Variation in rice cadmium related to human exposure.

Cereal grains are the dominant source of cadmium in the human diet, with rice being to the fore. Here we explore the effect of geographic, genetic, and processing (milling) factors on rice grain cadmium and rice consumption rates that lead to dietary variance in cadmium intake. From a survey of 12 countries on four continents, cadmium levels in rice grain were the highest in Bangladesh and Sri Lanka, with both these countries also having high per capita rice intakes. For Bangladesh and Sri Lanka, there was high weekly intake of cadmium from rice, leading to intakes deemed unsafe by international and national regulators. While genetic variance, and to a lesser extent milling, provide strategies for reducing cadmium in rice, caution has to be used, as there is environmental regulation as well as genetic regulation of cadmium accumulation within rice grains. For countries that import rice, grain cadmium can be controlled by where that rice is sourced, but for countries with subsistence rice economies that have high levels of cadmium in rice grain, agronomic and breeding strategies are required to lower grain cadmium.

Effects of short-term pH fluctuations on cadmium, nickel, lead, and zinc availability to ryegrass in a sewage sludge-amended field

In this field experiment, sewage sludge was applied at 0, 5, 10, and 50 t ha(-1), and the availability of Cd, Ni, Pb, and Zn was assessed both by ryegrass uptake and by DTPA extractions. The aim was to investigate the role of important soil parameters, particularly pH, on heavy metal availability. It was found that metal uptake and extractability increased significantly in the 50 t ha(-1) treatment. In the 16th week of the experiment there was a significant, although temporary, increase in DTPA-extractable Cd, Ni, and Zn concentrations. Metal concentrations in ryegrass were also significantly elevated in week 20 compared to the subsequent cuttings. These fluctuations in both DTPA and ryegrass uptake occurred only at 50 t ha(-1) and were probably induced by a sudden pH decrease measured in the same treatment in week 16. This suggests that soils which have received high applications of sewage sludge may be prone to fluctuations in metal availability. (c) 2007 Elsevier Ltd. All rights reserved.

Food-chain transfer of cadmium and zinc from contaminated Urtica dioica to Helix aspersa and Lumbricus terrestris

The present study examines the potential of Urtica dioica as an ecologically relevant species for use in ecotoxicological testing. It is prevalent in degraded ecosystems and is a food source for invertebrates. Urtica dioica grown in hydroponic solutions containing from less than 0.003 to 5.7 mg Cd/L or from 0.02 to 41.9 mg Zn/L accumulated metals resulting in leaf tissue concentrations in the range of 0.10 to 24.9 mg Cd/kg or 22.5 to 2,772.0 mg Zn/kg. No toxicological effects were apparent except at the highest concentrations tested, suggesting that this species may be an important pathway for transfer of metals to primary plant consumers. Helix aspersa and Lumbricus terrestris were fed the Cd- and Zn-rich leaves of U. dioica for six and four weeks, respectively. Cadmium and Zn body load increased with increasing metal concentration in the leaves (p < 0.001). Ratios of invertebrate metal concentration to leaf metal concentration were in the range of 1:0.03 to 1:1.4 for Cd and 1:0.2 to 1:2.8 for Zn in H. aspersa and 1:0.002 to 1:3.9 for Cd and 1:0.2 to 1:8.8 for Zn in L. terrestris. Helix aspersa Cd and Zn tissue concentrations (15.5 and 1,220.2 mg/kg, respectively) were approximately threefold those in L. terrestris when both species were fed nettle leaves with concentrations of approximately 23 mg Cd/ kg and 3,400 mg Zn/kg. Models demonstrate that L. terrestris Cd tissue concentrations (r(2) = 0.74, p < 0.001) and H. aspersa Zn tissue concentrations (r(2) = 0.69, p < 0.001) can be estimated from concentrations of Cd and Zn within the leaves of U. dioica and suggest that reasonably reproducible results can be obtained using these species for ecotoxicological testing.

Field trial using bone meal amendments to remediate mine waste derived soil contaminated with zinc, lead and cadmium

Bone meal amendments are being considered as a remediation method for metal-contaminated wastes. In various forms (biogenic, geogenic or synthetic), apatite, the principal mineral constituent of bone, has shown promise as an amendment to remediate metal-contaminated soils via the formation of insoluble phosphates of Pb and possibly other metals. The efficacy of commercially available bovine bone meal in this role was investigated in a field trial at Nenthead, Cumbria with a mine waste derived soil contaminated with Zn, Pb and Cd. Two 5 m(2) plots were set up: the first as a control and the second, a treatment plot where the soil was thoroughly mixed with bone meal to a depth of 50 cm at a soil to amendment ratio of 25:1 by weight. An array of soil solution samplers (Rhizon SMS (TM)) were installed in both plots and the soil pore water was collected and analysed for Ca, Cd, Zn and Pb regularly over a period of 2 a. Concurrently with the field trial, a laboratory trial with 800 mm high and 100 mm wide leaching Columns Was conducted using identical samplers and with soil from the held site. A substantial release of Zn, Pb, Cd and Ca was observed associated with the bone meal treatment. This release was transient in the case of the leaching columns, and showed seasonal variation in the case of the field trial. It is proposed that this effect resulted from metal complexation with organic acids released during breakdown of the bone meal organic fraction and was facilitated by the relatively high soil pH of 7.6-8.0. Even after this transient release effect had subsided or when incinerated bone meal was substituted in order to eliminate the organic fraction, no detectable decrease in dissolved metals was observed and no P was detected in solution, in contrast with an earlier small column laboratory study. It is concluded that due to the relative insolubility of apatite at above-neutral pH, the rate of supply of phosphate to soil solution was insufficient to result in significant precipitation of metal phosphates and that this may limit the effectiveness of the method to more acidic soils. (c) 2008 Elsevier Ltd. All rights reserved.

Selenium persistency and speciation in the tissues of lambs following the withdrawal of dietary high-dose selenium-enriched yeast

The objective was to determine the concentration of total selenium (Se) and the proportion of total Se comprised as selenomethionine (SeMet) and selenocysteine (SeCys) in post mortem tissues of lambs in the six weeks period following the withdrawal of a diet containing high dose selenized yeast (SY), derived from a specific strain of Saccharomyces cerevisae CNCM (Collection Nationale de Culture de Micro-organism) I-3060. Thirty Texel x Suffolk lambs used in this study had previously received diets (91 days) containing either high dose SY (HSY; 6.30 mg Se/kg DM) or an unsupplemented control (C; 0.13 mg Se/kg DM). Following the period of supplementation all lambs were then offered a complete pelleted diet, without additional Se (0.15 mg Se/kg DM), for 42 days. At enrollment and 21 and 42 days later, five lambs from each treatment were blood sampled, euthanased and samples of heart, liver, kidney and skeletal muscle (Longissimus Dorsi and Psoas Major) tissue were retained. Total Se concentration in whole blood and tissues was significantly (P < 0.001) higher in HSY lambs at all time points that had previously received long term exposure to high dietary concentrations of SY. The distribution of total Se and the proportions of total Se comprised as SeMet and SeCys differed between tissues, treatment and time points. Total Se was greatest in HSY liver and kidney (22.64 and 18.96 mg Se/kg DM, respectively) and SeCys comprised the greatest proportion of total Se. Conversely, cardiac and skeletal muscle (Longissimus Dorsi and Psoas Major) tissues had lower total Se concentration (10.80, 7.02 and 7.82 mg Se/kg DM, respectively) and SeMet was the predominant selenized amino acid. Rates of Se clearance in HSY liver (307 µg Se/day) and kidney (238 µg Se/day) were higher compared with HSY cardiac tissue (120 µg Se/day) and skeletal muscle (20 µg Se/day). In conclusion differences in Se clearance rates were different between tissue types, reflecting the relative metabolic activity of each tissue, and appear to be dependant upon the proportions of total Se comprised as either SeMet or SeCys.

Effect of dietary supplementation with selenium-enriched yeast or sodium selenite on selenium tissue distribution and meat quality in beef cattle

The objective was to determine the concentration of total selenium (Se) and the proportion of total Se comprised as selenomethionine (SeMet) and selenocysteine (SeCys) in post mortem tissues of beef cattle offered diets containing graded additions of selenized enriched yeast (SY) [Saccharomyces cerevisae CNCM I-3060]), or sodium selenite (SS). Oxidative stability and tissue glutathione peroxidase (GSH-Px) activity of edible muscle tissue were assessed 10 d post-mortem. Thirty two beef cattle were offered, for a period of 112 d, a total mixed ration which had either been supplemented with SY (0, 0.15 or 0.35 mg Se/kg DM) or SS (0.15 mg Se/kg DM). At enrollment (0 d) and at 28, 56, 84 and 112 d following enrollment, blood samples were taken for Se and Se species determination, as well as whole blood GSH-Px activity. At the end of the study beef cattle were euthanized and samples of heart, liver, kidney, and skeletal muscle (LM and psoas major) were retained for Se and Se species determination. Tissue GSH-Px activity and thiobarbituric acid reactive substances (TBARS) were determined in skeletal muscle tissue (LM only). The incorporation into the diet of ascending concentrations of Se as SY increased whole blood total Se and the proportion of total Se comprised as SeMet, as well as GSH-Px activity. There was also a dose dependant response to the graded addition of SY on total Se and proportion of total Se as SeMet in all tissues and GSH-Px activity in skeletal muscle tissue. Furthermore, total Se concentration of whole blood and tissues was greater in those animals offered SY when compared with those receiving a comparable dose of SS, indicating an improvement in Se availability and tissue Se retention. Likewise, GSH-Px activity in whole blood and LM was greater in those animals offered SY when compared with those receiving a comparable dose of SS. However, these increases in tissue total Se and GSH-Px activity appeared to have little or no effect in meat oxidative stability.

Effects of dietary supplementation with selenium enriched yeast or sodium selenite on selenium tissue distribution and meat quality in lambs

The objective was to determine the concentration of total selenium (Se) and the proportion of total Se comprised as selenomethionine (SeMet) and selenocysteine (SeCys), as well as meat quality in terms of oxidative stability in post mortem tissues of lambs offered diets with an increasing dose rate of selenized enriched yeast (SY), or sodium selenite (SS). Fifty lambs were offered, for a period of 112 d, a total mixed ration which had either been supplemented with SY (0, 0.11, 0.21 or 0.31 mg/kg DM to give total Se contents of 0.19, 0.3, 0.4 and 0.5 mg Se/kg DM for treatments T1, T2, T3 and T4, respectively) or SS (0.11 mg/kg DM to give 0.3 mg Se/kg DM total Se [T5]). At enrolment and at 28, 56, 84 and 112 d following enrolment, blood samples were taken for Se and Se species determination, as well as glutathione peroxidase (GSH-Px) activity. At the end of the study lambs were euthanased and samples of heart, liver, kidney, and skeletal muscle were retained for Se and Se species determination. Tissue GSH-Px activity and thiobarbituric acid reactive substances (TBARS) were determined in Longissimus Thoracis. The incorporation into the diet of ascending concentrations of Se as SY increased whole blood total Se and the proportion of total Se comprised as SeMet, and erythrocyte GSH-Px activity. Comparable doses of SS supplementation did not result in significant differences between these parameters. With the exception of kidney tissue, all other tissues showed a dose dependant response to increasing concentrations of dietary SY, such that total Se and SeMet increased. Selenium content of Psoas Major was higher in animals fed SY when compared to a similar dose of SS, indicating improvements in Se availability and retention. There were no significant treatment effects on meat quality assessments GHS-Px and TBARS, reflecting the lack of difference in the proportion of total Se that was comprised as SeCys. However, oxidative stability improved marginally with ascending tissue Se content, providing an indication of a linear dose response whereby TBARS improved with ascending SY inclusion.

Dietary fatty acids and chylomicron synthesis and secretion

There is currently considerable interest in potential atherogenic and thrombogenic consequences of elevated concentrations of triacylglycerols, especially in the post-prandial state. Despite this, there is limited information on the effects of dietary fatty acids on the synthesis, secretion and metabolism of chylomicrons, the large triacylglycerol-rich lipoproteins synthesized in the enterocyte following the digestion and absorption of dietary fat. This brief review considers current approaches to the investigation of chylomicron synthesis and summarizes some of the human, cell and animal studies that have investigated effects of different fatty acids on these pathways. Potential sites for modulatory effects of dietary fatty acids on the molecular events of chylomicron synthesis are proposed in the light of the recent model that has been developed from cell and animal studies and observations based on abnormalities in chylomicron formation in human inherited autosomal recessive diseases.

Platelet-mediated metabolism of the common dietary flavonoid, quercetin.

BACKGROUND: Flavonoid metabolites remain in blood for periods of time potentially long enough to allow interactions with cellular components of this tissue. It is well-established that flavonoids are metabolised within the intestine and liver into methylated, sulphated and glucuronidated counterparts, which inhibit platelet function. METHODOLOGY/PRINCIPAL FINDINGS: We demonstrate evidence suggesting platelets which contain metabolic enzymes, as an alternative location for flavonoid metabolism. Quercetin and a plasma metabolite of this compound, 4'-O-methyl quercetin (tamarixetin) were shown to gain access to the cytosolic compartment of platelets, using confocal microscopy. High performance liquid chromatography (HPLC) and mass spectrometry (MS) showed that quercetin was transformed into a compound with a mass identical to tamarixetin, suggesting that the flavonoid was methylated by catechol-O-methyl transferase (COMT) within platelets. CONCLUSIONS/SIGNIFICANCE: Platelets potentially mediate a third phase of flavonoid metabolism, which may impact on the regulation of the function of these cells by metabolites of these dietary compounds.

The two Caenorhabditis elegans metallothioneins (CeMT-1 and CeMT-2) discriminate between essential zinc and toxic cadmium

The nematode Caenorhabditis elegans expresses two metallothioneins (MTs), CeMT-1 and CeMT-2, that are believed to be key players in the protection against metal toxicity. In this study, both isoforms were expressed in vitro in the presence of either Zn(II) or Cd(II). Metal binding stoichiometries and affinities were determined by ESI-MS and NMR, respectively. Both isoforms had equal zinc binding ability, but differed in their cadmium binding behaviour, with higher affinity found for CeMT-2. In addition, wild-type C. elegans, single MT knockouts and a double MT knockout allele were exposed to zinc (340 μm) or cadmium (25 μm) to investigate effects in vivo. Zinc levels were significantly increased in all knockout strains, but were most pronounced in the CeMT-1 knockout, mtl-1 (tm1770), while cadmium accumulation was highest in the CeMT-2 knockout, mtl-2 (gk125) and the double knockout mtl-1;mtl-2 (zs1). In addition, metal speciation was assessed by X-ray absorption fine-structure spectroscopy. This showed that O-donating, probably phosphate-rich, ligands play a dominant role in maintaining the physiological concentration of zinc, independently of metallothionein status. In contrast, cadmium was shown to coordinate with thiol groups, and the cadmium speciation of the wild-type and the CeMT-2 knockout strain was distinctly different to the CeMT-1 and double knockouts. Taken together, and supported by a simple model calculation, these findings show for the first time that the two MT isoforms have differential affinities towards Cd(II) and Zn(II) at a cellular level, and this is reflected at the protein level. This suggests that the two MT isoforms have distinct in vivo roles.

Effect of dietary supplementation of different oils during the first or second half of pregnancy on the glucose tolerance of the sow

Poor glucose tolerance may be an under-researched contributory factor in the high (10% to 20%) pre-weaning mortality rate observed in pigs. Insulin resistance commences at around week 12 of gestation in the sow, although there are conflicting reports in the literature about the extent to which insulin resistance is modulated by maternal diet. The aim of the study was to determine the effects of supplementing the maternal diet with different dietary oils during either the first half or the second half of gestation on the glucose tolerance of the sow. Sows were offered the control (C: n = 5) diet as pellets or the C diet plus 10% extra energy (h = 16 per group) derived from either. (i) extra pellets; (ii) palm oil; (iii) olive oil; (iv) sunflower oil; or (v) fish oil. Experimental diets were fed during either the first (G1) or second (G2) half of gestation. A glucose tolerance test (GTT) was conducted on day 108 of gestation by administering 0.5g/kg glucose i.v. Blood samples were taken every 5 to 10 min for 90 min post administration. The change in body weight and backfat thickness during gestation was similar but both type and timing of dietary supplementation influenced litter size and weight. With the exception of the sunflower oil group, supplementing the maternal diet in G1 resulted in larger and heavier litters, particularly in mothers offered palm oil. Basal blood glucose concentrations tended to be more elevated in G1 than G2 groups, whilst plasma insulin concentrations were similar Following a GTT, the adjusted area under the curve was greater in G1 compared to G2 sows, despite no differences in glucose clearance. Maternal diet appeared to influence the relationship between glucose curve characteristics following a GTT and litter outcome. In conclusion, the degree of insulin sensitivity can be altered by both the period during which maternal nutritional supplementation is offered and the fatty acid profile of the diet.

Dietary supplements of whole linseed and vitamin E to increase levels of alpha-linolenic acid and vitamin E in bovine milk

The potential to increase the concentrations of n-3 polyunsaturated fatty acids (PUFAs) in milk fat was investigated by studying the effects of feeding a xylose-treated, whole cracked linseed supplement ( rich in alpha-linolenic acid) to dairy cows. Also the effect of increasing the dietary intake of vitamin E on the vitamin E status of milk was investigated. The effect of pasteurisation on milk fatty acid composition was also examined. Using a 3 x 2 factorial design, a total of 60 Holstein dairy cows were fed a total mixed ration based on grass silage supplemented with one of three levels of whole cracked linseed (78, 142 or 209 g . kg(-1) diet dry matter (DM); designated LL, ML or HL, respectively) in combination with one of two levels of additional dietary vitamin E intake ( 6 or 12 g vitamin E . animal(-1) . day(-1); designated LE or HE, respectively). Increasing lipid supplementation reduced (P < 0.01) diet DM intake and milk yield, and increased (P < 0.001) the overall content of oleic, vaccenic, alpha-linolenic and conjugated linoleic acids, and total PUFAs and monounsaturated fatty acids (MUFA). Myristic and palmitic acids in milk fat were reduced ( P < 0.001) through increased lipid supplementation. While α-linolenic acid concentrations were substantially increased this acid only accounted for 0.02 of total fatty acids in milk at the highest level of supplementation (630 g α-linolenic acid &BULL; animal(-1) &BULL; day(-1) for HL). Conjugated linoleic acid concentrations in milk fat were almost doubled by increasing the level of lipid supplementation (8.9, 10.4 and 16.1 g &BULL; kg(-1) fatty acids for LL, ML and HL, respectively). Although milk vitamin E contents were generally increased there was no benefit (P > 0.05) of increasing vitamin E intake from 6 to 12 g . animal(-1) . day(-1). The fatty acid composition of milk was generally not affected by pasteurisation.

Enhancement of oleic acid and vitamin E concentrations of bovine milk using dietary supplements of whole rapeseed and vitamin E

With the aim of reducing the degree of saturation and increasing the C18:1 cis fatty acid content of milk fat, the effects of feeding high levels of whole cracked rapeseed to dairy cows was investigated together with the effect of increasing dietary intake of vitamin E on the vitamin E content of milk. Using a 3 x 3 factorial design, 90 Holstein dairy cows were fed one of three levels of whole cracked rapeseed (0 (ZR), 134 (MR) and 270 g . kg(-1) diet dry matter (DM) (HR)) in combination with one of three intakes of supplementary vitamin E (0 (ZE), 2 (ME) and 4 g . cow(-1) . d(-1) (HE)). Supplementing with up to almost 2 kg . d(-1) of rapeseed oil (diet HR) significantly (P < 0.001) increased C18: 1cis in milk fat, from 181 (ZR) to over 400 g &BULL; kg(-1) (HR) of total milk fatty acids. Concentrations of C18: 0, C18: 2 and C18: 3 fatty acids were also increased ( P < 0.001) but by a much lesser degree, and the saturated fatty acids C4: 0 to C16: 0 decreased substantially. Vitamin E supplementation increased ( P < 0.01) milk vitamin E concentrations from 1.29 (ZE) to 1.68 mg &BULL; kg(-1) whole milk (HE). Thus substantial changes in milk fat composition with potentially beneficial effects on human health were achieved and without any adverse effects on milk taste. However, these improvements must be offset against the substantial reductions ( P < 0.001) observed in voluntary feed DM consumption (ZR, 20.6; HR, 15.2 kg DM . d(-1)), milk yield (ZR, 22.9; HR, 13.2 kg . d(-1)) and milk fat concentration (ZR, 42.1; HR, 33.4 g . kg(-1)) which would not be commercially sustainable unless a considerable premium was paid for this modified milk. It seems likely that the optimum dose of dietary rapeseed is lower than used in this study.

Effects of dietary vitamin A concentration of roasted soybean inclusion on marbling, adipose cellularity, and fatty acid composition of beef

A feedlot trial was conducted to determine the effect of dietary vitamin A concentration and roasted soybean (SB) inclusion on carcass characteristics, adipose tissue cellularity, and muscle fatty acid composition. Angus-crossbred steers (n = 168; 295 +/- 1.8 kg) were allotted to 24 pens (7 steers each). Four treatments, in a 2 x 2 factorial arrangement, were investigated: no supplemental vitamin A, no roasted soybeans (NANS); no vitamin A, roasted SB (20% of the diet on a DM basis; NASB); with supplemental (2,700 IU/kg) vitamin A, no roasted SB (WANS); and with supplemental vitamin A, roasted SB (WASB). Diets included high moisture corn, 5% corn silage, 10 to 20% supplement, and 20% roasted SB in the SB treatments on a DM basis. The calculated vitamin A concentration in the basal diet was < 1,300 IU/kg of DM. Blood samples (2 steers/pen) were collected for serum vitamin A determination. Steers were slaughtered after 168 d on feed. Carcass characteristics and LM composition were determined. Fatty acid composition of LM was analyzed, and adipose cellularity in the i.m. and s.c. depots was determined. No vitamin A x SB interactions were detected (P > 0.10) for cattle performance, carcass composition, or muscle fatty acid composition. Low vitamin A diets (NA) did not affect (P > 0.05) ADG, DMI, or G:F. Quality grade tended (P = 0.07) to be greater in NA steers. Marbling scores and the percentage of carcasses grading > or = Choice(-) were 10% greater for NA steers, although these trends were not significant (P = 0.11 and 0.13, respectively). Backfat thickness and yield grade were not affected (P > 0.26) by vitamin A supplementation. Composition of the LM was not affected (P > 0.15) by vitamin A or SB supplementation. Serum retinol at slaughter was 44% lower (P < 0.01) for steers fed NA than for steers supplemented with vitamin A (23.0 vs. 41.1 microg/dL). A vitamin A x SB interaction occurred (P < 0.05) for adipose cellularity in the i.m. depot; when no SB was fed, vitamin A supplementation decreased cell density and increased cell size. However, when SB was fed, vitamin A supplementation did not affect adipose cellularity. Adipose cellularity at the s.c. depot was not affected (P > 0.18) by vitamin A or SB treatments. Fatty acid profile of the LM was not affected by vitamin A (P > 0.05), but SB increased (P < 0.05) PUFA (7.88 vs. 4.30 g/100 g). It was concluded that feeding NA tended to increase marbling without affecting back-fat and yield grade. It appeared that NA induced hyperplasia in the i.m. but not in the s.c. fat depot.