucosa along the greater curvature is effective in weight loss and glycemic control in a rodent model.

Circulating Growth Differentiation Factor 15 Is Increased Preceding Preeclampsia Diagnosis: Implications as a Disease Biomarker

Background

We investigated the biomarker potential of growth differentiation factor 15 (GDF‐15), a stress response protein highly expressed in placenta, to predict preeclampsia.

Methods and Results

In 2 prospective cohorts (cohort 1: 960 controls, 39 women who developed preeclampsia; cohort 2: 950 controls, 41 developed preeclampsia), plasma concentrations of GDF‐15 at 36 weeks' gestation were significantly increased among those who developed preeclampsia (P<0.001), area under the receiver operating characteristic curves (AUC) of 0.66 and 0.71, respectively. In cohort 2 a ratio of sFlt‐1/PlGF (a clinical biomarker for preeclampsia) had a sensitivity of 61.0% at 83.2% specificity to predict those who will develop preeclampsia (AUC of 0.79). A ratio of GDF‐15×sFlt‐1/PlGF yielded a sensitivity of 68.3% at 83.2% specificity (AUC of 0.82). GDF‐15 was consistently elevated across a number of international cohorts: levels were higher in placenta and blood from women delivering <34 weeks' gestation due to preterm preeclampsia in Melbourne, Australia; and in the blood at 26 to 32 weeks' gestation among 57 women attending the Manchester Antenatal Vascular Service (MAViS, UK) who developed preeclampsia (P=0.0002), compared with 176 controls. In the Preeclampsia Obstetric adVerse Events biobank (PROVE, South Africa), plasma GDF‐15 was significantly increased in women with preeclampsia with severe features (P=0.02; n=14) compared to controls (n=14).

Conclusions

We conclude circulating GDF‐15 is elevated among women more likely to develop preeclampsia or diagnosed with the condition. It may have value as a clinical biomarker, including the potential to improve the sensitivity of sFlt‐1/PlGF ratio.

Growth-differentiation-factor 15 levels in obese and healthy pregnancies: Relation to insulin resistance and insulin secretory function

OBJECTIVE/AIM

Growth-differentiation-factor 15 (GDF15) has been suggested to improve or protect beta cell function. During pregnancy, beta cell numbers and function increase to overcome the natural rise in insulin resistance during gestation. In this study, we longitudinally measured serum GDF15 levels during and after pregnancy in women of normal weight (NW) and in women with obesity (OB) and explored associations between GDF15 and changes in beta cell function by homeostatic model assessment (HOMA).

METHODS

The cohort participants were 38 NW (BMI 22.3 ± 1.7) and 35 OB (BMI 35.8 ± 4.2). Blood was sampled and body composition measured at each trimester (T1, T2, and T3) and at 6, 12 and 18 months postpartum. Fasting glucose, insulin and GDF15 were measured, and HOMA for insulin resistance (HOMA-IR) and beta cell function (HOMA-B) determined.

RESULTS

GDF15 levels increased significantly each trimester and were ~200-fold higher at T3 than in the nonpregnant postpartum state. GDF15 was higher in NW than OB during pregnancy, but was reversed after pregnancy with a significant interaction effect. GDF15 correlated inversely with BMI and fat-free mass at T3. Low GDF15 was associated with lower incidence of nausea and with carrying a male foetus. The pregnancy induced increase in GDF15 associated with increased HOMA-B in OB and with reduced fasting glucose in all women.

CONCLUSION

Large gestational upregulation of GDF15 levels may help increase insulin secretory function to overcome pregnancy-induced insulin resistance.

Noncanonical open reading frames encode functional proteins essential for cancer cell survival

Although genomic analyses predict many noncanonical open reading frames (ORFs) in the human genome, it is unclear whether they encode biologically active proteins. Here we experimentally interrogated 553 candidates selected from noncanonical ORF datasets. Of these, 57 induced viability defects when knocked out in human cancer cell lines. Following ectopic expression, 257 showed evidence of protein expression and 401 induced gene expression changes. Clustered regularly interspaced short palindromic repeat (CRISPR) tiling and start codon mutagenesis indicated that their biological effects required translation as opposed to RNA-mediated effects. We found that one of these ORFs, G029442-renamed glycine-rich extracellular protein-1 (GREP1)-encodes a secreted protein highly expressed in breast cancer, and its knockout in 263 cancer cell lines showed preferential essentiality in breast cancer-derived lines. The secretome of GREP1-expressing cells has an increased abundance of the oncogenic cytokine GDF15, and GDF15 supplementation mitigated the growth-inhibitory effect of GREP1 knockout. Our experiments suggest that noncanonical ORFs can express biologically active proteins that are potential therapeutic targets.

Growth differentiation factor 15 increases in both cerebrospinal fluid and serum during pregnancy

Aim

Growth differentiation factor 15 (GDF15) increases in serum during pregnancy to levels not seen in any other physiological state and is suggested to be involved in pregnancy-induced nausea, weight regulation and glucose metabolism. The main action of GDF15 is regulated through a receptor of the brainstem, i.e., through exposure of GDF15 in both blood and cerebrospinal fluid (CSF). The aim of the current study was to measure GDF15 in both CSF and serum during pregnancy, and to compare it longitudinally to non-pregnant levels.

Methods

Women were sampled at elective caesarean section (n = 45, BMI = 28.1±5.0) and were followed up 5 years after pregnancy (n = 25). GDF15, insulin and leptin were measured in CSF and serum. Additional measurements included plasma glucose, and serum adiponectin and Hs-CRP.

Results

GDF15 levels were higher during pregnancy compared with follow-up in both CSF (385±128 vs. 115±32 ng/l, P<0.001) and serum (73789±29198 vs. 404±102 ng/l, P<0.001). CSF levels correlated with serum levels during pregnancy (P<0.001), but not in the non-pregnant state (P = 0.98). Both CSF and serum GDF15 were highest in women carrying a female fetus (P<0.001). Serum GDF15 correlated with the homeostatic model assessment for beta-cell function and placental weight, and CSF GDF15 correlated inversely with CSF insulin levels.

Conclusion

This, the first study to measure CSF GDF15 during pregnancy, demonstrated increased GDF15 levels in both serum and CSF during pregnancy. The results suggest that effects of GDF15 during pregnancy can be mediated by increases in both CSF and serum levels.

GDF15 Induces an Aversive Visceral Malaise State that Drives Anorexia and Weight Loss

The anorectic and weight-suppressive effects of growth differentiation factor-15 (GDF15) are attracting considerable attention for treating obesity. Current experiments in rats investigate whether GDF15 induces an aversive visceral malaise-based state that mediates its acute anorectic effect and, through aversion conditioning, exerts longer-term anorexia. Visceral malaise, conditioned affective food responses (taste reactivity), gastric emptying (GE), food intake, and body weight are evaluated after acute and chronic systemic dosing of GDF15 or long-acting Fc-GDF15. Pica, a marker of visceral malaise, is present at all anorectic GDF15 doses. Moreover, malaise induced by GDF15 does not decline over time, suggesting the lack of an improved tolerance after prolonged exposure. One association between GDF15 and novel food conditions a disgust/aversive response that persists beyond GDF15 acute action. Delayed GE is not a requirement for GDF15-induced anorexia. Clinical studies are required to evaluate whether GDF15's aversive-state-based anorexia will be contraindicated as an obesity treatment.