Determination of insulin levels of the common dormouse (glis glis) and hedgehog (Erinaceus europaeus) with reference to the rat

GPR15-C10ORF99 functional pairing initiates colonic Treg homing in amniotes

Regulatory T lymphocyte (Treg) homing reactions mediated by G protein-coupled receptor (GPCR)-ligand interactions play a central role in maintaining intestinal immune homeostasis by restraining inappropriate immune responses in the gastrointestinal tract. However, the origin of Treg homing to the colon remains mysterious. Here, we report that the C10ORF99 peptide (also known as CPR15L and AP57), a cognate ligand of GPR15 that controls Treg homing to the colon, originates from a duplication of the flanking CDHR1 gene and is functionally paired with GPR15 in amniotes. Evolutionary analysis and experimental data indicate that the GPR15-C10ORF99 pair is functionally conserved to mediate colonic Treg homing in amniotes and their expression patterns are positively correlated with herbivore diet in the colon. With the first herbivorous diet in early amniotes, a new biological process (herbivorous diet short-chain fatty acid-C10ORF99/GPR15-induced Treg homing colon immune homeostasis) emerged, and we propose an evolutionary model whereby GPR15-C10ORF99 functional pairing has initiated the first colonic Treg homing reaction in amniotes. Our findings also highlight that GPCR-ligand pairing leads to physiological adaptation during vertebrate evolution.

Hibernation depth influences the edible dormouse pancreatic B cell during the spring arousal

In order to determine the influence of hibernation depth upon the secretion and the effect of insulin, two groups of edible dormice were maintained in winter under different climatic and nutritional conditions, and their pancreatic B-cell function was tested during the spring arousal. The first group of animals was exposed to a moderate temperature and fed ad libitum. Their periods of hypothermia were short and irregular and the active periods sometimes lasted several days; their body weight increased during the winter months; in spring, the sensitivity of B cells to glucose was low, decreasing insulin secretion in vivo and in vitro, and the adipocytes were insulin resistant. The second group of fasting animals was exposed to a low and constant temperature (5 degrees). Their phases of lethargy were long and regular (about 15 days), separated by active periods (6-8 hr); their body weight decreased during the winter months; in spring the B-cell secretion was increased and the sensitivity of the tissues to insulin ensured a high peripheral glucose utilization. These data show that the winter climatic and nutritional conditions which influence the depth of hibernation modify the edible dormouse B-cell activity during the spring arousal.

Insulin secretion in the hibernating edible dormouse (Glis glis): in vivo and in vitro studies

Plasma glucose and insulin have been studied during lethargy and spontaneous arousal of hibernating edible dormouse. During lethargy blood glucose was low while plasma insulin remained at the same level as in other seasons. Plasma glucose and insulin did not fluctuate along the phase of lethargy. During spontaneous arousal plasma insulin rose strongly from the 17 degrees C stage, reaching the higher values at 26 degrees C while blood glucose was only 85 mg/100 ml, then decreased at 37 degrees C. The effect of glucose and temperature on insulin secretion was studied using perfused pancreas preparation from hibernating edible dormice. During the rewarming of the edible dormouse pancreas the insulin release did not occur in response to the absolute extracellular glucose level but occurred in response to a B cell membrane phenomenon which was dependent on the changing rate of glucose level. The effect of glucose and temperature on insulin secretion from perfused pancreas was compared between edible dormouse and homeotherm permanent, the rat. The B cell response to glucose of the dormouse pancreas increased up to 15 degrees C whereas that of the rat only from 25 degrees C. The dormouse insulin secretion reached a peak value at the 30 degrees C of temperature, whereas that of the rat progressively increased until 37 degrees C. These results showed that some biochemical adjustment or process of acclimatization took place in the B cells of the hibernators.

In vitro B cell response to glucose in the hibernating hedgehog: comparison with the homeothermic hedgehog and the rat

The effect of glucose and temperature on insulin secretion was studied using pieces of pancreas from hibernating hedgehogs, homeothermic hedgehogs and rats. The rewarming of the perfusion medium progressively stimulated insulin release from the pancreases from lethargic hedgehogs above 13 degrees C even in the absence of glucose. At low temperature (20 degrees C), insulin probably resulted from labile compartments as suggested by the great first phase of glucose-induced insulin secretion from pancreases from lethargic hedgehogs. The insulin release from pancreases from homeothermic animals (hedgehogs and rats) was temperature dependent only above 23-25 degrees C and only with stimulating glucose concentrations (100 or 300 mg/100 ml). These main differences between B cell physiology of lethargic or homeothermic animals suggest that hibernation induces modifications in the secretory processes which facilitate insulin secretion during the in vivo spontaneous arousal from lethargy.

Seasonal effect of catecholamines on glucose-induced insulin secretion in the edible dormouse (Glis glis L.): in vivo and in vitro studies

The results of the present study support the view that catecholamines are important for insulin secretion during the annual cycle of the edible dormouse exposed to seasonal changes in southwest France. Glucose tolerance tests and perfusion of the isolated pancreas have shown that in spring and summer, the B cell secretion mechanism is less sensitive to glucose than in other seasons. In spring and summer, insulin secretion induced by glucose is enhanced after in vivo and in vitro phentolamine treatment. The autumn and winter control insulin levels were not modified by phentolamine treatment. These results indicate that the inhibition of insulin secretion in spring and summer is due to noradrenaline liberated at the nerve endings adjacent to the B cells rather than to circulating catecholamines. This seasonal effect of noradrenaline may be attributed either to seasonal changes in the sensitivity of the alpha-adrenergic receptors of B cells or to an increase in noradrenaline release at the nerve endings in the islet during spring and summer.