The effect of cysteine-containing peptides released during meat digestion on iron absorption in humans

Iron Nutrition of Pre-Schoolers in High-Income Countries: A Review

Pre-schoolers are vulnerable to iron deficiency, which, in high-resource countries, is mainly caused by suboptimal or poorly absorbable iron intakes. This review examines the prevalence of inadequate iron intakes and status, and the non-dietary factors associated with these, among children aged between 2 and 5 years within high-income countries. It then considers the quality of the pre-schooler diet in terms of dietary factors, dietary patterns, and iron intakes. Additionally, it discusses the assessment of iron bioavailability and examines the various methods used to estimate the amount of absorbable iron in pre-schooler diets. Knowledge of the adequacy of iron intakes and bioavailability of iron intakes, and dietary patterns associated with iron intakes can facilitate the design and implementation of effectively targeted community-based intervention studies to improve iron intakes and iron bioavailability to minimise the risk of iron deficiency.

Tagging Recombinant Proteins to Enhance Solubility and Aid Purification

Protein fusion technology has had a major impact on the efficient production and purification of individual recombinant proteins. The use of genetically engineered affinity and solubility-enhancing polypeptide "tags" has a long history, and there is a considerable repertoire of these that can be used to address issues related to the expression, stability, solubility, folding, and purification of their fusion partner. In the case of large-scale proteomic studies, the development of purification procedures tailored to individual proteins is not practicable, and affinity tags have become indispensable tools for structural and functional proteomic initiatives that involve the expression of many proteins in parallel. In this chapter, the rationale and applications of a range of established and more recently developed solubility-enhancing and affinity tags is described.

The effect of dechitinization on iron absorption from mealworm larvae (Tenebrio molitor) flour added to maize meals: stable-isotope studies in young females with low iron stores

BACKGROUND

Edible insects have a low ecological footprint and could serve as an alternative dietary iron source. However, chitin, a major component of insects, avidly binds iron and might inhibit iron absorption.

OBJECTIVES

We aimed to measure fractional iron absorption (FIA) from Tenebrio molitor-based test meals with and without dechitinization, and to assess the effect of native and low chitin T. molitor on FIA from iron-fortified maize porridge.

METHODS

We measured iron absorption in young females with low iron stores (n = 21) from 1) labeled (54FeSO4) fortified maize porridge (maize alone); 2) intrinsically labeled (57Fe added during rearing) T. molitor larvae with native chitin content (NC) added to maize alone; and 3) dechitinized intrinsically labeled (57Fe) T. molitor larvae with low chitin content (LC) added to maize alone. We determined FIA using erythrocyte isotope incorporation and measured in vitro iron dialyzability from the 3 meals.

RESULTS

NC and LC T. molitor had similar mean ± SD iron content (12.0 ± 0.1 mg/100 g). Geometric mean (95% CI) FIAs from the 3 test meals were 1) maize alone: 5.8% (3.2%, 10.8%); 2) maize + NC T. molitor: 5.3% (2.5%, 11.3%) and 4.1% (1.9%, 8.7%); and 3) maize + LC T. molitor: 4.6% (2.0%, 10.3%) and 4.0% (1.8%, 9.2%), for extrinsic and intrinsic labels, respectively. FIA from NC and LC T. molitor did not significantly differ, and both were lower (P < 0.005) than FIA from the labeled maize porridge in the 3 meals, which did not significantly differ. The slopes of the relations between FIA and serum ferritin in the different meals and from the intrinsic and extrinsic labels did not significantly differ.

CONCLUSIONS

T. molitor biomass does not strongly affect iron absorption when added to maize porridge. Our data suggest T. molitor iron is absorbed from the common nonheme iron pool. Native T. molitor is high in iron which is moderately well absorbed, suggesting it could be a valuable dietary iron source.This trial was registered at clinicaltrials.gov as NCT04510831.

Iron delivery systems for controlled release of iron and enhancement of iron absorption and bioavailability

Iron deficiency is a global nutritional problem, and adding iron salts directly to food will have certain side effects on the human body. Therefore, there is growing interest in food-grade iron delivery systems. This review provides an overview of iron delivery systems, with emphasis on the controlled release of iron during gastrointestinal digestion, as well as the enhancement of iron absorption and bioavailability. Iron-bearing proteins are easily degraded by digestive enzymes and absorbed through receptor-mediated endocytosis. Instead, protein aggregates are slowly degraded in the stomach, which delays iron release and serves as a potential iron supplement. Amino acids, peptides and polysaccharides can bind iron through iron binding sites, but the formed compounds are prone to dissociation in the stomach. Moreover, peptides and polysaccharides can deliver iron by mediating the formation of ferric oxyhydroxide which is absorbed through endocytosis or bivalent transporter 1. In addition, liposomes are unstable during gastric digestion and iron is released in large quantities. Complexes formed by polysaccharides and proteins, and microcapsules formed by polysaccharides can delay the release of iron in the gastric environment and prolong iron release in the intestinal environment. This review is conducive to the development of iron functional ingredients and dietary supplements.

Prevalence and approaches to manage iron deficiency anemia (IDA)

Iron is a vital micronutrient required for growth and development at all stages of human life. Its deficiency is the primary cause of anemia that poses a significant global health problem and challenge for developing countries. Various risks are involved during iron deficiency anemia (IDA), such as premature delivery, low birth weight, etc. Further, it affects children's cognitive functioning, delays motor development, hampers physical performance and quality of life. It also speeds up the morbidity and mortality rate among women. The major reasons accountable are elevated iron demand in diet, socio-economic status, and disease condition. Various strategies have been adopted to reduce the IDA occurrence, such as iron supplementation, iron fortificants salts, agronomic practices, dietary diversification, biofortification, disease control measures, and nutritional education. Usually, the staple food groups for fortification are considered, but the selection of food fortificants and their combination must be safe for the consumers and not alter the finished product's stability and acceptability. Genetically modified breeding practices also increase the micronutrient levels of cereal crops. Therefore, multiple strategies could be relied on to combat IDA.

Delivery systems for improving iron uptake in anemia

Anemia poses a threat to a broad population globally as depleted hemoglobin leads to a plethora of conditions, and the most common cause includes iron deficiency. Iron is an essential element important for erythropoiesis, DNA synthesis, protection of the immune system, energy production, and cognitive function and hence should be maintained at appropriate levels. Various proteins are involved in transporting and absorption of iron, activation of heme synthesis, and RBC production that could be possible targets to improve iron delivery. Oral supplementation of iron either from dietary or synthetic sources has been the frontline therapy for treating iron deficiency in anemia. At the same time, intravenous administration is provided in chronic anemia, such as chronic kidney diseases (CKD). This review focuses on the strategies developed to overcome the disadvantages of available iron therapies and increase iron absorption and uptake in the body to restore iron content. Nanotechnology combined with the food fortification processes gained attention as they help develop new delivery systems to improve iron uptake by enterocytes. Furthermore, naturally obtained products such as polysaccharides, peptides, proteins, and new synthetic molecules have been used in fabrication of iron-carrier systems. The establishment of transdermal iron delivery systems such as microneedle arrays or iontophoresis, or the discovery of new molecules also proved to be an effective way for delivering iron in patients non-compliant to oral therapy.

Opportunities for plant-derived enhancers for iron, zinc, and calcium bioavailability: A review

Understanding of the mechanism of interactions between dietary elements, their salts, and complexing/binding ligands is vital to manage both deficiency and toxicity associated with essential element bioavailability. Numerous mineral ligands are found in both animal and plant foods and are known to exert bioactivity via element chelation resulting in modulation of antioxidant capacity or micobiome metabolism among other physiological outcomes. However, little is explored in the context of dietary mineral ligands and element bioavailability enhancement, particularly with respect to ligands from plant-derived food sources. This review highlights a novel perspective to consider various plant macro/micronutrients as prospective bioavailability enhancing ligands of three essential elements (Fe, Zn, and Ca). We also delineate the molecular mechanisms of the ligand-binding interactions underlying mineral bioaccessibility at the luminal level. We conclude that despite current understandings of some of the structure-activity relationships associated with strong mineral-ligand binding, the physiological links between ligands as element carriers and uptake at targeted sites throughout the gastrointestinal (GI) tract still require more research. The binding behavior of potential ligands in the human diet should be further elucidated and validated using pharmacokinetic approaches and GI models.

Dietary Iron Intake and Availability in Hill Tribe and Urban Women, Chiang Rai Province, Northern Thailand

Data were collected as part of a cross-sectional study. The objectives were to compare dietary intakes of iron and enhancers and inhibitors of non-heme iron absorption in hill tribe and urban women of Chiang Rai province, northern Thailand, and compare iron- and vitamin C- containing foods sold in markets in both settings. Dietary data were collected using three 24- hour recalls from 128 women aged 19-50 years (hill tribe: n = 65; urban n = 63), and proportions of low-, medium- and high-iron/vitamin C containing foods were surveyed in local markets. Hill tribe women consumed less iron, animal protein, vitamin C and calcium, but market availability of iron/vitamin C foods was similar. Future interventions should focus on food choice modification, to improve intakes of iron and foods that enhance its absorption, especially among hill tribe women.

Effects of different sources and levels of dietary iron and selenium on the postprandial net portal appearance of these minerals in growing pigs

The present study compares the net portal appearance of dietary iron (Fe) and selenium (Se) after meals containing different sources and levels of these minerals. Twelve pigs (55.1 ± 3.7 kg) were used in a cross-over design to assess the 11-h net portal-drained viscera (PDV) flux of serum Fe and Se after ingestion of boluses containing inorganic (I) or organic (O) dietary Fe and Se at industry average (A; 200 and 0.6 mg, respectively) or high (H; 400 and 1.2 mg, respectively) levels. Arterial serum Fe concentrations increased by an average of 158% within 6 h post-meal and gradually decreased thereafter (P < 0.001). Values were greater (P < 0.001) for I than for O until 6 h post-meal and greater (P ≤ 0.001) for A than for H from 4 to 8 h post-meal. For the whole post-prandial period (11 h), arterial serum Fe concentrations tended (P = 0.06) to be greater for I than for O and were lowest for HO (P ≤ 0.03). Net PDV flux of Fe tended to be greater for AI than for AO (P ≥ 0.07). Cumulative appearance of Fe in PDV serum (% of dietary intake) was greater for I than for O (2.43 vs. -0.76%; P = 0.02) and A tended to be greater than H (1.96 vs. -0.29 %; P = 0.09) until 3 h post-meal, but these effects further faded out (P ≥ 0.43). Arterial serum Se concentration decreased for all treatments (average of 7%) from premeal values (P < 0.001), and this was more pronounced for O than for I (P = 0.03). Irrespective of treatment, net PDV flux of Se was positive (different from 0, P ≤ 0.03) during the first 90 min post-meal, decreased to negative minimum values (different from 0, P = 0.03) at 5 h post-meal, and was not different from 0 thereafter (P ≥ 0.11). Cumulative appearance of Se in PDV serum (% of dietary intake) was greater for I than for O (20.0 vs. -3.8%; P = 0.04) only at 45 min post-meal. In conclusion, both dietary Fe and Se absorption are limited to the early post-meal period. Whereas for Fe, the level effect is in accordance with the known negative correlation between its dietary concentration and percentage of intestinal absorption, this was not the case for dietary Se. The postabsorptive availability of dietary I was greater than O for both minerals and, particularly for Fe, at low levels.

Rice Biofortification: High Iron, Zinc, and Vitamin-A to Fight against “Hidden Hunger”

One out of three humans suffer from micronutrient deficiencies called “hidden hunger”. Underprivileged people, including preschool children and women, suffer most from deficiency diseases and other health-related issues. Rice (Oryza sativa), a staple food, is their source of nutrients, contributing up to 70% of daily calories for more than half of the world’s population. Solving “hidden hunger” through rice biofortification would be a sustainable approach for those people who mainly consume rice and have limited access to diversified food. White milled rice grains lose essential nutrients through polishing. Therefore, seed-specific higher accumulation of essential nutrients is a necessity. Through the method of biofortification (via genetic engineering/molecular breeding), significant increases in iron and zinc with other essential minerals and provitamin-A (β-carotene) was achieved in rice grain. Many indica and japonica rice cultivars have been biofortified worldwide, being popularly known as ‘high iron rice’, ‘low phytate rice’, ‘high zinc rice’, and ‘high carotenoid rice’ (golden rice) varieties. Market availability of such varieties could reduce “hidden hunger”, and a large population of the world could be cured from iron deficiency anemia (IDA), zinc deficiency, and vitamin-A deficiency (VAD). In this review, different approaches of rice biofortification with their outcomes have been elaborated and discussed. Future strategies of nutrition improvement using genome editing (CRISPR/Cas9) and the need of policy support have been highlighted.

Effect of duck egg white peptide-ferrous chelate on iron bioavailability in vivo and structure characterization

BACKGROUND

In order to utilize the industrial by-product 'salted duck egg white' as novel iron additives, the effects of desalted duck egg white peptides-ferrous chelate (DPs-Fe) on the promotion of iron uptake and the structure were investigated.

RESULTS

Different doses of DPs-Fe were given and iron sulfate (FeSO₄ ) was used as a positive control. After three weeks, hemoglobin (Hb), hematocrit (HCT), red blood cells (RBCs), mean corpuscular volume (MCV), serum iron (SI) and serum ferritin (SF) in iron-deficiency anemia (IDA) rats could be significantly (P < 0.05) increased to the normal levels by DPs-Fe. The gene expressions of divalent metal transporter 1 (DMT1), ferroportin 1 (FPN1) and Hepcidin could be regulated by DPs-Fe. Additionally, DPs-Fe was formed during the chelation process and the structure was characterized. Eight crucial iron-chelating peptides of duck egg white peptides (DPs) were identified by HPLC-ESI-MS/MS, such as Pro-Val-Glu-Glu and Arg-Ser-Ser. It indicated that Glu, Asp, Lys, His, Ser, Cys residues might play crucial roles in the chelating of DPs with iron.

CONCLUSION

DPs-Fe could be a potential iron supplement, and the Glu, Asp, Lys, His played important roles in binding iron and promoting iron uptake. This research expands the understanding of iron uptake by DPs and provides an opportunity for recycling a discarded processing byproduct. © 2018 Society of Chemical Industry.

The Effect of Different Iron Fortificants on Iron Absorption from Iron-Fortified Rice

Iron absorption from rice fortified with different iron fortificants, e.g., ferrous sulfate (FeS04), sodium iron EDTA (NaFeEDTA), ferrous fumarate (FeFum), and ferrous bisglycinate (FeBis) was determined using an in vitro enzymatic digestion method simulating conditions in the small intestine and an in vivo method using radioisotope techniques. The in vitro method showed that the percentage of dialyzable iron from NaFeEDTA (15.7 ± 0.9) and FeS04-fortified rice (13.2 ± 1.5) was significantly greater than that from FeFum (6.4 ± 0.6; p < .05) and FeBis fortified rice (3.3 ± 0.8; p < .05). Iron absorption in vivo was investigated from FeS04 and NaFeEDTA fortified rice with and without fish and vegetables in 10 borderline iron-deficient subjects. Iron absorption (mg) from NaFeEDTA fortified rice (0.44 ± 0.11) was significantly greater than from FeS04-fortified rice (0.22 ± 0.05; p < .05) and the unfortified rice (0.17 ± 0.02; p < .05). Iron absorption (mg) from a meal consisting of iron-fortified rice, fish, and vegetables was significantly greater from NaFeEDTA (0.88 ± 0.24) and FeS04 (0.67 ± 0.10) -fortified rice than from the unfortified rice (0.41 ± 0.08; p < .05). This study concluded that both NaFeEDTA and FeS04 are effective iron fortificants for rice. The binder used in the study may have a significant role in the release of iron from iron-fortified rice for absorption. Further studies on the use of other binders to maximize iron release and minimize iron loss during cooking should be conducted to improve iron absorption from the fortified rice/rice-fish-vegetable meals. Results from this study can be used as a basis for food iron fortification programs as well as in the establishment of recommended dietary allowances for iron among Filipinos.

Antioxidant and angiotensin I-converting enzyme inhibitory activities of Xuanwei ham before and after cooking and in vitro simulated gastrointestinal digestion

Xuanwei ham is especially rich in a large amount of peptides and free amino acids under the action of protein degradation. Some of these peptides can potentially exert bioactivities of interest for human health. Traditionally, Xuanwei ham should undergo Chinese household cooking treatments before eating. However, it has not been known how its bioactivity changes after cooking and gastrointestinal digestion. Herein, Xuanwei ham is analysed before and after cooking, as well as gastrointestinal digestion being simulated so as to evaluate and compare its effect on antioxidant and angiotensin I-converting enzyme (ACE) inhibitory activities. The antioxidant activity is analysed using five different methods, and results demonstrate that cooking has some negative effects on antioxidative capacity when determined using different antioxidant methods except for a significant increment in 1,1'-diphenyl-2-picrylhydrazyl radical-scavenging activity, while ACE inhibitory activity increases significantly after cooking compared with control samples. After gastrointestinal digestion of samples, there is a significant increment of the antioxidant and ACE inhibitory activities in comparison with control and cooked samples. Particularly, after gastrointestinal digestion, free thiols content and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical-cation-scavenging activity of Xuanwei ham, respectively, increase about twice and fourfold, while ACE inhibitory activity increases about twice compared to cooked samples, reaching the value of 83.73%. Therefore, through cooking the antioxidant activity and ACE inhibitory activity of Xuanwei ham are not completely lost and a part of them is still maintained, while gastrointestinal digestion produces a significant enhancement in both bioactivities, highlighting a greater potential for a beneficial physiological effect on human health after eating it.

Biomarkers of Nutrition for Development (BOND)-Iron Review

This is the fifth in the series of reviews developed as part of the Biomarkers of Nutrition for Development (BOND) program. The BOND Iron Expert Panel (I-EP) reviewed the extant knowledge regarding iron biology, public health implications, and the relative usefulness of currently available biomarkers of iron status from deficiency to overload. Approaches to assessing intake, including bioavailability, are also covered. The report also covers technical and laboratory considerations for the use of available biomarkers of iron status, and concludes with a description of research priorities along with a brief discussion of new biomarkers with potential for use across the spectrum of activities related to the study of iron in human health.The I-EP concluded that current iron biomarkers are reliable for accurately assessing many aspects of iron nutrition. However, a clear distinction is made between the relative strengths of biomarkers to assess hematological consequences of iron deficiency versus other putative functional outcomes, particularly the relationship between maternal and fetal iron status during pregnancy, birth outcomes, and infant cognitive, motor and emotional development. The I-EP also highlighted the importance of considering the confounding effects of inflammation and infection on the interpretation of iron biomarker results, as well as the impact of life stage. Finally, alternative approaches to the evaluation of the risk for nutritional iron overload at the population level are presented, because the currently designated upper limits for the biomarker generally employed (serum ferritin) may not differentiate between true iron overload and the effects of subclinical inflammation.

Protein Hydrolysates as Promoters of Non-Haem Iron Absorption

Iron (Fe) is an essential micronutrient for human growth and health. Organic iron is an excellent iron supplement due to its bioavailability. Both amino acids and peptides improve iron bioavailability and absorption and are therefore valuable components of iron supplements. This review focuses on protein hydrolysates as potential promoters of iron absorption. The ability of protein hydrolysates to chelate iron is thought to be a key attribute for the promotion of iron absorption. Iron-chelatable protein hydrolysates are categorized by their absorption forms: amino acids, di- and tri-peptides and polypeptides. Their structural characteristics, including their size and amino acid sequence, as well as the presence of special amino acids, influence their iron chelation abilities and bioavailabilities. Protein hydrolysates promote iron absorption by keeping iron soluble, reducing ferric iron to ferrous iron, and promoting transport across cell membranes into the gut. We also discuss the use and relative merits of protein hydrolysates as iron supplements.

Tagging Recombinant Proteins to Enhance Solubility and Aid Purification

Protein fusion technology has had a major impact on the efficient production and purification of individual recombinant proteins. The use of genetically engineered affinity and solubility-enhancing polypeptide "tags" has increased greatly in recent years and there now exists a considerable repertoire of these that can be used to solve issues related to the expression, stability, solubility, folding, and purification of their fusion partner. In the case of large-scale proteomic studies, the development of purification procedures tailored to individual proteins is not practicable, and affinity tags have therefore become indispensable tools for structural and functional proteomic initiatives that involve the expression of many proteins in parallel. Here, the rationale and applications of a range of established and more recently developed solubility-enhancing and affinity tags is described.

Affinity chromatography: A versatile technique for antibody purification

Antibodies continue to be extremely utilized entities in myriad applications including basic research, imaging, targeted delivery, chromatography, diagnostics, and therapeutics. At production stage, antibodies are generally present in complex matrices and most of their intended applications necessitate purification. Antibody purification has always been a major bottleneck in downstream processing of antibodies, due to the need of high quality products and associated high costs. Over the years, extensive research has focused on finding better purification methodologies to overcome this holdup. Among a plethora of different techniques, affinity chromatography is one of the most selective, rapid and easy method for antibody purification. This review aims to provide a detailed overview on affinity chromatography and the components involved in purification. An array of support matrices along with various classes of affinity ligands detailing their underlying working principles, together with the advantages and limitations of each system in purifying different types of antibodies, accompanying recent developments and important practical methodological considerations to optimize purification procedure are discussed.

Application of Biotechnology to Improving the Nutritional Quality of Rice

This paper summarizes research to date on improving the nutritional characteristics of rice by using biotechnology, including efforts to produce β-carotene in the rice endosperm, to introduce a heat-stable phytase gene, and to increase iron concentration. The results obtained using biotechnology are compared with the results of breeding research by conventional techniques. Based on this comparison, the following lessons are drawn as to the potential usefulness of biotechnology in providing more nutritious food staples: (1) It must be established that plant-breeding is more cost-effective than alternative interventions. This is apparently the case, in large measure because of the multiplier effects of plant-breeding, over time and space, as compared with supplementation and fortification. (2) There must be aspects of breeding for which biotechnology is superior to conventional techniques. For rice, this is the case for adding β-carotene-related and heat-stable phytase genes. For increasing mineral concentration, conventional breeding techniques work as well and may be applied more quickly. (3) For those aspects of the plant-breeding strategy for which biotechnology is superior to conventional breeding, it must be established that there are no serious negative agronomic consequences; that consumers will accept any changes in the colour, taste, texture, and cooking qualities; and that the characteristic being added will result in a measurable improvement in the nutritional status of the malnourished target population. The conditions under lesson three, in particular, have yet to be firmly established. However, it is important not be overly cautious, in view of the potentially enormous benefits to the poor.

Relationship of dietary factors with dialyzable iron and in vitro iron bioavailability in the meals of farm women

Sixty rural women with age varying between 25 and 35 were selected randomly to determine the role of dietary factors on bioavailability of iron in their diets. Food samples of selected subjects were collected for three major meals i.e. breakfast, lunch and dinner for three consecutive days. The samples were analyzed for meal constituents associated with iron absorption as well as for total and dialyzable iron. Based on dietary characteristics, the diets of the farm women were in the class of intermediate diets as per FAO/WHO classification with iron bioavailability of 8.11 %. The statistical analysis revealed that the meal constituents which were found to influence iron absorption positively were ascorbic acid and β-carotene in breakfast and only β-carotene in dinner. The meal constituents which affected iron absorption negatively were zinc and calcium in breakfast as well as lunch and phytates and NDF in dinner, however, polyphenols present in the meals of the subjects did not show any relationship with iron absorption.

Review: The potential of the common bean (Phaseolus vulgaris) as a vehicle for iron biofortification

Common beans are a staple food and the major source of iron for populations in Eastern Africa and Latin America. Bean iron concentration is high and can be further increased by biofortification. A major constraint to bean iron biofortification is low iron absorption, attributed to inhibitory compounds such as phytic acid (PA) and polyphenol(s) (PP). We have evaluated the usefulness of the common bean as a vehicle for iron biofortification. High iron concentrations and wide genetic variability have enabled plant breeders to develop high iron bean varieties (up to 10 mg/100 g). PA concentrations in beans are high and tend to increase with iron biofortification. Short-term human isotope studies indicate that iron absorption from beans is low, PA is the major inhibitor, and bean PP play a minor role. Multiple composite meal studies indicate that decreasing the PA level in the biofortified varieties substantially increases iron absorption. Fractional iron absorption from composite meals was 4%–7% in iron deficient women; thus the consumption of 100 g biofortified beans/day would provide about 30%–50% of their daily iron requirement. Beans are a good vehicle for iron biofortification, and regular high consumption would be expected to help combat iron deficiency (ID).

Cooking Chicken Breast Reduces Dialyzable Iron Resulting from Digestion of Muscle Proteins

The purpose of this research was to study the effect of cooking chicken breast on the production of dialyzable iron (an in vitro indicator of bioavailable iron) from added ferric iron. Chicken breast muscle was cooked by boiling, baking, sautéing, or deep-frying. Cooked samples were mixed with ferric iron and either extracted with acid or digested with pepsin and pancreatin. Total and ferrous dialyzable iron was measured after extraction or digestion and compared to raw chicken samples. For uncooked samples, dialyzable iron was significantly enhanced after both extraction and digestion. All cooking methods led to markedly reduced levels of dialyzable iron both by extraction and digestion. In most cooked, digested samples dialyzable iron was no greater than the iron-only (no sample) control. Cooked samples showed lower levels of histidine and sulfhydryls but protein digestibility was not reduced, except for the sautéed sample. The results showed that, after cooking, little if any dialyzable iron results from digestion of muscle proteins. Our research indicates that, in cooked chicken, residual acid-extractable components are the most important source of dialyzable iron.

Predictors of iron levels in 14,737 Danish blood donors: results from the Danish Blood Donor Study

Background

Dietary studies show a relationship between the intake of iron enhancers and inhibitors and iron stores in the general population. However, the impact of dietary factors on the iron stores of blood donors, whose iron status is affected by blood donations, is incompletely understood.

Study Design and Methods

In the Danish Blood Donor Study, we assessed the effect of blood donation frequency, physiologic factors, lifestyle and supplemental factors, and dietary factors on ferritin levels. We used multiple linear and logistic regression analyses stratified by sex and menopausal status.

Results

Among high-frequency donors (more than nine donations in the past 3 years), we found iron deficiency (ferritin below 15 ng/mL) in 9, 39, and 22% of men, premenopausal women, and postmenopausal women, respectively. The strongest predictors of iron deficiency were sex, menopausal status, the number of blood donations in a 3-year period, and the time since last donation. Other significant factors included weight, age, intensity of menstruation, iron tablets, vitamin pills, and consumption of meat and wine.

Conclusion

The study confirms iron deficiency as an important problem, especially among menstruating women donating frequently. The risk of iron depletion was largely explained by sex, menopausal status, and donation frequency. Other factors, including dietary and supplemental iron intake, had a much weaker effect on the risk of iron depletion.

Differential iron-bioavailability with relation to nutrient compositions in polished rice among selected Chinese genotypes using Caco-2 cell culture model

Genotypic variation of iron bioavailability and the relationship between iron bioavailability and nutrient composition in polished rice among 11 rice genotypes were assessed using an in vitro digestion/Caco-2 cell model. The results indicated that significant differences in iron bioavailability were detected among tested rice genotypes, with a 3-fold range, suggesting a possibility of selecting high bioavailable iron by plant breeding. Although iron bioavailability was not significantly correlated with Fe concentration in polished rice among tested rice genotypes, the results also indicated that most of the iron dense genotypes showed relatively high ferritin formation in Caco-2 cell and transported iron. Additionally, iron bioavailability in polished rice was enhanced by addition of ascorbic acid, with a much wider range of Fe bioavailability variation in polished rice with addition of ascorbic acid than that without addition of ascorbic acid. The positive relationship between iron bioavailability in polished rice and cysteine concentration (R = 0.669) or sulfur (S) concentration (R = 0.744) among tested rice genotypes, suggests that cysteine and sulfur concentration in polished rice could be used as an indicator for high iron bioavailability.

Iron-chelating activity of chickpea protein hydrolysate peptides

Chickpea-chelating peptides were purified and analysed for their iron-chelating activity. These peptides were purified after affinity and gel filtration chromatography from a chickpea protein hydrolysate produced with pepsin and pancreatin. Iron-chelating activity was higher in purified peptide fractions than in the original hydrolysate. Histidine contents were positively correlated with the iron-chelating activity. Hence fractions with histidine contents above 20% showed the highest chelating activity. These results show that iron-chelating peptides are generated after chickpea protein hydrolysis with pepsin plus pancreatin. These peptides, through metal chelation, may increase iron solubility and bioavailability and improve iron absorption.

Separation and identification of zinc-chelating peptides from sesame protein hydrolysate using IMAC-Zn²⁺ and LC-MS/MS

The metal chelating peptides from sesame protein hydrolysates (SPH), treated by papain, alcalase and trypsin, respectively, were investigated. The hydrolysates treated by trypsin had the highest metal chelating ability. The metal chelating peptides were isolated from the trypsin hydrolysates using immobilized metal affinity chromatography (IMAC-Zn(2+)). Further, six zinc-chelating peptides were identified with reversed phase (RP)-HPLC and mass spectrometry (LC-MS/MS). Three of these metal-chelating peptides, Ser-Met, Leu-Ala-Asn and Asn-Cys-Ser, were synthesized and the metal-chelating ability of peptides was measured. The Asn-Cys-Ser peptide showed the highest zinc and iron chelating ability, which was even higher than reduced glutathione (GSH). The results confirm that the zinc or iron chelating activity of these peptides, and provide further support to its feasibility as natural metal chelating agents from sesame protein.

Heating chicken breast muscle reduces the amount of dialyzable iron after extraction and digestion

We studied the effect of heating chicken breast muscle on the amount of dialyzable iron derived from added ferric iron. The chicken was homogenized and heated to temperatures in the range of 130-195°F. The heated muscle was mixed with ferric iron and either extracted with acid or digested with pepsin and pancreatin. Similar amounts of dialyzable iron were observed after extraction and proteolytic digestion; however, digestion led to more dialyzable ferrous iron. Heating caused markedly reduced levels of dialyzable iron and dialyzable ferrous iron both by extraction and digestion. In the range of 130-165°F the losses were due mainly to reduced levels of ferrous iron. At 195°F both ferric and ferrous dialyzable iron levels were markedly reduced (>80%) compared to raw muscle. At 165°F losses in dialyzable iron after extraction were much greater than after digestion. Heating caused progressive losses in sulfhydryl and histidine residues and mostly lowered protein digestibility. Our results demonstrate that heating muscle above 130°F causes losses in dialyzable iron, coincident with (and possibly due to) losses in amino acid residues that reduce and chelate iron. The results suggest that cooking chicken muscle will reduce its ability to promote non-haem iron uptake and that the magnitude of the reduction will tend to increase with increasing temperature.

Affinity chromatography as a tool for antibody purification

The global antibody market has grown exponentially due to increasing applications in research, diagnostics and therapy. Antibodies are present in complex matrices (e.g. serum, milk, egg yolk, fermentation broth or plant-derived extracts). This has led to the need for development of novel platforms for purification of large quantities of antibody with defined clinical and performance requirements. However, the choice of method is strictly limited by the manufacturing cost and the quality of the end product required. Affinity chromatography is one of the most extensively used methods for antibody purification, due to its high selectivity and rapidity. Its effectiveness is largely based on the binding characteristics of the required antibody and the ligand used for antibody capture. The approaches used for antibody purification are critically examined with the aim of providing the reader with the principles and practical insights required to understand the intricacies of the procedures. Affinity support matrices and ligands for affinity chromatography are discussed, including their relevant underlying principles of use, their potential value and their performance in purifying different types of antibodies, along with a list of commercially available alternatives. Furthermore, the principal factors influencing purification procedures at various stages are highlighted. Practical considerations for development and/or optimizations of efficient antibody-purification protocols are suggested.

Tagging recombinant proteins to enhance solubility and aid purification

Protein fusion technology has enormously facilitated the efficient production and purification of individual recombinant proteins. The use of genetically engineered affinity and solubility-enhancing polypeptide "tags" has increased greatly in recent years and there now exists a considerable repertoire of these that can be used to solve issues related to the expression, stability, solubility, folding, and purification of their fusion partner. In the case of large-scale proteomic studies, the development of purification procedures tailored to individual proteins is not practicable, and affinity tags have therefore become indispensable tools for structural and functional proteomic initiatives that involve the expression of many proteins in parallel. Here, the rationale and applications of a range of established and more recently developed solubility-enhancing and affinity tags are outlined.

Iron bioavailability and dietary reference values

Iron differs from other minerals because iron balance in the human body is regulated by absorption only because there is no physiologic mechanism for excretion. On the basis of intake data and isotope studies, iron bioavailability has been estimated to be in the range of 14-18% for mixed diets and 5-12% for vegetarian diets in subjects with no iron stores, and these values have been used to generate dietary reference values for all population groups. Dietary factors that influence iron absorption, such as phytate, polyphenols, calcium, ascorbic acid, and muscle tissue, have been shown repeatedly to influence iron absorption in single-meal isotope studies, whereas in multimeal studies with a varied diet and multiple inhibitors and enhancers, the effect of single components has been, as expected, more modest. The importance of fortification iron and food additives such as erythorbic acid on iron bioavailability from a mixed diet needs clarification. The influence of vitamin A, carotenoids, and nondigestible carbohydrates on iron absorption and the nature of the "meat factor" remain unresolved. The iron status of the individual and other host factors, such as obesity, play a key role in iron bioavailability, and iron status generally has a greater effect than diet composition. It would therefore be timely to develop a range of iron bioavailability factors based not only on diet composition but also on subject characteristics, such as iron status and prevalence of obesity.

Comparative analysis of influence of promoters and inhibitors onin vitroavailable iron using two methods

The investigation was undertaken with the objective of comparing two in vitro techniques, measuring dialyzable iron (method A) and measuring ionizable iron (method B), for iron bioavailability in a model system. The effect of the time of introduction of the additives on the available iron was also determined. FeSO4 solution was used as the reference source of iron, to which a series of enhancers (ascorbic acid, citric acid, maleic acid and tartaric acid) and inhibitors (tannic acid, calcium oxalate, oxalic acid, calcium carbonate and sodium phytate) were added individually at various concentrations, and available iron was estimated. From FeSO4 solution, 0.1% (method A) and 3.9% (method B) of iron was available. The addition of ascorbic acid, citric acid and tartaric acid increased this by 33-50%, 28-57% and 23-90%, respectively, for method A and by 15-89%, 24-78% and 24-93% for method B. Tannic acid, sodium phytate and calcium oxalate exhibited an inhibitory effect irrespective of the concentrations, while oxalic acid and calcium carbonate exhibited a dose-dependent inhibitory pattern. The iron availability analyzed by both methods showed a positive correlation with seven out of nine additives. An inverse relation was seen between the inhibitory effect of calcium carbonate and calcium oxalate and their time of introduction into the system. The overall observations showed that although absolute values varied widely, a positive correlation existed between the methods.