Zinc metabolism in patients with severe burns

Dietary phytate, zinc and hidden zinc deficiency

Epidemiological data suggest at least one in five humans are at risk of zinc deficiency. This is in large part because the phytate in cereals and legumes has not been removed during food preparation. Phytate, a potent indigestible ligand for zinc prevents it's absorption. Without knowledge of the frequency of consumption of foods rich in phytate, and foods rich in bioavailable zinc, the recognition of zinc deficiency early in the illness may be difficult. Plasma zinc is insensitive to early zinc deficiency. Serum ferritin concentration≤20μg/L is a potential indirect biomarker. Early effects of zinc deficiency are chemical, functional and may be "hidden". The clinical problem is illustrated by 2 studies that involved US Mexican-American children, and US premenopausal women. The children were consuming home diets that included traditional foods high in phytate. The premenopausal women were not eating red meat on a regular basis, and their consumption of phytate was mainly from bran breakfast cereals. In both studies the presence of zinc deficiency was proven by functional responses to controlled zinc treatment. In the children lean-mass, reasoning, and immunity were significantly affected. In the women memory, reasoning, and eye-hand coordination were significantly affected. A screening self-administered food frequency questionnaire for office might help caregiver's identify patients at risk of zinc deficiency.

Effects of scalding injury on the components of rabbit paw lymph

A technique for lymph collection has been described. Rabbit paw lymph was collected by this technique before and after scalding injury (75 degrees C for 20 s). The lymph concentrations of zinc, copper, iron, cobalt and lipid peroxide were measured. After scalding, the lymph flow increased rapidly and reached a maximum at 1 h, and then decreased gradually. The lymph concentrations of copper, iron and cobalt increased about two-fold in the first 30 min and the elevated levels persisted until 4 h. However, the increase of zinc was less than that of the other three metals. Total protein concentrations also increased twofold in lymph and the elevated level persisted for 4 h. Using gel filtration, the elution pattern of lymph after scalding was almost the same as that before scalding. Lipid peroxide in lymph increased about three-fold following scalding. However, the plasma concentrations of total protein and lipid peroxide did not change significantly following scalding.

Serum zinc response in thermal injury

Zinc is an essential trace element required for RNA and DNA synthesis and the function of over 200 zinc metalloenzymes. After surgery or trauma, the serum zinc concentration usually decreases. The magnitude and duration of this hypozincemia after thermal injury are unclear, as are mechanisms for this hypozincemia. In this study we evaluated, over the duration of their hospital course, serum zinc concentrations in 23 thermal injury patients. The initial mean serum zinc concentration was significantly depressed (42 +/- micrograms/dl; normal 66-110 micrograms/dl). By the second week of hospitalization, serum zinc concentrations gradually increased into the normal range in the majority of patients. Mechanisms for this hypozincemia were evaluated. Decreases in the serum zinc concentration did not correlate with increased urinary zinc excretion; thus increased urinary zinc excretion was an unlikely mechanism for the observed hypozincemia. Values for albumin, the major zinc binding protein in serum, generally were inversely correlated with the serum zinc concentration. Thus, hypoalbuminemia could not explain the decreased serum zinc concentration. Certain cytokines such as interleukin-1 are known to cause a decrease in the serum zinc concentration as part of the acute phase response. Therefore, we measured serum C reactive protein concentrations as an indicator of the acute phase response. Thermally injured patients initially had markedly elevated C-reactive protein levels which gradually decreased during hospitalization. We suggest that the initial hypozincemia observed in thermally injured patients may be a reflection of interleukin-1 mediated acute phase response. Whether one should vigorously attempt to correct this initial marked hypozincemia requires further investigation.

Clinical studies on zinc metabolism during total parenteral nutrition as related to zinc deficiency

In 99 adult patients receiving controlled total parenteral nutrition (TPN), a study was made on the time course of concentrations of zinc in plasma, erythrocyte and urine in relation to the development of zinc deficiency. Zinc deficiency developed in 11 cases receiving TPN solutions not containing zinc. The plasma zinc level was significantly lower at the time of onset of zinc deficiency than in normal subjects, before the procedure of TPN, or at the time of symptomatic relief achieved by administration of zinc. The erythrocyte zinc level was slightly but not significantly lower at time of onset of zinc deficiency than in normal subjects, before TPN or at time of symptomatic relief. The urinary zinc level at time of onset of zinc deficiency was significantly lower than that in normal subjects or at the time of symptomatic relief but not significantly lower than that before TPN. A comparison between patients developing and those not developing zinc deficiency within 4 wk of the outset of TPN showed that only the plasma zinc level was significantly lower in the former than the latter group. The urinary zinc level also tended to be lower, although not significantly, in the former than the latter group but varied widely. No difference was present between the groups as to the erythrocyte zinc level. Zinc deficiency developed in none of those patients who had a plasma zinc level of 50 micrograms/dl or more but in five of 10 (50%) patients with less than 50 micrograms/dl and in all three with less than 30 micrograms/dl of zinc in plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Association between urinary zinc excretion and lymphocyte dysfunction in patients with lung cancer

Patients with bronchogenic carcinoma often have low serum zinc concentrations and sometimes have markedly elevated renal zinc losses. Since normal zinc metabolism is critical for the proper function of T lymphocytes and natural killer cells, the effect of zinc status on T cell phytohemagglutinin response and peripheral blood lymphocyte natural killer cell activity was studied in patients with lung cancer. Mean (+/- SEM) serum zinc concentration in 75 patients with cancer was 67.4 +/- 2.2 micrograms/dl versus 96.0 +/- 8.0 micrograms/dl for normal subjects. Patients with low serum zinc levels (less than 70 micrograms/dl) had significantly higher urine zinc excretion than patients with normal serum zinc levels (1,385 +/- 240 micrograms per 24 hours versus 392 +/- 107 micrograms per 24 hours) (p less than 0.001). This pattern of zinc concentrations (i.e., low serum zinc in combination with high urine zinc) is typical of patients with mild zinc deficiency, and suggests that a mild chronic zinc deficiency state was present in some of these patients. When lymphocyte data were analyzed according to serum zinc concentrations and urinary zinc excretion, low serum zinc concentration and high urine zinc excretion both correlated with depressed T cell phytohemagglutinin response (p less than 0.005 and p less than 0.001, respectively). For instance, mean maximal phytohemagglutinin response in patients with urinary zinc excretion of more than 700 micrograms per 24 hours was 22,132 +/- 3,201 cpm (n = 14) compared with 68,130 +/- 6,850 cpm for patients with normal zinc excretion (n = 7). Peripheral blood lymphocyte natural killer cell activity did not correlate with either serum or urine zinc values. Oral zinc sulfate (220 mg, three times daily for six weeks) was then administered to patients with hyperzincuria (mean = 992 micrograms per 24 hours). Zinc-supplemented patients had normalization of T cell phytohemagglutinin response after zinc therapy, whereas control patients demonstrated continued T cell dysfunction. Natural killer cell activity did not change in either group during the study period. These data suggest that a mild subclinical zinc deficiency state may exist in some patients with lung cancer and may be an important cause of abnormal T cell function. Furthermore, zinc supplementation may be useful to improve lymphocyte function in selected patients. Whether zinc supplementation would alter the course of the disease or the patient's prognosis is presently unknown.

Studies on the serum levels of iron, copper and zinc and the urinary excretion of zinc after burn injury

The levels of iron, copper and zinc in the serum of patients suffering burn injuries were measured. It was observed that serum zinc and copper did not change significantly after burn injury; values lying outside the laboratory's own normal range were rarely observed. There was a considerable increase in the output of zinc in the urine after burn injury. Raised levels of zinc in the urine were not observed until about a week after injury, but after that time highly significant changes occurred. The considerable day-to-day variation in zinc output suggests that a variety of causes give rise to the increased zinc excretion.

[Serum levels of magnesium and zinc after a controlled thermal trauma of the rat (author's transl)]

After a thermal trauma similar changes of Mg and Zn levels in serum are observable. During the initial period of shock the concentration of both elements increases as a consequence of damage of cellular and subcellular compartments. During the catabolic phase a deficiency syndrome occurs as a result of renal excretion, loss through the wound secretion, and demarcation of necrotic tissue. On the other hand increasing requirements of Mg and Zn appear because of the anabolic process of wound healing. From these reasons a substitution of both elements is recommendable in all cases of proved deficiency after burns.

Treatment of burns with zinc-tape. A study of local absorption of zinc in humans

A report is given on local wound treatment in humans with adhesive zinc-tape. Measurements of the zinc content of the tape before and after treatment and in wound secretion and serum demonstrate that zinc is most likely absorbed into the granulation tissue and serum. The possible advantages of local absorption of zinc are discussed. The evaporative water losses through the tape have also been recorded. The fresh zinc-tape is almost impermeable to water. After 24 hours of burn treatment the evaporative water loss through the tape is similar to the water loss through a homograft.

[Study of the zinc levels in serum and erythrocytes in burn patients (author's transl)]

Following a statistical study of four groups of burned people, determined in function of the UBS coefficient, a curve of blood zinc variations has been drawn:Immediately after burning, blood zinc is low. It rises to normal and then increases above normal. A group of patients (very serious or lethal burns) definitely differs from the others in respect of an important and persistent fall of blood zinc. These blood zinc values suggest a possible need for a zinc supply to this group of patients.

Zinc and copper urinary excretions in children with burns and scalds

The daily urinary losses of zinc and copper have been measured over periods of up to 12 days following thermal injury in 18 children. Comparison with measurements of zinc and copper excretions in 35 control children showed that after injury by burning or scalding, the urinary excretions of both metals were increased in many of the patients. After severe injury, high urinary outputs of zinc and copper persisted for up to two months following injury.

Plasma and urinary zinc in patients with malabsorption syndromes or hepatic cirrhosis

Plasma and urinary zinc have been measured in 19 patients with malabsorption and 21 patients with hepatic cirrhosis. The results have been compared with those of 20 control subjects and 23 patients with a variety of other diseases. The diurnal variation in plasma zinc levels has been confirmed and is of such magnitude that this must be taken into account in comparing results in groups of subjects. Plasma zinc levels, both fasting and after a meal, are significantly lower in patients with cirrhosis (71 and 60 mug/100 ml) and malabsorption (76 and 64 mug/100 ml) than in controls (97 and 81 mug/100 ml). In the patients with cirrhosis or malabsorption similar correlations exist between plasma zinc and plasma albumin, suggesting that the low plasma zinc levels may be, at least in part, dependent on the plasma albumin level. Urinary zinc excretion is increased in cirrhosis, but not in malabsorption, indicating that increased urinary loss is unlikely to explain the low plasma levels.