Archives

  • 2018-07
  • 2019-04
  • 2019-05
  • 2019-06
  • 2019-07
  • 2019-08
  • 2019-09
  • 2019-10
  • 2019-11
  • 2019-12
  • 2020-01
  • 2020-02
  • 2020-03
  • 2020-04
  • 2020-05
  • 2020-06
  • 2020-07
  • 2020-08
  • 2020-09
  • 2020-10
  • 2020-11
  • 2020-12
  • 2021-01
  • 2021-02
  • 2021-03
  • 2021-04
  • 2021-05
  • 2021-06
  • 2021-07
  • 2021-08
  • 2021-09
  • 2021-10
  • 2021-11
  • 2021-12
  • 2022-01
  • 2022-02
  • 2022-03
  • 2022-04
  • 2022-05
  • 2022-06
  • 2022-07
  • 2022-08
  • 2022-09
  • 2022-10
  • 2022-11
  • 2022-12
  • 2023-01
  • 2023-02
  • 2023-03
  • 2023-04
  • 2023-05
  • 2023-06
  • 2023-07
  • 2023-08
  • 2023-09
  • 2023-10
  • 2023-11
  • 2023-12
  • 2024-01
  • 2024-02
  • 2024-03
  • fluvastatin sodium sale Despite the potential promise of

    2021-10-13

    Despite the potential fluvastatin sodium sale promise of both of these peptides, such compounds are still susceptible to efficient renal filtration (Emmanouel et al., 1978, Holst, 1991, Deacon et al., 1996). However, numerous studies have demonstrated that fatty fluvastatin sodium sale dervatisation of related regulatory peptides results in longer-acting analogues, largely through encouraging binding to plasma proteins to reduce renal clearance (Knudsen et al., 2000, Irwin et al., 2006, Grossman, 2009). As such, the addition of a C-16 palmitate fatty acid to either the mid-chain or C-terminal regions of the incretin hormone, glucose-dependent insulinotropic polypeptide (GIP), has yielded encouraging results (Irwin et al., 2005). Building on these approaches to prolong the biological half-life of other peptide hormones, we have developed two acylated analogues, namely desHis1Pro4Glu9Lys12FA-glucagon and desHis1Pro4Glu9Lys30FA-glucagon. Both peptides have a C-16 palmitate fatty acid covalently attached via a γ-glutamyl spacer on the ε-amino side chain of the Lys residue at position 12 or 30, respectively. In the present study we assessed the in vitro and in vivo biological actions of the four novel glucagon-based analogues. Initially, we examined the enzymatic stability and effects of the peptides either alone or on glucagon-induced elevations of cAMP production and insulin secretion in vitro. In addition, we used normal, high fat fed and obese diabetic (ob/ob) mice, to determine the ability of the analogues to suppress the biological actions of glucagon in vivo. Finally, the duration of biological action of all four novel peptides was examined in normal mice. The results suggest that peptide-based glucagon receptor antagonists could offer an effective targeted means of treating type 2 diabetes.
    Materials and methods
    Results
    Discussion In the present study, four novel peptide-based glucagon analogues have been developed based, in part, on the established glucagon receptor antagonist desHis1Glu9-glucagon (Hruby, 1982, Unson et al., 1987, Unson et al., 1989). Initially we confirmed that all novel analogues were resistant to DPP-4 degradation, in contrast to native glucagon. It is well established that glucagon is rapidly degraded by DPP-4 yielding the degradation product glucagon (3–29) (Hinke et al., 2000, Pospisilik et al., 2001). Thus, in harmony with other studies, substitution with a Proline amino acid three residues from the N-terminus of DPP-4 susceptible peptides, imparts profound enzymatic resistance (Gault et al., 2002). As expected, in HEK294SGnT1- and BRIN-BD11 cells all four glucagon analogues, desHis1Pro4-glucagon, desHis1Pro4Glu9-glucagon, desHis1Pro4Glu9Lys12FA-glucagon and desHis1Pro4Glu9Lys30FA-glucagon had nominal effects on cAMP production or insulin release, respectively. Subsequent studies confirmed the potent antagonistic properties of these analogues on glucagon-mediated biological activity in vitro. Antagonistic effects on cAMP production were more prominent than corresponding actions on insulin secretion, suggesting that alternative signalling pathways may be involved in glucagon-induced insulin secretion (Rodgers, 2012). For example, it is possible that KATP channel-dependent or other related signalling pathways could be involved. Additionally, the ability of physiological concentrations of circulating glucagon (<0.1nM) to affect insulin secretion could differ from the pharmacological dose of glucagon agonist (100nM) tested in the current in vitro system (Rodgers, 2012). Earlier work has revealed that potential physiological glucagon antagonists, which possess even weak agonist activity at the glucagon receptor, can have detrimental metabolic effects (Corvera et al., 1984). Indeed, this was shown to possibly be related to a dissociation between cAMP concentrations and the metabolic effects of glucagon (García-Sáinz et al., 1985). As such, this could have important implications for the current study. From the IC50 values determined here the fatty acid modified analogues appeared less potent that their non-acylated counterparts, presumably reflecting efficient albumin binding of these peptides (Irwin et al., 2006). Nonetheless, we have clearly shown that the fatty acid derivatised molecules retained affinity and effectiveness as glucagon receptor antagonists, which is encouraging given that the process of peptide hormone acylation can be accompanied by some loss of intrinsic biological efficacy (Gault et al., 2011).