phenanthrenes and Hypoglycemia

Activation of central type II glucocorticoid receptors (GR) during neutral protamine Hagedorn insulin (NPH) administration exacerbates recurring hypoglycemia. The hypothalamic paraventricular nucleus (PVN) integrates metabolic sensory input, controls autonomic and neuroendocrine motor outflow, and is characterized by abundant GR expression. The present studies investigated the hypothesis that PVN GR mediate intensification of hypoglycemia by serial NPH dosing, and that PVN glucokinase (GCK) and glucoregulatory neuropeptide genes acclimate to this treatment paradigm through GR-dependent mechanisms. Groups of adult male rats were injected subcutaneously with one or four doses of NPH, on as many days, while controls received vehicle. Bilateral administration of the selective GR antagonist, CP-472555, into the PVN prior to the first three NPH injections prevented amplification of hypoglycemia in response to the final insulin dose, while intra-PVN delivery of the GR agonist, dexamethasone, to euglycemic rats did not modify ensuing NPH-induced hypoglycemia. Quantitative real-time RT-PCR analysis of microdissected PVN tissue revealed that GCK, corticotropin-releasing hormone (CRH), oxytocin (OT), and vasopressin (VP) mRNA levels were unchanged in response to acute NPH, and baseline gene profiles measured 24 h after antecedent injections were similar to vehicle controls. In contrast, serial dosing with NPH elevated CRH and GCK, diminished OT, but did not alter VP gene transcripts. Intracerebroventricular CP-472555 delivery in conjunction with antecedent NPH dosing prevented transcriptional habituation of GCK and OT genes, but did not modify CRH or VP mRNA profiles. The present data show that activation of PVN GR during antecedent intermediate insulin-induced hypoglycemia is required for exacerbation of recurring hypoglycemia, and receptor stimulation in the absence of hypoglycemia and/or its sequelae does not intensify the effects of subsequent NPH administration. The results also provide evidence for acclimation of PVN CRH, GCK, and OT gene profiles to serial NPH dosing, and demonstrate that GR may be involved in GCK and OT transcriptional adaptation to ongoing intermediate insulin-induced hypoglycemia.

Topics: Animals; Corticotropin-Releasing Hormone; Dexamethasone; Gene Expression Profiling; Gene Expression Regulation; Glucokinase; Hypoglycemia; Injections, Intraventricular; Insulin, Isophane; Male; Neuropeptides; Oxytocin; Paraventricular Hypothalamic Nucleus; Phenanthrenes; Pyridines; Rats; Receptors, Glucocorticoid; RNA, Messenger; Transcriptional Activation; Vasopressins

Current studies show that type II glucocorticoid receptor (GR) stimulation during recurring insulin-induced hypoglycemia (RIIH) results in diminished hypoglycemic activation of neurons in discrete CNS metabolic structures, namely the lateral hypothalamic area (LHA), hypothalamic paraventricular (PVH) and dorsomedial (DMH) nuclei, and nucleus of the solitary tract (NTS). The present work utilized immunofluorescence histochemistry to evaluate the reactivity of GR-expressing neurons in characterized hypothalamic, thalamic, and hindbrain metabolic structures to glucoprivation, and to determine if antecedent hypoglycemic stimulation of central GR decreases Fos protein expression by these neurons. Groups of adult male rats were injected subcutaneously with one or four doses of the intermediate-acting insulin, Humulin NPH, on as many days, while controls received diluent only. Rats injected with four doses of insulin were pretreated by intracerebroventricular administration of the selective GR antagonist, CP-475222, or vehicle alone prior to insulin doses 1-3. All animals were sacrificed by trancardial perfusion 2 h after injections on day four of the study. Mean numbers of GR-immunoreactive (-ir) neurons did not differ between groups injected with diluent versus one dose of insulin in each structure evaluated, but were significantly elevated above baseline on the fourth day of RIIH in the LHA and DMH, but not the PVH, VMH, ARC, thalamic paraventricular (PVT), or NTS. Counts of GR-ir-positive neurons in each site were similar between groups treated with CP-475222 or vehicle icv during RIIH. While mean numbers of GR-plus Fos-ir neurons in the PVH, DMH, LHA, and NTS, but not the PVT were significantly elevated after one dose of NPH, this increase was abolished in each site by RIIH. Pharmacological antagonism of central GR during antecedent hypoglycemia prevented RIIH-associated habituation of Fos colabeling of GR-expressing neurons in the PVH, DMH, and LHA. These data show that RIIH increases nuclear immunolabeling for GR in discrete CNS metabolic structures, evidence that recurring metabolic stress may amplify receptor-mediated genomic regulatory function in local neurons. The results also demonstrate that GR-containing neurons in the LHA, DMH, PVH, and NTS react to hypoglycemia by induction of the Fos stimulus-transcription cascade, and that precedent stimulation of central GR is critical for RIIH-associated habituation of this functional response in the former

Topics: Animals; Cell Count; Gene Expression Regulation; Hypoglycemia; Hypothalamus; Insulin; Male; Neurons; Oncogene Proteins v-fos; Phenanthrenes; Pyridines; Rats; Rats, Sprague-Dawley; Receptors, Glucocorticoid; Time Factors

Hypoglycemia elicits an integrated array of CNS-mediated counterregulatory responses, including activation of the hypothalamic-pituitary-adrenal axis. The role of antecedent adrenocortical hypersecretion in impaired glucose counterregulation remains controversial. The present studies utilized the selective, nonsteroidal glucocorticoid receptor antagonist, CP-472555, as a pharmacological tool to investigate the hypothesis that hypoglycemic hypercorticosteronemia modulates CNS efferent autonomic and neuroendocrine motor responses to recurring insulin-induced hypoglycemia via glucocorticoid receptor-dependent mechanisms. Groups of adult male rats were injected s.c. with either one or four doses of the intermediate-acting insulin, Humulin neutral protamine Hagedorn (NPH), on as many days, while controls were injected with diluent alone. Animals injected with four doses of insulin were pretreated by i.c.v. administration of graded doses of the glucocorticoid receptor antagonist or vehicle alone prior to the first three doses of insulin. Repeated daily injection of NPH exacerbated hypoglycemia, attenuated patterns of glucagon and epinephrine secretion, and diminished neuronal transcriptional activation in discrete CNS metabolic loci, including the lateral hypothalamic area, dorsomedial hypothalamic nucleus, paraventricular hypothalamic nucleus, and nucleus of the solitary tract. While i.c.v. delivery of 25 or 100 ng doses of CP-472555 did not alter any of these parameters, animals treated with 500 ng exhibited circulating glucose, glucagon, and epinephrine levels that were similar to those in rats injected with one dose of insulin, as well as a reversal of recurring insulin-induced hypoglycemia-associated reductions in Fos immunolabeling in the lateral hypothalamic area, dorsomedial hypothalamic nucleus, and paraventricular hypothalamic nucleus. These results provide unique pharmacological evidence that antecedent activation of central glucocorticoid receptor is required for exacerbation of hypoglycemia during recurring insulin-induced hypoglycemia, and that these receptors mediate modulatory effects of hypoglycemic hypercorticosteronemia on autonomic efferent responses to recurring insulin-induced hypoglycemia. The data also suggest that neurons in central loci characterized here by antagonist-mediated overturn of recurring insulin-induced hypoglycemia-induced decreases in neuronal transcriptional activation may be direct or indirect substrates for this hormon

Topics: Animals; Autonomic Nervous System; Corticosterone; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Epinephrine; Glucagon; Hypoglycemia; Hypoglycemic Agents; Hypothalamus; Insulin; Male; Neurosecretory Systems; Phenanthrenes; Proto-Oncogene Proteins c-fos; Pyridines; Rats; Rats, Sprague-Dawley; Receptors, Glucocorticoid; Transcriptional Activation

Neurons that synthesize the potent orexigenic neuropeptide, orexin-A (ORX-A) are confined to the lateral hypothalamic area (LHA) and adjacent structures, and project throughout the central neuroaxis to structures that govern central nervous system responses to energy imbalance. Insulin-induced hypoglycemia (IIH) upregulates prepro-orexin mRNA and Fos immunostaining of LHA ORX-A neurons. These neurons apparently become desensitized to this metabolic challenge, since both responses are diminished by recurrent insulin-induced hypoglycemia (RIIH). Recent studies implicate central type II glucocorticoid receptors (GR) in RIIH-associated glucose counterregulatory collapse and decline in Fos labeling of central metabolic loci, including the LHA. The present studies evaluated the role of GR in patterns of LHA ORX-A neuronal transcriptional activation during RIIH. Groups of adult male rats were injected subcutaneously with one or four doses of the intermediate-acting insulin, Humulin NPH, on as many days, or with diluent alone. Rats injected with four doses of insulin were pretreated by intracerebroventricular (icv) administration of the selective GR antagonist, CP-472555, or the vehicle, propylene glycol, prior to insulin administration on days 1-3. All animals were sacrificed by transcardial perfusion 2h after injections on day 4. Processing of LHA tissue sections for dual-immunoperoxidase staining of ORX-A- and Fos-immunoreactivity (-ir) showed that colabeling of ORX-A neurons for Fos was increased by a single injection of NPH, whereas this genomic response was diminished by RIIH. Icv administration of CP-472555 during antecedent hypoglycemia prevented RIIH-associated reductions in Fos expression by these neurons. Antagonist treatment of diluent-injected controls did not alter mean numbers of ORX-A- plus Fos-ir neurons. Total numbers of ORX-A-immunopositive neurons were not different among treatment groups. These data demonstrate that precedent central GR blockade prevents adaptation of LHA ORX-A neuronal reactivity to RIIH. These results provide unique pharmacological evidence that hypoglycemic hypercorticosteronemia diminishes activation of this neurotransmitter phenotype in this critical metabolic structure to subsequent hypoglycemia via central GR-dependent mechanisms.

Topics: Animals; Behavior, Animal; Drug Interactions; Hypoglycemia; Hypoglycemic Agents; Hypothalamic Area, Lateral; Immunohistochemistry; Insulin; Insulin, Isophane; Intracellular Signaling Peptides and Proteins; Male; Neurons; Neuropeptides; Oncogene Proteins v-fos; Orexins; Phenanthrenes; Pyridines; Rats; Rats, Sprague-Dawley; Receptors, Glucocorticoid; Time Factors

Life threatening hypoglycaemia has been closely associated with the use of quinine, but the effect of quinidine and the synthetic antimalarials on the homoeostasis of glucose has not been investigated. In volunteers given a fixed dose of 500 mg base and patients with malaria given a quinidine loading dose (15 mg base/kg) mean (SEM) plasma insulin concentrations rose from 6.1 (1.5) mU/l to 10.9 (4.4) mU/l (p less than 0.02) and 10.4 (2.0) mU/l to 18.5 (5.3) mU/l (p less than 0.04), respectively. Plasma glucose concentrations fell from 4.5 (1.1) mmol/l (81 (20) mg/100 ml) to 4.0 (0.3) mmol/l (72 (5) mg/100 ml) in volunteers (p less than 0.04) and from 5.7 (1.3) mmol/l (102 (23) mg/100 ml) to 4.8 (1.6) mmol/l (86 (29) mg/100 ml) in patients (p less than 0.05). One of two patients with cerebral malaria and acute renal failure became profoundly hypoglycaemic (plasma glucose concentration 1.4 mmol/l (25 mg/100 ml), plasma insulin concentration 3.1 mU/l). Hypoglycaemia may occur in any severely ill fasting patient given parenteral quinidine. The other antimalarials tested, chloroquine, amodiaquine, mefloquine, and halofantrine, did not stimulate the release of insulin, an important advantage that should be taken into account when treatment is chosen for Plasmodium falciparum malaria.

Topics: Amodiaquine; Antimalarials; Blood Glucose; Chloroquine; Humans; Hypoglycemia; Insulin; Mefloquine; Phenanthrenes; Quinidine; Quinolines; Thailand