Probes for INSULIN

Insulin-induced hypoglycemia in diabetes is associated with impaired glucagon secretion. Here we tested whether stimulation of GPR119, a G-protein coupled receptor expressed in pancreatic islet as well as enteroendocrine cells, and previously shown to stimulate insulin and incretin secretion might enhance glucagon secretion during hypoglycemia. In the study, GPR119 agonists were applied to isolated islets or perfused pancreata perfusions to assess insulin and glucagon secretion during hypoglycemia or hyperglycemic conditions. Insulin infusion hypoglycemic clamps were performed with or without GPR119 agonist pre-treatment to assess glucagon counter-regulation in healthy and STZ-diabetic rats, including those exposed to recurrent bouts of insulin-induced hypoglycemia that leads to suppression of hypoglycemia-induced glucagon release. Hypoglycemic clamp studies were also conducted in GPR119 KO mice to evaluate whether the pharmacologic stimulatory actions of GPR119 agonists on glucagon secretion during hypoglycemia were an on-target effect. The results revealed that GPR119 agonist-treated pancreata or cultured islets had increased glucagon secretion during low glucose perfusion. In vivo, GPR119 agonists also significantly increased glucagon secretion during hypoglycemia in healthy and STZ-diabetic rats, a response that was absent in GPR119 KO mice. In addition, impaired glucagon counter-regulatory responses were restored by a GPR119 agonist in STZ-diabetic rats that were exposed to antecedent bouts of hypoglycemia. Thus, GPR119 agonists have the ability to pharmacologically augment glucagon secretion, specifically in response to hypoglycemia in diabetic rodents. Whether this effect might serve to diminish the occurrence and severity of iatrogenic hypoglycemia during intensive insulin therapy in diabetic patients remains to be established.

Chemokine (C-C motif) ligand 5 (CCL5) belongs to a group of chemokines that play a role in the peripheral immune system, mostly as chemoattractant molecules, and mediate tactile allodynia. In the central nervous system (CNS), CCL5 and its receptors have multiple functions, including promoting neuroinflammation, insulin signaling, neuromodulator of synaptic activity and neuroprotection against a variety of neurotoxins. Evidence has also suggested that this chemokine may regulate opioid response. The multifunctional profile of CCL5 might correlate with its ability to bind different chemokine receptors, as well as with its unique cellular expression. In this work, we have used fluorescence in situ hybridization combined with immunohistochemistry to examine the expression profile of CCL5 mRNA in the adult rat brain and provide evidence of its cellular localization. We have observed that the highest expression of CCL5 mRNA occurs in all major fiber tracts, including the corpus callosum, anterior commissure, and cerebral peduncle. In these tracts, CCL5 mRNA was localized in oligodendrocytes, astrocytes and microglia. Astrocytic and microglial expression was also evident in several brain areas including the cerebral cortex, caudate/putamen, hippocampus, and thalamus. Furthermore, using a specific neuronal marker, we observed CCL5 mRNA expression in discrete layers of the cortex and hippocampus. Interestingly, in the midbrain, CCL5 mRNA co-localized with tyrosine hydroxylase (TH) positive cells of the ventral tegmental area, suggesting that CCL5 might be expressed by a subset of dopaminergic neurons of the mesolimbic system. The expression of CCL5 mRNA and protein, together with its receptors, in selected brain cell populations proposes that this chemokine could be involved in neuronal/glial communication.