Leibniz-Institut für Lebensmittel-Systembiologie
an der Technischen Universität München

Programmbereich IIIWorking Group III

Working Group III. Physiology – Chemoreception of food ingredients

Head: Dr. Dietmar Krautwurst, Associate Professor

Research:

We aim to clarify the interaction of food ingredients with cellular target molecules (i.e. receptors, ion channels), and their potential role as bioactives. One focus is on the clarification of the molecular mechanisms of odorant coding at the receptor level, that is the specific interaction of key food odorants or their mixtures with the 390 human odorant receptors (or other bio-molecules, such as ion channels). We further investigate physiological effects of food ingredients and their metabolites on cells of the immune system, as well as on cells of the gastrointestinal tract.

Identification and Characterisation of odorant receptors specific for key food odorants

The detection of volatiles is thought to be achieved predominantly by the large family of odorant receptors, in humans encoded by ca. 390 genes. In food, there are several hundreds of known volatiles present at concentrations above their odour threshold, termed 'key food odorants', which significantly determine the aroma of food. As biologically relevant odorants, the key food odorants are among the best activators of our odorant receptors. Screening key food odorants, or food-relevant odorant recombinates, versus 390 human odorant receptors expressed in human cell systems, we identify specific and functional odorant-receptor pairs. The knowledge of cognate odorant-receptor combinations is a prerequisite for the development of antagonists for malodours, and will help to clarify the mechanisms of specific anosmias for certain odorants, as well. Moreover, the clarification of structure-activity relations of key food odorants, and structure-function relations of their receptors will lead to an understanding of the molecular mechanisms of odorant coding.

Odorant receptors are expressed in a variety of non-olfactory tissues and organs. Here, they might have adopted new chemosensory tasks. Beyond, key food odorants can directly activate or inhibit ion channels (e.g. TRP channels), which are expressed in the nose, as well as in many other tissues and organs.

Today, consumers appreciate a healthy and balanced nutrition almost as much as a pleasant sensory aspect of food. Thus, we investigate the physiological effects of food ingredients on cells of the gastrointestinal tract, and cells of the immune system.

Physiological effects of food ingredients on cells of the gastrointestinal tract

On their passage through the gastrointestinal tract, food ingredients may trigger a cellular activity. Knowledge of the interaction of food ingredients with specific molecular targets on gastrointestinal cells is a prerequisite for an understanding of putative constitutional or unhealthy effects. For our research, we use cell-based screening methods to elucidate the effects of single food ingredients on functional parameters, such as gastric acid secretion, and cell physiological parameters such as signal transduction and gene regulation.

Physiological effects of food ingredients and their metabolites on the cellular immune system

Food ingredients, via the gastrointestinal tract, enter the blood stream. Here, they may exert effects on the cellular immune system. We aim to identify and quantify physiologically active food ingredients and their metabolites. The latter may not exert the same physiological functions as their lead compound. For both, lead food ingredients and metabolites, we thus aim to clarify their structure-activity relations, as well as the structure-function relations of the molecular target structures on the cells, (i.e. chemoreceptors, TRP channels). A single substance, however, has to be seen in the context of a complex effector system of food ingredients (e.g. coffee, tea, wine). We thus aim to clarify the cell physiological effects of simple binary mixtures, as well as more complex mixtures, of food ingredients. For our research, we use flow cytometrie and other cell-based methods on isolated blood leukocyte types to elucidate the effects of single food ingredients on functional parameters, such as chemotaxis, cytokine and antibody secretion, and cell physiological parameters such as signal transduction and gene regulation. Human intervention studies will help the interpretation of the results obtained in the in-vitro experiments with single food ingredients and complex food compounds.

Methods

Standard methods in molecular biology, molecular & cellular physiology and chemoreception. Genetically engineered cell lines, primary cell culture, RT-qPCR, siRNA knock-down, in-situ hybridization, immunocytochemistry, confocal fluorescence microscopy, flow cytometry, single-cell Ca2+ imaging, chemotaxis, bioluminescence, and impedance measurements, human sensory tests, and analytical chemistry (HPLC-DAD, -UV, NMR-, LC- and GC-MS/MS).