Association of Growth Differentiation Factor 15 with Mortality in a Prospective Hemodialysis Cohort

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

BACKGROUND

Growth differentiation factor-15 (GDF15) is a member of the growth differentiation factor subfamily in the transforming growth factor beta superfamily. GDF15 has multiple functions and can regulate biological processes. High levels of GDF15 in the circulation can affect metabolic processes. Studies have shown that GDF15 is associated with changes in body weight.

SUMMARY

This review reviews the current knowledge on the relationship between GDF15 and body weight change, focusing on the role and mechanism of GDF15 in body weight regulation. GDF15 plays an important role in reducing food intake, improving insulin resistance, and breaking down fat, suggesting that GDF15 has an important regulatory effect on body weight. The mechanism by which GDF15 causes reduced food intake may be related to changes in food preference, delayed gastric emptying, and conditioned taste aversion. GDF15 can combat insulin resistance induced by inflammation or protect β cell from apoptosis. GDF15 probably promotes lipolysis through a brain-somatic tissue circuit. Several factors and related signaling pathways are also mentioned that can contribute to the effects of GDF15 on reducing weight.

KEY MESSAGE

GDF15 plays an important role in weight regulation and provides a new direction for the treatment of obesity. Its effects on resisting obesity are of great significance to inhibiting the progression of metabolic diseases. It is expected to become a new target for regulating body weight, improving obesity, and treating metabolic diseases such as diabetes.

Vascular endothelial growth factor-D plasma levels in fluid overload and cardiac function evaluation of elderly patients with cardiovascular disease

This study aimed to investigate the clinical significance of vascular endothelial growth factor (VEGF) subtypes and growth differentiation factor-15 (GDF-15) plasma levels in evaluating the fluid overload and cardiac function of elderly patients with cardiovascular disease. The plasma levels of VEGF-C, VEGF-D, and GDF-15 were measured using ELISA. Their correlations with N-terminal pro B-type natriuretic peptide (NT-Pro BNP) and echocardiography data were analyzed. 1. Higher plasma levels of VEGF-D and GDF-15 were observed in elderly patients with cardiovascular disease and heart failure(P < .01). VEGF-D plasma levels were higher in patients with chronic heart failure than those with acute myocardial infarction (P < .01). VEGF-D plasma levels were positively correlated with amino-terminal pro-B type natriuretic peptide (NT-pro BNP) (P < .001). VEGF-D plasma levels were positively correlated with echocardiographic parameters, including left atrial diameter, left ventricular end-diastolic diameter and left ventricular ejection fraction, in patients with cardiovascular disease (P < .01). 2. VEGF-C plasma levels were higher in acute myocardial infarction group (P < .05). The plasma levels of VEGF-C were not correlated with either VEGF-D or NT-pro BNP plasma levels. VEGF-C plasma levels had no correlation with echocardiographic parameters. 3. GDF-15 plasma levels were positively correlated with sera biomarkers of cardiac injury (creatine kinase isoenzyme MB and cardiac troponin I). GDF-15 plasma levels were positively correlated with urinary biomarkers of tubular injury (N-acetyl-β-galactosidase and α1-microglobulin). Both GDF-15 and NT-pro BNP plasma levels were correlated with age, estimated glomerular filtration rate (eGFR), and nutritional biomarkers (albumin and hemoglobin plasma levels). VEGF-D plasma levels is a potential biomarker of fluid overload and cardiac function in elderly patients with cardiovascular disease. Age, nutrition, and kidney injury are factors influencing both GDF-15 and NT-pro BNP plasma levels in estimating cardiac function and fluid overload.

Development and Validation of a Prediction Model for Incident Hypothyroidism in a National Chronic Kidney Disease Cohort

CONTEXT

Hypothyroidism is a common yet under-recognized condition in patients with chronic kidney disease (CKD), which may lead to end-organ complications if left untreated.

OBJECTIVE

We developed a prediction tool to identify CKD patients at risk for incident hypothyroidism.

METHODS

Among 15 642 patients with stages 4 to 5 CKD without evidence of pre-existing thyroid disease, we developed and validated a risk prediction tool for the development of incident hypothyroidism (defined as thyrotropin [TSH] > 5.0 mIU/L) using the Optum Labs Data Warehouse, which contains de-identified administrative claims, including medical and pharmacy claims and enrollment records for commercial and Medicare Advantage enrollees as well as electronic health record data. Patients were divided into a two-thirds development set and a one-third validation set. Prediction models were developed using Cox models to estimate probability of incident hypothyroidism.

RESULTS

There were 1650 (11%) cases of incident hypothyroidism during a median follow-up of 3.4 years. Characteristics associated with hypothyroidism included older age, White race, higher body mass index, low serum albumin, higher baseline TSH, hypertension, congestive heart failure, exposure to iodinated contrast via angiogram or computed tomography scan, and amiodarone use. Model discrimination was good with similar C-statistics in the development and validation datasets: 0.77 (95% CI 0.75-0.78) and 0.76 (95% CI 0.74-0.78), respectively. Model goodness-of-fit tests showed adequate fit in the overall cohort (P = .47) as well as in a subcohort of patients with stage 5 CKD (P = .33).

CONCLUSION

In a national cohort of CKD patients, we developed a clinical prediction tool identifying those at risk for incident hypothyroidism to inform prioritized screening, monitoring, and treatment in this population.

Growth Differentiation Factor-15 and Clinical Outcomes in Japanese Patients With Ischemic Heart Disease

Background

Despite a reduction in the rate of thrombotic events, ischemic heart disease (IHD) remains a key medical problem associated with high major bleeding and mortality in Asian patients with IHD. Growth differentiation factor (GDF)-15, a stress-response cytokine belonging to the transforming growth factor beta superfamily, is reportedly associated with poor clinical outcomes in Western patients with IHD. However, the clinical significance of GDF-15 in Asian patients with IHD has not yet been fully elucidated.

Objectives

The aim of the present study was to examine the impact of serum GDF-15 on clinical outcomes in Japanese patients with IHD.

Methods

Serum GDF-15 levels were evaluated in 632 consecutive patients with IHD. All patients were followed up for a median period of 2.8 years. The primary endpoint was the all-cause mortality rate. Secondary endpoints were major adverse cardiovascular events (MACE), heart failure (HF)-related rehospitalization, bleeding, and thrombotic events.

Results

Serum GDF-15 levels were elevated in acute coronary syndrome, severe coronary artery disease, and the major Japanese version of the high bleeding risk criteria. Multivariate Cox proportional hazards regression analysis demonstrated that GDF-15 was an independent predictor of all-cause mortality, MACE, HF-related rehospitalizations, and bleeding events after adjusting for confounding risk factors but not for thrombotic events. Adding GDF-15 to risk factors significantly improved the net reclassification index and integrated discrimination improvement for all-cause deaths, MACE, HF-related rehospitalization, and bleeding events.

Conclusions

Serum GDF-15 could be a feasible marker for major bleeding and adverse clinical outcomes in Japanese patients with IHD.

Cardiac markers and cardiovascular disease in chronic kidney disease

Cardiovascular disease (CVD) is prevalent in patients with chronic kidney disease (CKD) and it is responsible for approximately half of all CKD-related deaths. CVDs are the primary cause of death in hemodialysis patients due to major adverse cardiovascular events. Therefore, better approaches for differentiating chronic hemodialysis patients at higher cardiovascular risk will help physicians improve clinical outcomes. Hence, there is an urgent need to discover feasible and reliable cardiac biomarkers to improve diagnostic accuracy, reflect myocardial injury, and identify high-risk patients. Numerous biomarkers that have significant prognostic value with respect to adverse CVD outcomes in the setting of mild to severe CKD have been identified. Therefore, a better understanding of the positive clinical impact of cardiac biomarkers on CVD patient outcomes is an important step toward prevention and improving treatment in the future. In this review, we address the relationship between cardiovascular biomarkers and CKD treatment strategies to elucidate the underlying importance of these biomarkers to patient outcomes.

Circulating GDF-15 in relation to the progression and prognosis of chronic kidney disease: A systematic review and dose-response meta-analysis

BACKGROUND

Patients with chronic kidney disease (CKD) typically exhibit circulating growth differentiation factor-15 (GDF-15) at high levels. This meta-analysis aimed to evaluate the potential value of GDF-15 in predicting CKD progression and prognosis. Furthermore, when sufficient information was provided, the dose-response correlation was studied.

METHODS

Studies were searched in Web of Science, Embase, and PubMed from inception until November 2022. By using random- or fixed-effects models, the pooled effect size was estimated in accordance with heterogeneity in existing research.

RESULTS

This study covered 14 studies from 12 articles with 7813 subjects participating in the research. CKD patients in the top GDF-15 tertile had notably higher risks of CKD progression (HR 2.60, 95% CI 2.06-3.27), all-cause mortality (HR 2.05, 95% CI 1.44-2.92), cardiovascular mortality (HR 2.82, 95% CI 1.85-4.30), and cardiovascular events (HR 2.74, 95% CI 2.21-3.40), as compared to CKD patients in the bottom tertile. In the dose-response study, the risks for CKD progression, all-cause death, cardiovascular death, and cardiovascular events were increased by 31% (HR 1.31, 95% CI 1.06-1.61), 44% (HR 1.44, 95% CI 1.08-1.92), 67% (HR 1.67, 95% CI 1.37-2.03), and 55% (HR 1.55, 95% CI 1.31-1.83), respectively, with per 1 ng/mL increase in GDF-15. The positive linear correlations between GDF-15 and CKD progression and prognosis in a certain GDF-15 concentration range of approximately 0-3 ng/mL were indicated by the dose-response curve.

CONCLUSIONS

Circulating GDF-15 independently predicted CKD progression and worse prognosis; however, the predicted correlations may fall into a specific range of GDF-15 concentrations.

Growth differentiation factor-15 preserves Klotho expression in acute kidney injury and kidney fibrosis

Growth differentiation factor-15 (GDF15) is a member of the GDF subfamily with potential kidney protective functions. Here, we explored the impact of GDF15 on the expression of the kidney protective factor Klotho in models of acute kidney injury and kidney fibrosis in mice. GDF15 was the most upregulated GDF family gene in experimental toxic acute kidney injury and in kidney fibrosis transcriptomics. GDF15 function was explored in toxic acute kidney injury in genetically modified mice and following treatment with GDF15. Gdf15-deficient mice developed more severe toxic acute kidney injury (folic acid or cisplatin) while GDF15 overexpression or GDF15 administration were protective. Kidney expression of Klotho was more severely depressed in Gdf15-deficient mice and was preserved by GDF15 overexpression or GDF15 treatment. Moreover, increased plasma calcitriol levels inversely correlated with kidney Klotho across models with diverse levels of GDF15 availability. Kidney fibrosis induced by unilateral ureteral obstruction was more severe in Gdf15-deficient mice while GDF15 overexpression decreased kidney injury and preserved Klotho expression. GDF15 increased Klotho expression in vivo in healthy mice, in cultured tubular cells, and prevented Klotho downregulation by inflammatory factors in tubular cells by preventing transcription factor NF-ĸB activation. Thus, spontaneous increased kidney expression of endogenous GDF15 is not enough to prevent kidney injury, but further increments in GDF15 are kidney protecting and preserve expression of the kidney protective factor Klotho within the kidney in acute and chronic settings.

Serum Growth Differentiation Factor-15/Albumin Ratio as a 2-Year Survival Marker of End-Stage Renal Disease Patients Initiating Maintenance Hemodialysis

It is important to identify risk factors related to mortality in end-stage renal disease (ESRD) patients starting renal replacement therapy. Recently, several studies proposed that growth-differentiation factor-15 (GDF-15) is a possible biomarker for the prognosis of patients on maintenance hemodialysis. Here, we investigated the predictive value of serum GDF-15/Albumin ratio on two-year mortality in ESRD patients initiating maintenance hemodialysis. The study was a single center, retrospective study on ESRD patients starting maintenance hemodialysis with a follow-up of two years. All patients completed laboratory test and bioimpedance spectroscopy prior to the initiation of the first dialysis. The patients were stratified into quartiles according to the quartiles of serum GDF-15/Albumin ratio. Among the 159 patients, the mean age was 61.78 ± 12.52 years and median survival was 20.03 ± 7.73 months. The highest GDF-15/Albumin quartile was significantly more associated with the increased risk of all-cause mortality than other quartiles (unadjusted hazard ratio (HR): 8.468, 95% CI 2.981–24.054, p < 0.001). Older age and a higher overhydration state were associated with GDF-15/Albumin ratio. The ROC analysis confirmed that the ability of the GDF-15/Albumin ratio to predict mortality was superior to GDF-15 or albumin alone. In conclusion, the GDF-15/Albumin ratio measured at the initial maintenance hemodialysis is an independent prognostic marker of two-year mortality in ESRD patients.

Dietary Potassium Intake and Mortality in a Prospective Hemodialysis Cohort

OBJECTIVES

Among hemodialysis patients, clinical practice guidelines recommend dietary potassium restriction given concerns about potential hyperkalemia leading to malignant arrhythmias and mortality. However, there are sparse data informing recommendations for dietary potassium intake in this population. We thus sought to examine the relationship between dietary potassium intake and death risk in a prospective cohort of hemodialysis patients.

DESIGN AND METHODS

Among 415 hemodialysis patients from the prospective "Malnutrition, Diet, and Racial Disparities in Chronic Kidney Disease" cohort recruited across 16 outpatient dialysis clinics, information regarding dietary potassium intake was obtained using Food Frequency Questionnaires administered over October 2011 to March 2015. We first examined associations of baseline dietary potassium intake categorized as tertiles with mortality risk using Cox regression. We then examined clinical characteristics associated with low dietary potassium intake (defined as the lowest tertile) using logistic regression.

RESULTS

In expanded case-mix Cox analyses, patients whose dietary potassium intake was in the lowest tertile had higher mortality (ref: highest tertile) (adjusted hazard ratio 1.74, 95% confidence interval 1.14-2.66). These associations had even greater magnitude of risk following adjustment for laboratory and nutritional covariates (adjusted hazard ratio 2.65, 95% confidence interval 1.40-5.04). In expanded case-mix restricted cubic spline analyses, there was a monotonic increase in mortality risk with incrementally lower dietary potassium intake. In expanded case-mix logistic regression models, female sex; higher serum bicarbonate; and lower dietary energy, protein, and fiber intake were associated with low dietary potassium intake.

CONCLUSIONS

In a prospective cohort of hemodialysis patients, lower dietary potassium intake was associated with higher mortality risk. These findings suggest that excessive dietary potassium restriction may be deleterious in hemodialysis patients, and further studies are needed to determine the optimal dietary potassium intake in this population.

Urinary Growth Differentiation Factor-15 (GDF15) levels as a biomarker of adverse outcomes and biopsy findings in chronic kidney disease

BACKGROUND

Growth Differentiation Factor-15 (GDF15) is a member of the TGF-β superfamily. Increased serum GDF15 has been associated with increased risk of chronic kidney disease (CKD) progression. However, no prior studies have addressed the significance of urinary GDF15 in adult CKD.

METHODS

We measured serum and urinary GDF15 in a prospective cohort of 84 patients who underwent kidney biopsy and assessed their association with outcomes (survival, kidney replacement therapy) during a follow-up of 29 ± 17 months.

RESULTS

There was a statistically significant correlation between serum and urine GDF15 values. However, while serum GDF15 values increased with decreasing glomerular filtration rate, urinary GDF15 did not. Immunohistochemistry located kidney GDF15 expression mainly in tubular cells, and kidney GDF15 staining correlated with urinary GDF15 values. Urine GDF15 was significantly higher in patients with a histologic diagnosis of diabetic nephropathy than in diabetic patients without diabetic nephropathy. This was not the case for serum GDF15. Both serum and urine GDF15 were negatively associated with patient survival in multivariate models. However, when both urine and serum GDF15 were present in the model, lower urine GDF15 predicted patient survival [B coefficient (SEM) - 0.395 (0.182) p 0.03], and higher urine GDF15 predicted a composite of mortality or kidney replacement therapy [0.191 (0.06) p 0.002], while serum GDF15 was not predictive. Decision tree analysis yielded similar results. The area under the curve (AUC) of the receiver operating curve (ROC) for urine GDF15 as a predictor of mortality was 0.95 (95% CI 0.89-1.00, p < 0.001).

CONCLUSIONS

In conclusion, urinary GDF15 is associated with kidney histology patterns, mortality and the need for renal replacement therapy (RRT) in CKD patients who underwent a kidney biopsy.

A Growth Differentiation Factor 15-Based Risk Score Model to Predict Mortality in Hemodialysis Patients

BACKGROUND

The risk of cardiovascular (CV) and fatal events remains extremely high in patients with maintenance hemodialysis (MHD), and the growth differentiation factor 15 (GDF15) has emerged as a valid risk stratification biomarker. We aimed to develop a GDF15-based risk score as a death prediction model for MHD patients.

METHODS

Age, biomarker levels, and clinical parameters were evaluated at study entry. One hundred and seventy patients with complete information were finally included for data analysis. We performed the Cox regression analysis of various prognostic factors for mortality. Then, age, GDF15, and robust clinical predictors were included as a risk score model to assess the predictive accuracy for all-cause and CV death in the receiver operating characteristic (ROC) curve analysis.

RESULTS

Age, GDF15, and albumin were significantly associated with higher all-cause and CV mortality risk that were combined as a risk score model. The highest tertile of GDF-15 (>1707.1 pg/mL) was associated with all-cause mortality (adjusted hazard ratios (aHRs): 3.06 (95% confidence interval (CI): 1.20-7.82), p < 0.05) and CV mortality (aHRs: 3.11 (95% CI: 1.02-9.50), p < 0.05). The ROC analysis of GDF-15 tertiles for all-cause and CV mortality showed 0.68 (95% CI = 0.59 to 0.77) and 0.68 (95% CI = 0.58 to 0.79), respectively. By contrast, the GDF15-based prediction model for all-cause and CV mortality showed 0.75 (95% CI: 0.67-0.82) and 0.72 (95% CI: 0.63-0.81), respectively.

CONCLUSION

Age, GDF15, and hypoalbuminemia predict all-cause and CV death in MHD patients, yet a combination scoring system provides more robust predictive powers. An elevated GDF15-based risk score warns clinicians to determine an appropriate intervention in advance. In light of this, the GDF15-based death prediction model could be developed in the artificial intelligence-based precision medicine.

Growth Differentiation Factor 15: A Biomarker with High Clinical Potential in the Evaluation of Kidney Transplant Candidates

Kidney transplantation implies a significant improvement in patient survival. Nevertheless, early mortality after transplant remains high. Growth differentiation factor 15 (GDF-15) is a novel biomarker under study as a mortality predictor in multiple scenarios. The aim of this study is to assess the utility of GDF-15 to predict survival in kidney transplant candidates. For this purpose, 395 kidney transplant recipients with pretransplant stored serum samples were included. The median GDF-15 was 5331.3 (50.49-16242.3) pg/mL. After a mean of 90.6 ± 41.5 months of follow-up, 82 (20.8%) patients died. Patients with higher GDF-15 levels (high risk tertile) had a doubled risk of mortality after adjustment by clinical characteristics (p = 0.009). After adjustment by EPTS (Estimated Post Transplant Survival score) the association remained significant for medium hazards ratios (HR) 3.24 95%CI (1.2-8.8), p = 0.021 and high risk tertiles HR 4.3 95%CI (1.65-11.54), p = 0.003. GDF-15 improved the prognostic accuracy of EPTS at 1-year (ΔAUC = 0.09, p = 0.039) and 3-year mortality (ΔAUC = 0.11, p = 0.036). Our study suggests an independent association between higher GDF-15 levels and mortality after kidney transplant, adding accuracy to the EPTS score, an established risk prediction model currently used in kidney transplant candidates.

The GDF15-GFRAL Pathway in Health and Metabolic Disease: Friend or Foe?

GDF15 is a cell activation and stress response cytokine of the glial cell line-derived neurotrophic factor family within the TGF-β superfamily. It acts through a recently identified orphan member of the GFRα family called GFRAL and signals through the Ret coreceptor. Cell stress and disease lead to elevated GDF15 serum levels, causing anorexia, weight loss, and alterations to metabolism, largely by actions on regions of the hindbrain. These changes restore homeostasis and, in the case of obesity, cause a reduction in adiposity. In some diseases, such as advanced cancer, serum GDF15 levels can rise by as much as 10-100-fold, leading to an anorexia-cachexia syndrome, which is often fatal. This review discusses how GDF15 regulates appetite and metabolism, the role it plays in resistance to obesity, and how this impacts diseases such as diabetes, nonalcoholic fatty liver disease, and anorexia-cachexia syndrome. It also discusses potential therapeutic applications of targeting the GDF15-GFRAL pathway and lastly suggests some potential unifying hypotheses for its biological role.

Cardiac biomarkers of heart failure in chronic kidney disease

Heart failure remains a continuing threat to patients with chronic kidney disease (CKD). Although various heart failure biomarkers have been applied for early detection, diagnosis and prognosis in CKD, these are easily affected by renal insufficiency thus limiting use in these patients. In this review, the major four groups of heart failure biomarkers are explored. These include those associated with: myocardial stretch, ie, brain natriuretic peptide (BNP), N-terminal pro-BNP (NT-proBNP) and mid-regional proatrial natriuretic peptide (MR-proANP); myocyte injury, ie, high-sensitivity troponin T (hsTnT), heart-type fatty acid-binding protein (H-FABP); fibrosis, matrix remodelling and inflammation, ie, soluble growth stimulating gene 2 (sST2), galectin-3 (Gal-3), growth differentiation factor-15 (GDF-15); and renal function, ie, neutrophil gelatinase-associated lipocalin (NGAL) kidney injury molecule-1 (KIM-1), cystatin C (CysC), urinary sodium and urinary albumin. This review highlights classic heart failure biomarkers with critical values adjusted to glomerular filtration rate, summarizes research progress of new heart failure biomarkers and future research directions. Because diagnostic and prognostic usefulness of a single time point biomarker is limited, biomarkers should be combined and monitored at multiple times for optimal clinical impact.

Residual Urine Output and Mortality in a Prospective Hemodialysis Cohort

Introduction

Although residual urine output (UOP) is associated with better survival and quality of life in dialysis patients, frequent measurement by 24-hour urine collection is burdensome. We thus sought to examine the association of patients’ self-reported residual UOP, as an alternative proxy of measured residual UOP, with mortality risk in a prospective hemodialysis cohort study.

Methods

Among 670 hemodialysis patients from the prospective multicenter Malnutrition, Diet, and Racial Disparities in Kidney Disease study, we examined associations of residual UOP, ascertained by patient self-report, with all-cause mortality. Patients underwent protocolized surveys assessing presence and frequency of UOP (absent, every 1–3 days, >1 time per day) every 6 months from 2011 to 2015. We examined associations of baseline and time-varying UOP with mortality using Cox regression.

Results

In analyses of baseline UOP, absence of UOP was associated with higher mortality in expanded case-mix adjusted Cox models (ref: presence of UOP): hazard ratio (HR), 1.78 (95% confidence interval [CI], 1.16–2.72). In analyses examining baseline frequency of UOP, point estimates suggested a graded association between lower frequency of UOP and higher mortality, although estimates for UOP every 1 to 3 days did not reach statistical significance (reference: UOP >1 time per day): HR, 1.29 (95% CI, 0.82–2.05) and HR, 1.97 (95% CI, 1.24–3.12) for UOP every 1 to 3 days and absence of UOP, respectively. Similar findings were observed in analyses of time-varying UOP.

Conclusion

In hemodialysis patients, there is a graded association between lower frequency of self-reported UOP and higher mortality. Further studies are needed to determine the clinical impact of more frequent assessment of residual UOP using self-reported methods.

Prognostic Value of Growth Differentiation Factor 15 in Kidney Donors and Recipients

Growth differentiation factor-15 (GDF15) is associated with inflammatory conditions, chronic kidney disease, cardiovascular disease and mortality. There is very limited data on GDF15 after kidney donation and transplantation. We analyzed serum samples of patients who donated a kidney (54 living donors) or who underwent kidney transplantation (104 recipients) at the University Hospital of Münster (Germany) between 2013 and 2015, for GDF15 levels immediately prior and one year after surgery. GDF15 levels were significantly elevated in end-stage renal disease patients compared to healthy individuals (2844 (IQR 2087, 3361) pg/ml vs. 384 (IQR 307, 487) pg/ml, p < 0.001). GDF15 was strongly associated with the dialysis vintage. While kidney transplantation led to a significant decrease of GDF15 (913 (IQR 674, 1453) pg/ml, p < 0.001), kidney donation caused a moderate increase of GDF15 (510 (IQR 420, 626), p < 0.001) one year after surgery. GDF15 levels remained significantly higher in recipients and kidney donors than in healthy controls (735 (IQR 536, 1202) pg/ml vs. 384 (IQR 307, 487) pg/ml, p < 0.001). GDF15 is increased in patients with kidney disease and is associated with dialysis vintage. Given its decrease after transplantation and its increase after uni-nephrectomy, GDF15 might be a marker of kidney function. However, since it correlates only to the eGFR in transplanted patients it may indicate chronic kidney disease.

GDF15 Is Elevated in Conditions of Glucocorticoid Deficiency and Is Modulated by Glucocorticoid Replacement

CONTEXT

GDF15 is a stress-induced hormone acting in the hindbrain that activates neural circuitry involved in establishing aversive responses and reducing food intake and body weight in animal models. Anorexia, weight loss, nausea and vomiting are common manifestations of glucocorticoid deficiency, and we hypothesized that glucocorticoid deficiency may be associated with elevated levels of GDF15.

OBJECTIVE

To determine the impact of primary adrenal insufficiency (PAI) and glucocorticoid replacement on circulating GDF15 levels.

METHODS AND RESULTS

We measured circulating concentrations of GDF15 in a cohort of healthy volunteers and Addison's disease patients following steroid withdrawal. Significantly higher GDF15 (mean ± standard deviation [SD]) was observed in the Addison's cohort, 739.1 ± 225.8 pg/mL compared to healthy controls, 497.9 ± 167.7 pg/mL (P = 0.01). The effect of hydrocortisone replacement on GDF15 was assessed in 3 independent PAI cohorts with classical congenital adrenal hyperplasia or Addison's disease; intravenous hydrocortisone replacement reduced GDF15 in all groups. We examined the response of GDF15 to increasing doses of glucocorticoid replacement in healthy volunteers with pharmacologically mediated cortisol deficiency. A dose-dependent difference in GDF15 (mean ± SD) was observed between the groups with values of 491.0 ± 157.7 pg/mL, 427.0 ± 152.1 pg/mL and 360 ± 143.1 pg/mL, in the low, medium and high glucocorticoid replacement groups, respectively, P < .0001.

CONCLUSIONS

GDF15 is increased in states of glucocorticoid deficiency and restored by glucocorticoid replacement. Given the site of action of GDF15 in the hindbrain and its effects on appetite, further study is required to determine the effect of GDF15 in mediating the anorexia and nausea that is a common feature of glucocorticoid deficiency.

GDF-15 as a Weight Watcher for Diabetic and Non-Diabetic People Treated With Metformin

Weight gain and obesity are global health concerns contributing to morbidity with increased risks of cardiovascular disease, diabetes, liver steatohepatitis and cancer. Pharmacological therapies or bariatric surgery are often required for those who fail to adhere to diet and lifestyle modifications. Metformin, a widely used antidiabetic agent, seems to have a health benefit beyond its anti-hyperglycemic properties, with few side effects. Emerging evidence shows weight loss to be associated with metformin in both diabetic and non-diabetic individuals. Recently, the growth differentiation factor 15 (GDF-15), a member of the transforming growth factor beta superfamily, has been identified as a key mediator of metformin-induced weight loss. Metformin increases the secretion of GDF-15, which binds exclusively to glial cell-derived neurotrophic factor family receptor alpha-like (GFRAL). This gut-brain cytokine works as a prominent player in reducing food intake and body weight in health and disease, like anorexia nervosa and cancer. Herein, we critically review advances in the understanding of the weight-reducing effects of metformin via the GDF-15 pathway.

The Impact of Race and Ethnicity Upon Health-Related Quality of Life and Mortality in Dialysis Patients

Rationale & Objective

Health-related quality of life (HRQoL) has been recognized as a strong predictor of mortality among hemodialysis patients. However, differences in the association of HRQoL with survival across diverse racial/ethnic groups have not been well studied in this population.

Study Design

Observational cohort study.

Setting & Participants

We examined the relationship between HRQoL and mortality in a prospective cohort of racially/ethnically diverse hemodialysis patients recruited from 18 outpatient dialysis units during 2011 to 2016.

Exposure

Using the 36-Item Short Form Health Survey (SF-36) administered every 6 months, HRQoL was ascertained by 36 questions summarized as 2 Physical and Mental Component and 8 subscale scores.

Outcome

All-cause mortality.

Analytical Approach

Associations of time-varying SF-36 scores with mortality were estimated using Cox models in the overall cohort and within racial/ethnic subgroups.

Results

Among 753 hemodialysis patients who met eligibility criteria, expanded case-mix analyses showed that the lowest quartiles of time-varying Physical and Mental Component scores were associated with higher mortality in the overall cohort (reference: highest quartile): adjusted HRs, 2.30 (95% CI, 1.53-3.47) and 1.54 (95% CI, 1.05-2.25), respectively. In analyses stratified by race/ethnicity, the lowest quartile of Physical Component scores was significantly associated with higher mortality across all groups: adjusted HRs, 2.64 (95% CI, 1.31-5.29), 1.84 (95% CI, 1.01-3.38), and 3.18 (95% CI, 1.13-8.91) for Hispanic, African American, and other race/ethnicity patients, respectively. The lowest quartile of time-varying physical functioning, role limitations due to physical health, role limitations due to emotional problems, social functioning, and pain subscale scores were associated with higher mortality in the overall cohort and particularly in Hispanics and blacks.

Limitations

Residual confounding cannot be excluded.

Conclusions

Lower SF-36 Physical Component and subscale scores were associated with higher mortality in hemodialysis patients, including those of minority background. Further studies are needed to determine whether interventions that augment physical health might improve the survival of these diverse populations.

Targeting the divergent TGFβ superfamily cytokine MIC-1/GDF15 for therapy of anorexia/cachexia syndromes

PURPOSE OF REVIEW

To review recent finding on MIC-1/GDF15 and re-evaluate it as a potential target for the therapy of anorexia/cachexia syndromes.

RECENT FINDINGS

MIC-1/GDF15 consistently induces anorexia/cachexia in animal models. Its actions on brainstem feeding centers leads to anorexia, inducing prolonged undernutrition and consequent loss of both lean and fat mass. Epidemiological studies by multiple groups have linked substantially elevated serum levels of this cytokine to anorexia/cachexia syndromes in diverse diseases such as cancer, chronic renal and cardiac failure, and chronic obstructive lung disease. These elevated serum levels are similar to those required to induce this syndrome in animals. Recent identifications of its previously elusive receptor as GFRAL, has enhanced understanding of its biology and suggests that modulating the MIC-1/GDF15-GFRAL pathway may be a therapeutic target for anorexia/cachexia syndrome.

SUMMARY

Inhibiting MIC-1/GDF15 or its receptor GFRAL are high-value potential targets for treatment of anorexia/cachexia syndrome in patients whose elevated serum levels may justify its use.

Growth differentiation factor 15 is decreased by kidney transplantation

BACKGROUND

Growth differentiation factor 15 (GDF15) is markedly increased in end-stage kidney disease and has been related to increased mortality in patients on dialysis. We hypothesized that kidney transplantation would decrease both GDF15 and N-terminal pro-B-type natriuretic peptide (NT-proBNP) and that GDF-15 decrease relates to post-kidney transplantation allograft function.

METHODS

End-stage kidney disease patients on dialysis awaiting a living donor kidney transplantation (n = 39), and those expected to be on the deceased donor waitlist for at least 12 months (n = 43) were enrolled at three transplant centers. Serum GDF15 and NT-proBNP were measured at 0, 3, and 12 months post-kidney transplantation or post-enrollment. Change in serum GDF15 and NT-proBNP concentrations, and their relation to estimated glomerular filtration rate (eGFR) were assessed by non-parametric tests and regression analyses.

RESULTS

Median baseline GDF15 was 4744 pg/ml and 5451 pg/ml for the kidney transplantation and dialysis groups, respectively (p = 0.09). Kidney transplantation resulted in a significant decrease in GDF15 (month 12 median 1631 pg/ml, p < 0.0001 vs. baseline), whereas there was no change for the dialysis group (month 12 median 5658 pg/ml, p = 0.31). Post-kidney transplantation NT-proBNP highly correlated with GDF15 (ρ = 0.64, p < 0.0001). GDF15 inversely correlated with post-transplant eGFR for the kidney transplantation group (ρ = -0.42, p = 0.0081). Month 12 NT-proBNP explained 15.8% and 40.1% of the variance in month 12 GDF15 in the dialysis and kidney transplantation groups, respectively. The relationship of GDF15 with eGFR was no longer significant when NT-proBNP was included in the models.

CONCLUSIONS

Kidney transplantation significantly decreases serum GDF15 concentrations. The post-kidney transplantation association of GDF15 with NT-proBNP is consistent with a gradient of post- kidney transplantation cardiovascular risk.

Towards frailty biomarkers: Candidates from genes and pathways regulated in aging and age-related diseases

OBJECTIVE

Use of the frailty index to measure an accumulation of deficits has been proven a valuable method for identifying elderly people at risk for increased vulnerability, disease, injury, and mortality. However, complementary molecular frailty biomarkers or ideally biomarker panels have not yet been identified. We conducted a systematic search to identify biomarker candidates for a frailty biomarker panel.

METHODS

Gene expression databases were searched (http://genomics.senescence.info/genes including GenAge, AnAge, LongevityMap, CellAge, DrugAge, Digital Aging Atlas) to identify genes regulated in aging, longevity, and age-related diseases with a focus on secreted factors or molecules detectable in body fluids as potential frailty biomarkers. Factors broadly expressed, related to several "hallmark of aging" pathways as well as used or predicted as biomarkers in other disease settings, particularly age-related pathologies, were identified. This set of biomarkers was further expanded according to the expertise and experience of the authors. In the next step, biomarkers were assigned to six "hallmark of aging" pathways, namely (1) inflammation, (2) mitochondria and apoptosis, (3) calcium homeostasis, (4) fibrosis, (5) NMJ (neuromuscular junction) and neurons, (6) cytoskeleton and hormones, or (7) other principles and an extensive literature search was performed for each candidate to explore their potential and priority as frailty biomarkers.

RESULTS

A total of 44 markers were evaluated in the seven categories listed above, and 19 were awarded a high priority score, 22 identified as medium priority and three were low priority. In each category high and medium priority markers were identified.

CONCLUSION

Biomarker panels for frailty would be of high value and better than single markers. Based on our search we would propose a core panel of frailty biomarkers consisting of (1) CXCL10 (C-X-C motif chemokine ligand 10), IL-6 (interleukin 6), CX3CL1 (C-X3-C motif chemokine ligand 1), (2) GDF15 (growth differentiation factor 15), FNDC5 (fibronectin type III domain containing 5), vimentin (VIM), (3) regucalcin (RGN/SMP30), calreticulin, (4) PLAU (plasminogen activator, urokinase), AGT (angiotensinogen), (5) BDNF (brain derived neurotrophic factor), progranulin (PGRN), (6) α-klotho (KL), FGF23 (fibroblast growth factor 23), FGF21, leptin (LEP), (7) miRNA (micro Ribonucleic acid) panel (to be further defined), AHCY (adenosylhomocysteinase) and KRT18 (keratin 18). An expanded panel would also include (1) pentraxin (PTX3), sVCAM/ICAM (soluble vascular cell adhesion molecule 1/Intercellular adhesion molecule 1), defensin α, (2) APP (amyloid beta precursor protein), LDH (lactate dehydrogenase), (3) S100B (S100 calcium binding protein B), (4) TGFβ (transforming growth factor beta), PAI-1 (plasminogen activator inhibitor 1), TGM2 (transglutaminase 2), (5) sRAGE (soluble receptor for advanced glycosylation end products), HMGB1 (high mobility group box 1), C3/C1Q (complement factor 3/1Q), ST2 (Interleukin 1 receptor like 1), agrin (AGRN), (6) IGF-1 (insulin-like growth factor 1), resistin (RETN), adiponectin (ADIPOQ), ghrelin (GHRL), growth hormone (GH), (7) microparticle panel (to be further defined), GpnmB (glycoprotein nonmetastatic melanoma protein B) and lactoferrin (LTF). We believe that these predicted panels need to be experimentally explored in animal models and frail cohorts in order to ascertain their diagnostic, prognostic and therapeutic potential.

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.

Dialysate Potassium and Mortality in a Prospective Hemodialysis Cohort

BACKGROUND

Studies examining the association of dialysate potassium concentration and mortality in hemodialysis patients show conflicting findings. We hypothesized that low dialysate potassium concentrations are associated with higher mortality, particularly in patients with high pre-dialysis serum potassium concentrations.

METHODS

We evaluated 624 hemodialysis patients from the prospective Malnutrition, Diet, and Racial Disparities in Kidney Disease study recruited from 16 outpatient dialysis facilities over 2011-2015 who underwent protocolized collection of dialysis treatment characteristics every 6 months. We examined the association of dialysate potassium concentration, categorized as 1, 2, and 3 mEq/L, with all-cause mortality risk in the -overall cohort, and stratified by pre-dialysis serum potassium (< 5 vs. ≥5 mEq/L) using case-mix adjusted Cox models.

RESULTS

In baseline analyses, dialysate potassium concentrations of 1 mEq/L were associated with higher mortality, whereas concentrations of 3 mEq/L were associated with similar mortality in the overall cohort (reference: 2 mEq/L): adjusted hazard ratios (aHRs; 95% CI) 1.70 (1.01-2.88) and 0.95 (0.64-1.39), respectively. In analyses stratified by serum potassium, baseline dialysate potassium concentrations of 1 mEq/L were associated with higher mortality in patients with serum potassium ≥5 mEq/L but not in those with serum potassium < 5 mEq/L: aHRs (95% CI) 2.87 (1.51-5.46) and 0.74 (0.27-2.07), respectively (p interaction = 0.04). These findings were robust with incremental adjustment for serum potassium, potassium-binding resins, and potassium-modifying medications.

CONCLUSION

Low (1 mEq/L) dialysate potassium -concentrations were associated with higher mortality, particularly in hemodialysis patients with high pre-dialysis serum potassium. Further studies are needed to identify therapeutic strategies that mitigate inter-dialytic serum potassium accumulation and subsequent high dialysate serum potassium gradients in this population.