Abstract: This study was done in order to understand the regulatory effect and underlying mechanism of alkylamides from Zanthoxylum bungeanum Maxim. on protein metabolism in rats. A total of 40 healthy male SD rats were randomly divided into four groups according to body weight: control group, high dose group (8 mg/(kg·d) alkylamides in soybean oil solution, ig), middle dose group (4 mg/(kg·d)), and low dose group (2 mg/(kg·d)). After 28 days of administration, blood urea nitrogen, total protein, insulin-like growth factor I (IGF-I) and amino acids in serum, as well as amino acids in skeletal muscle were assayed. The mRNA transcription levels of IGF-I, insulin growth factor I receptor (IGF-IR) in liver and IGF-I, IGFIR, myogenin (MyoG), myostatin (MSTN), μ-calpain (CAPN-1) and calpastatin (CAST) in skeletal muscle was analysed by qPCR. The results showed that alkylamides significantly increased the relative weight of skeletal muscle (P < 0.05) and decreased abdominal fat ratio (P > 0.05) when compared with the control. There was no significant difference in the relative weight of other organs. Alkylamides also significantly decreased BUN concentration and increased total protein concentration in serum. In addition, the mRNA expression of IGF-I, MyoG, CAPN-1 and CAST was significantly upregulated whereas the mRNA expression of MSTN was down-regulated in skeletal muscle. These results suggested that alkylamides increased the relative weight of skeletal muscle mainly through the up-regulation of MyoG and the downregulation of MSTN, promoting the growth of skeletal muscle. In addition, alkylamides could enhance protein metabolism in skeletal muscle through CAPN-1/CAST system and promote protein deposition.

Key words: alkylamides, skeletal muscle, protein deposition, rat, mechanism