Independent association of circulating vitamin D metabolites with anemia risk in patients scheduled for cardiac surgery

Fibroblast growth factor 23 is pumping iron: C-terminal-fibroblast growth factor 23 cleaved peptide and its function in iron metabolism

PURPOSE OF REVIEW

Iron deficiency regulates the production of the bone-derived phosphaturic hormone fibroblast growth factor 23 (FGF23) but also its cleavage, to generate both intact (iFGF23) and C-terminal (Cter)-FGF23 peptides. Novel studies demonstrate that independently of the phosphaturic effects of iFGF23, Cter-FGF23 peptides play an important role in the regulation of systemic iron homeostasis. This review describes the complex interplay between iron metabolism and FGF23 biology.

RECENT FINDINGS

C-terminal (Cter) FGF23 peptides antagonize inflammation-induced hypoferremia to maintain a pool of bioavailable iron in the circulation. A key mechanism proposed is the down-regulation of the iron-regulating hormone hepcidin by Cter-FGF23.

SUMMARY

In this manuscript, we discuss how FGF23 is produced and cleaved in response to iron deficiency, and the principal functions of cleaved C-terminal FGF23 peptides. We also review possible implications anemia of chronic kidney disease (CKD).

Increased Early Postoperative Complication Rate after Osteoporotic Hip Fracture in Patients with Low 25 (OH) Vitamin D Levels

This study investigated the association of preoperative 25-hydroxy (25 (OH)) vitamin D levels with postoperative complications in osteoporotic hip fracture patients following surgery. We hypothesized that patients with low concentrations of 25 (OH) vitamin D might have an increased risk of developing adverse outcomes. Between January 2019 and December 2020, a retrospective observational study was conducted, including low-energy fragility fractures at the proximal femur. Regarding preoperative 25 (OH) vitamin D levels, patients were divided into two groups (<30 ng/mL and ≥30 ng/mL). Early and late postoperative complications were assessed and graded according to the Clavien-Dindo classification system. Logistic regression analysis was performed to demonstrate the association between preoperative 25 (OH) vitamin D levels (<30 ng/mL, ≥30 ng/mL) and postoperative complications after adjusting for age and sex. Of 314 patients, 222 patients (70.7%) had a 25 (OH) vitamin D level of <30 ng/mL. The mean serum 25 (OH) vitamin D level was 22.6 ng/mL (SD 13.2). In 116 patients (36.9%), postoperative complications were observed, with the most occurring in the short term (95 patients, 30.2%). Late postoperative complications were present in 21 patients (6.7%), most graded as Clavien I (57.1%). Logistic regression analysis identified a low vitamin D level (<30 ng/mL) as an independent risk factor for early postoperative complications (OR 2.06, 95% CI 1.14-3.73, p = 0.016), while no significant correlation was found in late complications (OR 1.08, 95% CI 0.40-2.95, p = 0.879). In conclusion, preoperative 25 (OH) vitamin D serum level might be an independent predictor for early postoperative complications. However, future studies are warranted to determine risk factors for long-term complications and establish appropriate intervention strategies.

The effect of high-dose vitamin D supplementation on hepcidin-25 and erythropoiesis in patients with chronic kidney disease

BACKGROUND

Hepcidin is considered to play a central role in the pathophysiology of renal anemia. Recent studies in healthy individuals have demonstrated a suppressive effect of vitamin D (VD) on the expression of hepcidin. In this post-hoc analysis based on a randomized controlled study, we evaluated the effect of supplementing chronic kidney disease (CKD) patients (stage G3-G4) with a high daily dose of native VD on serum levels of hepcidin-25, the hepcidin/ferritin ratio, as well as on markers of erythropoiesis.

METHODS

Patients with CKD stage G3-G4 included in a double blind, randomized, placebo (PBO) controlled study with available hepcidin measurements were analyzed. Study subjects received either 8000 international units (IU) of cholecalciferol daily or PBO for 12 weeks. We evaluated the change in markers of hepcidin expression, erythropoiesis, and iron status from baseline to week 12 and compared the change between the groups.

RESULTS

Eighty five patients completed the study. Calcitriol, but not 25-hydroxyvitamin D (25(OH) D), was inversely correlated with serum levels of hepcidin-25 (rho = -0,38; p =  < 0, 01 and rho = -0,02; p = 0, 89, respectively) at baseline. Supplementation with VD significantly raised the serum concentration of serum 25(OH)D in the treatment group (from 54 (39-71) to 156 (120-190) nmol/L; p =  < 0, 01)) but had no effect on any of the markers of hepcidin, erythropoiesis, or iron status in the entire cohort. However, we did observe an increase in hemoglobin (HB) levels and transferrin saturation (TSAT) as compared to the PBO group in a subgroup of patients with low baseline 25(OH)D levels (< 56 nmol/L). In contrast, in patients with high baseline 25(OH)D values (≥ 56 nmol/L), VD supplementation associated with a decrease in HB levels and TSAT (p = 0,056) within the VD group in addition to a decrease in hepcidin levels as compared to the PBO group.

CONCLUSION

High-dose VD supplementation had no discernible effect on markers of hepcidin or erythropoiesis in the entire study cohort. However, in patients with low baseline 25(OH)D levels, high-dose VD supplementation associated with beneficial effects on erythropoiesis and iron availability. In contrast, in patients with elevated baseline 25(OH)D levels, high-dose VD supplementation resulted in a decrease in hepcidin levels, most likely due to a deterioration in iron status.

Low vitamin D status is associated with anaemia in hospitalised cats

BACKGROUND

The major physiological role of vitamin D has traditionally been considered to be the regulation of calcium homeostasis and maintenance of skeletal health. However, there is increasing evidence that vitamin D influences a wider range of physiological processes including erythropoiesis. Vitamin D (25-hydroxyvitamin D, 25(OH)D) deficiency concentrations have been associated with anaemia in human beings. In contrast, the relationship between vitamin D status and erythropoiesis has not been investigated in cats.

METHODS

Clinical records of cats consecutively presenting between November 2013 and February 2015 were reviewed. For each cat, data including sex, age, breed, serum albumin and creatinine concentrations, and appetite scores were extracted. A multivariable linear regression model was constructed to examine the relationship between 25(OH)D concentrations and these variables.

RESULTS

Cats with anaemia had significantly lower 25(OH)D concentrations (median 49.5 nmol/l, n=31) than cats with packed cell volume above the lower limit of the reference range (median 109.0 nmol/l, n=130) (P<0.001). A binary logistic regression found that red blood cell count and mean corpuscular volume were negatively correlated with serum 25(OH)D concentrations (P<0.001 and P=0.007, respectively).

CONCLUSION

Vitamin D (25(OH)D) concentration is positively associated with red blood cell count and mean corpuscular volume in cats with a wide range of different illnesses.

Serum Retinol but Not 25(OH)D Status Is Associated With Serum Hepcidin Levels in Older Mexican Adults

1) Background: Elevated hepcidin levels have been linked to anemia of inflammation (AI). Retinol deficiency has shown to upregulate hepcidin expression in animals, while conflicting evidence links VD status with hepcidin concentration in humans. The purpose of the study is to explore if VA and VD status are associated with hepcidin concentrations in older Mexican adults (OA). 2) Methods: A cross-sectional study was conducted in summer 2015, using serum samples from 783 fasting OA ages 60 and above residents from Campeche and Yucatán. VA deficiency (VAD) was defined as serum retinol concentration <20 μg/dL and VD deficiency (VDD) as 25(OH)D <50 nmol/L. The log-hepcidin was the outcome variable expressed as continuous and tertiles of its distribution. Linear and ordinal regression models were used. 3) Results: VAD was present in 3.4% and VDD in 9.5% of OA. Log-retinol was inversely associated with log-hepcidin (coeff.: -0.15, 95%CI: -0.2, -0.09). VAD status shown a higher probability than non-VAD for higher hepcidin tertiles (OR = 2.15, 95%CI: 1.24, 3.74). VDD states was not associated with hepcidin in the linear (coeff.: 0.16, 95%CI: -0.02, 0.34) nor the ordinal model (OR = 0.74, 95%CI: 0.42, 1.28). 4) Conclusions: VAD, but not VDD, status was inversely associated with hepcidin concentrations in OA.

Vitamin D deficiency and anemia is highly prevalent and dependent on the etiology of heart failure: A pilot study

BACKGROUND

Anemia and vitamin D deficiency are common factors in chronic heart failure (CHF). The aim of this study was to assess vitamin D levels as well as its binding protein and anemia in relation to a cause of CHF: coronary heart disease, valvular disease and cardiomyopathy.

METHODS

One hundred and sixteen consecutive patients (36 females and 80 males) with CHF were admitted for percutaneous coronary interventions (PCI). Hemoglobin concentration, serum creatinine, B-type natriuretic peptide (BNP), 25-hydroxyvitamin D [25(OH)D] and its binding protein-VDBP were measured.

RESULTS

The prevalence of anemia was 22%. BNP was the highest in the group with coronary artery disease. Ejection fraction was the lowest in cardiomyopathy group. 25(OH)D was lowest in valvular disease group, significantly lower than in the coronary artery group. A similar pattern of change showed vitamin D binding protein. The prevalence of vitamin D deficiency (level below 20 ng/mL) in the whole group was 95%, in 49% of the patients 25(OH)D was below 10 ng/mL. In univariate analysis 25(OH)D correlated with hemoglobin, red blood cell count, hematocrit, mean corpuscular volume and BNP in patients with CHF in the whole group. In multiple regression analysis, predictors of 25(OH)D were estimated, glomerular filtration rate, BNP and valvular disease.

CONCLUSIONS

25(OH)D deficiency is common in CHF patients. Valvular disease is associated the most severe vitamin D deficiency and worsened kidney function. A higher prevalence of anemia in CHF due to coronary heart disease may be associated with wider use of angiotensin converting enzyme inhibitors and acetylsalicylic acid. Heart and kidney function are predictors of 25(OH)D level in the patients of this study.

Vitamin D Status Is Associated with Hepcidin and Hemoglobin Concentrations in Children with Inflammatory Bowel Disease

BACKGROUND

Anemia, iron deficiency, and hypovitaminosis D are well-known comorbidities in inflammatory bowel disease (IBD). Epidemiologic studies have linked vitamin D deficiency with increased risk of anemia, and in vitro studies suggest that vitamin D may improve iron recycling through downregulatory effects on hepcidin and proinflammatory cytokines.

METHODS

We aimed to investigate the association of vitamin D status with inflammation, iron biomarkers, and anemia in pediatric IBD. Cross-sectional data were obtained from N = 69 patients with IBD aged 5 to <19 years. Iron biomarkers (ferritin, soluble transferrin receptor), and 25-hydroxyvitamin D (25(OH)D), inflammatory biomarkers (C-reactive protein and α-1-acid glycoprotein), hepcidin, and hemoglobin were collected. Iron biomarkers were regression corrected for inflammation. Multivariable logistic/linear models were used to examine the associations of 25(OH)D with inflammation, iron status, hepcidin, and anemia.

RESULTS

Approximately 50% of subjects were inflamed (C-reactive protein >5 mg/L or α-1-acid glycoprotein >1 g/L). Iron deficiency prevalence (inflammation-corrected ferritin <15 μg/L or soluble transferrin receptor >8.3 mg/L) was 67%; anemia was 36%, and vitamin D insufficiency (25(OH)D <30 ng/mL) was 77%. In linear regression models, vitamin D insufficiency was associated with increased hepcidin levels (β [SE] = 0.6 [0.2], P = 0.01) and reduced hemoglobin (β [SE] = -0.9 [0.5], P = 0.046), controlling for age, sex, race, insurance status, body mass index for age, inflammation, disease diagnosis (ulcerative colitis versus Crohn's disease), and disease duration, compared with 25(OH)D ≥30 ng/mL.

CONCLUSIONS

Our results suggest that concentrations of 25(OH)D ≥30 ng/mL are associated with lower hepcidin and higher hemoglobin levels. Further research is needed to clarify the association of vitamin D with inflammation, iron status, and anemia in pediatric IBD.

Randomized supplementation of 4000 IU vitamin D3 daily vs placebo on the prevalence of anemia in advanced heart failure: the EVITA trial

Background

Low 25-hydroxyvitamin D (25OHD) levels (< 75 nmol/l) are inversely associated with anemia prevalence. Since anemia and low 25OHD levels are common in patients with heart failure (HF), we aimed to investigate whether vitamin D supplementation can reduce anemia prevalence in advanced HF.

Methods

EVITA (Effect of Vitamin D on Mortality in Heart Failure) is a randomized, placebo-controlled clinical trial in patients with initial 25OHD levels < 75 nmol/l. Participants received either 4000 IU vitamin D₃ daily or a matching placebo for 36 months. A total of 172 patients (vitamin D group: n = 85; placebo group: n = 87) were investigated in this pre-specified secondary data analysis. Hemoglobin (Hb) and other hematological parameters were measured at baseline and study termination. Assessment of between-group differences in anemia prevalence and Hb concentrations was performed at study termination, while adjusting for baseline differences.

Results

In the vitamin D and placebo group, baseline proportions of patients with anemia (Hb < 12.0 g/dL in females and < 13.0 g/dL in males) were 17.2% and 10.6%, respectively (P = 0.19). At study termination, the proportion of patients with anemia in the vitamin D and placebo groups was 32.2% and 31.8%, respectively (P > 0.99). There was no between-group difference in change in the Hb concentrations (− 0.04 g/dL [95%CI:-0.53 to 0.45 g/dL]; P = 0.87). Results regarding anemia risk and Hb concentrations were similar in the subgroup of patients with chronic kidney disease (vitamin D group: n = 26; placebo group: n = 23). Moreover, results did not differ substantially when data analysis was restricted to patients with deficient baseline 25OHD levels.

Conclusions

A daily vitamin D supplement of 4000 IU did not reduce anemia prevalence in patients with advanced HF. Data challenge the clinical relevance of vitamin D supplementation to increase Hb levels.

Trial registration

The study was registered at EudraCT (No. 2010–020793-42) and clinicaltrials.gov (NCT01326650).

Electronic supplementary material

The online version of this article (doi:10.1186/s12937-017-0270-5) contains supplementary material, which is available to authorized users.

Vitamin D deficiency and anemia risk in children: a review of emerging evidence

There has been renewed scientific interest in the sequelae of vitamin D deficiency, given the emerging evidence on the diverse biologic functions of vitamin D, besides its fundamental role in bone and mineral metabolism. For the past decade, the evidence in the medical literature pointing to a relationship between anemia risk and vitamin D deficiency has been accumulating. This paper critically reviews the current evidence linking vitamin D deficiency to anemia risk in children. The synthesized evidence indicates that the studies, which were preponderantly conducted among the adult population, not only reported a bidirectional relationship between vitamin D deficiency and anemia but also showed a racial effect. In studies conducted among children, similar results were reported. Although the causal association of vitamin D deficiency with anemia risk (especially iron-deficiency anemia) remains debatable, the noncalcemic actions of the vitamin and its analogs hold prospects for several novel clinical applications. There is, however, unanimity in many reports suggesting that vitamin D deficiency is directly associated with anemia of chronic disease or inflammation. Despite the advances in unraveling the role of vitamin D in iron homeostasis, further research is still required to validate causality in the relationship between vitamin D deficiency and anemia, as well as to determine its optimal dosing, the ideal recipients for therapeutic intervention, and the preferred analogs to administer.

Effects of Iron on Vitamin D Metabolism: A Systematic Review

Vitamin D is a prohormone nutrient, which is involved in skeletal and extra-skeletal functions. Iron is another essential nutrient that is necessary for the production of red blood cells and oxygen transport. This element plays important roles in enzymatic systems including those required for Vitamin D activation. To the best of our knowledge, there is no exclusive review on the relationship between iron deficiency anemia (IDA), as the most prevalent type of anemia, and Vitamin D deficiency and the effect of recovery from iron deficiency on Vitamin D status. The aim of this study was to conduct a systematic search of observational and clinical trials in this field. The databases of PubMed, ProQuest, Cochrane Library, ISI Web of Knowledge, and SCOPUS were searched comprehensively. English-language human studies conducted on iron deficient patients or interventions on the effect of iron therapy on Vitamin D were extracted (n = 10). Our initial search yielded 938 articles. A total of 23 papers met the inclusion criteria. Thirteen studies were excluded because they were not relevant or not defining anemia types. The final analysis was performed on ten articles (3 cross-sectional and 7 interventional studies). Observational data indicated a positive relationship between iron status and Vitamin D, while trials did not support the effectiveness of iron supplementation on improving Vitamin D status. The mechanism underlying this association may involve the reduction of the activation of hydroxylases that yield calcitriol. Future randomized controlled trials with large sample sizes and proper designs are needed to highlight underlying mechanisms.

Independent associations of vitamin D metabolites with anemia in patients referred to coronary angiography: the LURIC study

PURPOSE

Anemia and vitamin D deficiency are both frequent in adult patients. Whether low vitamin D metabolite levels are an independent risk factor for different subtypes of anemia remains to be studied in detail.

METHODS

In 3299 patients referred for coronary angiography, we investigated the association of 25-hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D [1,25(OH)₂D] with anemia [hemoglobin (Hb) <12.5 g/dl] of specific subtypes.

RESULTS

Compared with patients with 25OHD levels in the adequate range (50-125 nmol/l), patients with deficient 25OHD concentrations (<30 nmol/l; 33.6 % of patients) had 0.6 g/dl lower Hb levels. Hb values were 1.3 g/dl lower in patients with 1,25(OH)₂D levels <40 pmol/l (5.4 % of patients), compared with patients in the highest 1,25(OH)₂D category (>70 pmol/l). Of the participants, 16.7 % met the criteria for anemia. In multivariate-adjusted regression analyses, the odds ratios for anemia in the lowest 25OHD and 1,25(OH)₂D categories were 1.52 (95 % CI 1.15-2.02) and 3.59 (95 % CI 2.33-5.52), compared with patients with 25OHD levels in the adequate range and patients with 1,25(OH)₂D levels >70 pmol/l. The probability of anemia was highest in patients with combined 25OHD and 1,25(OH)₂D deficiency [multivariable-adjusted odds ratio 5.11 (95 % CI 2.66-9.81)]. Patients with anemia of chronic kidney disease had the highest prevalence of 25OHD deficiency and 1,25(OH)₂D concentrations of <40 pmol/l.

CONCLUSIONS

Low 25OHD and 1,25(OH)₂D concentrations are independently associated with anemia. Patients with poor kidney function are most affected. Interventional trials are warranted to prove whether administration of plain or activated vitamin D can prevent anemia.

Vitamin D Supplementation and Hemoglobin Levels in Hypertensive Patients: A Randomized Controlled Trial

Epidemiological evidence suggests that circulating 25-hydroxyvitamin D (25OHD) levels are inversely associated with hemoglobin (Hb) levels and anemia risk. We evaluated whether vitamin D supplementation improves Hb levels and reduces anemia risk in hypertensive patients. Two hundred patients with 25OHD levels <75 nmol/L who attended the Styrian Vitamin D Hypertension Trial were included, of whom 188 completed the trial. Patients randomly received 2800 IU vitamin D3 daily or a matching placebo for eight weeks. Initially, the prevalence of anemic status (Hb levels <12.5 g/dL) and deficient 25OHD levels (<30 nmol/L) was 6.5% and 7.5%, respectively. All anemic patients had 25OHD levels >50 nmol/L. The mean (95% confidence interval) vitamin D effect on Hb levels was 0.04 (-0.14 to 0.22) g/dL (P = 0.661). Moreover, vitamin D treatment did not influence anemic status significantly (P > 0.999). Likewise, vitamin D had no significant effect on Hb levels in the subgroups of anemic patients or in patients with initial 25OHD levels <30 nmol/L. In conclusion, a daily vitamin D supplement of 2800 IU for eight weeks did not improve Hb levels or anemic status in hypertensive patients. Future trials should focus on anemic patients with deficient 25OHD levels (e.g., <30 nmol/L). This trial is registered with clinicaltrials.gov [NCT02136771].

Vitamin D and anemia: insights into an emerging association

PURPOSE OF REVIEW

The current review highlights recent findings in the emerging association between vitamin D and anemia through discussion of mechanistic studies, epidemiologic studies, and clinical trials.

RECENT FINDINGS

Vitamin D has previously been found to be associated with anemia in various healthy and diseased populations. Recent studies indicate that the association may differ between race and ethnic groups and is likely specific to anemia of inflammation. The mechanism underlying this association involves the reduction of proinflammatory cytokines by vitamin D and the direct suppression of hepcidin mRNA transcription. There is also evidence that vitamin D may be protective against anemia by supporting erythropoiesis. Other calciotropic hormones including fibroblast growth factor 23, and parathyroid hormone have also been found to be associated with iron homeostasis and erythropoiesis.

SUMMARY

Recent advances in our understanding of the association between vitamin D and anemia suggest that maintenance of sufficient vitamin D status may be important in preventing anemia, particularly in diseases characterized by inflammation. Early clinical trials have been promising, but further research is needed to define the efficacy of vitamin D as a future approach for the treatment of anemia.

Vitamin D Status and the Risk of Anemia in Community-Dwelling Adults: Results from the National Health and Nutrition Examination Survey 2001-2006

Low vitamin D status has been implicated in several chronic medical conditions and unfavorable health outcomes. Our goal was to investigate whether serum 25-hydroxyvitamin D (25OHD) levels are a potentially modifiable risk factor for anemia in a nationally representative cohort of community-dwelling individuals in the United States. We performed a cross-sectional study of 5456 individuals (≥17 years) from the National Health and Nutrition Examination Survey from 2001 to 2006. Locally weighted scatterplot smoothing (LOWESS) was used to graphically depict the relationship between serum 25OHD levels and the cumulative frequency of anemia. Multivariable logistic regression models were then used to assess the independent association of 25OHD levels with anemia, while controlling for age, sex, race, body mass index, chronic kidney disease, as well as serum levels of C-reactive protein, ferritin, iron, vitamin B12, and folic acid. The mean (standard error) 25OHD and hemoglobin levels in the analytic group were 23.5 (0.4) ng/mL and 14.4 (0.1) g/dL, respectively. Prevalence of anemia was 3.9%. Locally weighted scatterplot smoothing analysis demonstrated a near-linear relationship between vitamin D status and cumulative frequency of anemia up to 25OHD levels of approximately 20  ng/mL. With increasing 25OHD levels, the curve flattened out progressively. Multivariable regression analysis demonstrated an inverse association of 25OHD levels with the risk of anemia (adjusted odds ratio 0.97; 95% confidence interval 0.95-0.99 per 1  ng/mL change in 25OHD). Compared to individuals with ≥20  ng/mL, individuals with 25OHD levels <20  ng/mL were more likely to be anemic (adjusted odds ratio 1.64; 95% confidence interval 1.08-2.49). In a nationally representative sample of community-dwelling individuals in the United States, low 25OHD levels were associated with increased risk of anemia. Randomized controlled trials are needed to determine whether optimizing vitamin D status can reduce the burden of anemia in the general population.