Heterologous Expression and Delivery of Biologically Active Exendin 4 by Lactobacillus paracasei L14
Exendin 4, a glucagon like protein 1 (GLP 1) receptor agonist, is an excellent therapeutic peptide drug for type 2 diabetes due to longer lasting biological activity compared to GLP 1. This study explored the feasibility of using probiotic Lactobacillus paracasei as an oral vector for recombinant exendin 4 peptide delivery, an alternative to costly chemical synthesis and inconvenient administration by injection. L. paracasei transformed with a plasmid encoding the exendin 4 gene (L. paracasei L14/pMG76e exendin 4) with a constitutive promotor was successfully constructed and showed efficient secretion of exendin 4. The secreted exendin 4 significantly enhanced insulin secretion of INS 1 b cells, along with an increment in their proliferation and inhibition of their apoptosis, corresponding to the effect of GLP 1 on these cells. The transcription level of the pancreatic duodenal homeobox 1 gene (PDX 1) a key transcription factor for cellular insulin synthesis and secretion, was upregulated by the treatment with secreted exendin 4, paralleling the upregulation of insulin gene expression. Caco 2 cell monolayer permeability assay showed a 34 fold increase in the transport of exendin 4 delivered by L. paracasei vs. that of free exendin 4 (control) suggesting effective facilitation of exendin 4 transport across the intestinal barrier by this delivery system. This study demonstrates that the probiotic Lactobacillus can be engineered to secrete bioactive exendin 4 and facilitate its transport through the intestinal barrier, providing a novel strategy for oral exendin 4 delivery using this lactic acid bacterium.
PloS one