Oregon Health and Science University (OHSU), 3181 SW Sam Jackson Park Road, OP05DC, Portland, OR 97239, USA.
Curr Diab Rep. 2012 Dec;12(6):705-10. doi: 10.1007/s11892-012-0320-5.
Small doses of glucagon given subcutaneously in the research setting by an automated system prevent most cases of hypoglycemia in persons with diabetes. However, glucagon is very unstable and cannot be kept in a portable pump. Glucagon rapidly forms amyloid fibrils, even within the first day after reconstitution. Aggregation eventually leads to insoluble gels, which occlude pump catheters. Fibrillation occurs rapidly at acid pH, but is absent or minimal at alkaline pH values of ~10. Glucagon also degrades over time; this problem is greater at alkaline pH. Several studies suggest that its primary degradative pathway is deamidation, which results in a conversion of asparagine to aspartic acid. A cell-based assay for glucagon bioactivity that assesses glucagon receptor (GluR) activation can screen promising glucagon formulations. However, mammalian hepatocytes are usually problematic as they can lose GluR expression during culture. Assays for cyclic AMP (cAMP) or its downstream effector, protein kinase A (PKA), in engineered cell systems, are more reliable and suitable for inexpensive, high-throughput assessment of bioactivity.
在研究环境中，通过自动化系统皮下给予小剂量的胰高血糖素可预防大多数糖尿病患者发生低血糖。然而，胰高血糖素非常不稳定，无法保存在便携式泵中。胰高血糖素在重新配制后的第一天内就会迅速形成淀粉样原纤维，甚至会形成不可溶的凝胶，从而阻塞泵导管。在酸性 pH 值下，纤维会迅速发生，但在碱性 pH 值（约 10）时则不存在或很少发生。随着时间的推移，胰高血糖素也会降解；在碱性 pH 值下，这个问题更为严重。几项研究表明，其主要降解途径是脱酰胺作用，导致天冬酰胺转化为天冬氨酸。一种基于细胞的胰高血糖素生物活性测定法，可评估胰高血糖素受体（GluR）的激活情况，从而筛选有前途的胰高血糖素配方。然而，哺乳动物肝细胞通常存在问题，因为它们在培养过程中可能会失去 GluR 表达。在工程细胞系统中测定环磷酸腺苷（cAMP）或其下游效应物蛋白激酶 A（PKA），更可靠，适合于以较低的成本、高通量评估生物活性。
