title: Biochemical stabilization of glucagon at alkaline pH.
abstract: BACKGROUND
  For patients with type 1 diabetes mellitus, a bihormonal artificial endocrine pancreas system utilizing glucagon and insulin has been found to stabilize glycemic control. However, commercially available formulations of glucagon cannot currently be used in such systems because of physical instability characterized by aggregation and chemical degradation. Storing glucagon at pH 10 blocks protein aggregation but results in chemical degradation. Reductions in pH minimize chemical degradation, but even small reductions increase protein aggregation. We hypothesized that common pharmaceutical excipients accompanied by a new excipient would inhibit glucagon aggregation at an alkaline pH.
  
  
  RESULTS
  As measured by tryptophan intrinsic fluorescence shift and optical density at 630 nm, protein aggregation was indeed minimized when glucagon was formulated with curcumin and albumin. This formulation also reduced chemical degradation, measured by liquid chromatography with mass spectrometry. Biological activity was retained after aging for 7 days in an in vitro cell-based bioassay and also in Yorkshire swine.
  
  
  CONCLUSIONS
  Based on these findings, a formulation of glucagon stabilized with curcumin, polysorbate-80, l-methionine, and albumin at alkaline pH in glycine buffer may be suitable for extended use in a portable pump in the setting of a bihormonal artificial endocrine pancreas.
authors: 1 Harold Schnitzer Diabetes Health Center, Oregon Health and Science University , Portland, Oregon.
authors: Nicholas
authors: N
authors: Caputo
authors: Melanie A
authors: MA
authors: Jackson
authors: Jessica R
authors: JR
authors: Castle
authors: Joseph
authors: J
authors: El Youssef
authors: Parkash A
authors: PA
authors: Bakhtiani
authors: Colin P
authors: CP
authors: Bergstrom
authors: Julie M
authors: JM
authors: Carroll
authors: Matthew E
authors: ME
authors: Breen
authors: Gerald L
authors: GL
authors: Leonard
authors: Larry L
authors: LL
authors: David
authors: Charles T
authors: CT
authors: Roberts
authors: W Kenneth
authors: WK
authors: Ward
mesh_terms: D000818:Animals; D002021:Buffers; D011232:Chemical Precipitation; D002626:Chemistry, Pharmaceutical; D002853:Chromatography, Liquid; D003474:Curcumin / Q000737:chemistry; D004355:Drug Stability; D004791:Enzyme Inhibitors / Q000737:chemistry*; D005934:Glucagon / Q000031:analogs & derivatives / Q000737:chemistry*; D006801:Humans; D007332:Insulin Infusion Systems; D008715:Methionine / Q000737:chemistry; D011136:Polysorbates / Q000737:chemistry; D055550:Protein Stability; D013050:Spectrometry, Fluorescence; D013552:Swine; D014364:Tryptophan / Q000737:chemistry
chemical_list: D002021:Buffers; D004791:Enzyme Inhibitors; D011136:Polysorbates; D014364:Tryptophan; D005934:Glucagon; D008715:Methionine; D003474:Curcumin