Abstract
Improved procedures for sample preparation and proteomic data analysis allowed us to identify 7700 different proteins in mouse small intestinal mucosa and calculate the concentrations of >5000 proteins. We compared protein concentrations of small intestinal mucosa from mice that were fed for two months with normal diet (ND) containing 34.4% carbohydrates, 19.6% protein, and 3.3% fat or high-fat diet (HFD) containing 25.3% carbohydrates, 24.1% protein, and 34.6% fat. Eleven percent of the quantified proteins were significantly different between ND and HFD. After HFD, we observed an elevation of proteins involved in protein synthesis, protein N-glycosylation, and vesicle trafficking. Proteins engaged in fatty acid absorption, fatty acid β-oxidation, and steroid metabolism were also increased. Enzymes of glycolysis and pentose phosphate cycle were decreased, whereas proteins of the respiratory chain and of ATP synthase were increased. The protein concentrations of various nutrient transporters located in the enterocyte plasma membrane including the Na(+)-d-glucose cotransporter SGLT1, the passive glucose transporter GLUT2, and the H(+)-peptide cotransporter PEPT1 were decreased. The concentration of the Na(+),K(+)-ATPase, which turned out to be the most strongly expressed enterocyte transporter, was also decreased. HFD also induced concentration changes of drug transporters and of enzymes involved in drug metabolism, which suggests effects of HFD on pharmacokinetics and toxicities. Finally, we observed down-regulation of antibody subunits and of components of the major histocompatibility complex II that may reflect impaired immune defense and immune tolerance in HFD. Our work shows dramatic changes in functional proteins of small intestine mucosa upon excessive fat consumption.
Highlights
The small intestine of mammalians provides an extensive contact surface for ingested compounds that allows the absorption and metabolism of nutrients, xenobiotics, and drugs as well as immune defense against antigenic food components, bacterial and viral pathogens, and immune response to allergens
By trying to apply this powerful approach to a biomedical important question, we investigated whether the protein concentrations in the mucosa were different when the mice were kept for two months on a Western-type hypercaloric high-fat diet (HFD) compared to a standard diet
Small intestinal mucosa was isolated from male mice that were fed for two months postweaning with a normal diet (ND) containing 29.0% polysaccharides, 5.4% disaccharides, 19.6% protein, 4.1% fiber, and 3.3% fat or with a HFD containing 15.8% polysaccharides, 9.5% disaccharides, 24.1% protein, 6% fiber, and 34.6% fat
Summary
The small intestine of mammalians provides an extensive contact surface for ingested compounds that allows the absorption and metabolism of nutrients, xenobiotics, and drugs as well as immune defense against antigenic food components, bacterial and viral pathogens, and immune response to allergens. The performance of these different functions is enabled by unique morphological and functional properties of small intestine. We performed an in-depth proteomic analysis of homogenized mucosa that was scraped from everted mice small intestines This preparation contained enterocytes and some components of the underlying soft connective tissue. Significant changes with impact on nutrient transport, energetic metabolism, drug transport, drug metabolism, immune defense, and susceptibility to inflammation were observed
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