Impaired zinc and copper status in children with burn injuries: Need to reassess nutritional requirements
Introduction
Burn injuries are accompanied by major metabolic, endocrine and immune changes. Patients with these injuries have higher energy expenditure and greater chances of infections and malnutrition [1]. In addition, impaired intestinal motility and hormonal imbalance may induce nutritional deficiencies [2]. Trace element alterations that have been associated with burns are primarily zinc (Zn) and copper (Cu) [1], [3], [4], [5], [6], [7]. Presumably, these effects are the result of tissue breakdown and increased urinary excretion. This paper will focus on the status of these two nutrients, zinc and copper, that are known for their role in wound healing [1], [8], immunity [9], [10], [11], and anti-oxidant activities [8], [9].
Major burns are associated with reduced bone formation and resorption in both adults and children [13], [14]. Both zinc and copper play a role in collagen cross-linking and, therefore, aid in the normal formation of bone matrix [12]. Zinc stimulates bone formation and mineralization, and reduces bone resorption [12]. Copper is involved in the cross-linking of the collagen and bone turnover [8]. Deficiencies of zinc [1], [3], [4], [5], [6], [7] and copper [1], [3], [4], [5], [6], [7] have been reported following burn injury, but the pathogenesis of these deficiencies remains unclear. However, urinary zinc and copper excretion have been reported to be elevated post-burn [1], [23].
Calcium (Ca) also plays a major role in bone formation. This nutrient is essential for growth, development, and strength of bone, as well as serving as a reservoir to support the body's increased metabolic needs following burn injury [15]. Calcium deficiency in childhood, especially the prepubertal period, also can impair bone development [15]. Thus, calcium supplements are given to children with burn injury to offset bone loss. However, it is possible that excessive calcium might have negative consequences on bone if it diminishes absorption of minerals such as zinc and copper [16], [17].
Adequate status of zinc is critical in children as it is required for the functioning of numerous enzymes involved in growth and development [18], structural strength of bone, regulation of gene function and stability of cell membranes [9], [28], [37]. Copper functions as a co-factor of several cellular enzymes that are involved in free radical scavenging, electron transport system, pigmentation and elastin and collagen cross-linking [8]. Adequate status of these minerals may be particularly difficult to monitor in children with burns due to rapid growth and hormonal changes [19]. Thus, the aims of this preliminary study were to assess Zn and Cu status in children following burn injury and the adequacy of provision of these micronutrients during hospitalization.
Section snippets
Methods
Study subjects (n = 6) were recruited from children admitted to the Shriners Burns Hospital, Galveston, TX, with burns ≥40% total body surface area (TBSA). Patients were excluded if they had chronic disease or renal failure. Parents of the children were explained the nature and risks of the study and informed consent was obtained. This study was approved by the Institutional Review Boards of The University of Texas Medical Branch at Galveston and The University of Texas at Austin.
Blood, wound
Results
The profile of the children with burn injuries is shown in Table 1. The subjects were of both sexes, with an average 10.2 ± 2.3 years of age and 29.3 ± 7.5 kg of weight. The mean TBSA was 54 ± 9%, ranging from 47% to 72%. All the children, except one, had their burn injuries due to flame. Three patients lost weight, two gained weight, and the sixth did not have a discharge weight available.
Selected nutrient intakes of children with burn injuries in the hospital are given in Table 2. All the children
Discussion
This study suggests that zinc and copper depletion accompanied major burns in children, despite dietary intakes that were at least three times that of the DRIs [21]. Thus, a diet that satisfies the DRI for mineral intakes (5–8 mg/d for zinc, 0.44–0.7 mg/d for copper and 800–1300 mg/d for calcium) [21] for normal children did not appear to be sufficient to restore plasma levels in children with burn injuries. Given that bone mineral content, formation and resorption are reduced following severe
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