Lisa Sanders

The Effect of the Undigested Fraction of Maize Products on the Activity and Composition of the Microbiota Determined in a Dynamic in Vitro Model of the Human Proximal Large Intestine

Objective: To investigate the effect of 5 newly developed maize-based fibers on the activity and composition of the microbiota in the colon. The fibers tested were glucose-based and had variable structures, including 2 resistant starch preparations, soluble corn fiber, pullulan, and soluble fiber dextrin. Methods: The fibers were predigested, mono- and disaccharides were removed, and the residual polymer was used to assess the production of microbial metabolites and changes in composition of the microbiota using a dynamic, validated, in vitro model of the large intestine. Results: Microbial metabolite analysis showed an increase in short-chain fatty acids for all fibers, with varying levels of butyrate production for each fiber. The greatest increase of butyrate, both in terms of absolute amounts and as a proportion of total short-chain fatty acids, was observed for pullulan. All fibers also reduced toxic metabolites from protein fermentation compared to the poorly fermentable control (cellulose). Microbial composition was assessed using a micro-array platform. All fibers showed increases of bifidobacteria and some Lactobacillus species, although different species were stimulated by different fibers. Pullulan showed the largest increase of bifidobacteria. Conclusions: All fibers showed prebiotic activity in terms of increases in growth and/or activity of beneficial microbes. In addition, compared to the control, health-promoting metabolites were produced in higher amounts, while putrefactive metabolites were reduced for all fibers. The importance of the findings lies in the fact that the newly developed, maize-based fibers shift the intestinal environment to a healthier milieu, with increased health-promoting metabolites and health-beneficial microbes.

Effect of Novel Maize-based Dietary Fibers on Postprandial Glycemia and Insulinemia

Background: Postprandial hyperglycemia has been associated with increased oxidative stress and the development of diabetes, heart disease and all-cause mortality. Objective: To assess the effect of novel maize-based dietary fibers on postprandial glycemia and to assess the correlation between a rapid in vitro digestibility system and the blood glucose response. Methods: In a clinical study, 12 healthy volunteers were fed seven test beverages containing maize-based fiber ingredients (25g total carbohydrate) along with 2 control meals on separate occasions in random order. Capillary blood samples were obtained and the relative glycemic and insulinemic responses were assessed by calculating the incremental area under the 2 h blood response curves. In vitro digestibility studies of the test fibers and control were also undertaken to determine if these correlated with the clinical findings. Results: All test fibers resulted in significantly lower glycemic and insulinemic responses for the incremental area under the curve (iAUC) and at all time points compared with the control (P < 0.05). The in vitro digestibility curves were comparable to the cumulative in vivo iAUCs. In vitro data expressed as percent digestion correlated significantly with the in vivo iAUC for the first 30min of the test meal (P < 0.05). Conclusion: These novel maize-based dietary fibers all produce lower postprandial glycemic and insulinemic responses than the control. While further assessment is necessary in beverage and foods containing these fibers, they may be effective in applications for dietary strategies to control diabetes and other chronic diseases. In addition, the in vitro digestibility assay correlated well with in vivo data and may be useful in guiding product development.

Docosahexaenoic acid in plasma phosphatidylcholine may be a potential marker for in vivo phosphatidylethanolamine N-methyltransferase activity in humans

BACKGROUND Choline is an essential nutrient for humans, and part of this requirement is met by endogenous synthesis catalyzed by hepatic phosphatidylethanolamine N-methyltransferase (PEMT). PEMT activity is difficult to estimate in humans because it requires a liver biopsy. Previously, we showed that mice that lack functional PEMT have dramatically reduced concentrations of docosahexaenoic acid (DHA; 22:6n-3) in plasma and of liver phosphatidylcholine (PtdCho)-a phospholipid formed by PEMT. OBJECTIVE The objective was to evaluate plasma PtdCho-DHA concentrations as a noninvasive marker of liver PEMT activity in humans. DESIGN Plasma PtdCho-DHA concentrations were measured in 72 humans before and after they consumed a low-choline diet, and correlations were analyzed in relation to estrogen status, PEMT polymorphism rs12325817, the ratio of plasma S-adenosylmethionine (AdoMet) to S-adenosylhomocysteine (AdoHcy), and dietary choline intake; all of these factors are associated with changes in liver PEMT activity. PtdCho-DHA and PEMT activity were also measured in human liver specimens. RESULTS At baseline, the portion of PtdCho species containing DHA (pmol PtdCho-DHA/nmol PtdCho) was higher in premenopausal women than in men and postmenopausal women (P < 0.01). This ratio was lower in premenopausal women with the rs12325817 polymorphism in the PEMT gene (P < 0.05), and PtdCho-DHA concentration and PEMT activity were lower in human liver samples from women who were homozygous for PEMT rs12325817 (P < 0.05). The ratio of DHA-PtdCho to PtdCho in plasma was directly correlated with the ratio of AdoMet to AdoHcy (P = 0.0001). The portion of PtdCho species containing DHA in plasma was altered in subjects who consumed a low-choline diet. CONCLUSION PtdCho-DHA may be useful as a surrogate marker for in vivo hepatic PEMT activity in humans. This trial was registered at clinicaltrials.gov as NCT00065546.

Dietary Docosahexaenoic Acid Supplementation Modulates Hippocampal Development in the Pemt−/− Mouse

The development of fetal brain is influenced by nutrients such as docosahexaenoic acid (DHA, 22:6) and choline. Phosphatidylethanolamine-N-methyltransferase (PEMT) catalyzes the biosynthesis of phosphatidylcholine from phosphatidylethanolamine enriched in DHA and many humans have functional genetic polymorphisms in the PEMT gene. Previously, it was reported that Pemt−/− mice have altered hippocampal development. The present study explores whether abnormal phosphatidylcholine biosynthesis causes altered incorporation of DHA into membranes, thereby influencing brain development, and determines whether supplemental dietary DHA can reverse some of these changes. Pregnant C57BL/6 wild type (WT) and Pemt−/− mice were fed a control diet, or a diet supplemented with 3 g/kg of DHA, from gestational day 11 to 17. Brains from embryonic day 17 fetuses derived from Pemt−/− dams fed the control diet had 25–50% less phospholipid-DHA as compared with WT (p < 0.05). Also, they had 60% more neural progenitor cell proliferation (p < 0.05), 60% more neuronal apoptosis (p < 0.01), and 30% less calretinin expression (p < 0.05; a marker of neuronal differentiation) in the hippocampus compared with WT. The DHA-supplemented diet increased fetal brain Pemt−/− phospholipid-DHA to WT levels, and abrogated the neural progenitor cell proliferation and apoptosis differences. Although this diet did not change proliferation in the WT group, it halved the rate of apoptosis (p < 0.05). In both genotypes, the DHA-supplemented diet increased calretinin expression 2-fold (p < 0.05). These results suggest that the changes in hippocampal development in the Pemt−/− mouse could be mediated by altered DHA incorporation into membrane phospholipids, and that maternal dietary DHA can influence fetal brain development.

Beneficial effects of resistant starch on laxation in healthy adults

Objective This randomized, double-blind crossover trial evaluated the effects of a type 3 novel resistant starch (RS) versus wheat bran (WB) on faecal weight, frequency, and consistency in healthy adults. Methods Following a 14-day baseline period during which subjects (n=14) consumed low-fibre (<2 g) test products, participants were assigned to receive 25 g RS or WB fibre daily for 14 days, then crossed over to the opposite treatment after a 7-day washout. Results Daily faecal output increased from 128.8±68.7 g at baseline to 164.2±88.4 g with RS and 194.5±92.0 g with WB (both P<0.02 versus baseline). No significant differences among the three conditions were observed for bowel movement frequency. Faecal consistency ratings were increased with WB (P=0.001), but unchanged with RS. Conclusions Dietary RS and WB increase faecal output in healthy adults.

M2028 The use of a New Wireless Motility Device (SmartPill®) for Measurement of Gastrointestinal Transit Time After Dietary Fiber Intervention

G A A b st ra ct s tension recordings of KCland bethanechol-induced contractions in circular orientated myenteric strips. Intracellular calcium was determined by fluorescencemicroscopy in isolated smooth muscle cells loaded with fura-2-AM (ExWL 340/380nm, EmWL 510nm) and calcium changes were expressed as the ratio between elicited fluorescence at 340nm and 380nm (F340/380). Mitochondrial membrane potential was measured in isolated colonic smooth muscle cells using the cell-permeant green fluorescent dye rhodamine 123 Results: Aging caused an increase in caffeine-induced Ca2+ release (140 % respect to adult cells) and a decrease in mitochondrial membrane potential, as indicated by the reduction of the heterogeneity of the rhodamine123 fluorescence signal in isolated cells. When mitochondria function was impaired using rotenone (1 μM) plus oligomycin (5 μM) the amplitude of Ca2+ release was significantly reduced (by 45%) and the [Ca2+]i decay showed a slower rate in senescent cells. Melatonin treatment protected from the deleterious effects of these agents. These changes in Ca2+ homeostasis did not translate into alterations in contractility, since pretreatment of both proximal and distal circular myenteric strips with rotenone, oligomicin of both for 30 min did not modify significantly the contractile response to neither KCl (60 mM) nor bethanechol (100 μM). Conclusion: Mitochondria play a more important role in Ca2+ homeostasis in aged than adult cells, however these changes are not enough to modify contractility, which suggest that in colonic smooth muscle mitochondrial respiratory chain is not essencial for contraction and that more sources of ATP than ATP synthase coexist in these cells. Supported by BFU2007-60563 and JEX