Clinical, endocrinological and biochemical effects of zinc deficiency

Zinc levels in women and newborns

Zinc is an important trace element having a definitive role in the metabolism, growth and development and reproduction. During pregnancy the requirements for zinc increase. This study was designed to evaluate the zinc status of normal women, normal pregnant women and their newborn babies. Forty normal adult females, 40 normal pregnant women and their newborn babies were randomly selected and their serum and hair zinc levels were analysed using atomic absorption spectrophotometer. The mean serum and hair zinc levels in normal women were 69.47 +/- 1.4 micrograms/dl and 147.45 +/- 6.12 micrograms/g respectively. The mean serum and hair zinc levels in normal pregnant women were 69.0 +/- 3.22 micrograms/dl and 142.83 +/- 4.39 micrograms/g respectively while the mean serum (cord blood) and hair levels in normal new born babies were 72.77 +/- 5.14 micrograms/dl and 188.36 +/- 4.12 micrograms/g respectively. There was a significant (p < 0.001) decrease in hair zinc levels during pregnancy. There was a significant (p < 0.05) decrease in zinc levels in new born babies when the time interval between the previous delivery and the present delivery was less than 3.4 years. The results of the present study reinforce the need for zinc supplementation during pregnancy especially if the interval between pregnancies is short.

Zinc sulfate supplementation improves thyroid function in hypozincemic Down children

In subjects affected by trisomy 21 (Down syndrome), hypothyroidism is the most common endocrinological deficit. Plasma zinc levels, which are commonly detected below the normal range in Down patients, are related to some endocrinological and immunological functions; in fact, zinc deficiency has been shown to impair immune response and growth rate. Aims of this study were to evaluate (1) the role of zinc deficiency in subclinical hypothyroidism and (2) thyroid function changes in Down children cyclically supplemented with zinc sulfate. Inverse correlations have been observed between age and triiodotironine (T3) and between zinc and thyroid-stimulating hormone (TSH); higher TSH levels have been found in hypozincemic patients at the beginning of the study. After 6 mo of supplementation, an improvement of thyroid function (TSH levels: 3.96 +/- 1.84 vs 2.64 +/- 1.33 mUI/mL basally and after 6 mo, respectively) was observed in hypozincemic patients. In the second cycle of supplementation, a similar trend of TSH was observed. At the end of the study, TSH significantly decreased in treated hypozincemic subjects (4.48 +/- 1.93 vs 2.96 +/- 1.20 mUI/mL) and it was no longer different in comparison to normozincemic patients. We suggest zinc supplementation to the diet in hypozincemic Down children as a simple and useful therapeutic tool.

Melatonin administration in tumor-bearing mice (intact and pinealectomized) in relation to stress, zinc, thymulin and IL-2

Melatonin (MEL) may counteract tumors through a direct oncostatic role. MEL is also an antistress agent with immunoenhancing properties against tumors due to a suppressive role of MEL on corticosterone release. Rotational stress (RS) (spatial disorientation) facilitates metastasis progression in mice. Also, MEL counteracts tumors because of its influence on immune responses via the metabolic zinc pool, which, is reduced in tumors and stress. Zinc is required for normal thymic endocrine activity (i.e. thymulin) and interleukin-2 (IL-2) production. Because in vivo data is still controversial, exogenous MEL treatment (22 days in drinking water) in both intact and pinealectomized (px) mice bearing Lewis lung carcinoma leads to significant decrements of metastasis volume, restoration of the negative crude zinc balance, recovery of thymulin activity and increment of IL-2 exclusively in intact and px tumor bearing mice subjected to RS. Significant inverse correlations are found in both stressed intact and px tumor bearing mice after MEL treatment between zinc and corticosterone (r = 0.78, P < 0.01; r = 0.80, P < 0.01, respectively). Positive correlations between zinc and IL-2 (r = 0.75, P < 0.01; r = 0.73, P < 0.01, respectively) or thymulin (r = 0.75, P < 0.01; r = 0.82, P < 0.01, respectively) are observed in same models of mice. These findings suggest a MEL action to decrease metastasis mediated by a possible interplay between zinc and MEL, via corticosterone, with consequent restoration of thymic efficiency and IL-2 production. MEL as an antistress agent with immunoenhancing properties in cancer deserves further consideration.nuclear factor-kb; POMC, proopiomelanocortin; Px, pinealectomized mice; RIA, radioimmunoassay; RS, rotational stress; SDI, stressed intact mice; SDPx, stressed pinealectomized mice; TNF-alpha, tumor necrosis factor-alpha; ZnFTS, active zinc-bound thymulin; ZnFTS + FTS, total thymulin.

Treatment of asthenozoospermia with zinc sulphate: andrological, immunological and obstetric outcome

OBJECTIVES

The role of zinc therapy on infertility caused by defective sperm quality is examined.

STUDY DESIGN

In this study, 100 men with asthenozoospermia were randomised into two groups--250 mg twice daily zinc therapy for 3 months and no therapy. The patients were followed up for another 6 months. Sperm parameters, circulating antisperm antibodies, sex hormones and T helper cytokines were evaluated before and after treatment for the two groups.

RESULTS

There was significant improvement in the sperm quality; sperm count (P<.02), progressive motility (P<.05), fertilising capacity (P<.01) and a reduction in the incidence of antisperm antibodies (P<.01). Zinc/cadmium was higher in the zinc therapy group (P<.02). T helper cytokine, interleukin-4 level was significantly higher after zinc therapy (P<.02) while TNFalpha showed a significant decrease (P<.05).

CONCLUSIONS

Zinc therapy has a role in improving sperm parameters in men with asthenozoospermia, probably through its membrane stabilising effect as an antioxidant and its effect on cellular and humoral immunity by reducing the levels of antisperm antibodies and TNFalpha and increasing that of IL-4.

Presence of links between zinc and melatonin during the circadian cycle in old mice: effects on thymic endocrine activity and on the survival

Links between zinc and melatonin in old melatonin treated mice with a reconstitution of thymic functions have been recently documented. Concomitant increments of the nocturnal peaks of zinc and melatonin, with a synchronization of their circadian patterns, are achieved in old mice after melatonin treatment. A recovery of the nocturnal peaks of thymulin plasma levels and of the number of thymulin-secreting cells with a synchronization of their circadian patterns are also achieved. The existence of significant positive correlations between melatonin and zinc and between melatonin and thymulin or the number of thymulin-secreting cells supports the presence of links between zinc and melatonin also during the circadian cycle with a beneficial effect on thymic functions. The altered circadian pattern of corticosteron in old mice is normalized by melatonin. The existence of inverse correlations between corticosteron and melatonin, between corticosteron and zinc and between corticosteron and thymulin or the number of thymulin-secreting cells during the whole circadian cycle, suggests the involvement of glucocorticoids pathway in the melatonin thymic reconstitution, via zinc. The presence of an interplay among zinc, melatonin, glucocorticoids and thymulin may be, therefore, supported during the circadian cycle. 'In vitro' experiments from old thymic explants show a direct action of zinc, rather than melatonin, on thymulin production, further suggesting that the action of melatonin on the thymic efficiency is mediated by the zinc bioavailability. The beneficial effect of the links between zinc and melatonin on thymic functions during the circadian cycle, may be extended to a prolonged survival in aging, where, however, zinc may be more involved.

Zinc, thymic endocrine activity and mitogen responsiveness (PHA) in piglets exposed to maternal aflatoxicosis B1 and G1

Growth retardation, thymic involution and impaired peripheral immune efficiency are constant events in piglets exposed to maternal aflatoxicosis. Zinc may play a key role because of its requirement for good immune responses, including thymic endocrine activity. Zinc is required to activate a thymic hormone, i.e. thymulin (ZnFTS), which is responsible for cell-mediated immunity. Zinc deficiency and decreased thymic endocrine activity are present in piglets fed from sows exposed to aflatoxins (AF) B1 and G1 as compared with healthy control piglets. In particular, active ZnFTS is decreased while concentrations of inactive thymulin (FTS) are high. The in vitro addition of zinc up to the plasma samples induces a reduction of inactive thymulin. The lymphocytes mitogen responsiveness (PHA) is decreased and a thymic cortical lymphocyte depletion is also present. These data suggest that the thymic defect, followed by impaired peripheral immune efficiency, may largely depend by the low peripheral zinc bioavailability to saturate all thymulin molecules produced.

Zinc-induced alterations in contractile properties of rat diaphragm muscle in vitro

The effect of zinc ions on the isometric contraction of rat diaphragm muscles in the presence and in the absence of external calcium was studied. Using a transducer, the isometric force was measured as a function of supramaximal electrical stimulation, either directly or indirectly applied to the muscle. The following parameters were measured: peak twitch tension, PT, twitch contraction time, CT, relaxation half-time, RT-1/2, and peak rates of tension increase and decrease, +dP/dt and -dP/dt. The following zinc-induced alterations were observed: an increase of the PT; a decrease of the RT-1/2; an increase in the +dP/dt and -dP/dt. The CT was not changed significantly. Our results suggest that zinc ions have a positive inotropic effect on isolated diaphragm muscle. The increase in PT may be explained by a zinc-activated Ca2+ uptake by sarcoplasmic reticulum. This was followed by an increase in the rate of rise of tension development, which was secondary to increased -dP/dt. The mechanism(s) by which extracellular Ca2+ contributes to this action of zinc is not known.

Studies on 'zinc deficiency syndrome' in black bengal goats (Capra hircus) fed with fodder (Andropogon gayanus) grown on soil treated with an excess of calcium and phosphorus fertilizer

Overliming and excessive application of superphosphate caused a zinc deficiency in the soil and so reduced the uptake of zinc by fodder plants. Bucks reared on such fodder had significantly (p < 0.01) less zinc in their hair compared with controls and suffered from 'conditioned zinc deficiency syndrome' with a significant (p < 0.01) loss of body weight, stunted growth, alopecia, lethargy, abnormal (kyphotic) gait, anorexia, digestive and respiratory problems. Oral supplementation with zinc sulphate very rapidly improved these conditions to near normality. Histological examination of samples of skin and testis from the zinc-deficient bucks revealed formation of excessive keratin, retention of nuclei in the stratum corneum and reduction in the width of the stratum granulosum in the skin, while samples of testis indicated degenerative changes, including atrophy of the seminiferous tubules, hyperplasia of the germinal epithelium and thickening of the walls of blood vessels.

Zinc and metallothioneins on cellular immune effectiveness during liver regeneration in young and old mice

Partial hepatectomy in young mice (pHx) induces thymic atrophy, disregulation of thymocytes subsets and a strong accumulation of zinc in thymic tissue after 1-2 days of liver regeneration. Zinc is relevant for good immune functioning. Restoration of zinc into both the thymus and thymocytes subsets in the late period of liver regeneration is observed in young pHx mice. These findings have suggested a link between the thymus and the liver influencing T-cell functions and involving zinc. This kind of link could be relevant in aging because thymic involution, negative crude zinc balance and crippled immune functions are constant events. The preminence of a liver extrathymic T-cell pathway after pHx or during aging has been suggested. Thus the study of pHx in young and old mice may offer a good model to better understand the role played both by thymic involution and by liver extrathymic T-cell pathway and the role of zinc in these physiological processes during aging. Young pHx mice after 1-2 days of liver regeneration show: reduced thymic endocrine activity, increment of double negative (DN) thymocytes subsets, impairment of peripheral immune efficiency (PHA, NK activity and IL-2) and negative crude zinc balance, which are all restored in the late period of liver regeneration. By contrast the thymic and peripheral immune defects and the negative crude zinc balance, already present in old sham mice, are not modified during liver regeneration in old pHx mice. Circulating leukocytes and lymphocytes are not significantly modified both in young and old pHx mice as compared to respective sham controls. Zinc may also be crucial for extrathymic T-cells pathway, being preminent in aging, rather than in young age, due to its metallothioneins (MT) binding capacity. MT are significantly increased in young pHx and in aging inducing a low zinc-free quota for thymic and peripheral immune efficiency in young pHx mice, and for extrathymic T-cell pathway, in old age. Thus low zinc bioavailability, due to MT, may play a pivotal role, not only for thymocytes but also for liver extrathymic T-cell pathway.

Circadian melatonin and young-to-old pineal grafting postpone aging and maintain juvenile conditions of reproductive functions in mice and rats

Chronic, night administration of melatonin to aging mice and transplantation of a young pineal gland into the thymic rudiment of older mice and rats have been studied with the aim of evaluating their effects on aging of gonadal, sexual, and reproductive functions. Both melatonin administration and young-to-old pineal grafting positively affect size and function of testes and maintenance of juvenile hippocampal and testicular LHRH-receptors and beta-adrenergic receptors in the tests of old rats and mice. These results demonstrate that a pineal-directed circadian function and cyclicity is fundamental for the regulation of sexual, reproductive physiology, and that proper intervention with melatonin may potentially postpone aging of both neural and gonadal sexual function.

pH-induced transition and Zn2+-binding properties of bovine prolactin

A pH-induced conformational transition was found in bovine prolactin within the physiologically significant pH region from 6.5 to 8.5. The thermal stability of prolactin at pH 6.5 is essentially higher than at pH 8.5. Bovine prolactin binds zinc ions with an apparent association constant of 2 x 10(5) M(-1) at pH 6.5 and 1 x 10(4) M(-1) at pH 8.5. The pH dependence of both thermal stability and zinc binding surrounding the pKa of histidine suggests that these residues plays a key role in the structural integrity of bovine prolactin.

Effect of melatonin and pineal grafting on thymocyte apoptosis in aging mice

We have evaluated the effect of chronic melatonin (MEL) treatment or pineal grafting (PG) in old mice on the apoptosis of both thymocytes and spleen lymphocytes under conditions of either serum deprivation or glucocorticoid or zinc administration. The apoptosis was correlated with the modulation of thymus and adrenal weight and corticosterone and zinc plasma levels induced by MEL treatment or PG in old mice. Balb/c mice (17-18 months old) were given supplements of MEL (40-50 micrograms/day/mouse) or grafted with a young pineal gland and then sacrificed after 8 months. Both the MEL treatment and PG partially prevented thymic involution in very old mice. Both treatments protected the thymic and spleen lymphocytes in old mice from the apoptosis induced by serum deprivation and recovered the reduced thymocyte sensitivity to the apoptosis induced by dexamethasone (DEX), present in old untreated animals, to the values found in young mice. DEX caused a bigger loss of G D /G 1 phase cells in MEL treated mice than in old untreated mice. The protective action of MEL treatment or PG on serum deprivation induced apoptosis was correlated with increased thymus weight, reduced adrenal weight and corticosterone levels and increased zinc plasma levels. The greater DEX-induced apoptosis found in MEL treated and PG mice was correlated with reduced adrenal weight and function. In vitro MEL did not affect thymocyte apoptosis in young or old mice. These results suggest that MEL treatment or PG prevent age-related thymus involution through regulation of thymocyte apoptosis which, in turn, occurs through modulation of the pituitary-adrenal axis and zinc turnover determined by the pineal hormone.

Case report: recurrent hyperammonaemic encephalopathy due to citrullinaemia in a 52 year old man

The present report describes a Chinese male who presented for the first time with recurrent encephalopathy and hyperammonaemia at the age of 52 years. He was found to have citrullinaemia. To our knowledge, this is the first Chinese with citrullinaemia and the first non-Japanese who has the variant form of presentation. The patient also has the longest asymptomatic period for citrullinaemia so far described. The patient's biochemical derangement, clinical features and the postulation of his late presentation are discussed. It is noteworthy that simple therapeutic measures, such as lactulose and dietary protein restriction, controlled his symptoms well.

Selected metals status in patients with noninsulin-dependent diabetes mellitus

In order to investigate the relationships between metals zinc [Zn], copper [Cu], magnesium [Mg], or Calcium [Ca] and noninsulin-dependent diabetes mellitus, 65 patients of newly diagnosed noninsulin-dependent diabetes mellitus and 54 nondiabetic healthy controls were studied. The concentrations of selected metals in fasting blood samples and 24-h urine collections were determined. Hyperzincuria and hypermagnesuria were detected in diabetic patients (p < 0.01). The diabetics also had lower Zn and Mg, and higher Cu, and Ca levels in their plasma than those of the controls, but the statistical differences in Ca and Mg were not significant. Significantly lower Zn and higher Ca levels in erythrocytes were found in diabetic patients (p < 0.01). There is evidence of a significant difference in metals status between diabetic patients with or without the specific complications. This study further indicates that patients with NIDDM on Taiwan also have distinct changes in their metals status, and these perturbations are associated with some diabetic complications.

Dose-dependent opposite effect of zinc on apoptosis in mouse thymocytes

Zinc is a crucial nutritional component required for the normal development and maintenance of immune functions. It has been reported that zinc is a potent inhibitor of DNA fragmentation, the specific marker of apoptosis. The effect of zinc on apoptotic cell death has been previously studied in a narrow range of high zinc concentrations, and the role of physiological zinc doses has not yet been elucidated. In this paper we evaluate the effect of in vitro Zn2+ administration at concentrations higher than, corresponding to, and lower than the physiological concentration, in thymocytes from young mice. We demonstrate that Zn2+ has an opposite effect on apoptosis, inhibiting or increasing it depending on the Zn2+ concentration used. High Zn2+ concentrations (from 600 to 75 microM) inhibit both serum-free medium and DEX-induced thymocyte apoptosis. Low Zn2+ concentrations (from 15 to 7.5 microM) induce apoptosis or increase serum-free medium-induced apoptosis. The effect of low Zn2+ concentrations on DEX-induced apoptosis is dependent on the length of incubation, since Zn2+ has an additive effect with DEX in inducing DNA fragmentation at 8 h of culture, whereas it blocks DEX-induced apoptosis after 20 h incubation. Both DEX and 15 microM Zn(2+)-induced DNA fragmentation require protein synthesis, being blocked through cycloheximide. The inhibiting and inducing effects of Zn2+ on apoptosis are exerted on G0/G1 phase thymocytes. The inhibiting effect of Zn2+ on apoptosis is related to an increase in the number of CD4+CD8+ thymocytes. Concentrations of Zn2+ inducing apoptosis sometimes cause a decrease of CD4+CD8+ cells with a corresponding increase of CD4+CD8-thymocytes. These data show that in vitro Zn2+ has a dose-dependent opposite effect on apoptosis, suggesting that Zn2+ not only acts as an inhibitor but also plays a more complex role in physiological intrathymic cell selection.

Reversibility of the thymic involution and of age-related peripheral immune dysfunctions by zinc supplementation in old mice

With advanced ageing the zinc pool undergoes progressive reduction as shown by the low zinc plasma levels and the negative crude zinc balance, both in humans and in rodents. It has been suggested that such zinc deficiency might be involved in many age-related immunological dysfunctions, including thymic failure. The relevance of zinc for good functioning of the entire immune system is, at present, well documented. In particular, zinc is required to confer biological activity to one of the best-known thymic peptides, thymulin, which is responsible for cell-mediated immunity. In deep zinc deficiencies, in humans and other animals, the low thymulin levels are due not to a primary failure of the thymus, but to a reduced peripheral saturation of thymic hormones by zinc ions. In aged mice both a reduced peripheral saturation of the hormone and a decreased production by the thymus were present. Oral zinc supplementation in old mice (22 months old) for 1 month induced a complete recovery of crude zinc balance from negative (-1.82) to positive values (+1.47), similar to those of young animals (+1.67). A full recovery of thymic functions with a regrowth of the organ and a partial restoration of the peripheral immune efficiency, as measured by mitogen responsiveness (PHA and ConA) and natural killer cell (NK) activity, were observed after zinc supplementation. These findings clearly pin-point for relevance of zinc for immune efficiency and suggest that the age-related thymic involution and peripheral immunological dysfunctions are not intrinsic and irreversible events but are largely dependent on the altered zinc pool.

Zinc, human diseases and aging

Zinc is one of the most important trace elements in the body for many biological functions; it is required as a catalytic component for more than 200 enzymes, and as a structural constituent of many proteins, hormones, neuropeptides, hormone receptors, and probably polynucleotides. Due to its role in cell division and differentiation, programmed cell death, gene transcription, biomembrane functioning and obviously many enzymatic activities, zinc is considered a major element in assuring the correct functioning of an organism, from the very first embryonic stages to the last periods of life. This biological role together with the many factors that modulate zinc turnover explains on one hand, the variety of clinical and laboratory signs resulting from its reduced bioavailability, and on the other, the high number of human pathologies characterized by alterations in the zinc pool. As zinc supplementation is efficacious in most of these conditions, it is regarded more as an oriented therapeutical support, than a simple dietary integrator. Furthermore, the relevance of zinc status to many age-associated diseases and, according to experimental studies, the aging itself of the major homeostatic mechanisms of the body, i.e., the nervous, neuroendocrine and immune systems, places zinc in a pivotal position in the economy of the aging organism.

The immuno-reconstituting effect of melatonin or pineal grafting and its relation to zinc pool in aging mice

It has been demonstrated that melatonin, the main neuro-hormone of the pineal gland, affects thymic functions and the regulation of the immune system. In addition, experimental evidences indicate that melatonin can modulate zinc turnover. The knowledge that with advancing age both melatonin and zinc plasma levels decline, and that zinc supplementation in old mice is able to restore the reduced immunological functions, has prompted investigations on the effect of chronic melatonin treatment or pineal graft in old mice on the age-related decline of thymic endocrine activity, peripheral immune functions and zinc turnover. Both melatonin treatment in old mice and pineal graft into the thymus of old mice correct the reduced thymic endocrine activity and increase the weight of the thymus and its cellularity. A restoration of cortical thymic volume, as detected by the percentage of tissue in active proliferation, is also observed in old mice after both treatments. Thymocyte CD phenotype expression is also restored to young values. At peripheral level, recovery of peripheral blood lymphocyte number and of spleen cell subsets, with increased mitogen responsiveness also occurs. Melatonin treatment or pineal graft induce also a restoration of the altered zinc turnover in aged mice with an increment of the crude zinc balance from negative (-1.6 microgram/day/mouse) to positive value (+1.2 microgram/day/mouse), similar to that one of young mice (+1.4 microgram/day/mouse). The reduced zinc plasma level is restored to normal values. These findings support the idea that the effect of melatonin on thymic endocrine activity and peripheral immune functions may be mediated by the zinc pool.

Thyroid function and plasma immunoglobulins in subjects with Down's syndrome (DS) during ontogenesis and zinc therapy

Thyroid function parameters and immunoglobulin concentrations in sera of outpatients with Down's syndrome (DS, n = 110) of different ages (DS1 = 1-9 years; DS2 = 6-15; DS3 = 15-35) were compared with those of age-matched controls (n = 110). Although mean serum TSH was higher in all DS groups, thyroid hormone concentrations were significantly lower only in DS3. In DS1, a notable frequency rate of high T4 and T3 was found. Serum concentrations of thyroxine binding globulin (TBG) were significantly higher in all DS groups. Free T4 and T3 indexes, calculated as the ratio of total hormone: TBG concentrations, were lower in all DS groups. IgA serum concentrations were significantly higher in all DS groups, IgA was higher in DS1 and DS2. Serum zinc levels were lower in all DS groups. Repeated examination after one year revealed lower T4 and higher TSH in DS patients treated with zinc during this interval as compared to values observed before treatment. Our results suggest a high occurrence rate of complex immune and endocrine disorders with thyroid dysregulation in DS patients, with zinc deficiency playing a considerable role.

Protein energy malnutrition and the nervous system

Protein-energy malnutrition (PEM), a natural ramification of poverty, continues to be a perennial source of concern to a large segment of the world population. The developing nervous system of a child is specially vulnerable to deprivations in nurture. Peripheral nerve and muscle derangements are clinically evident by weakness, hypotonia and hyporeflexia in accordance with severity and duration of PEM. Motor and sensory nerve conduction studies exhibit significant abnormalities and often furnish useful and ominous correlation with grades of PEM. The human sural nerve histology in cases of severe PEM is characterized by persistence of small myelinated fibres, striking failure of internodal elongation and significant segmental demyelination. Young rhesus monkeys are ideal experimental PEM models and they show myopathic EMG changes amenable to rehabilitation. Muscle pathology comprises obliteration of cross-striations, streaming of Z bands, increased interfibrillary spaces, mitochondriomegaly and small-for-age fibres. Radioisotope assays reveal anomalous incorporation into various nerve and muscle constituents. Central nervous system, specially the neuropsychological functions are affected in a lasting manner. Learning deficits, behavioural problems and manual indexterity are most obtrusive features.

Clinical implications of trace elements in endocrinology

The implications of essential trace elements in endocrinological processes, mainly thyroid function, growth, gonadal function, adrenal hormones, prolactin, glucose homeostasis, calcium-phosphorus metabolism, and thymulin activity, are reviewed. Most concerned elements in this field include iodine, zinc, selenium, copper, chromium, manganese and vanadium. The minerals are powerful modulators of several physiological functions that can be considerably perturbed in deficiency states. The resulting biochemical and clinical modifications can be prevented and/or corrected by adequate supplementation. Sometimes, however, they act like pharmacological agents when their beneficial effects are not the result of a correction of a nutritional deficiency state. Their potentialities as therapeutic agents are perfectly described in many cases, but some indications deserve further investigations.

Effect of administration of Aroclor 1254 on the activities of hepatic drug metabolizing enzymes in zinc deficiency

In order to understand the mechanisms of carcinogenesis in zinc deficiency, a study was conducted in experimental animals to investigate the effect of administration of an inducer. After the production of zinc deficiency in NIN/Wistar strain of rats by feeding an egg albumin-starch based diet almost devoid of zinc, the animals were administered a potent inducer of mixed-function oxidases: Aroclor 1254 and various Phase I and Phase II enzymes of drug metabolism like benzo[a]pyrene hydroxylase, microsomal epoxide hydrolase, cytosolic epoxide hydrolase, and cytosolic glutathione-S-transferase studied in liver tissues. Control and pair-fed groups were also run alongside. The results showed that while the activities of various enzymes studied were low in the uninduced basal condition, these activities increased many-fold after induction. This induction was observed not only in the control group, but in the pair-fed and deficient groups as well. These results suggest that the ability to respond to a carcinogenic insult, though initially present in zinc deficiency, may not be adequate to counteract an excess or chronic exposure to carcinogen in the long run.

Infusion of zinc inhibits serum calcitonin levels in patients with various zinc status

Serum concentrations of ionized calcium, parathyroid hormone, and calcitonin were measured during zinc infusion in patients of short stature (n = 15); those with insulin-dependent diabetes mellitus (n = 13); and age-matched controls (n = 10). The increase in serum zinc concentrations after zinc infusion resulted in a decrease in the serum calcitonin concentrations but not in concentrations of ionized calcium and parathyroid hormone. A significant negative correlation was obtained between body zinc clearances and decreases in serum calcitonin levels at 60 minutes after the infusion of zinc. Thus, we found a relationship between infusion of zinc and the regulation of calcitonin secretion. We propose that an increase in the serum zinc pool plays a definite role in inhibiting calcitonin secretion from thyroid tissue.

Effect of zinc supplementation on oxidative drug metabolism in patients with hepatic cirrhosis

The pharmacokinetics of antipyrine were studied in seven zinc deficient patients with hepatic cirrhosis, before and after zinc supplementation. Each patient received zinc sulphate 660 mg daily for 30 days, restoring zinc status to normal as assessed by leucocyte zinc concentration. Antipyrine clearance was significantly reduced (P less than 0.05) and antipyrine elimination half-life increased (P less than 0.05) following administration of zinc sulphate without significant alteration in the apparent volume of distribution. It is concluded that supplementation of the zinc deficiency associated with hepatic cirrhosis impaired the hepatic oxidative metabolism of antipyrine.

Neuroendocrine-immune interactions: a theoretical approach to aging

Among the systemic theories of aging, both a 'nervous-neuroendocrine' and an 'immune' hypothesis have been proposed. The discovery of the complex interactions working among the neuroendocrine and the immune systems suggests the revision of the systemic theories of aging, particularly in the light of the recent evidence that some age-associated alterations in the neuroendocrine and in the immune systems are mutually interdependent even at very old age, as revealed by the fact that experimental manipulation of one of the two systems modifies and sometimes restores the function of the other one. These findings clearly demonstrate that at least some of the age-related alterations of the nervous, neuroendocrine and immune networks are not per se intrinsic and irreversible and that the definition of the temporal priority in the age-related deterioration is rather is rather difficult to be assigned to one or other homeostatic apparatuses. As an alternative to pure, either 'neuroendocrine' or 'immune', theories of aging, it has been hypothesized that, due to the strict interactions existing among the nervous, neuroendocrine and immune systems during the whole life of the organism, it is the disruption of such interactions in old age which is responsible for most of the age-associated dysfunctions (Fabris, 1986). This theoretical approach is discussed in the light of a stochastic or single-cause oriented hypothesis of aging.

Zinc mediation of the binding of human growth hormone to the human prolactin receptor

Human growth hormone (hGH) elicits a diverse set of biological activities including lactation that derives from binding to the prolactin (PRL) receptor. The binding affinity of hGH for the extracellular binding domain of the hPRL receptor (hPRLbp) was increased about 8000-fold by addition of 50 micromolar ZnCl2. Zinc was not required for binding of hGH to the hGH binding protein (hGHbp) or for binding of hPRL to the hPRLbp. Other divalent metal ions (Ca2+, Mg2+, Cu2+, Mn2+, and Co2+) at physiological concentrations did not support such strong binding. Scatchard analysis indicated a stoichiometry of one Zn2+ per hGH.hPRLbp complex. Mutational analysis showed that a cluster of three residues (His18, His21, and Glu174) in hGH and His188 from the hPRLbp (conserved in all PRL receptors but not GH receptors) are probable Zn2+ ligands. This polypeptide hormone.receptor "zinc sandwich" provides a molecular mechanism to explain why nonprimate GHs are not lactogenic and offers a molecular link between zinc deficiency and its association with altered functions of hGH.

An inverse relationship between serum zinc and C-reactive protein levels in acutely ill elderly hospital patients

Serum zinc and C-reactive protein (CRP) levels were measured in two groups of acutely ill geriatric hospital in-patients. Serum CRP levels were greater than 10 mg/l in 62% of the first group and 47% of the second. There was a significant negative correlation between zinc and CRP in both groups (r = -0.33, P less than 0.001, n = 103) and (r = -0.29, P less than 0.001, n = 135 respectively). The serum CRP was raised in 30% of long stay patients (n = 50) and 23% of a control group of elderly hospital patients with a normal serum albumin (n = 71), but there was no correlation between zinc and CRP in these patient groups. The results indicate that an acute phase response influences serum zinc levels in acutely ill geriatric patients. There is reason to believe that a distinction should be made between true zinc deficiency and a low serum zinc secondary to acute zinc redistribution during an inflammatory response. Measurement of CRP may help to distinguish between these two situations. We advise that if the serum zinc is low and CRP is significantly raised, zinc supplements should be avoided and a source of infection should be sought. Following recovery from severe infection low serum zinc levels return to normal while elevated CRP levels fall.

Prolactin, thymulin and zinc in chronic hemodialysis: effect of renal transplant

The interrelationships between PRL, thymulin and Zn, were studied in 25 patients with chronic renal failure (CRF) undergoing kidney transplantation and immunosuppressed with cyclosporine A (CsA). The possible role of serum PRL levels in predicting allograft rejection was also investigated. Before the kidney transplant serum PRL levels were significantly higher than in normals (mean +/- SE, 28.3 +/- 7.1 vs 7.5 +/- 0.6 micrograms/l, p less than 0.001) and their response to TRH (200 micrograms iv) was impaired (mean delta % at peak, 45.4 +/- 9.5 vs + 641 +/- 47.5, p less than 0.001). After kidney transplantation a dramatic decrease in serum PRL concentrations was observed in all patients, followed by a slight upward trend in the following two weeks, while TRH test administered on 3rd, 7th and 14th day, induced a progressive increase in serum PRL responses (delta % at peak, 201 +/- 43.3, 220 +/- 37.1 and 305 +/- 15.5, respectively). No difference in serum PRL patterns was observed between patients with (8 cases) and without (17 cases) clinical features and kidney fine needle biopsies suggestive of rejection. Basal serum Zn levels of patients with CRF (18.1 +/- 0.6 mumol/l) were similar to those observed in normals (17.7 +/- 0.2 mumol/l) and without any correlation with serum PRL levels. A decrement in serum Zn was recorded during CsA infusion and on the first day after the surgery, followed by a slight and slow upward trend. Basal serum thymulin titers were low [2.92 +/- 0.18 (1/log2)], were further reduced after CsA infusion [1.68 +/- 0.15 (1/log2)] and returned to the pretransplant levels in the two weeks after grafting.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of diuretics on captopril-induced urinary zinc excretion

The urinary zinc/creatinine ratio has been measured in five groups of patients with essential hypertension and in a group of healthy controls. The first four groups of patients consisted of subjects being treated for at least three months with captopril alone, hydrochlorothiazide alone, captopril plus hydrochlorothiazide, or captopril and furosemide. The fifth group comprised hypertensive patients not on any medication. The first four patient groups exhibited significantly increased urinary zinc/creatinine ratios when compared to the control and untreated hypertensive groups, but in the two combination regimens there was little zincuria. It is suggested that both diuretics inactivate the zincuric effect of captopril by binding to its sulphydryl group within the tubular lumen.

A study of serum zinc, albumin, alpha-2-macroglobulin and transferrin levels in acute and long stay elderly hospital patients

Serum zinc levels measured by atomic absorption spectrophotometry were found to be low (less than 10.5 mumols/l) in 38% of acute geriatric admissions, 69% of long stay geriatric patients and 19% of a control group of elderly hospital patients with a normal serum albumin. There was a significant positive correlation between serum zinc and serum albumin in all groups. In acutely ill geriatric patients only, there was a weak but statistically significant positive correlation between serum zinc and alpha-2-macroglobulin (A2M) (r = 0.20), P less than 0.05). Serum transferrin was low in 46% of acute geriatric patients and 22% of long stay geriatric patients but there was no correlation between serum zinc and serum transferrin levels in any patient group. There were significant differences in serum zinc, A2M and transferrin levels between the acute and long stay geriatric patients. The differences in serum zinc levels between these patients groups could not be explained by changes in serum A2M, transferrin or albumin. Changes mediated by an acute phase response may have influenced results in the acute geriatric group of patients.

Fibrillary cytoplasmic inclusions in neoplastic Paneth cells

Paneth cell differentiation was investigated in two colorectal carcinomas. Ultrastructural study showed a range of granules and, in one case, fibrillary cytoplasmic inclusions. Similar inclusions in normal Paneth cells have been associated with zinc deficiency. However, there was no clinical evidence of abnormal zinc metabolism in this patient, nor were inclusions seen in adjacent non-neoplastic Paneth cells. It is speculated that these fibrillary inclusions might reflect an intrinsic zinc-related metabolic defect in the tumour cells.

Plasma zinc concentrations during the first 2 years after diagnosis of insulin-dependent diabetes mellitus: a prospective study

Studies of zinc status in insulin-dependent diabetes mellitus (IDDM) have shown contradictory results. Zinc is essential for many enzymes involved in the human metabolism and may play a role in the biosynthesis and storage of insulin in the B-cell. We therefore prospectively followed 26 patients (14 males and 12 females) with newly diagnosed IDDM in order to determine the plasma zinc variation at the time of diagnosis and after 1, 3, 6, 12 and 24 months. Seventy-two healthy persons (36 males and 36 females) served as controls. Only minor differences in plasma zinc were demonstrated during the first 2 years of IDDM. A sex difference was found in healthy controls but only after 24 months in the diabetics. Quantitative changes of the B-cell function, development of insulin antibodies, age, body weight and serum albumin did not correlate with the course of plasma zinc.

Transient partial growth hormone deficiency due to zinc deficiency

We present here a 13-year-old boy with partial growth hormone deficiency due to chronic mild zinc deficiency. When zinc administration was started, his growth rate, growth hormone levels, and plasma zinc concentrations increased significantly. His poor dietary intake resulted in chronic mild zinc deficiency, which in turn could be the cause of a further loss of appetite and growth retardation. There was also a possibility of renal zinc wasting which may have contributed to zinc deficiency. Zinc deficiency should be carefully ruled out in patients with growth retardation.

Inhibition of 5 alpha-reductase activity in human skin by zinc and azelaic acid

The effects of zinc sulphate and azelaic acid on 5 alpha-reductase activity in human skin were studied using an in vitro assay with 1,2[3H]-testosterone as substrate. When added at concentrations of 3 or 9 mmol/l, zinc was a potent inhibitor of 5 alpha-reductase activity. At high concentrations, zinc could completely inhibit the enzyme activity. Azelaic acid was also a potent inhibitor of 5 alpha-reductase; inhibition was detectable at concentrations as low as 0.2 mmol/l and was complete at 3 mmol/l. An additive effect of the two inhibitors was observed. Vitamin B6 potentiated the inhibitory effect of zinc, but not of azelaic acid, suggesting that two different mechanisms are involved. When the three substances were added together at very low concentrations which had been shown to be ineffective alone, 90% inhibition of 5 alpha-reductase activity was obtained. If this inhibition is confirmed in vivo, zinc sulphate combined with azelaic acid could be an effective agent in the treatment of androgen related pathology of human skin.

Selenium, rubidium and zinc in human semen and semen fractions

The levels of selenium, rubidium and zinc were determined in samples of semen, seminal plasma and spermatozoa from men with suspected infertility, together with several parameters of semen quality. The proportion of whole semen selenium present in sperm increased with increasing sperm count from 0 to 40%. For rubidium 98 +/- 4% and for zinc 95 +/- 8% of the total amount in semen was contained in seminal plasma. In seminal plasma a positive correlation was found between the levels of zinc and selenium, and between the levels of zinc and rubidium, indicating that, like zinc, selenium and rubidium in seminal plasma also derive mainly from the prostate gland. Semen quality parameters, such as sperm motility, vitality, speed and morphology, were not correlated with the contents of the three elements in either whole semen or seminal plasma. As the seminal content of selenium is dependent on the proportion of prostatic secretion in seminal plasma and on the sperm count, and both factors can vary considerably, the selenium level of whole semen does not appear to be a suitable parameter for investigation of the relationship between selenium and semen quality. Provisional measurements suggest lower sperm selenium levels at abnormally low or high sperm counts.

Evaluation of zinc status in subjects with Crohn's disease

Zinc status was evaluated in 30 subjects with Crohn's disease. Intestinal resection had previously been performed in 23 of the subjects. The concentrations of zinc were determined in plasma, erythrocytes, percutaneous muscle biopsies, and in urine collected during 24 hours. The results were compared with those in 19 healthy controls. Most of the patients had a normal zinc status. The levels of zinc were, however, reduced (i.e., less than mean -2 SD for controls) in plasma for five, in erythrocytes for two, and in muscle biopsies for six subjects with Crohn's disease. The mean concentrations of zinc in plasma and erythrocytes were reduced (P less than 0.05), whereas the mean content of zinc in muscle biopsies and the mean urinary excretion of zinc were not significantly different, in subjects with Crohn's disease. The various zinc parameters did not correlate to each other. The results indicate that some subjects with Crohn's disease had an intracellular zinc depletion, which, however, was not reflected by a reduction in levels of zinc in plasma.