Modulation of pH-regulatory transport proteins by free fatty acid receptors in the ruminal epithelium

• Applicant: Professor Dr. Gotthold Gäbel
• Subject Area: Veterinary Medical Science ; Animal Breeding, Animal Nutrition, Animal Husbandry
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 280642578

Our own studies have shown that the ovine ruminal epithelium is able to express the free fatty acid receptors FFAR2 and GPR109A on the mRNA and protein level. In non ruminal tissues these receptors can bind short chain fatty acids leading to a decreased intracellular level of cAMP and altered cell functions including cAMP sensitive transport proteins. In the forestomach SCFA are produced in large quantities and directly absorbed which makes them the main energy source for the animal. The uptake of SCFA into the ruminal epithelium, however, acidifies the cytosol of the cells. We thus assume that SCFA binding at the epithelial FFA-receptors particularly modifies the transport proteins involved in the SCFA transfer and/or regulation of intracellular pH. To check the assumption, we want to elucidate if stimulation of the FFAR leads to a decrease of the intracellular cAMP level and modifies the activity of the transport proteins NHE3, NHE1, MCT1 and MCT4. All these transport proteins influence the intracellular pH. Additionally, MCT1 and MCT4 are involved in the transmembranal transfer of SCFA and/or their intraepithelial catabolites. To examine the interrelationship between SCFA, FFAR, cAMP and modulation of the transport proteins, we plan to conduct studies on isolated ovine ruminal epithelia and ruminal epithelial cells kept in culture. In the epithelia and the cultured cells, the intracellular cAMP levels shall be measured both with and without stimulating the FFAR receptors by acetate or butyrate or by pharmacological agonist of the receptors and by pharmacological variation of the intracellular cAMP level. Activity and protein expression of NHE3, NHE1, MCT1 and MCT4 will then be measured in the isolated epithelial and cultured cells by various techniques and both with and without stimulating the receptors the way mentioned. The study may thus reveal short term adaptive responses of the animal to an elevated SCFA exposure for example after intake of a ratio rich in easily fermentable carbohydrates.

• DFG Programme: Research Grants