Research On Bat Animal Models For Diabetes And SLC2A2 Gene In Bats

Bats are mammals in Chiroptera and account for about one fifth of the world's mammalian species. The fruit-and insect-eating bats had showed better capabilities of maintaining glucose homeostasis, lowing blood glucose by insulin and of increasing body weight and fat for hibernation, transforming the white adipose tissue into the brown adipose, respectively. Thus it made bats the excellent animal models for diabetes research and treatment. It inspired the establishment of chiropteran animal models for diabetes. The body mass index and blood glucose level are common methods for diabetes research. For this purpose, we explored and calculated the body mass index (BMI) and the forearm mass index (FMI) as well as the correlation between BMI, FMI and blood glucose of bats. Then the acute glucose tolerance tests (GTT) as well as the molecular mechanisms were carried on within bats with different dietary habits.Totally,149 BMI and 860 FMI were calculated based on the data of bats. The insect-eating bats had lower body weight and lower BMI and FMI while the fruit-eating bats had higher body weight and higher BMI and FMI. The carnivorous, sanguivorous, and omnivorous bats had intermediate values, showing the higher baselines for normal frugivorous bats than insectivorous bats. For the huge differences between bats and human BMI values, the standards for overweight or obesity should be founded for bats species. Researches on glucose tolerance tests and the relationship between BMI, FMI and blood glucose levels in omnivorous bats which feed mainly or totally on fruits or insects will resolve these issues. Both fruit-and insect-eating bats had showed inter-species negative correlations between their BMI, FMI and blood glucose levels. The bats with higher BMI, FMI had lower blood glucose while those with lower BMI, FMI had higher blood glucose, which is quite different with the positive correlations between BMI and blood glucose levels usually seen in intra-species.The acute glucose tolerance tests were then conducted in six fruit-eating Leschenault's Rousette bats (Rousettus leschenaulti) and nine insect-eating great roundleaf bats (Hipposideros armiger). Leschenault's Rousette bats showed lower fast blood glucose, lower peak blood glucose, smaller area under the blood glucose curve, indicating a better capability of maintaining blood glucose and lowering blood glucose by insulin than the insect-eating great roundleaf bats did. The blood glucose could be transported into the liver, muscle, and fat tissues by the glucose transporter (GLUT) for glycogen synthesis.The Glut2 (encoded by SLC2A2 gene) involves in blood glucose and is an important glucose transporter for transporting the glucose in and out of liver. To explore the role of Glut2 in maintaining glucose homeostasis, lowing blood glucose by insulin, researches on the molecular evolutionary analysis as well as the expression in transcriptional and translational levels of SLC2A2 gene were carried on in bats. The molecular evolutionary analysis on SLC2A2 genes in bats indicated that neither the branches leading to the ancestor nor to the descendant bats showed positively selected sites under the branch-site models. But the proximal promoter sequences of SLC2A2 cloned in bats showed that a deletion with 11 bp in length was in all fruit-eating bats examined. The followed qPCR and western blot proved that the bats with this 11 bp deletion had a higher relative expression 6f SLC2A2 in transcriptional and translational levels than the bats without this deletion did, probably resulting for the better capabilities of maintaining the blood glucose and lowing the blood glucose by insulin for the fruit-eating bats.