Secreção e sensibilidade periférica à insulina e hormônios contra-regulatórios do morcego hematófago Desmodus rotundus

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

In general, mammals fed on high protein diets (HP) are more resistant to starvation. However, the hematophagous bat Desmodus rotundus, althougth having a HP diet (blood), is markedly susceptive to the food deprivation, presenting severe hypoglycemia after 24h of starvation. Besides, this species has small stores of hepatic glycogen and adipose tissue lipid, low concentration of plasma and pancreatic insulin and a few numbers of á and â cells in its Islets of Langerhans. This work aimed to study in D. rotundus: the response to Intraperitonial Glucose Tolerance Test (ipGTT); Intraperitonial Insulin Tolerance Test (ipITT); static insulin secretion stimulated by many secretagogues; insulin tecidual signaling, and insulin glucagon and cortisol plasma levels in fed and fasted animals. The results from ipGTT showed that these bats cannot handle with an overload of glucose, suggesting intolerance to this substrate. The results from ipITT showed that there are not changes in glycemia after insulin injection suggesting that, besides the low insulin concentration, D. rotundus seems to present resistance to this hormone. Plasma glucagon and insulin concentrations of fed and starved bats were lower than most mammals, including humans. On the other side, the high levels of plasma cortisol suggest that this hormone seem not to contribute to glycemic homeostasis maintenance, as normally happens in mammals. The experiments with static insulin secretion showed that the â cells from D. rotundus presented a significant insulin secretion increase in response to glucose and leucina, but did not present to K+. Finally, we did not find changes in liver Akt phosphorilation levels in response to insulin stimulation. However, there was a significant increase in ERK expression in response to this hormone. Albeit we have found increase in ERK expression in response to insulin, this pathway should not be involved in glucose uptake stimulated by insulin. The metabolic pattern presented by D. rotundus could be related to an adaptative strategy, which guarantee high circulating glucose levels considering that these species deals with great possibility of not attaining to food. Although its fragility to starvation, D. rotundus shows a huge population density. This is possibly related to the reciprocal sharing food behavior (Wilkinson, 1984), where an animal that was not able to feed itself for one night receives blood from another bat by regurgitation.

ASSUNTO(S)

insulina hormônios ciencias da saude secreção morcego

ACESSO AO ARTIGO

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