Quantifying Insulin Sensitivity and Entero-Insular Responsiveness to Hyper- and Hypoglycemia in Ferrets

Ferrets are an important emerging model of cystic fibrosis related diabetes. However, there is little documented experience in the use of advanced techniques to quantify aspects of diabetes pathophysiology in the ferret. Glycemic clamps are the gold standard technique to assess both insulin sensitivity and insulin secretion in humans and animal models of diabetes. We therefore sought to develop techniques for glycemic clamps in ferrets. To assess insulin sensitivity, we performed euglycemic hyperinsulinemic clamps in 5–6 week old ferrets in the anesthetized and conscious states. To assess insulin secretion, we performed hyperglycemic clamps in conscious ferrets. To evaluate responsiveness of ferret islet and entero-insular hormones to low glucose, a portion of the hyperglycemic clamps were followed by a hypoglycemic clamp. The euglycemic hyperinsulinemic clamps demonstrated insulin responsiveness in ferrets similar to that previously observed in humans and rats. The anesthetic isoflurane induced marked insulin resistance, whereas lipid emulsion induced mild insulin resistance. In conscious ferrets, glucose appearance was largely suppressed at 4 mU/kg/min insulin infusion, whereas glucose disposal was progressively increased at 4 and 20 mU/kg/min insulin. Hyperglycemic clamp induced first phase insulin secretion. Hypoglycemia induced a rapid diminishment of insulin, as well as a rise in glucagon and pancreatic polypeptide levels. The incretins GLP-1 and GIP were affected minimally by hyperglycemic and hypoglycemic clamp. These techniques will prove useful in better defining the pathophysiology in ferrets with cystic fibrosis related diabetes.雪貂是囊性纤维化相关糖尿病（cystic fibrosis related diabetes）的重要新兴动物模型。然而，现有文献中鲜有应用先进技术量化雪貂糖尿病病理生理学特征的相关报道。血糖钳夹技术（glycemic clamp）是评估人类及糖尿病动物模型胰岛素敏感性与胰岛素分泌的金标准方法。为此，本研究旨在建立适用于雪貂的血糖钳夹技术。 为评估胰岛素敏感性，我们对5~6周龄的雪貂分别在麻醉与清醒状态下开展了正糖高胰岛素钳夹技术（euglycemic hyperinsulinemic clamp）。为评估胰岛素分泌，我们对清醒雪貂实施了高糖钳夹技术（hyperglycemic clamp）。为评估雪貂胰岛与肠胰岛激素（entero-insular hormone）对低葡萄糖的反应性，部分高糖钳夹实验后追加了低血糖钳夹技术（hypoglycemic clamp）。 正糖高胰岛素钳夹实验结果显示，雪貂的胰岛素反应性与此前在人类及大鼠中观察到的结果相似。异氟烷（isoflurane）麻醉可诱导显著的胰岛素抵抗，而脂肪乳剂（lipid emulsion）则可诱导轻度胰岛素抵抗。在清醒雪貂中，当胰岛素输注速率为4 mU/kg/min时，葡萄糖生成（glucose appearance）基本被抑制；而当胰岛素输注速率分别为4和20 mU/kg/min时，葡萄糖处置（glucose disposal）呈进行性升高。高糖钳夹可诱导第一时相胰岛素分泌（first phase insulin secretion）。低血糖可快速降低胰岛素水平，同时升高胰高血糖素（glucagon）与胰多肽（pancreatic polypeptide）水平。肠促胰素（incretin）中的胰高血糖素样肽-1（glucagon-like peptide-1, GLP-1）与葡萄糖依赖性促胰岛素多肽（glucose-dependent insulinotropic polypeptide, GIP）受高糖与低血糖钳夹的影响极小。 上述技术将有助于更清晰地阐明囊性纤维化相关糖尿病雪貂的病理生理学机制。