Effects Of Short-term Starvation On KLF15-BCAA Signaling Pathway In The Muscle Tissue Of Rice Flower Carp

Fish Skeletal muscle is not only the main protein reservoir in the body,but also a highly dynamic tissue that is metabolically active and adaptable to nutritional changes.KLF15(krüppel-like factor 15,KLF15)is a transcription factor in the KLF family with a highly conserved zinc finger domain at the carboxyl terminus.It plays an important function in regulating BCAA(branched chain amino acids)metabolism of muscle tissue and is of great significance to maintaining the blood sugar steady state of the organism.BCAA is the only essential amino acid that is highly metabolized in skeletal muscle and plays an important role in gluconeogenesis.In this paper,the adaptive regulation mechanism of nutrition changes on muscle BCAA metabolism in rice flower carp were studied and KLF15 cDNA was cloned in muscle tissue of rice flower carp.After the fasting treatments,protein and m RNA expression of KLF15,a key transcription regulator of BCAA metabolism,BCAA metabolism related enzyme genes(BCAT2,ALT),activity of metabolism related enzymes(BCAT2,ALT,AST),as well as dynamic changes of BCAA level were investigated in rice flower carp.The main results were as follows:The total length of KLF15 cDNA sequence was 1964 bp,including ORF region 1347 bp,5’ end 207 bp,3’ end 410 bp,encoding 448 amino acids.It was found that KLF15 carboxyl terminus had 3 continuous conserved Cys2/His2 zinc finger domains.Using comprehensive biochemical and molecular biological analysis,it was found that the expression level of KLF15 significantly changed under the condition of starvation.Expression of KLF15 increased at first and then decreased.It reached the highest level in 3 days of starvation,and significantly decreased in 5 days of starvation,which was basically consistent with the expression level of KLF15 protein.The expression of BCAT2 and ALT genes increased at first and then decreased,and reached the highest expression in 3 days of starvation,and then decreased.The activity of BCAA decomposition key enzymes(BCAT2,ALT and AST)increased at first and then decreased,which was consistent with the change trend of BCAT2 and ALT genes in muscle.However,the BCAA content decreased at first and then increased,which was contrary to the trend of the enzyme activity changes of muscle BCAT2,ALT and AST.The BCAA content decreased to the lowest level in 3 days of starvation,and then gradually increased.The results showed that starvation induced KLF15 and regulated the catabolism of BCAA.In addition,with curcumin intraparitoneally invo injection,KLF15 expression in skeletal muscle was much down-regulated.The expression level of KLF15 reached the lowest when curcumin dose was 100mg/kg.The expression of BCAT2 and ALT also showed a continuous decrease under curcumin treatment,which was basically consistent with the trend of KLF15 gene expression.When curcumin dose was 50mg/kg,the activity of ALT and AST decreased,revealing the regulatory effect of curcumin on KLF15.All of the obtained results indicates that nutrient deficiency and curcumin could affect KLF15 expression at a certain extent,and KLF15 may be involved in regulating the muscle BCAA catabolism so as adaptated to nutritional stimilation.In summary,the study is helpful to further understand the regulatory mechanism of KLF15 on BCAA metabolism in response to dietary depletion and to provide a theoretical basis for maintaining nutritional balance fish culture limilating related metabolic diseases.