Journal Article

Mucosal absorption of therapeutic peptides by harnessing the endogenous sorting of glycosphingolipids

Chinnapen, Daniel J-F, Garcia-Castillo, Maria Daniela, Gonzalez, Rodrigo J, Kahn, C Ronald, von Andrian, Ulrich H, Mrsny, Randall J, Softic, Samir, te Welscher, Yvonne M, Pentelute, Bradley L, Lencer, Wayne I, Pacheco, Michele, Lau, Jesper

2018

Overview

Transport of biologically active molecules across tight epithelial barriers is a major challenge preventing therapeutic peptides from oral drug delivery. Here, we identify a set of synthetic glycosphingolipids that harness the endogenous process of intracellular lipid-sorting to enable mucosal absorption of the incretin hormone GLP-1. Peptide cargoes covalently fused to glycosphingolipids with ceramide domains containing C6:0 or smaller fatty acids were transported with 20-100-fold greater efficiency across epithelial barriers in vitro and in vivo. This was explained by structure-function of the ceramide domain in intracellular sorting and by the affinity of the glycosphingolipid species for insertion into and retention in cell membranes. In mice, GLP-1 fused to short-chain glycosphingolipids was rapidly and systemically absorbed after gastric gavage to affect glucose tolerance with serum bioavailability comparable to intraperitoneal injection of GLP-1 alone. This is unprecedented for mucosal absorption of therapeutic peptides, and defines a technology with many other clinical applications. To work properly, drugs need to be absorbed efficiently into the body. Medications that are injected directly into the bloodstream are often quickly transported to the organs or tissues they target. But injections are not always convenient, and many patients would instead prefer to swallow a pill or tablet. If a drug is swallowed, however, it must first be absorbed through the gut before it can enter the bloodstream. The lining of the gut consists of tightly linked layers of cells that readily take up small molecules, such as water and simple nutrients, but exclude almost all larger ones. Since several important types of drugs are large or poorly absorbed molecules, such as proteins, finding methods to help them cross the gut barrier is a major part of drug development. Originally from bacteria, cholera toxin is an example of a large, naturally occurring protein that does cross the gut lining. To do this, the toxin specifically attaches onto GM1, a type of lipid molecule that is found on the outer surface of gut cells, and hijacks the system that moves this lipid within cells. Previous studies identified several key features of GM1’s structure that enable this movement; and, in 2014, researchers tested GM1 as a ‘carrier’ to help the gut to absorb large therapeutic molecules. This approach was successful in cells grown in the laboratory, but not when the drugs were fed to animals. To overcome this issue, Garcia-Castillo, Chinnapen et al. – who include some of the researchers involved in the earlier studies – set out to further boost GM1’s ability to transport drugs across the gut lining. First several hybrid molecules were made, consisting of different structures of GM1 (the ‘carrier’) fused to a reporter peptide (the ‘cargo’). Laboratory experiments with human intestinal cells and dog kidney cells, both of which form tightly-linked layers much like the actual lining of the gut, revealed specific structural variations of the GM1-derived carrier that transported the cargo across the cell barrier more efficiently. Garcia-Castillo, Chinnapen et al. went on to test the efficiency of these carriers further by switching the reporter cargo to a therapeutic hormone called GLP-1. This hormone is used to treat people with type II diabetes but is currently given via an injection. The same structural variants of GM1 that enhanced delivery of the reporter cargo also worked for the larger GLP-1 hormone. Garcia-Castillo, Chinnapen et al. then fed the GM1-GLP-1 fusions to mice, and measured the amount of GLP-1 hormone absorbed into the blood. Crucially, the mice fed GM1-GLP-1 molecules absorbed the drug just as well as mice injected with the GLP-1 that is normally given to diabetes patients. Together these findings represent a major contribution to the pharmaceutical toolbox. They may also ultimately lead to more drugs that can be given as a patient-friendly pill or tablet, readily cross the gut barrier and achieve widespread drug delivery around the body.

• Publisher: eLife Science Publications, Ltd,eLife Sciences Publications Ltd,eLife Sciences Publications, Ltd
• Subject: Absorption, Physiological / Animal experimentation / Animals / Bacteria / Bioavailability / Biological activity / Biological Transport, Active / Blood Glucose - metabolism / Cell Biology / Cell membranes / Cell Nucleus - metabolism / Ceramide / Ceramides - chemistry / Cholera / Cholera toxin / Diabetes / Dogs / Drug delivery / Drug delivery systems / Drugs / epithelial cells / Epithelial Cells - metabolism / Fatty acids / G(M1) Ganglioside - chemistry / G(M1) Ganglioside - metabolism / GLP-1/ diabetes / Glucagon-Like Peptide 1 - metabolism / Glucose / Glucose tolerance / glycolipids/gangliosides / Glycosphingolipids / Glycosphingolipids - metabolism / Hormones / Human Biology and Medicine / Intracellular / lipid sorting / Lipids / Madin Darby Canine Kidney Cells / Male / Mass spectrometry / Medical schools / membrane transport / Mice, Inbred C57BL / Microscopy / Mucosa / Mucous Membrane - metabolism / Oligosaccharides - chemistry / Oligosaccharides - metabolism / Peptides / Peptides - therapeutic use / Physiological aspects / Proteins / Reproducibility of Results / Scientific imaging / Solutions / Sphingolipids / Structure-Activity Relationship / Structure-function relationships / Technology / Therapeutic applications / Transcytosis