Urinary zinc excretion and zinc status of patients with beta-thalassemia major

Toward revising dietary zinc recommendations for children aged 0 to 3 years: a systematic review and meta-analysis of zinc absorption, excretion, and requirements for growth

CONTEXT

The Food and Agriculture Organization of the United Nations and the World Health Organization are updating their dietary zinc recommendations for children aged 0 to 3 years.

OBJECTIVE

The aim of this review was to retrieve and synthesize evidence regarding zinc needs for growth as well as zinc losses, absorption, and bioavailability from the diet.

DATA SOURCES

MEDLINE, Embase, and Cochrane Library databases were searched electronically from inception to August 2020. Studies assessing the above factors in healthy children aged 0 to 9 years were included, with no limits on study design or language.

DATA EXTRACTION

Ninety-four studies reporting on zinc content in tissue (n = 27); zinc absorption (n = 47); factors affecting zinc bioavailability (n = 30); and endogenous zinc losses via urine, feces, or integument (n = 40) met the inclusion criteria. Four reviewers extracted data and two reviewers checked for accuracy.

DATA ANALYSES

Studies were synthesized narratively, and meta-analyses of zinc losses and gains as well the subgroups of age, type of feeding, country's income, and molar ratio of phytate to zinc were conducted. Meta-analysis revealed an overall mean (95%CI) urinary and endogenous fecal zinc excretion of 17.48 µg/kg/d (11.80-23.15; I2 = 94%) and 0.07 mg/kg/d (0.06-0.08; I2 = 82%), respectively, with a mean fractional zinc absorption of 26.75% (23.69-29.81; I2 = 99%). Subgrouping by age revealed differences in mean values associated with the transition from milk-based diets to solid food during the first 3 years of life.

CONCLUSION

This review synthesizes data that may be used to formulate zinc requirements in young children. Results should be interpreted with caution because of considerable heterogeneity in the evidence.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42020215236.

Age as a major factor associated with zinc and copper deficiencies in pediatric thalassemia

BACKGROUND

Patients with thalassemia encounter increased consumption of zinc (Zn) and copper (Cu) from chronic hemolysis and increased excretion from iron chelation. Iron-enriched diet restriction may result in low Zn and Cu intakes. Recent data on Zn and Cu status among Thai pediatric patients with thalassemia are lacking. This study aimed to identify frequencies and determine risk factors of Zn and Cu deficiencies among patients with thalassemia.

METHODS

Patients with transfusion-dependent thalassemia (TDT) receiving iron chelation ≥12 months and nonTDT (NTDT) aged 2-20 years were recruited. Serum Zn and Cu were measured. Dietary intakes were ascertained by interviews.

RESULTS

A total of 209 patients (TDT = 126, NTDT = 83) were enrolled. Zn deficiency seemed to be associated with disease severity as median (IQR) Zn level of TDT was lower than that of NTDT [77 (69-85) vs. 80 (72-88) mcg/dL, p = 0.05], while higher frequency of Zn deficiency was identified in the former (24 % vs. 14 %). In TDT, Zn deficiency was associated with patients >10 years (OR 4.6; 95 %CI 1.1-6.4, p = 0.03), which likely resulted from combined low dietary Zn intake, prolonged exposures to hemolysis and iron chelators. Frequencies of Cu deficiency were similarly low in TDT and NTDT (8% and 7%) with comparable median (IQR) Cu levels of 103 (90-124) and 110 (92-132) mcg/dL, respectively (p = 0.13). Cu levels were inversely associated with age (r=-0.65 and r=-0.62 in TDT and NTDT, respectively; p < 0.001).

CONCLUSION

Compared with younger patients, Zn and Cu deficiencies were more common among patients with thalassemia >10 years. Age was a major factor associated with both Zn and Cu deficiencies.

Beta-thalassemia: renal complications and mechanisms: a narrative review

OBJECTIVES

Beta-thalassemias are a group of recessively autosomal inherited disorders of hemoglobin synthesis, which, due to mutations of the beta-globin gene, lead to various degrees of defective beta-chain production, an imbalance in alpha/beta-globin chain synthesis, ineffective erythropoiesis, and anemia. Improved survival in thalassemic patients has led to the emergence of previously unrecognized complications, such as renal disease.

METHODS

A comprehensive literature review through PubMed was undertaken to summarize the published evidence on the epidemiology and pathophysiology of renal disease in thalassemia. Literature sources published in English since 1990 were searched, using the terms beta-thalassemia, renal disease.

RESULTS

Renal disease is considered to be the 4th cause of morbidity among patients with transfusion dependent thalassemia. Chronic anemia, hypoxia and iron overload are the main mechanisms implicated in development of renal injury, whereas several studies also suggested a contributive role of iron chelators.

DISCUSSION AND CONCLUSION

Kidney disease may develop through progressive renal tubular and glomerular damage; thus, its early recognition is important in order to prevent and/or reverse deterioration. This review will provide an insight on the involved mechanisms implicated in kidney disease in thalassemic patients and will discuss the updates on diagnosis and prevention of renal complications in thalassemia.

Nutritional Deficiencies Are Common in Patients with Transfusion-Dependent Thalassemia and Associated with Iron Overload

Patients with thalassemia are frequently deficient in key micronutrients. Attempts to correct these inadequacies through nutritional supplementation have been met with some success, although disparities between intake and circulating levels continue to be observed. This study employed a convenience sample of 41 well-nourished transfusion dependent patients with thalassemia to identify possible mechanisms behind nutritional deficiencies. Each subject completed a Block 2005© Food Frequency Questionnaire (FFQ), through which macro and micronutrient intake was quantified. Fasting blood was drawn to assess vitamins A, C, D, E, copper, selenium, zinc and hematologic parameters. Dietary intake was found to be inadequate compared to Institute of Medicine (IOM) recommendations for many of the fat-soluble vitamins, as well as calcium and zinc. Circulating deficiencies of vitamins C, D, copper, zinc and γ tocopherol were also present in over 20% of patients. Many individuals who consumed an adequate dietary intake had deficient levels of circulating nutrients, which suggest alternative etiologies of nutrient excretion or loss, in addition to higher micronutrient requirements. Liver iron concentration displayed a significant negative relationship with vitamins C (r=-0.62, p<0.001), E (r=-0.37, p=0.03), and zinc (r=-0.35, p=0.037), indicating that in iron-overloaded patients, these nutrients are either endogenously consumed at higher rates or sequestered within the liver, resulting in a functional nutrient deficiency. While this study identified hepatic iron overload to be a significant cause of nutritional deficits commonly observed in patients with thalassemia, multiple etiologies are simultaneously responsible. In response to these findings, nutritional status should be monitored regularly in at-risk patients with thalassemia, and prophylactically addressed with supplementation or aggressive chelation to avoid associated co-morbidities.

The effects of chelators on zinc levels in patients with thalassemia major

Zinc which is an essential element has very important effects on growth and immune system in patients with thalassemia major (TM). The effects of two oral iron chelator agents, desferrioxamine (DFO) and deferiprone (DFP), on zinc levels were investigated in previous studies and they were found to cause zinc deficiency. Zinc level alteration by the new chelator deferasirox (DFX) is not present in the literature. The aim of this study was to examine the effects of different oral chelators on serum and urine zinc levels in TM patients. Zinc levels are compared in the patients who received different chelators: only DFX, combined chelation with DFO plus DFP and the healthy control group. A total of 56 patients with TM were involved in this study: 39 patients received only DFX and 17 patients were given combined treatment DFO+DFP between August 2008 and August 2009. In addition, a control group was established from the healthy population. Blood was taken from all the patients for serum zinc levels and 24hour-urine samples were collected for urine zinc levels. Serum zinc levels were found to be 64.8±14.8μg/dL in DFX group and 66.5±15.1μg/dL in DFO+DFP group. These levels were statistically lower than that in the control group (149±54.3μg/dL) (p<0.05), but there was no statistically difference between the two different chelation groups (p>0.05). The urine zinc levels of DFX and DFO+DFP group were 662.2±428.2μg/day and 1182.3±980.3μg/day respectively (p<0.05). Urinary zinc excretion in the chelation groups (DFX and DFO+DFP) was significantly higher than the control group (395.1±208.9μg/day) (p<0.05). As a conclusion, the new chelation agent, DFX, also leads to zinc deficiency, though its urinary zinc excretion is lower. New studies are required to examine the effects of DFX on zinc extensively. Zinc levels of patients with TM should be followed up regularly and zinc supply should be given at early ages.

Protein antioxidants in thalassemia

It is common knowledge that thalassemic patients are under significant oxidative stress. Chronic hemolysis, frequent blood transfusion, and increased intestinal absorption of iron are the main factors that result in iron overload with its subsequent pathophysiologic complications. Iron overload frequently associates with the generation of redox-reactive labile iron, which in turn promotes the production of other reactive oxygen species (ROS). If not neutralized, uncontrolled production of ROS often leads to damage of various intra- and extracellular components such as DNA, proteins, lipids, and small antioxidant molecules among others. A number of endogenous and exogenous defense mechanisms can neutralize and counteract the damaging effects of labile iron and the reactive substances associated with it. Endogenous antioxidant enzymes, such as superoxide dismutase, catalase, glutathione peroxidase, and ferroxidase, may directly or sequentially terminate the activities of ROS. Nonenzymatic endogenous defense mechanisms include metal binding proteins (ceruloplasmin, haptoglobin, albumin, and others) and endogenously produced free radical scavengers (glutathione (GSH), ubiquinols, and uric acid). Exogenous agents that are known to function as antioxidants (vitamins C and E, selenium, and zinc) are mostly diet-derived. In this review, we explore recent findings related to various antioxidative mechanisms operative in thalassemic patients with special emphasis on protein antioxidants.

Tissue zinc levels in a child with hypercalprotectinaemia and hyperzincaemia: A case report and a review of the literature

BACKGROUND

A girl suffering from a rare syndrome of unknown aetiology, termed hypercalprotectinaemia, was evaluated for tissue zinc status, because calprotectin is a protein which chelates Zn at multiple binding-sites, which might have affected the distribution of Zn in her body.

METHODS

Measurement of serum, urine, hair and nail zinc (Zn) concentration, complemented with measurement of total Zn in ultrafiltrates of plasma.

RESULTS

Her serum Zn concentration was 105-133 μmol/L. Zn levels in her hair (102 μg/g), nail (90 μg/g) and urine (3-12 μmol/L; 20-80 μg/dL) were all at the lower end of the reference intervals described in the sparse literature. Zn concentrations in ultrafiltrates of plasma were below the detection limit (<100 nmol/L). Thus, the elevated serum Zn did not translate into a similarly increased level of Zn in any of the tissues tested, nor in free Zn concentrations. Instead it appeared to be a result of Zn being chelated to binder proteins, most probably calprotectin.

CONCLUSION

Her grossly elevated serum calprotectin concentration is probably able to raise circulating total Zn concentrations without raising ionized concentrations, but this Zn remains confined to the circulating blood as well as to excreted body fluids, particularly faeces.

Early markers of renal dysfunction in patients with beta-thalassemia major

Studies of renal involvement in thalassemia syndromes have been varied and few. The most important cause of mortality and morbidity in these patients is organ failure due to iron deposition. We report here a cross-sectional study carried out between February 2005 and February 2006 on all beta-thalassemia major patients being treated in Mofid Children's hospital, Tehran. The aim of the study was to detect renal dysfunction in these patients. The patient cohort consisted of 103 patients with various disease severities. Fresh first morning urine samples were collected and analyzed for sodium (Na), potassium (K), calcium (Ca), creatinine (Cr), phosphate, uric acid (UA), N-acetyl beta-D-glucosaminidase (NAG) and amino acids. We also carried out a complete blood count evaluation and assayed fasting blood sugar and serum ferritin, sodium, potassium, creatinine, uric acid and amino acids in all patients. The mean age of our patient cohort was 12.5+/-5.53 years and 53.4% were female. Abnormal levels of urinary NAG were detected in 35.9% of patients (confidence interval 26-45%). Abnormal levels of fractional excretion (FE)-Na, FE-K and FE-UA and abnormal urine protein Pr/Cr and urine Ca/Cr ratios were present in 29.1, 7.8, 52.4, 0.3 and 22.3% of the patients, respectively. There was a significant relationship between urinary NAG and the age of the patient (R=0.35), duration of deferoxamine therapy (R= 0.31), duration of receiving blood transfusions (R=0.34) and level of fasting blood sugar (R=0.2). We concluded that renal disorders are not rare in patients with beta-thalassemia major and that they may increase in terms of frequency with age, increased duration of transfusion and deferoxamine usage and high levels of blood sugar.

Zinc status in patients with major beta-thalassemia

To determine the zinc status in patients with major beta-thalassemia and its effect on their growth, the authors studied 64 thalassemic patients in comparison with 64 healthy matched individuals. Demographic and anthropometric data and history of the therapies were collected. Serum zinc level in both groups and ferritin in the thalassemic group were assigned. Interestingly, mean serum zinc level was significantly higher in the thalassemic group. No significant correlation between serum zinc level and short stature, serum ferritin level, desferrioxamine dose, initiating time of blood transfusion, and chelation therapy was found. The study indicates zinc deficiency in thalassemic patients who are on regular blood transfusion is rare and it seems that routine zinc supplementation is not necessary.

Growth impairment in beta-thalassemia major: the role of trace element deficiency and other potential factors

A serious problem in thalassemia major is growth impairment for which several possible etiologies have been proposed. Sixty-seven patients with thalassemia were randomly enrolled into the study, divided into 2 groups with and without growth failure and the correlation between growth failure and the following parameters was evaluated: age, sex, serum ferritin level, serum zinc and copper concentrations, serum copper-zinc ratio, regularity of blood transfusion, and the regularity and duration of chelation therapy. Among all studied parameters, only age, duration, and type of chelation therapy and age of beginning chelation therapy were significantly different between the 2 groups. Binomial multivariate logistic regression showed that the only significant independent correlation was between age and growth failure. A 1-year increase in age is associated with a 1.57-fold increase in the risk of growth impairment. The results of this study indicated that a temporally cumulative damage to growth-mediating mechanisms except those considered here is responsible for growth failure in thalassemia major.

Neurological complications in beta-thalassemia

Over the years, several reports have demonstrated involvement of the nervous system in beta-thalassemia patients. Neurological complications have been attributed to various factors such as chronic hypoxia, bone marrow expansion, iron overload, and desferrioxamine neurotoxicity. In most cases, neurological involvement does not initially present with relevant signs or symptoms (i.e., is subclinical) and can only be detected during neurophysiological or neuroimaging evaluation. Abnormal findings in the visual, auditory, and somatosensory evoked potential recordings are mainly attributed to DFO neurotoxicity. On the other hand, nerve conduction velocity abnormalities are associated either to chronic hypoxia and older age or to hemosiderosis, whether by means of pancreas involvement or not. Neuropsychological studies available reveal a considerably high prevalence of abnormal IQ, not correlating, however, to factors such as hypoxia or iron overload. It is proposed that factors associated to severe chronic illness, rather than the disease per se, could be responsible for these findings. Such factors include regular school absence due to transfusions and frequent hospitalizations, physical and social restrictions resulting from the disease and its treatment, abnormal mental state due to the awareness of being chronically ill, and, last, the overly protective family attitude that leads to restricted initiative and psychosocial development. As life expectancy for beta-thalassemia patients extends, the use of neurophysiologic and neuropsychologic monitoring becomes imperative, enabling early detection of neural pathway impairment and allowing for appropriate management, in order to achieve a better life quality for this patient group.

Desferrioxamine mesylate for managing transfusional iron overload in people with transfusion-dependent thalassaemia

BACKGROUND

Thalassaemia major is a genetic disease characterised by a reduced ability to produce haemoglobin. Management of the resulting anaemia is through transfusions of red blood cells. Repeated transfusions results in excessive accumulation of iron in the body (iron overload), removal of which is achieved through iron chelation therapy. Desferrioxamine is the most widely used iron chelator. Substantial data have shown the beneficial effects of desferrioxamine. However, important questions exist about whether desferrioxamine is the best schedule for iron chelation therapy.

OBJECTIVES

To determine the effectiveness (dose and method of administration) of desferrioxamine in people with transfusion-dependent thalassaemia.

SEARCH STRATEGY

We searched the Cochrane Haemoglobinopathies Trials Register, MEDLINE, EMBASE, ZETOC, Current Controlled Trials and bibliographies of relevant publications. We also contacted the manufacturers of desferrioxamine and other iron chelators. Date of last searches: April 2004.

SELECTION CRITERIA

Randomised controlled trials comparing desferrioxamine with placebo; with another iron chelator; or comparing two schedules of desferrioxamine, in people with transfusion-dependent thalassaemia.

DATA COLLECTION AND ANALYSIS

Four authors working independently, were involved in trial quality assessment and data extraction. Missing data were requested from the original investigators.

MAIN RESULTS

Eight trials involving 334 people (range 20 to 144 people) were included. One trial compared desferrioxamine with placebo, five compared desferrioxamine with another iron chelator (deferiprone) and two compared different schedules of desferrioxamine. Overall, few trials measured the same outcomes.Compared to placebo, desferrioxamine significantly reduced iron overload. The number of deaths at 12 years follow up and evidence of reduced end-organ damage was less for desferrioxamine than placebo. When desferrioxamine was compared to deferiprone or a different desferrioxamine schedule there were no statistically significant differences in measures of iron overload. Compliance was recorded by two trials. Compliance was less for desferrioxamine than deferiprone in one trial and of no difference in comparison with desferrioxamine and deferiprone combined with a second trial. Adverse events were recorded in trials comparing desferrioxamine with other iron chelators. There was evidence of adverse events in all treatment groups. In one trial, adverse events were significantly less likely with desferrioxamine than deferiprone, relative risk 0.45 (95% confidence interval 0.24 to 0.84). Assessment of the methodological quality of included trials was not possible, given the general absence of these data in the trials.

AUTHORS' CONCLUSIONS

We found no reason to change current treatment recommendations. However, considerable uncertainty continues to exist about the optimal schedule for desferrioxamine in people with transfusion-dependent thalassaemia.