Researchers determine whether a smaller concentration of arginine affects the integrity of intestinal cells and their ability to absorb nutrients.
What factors affect our digestive tract’s ability to absorb nutrients? To answer this question, we need to consider many processes of the digestive tract, as digestion is a combination of many mechanisms that begin even before food enters our mouths. From the moment we salivate at the sight of something delicious to actually chewing and swallowing our food, our bodies have already coordinated the actions of multiple organs, muscles, and nerves. However, we can zoom in on one part of the digestive process in particular: absorption by the small intestine.
Absorption by the mucosa
Ninety percent of digestion and absorption occurs in the small intestine. The innermost layer of the small intestine (and the digestive tract as a whole) is the mucosa. It secretes digestive enzymes and absorbs nutrients. The mucosa is an important layer as the integrity of its barrier plays an important role in nutrition. If its barrier isn’t strong, it will affect its ability to absorb nutrients and maintain an ideal immune function, both of which are necessary for a healthy gut.
To study the mucosa’s role in nutrition in more detail, scientists have isolated and cultured cells from the tissue of pigs’ small intestines. This cell line, named IPEC-J2, allows researchers to study swine-based diseases and nutrition in more detail. With the similarity between pig and human intestinal structure and function, studies using IPEC-J2 cells may also shed light on interactions between human intestinal mucosa and nutrient uptake.
Arginine and the digestive tract
Arginine is a critical amino acid to the normal functioning of the digestive tract. It protects the mucosal barrier and improves its structure and function by stimulating protein synthesis and enhancing cell survival.
Past studies have found that dietary arginine could affect the absorption of other amino acids in the small intestinal mucosa. They also found that dietary arginine promotes the development of the intestine and growth of piglets, and may improve mucosal recovery after an intestinal injury. However, we have little knowledge on how changes in arginine concentration may affect the intestinal cell barrier and nutrient uptake.
A recently published study in the British Journal of Nutrition investigated the effects of reducing arginine concentration on cell integrity and nutrient absorption by using IPEC-J2 cells.
Testing arginine at different concentrations
In short, researchers cultured and maintained IPEC-J2 cells in a medium and nutrient mixture. When the culture reached a certain number of cells, they changed the cell culture medium to a new medium supplemented with arginine at different concentrations.
They found that reducing the concentration of arginine [from 0.7 to 0.2 milliMolar (mM)] did not change cellular integrity. However, a lower concentration of arginine (0.2 mM) stimulated the efficiency of amino acid absorption. This suggests that a lower concentration of arginine essentially allows for better uptake of nutrients and sufficient energy supply.
Arginine necessary for intestinal integrity and nutrient uptake
This study showed that arginine is necessary to maintain intestinal cell integrity and a lower concentration may allow for a better absorption of nutrients. The study also showed that reducing arginine concentration can be easily done in IPEC-J2 cells, providing researchers with guidance in developing dietary formulas for pigs. And with the similarity in pig and human intestinal structure and function, perhaps these findings will also guide researchers in developing better dietary formulas for humans.
Written By: Jessica Gelar, HBSc