Department of Zoology and Physiology, University of Wyoming, Laramie, WY, USA.
Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México (UNAM), Mexico City, Mexico.
J Mol Evol. 2020 Dec;88(10):715-719. doi: 10.1007/s00239-020-09970-0. Epub 2020 Nov 8.
Relative to other vertebrates, birds have unusually high blood glucose levels. In humans, the hyperglycemia observed in birds would be associated with diabetes mellitus and the non-enzymatic glycation of proteins, which leads to the accumulation of advanced glycation products and to a plethora of microvascular pathologies. How do birds avoid the negative effects of hyperglycemia? Anthony-Regnitz et al. (J Mol Evol 88: 653-661, 2020) discovered that birds might have evolved glycation-resistant proteins. Serum albumin is an important multifunctional protein susceptible to glycation. Anthony-Regnitz et al. (J Mol Evol 88: 653-661, 2020) found that chicken albumin is resistant to glycation relative to bovine serum albumin. Protein glycation takes place primarily in lysine residues, which are less abundant in chicken than in bovine serum albumin. A multispecies comparison of serum albumin sequences revealed lower numbers of lysine residues in birds than in mammals. Benign hyperglycemia is a shared derived trait of birds and glycation resistance mechanisms appear to have accompanied its evolution. The evolution of benign hyperglycemia in birds coincided with a genomic upheaval that included the loss of important genes, including the one that codes for GLUT4, the transporter responsible for insulin-dependent glucose transport in other vertebrates' insulin-sensitive cells. This loss seems to have resulted in the remodeling of the insulin-signaling pathway in bird tissues. Avian hyperglycemia has been considered a mystery for a long time. Although we remain ignorant of its origins and its repercussions for the physiology of birds, the discovery of resistance to glycation in bird serum albumin offers a path forward to solve this mystery.
与其他脊椎动物相比，鸟类的血糖水平异常高。在人类中，鸟类观察到的高血糖与糖尿病和蛋白质的非酶糖基化有关，这会导致晚期糖基化产物的积累和大量微血管病变。鸟类如何避免高血糖的负面影响？Anthony-Regnitz 等人（J Mol Evol 88: 653-661, 2020）发现，鸟类可能已经进化出了抗糖基化蛋白。血清白蛋白是一种重要的多功能蛋白质，易发生糖基化。Anthony-Regnitz 等人（J Mol Evol 88: 653-661, 2020）发现，与牛血清白蛋白相比，鸡白蛋白具有抗糖基化作用。蛋白质糖基化主要发生在赖氨酸残基上，而鸡白蛋白中的赖氨酸残基比牛血清白蛋白中的少。对血清白蛋白序列的多物种比较表明，鸟类中的赖氨酸残基数量低于哺乳动物。良性高血糖是鸟类的一个共同衍生特征，糖基化抗性机制似乎伴随着它的进化而出现。鸟类良性高血糖的进化与基因组剧变同时发生，包括丧失了一些重要基因，包括编码 GLUT4 的基因，GLUT4 是其他脊椎动物胰岛素敏感细胞中胰岛素依赖的葡萄糖转运的载体。这一缺失似乎导致了鸟类组织中胰岛素信号通路的重塑。鸟类的高血糖一直是个谜。尽管我们仍然不知道它的起源及其对鸟类生理学的影响，但在鸟类血清白蛋白中发现抗糖基化的能力为解决这个谜团提供了一个途径。
