The Cytokine Growth Differentiation Factor-15 and Skeletal Muscle Health: Portrait of an Emerging Widely Applicable Disease Biomarker.

Growth differentiation factor 15 (GDF-15) is a stress-induced transforming growth factor-ß superfamily cytokine with versatile functions in human health. Elevated GDF-15 blood levels associate with multiple pathological conditions, and are currently extensively explored for diagnosis, and as a means to monitor disease progression and evaluate therapeutic responses. This review analyzes GDF-15 in human conditions specifically focusing on its association with muscle manifestations of sarcopenia, mitochondrial myopathy, and autoimmune and viral myositis. The use of GDF-15 as a widely applicable health biomarker to monitor muscle disease is discussed, and its potential as a therapeutic target is explored.

The Potential Role of Growth Differentiation Factor 15 in COVID-19: A Corollary Subjective Effect or Not?

Coronavirus disease 2019 (COVID-19) is primarily caused by various forms of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) variants. COVID-19 is characterized by hyperinflammation, oxidative stress, multi-organ injury (MOI)-like acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Different biomarkers are used in the assessment of COVID-19 severity including D-dimer, ferritin, lactate dehydrogenase (LDH), and hypoxia-inducible factor (HIF). Interestingly, growth differentiation factor 15 (GDF15) has recently become a potential biomarker correlated with the COVID-19 severity. Thus, this critical review aimed to determine the critical association between GDF15 and COVID-19. The perfect function of GDF15 remains not well-recognized; nevertheless, it plays a vital role in controlling cell growth, apoptosis and inflammatory activation. Furthermore, GDF15 may act as anti-inflammatory and pro-inflammatory signaling in diverse cardiovascular complications. Furthermore, the release of GDF15 is activated by various growth factors and cytokines including macrophage colony-stimulating factor (M-CSF), angiotensin II (AngII) and p53. Therefore, higher expression of GDF15 in COVID-19 might a compensatory mechanism to stabilize and counteract dysregulated inflammatory reactions. In conclusion, GDF15 is an anti-inflammatory cytokine that could be associated with the COVID-19 severity. Increased GDF15 could be a compensatory mechanism against hyperinflammation and exaggerated immune response in the COVID-19. Experimental, preclinical and large-scale clinical studies are warranted in this regard.

Biomarker Identification in Fatal Covid-19 and Post-Acute Sequalae of SARS-CoV-2 (PASC) Lungs

Rationale: SARS-CoV-2 has affected millions worldwide. Among those individuals infected with this coronavirus, most recover without hospitalization. However, COVID-19 is characterized by chronic lung failure and death in a significant number of hospitalized patients. Indeed, there is growing evidence that SARS-CoV-2 causes ARDS leading to lung fibrosis that shares similarities with interstitial lung diseases (ILDs) including idiopathic pulmonary fibrosis (IPF). Herein, we addressed the hypothesis that fatal COVID-19, PASC, and ILDs share key biomarkers of interest in lung fibrosis. Methods: This study included 9 fatal COVID-19 and 13 PASC cases, who received lung transplants due COVID-19 associated lung failure. Clinical characteristics such as duration of mechanical ventilation, length of hospitalization, age, sex, and BMI were evaluated in each patient. Autopsy and explanted lung samples were subjected to histopathological and/or immunohistochemical (IHC) analysis for key biomarkers of interest in lung fibrosis including bromodomain-containing protein-4(BRD4), interferon alpha 2(IFNα2), interleukin-1(IL-11), growth differentiation factor 15(GDF15), and keratin 8(KRT8). COVID-19 and PASC lung samples were also compared with lung samples from fatal ARDS due to other causes (i.e., non-COVID-19 ARDS).Results: In the fatal COVID-19 patient group, the mean age was 60.6(50-71) years-old and included 6 males and 3 females. In the transplanted-PASC patient group, the mean age was 46(31-71) years-old and included 12 males and 2 females. The average BMI was 28.3(21-35.5) for fatal COVID-19 and 25.2(19-29.5) for PASC. In fatal COVID-19, comorbidities included hypertension(22%), diabetes(44%), immunocompromised status(11%). The mean duration of mechanical ventilation was 23(8-65) days while hospitalization was 25(8-67) days. Conversely, PASC patients averaged 168(71-539) days from diagnosis to transplant date. The SARS-CoV-2 ARDS survivors that developed chronic lung failure had diffuse interstitial fibrosis frequently with organization into a non-specific interstitial fibrosis (NSIP) pattern. Key IHC findings in fatal COVID-19 and in PASC lung samples included BRD4, IFNalpha2, and IL-11 receptor alpha (IL-11RA) protein expression, which were markedly increased in several cell types most notably macrophages or myeloid cells localized in the alveolar space in COVID-19 lung samples. Although these markers were detected in non-COVID-19 ARDS the levels of each were markedly lower than that detected in the COVID-19 lung samples.Conclusions: These data suggest that key profibrotic pathways in the lung are shared among COVID-19 and chronic fibrotic ILDs. The identification of these pathways provides the impetus to further explore treatment strategies which might survival benefit to chronically ventilated COVID-19 patients and mitigate the need from lung transplantation in PASC patients.

GDF-15 IS A PREDICTOR OF MORTALITY IN CHRONIC KIDNEY DISEASE PATIENTS WITH COVID-19 INFECTION

BACKGROUND AND AIMS: A cytokine storm drives the pathogenesis of severe coronavirus disease (COVID-19) and several biomarkers with different mechanisms of action have been linked to mortality. Chronic kidney disease (CKD) emerged as a very common risk factor for severe COVID-19. Indeed, CKD patients are at increased risk of premature death from many causes, including, but not limited to, cardiovascular disease (CVD) and infections. In this study, we aimed to investigate the associations between the growth differentiation factor 15 (GDF-15), an established cardiovascular and inflammatory biomarker and outcomes in CKD patients hospitalized for COVID-19. METHOD: A retrospective study on COVID-19 hospitalized subjects in the acute phase of the disease. A broad range of cytokines (CD25, IL-18, TNF-α, TNF RI, TNF RII, GDF-15, IL-7, LIF, IL-6, CHITINASE3-LIKE1, RAGE and Pentraxin-3) were assessed in plasma (Luminex, ELISA) collected upon hospitalization. A total of 77 subjects were divided into two groups according to their estimated glomerular filtration rate (eGFR, by CKD-EPI formula), ≥45 mL/min (n = 44), or <45 mL/min (n = 33). RESULTS: We found no statistical differences between the two groups in terms of demographic features. Among comorbidities, we found a higher percentage of patients with diabetes in the eGFR < 45 group. Likewise, the serum tests upon admission showed in the eGFR < 45 group a higher value of neutrophilic count. Upon hospital admission, the patient groups were comparable in terms of symptoms, time from symptom onset to admission and death or discharge, radiological evidence of pneumonia and respiratory parameters and time of hospitalization. Furthermore, there were no statistical differences between medical therapy during hospitalization, need for respiratory support with Continuous Positive Airways Pressure or Non-Invasive Mechanical Ventilation, or death rather than discharge as the clinical outcome. Serum levels of 20 different compounds were measured in COVID-19 patients admitted to the hospital 4-5 days after the onset of symptoms. Interestingly, we found that patients with lower renal function (eGFR < 45 mL/min) had a significant increase of GDF-15, CD-25 and RAGE and, furthermore, higher serum levels of these molecules were detected in non-survivor patients and in those who needed ventilation. Also, TNFα, TNFR I, TNFR II, IL-7 and LIF had a significant increase in patients with eGFR < 45 mL/min with more elevated levels in non-survivor patients. In univariate analysis low and mid-low GDF-15 quartiles (<4.45 ng/mL) were associated with lower mortality risk, while mid-high and high quartiles (>4.45 ng/mL) were associated with higher mortality risk (Figure 1). Independent association between GDF-15 quartiles and mortality risk was confirmed in Cox model adjusted for eGFR, age, fever, dyspnoea and P/F [hazard ratio (HR) 2.28, 95% confidence interval (CI) 1.53-3.39, P < 0.0001) The strength of association between GDF-15 quartiles and mortality risk was increased in patients with eGFR < 45 mL/min/1.73 m2 (HR 2.53, CI 1.34-4.79) compared with the other eGFR group (HR 1.99, CI 1.17-3.39) (Table 1). CONCLUSION: Our results demonstrate that GDF-15 is an independent predictor of COVID-19 mortality in CKD patients. Given the reported increase of this cytokine with age and its possible mechanistic role in various pathological conditions, our findings suggest that GDF-15 signalling pathway inhibitors may be included as possible therapeutic candidates for COVID-19 in CKD. (Table Presented).

SARS-COV-2 INFECTION CAUSES MASSIVE LUNG-CELL SENESCENCE

Introduction: Older age is an important risk factor for severe COVID-19 disease. Understanding the biological mechanisms that link aging to the pathogenesis of COVID-19 is essential for developing of therapeutic strategies. We hypothesized that cell senescence, a basic aging process that plays a pivotal role in lung diseases, is involved in the pathogenesis of COVID-19 including the development of long-lasting lung alterations. Methods: To evaluate the impact of SARS-CoV-2 infection on cell senescence, we 1) analyzed publicly available datasets of scRNA-seq performed in BALF cells from patients with moderate or severe/critical COVID-19;2) investigated lung samples from cynomolgus macaques infected with 106 pfu of a SARS-CoV-2 clinical isolate. Two macaques were sacrificed at 4 days post-infection (dpi.) and two others at 30 dpi. Results: In BALF obtained within 10 days after symptom onset, the expression of several senescence markers, i.e., CDKN2A, CDKN1A (encoding p21), uPAR, CXCL8, IGFBP3, and GDF15 was significantly increased in epithelial cells in BALF from patients with severe COVID-19, suggesting that lung-cell senescence induction was contemporary of viral detection. Next, we investigated macaques at 4 and 30 dpi, corresponding respectively to the viral load peak and to the absence of detectable viral RNA in BALF (1). Immunohistochemical analysis revealed numerous SARS-CoV-2 antigen-stained cells, also co-stained for senescence markers p16- and p21. The lungs at 30 dpi no longer contained the consolidated parenchymal areas seen at 4 dpi but showed extensive lung parenchyma remodelling, with thickening of the alveoli and pulmonary vessel walls and abundant extracellular matrix deposits as assessed by collagen staining. These lesions were accompanied with massive accumulation of p16- and p21-positive cells, mostly pneumocytes II and ECs. Of note, p16 staining of most ECs was seen in pulmonary vessels, notably those occluded by thrombosis and showing intraluminal vWF staining. Cells stained for p16 were also stained for the DNA damage markers γ-H2AX protein and p53-binding protein 1. Conclusions: Our data constitute the first evidence of temporal and topographic relations between senescent-cell accumulation and pulmonary lesions induced by SARS-CoV-2 infection.

GDF-15 AS A PREDICTOR of MORTALITY in COVID-19: IMPLICATIONS for TREATMENT

Background: A cytokine storm drives the pathogenesis of severe COVID-19 and has therefore prompted the use of cytokine/transduction pathway inhibitors in the treatment of disease. However, numerous markers with different mechanisms of action have been linked to mortality, complicating the understanding of disease pathogenesis and the elaboration of therapeutic strategies. Methods: Retrospective study on COVID-19 hospitalized subjects in the acute phase of disease. A broad range of cytokines (CD25, IL-18, TNF-α, TNF RI, TNF RII, GDF-15, IL-7, LIF, IL-6, CHITINASE3-LIKE1, RAGE and Pentraxin-3) was assessed on plasma samples (Luminex, ELISA) collected upon hospitalization. Subjects were divided into two groups according to their clinical in-hospital death (Survivors: S;Non-Survivors: NS). Comparisons between groups were performed by Fisher's exact test or Mann-Whitney U test as appropriate. The association between each variable and mortality was analysed through univariate and multiple logistic regression models. Subsequently, survival analysis was conducted with Cox proportional hazard models. Results: 77 hospitalised Covid-19 patients were enrolled: 42 S and 35 NS (Figure 1A). As expected, in the NS group we found a higher proportion of subjects with fever and dyspnoea upon admission, development of ARDS and need of PEEP respiratory support (Figure 1A). NS also displayed significantly higher blood neutrophils/lymphocytes, C-reactive protein, LDH and procalcitonin as well as lower PaO2/FiO2 and peripheral O2 saturation values at admission (Figure 1A). In keeping with these findings, CD25, IL-18, IL-6, TNF-α, TNFRI, TNFRII, GDF-15, IL-7, LIF and Chitinase3-Like1, Pentraxin-3 and RAGE were significantly higher in NS than S (Figure 1B) and were associated to mortality in univariate regression models. In the multivariate regression model GDF-15 and fever were the two more relevant features associated with mortality (Figure 1C). In the survival analysis GDF-15 was the strongest predictor of mortality (HR 2,26, 1,55-3,31;p<0,01 reference group bottom quartile Figure 1D, E). Conclusion: Our in-depth characterization of the cytokine storm demonstrates that GDF-15 is an independent predictor of Covid-19 mortality. Given the reported increase of this cytokine with age and its possible mechanistic role in various pathological conditions, our findings suggest that GDF-15 signalling pathway inhibitors may be included as possible therapeutic candidates for Covid-19.

Growth Differentiation Factor 15 Provides Prognostic Information Superior to Established Cardiovascular and Inflammatory Biomarkers in Unselected Patients Hospitalized With COVID-19.

BACKGROUND: Growth differentiation factor 15 (GDF-15) is a strong prognostic marker in sepsis and cardiovascular disease (CVD). The prognostic value of GDF-15 in coronavirus disease 2019 (COVID-19) is unknown. METHODS: Consecutive, hospitalized patients with laboratory-confirmed infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and symptoms of COVID-19 were enrolled in the prospective, observational COVID Mechanisms Study. Biobank samples were collected at baseline, day 3 and day 9. The primary end point was admission to the intensive care unit or death during hospitalization, and the prognostic performance of baseline and serial GDF-15 concentrations were compared with that of established infectious disease and cardiovascular biomarkers. RESULTS: Of the 123 patients enrolled, 35 (28%) reached the primary end point; these patients were older, more often had diabetes, and had lower oxygen saturations and higher National Early Warning Scores on baseline. Baseline GDF-15 concentrations were elevated (>95th percentile in age-stratified healthy individuals) in 97 (79%), and higher concentrations were associated with detectable SARS-CoV-2 viremia and hypoxemia (both P<0.001). Patients reaching the primary end point had higher concentrations of GDF-15 (median, 4225 [IQR, 3197-5972] pg/mL versus median, 2187 [IQR, 1344-3620] pg/mL, P<0.001). The area under the receiver operating curve was 0.78 (95% CI, 0.70-0.86). The association between GDF-15 and the primary end point persisted after adjusting for age, sex, race, body mass index, estimated glomerular filtration rate, previous myocardial infarction, heart failure, and atrial fibrillation (P<0.001) and was superior and incremental to interleukin-6, C-reactive protein, procalcitonin, ferritin, D-dimer, cardiac troponin T, and N-terminal pro-B-type natriuretic peptide. Increase in GDF-15 from baseline to day 3 was also greater in patients reaching the primary end point (median, 1208 [IQR, 0-4305] pg/mL versus median, -86 [IQR, -322 to 491] pg/mL, P<0.001). CONCLUSIONS: GDF-15 is elevated in the majority of patients hospitalized with COVID-19, and higher concentrations are associated with SARS-CoV-2 viremia, hypoxemia, and worse outcome. The prognostic value of GDF-15 was additional and superior to established cardiovascular and inflammatory biomarkers. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04314232.

Pro- and Anti-Inflammatory Responses in Severe COVID-19-Induced Acute Respiratory Distress Syndrome-An Observational Pilot Study.

Objectives: The severity of Coronavirus Disease 2019 (COVID-19) is largely determined by the immune response. First studies indicate altered lymphocyte counts and function. However, interactions of pro- and anti-inflammatory mechanisms remain elusive. In the current study we characterized the immune responses in patients suffering from severe COVID-19-induced acute respiratory distress syndrome (ARDS). Methods: This was a single-center retrospective study in patients admitted to the intensive care unit (ICU) with confirmed COVID-19 between March 14th and May 28th 2020 (n = 39). Longitudinal data were collected within routine clinical care, including flow-cytometry of lymphocyte subsets, cytokine analysis and growth differentiation factor 15 (GDF-15). Antibody responses against the receptor binding domain (RBD) of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Spike protein were analyzed. Results: All patients suffered from severe ARDS, 30.8% died. Interleukin (IL)-6 was massively elevated at every time-point. The anti-inflammatory cytokine IL-10 was concomitantly upregulated with IL-6. The cellular response was characterized by lymphocytopenia with low counts of CD8+ T cells, natural killer (NK) and naïve T helper cells. CD8+ T and NK cells recovered after 8 to 14 days. The B cell system was largely unimpeded. This coincided with a slight increase in anti-SARS-CoV-2-Spike-RBD immunoglobulin (Ig) G and a decrease in anti-SARS-CoV-2-Spike-RBD IgM. GDF-15 levels were elevated throughout ICU treatment. Conclusions: Massively elevated levels of IL-6 and a delayed cytotoxic immune defense characterized severe COVID-19-induced ARDS. The B cell response and antibody production were largely unimpeded. No obvious imbalance of pro- and anti-inflammatory mechanisms was observed, with elevated GDF-15 levels suggesting increased tissue resilience.