Abstract
The branched-chain amino acids (BCAAs) play a key role in the energy metabolism of the muscle tissue and the Krüppel-like factor 15 (KLF15) as a transcription factor, which is a key regulator of BCAA metabolism in the skeletal muscle. This study assessed the effect of starvation for 0, 3, 7, and 15 days on BCAA metabolism in the skeletal muscle of Nile tilapia. The results showed that the expression of KLF15 showed a trend of increasing first and then decreasing during starvation, as well as the expression and activity of branched-chain aminotransferase 2 (BCAT2) and alanine aminotransferase (ALT). On the other hand, the content of BCAA was at first decreased and then upregulated, and it reached the lowest level after starvation for 3 days. In addition, through dual-luciferase reporter assay and injection experiments, it was found that KLF15 is the target gene of miR-125a-3p, which further verified that miR-125a-3p can regulate the BCAA metabolism by targeting KLF15 in the skeletal muscle. Thus, our work investigated the possible mechanisms of BCAA metabolism adapting to nutritional deficiency in the skeletal muscle of Nile tilapia and illustrated the regulation of BCAA metabolism through the miR-125a-3p-KLF15-BCAA pathway in the skeletal muscle.
Highlights
Branched-chain amino acids (BCAAs) include leucine (Leu), isoleucine (Ile), and valine (Val)
Some studies have shown that the branched-chain amino acids (BCAAs) metabolism is mainly through intramuscular transamination, which is the primary way of endogenous synthesis of glutamic acid (Glu), glutamine, and aspartic acid (Asp) (She et al, 2007; She et al, 2010)
When the body is in a resting state, about 14% of the total energy consumed by the skeletal muscle was provided by the process of BCAA oxidation
Summary
Branched-chain amino acids (BCAAs) include leucine (Leu), isoleucine (Ile), and valine (Val). Studies have shown that the decomposition of BCAA is very active in the skeletal muscle It can carry out transamination and complete oxidation at a fairly fast rate. When the body is in a resting state, about 14% of the total energy consumed by the skeletal muscle is provided by the process of BCAA oxidation. Under particular conditions such as starvation, exercise, and lactation, the increase in BCAA oxidation function is an important energy source in vivo. The pyruvate receives amino acids from glutamic acid generated by BCAAs in the skeletal muscle, which is converted into alanine by the transamination of alanine aminotransferase (ALT) and transported to the liver. Pyruvate was generated by deamination and converted into glucose, which provides gluconeous substrate for the liver to maintain energy metabolism and homeostasis balance (Felig, 1973; Perry et al, 2018)
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