Lysine, an essential amino acid, cannot be de novo synthesized or synthesized enough for metabolic needs in human and animals and must be absorbed from food.

As lysine is the most deficient amino acid in nearly all wheat and corn diets (especially for pig), there is a potential risk of lysine deficiency existing in developing countries where such diets are consumed frequently if the amino acid fails to be supplied enough.

In addition, free amino acid or its salts show lower bioavailability. Currently, small peptides, especially di- and tripeptides, are considered to be more efficiently utilized than intact proteins or free amino acids and have greater nutritional value. 

Prof. YIN Yulong's group in the Institute of Subtropical Agricultural, Chinese Academy of Sciences (ISA) focused on amino acid nutrition for many years and found that dietary lysine restriction impaired intestinal absorption and metabolism.

In this study, the researchers further investigated the effects of lysine deficiency and Lys-Lys dipeptide on apoptosis and amino acid transport and metabolism in IPEC-J2 and mice.

They confirmed that dietary lysine restriction influenced amino acid metabolism and caused apoptosis, which may be regulated by SLC7A11 expression and cellular cystine and glutamate metabolism.

Then, Lys-Lys dipeptide was firstly synthesized and exhibited that Lys-Lys dipeptide compensated for the reduced lysine absorption and alleviated intestinal dysfunction in the lysine deficient condition.

This study was supported by the National Basic Research Program of China (973), National Natural Science Foundation of China, and Key Projects in the National Science & Technology Pillar Program.

The study entitled "Effects of Lys deficiency and Lys-Lys dipeptide on cellular apoptosis and amino acids metabolism" has been published online at Molecular Nutrition & Food Research.