Novel findings on the metabolic effects of the low glycaemic carbohydrate isomaltulose (Palatinose™)

The slow digestible disaccharide isomaltulose (iso; Palatinose™) is available as novel functional carbohydrate ingredient for manufacturing of low glycaemic foods and beverages. Although basically characterised, various information on physiological effects of iso are still lacking. Thus, the objective of the present study was to expand scientific knowledge of physiological characteristics of iso by a set of three human intervention trials. Using an ileostomy model, iso was found to be essentially absorbed, irrespective of the nature of food (beverage and solid food). Apparent digestibility of 50 g iso from two different meals was 95·5 and 98·8 %; apparent absorption was 93·6 and 96·1 %, respectively. In healthy volunteers, a single dose intake of iso resulted in lower postprandial blood glucose and insulin responses than did sucrose (suc), while showing prolonged blood glucose delivery over 3 h test. In a 4-week trial with hyperlipidaemic individuals, regular consumption of 50 g/d iso within a Western-type diet was well tolerated and did not affect blood lipids. Fasting blood glucose and insulin resistance were lower after the 4-week iso intervention compared with baseline. This would be consistent with possible beneficial metabolic effects as a consequence of the lower and prolonged glycaemic response and lower insulinaemic burden. However, there was no significant difference at 4 weeks after iso compared with suc. In conclusion, the study shows that iso is completely available from the small intestine, irrespective of food matrix, leading to a prolonged delivery of blood glucose. Regular iso consumption is well tolerated also in subjects with increased risk for vascular diseases

Enhancement of butyrate induced apoptosis in colorectal carcinoma cells by aspirin and tumour necrosis factor alpha

Epidemiologische Studien weisen auf einen protektiven Einfluß einer ballaststoffreichen Ernährung gegenüber der Entstehung eines kolorektalen Karzinoms hin. Die kurzkettige Fettsäure Butyrat ist ein wichtiges Produkt bakterieller Fermentation von Ballaststoffen bzw. von unverdaubaren Kohlenhydraten im Kolon. Butyrat hat paradoxe Effekte auf Epithelzellen des Kolons: Haupternergieträger und Wachstumsstimulator normaler Mukosa einerseits, Proliferationshemmer und Apoptoseinduktor kolorektaler Karzinomzellen in vitro andererseits. Auch für NSAID wie Aspirin belegen epidemiologische Studien einen chemoprotektiven Effekt gegenüber dem Kolonkarzinom. Für das Zytokin TNFalpha werden einerseits apoptoseinduzierende Effekte für kolorektale Karzinomzellen in vitro beschrieben, jedoch gelten einige Kolonkarzinomzellinien als resistent gegen TNFalpha. Andererseits besitzt TNFalpha auch proinflammatorische und antiapoptotische Wirkung über Aktivierung des nukleären Faktors kappa B (NF-kappaB). In der vorliegenden Arbeit wurden die Einflüsse sowohl von Aspirin als auch von TNFalpha auf die durch Butyrat induzierte Apoptose an humanen kolorektalen Karzinomzellinien untersucht. Zu diesem Zweck wurde ein durchflußzytometrischer Annexin V – Propidiumjodid – Assay etabliert. Mit Hilfe dieses Assays konnte gezeigt werden, daß der Apoptose induzierende Effekt sich sowohl durch eine Kombination mit Aspirin als auch durch eine Kombination mit TNFalpha im Sinne einer additiven Wirkung steigern läßt. Der Einfluß von Butyrat auf die antiapoptotische Wirkung von TNFalpha über Modulation von NF-kappaB wurde in einem Electophoretic Mobility Shift Assay (EMSA) untersucht. Die Verstärkung der Butyrat-induzierten Apoptose durch eine Kombination mit TNFalpha ist mit einer Hemmung der TNFalpha induzierten Aktivierung von NF-kappaB assoziiert. In einem RNase Protection Assay war auf mRNA-Ebene keine Beeinflussung der NF-kappaB abhängigen antiapoptotischer Faktoren (TRAF-1 und -2, c-IAP1 und 2 und XIAP) durch Butyrat nachweisbar. Die Verstärkung der Apoptose durch TNFalpha zeigt, daß Butyrat in seiner protektiven Wirkung in der Lage ist, neben einer direkten Beeinflussung der Kolonozyten auch auf körpereigene Signalwege zu wirken. Die Untersuchungen dieser Arbeit leisten einen Beitrag zur weiteren Klärung der molekularen Grundlagen der Butyratwirkung auf Kolonepithelzellen. Evtl. besteht in Zukunft die Möglichkeit, Butyrat als adjuvantes Therapeutikum bei Prävention und Therapie kolorektaler Karzinome zu verwenden.Epidemiological studies suggest a protective effect of a high fibre enriched diet against the development of colorectal cancer. The short chain fatty acid butyrate is an important product of bacterial fermentation of fibres, respectively of undigested carbohydrates within the colon. Butyrate has paradoxical effects on colonic epithelial cells: main energy source and growth stimulus for normal mucosa on the one hand, inhibition of proliferation induction of apoptosis of colorectal carcinoma cells in vitro on the other hand. Also for NSAID like aspirin by epidemiological studies there is body of evidence for a chemo protective effect against colon cancer. For the cytokine TNFalpha apoptosis inducing effects on colorectal carcinoma cells in vitro are also described, but some colorectal carcinoma cell lines are considered to be reisstent to TNFalpha induced apoptosis. Furthermore, TNFalpha also has pro-inflammatory and anti-apoptotic properties by activating the nuclear factor kappa B. Aim of this work was to investigate the effects of aspirin and TNFalpha on the butyrate induced apoptosis in human colorectal carcinoma cell lines. For this reason a flow cytometric annexin V – propidium iodine – assay was established. It was possible to show by this assay that the apoptosis inducing effect of butyrate was enhanced to an additive effect by combining as well with aspirin as well as with TNFalpha. To further investigate whether butyrate influences the anti-apoptotic effect of TNFalpha by modulating NF-kappaB, an electrophoretic mobility shift assay (EMSA) was performed. The enhancement of butyrate induced apoptosis by combination with TNFalpha is associated with an inhibition of TNFalpha induced NF-kappaB activation. A RNase protection assay did show no influence of on the mRNA expression of NF-kappaB dependent factors (TRAF-1 and -2, c-IAP1 and 2, and XIAP). The enhancement of TNFalpha induced apoptosis demonstrates that the protective effects of butyrate not only are a result of direct influencing colonocytes but also by modulating signal cascades within the body. The results of this study support understanding the molecular effects of butyrate on colorectal epithelial cells. Maybe, in future there will be possibilities to use butyrate as an adjuvant therapeutic agent by prevention and therapy of colorectal carcinomas

Wnt/β-catenin signaling regulates CXCR4 expression and [68^{68}Ga] Pentixafor internalization in neuroendocrine tumor cells

Loss of Somatostatin Receptor 2 (SSTR2) expression and rising CXC Chemokine Receptor Type 4 (CXCR4) expression are associated with dedifferentiation in neuroendocrine tumors (NET). In NET, CXCR4 expression is associated with enhanced metastatic and invasive potential and worse prognosis but might be a theragnostic target. Likewise, activation of Wnt/β-catenin signaling may promote a more aggressive phenotype in NET. We hypothesized an interaction of the Wnt/β-catenin pathway with CXCR4 expression and function in NET. The NET cell lines BON-1, QGP-1, and MS-18 were exposed to Wnt inhibitors (5-aza-CdR, quercetin, and niclosamide) or the Wnt activator LiCl. The expressions of Wnt pathway genes and of CXCR4 were studied by qRT-PCR, Western blot, and immunohistochemistry. The effects of Wnt modulators on uptake of the CXCR4 ligand [$^{68}$Ga] Pentixafor were measured. The Wnt activator LiCl induced upregulation of CXCR4 and Wnt target gene expression. Treatment with the Wnt inhibitors had opposite effects. LiCl significantly increased [$^{68}$Ga] Pentixafor uptake, while treatment with Wnt inhibitors decreased radiopeptide uptake. Wnt pathway modulation influences CXCR4 expression and function in NET cell lines. Wnt modulation might be a tool to enhance the efficacy of CXCR4-directed therapies in NET or to inhibit CXCR4-dependent proliferative signaling. The underlying mechanisms for the interaction of the Wnt pathway with CXCR4 expression and function have yet to be clarified

Imaging of chemokine receptor 4 expression in neuroendocrine tumors: a triple tracer comparative approach

C-X-C motif chemokine receptor 4 (CXCR4) and somatostatin receptors (SSTR) are overexpressed in gastro-entero-pancreatic neuroendocrine tumors (GEP-NET). In this study, we aimed to elucidate the feasibility of non-invasive CXCR4 positron emission tomography/computed tomography (PET/CT) imaging in GEP-NET patients using [$^{68}$Ga]Pentixafor in comparison to $^{68}$Ga-DOTA-D-Phe-Tyr3-octreotide ([$^{68}$Ga]DOTATOC) and $^{18}$F-fluorodeoxyglucose ([$^{18}$F]FDG). Twelve patients with histologically proven GEP-NET (3xG1, 4xG2, 5xG3) underwent [$^{68}$Ga]DOTATOC, [$^{18}$F]FDG, and [$^{68}$Ga]Pentixafor PET/CT for staging and planning of the therapeutic management. Scans were analyzed on a patient as well as on a lesion basis and compared to immunohistochemical staining patterns of CXCR4 and somatostatin receptors SSTR2a and SSTR5. [$^{68}$Ga]Pentixafor visualized tumor lesions in 6/12 subjects, whereas [$^{18}$F]FDG revealed sites of disease in 10/12 and [$^{68}$Ga]DOTATOC in 11/12 patients, respectively. Regarding sensitivity, SSTR-directed PET was the superior imaging modality in all G1 and G2 NET. CXCR4-directed PET was negative in all G1 NET. In contrast, 50% of G2 and 80% of G3 patients exhibited [$^{68}$Ga]Pentixafor-positive tumor lesions. Whereas CXCR4 seems to play only a limited role in detecting well-differentiated NET, increasing receptor expression could be non-invasively observed with increasing tumor grade. Thus, [$^{68}$Ga]Pentixafor PET/CT might serve as non-invasive read-out for evaluating the possibility of CXCR4-directed endoradiotherapy in advanced dedifferentiated SSTR-negative tumors