Tanja Nurmi

Tocopherols and Tocotrienols in Wheat Genotypes in the HEALTHGRAIN Diversity Screen

Tocopherol and tocotrienol compositions were studied in 175 genotypes of different wheat types grown under similar conditions to screen for natural diversity. The main focus was on bread wheats, including 130 and 20 winter and spring types, respectively. The average total content of tocopherols and tocotrienols was 49.4 microg/g of dm, with a range of 27.6-79.7 microg/g of dm, indicating a 2.9-fold variation among genotypes. Beta-tocotrienol and alpha-tocopherol were the major vitamers, and in general there were more tocotrienols than tocopherols. In the early cultivated forms of wheat the proportion of tocotrienols was especially high, at >or=62.5%. In conclusion, there was a large variation in total tocopherol and tocotrienol contents in bread wheats and this, along with the high proportions of tocotrienols in other types of wheat, demonstrates the great genetic potential of genotypes to be exploited by plant breeders.

The HEALTHGRAIN Wheat Diversity Screen: Effects of Genotype and Environment on Phytochemicals and Dietary Fiber Components

Analysis of the contents of bioactive components (tocols, sterols, alkylresorcinols, folates, phenolic acids, and fiber components) in 26 wheat cultivars grown in six site x year combinations showed that the extent of variation due to variety and environment differed significantly between components. The total contents of tocols, sterols, and arabinoxylan fiber were highly heritable and hence an appropriate target for plant breeding. However, significant correlations between the contents of bioactive components and environmental factors (precipitation and temperature) during grain development also occurred, with even highly heritable components differing in amount between grain samples grown in different years on different sites.

Phytosterols in Wheat Genotypes in the HEALTHGRAIN Diversity Screen

The phytosterol contents of 130 winter wheat, 20 spring wheat, 10 durum wheat, 5 spelt, 5 einkorn, and 5 emmer wheat genotypes, grown at the same location in the same year, were analyzed with gas chromatography. Considerable variation was observed in total phytosterol contents in all wheat types. The total sterol contents ranged from 670 to 959 microg/g of dm in winter wheat and from 797 to 949 microg/g of dm in spring wheat. The highest sterol contents were found in spelt, durum wheat, and einkorn wheat. The proportions of the main phytosterols also varied substantially among the different genotypes. The most abundant phytosterol in all wheat genotypes was sitosterol (40-61% of total sterols), whereas the highest variation was seen in total stanols (7-31% of total sterols). The comprehensive data set produced in this study constitutes a valuable basis for plant breeding and selection of phytosterol-rich genotypes.

Effects of Genotype and Environment on the Content and Composition of Phytochemicals and Dietary Fiber Components in Rye in the HEALTHGRAIN Diversity Screen

The effects of genotype and environment on the content of bioactive components in rye were determined with four varieties being grown on one site for three years and on three additional sites in the third year and a fourth variety being included in all trials except year 1. Clear differences were observed in the extent to which the contents of dietary fiber components (arabinoxylan, beta-glucan, total dietary fiber) and phytochemicals (folates, alkylresorcinols, sterols, tocols, phenolic acids) varied between varieties and between the same varieties grown in different sites (United Kingdom, France, Hungary, Poland) and years (2005-2007 in Hungary), with sterols being the most stable and phenolic acids the least. However, no single variety could be selected as having the highest overall level of bioactive components or as being more stable in comparison across environments.

Effects of the Environment and Genotype on Tocopherols and Tocotrienols in Wheat in the HEALTHGRAIN Diversity Screen

Tocol composition was studied in 26 genotypes of wheat grown in one location for three years and in three other locations for one year. Special emphasis was placed on evaluating the variation of tocols within wheat genotypes and among various growing conditions. In general, both genetic and environmental effects had a strong impact on tocols in wheat genotypes. Because the growing locations and years differed considerably, greater variation due to the environment was found in this study than in earlier ones. Some of the genotypes were more sensitive to the impact of the environment, whereas others were relatively stable. Of the wheat genotypes with an average total tocol content of >or=55 microg/g of dry matter, five genotypes showed relatively low variation: Claire, Cadenza, Lynx, Atlas 66, and Disponent. These genotypes could be potential candidates for the breeding of stable and high-tocol content wheat cultivars.

Effects of genotype and environment on steryl ferulates in wheat and rye in the HEALTHGRAIN diversity screen.

The effects of genetic and environmental factors on the content and composition of steryl ferulates in wheat and rye were studied. The wheat and rye genotypes were grown at the same location in Hungary over three consecutive years (28 genotypes) or at four different locations across Europe during a single year (12 genotypes). The steryl ferulates were analyzed using HPLC. The genotype and growing location significantly affected the content and composition of wheat steryl ferulates, whereas the year of growth did not result in considerable variation. Less variation was observed in rye, due to fewer genotypes. Campestanyl and sitostanyl ferulates were the main species in both cereals. Knowledge of the natural variation in steryl ferulates and other bioactive compounds allows cultivators and plant breeders to select genotypes with high, stable levels of beneficial compounds. Thus, it is possible to enhance the intake of health-promoting compounds from natural sources.

Effects of Environment and Genotype on Phytosterols in Wheat in the HEALTHGRAIN Diversity Screen

The effects of environment on the content and composition of phytosterols were examined in 26 wheat genotypes grown at four locations in Europe during a single year and at one location over three consecutive years. Total phytosterol contents varied among the locations, whereas no effect was found for the harvesting year. A significant genetic variation was observed in total sterol contents (700-928 microg/g of dm). The genotype and environment resulted in statistically significant differences in the proportions of the main phytosterols. The high phytosterol contents were characterized by low proportions of sitosterol and high proportions of stanols. Small wheat kernels with proportionally high bran yield and lipid content contained higher levels of phytosterols than large kernels. Knowledge of the level and variability of phytosterols in wheat enables the selection of genotypes with high and stabile phytosterol contents for cultivation or plant breeding purposes.

Plant sterol feeding induces tumor formation and alters sterol metabolism in the intestine of Apc(Min) mice.

Dietary plant sterols reduce the absorption of cholesterol and therefore increase intraluminal cholesterol concentration. We examined how plant sterol esters from functional foods affect intestinal tumorigenesis in tumor-prone adenomatous polyposis coli (Apc) Minmice. Feeding plant sterols at 0.8% increased the number of intestinal adenomas, and the effect was significant in female mice. The concentration of mucosal free sitosterol increased by eightfold in plant sterol males and by threefold in plant sterol females when compared with respective controls. The concentration of mucosal free cholesterol was significantly lower in plant sterol males than in control males, and the decrease in free cholesterol was accompanied with a significant increase in nuclear sterol regulatory element binding protein-2. No difference was found in the levels of β-catenin, cyclin D1, epidermal growth factor receptor, extracellular signal-regulated kinase 1/2, or caveolin-1 in either gender after plant sterol feeding. Among all measured parameters, higher levels of estrogen receptor β and free cholesterol in the mucosa were among the strongest predictors of increased intestinal tumorigenesis. In addition, gene expression data showed significant enrichment of up-regulated genes of cell cycle control and cholesterol biosynthesis in plant sterol females. The results indicate that high intake of plant sterols accelerates intestinal tumorigenesis in female Apc Minmice; however, the mechanism behind the adverse effect remains to be discovered.

Plant sterols induce intestinal tumor formation in gender-related manner in ApcMin mice

Background Plant sterols are plant derived dietary compounds that are structurally similar to cholesterol. Plant sterols reduce cholesterol absorption, and therefore plant sterol enriched functional foods are designed to lower blood cholesterol level. Reduction of cholesterol absorption increases the level of intraluminal cholesterol, and high intraluminal cholesterol concentration has been associated with enhanced cell proliferation, aberrant crypt formation and tumor formation [1,2]. The aim of this study was to investigate, how plant sterols affect intestinal tumorigenesis, sterol composition of the faeces and the intestinal mucosa, and cell signaling in tumor-prone ApcMin mice.