Wiebke Schlörmann

Anticancer effects of vitamin E (tocopherols) have been studied extensively. While in vitro and animal studies showed promising results regarding anticancer effects of tocopherols, human intervention studies failed to reproduce these results. In vivo, α-tocopherol (α-TOH) is metabolized to the long-chain metabolites (LCM) 13′-hydroxychromanol (α-13′-OH) and 13′-carboxychromanol (α-13′-COOH), which likely reach the large intestine. The LCM showed antiproliferative effects in different colon cancer cell lines, but the exact mechanism of action remains unclear. To further clarify the chemopreventive action of the LCM, premalignant LT97 colon adenoma cells were treated with α-TOH, α-13′-OH and α-13′-COOH to study their impact on growth, apoptosis, antigenotoxicity, and ROS-scavenging capacity as well as expression of selected genes involved in detoxification and the cell cycle. Growth inhibitory potential was observed for α-13′-OH (IC₅₀: 37.4 μM) and α-13′-COOH (IC₅₀: 5.8 μM) but not for α-TOH in the tested concentrations. Levels of caspase-3 activity and expression of genes regulating the cell cycle and detoxification remained unchanged. However, α-TOH, α-13′-OH and α-13′-COOH exhibited antigenotoxic and partly ROS-scavenging capacity. The results indicate that the LCM exert chemopreventive effects via ROS-scavenging capacity, the protection against DNA damage and the induction of cell death via caspase-independent mechanisms in premalignant colon cells.

The aim of the present study was to examine whether reactive oxygen species (ROS) contribute to chemopreventive effects of fermentation supernatants (FS) of different dietary fibers (Synergy1^®, oat-, barley-, yeast β-glucan, Curdlan) and butyrate as a fermentation metabolite. LT97 and HT29 cells were treated with butyrate and FS alone or with N-acetyl-cysteine (NAC) and their impact on ROS formation, cell growth, and protein expression (Cyclin D2, p21, PARP, Bid, GPx2) was investigated. Butyrate and FS significantly decreased cell growth. ROS levels were significantly increased, particularly in LT97 cells, while co-treatment with NAC decreased ROS formation and growth inhibitory effects in both cell lines. After treatment with butyrate and FS, Cyclin D2 expression was reduced in LT97 cells and p21 expression was increased in both cell lines. Levels of full-length PARP and Bid were decreased, while levels of cleaved PARP were enhanced. GPx2 expression was significantly reduced by fiber FS in HT29 cells. A notable effect of NAC on butyrate- and FS-modulated protein expression was observed exclusively for PARP and Bid in HT29 cells. From the present results, a contribution of ROS to growth inhibitory and apoptotic effects of butyrate and FS on LT97 and HT29 cells cannot be excluded.

The aim of the present study was to examine β-glucan production and the potential prebiotic and chemopreventive effects of wheat and rye sourdoughs and breads generated with wild-type and non-β-glucan-forming isogenic mutant strains of Levilactobacillus brevis and Pediococcus claussenii. Sourdough and bread samples were subjected to in vitro digestion and fermentation. Fermentation supernatants (FS) and pellets (FP) were analyzed (pH values, short-chain fatty acids (SCFA), ammonia, bacterial taxa) and the effects of FS on LT97 colon adenoma cell growth, viability, caspase-2 and -3 activity, genotoxic and antigenotoxic effects and on gene and protein expression of p21, cyclin D2, catalase and superoxide dismutase 2 (SOD2) were examined. Concentrations of SCFA were increased and concentrations of ammonia were partly reduced in the FS. The relative abundance of Bifidobacteriaceae was increased in all FPs. Treatment with FS reduced the growth and viability of LT97 cells and significantly increased caspase-2 and -3 activities without exhibiting genotoxic or antigenotoxic effects. The p21 mRNA and protein levels were increased while that of cyclin D2 was reduced. Catalase and SOD2 mRNA and protein expression were marginally induced. The presented results indicate a comparable chemopreventive potential of wheat and rye sourdoughs and breads without an additional effect of the formed β-glucan.

Olive oil contains high amounts of oleic acid (OA). Although OA has been described to inhibit inflammatory processes, the effects of olive oil on cellular mechanisms remain poorly understood. Therefore, we compared the effects of major fatty acids (FA) from olive oil with those of olive oil extracts (OOE) on inflammatory mediators and alterations in the cellular phospholipid composition in murine macrophages. Upon treatment with different OOE, FA compositions of lipopolysaccharide (LPS)-stimulated murine RAW264.7 macrophages were analyzed using gas chromatography. Olive oil extracts and OA significantly reduced the LPS-induced expression of inducible nitric oxide synthase (iNos), cyclooxygenase (Cox2), and interleukin-6 mRNA. In addition, a significant decrease in Cox2 and iNos protein expression was observed. The formation of nitric oxide was significantly reduced, while the formation of prostaglandin (PG) E₂ from arachidonic acid significantly increased after treatment with OOE or OA. The latter was associated with a shift in the phospholipid FA composition from arachidonic acid to OA, resulting in an elevated availability of arachidonic acid. Together, OOE and OA mediate anti-inflammatory effects in vitro but increase the release of arachidonic acid and hereinafter PGE₂, likely due to elongation of OA and competitive incorporation of fatty acids into membrane phospholipids.

β-glucans from the lactic acid bacteria L. brevis and P. claussenii as well as β-glucans from oat, barley, yeast, and curdlan were analyzed regarding their cholesterol-binding capacity, fermentation profile, and chemopreventive potential.

The unique dietary fiber composition with high contents of β-glucan contributes to the health-promoting properties of oat and barley and may mediate a reduction of colon cancer risk. In the present study, chemopreventive effects of oat and barley (beta^®barley) kernels were investigated. In order to address the impact of thermal processing on these effects, kernels were roasted (150–180 °C, approx. 20 min), digested and fermented using an In Vitro human digestion model. Concentrations of short-chain fatty acids (SCFA) and ammonia were determined in fermentation supernatants (FS). Growth inhibition, apoptosis, DNA integrity and gene expression of catalase were analyzed in LT97 colon adenoma cells. Concentrations of SCFA, particularly butyrate, were higher in oat/barley FS (2.2-fold, on average), while ammonia levels were significantly lower (0.7-fold, on average) than in the fermentation control. Treatment of LT97 cells with FS of oat/barley kernels led to a significant time- and dose-dependent growth reduction, a significant increase in caspase-3 activity and enhanced levels of catalase mRNA, without exhibiting genotoxic effects. In general, the results indicate a chemopreventive potential of In Vitro fermented oat and waxy winter barley mediated mainly by growth inhibitory and apoptotic effects, which are preserved after thermal processing.

The chemopreventive effects of β-glucan-rich cereals such as oat and barley (beta®barley) have been examined previously, but studies comparing fermentation characteristics and chemopreventive effects of oat and barley of different processing stages are rare. Therefore, the present study aims at investigating the fermentation end points (pH values, concentrations of short-chain fatty acids (SCFA) and ammonia) in fermentation supernatants (FS) obtained from differently processed oat and barley samples (kernels, thick and thin flakes). Chemopreventive effects of FS, such as growth inhibition, apoptosis, and induction of cell cycle- and redox-relevant genes (p21, SOD2), were analysed in LT97 colon adenoma cells. After fermentation, pH values were reduced (∆ pH − 1.3, on average) and SCFA concentrations were increased (∆ + 59 mmol/L, on average) with a shift towards butyrate formation in FS obtained from oat and barley samples compared to the fermentation negative control (FS blank). Ammonia was reduced more effectively in FS obtained from barley (∆ − 4.6 mmol/L, on average) than from oat samples (∆ − 1.0 mmol/L, on average). Treatment of LT97 cells with FS resulted in a time- and dose-dependent reduction of cell number, an increase in caspase-3 activity (up to 9.0-fold after 24 h, on average) and an induction of p21 (2.1-fold, on average) and SOD2 (2.3-fold, on average) mRNA expression, while no genotoxic effects were observed. In general, the results indicate no concrete effect of the type of cereal or processing stage on fermentation and chemopreventive effects of oat and barley.

The aim of the present study was to analyse chemopreventive effects of oat flakes under consideration of processing. Thin and thick flakes were roasted and subjected to an in vitro digestion and fermentation. Fermentation supernatants (FS) were characterised and chemopreventive effects were analysed in LT97 colon adenoma cells. Compared to the fermentation control, pH values were decreased (from pH 6.3 to pH 5.0) and concentrations of SCFA, in particular butyrate, were increased in oat FS (2.6-fold, on average). Ammonia levels were not altered. Oat FS significantly decreased cell growth time- and dose-dependently. Caspase 3 activity was significantly increased (9.7-fold, on average). Oat FS slightly increased the mRNA expression of CAT (2.0-fold), SOD2 (1.7-fold) and GSTP1 (2.8-fold), on average, while GPX1 mRNA (0.3-fold) was decreased. The results indicate a chemopreventive potential of in vitro digested oat flakes regarding colon cancer development mediated mostly by growth inhibition and apoptosis, unaffected by roasting.

Due to their unique dietary fibre composition, in particular β-glucan, the consumption of barley may contribute to a healthy diet and the prevention of colon cancer. The aim of the present study was to analyse chemopreventive effects of barley flakes obtained from a β-glucan-rich barley cultivar. In order to address the impact of heat treatment on potential chemopreventive effects, barley flakes were roasted (160 °C–180 °C, approx. 20 min). The flakes were subjected to in vitro digestion and fermentation. Fermentation supernatants (FS) were analysed for the concentrations of short-chain fatty acids (SCFA) and ammonia. Chemopreventive endpoints (growth inhibition, apoptosis, DNA integrity, gene expression of detoxifying enzymes) were analysed in LT97 colon adenoma cells. Concentrations of SCFA were increased in barley FS (2.5-fold, on average) with a shift of molar ratios towards butyrate production, while ammonia levels were significantly decreased (0.7-fold, on average) compared to the fermentation control. The growth of LT97 cells was significantly reduced by barley FS in a time- and dose-dependent manner, and caspase-3 activity of treated cells was significantly enhanced (up to 6.3-fold, on average). On average, treatment of cells resulted in increased mRNA levels of CAT (2.1-fold), SOD2 (2.2-fold) and GSTP1 (3.9-fold), while expression of GPx1 (0.3-fold) was significantly decreased in some cases. The roasting process did not cause genotoxic effects of barley FS and had no impact on chemopreventive properties. Our results indicate chemopreventive potential of in vitro fermented waxy winter barley, mediated primarily by growth inhibitory and apoptotic effects, which is largely unaffected by roasting.