A. J. A. Wright

No Significant Effects of Lutein, Lycopene or β-Carotene Supplementation on Biological Markers of Oxidative Stress and LDL Oxidizability in Healthy Adult Subjects

Objective: The objective of this study was to determine the effect of individual carotenoid supplementation on biochemical indices of oxidative status in apparently healthy adult males. Methods:The study was a placebo controlled single blind study. Healthy male volunteers (n=175) were assigned to four groups. They received daily supplements of β-carotene (15 mg), lutein (15 mg), lycopene (15 mg) and placebo for three months. The effects of the supplementation on antioxidant status were monitored by plasma carotenoid, vitamin C and A levels, glutathione (GSH and GSSG) concentrations, protein SH groups, erythrocyte antioxidant enzyme activities (Cu-Zn SOD, Se-GSH-Px) and susceptibility of LDL to copper-induced oxidation. Results:β-carotene, lycopene and lutein supplementation led to significant plasma and LDL increases in each of these carotenoids, without modifications of other carotenoid levels in plasma or in LDL. The supplementation failed to enhance the resistance of LDL to oxidation or to modify the LDL polyunsaturated/saturated fatty acid ratio. Vitamin C, GSH, protein SH groups and antioxidant metalloenzyme activities were also unchanged. Conclusion: We did not observe beneficial or adverse effects of lutein, lycopene or β-carotene supplementation on biomarkers of oxidative stress. In apparently healthy subjects, carotenoid supplementation does not lead to significantly measurable improvement in antioxidant defenses.

DNA damage and susceptibility to oxidative damage in lymphocytes: effects of carotenoids in vitro and in vivo

Reports on the effects of carotenoids are conflicting. The present paper examines similarities and differences from contiguous studies in vitro and in vivo. Single-cell gel electrophoresis was used to measure the frequency of single-strand breaks (SSB) in the cell line MOLT-17 (as a model system) and human peripheral blood lymphocytes (PBL). MOLT-17 cells were supplemented with beta-carotene, lutein or lycopene at a range of concentrations (0.00-8.00 micromol/l) using a liposome delivery method. Uptake was dose-dependent. beta-Carotene concentration in the media had no effect on SSB in control cells, but incubation with lycopene or lutein (>2.00 micromol/l) increased the numbers of SSB in control cells. MOLT-17 DNA was less susceptible to oxidative damage (100 micromol H2O2/l, 5 min, 4 degrees C) following incubation with carotenoids between 0.50 and 1.00 micromol/l; at >1.00 micromol/l the effects were ambiguous. Apparently healthy male volunteers supplemented their habitual diets with lutein, beta-carotene or lycopene (natural isolate capsules, 15 mg/d, 4 weeks) in three independent studies, raising plasma concentrations to different extents. Lycopene and lutein had no effect on SSB in control PBL or following oxidative challenge. However, increased plasma beta-carotene was associated with more SSB in control cells whilst PBL DNA resistance to oxidative damage ex vivo was unaffected. These results suggest that the carotenoids are capable of exerting two overlapping but distinct effects: antioxidant protection by scavenging DNA-damaging free radicals and modulation of DNA repair mechanisms.

The effect of β-carotene supplementation on the immune function of blood monocytes from healthy male nonsmokers

Although there is strong epidemiologic evidence that diets rich in carotenoids such as beta-carotene are associated with a reduced incidence of cancer, the cellular mechanisms underlying this phenomenon remain unknown. This article describes the effect of dietary beta-carotene supplementation on both the expression of functionally associated surface molecules on human monocytes and on the secretion of the cytokine tumor necrosis factor-alpha (TNF-alpha) by monocytes, all of which are involved in the initiation and regulation of immune responses involved in tumor surveillance. A double-blind, placebo-controlled, crossover study was undertaken in which 25 healthy, adult male nonsmokers were randomly assigned to receive beta-carotene (15 mg daily) or placebo for 26 days, followed by the alternative treatment for a further 26 days. The expression of functionally related monocyte surface molecules was quantified by flow cytometry, and ex vivo secretion of TNF-alpha was quantified by an enzyme-linked immunosorbent assay, before and after each treatment period. After dietary supplementation there were significant increases in plasma levels of beta-carotene and in the percentages of monocytes expressing the major histocompatibility complex class II molecule HLA-DR and the adhesion molecules intercellular adhesion molecule-1 and leukocyte function-associated antigen-3. In addition, the ex vivo TNF-alpha secretion by blood monocytes was significantly increased after supplementation. These findings suggest that moderate increases in the dietary intake of beta-carotene can enhance cell-mediated immune responses within a relatively short period of time, providing a potential mechanism for the anticarcinogenic properties attributed to beta-carotene.

Isolation and characterization of amyloplast envelope membranes from Solanum tuberosum.

Abstract Amyloplasts were separated from other subcellular organelles by sedimentation through a discontinuous sucrose density gradient. Purified amyloplast envelope membranes were similar in most characteristics to those from other types of plastids. A substantial proportion of the carotenoid content of these membranes was present in the esterified form. In contrast to published work on chloroplasts of photosynthetic tissue, our results showed that the acylase (acyl-CoA:sn-glycerol 3-phosphate acyltransferase) is firmly bound to the envelope membranes. Evidence was obtained to indicate that digalactosyldiacylglycerol, phosphatidylglycerol and sulpholipid, but not monogalactosyldiacylglycerol, are exclusively found in the cell as amyloplast lipids.

Studies on the response of Lactobacillus casei to different folate monoglutamates

1. The response of Lactobacillus casei was measured for a number of the monoglutamyl forms of folate derivatives. 2. At the concentrations of folate commonly used in the assay of folate vitamin in foods the response of L. casei to folic acid, (pteroylglutamic acid) and 5-formyl-tetrahydrofolic acid was similar, but 5-methyl-tetrahydrofolic acid gave as little as half the response of folic acid. 3. The response was modified by altering pH but not by concentration of ascorbate. 4. These results have implications for the assays of foods for folate where mixtures of folate derivatives are present. 5. A modified procedure is suggested in which the monoglutamates give similar responses.

Peripheral arterial disease and methylenetetrahydrofolate reductase (MTHFR) C677T mutations: A case-control study and meta-analysis

OBJECTIVE Hyperhomocysteinaemia is associated with peripheral arterial disease (PAD). There are inter-individual variations in the metabolism of homocysteine because of genetic polymorphisms. This study analyzed the role of one polymorphism that is associated with raised homocysteine, as a risk factor for PAD. METHODS This study considered the association of methylenetetrahydrofolate reductase (MTHFR) C677T polymorphisms with the incidence of PAD by performing a case-control study and a cross sectional study of homocysteine levels. We recruited 133 patients with PAD in Norfolk and compared the MTHFR allele distribution with 457 healthy individuals. We also carried out a meta-analysis to place our data within the context of other published studies. We searched Medline, Embase, and Cochrane databases up to March 2008 for any studies on the association between MTHFR C677T polymorphism and PAD. RESULTS The MTHFR C677T allele frequencies in the cases and controls were 0.37 and 0.33, and the odds ratios for the association of the 677 T allele or TT genotype with PAD were 1.18 (95% Confidence Interval [CI] 0.89, 1.58) and 1.99 (95% CI 1.09, 3.63). Homozygotes for the MTHFR C677T mutation had higher concentrations of plasma total homocysteine, odds ratio 2.82 (95% CI 1.03, 7.77) compared to homozygotes for the MTHFR 677 CC genotype. Twelve of 72 articles retrieved from the database search reported the prevalence of mutations in PAD patients. A meta-analysis of 9 appropriate studies, including our own, showed that being homozygous for the C677T allele was associated with an increased risk of PAD, pooled odds ratio 1.36 (95% CI 1.09, 1.68). CONCLUSION We have found a strong association between raised homocysteine, the TT genotype, and PAD.

The influence of previous iron intake on the estimation of bioavailability of Fe from a test meal given to rats

Iron retention and its subsequent distribution from 3 g 59Fe extrinsically-labelled wholewheat four in rats given a low (8 micrograms Fe/g)- or high (566 micrograms Fe/g)-Fe diet during the previous 3 d was measured (Expt 1). The mean (with SE) proportion of Fe retained from wholewheat flour was 0.46 (0.04) in the group given the low-Fe diet and 0.15 (0.01) in the group given the high-Fe diet (P less than 0.001). There was no difference in distribution of absorbed 59Fe in the tissues examined. The procedure was repeated in rats given diets containing a range of Fe concentrations, groups 1-6 respectively: 8, 77, 136, 334, 566, 1270 micrograms Fe/g (Expt 2). The mean (with SE) proportions of Fe retained in groups 1-6 respectively were 0.60 (0.02), 0.34 (0.02), 0.30 (0.02), 0.20 (0.20), 0.17 (0.02), 0.09 (0.01). Regression analysis showed that Fe retention was a function of the logarithm of the Fe concentration of the diet consumed before the test meal (R -0.997, P less than 0.0001) where Fe retained (microgram) = 95 -28 log10 Fe concentration of diet. Rats were given a low-, medium- or high-Fe diet (8, 136 or 1270 micrograms Fe/g respectively) for 1 or 2 d instead of 3 d before measuring Fe retention from 3 g wholewheat flour (Expt 3). The mean (with SE) proportions of Fe retained in rats given the low-, medium- or high-Fe diets for 1 d were 0.45 (0.02), 0.25 (0.02) and 0.13 (0.01) (P less than 0.001) and for 2 d 0.47 (0.03), 0.31 (0.03) and 0.18 (0.02) (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary intake and micronutrient status of adolescents: effect of vitamin and trace element supplementation on indices of status and performance in tests of verbal and non-verbal intelligence

Relationships between micronutrient intake and status, and micronutrient status and performance in tests of intelligence were investigated in a group of adolescents (13-14 years old). Dietary intakes were assessed using a 7 d weighed dietary record method, coupled with the collection of duplicate diets. Vitamin and trace mineral intakes calculated using food composition tables were compared with those obtained by direct analysis of duplicate diets. Micronutrient status was judged via a range of biochemical indices measured in blood samples taken after a 12-15 h fast. Blood samples were taken both before and after a 16-week period of vitamin and trace mineral supplementation. Individual tests of verbal and nonverbal intelligence were also performed pre- and post-supplementation. The results of this study indicate that the use of food table data may lead to substantial over- or underestimation of the intake of several micronutrients. In general, the total calculated or analysed amount of a specific micronutrient consumed did not adequately predict status, as judged by a range of biochemical indices. There were significant changes in status measurements over the 16-week study period, irrespective of supplementation, and these changes were markedly influenced by the initial status of the subject. There was no effect of supplementation on performance in tests of intelligence. However, there was a significant association between plasma ascorbic acid and initial non-verbal intelligence quotient (IQ) in the boys, and between whole blood glutathione peroxidase (EC 1.11.1.9) activity and non-verbal and verbal IQ in both sexes. These findings are discussed in relation to other recent studies of the influence of micronutrient supplementation on the psychological performance of children.

Comparison of methods for the extraction of plant lipids

Abstract The ability of a number of different solvent systems to extract lipid from a range of plant tissues was compared by measurement of phospholipid, glycolipid, sterol lipid and total acyl lipid content. A chloroform-methanol extraction method based upon the principles of Bligh and Dyer was considered to be the most efficient system for use with the majority of plant tissues. Cereal seeds were anomalous in that water saturated n - butanol was the preferred solvent system due to its superior ability to extract bound lysophospholipids present in large amounts in the endosperm portion of the tissue.

Proposed mandatory fortification of the UK diet with folic acid: have potential risks been underestimated?

Abstract This article discusses the recent consultation by the UK Department of Health and Food Standards Agency on the risk-benefit of a whole population strategy for increased intake of folic acid via the fortification of flour. The potential benefit of folic acid in relation to decreased incidence of Neural Tube Defects in the newly born is contrasted to the potential risk of increasing permanent neuropathy (nerve damage) in those suffering from vitamin B12 deficiency. Questions are also raised with regard to the potential risk of folic acid addition in the context of pre-existing malignant neoplasms, and the incidence of dichorionic twin births.