Effects of zinc deficiency on food intake and feeding patterns of rats

Effect of zinc depletion/repletion on intestinal iron absorption and iron status in rats

Iron and zinc deficiencies likely coexist in general population. We have previously demonstrated that zinc treatment induces while zinc deficiency inhibits iron absorption in intestinal cell culture models, but this needs to be tested in vivo. In the present study we assessed intestinal iron absorption, iron status (haemoglobin), red blood cell number, plasma ferritin, transferrin receptor, hepcidin) and tissue iron levels in zinc depleted, replete and pair fed control rats. Zinc depletion led to reduction in body weight, tissue zinc levels, intestinal iron absorption, protein and mRNA expression of iron transporters, the divalent metal ion transporter-1, hephaestin and ferroportin, but elevated the intestinal and liver tissue iron levels compared with the pair fed control rats. Zinc repletion led to a significant weight gain compared to zinc deficient rats and normalized the iron absorption, iron transporter expression, tissue iron levels to that of pair fed control rats. Surprisingly, haemoglobin levels and red blood cell number reduced significantly in zinc repleted rats, which could be due to rapid weight gain. Together, these results indicate that whole body zinc status has profound influence on growth, intestinal absorption and systemic utilization of iron, mediated via modulation of iron transporter expression.

Membrane excitabilities in neonatal rat mesencephalic trigeminal neurons under dietary zinc deficiency

PURPOSE

The present study aimed to evaluate the effects of zinc deprivation on the properties of membrane and spike-discharge features of mesencephalic trigeminal neurons (MTNs), which are important sensory neurons for oral-motor reflexes and rhythmical jaw movements.

METHODS

Neonatal Sprague Dawley rats (P10-12) were distributed equally into a normal diet group and a zinc-deficient diet (ZD) group. Whole cell patch-clamp recordings were obtained from MTNs from coronal brain slices.

RESULTS

Passive membrane properties showed a modest depolarized membrane potential and decreased cell capacitance in the ZD group. Zinc deprivation decreased the minimal current amplitude, which induced an action potential and increased the amplitude of afterhyperpolarization following the action potential. Negligible changes were observed for other action potential properties. A decreased burst duration was observed, accompanied by hastened spike frequency adaptation in the burst discharge. There was no difference in the resonant properties at both the subthreshold depolarized potential and hyperpolarized membrane potential between the control and ZD groups.

CONCLUSION

These results suggests that neither the persistent sodium conductance nor slow inwardly rectifying conductance were altered; however, there appeared to be an increase in Ca²⁺-dependent K⁺ conductance in zincdeficient MTNs.

Behavioral and Neural Responses to Vitamin C Solution in Vitamin C-deficient Osteogenic Disorder Shionogi/Shi Jcl-od/od Rats

To investigate the appetite for vitamin C (VC), we conducted behavioral and neural experiments using osteogenic disorder Shionogi/Shi Jcl-od/od (od/od) rats, which lack the ability to synthesize VC, and their wild-type controls osteogenic disorder Shionogi/Shi Jcl- +/+ (+/+) rats. In the behavioral study, rats were deprived of VC for 25 days and then received two-bottle preference tests with a choice between water and 10 mM VC. The preference for 10 mM VC solution of od/od rats was significantly greater than that of +/+ rats. In the neural study, the relative magnitudes of the whole chorda tympani nerve (CTN) responses to 100-1000 mM VC, 3-10 mM HCl, 100-1000 mM NaCl, and 20 mM quinine▪HCl in the VC-deficient rats were significantly smaller than those in the nondeficient ones. Further, we conducted additional behavioral experiments to investigate the appetite for sour and salty taste solutions of VC-deficient od/od rats. Preference scores for 3 mM citric acid increased in od/od rats after VC removal, compared with before, whereas preference scores for 100 and 150 mM NaCl were decreased in VC-deficient od/od rats. The preference for 300 mM NaCl was not changed. Hence, our results suggest that the reduction of the aversive taste of VC during VC deficiency may have involved the reduction of CTN responses to acids. Overall, our results indicate that VC-deficient rats ingest sufficient VC to relieve their deficiency and that VC deficiency causes changes in peripheral sensitivity to acids, but nongustatory factors may also affect VC intake and choice.

The effect of a moderate zinc deficiency and dietary fat source on the activity and expression of the Δ(3)Δ (2)-enoyl-CoA isomerase in the liver of growing rats

Auxiliary enzymes participate in β-oxidation of unsaturated fatty acids. The objective of the study was to investigate the impact of a moderate zinc deficiency and a high intake of polyunsaturated fat on Δ(3)Δ(2)-enoyl-CoA isomerase (ECI) in the liver and other tissues. Five groups of eight weanling rats each were fed moderately zinc-deficient (ZD) or zinc-adequate (ZA) semisynthetic diets (7 or 50 mg Zn/kg) enriched with 22 % cocoa butter (CB) or 22 % safflower oil (SO) for 4 weeks: (1) ZD-CB, fed free choice; (2) ZA-CBR, ZA-CB diet fed in equivalent amounts consumed by the ZD-CB group; (3) ZD-SO, fed free choice; (4) ZA-SOR, ZA-SO diet fed in equivalent amounts consumed by the ZD-SO group; and (5) ZA-SO, fed free choice. Growth and Zn status markers were markedly reduced in the ZD groups. ECI activity in the liver of the animals fed the ZD- and ZA-SO diets were significantly higher (approximately 2- and 3-fold, respectively) as compared with the CB-fed animals, whereas activities in extrahepatic tissues (kidneys, heart, skeletal muscle, testes, adipose tissue) were not altered by dietary treatments. Transcript levels of the mitochondrial Eci gene in the liver did not significantly differ between ZD and ZA rats, but were 1.6-fold higher in the ZA-SO- than in the ZD-CB-fed animals (P < 0.05). It is concluded that diets enriched with safflower oil as a source high in linoleic acid induce markedly increased hepatic ECI activities and that a moderate Zn deficiency does not affect transcription of the mitochondrial Eci gene in the liver.

A Moderate Zinc Deficiency Does Not Impair Gene Expression of PPARα, PPARγ, and Mitochondrial Enoyl-CoA Delta Isomerase in the Liver of Growing Rats

The aim of the study was to investigate the impact of a moderate zinc deficiency and a high intake of polyunsaturated fat on the mRNA expression of peroxisome-proliferator-activated receptor alpha (PPARα), peroxisome-proliferator-activated receptor gamma (PPARγ), and mitochondrial Δ3Δ2-enoyl-CoA isomerase (ECI) in the liver. Weanling rats were assigned to five groups (eight animals each) and fed semi-synthetic, low-carbohydrate diets containing 7 or 50 mg Zn/kg (low-Zn (LZ) or high-Zn (HZ)) and 22% cocoa butter (CB) or 22% safflower (SF) oil for four weeks. One group each was fed the LZ-CB, LZ-SF, or HZ-SF diet free choice, and one group each was fed the HZ-CB and HZ-SF diets in restricted amounts according to intake of the respective LZ diets. The LZ diets markedly lowered growth and zinc concentrations in plasma and femur. Hepatic mRNA levels of PPARα, PPARγ, and ECI were not reduced by the moderate zinc deficiency. Overall, ECI-mRNA abundance was marginally higher in the SF-fed than in the CB-fed animals.

Apparent zinc absorption and zinc status of weanling rats fed moderately zinc-deficient diets enriched with beef tallow or sunflower oil

The aim of the study was to compare apparent Zn absorption and Zn status of weanling rats fed diets that differed in Zn level, fat level and fat source. Semi-synthetic diets, which were about isoenergetic and contained 3% soyabean oil, were supplemented with 7 or 100 mg Zn/kg to create a mild Zn deficiency (LZ) or a high Zn supply (HZ) and with 0 (LF), 22% beef tallow (BT) or 22% sunflower oil (SF) according to a 2 × 3 factorial design of treatments. They were fed ad libitum to 6 × 8 rats for 28 days. Energy intake and growth rates were comparable among the HZ groups. Weight gains in the LZ-LF, LZ-BT and LZ-SF groups averaged 5.54, 4.95 and 4.15 g/day, and apparent Zn absorption averaged 79.4, 60.3 and 48.0 μg Zn/day, respectively, whereas faecal Zn excretion was comparable among these groups. Apparent Zn absorption, and plasma and femur Zn concentrations were lower in the high-fat groups than in the LF group, possibly due to the high cellulose content of the BT and SF diets. Plasma Zn concentrations were higher in the animals fed the BT-based than in the SF-based diets, whereas femur and soft tissue Zn concentrations were comparable among these groups. The differences between the LZ-BT and LZ-SF groups in growth rate, Zn absorption rate and Zn status were confirmed in a second experiment. The results indicate that moderately Zn-deficient diets enriched with SF in relation to BT affect Zn metabolism of weanling rats by a yet unknown mechanism.

Dietary zinc status reversibly alters both the feeding behaviors of the rats and gene expression patterns in diencephalon

Nutritional status influences feeding behaviors, food preferences, and taste sensations. For example, zinc-deficient rats have been reported to show reduced and cyclic food intake patterns with increased preferences for NaCl. Although some impairments of the central nervous and endocrine systems have been speculated to be involved in these phenomena, the effects of short-term zinc deficiency on the brain have not been well examined to date. In this study, we performed a comprehensive analysis of the gene expression patterns in the rat diencephalon, which is a portion of the brain that includes the hypothalamus and thalamus, after short-term zinc deficiency and also during zinc recovery. The rats showed reduced and cyclic food intake patterns with increased salt preferences after a 10-day dietary zinc deficiency. A comparative analysis of their diencephalons using cDNA microarrays revealed that approximately 1% of the genes expressed in the diencephalons showed significantly altered expression levels. On the other hand, a 6-day zinc supplementation following the deprivation allowed for the recovery to initial food intake behaviors and salt preferences. The expression levels of most of the genes that had been altered by exposure to zinc deficient conditions were also recovered. These results show that feeding behaviors, taste preferences and gene expression patterns in the diencephalon respond quickly to changing zinc levels.

Effects of actinomycin D and cycloheximide on zinc status in marginally zinc-deficient rats

During deficient zinc intake, rats are liable to suffer zinc deficiency under the following conditions: higher protein diet, diet containing higher quality (higher nutritive value) protein, and higher dietary intake. This suggests that a higher protein nutritional status (rapid increase in body protein) in rats leads to a lower zinc nutritional status (higher zinc requirement). In contrast, it is expected that a lower protein nutritional status (lowered body protein biosynthesis) is not liable to result in a lower zinc nutritional status. Therefore, the effects of protein biosynthesis inhibitors on zinc status were studied. Actinomycin D and cycloheximide were administered to rats under a marginally zinc-deficient condition. The growth of rats was depressed and serum and femur zinc concentrations were increased by administration of protein biosynthesis inhibitors. The carcasses of rats administered protein synthesis inhibitors had a higher zinc/protein ratio than those of the respective pair-fed (calorically equivalent to the zinc-deficient group) rats. Results suggest that zinc deficiency in rats is mainly alleviated by decreased food intake with administration of protein synthesis inhibitors. Furthermore, protein biosynthesis inhibition alone alleviated zinc deficiency.

Interaction between marginal zinc and high fat supply on lipid metabolism and growth of weanling rats

The impact of a moderate Zn deficiency on growth and plasma and liver lipids was investigated in two 4-week experiments with male weanling rats fed fat-enriched diets. Semisynthetic, approximately isocaloric diets containing 3% soybean oil were supplemented with either 7 or 100 mg Zn/kg diet and with 22% beef tallow (BT) or sunflower oil (SF). In Experiment 1, which compared the dietary fat level and the fat source in a factorial design of treatments, all diets were fed ad libitum to 6 × 8 animals, whereas intake of the high-Zn BT and SF diets was restricted in Experiment 2 (5 × 6 rats) to the level of intake of the respective low-Zn diets. The low-Zn SF diet consistently depressed food intake and final live weights of the animals to a greater extent than the other low-Zn diets, while intake and growth were comparable among the animals fed the high-Zn diets. The marginal Zn deficit per se did not alter plasma triglyceride and cholesterol concentrations nor hepatic concentrations of triglyceride, cholesterol and phospholipids. The fatty acid pattern of liver phospholipids did not indicate that chain elongation and desaturation of fatty acids was impaired by a lack of zinc. It was concluded that dietary energy and fat intake, and fat source have a greater effect on plasma and liver lipids than a moderate Zn deficiency. Marginally Zn-deficient diets enriched with sunflower oil as a major energy source cause a greater growth retardation than diets rich in carbohydrates or beef tallow.

Decreased preference for sucrose in rats fed a low protein diet and its intensification by zinc-deficiency

This study examined whether protein concentrations in the diet of rats fed adequate Zn or deficient Zn affect their preference for disaccharides of sucrose and maltose. Sucrose and maltose were used as a source of carbohydrate and the selection patterns of rats were analyzed for 28 d by a two-choice selection method. Diets provided as a set of two either Zn-adequate or Zn-deficient diets containing 10, 20 and 40% protein each were changed in position daily. For the first 24 h, both the control Zn-adequate and Zn-deficient rats preferred sucrose to maltose and then gradually selected the maltose diet. Protein in the diet affected the selection of the disaccharides for both the control and Zn-deficient rats. The decrease order of the ratio of consumed sucrose to maltose over 28 d was 10% > 20% > 40% protein diet group, and Zn-deficiency emphasized the decrease. These results suggest that sucrose has a stronger taste effect than maltose in rats, but that the selection of sucrose is decreased by the post-ingestive effect which is stimulated in low-protein and Zn-deficient diets.

Zinc deficiency enhances sensitivity to carbon tetrachloride-induced hepatotoxicity in rats

Zinc (Zn) is an essential nutrient that is required in humans and animals for many physiological functions, including immune and antioxidant functions, growth and reproduction. The present study was conducted to examine the influence of Zn deficiency on the protective action against mild oxidative stress induced by a low dose of carbon tetrachloride (CCl(4)) in rats. Male Wistar rats were administered 125 or 250 μL/kg body weight CCl(4), which caused mild or no elevation of serum LDH, AST and ALT enzyme levels in rats fed a diet with adequate Zn. Treatment with CCl(4) (125 μL/kg) caused a significant release of these enzymes into the serum of rats fed a Zn-deficient diet but not in those given a diet with adequate Zn. Furthermore, no histological abnormalities were observed in CCl(4)-untreated rats fed either a diet with adequate Zn or a Zn-deficient diet or in CCl(4) (125 μL/kg)-treated rats fed a diet with adequate Zn. In CCl(4) (125 μL/kg)-treated rats fed a Zn-deficient diet, however, we observed associated collagen accumulation in the liver and hepatic necrosis. The degree of fibrosis was also more severe in CCl(4) (250 μL/kg)-treated rats fed a Zn-deficient diet. These results show that zinc deficiency during an oxidative stress injury negates the protective actions of certain treatments that normally block oxidative damage. The present study suggests that Zn plays an important role in regulating the antioxidative defense system under mild CCl(4) toxic conditions.

Fat source affects growth of weanling rats fed high-fat diets low in zinc

In two 3-week experiments with a 2-factorial design, weanling rats were fed semi-purified diets in which the zinc concentration was either suboptimal or adequate for maximum growth. In experiment 1, one low-fat diet and four diets enriched with 26% beef tallow (BT), butterfat (BF), coconut oil or sunflower oil (SF) were compared. The low-Zn SF diet did not support growth. The animals fed the high-Zn SF diet had the lowest final weights among all other groups, and their serum and femur Zn concentrations were markedly depressed. In experiment 2, the low- and high-Zn diets were enriched with 18% BT, SF, BT + SF (1:1 w/w), or olive oil (OL). Final live weights showed a Zn × fat source interaction. The low-Zn SF and OL groups consumed less food and weighed less than the low-Zn BT group. At the high-Zn level, final weights were comparable among groups. Serum and femur Zn concentrations did not significantly vary among groups fed diets with the same Zn level. Possibilities for the growth-retarding effect of the diets rich in unsaturated fatty acids (SF and OL) are discussed. Metabolic studies are needed to clarify the observed zinc × fat source interaction.

Systemic zinc redistribution and dyshomeostasis in cancer cachexia

Cachexia affects up to two thirds of all cancer patients and is a significant cause of morbidity and mortality. It is a complex metabolic syndrome associated with the underlying illness and characterized by loss of skeletal muscle tissue with or without loss of fat mass. Cachexia's other prominent clinical symptoms include anorexia, systemic inflammation, pediatric growth failure, and hypogonadism. The relationship between the symptoms of cancer cachexia and the underlying illness is unclear, and there is an urgent need for a better understanding of the pathophysiology of this syndrome. Normal Zn metabolism is often disrupted in cancer patients, but the possible effects of systemic Zn dyshomeostasis in cachexia have not been investigated. We propose that the acute phase response can mediate Zn redistribution and accumulation in skeletal muscle tissue and contribute to the activation of the ubiquitin-proteasome pathway that regulates protein catabolism. This chronic redistribution deprives Zn from other tissues and organs and compromises critical physiological functions in the body. The cardinal symptoms of Zn deficiency are anorexia, systemic inflammation, growth failure in children, and hypogonadism. These symptoms also prominently characterize cancer cachexia suggesting that the role of systemic Zn dyshomeostasis in cachexia should be investigated.

Change to a preference for maltose from sucrose over days in Zn-deficient rats selecting from maltose and sucrose diets

This paper describes a preference for two disaccharides in the diets of Zn-adequate and Zn-deficient rats. Maltose and sucrose were used as a source of carbohydrate in the diet and the selection patterns of rats were analyzed for 28 d by a two-choice selection method. Diets provided as a set of two either Zn-adequate or Zn-deficient diets were changed in position daily. Control Zn-adequate and Zn-deficient rats both exclusively selected the sucrose diet at days 1 and 2, after onset of the feeding experiment, and then gradually selected the maltose-diet. After changing their preference from sucrose to maltose, the Zn-adequate control rats selected widely from both the maltose and sucrose diets, while the Zn-deficient rats exclusively and continuously selected the maltose diet from the two diets over the experimental period. The level of selection of sucrose-diet on day 28 had a correlation with the intestinal sucrase activity in the control rats. The sum of daily maltose and sucrose diet intake in rats fed a Zn-deficient diet showed a characteristic variation with the cyclic period of 3.6+/-0.2 d. The daily body-weight change of rats fed a Zn-deficient diet was well synchronized with their own food intake cycle. The day before changing preference from sucrose to maltose in rats fed a Zn-deficient diet represented a trough in their own food intake and body-weight cycles. These results suggest that one sign of a change in preference from sucrose to maltose in Zn-deficient rats is caused by a stage of negative energy balance.

Long-term marginal zinc supply is not detrimental to the skeleton of aged female rats

In this experiment, we investigated the long-term effects of a marginal zinc (Zn) supply on bone metabolism in aged rats. Nine-mo-old female Fischer-344 rats were divided into 8 weight-matched groups of 8 rats each. All rats were adapted for 1 mo to restrictive feeding (7.5 g/d) of a purified diet containing 8 g/kg sodium phytate and 64 mg/kg Zn. Control rats were pair-fed throughout the experiment. During the 1-mo depletion phase, controls received the Zn-replete diet with 64 mg/kg Zn, whereas Zn-deficient rats were fed the same diet with 2.2 mg/kg Zn. The depletion phase was followed by a 3-mo marginal phase in which the rats fed the diet with 2.2 mg/kg Zn received an additional daily Zn supplement of 75 microg Zn/rat by gavage. In the following 2-mo repletion phase, a marginal group was switched to the Zn-replete diet, while the other groups were maintained on marginal Zn supply or on the Zn-replete diet. Zn depletion and marginal Zn reduced serum and bone Zn and serum alkaline phosphatase activity. Zn repletion normalized serum Zn. However, apart from subtle changes in bone mineralization density distribution, Zn deficiency was not associated with detrimental effects on bone mineral density, turnover, architecture, or biomechanics relative to control rats at any time point. Our data suggest that Zn does not play an essential role in bone metabolism in aged rats and cast doubt on the hypthosis that Zn deficiency is a risk factor for osteoporosis.

Recent developments in calcium-related obesity research

The influence of calcium and dairy food intake on energy balance is the object of a growing scientific literature. This manuscript presents the information discussed by subject experts during a symposium on calcium and obesity, initially planned to document in a comprehensive manner the role of calcium and dairy food on energy balance and body composition. This manuscript is organized into 13 propositions statements which either resume the presentation of an invited speaker or integrate recent developments in calcium-related obesity research. More specifically, the effects of calcium and dairy consumption on body weight and adiposity level, appetite, weight loss intervention outcome, lipid-lipoprotein profile and the risk to develop metabolic syndrome are discussed together with the metabolic mechanisms proposed to explain these effects. Taken together, the observations presented in this manuscript suggest that calcium and dairy food intake can influence many components of energy and fat balance, indicating that inadequate calcium/dairy intake may increase the risk of positive energy balance and of other health problems.

The effect of peripheral administration of zinc on food intake in rats fed Zn-adequate or Zn-deficient diets

Zinc deficiency induces a striking reduction of food intake in animals. To elucidate the mechanisms for this effect, two studies were connectedly conducted to determine the effects of peripheral administration of zinc on food intake in rats fed the zinc-adequate or zinc-deficient diets for a 3-week period. In study 1, two groups of male Sprague-Dawley rats were provided diets made either adequate (ZA; 38.89 mg/kg) or deficient (ZD; 3.30 mg/kg) in zinc. In study 2, after feeding for 3 weeks, both ZA and ZD groups received intraperitoneal (IP) injection of zinc solution with three levels (0.5, 1.0, and 2.0 microg zinc/g body weight, respectively) and cumulative food intake at 0.5, 1, 2, 4, and 24 h, and plasma hormones concentrations were measured. The results in study 1 showed rats fed the ZD diets revealed symptoms of zinc deficiency, such as sparse and coarse hair, poor appetite, susceptibility to surroundings, lethargy, and small movements. Zinc concentrations in serum, femur, and skeletal muscle of rats fed the ZD diets declined by 26.58% (P < 0.01), 27.32% (P < 0.01), and 24.22% (P < 0.05), respectively, as compared with ZA control group. These findings demonstrated that rat models with zinc deficiency and zinc adequacy had been fully established. The results in study 2 showed that IP administration of zinc in both ZA and ZD rats did not influence food intake at each time points (P > 0.05), although zinc deficiency suppressed food intake. Plasma neuropeptide Y (NPY) was higher, but insulin and glucagon were lower in response to zinc deficiency or zinc administration by contrast with their respective controls (P < 0.05). Leptin, T3, and T4 concentrations were uniformly decreased (P < 0.05) in rats fed the ZD diets in contrast to ZA diets; however, no differences (P > 0.05) were observed during zinc injection. Calcitonin gene-related peptide was unaffected (P > 0.05) by either zinc deficiency or zinc administration. The present studies suggested that zinc administration did not affect short-term food intake in rats even in the zinc-deficient ones; the reduced food intake induced by zinc deficiency was probably associated with the depression in thyroid hormones. The results also indicated that NPY and insulin varied conversely during the control of food intake.

Growth of zinc-deficient rats during intra-gastric tube feeding

This study aimed to examine the reasons for the lack of growth in rats fed a zinc-deficient (ZnD) diet via gastric tube. Four days after rats were given free access to the ZnD diet (0.3 mg/kg Zn), their food intake had decreased, and their growth had stopped. Rats were then fed via gastric tube; growth was restored in rats fed a control diet (25 mg/kg Zn; restored group) but not in those fed the ZnD diet (ZnD group). In the ZnD group, there was no reduction in the apparent absorption of dry matter, protein, or ash during 3 days of tube feeding. Dry matter in urine was markedly higher on day 3 and mainly consisted of glucose. Urinary nitrogen was also elevated in the ZnD group, but nitrogen balance remained positive; i.e., bodily protein continued to increase during the 3 days of tube feeding. Drinking water consumption in the ZnD group was markedly reduced from the second day of tube feeding. On the other hand, urine volume in the ZnD group was comparable to that in the restored group. Water content in the bodies of the ZnD group was reduced. These observations demonstrate that the ZnD group was dehydrated. In conclusion, rats fed a ZnD diet via gastric tube did not grow because their drinking water consumption decreased with progression of zinc deficiency, thereby, decreasing bodily water content. Administration of water led to growth in the ZnD group.

Licking for taste solutions by potassium-deprived rats: specificity and mechanisms

There has been little work on the specificity and mechanisms underlying the appetite of potassium (K(+)) deprived rats, and there are conflicting results. To investigate the contribution of oral factors to changes in intake induced by K(+) deficiency, we conducted two experiments using 20-s "brief access" tests. In Experiment 1, K(+)-deprived rats licked less for water than did replete rats. After adjusting for this difference, K(+)-deprived rats exhibited increased licking for 100 mM CaCl(2), 100 mM MgCl(2), and 100 mM FeCl(2) compared with K(+)-replete rats. In Experiment 2, which used larger rats, the K(+)-deprived and replete groups licked equally for water, 500 mM Na.Gluconate, 350 mM KCl, 500 mM KHCO(3), and 1 mM quinine.HCl, but the K(+)-deprived rats licked more for 500 mM KCl, 500 mM CsCl, and 500 mM NaCl than did the replete rats. Licking was unaffected by addition to NaCl of 200 muM amiloride, an epithelial Na(+) channel (ENaC) blocker, or 100 muM ruthenium red, a vanilloid receptor 1 (VR-1) antagonist, or by addition to KCl of 50 muM 4-aminopyridine, a K(+) channel blocker. These findings suggest that K(+)-deprivation produces a non-specific appetite that is guided by oral factors. We found no evidence that this response was mediated by ENaC, VR-1, or K(+) channels in taste receptor cells.

Longitudinal measures of circulating leptin and ghrelin concentrations are associated with the growth of young Peruvian children but are not affected by zinc supplementation

BACKGROUND

Leptin, ghrelin, and insulin are hormonal regulators of energy balance and, therefore, may be related to growth during infancy. Zinc is essential for growth, and its growth effects may be mediated through these hormones.

OBJECTIVE

We examined the effects of supplemental zinc on plasma leptin, ghrelin, and insulin concentrations among young children at risk of zinc deficiency and examined the relations between these hormones and physical growth.

DESIGN

Children (n = 142) aged 6-8 mo were randomly assigned to receive 3 mg Zn/d as a supplement, in a fortified food, or as a placebo for 6 mo. Relations between hormones and anthropometric z scores, body composition, and growth rates were examined at baseline and 3 and 6 mo after the start of the intervention.

RESULTS

No treatment group-related differences were found in plasma leptin, ghrelin, or glucose concentrations or in anthropometric z scores at 3 or 6 mo after the start of the zinc intervention. Neither plasma leptin nor ghrelin concentrations at baseline or 3 mo were predictive of subsequent changes in growth. However, changes in weight-for-age z scores over the two 3-mo time intervals were positively associated with subsequent leptin concentrations and inversely associated with subsequent plasma ghrelin concentrations.

CONCLUSIONS

Supplemental zinc did not affect the children's growth, anthropometric indexes, or plasma hormone concentrations in this study population. Our results suggest that plasma leptin and ghrelin concentrations in later infancy are a consequence of previous weight changes rather than predictors of short-term growth.

Zinc deficiency negatively affects alkaline phosphatase and the concentration of Ca, Mg and P in rats

Zn is an essential nutrient that is required in humans and animals for many physiological functions, including immune and antioxidant function, growth, and reproduction. The present study evaluated whether Zn deficiency would negatively affect bone-related enzyme, ALP, and other bone-related minerals (Ca, P and Mg) in rats. Thirty Sprague Dawley rats were assigned to one of the three different Zn dietary groups, such as Zn adequate (ZA, 35 mg/kg), pair fed (PF, 35 mg/kg), Zn deficient (ZD, 1 mg/kg) diet, and fed for 10 weeks. Food intake and body weight were measured daily and weekly, respectively. ALP was measured by spectrophotometry and mineral contents were measured by inductively coupled plasma-mass spectrophotometer (ICP-MS). Zn deficient rats showed decreased food intake and body weight compared with Zn adequate rats (p<0.05). Zn deficiency reduced ALP activity in blood (RBC, plasma) and the tissues (liver, kidney and small intestine) (p<0.05). Also, Zn deficiency reduced mineral concentrations in rat tissues (Ca for muscle and liver, and Mg for muscle and liver) (p<0.05). The study results imply the requirement of proper Zn nurture for maintaining bone growth and formation.

Noradrenergic activity in the paraventricular nucleus and macronutrient choice during early dark onset by zinc deficient rats

Carbohydrate is a preferred macronutrient of rats during the early dark phase and associated with an increase in norepinephrine (NE) and neuropeptide Y (NPY) in the paraventricular nucleus (PVN). Macronutrient choice is altered during zinc deficiency (ZD). The relationship between NE activity in the PVN and macronutrient choice during early dark was evaluated in rats fed zinc adequate (ZA) or ZD diet for 14 days. Total caloric intake was similar for ZA and ZD groups (-20 kJ) but ZA rats selected 63 +/- 5% of calories as carbohydrate while ZD rats selected 53 +/- 5% of their calories from protein (p < 0.01). Pair-fed (PF) rats selected 62 +/- 5% of calories as carbohydrate. Noradrenergic activity was lower (p < 0.01) in ZD and PF compared to ZA. The association between increased NE in the PVN at dark onset and selection of carbohydrate is not supported by the present results.

Eating and drinking activity of newly weaned piglets: Effects of individual characteristics, social mixing, and addition of extra zinc to the feed1

In production systems, piglets usually fast for a period after weaning, thereby increasing the risk of diarrhea and a reduction in growth. The low level of eating may relate to insufficient drinking activity, as solid feed intake must be accompanied by water intake. Mixing of newly weaned piglets is a well-known stressor and a common procedure in pig production. The effect of mixing on the temporal development of eating and drinking activity in newly weaned piglets has not been elucidated. High concentrations of zinc (Zn) in the feed improve the health and performance of piglets after weaning, but the underlying mechanisms are still obscure. One possibility is that Zn affects eating and drinking behavior. The effects of mixing 4 littermates from each of 2 litters and adding zinc oxide (ZnO; 2,500 ppm of Zn) to the feed were studied in a 2 x 2 factorial experiment using 123 piglets weaned at 27 d of age. Individual eating and drinking times during the initial 48 h after weaning were analyzed on 2 levels of aggregation, day and hour. The piglets spent less time eating on the first day after weaning compared with the second day (20 +/- 5 vs. 98 +/- 10 min, respectively; P < 0.001), whereas they spent more time drinking on the first day compared with the second day (13 +/- 1 vs. 9 +/- 0.5 min, respectively; P < 0.001). Eating and drinking times were positively associated (P < 0.001). Females ate for longer than males (61 +/- 8 vs. 44 +/- 7 min/24 h, respectively, P = 0.002), whereas sex did not affect drinking time. Drinking time increased (P = 0.003) and eating time decreased (P = 0.001) with increasing preweaning growth rate and weaning weight. Neither mixing nor addition of ZnO affected the daily eating time. However, nonmixed piglets given 2,500 ppm of Zn as ZnO in the feed spent more time drinking per day (12 +/- 1 min) than did nonmixed piglets offered 100 ppm of Zn as ZnO (10 +/- 1 min; P = 0.002). Mixing also affected the hourly distribution of the drinking activity (P < 0.05). In conclusion, the drinking behavior of newly weaned piglets was more affected by the external factors, mixing and addition of ZnO to the feed, than the eating behavior. As eating and drinking are strongly associated, more focus should be paid to the water intake and the interplay between eating and drinking behavior in future studies aiming to reduce weaning problems.

EFFECT OF ZINC SULPHATE AND ZINC METHIONINE ON GROWTH, PLASMA GROWTH HORMONE CONCENTRATION, GROWTH HORMONE RECEPTOR AND INSULIN-LIKE GROWTH FACTOR-I GENE EXPRESSION IN MICE

1. The current experiment was conducted to investigate the effect of zinc sulphate (ZnSO4) and zinc methionine (Zn-Met) on growth and their effect on plasma growth hormone (GH) concentration, growth hormone receptor (GHR) and insulin-like growth factor I (IGF-I) mRNA expression in mice. 2. Ninety male KunMing (KM) mice were randomly divided into three treatments. The control group was fed on a basal diet containing 11.67 mg/kg of zinc. The ZnSO4 group and Zn-Met group were fed on the diets supplemented with ZnSO4 or Zn-Met at 30 mg/kg (containing zinc of 40.05 and 40.75 mg/kg, respectively). The mice were offered the test diets for 10 days. Weight gains and food intake were measured at the end of the experiment, zinc contents in liver and serum were determined using atomic absorption spectrophotometry; GH was determined by radioimmunoassay, the levels of GHR and IGF-I mRNA were determined with reverse transcript polymerase chain reaction. 3. Both ZnSO4 and Zn-Met enhanced weight gain and food intake in the mice, Zn-Met improved the growth and food intake more effectively than ZnSO4 did (P < 0.05). The both forms of zinc had no effect on GH and the level of GHR mRNA expression (P > 0.05) and they up-regulated the expression of IGF-I mRNA (P < 0.05). As compared to ZnSO4, Zn-Met enhanced the level of IGF-I mRNA significantly (P < 0.05). 4. Both ZnSO4 and Zn-Met had no effect on plasma GH and the expression of GHR mRNA, but they enhanced the expression of IGF-I mRNA. Zinc methionine enhanced the weight gain and up-regulated IGF-I mRNA expression more effectively than ZnSO4.

Choice feeding of selenium-deficient laying hens affects diet selection, selenium intake and body weight

Inadequate selenium (Se) supply often in combination with low vitamin E status causes deficiency symptoms in many species. It is likely that a vague discomfort or sickness is perceived before clear deficiency signs become apparent. We investigated whether Se-deficient hens reduce their Se deficit by selecting a diet containing more selenium when offered two diets with different Se concentrations. A Low-Se diet (0.07 mg Se/kg) was supplemented with Se-enriched yeast (Sel-Plex 50) to produce Medium-Se (0.20 mg Se/kg) and High-Se (1.50 mg Se/kg) diets. Each of two consecutive study parts (I and II) with the same hens and treatments began with a 6-wk baseline period (Medium-Se diet), subsequently followed a 9-wk depletion period (Low-Se diet or Medium-Se diet), then a 6-wk choice feeding period in which two diets with different Se concentrations (Low-Se and Medium-Se, Medium-Se and High-Se, or Low-Se and High-Se) were offered. A control group received the Medium-Se diet throughout the study. Daily Se intake, calculated from daily feed intake, followed similar patterns in both parts of the study, but Se-deficient hens preferred (P < 0.05) the High-Se diet to the Low-Se diet during the first 3 wk of choice feeding only in part I. We conclude that young Se-deficient laying hens reduce their Se deficit if they have a choice between a Low-Se and a High-Se diet by preferentially selecting the High-Se diet, possibly based on learned place preference and/or learned taste aversion to the Low-Se diet, presumably in response to discomfort due to Se-deficiency.

Growth hormone-releasing factor affects macronutrient intake during the anabolic phase of zinc repletion: total hypothalamic growth hormone-releasing factor content and growth hormone-releasing factor immunoneutralization during zinc repletion

Growth hormone-releasing factor (GRF) is thought to perform two distinct functions within the brain. GRF synthesized in the median eminence (ME) stimulates the release of growth hormone (GH) from the pituitary, while GRF in the suprachiasmatic nucleus and median preoptic area (SCN/MPOA) may stimulate selection of dietary protein. These two functions may be coupled to regulate and enhance growth. During zinc repletion, a period characterized by increased protein intake and accelerated growth, we examined this coupling by measuring GRF peptide content in hypothalamic sites and neutralizing GRF function by infusing anti-GRF antibody into the hypothalamus during zinc repletion. Total GRF content and GRF content in the ME and SCN/MPOA were decreased in zinc-deficient (Zn-) rats compared to zinc-adequate (Zn+) rats (P < 0.05). There were no differences in GRF content during zinc repletion in either nuclei. Subsequently, we investigated the macronutrient feeding patterns of rats chronically infused with anti-GRF IgG into the lateral ventricle of the brain during zinc repletion. All Zn- and Zn+ rats administered anti-GRF IgG exhibited a reduction in protein intake during zinc repletion. The Zn- rats receiving anti-GRF-IgG consumed equal amounts of total diet compared to those receiving vehicle during the repletion period however they consumed less carbohydrate (P < 0.05) and considerably more fat (P < 0.02). There were no significant differences in carbohydrate or fat intake in Zn+ rats receiving anti-GRF antibody. These results suggest that GRF likely directs protein intake during normal growth, but may interact with additional appetite-controlling neuropeptides during zinc repletion.

Magnesium appetite in the rat

Rats modify their ingestive behaviour to correct deficiencies of minerals such as sodium and calcium. Here, we examined the effect of magnesium deprivation on the ingestion of MgCl2 and other solutions. Male Sprague-Dawley rats were fed a nutritionally complete or magnesium-deficient diet and were then given 3.2, 10, 32, or 100mM MgCl2, 32mM CaCl2, 32mM NaCl, 10mM HCl, or 2.5mM saccharin, and their intake was measured for 24h in a two-bottle choice test with water. Within the first 5 min, magnesium-deprived subjects given 3.2, 32, or 100mM MgCl2 or 32mM CaCl2 drank significantly more of these solutions than did replete rats. In a separate study, rats fed replete, magnesium-deficient, or calcium-deficient diets were given a three-bottle choice between water, 32mM MgCl2, and 32mM CaCl2. The deprived rats preferred the solution that ameliorated their deficiency; for example, during the first 1h, the magnesium-deprived rats drank 3.1 +/- 0.5ml MgCl2 and 1.1 +/- 0.4ml CaCl2, whereas the calcium-deprived rats drank 1.8 +/- 0.5ml MgCl2 and 3.9 +/- 0.4ml CaCl2. Thus, magnesium deprivation leads to a compensatory appetite for magnesium, and the appetites for magnesium and calcium are distinct and specific. The rapid expression of magnesium appetite suggests that it depends in part on innate, gustatory factors.

Zinc status affects neurotransmitter activity in the paraventricular nucleus of rats

Alterations in neurochemical activity in the paraventricular nucleus (PVN) of the hypothalamus may account for decreased intake of zinc-deficient diets. Male Sprague-Dawley rats were fed zinc-deficient (ZD) or zinc-adequate (ZA) diet for 14 d before samples of extracellular fluid in the PVN were collected by microdialysis or push-pull perfusion. A third set of rats was pair-fed (PF) an amount of ZA diet equal to the intake of ZD rats. Samples were collected over a 2-h period spanning the transition from light to dark. All rats then consumed the zinc adequate diet ad libitum for 3 d before a second set of samples was collected. The increase in extracellular norepineprhrine (NE) during h 1 of the dark period to 147 +/- 13% of baseline (P < 0.05) was apparent only in ZA rats at d 14. After the 3-d repletion period, the increase in NE at dark onset occurred in all three groups. An increase in extracellular neuropeptide Y (NPY) at dark onset to 174 +/- 32% of baseline in rats fed ZA (P < 0.01) was measured in all three groups at both d 14 and 17. Basal NPY concentrations were significantly elevated in PF rats on d 14 (7.45 +/- 2.01 vs. 0.58 +/- 0.23 pmol/L, P = 0.01) and returned to ZA levels by d 17. The activities of the NE and NPY systems in the PVN were altered in rats fed a zinc-deficient diet; however, it is unclear whether the disruption in the NE and NPY neural systems in the PVN results in the altered feeding behavior accompanying zinc deficiency.

Neuropeptide Y fails to normalize food intake in zinc-deficient rats

Zinc deprivation results in decreased and cyclic food intake in rats. We determined the response of zinc-deprived rats to neuropeptide Y (NPY). In a preliminary experiment, rats were fed a low (-Zn; <1 mg/kg) or adequate zinc diet (+Zn; 100 mg/kg) for 4 days. NPY (5 or 10 microg) was then administered via an intracerebroventricular (ICV) cannula and food intake measured for 4 h. NPY stimulated food intake in all rats, but the difference in food intake due to zinc deprivation persisted. In a subsequent experiment, rats were fed the low zinc and adequate zinc diets for 4, 5 or 6 days. Food intake was suppressed in rats fed the low zinc compared to the adequate zinc diet on all of these days. When NPY (10 microg) was administered at the onset of the light cycle, the food intake was approximately 2.5-fold greater regardless of dietary zinc status, but the amount of food consumed by rats fed low zinc was approximately one-half the quantity consumed by NPY-stimulated zinc-adequate rats. NPY administered at the onset of dark failed to stimulate food intake in either dietary group although the total intake difference due to zinc status persisted. ICV administration of 5 nmol of zinc prior to NPY injection failed to correct the food intake response of the zinc-deficient rats. We conclude that the basis of the reduced food intake of zinc-deficient rats does not relate to NPY quantity or release, or to impairment of its signal transduction. There appears to be another undefined factor that limits food intake in zinc deficiency.

Age-dependent influence of dietary zinc restriction on short-term memory in male rats

Zinc is an essential micro-nutrient involved in numerous physiological functions. The high content of zinc in the hippocampus, coupled with the integral involvement of the hippocampus in memory, strongly implicates zinc in memory processing. The hypothesis of the current study was that dietary zinc restriction influenced short-term memory in postweaned rats, and this influence was age-dependent. Male rats (43 days to 18 months old) were divided into five experimental groups based on age, and fed zinc-adequate (zinc at 20 mg/kg as zinc chloride) or zinc-deficient (zinc less than 1-2 mg/kg) diets for a minimum of 3 weeks. Short-term memory was assessed using the distal-cue version of the Morris water maze (MWM). All rats fed the zinc-restricted diet exhibited cyclic anorexia, decreased weight gain, and significantly lower liver and femur zinc concentrations compared to age-matched controls. Further, whole brain, hippocampal, and cerebral wet weights were significantly reduced in the zinc-restricted treatment groups of all the age groups. Only zinc-restricted rats that were less than 62 days of age at the start of zinc restriction demonstrated significantly prolonged escape latencies in the water maze, indicating deficits in short-term memory. Regression analyses confirmed that the short-term memory deficits were correlated with significantly lower hippocampal and cerebral zinc concentrations compared to age-matched control and pair-fed rats. These results emphasize the significance of a critical age of influence for dietary zinc in memory processing, and the importance of considering age when studying zinc nutriture and CNS function.

Induction of metallothionein by exposure to normobaric 100% oxygen atmosphere in rats with different zinc supply

The objective of this study was to determine the effects of an oxygen enriched environment on the induction of the metalloprotein metallothionein (MT) and its relation to zinc metabolism in rats supplied with different levels of dietary zinc. Male albino rats were fed purified diets based on maize starch, egg white, saccharose and soybean oil differing in the concentration of zinc (1; 20; 100; 500 mg Zn/kg diet). At a dietary zinc supply of 1 mg/kg, the rats developed a zinc deficiency indicated by visual and biochemical parameters. At the end of the 37-day feeding period, half of the rats were exposed to 100% oxygen for 12 h. The oxygen treatment significantly reduced plasma zinc in the zinc supplemented rats and reduced it in tendency in the zinc deficient rats. The MT concentration was increased in the zinc supplemented groups in the liver, kidney and lung. The oxygen treatment elevated the metallothionein concentration in the two high zinc supplemented groups (100 and 500 mg Zn/kg diet) in the liver. The response of the zinc concentration in plasma and of hepatic metallothionein levels to oxygen exposure indicates a role of metallothionein in zinc distribution or interactions with other trace elements to support antioxidant capacity, rather than an impact on direct scavenging activity of free radicals.

Self-selection of copper-containing diets by copper-deficient and overloaded rats

To determine the effect of copper status on the preference for copper-containing food, male Sprague-Dawley rats were weaned to a copper-deficient, copper-adequate or high-copper diet. Four weeks later, alterations in copper status were confirmed by measurement of liver copper concentrations. Rats (n=10) were then given the choice between a copper-adequate or a copper-restricted diet of similar composition. Preference scores indicated that control rats preferred copper-deficient food. Preferences of rats on the high-copper diet were not different from control rats, suggesting that copper overload did not alter the pattern of selection. However, 7 of the 10 copper-deficient rats ate 80% or more of their intake as copper-adequate food resulting in preference scores that were significantly different from controls (p<0.03). This alteration in preference was corrected within 1 day of access to copper-adequate food.

Zinc elevates neuropeptide Y levels in rat pheochromocytoma cells by a mechanism independent of L-channel mediated inhibition of release

Both zinc and neuropeptide Y (NPY) have been implicated as playing a role in seizures and feeding behavior. We investigated the hypothesis that zinc could regulate levels of NPY, and found that chronic exposure to 50-100 microM zinc increased levels of cellular NPY in cultured PC12 cells grown in the presence of nerve growth factor. Zinc's effect on NPY was specific, time- and concentration-dependent, and independent of inhibition of NPY release secondary to blockade of dihydropyridine-sensitive calcium channels. These results are consistent with a role for zinc in regulating hippocampal NPY following high-frequency neuronal activity.

Neurobiology of zinc-influenced eating behavior

Zinc is an essential nutrient that is required in humans and animals for many physiological functions, including immune and antioxidant function, growth and reproduction. Many aspects of zinc deficiency-induced anorexia have been well studied in experimental animals, most notably the laboratory rat. There is evidence that suggests zinc deficiency may be intimately involved with anorexia in humans: if not as an initiating cause, then as an accelerating or exacerbating factor that may deepen the pathology of the anorexia. The present review describes recent research investigating the relationship between zinc deficiency and the regulation of food intake, along with advances in the understanding of the food intake and body weight regulation systems. For more comprehensive reviews of zinc nutrition and zinc deficiency, readers are referred to the other reviews in this volume and the review text of Mills (1989). An excellent review focused solely on zinc status and food intake has been presented by O'Dell and Reeves (1989).

Effects of dietary zinc deficiency on homocysteine and folate metabolism in rats

In rats, zinc deficiency has been reported to result in elevated hepatic methionine synthase activity and alterations in folate metabolism. We investigated the effect of zinc deficiency on plasma homocysteine concentrations and the distribution of hepatic folates. Weanling male rats were fed ad libitum a zinc-sufficient control diet (382.0 nmol zinc/g diet), a low-zinc diet (7.5 nmol zinc/g diet), or a control diet pair-fed to the intake of the zinc-deficient rats. After 6 weeks, the body weights of the zinc-deficient and pair-fed control groups were lower than those of controls, and plasma zinc concentrations were lowest in the zinc-deficient group. Plasma homocysteine concentrations in the zinc-deficient group (2.3 +/- 0.2 micromol/L) were significantly lower than those in the ad libitum-fed and pair-fed control groups (6.7 +/- 0.5 and 3.2 +/- 0.4 micromol/L, respectively). Hepatic methionine synthase activity in the zinc-deficient group was higher than in the other two groups. Low mean percentage of 5-methyltetrahydrofolate in total hepatic folates and low plasma folate concentration were observed in the zinc-deficient group compared with the ad libitum-fed and pair-fed control groups. The reduced plasma homocysteine and folate concentrations and reduced percentage of hepatic 5-methyltetrahydrofolate are probably secondary to the increased activity of hepatic methionine synthase in zinc deficiency.

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.

History of zinc as related to brain function

Zinc (Zn) is essential for synthesis of coenzymes that mediate biogenic-amine synthesis and metabolism. Zn from vesicles in presynaptic terminals of certain glutaminergic neurons modulates postsynaptic N-methyl-D-aspartate (NMDA) receptors for glutamate. Large amounts of Zn released from vesicles by seizures or ischemia can kill postsynaptic neurons. Acute Zn deficiency impairs brain function of experimental animals and humans. Zn deficiency in experimental animals during early brain development causes malformations, whereas deficiency later in brain development causes microscopic abnormalities and impairs subsequent function. A limited number of studies suggest that similar phenomena can occur in humans.

Plasma apolipoprotein B-48, hepatic apolipoprotein B mRNA editing and apolipoprotein B mRNA editing catalytic subunit-1 mRNA levels are altered in zinc-deficient rats

Apolipoprotein B (apoB) exists as two major isoforms and serves as an obligatory component of lipid-rich plasma lipoprotein particles. Apolipoprotein B mRNA editing is a zinc-dependent, site-specific cytidine deamination that determines whether the apoB-100 or apoB-48 isoform is synthesized. The objective of this work was to examine whether dietary zinc levels affect apoB mRNA editing in vivo. Adult male Sprague-Dawley rats were randomly assigned to zinc-deficient (ZD, <0.5 mg Zn/kg diet), zinc-adequate (ZA, 30 mg Zn/kg diet) or zinc-replenished (ZDA, ZD rats fed the ZA diet for last 2 d) dietary groups for 18 d. The ratio of plasma apolipoprotein B-48 (apoB-48) to total apoB was significantly lower in zinc-deficient compared with zinc-adequate rats. Primer extension analysis indicated a modest but significant reduction in hepatic apoB mRNA editing in ZD rats compared with that of the ZA group. In ZDA rats, hepatic apoB mRNA editing and the percentage of plasma apoB-48 to total apoB were not different from ZA rats. The mRNA abundance of hepatic apobec-1 (apoB mRNA editing catalytic subunit 1) was significantly lower in ZD and ZDA rats than in ZA rats. In summary, the plasma ratio of apoB-48 to total apoB protein as well as hepatic apoB mRNA editing and hepatic apobec-1 mRNA levels were reduced in rats consuming a zinc-deficient diet. These data suggest that one or more components of apoB metabolism may be influenced by dietary zinc status.

Regulation of neuropeptide Y mRNA and peptide concentrations by copper in rat olfactory bulb

Neuropeptide Y is highly abundant in both the peripheral and central nervous systems and is known to have diverse functions including regulation of feeding behavior, blood pressure, circadian rhythms, reproductive behavior and the response to stress. Northern analysis showed that copper deficiency increased brain NPY mRNA abundance particularly in the olfactory bulb (OB). These increases were not accompanied by alterations in food intake or blood pressure. After 4 weeks of a copper-restricted diet, OB copper concentrations decreased to 44% of control and NPY mRNA increased 1.5-fold. Addition of a copper chelator to the restricted diet, resulted in a two-fold increase in OB NPY mRNA over copper adequate controls. These results were confirmed in primary cultures of OB neurons suggesting that the regulation of NPY mRNA is at the level of the bulb rather than by a hormonal or other copper-regulated factor external to the OB. Immunoreactive NPY (IR-NPY) levels were not, however, increased following the 4 weeks of copper deficiency. Addition of the chelator resulted in a 1.4-fold increase in IR-NPY that, while statistically significant, was not proportional to the two-fold increase in NPY mRNA in the same study. This may suggest that copper deficiency inhibits the translational mechanisms responsible for the synthesis of NPY or that NPY is exported from the bulb in copper deficiency.

Personal reflections on a galvanizing trail

This article encompasses my perception of, and experience in, an exciting segment of the trace element era in nutrition research: the role of zinc in the nutrition of animals and humans. Zinc has been a major player on the stage of trace element research, and it has left a trail that galvanized the attention of many researchers, including myself. It is ubiquitous in biological systems, and it plays a multitude of physiologic and biochemical functions. A brief historical overview is followed by a discussion of the contributions the work done in my laboratory has made toward understanding the physiological and biochemical functions of zinc. The effort of 40 years has led to the belief that one of zinc's major roles, and perhaps its first limiting role, is to preserve plasma-membrane function as regards ion channels and signal transduction. Although substantial knowledge has been gained relating to the importance of zinc in nutrition, much remains to be discovered.

[Protein and energy needs of the infant with severe malnutrition. Application in a hospital environment for the treatment of malnutrition caused by deficient intake]

Severe malnutrition is defined by a weight for height below 70% of international standards or by presence of oedema in a clinically undernourished child. Severe malnutrition associated with oedema is called kwashiorkor. The origin of oedemas of kwashiorkor is still debated, but its relation with protein deficiency is strongly questioned. The same dietary management is now recommended for malnutrition with or without oedema. Present recommendations are based, as for well nourished children, on the separate estimation of nutritional requirements for maintenance and growth. Total requirements vary between 0.7 g/kg/day in the first few days of treatment to 5 g/kg/day or more when weight gain is maximum. As a result of high energy requirement during catch-up growth, protein requirements never exceed 10 to 12% of total energy needs.

Zinc deficiency increases hypothalamic neuropeptide Y and neuropeptide Y mRNA levels and does not block neuropeptide Y-induced feeding in rats

Zinc deficiency reduces intake and produces an unusual approximately 3.5-d cycle of intake in rats. The mechanism underlying the anorexia and cycling has not yet been defined; current hypotheses suggest that alterations in amino acid metabolism and neurotransmitter concentrations may be a part of this anorexia. Recent reports indicate that appetite-stimulating neuropeptide Y (NPY) may be elevated during zinc deficiency. This suggests that a resistance to NPY may exist during zinc deficiency because NPY levels are high, yet appetite is low. The purpose of this study was to measure NPY peptide and mRNA concentrations during zinc deficiency in specific nuclei of the hypothalamus in which peptide and mRNA for NPY are known to be associated with appetite, and also to determine whether zinc-deficient rats are responsive to central infusions of NPY. Both NPY peptide levels in the paraventricular nucleus and NPY mRNA levels in the arcuate nucleus were higher (P < 0.05) in zinc-deficient rats than in zinc-adequate rats. When rats were administered exogenous NPY to the paraventricular nucleus, both zinc-deficient and zinc-adequate rats responded similarly by increasing food intake. These results suggest that NPY is elevated during zinc deficiency in an attempt to restore normal food intake levels, rather than being reduced and thereby contributing to the anorexia associated with zinc deficiency. During zinc deficiency, NPY receptors are able to bind NPY and initiate an orexigenic response.