Asgeir Brevik

Evaluation of the odd fatty acids 15:0 and 17:0 in serum and adipose tissue as markers of intake of milk and dairy fat.

Background:There is a need for biomarkers of dietary saturated fatty acids, because several diseases have been related to intake of these fatty acids.Objective:To examine the relation between intake of dairy fat and the proportion of pentadecanoic (15:0) and heptadecanoic (17:0) acid in serum and adipose tissue.Design:Healthy men aged 21–55 y provided serum (n=110) and adipose tissue samples (n=107) and completed both 14 days weighed records (WR) and a 180-item food frequency questionnaire (FFQ). The proportions of 15:0 and 17:0 acid in serum and adipose tissue as measured by gas liquid chromatography were evaluated as biomarkers for fat intake from dairy products using Pearsons correlation coefficient and the method of triads.Results:The strongest correlation coefficients were observed between total intake of dairy fat estimated from WR and relative content of 15:0 in adipose tissue (0.52, 95% CI: 0.37, 0.65) and total serum (0.43, 95% CI 0.26, 0.57). A consistent inverse association was observed between the intake of milk fat and relative serum content of 17:0. The validity coefficients observed for the intake of dairy fat estimated from weighed records, the 180-item FFQ and by the relative content of 15:0 in serum and adipose tissue were 0.94 (95% CI: 0.68, 1.00), 0.50 (95% CI: 0.29, 0.67), 0.49 (95% CI: 0.32, 0.67) and 0.56 (95% CI: 0.28, 0.82), respectively.Conclusion:Relative content of 15:0 in serum and adipose tissue may be a useful biomarker for the intake of total dairy fat, whereas FFQs and WRs may provide better estimates of the intake of fat from milk.

Comet assay-based methods for measuring DNA repair in vitro; estimates of inter- and intra-individual variation

DNA repair is one of the important determinants of susceptibility to cancer. It is therefore useful to be able to measure DNA repair capacity in samples from population studies. Our aim was, first, to develop a simple comet-based in vitro assay for nucleotide excision repair (NER), similar to that already in use for base excision repair (BER), and then to apply these in vitro assays to lymphocyte samples collected on several occasions from healthy subjects, to gain an impression of the degree of intra- and inter-individual variability. The in vitro assay consists of an incubation of lymphocyte extract with substrate nucleoid DNA from cells pretreated with specific damaging agent; either photosensitiser plus light to induce 8-oxoguanine, for BER, or short wavelength ultraviolet light irradiation for NER. In the new NER assay, which requires magnesium but not adenosine triphosphate, there was significant accumulation of UV-dependent incisions during a 30-min incubation of extract with DNA. We found significant correlations between individual repair rates from samples taken on different occasions; i.e. individuals have a characteristic repair capacity. There was also significant variation between individuals, to the extent of about fourfold for BER and tenfold for NER. There was no correlation between BER and NER rates. The BER and NER assays are simple to perform and can provide valuable information in molecular epidemiological studies in which DNA instability is an endpoint.

Six carotenoids in plasma used to assess recommended intake of fruits and vegetables in a controlled feeding study

Background: There is a need for objective and universally applicable biomarkers for the intake of foods believed to affect human health.Objective: The purpose of this feeding study was to test whether plasma concentrations of carotenoids could be used to distinguish recommended consumption of mixed fruits and vegetables (five a day) from the current national intake of fruits and vegetables (two a day).Design: A strict crossover design was chosen to correct for observed interindividual variations in carotenoid response. A total of 40 healthy subjects were included in the study. After 1 week run-in period with no fruits and vegetables in the diet, one group was given two portions (300 g) of fruits and vegetables daily, while another group was given five portions (750 g) for 14 days. Following a 2 week wash-out period and 1 week run-in, the regimens were switched between the groups. Fruits and vegetables were combined to match a typical Norwegian diet.Results: Enhanced intake from two to five portions of mixed fruits and vegetables increased plasma concentrations of α-carotene (P=0.033) and lutein (P=0.051) in a crossover analysis. Analysis of data in the parallel part of the study revealed differences between the high and low intake for plasma concentrations of α-carotene (P=0.013) and β-carotene (P=0.016). A trend was also evident for plasma concentrations of lycopene (P=0.057) and lutein (P=0.076) in the parallel analysis. No effect of high vs low intake of fruits and vegetables was observed for plasma concentrations of β-cryptoxanthin, zeaxanthin, cholesterol and triacylglycerols.Conclusion: The study indicates that plasma concentration of α-carotene, β-carotene and lutein may be used to assess changes of fruit and vegetable intake corresponding to an increase from the present national intake in Norway to the recommended amount of five portions of fruits and vegetables daily.Sponsorship: Norwegian Research Council, National Nutrition Council, Throne Holst Foundation for Nutrition Research and Freia Chokoladefabriks Medisinske Fond.

Supplementation of a western diet with golden kiwifruits (Actinidia chinensis var.'Hort 16A':) effects on biomarkers of oxidation damage and antioxidant protection

BackgroundThe health positive effects of diets high in fruits and vegetables are generally not replicated in supplementation trials with isolated antioxidants and vitamins, and as a consequence the emphasis of chronic disease prevention has shifted to whole foods and whole food products.MethodsWe carried out a human intervention trial with the golden kiwifruit, Actinidia chinensis, measuring markers of antioxidant status, DNA stability, plasma lipids, and platelet aggregation. Our hypothesis was that supplementation of a normal diet with kiwifruits would have an effect on biomarkers of oxidative status. Healthy volunteers supplemented a normal diet with either one or two golden kiwifruits per day in a cross-over study lasting 2 × 4 weeks. Plasma levels of vitamin C, and carotenoids, and the ferric reducing activity of plasma (FRAP) were measured. Malondialdehyde was assessed as a biomarker of lipid oxidation. Effects on DNA damage in circulating lymphocytes were estimated using the comet assay with enzyme modification to measure specific lesions; another modification allowed estimation of DNA repair.ResultsPlasma vitamin C increased after supplementation as did resistance towards H2O2-induced DNA damage. Purine oxidation in lymphocyte DNA decreased significantly after one kiwifruit per day, pyrimidine oxidation decreased after two fruits per day. Neither DNA base excision nor nucleotide excision repair was influenced by kiwifruit consumption. Malondialdehyde was not affected, but plasma triglycerides decreased. Whole blood platelet aggregation was decreased by kiwifruit supplementation.ConclusionGolden kiwifruit consumption strengthens resistance towards endogenous oxidative damage.

Three-dimensional computerised atlas of the rat brain stem precerebellar system: approaches for mapping, visualization, and comparison of spatial distribution data.

Comparisons of microscopical neuroanatomic data from different experiments and investigators are typically hampered by the use of different section planes and dissimilar techniques for data documentation. We have developed a framework for visualization and comparison of section-based, spatial distribution data, in brain stem nuclei. This framework provides opportunities for harmonized data presentation in neuroinformatics databases. Three-dimensional computerized reconstructions of the rat brain stem and precerebellar nuclei served as a basis for establishing internal coordinate systems for the pontine nuclei and the precerebellar divisions of the sensory trigeminal nuclei. Coordinate based diagrams were used for presentation of experimental data (spatial distribution of labelled neurons and axonal plexuses) from standard angles of view. Each nuclear coordinate system was based on a cuboid bounding box with a defined orientation. The bounding box was size-adjusted to touch cyto- and myeloarchitectonically defined boundaries of the individual nuclei, or easily identifiable nearby landmarks. We exemplify the use of these internal coordinate systems with dual retrograde neural tracing data from pontocerebellar and trigeminocerebellar systems. The new experimental data were combined, in the same coordinate based diagrams, with previously published data made available via a neuroinformatics data repository (www.nesys.uio.no/Database, see also www.cerebellum.org). Three-dimensional atlasing, internal nuclear coordinate systems, and consistent formats for presentation of neuroanatomic data in web-based data repositories, offer new opportunities for efficient analysis and re-analysis of neuroanatomic data.

Both base excision repair and nucleotide excision repair in humans are influenced by nutritional factors

Lack of reliable assays for DNA repair has largely prevented measurements of DNA repair from being included in human biomonitoring studies. Using newly developed modifications of the comet assay we tested whether a fruit‐ and antioxidant‐rich plant‐based intervention could affect base excision repair (BER) and nucleotide excision repair (NER) in a group of 102 male volunteers. BER and NER repair capacities were measured in lymphocytes before and after a dietary intervention lasting 8 weeks. The study had one control group, one group consuming three kiwifruits per day and one group consuming a variety of antioxidant‐rich fruits and plant products in addition to their normal diet. DNA strand breaks were reduced following consumption of both kiwifruits (13%, p = 0.05) and antioxidant‐rich plant products (20%, p = 0.02). Increased BER (55%, p = 0.01) and reduced NER (−39%, p < 0.01) were observed in the group consuming a wide variety of plant products. Reduced NER was also observed in the kiwifruit group (−38%, p = 0.05), but BER was not affected in this group. Here we have demonstrated that DNA repair is affected by diet and that modified versions of the comet assay can be used to assess activity of different DNA repair pathways in human biomonitoring studies. Copyright

Paternal Benzo[a]pyrene Exposure Modulates MicroRNA Expression Patterns in the Developing Mouse Embryo

Little attention has been given to how microRNA expression is affected by environmental contaminants exposure. We investigate the effects of paternal exposure to benzo[a]pyrene (B[a]P) on miRNA expression in the developing mouse embryo. Male mice were exposed to B[a]P (150 mg/kg i.p.), and their sperm was used four days later in in-vitro fertilization experiments. Twenty embryos each from 2-, 8-cell and the blastocyst stage were used for genome-wide miRNA expression profiling. Paternal exposure to B[a]P affected the expression of several miRNAs, and the target genes for some of the dysregulated miRNAs were enriched in many different pathways that are likely to be relevant for the developing mouse embryo. By linking the miRNA target genes to publicly available databases, we identified some miRNA target genes that may serve as global markers of B[a]P-mediated genotoxic stress. The dysregulated miRNAs may provide valuable knowledge about potential transgenerational effects of sublethal exposure to chemicals.

Impaired sperm chromatin integrity in obese mice.

An increased global prevalence of obesity coincides with an apparent decline in male sperm quality and a possible association between these pathologies has been suggested. In this study, we examined the effects of obesity on sperm chromatin integrity using two mouse models of obesity. In one group of mice, obesity was induced by a high‐fat diet (HFD) (diet‐induced obesity; DIO model), whereas in the other group, leptin deficiency was used to study the effects of obesity independently of the influence of dietary factors. Sperm chromatin integrity is recognized as an important measure of male infertility, and was analysed by the sperm chromatin structure assay. We found increased sperm DNA fragmentation in both groups of obese mice compared to lean mice, whereas the percentage of immature spermatozoa was not increased by obesity. The DIO model reflects the human condition more closely than the leptin‐deficient model and was therefore selected for examination of the transcriptional response of a selection of marker genes in the testis by quantitative real‐time PCR. The analysis of transcript levels of the selected testicular marker genes showed moderate, but significant, up‐regulation of the Cyp2e1, Cyp19a1, Tnf and Pparg genes in DIO mice compared to lean mice. In conclusion, a clear positive correlation between body mass index and sperm DNA fragmentation was found in two mouse models of obesity. However, the variability in sperm DNA fragmentation within the two groups of obese animals was high. The observed changes in the transcript level of the marker genes suggest that there may be a local response in testicular cells to the HFD regimen with a potential impact on intratesticular signalling and spermatogenesis.

Paternal Benzo(a)pyrene Exposure Affects Gene Expression in the Early Developing Mouse Embryo

The health of the offspring depends on the genetic constitution of the parental germ cells. The paternal genome appears to be important; e.g., de novo mutations in some genes seem to arise mostly from the father, whereas epigenetic modifications of DNA and histones are frequent in the paternal gonads. Environmental contaminants which may affect the integrity of the germ cells comprise the polycyclic aromatic hydrocarbon, benzo[a]pyrene (B[a]P). B[a]P has received much attention due to its ubiquitous distribution, its carcinogenic and mutagenic potential, and also effects on reproduction. We conducted an in vitro fertilization (IVF) experiment using sperm cells from B[a]P-exposed male mice to study effects of paternal B[a]P exposure on early gene expression in the developing mouse embryo. Male mice were exposed to a single acute dose of B[a]P (150mg/kg, ip) 4 days prior to isolation of cauda sperm, followed by IVF of oocytes from unexposed superovulated mice. Gene expression in fertilized zygotes/embryos was determined using reverse transcription-qPCR at the 1-, 2-, 4-, 8-, and blastocyst cell stages of embryo development. We found that paternal B[a]P exposure altered the expression of numerous genes in the developing embryo especially at the blastocyst stage. Some genes were also affected at earlier developmental stages. Embryonic gene expression studies seem useful to identify perturbations of signaling pathways resulting from exposure to contaminants, and can be used to address mechanisms of paternal effects on embryo development.

Compliance, tolerability and safety of two antioxidant-rich diets: a randomised controlled trial in male smokers.

It has been suggested that antioxidants attenuate oxidative stress and prevent oxidative stress-related diseases. Paradoxically, randomised controlled trials (RCT) using pharmacological doses of antioxidant supplements have demonstrated harmful effects in smokers. The aim of the present study was to test the compliance, tolerability and safety of two food-based antioxidant-rich diets in smokers. One of the diets provided antioxidants at levels similar to that used in RCT using supplements which previously have generated harmful effects. The present study followed a randomised, parallel-arm dietary intervention for 8 weeks (n 102) in male smokers (age ≥ 45 years). Participants were randomised to either antioxidant-rich diet, kiwi fruit or control groups. The antioxidant-rich foods provided about 300 mmol antioxidants/week from a wide range of plant-based food items. The kiwi fruit group consumed three kiwi fruits/d. Compliance to both diets was good. Only mild, undesirable events were reported by a minority of the participants. The safety of both diets was demonstrated as no potentially harmful or pro-oxidative effects were observed. In the antioxidant-rich diet group, the mean intake of antioxidants increased from 30 mmol/d at baseline to 62 mmol/d during the intervention. In conclusion, we have demonstrated that male smokers can comply with two food-based antioxidant-rich diets. Furthermore, the present study is the first to demonstrate the tolerability and safety of dietary antioxidants at levels similar to dosages provided in RCT using supplements. Such diets may be useful in future studies investigating whether dietary antioxidants may reduce oxidative stress and related diseases.