Hypoglycemia In Rats Research Articles

6-LB: GPR119 Agonist PRM A Increases Glucagon Response to Hypoglycemia in Rats

Glucagon (Gcg) is crucial in the counter-regulatory response (CRR) to hypoglycemia yet this is severely impaired in T1D. This pathophysiology was recognized 50 years ago, but only recently have drug targets emerged to amplify Gcg CRR in T1D. One promising target is the receptor GPR119, expressed in gut endocrine cells and pancreatic islets with highest expression on α-cells, 10-fold greater than on β-cells. In the current study, a GPR119 agonist (PRM A) was given by oral gavage at doses of 3, 10 and 30 mg per kg (mpk), to rats (Sprague-Dawley, groups of 8) two hours prior to induction of hypoglycemia by an insulin tolerance test (ITT), using a dose of 1.25 Units per kg, given by intra-peritoneal injection at t=0 min. A vehicle-treated (V) control and a positive comparator group, given the GPR119 agonist MBX-2982 (10 mpk) were also studied. MBX-2982 is currently being used in a clinical trial to assess its effect on Gcg CRR in volunteers with T1D challenged with a hypoglycemic clamp. In rats in the current study, severe hypoglycemia was induced during the ITT; blood glucose nadir was achieved by 60 min in association with peak insulin ≥ 100 µU/ml. Glucose and insulin were similar across groups. The healthy V rats mounted a normal Gcg CRR, with a peak value of 26±10 pM, 5-fold above baseline. Pre-treatment with PRM A significantly amplified Gcg CRR relative to V (to 86±17, 79±18, and 85±12 pM; at 3, 10, and 30 mpk; p<0.0001 vs V). The Gcg AUC during the ITT was nearly 50% greater with all doses of PRM A (p<0.05 vs V) and the peak Gcg CRR was shifted earlier (p<0.01 vs V). MBX-2982 pre-treated rats, relative to V, trended to a higher peak (49±14 vs 26±10 pM) and AUC Gcg (7292±2039 vs 6855±1306 pM*h), but neither difference was significant, whereas the differences for PRM A were strongly significant for time and treatment. In summary, PRM A, a potent GPR119 agonist, tripled peak Gcg CRR during an ITT in healthy rats, affirming that the target of GPR119 holds promise as a novel means to mitigate the dangerous risk of hypoglycemia for individuals with T1D. Disclosure D. W. K. Kwok: None. D. Alexander: None. N. R. A. Beeley: None. D. Kelley: Consultant; Pramana Pharmaceuticals, Inc, Kallyope. Funding Pramana Pharmaceuticals Inc.

Modulation of the autophagy-lysosomal pathway and endoplasmic reticulum stress by ketone bodies in experimental models of stroke.

Ischemic stroke is a leading cause of disability worldwide. There is no simple treatment to alleviate ischemic brain injury, as thrombolytic therapy is applicable within a narrow time window. During the last years, the ketogenic diet (KD) and the exogenous administration of the ketone body β-hydroxybutyrate (BHB) have been proposed as therapeutic tools for acute neurological disorders and both can reduce ischemic brain injury. However, the mechanisms involved are not completely clear. We have previously shown that the D enantiomer of BHB stimulates the autophagic flux in cultured neurons exposed to glucose deprivation (GD) and in the brain of hypoglycemic rats. Here, we have investigated the effect of the systemic administration of D-BHB, followed by its continuous infusion after middle cerebral artery occlusion (MCAO), on the autophagy-lysosomal pathway and the activation of the unfolded protein response (UPR). Results show for the first time that the protective effect of BHB against MCAO injury is enantiomer selective as only D-BHB, the physiologic enantiomer of BHB, significantly reduced brain injury. D-BHB treatment prevented the cleavage of the lysosomal membrane protein LAMP2 and stimulated the autophagic flux in the ischemic core and the penumbra. In addition, D-BHB notably reduced the activation of the PERK/eIF2α/ATF4 pathway of the UPR and inhibited IRE1α phosphorylation. L-BHB showed no significant effect relative to ischemic animals. In cortical cultures under GD, D-BHB prevented LAMP2 cleavage and decreased lysosomal number. It also abated the activation of the PERK/eIF2α/ATF4 pathway, partially sustained protein synthesis, and reduced pIRE1α. In contrast, L-BHB showed no significant effects. Results suggest that protection elicited by D-BHB treatment post-ischemia prevents lysosomal rupture allowing functional autophagy, preventing the loss of proteostasis and UPR activation.

Effects of somatostatin receptor type 2 antagonism during insulin-induced hypoglycaemia in male rats with prediabetes.

To examine if glucagon counterregulatory defects exist in a rat model of prediabetes (pre-T2D) and toassess if a selective somatostatin receptor 2 antagonist (SSTR2a), ZT-01, enhances the glucagon response to insulin-induced hypoglycaemia. Hyperglycaemia was induced in 8- to 9-week-old male, Sprague-Dawley rats via 7 weeks of high-fat diet followed by a single, low-dose intraperitoneal injection of streptozotocin (30 mg/kg). After 2 weeks of basal insulin therapy (0-4U/d insulin glargine, administered subcutaneously [SC]) to facilitate partial glycaemic recovery and a pre-T2D phenotype, n=17 pre-T2D and n=10 normal chow-fed control rats underwent the first of two hypoglycaemic treatment-crossover experiments, separated by a 1-week washout period. On each experimental day, SSTR2a (3mg/kg ZT-01, SC) or vehicle was administered 1hour prior to insulin-induced hypoglycaemia (insulin aspart, 6U/kg, SC). Glucagon counterregulation was marginally reduced with the induction of pre-T2D. Treatment with SSTR2a raised peak plasma glucagon levels and glucagon area under the curve before and after insulin overdose in both and pre-T2D rats. Blood glucose concentration was elevated by 30 minutes after SSTR2a treatment in pre-T2D rats, and hypoglycaemia onset (≤3.9 mmol/L) was delayed by 15 ± 12 minutes compared with vehicle (P < 0.001), despite similar glucose nadirs in the two treatment groups (1.4 ± 0.3 mmol/L). SSTR2a treatment had no effect on blood glucose levels in the control group or on the hypoglycaemia-induced decline in plasma C-peptide levels in either group. Treatment with an SSTR2a increases glucagon responsiveness and delays the onset of insulin-induced hypoglycaemia in this rat model of pre-T2D where only a modest deficiency in glucagon counterregulation exists.

Disruption of fetal eye development caused by insulin-induced maternal hypoglycemia in rats

We previously revealed that insulin-induced severe and long-lasting maternal hypoglycemia in rats caused anophthalmia and microphthalmia in fetuses; however, it remained unclear whether hypoglycemia-induced eye anomalies were developmental retardation or disruption, and when and how they developed. Hence, we induced hypoglycemia in pregnant Sprague-Dawley rats by injecting insulin from Days 6 to 11 of pregnancy and performed periodical histopathological examination of fetal eyes from embryonic days (E)10 to 20.On E10, optic vesicle had developed normally both in the control and insulin-treated group; however, on E11, optic cup (OC) had developed in the control group but not in the insulin-treated group. On E12, neural retina (NR), retinal pigmented epithelium (RPE), lens, and presumptive cornea had been observed in the control group. In contrast, lens pit and OC with remaining space between RPE and NR had developed in the insulin-treated group. From E13 to E15, developmental disruption characterized by defects, hypoplasia, and degeneration in the retina, lens, and cornea was observed in the insulin-treated group, resulting in anophthalmia or microphthalmia on E20. Moreover, the expression of MITF and chx10, which are essential for early eye development by expressing in the presumptive retina and lens and regulating each other’s expression level, was ectopic and suppressed on E11.In conclusion, insulin-induced maternal hypoglycemia caused developmental disruption, but not simple developmental retardation of fetal eyes, and its trigger might be a failure of presumptive retina and lens to interact on E11.

Hypoglycemic, Antihyperglycemic, and Toxic Effects of Physalis peruviana L. Aqueous and Methanolic Leaf Extracts in Wistar Rats.

BackgroundPhysalis peruviana L. (Solanaceae) is a plant widely used in traditional medicine systems to manage various diseases, including diabetes mellitus, which remains a global health problem in developing and developed countries. This study aimed to scientifically evaluate its antidiabetic bioactivity and short-term toxicity in rats.MethodsWe prepared various doses (100, 200, 400 mg/kg) of aqueous and methanolic leaf extracts for the antidiabetic study, and a dose of 2000 mg/Kg was prepared for the acute toxicity test. The first group that evaluated the hypoglycemic effect consisted of forty normoglycemic Wistar rats aged 7–8 months old with a weighted average of 265.8 ± 24.6 g. The second group consisted of intraperitoneal glucose-loaded male animals to evaluate the antihyperglycemic effect. The third group contained two groups of normoglycemic female rats (n = 3), aged 3 and 4 months old (weight average: 187.45 ± 14.82 g), treated for 14 days with aqueous and methanolic extracts (2 g/kg b.w) to assess mortality and toxic effects. Blood samples were taken at 30, 60, 90, and 120 min post-treatment in hypoglycemic and antihyperglycemic evaluations. Glibenclamide (5 mg/kg) was used as a reference drug. The control animals in each group did not receive the extracts.ResultsIn hypoglycemic rats, 100 mg/kg of aqueous and methanolic extracts significantly lowered the fasting blood glucose level by 13.92% (p < 0.0001) and 21.95% (p < 0.01), respectively, compared to the control group. In glucose tolerance test group, methanolic extracts significantly reduced hyperglycemia by 54.55% (p < 0.0001), 46.50% (p < 0.0001), 39.78% (p < 0.0001) at 400, 200 and 100 mg/kg b.w, respectively, compared to control; aqueous extract 400 mg/kg reduced hyperglycemia by 39.44% (p < 0.05). At the 2000 mg/kg dose, leaf aqueous and methanolic extracts did not show any signs of intoxication and mortality.ConclusionCrude aqueous and methanolic leaf extracts of P. peruviana ambrosioides appeared safe at 2000 mg/kg and have bioactivity in controlling the blood glucose levels, supporting their use in treating diabetes.

Placental nutrient transporters adapt during persistent maternal hypoglycaemia in rats

Maternal malnutrition is associated with decreased nutrient transfer to the foetus, which may lead to foetal growth restriction, predisposing children to a variety of diseases. However, regulation of placental nutrient transfer during decreased nutrient availability is not fully understood. In the present study, the aim was to investigate changes in levels of placental nutrient transporters accompanying maternal hypoglycaemia following different durations and stages of gestation in rats. Maternal hypoglycaemia was induced by insulin-infusion throughout gestation until gestation day (GD)20 or until end of organogenesis (GD17), with sacrifice on GD17 or GD20. Protein levels of placental glucose transporters GLUT1 (45/55 kDa isotypes) and GLUT3, amino acid transporters SNAT1 and SNAT2, and insulin receptor (InsR) were assessed. On GD17, GLUT1-45, GLUT3, and SNAT1 levels were increased and InsR levels decreased versus controls. On GD20, following hypoglycaemia throughout gestation, GLUT3 levels were increased, GLUT1-55 showed the same trend. After cessation of hypoglycaemia at end of organogenesis, GLUT1-55, GLUT3, and InsR levels were increased versus controls, whereas SNAT1 levels were decreased. The increases in levels of placental nutrient transporters seen during maternal hypoglycaemia and hyperinsulinemia likely reflect an adaptive response to optimise foetal nutrient supply and development during limited availability of glucose.

Citric Acid Administration Protects Against Insulin-Induced Hypoglycemic Brain and Liver Injury

We aimed to investigate the effect of treatment with citric acid on oxidative stress and tissue injury in brain and liver of rats subjected to hypoglycaemia. Rats received intraperitoneal injections of insulin (5 IU/kg) followed 30 min later by oral administration of saline or citric acid at doses of 0.2, 0.4 or 1 g/kg. Rats were euthanized 1 h after insulin injection and their brains and livers were dissected out for biochemical studies including determination of malondialdehyde (MDA), reduced glutathione (GSH), nitric oxide (NO), paraoxonase-1 (PON-1), 5-lipoxygenase, and cholinesterase. Serum alanine aminotransferase and aspartate aminotransferase were determined and histological investigations for the liver were carried out. Results indicated that in insulin only treated rats, MDA and NO levels were significantly increased whereas GSH content and PON-1 activity significantly decreased in brain and liver tissue. In addition, cholinesterase activity significantly decreased while 5-lipoxygenase increased in brain with respect to the saline control group after insulin injection. Serum aminotransferases showed significant elevation in insulin-treated rats together with distorted hepatic architecture, hydropic degeneration, and extensive cytoplasmic vacuolation of hepatocytes. The biochemical alterations in the brain and liver of hypoglycaemic rats were markedly alleviated in a dose-dependant manner by the administration of citric acid which also markedly reduced the histological liver injury with the group treated with insulin and citric acid at 1 g/kg exhibiting more or less preserved hepatic architecture. These results indicate that citric acid was effective in alleviating the biochemical alterations in brain and liver and protecting against liver injury during hypoglycaemia. It could thus prove of benefit in patients on insulin therapy with accidental hypoglycaemia from over dosing.

Brain Permeable AMP-Activated Protein Kinase Activator R481 Raises Glycaemia by Autonomic Nervous System Activation and Amplifies the Counterregulatory Response to Hypoglycaemia in Rats.

AimWe evaluated the efficacy of a novel brain permeable “metformin-like” AMP-activated protein kinase activator, R481, in regulating glucose homeostasis.Materials and MethodsWe used glucose sensing hypothalamic GT1-7 neuronal cells and pancreatic αTC1.9 α-cells to examine the effect of R481 on AMPK pathway activation and cellular metabolism. Glucose tolerance tests and hyperinsulinemic-euglycemic and hypoglycemic clamps were used in Sprague-Dawley rats to assess insulin sensitivity and hypoglycemia counterregulation, respectively.Results In vitro, we demonstrate that R481 increased AMPK phosphorylation in GT1-7 and αTC1.9 cells. In Sprague-Dawley rats, R481 increased peak glucose levels during a glucose tolerance test, without altering insulin levels or glucose clearance. The effect of R481 to raise peak glucose levels was attenuated by allosteric brain permeable AMPK inhibitor SBI-0206965. This effect was also completely abolished by blockade of the autonomic nervous system using hexamethonium. During hypoglycemic clamp studies, R481 treated animals had a significantly lower glucose infusion rate compared to vehicle treated controls. Peak plasma glucagon levels were significantly higher in R481 treated rats with no change to plasma adrenaline levels. In vitro, R481 did not alter glucagon release from αTC1.9 cells, but increased glycolysis. Non brain permeable AMPK activator R419 enhanced AMPK activity in vitro in neuronal cells but did not alter glucose excursion in vivo.ConclusionsThese data demonstrate that peripheral administration of the brain permeable “metformin-like” AMPK activator R481 increases blood glucose by activation of the autonomic nervous system and amplifies the glucagon response to hypoglycemia in rats. Taken together, our data suggest that R481 amplifies the counterregulatory response to hypoglycemia by a central rather than a direct effect on the pancreatic α-cell. These data provide proof-of-concept that central AMPK could be a target for future drug development for prevention of hypoglycemia in diabetes.

Activation of AMPK/mTOR-driven autophagy and inhibition of NLRP3 inflammasome by saxagliptin ameliorate ethanol-induced gastric mucosal damage

AimsSaxagliptin, a selective/potent dipeptidyl peptidase-4 inhibitor, has revealed remarkable anti-inflammatory features in murine models of nephrotoxicity, hepatic injury, and neuroinflammation. However, its potential effect on ethanol-induced gastric mucosal injury has not been examined. Hence, the present work investigated the prospect of saxagliptin to attenuate ethanol-evoked gastric injury, with emphasis on the AMPK/mTOR-driven autophagy and NLRP3/ASC/caspase-1 pathway. Materials and methodsIn ethanol-induced gastropathy, the gastric tissues were examined by immunohistochemistry, immunoblotting, histopathology, and ELISA. Key findingsThe results demonstrated that saxagliptin (10 mg/kg; by gavage) suppressed the gastric pathological signs (area of gastric ulcer and ulcer index scores), histopathologic aberrations/damage scores, without provoking hypoglycemia in rats. These protective features were attributed to the enhancement of gastric mucosal autophagy flux, as proven with increased expression of LC3-II and Beclin 1, decreased accumulation of p62 SQSTM1, and activation of the autophagy-linked AMPK/mTOR pathway by increasing the expression of p-AMPK/AMPK and decreasing the expression of the autophagy suppressor p-mTOR/mTOR signal. In tandem, saxagliptin counteracted the ethanol-induced pro-apoptotic events by downregulating Bax, upregulating Bcl2 protein, and lowering the Bax/Bcl2 ratio. Equally important, saxagliptin suppressed the NLRP3 inflammasome in the gastric tissue by lowering the expression of NLRP3, ASC, and nuclear NF-κBp65, decreasing the activity of caspase-1, and diminishing the IL-1β levels. In the same regard, saxagliptin suppressed the mucosal oxidative stress by lowering lipid peroxide levels, increasing GSH and GPx antioxidants, and activating Nrf2/HO-1 pathway. SignificanceSaxagliptin may be a promising intervention against ethanol-evoked gastropathy by activating AMPK/mTOR-driven autophagy and inhibiting NLRP3 inflammasome.

Ketogenic Diet‐Induced Ketosis Delays the Onset, but Preserves the Magnitude of The Sympathoadrenal Response to Hypoglycemia in Rats

The sympathoadrenal counterregulatory response to hypoglycemia is critical for individuals with type 1 diabetes due to impaired ability to produce glucagon. Ketogenic diets (KD) are an increasingly popular diabetes management tool, however the effects of KD on the sympathoadrenal response to hypoglycemia, and hence safety, are largely unknown. We propose that the KD could delay the sympathoadrenal response to hypoglycemia due to the availability of an additional energy substrate to the brain in the form of ketone bodies, but the magnitude of the response will not be affected. The aim of this study was to investigate the effects of KD on the main peripheral components of the sympathoadrenal counterregulatory response: adrenal sympathetic nerve activity (ASNA), adrenal gland activity and plasma epinephrine in non-diabetic male rats. Methods Male Sprague-Dawley rats fed KD or chow diet (CHOW) for 3 weeks were anaesthetised and ASNA recorded. Insulin (5 U/kg; iv) induced hypoglycemia and the sympathoadrenal counterregulatory response. Blood glucose and β-hydroxybutyrate (BHB, ketone body) were measured every 15 min post-insulin for 2 hours. Plasma epinephrine was determined via ELISA. Adrenal gland activity was assessed by immunohistochemistry for Fos. Results Rats on KD, compared to the control chow diet (CHOW) group, had similar blood glucose (BG) levels, and had elevated ketone body β-hydroxybutyrate (BHB) levels. None of the KD rats developed clonic convulsions post-insulin, while >40% of the CHOW rats did. CHOW rats had either a strong ASNA response without convulsions, or a failed ASNA response with convulsions. All KD rats responded to hypoglycemia with a robust increase in ASNA, which was initiated at lower BG levels compared to convulsion-free CHOW rats. Both adrenal gland activity and epinephrine levels positively correlated with ASNA response. Conclusions KD-induced ketosis was associated with initiation of the sympathoadrenal response at lower blood glucose levels, however the magnitude of the response was not diminished. Furthermore, KD appeared to be protective against sympathoadrenal failure and severe hypoglycemia-induced neuroglycopenia.

Therapeutic potential of tectoridin in the medicine for their hypoglycemic activity and rat lens aldose reductase inhibitory potential: Medicinal importance through scientific data analysis

Therapeutic potential of tectoridin in the medicine for their hypoglycemic activity and rat lens aldose reductase inhibitory potential: Medicinal importance through scientific data analysis

Assessment of α-amylase and α-glucosidase inhibitory potential of Citrus reticulata peel extracts in hyperglycemic/hypoglycemic rats.

Diabetes mellitus is a metabolic disorder of carbohydrate metabolism. The management of Diabetes mellitus with phytochemicals is hallmark of this research. Citrus species are known for their health benefits and are used as traditional food in South East Asia. The total phenolic content of peels was analyzed using different solvents, while Gallic acid was used as standard. Both ethanolic, aqueous extracts of Citrus reticulata peel showed good inhibitory activity against amylase (90.67%, 15.33%) and moderate against glucosidase (70.8%, 14.8%), respectively. Sixteen rats were randomly divided into four groups (G1, G2, G3, and G4); G1 is a negative control (water), G4 is a positive control (Acarbose), while other two are experimental groups like G2 (fed with 100mL and 20mg/mL in hypoglycemic and hyperglycemic trials) and G3 fed with 200mL and 40mg/mL in hypoglycemic and hyperglycemic trials. A significant effect of treatments and value of time was found in hyperglycemic rats. Ethanolic extract showed a significant reduction in blood glucose levels in hypoglycemic (overnight fasting) rats which was comparable to the positive control. These results suggest that C. reticulata peels can contribute as a useful food ingredient as a potential antihyperglycemic agent in managing type 2 diabetes mellitus. In future, C. reticulata peel will be a good candidate for pharmaceutical industry.

Dasiglucagon Is a Novel Stable Glucagon Analog With Rapid Glucose Response Following Subcutaneous Injection in Hypoglycemic Rats

Dasiglucagon Is a Novel Stable Glucagon Analog With Rapid Glucose Response Following Subcutaneous Injection in Hypoglycemic Rats

A novel glucokinase activator TMG-123 causes long-lasting hypoglycemia and impairs spermatogenesis irreversibly in rats.

The importance of glucose is well known as an energy source in testes. In order to evaluate the effects of long-lasting hypoglycemia on testes, a novel glucokinase activator, TMG-123, was dosed to rats at 5, 20 and 100 mg/kg for 13 weeks. As a result, plasma glucose levels decreased for several hours with increasing doses over the dose range of 5 to 100 mg/kg. No toxicological findings attributable to the test article were observed in clinical observation, measurements of body weight and food consumption, necropsy, and organ weight measurement. Histopathology showed scattered degeneration of seminiferous tubules in testes, and exfoliation of germ cells related to the degeneration of seminiferous tubules was observed in the lumen of both epididymides in the same animals at the end of the dosing period. Similar histopathological findings were noted at the end of the recovery period. In addition, a fertility study was conducted at the same doses for 13 weeks for males and 5 weeks for females. Sperm analysis showed decreases in the sperm concentration and the motility index and an increase in the incidences of sperm malformations. However, there were no abnormalities in the copulation or fertility rate. These results suggest that long-lasting hypoglycemia in rats is harmful to spermatogenesis and the testicular damage does not recover.

Glycogen Phosphorylase Isoform Regulation of Ventromedial Hypothalamic Nucleus Gluco-Regulatory Neuron 5'-AMP-Activated Protein Kinase and Transmitter Marker Protein Expression.

Brain glycogen is remodeled during metabolic homeostasis and provides oxidizable L-lactate equivalents. Brain glycogen phosphorylase (GP)-brain (GPbb; AMP-sensitive) and -muscle (GPmm; norepinephrine-sensitive) type isoforms facilitate stimulus-specific control of glycogen disassembly. Here, a whole animal model involving stereotactic-targeted delivery of GPmm or GPbb siRNA to the ventromedial hypothalamic nucleus (VMN) was used to investigate the premise that these variants impose differential control of gluco-regulatory transmission. Intra-VMN GPmm or GPbb siRNA administration inhibited glutamate decarboxylate65/67 (GAD), a protein marker for the gluco-inhibitory transmitter γ--aminobutyric acid (GABA), in the caudal VMN. GPbb knockdown, respectively overturned or exacerbated hypoglycemia-associated GAD suppression in rostral and caudal VMN. GPmm siRNA caused a segment-specific reversal of hypoglycemic augmentation of the gluco-stimulatory transmitter indicator, neuronal nitric oxide synthase (nNOS). In both cell types, GP siRNA down-regulated 5′-AMP-activated protein kinase (AMPK) during euglycemia, but hypoglycemic suppression of AMPK was reversed by GPmm targeting. GP knockdown elevated baseline GABA neuron phosphoAMPK (pAMKP) content, and amplified hypoglycemic augmentation of pAMPK expression in each neuron type. GPbb knockdown increased corticosterone secretion in eu- and hypoglycemic rats. Outcomes validate efficacy of GP siRNA delivery for manipulation of glycogen breakdown in discrete brain structures in vivo, and document VMN GPbb control of local GPmm expression. Results document GPmm and/or -bb regulation of GABAergic and nitrergic transmission in discrete rostro-caudal VMN segments. Contrary effects of glycogenolysis on metabolic-sensory AMPK protein during eu- versus hypoglycemia may reflect energy state-specific astrocyte signaling. Amplifying effects of GPbb knockdown on hypoglycemic stimulation of pAMPK infer that glycogen mobilization by GPbb limits neuronal energy instability during hypoglycemia.

Neuroestradiol regulation of ventromedial hypothalamic nucleus 5'-AMP-activated protein kinase activity and counterregulatory hormone secretion in hypoglycemic male versus female rats.

Hypoglycemia activates the ultra-sensitive energy gauge 5′-AMP-activated protein kinase (AMPK) in ventromedial hypothalamic nucleus (VMN) gluco-regulatory neurons. The VMN is exemplified by high levels of expression of the enzyme aromatase, which converts testosterone to estradiol. This study examined the hypothesis that neuroestradiol imposes sex-dimorphic control of VMN AMPK activity during eu- and/or hypoglycemia. VMN tissue corresponding to distinct rostro-caudal segments was obtained by micropunch dissection from testes-intact male and estradiol-replaced ovariectomized female rats that were infused intracerebroventricularly with the aromatase inhibitor letrozole (Lz) before subcutaneous insulin (INS) injection. In euglycemic rats, Lz treatment elevated (male) or decreased (female) middle VMN phosphoAMPK content, with concurrent effects on total AMPK expression. Lz prevented hypoglycemic up-regulation of the mean pAMPK/AMPK ratio in rostral and middle segments of the male VMN, and significantly inhibited this proportion throughout the VMN of hypoglycemic female rats. Lz prevented glucagon secretion in hypoglycemic rats of each sex, and abolished hypoglycemic hypercorticosteronemia in males. Results show that neuroestradiol regulation of VMN AMPK activity during euglycemia is region-specific and gender-divergent, e.g. inhibitory in males versus stimulatory in females. Intra-VMN distribution of hypoglycemia-activated AMPK varies between sexes, but in each sex, locally-generated estradiol is critical for sensor reactivity to this stimulus. Coincident Lz attenuation of VMN AMPK and counter-regulatory hormone responses to hypoglycemia infers a possible cause-and-effect association. Further effort is needed to elucidate the cellular and molecular mechanisms that underlie sex-dimorphic neuroestradiol control of VMN total AMPK and phosphoAMPK expression during distinct metabolic states.

Hypoxia-Preconditioned Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells Mitigate Hypoglycemic Testicular Injury Induced by Insulin in Rats

Hypoglycemia is a neglected metabolic disorder. Thus, we evaluated the protective effect of hypoxia-preconditioned human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) on hypoglycemic testicular injury. We examined 56 testes from 28 animals: 7 rats with insulin-induced hypoglycemia (HG group), 7 hypoglycemic rats which received an intratesticular injection of hUCB-MSCs (HG-MSC group), and 14 untreated control rats. Testosterone level, testicular catalase (CAT) activity, and malondialdehyde (MDA) level were analyzed. Immunostaining for specific testicular germ and somatic cell markers was performed. Proliferating and apoptotic cells were detected by anti-PCNA and anti-caspase-3, respectively. Morphometrical data were statistically analyzed. The hypoglycemic rats showed a significant decrease in testosterone level and CAT activity and a significant increase in MDA production. Examination of histological structure and protein expression of diverse germ cell markers revealed collapsed tubules that were lined by degenerated germ cells, decreased lactate dehydrogenase type C immune expression, as well as decreased proliferating and increased apoptotic cells number in hypoglycemic testes. Injection of MSCs improved testicular biochemical parameters, preserved germ cells and somatic cells, and decreased apoptosis. In conclusion, hypoxia-preconditioned hUCB-MSCs attenuate rat testicular injury caused by insulin-induced hypoglycemia. Avoidance and rapid management of hypoglycemia are necessary to avoid significant testicular injury.

Sex-dimorphic aromatase regulation of ventromedial hypothalamic nucleus glycogen content in euglycemic and insulin-induced hypoglycemic rats

Estrogen receptors control hypothalamic astrocyte glycogen accumulation in vitro. Glycogen metabolism impacts metabolic transmitter signaling in the ventromedial hypothalamic nucleus (VMN), a key glucoregulatory structure. Aromatase, the enzyme that converts testosterone to estradiol, is expressed at high levels in the VMN. Here, the aromatase inhibitor letrozole (Lz) was used alongside high-resolution microdissection/UPHLC-electrospray ionization-mass spectrometric methods to determine if neuroestradiol imposes sex-specific control of VMN glycogen content during glucostasis and/or glucoprivation. Testes-intact male and estradiol-replaced ovariectomized female rats were pretreated by lateral ventricular letrozole (Lz) infusion prior to subcutaneous insulin (INS) injection. Vehicle-treated female controls exhibited higher VMN glycogen content compared to males. Lz increased VMN glycogen levels in males, not females. INS-induced hypoglycemia (IIH) elevated (males) or diminished (females) rostral VMN glycogen accumulation. Induction of IIH in Lz-pretreated animals reduced male VMN glycogen mass, but augmented content in females. Data provide novel evidence for regional variation, in both sexes, in glycogen reactivity to IIH. Results highlight sex-dimorphic neuroestradiol regulation of VMN glycogen amassment during glucostasis, e.g. inhibitory in males versus insignificant in females. Locally-generated estradiol is evidently involved in hypoglycemic enhancement of male VMN glycogen, but conversely limits glycogen content in hypoglycemic females. Further research is needed to characterize mechanisms that underlie the directional shift in aromatase regulation of VMN glycogen in eu- versus hypoglycemic male rats and gain in negative impact in hypoglycemic females.

A comparative study of effect of fluoroquinolones on blood glucose levels in rats

Background: Fluoroquinolones (FQ) are frequently prescribed because of their broad-spectrum applicability in treatment of community acquired pneumonia and urinary tract infections. Increased use has raised some concerns regarding side effects like dysglycaemia, tendon rupture and QT interval prolongation. Gatifloxacin was banned in India in 2011 for causing fatal hypoglycemia. This study compares the effect of different fluoroquinolones on blood glucose levels in rats.Methods: 24 rats were divided into four study groups. Each group was administered one fluoroquinolone namely levofloxacin 9 mg, moxifloxacin 7.2 mg, ciprofloxacin 18 mg and ofloxacin 14.4 mg respectively for five days. The changes in blood glucose levels were observed for 10 days.Results: The mean blood glucose levels in all the four groups dropped below the baseline by day five. A statistically significant reduction in mean glucose levels was found in the moxifloxacin, ciprofloxacin and levofloxacin group. Among the rats that were given ofloxacin, the reduction in the mean blood glucose levels was not statistically significant. After stopping the drugs, the blood glucose levels in all the four groups returned near to the baseline within five days.Conclusions: The use of fluoroquinolones causes hypoglycemia in rats. The blood glucose level reduction associated with moxifloxacin was maximum, whereas ofloxacin appeared to have the minimum effect on blood glucose levels. These effects do not appear to be permanent and the dysglycaemia subsided after the drugs were stopped.

Sex-specific acclimation of A2 noradrenergic neuron dopamine-β-hydroxylase and estrogen receptor variant protein and 5’-AMP-Activated protein kinase reactivity to recurring hypoglycemia in rat

Hindbrain estrogen receptors (ER) impose sex-dimorphic control of counter-regulatory hormone and hypothalamic glucoregulatory transmitter and glycogen metabolic responses to hypoglycemia. A2 noradrenergic neurons are estradiol- and metabolic-sensitive. Estradiol controls dopamine-beta-hydroxylase (DBH) protein habituation to recurrent insulin-induced hypoglycemia (RIIH) in females. Current research investigated the premise that sex-dimorphic patterns of A2 ER variant acclimation to RIIH correlate with differential A2 DBH and 5’-AMP-activated protein kinase (AMPK) adaptation to RIIH. A2 neurons were laser-catapult-microdissected from male and female rats after one or four insulin injections for Western blot analysis. A2 pAMPK and DBH levels were increased in males, but suppressed in females after single insulin dosing. ER-alpha (ERα) and -beta (ERβ) protein profiles were unaffected or decreased by acute hypoglycemia in each sex, whereas G protein-linked ER-1 (GPER) reactivity varied by sex. Antecedent hypoglycemia diminished basal A2 ERα/GPER and elevated ERβ content in each sex, yet reduced pAMPK and DBH levels in female rats only. Reintroduced hypoglycemia suppressed A2 ERβ levels in each sex, but altered DBH (↓), ERα (↓), and GPER (↑) levels in males only. Data document sex differences in A2 DBH adaptation to RIIH, e.g. a shift from positive-to-negative response in males versus loss of negative reactivity in females, as well as attenuated AMPK activation in both sexes. Between hypoglycemic episodes, A2 neurons in each sex likely exhibit diminished sensitivity to ERα/GPER signaling, but heightened receptivity to ERβ input. RIIH-induced changes in ERα and GPER expression in male but not female may contribute to DBH suppression (males) versus no change (females) relative to adapted baseline expression.