Micronutrients in pregnancy: current knowledge and unresolved questions

Micronutrient status is increasingly recognized to play an important role in the health and well-being of pregnant women and in the development and long-term health of the offspring. On 26th - 28th February 2009, The Child Health Foundation invited leading experts in this area to a scientific workshop at Obergurgl, Austria to review and critically discuss current knowledge, to identify issues that may need to be addressed in future recommendations, and to highlight priorities and opportunities for future research. This report summarizes updated key conclusions of the workshop with regards to micronutrients' intake and physiological role related to mother, placenta and fetus, as well as relevance for adverse pregnancy and long-term outcomes.

Beta-carotene is an important vitamin A source for humans

Experts in the field of carotenoids met at the Hohenheim consensus conference in July 2009 to elucidate the current status of β-carotene research and to summarize the current knowledge with respect to the chemical properties, physiological function, and intake of β-carotene. The experts discussed 17 questions and reached an agreement formulated in a consensus answer in each case. These consensus answers are based on published valid data, which were carefully reviewed by the individual experts and are justified here by background statements. Ascertaining the impact of β-carotene on the total dietary intake of vitamin A is complicated, because the efficiency of conversion of β-carotene to retinol is not a single ratio and different conversion factors have been used in various surveys and following governmental recommendations within different countries. However, a role of β-carotene in fulfilling the recommended intake for vitamin A is apparent from a variety of studies. Thus, besides elucidating the various functions, distribution, and uptake of β-carotene, the consensus conference placed special emphasis on the provitamin A function of β-carotene and the role of β-carotene in the realization of the required/recommended total vitamin A intake in both developed and developing countries. There was consensus that β-carotene is a safe source of vitamin A and that the provitamin A function of β-carotene contributes to vitamin A intake.

Reexamination of a meta-analysis of the effect of antioxidant supplementation on mortality and health in randomized trials

A recent meta-analysis of selected randomized clinical trials (RCTs), in which population groups of differing ages and health status were supplemented with various doses of β-carotene, vitamin A, and/or vitamin E, found that these interventions increased all-cause mortality. However, this meta-analysis did not consider the rationale of the constituent RCTs for antioxidant supplementation, none of which included mortality as a primary outcome. As the rationale for these trials was to test the hypothesis of a potential benefit of antioxidant supplementation, an alternative approach to a systematic evaluation of these RCTs would be to evaluate this outcome relative to the putative risk of greater total mortality. Thus, we examined these data based on the primary outcome of the 66 RCTs included in the meta-analysis via a decision analysis to identify whether the results provided a positive (i.e., benefit), null or negative (i.e., harm) outcome. Our evaluation indicated that of these RCTs, 24 had a positive outcome, 39 had a null outcome, and 3 had a negative outcome. We further categorized these interventions as primary (risk reduction in healthy populations) or secondary (slowing pathogenesis or preventing recurrent events and/or cause-specific mortality) prevention or therapeutic (treatment to improve quality of life, limit complications, and/or provide rehabilitation) studies, and determined positive outcomes in 8 of 20 primary prevention studies, 10 of 34 secondary prevention studies, and 6 out of 16 therapeutic studies. Seven of the eight RCTs with a positive outcome in primary prevention included participants in a population where malnutrition is frequently described. These results suggest that analyses of potential risks from antioxidant supplementation should be placed in the context of a benefit/risk ratio.

More than the sum of its parts? Nutrition in Alzheimer's disease

The aim of this article is to emphasize the importance of malnutrition and micronutrient deficiencies in Alzheimer's disease and discuss recent supplementation trials. Alzheimer's disease (AD) is a devastating neurodegenerative disease with increasing socio-economic impact. It leads to cognitive decline over the years, finally resulting in brain atrophy and gradually destroying a person's ability to learn, reason, make judgments, and communicate. Most of the cases are sporadic and risk factors evolve. There is evidence that malnutrition, oxidative stress, and homocysteine-related vitamins play a role in the pathogenesis of AD. A plethora of epidemiologic studies have explored the associations between nutrients and AD. In addition, more and more data from recent trials are evolving to analyze the impact of micronutrient supplementation in AD and incipient AD concerning B vitamin status and antioxidants. Available data do not support definitive conclusions regarding specific recommendations on micronutrient supplementation for the prevention or treatment of AD; however, more data from prospective trials are needed. Approaches with multiple nutritional components might be promising.

Qualitative and quantitative analysis of retinol, retinyl esters, tocopherols and selected carotenoids out of various internal organs form different species by HPLC

We report the validation of a reversed-phase gradient HPLC method allowing simultaneous quantification of retinol, retinyl esters, tocopherols and selected carotenoids in lung, liver and plasma of mouse, rat and guinea pig (gp) using a diode array detector. A significant species difference was observed regarding the distribution of retinol and retinyl esters. The levels of total retinol in lung, liver and plasma were in the following order: mouse >> rat > gp; rat >mouse > gp; and gp >> rat > mouse, respectively. Furthermore, comparison studies revealed similarities between the vitamin A profiles of human and gp lung samples.

Water, electrolytes, vitamins and trace elements - Guidelines on Parenteral Nutrition, Chapter 7

A close cooperation between medical teams is necessary when calculating the fluid intake of parenterally fed patients. Fluids supplied parenterally, orally and enterally, other infusions, and additional fluid losses (e.g. diarrhea) must be considered. Targeted diagnostic monitoring (volume status) is required in patients with disturbed water or electrolyte balance. Fluid requirements of adults with normal hydration status is approximately 30-40 ml/kg body weight/d, but fluid needs usually increase during fever. Serum electrolyte concentrations should be determined prior to PN, and patients with normal fluid and electrolyte balance should receive intakes follwing standard recommendations with PN. Additional requirements should usually be administered via separate infusion pumps. Concentrated potassium (1 mval/ml) or 20% NaCl solutions should be infused via a central venous catheter. Electrolyte intake should be adjusted according to the results of regular laboratory analyses. Individual determination of electrolyte intake is required when electrolyte balance is initially altered (e.g. due to chronic diarrhea, recurring vomiting, renal insufficiency etc.). Vitamins and trace elements should be generally substituted in PN, unless there are contraindications. The supplementation of vitamins and trace elements is obligatory after a PN of >1 week. A standard dosage of vitamins and trace elements based on current dietary reference intakes for oral feeding is generally recommended unless certain clinical situations require other intakes.

Vitamin E requirements in parenteral nutrition

Patients with parenteral nutrition depend on an adequate supply of micronutrients, in particular, antioxidant vitamins and cofactors such as selenium. In cases of oxidative stress (eg, chronic inflammation, sepsis, lung distress syndrome, and organ failure), there is a higher need for antioxidants. One of the most important antioxidant vitamins is vitamin E. For very low birth weight infants the plasma level is an indicator for adequate supply and for safety. Safe and effective blood levels are between 23 and 46 micromol/L, maintained with a dose of 2.8 IU/kg body weight (1-2 mg/day). For safety reasons a plasma level of 80 micromol/L should not be exceeded. For adults, 10 IU/day (9.1 mg/day) are recommended. Whether this dose is sufficient to ensure body stores and sufficient antioxidant activity is controversial. If parenteral lipid emulsions are supplied there is an additional need for vitamin E to protect the lipids (polyunsaturated fatty acids) from lipid peroxidation and to deliver additional vitamin E. Dietary guidelines for healthy adults recommend an intake of polyunsaturated fatty acids equal to 10% of total energy and an intake of alpha-tocopherol greater than 0.4 mg/g of polyunsaturated fatty acids. Randomized clinical trials are performed using special formulations of vitamin E solutions because vitamin E is available only in lipid emulsions to protect lipids, but not in an isolated solution for parenteral supply.

Parenteral ascorbic acid in haemodialysis patients

PURPOSE OF REVIEW

Parenteral ascorbic acid has been frequently used to overcome problems of vitamin C deficiency in haemodialysis patients. The benefits of vitamin C supplementation in clinical studies have been controversial and did not consider toxicological aspects. The review summarizes recent findings of the effects of parenteral ascorbic acid and discusses toxicological effects.

RECENT FINDINGS

Vitamin C deficiency in haemodialysis patients, which has been frequently described, cannot be improved with oral supplementation due to limited absorption of high dosages. To avoid consequences of vitamin C deficiency, parenteral vitamin C solutions should be administered because this intervention is the only way to guarantee a sufficient supply to the cells. A beneficial consequence of parenteral vitamin C on the recombinant human erythropoietin resistance is an additional therapeutic effect, which contributes to the prevention of iron deficiency anaemia in haemodialysis patients. Thus, large amount of supplemental vitamin C are required for extended periods of time (up to 500 mg 3 times a week). To avoid hyperoxaluria, plasma oxalate levels should be monitored on a regular basis, for example, once a week.

SUMMARY

Parenteral administration of ascorbic acid may be an approach that can overcome problems of vitamin C deficiency in haemodialysis patients - in particular problems of iron overload, erythropoetin resistance, and chronic inflammation.

Inhibition of heme oxygenase-1 increases responsiveness of melanoma cells to ALA-based photodynamic therapy

Based on the observation that 5-aminolevulinic acid (ALA) induces the expression of heme oxygenase-1 (HO-1) in cultured melanoma cells, the role of HO-1 on the effectiveness of 5-aminolevulinic acid-based photodynamic therapy (ALA-PDT) was examined. Transcriptional activation of the HO-1 gene is considered to be an adaptive response to oxidative and cellular stress and confers a protective capacity against cell and tissue injury, which could affect the responsiveness to ALA-PDT. A time-dependent accumulation (0-16 h) of protoporphyrin IX (PPIX) within melanoma cells was seen after incubation with ALA (0.5 mM ALA). Over the same time interval, a significant increase (up to 25-fold) in HO-1 protein expression was observed. Thus, the production and degradation of PPIX (via heme by HO-1) were simultaneously enhanced, leading to a reduced intracellular concentration of the photodynamically active substance PPIX. Diminishing HO-1 activity by the HO-1 inhibitor tin protoporphyrin IX (SnPPIX) significantly enhanced the formation of PPIX up to 1.8 fold. A further strong increase in HO-1 protein expression (up to 128-fold) was seen after ALA-PDT treatment. Induction of HO-1 is an essential step in the 'rescue response' of tumor cells. The pharmacological inhibition of HO-1 activity by SnPPIX leads to a considerable increase in the sensitivity of tumor cells to ALA-PDT treatment. At low radiation doses (0.42 J/cm(2)), the percentages of death cells increased significantly from 7.3+/-1.3% to 43.7+/-6.4%. This effect could be further intensified by cellular depletion of HO-1 mRNA by siRNA. The combination of pharmacological inactivation of HO-1 with gene silencing led to an increase in the death rate of up to 54.1+/-8.6%. The results presented indicate that HO-1 can play a protective role against ALA-PDT mediated cytotoxicity so that a specific inhibition of HO-1 activity and/or expression might be used to increase the efficacy of ALA-based photodynamic therapy.

Polyphenols and inflammation: basic interactions

PURPOSE OF REVIEW

For more than 20 years polyphenols, food-derived bioactive compounds in fruits and vegetables, are claimed to help prevent cancer, degenerative diseases and chronic and acute inflammation. Modern methods in cell and molecular biology allow us to understand the interactions of different polyphenols with basic mechanisms of inflammatory response. This review summarizes recent papers dealing with the effect of polyphenols on modulators of the inflammatory cascade.

RECENT FINDINGS

The majority of papers deal with the effects of different antioxidants on the redox sensitive transcription factor nuclear factor kappaB, inducible nitric oxide synthase expression and cyclooxygenase inhibition. Understanding the regulatory steps and the multiple potential actions of polyphenols within the inflammatory cascade may help to define special polyphenols to be used for prevention and intervention in clinical conditions of inflammation. The relation between formation of advanced glycation end products as a consequence of high glucose and the activation of defence mechanisms through polyphenols opens new fields in the prevention and treatment of oxidative stress and hyperglycemia.

SUMMARY

Polyphenols are promising compounds that may help to control oxidative stress and consequently inflammatory response. To date, however, clinical studies are missing and should be carried out with specific polyphenols.

Impact of therapeutically induced reactive oxygen species and radical scavenging by alpha-tocopherol on tumor cell adhesion

Many tumor treatment modalities such as ionizing radiation or some chemotherapy induce reactive oxygen species (ROS) resulting in therapeutic cell damage. The aim of this study was to analyze whether such ROS induction may affect the mechanical stability of solid tumor tissue by degradation of the extracellular matrix proteins or by a loss of cell adhesion molecules. Additionally, the protective impact of alpha-tocopherol treatment on these processes was studied. Experimental DS-sarcomas in rats were treated with a combination of localized 44 degrees C hyperthermia, inspiratory hyperoxia and xanthine oxidase in order to induce pronounced oxidative stress. A second group of animals were pretreated with alpha-tocopherol. The in vivo expression of E- and N-cadherin, alpha-catenin, integrins alphav, beta3 and beta5 as well as the expression of the integrin dimer alphavbeta3 were assessed by flow cytometry. The activity of the matrix metalloproteinases MMP-2 and -9 and the activity of the urokinase-type plasminogen activator (uPA) were determined by zymography. The expression of E-cadherin, the alphav-, beta3-integrin and the alphavbeta3-integrin dimer was significantly reduced by ROS induction, an effect which was at least partially reversible by alpha-tocopherol. N-cadherin, alpha-catenin and the beta5-integrin expression was not affected by ROS. In addition, MMP-2, MMP-9 and uPA activities were markedly reduced immediately after hyperthermia. Whereas 24 h later the effects on MMP-2 and -9 were no longer evident, for uPA the impact of oxidative stress became even more pronounced at this time. These results show that several processes responsible for the structural stability of the tumor tissue are affected by therapeutic ROS generation. Changes in some of the markers assessed suggested a decrease in tissue stability upon ROS induction, whereas others indicated changes which could lead to a more stable tumor cell cluster. Depending on the individual tumor entity ROS may therefore influence the mechanical stability of solid tumors and by this affect metastatic behavior.

Comparison of the relative bioavailability of different coenzyme Q10 formulations with a novel solubilizate (Solu Q10)

The relative bioavailability of coenzyme Q10 (CoQ10) is markedly influenced by its delivery systems. The aim of this study was to compare four standard CoQ10 supplements available on the market with a novel solubilizate formulation of CoQ10 (Solu Q10). Pharmacokinetic parameters were assessed in 54 healthy volunteers after single and multiple intakes of 60 mg CoQ10 over a time period of 14 days. Solubilizates showed earlier flooding compared with oily dispersions and crystalline CoQ10, resulting in significantly elevated area under the curve between 0 and 4 h (P<0.01 solubilizates versus crystalline). The difference in the pharmacokinetic parameters of maximum plasma concentration, time to reach the peak plasma concentration and area under the curve between 0 and 12 h was not statistically significant between formulations. Long-term supplementation resulted in significantly higher plasma levels (P<0.01) for all formulations, with Solu Q10 performing best. Intracellular CoQ10 levels measured in buccal mucosa cells were increased (P<0.05) in response to supplementation when starting within the physiological range. In summary, solubilizates were clearly superior to oily dispersions and crystalline CoQ10 in their overall bioavailability, with the best absorption characteristics seen for the novel Solu Q10 solubilizate.

No evidence for prooxidative effects of homocysteine in vascular endothelial cells

Many epidemiological studies predict a role for homocysteine (HCys) in cardiovascular disease occurrence, progression, and risk factors. In vitro studies demonstrated that HCys is an atherogenic determinant that promotes oxidant stress, inflammation, endothelial dysfunction and cell proliferation. This study originally attempted to examine the mechanism by which exposure of endothelial cells to HCys (0-250 microM) initiates inflammatory reaction and oxidative stress, by (i) investigating whether physiological and pathophysiological concentrations of HCys exhibit a prooxidative activity in vitro, (ii) examining the interaction of monocyte adhesion (Mono Mac 6) to monolayers of human microvascular endothelial cells (HMEC-1) exposed to different HCys concentrations, and (iii) examining if adherent monocytes increase reactive oxygen species either in endothelial cells or in monocytes themselves. However, our results demonstrate that HCys had neither prooxidative nor cytotoxic effects on endothelial cells. Only a moderate time- and concentration-dependent increase in monocyte adhesion up to 28.3 +/- 5.5% was achieved relative to control after 4 h of HCys stimulation. This effect was accompanied by an increased VCAM and ICAM-1 mRNA expression. This "proinflammatory" effect appeared also when HMEC-1 cells were incubated with cysteine or glutathione at the concentration range 0-250 microM, demonstrating a non-specific rather than a specific HCys effect. In addition, adherent monocytes did not increase ROS formation neither in endothelial cells nor in monocytes themselves, indicating no direct or indirect cytotoxic or prooxidative effects of HCys.

β-Carotene and α-tocopherol concentration and antioxidant status in buccal mucosal cells and plasma after oral supplementation

The uptake of α-tocopherol and β-carotene and their antioxidative effect in plasma and buccal mucosal cells after oral application in twelve subjects is demonstrated in our study. The effect on the antioxidative status was evaluated using a modified thiobarbituric acid-reactive substance (TBARS) method. As expected, the supplement of 134·2 mg α-tocopherol/d and 25 mg β-carotene/d for 7 d resulted in a significant increase of α-tocopherol and β-carotene concentration in plasma (P<0·05). In buccal mucosal cells, the concentration of β-carotene increased after supplementation (P<0·05), whereas the concentration of α-tocopherol remained constant. A decrease in TBARS (P<0·05) was found in buccal mucosal cells but not in plasma. In conclusion, an uptake of the supplemented antioxidants was detected in plasma and in buccal mucosal cells. There was significant change in β-carotene concentration and oxidative stress as measured using a modified TBARS test in buccal mucosal cells, but not in the plasma.

Antioxidanzien – hilfreich oder schädlich?

Angereicherte und daher oft mit einer besonderen Funktionalität beworbene Lebensmittel werden in zunehmendem Maße angeboten. Dabei erfolgt besonders eine Anreicherung mit Antioxidanzien (Vitamine C, E und Provitamin A). Da die gewählten Dosierungen unterhalb der Empfehlungen liegen und bei verzehrsüblichen Mengen diese auch nur unwesentlich überschritten werden, besteht vom einzelnen Lebensmittel her kein Risiko für den Verbraucher. Auch bei Verzehr mehrerer angereicherter Lebensmittel führt eine Kumulation nicht zu bedenklichen Werten. Allerdings sollten angereicherte Lebensmittel nicht als Ersatz für eine ungesunde Ernährung genommen werden. Hierin liegt viel eher ein Risiko, da meist nur sehr wenige Antioxidanzien im Lebensmittel angereichert sind. In wie weit der Verbraucher einen Nutzen von angereicherten Lebensmitteln hat ist im Falle der Antioxidanzien nicht gesichert.

Solubility, uptake and biocompatibility of lutein and zeaxanthin delivered to cultured human retinal pigment epithelial cells in tween40 micelles

Carotenoids lutein and zeaxanthin are proposed to protect ocular tissues from free-radical damage that can cause cataract and age-related macular degeneration (AMD). They accumulate selectively in the lens and macular region of the retina. Changes in the retinal pigment epithelium are characteristic in AMD. Efficient uptake is essential to study the intracellular effects of carotenoids in cell cultures. For in vitro experiments carotenoids are often dissolved in organic solvents like tetrahydrofuran (THF), dimethylsulfoxide (DMSO) and n-hexane, but difficulties have been associated with these application methods. Recently, O'Sullivan et al. (SM O'Sullivan et al., Br J Nutr 91 (2004) 757) developed a method whereby carotenoids could be delivered to cultured cells without the cytotoxic side effects often observed when organic solvents are used. We modified this method and investigated the effects of different carotenoid-formulations (ethanol/Tween40, methanol/tween40 and acetone/Tween40) on the uptake of lutein and zeaxanthin by differentiated ARPE-19 cells, cell viability and the expression of the "stress" gene HO-1, which is easily induced by a range of stimuli including chemical and physical agents. Micelle formulations prepared with ethanol/Tween40 resulted in the lowest LDH release, the highest carotenoid uptake and the lowest stress response (changes in HO-1 mRNA expression).

Conversion of beta-carotene to retinal pigment

Vitamin A and its active metabolite retinoic acid (RA)(1) play a major role in development, differentiation, and support of various tissues and organs of numerous species. To assure the supply of target tissues with vitamin A, long-lasting stores are built in the liver from which retinol can be transported by a specific protein to the peripheral tissues to be metabolized to either RA or reesterified to form intracellular stores. Vitamin A cannot be synthesized de novo by animals and thus has to be taken up from animal food sources or as provitamin A carotenoids, the latter being converted by central cleavage of the molecule to retinal in the intestine. The recent demonstration that the responsible beta-carotene cleaving enzyme beta,beta-carotene 15,15'-monooxygenase (Bcmo1) is also present in other tissues led to numerous investigations on the molecular structure and function of this enzyme in several species, including the fruit fly, chicken, mouse, and also human. Also a second enzyme, beta,beta-carotene-9',10'-monooxygenase (Bcmo2), which cleaves beta-carotene eccentrically to apo-carotenals has been described. Retinal pigment epithelial cells were shown to contain Bcmo1 and to be able to cleave beta-carotene into retinal in vitro, offering a new pathway for vitamin A production in another tissue than the intestine, possibly explaining the more mild vitamin A deficiency symptoms of two human siblings lacking the retinol-binding protein for the transport of hepatic vitamin A to the target tissues. In addition, alternative ways to combat vitamin A deficiency of specific targets by the supplementation with beta-carotene or even molecular therapies seem to be the future.

Consensus meeting on "Relevance of parenteral vitamin C in acute endothelial dependent pathophysiological conditions (EDPC)"

The 22 supersetnd Hohenheim Consensus Workshop took place in at the University of Stuttgart-Hohenheim. The subject of this conference was vitamin C and its role in the treatment of endothelial dysfunction. Scientists, who had published and reviewed scientific and regulatory papers on that topic were invited, among them basic researchers, toxicologists, clinicians and nutritionists. The participants were presented with eleven questions, which were discussed and answered at the workshop, with the aim of summarising the current state of knowledge. The explicatory text accompanying the short answers was produced and agreed on after the conference and was backed up by corresponding references. The therapeutic relevance of administration of the physiological antioxidant vitamin C in high parenteral doses in Endothelial Dependent Pathophysiological Conditions (EDPC) was discussed. Endothelial dysfunction is defined as including disturbed endothelial dependant relaxation of resistance vessels, breakdown of the microvascular endothelial barrier and/or loss of anti-adhesive function. It occurs in severe burn injury, intoxications, acute hyperglycemia, sepsis, trauma, and ischemic-reperfusion tissue injury and is induced by oxidative stress. Reduced plasma ascorbate levels are a hallmark of oxidative stress and occur in severe burns, sepsis, severe trauma, intoxication, chemotherapy/radiotherapy and organ transplantation. Vitamin C directly enhances the activity of nitric oxide synthase, the acyl CoA oxidase system and inhibits the actions of proinflammatory lipids. There is experimental evidence that parenteral high-dose vitamin C restores endothelial function in sepsis. In vitro, supraphysiological concentrations (> 1mM) of ascorbate restore nitric oxide bioavailability and endothelial function. Only parenterally, can enough vitamin C be administered to combat oxidative stress. There is no evidence that parenteral vitamin C exerts prooxidant effects in humans. Theoretical concerns in relation to competitive interactions between vitamin C and glucose cellular uptake are probably only relevant for oxidised vitamin C (dehydroascorbate).