Date of this Version
Plant Biotechnology Journal
Glucagon like peptide (GLP-1) increases insulin secretion but is rapidly degraded (half-life: 2 min in circulation). GLP-1 analog, Exenatide (Byetta) has a longer half life (3.3–4 hrs) with potent insulinotropic effects but requires cold storage, daily abdominal injections with short shelf life. Because diabetic patients take >60,000 injections in their life time, alternative delivery methods are highly desired. Exenatide is ideal for oral delivery because insulinotropism is glucose dependent, with reduced risk of hypoglycemia even at higher doses. Therefore, exendin-4 (EX4) was expressed as a cholera toxin B subunit (CTB)-fusion protein in tobacco chloroplasts to facilitate bioencapsulation within plant cells and transmucosal delivery in the gut via GM1 receptors present in the intestinal epithelium. The transgene integration was confirmed by PCR and Southern blot analysis. Expression level of CTB-EX4 reached up to 14.3% of total leaf protein (TLP). Lyophilization of leaf material increased therapeutic protein concentration by 12–24 fold, extended their shelf life up to 15 months when stored at room temperature and eliminated microbes present in fresh leaves. The pentameric structure, disulfide bonds and functionality of CTB-EX4 were well preserved in lyophilized materials. Chloroplast derived CTB-EX4 showed increased insulin secretion similar to the commercial EX4 in beta-TC6, a mouse pancreatic cell line. Even when 5,000-fold excess dose of CTB-EX4 was orally delivered, it stimulated insulin secretion similar to the intraperitoneal injection of commercial EX4 but didn’t cause hypoglycemia in mice. Oral delivery of the bioencapsulated EX4 should eliminate injections, increase patient compliance/convenience and significantly lower their cost.
This is the peer reviewed version of the following article: Kwon, K.-C., Nityanandam, R., New, J. S., & Daniell, H. (2013). Oral delivery of bioencapsulated exendin-4 expressed in chloroplasts lowers blood glucose level in mice and stimulates insulin secretion in beta-TC6 cells. Plant Biotechnology Journal, 11(1), 77–86. http://doi.org/10.1111/pbi.12008, which has been published in final form at [ https://doi.org/10.1111/pbi.12008]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving [link to http://olabout.wiley.com/WileyCDA/Section/id-820227.html#terms].
chloroplast transformation; abiotic stress tolerance; γ-tocopherol methyltransferase
Kwon, K., Nityanandam, R., New, J. S., & Daniell, H. (2013). Oral Delivery of Bioencapsulated Exendin-4 Expressed in Chloroplasts Lowers Blood Glucose Level in Mice and Stimulates Insulin Secretion in Beta-TC6 Cells. Plant Biotechnology Journal, 11 (1), 77-86. http://dx.doi.org/10.1111/pbi.12008
Date Posted: 01 March 2022
This document has been peer reviewed.