title: Acylation of Glucagon-like peptide-2: interaction with lipid membranes and in vitro intestinal permeability.
abstract: BACKGROUND
  Acylation of peptide drugs with fatty acid chains has proven beneficial for prolonging systemic circulation as well as increasing enzymatic stability without disrupting biological potency. Acylation has furthermore been shown to increase interactions with the lipid membranes of mammalian cells. The extent to which such interactions hinder or benefit delivery of acylated peptide drugs across cellular barriers such as the intestinal epithelia is currently unknown. The present study investigates the effect of acylating peptide drugs from a drug delivery perspective.
  
  
  OBJECTIVE
  We hypothesize that the membrane interaction is an important parameter for intestinal translocation, which may be used to optimize the acylation chain length for intestinal permeation. This work aims to characterize acylated analogues of the intestinotrophic Glucagon-like peptide-2 by systematically increasing acyl chain length, in order to elucidate its influence on membrane interaction and intestinal cell translocation in vitro.
  
  
  RESULTS
  Peptide self-association and binding to both model lipid and cell membranes was found to increase gradually with acyl chain length, whereas translocation across Caco-2 cells depended non-linearly on chain length. Short and medium acyl chains increased translocation compared to the native peptide, but long chain acylation displayed no improvement in translocation. Co-administration of a paracellular absorption enhancer was found to increase translocation irrespective of acyl chain length, whereas a transcellular enhancer displayed increased synergy with the long chain acylation.
  
  
  CONCLUSIONS
  These results show that membrane interactions play a prominent role during intestinal translocation of an acylated peptide. Acylation benefits permeation for shorter and medium chains due to increased membrane interactions, however, for longer chains insertion in the membrane becomes dominant and hinders translocation, i.e. the peptides get 'stuck' in the cell membrane. Applying a transcellular absorption enhancer increases the dynamics of membrane insertion and detachment by fluidizing the membrane, thus facilitating its effects primarily on membrane associated peptides.
authors.affiliation: Dept. of Micro- and Nanotechnology, Center for Nanomedicine and Theranostics, Technical University of Denmark, Kgs. Lyngby, Denmark; Diabetes Research Unit, Novo Nordisk, Maaloev, Denmark.
authors.forename: Sofie
authors.initials: S
authors.lastname: Trier
authors.affiliation: Diabetes Research Unit, Novo Nordisk, Maaloev, Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Linderoth
authors.affiliation: Diabetes Research Unit, Novo Nordisk, Maaloev, Denmark.
authors.forename: Simon
authors.initials: S
authors.lastname: Bjerregaard
authors.affiliation: Dept. of Micro- and Nanotechnology, Center for Nanomedicine and Theranostics, Technical University of Denmark, Kgs. Lyngby, Denmark.
authors.forename: Thomas Lars
authors.initials: TL
authors.lastname: Andresen
authors.affiliation: Diabetes Research Unit, Novo Nordisk, Maaloev, Denmark.
authors.forename: Ulrik Lytt
authors.initials: UL
authors.lastname: Rahbek
mesh_terms: D000215:Acylation; D000595:Amino Acid Sequence; D018938:Caco-2 Cells; D002462:Cell Membrane / Q000378:metabolism*; D053767:Glucagon-Like Peptide 2 / Q000737:chemistry / Q000378:metabolism*; D000067758:Glucagon-Like Peptide-2 Receptor; D006801:Humans; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology*; D008969:Molecular Sequence Data; D010539:Permeability; D011485:Protein Binding; D021381:Protein Transport; D018027:Receptors, Glucagon / Q000378:metabolism
chemical_list: D053767:Glucagon-Like Peptide 2; D000067758:Glucagon-Like Peptide-2 Receptor; D018027:Receptors, Glucagon