Chronic erythropoietin treatment improves diet-induced glucose intolerance in rats

Erythroferrone Expression in Anemic Rheumatoid Arthritis Patients: Is It Disordered Iron Trafficking or Disease Activity?

Purpose

Erythroferrone (ERFE) is well acknowledged for its inhibitory function on hepcidin synthesis in the liver during stress erythropoiesis, thereby ensuring sufficient iron supply to bone marrow erythroblasts. Hepcidin plays an indispensable role in the pathogenesis of anemia of chronic disease (ACD). Thus, ERFE was suggested to protect against ACD in various diseases. Rheumatoid arthritis (RA) is commonly involved with ACD and high hepcidin levels, with a further increase of the latter in active states. The present study is a case-control study that aimed to determine the pattern of ERFE expression in RA patients with concomitant ACD and study its relationship with hepcidin, erythropoietin (EPO) and disease activity.

Patients and Methods

Fifty-five RA patients with ACD were categorized into active and inactive RA using the disease activity score (DAS28); 15 healthy subjects were included as control subjects. ERFE was measured for patients and control subjects using quantitative real-time polymerase chain reaction, in addition to testing for CBC, ESR, CRP, iron profile parameters and hepcidin. EPO was assessed for patients of both active and inactive RA groups.

Results

ERFE and hepcidin showed the highest levels in active RA; ERFE values were similar in control subjects and inactive RA patients, while hepcidin was significantly higher in inactive RA than control subjects. Patients with high ERFE levels had higher RBC, Hct, MCV, hepcidin and EPO levels. Stepwise regression analysis has identified DAS28 and disease duration as the best predictors of ERFE values, whereas ERFE and hepcidin were independent predictors of disease activity.

Conclusion

We introduce ERFE as a novel marker of RA activity. Although the inhibitory effect of ERFE on hepcidin is not evident, our results still indicate that ERFE may have a beneficial erythropoietic effect in the context of ACD in RA disease activity.

Latest advances in STAT signaling and function in adipocytes

Adipocytes and adipose tissue are not inert and make substantial contributions to systemic metabolism by influencing energy homeostasis, insulin sensitivity, and lipid storage. In addition to well-studied hormones such as insulin, there are numerous hormones, cytokines, and growth factors that modulate adipose tissue function. Many endocrine mediators utilize the JAK-STAT pathway to mediate dozens of biological processes, including inflammation and immune responses. JAKs and STATs can modulate both adipocyte development and mature adipocyte function. Of the seven STAT family members, four STATs are expressed in adipocytes and regulated during adipogenesis (STATs 1, 3, 5A, and 5B). These STATs have been shown to play influential roles in adipose tissue development and function. STAT6, in contrast, is highly expressed in both preadipocytes and mature adipocytes, but is not considered to play a major role in regulating adipose tissue function. This review will summarize the latest research that pertains to the functions of STATs in adipocytes and adipose tissue.

Erythropoietin Treatment Is Associated with Decreased Blood Glucose Levels in Hematologic Patients

BACKGROUND

Erythroid stimulating agents (ESAs) have pleiotropic effects, and in animal and human studies those exposed to high erythropoietin had lower blood glucose.

OBJECTIVE

To determine the association between ESA and glucose in anemia-treated patients with myelodysplastic syndromes (MDS) or multiple myeloma (MM).

PATIENTS AND METHODS

Patients' glucose levels were compared while on to while off ESA, and all served as their own controls. To test the association between ESA and blood glucose, we employed a linear mixed model, accounting for variability in the number of measurements for each patient.

RESULTS

Charts of 20 patients were reviewed. Mean age was 77 ± 9.8 years (range 50-91). Thirteen patients had MDS, and 8 had MM (1 with both). Glucose (mean ± standard error of the mean) was 116.38 ± 5.21 mg/dL without ESA, as opposed to 105.64 ± 5.11 mg/dL with ESA (p < 0.0001). The 3 diabetic and 5 steroid-treated patients also demonstrated reduced glucose by approximately 19 mg/dL with ESA (p = 0.003 and p = 0.0001, respectively). There was no difference in collective hemoglobin levels between the 2 groups.

CONCLUSION

ESA treatment for anemia is associated with lower blood glucose in hematologic patients. In those who also have diabetes mellitus, ESA might contribute to glucose control, and even to hypoglycemia. Glucose monitoring is thus advised. Further studies with both diabetic and nondiabetic patients are needed to clarify this association and underlying mechanisms.

Prolyl Hydroxylase Domain Inhibitor Protects against Metabolic Disorders and Associated Kidney Disease in Obese Type 2 Diabetic Mice

BACKGROUND

Prolyl hydroxylase domain (PHD) inhibitors, which stimulate erythropoietin production through the activation of hypoxia-inducible factor (HIF), are novel therapeutic agents used for treating renal anemia. Several PHD inhibitors, including enarodustat, are currently undergoing phase 2 or phase 3 clinical trials. Because HIF regulates a broad spectrum of genes, PHD inhibitors are expected to have other effects in addition to erythropoiesis, such as protection against metabolic disorders. However, whether such beneficial effects would extend to metabolic disorder-related kidney disease is largely unknown.

METHODS

We administered enarodustat or vehicle without enarodustat in feed to diabetic black and tan brachyury (BTBR) ob/ob mice from 4 to 22 weeks of age. To elucidate molecular changes induced by enarodustat, we performed transcriptome analysis of isolated glomeruli and in vitro experiments using murine mesangial cells.

RESULTS

Compared with BTBR ob/ob mice that received only vehicle, BTBR ob/ob mice treated with enarodustat displayed lower body weight, reduced blood glucose levels with improved insulin sensitivity, lower total cholesterol levels, higher adiponectin levels, and less adipose tissue, as well as a tendency for lower macrophage infiltration. Enarodustat-treated mice also exhibited reduced albuminuria and amelioration of glomerular epithelial and endothelial damage. Transcriptome analysis of isolated glomeruli revealed reduced expression of C-C motif chemokine ligand 2/monocyte chemoattractant protein-1 (CCL2/MCP-1) in enarodustat-treated mice compared with the vehicle-only group, accompanied by reduced glomerular macrophage infiltration. In vitro experiments demonstrated that both local HIF-1 activation and restoration of adiponectin by enarodustat contributed to CCL2/MCP-1 reduction in mesangial cells.

CONCLUSIONS

These results indicate that the PHD inhibitor enarodustat has potential renoprotective effects in addition to its potential to protect against metabolic disorders.

Regulation of muscle and metabolic physiology by hypothalamic erythropoietin independently of its peripheral action

Objective

The glycoprotein hormone erythropoietin (EPO) is required for erythropoiesis, and the kidney is the primary site of adult EPO synthesis. Limited evidence has suggested that EPO could be detectable in the brain under certain conditions, but it remains unknown if the brain might have its own EPO system for biological functions that are independent of peripheral EPO production and action. We performed this study to address this question using mice under normal conditions versus pathophysiological conditions including aging and dietary obesity.

Methods

EPO expression was measured in different brain regions as well as in the cerebrospinal fluid. Hypothalamic ventricular EPO was administered to physiologically examine possible therapeutic effects on the conditions of aging and dietary obesity. Body weight, body composition, insulin tolerance, and glucose tolerance were measured to assess the central effects of EPO on metabolic physiology, and muscle strength and histology were analyzed to assess the central effects of EPO on muscle function. In addition, β2-adrenergic receptor knockout bone marrow transplant was employed to determine the potential role of bone marrow in linking the brain to some of these peripheral functions.

Results

This study revealed that EPO is expressed in the ventromedial hypothalamus in addition to a few other brain regions and is present in the cerebrospinal fluid. Unlike blood EPO concentration, which increased with aging and dietary obesity, hypothalamic EPO decreased in these disease conditions. Therapeutically, aged mice were chronically treated with EPO in the hypothalamic ventricle, showing an increase in lean mass, while body weight and fat mass decreased as a result of a moderate reduction of food intake. Both muscle and metabolic functions were improved by this central treatment, and mechanistically, adrenergic signals to the bone marrow played a role in conveying hypothalamic EPO to these peripheral actions. Dietary obesity was also studied, showing that hypothalamic EPO treatment caused a reduction in food intake and obesity, leading to improved metabolic functions related to decreased fat as well as increased lean mass.

Conclusions

Hypothalamic EPO plays a role in the central regulation of muscle and metabolic physiology, while its decline contributes to aging and obesity physiology in a manner that is independent of peripheral EPO.

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Hypothalamic EPO plays a role in regulating muscle and metabolic physiology independently of its peripheral action.

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Hypothalamic EPO expression and the cerebrospinal fluid EPO concentration decrease in aging and obesity conditions.

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Hypothalamic EPO treatment blunts the effects of aging and obesity conditions in impairing muscle and metabolic functions.

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There exists a connection between the hypothalamus and bone marrow in mediating the physiological effects of central EPO.

Effects of erythropoietin on bile duct ligation-induced neuro-inflammation in male rats

Hepatic encephalopathy (HE) is a brain disorder as a result of liver failure. Previous studies have indicated that erythropoietin (EPO) has neuroprotective effects in different neurological diseases. This study addressed the therapeutic effect of a four-week treatment with EPO on neuronal damages in bile duct-ligated rats. Forty male Wistar rats (250-280 g) were used in the present study. The animals were randomly divided into four groups consisting of 10 animals each, including sham, sham + EPO, bile duct ligation (BDL), and BDL + EPO. EPO was intraperitoneally administered every other day (5,000 U/Kg) in the last four weeks after BDL. Biochemical and histological studies were performed to evaluate neurodegeneration. The results revealed that BDL increases the level of hepatic enzymes and total bilirubin. Furthermore, neurodegeneration was significantly increased in the BDL group compared to sham groups. EPO preserved hepatic enzymes and total bilirubin in the treated group. In addition, EPO significantly decreased the neurodegeneration in BDL + EPO compared to the BDL group. Results of this study showed that EPO has neuroprotective effects in the rat model of HE, possibly due to its anti-inflammatory and anti-oxidant properties. Complementary studies are required to clarify the exact mechanisms.

Erythroferrone: An Erythroid Regulator of Hepcidin and Iron Metabolism

Iron homeostasis ensures adequate iron for biological processes while preventing excessive iron accumulation, which can lead to tissue injury. In mammalian systems, iron availability is controlled by the interaction of the iron-regulatory hormone hepcidin with ferroportin, a molecule that functions both as the hepcidin receptor as well as the sole known cellular exporter of iron. By reducing iron export through ferroportin to blood plasma, hepcidin inhibits the mobilization of iron from stores and the absorption of dietary iron. Among the many processes requiring iron, erythropoiesis is the most iron-intensive, consuming most iron circulating in blood plasma. Under conditions of enhanced erythropoiesis, more iron is required to provide developing erythroblasts with adequate iron for heme and hemoglobin synthesis. Here the hormone erythroferrone, produced by erythroblasts, acts on hepatocytes to suppress hepcidin production, and thereby increase dietary iron absorption and mobilization from stores. This review focuses on the discovery of erythroferrone and recent advances in understanding the role of this hormone in the regulation of iron homeostasis during states of increased erythropoietic demand. Gaps in our understanding of the role of erythroferrone are highlighted for future study.

A central role for hypoxia-inducible factor (HIF)-2α in hepatic glucose homeostasis

Hepatic glucose production is regulated by hormonal and dietary factors. At fasting, 80% of glucose released into the circulation is derived from the liver, among which gluconeogenesis accounts for 55% and the rest by glycogenolysis. Studies suggest a complex mechanism involved in the regulation of hepatic glucose metabolism during fasting and post-absorptive phase. Oxygen plays a key role in numerous metabolic pathways such as TCA cycle, gluconeogenesis, glycolysis and fatty acid oxidation. Oxygenation of the gastrointestinal tract including liver and intestine is dynamically regulated by changes in the blood flow and metabolic activity. Cellular adaptation to low oxygen is mediated by the transcription factors HIF-1α and HIF-2α. HIF-1α regulates glycolytic genes whereas HIF-2α is known to primarily regulate genes involved in cell proliferation and iron metabolism. This review focuses on the role of the oxygen sensing signaling in the regulation of hepatic glucose output with an emphasis on hypoxia inducible factor (HIF)-2α. Recent studies have established a metabolic role of HIF-2α in systemic glucose homeostasis. Understanding the HIF-2α dependent mechanism in hepatic metabolism will greatly enhance our potential to utilize the oxygen sensing mechanisms to treat metabolic diseases.

Erythropoietin Reduces Insulin Resistance via Regulation of Its Receptor-Mediated Signaling Pathways in db/db Mice Skeletal Muscle

Erythropoietin (EPO) can reduce insulin resistance (IR) in adipocytes; however, it is unknown whether EPO can decrease IR in skeletal muscle. Here we investigated whether EPO could reduce IR in type 2 diabetic mouse skeletal muscle and its possible signaling mechanisms of action. Twelve-week-old db/db diabetic mice were employed in this study. Systemic use of EPO improved glucose profiles in type 2 diabetic mice after 4 and 8 weeks treatment. EPO up-regulated EPOR protein expression in skeletal muscle, and subsequently activated downstream signaling molecules such as JAK2, IRS-1, PI3K, AKT, and eNOS. We next constructed lentivirally-delivered shRNAs against EPOR and transfected skeletal muscle cells to knockdown EPOR. EPOR knockdown inhibited EPO induced JAK2, IRS-1, PI3K, AKT, eNOS signaling transduction, autophagy and Glut 4 translocation, as well as promoted apoptosis in skeletal muscle. Thus, EPO reduces skeletal muscle IR in type 2 diabetic mice via its specific receptor, EPOR. Possible mechanisms involved in its action may include increased autophagy and reduced apoptosis in type 2 diabetic skeletal muscles, which provides a new strategy for the treatment of IR.

Erythropoietin (EPO) ameliorates obesity and glucose homeostasis by promoting thermogenesis and endocrine function of classical brown adipose tissue (BAT) in diet-induced obese mice

Erythropoietin (EPO), clinically used as a hematopoietic drug, has received much attention due to its nonhematopoietic effects. EPO reportedly has beneficial effects on obesity and diabetes mellitus. We investigated whether interscapular brown adipose tissue (iBAT: main part of classical BAT) could play a role in EPO’s anti-obesity and anti-diabetic effects in diet-induced obese mice. Four-week-old male C57BL/6J mice were fed a high-fat diet (HFD-Con), and half were additionally given an intraperitoneal injection of recombinant human EPO (200 IU/kg) (HFD-EPO) thrice a week for four weeks. At 8 weeks, EPO-injected mice showed significantly reduced body weight with reduced epididymal and subcutaneous white fat mass and unchanged caloric intake and locomotor activity. HOMA-IR (insulin resistance index) and glucose levels during intraperitoneal glucose tolerance test (IPGTT) were significantly lower in HFD-EPO mice than in HFD-Con mice. EPO-injected mice also showed increased oxygen consumption, indicative of metabolic rate, and skin temperature around iBAT tissue masses. EPO significantly upregulated the PRD1-BF1-RIZ1 homologous domain containing 16 (PRDM16), a transcriptional factor with a crucial role in brown adipocyte differentiation. EPO significantly increased phosphorylated signal transducer and activator of transcription 3 (STAT3), which is downstream of erythropoietin receptor (EpoR) and known to stabilize PRDM16. EPO’s suppression of myocyte enhancer factor 2c (Mef2c) and microRNA-133a (miR-133a) via β3-adrenergic receptor caused PRDM16 upregulation. EPO-mediated enhancement of EpoR/STAT3 and β-adrenergic receptor/Mef2c/miR-133 pathways dramatically increases total uncoupling protein 1 (UCP1), an essential enzyme for BAT thermogenesis. Furthermore, EPO activated BAT’s endocrine functions. EPO facilitated fibroblast growth factor 21 (FGF21) production and excretion in iBAT, associated with reduction of liver gluconeogenesis-related genes. Thus, EPO’s improvement of obesity and glucose homeostasis can be attributed to increased iBAT thermogenic capacity and activation of BAT’s endocrine functions.

Sex difference in mouse metabolic response to erythropoietin

Erythropoietin (EPO) is the cytokine that regulates red blood cell production. Less understood is the nonerythroid action of EPO, including metabolic regulation of fat accumulation and glucose homeostasis. Although EPO treatment increased hematocrit and improved glucose tolerance in male and female mice, we observed a gender difference in EPO effects in weight control. EPO treatment reduced diet-induced weight gain from 9.6 ± 1.5 to 4.2 ± 1.4 g in male mice (P < 0.001), while the weight gain in female mice was similar (4.7 ± 2.0 g with PBS treatment and 3.3 ± 2.1 g with EPO treatment). EPO treatment also reduced weight gain in ovariectomized female mice, while the effect was abrogated with estradiol supplementation, suggesting that the sex-differential response to EPO was associated with estrogen. Furthermore, mice with targeted deletion of EPO receptor in white adipose tissue exhibited sex-differential phenotype in weight control and glucose sensitivity, and EPO receptor gene expression was reduced in wild-type female mice, suggesting that white adipose tissue plays an integral role in mediating the metabolic effects of EPO. Our data provide evidence for a sex-differential response to EPO in weight control in mice and underscore the potential for gender specific EPO action beyond erythropoiesis.-Zhang, Y., Rogers, H. M., Zhang, X., Noguchi, C. T. Sex difference in mouse metabolic response to erythropoietin.

Erythropoietin ameliorates hyperglycemia in type 1-like diabetic rats

Background

Erythropoietin (EPO) is widely used in diabetic patients receiving hemodialysis. The role of EPO in glucose homeostasis remains unclear. Therefore, we investigated the effect of EPO on hyperglycemia in rats with type 1-like diabetes.

Methods

Rats with streptozotocin-induced type 1-like diabetes (STZ rats) were used to estimate the blood glucose-lowering effects of EPO, and changes in the expression levels of glucose transporter 4 (GLUT4) and the hepatic enzyme phosphoenolpyruvate carboxykinase (PEPCK) were identified by Western blot analysis.

Results

EPO attenuated the hyperglycemia in the STZ rats in a dose-dependent manner without altering the hematopoietic parameters, including the hematocrit and number of red blood cells. The involvement of the EPO receptor (EPOR) was identified using EPOR-specific antibodies. In addition, injection of EPO enhanced the glucose utilization, which was assessed using an intravenous glucose tolerance test in rats. However, blood insulin was not changed by EPO in this assay, showing the insulinotropic action of EPO. Moreover, EPO treatment increased the insulin sensitivity. Western blots indicated that the phosphorylation of AMP-activated protein kinase was enhanced by EPO to support the signaling caused by EPOR activation. Furthermore, the decrease in the GLUT4 level in skeletal muscle was reversed by EPO, and the increase in the PEPCK expression in liver was reduced by EPO, as shown in STZ rats.

Conclusion

Taken together, the results show that EPO injection may reduce hyperglycemia in diabetic rats through activation of EPO receptors. Therefore, EPO is useful for managing diabetic disorders, particularly hyperglycemia-associated changes. In addition, EPO receptor will be a good target for the development of antihyperglycemic agent(s) in the future.

Combination of exercise training and erythropoietin prevents cancer-induced muscle alterations

Cancer cachexia is a syndrome characterized by loss of skeletal muscle mass, inflammation, anorexia and anemia, contributing to patient fatigue and reduced quality of life. In addition to nutritional approaches, exercise training (EX) has been proposed as a suitable tool to manage cachexia. In the present work the effect of mild exercise training, coupled to erythropoietin (EPO) administration to prevent anemia, has been tested in tumor-bearing mice. In the C26 hosts, acute exercise does not prevent and even worsens muscle wasting. Such pattern is prevented by EPO co-administration or by the adoption of a chronic exercise protocol. EX and EPO co-treatment spares oxidative myofibers from atrophy and counteracts the oxidative to glycolytic shift, inducing PGC-1α. LLC hosts are responsive to exercise and their treatment with the EX-EPO combination prevents the loss of muscle strength and the onset of mitochondrial ultrastructural alterations, while increases muscle oxidative capacity and intracellular ATP content, likely depending on PGC-1α induction and mitophagy promotion. Consistently, muscle-specific PGC-1α overexpression prevents LLC-induced muscle atrophy and Atrogin-1 hyperexpression. Overall, the present data suggest that low intensisty exercise can be an effective tool to be included in combined therapeutic approaches against cancer cachexia, provided that anemia is coincidently treated in order to enhance the beneficial action of exercise.