Zinc deficiency reduces leptin gene expression and leptin secretion in rat adipocytes

The present study was conducted to measure ob mRNA abundance in the zinc-deficient (ZD) rats and the secretion of leptin from adipose tissue obtained from ZD, zinc-adequate (ZA), and pair-fed (PF) rats. It was found that ob mRNA abundance was greatest (P < 0.05) in adipose tissue obtained from ZA and PF rats. Ob mRNA abundance was similar in PF and ZD rats. To study leptin secretion from adipose tissue in a cell culture model, a method was developed to use excised epididymal adipose tissue from ZD, ZA, and PF rats. Tissue was incubated in Opti-modified Eagle's medium (MEM) cell culture medium in which concentrations of zinc and insulin were manipulated. It was observed that leptin secretion was higher (P < 0.05) in adipose tissue obtained from ZA than ZD and PF rats. Secretion of leptin was higher in adipose tissue of PF than ZD rats (P < 0.05). Surprisingly, media zinc content in this ex vivo model tended to suppress secretion of leptin. This suppression seems to be zinc specific and might be caused by the sequestration of insulin in the culture medium. Our results indicate that the reduction in serum leptin observed in ZD rats is likely caused by not only a reduction in body fat, but also by a decrease in leptin synthesis and secretion per gram of adipose tissue. Taking these results into account along with a prior study (1), it is possible that even a marginal zinc deficiency could affect leptin secretion and serum leptin concentrations. Impaired leptin secretion caused by zinc deficiency might be one factor contributing to hypogonadism observed in zinc deficiency.     

Redistribution of tissue zinc pools during lactation and dyshomeostasis during marginal zinc deficiency in mice

Zinc (Zn) requirements are increased during lactation. Increased demand is partially met through increased Zn absorption from the diet. It is estimated that 60–80% of women of reproductive age are at risk for Zn deficiency due to low intake of bioavailable Zn and increased demands during pregnancy and lactation. How Zn is redistributed within the body to meet the demands of lactation, and how Zn deficiency affects this process, is not understood. Female C57bl/6J mice were fed a control (ZA; 30 mg Zn/kg) or a marginally Zn deficient (ZD; 15 mg Zn/kg) diet for 30 days prior to mating through mid-lactation and compared with nulliparous mice fed the same diets. While stomach and plasma Zn concentration increased during lactation in mice fed ZA, mice fed ZD had lower stomach Zn concentration and abrogated plasma Zn levels during lactation. Additionally, femur Zn decreased during lactation in mice fed ZA, while mice fed ZD did not experience this decrease. Furthermore, red blood cell, pancreas, muscle and mammary gland Zn concentration increased, and liver and adrenal gland Zn decreased during lactation, independent of diet, while kidney Zn concentration increased only in mice fed ZD. Finally, maternal Zn deficiency significantly increased the liver Zn concentration in offspring but decreased weight gain and survival. This study provides novel insight into how Zn is redistributed to meet the increased metabolic demands of lactation and how marginal Zn deficiency interferes with these homeostatic adjustments.     

The effect of zinc defficiency and food restriction on prostaglandin E2 and thromboxane B2 in saliva and plasma of rats

Zinc has been implicated in the regulation of prostaglandins and other arachidonic acid derivatives. Studies of zinc-deficient animals, however, are compromised by concomitant reduction in food intake that may also alter eicosanoid levels in body tissues and fluids. In this study, three groups of rats, designated as zinc-deficient, pair-fed and control, were fed diets containing 1 ppm, 15 ppm (in amounts paired to deficient rats) and 15 ppm Zn adlibitum, respectively, for 6 weeks. Saliva and blood were analyzed for PGE₂ adn TXB₂ by radioimmunoassay. Saliva concentrations of both eicosanoids were lower (p<0.05) in the pair-fed animals, but not significantly altered by zinc deficiency. Plasma levels of PGE₂ and TXB₂ were unchanged by either zinc deficiency or food restriction. The results of this study support the contention that the effect of zinc on these prostaglandins is not mediated by altered rates of synthesis or degradation but rather by effects on eicosanoid function.     

The effect of zinc deficiency and food restriction on prostaglandin E2 and thromboxane B2 in saliva and plasma of rats

Zinc has been implicated in the regulation of prostaglandins and other arachidonic acid derivatives. Studies of zinc-deficient animals, however, are compromised by concomitant reduction in food intake that may also alter eicosanoid levels in body tissues and fluids. In this study, three groups of rats, designated as zinc-deficient, pair-fed and control, were fed diets containing 1 ppm, 15 ppm (in amounts paired to deficient rats) and 15 ppm Zn ad libitum, respectively, for 6 weeks. Saliva and blood were analyzed for PGE2 and TXB2 by radioimmunoassay. Saliva concentrations of both eicosanoids were lower (p less than 0.05) in the pair-fed animals, but not significantly altered by zinc deficiency. Plasma levels of PGE2 and TXB2 were unchanged by either zinc deficiency or food restriction. The results of this study support the contention that the effect of zinc on these prostaglandins is not mediated by altered rates of synthesis or degradation but rather by effects on eicosanoid function.     

Zinc deficiency inhibits the direct growth effect of growth hormone on the tibia of hypophysectomized rats

The effect of zinc deficiency on the direct-growth effect of growth hormone (GH) on tibia growth in hypophysectomized rats was studied. There were three dietary groups. Zinc deficient (ZD) group (0.9 mg/kg diet), control (C) group (66 mg/kg diet) and zinc adequate pair fed (PF) group (66 mg zinc/kg diet). All rats in each group received local infusion of recombinant human-growth hormone (hGH) (1 Μg/d), except for half of the animals in the control group, which were sham-treated, receiving vehicle infusion only. The substances were infused continuously for 13 d by osmotic minipumps through a catheter implanted into the right femoral artery. Food intake was lower and body weight loss was greater in ZD, and PF animals compared with C animals (p < 0.001). Tissuezinc concentration and plasma alkaline-phosphatase activity were decreased (p < 0.05) by dietary-zinc deficiency. GH infusion increased the tibial-epiphyseal width of the treated right limb, but not of the noninfused left limb in C and PF animals. However, in ZD rats, no difference was found between the infused and the noninfused limbs. These results demonstrate that zinc deficiency inhibits the direct-growth effect of GH on long-bone growth.     

Zinc deficiency and the activities of lipoprotein lipase in plasma and tissues of rats force-fed diets with coconut oil or fish oil

The present study was performed to investigate the effect of zinc deficiency on the activities of lipoprotein lipase in postheparin serum and tissues of rats fed diets containing either coconut oil or fish oil as dietary fat, using a bifactorial experimental design. To ensure an adequate food intake, all the rats were force-fed by gastric tube. Experimental diets contained either 0.8 mg zinc/kg (zinc-deficient diets) or 40 mg zinc/kg (zinc-adequate diets). The effects of zinc deficiency on the activities of lipoprotein lipase in postheparin serum and postprandial triglyceride concentrations and distribution of apolipoproteins in serum lipoproteins depended on the type of dietary fat. Zinc-deficient rats fed the coconut oil diet exhibited a reduced activity of lipoprotein lipase in postheparin serum and adipose tissue, markedly increased concentrations of triglycerides in serum, and a markedly reduced content of apolipoprotein C in triglyceride-rich lipoproteins and high density lipoproteins compared with zinc-adequate rats fed coconut oil. By contrast, zinc-deficient rats fed the fish oil diet did not exhibit reduced activities of lipoprotein lipase in postheparin serum and adipose tissue and increased concentrations of serum lipids compared with zinc-adequate rats fed the fish oil diet. This study suggests that a reduced activity of lipoprotein lipase might contribute to increased postprandial concentrations of serum triglycerides observed in zinc-deficient animals. However, it also demonstrates that the effects of zinc deficiency on lipoprotein metabolism are influenced by dietary fatty acids.     

Zinc deficiency and the desaturation of linoleic acid in rats force-fed fat-free diets

Recent studies with rats force-fed zinc-deficient diets containing various types of fat failed to demonstrate a role of zinc in desaturation of linoleic acid. The present study was conducted to investigate the effect of zinc deficiency on desaturation of linoleic acid in rats that were initially force-fed fat-free diets to stimulate activity of desaturases. Therefore, rats were fed zinc-adequate and zinc-deficient fat-free diets for 6 d. After that period, the groups were divided and half of the rats continued feeding the fat-free diet for another 3.5 d whereas the other half was switched to a fat diet by supplementing the fat-free diet with 5% safflower oil. In order to assess desaturation of linoleic acid, fatty acid compositions of liver phosphatidylcholine, ethanolamine, and-serine were considered, particularly levels of individual (n-6) polyunsaturated fatty acids (PUFA). Levels of total and individual (n-6) PUFA were similar in zinc-adequate and zinc-deficient rats fed the fat-free diet throughout the experiment. Addition of 5% safflower oil increased levels of total and individual (n-6) PUFA in both zinc-adequate and zinc-deficient rats. However, total (n-6) PUFA in all types of phospholipids were higher in zinc-adequate rats than in zinc-deficient rats. Additionally, in zinc-deficient rats there were changes of (n-6) PUFA levels typical for impaired Δ5 and Δ6 desaturation: linoleic acid and dihomo-γ-linolenic acid were elevated; arachidonic acid, docosatetraenoic acid, and docosapentaenoic were lowered by zinc deficiency. Therefore, the study shows that zinc deficiency impairs desaturation of linoleic acid in rats force-fed fat-free diets and therefore supports results from former convential zinc deficiency experiments suggesting a role of zinc for desaturation of linoleic acid.     

Zinc-deficient rats have more limited bone recovery during repletion than diet-restricted rats

The objective of this study was to investigate the effects of dietary zinc deficiency and diet restriction on bone development in growing rats, and to determine whether any adverse effects could be reversed by dietary repletion. Weanling rats were fed either a zinc-deficient diet ad libitum (ZD; <1 mg zinc/kg) or nutritionally complete diet (30 mg zinc/kg) either ad libitum (CTL) or pair-fed to the intake of the ZD group (DR; diet-restricted) for 3 weeks (deficiency phase) and then all groups were fed the zinc-adequate diet ad libitum for 3, 7, or 23 days (repletion phase). Excised femurs were analyzed for bone mineral density (BMD) using dual-energy x-ray absorptiometry, and plasma was analyzed for markers of bone formation (osteocalcin) and resorption (Ratlaps). After the deficiency phase, ZD had lower body weight and reduced femur BMD, zinc, and phosphorus concentrations compared with DR; and these parameters were lower in DR compared with CTL. Femur calcium concentrations were unchanged among the groups. Reduced plasma osteocalcin in ZD and elevated plasma Ratlaps in DR suggested that zinc deficiency limits bone formation while diet restriction accelerates bone resorption activity. After 23 days of repletion, femur size, BMD, and zinc concentrations remained lower in ZD compared with DR and CTL. Body weight and femur phosphorus concentrations remained lower in both ZD and DR compared with CTL after repletion. There were no differences in plasma osteocalcin concentrations after the repletion phase, but the plasma Ratlaps concentrations remained elevated in DR compared with CTL. In summary, both ZD and DR lead to osteopenia during rapid growth, but the mechanisms appear to be due to reduced modeling in ZD and higher turnover in DR. Zinc deficiency was associated with a greater impairment in bone development than diet restriction, and both deficiencies limited bone recovery during repletion in growing rats.     

The relationship between beta cell activation and SLC30A8/ZnT8 levels of the endocrine pancreas and maternal zinc deficiency in rats

ObjectivesZinc, which is found in high concentrations in the β-cells of the pancreas, is also a critical component for the endocrine functions of the pancreas. SLC30A8/ZnT8 is the carrier protein responsible for the transport of zinc from the cytoplasm to the insulin granules. The aim of this study was to investigate how dietary zinc status affects pancreatic beta cell activation and ZnT8 levels in infant male rats born to zinc-deficient mothers.MethodsThe study was performed on male pups born to mothers fed a zinc-deficient diet. A total of 40 male rats were divided into 4 equal groups. Group 1: In addition to maternal zinc deficiency, this group was fed a zinc-deficient diet. Group 2: In addition to maternal zinc deficiency, this group was fed a standard diet. Group 3: In addition to maternal zinc deficiency, this group was fed a standard diet and received additional zinc supplementation. Group 4: Control group. Pancreas ZnT8 levels were determined by ELISA method and insulin-positive cell ratios in β-cells by immunohistochemistry.ResultsThe highest pancreatic ZnT8 levels and anti-insulin positive cell ratios in the current study were obtained in Group 3 and Group 4. In our study, the lowest pancreatic ZnT8 levels were obtained in Group 1 and Group 2, and the lowest pancreatic anti-insulin positive cell ratios were obtained in Group 1.ConclusionThe results of the present study; in rats fed a zinc-deficient diet after maternal zinc deficiency has been established shows that ZnT8 levels and anti-insulin positive cell ratios in pancreatic tissue, which is significantly suppressed, reach control values with intraperitoneal zinc supplementation.     

Maternal zinc deficiency impairs brain nestin expression in prenatal and postnatal mice

INTRODUCTIONZinc is essential for normal brain development,evidenced by the fact that zinc deficiency in lactating mothers is characterized by a high incidence ofneuroanatomical maiformatinns and functional abnormalities in suckling offspring[1-3]. By colltrast,relatively little is known about the relationship be{tween maternal zinc nutrition and fetal brain development[2, 4, 5]. Dvergsten et al[6-81 investigated theeffects of maternal zinc deficiency on postnatal development of the rat ce…     

Maternal zinc deficiency reduces NMDA receptor expression in neonatal rat brain, which persists into early adulthood

Prenatal and early postnatal zinc deficiency impairs learning and memory and these deficits persist into adulthood. A key modulator in this process may be the NMDA receptor; however, effects of zinc deficiency on the regulation of NMDA receptor activity are not well understood. Female Sprague-Dawley rats were fed diets containing 7 (zinc deficient, ZD), 10 (marginally zinc deficient, MZD) or 25 (control) mg Zn/g diet preconception through postnatal day (PN) 20, at which time pups were weaned onto their maternal or control diet. Regulation of NMDA receptor expression was examined at PN2, PN11, and PN65. At PN2, expression of whole brain NMDA receptor subunits NR1, NR2A, and NR2B was lower in pups from dams fed ZD and MZD compared to controls, as analyzed using relative RT-PCR and immunoblotting. At PN11, whole brain and hippocampi NR1, NR2A, NR2B and PSA-NCAM (polysialic acid-neural cell adhesion molecule) expression and the number of PSA-NCAM immunoreactive cells were lower in pups from dams fed ZD compared to controls. Whole brain brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) concentrations were lower in pups from dams fed ZD or both low zinc diets, respectively. Whole brain NR1 expression remained lower in previously zinc-deficient rats at PN65. These data indicate potential mechanisms through which developmental zinc deficiency can impair learning and memory later in life.     

Activities of liver microsomal fatty acid desaturases in zinc-deficient rats force-fed diets with a coconut oil/safflower oil mixture of linseed oil

The present study was conducted to investigate the effect of zinc deficiency on fatty acid desaturation in rats fed two different types of dietary fat, a mixture of coconut oil and safflower oil (7∶1, w/w, “coconut oil diet”) or linseed oil (“linseed oil diet”). In order to ensure an adequate food intake, all rats were force-fed by gastric tube. Zinc deficiency caused statistical significant reducion of Δ9-desaturase activity in liver microsomes of rats fed coconut oil diet and tendencial reduction (p<0.15) in rats fed linseed oil diet compared with control rats fed diets with the same type of fat. In agreement with this effect, zinc deficiency in the rats fed both types of dietary fat increased the ratio between total saturated and total monounsaturated fatty in liver phospholipids and liver microsomes. Zinc deficient rats on the coconut oil diet had unchanged Δ6-desaturase activity with linoleic acid as substrate and lowered activity with α-linolenic acid as substrate. In contrast, zinc deficient rats on the linseed oil diet had increased Δ6-desaturase activity with linoleic acid as substrate and unchanged activity with α-linolenic acid. Because linoleic acid is the main substrate for Δ6-desaturase in the rats fed coconut oil diet, and α-linolenic acid is the main substrate in the rats fed linseed oil diet, it is concluded that in vivo Δ6-desaturation was not changed by zinc deficiency in the rats fed both types of dietary fat. Activity of Δ5-desaturase was also not changed by zinc deficiency in the rats fed both dietary fats. Levels of fatty acids in liver phospholipids and microsomes derived by Δ4-, Δ5-, and Δ6-desaturation were not consistently changed by zinc deficiency in the rats fed both types of dietary fat. Thus, the enzyme studies and also fatty acid composition data of liver phospholipids and microsomes indicate that zinc deficiency does not considerably disturb desaturation of linoleic and α-linolenic acid. Therefore, it is suggested that similarities between deficiencies of zinc and essential fatty acids described in literature are not due to disturbed desaturation of linoleic acid in zinc deficiency. The present study also indicates that zinc deficiency enhances incorporation of eicosapentaenoic acid into phosphatidylcholine of rats fed diets with large amounts ofn-3 polyunsaturated fatty acids.     

Hepatic responses to dietary stress in zinc- and metallothionein-deficient mice

Metallothionein (MT) and zinc are both reported to be protective against oxidative and inflammatory stress and may also influence energy metabolism. The role of MT in regulating intracellular labile zinc, thus influencing zinc (Zn)-modulated protein activity, may be a key factor in the response to stress and other metabolic challenges. The objective of this study was to investigate the influence of dietary zinc intake and MT on hepatic responses to a pro-oxidant stress and energy challenge in the form of a high dietary intake of linoleic acid, an omega-6 polyunsaturated fatty acid. Male MT-null (KO) and wild-type (WT) mice, aged 16 weeks, were given semisynthetic diets containing 16% fat and either 5 (marginally zinc-deficient [ZD]) or 35 (zinc-adequate [ZA]) mg Zn/kg. For comparison, separate groups of KO and WT mice were given a rodent chow diet containing 3.36% fat and 86.6 mg Zn/kg. After 4 months on these diets, the body weights of all mice were equal, but liver size, weight, and lipid content were much greater in the animals that consumed semisynthetic diets compared to the chow diet. The increase in liver size was significantly lower in ZA but not ZD KO mice, compared with WT mice. Principally, MT appears to affect the diet-induced increase in liver tissue but it also influences the concentration of hepatic lipid. Plasma levels of C-reactive protein (CRP), a marker of inflammation, were increased by zinc deficiency in WT mice, suggesting that marginal zinc deficiency is proinflammatory. CRP was unaffected by zinc deficiency in KO mice, indicating a role for MT in modulating the influence of zinc. Neither zinc nor MT deficiency affects the level of soluble liver proteins, as determined using two-dimensional (2D) gel proteomics. This study highlights the close association between zinc and MT in the manifestation of stress responses.     

Decreased food intake rather than zinc deficiency is associated with changes in plasma leptin, metabolic rate, and activity levels in zinc deficient rats( small star, filled)

This study investigated the hypothesis that the reduced food intake and poor weight gain in zinc deficient rats is due to: increased plasma leptin concentration, increased physical activity and/or increased metabolic rate. Weanling rats were assigned to three groups: controls fed ad libitum (C), zinc deficient (ZD), and pair-fed controls (PF), and tested in a metabolic chamber and activity monitor at baseline and weekly for four weeks. At the end of the study, all groups were compared for differences in plasma leptin concentrations. ZD and PF animals had markedly reduced food intake and weight gain. ZD had reduced stereotypic and locomotor activity compared to PF animals and both groups demonstrated an abolished peri-nocturnal activity spike and were much less active than controls. This was associated with a reduced total metabolic rate by day 30: ZD (0.73 +/- 0.07 kcal/hr, p = 0.0001) and PF (0.83 +/- 0.06 kcal/hr, p = 0.0001) groups vs. controls (1.82 +/- 0.09 kcal/hr). Plasma leptin concentrations in ZD (1.55 +/- 0.06 &mgr;g/L) were lower than controls (2.01 +/- 0.18 &mgr;g/L, p < 0.03), but neither ZD nor controls were statistically different from PF (1.68 +/- 0.05 &mgr;g/L). Both low leptin concentrations and low metabolic rates in the ZD and PF rats were associated with decreased food intake rather than zinc deficiency. The reduced food intake and poor weight gain observed in zinc deficient rats could not be explained by elevated leptin concentrations, hypermetabolism, or increased activity. Low serum leptin concentrations, hypometabolism, and decreased activity are more likely the result of the anorexia of zinc deficiency.     

Differences in the mineral contents between falx cerebri and tentorium cerebelli

A study was performed to determine the effect of zinc deficiency on the zinc concentration of the retina, lens, and the retinal pigment epithelium and choroid. Weanling, male Sprague-Dawley rats were fed ad libitum modified AIN-93 diets containing 3 mg zinc/kg diet (−Zn; n=10) for 6 wk. Control animals were pair-fed (+ZnPF; n=10) or fed ad libitum (+ZnAL; n=10) diets containing 100 mg zinc/kg diet. At 6 wk, plasma and tibia zinc were measured by flame atomic absorption spectrophotometry to confirm zinc deficiency. The zinc concentration of ocular tissues was measured by inductively coupled plasma-mass spectrometry. Mean (±SEM) lens zinc concentration was significantly depressed in the zinc-deficient group as compared to that of pair-fed or ad libitum-fed controls, suggesting that the role of zinc in cataract formation should be investigated. The zinc concentration of total neural retina was preserved in zinc deficiency. Previously reported deterioration of retinal function in zinc deficiency may be the result of a decline in the zinc concentration of a specific cell layer of the retina that cannot be detected on gross analysis of the entire retina. This work was presented in part at Experimental Biology 98, April 1998, San Francisco, CA [P. G. Paterson, B. H. Grahn, and J. S. Fabe, Retinal and lens zinc concentration in the zinc-deficient rat. FASEB J. 12, A521 (1998)].     

Vitamin D Supplementation Modulates Blood and Tissue Zinc, Liver Glutathione and Blood Biochemical Parameters in Diabetic Rats on a Zinc-Deficient Diet

Previous studies suggest a protective effect of vitamin D3 on zinc deficiency-induced insulin secretion and on pancreas β-cell function. The aim of this study was to investigate the effect of vitamin D on blood biochemical parameters, tissue zinc and liver glutathione in diabetic rats fed a zinc-deficient diet. For that purpose, Alloxan-induced diabetic rats were divided into four groups. The first group was fed a zinc-sufficient diet while the second group was fed a zinc-deficient diet. The third and fourth groups received zinc-sufficient or zinc-deficient diets plus oral vitamin D3 for 27 days. At the end of the experiment, blood, femur, pancreas, kidney and liver samples were taken from all rats. The serum, femur, pancreas, kidney and liver zinc concentrations, liver glutathione, serum alkaline phosphatase activity, daily body weight gain and food intake were lower in the zinc-deficient rats in comparison with those receiving adequate amounts of zinc. These values were increased in the zinc-deficient group that was supplemented with vitamin D3. The serum total cholesterol, triglycerides, total protein, urea, glutamate oxaloacetate transaminase, glutamate pyruvate transaminase and blood glucose values were higher in rats fed a zinc adequate diet, but their concentrations were decreased by vitamin D3 supplementation. The serum total protein levels were not changed by zinc deficiency and vitamin D3 supplementation. These results suggest that vitamin D3 modulates tissue zinc, liver glutathione and blood biochemical values in diabetic rats fed a zinc-deficient diet.     

Tracing of Zinc Nanocrystals in the Anterior Pituitary of Zinc-Deficient Wistar Rats

The aim of this study was to trace zinc nanocrystals in the anterior pituitary of zinc-deficient Wistar rats by using autometallographic technique. Male Wistar rats (30–40 days of age, pre-pubertal period) of 40–50 g body weight were divided into the following: the ZC (zinc control) group—fed with 100 ppm zinc in diet, the ZD (zinc-deficient) group—fed with zinc-deficient (1.00 ppm) diet and the PF (pair-fed) group—received 100 ppm zinc in diet. The experiments were set for 2 and 4 weeks. Pituitary was removed and processed for the autometallographic technique. The control and pair-fed groups retained their normal morphological features. However, male Wistar rats fed on zinc-deficient diet for 2 and 4 weeks displayed a wide range of symptoms such as significant (P < 0.05) decrease in diet consumption, body weight and pituitary weight and decrease in gradation of intensity of zinc nanocrystals in the nuclei. The present findings suggest that the dietary zinc deficiency causes decreased intensity of zinc nanocrystals localization and their distribution in the pituitary thereby contributing to the dysfunction of the pituitary of the male Wistar rats. The severity of zinc deficiency symptoms progressed after the second week of the experiment. Decreased intensity of zinc nanocrystals attenuates the pituitary function which would exert its affect on other endocrine organs impairing their functions indicating that the metabolic regulation of pituitary is mediated to a certain extent by zinc and/or hypothalamus-hypophysial system which also reflects its essentiality during the period of growth.     

Teratogenicity of zinc deficiency in the rat: study of the fetal skeleton

Zinc deficiency (ZD) is teratogenic in rats, and fetal skeletal defects are prominent. This study identifies fetal skeletal malformations that affect calcified and non-calcified bone tissue as a result of gestational zinc deficiency in rats, and it assesses the effect of maternal ZD in fetal bone calcification. Pregnant Sprague-Dawley rats (180-250 g) were fed 1) a control diet (76.4 micrograms Zn/g diet) ad libitum (group C), 2) a zinc-deficient diet (0 microgram/g) ad libitum (group ZD), or 3) the control diet pair-fed to the ZD rats (group PF). On day 21 of gestation, laparotomies were performed. Fetuses were weighed, examined for external malformations, and stained in toto with a double-staining technique for the study of skeletal malformations. Maternal and fetal tissues were used for Zn, Mg, Ca, and P determinations. Gross external malformations were present in 97% of the ZD fetuses. No external malformations were found in fetuses from groups C and PF. Ninety-one percent of cleared ZD fetuses had multiple skeletal malformations, whereas only 3% of the fetuses of group PF had skeletal defects; no skeletal malformations were found in fetuses from group C. Some of the skeletal malformations described in the ZD fetuses, mainly affecting non-calcified bone, were not mentioned in previous reports, thus stressing the importance of using double-staining techniques. Examination of stained fetuses and counting of ossification centers revealed important calcification defects in ZD fetuses. These effects were confirmed by lower Ca and P concentrations in fetal bone with alteration of the Ca:P ratio.