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视角来理解动物形态和功能的多样性。我的一般研究计划集中在鸟类（通常是蜂鸟）和新世界蝙蝠，因为这些动物是最小的恒温动物之一，是挥发性的，因此在维持代谢稳态方面面临着特殊的挑战，同时包含具有丰富多样性饮食生态的物种。蜜食动物（在较小程度上，果食动物）的饮食结构看似简单，几乎完全由葡萄糖、果糖和双糖蔗糖组成。然而，这种简单的饮食给能量平衡带来了难以置信的挑战。在大多数脊椎动物中，碳水化合物的吸收、运输和直接氧化途径是非常有限的。此外，对大多数动物来说，高糖饮食总是致病的。然而，我的研究小组的工作表明，这些动物的饮食糖摄取和氧化途径，即所谓的“糖氧化级联”，是如何增强的，以促进高速率的即时氧化，并将糖转化为脂肪，以满足未来的需求。特别是，蜂鸟和采蜜蝙蝠不仅能利用葡萄糖，还能利用果糖；一种其他群体所没有的能力。然而，对于这些动物如何协调或优先使用饮食中的葡萄糖和果糖成分，同时处理相关的氧化和糖基化应激，我们知之甚少。在蝙蝠中，这个问题特别有趣，因为食果性和食糖性在几个谱系中是独立进化的，我实验室的初步数据表明，它们可能以不同的方式使用成分糖。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相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通量调节中的作用。此外，我将研究潜在的内源性抗氧化防御能力或耐受或避免糖基化应激有害后果的能力是否与蝙蝠的食蜜性或果性进化有关。这项工作的结果将揭示新热带蝙蝠的饮食和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了解觅食和运动行为以及能量学的种间差异，并将通过蝙蝠匹配燃料和能量摄入的能力来预测环境挑战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.