The advantages and challenges of a glucose and fructose-rich diet

我的实验室试图通过能量学和代谢生物化学的镜头来了解动物形态和功能的多样性。我的总体研究计划集中在鸟类(通常是蜂鸟)和新大陆蝙蝠，因为这些动物是最小的吸热动物之一，游荡，因此面临着维持新陈代谢动态平衡的特殊挑战，同时包含具有丰富多样化饮食生态的物种。食蜜者(在较小程度上是食果者)的饮食结构看起来很简单，几乎完全由葡萄糖、果糖和蔗糖组成。然而，这种简单化的饮食给能量平衡带来了令人难以置信的挑战。在大多数脊椎动物中，碳水化合物的吸收、运输和直接氧化的途径极其有限。此外，高糖饮食对大多数动物来说都是致病的。然而，我的团队的工作表明，这些动物如何通过饮食中的糖吸收和氧化途径，即所谓的“糖氧化级联反应”，促进快速氧化和糖到脂肪的转化，以满足未来的需求。特别是，蜂鸟和花蜜蝙蝠表现出非凡的能力，不仅能利用葡萄糖，还能利用果糖；这是其他物种所没有的能力。然而，关于这些动物如何在饮食中协调或优先使用葡萄糖和果糖成分，同时处理相关的氧化和糖化应激，人们仍然知之甚少。在蝙蝠中，这个问题特别有趣，因为果实和蜜汁在几个谱系中独立进化，我的实验室的初步数据显示，它们可能以不同的方式利用成分糖。我的团队将使用一套综合的方法来探索，1)葡萄糖和果糖的相对使用，以满足与新热带蝙蝠饮食生态有关的当前和未来的能量需求，2)碳水化合物转运体在这些糖的不同使用和调节中的作用。此外，我还将研究建立抗氧化防御系统的潜在内源性能力，或耐受或避免糖基化应激的有害后果的能力，是否与蝙蝠的蜜汁或果实的进化有关。这项拟议工作的结果将揭示新热带蝙蝠之间饮食和新陈代谢生理共同进化的方式。我们的发现将帮助生理学家和生态学家将觅食和运动行为的种间差异以及能量学联系起来，并将通过蝙蝠匹配燃料和能量摄入量与需求的能力，预测环境挑战可能如何不同地影响蝙蝠的生存和表现。

My lab seeks to understand the diversity of animal form and function through the lens of energetics and metabolic biochemistry. My general research program focuses on birds (typically hummingbirds) and new world bats because these animals are among the smallest endotherms, are volant, and thus face exceptional challenges to maintaining metabolic homeostasis, while containing species with a rich diversity of dietary ecologies. The makeup of a nectarivore (and to a lesser extent, frugivorous) diet is deceptively simple, composed almost exclusively of glucose, fructose, and the disaccharide sucrose. However, this simplistic diet imposes incredible challenges to energy homeostasis. Pathways for the absorption, transport, and direct oxidation of dietary carbohydrate in most vertebrates are extremely limited. Further, a high sugar diet is invariably pathogenic in most animals. However, work from my group has shown how dietary sugar uptake and oxidation pathways, the so-called "sugar oxidation cascade" are enhanced in these animals to facilitate high rates of both immediate oxidation, and conversion of sugars to fat to fuel future needs. In particular, hummingbirds and nectar bats show remarkable abilities to use not just glucose, but also fructose; an ability absent in other groups. Still, little is known about how these animals orchestrate or prioritize the use of glucose and fructose components in their diet while simultaneously dealing with associated oxidative and glycation stress. Within bats, this question is particularly interesting because frugivory and nectarivory have evolved independently in several lineages, and preliminary data from my lab shows that they may use component sugars in distinct ways. My group will use and integrative suite of approaches to explore, 1) the relative use of glucose and fructose to fuel immediate and future energy needs in relation to dietary ecology in neotropical bats and 2) the role of carbohydrate transporters in the differential use and regulation of flux of these sugars. Additionally, I will 3) examine whether the potential endogenous capacities for building antioxidant defense or the ability to tolerate or avoid the deleterious consequences of glycation stress are correlated with evolution of nectarivory or frugivory in bats. Results from this proposed work will reveal the ways in which diet and metabolic physiology co-evolve among neotropical bats. Our findings will help both physiologists and ecologists to contextualize interspecific variation in foraging and locomotor behaviour as well as energetics, and will inform predictions regarding how environmental challenges may differentially affect bat survival and performance via bats' abilities to match fuel and energy intake to demand.