Blood Plasma Glucose Regulation in Wahlberg's Epauletted Fruit Bat

Mqokeli, Babalwa R.; Downs, Colleen T.

doi:10.3377/004.047.0218

Cited by 3 publications

(1 citation statement)

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“…Earlier studies on several species of frugivore and nectarivore bats report unusually high postprandial blood glucose levels for their body size. For instance, the average postprandial blood glucose level (irrespective of sex) is around 8 mmol/l in the fruit bat, Epomophorus wahlbergi (body mass ∼100 g ) ( Mqokeli and Downs, 2012 ); around 15 mmol/l in the nectar bat, Eonycteris spelaea (body mass ∼60 g ) ( Peng et al, 2017 ); and around 25 mmol/l in the nectar bat, Glossophaga soricina (body mass ∼10 g ) ( Kelm et al, 2011 ). Notably, our results support previous findings that C. sphinx has high blood glucose for their body mass regardless of sex (>30 mmol/l here and ∼24 mmol/l in Peng et al, 2017 ).…”

Section: Discussionmentioning

confidence: 99%

Sex differences in postprandial blood glucose and body surface temperature are contingent on flight in the fruit bat, Cynopterus sphinx

Nagarajan-Radha

Devaraj²

2021

Biology Open

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The postprandial blood glucose level is very high for the body size in frugivorous bats. Like other homeotherms, bats release heat during digestion of dietary macronutrients. Despite males and females of the same species exhibiting different foraging behaviour, empirical support for sex-differences in blood glucose and body surface temperature in fruit bats is poor. Moreover, while flight affects postprandial metabolism, whether such effects are different in each sex of fruit bats is unclear. Here, we studied these questions in the fruit bat, Cynopterus sphinx. We first assessed whether there are sex differences in the postprandial level of blood glucose and body surface temperature over time in rested bats. We then assessed whether flight affects outcomes of sex-differences in both traits. We found that the estimated marginal means of both traits were generally higher in females than males, in rested bats. Notably, the sex-difference in both traits was only significant at specific sampling time of the assay. Further, the trait means significantly differed between the sexes only in the rested, but not active, bats. Meaning that signals of sex-difference in metabolic traits eroded when bats were active. Taken together, our findings suggest that in C. sphinx, the sex-specificity in the expression of metabolic traits is significantly dependent on physical activity.

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Section: Discussionmentioning

confidence: 99%

Sex differences in postprandial blood glucose and body surface temperature are contingent on flight in the fruit bat, Cynopterus sphinx

Nagarajan-Radha

Devaraj²

2021

Biology Open

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Sugar flux through the flight muscles of hovering vertebrate nectarivores: a review

Welch

Chen

2014

J Comp Physiol B

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In most vertebrates, uptake and oxidation of circulating sugars by locomotor muscles rises with increasing exercise intensity. However, uptake rate by muscle plateaus at moderate aerobic exercise intensities and intracellular fuels dominate at oxygen consumption rates of 50% of maximum or more. Further, uptake and oxidation of circulating fructose by muscle is negligible. In contrast, hummingbirds and nectar bats are capable of fueling expensive hovering flight exclusively, or nearly completely, with dietary sugar. In addition, hummingbirds and nectar bats appear capable of fueling hovering flight completely with fructose. Three crucial steps are believed to be rate limiting to muscle uptake of circulating glucose or fructose in vertebrates: (1) delivery to muscle; (2) transport into muscle through glucose transporter proteins (GLUTs); and (3) phosphorylation of glucose by hexokinase (HK) within the muscle. In this review, we summarize what is known about the functional upregulation of exogenous sugar flux at each of these steps in hummingbirds and nectar bats. High cardiac output, capillary density, and blood sugar levels in hummingbirds and bats enhance sugar delivery to muscles (step 1). Hummingbird and nectar bat flight muscle fibers have relatively small cross-sectional areas and thus relatively high surface areas across which transport can occur (step 2). Maximum HK activities in each species are enough for carbohydrate flux through glycolysis to satisfy 100 % of hovering oxidative demand (step 3). However, qualitative patterns of GLUT expression in the muscle (step 2) raise more questions than they answer regarding sugar transport in hummingbirds and suggest major differences in the regulation of sugar flux compared to nectar bats. Behavioral and physiological similarities among hummingbirds, nectar bats, and other vertebrates suggest enhanced capacities for exogenous fuel use during exercise may be more wide spread than previously appreciated. Further, how the capacity for uptake and phosphorylation of circulating fructose is enhanced remains a tantalizing unknown.

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Molecular evolution of growth hormone and insulin-like growth factor 1 receptors in long-lived, small-bodied mammals

Davies

Tsagkogeorga

Bennett

et al. 2014

Gene

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Mammals typically display a robust positive relationship between lifespan and body size.Two groups that deviate markedly from this pattern are bats and the African mole-rats; with members of both groups being extremely long-lived given their body size, with the maximum documented lifespan for many species exceeding 20 years. A recent genomics study of the exceptionally long-lived Brandt's bat, Myotis brandtii (41 years), suggested its longevity and small body size may be at least partly attributed to key amino acid substitutions in the transmembrane domains of the receptors of growth hormone (GH) and insulin-like growth factor 1 (IGF1). However, whereas elevated longevity is likely to be common across all 19 bat families, the reported amino acid substitutions were only observed in two closely related bat families. To test the hypothesis that an altered GH/IGF1 axis relates to the longevity of African mole-rats and bats, we compared and analysed the homologous coding gene sequences in genomic and transcriptomic data from 26 bat species, five mole-rats and 38 outgroup species. Phylogenetic analyses of both genes recovered the majority of nodes in the currently accepted species tree with high support. Compared to other clades, such as primates and carnivores, the bats and rodents had longer branch lengths. The single 24 amino acid transmembrane domain of IGF1R was found to be more conserved across mammals compared to that of GHR.Within bats, considerable variation in the transmembrane domain of GHR was found, including a previously unreported deletion within the Emballonuridae. The transmembrane domains of rodents were found to be more conserved, with mole-rats lacking uniquely conserved amino acid substitutions. Molecular evolutionary analyses showed that both genes were under purifying selection in bats and mole-rats. Our findings suggest that while the previously documented mutations may confer some additional lifespan to Myotis bats, other, as yet unknown, genetic differences are likely to account for the long lifespans observed in many bat and mole-rat species.

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Blood Plasma Glucose Regulation in Wahlberg's Epauletted Fruit Bat

Cited by 3 publications

References 31 publications

Sex differences in postprandial blood glucose and body surface temperature are contingent on flight in the fruit bat, Cynopterus sphinx

Sex differences in postprandial blood glucose and body surface temperature are contingent on flight in the fruit bat, Cynopterus sphinx

Sugar flux through the flight muscles of hovering vertebrate nectarivores: a review

Molecular evolution of growth hormone and insulin-like growth factor 1 receptors in long-lived, small-bodied mammals

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