Dybowskin-2CDYa

Metabolic associated fatty liver disease (MAFLD) is the leading common chronic liver disease affecting more than one-quarter of the population worldwide, but no pharmacological therapy was approved specifically. A synthetic peptide AWRK6 developed in our group based on the antimicrobial peptide Dybowskin-2CDYa was found to attenuated diabetes as a novel GLP-1 receptor agonist candidate. The effects of AWRK6 on MAFLD and its underlying mechanisms were investigated in this paper. In high energy diet (HED)-induced MAFLD mice, obesity and hepatic steatosis were alleviated by AWRK6 via intraperitoneal injection. The biochemistry measurements data indicated that the abnormal lipid metabolism was relieved and the glucose metabolism was improved significantly. Further, the phosphorylation of liver PI3K/AKT/AMPK/ACC was elevated significantly by AWRK6 treatment. Moreover, the effects of AWRK6 on lipid accumulation and insulin sensitivity in human cells were verified using oleic acid-induced HepG2 fatty liver cell model and insulin-induced HepG2 cells, respectively. These in vitro and in vivo results demonstrated that the peptide AWRK6 ameliorates MAFLD by improving lipid and glucose metabolism homeostasis, and it is mediated by the PI3K/AKT/AMPK/ACC signaling pathway. Thus, AWRK6 has a potential in preventing MAFLD.

Lipopolysaccharides (LPS) are major outer membrane components of Gram-negative bacteria and produce strong inflammatory responses in animals. Most antibiotics have shown little clinical anti-endotoxin activity while some antimicrobial peptides have proved to be effective in blocking LPS. Here, the anti-LPS activity of the synthetic peptide AWRK6, which is derived from antimicrobial peptide dybowskin-2CDYa, has been investigated in vitro and in vivo. The positively charged α-helical AWRK6 was found to be effective in blocking the binding of LBP (LPS binding protein) with LPS in vitro using ELISA. In a murine endotoxemia model, AWRK6 offered satisfactory protection efficiency against endotoxemia death, and the serum levels of LPS, IL-1β, IL-6, and TNF-α were found to be attenuated using ELISA. Further, histopathological analysis suggested that AWRK6 could improve the healing of liver and lung injury in endotoxemia mice. The results of real-time PCR and Western blotting showed that AWRK6 significantly reversed LPS-induced TLR4 overexpression and IκB depression, as well as the enhanced IκB phosphorylation. Additionally, AWRK6 did not produce any significant toxicity in vivo and in vitro. In summary, AWRK6 showed efficacious protection from LPS challenges in vivo and in vitro, by blocking LPS binding to LBP, without obvious toxicity, providing a promising strategy against LPS-induced inflammatory responses.

The skins of amphibians secrete small antimicrobial peptides that fight infection and are being explored as potential alternatives to conventional antibiotics. In this study we combined mass spectrometry with cDNA sequencing to examine antimicrobial peptides in skin secretions from the Chinese frog Rana dybowskii. Thirteen peptides having precursor sequences that resemble known antimicrobial peptides from this genus were identified, ten of which were members of previously described peptide families based on their primary structures; i.e., brevinin-1, Japonicin-1, brevinin-2 and temporin. The other three peptides from R. dybowskii, which were named dybowskin-1CDYa, dybowskin-2 CDYa and dybowskin-2CDYb, had different amino acid compositions and little sequence similarity to known antimicrobial peptides. The carboxyl terminus of dybowskin-1CDY lacked amidation and is therefore clearly distinct from temporin peptides, whereas dybowskin-2CDYa and dybowskin-2CDYb consisted of 18 amino acids and were rich in Arg residues. Chemically synthesized peptides corresponding to mature dybowskin-1CDYa and dybowskin-2CDYa had strong antimicrobial activity and caused little hemolysis of human erythrocytes, suggesting they may serve as interesting templates for the development of novel antibiotics.