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|Type:||Capítulo de livro|
|Title:||Metabolic Adaptations In Frugivorous Bats|
|Abstract:||Frugivorous bats like Artibeus lituratus and Artibeus jamaicensis are known to digest carbohydrate-rich meals rapidly and efficiently. These bats feed on variety of fruits with preference for figs, which presents an availability of 14.4 g of carbohydrate per 100 g wet mass. Ingesting the equivalent of their body weight every night, frugivorous bats have to deal with an overload of glucose daily and must have several physiological adaptations that include specialized gastrointestinal tract structures and hormonal response capable of avoiding post-prandial hyperglycemia. It has been shown that frugivorous bats present high paracellular absorption of an analog of D-glucose (3-O-methyl-D-glucose) in their intestine. This pathway seems to contribute at least for 55% of total glucose uptake in Rousettus aegyptiacus and 70% in Artibeus lituratus. This mechanism must have an important role considering that these bats have shorter intestinal tracts than similarly sized non-flying mammals. Besides the high intestinal absorptive capacity, some authors also pointed to a specialization of the endocrine pancreas of R. aegyptiacus as an additive mechanism to deal with high glucose influx. It has been demonstrated that the endocrine pancreas of R. aegyptiacus represents 9.1% of the total pancreas volume, far more than in some other mammals. In a similar way, A. lituratus presents an apparent large β-cell distribution with different islets sizes and shapes, similar to R. aegyptiacus. However, the pattern of β-cell distribution in A. lituratus differs from that found in other mammals. Their β cells seem to be located, mainly, at the periphery of the islets, a pattern not observed in R. aegyptiacus, rodents, humans, non-human primates or pigs, where β cells are located throughout the islets, but especially in the core. This pattern could reflect physiological and environmental adjustments to accommodate changing demands for insulin. This species also presents elevated glucose tolerance, high insulin sensitivity and efficient insulin signalization in the pectoral muscle and hepatic tissue. Another important adaptation in A. lituratus is the ability to maintain normoglycemia even after 6 days of starvation, possibly because of its high hepatic glycogen stores and increased hepatic gluconeogenesis. In conclusion, and from an evolutionary point of view, the rapid and efficient digestion, high sensitivity to glucose and insulin and the presence of an apparent large β-cell distribution represent adequate adaptations that guarantee the proper control of glucose homeostasis in fruit-eating bats, constantly challenged by a high influx of glucose from its carbohydrate-rich diet. © 2011 Nova Science Publishers, Inc. All rights reserved.|
|Editor:||Nova Science Publishers, Inc.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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