European Journal of Nutrition (v.47, #2)

Introduction by B. Åkesson; S. A. Kyrtopoulos (1-2).

Since antioxidant vitamins may affect an organism’s capacity for defence against reactive oxygen species, biological markers of the dietary exposure to these vitamins is of importance. There is also a need of effect biomarkers for determining the ability of these and other antioxidants to increase the overall antioxidant capacity and decrease the oxidative damage occurring in biological samples. This review is concerned with exposure markers and markers of lipid- or protein damage following intervention with vitamins A, C and E. While there are several high quality exposure markers available it is not possible to identify functional markers of lipid or protein oxidation, which respond reliably to human dietary intervention with vitamins A, C or E.
Keywords: retinol; ascorbic acid; tocopherol; vitamin supplementation; lipid oxidation; protein oxidation

Antioxidant vitamins and cancer risk: is oxidative damage to DNA a relevant biomarker? by Steffen Loft; Peter Møller; Marcus S. Cooke; Rafal Rozalski; Ryszard Olinski (19-28).
Oxidative damage to DNA is regarded as an important step in carcinogenesis. These lesions may arise as a consequence of exposure to xenobiotics, but are also generated as a consequence of endogenous generation of oxidizing compounds. Measurements of oxidative damage to guanines, such as 8-oxo-7, 8-dihydroguanine (8-oxodG) are increasingly being regarded as reliable biomarkers of oxidative stress and they may have a predictive value of cancer risk, although this needs to be established independently in several cohort studies. A survey of intervention studies of the ingestion of antioxidant-containing foods or tablets of antioxidants indicate that about one-third of the studies reported a protective effect in terms of lower levels of oxidative damage to DNA in white blood cells or decreased urinary excretion of 8-oxodG. Although firm conclusions cannot be reached, there appears to be links between ingestion of antioxidants, oxidative damage to DNA, and risk of cancer.
Keywords: antioxidants; comet assay; 8-oxodG; oxidative stress; oxidative damage to DNA

Selenium and cancer: biomarkers of selenium status and molecular action of selenium supplements by Jolanta Gromadzińska; Edyta Reszka; Katharina Bruzelius; Wojciech Wąsowicz; Björn Åkesson (29-50).
The relationship between selenium and cancer involves many different aspects. These include the forms of selenium present in the diet and in the body, their functions and mechanisms of action, and methods employed in assessing an individual’s selenium nutritional status—both in general, and in epidemiological studies of the risk of cancer in relation to diet, as well as in connection with long-term trials for investigating the disease-preventive potential of selenium supplementation.To review different aspects on selenium metabolism, the occurrence of different selenoproteins and their use as biomarkers of selenium status, the results of intervention trials of the cancer-preventive effects of selenium supplementation, the mechanisms of action involved, together with epidemiological findings on relations between the selenium status in the body and risk of cancer.The rapid advance in the knowledge of different selenoproteins and their biological functions has opened up new possibilities for the understanding of the biological effects of selenium supplementation. A wide variety of effects of different forms and doses of selenium has been observed in a number of experimental systems, and it is at present difficult to pinpoint the mechanism that may explain the positive preventive effects of selenium supplementation observed in some human long-term trials. Moreover, additional such trials are needed to define the benefits and risks of different types and doses of selenium supplements which in the future may be implemented for public health reasons. Another necessary focus for future research is a better understanding of the mechanisms by which selenium interferes with the carcinogenesis process.
Keywords: selenoproteins; forms of selenium; selenium status and cancer risk; cellular actions of selenium; chemopreventive effect of selenium

Mechanisms of combined action of different chemopreventive dietary compounds by Theo M. de Kok; Simone G. van Breda; Margaret M. Manson (51-59).
Consumption of fruits and vegetables has generally been associated with a decrease in cancer incidence and cardiovascular disease. Over the years, numerous bioactive compounds have been identified that contribute to these beneficial health effects. More recently, evidence is emerging that specific combinations of phytochemicals may be far more effective in protecting against cancer than isolated compounds. Combinatorial effects have been observed where any one of the single agents is inactive. Apart from interactions among dietary micronutrients, drug–phytochemical interactions have also been observed, indicating possibilities for improved cancer therapeutic strategies. Our understanding of the molecular mechanisms underlying such synergistic effects is still limited, but it appears that different combinations of complementary modes of actions are involved. In this review, we discuss the molecular mechanisms that are likely to be involved in cancer chemoprevention and summarize the most important findings of those studies that report synergistic chemopreventive effects of dietary compounds.
Keywords: chemoprevention; phytochemicals; synergistic effects; polyphenols; vegetables

Atherosclerosis is characterized by extensive thickening of the arterial intima partially resulting from deposition of collagen by vascular smooth muscle cells (SMCs). Polyunsaturated fatty acids stimulate collagen formation through NF-κB activation.The present study aimed to explore the effect of conjugated linoleic acids (CLAs) which are known to inhibit NF-κB activation on collagen formation by SMCs.Vascular SMCs were cultured with 50 µmol/l of CLA isomers (c9t11-CLA, t10c12-CLA) or linoleic acid (LA) and analysed for collagen formation and NF-κB p50 transactivation.Treatment with CLA isomers but not LA significantly reduced PDGF-stimulated [3H] proline incorporation into cell layer protein of SMCs without altering cell proliferation. Simultaneous treatment with the PPARγ inhibitor T0070907 abrogated this effect. Treatment of SMCs with c9t11-CLA and t10c12-CLA significantly reduced PDGF-induced NF-κB p50 activation.CLA isomers inhibit PDGF-stimulated collagen production by vascular SMCs, which is considered to be a hallmark of atherosclerosis, in a PPARγ-dependent manner. Whether inhibition of the NF-κB-pathway is of significance for the reduction of collagen formation by CLA isomers needs further investigation.
Keywords: conjugated linoleic acid; atherosclerosis; collagen formation; vascular smooth muscle cells; PPARγ

For many polyphenolic compounds found in plant-derived food, biological effects possibly relevant for cancer prevention have been shown. Since dietary intake estimates suffer from imprecision, the measurement of these compounds (or metabolites of) in biological specimens collected in epidemiological studies is expected to improve accuracy of exposure estimation.The current use of biomarkers in etiologic studies on polyphenolics and cancer risk is evaluated. In addition, available analytical methods are discussed with respect to the requirements for their integration in epidemiological studies, putting specific emphasis on the epidemiological validation of such markers.The scientific literature was screened for epidemiologic studies on the relationship of flavonoid and phenolic acid concentrations in human specimens (i.e. blood, urine) and cancer risk. In addition, original data on intra- and inter-subject variability of several flavonoids and phenolic acids are presented.Although several techniques are used in bioavailability or short-term intervention studies, their integration in epidemiological studies is very limited. An exception are phytoestrogens where validated immunoassays allow the rapid measurement of large sample numbers with small sample volume. For several polyphenols, the data on the epidemiologic validity encourages for their use in epidemiological studies.There are valid possibilities for additional biomarkers of flavonoid and phenolic acid intake that are best applied in prospective studies with more than one biological sample per subject. Currently, a combination of a single biomarker measurement with long-term dietary intake estimates will probably be the most valuable choice to decrease measurement error in exposure data.
Keywords: flavonoids; phenolic acids; biomarker; validity; cancer; epidemiology

Oat: unique among the cereals by Masood Sadiq Butt; Muhammad Tahir-Nadeem; Muhammad Kashif Iqbal Khan; Rabia Shabir; Mehmood S. Butt (68-79).
This review is intended to focus on the composition of oat and its therapeutic potential in the pharmacology that supports its use to cure various maladies. Oat (Avena sativa) is distinct among the cereals due to its multifunctional characteristics and nutritional profile. Recent advancement in food and nutrition has revealed the importance of its various components. It is a good source of dietary fiber especially β-glucan, minerals and other nutrients. Oat and oat by products have been proven to be helpful in the treatment of diabetes and cardiovascular disorders. Oat bran in particular, is good source of B complex vitamins, protein, fat, minerals besides heart healthy soluble fiber β-glucan. The β-glucan has outstanding functional properties and is of immense importance in human nutrition. Different physiological effects of β-glucan are related to its viscosity, attenuation of postprandial plasma glucose and insulin responses, high transport of bile acids towards lower parts of the intestinal tract and high excretion of bile acids thereby lowering of serum cholesterol levels. Moreover, it is helpful against coeliac disease. The incorporation of oat grains and oat bran in the food products improves not only the nutrition but also a therapy against various maladies.
Keywords: oat; oat bran; β-glucan; dietary fiber; cardiovascular diseases; hyperglycemia

Anticarcinogenic compounds of olive oil and related biomarkers by Theodore G. Sotiroudis; Soterios A. Kyrtopoulos (69-72).
Olive oil, one of the oldest vegetable oils consumed without any refining, is associated with a reduced risk of a number of common cancers. Minor constituents of virgin olive oil have been suggested to be among the major chemopreventive components. A brief overview is presented of recent findings concerning the bioavailability of certain important olive oil minor components including efficient antioxidant polyphenols, the triterpene hydrocarbon squalene and β-sitosterol, considered as putative nutritional biomarkers, in relation to the incidence of cancer.
Keywords: olive oil; anticarcinogenic compounds; biomarkers

The cancer chemopreventive actions of phytochemicals derived from glucosinolates by John D. Hayes; Michael O. Kelleher; Ian M. Eggleston (73-88).
This article reviews the mechanisms by which glucosinolate breakdown products are thought to inhibit carcinogenesis. It describes how isothiocyanates, thiocyanates, nitriles, cyano-epithioalkanes and indoles are produced from glucosinolates through the actions of myrosinase, epithiospecifier protein and epithiospecifier modifier protein released from cruciferous vegetables during injury to the plant. The various biological activities displayed by these phytochemicals are described. In particular, their abilities to induce cytoprotective genes, mediated by the Nrf2 (NF-E2 related factor 2) and AhR (arylhydrocarbon receptor) transcription factors, and their abilities to repress NF-κB (nuclear factor-κB) activity, inhibit histone deacetylase, and inhibit cytochrome P450 are outlined. Isothiocyanates appear to alter gene expression through modification of critical thiols in regulatory proteins such as Keap1 (Kelch-like ECH-associated protein 1) or IKK (IκB kinase), causing activation of Nrf2 and inactivation of NF-κB, respectively. Certain indoles act as ligands for AhR. Isothiocyanates and indoles are also capable of affecting cell cycle arrest and stimulating apoptosis. The mechanisms responsible for these anti-proliferative responses are discussed.
Keywords: antioxidant response element; apoptosis; arylhydrocarbon receptor; cytochrome P450; epithionitriles; gene induction; glucosinolates; glutathione S-transferase; isothiocyanates; NF-κB; Nrf2; quinone reductase; xenobiotic response element

α-Amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD) is a key enzyme in NAD biosynthesis from tryptophan. Dietary polyunsaturated fatty acids (PUFA) have been shown to suppress hepatic ACMSD activity and its mRNA level in rat. However the mechanism of the suppressive action has not been clarified yet. Although the phenomena that fatty acids suppress the expression of ACMSD in rat liver have been established in vivo experiment, it is still obscure whether the effect of fatty acids on the expression of the enzyme is caused by its direct or indirect action, because there have been very few investigations performed in vitro.In this study, to examine whether down-regulation of ACMSD mRNA by PUFA involves peroxisome proliferator-activated receptor (PPAR) α mediated mechanism or not, we investigated the effect of PUFA on the ACMSD expression by using primary cultured rat hepatocytes.For this purpose we investigated the effect of PUFA (linoleic acid and eicosapentanoic acid) on the ACMSD mRNA level in primary-cultured rat hepatocytes and compared its effect with that of WY-14,643 (a PPARα agonist). After the incubation of hepatocytes with fatty acids, WY-14,643 and/or MK886 (a PPARα antagonist), mRNA levels of ACMSD and a peroxisome marker enzyme acyl-CoA oxidase (ACO) were determined by competitive reverse transcription-polymerase chain reaction (RT-PCR) method.ACMSD mRNA level in primary hepatocytes were decreased by the incubation with high concentrations of linoleic acid, eicosapentaenoic acid (EPA) and WY-14,643. The appearance of ACO mRNA by WY-14,643 was remarkably increased, and those by linoleic acid and EPA were increased less than that by WY-14,643. Moreover, the suppression of ACMSD mRNA and the augmentation of ACO mRNA by WY-14,643 were inhibited by MK886, but the suppression by PUFA was not substantially affected by MK886.The present study suggesting that the mechanism of decrease in ACMSD mRNA level by PUFA was different from that by WY-14,643, and that there would be any pathway other than PPARα mediated one for PUFA to regulate ACMSD expression.
Keywords: α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase; polyunsaturated fatty acid; peroxisome proliferator-activated receptor α; primary cultured rat hepatocytes

Serum 1,25-dihydroxy vitamin D is inversely associated with body mass index by Steinar Konradsen; Harald Ag; Fedon Lindberg; Sofie Hexeberg; Rolf Jorde (87-91).
Based on in vitro studies, it has been hypothesized that 1,25-dihydroxy vitamin D (1,25-vit D) may promote weight gain in humans, but previous studies have demonstrated conflicting results regarding the association between serum 1,25-vit D and body mass index (BMI).To evaluate the relation between serum 1,25-vit D and BMI.Two thousand one hundred and eighty-seven subjects, recruited from a metabolic and medical lifestyle management clinic, were included in a cross-sectional study. BMI, 25-hydroxy vitamin D (25-OH-vit D) and 1,25-vit D were measured. The cohort was divided according to BMI in five groups (<25, 25–29.9, 30–34.9, 35–39.9 and >39.9 kg/m2). Statistical analyses were performed with multiple linear regression models. Age and gender were used as explanatory covariates.With increasing BMI group, there was a significant decrease in both serum 25-OH-vit D and 1,25-vit D (P < 0.001). Those with BMI > 39.9 kg/m2 had 24% lower serum 25-OH-vit D levels and 18 % lower 1,25-vit D levels than those with BMI < 25 kg/m2.There is an inverse association between BMI and the serum levels of 25-OH-vit D and 1,25-vit D. This makes it highly unlikely that high levels of circulating 1,25-vit D contribute to the development of obesity.
Keywords: body mass index; obesity; vitamin D

Estimated average folate intake in Sweden is less than 55% of the recommended daily intake (RDI) for women of childbearing age (Becker and Pearson in Riksmaten 1997–1998 Kostvanor och näringsintag i Sverige. National Food Administration, Uppsala, pp 34, 44, 121, 2002). Because a good folate status reduces the risk of neural tube defects, mandatory folic acid fortification is discussed in some European countries. This however, could lead to exposure to unintentionally high amounts of folic acid for some population groups, therefore targeted folic acid fortification could be an alternative.To (1) determine natural folate content in three popular brands of orange juice sold in Sweden, (2) determine stability of natural folate and folic acid fortificant during shelf life in a folic acid/iron fortified orange juice, (3) determine folate stability in four juices during simulated household consumption for one week and (4) determine the in vitro bioaccessibility of natural folate in one brand of orange juice using the TNO gastroIntestinal Model (TIM).Natural folate content in juices was determined using RP-HPLC-FL. To determine folic acid content and confirm RP-HPLC-FL values LCMS was used. Stability during shelf life was determined in unopened bottles of a folic acid/iron fortified juice and for one week in four popular juices under household consumption conditions with reopening of bottles daily. For an in vitro folate bioaccessibility experiment in orange juice the TNO TIM Model was used.5-CH3-H4folate was the dominant natural folate form in the juices with contents ranging from 16–30 µg/100 g. Shelf life losses of folic acid fortificant were 1–4%. During one week simulated household consumption 5-CH3-H4folate content decreased by up to 7% (n.s). Bioaccessibility of natural folate in orange juice was almost 100%. Most folate was released for absorption in jejunum between 60–120 min after trial start.Orange juice may be considered a good source of natural folate in respect to content and stability during storage and simulated digestion. Moreover, added folic acid fortificant in a folic acid/iron fortified orange juice was stable during shelf life.
Keywords: folate; folic acid; fortification; orange juice; in vitro bioaccessibility

Zeaxanthin is bioavailable from genetically modified zeaxanthin-rich potatoes by Achim Bub MD; Jutta Möseneder; Gerhard Wenzel; Gerhard Rechkemmer; Karlis Briviba (99-103).
The carotenoid zeaxanthin accumulates in the human macula lutea and protects retinal cells from blue light damage. However, zeaxanthin intake from food sources is low. Increasing zeaxanthin in common foods such as potatoes by traditional plant breeding or by genetic engineering could contribute to an increased intake of this carotenoid and, consequently, to a decreased risk of age-related macular degeneration. Our aim was to investigate whether zeaxanthin from genetically modified zeaxanthin-rich potatoes is bioavailable in humans. Three men participated in this randomized, controlled double-blinded, crossover pilot study. All subjects consumed 1,100 g of mashed potatoes, either genetically modified (Solanum tuberosum L. var. Baltica GM47/18; 3 mg zeaxanthin) or wild-type control potatoes (Solanum tuberosum L. var. Baltica; 0.14 mg zeaxanthin). A second treatment was followed after a 7-day wash-out period. The concentration of zeaxanthin was significantly increased in chylomicrons after consumption of genetically modified potatoes and 0.27 mg of the 3 mg zeaxanthin dose could be detected in chylomicrons. Consumption of control potatoes had no effect on concentrations of zeaxanthin in chylomicrons. After normalization of chylomicron zeaxanthin for plasma triacylglycerol, the time course of zeaxanthin concentrations peaked at 7 h after consumption of genetically modified potatoes. There were no significant differences in the concentrations of other major potato carotenoids such as lutein and β-carotene in chylomicrons after consumption of genetically modified and wild type control potatoes. Thus, consumption of zeaxanthin-rich potatoes significantly increases chylomicron zeaxanthin concentrations suggesting that potentially such potatoes could be used as an important dietary source of zeaxanthin.
Keywords: zeaxanthin; bioavailability; age-related macular degeneration; potato

The n-3 polyunsaturated fatty acid, eicosapentaenoic acid (EPA) has been found to process neuroprotective effects. However, the exact cellular mechanisms are not well understood. Brain-derived neurotrophic factor (BDNF) is one of neurotrophins, which is involved in neuron differentiation, survival, and synaptogenesis.In this study, the potential neuroprotective effects of EPA, and its possible effects on BDNF and BDNF receptor expression were investigated in SH-SY5Y cells.Both undifferentiated and retinoic acid (RA)-BDNF differentiated SH-SY5Y cells were treated with EPA and/or BDNF. The cell viability was determined by MTT assay. The expression of BDNF receptors, tyrosine kinase receptor B (TrkB) and p75NTR were tested by RT-PCR and Western blotting.In undifferentiated SH-SY5Y cells, either EPA or BDNF, or both did not affect the cell viability. In RA-BDNF differentiated SH-SY5Y cells, treatment with different doses of EPA (0.01, 0.1, 1.0, 10.0 µM) and BDNF (1 ng/ml) for 24 hours significantly increased the cell viability, while EPA or BDNF alone showed no effect. More importantly, RT-PCR and Western blotting results revealed that 24 hours treatment with EPA (0.01, 0.1, 1.0 µM) significantly increased the full-length TrkB (TrkBTK+), but not truncated TrkB (TrkBTK−) expression in these cells. An increase in p75NTR expression was also observed with 10.0 µM EPA treatment. Finally, co-incubation with either 100 nM staurosporine, a protein kinase inhibitor, or 500 nM K252a, a tyrosine kinase inhibitor completely abolished the EPA-induced increase in cell viability.Our results indicate that EPA exerts beneficial effects on cell survival through modulating neurotrophin receptor expression.
Keywords: eisosapentaenoic acid (EPA); brain-derived neurotrophic factor (BDNF); tyrosine kinase receptor B (TrkB); p75NTR ; neuroprotection