Canada thistle is a serious perennial weed found throughout the northern regions of the United States and Canada. The weevil, Ceutorhynchus litura (F.), was first released in Canada in 1965 as a potential biological control agent for Canada thistle; however, its impact as a control agent has been sporadic. The objective of this study was to characterize C. litura impacts on the carbohydrate profile in Canada thistle roots through the growing season and to evaluate the potential for this biological control agent in causing stress to Canada thistle. Field plots, infested with C. litura, were established and extensively sampled for C. litura infestations. By sampling C. litura–damaged and undamaged Canada thistle shoots–roots through the season, we were able to establish the profile of free sugars and fructans in the roots and compare these levels to the presence and extent of insect damage. Levels of all free sugars and fructans were consistently found to be depressed in roots from C. litura–damaged shoots early in the summer during and shortly after the larval feeding period. Ceutorhynchus litura feeding in Canada thistle shoots appears to disrupt the movement of photoassimilates from leaves to roots. Late-season levels of free sugars and fructans indicate that roots do recover from these depressed levels, and in several instances, significant overcompensation occurred in the damaged roots. Measurement of free sugars and fructans to identify sublethal impacts of control tactics may allow the strategic combining of complementary tactics to maximize the impact of stresses on Canada thistle.

The aim of this 28 d experiment was to examine the physiological response of growing rats to a dietary combination of prebiotic chicory fructans, with polyphenols originating from different parts of the chicory plant, i.e. roots, root peels, seeds and leaves. A total of forty rats were assigned to groups fed the following diets characterised by a similar content of oligofructose and inulin: control, with 10 % of a root extract (a low level of dietary polyphenols, 0·05 %), with 6·5 % of a root peel extract (a medium level of dietary polyphenols, 0·107 %), with a combination of 8 % of a peel extract and 0·8 % of a seed extract (a high level of dietary polyphenols, 0·208 %) and with 2·5 % of a leaf extract (a medium level of dietary polyphenols, 0·106 %, with chicoric acid constituting half of them). Chicory seeds are the richest source of polyphenols, especially abundant in dicaffeoylquinic acids. When applied as a dietary supplement, the mixture of monocaffeoylquinic and dicaffeoylquinic acids, from the extracts made of roots, root peels and seeds, elicited more favourable changes in parameters of the antioxidative status of the body and in the activity of bacterial β-glucuronidase in the faeces and caecal digesta. In turn, the extract from chicory leaves, containing considerable quantities of chicoric acid and polyphenolic glycosides, apart from chlorogenic acids, also triggered desirable changes in the lipid profile of the blood serum. The high concentration of polyphenols in the extracts examined enables their application as dietary supplements to be administered in low doses.

A new in vitro fermentation model with immobilised infant faecal microbiota simulating the proximal colon of a formula-fed baby was developed and used to test the effects of known prebiotic fructans. Intestinal fermentation, based on a previously developed colonic fermentation model, using a new feeding medium simulating a formula-fed infant ileal chyme, was carried out for seventy-one consecutive days divided into four stabilisation periods intercalated with four prebiotic treatment periods. At the end of the first stabilisation period, total bacterial concentration in colonised beads and in faecal sample was similar, metabolite concentrations returned to stabilisation values after each treatment period. As expected, the four prebiotic treatments significantly increased the bifidobacterial populations, whereas they decreased bacteroides and clostridia. No difference was observed in the prebiotic effect of these substrates selected. The treatments significantly increased total production of SCFA and decreased ammonia compared to stabilisation periods. Long-term stability of the system together with the reproducibility of the known prebiotic effects highlights the potential of the present model to quantify and compare the effects of different substrates in a formula-fed infant microbiota within the same fermentation experiment.

Recent data reported that inulin-type fructans extracted from chicory roots regulate appetite and lipid/glucose metabolism, namely, by promoting glucagon-like peptide-1 (GLP-1) production in the colon. The Agave genus growing in different regions of Mexico also contains important amounts of original fructans, with interesting nutritional and technological properties, but only few data report their physiological effect when added in the diet. Therefore, we decided to evaluate in parallel the effect of supplementation with 10 % agave or chicory fructans on glucose and lipid metabolism in mice. Male C57Bl/6J mice were fed a standard (STD) diet or diet supplemented with Raftilose P95 (RAF), fructans from Agave tequilana Gto. (TEQ) or fructans from Dasylirion spp. (DAS) for 5 weeks. The body weight gain and food intake in mice fed fructans-containing diets were significantly lower than the ones of mice fed the STD diet, TEQ leading to the lowest value. Serum glucose and cholesterol were similarly lower in all fructans-fed groups than in the STD group and correlated to body weight gain. Only RAF led to a significant decrease in serum TAG. As previously shown for RAF, the supplementation with agave fructans (TEQ and DAS) induced a higher concentration of GLP-1 and its precursor, proglucagon mRNA, in the different colonic segments, thus suggesting that fermentable fructans from different botanical origin and chemical structure are able to promote the production of satietogenic/incretin peptides in the lower part of the gut, with promising effects on glucose metabolism, body weight and fat mass development.

Yacon roots have been considered a functional food due to the high levels of fructans they contains. In the present study, Ca and Mg balance, bone mass and strength, and caecum mucosal morphometry were evaluated. Growing male Wistar rats (n 24) were fed ad libitum control diets or diets supplemented with yacon flour (5 or 7·5 % fructooligosaccharides) for 27 d. Mineral balance was evaluated in three periods of 5 d (starting on the 4th, 10th and 16th days). After the rats were killled, the bones were removed and bone mineral density was measured. Ca analyses were performed on left femurs and tibias and biomechanical testing on right femurs. The caecum was removed and tissue samples were collected for histological analysis. Caecal histology changed noticeably in rats fed yacon flour: there was an increase in the depth and number of total and bifurcated crypts as well. Yacon flour consumption significantly (P < 0·05) resulted in a positive Ca and Mg balance, leading to higher values of bone mineral retention and biomechanical properties (peak load and stiffness) when compared to the control group. The positive effects on mineral intestinal absorption, bone mass and biomechanical properties showed an important role of yacon roots in the maintenance of healthy bones. The increased number of bifurcating crypts might be related to the higher mineral absorption caused by the enlargement of the absorbing surface in the large intestine of the animals.

Prebiotics may be considered as functional food ingredients. They are attracting considerable interest from pet owners, pet food manufacturers, livestock producers and feed manufacturers. The most common forms of prebiotics are nondigestible oligosaccharides (NDO), including inulin, oligofructose mannanoligosaccharides, gluco-oligosaccharides, and galacto-oligosaccharides. These NDO are nondigestible by enzymes present in the mammalian small intestine, but are fermented by bacteria present in the hindgut of nonruminants. Inulin and oligofructose are present in measurable quantities in feed ingredients like wheat, wheat by-products, barley, and peanut hulls. Consumption of prebiotic oligosaccharides elicits several purported health benefits. In companion animals, prebiotics have been shown to improve gut microbial ecology and enhance stool quality. In production livestock and poultry, prebiotics are employed to control pathogenic bacteria, reduce faecal odour, and enhance growth performance. Research to date indicates positive effects of prebiotics on health status and performance of companion animals, livestock, and poultry.

Inulin and oligofructose, besides their effect on the gastro-intestinal tract, are also able to exert ‘systemic’ effect, namely by modifying the hepatic metabolism of lipids in several animal models. Feeding male Wistar rats on a carbohydrate-rich diet containing 10 % inulin or oligofructose significantly lowers serum triacylglycerol (TAG) and phospholipid concentrations. A lower hepatic lipogenesis, through a coordinate reduction of the activity and mRNA of lipogenic enzymes is a key event in the reduction of very low-density lipoprotein-TAG secretion by oligofructose. Oligofructose is also able to counteract triglyceride metabolism disorder occurring through dietary manipulation in animals, and sometimes independently on lipogenesis modulation: oligofructose reduces post-prandial triglyceridemia by 50 % and avoids the increase in serum free cholesterol level occurring in rats fed a Western-type high fat diet. Oligofructose protects rats against liver TAG accumulation (steatosis) induced by fructose, or occurring in obese Zucker fa/fa rats. The protective effect of dietary inulin and oligofructose on steatosis in animals, would be interesting, if confirmed in humans, since steatosis is one of the most frequent liver disorders, occurring together with the plurimetabolic syndrome, in overweight people. The panel of putative mediators of the systemic effects of inulin and oligofructose consists in either modifications in glucose/insulin homeostasis, the end-products of their colonic fermentation (i.e. propionate) reaching the liver by the portal vein, incretins and/or the availability of other nutrients. The identification of the key mediators of the systemic effects of inulin and oligofructose is the key to identify target function(s) (or dysfunction(s)), and finally individuals who would take an advantage of increasing their dietary intake.

The present study was carried out to examine the effect of the daily intake of 10 g inulin on fasting blood lipid, glucose and insulin levels in healthy middle-aged men and women with moderately raised total plasma cholesterol (TC) and triacylglycerol (TAG) levels. This study was a double-blind randomized placebo-controlled parallel study in which fifty-four middle-aged subjects received either inulin or placebo for a period of 8 weeks. Fasting blood samples were collected before the supplementation period (baseline samples 1 and 2, separated by 1 week) and at weeks 4 and 8, with a follow-up at week 12. Compared with baseline values, insulin concentrations were significantly lower at 4 weeks (P < 0·01) in the inulin group. There was a trend for TAG values, compared with baseline, to be lower in the inulin group at 8 weeks (P < 0·08) returning to baseline concentrations at week 12. On comparison of the inulin and placebo groups, the fasting TAG responses over the 8-week test period were shown to be significantly different (P < 0·05, repeated measures ANOVA), which was largely due to lower plasma TAG levels in the inulin group at week 8. The percentage change in TAG levels in the inulin group during the 8-week study was shown to correlate with the initial TAG level of the subjects (rs −0·499, P = 0·004). We therefore conclude that the daily addition of 10 g inulin to the diet significantly reduced fasting insulin concentrations during the 8-week test period and resulted in lower plasma TAG levels, particularly in subjects in whom fasting TAG levels were greater than 1·5 mmol/l. These data support findings from animal studies that fructans influence the formation and/or degradation of TAG-rich lipoprotein particles, and the insulin data are also consistent with recent studies showing attenuation of insulin levels in fructan-treated rats.

Nitrogen (N) allocated to leaf growth in forage grasses and legumes following severe defoliation is predominately mobilized from the remaining root and leaf sheath tissues, since both N uptake from the soil and N2 fixation are severely down-regulated for several days. The hypothesis that a low N reserve status at the time of defoliation limits N remobilization and leaf regrowth was tested with contrasting cultivars of Lolium perenne (cvs Aberelan and Cariad) in flowing solution culture. Plants were grown under ‘high’ or ‘low’ (uptake of N decreased by 50%) regimes of N supply for 10 d before a single severe defoliation. Labelling with 15N was used to assess the importance of N reserves, including putative vegetative storage proteins, relative to N translocated from concurrent uptake, as a source of leaf N during regrowth. Leaf regrowth, N uptake and N mobilization were all affected by previous N supply. Low plant N status at the time of defoliation increased regrowth dry weight of ‘Aberelan’ by 10% and translocation of N absorbed from the medium by 23%, while mobilization of N reserves was decreased by 56%. On the contrary, regrowth dry weight of ‘Cariad’ was decreased by 23%, and translocation of N absorbed by 21% in low plant N status, compared with high plant N status. Concentrations of soluble protein in roots and remaining leaf sheaths decreased after defoliation in plants only under optimal N supply. Analysis of soluble proteins in sheath material by SDS–PAGE suggested that three polypeptides (55, 36.6 and 24 kDa) might function as vegetative storage proteins, although they were of low abundance in plants, subjected to monthly harvests, grown in controlled conditions and in the field. The apparent antagonism between uptake of NH4+ or NO3− by roots and mobilization of N reserves is discussed together with evidence for functional vegetative storage proteins in L. perenne.

Previous work on Lolium perenne showed that sucrose[ratio ]sucrose fructosyltransferase (SST) activity did not increase concomitantly with fructan synthesis in regrowing leaves or in mature leaf blades of plants that have been subjected to carbohydrate-accumulating conditions. This was contrary to the pattern of SST activity in roots and stubble. To obtain further insight into the fructan synthesizing activities and to explain this discrepancy, total fructosyltransferase activity (FT) was assayed by increasing the sucrose and the soluble enzyme concentrations and was compared to sedimentable phlein sucrase activity (PS) throughout the regrowth period following defoliation in leaves, stubble and roots. Before analysis on 2-month-old plants, PS activity was characterized in dark-grown coleoptiles, using [U-14C]sucrose. PS activity had a pH optimum of 6.0 and produced 1-kestose in addition to high molecular weight fructans with a mean DP of 9. In 2-month-old plants, sedimentable PS and FT soluble reactions contained an initial sucrose concentration of 160 mM and 400 mM and proteins equivalent to 1.4 and 2.1 g f. wt of tissue, respectively. In stubble and roots, the FT preparation catalysed the synthesis of large fructans, and the overall pattern resembled the native fructans when separated by anion exchange HPLC. In regrowing leaves, the FT preparation produced low-DP fructans relatively more than in vivo but synthesized the high-DP fructan characteristic of the tissue. Moreover, FT activity did not remain at a low level like SST activity but increased from day 5 after defoliation when fructans began to accumulate. PS activity formed very few low- DP fructans and 1-kestose was the main product. Trisaccharides generated by PS activity represented 2–5% of the total trisaccharide synthesis. High-DP fructans were detectable only when the products of the reaction were concentrated 100 times. Results are discussed with respect to the relative contribution of FT and PS activities for the synthesis of 1-kestose and fructans in roots, stubble and leaves of Lolium perenne.

Barley yellow dwarf virus (BYDV) causes significant losses in yield and in overwintering ability of winter cereals. Mechanisms by which the physiology of plants is affected by the virus are not clear. To see how carbohydrates in the crown of winter cereals were affected by BYDV, fructan isomers of degree of polymerization (DP) 3–5, fructan DP>6 and the simple sugars, glucose, fructose and sucrose, were measured before and during cold hardening in three oat (Avena sativa L.) cultivars, ‘Wintok’, ‘Coast Black’ and ‘Fulghum’. On a fresh weight basis fructan DP>6 decreased by 50% in infected ‘Wintok’ and ‘Coast Black’ and by 25% in ‘Fulghum’. Two DP3, one DP4 and one DP5 isomer were significantly higher than non-infected controls. The percentages of simple sugars in infected crowns were significantly higher than controls in all three cultivars in every week except the first week of hardening. Crude enzyme extracts from BYDV infected plants incubated with sucrose suggested higher invertase and lower sucrose-sucrosyl transferase activity. When incubated with 1-kestose and neokestin, no significant difference was found in fructose fructosyl transferase or in hydrolase activity. The activity of unidentified enzymes catalysing the synthesis of larger (DP>5) fructan was altered by BYDV. The decrease of carbohydrates in the crown induced indirectly by BYDV may alter the plant's capacity to regenerate tillers in the spring. The ability of plants to prevent or tolerate carbohydrate fluctuations induced by BYDV infection may be an important genetically regulated characteristic for developing virus-resistant cultivars.

Wheat plants were grown at a day/night temperature of 18/13°C under glasshouse conditions. Twenty-two d after anthesis, one set of plants was shaded to 50% of the normal photon fluence rate, another was ‘degrained’ by selective spikelet removal which left only the grains in the five central spikelets; a further set was left as control. Individual plants were harvested at days 22, 30 or 42 after anthesis. Extracts from the peduncle and the penultimate internode were prepared to determine the activities of sucrose phosphate synthase, sucrose synthase, fructan exohydrolase and acid invertase, and to assess the concentration of hexose sugars, sucrose and fructans. Measurements were also made of ear and individual grain weights, and stem f. wt and d. wt. There was a decline in the amount of fructans with time, more pronounced in ‘shaded’ (source-limited) than in control plants. By contrast, in ‘degrained’ (sink-limited) plants, the amount of fructans in the stem initially rose, then decreased, with a concomitant increase in the amount of fructose. The shifts in sugar content of the wheat culm reflected both the sink demand of the ear and source activity. The activity of fructan exohydrolase correlated with the carbohydrate changes. Under limited photosynthate assimilation, the mobilization of fructans from the internodes towards the ear was related to an increase in this enzyme, whereas the other enzymes played a less direct role in the mobilization of fructan reserves from the wheat stem.

Fructans (polyfructosylsucrose) are synthesized by a number of plants and micro-organisms. Plant fructans are localized in the vacuole and have a low degree of polymerization (DP), whereas the fructans synthesized by micro-organisms are usually much bigger. There is an increasing interest in fructans for both food and non-food applications. In order to accumulate fructans of high DP in the plant vacuole, the levansucrase protein of Bacillus subtilis was fused to the vacuolar targeting sequence of sporamin and expressed in plants. Transgenic tobacco plants in which this fusion gene is expressed accumulate fructans to levels up to 21% of the d. wt. They showed a reduced translocation of carbohydrates, bleaching of the leaves, stunted growth and increased levels of hexoses and starch. The levansucrase protein was not translocated to the plant vacuole, but retained in the endomembrane system, even though the same targeting signal was able to translocate the E. coli GUS protein to the plant vacuole.

Dietary supplementation with oligofructose (OFS; 100 g/kg), a non-digestibleoligomer of β-D-fructose, decreases serum triacylglycerols in serum and VLDL of rats. In order to investigate the role of hepatic metabolism in the hypolipidaemic effect of OFS, male Wistar rats were fed on a standard diet with or without 1OOg Raftilose® P95/kg as OFS source for 30 d. OFS feeding (1) significantly decreased triacylglycerol and phospholipid concentrations in both blood and liver, (2) increased the glycerol-3-phosphate liver content but decreased the hepatic activity of glycerol-3-phosphate acyltransferase (EC 2.3.1.15), suggesting a decrease in acylglycerol synthesis, (3) did not affect the blood non-caterified fatty acid concentrations, but (4) reduced by 54% the capacity of isolated hepatocytesto synthesize and secrete triacylglycerols from labelled acetate; the activity of fatty acid synthase, a key lipogenic enzyme was also significantly decreased. These findings suggest that OFS decreases serum triacylglycerols by reducing de nova fatty acid synthesis in the liver; the lower insulin level in the serum of OFS-fed rats could explain, at least partly, the metabolic effect induced by such nondigestible carbohydrates.