Hypoxia-inducible factor-prolyl hydroxylase inhibitor Roxadustat (FG-4592) reduces renal fibrosis in Dahl salt-sensitive rats.

OBJECTIVE: Although hypoxia-inducible factor-prolyl hydroxylase (HIF-PH) inhibitors have been developed for the treatment of renal anemia, their effects on cardiac and renal dysfunction remain unknown. We previously reported on Dahl salt-sensitive rats, in a rat model of salt-sensitive hypertension, that exhibited anemia and impaired expression of duodenal iron transporters after the development of hypertensive cardiac and renal dysfunction. Therefore, we investigated the effects of Roxadustat (FG-4592), an HIF-PH inhibitor, on anemia, iron regulation, and cardiac and renal dysfunction in Dahl salt-sensitive rats. METHODS: Six-week-old male Dahl salt-sensitive rats were fed a normal or high-salt diet for 8 weeks. A further subset of Dahl salt-sensitive rats, that were fed a high-salt diet, was administered Roxadustat for 8 weeks. RESULTS: Dahl salt-sensitive rats fed a high-salt diet developed hypertension, cardiac and renal dysfunction, and anemia after 8 weeks of feeding. Roxadustat increased hemoglobin and serum erythropoietin levels in Dahl salt-sensitive rats fed a high-salt diet. With regard to the iron-regulating system, Roxadustat lowered hepatic hepcidin gene expression and increased the gene expression of duodenal iron transporters, such as cytochrome b and divalent metal transporter 1 , in Dahl salt-sensitive rats fed a high-salt diet. Roxadustat did not affect the development of hypertension and cardiac hypertrophy in Dahl salt-sensitive rats with a high-salt diet; however, Roxadustat treatment attenuated renal fibrosis in these rats. CONCLUSIONS: Roxadustat ameliorated anemia with affecting the gene expression of the iron-regulating system, and did not affect cardiac hypertrophy but attenuated renal fibrosis in Dahl salt-sensitive rats fed a high-salt diet.

Clinical utility of reticulocyte hemoglobin equivalent in patients with heart failure.

Anemia and iron deficiency (ID) are common in patients with heart failure (HF) and intravenous (IV) administration of iron to patients hospitalized for decompensated HF with ID improves outcome. The diagnosis of ID in routine practice is based on serum ferritin and transferrin saturation (TSAT) but both have limitations; alternatives should be considered. Reticulocyte hemoglobin equivalent (Ret-He) reflects iron content in reticulocytes but its clinical utility in patients with HF remains uncertain. We prospectively enrolled 142 patients hospitalized for decompensated HF. Sixty five percent had ID as defined in current international guidelines. Ret-He was directly correlated with serum iron and ferritin concentrations and with TSAT. There was a poor relationship between quartile of Ret-He and HF hospitalization or death but increases or decreases in Ret-He between admission and discharge were associated with a worse outcome. The clinical utility of Ret-He for identifying ID and predicting response to IV iron and prognosis for patients with HF requires further investigation.

Anemia has an impact on prognosis in heart failure with preserved ejection fraction with mild chronic kidney disease.

BACKGROUND: Anemia and chronic kidney disease (CKD) are common in patients with heart failure with preserved left ventricular fraction (HFpEF). However, it is entirely unknown about the impact of anemia on prognosis in HFpEF patients with CKD. In this study, we investigated the impact of anemia on prognosis and the optimal hemoglobin (Hb) levels to predict prognosis in HFpEF patients with CKD. METHODS AND RESULTS: We prospectively examined 523 consecutive HFpEF patients enrolled in Japanese heart failure syndrome with preserved ejection fraction registry. CKD was defined as an estimated glomerular filtration rate (eGFR) of <60 mL /min/1.73 m2. The prevalence rate of anemia was 78% in HFpEF patients with CKD by using the World Health Organization criteria. Kaplan-Meier analysis for all-cause mortality and heart failure rehospitalization demonstrated that anemic patients had poor prognosis compared with non-anemic patients in HFpEF patients with CKD, but not those without CKD. According to the degree of CKD, anemia affected prognosis in HFpEF patients with mild CKD (45 ≤ eGFR < 60), but not those with moderate to severe CKD (15 ≤ eGFR < 45). Additionally, multivariate analysis revealed that anemia and Hb levels were independent predictors of composite outcomes in HFpEF patients with mild CKD, but not those with moderate to severe CKD. Finally, survival classification and regression tree analysis showed that the optimal Hb levels to predict composite outcomes were 10.7 g/dL in those with mild CKD. CONCLUSIONS: Anemia has an impact on prognosis in HFpEF patients, especially among those with mild CKD.

Effects of Heterozygous TfR1 (Transferrin Receptor 1) Deletion in Pathogenesis of Renal Fibrosis in Mice.

Renal fibrosis is the final pathological process common for several types of end-stage renal diseases, including obstructive nephropathy and diabetic kidney disease. Substantial renal iron loads and oxidative stress have been reported to contribute to the development of renal diseases. TfR1 (transferrin receptor 1) plays a crucial role in cellular iron transport. However, there are no studies investigating TfR1 in the pathophysiology of renal fibrosis. Here, we investigate the role of TfR1 in the development of renal fibrosis. Primarily, to ascertain an association of TfR1 in the pathophysiology of renal fibrosis, we induced unilateral ureteral obstruction in wild-type (WT) and heterozygous TfR1 deleted (TfR1+/-) mice. TfR1+/- mice exhibited attenuated renal fibrosis, along with reduced renal expression of ferritin and 4-hydroxynonenal as compared with WT mice after unilateral ureteral obstruction. In addition, renal expression of TGFß-RI (transforming growth factor-ß receptor I) and Smad2, downstream signaling of TGFß-RI was attenuated in TfR1+/- mice compared with WT mice after unilateral ureteral obstruction. Next, we investigated the role of TfR1 in the development of diabetic kidney disease. No difference was observed in blood glucose levels and urinary albumin:creatinine ratios between WT and TfR1+/- diabetic mice after streptozotocin administration. In contrast, TfR1+/- mice showed suppressed renal fibrosis, along with reduced renal expression of ferritin, 4-hydroxynonenal, TGFß-RI, and Smad2 compared with WT mice after streptozotocin administration. These results suggest that TfR1 plays an important role in the development of renal fibrosis.

Haploinsufficiency of Transferrin Receptor 1 Impairs Angiogenesis with Reduced Mitochondrial Complex I in Mice with Limb Ischemia.

Limb ischemia (LI) is a major consequence of peripheral artery disease (PAD) with a high mortality rate. Iron is an essential mineral to maintain physiological function of multiple organs. Intracellular iron transport is regulated by transferrin receptor 1 (TfR1). Although increase in serum ferritin levels has been reported in PAD patients, the mechanism of iron metabolism in LI is still unclear. The aim of this study is to investigate whether TfR1 deletion attenuates LI formation. To generate LI, the left femoral artery of 8-10 week-old C57BL6/J male mice was ligated. Adductor muscles were harvested at 28 days after surgery to investigate iron metabolism. The level of ferritin, intracellular iron storage protein, was higher in ischemic adductor muscles compared to non-ischemic adductor muscles. Level of intracellular iron transport protein, TfR1, was decreased in ischemic adductor muscles. LI was then generated in TfR1 heterozygous deleted mice (TfR1+/-) to examine whether TfR1 contributes to the pathophysiology of LI. Laser Doppler blood flowmetry revealed that blood flow recovery was attenuated in TfR1+/- mice compared to wild type (WT) littermates, along with decreased expression of ferritin and CD31 in ischemic adductor muscles. Since iron is used for energy production in mitochondria, we then assessed mitochondrial complexes in the ischemic adductor muscle. Of interest, expression of mitochondrial complex I, but not complexes II, III, and V in ischemic adductor muscles was significantly reduced in TfR1+/- mice compared to WT mice. Haploinsufficiency of TfR1 attenuated angiogenesis via reduction of mitochondrial complex I in LI in mice.

Effective blood hemoglobin level to predict prognosis in heart failure with preserved left ventricular ejection fraction: results of the Japanese heart failure syndrome with preserved ejection fraction registry.

High prevalence of anemia in heart failure with preserved left ventricular ejection fraction (HFpEF) has been reported. However, little is known about the association of anemia and gender with prognosis in HFpEF patients. In addition, effective blood hemoglobin (Hb) level for prognosis in HFpEF patients remains largely unknown. In this study, we investigated the association between anemia, gender, and prognosis in 535 HFpEF patients enrolled in Japanese heart failure syndrome with preserved ejection fraction registry. Furthermore, we assessed effective blood Hb level to predict prognosis in HFpEF patients. According to the World Health Organization criteria, the prevalence rate of anemia on admission was about 70% in both male and female HFpEF patients. Kaplan-Meier analysis for all-cause mortality demonstrated that anemic patients had poor prognosis compared with non-anemic patients in both male and female HFpEF patients. Interestingly, multivariate analysis revealed that blood Hb level at discharge was an independent predictor of all-cause mortality in both male and female HFpEF patients. According to survival classification and regression tree analysis, blood Hb level at discharge of 9.4 g/dL for male and 12.3 g/dL for female was more accurate cutoff value to predict all-cause mortality in HFpEF patients. Anemia was implicated in poor prognosis in both male and female HFpEF patients. In particular, blood Hb level at discharge was an independent predictor of all-cause mortality in both male and female HFpEF patients. Effective cutoff value of blood Hb level at discharge to predict all-cause mortality was lower in male than in female HFpEF patients.

Influence of dietary iron intake restriction on the development of hypertension in weanling prehypertensive rats.

Hypertension is a major public health problem leading to death. To reduce the morbidity and mortality in patients with hypertension, it is crucial to develop a novel strategy for prevention of hypertension. We have currently reported an attempt at dietary iron intake restriction as non-pharmacological treatment of hypertension in patients with hypertension. However, it remains fully unknown whether dietary iron restriction prevents the development of hypertension. We investigated the influence of dietary iron restriction on the development of hypertension in weanling pre-hypertensive model rats. 3-week-old male stroke-prone spontaneously hypertensive rats (SHR-SP) were randomly divided into two groups and were given an ad libitum normal diet or an iron-restricted diet for 12 weeks. Blood pressure was progressively increased in SHR-SP according to growth, while dietary iron restriction attenuated the development of hypertension. Proteinuria was also increased in SHR-SP according to growth, whereas dietary iron restriction suppressed the increment of proteinuria. SHR-SP exhibited glomerulosclerosis and exacerbated renal interstitial fibrosis at 15 weeks old, indicating that SHR-SP developed hypertensive nephropathy in the adult stage; however, these changes were attenuated by dietary iron restriction. Gelatin zymography showed dietary iron restriction decreased both renal MMP-2 and MMP-9 activities in SHR-SP at 15 weeks old. Of interest, dietary iron restriction suppressed renal TGFß-RI expression and Smad2 phosphorylation in SHR-SP. Furthermore, dietary iron restriction decreased renal fibrosis, renal MMP-2 and MMP-9 activities, renal TGFß-RI expression, and Smad2 phosphorylation in rats with unilateral ureteral obstruction. Dietary iron restriction prevented the development of hypertension in weanling pre-hypertensive rats.

Altered expression of intestinal duodenal cytochrome b and divalent metal transporter 1 might be associated with cardio-renal anemia syndrome.

The interaction among heart failure (HF), chronic kidney disease (CKD), and anemia is called cardio-renal anemia syndrome. The mechanism of anemia in cardio-renal anemia syndrome is complex and remains completely unknown. We have previously reported that impaired intestinal iron transporters may contribute to the mechanism of anemia in HF using in vivo HF model rats. In this study, we assessed intestinal iron transporters in CKD model rats to investigate the association of intestinal iron transporters in the mechanism of cardio-renal anemia syndrome. CKD was induced by 5/6 nephrectomy in Sprague-Dawley rats. Sham-operated rats served as a control. After 24-week surgery, CKD rats exhibited normocytic normochromic anemia and normal serum erythropoietin levels despite of anemia. Serum iron levels were decreased in CKD rats compared with the controls. Of interest, intestinal expression of critical iron importers, such as duodenal cytochrome b (Dcyt-b) and divalent metal transporter 1 (DMT-1), was decreased in CKD rats compared with the controls. On the other hand, intestinal expression of ferroportin, an intestinal iron exporter, was not different in the control and CKD groups. Moreover, hepatic expression of hepcidin, a regulator of iron homeostasis, did not differ between the control and CKD groups. These results suggest that impaired intestinal expression of Dcyt-b and DMT-1 might be associated with the reduction of an iron uptake in CKD. Taken together, impaired these intestinal iron transporters may become a novel therapeutic target for cardio-renal anemia syndrome.

Iron-restricted pair-feeding affects renal damage in rats with chronic kidney disease.

BACKGROUND: We have previously shown that dietary iron restriction prevents the development of renal damage in a rat model of chronic kidney disease (CKD). However, iron deficiency is associated with appetite loss. In addition, calorie restriction is reported to prevent the development of end-stage renal pathology in CKD rats. Thus, the beneficial effect of iron restriction on renal damage may depend on calorie restriction. Here, we investigate the effect of pair-feeding iron restriction on renal damage in a rat model of CKD. METHODS: First, to determine the amount of food intake, Sprague-Dawley (SD) rats were randomly given an ad libitum normal diet or an iron-restricted diet, and the food intake was measured. Second, CKD was induced by a 5/6 nephrectomy in SD rats, and CKD rats were given either a pair-feeding normal or iron-restricted diet. RESULTS: Food intake was reduced in the iron-restricted diet group compared to the normal diet group of SD rats for 16 weeks (mean food intake; normal diet group and iron-restricted diet group: 25 and 20 g/day, respectively). Based on the initial experiments, CKD rats received either a pair-feeding normal or iron-restricted diet (20 g/day) for 16 weeks. Importantly, pair-feeding iron restriction prevented the development of proteinuria, glomerulosclerosis, and tubulointerstitial damage in CKD rats. Interestingly, pair-feeding iron restriction attenuated renal expression of nuclear mineralocorticoid receptor in CKD rats. CONCLUSIONS: Pair-feeding iron restriction affected renal damage in a rat model of CKD.