Forsøksdyr: Effect of orally delivered LPS on low-grade inflammation using NF-kB transgenic reporter mice

Godkjenningsdato 15.06.2018

Systemic low-grade inflammation is associated with a wide range of diseases, including atherosclerosis, type 2 diabetes and non-alcoholic fatty liver disease. Bacterial endotoxins, such as LPS induce inflammation, and is abundant in the human gut, and in certain foodstuffs. LPS has until recently mainly been associated with sepsis, but, lately LPS at low doses is associated development of metabolic disorders; a state called metabolic endotoxemia.
The transcription factor NF-kB promotes immunity by controlling expression of genes involved in inflammation. NF-kB is activated by a number of stressful stimuli, including LPS, which signals through Toll like receptor 4. Elevated NF-kB activity is associated with metabolic syndrome.
The largest quantities of LPS-producing bacteria are found in the large intestine. However, others have shown that most of the LPS reach the blood circulation via uptake from the small intestine.
The importance of endotoxins from food, and of gut-derived endotoxins in combination with foods is of growing interest. Intake of high-fat meals is shown to increase postprandial inflammation, most likely due to increased LPS leakage from gut. Secondly, various experiments suggest that certain foodstuffs are rich in LPS, which potentially could lead to increased LPS in blood and development of low grade inflammation per se. Processing and handling of the food items may also impact the levels of LPS in the food.
Our main aim is to establish whether LPS given orally at physiologically relevant doses are sufficient to trigger a systemic inflammatory response relevant for disease development, and further to investigate how different diets can affect the influence of orally derived LPS. We have previously developed a sensitive transgenic reporter model for NF-kB activation, which can be assessed by in vivo imaging. Hence, in our studies the NF-kB reporter mice will be a central tool. In addition, we will sample blood and assess cytokines and LPS. Furthermore, mice and food will be weighed regularly. At the end of the experiment, blood from heart will be collected from anesthetized mice, and mice will be euthanized followed by dissection of selected organs for further analyses.
Our first aim is to assess oral delivery of LPS and activation of NF-kB, and how it corresponds with the levels of LPS found in blood and other markers of low grade inflammation. Our second aim is to investigate the inflammatory response of LPS given in different food matrices, and how long term oral intake affects development of metabolic endotoxemia.
Number of animals applied for is 245.
These experiments can not be easily modelled or mimicked by in vitro studies. We do not expect that animals will experience pain or significant degree of discomfort. Nevertheless, animals are closely monitored on a daily basis to minimize discomfort. Number of animals in this study is calculated on the basis of power-analysis, literature searches and own experience. The animals are housed in individually ventilated cages, with controlled temperature, light regulation and humidity. Cages also contain running wheels, house and nesting material. The animals are looked after every day.