Relation of serum ferritin level to cardiovascular fitness among young men

Association Between Ferritin Levels and Altitude-Dependent Cardiorespiratory Fitness in Mountain Guides

Pühringer, Reinhard, Martina Muckenthaler, and Martin Burtscher. Association between ferritin levels and altitude-dependent cardiorespiratory fitness in mountain guides. High Alt Med Biol. 24:139-143, 2023. Background: Higher ferritin levels may be associated with lower cardiorespiratory fitness (CRF; i.e., maximal oxygen uptake, VO2max) and may represent early markers of cardiovascular risk but may also support high-altitude acclimatization. To evaluate these potential associations, data recordings from a large sample of male mountain guides have been analyzed. Methods: A total of 154 data sets (including anthropometric data, VO2max, blood lipids, hemoglobin, ferritin, and transferrin levels) of regularly physically active and well-acclimatized mountain guides were available for analyses. Participants performed equal incremental cycle ergometer tests to exhaustion at low (600 m) and (∼1 week later) at moderate altitude (2,000 m). Results: Ferritin levels were positively correlated with levels of hemoglobin (r = 0.29, p < 0.01), total cholesterol (r = 0.18, p < 0.05), triglycerides (r = 0.23, p < 0.01), and low-density lipoprotein (r = 0.22, p < 0.01), and negatively with high-density lipoprotein levels (r = -0.16, p < 0.05) and also with baseline (taken at low altitude) VO2max values (r = -0.19, p < 0.05). In contrast, higher ferritin levels were associated with less VO2max decline from low-to-moderate altitude (r = 0.26, p < 0.01). Conclusion: Higher ferritin levels in male mountain guides are weakly associated with lower CRF and higher prevalence of cardiovascular risk factors but with slightly less reduction in VO2max when acutely exposed to moderate altitude. The clinical relevance of these observations needs further investigation.

Iron and zinc homeostases in female rats with physically active and sedentary lifestyles

To determine the effects of repeated physical activity on iron and zinc homeostases in a living system, we quantified blood and tissue levels of these two metals in sedentary and physically active Long-Evans rats. At post-natal day (PND) 22, female rats were assigned to either a sedentary or an active treatment group (n = 10/group). The physically active rats increased their use of a commercially-constructed stainless steel wire wheel so that, by the end of the study (PND 101), they were running an average of 512.8 ± 31.9 (mean ± standard error) min/night. After euthanization, plasma and aliquots of liver, lung, heart, and gastrocnemius muscle were obtained. Following digestion, non-heme iron and zinc concentrations in plasma and tissues were measured using inductively coupled plasma optical emission spectroscopy. Concentrations of both non-heme iron and zinc in plasma and liver were significantly decreased among the physically active rats relative to the sedentary animals. In the lung, both metals were increased in concentration among the physically active animals but the change in zinc did not reach significance. Similarly, tissue non-heme iron and zinc levels were both increased in heart and muscle from the physically active group. It is concluded that repeated physical activity in an animal model can be associated with a translocation of both iron and zinc from sites of storage (e.g. liver) to tissues with increased metabolism (e.g. the lung, heart, and skeletal muscle).

Potential hazards of recent trends in liberal iron use for renal anemia

A randomized controlled trial,the Proactive IV Iron Therapy in Haemodialysis Patients (PIVOTAL), has recently shown that a high-dose (‘proactive’) intravenous iron regimen was superior to a low-dose (‘reactive’) regimen for hemodialysis patient outcomes and overall safety. However, even in the low-dose group, a substantial amount of iron was administered to maintain serum ferritin >200 ng/mL. This type of comparison may have strongly affected the safety results. Iron has two opposite effects on erythropoiesis: it activates erythroid differentiation directly by supplying iron but inhibits it indirectly by stimulating hepcidin and enhancing oxidative stress. Hepcidin plays an essential role not only in iron homeostasis and the anemia of chronic kidney disease, but also in its complications such as atherosclerosis and infection. Its main stimulation by iron—and to a lesser degree by inflammation—should urge clinicians to avoid prescribing excessive amounts of iron. Furthermore, as serum ferritin is closely correlated with serum hepcidin and iron storage, it would seem preferable to rely mainly on serum ferritin to adjust iron administration, defining an upper limit for risk reduction. Based on our estimations, the optimal range of serum ferritin is ∼50–150 ng/mL, which is precisely within the boundaries of iron management in Japan. Considering the contrasting ranges of target ferritin levels between end-stage renal disease patients in Japan and the rest of the world, the optimal range proposed by us will probably be considered as unacceptable by nephrologists abroad. Only well-balanced, randomized controlled trials with both erythropoiesis-stimulating agents and iron will allow us to settle this controversy.

Correlates and Determinants of Cardiorespiratory Fitness in Adults: a Systematic Review

Background

Enhanced cardiorespiratory fitness (CRF) is now a well-established predictor of numerous adverse health outcomes. Knowledge about the pathways leading to enhanced CRF is essential for developing appropriate interventions. Hence, the aim of this review was to provide a detailed overview of the current state of research regarding individual factors associated with or influencing CRF among the general adult population.

Methods

We searched the PubMed, EMBASE, and Cochrane Library databases and also conducted a search for grey literature (Google Scholar). Eligible indicators of CRF were objectively assessed measures of CRF by submaximal or maximal exercise testing measured using treadmill or cycle ergometer tests. We included quantitative observational studies of the general adult population. Using a semi-quantitative approach, we compiled summary tables aggregating the study results for each potential correlate or determinant of CRF.

Results

We identified 3005 studies, 78 of which met the inclusion criteria. Almost all of these studies were conducted in high-income countries. Study quality scores assessing the risk of bias in the individual studies ranged from 40 to 100%. Male sex, age (inverse), education, socioeconomic status, ethnicity, body mass index (inverse), body weight (inverse), waist circumference, body fat (inverse), resting heart rate (inverse), C-reactive protein (inverse), smoking (inverse), alcohol consumption, and multiple measures of leisure-time physical activity were independently and consistently associated with CRF.

Conclusions

In synthesizing the current research on the correlates and determinants of CRF among adults, this systematic review identified gaps in the current understanding of factors influencing CRF. Beyond the scope of this review, environmental and interpersonal determinants should be further investigated.

Systematic Review Registration

PROSPERO, CRD42017055456.

Electronic supplementary material

The online version of this article (10.1186/s40798-019-0211-2) contains supplementary material, which is available to authorized users.

Effects of an Acute Exercise Bout on Serum Hepcidin Levels

Iron deficiency is a frequent and multifactorial disorder in the career of athletes, particularly in females. Exercise-induced disturbances in iron homeostasis produce deleterious effects on performance and adaptation to training; thus, the identification of strategies that restore or maintain iron homeostasis in athletes is required. Hepcidin is a liver-derived hormone that degrades the ferroportin transport channel, thus reducing the ability of macrophages to recycle damaged iron, and decreasing iron availability. Although it has been suggested that the circulating fraction of hepcidin increases during early post-exercise recovery (~3 h), it remains unknown how an acute exercise bout may modify the circulating expression of hepcidin. Therefore, the current review aims to determine the post-exercise expression of serum hepcidin in response to a single session of exercise. The review was carried out in the Dialnet, Elsevier, Medline, Pubmed, Scielo and SPORTDiscus databases, using hepcidin (and “exercise” or “sport” or “physical activity”) as a strategy of search. A total of 19 articles were included in the review after the application of the inclusion/exclusion criteria. This search found that a single session of endurance exercise (intervallic or continuous) at moderate or vigorous intensity (60–90% VO_2peak) stimulates an increase in the circulating levels of hepcidin between 0 h and 6 h after the end of the exercise bout, peaking at ~3 h post-exercise. The magnitude of the response of hepcidin to exercise seems to be dependent on the pre-exercise status of iron (ferritin) and inflammation (IL-6). Moreover, oxygen disturbances and the activation of a hypoxia-induced factor during or after exercise may stimulate a reduction of hepcidin expression. Meanwhile, cranberry flavonoids supplementation promotes an anti-oxidant effect that may facilitate the post-exercise expression of hepcidin. Further studies are required to explore the effect of resistance exercise on hepcidin expression.

Reduction of Skeletal Muscle Power in Adolescent Males Carrying H63D Mutation in the HFE Gene

Iron overload resulting from the mutation of genes involved in iron metabolism or excess dietary intake has been reported to negatively influence human physical performance. The aim of this study was to test the hypothesis that adolescents bearing a hemochromatosis gene (HFE) mutation in contrast to adults with the same mutation will not experience iron accumulation and their aerobic capacity will be similar to that of age-matched controls. Thirteen boys participated in the study. Seven of them are carriers of H63D mutation in the HFE gene and six were wild type. Fitness levels were assessed using the cardiopulmonary exercise test. In addition, iron status and inflammatory markers were determined. We observed that cardiovascular fitness was significantly lower in the group bearing the HFE mutation compared to the control group. Moreover, the HFE mutation group achieved lower maximal power output compared to the control group. There were no differences in blood ferritin concentrations between the two groups which indicates similar amounts of stored iron. Obtained data do not confirm our hypothesis. On the contrary, it was demonstrated that HFE mutation is associated with a lower level of aerobic capacity, even in the absence of iron accumulation.

Independent relationship between serum ferritin levels and dyslipidemia in Chinese adults: A population study

Objective

Several studies have indicated that elevated levels of circulating ferritin are associated with disturbances in energy metabolism. But none of this gave a clearly pathologic mechanism. We aimed to explore the independent relationship between serum ferritin levels and dyslipidemia.

Methods

We performed multivariable logistic regression analyses to estimate the odds ratios (ORs) for dyslipidemia, lipid parameters, the homeostasis model assessment of insulin resistance (HOMA-IR) and the risk of diabetes, according to sex-specific quartiles of serum ferritin by using the data of China Health and Nutrition Survey (2009 CHNS). We used three models to estimate the strength of the correlation. The basic model (Model 1) is without adjustment and the Model 2 and Model 3 are adjusted for demographic, anthropometric, and lifestyle confounding factors.

Results

In both genders, the ORs for high TG level, TC level and LDL-C level increased progressively and for HDL-C decreased across the ferritin quartiles (P<0.001 for trend). After adjustment for confounding factors in different logistic regression models, the results remained unchanged. The ORs for the risk of diabetes and high HOMA-IR level in the highest quartile group of serum ferritin levels were significantly increased in Model 1, but after adjustment for lipid parameters, the ORs for the risk of diabetes was decreased from 1.91 (95% CI: 1.37–2.67; P<0.001 for trend) to 1.48 (95% CI: 1.03–2.12; P = 0.036 for trend) in men, and from 5.40 (95% CI: 3.38–8.63; P<0.001 for trend) to 1.43 (95% CI: 0.83–2.43; P = 0.498 for trend) in women, and the ORs for IR was decreased from 1.86 (95% CI: 1.57–2.20; P<0.001 for trend) to 1.25 (95% CI: 1.05–1.50; P = 0.114 for trend) in men, and from 1.93 (95% CI: 1.63–2.28; P<0.001 for trend) to 1.24 (95% CI: 1.01–1.51; P = 0.012 for trend) in women.

Conclusion

Our results provide evidence that serum ferritin levels are significantly associated with lipid parameters, independent of glucose metabolism disorders and components of metabolic syndrome (MetS). Thus, serum ferritin plays a key role in energy metabolism disorders and may affect glucose metabolism through lipid metabolism.

Simple sugar supplementation abrogates exercise-induced increase in hepcidin in young men

Background

At present many young people experience too much body iron accumulation. The reason of this phenomenon is not clear. There is accumulating evidences that not proper diet and lack of exercise could be a main contributing factors. This investigation assessed the effects of a diet rich in simple sugars (glucose or fructose) on exercise-induced hepcidin which is hormone regulating iron metabolism.

Methods

A group of physically active young men completed an incremental exercise test before and after a 3-day diet supplemented with fructose (4 g/kg BM) or glucose (4 g/kg BM). After a 1-week break, they crossed over to the alternate mode for the subsequent 3-days period. Venous blood samples were collected before and after 1 h exercise and were analysed for serum hepcidin, IL-6, CRP, iron, and ferritin. The physiological response to exercise was also determined.

Results

The concentration of hepcidin increased 1 h after exercise for the baseline test (p < 0.05), whereas no changes in hepcidin were observed in men whose diet was supplemented with fructose or glucose. Blood IL-6 increased significantly after exercise only in subjects supplemented with fructose. Changes in hepcidin did not correlate with shifts in serum IL-6.

Conclusions

These data suggest that protective effects of exercise on excess iron accumulation in human body which is mediated by hepcidin can be abrogated by high sugar consumption which is typical for contemporary people.

Nordic walking training attenuation of oxidative stress in association with a drop in body iron stores in elderly women

Excess body iron accumulation and oxidative stress has been associated with ageing. Regular exercise has been shown to reduce oxidative stress and induce some changes in iron metabolism. However, the effects of exercise on both of these parameters have been poorly investigated. In our study, 35 elderly women participated in 12 weeks of Nordic walking (NW) training (three times a week). We demonstrated that the training caused a significant reduction in malondialdehyde advanced oxidation protein products—markers of oxidative stress but had no effects on paraoxonase 1 activity. These changes were associated with the decrease of blood ferritin (99.4 ± 62.7 vs. 81.4 ± 61.7 ng/ml p < 0.05). Measurement of physical fitness revealed that the training caused a significant improvement in performance and a negative correlation between the blood ferritin and endurance test was recorded (r = −0.34, p = 0.03). In addition, a significant correlation between blood ferritin and fasting glucose level was noted. The training induced a rise of HDL cholesterol from 70.8 ± 19.3–75.3 ± 21.1, p < 0.05, whereas other lipid parameters remained unchanged. In conclusion, NW training reduced body iron stores and it was associated with lower oxidative stress and better endurance.

Impact of Oxidative Stress in Premature Aging and Iron Overload in Hemodialysis Patients

Background. Increased oxidative stress is a well described feature of patients in hemodialysis. Their need for multiple blood transfusions and supplemental iron causes a significant iron overload that has recently been associated with increased oxidation of polyunsaturated lipids and accelerated aging due to DNA damage caused by telomere shortening. Methods. A total of 70 patients were evaluated concomitantly, 35 volunteers with ferritin levels below 500 ng/mL (Group A) and 35 volunteers with ferritin levels higher than 500 ng/mL (Group B). A sample of venous blood was taken to extract DNA from leukocytes and to measure relative telomere length by real-time PCR. Results. Patients in Group B had significantly higher plasma TBARS (p = 0.008), carbonyls (p = 0.0004), and urea (p = 0.02) compared with those in Group A. Telomeres were significantly shorter in Group B, 0.66 (SD, 0.051), compared with 0.75 (SD, 0.155) in Group A (p = 0.0017). We observed a statistically significant association between relative telomere length and ferritin levels (r = −0.37, p = 0.001). Relative telomere length was inversely related to time on hemodialysis (r = −0.27, p = 0.02). Conclusions. Our findings demonstrate that iron overload was associated with increased levels of oxidative stress and shorter relative telomere length.

Asthma as a disruption in iron homeostasis

Over several decades, asthma has evolved from being recognized as a single disease to include a diverse group of phenotypes with dissimilar natural histories, pathophysiologies, responses to treatment, and distinctive molecular pathways. With the application of Occam's razor to asthma, it is proposed that there is one cause underlying the numerous phenotypes of this disease and that the responsible molecular pathway is a deficiency of iron in the lung tissues. This deficiency can be either absolute (e.g. asthma in the neonate and during both pregnancy and menstruation) or functional (e.g. asthma associated with infections, smoking, and obesity). Comparable associations between asthma co-morbidity (e.g. eczema, urticaria, restless leg syndrome, and pulmonary hypertension) with iron deficiency support such a shared mechanistic pathway. Therapies directed at asthma demonstrate a capacity to impact iron homeostasis, further strengthening the relationship. Finally, pathophysiologic events producing asthma, including inflammation, increases in Th2 cells, and muscle contraction, can correlate with iron availability. Recognition of a potential association between asthma and an absolute and/or functional iron deficiency suggests specific therapeutic interventions including inhaled iron.

Effect of Nordic Walking training on iron metabolism in elderly women

BACKGROUND

Despite several, well-documented pro-healthy effects of regular physical training, its influence on body iron stores in elderly people remains unknown. At the same time, body iron accumulation is associated with high risk of different morbidities.

PURPOSE

We hypothesized that Nordic Walking training would result in pro-healthy changes in an elderly group of subjects by reducing body iron stores via shifts in iron metabolism-regulating proteins.

METHODS

Thirty-seven women aged 67.7±5.3 years participated in this study. They underwent 32 weeks of training, 1-hour sessions three times a week, between October 2012 and May 2013. Fitness level, blood morphology, CRP, vitamin D, ferritin, hepcidin, and soluble Hjv were assessed before and after the training.

RESULTS

The training program caused a significant decrease in ferritin, which serves as a good marker of body iron stores. Simultaneously, the physical cardiorespiratory fitness had improved. Furthermore, blood hepcidin was positively correlated with the ferritin concentration after the training. The concentration of blood CRP dropped, but the change was nonsignificant. The applied training resulted in a blood Hjv increase, which was inversely correlated with the vitamin D concentration.

CONCLUSION

Overall the Nordic Walking training applied in elderly people significantly reduced blood ferritin concentration, which explains the observed decrease in body iron stores.

Repeated "all out" interval exercise causes an increase in serum hepcidin concentration in both trained and untrained men

This investigation assessed effects of high-intensity interval exercise (HIE; triple Wingate anaerobic test) on inflammatory markers, iron metabolism and hepcidin concentrations. Group of highly trained judo athletes (TR) and non-trained control males (CG) completed a triple Wingate test separated by 4.5min rest. Venous blood samples were collected before, immediately after, 1h, 24h, and 5days following exercise and analysed for serum of IL-6, IL-10, iron, and ferritin. Physiological response to exercise was also determined. Concentration of IL-6 and hepcidin increased 1h after exercise in both groups (p<0.05). Hepcidin returned post testing 24h in TR, whereas in CG it remained elevated during 5days following exercise. Changes in hepcidin did not correlate with shifts in serum IL-6, iron and ferritin concentrations. Gathered data suggest that following HIE, hepcidin increased independently of IL-6 and neither blood nor storage iron affected this phenomena.

Serum ferritin concentration and transferrin saturation before liver transplantation predict decreased long-term recipient survival

Serum ferritin (SF) concentration is a widely available parameter used to assess iron homeostasis. It has been described as a marker to identify high-risk patients awaiting liver transplantation (LT) but is also elevated in systemic immune-mediated diseases, metabolic syndrome, and in hemodialysis where it is associated with an inferior prognosis. This study analyzed whether SF is not only a predictor of liver-related mortality prior to LT but also an independent marker of survival following LT. In a dual-center, retrospective study, a cohort of 328 consecutive first-LT patients from Hannover Medical School, Germany (2003-2008, follow-up 1260 days), and 82 consecutive LT patients from Regensburg University Hospital, Germany (2003-2007, follow-up 1355 days) as validation cohort were analyzed. In patients exhibiting SF ≥365 μg/L versus <365 μg/L prior to LT, 1-, 3-, and 5-year post-LT survival was 73.3% versus 81.1%, 64.4% versus 77.3%, and 61.1% versus 74.4%, respectively (overall survival P = 0.0097), which was confirmed in the validation cohort (overall survival of 55% versus 83.3%, P = 0.005). Multivariate analyses identified SF ≥365 μg/L combined with transferrin saturation (TFS) <55%, hepatocellular carcinoma, and the survival after LT (SALT) score as independent risk factors for death. In patients with SF concentrations ≥365 μg/L and TFS <55%, overall survival was 54% versus 74.8% in the remaining group (P = 0.003). In the validation cohort, it was 28.6% versus 72% (P = 0.017), respectively.

CONCLUSION

SF concentration ≥365 μg/L in combination with TFS <55% before LT is an independent risk factor for mortality following LT. Lower TFS combined with elevated SF concentrations indicate that acute phase mechanisms beyond iron overload may play a prognostic role. SF concentration therefore not only predicts pre-LT mortality but also death following LT.