Assessment of selenium bioavailability from naturally produced high-selenium soy foods in selenium-deficient rats.

We assessed the bioavailability of selenium (Se) from a protein isolate and tofu (bean curd) prepared from naturally produced high-Se soybeans. The Se concentrations of the soybeans, the protein isolate and tofu were 5.2±0.2, 11.4±0.1 and 7.4±0.1mg/kg, respectively. Male weanling Sprague-Dawley rats were depleted of Se by feeding them a 30% Torula yeast-based diet (4.1µg Se/kg) for 56 days, and then they were replenished with Se for an additional 50 days by feeding them the same diet containing 14, 24 or 30 µg Se/kg from the protein isolate or 13, 23 or 31 µg Se/kg from tofu, respectively. l-Selenomethionine (SeMet) was used as a reference. Selenium bioavailability was determined on the basis of the restoration of Se-dependent enzyme activities and tissue Se concentrations in Se-depleted rats, comparing those responses for the protein isolate and tofu to those for SeMet by using a slope-ratio method. Dietary supplementation with the protein isolate or tofu resulted in linear or log-linear, dose-dependent increases in glutathione peroxidase activities in blood and liver and in thioredoxin reductase activity in liver. Furthermore, supplementation with the protein isolate or tofu resulted in linear or log-linear, dose-dependent increases in the Se concentrations of plasma, liver, muscle and kidneys. These results indicated an overall bioavailability of approximately 101% for Se from the protein isolate and 94% from tofu, relative to SeMet. We conclude that Se from naturally produced high-Se soybeans is highly bioavailable in this model and that high-Se soybeans may be a good dietary source of Se.

Selenium bioavailability from soy protein isolate and tofu in rats fed a torula yeast-based diet.

Selenium (Se) is an essential nutrient, and soy is a major plant source of dietary protein to humans. The United States produces one-third of the world's soybeans, and the Se-rich Northern Plains produce a large share of the nation's soybeans. The present study used a rat model to determine the bioavailability of Se from a protein isolate and tofu (bean curd) prepared from a soybean cultivar we recently developed specifically for food grade markets. The soybean seeds contained 2.91 mg Se/kg. Male Sprague-Dawley rats were depleted of Se by feeding them a 30% Torula yeast-based diet containing 5 microg Se/kg; after 56 days, they were replenished of Se for an additional 50 days by feeding them the same diet supplemented with 20, 30, or 40 microg Se/kg from soy protein isolate or tofu. l-Selenomethionine (SeMet) was used as a reference. Selenium bioavailability was determined on the basis of the responses of Se-dependent enzyme activities and tissue Se contents, comparing those responses for each soy product to those for SeMet using a slope-ratio method. Dietary supplementation with the protein isolate or tofu resulted in dose-dependent increases in glutathione peroxidase activities in blood and liver and thioredoxin reductase activity in liver, as well as dose-dependent increases in the Se contents of plasma, liver, muscle, and kidneys. These responses indicated an overall bioavailability of approximately 97% for Se from both the protein isolate and tofu, relative to SeMet. These results demonstrate that Se from this soybean cultivar is highly bioavailable in this model and that high-Se soybeans can be good dietary sources of Se.

Bioavailability as an issue in risk assessment and management of food cadmium: a review.

The bioavailability of cadmium (Cd) from food is an important determinant of the potential risk of this toxic element. This review summarizes the effects of marginal deficiencies of the essential nutrients zinc (Zn), iron (Fe), and calcium (Ca) on the enhancement of absorption and organ accumulation and retention of dietary Cd in laboratory animals. These marginal deficiencies enhanced Cd absorption as much as ten-fold from diets containing low Cd concentrations similar to that consumed by some human populations, indicating that people who are nutritionally marginal with respect to Zn, Fe, and Ca are at higher risk of Cd disease than those who are nutritionally adequate. Results from these studies also suggest that the bioavailability of Cd is different for different food sources. This has implications for the design of food safety rules for Cd in that if the dietary source plays such a significant role in the risk of Cd, then different foods would require different Cd limits. Lastly, the importance of food-level exposures of Cd and other potentially toxic elements in the study of risk assessment are emphasized. Most foods contain low concentrations of Cd that are poorly absorbed, and it is neither relevant nor practical to use toxic doses of Cd in experimental diets to study food Cd risks. A more comprehensive understanding of the biochemistry involved in the bioavailability of Cd from foods would help resolve food safety questions and provide the support for a badly needed advance in international policies regarding Cd in crops and foods.

Pinto bean consumption changes SCFA profiles in fecal fermentations, bacterial populations of the lower bowel, and lipid profiles in blood of humans.

Beans improve serum lipids and may reduce the risk of colon cancer by increasing colonic SCFA formation. We assessed whether pinto bean consumption affects in vitro fecal bacterial fermentation and production of SCFA, colonic bacterial populations, and serum lipids. Adults grouped as premetabolic syndrome (pre-MetSyn) (n = 40) or controls (n = 40) were randomly assigned to consume either a bean entrée [1/2 cup (130 g) of dried, cooked pinto beans] or an isocaloric chicken soup entrée daily for 12 wk. Measurements included in vitro fecal fermentation of various resistant starch substrates, fecal bacterial speciation, and blood lipids. When expressed as a difference between baseline and treatment, propionate production from fecal material fermented in vitro with bean flour was higher (P < 0.02) in volunteers consuming beans than in those consuming soup. During the treatment period alone, bean consumption did not affect propionic acid production with any substrate but lowered (P < 0.02) butyric acid production when cornstarch was the substrate. In all volunteers, bean consumption decreased fecal production of isovaleric (P < 0.05) and isobutyric (P < 0.002) acids from cornstarch by as much as 50%. Of the bacterial populations tested, only Eubacterium limosum was affected by bean consumption and was approximately 50% lower than in those consuming soup. Beans lowered serum total cholesterol (P < 0.014) by approximately 8% in the controls and 4% in the pre-MetSyn group. Bean consumption lowered serum HDL-cholesterol (P < 0.05) and LDL-cholesterol (P < 0.05) in both groups without affecting serum triglycerides, VLDL cholesterol, or glucose. This study provides evidence that bean consumption can improve lipid profiles associated with cardiovascular disease, but does not clearly confer health benefits related to colon cancer risk.

Copper deficiency decreases plasma homocysteine in rats.

The purpose of this study was to determine the effects of copper deficiency on key aspects of homocysteine metabolism that involve methionine recycling and transsulfuration. Male weanling Sprague-Dawley rats were fed AIN-93G-based diets containing <1 or approximately 6 mg Cu/kg. After 6 wk (Expt. 1) and 4 wk (Expt. 2) we found that plasma homocysteine was significantly decreased, and plasma glutathione significantly increased, in rats fed the low-Cu diet. Real-time RT-PCR was used to determine the expression of the subunits of glutamate-cysteine ligase (Gcl) in liver that catalyzes the rate-limiting step in glutathione biosynthesis. The expression of Gclc, the catalytic subunit of Gcl, was upregulated by Cu deficiency; Gclm, the modifier subunit, was not affected. Hepatic betaine-homocysteine methyltransferase (Bhmt), which catalyzes one of the two ways that homocysteine can be remethylated to methionine, was downregulated by Cu deficiency. Because Cu deficiency results in upregulation of Gclc and an increase in the biosynthesis of glutathione, it is plausible that the net flux of homocysteine through the transsulfuration pathway is increased. Furthermore, if Bhmt is downregulated, less homocysteine is available for remethylation (methionine recycling) and more is then available to irreversibly enter the transsulfuration pathway where it is lost. The net effect of increased Gclc and decreased Bhmt would be a decrease in homocysteine as a result of Cu deficiency.

Low concentrations of zinc in gastric mucosa are associated with increased severity of Helicobacter pylori-induced inflammation.

BACKGROUND: Chronic Helicobacter pylori infection is the most common cause of gastric cancer. H. pylori induces oxidative stress while zinc deficiency results in increased sensitivity to it. In Ecuador, the prevalence of gastric cancer and zinc deficiency are high. We hypothesized that zinc deficiency in Ecuadorian people would cause increased H. pylori-induced inflammation in the gastric mucosa associated with lower tissue zinc concentrations. METHODS: Three hundred and fifty-two patients with dyspepsia underwent endoscopy to obtain gastric mucosa biopsies. Diagnosis of H. pylori infection and its severity, histopathology, mucosal zinc concentration, and inflammation intensity were determined. RESULTS: H. pylori-infected patients with non-atrophic chronic gastritis had lower concentrations of zinc in gastric mucosa than uninfected patients with the same type of gastritis (251.3 +/- 225.3 vs. 426.2 +/- 279.9 ng/mg of protein; p = .016). Considering all patients, the more severe the H. pylori infection, the higher the percentage of subjects with infiltration by polymorphonuclear (PMN) cells (p = .0001). Patients with high PMN infiltration had lower mucosal zinc concentrations than patients with low PMN infiltration (35.2 +/- 20.7 vs. 242.9 +/- 191.8 ng/mg of protein; p = .021). CONCLUSIONS: The degree of inflammation in H. pylori-induced gastritis appears to be modulated by gastric tissue zinc concentrations.

Determination of selenium bioavailability from wheat mill fractions in rats by using the slope-ratio assay and a modified torula yeast-based diet.

Selenium is an essential mineral micronutrient for animals, and significant evidence supports an association between supranutritional Se intake and a reduction in the incidence of some forms of cancer. Thus, supplemental Se intake may provide an avenue for reducing cancer incidence. However, an important issue to consider is the form of Se that should be provided in such a supplement, because the bioavailability and bioactivity of Se can vary dramatically depending on the chemical form in which it is delivered. Because wheat products are the largest source of Se in U.S. diets, the absorption of Se was evaluated in different fractions of milled wheat that exhibits very high Se levels, owing to its production on naturally Se-rich soils. An experiment was conducted to determine the bioavailability of Se from three milled fractions of high-Se wheat. The method used was the slope-ratio assay, which measures the ability of Se from the wheat fractions to regenerate Se-dependent enzyme activities and tissue Se concentrations in Se-deficient rats. The responses generated from wheat Se were compared to a standard response curve generated by feeding graded amounts of Se as sodium selenite (Na2SeO3; NaSelenite) or selenomethionine (SeMet) in an AIN-93G-Torula yeast-based diet. Results showed that Se from wheat flour ( approximately 75% extraction) was nearly 100% available by a number of measures including plasma, liver, kidney, and muscle Se concentrations and liver and erythrocyte Se-dependent enzyme activities when compared with similar measures in rats fed NaSelenite or SeMet. However, on the basis of similar criteria, Se from wheat shorts was only about 85% available and that from wheat bran was about 60% available for absorption. These results indicate that high-Se wheat products, mainly those made from refined flour alone, might be particularly well suited for use as dietary Se supplements.

Nutritional, immunological and health status of the elderly population living in poor neighbourhoods of Quito, Ecuador.

The number of elderly people is increasing in less-developed countries. Although nutritional deficiencies and infectious diseases are generally more prevalent in resource-poor countries, the health and nutritional status of the elderly in South America in general, and in Ecuador, in particular, remains largely unstudied. The objective of the present study was to assess the nutritional, immunological and health status of elderly Ecuadorians. A cross-sectional study was conducted to evaluate a sample of elderly Ecuadorians with 24 h dietary recalls, biochemical and anthropometric measurements, delayed type hypersensitivity skin response and a health questionnaire. The 145 elders who enrolled had a mean age of 74.3 (SD 6.9) years. Of the subjects, 52 % exhibited BMI >or=25 kg/m(2), whereas 9.1 % had BMI

Pinto beans are a source of highly bioavailable copper in rats.

The trace element copper (Cu) is a required nutrient in the diets of humans. It has been found in animal studies to be essential for efficient iron absorption and oxygen utilization and for aiding free-radical degradation. Dry beans (Phaseolis vulgaris) are potentially good sources of Cu; thus, the objective of this study was to determine the bioavailability of Cu from dry beans using the pinto bean as the source. Dry beans were obtained from a local market, cooked according to package directions, and dried. Weanling male Sprague-Dawley rats (8 groups of 8 rats each) were fed a Cu-deficient diet (AIN-93G) for 4 wk followed by 2 wk of Cu repletion with diets containing 0-6.5 mg Cu/kg diet added as CuSO(4) or with 0.6 and 1.5 mg Cu/kg incorporated into rat diets as pinto beans at 10 and 20%. Standard response curves were developed based on repletion-induced recovery of 10 indices of Cu status, including organ Cu concentrations and Cu-dependent enzyme activities, in response to increasing dietary Cu as CuSO(4). Recovery of these variables in rats fed the pinto bean diets was compared with the standard response curve at similar levels of dietary Cu. Based on the recovery of all 10 variables, the relative bioavailability of Cu from dry beans was at least 100% of that with the highly available CuSO(4). For 3 of the variables, liver and heart Cu concentrations and serum superoxide dismutase 3 activity, estimated bioavailability values of Cu from beans were 138, 140, and 134%, respectively, of those from CuSO(4). We conclude that the dry pinto bean is a good source of dietary Cu with respect to both concentration and bioavailability.

Signs of iron deficiency in copper-deficient rats are not affected by iron supplements administered by diet or by injection.

The goal of this study was to determine the effects of Fe supplementation on the anemia of Cu deficiency in rats. In addition, we observed changes in serum and organ Cu and Fe during the development of Cu deficiency. In Experiment 1, weanling male Sprague-Dawley rats were fed AIN-93G diets containing either <0.3 mg Cu [Cu deficient (CuD)] or 6.0 mg Cu [Cu adequate (CuA)] per kilogram diet, and 35 mg Fe/kg. Five rats from each group were killed at intervals for the analysis of hematologic parameters and mineral content of various organs. In Experiment 2, two groups of 24 rats each were fed either the CuA diet or the CuD diet for 14 days. Then, three sets of eight rats in each group received three separate Fe treatments: (1) daily intraperitoneal injections of 400 mug Fe (Cu-free ferric citrate) per rat for another 14 days, (2) fed similar diets that contained three times the normal amount of Fe (105 mg/kg) for 14 days, or (3) received no further Fe treatment. At day 21, all rats were fed a 1-g meal labeled with (59)Fe to determine Fe absorption. After 28 days, rats were killed for the analyses of Fe and Cu status. Results of Experiment 1 showed that within 14 days, CuD rats had lower blood hemoglobin (Hgb), red blood cell count, and mean corpuscular volume than CuA rats. Copper concentrations in all tissues measured were lower in the CuD rats than in controls. Serum ceruloplasmin (Cp) activity in CuD rats was only 0.8% of CuA rats at day 7. During this period, enterocyte and liver Fe concentrations were elevated and serum Fe was reduced, but there was no change in spleen Fe. Results of Experiment 2 showed that CuD rats absorbed less Fe than CuA rats. Supplemental Fe by diet or by intraperitoneal injections did not prevent anemia in the CuD rats or affect other parameters of Cu status. Serum total iron binding capacity [transferrin (Tf)] was not changed by Cu deficiency or by Fe supplementation; however, percent Tf saturation was reduced in CuD rats but was not enhanced by Fe supplementation. These data suggest that anemia of Cu deficiency occurs because of reduced Fe absorption, and it inhibits release of Fe from the liver and inefficient loading of Fe into Tf because of very low plasma Cp activity. The latter then leads to inefficient delivery of Fe to the erythroid cells for heme and Hgb synthesis.

Selenium bioavailability from buckwheat bran in rats fed a modified AIN-93G torula yeast-based diet.

Selenium (Se) is an essential nutrient for humans and animals. The Se RDA for adult humans is 55 mug/d; however, dietary amounts as high as 200 mug/d in the highly available form of selenomethionine in yeast were shown to reduce the incidence of certain cancers. A number of natural foods contain relatively high amounts of Se; for the most part, however, the availability of food Se for absorption and utilization is unknown. This experiment was conducted to determine the bioavailability of Se from a high-protein, high-fiber bran-isolate of buckwheat groats that contains Se. The method used was based on the ability of Se from buckwheat bran to restore Se-dependent enzyme activities and tissue Se concentrations in Se-deficient rats. The responses produced from buckwheat bran Se were compared with a standard response curve generated by feeding graded amounts of Se as sodium selenite (Na(2)SeO(3); Na selenite) or selenomethionine (SeMet) in a newly reformulated AIN-93G-Torula yeast diet with a more balanced nutrient composition than older diets of this nature. Relative bioavailability was determined by using the slope-ratio assay method for enzyme data, or the parallel lines assay method for tissue Se concentration data. Results showed that Se availability from buckwheat bran based on the restoration of plasma Se was 70-80% as high as Na selenite or SeMet. However, when based on the restoration of muscle Se, buckwheat bran was 90% as high as Na selenite, but only 60% as high as SeMet. When using the ability of dietary Se to restore whole blood and liver glutathione peroxidase activity, buckwheat bran Se was 75-80% as high as Na selenite or SeMet. However, for the restoration of liver thioredoxin reductase, buckwheat bran Se was only 40% as high as Na selenite and 70% as high as SeMet. The relative bioavailability of Se from buckwheat bran with all variables considered was approximately 73% whether measured against Na selenite or SeMet. Although some variables indicated low bioavailability of Se from buckwheat bran, other factors such as Se speciation in the bran, digestibility of the bran, the cooking process, and combinations with other foods in the diet should be considered and analyzed before firm conclusions can be reached.

Repletion of copper-deficient rats with dietary copper restores duodenal hephaestin protein and iron absorption.

Copper (Cu) deficiency in rats reduces the relative concentration of duodenal hephaestin (Hp), reduces iron (Fe) absorption, and causes anemia. An experiment was conducted to determine whether these effects could be reversed by dietary Cu repletion. Five groups of eight weanling male rats each were used. Group 1 was fed a Cu-adequate diet (5.0 mg Cu/kg; CuA) and Group 2 was fed a Cu-deficient diet (0.25 mg Cu/kg; CuD) for 28 days. The rats were fed 1.0 g each of their respective diets labeled with 59Fe (37 kBq/g), and the amount of label retained was measured one week later by whole-body-counting (WBC). Group 3 was fed a CuA diet and Groups 4 and 5 were fed a CuD diet for 28 days. Group 5 was then fed the CuA diet for another week while Groups 3 and 4 continued on their previous regimens. Rats in Groups 3, 4, and 5 were fed 1.0 g of diet labeled with 59Fe, and the amount of label retained was measured by WBC one week later. Rats were killed and duodenal enterocytes isolated for Hp protein analysis, whole blood was analyzed for hematological parameters, and various organs for 59Fe content. CuD rats absorbed less (P<0.05) Fe than CuA rats, the relative amount of duodenal Hp was less (P<0.05) in CuD rats, and the CuD rats developed anemia. After the CuD rats had been repleted with Cu for one week, Fe retention rose to values even higher (P<0.05) than those in CuA rats. After two weeks, the relative amount of duodenal Hp was higher (P<0.05) than normal, and most signs of anemia were reversed. Liver 59Fe was elevated in CuD rats, but was restored to normal upon Cu repletion. These findings suggest a strong association between duodenal Hp abundance and Fe absorption in the CuD rat, and that reduced Fe absorption is an important factor in the cause of anemia.

Dietary copper deficiency reduces iron absorption and duodenal enterocyte hephaestin protein in male and female rats.

The mechanism for reduced Fe absorption in Cu deficiency is unknown, but may involve the intestinal Cu-dependent ferroxidase, Hephaestin (Hp). A 2 x 2 factorial experiment was designed to include Cu-deficient (CuD) and Cu-adequate (CuA) male and female rats. Weanling rats of both sexes were randomly divided into 2 groups each and fed an AIN-93G diet with low (<0.3 mg/kg; CuD) or adequate Cu (5.0 mg/kg; CuA). After 19 d, rats were fed 1.0 g each of their respective diets labeled with (59)Fe. Retained (59)Fe was monitored by whole-body counting for 12 d. Then, rats were killed for (59)Fe and Fe measurements in blood and various organs. Duodenal enterocytes were isolated for Western blot analysis of Hp. Signs of Cu and Fe deficiency were evident in both sexes. CuD male rats absorbed 60% as much Fe as CuA male rats (P < 0.001), whereas CuD female rats absorbed 70% (P < 0.001) as much as CuA females, with no difference between the sexes. Hp protein in enterocytes of CuD rats of both sexes was only 35% of that in CuA rats. The biological half-life of (59)Fe in CuD rats was only 50% (P < 0.001) of that in CuA rats, suggesting that Fe turnover was faster in CuD rats than CuA rats. Serum, spleen, and kidney Fe were lower (P < 0.001) in CuD rats than in CuA rats. Duodenal mucosa and liver Fe were higher (P < 0.01) in CuD male rats than CuA rats. Duodenal Fe but not liver Fe was higher in CuD female rats than CuA rats. Liver Fe was much higher (<0.001) overall in females than males. The data suggest that Cu deficiency reduces Fe absorption in rats through reduced expression of duodenal Hp protein.

Metallothionein induction is not involved in cadmium accumulation in the duodenum of mice and rats fed diets containing high-cadmium rice or sunflower kernels and a marginal supply of zinc, iron, and calcium.

Rats fed diets with cadmium (Cd) concentrations similar to that found in human diets, and nutritionally marginal with respect to iron (Fe), zinc (Zn), and calcium (Ca) retained 10 times more Cd in the duodenum than rats fed adequate mineral diets. In the current study, 2 experiments were performed to determine the role of intestinal metallothionein (MT) in the accumulation of duodenal Cd, and to determine whether endogenous rice grain Cd is as available as Cd exogenously incorporated into the grain. In Expt. 1, wild-type and MT-null mice were fed 40% rice diets containing marginal or adequate amounts of Fe, Zn, and Ca, and 240 mug Cd/kg. Duodenal Cd was 10 times higher in both wild-type and MT-null mice regardless of their mineral status. In Expt. 2, one group of rats was fed 40% rice diets in which Cd was incorporated into the rice during growth and maturation, and another group was fed 40% rice diets in which Cd was incorporated into the rice during cooking. Each group also was fed either marginal or adequate amounts of Zn, Fe, and Ca. After 5 wk, rats were given a single meal labeled with (109)Cd, and the amount of label retained after 7 d was determined by whole-body counting. Rats with marginal mineral status retained 10 times more (109)Cd than those with adequate status; however, there was no difference between rats fed endogenous or exogenous Cd rice. Although duodenal Cd concentration was 8 times higher in the marginally fed rats, MT concentration was unchanged. These 2 experiments indicate that MT induction is not involved in duodenal Cd accumulation in animals with marginal dietary status of Fe, Zn, and Ca. In addition, they support the hypothesis that marginal deficiencies of Fe, Zn, and Ca, commonly found in certain human populations subsisting on rice-based diets, play an important role in increasing the risk of dietary Cd exposure.

Marginal nutritional status of zinc, iron, and calcium increases cadmium retention in the duodenum and other organs of rats fed rice-based diets.

Dietary minerals Zn, Fe, and Ca are antagonistic to Cd absorption. We showed earlier that rats fed a rice-based diet with a marginal content of these nutrients absorbed more Cd than rats fed adequate Zn-Fe-Ca (Environ. Sci. Technol., 36 (2002) 2684-2692). The present experiment was designed to determine the effects of marginal dietary Zn, Fe, and Ca on the uptake and turnover of Cd in the gastrointestinal tract. Two groups of weanling female rats (six per treatment) were fed a diet containing 40% cooked, dried rice containing 0.6 mg Cd/kg. The diet of one group contained adequate Zn (35 mg/kg), Fe (30 mg/kg), and Ca (5000 mg/kg), while that of the other group contained marginal Zn (6 mg/kg), Fe (9 mg/kg), and Ca (2500 mg/kg). Rats were fed for 5 weeks and then orally dosed with 1g of diet containing rice extrinsically labeled with 109Cd. From 0.25 to 64 days after dosing, 109Cd and total Cd concentrations were determined in intestinal segments. Shortly after dosing, 109Cd, as a percentage of the dose, was about 4 times higher in the duodenum of marginally fed rats than in that of control rats (10% vs 40%, respectively). Sixty-four days after dosing, 109Cd was 10 times higher in marginally fed rats than in controls; however, of the amount at day 1, <0.1% remained at day 64. After 5 weeks, the concentration of elemental Cd in the duodenum of the marginally fed rats was 8 times higher than that of control rats (24 microg/g dry wt. vs 2.9 microg/g dry wt., respectively). Cd concentrations in liver and kidney were 5 times higher in the marginally fed rats than those in controls (liver, 0.81 microg/g dry wt. vs 0.14 microg/g dry wt.; kidney, 4.7 microg/g dry wt. vs 0.92 microg/g dry wt., respectively). These data suggest that marginal intakes of Zn, Fe, and Ca cause the accumulation of Cd in the duodenum, which results in a greater rate of Cd absorption and a greater accumulation in the internal organs. Results are discussed in relation to mineral nutrient status and risk assessment of Cd in natural food sources.

Copper deficiency reduces iron absorption and biological half-life in male rats.

Dietary copper deficiency (CuD) in rats leads to iron (Fe) deficiency anemia. Is this because CuD reduces Fe absorption? Fe absorption in CuD rats was determined by feeding diets labeled with (59)Fe and using whole-body counting (WBC) to assess the amount retained over time. Two groups, each with 45 male weanling rats, were fed an AIN-93G diet low in Cu (<0.3 mg/kg; CuD) or one containing adequate Cu (5.0 mg/kg; CuA). At intervals over the next 42 d, 5 rats per group were killed and blood was drawn to determine hematocrit, hemoglobin, and other indicators of Fe status. At d 7 and 25, 5 rats per group were fed 1.0 g of their respective diets that had been labeled with (59)Fe. Retained (59)Fe was monitored for 10 d by WBC; then rats were killed and (59)Fe was measured in various organs. Signs of Fe deficiency, such as low hemoglobin, hematocrit, and RBC count, were evident in CuD rats by d 14. At d 7, CuD rats absorbed 90% as much Fe as CuA rats (P > 0.20), but at d 25, CuD rats absorbed only 50% as much as CuA rats (P < 0.001). In the study beginning at d 7, the biological half-life (BHL) of (59)Fe in CuD rats was less (P < 0.02) than that in CuA rats [geometric mean (-SEM, +SEM); 75(62,91) d vs. 175(156,195) d]. In the study beginning at d 25, the BHL was again less (P < 0.02) in the CuD rats than in the CuA rats [33(23,49) d for CuD and 157(148,166) d for CuA]. Apparently, the route of Fe loss in the CuD rats was through the gut. At d 16 and 34, CuD rats lost 4 to 5 times more (P < 0.01) (59)Fe in the feces in a 24-h period than the CuA rats. Also, (59)Fe in the duodenal mucosa of CuD rats was approximately 100% higher (P < 0.01) than in CuA rats. These findings suggest that Fe deficiency anemia in CuD male rats is caused at least in part by reductions in Fe absorption and retention.

Contrasting and cooperative effects of copper and iron deficiencies in male rats fed different concentrations of manganese and different sources of sulfur amino acids in an AIN-93G-based diet.

Dietary nutrient interactions are important factors to consider in the study of nutrient status and requirements. Here, the effects of dietary interactions among copper (Cu), iron (Fe), manganese (Mn) and sulfur amino acids (SAA) on blood cell characteristics and enzyme activities were observed. Male rats (n = 8) were used in a 2 x 2 x 2 x 2 factorial design and fed an AIN-93G-based diet containing dietary Cu (<1 and 5 mg/kg), Fe (10 and 35 mg/kg), Mn (10 and 50 mg/kg) and either L-cystine (LCys) or DL-methionine (DLMet). Blood was analyzed by automated hematology cell counting and by flow cytometry. Severe Cu deficiency was verified by reductions in the activities of serum ceruloplasmin (1% of control), RBC superoxide dismutase (SOD1) (14% of control), liver cytochrome c oxidase activity (25% of control) and serum extracellular SOD (SOD3) activity (20% of controls). Because Cu is required for Fe utilization, many physiologic responses that require Fe were affected by both deficiencies, including lowered blood hemoglobin (Hgb), lower RBC volume and Hgb concentration, and an increased number of reticulocytes. Cu and Fe deficiencies together worsened some conditions, i.e., lower Hgb, lower RBC Hgb, increased RBC distribution width, increased number of reticulocytes and nucleated RBC, and a higher platelet count. Increasing dietary Mn had little effect on most variables, except to reduce serum Cu when dietary Cu was adequate but not when it was low, and to reduce RBC SOD1 activity when dietary Fe was low but not when it was adequate. Hgb concentrations were higher (P < 0.002) in Cu-deficient rats fed LCys than in those fed DLMet. There was no effect in Cu-adequate rats. Hgb was higher (P < 0.004) in Fe-adequate rats fed LCys than in those fed DLMet, with no effect in Fe-deficient rats. Although the anemia of Cu deficiency in AIN-93G-fed rats was not as pronounced as that reported in rats fed the AIN-76A-based diet, other manifestations of the deficiency were prominent.

An improved understanding of soil Cd risk to humans and low cost methods to phytoextract Cd from contaminated soils to prevent soil Cd risks.

We believe greater consideration should be given the agronomic and nutritional/bioavailability factors that influence risk from Cd-contaminated soils. We have argued that the ability of rice to accumulate soil Cd in grain while excluding Fe, Zn and Ca (even though the soil contains 100-times more Zn than Cd) was important in adverse effects of soil Cd is farm families in Asia. Further, polished rice grain is deficient in Fe, Zn and Ca for humans, which promotes Cd absorption into duodenal cells. New kinetic studies clarified that dietary Cd is absorbed into duodenum enterocytes; 109Cd from a single meal remained in the duodenum for up to 16 days; part of the turnover pool 109Cd moved to the liver and kidneys by the end of the 64-day 'chase' period. Thus malnutrition induced by subsistence rice diets caused a higher absorption of dietary Cd and much higher potential risk from soil Cd than other crops. Because rice-induced Fe-Zn-Ca-malnutrition is so important in soil Cd risk, it seems evident that providing nutritional supplements to populations of exposed subsistence rice farmers could protect them against soil Cd during a period of soil remediation. In the long term, high Cd rice soils need to be remediated. Remediation by removal and replacement of contaminated soil is very expensive (on the order of $3 million/ha); while phytoextraction using the high Cd accumulating ecotypes of the Zn-Cd hyperaccumulator, Thlaspi caerulescens, should provide low cost soil Cd remediation.

Patterns of food intake and self-selection of macronutrients in rats during short-term deprivation of dietary zinc.

Although it has been known for more than 50 years that zinc (Zn) deficiency regularly and consistently causes anorexia in many animal species, the basic mechanism(s) that cause this phenomenon still remain(s) an enigma. The following studies describe feeding behavior in the early stages of zinc deficiency in the rat model. In one experiment, we used computerized feeding monitors that measured the intake of individual rats at 10-min intervals over 24-hr periods. Male rats were acclimated to the cages and fed a Zn-adequate egg-white-based diet, or a similar diet with <1.0 mg Zn/kg. Food intake was monitored for seven, consecutive 24-hr periods. The 24-hr food intake pattern of the Zn-deprived rats did not differ from the controls; they simply ate less food, mainly during the night hours, with no differences between groups during the day. Although Zn-deprived rats ate less food than controls, the percentage of total diet consumed during night and day did not differ between groups. In another experiment, we simultaneously offered male rats three isocaloric diets with different macronutrient compositions and with or without adequate Zn, and measured the amount of each diet selected during seven, 24-hr periods. The three diets contained either 57% protein from egg white, 30% fat from soybean oil, or 80% carbohydrate from a combination of starch, hydrolyzed starch, and sucrose. For the first four days on experiment, rats selected similar amounts of each diet. Then the Zn-deprived rats began to select only 50% as much of the protein diet as the controls. Similar results were obtained when the data were expressed on the basis of each macronutrient as a percentage of the total diet selected. Zn-deprived rats selected a diet that contained 8% protein, 73% carbohydrate, and 6% fat while the Zn-adequate rats selected 12% protein, 69% carbohydrate, and 6% fat. Fat intake was not affected by Zn-deprivation. The results confirm our previous findings, and are discussed in terms of Zn-deprivation blunting the pathways of signal transduction that involve the peptide hormones known to affect food intake regulation.

Nutritional status affects the absorption and whole-body and organ retention of cadmium in rats fed rice-based diets.

Staple grains such as rice, wheat and maize consumed by different societal groups differ greatly in their concentrations and bioavailability of the cadmium (Cd) antagonists, zinc (Zn), iron (Fe), and calcium (Ca). We hypothesized thatthe low nutritional status of rice consumers, which results from an inadequate supply of these minerals from rice, could contribute significantly to a higher apparent susceptibility to soil Cd contamination from rice than the higher nutritional status of those who consume other grains with higher mineral content. To test this hypothesis, a 2 x 2 x 2 factorial study was conducted. Rats were fed diets with adequate or marginal amounts of dietary Zn, Fe, or Ca. The basal diets contained 40% unenriched, milled rice fortified with 0.62 mg of Cd/kg as CdCl2 (0.25 mg of Cd/kg diet). Rat consumed the diets for 5 weeks and then were fed 1 g of a similar diet containing 10(9)Cd-labeled rice. After 2 weeks, whole-body (WB) retention of 109Cd was determine. Rats then were killed, and the organs were removed for total Cd determinations. Rats fed marginal concentrations of dietary Zn had slightly but significantly more WB retention of 109Cd than controls; however, rats fed marginal Fe or Ca had as much as 3-fold higher retention of the label. Rats fed marginal amounts of Zn, Fe, and Ca combined retained as much as 8 times more 109Cd than rats fed adequate minerals. The effects on Cd concentrations in liver and kidney were similar to the effects on 109Cd retention. These results support the hypothesis that populations exposed to dietary sources of Cd and subsisting on marginal mineral intakes could be at greater risk than well-nourished populations exposed to similar amounts of dietary Cd. Thus, different food crops can cause unequal Cd risk at equal Cd concentration if diets containing the food are not balanced to provide adequate interacting mineral concentrations.