A55 LACK OF EXPERIMENTAL REPRODUCIBILITY IN PRECLINICAL RESEARCH IS INFLUENCED BY THE NUTRITIONAL PROFILE OF STANDARD RODENT CHOWS

Abstract

Background: The National Institutes of Health and other scientific organizations have raised concern about the lack of reproducibility of animal experimental results between laboratories, particularly in studies investigating the microbiota. Factors such as environment, stress and sex have been identified as contributors, whereas dietary composition has received less attention. The prebiotic properties of dietary fermentable carbohydrates (FODMAPs) are known to have a profound influence on the microbiota, but the FODMAP content of standard animal diets is not known. The aim of this study was to A) analyze the FODMAP content of common rodent diets and B) assess the impact of different standard chows on microbiota profiles and correlate the findings with the FODMAP content of those diets. Methods: Standard rodent chows used in research institutions were selected for analysis. Following sugar extraction, samples were analyzed for excess fructose, lactose, sorbitol, mannitol, galacto-oligosaccharide (GOS) and fructan using high-performance liquid chromatography and enzymatic assays. The FODMAP content was compared to custom-made low and high FODMAP rodent chows designed to mimic human consumption. Forty C57BL/6 mice were randomized to 4 groups (5 male, 5 female per group). Group A were sacrificed at baseline. Group B received the breeding institution chow (LabDiet 5066, derived from corn and wheat). Standard rodent chows of different composition were fed to group C (ResearchDiets AIN93G, derived from corn starch) and group D (LabDiet 5001, derived from corn and soybean meal). After 3-weeks, cecal (main site of fermentation) contents were collected and analyzed by 16s rRNA gene sequencing, and their content of short-chain fatty acids (SCFAs) and branched-chain fatty acids (BCFAs) were measured per mg of cecal content. Results: The custom-made low and high FODMAP diets contained 0.51 and 4.10 g/100 g total FODMAP, respectively. When comparing the three lowest to the three highest standard chows, a significant difference in FODMAP content was observed (mean±SD: 0.89±0.57 vs 4.26±0.34; p<0.01, unpaired t-test, Fig 1). Gut microbiota composition was significantly different between groups and sexes, as reflected by significant different clusters in β-diversity analysis (Fig 2). Total SCFA levels were lower (p=0.03) and BCFA were higher (p=0.01) in group C receiving the diet derived from cornstarch compared to group B receiving the diet derived from corn and wheat. Conclusions: Whilst further studies are required to elucidate the specific dietary compositional factors driving change, these results suggest that disparate composition of the diet can not only significantly impact gut microbiota profiles and fermentation patterns, but may also emphasize sex differences in preclinical studies. This has major implications for the reproducibility of results across labs. [Figure presented] [Figure presented]