Laura M'Rabet

Inflammatory Disease Processes and Interactions with Nutrition

Inflammation is a stereotypical physiological response to infections and tissue injury; it initiates pathogen killing as well as tissue repair processes and helps to restore homeostasis at infected or damaged sites. Acute inflammatory reactions are usually self-limiting and resolve rapidly, due to the involvement of negative feedback mechanisms. Thus, regulated inflammatory responses are essential to remain healthy and maintain homeostasis. However, inflammatory responses that fail to regulate themselves can become chronic and contribute to the perpetuation and progression of disease. Characteristics typical of chronic inflammatory responses underlying the pathophysiology of several disorders include loss of barrier function, responsiveness to a normally benign stimulus, infiltration of inflammatory cells into compartments where they are not normally found in such high numbers, and overproduction of oxidants, cytokines, chemokines, eicosanoids and matrix metalloproteinases. The levels of these mediators amplify the inflammatory response, are destructive and contribute to the clinical symptoms. Various dietary components including long chain omega-3 fatty acids, antioxidant vitamins, plant flavonoids, prebiotics and probiotics have the potential to modulate predisposition to chronic inflammatory conditions and may have a role in their therapy. These components act through a variety of mechanisms including decreasing inflammatory mediator production through effects on cell signaling and gene expression (omega-3 fatty acids, vitamin E, plant flavonoids), reducing the production of damaging oxidants (vitamin E and other antioxidants), and promoting gut barrier function and anti-inflammatory responses (prebiotics and probiotics). However, in general really strong evidence of benefit to human health through anti-inflammatory actions is lacking for most of these dietary components. Thus, further studies addressing efficacy in humans linked to studies providing greater understanding of the mechanisms of action involved are required.

A specific mixture of short-chain galacto-oligosaccharides and long-chain fructo-oligosaccharides induces a beneficial immunoglobulin profile in infants at high risk for allergy

Background:  It has been suggested that human breast milk oligosaccharides play a role in the development of the immune system in infants, and may consequently inhibit the onset of allergy. A specific prebiotic mixture of short‐chain galacto‐oligosaccharides and long‐chain fructo‐oligosaccharides (GOS/FOS) has been shown to reduce the incidence of atopic dermatitis (AD) at 6 months of age in infants at risk for allergy.

Dietary supplementation of neutral and acidic oligosaccharides enhances Th1-dependent vaccination responses in mice

Immunomodulatory effects of oligosaccharide preparations that resemble chemical and functional aspects of human milk oligosaccharides (HMOS) were studied for the development of new concepts in infant nutrition. A dose range of 1–5% (w/w) dietary pectin‐derived acidic oligosaccharides (AOS) was tested in a murine influenza vaccination model. In addition, combinations of AOS and a 9:1 mixture of galacto‐oligosaccharides and long‐chain fructo‐oligosaccharides (GOS/FOS) were tested at a fixed total dietary dose of 2% (w/w). It was found that AOS significantly enhanced vaccine‐specific delayed‐type hypersensitivity (DTH) responses in a dose‐dependent manner. This was accompanied by a reduction in T‐helper2 (Th2) cytokine production by splenocytes in vitro. Overall, this indicates that the systemic immune response to the vaccine was Th1‐skewed by the dietary intervention. Combinations of GOS/FOS and AOS were more effective in enhancing DTH responses than either of the oligosaccharides alone, suggesting interaction effects between these agents. Similar to effects in infants, supplementation of the murine diets with GOS/FOS and combinations of GOS/FOS and AOS for 6‐wk enhanced the proportion of fecal bifidobacteria and lactobacilli, but AOS alone did not. In conclusion, these data indicate that GOS/FOS and AOS enhance systemic Th1‐dependent immune responses in a murine vaccination model. As Th1‐responses are weak in early life in humans, this might suggest that application of these oligosaccharides in infant formulas will be beneficial for the development of the infants immune system.

In search of a function for the Ras-like GTPase Rap1

Rap1 (Krev‐1) is a small GTPase first identified as a transformation suppressor of K‐ras. This GTPase is very similar to Ras, particularly in the effector region, but its function is still elusive. Recent progress in the search for Rap1 function has come from the development of a novel assay to measure Rap1 activation. Using this assay activation of Rap1 was observed in human platelets and neutrophils after stimulation with various agonists. We speculate that Rap1 plays a role in one of the specialised functions of these cells.

Differential fMet-Leu-Phe- and Platelet-activating Factor-induced Signaling Toward Ral Activation in Primary Human Neutrophils

We have measured the activation of the small GTPase Ral in human neutrophils after stimulation with fMet-Leu-Phe (fMLP), platelet activating factor (PAF), and granulocyte macrophage-colony stimulating factor and compared it with the activation of two other small GTPases, Ras and Rap1. We found that fMLP and PAF, but not granulocyte macrophage-colony stimulating factor, induce Ral activation. All three stimuli induce the activation of both Ras and Rap1. Utilizing specific inhibitors we demonstrate that fMLP-induced Ral activation is mediated by pertussis toxin-sensitive G-proteins and partially by Src-like kinases, whereas fMLP-induced Ras activation is independent of Src-like kinases. PAF-induced Ral activation is mediated by pertussis toxin-insensitive proteins, Src-like kinases and phosphatidylinositol 3-kinase. Phosphatidylinositol 3-kinase is not involved in PAF-induced Ras activation. The calcium ionophore ionomycin activates Ral, but calcium depletion partially inhibits fMLP- and PAF-induced Ral activation, whereas Ras activation was not affected. In addition, 12-O-tetradecanoylphorbol-13-acetate-induced activation of Ral is completely abolished by inhibitors of protein kinase C, whereas 12-O-tetradecanoylphorbol-13-acetate-induced Ras activation is largely insensitive. We conclude that in neutrophils Ral activation is mediated by multiple pathways, and that fMLP and PAF induce Ral activation differently.

Specific prebiotic oligosaccharides modulate the early phase of a murine vaccination response

The immune-modulatory effect of specific prebiotic oligosaccharides was shown in previous preclinical and clinical studies. To enhance the understanding of this effect, kinetic aspects of immune modulation and the correlation between microbiological and immunological parameters were investigated in a murine vaccination model. C57BL/6 mice were supplemented with short-chain galactooligosaccharides and long-chain fructooligosaccharides (ratio 9:1; Immunofortis()) in combination with pectin-derived acidic oligosaccharides. The timing of supplementation was varied around the primary (day 0) and secondary (day 21) vaccinations. Supplementation before the primary vaccination was necessary to increase delayed-type hypersensitivity responses (DTH) significantly at day 30. Supplementation after day 8 did not affect the DTH response at day 30, indicating that immune modulation occurred during the early phase. Therefore, correlation analysis of microbiological and immunological parameters was performed in a shortened experiment to focus on the early phase. At day 9 post-priming, the percentages of cecal lactobacilli were correlated to the DTH responses (p=0.01). Furthermore, the results suggested that yet unidentified factors may play a role. Additional analysis of intestinal Peyers patch major lymphocyte populations did not show effects of supplementation. In conclusion, a specific oligosaccharide mixture was shown to exert its immune-modulatory effect during the early phase of a murine immune response. The results are consistent with a role of the microbiota and possibly other factors in oligosaccharide-induced immune modulation. Furthermore, the results demonstrate that it is critical to consider kinetic aspects of immune-modulatory and prebiotic effects in order to study their interaction in a meaningful way.

Nutrition and inflammatory processes

P. C. Calder, R. Albers, J.-M. Antoine, S. Blum, R. Bourdet-Sicard, G. A. Ferns, G. Folkerts, P. S. Friedmann, G. S. Frost, F. Guarner, M. Lovik, S. Macfarlane, P. D. Meyer, L. M’Rabet, M. Serafini, W. van Eden, J. van Loo, W. vas Dias, S. Vidry, B. M. Winklhofer-Roob and J. Zhao School of Medicine, University of Southampton, Southampton SO16 7PX, UK, Unilever Health Institute, 3130 AC, Vlaardingen, The Netherlands, Danone Vitapole, Palaiseau 91767, France, Nestle Research Centre, Lausanne 26, Switzerland, School of Biomedical & Molecular Sciences, University of Surrey, Guildford GU2 7XH, UK, Department of Pharmacology & Pathophysiology, University of Utrecht, 3508 TB, Utrecht, The Netherlands, Digestive System Research Unit, Hospital General Vall d’Hebron, 08035 Barcelona, Spain, Division of Environmental Medicine, Norwegian Institute of Public Health, Nydalen, 0403 Oslo, Norway, Division of Pathology and Neuroscience, Dundee University, Dundee DD1 9SY, UK, Sensus, 4804 RA, Roosendall, The Netherlands, Numico-Research, 6700 CA, Wageningen, The Netherlands, Unit of Human Nutrition, National Institute for Nutrition, 00178 Roma, Italy, Faculty of Veterinary Medicine, University of Utrecht, 5384 CL, Utrecht, The Netherlands, Raffinerie Tirlemontoise Orafti, 3300 Tienen, Belgium, Seven Seas Ltd, Marfleet, Hull HU9 5NJ, UK, ILSI Europe, 1200 Brussels, Belgium, Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria and Yakult Europe, 1332 EN, Almere, The Netherlands