Integrated analyses of growth differentiation factor-15 concentration and cardiometabolic diseases in humans

Revisiting the role of GDF15 in atherosclerosis in mouse and human

Growth differentiation factor 15 (GDF15) is a key regulator of food intake and energy metabolism. GDF15 mimetic drugs for the treatment of metabolic syndrome and obesity are under clinical development. While GDF15 presents a promising target for weight management, its potential cardiovascular actions remain elusive. In this study we investigated the role of GDF15 in macrophage function and atherosclerosis pathogenesis and whether GDF15 acts both as a biomarker and mediator of atherosclerosis severity. ApoE-/- mice were fed a high-cholesterol diet (HCD, 1.25% cholesterol) for 6, 12 or 18 weeks to establish atherosclerotic models. We showed that serum levels of GDF15 were elevated in ApoE-/- mice with atheroprogression; increased serum levels of GDF15 were also observed in patients with coronary artery disease. Enlightened by this finding, we established atherosclerotic model in Gdf15-/- mice by injecting with AAV8-PCSK9D377Y virus and feeding HCD for 12 or 16 weeks. We showed that global Gdf15 knockout, whether in male or female mice, did not alter plaque size in en face aorta, lesion in aortic sinus, size of necrotic core or plaque composition. In macrophage-derived foam cells isolated from atherosclerotic mice, neither Gdf15 deletion nor the treatment with recombinant GDF15 protein (1, 10, 100 ng/mL) affected lipid deposition or macrophage polarization. To translate this finding into a clinically relevant scenario, we performed Mendelian randomization (MR) analysis, and found no significant causal association between circulating GDF15 levels and the incidence of cardiovascular diseases. Furthermore, MR studies suggest that genetic associations between GDF15 and factors such as BMI, ApoB, LDL and HDL were not significant in plasma data from the UK Biobank and the deCODE cohort. In summary, this study demonstrates that global Gdf15 deficiency does not affect the development of atherosclerosis in male or female mice despite the positive association between circulating GDF15 levels and disease progression in mice and human. Thus, GDF15 in circulation is a potential biomarker, but not a causal mediator, of atherosclerosis. Long-term cardiovascular safety of GDF15-targeted therapies warrants further investigation.

GDF15 attenuates Parkinson's disease progression via suppressing the activation of cGAS-STING pathway

Growth differentiation Factor 15 (GDF15) plays an important role in the innate immune response. However, whether GDF15 could regulate Parkinson's disease (PD) remains unknown. In this study, we explored the function and underlying molecular mechanisms of GDF15 in PD. The protein and mRNA expressions were examined applying immunofluorescence staining, Western blot and qRT-PCR. Ferrous iron content was also assessed using an iron assay kit. The effect of GDF15 knockdown on mitochondrial membrane potential, ROS level, intracellular Fe2+ level and mitochondrial permeability transition pore opening in PD cell model was evaluated utilizing JC-1 staining, DCFH-DA fluorescent probe, ferro orange staining and calcein AM + Co2+ quencher staining. GDF15 was upregulated in the substantia nigra and striatum of PD mice and MPP+-caused SH-SY5Y cells. GDF15 knockdown aggravated parkinsonian symptoms in PD mice. Moreover, GDF15 knockdown aggravated dopamine neuronal damage, and promoted ferroptosis and inflammation in PD in vivo and in vitro. Besides, GDF15 knockdown could activate cGAS-STING pathway in vivo and in vitro PD model. We also found that the treatment of RU.521 could reverse the effect of GDF15 knockdown on dopamine neuronal damage, inflammation and ferroptosis in MPP+-induced SH-SY5Y cells. Similarly, the treatment of SR-717 could reverse the effect of GDF15 overexpression on dopamine neuronal damage, inflammation and ferroptosis in MPP+-induced SH-SY5Y cells. The results of this study demonstrated that GDF15 could attenuate dopamine neuronal damage, and inhibit ferroptosis and inflammation in PD via suppressing cGAS-STING pathway activation.

Cross-Ancestry Comparison of Aptamer and Antibody Proteomics Measures

Measures from affinity-proteomics platforms often correlate poorly, challenging interpretation of protein associations with genetic variants (pQTL) and phenotypes. Here, we examined 2,157 proteins measured on both SomaScan 7k and Olink Explore 3072 across 1,930 participants with genetic similarity to European, African, East Asian, and Admixed American ancestry references. Inter-platform correlation coefficients for these 2,157 proteins followed a bimodal distribution (median r=0.30). Protein measures from each platform were associated with genetic variants (pQTLs), and one-third of the pQTL signals were driven by protein-altering variants (PAVs). We highlight 80 proteins that correlate differently across ancestry groups likely due to differing PAV frequencies by ancestry. Furthermore, adjustment for PAVs with opposite directions of effect by platform improved inter-platform protein measure correlation and resulted in more concordant genetic and phenotypic associations. Hence, PAVs need to be accounted for across ancestries to facilitate platform-concordant and accurate protein measurement.

Risk prediction of ischemic heart disease using plasma proteomics, conventional risk factors and polygenic scores in Chinese and European adults

Plasma proteomics could enhance risk prediction for multiple diseases beyond conventional risk factors or polygenic scores (PS). To assess utility of proteomics for risk prediction of ischemic heart disease (IHD) compared with conventional risk factors and PS in Chinese and European populations. A nested case-cohort study measured plasma levels of 2923 proteins using Olink Explore panel in ~ 4000 Chinese adults (1976 incident IHD cases and 2001 sub-cohort controls). We used conventional and machine learning (Boruta) methods to develop proteomics-based prediction models of IHD, with discrimination assessed using area under the curve (AUC), C-statistics and net reclassification index (NRI). These were compared with conventional risk factors and PS in Chinese and in 37,187 Europeans. Overall, 446 proteins were associated with IHD (false discovery rate < 0.05) in Chinese after adjustment for conventional cardiovascular disease risk factors. Proteomic risk models alone yielded higher C-statistics for IHD than conventional risk factors or PS (0.855 [95%CI 0.841-0.868] vs. 0.845 [0.829-0.860] vs 0.553 [0.528-0.578], respectively). Addition of 446 proteins to PS improved C-statistics to 0.857 (0.843-0.871) and NRI by 109.1%; and addition to conventional risk factors improved C-statistics to 0.868 (0.854-0.882) and NRI by 86.9%. Boruta analysis identified 30 proteins accounting for ~ 90% of improvement in NRI for IHD conferred by all 2923 proteins. Similar proteomic panels yielded comparable improvements in risk prediction of IHD in Europeans. Plasma proteomics improved risk prediction of IHD beyond conventional risk factors and PS and could enhance precision medicine approaches for primary prevention of IHD.

Common pitfalls in drug target Mendelian randomization and how to avoid them

BACKGROUND

Drug target Mendelian randomization describes the use of genetic variants as instrumental variables for studying the effects of pharmacological agents. The paradigm can be used to inform on all aspects of drug development and has become increasingly popular over the last decade, particularly given the time- and cost-efficiency with which it can be performed even before commencing clinical studies.

MAIN BODY

In this review, we describe the recent emergence of drug target Mendelian randomization, its common pitfalls, how best to address them, as well as potential future directions. Throughout, we offer advice based on our experiences on how to approach these types of studies, which we hope will be useful for both practitioners and those translating the findings from such work.

CONCLUSIONS

Drug target Mendelian randomization is nuanced and requires a combination of biological, statistical, genetic, epidemiological, clinical, and pharmaceutical expertise to be utilized to its full potential. Unfortunately, these skillsets are relatively infrequently combined in any given study.

Growth Differentiation Factor 15 and Matrix Metalloproteinase 3 in Plasma as Biomarkers for Neuropathy and Nephropathy in Type 1 Diabetes

Diabetic neuropathy and nephropathy are common complications of type 1 diabetes (T1D). The symptoms are often elusive in the early stages, and available diagnostic methods can be improved using biomarkers. Matrix metalloproteinase 3 (MMP-3) has been identified in the kidneys and is thought to be involved in diabetic nephropathy. Growth differentiation factor 15 (GDF-15) has been suggested to have positive effects in diabetes, but is otherwise associated with adverse effects such as cardiovascular risk, declined kidney function, and neurodegeneration. This study aims to investigate plasma MMP-3 and GDF-15 as systemic biomarkers for diabetic neuropathy and nephropathy in T1D. The study involves patients with childhood-onset T1D (n = 48, age 38 ± 4 years) and a healthy control group (n = 30, age 38 ± 5 years). Neurophysiology tests, evaluations of albuminuria, and measurements of routine biochemical markers were conducted. The neuropathy impairment assessment (NIA) scoring system, where factors such as loss of sensation and weakened reflexes are evaluated, was used to screen for symptoms of neuropathy. MMP-3 and GDF-15 concentrations were determined in heparinized plasma using ELISA kits. In total, 9 patients (19%) had albuminuria, and 25 (52%) had diabetic neuropathy. No significant differences were found in MMP-3 concentrations between the groups. GDF-15 levels were higher in T1D, with median and interquartile range (IQR) of 358 (242) pg/mL in T1D and 295 (59) in controls (p < 0.001). In the merged patient group, a positive correlation was found between MMP-3 and plasma creatinine, a negative correlation was found between MMP-3 and estimated glomerular filtration rate (eGFR; rho = -0.358, p = 0.012), and there was a positive correlation between GDF-15 and NIA (rho = 0.723, p < 0.001) and high-sensitive C-reactive protein (rho = 0.395, p = 0.005). MMP-3 was increased in macroalbuminuria and correlated positively with NIA only in the nine T1D patients with albuminuria (rho = 0.836, p = 0.005). The present study indicates that high MMP-3 is associated with low eGFR, high plasma creatinine, and macroalbuminuria, and that GDF-15 can be a biomarker for diabetic neuropathy in T1D. MMP-3 may be useful as biomarker for neuropathy in T1D with albuminuria.

Total and H-specific GDF-15 levels increase in caloric deprivation independently of leptin in humans

Mitochondrial-secreted growth differentiation factor-15 (GDF-15) promotes weight loss in animals. Its effects in humans remain unclear, due to limited research and potential measurement interference from the H202D-variant. Our post-hoc analysis investigates total (irrespective of genetic variants) and H-specific GDF-15 (detected only in H202D-variant absence) in humans under acute and chronic energy deprivation, examining GDF-15 interaction with leptin (energy homeostasis regulator) and GDF-15 biologic activity modulation by the H202D-variant. Total and H-specific GDF-15 increased with acute starvation, and total GDF-15 increased with chronic energy deprivation, compared with healthy subjects and regardless of leptin repletion. Baseline GDF-15 positively correlated with triglyceride-rich particles and lipoproteins. During acute metabolic stress, GDF-15 associations with metabolites/lipids appeared to differ in subjects with the H202D-variant. Our findings suggest GDF-15 increases with energy deprivation in humans, questioning its proposed weight loss and suggesting its function as a mitokine, reflecting or mediating metabolic stress response.

Genetic determinants of plasma protein levels in the Estonian population

The proteome holds great potential as an intermediate layer between the genome and phenome. Previous protein quantitative trait locus studies have focused mainly on describing the effects of common genetic variations on the proteome. Here, we assessed the impact of the common and rare genetic variations as well as the copy number variants (CNVs) on 326 plasma proteins measured in up to 500 individuals. We identified 184 cis and 94 trans signals for 157 protein traits, which were further fine-mapped to credible sets for 101 cis and 87 trans signals for 151 proteins. Rare genetic variation contributed to the levels of 7 proteins, with 5 cis and 14 trans associations. CNVs were associated with the levels of 11 proteins (7 cis and 5 trans), examples including a 3q12.1 deletion acting as a hub for multiple trans associations; and a CNV overlapping NAIP, a sensor component of the NAIP-NLRC4 inflammasome which is affecting pro-inflammatory cytokine interleukin 18 levels. In summary, this work presents a comprehensive resource of genetic variation affecting the plasma protein levels and provides the interpretation of identified effects.

HFpEF: New biomarkers and their diagnostic and prognostic value

Heart failure characterized by preserved ejection fraction (HFpEF) poses a substantial challenge to healthcare systems worldwide and the diagnostic algorithms used currently mirror those utilized for reduced Ejection Fraction (HFrEF). This literature review aims to explore the diagnostic and prognostic credibility of numerous emerging biomarkers associated with HFpEF. We conducted a thorough analysis of the available medical literature and selected the biomarkers which yielded the maximum amount of published information. After reviewing the current literature we conclude that there are no biomarkers at present which are superior to natriuretic peptides in terms of diagnosis and prognosis of HFpEF. However biomarkers like Suppression of tumorigenicity2, Galectin3 and microRNAs are promising and can be researched further for future use. Although newer individual biomarkers may not be useful in diagnosing and prognosis of HFpEF, we believe that a specific biomarker profile may be identified in each phenotype,which can be used in future.

Growth differentiation factor-15 and prediction of cancer-associated thrombosis and mortality: a prospective cohort study

BACKGROUND

Patients with cancer are at increased risk of venous thromboembolism (VTE) and arterial thromboembolic/thrombotic events (ATEs). Growth differentiation factor-15 (GDF-15) improves cardiovascular risk assessment, but its predictive utility in patients with cancer remains undefined.

OBJECTIVES

To investigate the association of GDF-15 with the risks of VTE, ATE, and mortality in patients with cancer and its predictive utility alongside established models.

METHODS

The Vienna Cancer and Thrombosis Study (CATS)-a prospective, observational cohort study of patients with newly diagnosed or recurrent cancer-which was followed for 2 years, served as the study framework. Serum GDF-15 levels at study inclusion were measured, and any association with VTE, ATE, and death was determined using competing risk (VTE/ATE) or Cox regression (death) modeling. The added value of GDF-15 to established VTE risk prediction models was assessed using the Khorana and Vienna CATScore.

RESULTS

Among 1531 included patients with cancer (median age, 62 years; 53% men), median GDF-15 levels were 1004 ng/L (IQR, 654-1750). Increasing levels of GDF-15 were associated with the increased risks of VTE, ATE, and all-cause death ([subdistribution] hazard ratio per doubling, 1.16 [95% CI, 1.03-1.32], 1.30 [95% CI, 1.11-1.53], and 1.57 [95% CI, 1.46-1.69], respectively). After adjustment for clinically relevant covariates, the association only prevailed for all-cause death (hazard ratio, 1.21; 95% CI, 1.10-1.33) and GDF-15 did not improve the performance of the Khorana or Vienna CATScore.

CONCLUSION

GDF-15 is strongly associated with survival in patients with cancer, independent of the established risk factors. While an association with ATE and VTE was identified in univariable analysis, GDF-15 was not independently associated with these outcomes and failed to improve established VTE prediction models.

GDF15 Ameliorates Liver Fibrosis by Metabolic Reprogramming of Macrophages to Acquire Anti-Inflammatory Properties

BACKGROUND & AIMS

Liver fibrosis/cirrhosis is significant health burden worldwide, resulting in liver failure or cancer and accounting for many deaths each year. The pathogenesis of liver fibrosis is very complex, which makes treatment challenging. Growth differentiation factor 15 (GDF15), a cysteine knot protein belonging to the transforming growth factor β (TGF-β) superfamily, has been shown to play a protective role after tissue injury and to promote a negative energy balance during obesity and diabetes. However, paucity of literature is available about GDF15 function in liver fibrosis. This study aimed to investigate the immunomodulatory role and therapeutic potential of GDF15 in progression of hepatic fibrosis.

METHODS

GDF15 expression was studied in patients with fibrosis/cirrhosis and in 2 murine models of liver fibrosis, including mice treated with CCl4 or DDC diet. GDF15 involvement in the pathogenesis of liver fibrosis was assessed in Gdf15 knockout mouse using both CCl4 and DDC diet experimental models. We used the CCl4 and/or DDC diet-induced liver fibrosis model to examine the antifibrotic and anti-inflammatory effects of AAV8-mediated GDF15 overexpression in hepatocytes or recombinant mouse GDF15.

RESULTS

GDF15 expression is decreased in the liver of animal models and patients with liver fibrosis/cirrhosis compared with those without liver disease. In vivo studies showed that GDF15 deficiency aggravated CCl4 and DDC diet-induced liver fibrosis, while GDF15 overexpression mediated by AAV8 or its recombinant protein alleviated CCl4 and/or DDC diet-induced liver fibrosis. In Gdf15 knockout mice, the intrahepatic microenvironment that developed during fibrosis showed relatively more inflammation, as demonstrated by enhanced infiltration of monocytes and neutrophils and increased expression of proinflammatory factors, which could be diminished by AAV8-mediated GDF15 overexpression in hepatocytes. Intriguingly, GDF15 exerts its effects by reprogramming the metabolic pathways of macrophages to acquire an oxidative phosphorylation-dependent anti-inflammatory functional fate. Furthermore, adoptive transfer of GDF15-preprogrammed macrophages to mouse models of liver fibrosis induced by CCl4 attenuated inflammation and alleviated the progression of liver fibrosis.

CONCLUSION

GDF15 ameliorates liver fibrosis via modulation of liver macrophages. Our data implicate the importance of the liver microenvironment in macrophage programming during liver fibrosis and suggest that GDF15 is a potentially attractive therapeutic target for the treatment of patients with liver fibrosis.

Role of the Stress- and Inflammation-Induced Cytokine GDF-15 in Cardiovascular Diseases: From Basic Research to Clinical Relevance

Stress- and inflammation-induced growth differentiation factor-15 (GDF-15) is proposed as a biomarker for mortality and disease progression in patients with atherosclerosis and/or cardiovascular disease (CVD). The development of atherosclerotic lesions depends, among other factors, on inflammatory processes, oxidative stress, and impaired lipid homeostasis. As a consequence, activation and dysfunction of endothelial cells, release of chemokines, growth factors and lipid mediators occur. GDF-15 is suggested as an acute-phase modifier of transforming growth factor (TGF)-ßRII-dependent pro-inflammatory responses leading to rupture of atherosclerotic plaques, although the exact biological function is poorly understood to date. GDF-15 is upregulated in many disease processes, and its effects may be highly context-dependent. To date, it is unclear whether the upregulation of GDF-15 leads to disease progression or provides protection against disease. Concerning CVD, cardiomyocytes are already known to produce and release GDF-15 in response to angiotensin II stimulation, ischemia, and mechanical stretch. Cardiomyocytes, macrophages, vascular smooth muscle cells, endothelial cells, and adipocytes also release GDF-15 in response to oxidative as well as metabolic stress or stimulation with pro-inflammatory cytokines. Given the critically discussed pathophysiological and cellular functions and the important clinical significance of GDF-15 as a biomarker in CVD, we have summarized here the basic research findings on different cell types. In the context of cellular stress and inflammation, we further elucidated the signaling pathway of GDF-15 in coronary artery disease (CAD), the most common CVD in developing and industrial nations.