A systems-level analysis of bile acids effects on rat colon epithelial cells.

Bile acid diarrhoea is a chronic condition caused by increased delivery of bile acids to the colon. The underlying mechanisms remain to be elucidated. To investigate genes involved in bile acid diarrhoea, systems-level analyses were employed on a rat bile acid diarrhoea model. Twelve male Wistar Munich rats, housed in metabolic cages, were fed either control or bile acid-mixed (1% w/w) diets for ten days. Food intake, water intake, urine volume, bodyweight and faecal output were monitored daily. After euthanasia, colonic epithelial cells were isolated using calcium-chelation and processed for systems-level analyses, i.e. RNA-sequencing transcriptomics and mass spectrometry proteomics. Bile acid-fed rats suffered diarrhoea, indicated by increased drinking, faeces weight and faecal water content compared with control rats. Urine output was unchanged. With bile acid-feeding, RNA-sequencing revealed 204 increased and 401 decreased mRNAs; mass spectrometry 183 increased and 111 decreased proteins. Among the altered genes were genes associated with electrolyte and water transport (including Slc12a7, Clca4 and Aqp3) and genes associated with bile acid transport (Slc2b1, Abcg2, Slc51a, Slc51b and Fabps). Correlation analysis showed a significant positive correlation (Pearson's r=0.28) between changes in mRNA-expression and changes in protein-expression. However, caution must be exercised in making a direct correlation between experimentally determined transcriptomes and proteomes. Genes associated with bile acid transport responded to bile acid-feeding, suggesting that colonic bile acid transport also occur by regulated protein facilitated mechanisms in addition to passive diffusion. In summary, the study provides annotated rat colonic epithelial cell transcriptome and proteome with response to bile acid-feeding.