GDF-15 protects from macrophage accumulation in a mousemodel of advanced atherosclerosis

Pharmacological characterization of the antidiabetic drug metformin in atherosclerosis inhibition: A comprehensive insight

BACKGROUND

Atherosclerosis (AS) is a progressive disease that interferes with blood flow, leading to cardiovascular complications such as hypertension, ischemic heart disease, ischemic stroke, and vascular ischemia. The progression of AS is correlated with inflammation, oxidative stress, and endothelial dysfunction. Various signaling pathways, like nuclear erythroid-related factor 2 (Nrf2) and Kruppel-like factor 2 (KLF2), are involved in the pathogenesis of AS. Nrf2 and KLF2 have anti-inflammatory and antioxidant properties. Thus, activation of these pathways may reduce the development of AS. Metformin, an insulin-sensitizing drug used in the management of type 2 diabetes mellitus (T2DM), increases the expression of Nrf2 and KLF2. AS is a common long-term macrovascular complication of T2DM. Thus, metformin, through its pleiotropic anti-inflammatory effect, may attenuate the development and progression of AS.

AIMS

Therefore, this review aims to investigate the possible role of metformin in AS concerning its effect on Nrf2 and KLF2 and inhibition of reactive oxygen species (ROS) formation. In addition to its antidiabetic effect, metformin can reduce cardiovascular morbidities and mortalities compared to other antidiabetic agents, even with similar blood glucose control by the Nrf2/KLF2 pathway activation.

CONCLUSION

In conclusion, metformin is an effective therapeutic strategy against the development and progression of AS, mainly through activation of the KLF2/Nrf2 axis.

Role and Mechanism of Growth Differentiation Factor 15 in Chronic Kidney Disease

GDF-15 is an essential member of the transforming growth factor-beta superfamily. Its functions mainly involve in tissue injury, inflammation, fibrosis, regulation of appetite and weight, development of tumor, and cardiovascular disease. GDF-15 is involved in various signaling pathways, such as MAPK pathway, PI3K/AKT pathway, STAT3 pathway, RET pathway, and SMAD pathway. In addition, several factors such as p53, ROS, and TNF-α participate the regulation of GDF-15. However, the specific mechanism of these factors regulating GDF-15 is still unclear and more research is needed to explore them. GDF-15 mainly improves the function of kidneys in CKD and plays an important role in the prediction of CKD progression and cardiovascular complications. In addition, the role of GDF-15 in the kidney may be related to the SMAD and MAPK pathways. However, the specific mechanism of these pathways remains unclear. Accordingly, more research on the specific mechanism of GDF-15 affecting kidney disease is needed in the future. In conclusion, GDF-15 may be a therapeutic target for kidney disease.

Exploring the Role of GDF-15 in Inflammatory Bowel Disease: A Case-Controlled Study Comparing Crohn's Disease and Ulcerative Colitis with Non-Inflammatory Controls

Inflammatory bowel disease, encompassing Crohn's disease and ulcerative colitis, is a persistent immune-mediated inflammatory gastrointestinal disease. This study investigates the role of growth differentiation factor 15 in severe IBD cases, aiming to identify a reliable parameter to assess disease severity and monitor activity. We analyzed plasma samples from 100 patients undergoing biologic therapy for severe IBD and 50 control subjects. Our analysis included evaluations of GDF-15 levels, inflammatory markers, and clinical features. We employed statistical methods such as the Mann-Whitney U test, ANOVA, and Spearman's correlation for an in-depth analysis. Our results demonstrated consistently higher GDF-15 levels in patients with both Crohn's disease and ulcerative colitis compared to the control group, irrespective of the biologic treatment received. The correlation analysis indicated significant relationships between GDF-15 levels, patient age, fibrinogen, and IL-6 levels. This study positions GDF-15 as a promising biomarker for severe IBD, with notable correlations with age and inflammatory markers. These findings underscore GDF-15's potential in enhancing disease monitoring and management strategies in an IBD context and encourage further research to clarify GDF-15's role in the IBD pathophysiology.

Association of growth and differentiation factor-15 with coronary artery calcium score and ankle-brachial index in a middle-aged and elderly Caucasian population sample free of manifest cardiovascular disease

Growth and differentiation factor-15 (GDF-15) is a stress-associated cytokine of the transforming growth factor-β superfamily. The inflammatory and angiogenic effects of GDF-15 in atherosclerosis are controversial, and its correlation with the long asymptomatic phase of the disease is not well understood. Coronary artery calcium score (CACS) and ankle-brachial index (ABI) are sensitive markers of subclinical atherosclerosis. To date, only a few studies have examined the impact of GDF-15 on coronary artery calcification, and the association between GDF-15 and ABI has not been evaluated. Therefore, we aimed to investigate the possible relationship between serum GDF-15 concentrations and CACS and ABI in a Caucasian population sample of middle-aged (35-65 years) and elderly (> 65 years) people. In addition to recording demographic and anthropometric characteristics, atherosclerotic risk factors, and laboratory tests including serum HDL-cholesterol, LDL-cholesterol, hemoglobin A1c (HbA1c), high-sensitivity C-reactive protein, and N-terminal pro-B-type natriuretic peptide (NT-proBNP); GDF-15 level, cardiac computed tomography, and ABI measurements were also performed. A total of 269 asymptomatic individuals (men, n = 125; median age, 61.5 [IQR, 12.7] years) formed the basis of this study. Participants were divided into two groups according to their age (middle-aged, n = 175 and elderly, n = 94). Hypertension and diabetes mellitus were significantly more prevalent and CACS values and HbA1c, NT-proBNP, and GDF-15 levels were significantly higher (all p < 0.001) in the elderly group compared to the middle-aged group. Multivariate ridge regression analysis revealed a significant positive association between GDF-15 and CACS (middle-aged group: β = 0.072, p = 0.333; elderly group: β = 0.148, p = 0.003), and between GDF-15 and ABI (middle-aged group: β = 0.062, p = 0.393; elderly group: β = 0.088, p = 0.041) only in the elderly group. Our results show that GDF-15 is not only a useful biomarker of inflammation but can also predict early signs of asymptomatic atherosclerosis, especially in elderly people with chronic systemic inflammation associated with aging (inflammaging).

The correlation between serum growth differentiation factor 15 and malnutrition in patients with end-stage kidney disease on hemodialysis

OBJECTIVE

Malnutrition commonly occurs in patients undergoing maintenance hemodialysis. Early detection of malnutrition could allow early interventions to prevent later complications. At present, there are not many biomarkers with high predictive value of end-stage kidney disease (ESKD)-related malnutrition, especially for early malnutrition in hemodialysis patients, which needs more in-depth research. Therefore, we performed a cross-sectional study on 97 patients to identify biomarkers for malnutrition in hemodialysis patients.

RESEARCH METHODS & PROCEDURES

7-point subjective global assessment (SGA) was applied to evaluate the nutritional status of patients on hemodialysis. Serum levels of growth differentiation factor 15 (GDF15), albumin, pre-albumin, c-reactive protein (CRP), tumor necrosis factor alpha (TNF-α), hemoglobin, low density lipoprotein-cholesterol, and high density lipoprotein-cholesterol were detected before hemodialysis. Logistic analysis and linear regression were used to analyze the association between GDF15 levels and the SGA score after adjustment for basic characteristics and laboratory findings.

RESULTS

Among the 97 patients on hemodialysis, 51 had malnutrition (SGA < 6). There was no difference between the malnourished and well nourished (SGA ≥ 6) groups for dialysis duration, cholesterol, CRP, TNF-α, and hemoglobin. The malnutrition group had significantly lower grip strength (p < 0.05). GDF15 levels correlated negatively with the SGA score after adjustment for possible confounding factors [rho (male) = -0.312, rho(female)= -0.437;P(male) = 0.0181, P(female) = 0.005], and might contribute to the malnutritional status, the AUCs of GDF15 for malnutrition was 0.697 (p = 0.011) in male and 0.828 (p < 0.001) in female.

CONCLUSIONS

GDF15 is associated with malnutrition according to the SGA score in patients with ESKD on hemodialysis, suggesting that GDF15 might be involved in the pathogenesis of malnutrition patients with ESKD in this setting. Furthermore, GDF15 is likely to be a potential diagnostic biomarker for malnutrition according to the SGA score.

Evaluation of Arterial Stiffness Parameters and the Growth Differentiation Factor-15 Level in Patients with Premature Myocardial Infarction

BACKGROUND

Myocardial infarction (MI) is increasing at a younger age. Growth differentiation factor-15 (GDF-15) has been implicated in several key mechanisms of atherogenesis. Arterial stiffness parameters, including pulse wave velocity (PWV) and the augmentation index (AIx), can indicate the presence or progression of atherosclerosis. The aim of this study is to evaluate the GDF-15 level and arterial stiffness parameters in patients with premature MI.

METHOD

Thirty patients aged ≤45 years (mean age: 39 ± 5 years, 23 male) who recovered from a MI and 15 age and sex-matched subjects were consecutively included. The serum GDF-15 concentration levels and arterial stiffness parameters of the patients and controls were measured.

RESULTS

GDF-15 levels were significantly higher in patients with premature MI, while there were no significant differences in PWV and AIx between the groups. The GDF-15 level was correlated negatively with high-density lipoprotein (HDL) cholesterol and positively with uric acid levels. Both GDF-15 (p = 0.046, odds ratio: 1.092, 95% confidence interval: 1.003-1.196) and HDL cholesterol (p = 0.037, odds ratio: 0.925, 95% confidence interval: 0.859-0.995) were found as independent factors associated with premature MI.

CONCLUSIONS

GDF-15 could be a risk factor for premature MI. Further studies are needed to elucidate the central role of GDF-15 in the pathophysiology of early atherosclerosis and MI in the young population.

Loss of growth differentiation factor 15 exacerbates lung injury in neonatal mice

Growth differentiation factor 15 (GDF15) is a divergent member of the transforming growth factor-β (TGF-β) superfamily, and its expression increases under various stress conditions, including inflammation, hyperoxia, and senescence. GDF15 expression is increased in neonatal murine bronchopulmonary dysplasia (BPD) models, and GDF15 loss exacerbates oxidative stress and decreases cellular viability in vitro. Our overall hypothesis is that the loss of GDF15 will exacerbate hyperoxic lung injury in the neonatal lung in vivo. We exposed neonatal Gdf15-/- mice and wild-type (WT) controls on a similar background to room air or hyperoxia (95% [Formula: see text]) for 5 days after birth. The mice were euthanized on postnatal day 21 (PND 21). Gdf15-/- mice had higher mortality and lower body weight than WT mice after exposure to hyperoxia. Hyperoxia exposure adversely impacted alveolarization and lung vascular development, with a greater impact in Gdf15-/- mice. Interestingly, Gdf15-/- mice showed lower macrophage count in the lungs compared with WT mice both under room air and after exposure to hyperoxia. Analysis of the lung transcriptome revealed marked divergence in gene expression and enriched biological pathways in WT and Gdf15-/- mice and differed markedly by biological sex. Notably, pathways related to macrophage activation and myeloid cell homeostasis were negatively enriched in Gdf15-/- mice. Loss of Gdf15 exacerbates mortality, lung injury, and the phenotype of the arrest of alveolarization in the developing lung with loss of female-sex advantage in Gdf15-/- mice.NEW & NOTEWORTHY We show for the first time that loss of Gdf15 exacerbates mortality, lung injury, and the phenotype of the arrest of alveolarization in the developing lung with loss of female-sex advantage in Gdf15-/- mice. We also highlight the distinct pulmonary transcriptomic response in the Gdf15-/- lung including pathways related to macrophage recruitment and activation.

Browning of Adipocytes: A Potential Therapeutic Approach to Obesity

The increasing prevalence of overweight and obesity suggests that current strategies based on diet, exercise, and pharmacological knowledge are not sufficient to tackle this epidemic. Obesity results from a high caloric intake and energy storage, the latter by white adipose tissue (WAT), and when neither are counterbalanced by an equally high energy expenditure. As a matter of fact, current research is focused on developing new strategies to increase energy expenditure. Against this background, brown adipose tissue (BAT), whose importance has recently been re-evaluated via the use of modern positron emission techniques (PET), is receiving a great deal of attention from research institutions worldwide, as its main function is to dissipate energy in the form of heat via a process called thermogenesis. A substantial reduction in BAT occurs during normal growth in humans and hence it is not easily exploitable. In recent years, scientific research has made great strides and investigated strategies that focus on expanding BAT and activating the existing BAT. The present review summarizes current knowledge about the various molecules that can be used to promote white-to-brown adipose tissue conversion and energy expenditure in order to assess the potential role of thermogenic nutraceuticals. This includes tools that could represent, in the future, a valid weapon against the obesity epidemic.

Cardiac Biomarkers and Risk of Atherosclerotic Cardiovascular Disease in Patients with CKD

Background

Several cardiac biomarkers of cardiac stress, inflammation, and fibrosis (N-terminal pro brain-type natriuretic peptide [NT-proBNP], high-sensitivity troponin T [hsTnT], growth differentiation factor 15 [GDF-15], and soluble ST2 [sST2]) have been associated with atherosclerotic disease in the general population. We hypothesized that these cardiac biomarkers may also be associated with the atherosclerotic cardiovascular disease in patients with CKD.

Methods

We analyzed levels of NT-proBNP, hsTnT, GDF-15, and sST2 in a cohort of 2732 participants with mild to moderate CKD from the Chronic Renal Insufficiency Cohort (CRIC) study. Outcomes included incident atherosclerotic disease, defined as the first instance of myocardial infarction, stroke, or peripheral vascular disease. We used Cox proportional hazard models to the test the association of each cardiac biomarker with risk of incident atherosclerotic disease, adjusting for multiple possible confounders.

Results

When modeled continuously (per SD increase in the log-transformed biomarker), NT-proBNP, hsTnT, GDF-15, and sST2 were significantly associated with incident atherosclerotic disease after adjustment for multiple potential confounders: (NT-proBNP HR, 1.51; 95% CI, 1.27 to 1.81; hsTnT HR, 1.61; 95% CI, 1.38 to 1.89; GDF-15 HR, 1.44; 95% CI, 1.19 to 1.73; and sST2 HR, 1.19; 95% CI, 1.04 to 1.36).

Conclusions

NT-proBNP, hsTnT, GDF-15, and sST2 were significantly associated with incident atherosclerotic cardiovascular disease in patients with CKD. These associations may highlight important mechanisms for the development of atherosclerotic disease in CKD.

Growth Differentiation Factor-15 in Immunity and Aging

Aging increases susceptibility to and severity of a variety of chronic and infectious diseases. Underlying this is dysfunction of the immune system, including chronic increases in low-grade inflammation (inflammaging) and age-related immunosuppression (immunosenescence). Growth differentiation factor-15 (GDF-15) is a stress-, infection-, and inflammation-induced cytokine which is increased in aging and suppresses immune responses. This mini review briefly covers existing knowledge on the immunoregulatory and anti-inflammatory roles of GDF-15, as well as its potential importance in aging and immune function.

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.

Characterization of atherosclerotic plaques in blood vessels with low oxygenated blood and blood pressure (Pulmonary trunk): role of growth differentiation factor-15 (GDF-15)

BACKGROUND

Growth differentiation factor (GDF)-15 is linked to inflammation, cancer, and atherosclerosis. GDF-15 is expressed in most tissues but is extremely induced under pathological conditions. Elevated serum levels are suggested as a risk factor and a marker for cardiovascular diseases. However, the cellular sources and the effects of GDF-15 on the cardiovascular system have not been completely elucidated including progression, and morphology of atherosclerotic plaques. Thus, this work aimed to characterize the influence of GDF-15 deficiency on the morphology of atherosclerotic plaques in blood vessels with low-oxygen blood and low blood pressure as the pulmonary trunk (PT), in hypercholesterolemic ApoE-/- mice.

METHODS

GDF-15-/- ApoE-/- mice were generated by crossbreeding of ApoE-/-- and GDF-15-/- mice. After feeding a cholesterol-enriched diet (CED) for 20 weeks, samples of the brachiocephalic trunk (BT) and PT were dissected and lumen stenosis (LS) was measured. Furthermore, changes in the cellularity of the PT, amounts of apoptosis-, autophagy-, inflammation- and proliferation-relevant proteins were immunohisto-morphometrically analyzed. Additionally, we examined an atherosclerotic plaque in a human post mortem sample of the pulmonary artery.

RESULTS

After CED the body weight of GDF-15-/-ApoE-/- was 22.9% higher than ApoE-/-. Double knockout mice showed also an 35.3% increase of plasma triglyceride levels, whereas plasma cholesterol was similar in both genotypes. LS in the BT and PT of GDF-15-/-ApoE-/- mice was significantly reduced by 19.0% and by 6.7% compared to ApoE-/-. Comparing LS in PT and BT of the same genotype revealed a significant 38.8% (ApoE-/-) or 26.4% (GDF-15-/-ApoE-/-) lower LS in the PT. Immunohistomorphometry of atherosclerotic lesions in PT of GDF-15-/-ApoE-/- revealed significantly increased levels (39.8% and 7.3%) of CD68 + macrophages (MΦ) and α-actin + smooth muscle cells than in ApoE-/-. The density of TUNEL + , apoptotic cells was significantly (32.9%) higher in plaques of PT of GDF-15-/-ApoE-/- than in ApoE-/-. Analysis of atherosclerotic lesion of a human pulmonary artery showed sm-α-actin, CD68+, TUNEL+, Ki67+, and APG5L/ATG+ cells as observed in PT. COX-2+ and IL-6+ immunoreactivities were predominantly located in endothelial cells and subendothelial space. In BT and PT of GDF15-/-ApoE-/- mice the necrotic area was 10% and 6.5% lower than in ApoE-/-. In BT and PT of GDF15-/-ApoE-/- we found 40% and 57% less unstable plaques than ApoE-/- mice.

CONCLUSIONS

Atherosclerotic lesions occur in both, BT and PT, however, the size is smaller in PT, possibly due to the effect of the low-oxygen blood and/or lower blood pressure. GDF-15 is involved in atherosclerotic processes in BT and PT, although different mechanisms (e.g. apoptosis) in these two vessels seem to exist.

Biomarkers in AL Amyloidosis

Systemic AL amyloidosis is a rare complex hematological disorder caused by clonal plasma cells which produce amyloidogenic immunoglobulins. Outcome and prognosis is the combinatory result of the extent and pattern of organ involvement secondary to amyloid fibril deposition and the biology and burden of the underlying plasma cell clone. Prognosis, as assessed by overall survival, and early outcomes is determined by degree of cardiac dysfunction and current staging systems are based on biomarkers that reflect the degree of cardiac damage. The risk of progression to end-stage renal disease requiring dialysis is assessed by renal staging systems. Longer-term survival and response to treatment is affected by markers of the underlying plasma cell clone; the genetic background of the clonal disease as evaluated by interphase fluorescence in situ hybridization in particular has predictive value and may guide treatment selection. Free light chain assessment forms the basis of hematological response criteria and minimal residual disease as assessed by sensitive methods is gradually being incorporated into clinical practice. However, sensitive biomarkers that could aid in the early diagnosis and that could reflect all aspects of organ damage and disease biology are needed and efforts to identify them are continuous.

GDF15: emerging biology and therapeutic applications for obesity and cardiometabolic disease

Growth differentiation factor 15 (GDF15) is a member of the TGFβ superfamily whose expression is increased in response to cellular stress and disease as well as by metformin. Elevations in GDF15 reduce food intake and body mass in animal models through binding to glial cell-derived neurotrophic factor family receptor alpha-like (GFRAL) and the recruitment of the receptor tyrosine kinase RET in the hindbrain. This effect is largely independent of other appetite-regulating hormones (for example, leptin, ghrelin or glucagon-like peptide 1). Consistent with an important role for the GDF15-GFRAL signalling axis, some human genetic studies support an interrelationship with human obesity. Furthermore, findings in both mice and humans have shown that metformin and exercise increase circulating levels of GDF15. GDF15 might also exert anti-inflammatory effects through mechanisms that are not fully understood. These unique and distinct mechanisms for suppressing food intake and inflammation makes GDF15 an appealing candidate to treat many metabolic diseases, including obesity, type 2 diabetes mellitus, non-alcoholic fatty liver disease, cardiovascular disease and cancer cachexia. Here, we review the mechanisms regulating GDF15 production and secretion, GDF15 signalling in different cell types, and how GDF15-targeted pharmaceutical approaches might be effective in the treatment of metabolic diseases.

GDF-15 Deficiency Reduces Autophagic Activity in Human Macrophages In Vitro and Decreases p62-Accumulation in Atherosclerotic Lesions in Mice

(1) Background: Growth differentiation factor-15 (GDF-15) is associated with cardiovascular diseases and autophagy in human macrophages (MΦ). Thus, we are interested in investigating autophagic mechanisms with special respect to the role of GDF-15. (2) Methods: Recombinant (r)GDF-15 and siRNA GDF-15 were used to investigate the effects of GDF-15 on autophagic and lysosomal activity, as well as autophagosome formation by transmission electron microscopy (TEM) in MΦ. To ascertain the effects of GDF-15-/- on the progression of atherosclerotic lesions, we used GDF-15-/-/ApoE-/- and ApoE-/- mice under a cholesterol-enriched diet (CED). Body weight, body mass index (BMI), blood lipid levels and lumen stenosis in the brachiocephalic trunk (BT) were analyzed. Identification of different cell types and localization of autophagy-relevant proteins in atherosclerotic plaques were performed by immunofluorescence. (3) Results: siGDF-15 reduced and, conversely, rGDF-15 increased the autophagic activity in MΦ, whereas lysosomal activity was unaffected. Autophagic degradation after starvation and rGDF-15 treatment was observed by TEM. GDF-15-/-/ApoE-/- mice, after CED, showed reduced lumen stenosis in the BT, while body weight, BMI and triglycerides were increased compared with ApoE-/- mice. GDF-15-/- decreased p62-accumulation in atherosclerotic lesions, especially in endothelial cells (ECs). (4) Conclusion: GDF-15 seems to be an important factor in the regulation of autophagy, especially in ECs of atherosclerotic lesions, indicating its crucial pathophysiological function during atherosclerosis development.

Therapeutic wavelengths of ultraviolet B radiation activate apoptotic, circadian rhythm, redox signalling and key canonical pathways in psoriatic epidermis

Ultraviolet B radiation (UVB) exerts pleiotropic effects on human skin. DNA damage response and repair pathways are activated by UVB; if damage cannot be repaired, apoptosis ensues. Although cumulative UVB exposure predisposes to skin cancer, UVB phototherapy is widely used as an effective treatment for psoriasis. Previous studies defined the therapeutic action spectrum of UVB and showed that psoriasis is resistant to apoptosis. This study aimed to investigate early molecular responses within psoriasis plaques following irradiation with single equi-erythemogenic doses of clinically-effective (311 nm, narrow-band) compared to clinically-ineffective (290 nm) UVB. Forty-eight micro-dissected epidermal samples from 20 psoriatic patients were analyzed using microarrays. Our bioinformatic analysis compared gene expression between 311 nm irradiated, 290 nm irradiated and control psoriasis epidermis to specifically identify 311 nm UVB differentially expressed genes (DEGs) and their upstream regulatory pathways. Key DEGs and pathways were validated by immunohistochemical analysis. There was a dynamic induction and repression of 311 nm UVB DEGs between 6 h and 18 h, only a limited number of DEGs maintained their designated expression status between time-points. Key disease and function pathways included apoptosis, cell death, cell migration and leucocyte chemotaxis. DNA damage response pathways, NRF2-mediated oxidative stress response and P53 signalling were key nodes, interconnecting apoptosis and cell cycle arrest. Interferon signalling, dendritic cell maturation, granulocyte adhesion and atherosclerotic pathways were also differentially regulated. Consistent with these findings, top transcriptional regulators of 311 nm UVB DEGs related to: a) apoptosis, DNA damage response and cell cycle control; b) innate/acquired immune regulation and inflammation; c) hypoxia/redox response and angiogenesis; d) circadian rhythmicity; f) EGR/AP1 signalling and keratinocyte differentiation; and g) mitochondrial biogenesis. This research provides important insights into the molecular targets of 311 nm UVB, underscoring key roles for apoptosis and cell death. These and the other key pathways delineated may be central to the therapeutic effects of 311 nm in psoriasis.

Elevated circulating growth differentiation factor 15 is related to decreased heart rate variability in chronic kidney disease patients

Background

Growth differentiation factor 15(GDF15) is a distant member of the superfamily of the transforming growth factor beta (TGF-β). It has been established that increased GDF15 levels are associated with an increased risk of cardiovascular disease. However, the detail effect of GDF15 on cardiovascular system in patients with chronic kidney disease (CKD) needs detail analysis.

Methods

Patients with CKD who did not need dialysis were enrolled in the study. Blood pressure (BP), endothelial function, pulse wave velocity (PWV) and heart rate variability (HRV) were taken in all subjects. Plasma GDF15 concentration was measured by an enzyme-linked immunosorbent assay.

Results

Among the 355 participants, the mean age was 57.4 (±14.2) years old and the mean estimated glomerular filtration rate (eGFR) was 50.1 (±33.2) mL/min/1.73m². The average plasma GDF15 level was 1394.7 (±610.1) pg/mL. Higher GDF15 concentrations were significantly associated with decreased eGFR and increased urine protein-to-creatinine ratio (uPCR). In multivariable models, after adjusting for potential confounders, plasma GDF15 has negative concerning with HRV parameters including the standard deviation of the normal-to-normal (NN) interval (SDNN), the square root of the mean of the sum of the squares of differences between adjacent NN intervals (RMSSD) and Triangular Index.

Conclusion

We observed there was a link between increased plasma of GDF15 and decreased HRV. The mechanisms and prediction of GDF15 in the cardiovascular disease with CKD needs further discussion and study.

Cellular and Intercellular Homeostasis in Adipose Tissue with Mitochondria-Specific Stress

Paracrine interactions are imperative for the maintenance of adipose tissue intercellular homeostasis, and intracellular organelle dysfunction results in local and systemic alterations in metabolic homeostasis. It is currently accepted that mitochondrial proteotoxic stress activates the mitochondrial unfolded protein response (UPRmt) in vitro and in vivo. The induction of mitochondrial chaperones and proteases during the UPRmt is a key cell-autonomous mechanism of mitochondrial quality control. The UPRmt also affects systemic metabolism through the secretion of cell non-autonomous peptides and cytokines (hereafter, metabokines). Mitochondrial function in adipose tissue plays a pivotal role in whole-body metabolism and human diseases. Despite continuing interest in the role of the UPRmt and quality control pathways of mitochondria in energy metabolism, studies on the roles of the UPRmt and metabokines in white adipose tissue are relatively sparse. Here, we describe the role of the UPRmt in adipose tissue, including adipocytes and resident macrophages, and the interactive roles of cell non-autonomous metabokines, particularly growth differentiation factor 15, in local adipose cellular homeostasis and systemic energy metabolism.

GDF-15 in Pulmonary and Critical Care Medicine

GDF-15 (growth differentiation factor 15) acts both as a stress-induced cytokine with diverse actions at different body sites and as a cell-autonomous regulator linked to cellular senescence and apoptosis. For multiple reasons, this divergent transforming growth factor-β molecular superfamily member should be better known to pulmonary researchers and clinicians. In ambulatory individuals, GDF-15 concentrations in peripheral blood are an established predictive biomarker of all-cause mortality and of adverse cardiovascular events. Concentrations upon admission of critically ill patients (without or with sepsis) correlate with organ dysfunction and independently predict short- and long-term mortality risk. GDF-15 is a major downstream mediator of p53 activation, but it can also be induced independently of p53, notably by nonsteroidal antiinflammatory agents. GDF-15 blood concentrations are markedly elevated in adults and children with pulmonary hypertension. Concentrations are also increased in chronic obstructive pulmonary disease, in which they contribute to mucus hypersecretion, airway epithelial cell senescence, and impaired antiviral defenses, which together with murine data support a role for GDF-15 in chronic obstructive pulmonary disease pathogenesis and progression. This review summarizes biological and clinical data on GDF-15 relevant to pulmonary and critical care medicine. We highlight the recent discovery of a central nervous system receptor for GDF-15, GFRAL (glial cell line-derived neurotrophic factor family receptor-α-like), an important advance with potential for novel treatments for obesity and cachexia. We also describe limitations and controversies in the existing literature, and we delineate research questions that must be addressed to determine whether GDF-15 can be therapeutically manipulated in other clinical settings.

Cardiac and Stress Biomarkers and Chronic Kidney Disease Progression: The CRIC Study

BACKGROUND

Increases in cardiac and stress biomarkers may be associated with loss of kidney function through shared mechanisms involving cardiac and kidney injury. We evaluated the associations of cardiac and stress biomarkers [N-terminal pro-B-type natriuretic peptide (NT-proBNP), high-sensitivity troponin T (hsTnT), growth differentiation factor 15 (GDF-15), soluble ST-2 (sST-2)] with progression of chronic kidney disease (CKD).

METHODS

We included 3664 participants with CKD from the Chronic Renal Insufficiency Cohort study. All biomarkers were measured at entry. The primary outcome was CKD progression, defined as progression to end-stage renal disease (ESRD) or 50% decline in estimated glomerular filtration rate (eGFR). Cox models tested the association of each biomarker with CKD progression, adjusting for demographics, site, diabetes, cardiovascular disease, eGFR, urine proteinuria, blood pressure, body mass index, cholesterol, medication use, and mineral metabolism.

RESULTS

There were 1221 participants who had CKD progression over a median (interquartile range) follow-up of 5.8 (2.4-8.6) years. GDF-15, but not sST2, was significantly associated with an increased risk of CKD progression [hazard ratios (HRs) are per SD increase in log-transformed biomarker]: GDF-15 (HR, 1.50; 95% CI, 1.35-1.67) and sST2 (HR, 1.07; 95% CI, 0.99-1.14). NT-proBNP and hsTnT were also associated with increased risk of CKD progression, but weaker than GDF-15: NT-proBNP (HR, 1.24; 95% CI, 1.13-1.36) and hsTnT (HR, 1.11; 95% CI, 1.01-1.22).

CONCLUSIONS

Increases in GDF-15, NT-proBNP, and hsTnT are associated with greater risk for CKD progression. These biomarkers may inform mechanisms underlying kidney injury.

Cardiac Biomarkers and Risk of Atrial Fibrillation in Chronic Kidney Disease: The CRIC Study

Background

We tested associations of cardiac biomarkers of myocardial stretch, injury, inflammation, and fibrosis with the risk of incident atrial fibrillation (AF) in a prospective study of chronic kidney disease patients.

Methods and Results

The study sample was 3053 participants with chronic kidney disease in the multicenter CRIC (Chronic Renal Insufficiency Cohort) study who were not identified as having AF at baseline. Cardiac biomarkers, measured at baseline, were NT‐proBNP (N‐terminal pro‐B‐type natriuretic peptide), high‐sensitivity troponin T, galectin‐3, growth differentiation factor‐15, and soluble ST‐2. Incident AF (“AF event”) was defined as a hospitalization for AF. During a median follow‐up of 8 years, 279 (9%) participants developed a new AF event. In adjusted models, higher baseline log‐transformed NT‐proBNP (N‐terminal pro‐B‐type natriuretic peptide) was associated with incident AF (adjusted hazard ratio [HR] per SD higher concentration: 2.11; 95% CI, 1.75, 2.55), as was log‐high‐sensitivity troponin T (HR 1.42; 95% CI, 1.20, 1.68). These associations showed a dose–response relationship in categorical analyses. Although log‐soluble ST‐2 was associated with AF risk in continuous models (HR per SD higher concentration 1.35; 95% CI, 1.16, 1.58), this association was not consistent in categorical analyses. Log‐galectin‐3 (HR 1.05; 95% CI, 0.91, 1.22) and log‐growth differentiation factor‐15 (HR 1.16; 95% CI, 0.96, 1.40) were not significantly associated with incident AF.

Conclusions

We found strong associations between higher NT‐proBNP (N‐terminal pro‐B‐type natriuretic peptide) and high‐sensitivity troponin T concentrations, and the risk of incident AF in a large cohort of participants with chronic kidney disease. Increased atrial myocardial stretch and myocardial cell injury may be implicated in the high burden of AF in patients with chronic kidney disease.

MIC-1/GDF15 Overexpression Is Associated with Increased Functional Recovery in Traumatic Spinal Cord Injury

Spinal cord injury (SCI) has devastating consequences, with limited therapeutic options; therefore, improving its functional outcome is a major goal. The outcome of SCI is contributed to by neuroinflammation, which may be a target for improved recovery and quality of life after injury. Macrophage inhibitory cytokine-1/growth differentiation factor 15 (MIC-1/GDF15) has been identified as a potential novel therapy for central nervous system (CNS) injury because it is an immune regulatory cytokine with neurotrophic properties. Here we used MIC-1/GDF15 knockout (KO) and overexpressing/transgenic (Tg) and wild type (WT) animals to explore its putative therapeutic benefits in a mouse model of contusive SCI. MIC-1/GDF15 Tg mice had superior locomotor recovery and reduced secondary tissue loss at 28 days compared with their KO and WT counterparts. Overexpression of MIC-1/GDF15 coincided with increased expression of monocyte chemoattractant protein-1 (MCP-1)/C-C Motif Chemokine Ligand 2 (CCL2) at the lesion site (28 days post-SCI) and enhanced recruitment of inflammatory cells to the injured spinal cord. This inflammatory cellular infiltrate included an increased frequency of macrophages and dendritic cells (DCs) that mostly preceded recruitment of cluster of differentiation (CD)4⁺ and CD8⁺ T cells. Collectively, our findings suggest hat MIC-1/GDF15 is associated with beneficial changes in the clinical course of SCI that are characterized by altered post-injury inflammation and improved functional outcome. Further investigation of MIC-1/GDF15 as a novel therapeutic target for traumatic SCI appears warranted.

Growth differentiation factor-15 regulates oxLDL-induced lipid homeostasis and autophagy in human macrophages

BACKGROUND AND AIMS

Growth differentiation factor-15 (GDF-15)/macrophage inhibitory cytokine-1 (MIC-1/GDF15) is associated with cardiovascular disease, inflammation and development of atherosclerosis and is highly expressed in macrophages (MΦ) of atherosclerotic lesions. Thus, we were interested in investigating the influence of GDF-15 in lipid homeostasis and autophagy in human MΦ during foam cell formation.

METHODS AND RESULTS

Oxidized-low density lipoprotein (50 μg/ml oxLDL), recombinant (r)GDF-15, transiently silenced GDF-15 (siGDF-15 MΦ), as well as with negative siRNA transfected (nsiGDF-15 MΦ) PMA-differentiated human THP-1 MΦ, were used to investigate the effects of GDF-15 on autophagic processes and lipid accumulation. Oil Red O staining revealed that rGDF-15 alone, but also in combination with oxLDL, significantly increased the lipid accumulation in THP-1 MΦ; a reverse effect was detected in siGDF-15 MΦ. Western-blot analyses and confocal laser scanning microscopy showed an increase of Atg5, Atg12/Atg5 protein complex and p62 protein in THP-1 MΦ co-incubated with rGDF-15 and oxLDL, as well as an increase of p62 accumulation compared to rGDF-15-treated MΦ. Vice versa, siGDF-15 MΦ showed a reduced p62 accumulation compared to nsiGDF-15 MΦ. The present study indicates that GDF-15, especially in combination with oxLDL, regulates the expression of autophagy-relevant proteins (p62, Atg5 and Atg12/Atg5 protein complex) and p62 accumulation in human MΦ.

CONCLUSIONS

GDF-15, in combination with oxLDL, impairs autophagic processes with consequences for lipid homeostasis in human MΦ, indicating its novel important pathophysiological role in atherosclerotic plaque development and progression.

GDF15 and Growth Control

Growth/differentiation factor-15 (GDF-15) is a distant member of the transforming growth factor β (TGF-β) superfamily and is widely expressed in multiple mammalian tissues. Its expression is highly regulated and is often induced in response to conditions associated with cellular stress. GDF15 serum levels have a strong association with many diseases, including inflammation, cancer, cardiovascular diseases, and obesity, and potentially serve as reliable predictor of disease progression. A functional role for GDF15 has been suggested in cancer, cardiovascular disease, kidney disease and metabolic disease. However, the knowledge of its pathophysiological function at the molecular level is still limited and requires more investigation. Recent identification of the endogenous receptor for GDF15 may provide additional insight in to its' molecular mechanisms and relationship to disease states.

The MIC-1/GDF15-GFRAL Pathway in Energy Homeostasis: Implications for Obesity, Cachexia, and Other Associated Diseases

MIC-1/GDF15 is a stress response cytokine and a distant member of the transforming growth factor beta (TGFb) superfamily, with no close relatives. It acts via a recently identified receptor called glial-derived neurotrophic factor (GDNF) receptor alpha-like (GFRAL), which is a distant orphan member of the GDNF receptor family that signals through the tyrosine kinase receptor Ret. MIC-1/GDF15 expression and serum levels rise in response to many stimuli that initiate cell stress and as part of a wide variety of disease processes, most prominently cancer and cardiovascular disease. The best documented actions of MIC-1/GDF15 are on regulation of energy homeostasis. When MIC-1/GDF15 serum levels are substantially elevated in diseases like cancer, it subverts a physiological pathway of appetite regulation to induce an anorexia/cachexia syndrome initiated by its actions on hindbrain neurons. These effects make it a potential target for the treatment of both obesity and anorexia/cachexia syndromes, disorders lacking any highly effective, readily accessible therapies.

Growth differentiation factor 15 ameliorates nonalcoholic steatohepatitis and related metabolic disorders in mice

Growth differentiation factor 15 (GDF15) is an endocrine hormone belonging to the TGFβ superfamily member. GDF15 administration or GDF15 overexpression has been reported to have anti-obesity and anti-diabetic effects. Although non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH) is frequently associated with obesity and insulin resistance, the functional role of endogenous GDF15 and therapeutic effect of GDF15 overexpression in NASH and related metabolic deterioration have not been evaluated. Here, we found that GDF15 expression was increased in the livers of NASH animal models and human subjects with NASH. Elevated expression of GDF15 was due to diet-induced hepatic endoplasmic reticulum (ER) stress. Gdf15-knockout mice exhibited aggravated NASH phenotypes such as increased steatosis, hepatic inflammation, fibrosis, liver injury, and metabolic deterioration. Furthermore, GDF15 directly suppressed expression of fibrosis-related genes and osteopontin (OPN), contributing factors for NASH-related fibrosis, in hepatic stellate cells in vitro and in the liver of mice in vivo. Finally, we found that GDF15-transgenic mice showed attenuation of NASH phenotypes and metabolic deterioration. Therefore, our results suggest that induction of endogenous GDF15 is a compensatory mechanism to protect against the progression of NASH and that GDF15 could be an attractive therapeutic candidate for treatment of NASH and NASH-related metabolic deterioration.

Growth Differentiation Factor 15 Is Associated With Major Amputation and Mortality in Patients With Peripheral Artery Disease

Background

Peripheral artery disease (PAD) is one of the most common clinical presentations of atherosclerosis, and its prevalence is still increasing. Despite improvement of health care, morbidity and mortality risks remain high, including the risk of amputation. GDF15 (growth differentiation factor 15) is a member of the transforming growth factor family that is involved in apoptosis and inflammation; therefore, GDF15 is a potential biomarker to identify patients at high risk of adverse clinical outcomes.

Methods and Results

Circulating GDF15 levels were measured using a multiplex immunoassay in patients with critical limb ischemia and PAD from 2 different patient cohorts that included patients with clinically manifest PAD: the JUVENTAS (Rejuvenating Endothelial Progenitor Cells via Transcutaneous Intra‐Arterial Supplementation) trial (n=160, 67 major events; critical limb ischemia) and the Athero‐Express Biobank (n=386, 64 major events; PAD). Kaplan–Meier curves demonstrated that high levels of GDF15 were associated with increased risk of major events, defined as major amputation (at or above the ankle joint) and all‐cause mortality, in both cohorts (highest versus lowest, JUVENTAS: hazard ratio: 4.01 [95% confidence interval, 2.05–7.84; P<0.0001]; Athero‐Express: hazard ratio: 3.27 [95% confidence interval, 1.64–6.54; P=0.0008]). In the JUVENTAS trial, this was more pronounced in women. Cox proportional multivariable regression models with median follow‐up of 3 years, corrected for common confounders, showed hazard ratios of 1.70 (95% confidence interval, 1.18–2.69; P=0.0053) and 1.57 (95% confidence interval, 1.02–2.41; P=0.041) per 2.78‐fold increase of GDF15 in JUVENTAS and Athero‐Express, respectively.

Conclusions

High GDF15 levels are associated with increased risk of major amputation and/or death in PAD patients. GDF15 levels could be of additive value to identify patients who are at high risk of amputation or death and could help guide treatment choices.

Growth Differentiation Factor-15 and Risk of CKD Progression

Growth differentiation factor-15 (GDF-15) is a member of the TGF-β cytokine superfamily that is widely expressed and may be induced in response to tissue injury. Elevations in GDF-15 may identify a novel pathway involved in loss of kidney function among patients with CKD. Among participants in the Clinical Phenotyping and Resource Biobank (C-PROBE) study and the Seattle Kidney Study (SKS), we tested whether kidney tissue expression of GDF15 mRNA correlates with circulating levels of GDF-15 and whether elevations in circulating GDF-15 are associated with decline in kidney function. In matching samples of 24 patients with CKD from the C-PROBE study, circulating GDF-15 levels significantly correlated with intrarenal GDF15 transcript levels (r=0.54, P=0.01). Among the 224 C-PROBE and 297 SKS participants, 72 (32.1%) and 94 (32.0%) patients, respectively, reached a composite end point of 30% decline in eGFR or progression to ESRD over a median of 1.8 and 2.0 years of follow up, respectively. In multivariable models, after adjusting for potential confounders, every doubling of GDF-15 level associated with a 72% higher (95% confidence interval, 1.21 to 4.45; P=0.003) and 65% higher (95% confidence interval, 1.08 to 2.50; P=0.02) risk of progression of kidney disease in C-PROBE and SKS participants, respectively. These results show that circulating GDF-15 levels strongly correlated with intrarenal expression of GDF15 and significantly associated with increased risk of CKD progression in two independent cohorts. Circulating GDF-15 may be a marker for intrarenal GDF15-related signaling pathways associated with CKD and CKD progression.

Growth differentiation factor 15 is a myomitokine governing systemic energy homeostasis

Chung et al. show that the myomitokine GDF15 can act to modulate oxidative and lipolytic function in a non–cell-autonomous manner, thereby regulating systemic energy homeostasis in skeletal muscle-specific Crif1-deficient mice. This pathway may be a potential therapeutic target for preventing the onset of obesity and insulin resistance.

Reduced mitochondrial electron transport chain activity promotes longevity and improves energy homeostasis via cell-autonomous and –non-autonomous factors in multiple model systems. This mitohormetic effect is thought to involve the mitochondrial unfolded protein response (UPR^mt), an adaptive stress-response pathway activated by mitochondrial proteotoxic stress. Using mice with skeletal muscle–specific deficiency of Crif1 (muscle-specific knockout [MKO]), an integral protein of the large mitoribosomal subunit (39S), we identified growth differentiation factor 15 (GDF15) as a UPR^mt-associated cell–non-autonomous myomitokine that regulates systemic energy homeostasis. MKO mice were protected against obesity and sensitized to insulin, an effect associated with elevated GDF15 secretion after UPR^mt activation. In ob/ob mice, administration of recombinant GDF15 decreased body weight and improved insulin sensitivity, which was attributed to elevated oxidative metabolism and lipid mobilization in the liver, muscle, and adipose tissue. Thus, GDF15 is a potent mitohormetic signal that safeguards against the onset of obesity and insulin resistance.

Role of GDF15 (growth and differentiation factor 15) in pulmonary oxygen toxicity

GDF15 (growth and differentiation factor 15) is a secreted cytokine, a direct target of p53 and plays a role in cell proliferation and apoptosis. It is induced by oxidative stress and has anti-apoptotic effects. The role of GDF15 in hyperoxic lung injury is unknown. We tested the hypothesis that GDF15 will be induced in vitro, in a model of pulmonary oxygen toxicity, and will play a critical role in decreasing cell death and oxidative stress. BEAS-2B (human bronchial epithelial cells) and human pulmonary vascular endothelial cells (HPMEC) were exposed to hyperoxia, and expression of GDF15 and effect of GDF15 disruption on cell viability and oxidative stress was determined. Furthermore, we studied the effect of p53 knockdown on GDF15 expression. In vitro, both BEAS-2B and HPMEC cells showed a significant increase in GDF15 expression upon exposure to hyperoxia. After GDF15 knockdown, there was a significant decrease in cell viability and increase in oxidative stress compared to control cells transfected with siRNA with a scrambled sequence. Knockdown of p53 significantly decreased the induction of GDF15 by hyperoxia. In conclusion, we show that GDF15 has a pro-survival and anti-oxidant role in hyperoxia and that p53 plays a key role in its induction.

Cytokines in atherosclerosis: Key players in all stages of disease and promising therapeutic targets

Atherosclerosis, a chronic inflammatory disorder of the arteries, is responsible for most deaths in westernized societies with numbers increasing at a marked rate in developing countries. The disease is initiated by the activation of the endothelium by various risk factors leading to chemokine-mediated recruitment of immune cells. The uptake of modified lipoproteins by macrophages along with defective cholesterol efflux gives rise to foam cells associated with the fatty streak in the early phase of the disease. As the disease progresses, complex fibrotic plaques are produced as a result of lysis of foam cells, migration and proliferation of vascular smooth muscle cells and continued inflammatory response. Such plaques are stabilized by the extracellular matrix produced by smooth muscle cells and destabilized by matrix metalloproteinase from macrophages. Rupture of unstable plaques and subsequent thrombosis leads to clinical complications such as myocardial infarction. Cytokines are involved in all stages of atherosclerosis and have a profound influence on the pathogenesis of this disease. This review will describe our current understanding of the roles of different cytokines in atherosclerosis together with therapeutic approaches aimed at manipulating their actions.

Atherosclerosis - A matter of unresolved inflammation

Atherosclerosis is commonly looked upon as a chronic inflammatory disease of the arterial wall arising from an unbalanced lipid metabolism and a maladaptive inflammatory response. However, atherosclerosis is not merely an inflammation of the vessel wall. In fact, the cardinal signs of unstable atherosclerotic lesions are primarily characteristics of failed resolution of a chronic inflammation. In contrast to acute inflammatory events which are typically self-limiting, atherosclerosis is an unresolved inflammatory condition, lacking the switch from the pro-inflammatory to the pro-resolving phase, the latter characterized by termination of inflammatory cell recruitment, removal of inflammatory cells from the site of inflammation by apoptosis and dead cell clearance, reprogramming of macrophages toward an anti-inflammatory, regenerative phenotype, and finally egress of effector cells and tissue regeneration. Here we present an overview on mechanisms of failed resolution contributing to atheroprogression and deliver a summary of novel therapeutic strategies to restore resolution in inflamed arteries.