title: Nonlinear transcriptomic response to dietary fat intake in the small intestine of C57BL/6J mice.
abstract: BACKGROUND
  A high caloric diet, in conjunction with low levels of physical activity, promotes obesity. Many studies are available regarding the relation between dietary saturated fats and the etiology of obesity, but most focus on liver, muscle and white adipose tissue. Furthermore, the majority of transcriptomic studies seek to identify linear effects of an external stimulus on gene expression, although such an assumption does not necessarily hold. Our work assesses the dose-dependent effects of dietary fat intake on differential gene expression in the proximal, middle and distal sections of the small intestine in C57BL/6J mice. Gene expression is analyzed in terms of either linear or nonlinear responses to fat intake.
  
  
  RESULTS
  The highest number of differentially expressed genes was observed in the middle section. In all intestine sections, most of the identified processes exhibited a linear response to increasing fat intake. The relative importance of logarithmic and exponential responses was higher in the proximal and distal sections, respectively. Functional enrichment analysis highlighted a constantly linear regulation of acute-phase response along the whole small intestine, with up-regulation of Serpina1b. The study of gene expression showed that exponential down-regulation of cholesterol transport in the middle section is coupled with logarithmic up-regulation of cholesterol homeostasis. A shift from linear to exponential response was observed in genes involved in the negative regulation of caspase activity, from middle to distal section (e.g., Birc5, up-regulated).
  
  
  CONCLUSIONS
  The transcriptomic signature associated with inflammatory processes preserved a linear response in the whole small intestine (e.g., up-regulation of Serpina1b). Processes related to cholesterol homeostasis were particularly active in the middle small intestine and only the highest fat intake down-regulated cholesterol transport and efflux (with a key role played by the down-regulation of ATP binding cassette transporters). Characterization of nonlinear patterns of gene expression triggered by different levels of dietary fat is an absolute novelty in intestinal studies. This approach helps identifying which processes are overloaded (i.e., positive, logarithmic regulation) or arrested (i.e., negative, exponential regulation) in response to excessive fat intake, and can shed light on the relationships linking lipid intake to obesity and its associated molecular disturbances.
authors: The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Rovereto, Italy. nyima@cosbi.eu.
authors: Tenzin
authors: T
authors: Nyima
authors: Nutrition, Metabolism and Genomics group, Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands. michael.muller@uea.ac.uk.|Norwich Medical School, University of East Anglia, Norwich, UK. michael.muller@uea.ac.uk.
authors: Michael
authors: M
authors: Müller
authors: Nutrition, Metabolism and Genomics group, Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands. guido.hooiveld@wur.nl.
authors: Guido J E J
authors: GJ
authors: Hooiveld
authors: The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Rovereto, Italy. morine@cosbi.eu.
authors: Melissa J
authors: MJ
authors: Morine
authors: The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Rovereto, Italy. marcoscot@gmail.com.|GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany. marcoscot@gmail.com.
authors: Marco
authors: M
authors: Scotti
mesh_terms: D000818:Animals; D004041:Dietary Fats; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D007421:Intestine, Small / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D059467:Transcriptome
chemical_list: D004041:Dietary Fats