Expression of CTB-10×rolGLP-1 in E. coli and its therapeutic effect on type 2 diabetes

Glucagon-like peptide-1 (GLP-1) is a short peptide that can significantly reduce blood glucose level. Recombination oral long-acting glucagon-like peptide-1 (rolGLP-1), is a GLP-1 analog generated from site-specific mutation of GLP-1. CTB is a non-toxic portion of the cholera toxin and an ideal protein antigen carrier. In this study, we firstly constructed a vector pET-22b (+)-CTB-10×rolGLP-1 to express a fusion protein composed of CTB and ten tandem repeated rolGLP-1 in BL21 (DE3) line of E. coli. The CTB-10×rolGLP-1 was expressed efficiently in the inclusion bodies. The expression product was analyzed by SDS-PAGE electrophoresis and Western blotting. The inclusion bodies were then denatured, refolded and purified by ion exchange chromatography to obtain a high-purity CTB- 10×rolGLP-1. The therapeutic effect of CTB-10×rolGLP-1 was assessed in comparison with 10×rolGLP-1 alone by daily oral-gavage administration up to 10 days in streptozotocin-induced type 2 diabetic mice. The results showed that the level of blood glucose was reduced more effectively and the oral glucose tolerance of mice was improved more significantly with the administration of CTB-10×rolGLP-1. Our results provided a potentially promising oral biological drug for the treatment of type 2 diabetes.