Effect of dietary phytate on bioavailability of iron

Experiments were carried out on iron-chelating capacity of phytic acid in fortified and unfortified diets of whole wheat, white flour and wheat bran using albino rats in a 10-day balance study. The results revealed that gross digestibility was highest in control diet (93.25%), least in the wheat brain diet with added ferrous sulfate (86.70%) and intermediate in other diets. Among the unfortified and fortified diets, the highest amount of phytate was present in the diet having wheat bran (2.69–4.99 mg/g). Phytate concentration of the rat faeces followed the pattern of dietary phytate content of test diets. The data indicated high values for iron (200.00–236.64 mg/g) in fortified diets while in the unfortified diets, the value was the same (16.67 mg/g) except the casein diet, which contained 69.99 mg/g of iron. Iron concentration of the fat faeces ranged 16.25–23.50 mg/g; the higher value being in the excreta of animals given fortified diets. The casein diet had iron 46.75 mg/g. The overall results showed that the phytate absorption was relatively higher in groups fed fortified diets. Iron absorption almost followed the pattern of phytate absorption. Correlation co-efficient analysis showed insignificant relationship between iron and phytate absorption indicating little effect of dietary phytate on the biovailability of iron.     

The effects of phytate on intestinal absorption and secretion of zinc, and whole-body retention of Zn, copper, iron and manganese in rats.

1. The inclusion of phytate (10 g/kg) in a purified diet containing zinc (15 mg/kg) fed to young male rats significantly reduced growth rate and food intake, and promoted a cyclic pattern of food intake characteristic of an uncomplicated Zn deficiency. The decreased growth rate could be accounted for by the reduced food consumption. 2. Rats maintained on a Zn-deficient diet (0.5 mg Zn/kg) were found to have a cyclic pattern of food intake and a very slight weight gain. The addition of phytate (10 g/kg) to the Zn-deficient diet promoted a net loss of mean body-weight. 3. Rats maintained on the Zn-supplemented diet containing phytate excreted significantly more Zn in their faeces than either pair-fed or ad lib.-fed control rats. Rats given the Zn-deficient diet supplemented with phytate excreted more Zn in their faeces than Zn-deficient control rats. 4. Dietary phytate significantly reduced the average daily accumulation (mug/d) and whole-body retention (relative to dietary intake) of iron, copper, manganese and Zn, whether or not the diet was supplemented with Zn. 5. The addition of phytate to the lumen fluid of ligated loops of rat duodenum maintained in situ significantly inhibited 65Zn absorption, compared with the control systems without added phytate. 6. Other studies using ligated duodenal and ileal loops indicated that Zn is secreted into the gut lumen and approximately one-third of this is normally reabsorbed. Recycling of endogenous Zn may be a significant process in the over-all body economy of this trace element. 7. The absorption of 65Zn added to the diet was significantly reduced by dietary phytate. Dietary phytate also reduced the biological half-life of body 65Zn from 61 to 211 h post-administration, possibly by inhibiting reabsorption of endogenous 65Zn and thus promoting a more rapid loss from the body.     

Modification of a selenium toxicity in chicks by dietary silver and copper.

Studies were conducted to determine the effects of high levels of dietary silver nitrate and copper sulfate on the response of chicks to toxic levels of dietary selenium. Adding 5 ppm or more selenium to a basal stock diet significantly reduced growth rate, and 40 ppm or high significantly increased mortality during the 2-week experiments. Deitary silver or copper (1,000 ppm) counteracted the growth depression and prevented mortality at the higher levels of selenium. Hepatic selenium reached a maxiumum in chicks fed the basal diet with 10 ppm dietary selenium. Hepatic selenium of chicks fed silver was less than that of the control chicks when diets containing 10 ppm or less selenium were fed. Adding copper to the diet resulted in considerable accumulation of selenium in the liver, which was evident even at the lower levels of added selenium. Rseults of an experiment to determine the effects of deitray silver and copper on the distribution of 75-Se administered either orally or in tramusculary showed that silver interfered with absorption of selenium. The results of these experiments suggest that silver modifies selenium toxity both by interfering with selenium absorption and by causing the accumulation of a nondeleterious selenium compound in the tissues. Copper modifies selenium toxicity primarily by causing the accumulation of a nondeleterious compound in the tissues.     

Fecal phytate excretion varies with dietary phytate and age in women

OBJECTIVE: Information on the excretion of dietary phytate in humans under different conditions is limited. The purpose of this study was to investigate fecal excretion of dietary phytate and phosphorus in a group of young and elderly women consuming high and low phytate diets. METHODS: Fifteen young and fourteen elderly women were fed two experimental diets, high phytate and low phytate, for 10 days each with a washout period of 10 days between the two diet periods. Duplicate diet samples from two different menus and complete fecal samples were collected for 5 days during each diet period and analyzed for phytate and phosphorus contents. Mean daily excretions and percentages of dietary intakes of phytate and phosphorus were calculated. RESULTS: Dietary phytate level does impact phytate excretion, but the effect was observed only in young subjects. Fecal phytate excretion of young subjects during the high phytate diet (313 mg/d) was significantly higher than during the low phytate diet (176 mg/d), however, that of elderly subjects did not vary with dietary phytate levels. Phosphorus excretion, net absorption, and apparent absorption rate were affected by dietary phytate level but not by the age of the subjects. CONCLUSIONS: Results of this study indicate that phytate degradation in the gastrointestinal tract is substantial and more variable in young women than in elderly women. The high capacity of phytate degradation in elderly subjects may be related to long-term phytate intake but needs further clarification. Both beneficial and adverse health effects of phytate need to be studied considering the long-term phytate intake and age of subjects as well as dietary phytate levels.     

Inhibitory effect of dietary soybean protein vs. casein on magnesium absorption in rats

The effects of casein and soybean protein on magnesium absorption and magnesium concentration in the femur were investigated in rats. Purified diets containing either casein or soybean protein and three concentrations of added magnesium (0.82, 1.64 or 2.46 mmol/100 g diet) were used. The isonitrogenous diets were carefully balanced for the different mineral concentrations in the protein preparations. Absolute and percent magnesium absorption and urinary magnesium excretion were significantly decreased in rats fed soybean protein when compared with casein, irrespective of the dietary concentration of added magnesium. The magnesium content of femur was significantly lower in rats fed soybean protein, but this effect was seen only when the diet contained 0.82 mmol magnesium/100 g diet. The addition of sodium phytate to the casein diets, to a concentration identical to that in the diets containing soybean protein as provided by the soybean protein preparation, produced similar effects on magnesium absorption as the diets containing soybean protein. These results indicate that soybean protein, when compared with casein, decreases magnesium absorption through its phytate component.     

Studies on the phytate: zinc molar contents in diets as a determinant of Zn availability to young rats

1. Studies were carried out in vitro to examine the effects of phytate on the solubility of the trace elements zinc, copper and manganese. Appropriate volumes of a solution of sodium phytate were added to a mineral solution to achieve phytate: Zn values of from 0 : 1 to 45 : 1. In a second series the same values for phytate: Zn were achieved by varying the amount of added Zn at a fixed phytate concentration. 2. In both experiments greater than 85% of the Zn was rendered insoluble at pH 6.5 even at the lowest value for phytate: Zn (5 : 1). The effect of phytate on Zn solubility was greater than effects on Cu or Mn. 3. In a dietary study, rats were offered a semi-synthetic egg-albumin-based diet with added phytate. Two series of diets were prepared, the first had a constant Zn content (18.5 mg Zn/kg) and the amount of sodium phytate varied so as to achieve values for phytate: Zn of from 0 : 1 to 40 : 1 (series 1). In the second series, the same values for phytate: Zn were achieved by adding a fixed amount of phytate (7.4 g phytic acid/kg) while the amount of Zn was varied (series 2). 4. Dietary phytate caused significant reductions in growth rates, plasma Zn concentrations and hair Zn concentrations and greying of the coat at values for phytate: Zn of 15 : 1, 10 : 1, 15 : 1 and 15 : 1, respectively. 5. While phytate was apparently slightly more effective in reducing Zn status when phytate: Zn values were achieved at the lower absolute levels of phytate and zn (series 1 diets), the differences at equivalent phytate: Zn values were small. It was concluded that phytate: Zn values can be used as an indicator of Zn availability from phytate-rich diets. 6. Rats offered three diets containing soya-bean-based textured-vegetable-protein (TVP) exhibited low rates of weight gain compared with rats offered an egg-albumen-based diet of similar Zn content (14.5 mg Zn/kg). Additional Zn supplied in drinking-water (25 mg Zn//l) was without effect on rats consuming the egg-albumin diet but significantly improved the weight gain of rats on the TVP diets. 7. It was concluded that phytate naturally present in TVP behaves similarly to phytate added to an otherwise phytate-free diet and that the reduced availability of Zn in TVP diets can be accounted for entirely by their phytate contents.     

Excess levels of cysteine and homocysteine induce tibial dyschondroplasia in broiler chicks.

The effect of excessive levels of cysteine and homocysteine on tibial dyschondroplasia (TD) in broiler chicks was studied. In the first experiment, graded levels of L-cysteine as well as one level of L-homocysteine were supplemented to a corn-soybean-based diet adequate in sulfur amino acids. Levels equal to or above 0.5% supplemental cysteine increased the incidence of TD, and levels equal to or above 0.75% supplemental cysteine increased the severity of TD above that found in chicks fed the basal diet. Also, L-homocysteine at 0.5% induced TD. In the second experiment, graded levels of DL-homocystine were added to the basal diet to determine the threshold value of homocystine needed to induce TD, and a level of ammonium sulfate isosulfurous to 0.45% homocystine was added to a basal diet. The results showed that 0.45% DL-homocystine was the lowest level that increased the severity of TD above that found in chicks fed the basal diet and that sulfate did not induce TD. In the third experiment, a 2 x 2 factorial design was used to investigate the interaction between DL-homocystine and copper. Copper supplementation lessened the severity of TD caused by DL-homocystine. Copper supplementation also tended to improve growth, especially in birds fed DL-homocystine.     

Effect of dietary phytase on the digestion of phytate in the stomach and small intestine of humans

The purpose of this study was to investigate whether dietary phytase is involved in the hydrolysis of phytate in the stomach and small intestine of humans. The digestibility of phytase-deactivated wheat bran was studied on eight occasions and untreated wheat bran on two occasions in healthy ileostomates. Five subjects were studied for two 4-d periods and one subject on two occasions for two 4-d periods while fed a constant low fiber diet. The low fiber diet was supplemented with 16 g/d wheat bran in the second period. Three other subjects fed a low fiber diet were studied for 10 consecutive days, bran being added to the diet on d 5, 6 and 7. Inositol hexaphosphate and its degradation products were analyzed with a recently developed HPLC method. On average, 95% of the ingested phytate from phytase-deactivated wheat bran and 40% of the ingested phytate from untreated wheat bran were recovered in ileostomy contents. These results differ from those of a previous analysis using an iron precipitation method. Mucosal phytase and alakaline phosphatase, if present in the human small intestine, do not seem to play a significant role in phytate digestion in humans, whereas the dietary phytase may be an important factor for phytate hydrolysis. Iron precipitation methods are not adequate for determinations of phytate digestion.     

Ingestion of insoluble dietary fibre increased zinc and iron absorption and restored growth rate and zinc absorption suppressed by dietary phytate in rats

We examined the effects of ingestion of five types of insoluble fibre on growth and Zn absorption in rats fed a marginally Zn-deficient diet (6.75 mg (0.103 mmol) Zn/kg diet) with or without added sodium phytate (12.6 mmol/kg diet). The types of insoluble fibre tested were corn husks, watermelon skin, yam-bean root (Pachyrhizus erosus) and pineapple core, and cellulose was used as a control (100 g/kg diet). Body-weight gain in the cellulose groups was suppressed by 57 % by feeding phytate. Body-weight gain in phytate-fed rats was 80 % greater in the watermelon skin fibre and yam-bean root fibre group than that in the cellulose group. Zn absorption ratio in the cellulose groups was lowered by 46 and 70 % in the first (days 7-10) and second (days 16-19) measurement periods with feeding phytate. In the rats fed the phytate-containing diets, Zn absorption ratio in the watermelon skin, yam-bean root and pineapple core fibre groups was 140, 80 and 54 % higher respectively than that in the cellulose group, in the second period. Fe absorption was not suppressed by phytate, however, feeding of these three types of fibre promoted Fe absorption in rats fed phytate-free diets. The concentration of soluble Zn in the caecal contents in the watermelon skin fibre or yam-bean root fibre groups was identical to that in the control group in spite of a higher short-chain fatty acid concentration and lower pH in the caecum. These findings indicate that ingestion of these types of insoluble fibre recovered the growth and Zn absorption suppressed by feeding a high level of phytate, and factors other than caecal fermentation may also be involved in this effect of insoluble fibre.     

The addition of milk or yogurt to a plant-based diet increases zinc bioavailability but does not affect iron bioavailability in women

The addition of milk and milk-based products to the diets of individuals subsisting on plant-based diets was reported to have positive effects on nutritional status and functional outcomes such as growth, morbidity, and cognition. We examined the effect of the addition of milk or yogurt on the bioavailability of zinc and iron from a plant-based rural diet. The subjects were 48 Mexican women (30.9 +/- 5.7 y) who habitually consumed a plant-based diet. The women were assigned to 1 of 3 groups: 1) the typical rural Mexican diet, 2) that diet with milk added, or 3) that diet with yogurt for 13 d. Zinc absorption was measured after extrinsically labeling meals with (67)Zn and an i.v. dose of (70)Zn; iron absorption was measured by extrinsically labeling meals with (58)Fe and a reference oral dose of (57)Fe. Including milk and yogurt in the diet increased zinc absorption by 50 and 68%, respectively (P < 0.05). The 3 groups did not differ in the percentage iron absorption. The total amount of zinc absorbed was increased (P < 0.05) by 70% when milk was added to the meal and 78% when yogurt was added. The total amount of iron absorbed did not differ among the groups. The addition of milk and yogurt to a plant-based diet high in phytate increases zinc bioavailability without affecting iron bioavailability.     

Effect of reducing the phytate content and of partially hydrolyzing the protein in soy formula on zinc and copper absorption and status in infant rhesus monkeys and rat pups

BACKGROUND: Although soy formulas have been designed to meet the nutrient requirements of human infants, they also contain phytate, which may negatively affect trace element absorption. OBJECTIVE: We evaluated the effect of removing phytate on zinc and copper absorption and status in infant rhesus monkeys and suckling rat pups and evaluated differences between intact and partially hydrolyzed soy protein. DESIGN: In monkeys, regular and low-phytate soy formulas were fed exclusively for 4 mo and whole-body absorption and retention of 65Zn, 67Cu, 59Fe, 54Mn, and 47Ca were determined at different time points with a whole-body counter. Subsequently, zinc and copper absorption from several human infant formulas and the effect of phytate concentration were evaluated in suckling rat pups by using 65Zn and 64Cu. Finally, infant rhesus monkeys were fed low-phytate formulas with intact or hydrolyzed soy protein for 4 mo and plasma zinc and copper were measured monthly. RESULTS: In the first monkey study, zinc absorption at 1 mo was higher from low-phytate soy formula (36%) than from regular soy formula (22%), whereas there was no significant difference between groups in the absorption of other minerals. Plasma copper was significantly lower in monkeys fed low-phytate soy formula from 2 to 4 mo. In rat pups, zinc absorption was significantly higher from low-phytate soy formula (78%) than from regular soy formula (51%) and hydrolysis of the protein had no significant effect. Phytate content or protein hydrolysis did not significantly affect copper absorption. In the second monkey study, plasma copper concentrations were highest in monkeys fed the low-phytate, hydrolyzed-protein soy formula. CONCLUSION: Reducing the phytate content and partially hydrolyzing the protein in soy formula had a beneficial effect on zinc and copper absorption and status in infant rhesus monkeys.     

Ascorbic acid prevents the dose-dependent inhibitory effects of polyphenols and phytates on nonheme-iron absorption

The effects of maize-bran phytate and of a polyphenol (tannic acid) on iron absorption from a white-bread meal were tested in 199 subjects. The phytate content was varied by adding different concentrations of phytate-free and ordinary maize bran. Iron absorption decreased progressively when maize bran containing increasing amounts of phytate phosphorous (phytate P) (from 10 to 58 mg) was given. The inhibitory effect was overcome by 30 mg ascorbic acid. The inhibitory effects of tannic acid (from 12 to 55 mg) were also dose dependent. Studies suggested that greater than or equal to 50 mg ascorbic acid would be required to overcome the inhibitory effects on iron absorption of any meal containing greater than 100 mg tannic acid. Our findings indicate that it may be possible to predict the bioavailability of iron in a diet if due account is taken of the relative content in the diet of the major promoters and inhibitors of iron absorption.     

Iron bioavailability in humans from breakfasts enriched with iron bis-glycine chelate, phytates and polyphenols

This study was conducted to determine the bioavailability of iron amino acid chelate (ferrochel) added to fortify breads prepared from either precooked corn flour or white wheat flour + cheese and margarine compared with the same basal breakfast enriched with either ferrous sulfate or iron-EDTA. The inhibitory effect of phytate and polyphenols on iron absorption from ferrochel was also tested. A total of 74 subjects were studied in five experiments. Iron absorption from ferrochel was about twice the absorption from ferrous sulfate (P: < 0.05). When ferrous sulfate and ferrochel were administered together or in different meals, absorption from ferrochel was about twice the absorption from ferrous sulfate (P: < 0.05). Polyphenols present in coffee and tea inhibited iron absorption in a dose-dependent manner. American-type coffee did not modify iron absorption significantly, whereas both espresso-type coffee and tea reduced iron absorption from ferrochel by 50% (P: < 0. 05). Ferrochel partially prevented the inhibitory effect of phytates. Because of its high solubility in aqueous solutions even at pH 6, its low interactions with food and high absorption, ferrochel is a suitable compound for food fortification.     

The effect of wheat bran on the absorption of minerals in the small intestine

1. Studies on mineral absorption were carried out in ileostomy patients using the metabolic balance technique. The effect of wheat bran on the absorption of phosphorus, calcium, magnesium, zinc and iron was studied. The extent of digestion of bran phytate in the stomach and small intestine was also investigated. 2. Eight patients with well established conventional ileostomies were studied during two periods while on a constant low-fibre diet. In the second period, 16 g wheat bran/d (American Association of Cereal Chemists) was added to the diet. The amount of phytate-P, non-phytate-P, Ca, Mg, Zn and Fe was determined in the ileostomy contents and in duplicate portions of the diet. 3. Of the added bran phytate-P 24-61% was recovered in the ileostomy contents. In the bran period a significantly decreased amount of Zn was absorbed, while the apparent absorption of Fe and phytate-P increased and that of non-phytate-P, Ca and Mg remained constant. Due to the mineral content of bran, the relative absorption differed in some respects from the absolute absorption, being decreased for Zn, Mg and phytate-P but unchanged for Ca, Fe and non-phytate-P. 4. It is concluded that phytate is partly digested in the stomach and small intestine or possibly absorbed. Addition of 16 g bran/d to the diet does not seem to impair the mineral absorption from the small intestine except that of Zn.     

Calcium: effect of different amounts on nonheme- and heme-iron absorption in humans

We investigated the effect of calcium on iron absorption in 126 human subjects. Addition of calcium chloride to wheat rolls significantly reduced iron absorption. Doses between 40 and 600 mg Ca were studied. The inhibition was clearly dose related up to 300 mg Ca. Calcium added to the dough when making the rolls reduced phytate degradation during fermentation and baking. As little as 40 mg Ca added to 80 g flour reduced phytate degradation by 50%, thus increasing the phytate content of the rolls to levels interfering with iron absorption. Calcium also had a direct dose-related inhibiting effect on iron absorption, noted by adding calcium to the rolls after they had been baked instead of to the dough. Iron absorption was reduced by 50-60% at doses of 300-600 mg Ca. Giving 165 mg Ca as milk, cheese, or calcium chloride reduced absorption by 50-60%. The same amount of calcium also significantly reduced heme-iron absorption, suggesting that the effect of calcium is related to the mucosal transfer of iron. The observed marked inhibitory effect on iron absorption of calcium in amounts frequently encountered in normal meals has important nutritional implications.     

Soy protein isolate enhances hepatic copper accumulation and cell damage in LEC rats

In a series of experiments, the effects of soy protein isolate (SPI), defatted soy (DFS) or SPI supplemented with L-methionine (SPIM) were examined in the Long-Evans rat with a cinnamon coat color (LEC rat), a model animal of Wilson's disease with a hereditary defect in the Atp7b gene resulting in defective copper metabolism and copper accumulation in hepatocytes. Milk casein in the control AIN-93G diet (20 g/100 g) was totally or 60% replaced by the soy products, SPI, DFS or SPIM (L-Met added to be equal to that in the control diet) beginning when rats were 6 wk old. Copper and iron concentrations in SPI and DFS were measured and the concentrations of these metals in the salt mix were adjusted so that test and the control diets had the same final concentrations. Food intake did not differ among groups. Rats were euthanized when they became moribund with jaundice. Survival time in the SPI diet group was shorter (14.0 +/- 0.8 wk) than in the control group (19.1 +/- 1.7 wk) (P < 0.001), and that in the DFS diet group was intermediate (16.0 +/- 1.7 wk). Survival time in the SPIM diet group did not differ from that of the SPI diet group. Copper concentrations in the livers of rats in the SPI and SPIM diet groups were approximately 80% higher than in rats fed the control diet. Liver iron concentrations did not differ among the groups. The results, including histological analyses, indicate that SPI enhances copper uptake into the liver cells and promotes liver cell damage in LEC rats. However, this did not occur in the livers of F344 rats with wild-type Atp7b. Recommendations to individuals suffering from Wilson's disease to avoid consuming soy protein may be warranted.     

Prediction of dietary iron absorption: an algorithm for calculating absorption and bioavailability of dietary iron

BACKGROUND: Dietary iron absorption from a meal is determined by iron status, heme- and nonheme-iron contents, and amounts of various dietary factors that influence iron absorption. Limited information is available about the net effect of these factors. OBJECTIVE: The objective was to develop an algorithm for predicting the effects of factors known to influence heme- and nonheme-iron absorption from meals and diets. DESIGN: The basis for the algorithm was the absorption of iron from a wheat roll (22.1 +/- 0.18%) containing no known inhibitors or enhancers of iron absorption and adjusted to a reference dose absorption of 40%. This basal absorption was multiplied by the expected effect of different amounts of dietary factors known to influence iron absorption: phytate, polyphenols, ascorbic acid, meat, fish and seafood, calcium, egg, soy protein, and alcohol. For each factor, an equation describing the dose-effect relation was developed. Special considerations were made for interactions between individual factors. RESULTS: Good agreement was seen when measurements of iron absorption from 24 complete meals were compared with results from use of the algorithm (r(2) = 0.987) and when mean iron absorption in 31 subjects served a varied whole diet labeled with heme- and nonheme-iron tracers over a period of 5 d was compared with the mean total iron absorption calculated by using the algorithm (P = 0.958). CONCLUSIONS: This algorithm has several applications. It can be used to predict iron absorption from various diets, to estimate the effects expected by dietary modification, and to translate physiologic into dietary iron requirements from different types of diets.     

[Phytate][calcium]/[zinc] ratios in Asian immigrant lacto-ovo vegetarian diets and their relationship to zinc nutriture

Lacto-ovo vegetarians often have low zinc intakes coupled with concomitant high intakes of dietary fiber, phytate and calcium. The latter two dietary components appear to exert a synergistic inhibitory effect on zinc absorption. In this study 30 1-day diet composites were prepared for analysis from 3-day weighed diet records completed by 112 Asian immigrants consuming predominantly lacto-ovo vegetarian diets and compared with 30 omniverous diet composites. Analysed mean (±S.D.) daily intakes were: energy (kcal) 1892±445, calcium (mg) 1093±467, zinc (mg) 8.5±4.5, phytate (mg) 1487±791, neutral detergent fiber (g) 26.8±13.2. Median phytate: Zn molar ratio for Punjabi diets was 17.7 (range=5-50) and median [phytate][Ca]/[Zn] molar ratio was 475.4 (range=48-1150) compared with median values of 8.3 and 130.9 respectively for omniverous diets. Thirty-seven percent of the Punjabi diets had phytate:Zn ratios>20 and 80% had [phytate][Ca]/[Zn] ratios>200, levels shown to jeopardize zinc status in man. Thirty-two percent of the Punjabi subjects had low serum zinc levels (ie<70 g/dl) which may be associated with the unusually high dietary [phytate][Ca]/[Zn] ratios. The latter are attributed to high intakes of unleavened wholemeal chapatti bread, dairy products, and low intakes of flesh foods.     

Activation of chick tendon lysyl oxidase in response to dietary copper

Lysyl oxidase (EC 1.4.3.13), a cuproenzyme, can account for 10-30% of the copper present in connective tissue. Herein, we assess the extent to which tissue copper concentrations and lysyl oxidase activity are related because the functional activity of lysyl oxidase and the copper content of chick tendon are both related to dietary copper intake. Chicks (1-d old) were fed diets (basal copper concentration, 0.4 microg/g diet) to which copper was added from 0 to 16 microg/g diet. Liver and plasma copper levels tended to normalize in chickens that consumed from 1 to 4 microg copper/g of diet, whereas tendon copper concentrations suggested an unusual accumulation of copper in chickens that consumed 16 microg copper/g diet. The molecular weight of lysyl oxidase was also estimated using matrix-assisted laser desorption ionization/time-of-flight/mass spectrometry (MALDI/TOF/MS). A novel aspect of these measurements was estimation of protein mass directly from the surface of chick tendons and aortae. Whether copper deficiency (0 added copper) or copper supplementation (16 microg copper/g of diet) caused changes in the molecular weight of protein(s) in tendon corresponding to lysyl oxidase was addressed. The average molecular weight of the peak corresponding to lysyl oxidase in tendon and aorta from copper-deficient birds was 28,386 Da +/- 86, whereas the average molecular weight of corresponding protein in tendon from copper-supplemented birds was 28,639 Da +/- 122. We propose that the shift in molecular weight is due in part to copper binding and the formation of lysyl tyrosyl quinone, the cofactor at the active site of lysyl oxidase.     

Aspirin hypocholesterolemia associated with increased microsomal copper in liver

Aspirin was fed to rats (2.4 g/kg of diet) in a diet deficient in copper because of an hypothesis linking the etiology of ischemic heart disease to copper metabolism and because of the apparently protective effect of aspirin in this disease. Cholesterol was measured by fluorometry and copper was measured by atomic absorption spectrometry. Aspirin decreased cholesterol in plasma approximately 18% (p<0.003) in each of two experiments. Copper in liver microsomes was doubled by aspirin (p<0.002). The effects of aspirin were compared to those of clofibrate in a similar experiment (Drug-Nutrient Interactions 2:131, 1983) and to other chemicals that alter both cholesterol metabolism and copper metabolism. Effects on copper may be central to the action of cholesterotropic agents.