Department of Biology, Utah State University, Logan, UT 84322, USA.
Ecology Center, Utah State University, Logan, UT 84322, USA.
J Exp Biol. 2022 Apr 15;225(8). doi: 10.1242/jeb.243932. Epub 2022 Apr 21.
There is great interspecific variation in the nutritional composition of natural diets, and the varied nutritional content is physiologically tolerated because of evolutionarily based balances between diet composition and processing ability. However, as a result of landscape change and human exposure, unnatural diets are becoming widespread among wildlife without the necessary time for evolutionary matching between the diet and its processing. We tested how a controlled, unnatural high glucose diet affects glucose tolerance using captive green iguanas, and we performed similar glucose tolerance tests on wild Northern Bahamian rock iguanas that are either frequently fed grapes by tourists or experience no such supplementation. We evaluated both short and longer-term blood glucose responses and corticosterone (CORT) concentrations as changes have been associated with altered diets. Experimental glucose supplementation in the laboratory and tourist feeding in the wild both significantly affected glucose metabolism. When iguanas received a glucose-rich diet, we found greater acute increases in blood glucose following a glucose challenge. Relative to unfed iguanas, tourist-fed iguanas had significantly lower baseline CORT, higher baseline blood glucose, and slower returns to baseline glucose levels following a glucose challenge. Therefore, unnatural consumption of high amounts of glucose alters glucose metabolism in laboratory iguanas with short-term glucose treatment and free-living iguanas exposed to long-term feeding by tourists. Based on these results and the increasing prevalence of anthropogenically altered wildlife diets, the consequences of dietary changes on glucose metabolism should be further investigated across species, as such changes in glucose metabolism have health consequences in humans (e.g. diabetes).
自然饮食的营养成分在种间存在很大差异，由于饮食成分和处理能力之间基于进化的平衡，多样化的营养含量在生理上是可以耐受的。然而，由于景观变化和人类接触，非自然饮食在野生动物中变得越来越普遍，而它们没有时间在饮食与其处理能力之间进行必要的进化匹配。我们使用圈养绿鬣蜥测试了一种受控的、非自然的高葡萄糖饮食如何影响葡萄糖耐量，并对经常被游客喂食葡萄的北巴哈马岩鬣蜥或没有这种补充的野生岩鬣蜥进行了类似的葡萄糖耐量测试。我们评估了短期和长期的血糖反应和皮质酮 (CORT) 浓度，因为这些变化与改变的饮食有关。实验室中的实验性葡萄糖补充和野外的游客喂养都显著影响了葡萄糖代谢。当鬣蜥摄入富含葡萄糖的饮食时，我们发现葡萄糖挑战后血糖急性升高更大。与未喂食的鬣蜥相比，游客喂养的鬣蜥的基础 CORT 显著降低，基础血糖更高，以及在葡萄糖挑战后血糖恢复到基线水平的速度更慢。因此，非自然地大量摄入葡萄糖会改变实验室鬣蜥的短期葡萄糖处理和长期接受游客喂养的自由生活鬣蜥的葡萄糖代谢。基于这些结果以及人为改变的野生动物饮食的日益普及，应该在不同物种中进一步研究饮食变化对葡萄糖代谢的影响，因为葡萄糖代谢的这种变化对人类（例如糖尿病）的健康有影响。
