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

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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.