Abstract
Energy-rich diets can challenge metabolic and protective functions of the rumen epithelial cells, but the underlying factors are unclear. This study sought to evaluate proteomic changes of the rumen epithelium in goats fed a low, medium, or high energy diet. Expression of protein changes were compared by two-dimensional differential gel electrophoresis followed by protein identification with matrix assisted laser desorption ionisation tandem time-of-flight mass spectrometry. Of about 2,000 spots commonly detected in all gels, 64 spots were significantly regulated, which were traced back to 24 unique proteins. Interestingly, the expression profiles of several chaperone proteins with important cellular protective functions such as heat shock cognate 71 kDa protein, peroxiredoxin-6, serpin H1, protein disulfide-isomerase, and selenium-binding protein were collectively downregulated in response to high dietary energy supply. Similar regulation patterns were obtained for some other proteins involved in transport or metabolic functions. In contrast, metabolic enzymes like retinal dehydrogenase 1 and ATP synthase subunit beta, mitochondrial precursor were upregulated in response to high energy diet. Lower expressions of chaperone proteins in the rumen epithelial cells in response to high energy supply may suggest that these cells were less protected against the potentially harmful rumen toxic compounds, which might have consequences for rumen and systemic health. Our findings also suggest that energy-rich diets and the resulting acidotic insult may render rumen epithelial cells more vulnerable to cellular damage by attenuating their cell defense system, hence facilitating the impairment of rumen barrier function, typically observed in energy-rich fed ruminants.
Highlights
Rumen is a classical host-microbial ecosystem that enables ruminant animals the conversion of largely indigestible plant biomass into valuable food products, making them highly significant to human nutrition
The analysis indicated that 40 protein spots were differentially regulated in the rumen epithelium between goats fed low vs. high energy diets, whereby 33 of these spots were downregulated and 7 were upregulated when animals were shifted from low to high energy diet (Table 1)
The study expands our previous article where we demonstrated an impairment of the barrier functions of rumen epithelium in an Ussing chamber experiment due to high energy supply and the resulting acidotic insult [4]
Summary
Rumen is a classical host-microbial ecosystem that enables ruminant animals the conversion of largely indigestible plant biomass into valuable food products, making them highly significant to human nutrition. Complex dietary carbohydrates are degraded in the rumen by microbial glycosidases to shortchain fatty acids, which are absorbed and subsequently metabolized in the rumen epithelium, supplying energy to the host [1]. Besides their central metabolic roles, rumen epithelial cells are the first line of defence against hostile rumen conditions such as acidic pH, high osmotic pressure, and harmful microbial-derived metabolites, in particular when ruminants are fed energy-rich diets to enhance cost efficiency [2]. There is a paucity of information with regard to the underlying mechanisms behind the disruption of protective functions of rumen epithelium and its metabolic consequences in response to energy-rich diets
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