Work performance in the iron-deficient rat: improved endurance with exercise training

Endurance training and hydroxyurea have synergistic effects on muscle function and energetics in sickle cell disease mice

Sickle cell disease (SCD) is an hemoglobinopathy resulting in the production of an abnormal Hb (HbS) which can polymerize in deoxygenated conditions, leading to the sickling of red blood cells (RBC). These alterations can decrease the oxygen-carrying capacity leading to impaired function and energetics of skeletal muscle. Any strategy which could reverse the corresponding defects could be of interest. In SCD, endurance training is known to improve multiples muscle properties which restores patient's exercise capacity but present reduced effects in anemic patients. Hydroxyurea (HU) can increase fetal hemoglobin production which can reduce anemia in patients. The present study was conducted to determine whether HU can improve the effects of endurance training to improve muscle function and energetics. Twenty SCD Townes mice have been trained for 8 weeks with (n = 11) or without (n = 9) HU. SCD mice muscle function and energetics were analyzed during a standardized rest-exercise-recovery protocol, using Phosphorus-31 Magnetic resonance spectroscopy (31P-MRS) and transcutaneous stimulation. The combination of training and HU specifically decreased fatigue index and PCr consumption while muscle oxidative capacity was improved. These results illustrate the potential synergistic effects of endurance training and HU on muscle function and energetics in sickle cell disease.

Iron deficiency associates with deterioration in several symptoms independently from hemoglobin level among chronic hemodialysis patients

Background

While iron deficiency (ID) is a frequent cause of anemia in hemodialysis patients, the clinical impact of ID without anemic level of hemoglobin remains unclear. As such, this study was designed to clarify the manifestations of ID itself in subjects on hemodialysis.

Methods

Maintenance hemodialysis patients achieving target hemoglobin levels (≥ 10.0g/dL) under treatment in our clinic were stratified for comparison from three perspectives: ID (transferrin saturation [TSAT] < 20% or ferritin < 100ng/mL) vs non-ID, level of TSAT (< or ≥ 20%), and level of serum ferritin concentration (< or ≥ 100ng/mL). The severity of frequent symptoms was determined by a self-rating symptom score questionnaire, and the rate of those with severe manifestations was calculated for each symptom. Significant difference was examined between groups; univariate and adjusted multivariate odds ratios and 95% confidence intervals were obtained by logistic regression.

Results

Among 154 subjects selected for analysis, the ratio of severe arthralgia and fatigue was significantly higher in the ID group (n = 94) compared to the non-ID group (n = 60), in both univariate and adjusted multivariate analyses. Moreover, in multivariate analysis, low TSAT was significantly associated with exacerbation of pain during vascular access puncture and intradialytic leg cramps, while low serum ferritin concentration was related to significant increase in severe arthralgia, fatigue, intradialytic headache and leg cramps.

Conclusions

ID was identified as a risk factor regarding severity of several symptoms even without low hemoglobin level among chronic hemodialysis patients, and supplementation of iron was considered efficacious for improving critical symptoms affecting those undergoing maintenance dialysis.

Responses of HSC70 expression in diencephalon to iron deficiency anemia in rats

A powdered diet containing 100 or 3 ppm Fe was fed to rats starting at the age of 3 weeks. The voluntary activity level was checked using a wheel in the cage during the 17th week after the beginning of supplementation. Significantly less activity was seen in the 3 ppm Fe group during both light and dark periods. After 20 weeks, the blood and diencephalon were sampled from both groups. Lower hematocrit and blood hemoglobin content was observed in the 3 ppm Fe group. The level of 70 kDa heat shock cognate (HSC70) expression was greater in the diencephalon of the 3 ppm Fe group. In addition, the distribution of HSC70 was determined by proximity ligation assay. More HSC70-positive as well as total cells were noted in several areas of the diencephalon of the iron-deficient rats. The altered expression and distribution of HSC70 might play some role in the neurological changes.

Treatment of anemia in heart failure: potential risks and benefits of intravenous iron therapy in cardiovascular disease

Iron-deficiency anemia is common in patients with heart failure (HF), but the optimum diagnostic tests to detect iron deficiency and the treatment options to replete iron have not been fully characterized. Recent studies in patients with HF indicate that intravenous iron can rapidly replenish iron stores in patients having iron-deficiency anemia, with resultant increased hemoglobin levels and improved functional capacity. Preliminary data from a subgroup analysis also suggest that supplemental intravenous iron therapy can improve functional capacity even in those subjects without anemia. The mechanisms responsible for this observation are not fully characterized, but may be related to beneficial effects of iron supplementation on mitochondrial respiration in skeletal muscle. The long-term safety of using intravenous iron supplementation in HF populations is not known. Iron is a known pro-oxidant factor that can inhibit nitric oxide signaling and irreversibly injury cells. Increased iron stores are associated with vascular endothelial dysfunction and increased risk of coronary heart disease events. Additional clinical trials are needed to more fully characterize the therapeutic potential and safety of intravenous iron in HF patients.