Decreased gluconeogenesis and increased glucose disposal without hyperinsulinemia in 10-day-old rats with endotoxic shock

ω3-PUFA alleviates neuroinflammation by upregulating miR-107 targeting PIEZO1/NFκB p65

BACKGROUND

MiR-107 is reduced in sepsis and associated with inflammation regulation. Dietary supplementation with polyunsaturated fatty acids (ω3-PUFA) can increase the expression of miR-107; this study investigated whether the ω3-PUFA can effectively inhibit neuroinflammation and improve cognitive function by regulating miR-107 in the brain.

METHODS

The LPS-induced mouse model of neuroinflammation and the BV2 cell inflammatory model were used to evaluate the effects of ω3-PUFA on miR-107 expression and inflammation. Intraventricular injection of Agomir and Antagomir was used to modulate miR-107 expression. HE and Nissl staining for analyzing hippocampal neuronal damage, immunofluorescence analysis for glial activation, RT-qPCR, and Western blot were conducted to examine miR-107 expression and inflammation signalling.

RESULTS

The result shows that LPS successfully induced the mouse neuroinflammation model and BV2 cell inflammation model. Supplementation of ω3-PUFA effectively reduced the secretion of pro-inflammatory factors TNFα, IL1β, and IL6 induced by LPS, improved cognitive function impairment, and increased miR-107 expression in the brain. Overexpression of miR-107 in the brain inhibited the nuclear factor κB (NFκB) pro-inflammatory signalling pathway by targeting PIEZO1, thus suppressing microglial and astrocyte activation and reducing the release of inflammatory mediators, which alleviated neuroinflammatory damage and improved cognitive function in mice. miR-107, as an intron of PANK1, PANK1 is subject to PPAR α Adjust. ω3-PUFA can activate PPARα, but ω3-PUFA upregulates brain miR-107, and PPARα/PANK1-related pathways may not be synchronized, and further research is needed to confirm the specific mechanism by which ω3-PUFA upregulates miR-107.

CONCLUSION

The miR-107/PIEZO1/NFκB p65 pathway represents a novel mechanism underlying the improvement of neuroinflammation by ω3-PUFA.

Association Between Hypoglycemia and the Occurrence of Early Onset Sepsis in Premature Infants

BACKGROUND

We examined the association between hypoglycemia and the occurrence of early onset sepsis (EOS) in premature infants admitted to the neonatal intensive care unit (NICU).

METHODS

We included infants discharged from 358 NICUs between 1997 and 2020 with gestational age <34 weeks, ≥1 culture collected in the first 3 days of life, and ≥1 serum glucose value recorded on the day of or day prior to culture collection. We used multivariable logistic regression and inverse probability weighting (IPW) and constructed models for three definitions of hypoglycemia: American Academy of Pediatrics (AAP), Pediatric Endocrine Society, and a definition based on neurodevelopmental studies. We performed subgroup analysis in EOS episodes caused by Gram-negative and Gram-positive organisms.

RESULTS

Of the 62,178 infants and 64,559 cultures that met study inclusion criteria, 739 (1%) cultures were positive. The median (25th, 75th percentile) glucose value was 75 mg/dL (50, 106) on the day of or day prior to a positive culture versus 70 mg/dL (50, 95) on the day of or day prior to a negative culture. We found that hypoglycemia was not associated with the occurrence of EOS for all organisms and Gram-positive organisms, whereas there was a small but significant association between the lower AAP glucose cutoff value and EOS due to Gram-negative organisms (logistic regression: risk difference [RD] 0.24% [95% CI, 0.01-0.47]; IPW: RD 0.22% [95% CI, 0.00-0.43]).

CONCLUSIONS

Hypoglycemia may be an early marker of EOS, particularly in episodes caused by Gram-negative organisms and when using a stricter definition of hypoglycemia.

Lipopolysaccharide inhibits hepatic gluconeogenesis in rats: The role of immune cells

AIMS/INTRODUCTION

Bacterial septicemia has diverse clinical symptoms including severe hypoglycemia. However, sepsis-induced hypoglycemia has not yet been examined in detail. The aim of the present study was to investigate the mechanisms underlying hypoglycemia in sepsis.

MATERIALS AND METHODS

We induced endotoxin shock in rats using lipopolysaccharide (LPS). After an intraperitoneal injection of LPS, we measured gluconeogenesis using the pyruvate tolerance test. The effects of LPS on glucose metabolism were investigated in perfused livers and isolated hepatocytes. Furthermore, its effects on the production of inflammatory cytokines were examined in isolated splenocytes. The interaction between splenocytes and hepatocytes in response to LPS was investigated in vitro using a co-culture of splenocytes and hepatocytes.

RESULTS

In the pyruvate tolerance test, the pretreatment with LPS decreased gluconeogenesis. The in vivo pretreatment of rats with LPS did not inhibit glucose production in perfused livers. The in vitro treatment of isolated hepatocytes with LPS did not decrease hepatic gluconeogenesis. Although LPS increased the production of inflammatory cytokines (tumor necrosis factor-α, interferon-γ, interleukin-1β, interleukin-6 and interleukin-10) and nitric oxide in isolated splenocytes, only nitric oxide significantly inhibited gluconeogenesis in isolated hepatocytes. When splenocytes and hepatocytes were co-cultured in medium containing LPS, the messenger ribonucleic acid expression of glucose-6-phosphatase in hepatocytes was suppressed.

CONCLUSIONS

LPS reduced hepatic gluconeogenesis, at least in part, by stimulating the production of nitric oxide in splenocytes. This effect could contribute to the mechanisms responsible for septicemia-induced hypoglycemia.

Recognition, assessment and management of hypoglycaemia in childhood

Hypoglycaemia is frequent in children and prompt management is required to prevent brain injury. In this article we will consider hypoglycaemia in children after the neonatal period. The most common causes are diabetes mellitus and idiopathic ketotic hypoglycaemia (IKH) but a number of endocrine disorders and inborn errors of metabolism (IEMs) need to be excluded. Elucidation of the diagnosis relies primarily on investigations during a hypoglycaemic episode but may also involve biochemical tests between episodes, dynamic endocrine tests and molecular genetics. Specific treatment such as cortisol replacement and pancreatic surgery may be required for endocrine causes of hypoglycaemia, such as adrenal insufficiency and congenital hyperinsulinism. In contrast, in IKH and most IEMs, hypoglycaemia is prevented by limiting the duration of fasting and maintaining a high glucose intake during illnesses.

Toll-like receptor-4 (TLR4) down-regulates microRNA-107, increasing macrophage adhesion via cyclin-dependent kinase 6

Toll-like receptors (TLRs) modulate the expression of multiple microRNAs (miRNAs). Here, we report the down-regulation of miR-107 by TLR4 in multiple cell types. The miR-107 sequence occurs in an intron within the sequence encoding the gene for pantothenate kinase 1α (PanK1α), which is regulated by the transcription factor peroxisome proliferator-activating receptor α (PPAR-α). PanK1α is also decreased in response to lipopolysaccharide (LPS). The effect on both miR-107 and PanK1α is consistent with a decrease in PPAR-α expression. We have found that the putative miR-107 target cyclin-dependent kinase 6 (CDK6) expression is increased by TLR4 as a result of the decrease in miR-107. This effect is required for increased adhesion of macrophages in response to LPS, and CDK6-deficient mice are resistant to the lethal effect of LPS. We have therefore identified a mechanism for LPS signaling which involves a decrease in miR-107 leading to an increase in CDK6.

Amino acids augment muscle protein synthesis in neonatal pigs during acute endotoxemia by stimulating mTOR-dependent translation initiation

In skeletal muscle of adults, sepsis reduces protein synthesis by depressing translation initiation and induces resistance to branched-chain amino acid stimulation. Normal neonates maintain a high basal muscle protein synthesis rate that is sensitive to amino acid stimulation. In the present study, we determined the effect of amino acids on protein synthesis in skeletal muscle and other tissues in septic neonates. Overnight-fasted neonatal pigs were infused with endotoxin (LPS, 0 and 10 microg.kg(-1).h(-1)), whereas glucose and insulin were maintained at fasting levels; amino acids were clamped at fasting or fed levels. In the presence of fasting insulin and amino acids, LPS reduced protein synthesis in longissimus dorsi (LD) and gastrocnemius muscles and increased protein synthesis in the diaphragm, but had no effect in masseter and heart muscles. Increasing amino acids to fed levels accelerated muscle protein synthesis in LD, gastrocnemius, masseter, and diaphragm. LPS stimulated protein synthesis in liver, lung, spleen, pancreas, and kidney in fasted animals. Raising amino acids to fed levels increased protein synthesis in liver of controls, but not LPS-treated animals. The increase in muscle protein synthesis in response to amino acids was associated with increased mTOR, 4E-BP1, and S6K1 phosphorylation and eIF4G-eIF4E association in control and LPS-infused animals. These findings suggest that amino acids stimulate skeletal muscle protein synthesis during acute endotoxemia via mTOR-dependent ribosomal assembly despite reduced basal protein synthesis rates in neonatal pigs. However, provision of amino acids does not further enhance the LPS-induced increase in liver protein synthesis.

Impact of interleukin-6 on the glucose metabolic capacity in rat liver

The acute phase reaction mediated by the proinflammatory cytokine IL6 initiates a number of metabolic changes in the liver, which may contribute to the pathogenesis of the septic shock during prolonged exposition. Here, the impact of IL6 on the hepatic glucose providing capacity was studied by monitoring glycogen degradation and the expression of the gluconeogenic phosphoenolpyruvate carboxykinase (PCK1) in rat livers during the daily feeding rhythm. Eight hours after i.p. injection of IL6, mRNA levels of alpha2-macroglobulin, a prominent acute phase reactant in rat liver, were elevated as shown by Northern blot analysis and in situ hybridization (ISH). PCK1 mRNA levels were decreased by IL6 to 50% of levels in untreated animals due to the reduction of PCK1 mRNA in the periportal zone of the liver as shown by ISH. PCK1 enzyme activity was not affected by IL6. Glycogen degradation was accelerated by IL6, which led to nearly complete depletion of glycogen pools in periportal areas 8 h after IL6 injection. This was very likely due to inhibition of glycogen pool replenishment. Thus, the depletion of glycogen stores in the liver might contribute to the impairment of hepatic glucose production during prolonged acute phase challenge.

Modulation of muscle protein synthesis by insulin is maintained during neonatal endotoxemia

Sepsis promotes insulin resistance and reduces protein synthesis in skeletal muscle of adults. The effect of sepsis on insulin-stimulated muscle protein synthesis has not been determined in neonates, a highly anabolic population that is uniquely sensitive to insulin. Overnight fasted neonatal pigs were infused for 8 h with endotoxin [lipopolysaccharide (LPS), 0 and 10 mug.kg(-1).h(-1)]. Glucose and amino acids were maintained at fasting levels, insulin was clamped at either fasting or fed (2 or 10 muU/ml) levels, and fractional protein synthesis rates were determined at the end of the infusion. LPS infusion induced a septic-like state, as indicated by a sustained elevation in body temperature, heart rate, and cortisol. At fasting insulin levels, LPS reduced fractional protein synthesis rates in gastrocnemius muscle (-26%) but had no effect on the masseter and heart. By contrast, LPS stimulated liver protein synthesis (+28%). Increasing insulin to fed levels accelerated protein synthesis rates in gastrocnemius (controls by +38%, LPS by +60%), masseter (controls by +50%, LPS by +43%), heart (controls by +34%, LPS by +40%), and diaphragm (controls by +54%, LPS by +29%), and the response to insulin was similar in LPS and controls. Insulin did not alter protein synthesis in liver, kidney, or jejunum in either group. These findings suggest that acute endotoxemia lowers basal fasting muscle protein synthesis in neonates but does not alter the response of protein synthesis to insulin.

Expression of inducible nitric oxide synthase and cyclooxygenase-2 mRNA in brain damage induced by lipopolysaccharide and intermittent hypoxia-ischemia in neonatal rats

AIM

The purpose of the present study was to examine the effect of lipopolysaccharide (LPS) and intermittent hypoxia-ischemia (HI) on brain damage in neonatal rats.

METHODS

Seven-day-old Wistar rats were injected with saline or LPS (1 mg/kg), and then underwent left common carotid artery ligation followed by a repetitive 8% hypoxia (2.0-4.5 min) at 10-min intervals 10 times. The rats were divided into three groups: LPS with HI (LPS/HI, n = 46), saline with HI (HI alone, n = 42) and LPS alone (n = 16). Seven days later, brains were assessed for neuronal damage and inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) mRNA expression.

RESULTS

Neuronal damage in the ligated side was significantly higher in LPS/HI than the other two groups (P < 0.01). The expression of iNOS and COX-2 mRNA was observed in the affected brain in LPS/HI, which corresponded well to histologic neuronal loss.

CONCLUSIONS

LPS enhanced intermittent HI brain damage in immature animals. The expression of iNOS and COX-2 mRNA is considered to be associated with perinatal brain injury processes.

The role of glucose in brain injury following the combination of lipopolysaccharide or lipoteichoic acid and hypoxia-ischemia in neonatal rats

We have previously shown that lipopolysaccharide (LPS) sensitizes the immature rat brain to subsequent hypoxic-ischemic (HI) injury; however, the underlying mechanisms remain unclear. In this study, we examined the role of glucose in the sensitizing effects of LPS and lipoteichoic acid (LTA) in combination with HI in 7-day-old rats. LPS/HI resulted in hypoglycemia which lasted 24 h and lactate levels were increased from 6 to 10 h after LPS administration. LPS/HI induced severe brain injury, which persisted 2 weeks after LPS/HI. Administration of glucose to LPS-treated animals with HI reduced brain injury in the cerebral cortex and hippocampus, while striatal damage remained. LTA/HI did not affect blood glucose, lactate or brain injury. In conclusion, enhanced blood glucose levels during HI after LPS administration conferred protection in some brain regions but not in the striatum, suggesting that alterations in glucose can only partly explain the sensitizing effect of LPS.

Regulation of muscle protein synthesis in neonatal pigs during prolonged endotoxemia

In adults, protein synthesis in skeletal muscle is reduced by as much as 50% after a septic challenge, and is associated with repression of translation initiation. Neonates are highly anabolic and their muscle protein synthesis rates are elevated and uniquely sensitive to amino acid and insulin stimulation. In the present study, neonatal piglets were infused with Endotoxin (lipopolysaccharide, LPS) for 20 h at 0 (n = 6) and 13 microg/kg*h (n = 8). During the last 2 h, dextrose and an amino acid mixture were infused to attain fed plasma concentrations of amino acids, glucose, and insulin. Fractional protein synthesis rates and translational control mechanisms were examined. LPS reduced protein synthesis in glycolytic muscles by only 13% and had no significant effect in oxidative muscles. This depression was associated with reductions in the phosphorylation of 4E-BP1 (-31%) and S6 K1 (-78%), and a decrease in eIF4G binding to eIF4E (-62%), an event required for formation of the active mRNA binding complex. By comparison, LPS increased protein synthesis in the liver (+29%), spleen (+32%), and kidney (+27%), and in the liver, this increase was associated with augmented eIF4G to eIF4E binding (+88%). In muscle and liver, LPS did not alter eIF2B activity, an event that regulates initiator met-tRNA(i) binding to the 40S ribosomal complex. These findings suggest that during sustained endotoxemia, the high rate of neonatal muscle protein synthesis is largely maintained in the presence of substrate supply, despite profound changes in translation initiation factors that modulate the mRNA binding step in translation initiation.

On the significance of the role of cellular stress response reactions in the toxic actions of dioxin

Dioxin is known to cause many toxic effects that vary greatly in different tissues, ages, genders, and species. In this review, an attempt has been made to sort out major signaling pathways involved in the expression of the toxicities of dioxin. The major strategy adopted in analyzing its major signaling pathways is to view the toxic actions of dioxin as the result of the Ah receptor-mediated expression of a major cellular emergency stress response signal. Evidence pointing to the similarities between the symptoms of poisoning by dioxin and those produced by chronic administration of typical stressors, particularly lipopolysaccharides (LPS), bacterial endotoxins, has been assembled and analyzed. The common symptoms are wasting syndrome, atherosclerosis, fatty liver, and thymic atrophy. On the other hand, oxidative stress caused by cytochrome P450 induction is one of the typical stresses of dioxin poisoning, but not LPS poisoning. One of the major means through which dioxin triggers stress responses via "stress-activated kinase pathways" is stimulation of the cellular production of cytokines/autocrines, particularly growth factors. In the case of hepatocytes for instance, transforming growth factor-alpha plays a pivotal role in the dioxin-induced activation of the epidermal growth factor receptor and the extracellular signal-related kinase pathway, which acts as a signal to suppress apoptosis induced by cellular stress. These observations as well as additional experimental data support the idea that one of the major functions of the Ah receptor could be the elicitation of cellular stress response reactions. Another key point in understanding the toxic action of dioxin is that, unlike other cases of stressors, dioxin signaling becomes chronically sustained because of its extreme persistence in the human body, its half-life of 7-10 years, and its selective accumulation in fatty target tissues.

Omega-3 polyunsaturated fatty acid enriched diet attenuates stress-induced lactacidemia in 10-day-old rats

BACKGROUND

Lactacidemia is often seen under stress conditions including septic shock in the newborn. Under stress conditions, plasma catecholamine concentrations are increased and play an important role in lactate metabolism. Our previous study shows that perinatal feeding of omega-3 polyunsaturated fatty acid enriched diet (omega-3PUFA) attenuates lactacidemia of endotoxic shock in 10-day-old rats. In the omega-6 fatty acids series, decosapentanoic acid, two series prostaglandins and four series leukotrienes are synthesized through linoleic acids. As plasma lactate concentration correlates with the outcome of septic shock in the newborn, it is important to understand the effects of omega-3PUFA on lactate metabolism. Thus, we tested the hypothesis that perinatal feeding of omega-3 polyunsaturated fatty acid enriched diet (omega-3PUFA) alters responses to catecholamines and attenuates the stress-induced lactacidemia in 10-day-old rats.

METHODS

Ten-day-old rats which perinatally fed omega-3PUFA. Lactacidemia was induced by swimming for 5 min. Ten-day-old rats which perinatally fed omega-6PUFA were controls. Omega-6 fatty acids series are contained in animal fats and corn oil. Adrenergic blockers were used to assess roles of catecholamines in swimming-induced lactacidemia.

RESULTS

Swimming increased plasma lactate concentration less (P<0.05) in rats fed omega-3PUFA than rats fed omega-6PUFA. Swimming increased plasma concentrations of glucose and glucagon, cyclic adenosine monophosphate (cAMP) concentration and phosphoenolypruvate carboxykinase mRNA in the liver, and cAMP concentration in the hindlimb muscle more (P<0.05) in rats fed omega-3PUFA than in rats fed omega-6PUFA. Phentolamine and propranolol enhanced swim-induced lactacidemia in the omega-3PUFA group, while they decreased the lactacidemia in the omega-6PUFA group. Propranolol enhanced swimming-induced hyperglycemia in the omega-6PUFA group more than in the omega-3PUFA group.

CONCLUSIONS

Omega-3PUFA might increase beta-adrenergic response in the liver and increase gluconeogenesis in response to stress, resulting in decreased lactacidemia.

TNFalpha decreases gluconeogenesis in hepatocytes isolated from 10-day-old rats

Gluconeogenesis decreases during septic shock, but its mechanism is not well known. Tumor necrosis factor alpha (TNF-alpha), which is a key cytokine in septic shock, can increase GLUT1 gene expression and glucose uptake in muscles and fatty tissues. TNF-alpha does not alter the metabolism of hepatocytes in which GLUT2 is the predominant glucose transporter. However, GLUT1 is the predominant glucose transporter in hepatocytes of 10-d-old rats. Thus, we hypothesized that TNF-alpha might increase glucose uptake and glycolysis in those cells, and decrease gluconeogenesis. In the present study, hepatocytes isolated from 10-d-old rats were incubated with TNF-alpha at the concentrations of 0, 0.98, 9.8, 98, and 980 ng/mL to evaluate TNF-alpha effects on gluconeogenesis and glucose uptake. TNF-alpha increased glucose uptake (41.1 +/- 8 to 114 +/- 21.4 micromol/10(6) cells at the concentration of 980 ng/mL of TNF-alpha) in a dose-dependent manner, and decreased gluconeogenesis (98.2 +/- 8.2 to 1.1 +/- 3.2 micromol/10(6) cells at the concentration of 980 ng/mL of TNF-alpha) in a dose-dependent manner. The decrease of glucokinase mRNA and GLUT1 mRNA abundance correlated with glucose uptake (r = 0.988 and 0.997, respectively), and the decrease of phosphoenolpyruvate carboxykinase mRNA abundance correlated with the decrease of gluconeogenesis (r = 0.972). The decrease of gluconeogenesis by TNF-alpha correlated with the increase of glucose uptake (r = -0.988). We concluded that TNF-alpha reciprocally suppressed gluconeogenesis in hepatocytes isolated from 10-d-old rats.

Insulin tolerance during endotoxic shock in 10-day-old rats

PURPOSE

The purpose was to investigate insulin tolerance during endotoxic shock in 10-day-old rats.

MATERIALS AND METHODS

[(14)C]Deoxy-glucose (2DG) with or without insulin (1 unit/kg) was injected to 10-day-old and 6-week-old rats 3 h after an injection of endotoxin (lipopolysaccharide: LPS). Plasma concentrations of glucose and 2DG were serially measured for 45 min. Gluconeogenesis was measured in hepatocytes isolated from control and endotoxic 10-day-old rats to evaluate effects of insulin on gluconeogenesis.

RESULTS

In endotoxic 10-day-old rats, plasma glucose concentration at 45 min was 48 +/- 3% (P < 0.05) of value at 0 min, and when insulin was injected with 2DG, it was 29 +/- 4% (P < 0.05) after insulin injection. Plasma 2DG disappearance was enhanced by insulin injection in the control (t(1/2) = 17.9 vs 20.5 min, P < 0.05), but not in the endotoxic rats (t(1/2) = 17.9 vs 18.4 min), indicating the presence of insulin tolerance in septic rats. Insulin decreased gluconeogenesis (P < 0.05) in hepatocytes from both control and endotoxic 10-day-old rats. In endotoxic 6-week-old rats, plasma glucose concentration was decreased to 46 +/- 10% at 45 min and further decreased to 38 +/- 4% (P < 0.05) by insulin injection. Plasma 2DG disappearance was enhanced by insulin injection in the control (t(1/2) = 11.8 vs 17.4 min, P < 0.05) and in the septic rats (t(1/2) = 14.8 vs 12.2 min). However, the enhancement of plasma 2DG disappearance by insulin was less (P < 0.05) in the septic rats than in the control, confirming reports of other investigators which showed insulin tolerance in septic shock.

CONCLUSION

Although hepatocytes from endotoxic rats retained insulin sensitivity, insulin tolerance which was evaluated by 2DG disappearance occurred during septic shock in newborn rats.

Phosphatidylinositol 3-kinase and protein kinase C contribute to the inhibition by interleukin 6 of phosphoenolpyruvate carboxykinase gene expression in cultured rat hepatocytes

The participation of phosphatidylinositol 3-kinase (PI3-kinase), protein kinase C, and mitogen-activated protein kinase (MAP-kinase) in the inhibition by interleukin 6 (IL-6) and insulin of phosphoenolpyruvate carboxykinase (PCK) gene expression was investigated in cultured rat hepatocytes. IL-6 or insulin inhibited the glucagon-stimulated increase in PCK messenger RNA (mRNA) by about 70%. In the presence of either the PI3-kinase inhibitor, wortmannin, or the protein kinase C inhibitor, GF109203x, the inhibition by IL-6 was only about 40%, although it was abolished with both inhibitors in combination. Wortmannin alone but not GF109203x prevented the inhibition by insulin of glucagon-stimulated PCK gene expression. The MAP-kinase pathway inhibitor, PD98059, did not affect IL-6 or insulin inhibition of PCK mRNA increase. When chlorophenylthio-cyclic 3',5' adenosine monophosphate (CPT-cAMP) was used instead of glucagon, IL-6 or insulin inhibited the increase in PCK mRNA by 75% and 85%, respectively. The inhibition by IL-6 was only about 50% in the presence of either wortmannin or GF109203x alone but was abolished with the combination of both inhibitors. The inhibition by insulin was only about 50% in the presence of GF109203x and was abolished by wortmannin. The inhibitors did not affect the inhibition by IL-6 or insulin of the glucagon-stimulated increase in cAMP. It is concluded that the inhibition by IL-6 of PCK gene expression involved both PI3-kinase and protein kinase C, whereas the inhibition by insulin required only PI3-kinase. The inhibition occurred downstream from cAMP formation. Hence, IL-6 and insulin may share, in part, common signal transduction pathways in the inhibition of PCK gene expression.

Tumor necrosis factor-alpha alters glucose metabolism in suckling rats

Tumor necrosis factor-alpha (TNF-alpha), an important mediator of endotoxic shock, induces hypoglycemia and shock in adult animals. Indomethacin ameliorates TNF-alpha-induced hypoglycemia in the adult. However, effects of TNF-alpha on glucose metabolism in the newborn have not been well documented. The present study showed that in 10-day-old rats injected with TNF-alpha (4.5 x 10(7) U/kg, intraperitoneally) the plasma glucose concentration increased from 4.1 +/- 0.3 mmol/L to 6.9 +/- 0.5 mmol/L (P < .05) at 2 hours and subsequently decreased to 1.4 +/- 0.5 mmol/L (P < .05) at 6 hours, although plasma lactate concentration increased from 1.1 +/- 0.1 mmol/L to 5.5 +/- 0.3 mmol/L (P < .05) at 6 hours. Plasma insulin concentration remained unchanged throughout the experiment. TNF-alpha increased GLUT 1 messenger RNA (mRNA) abundance in the brain, liver, muscle, and fatty tissue (P < .05). Glucose uptake increased in association with the increase of GLUT1 mRNA abundance. TNF-alpha decreased mRNA abundance of GLUT 2 and phosphoenolpyruvate carboxykinase (PEPCK) in liver, suggesting decreased gluconeogenesis. Indomethacin (1.5 mg/kg 20 minutes before TNF-alpha, intraperitoneally) attenuated the hypoglycemia, the lactacidemia, and the increase of GLUT1 mRNA abundance and glucose uptake. Indomethacin attenuated the decrease of PEPCK mRNA abundance. We concluded that TNF-alpha induced hypoglycemia, increasing GLUT1 mRNA abundance and glucose uptake and decreasing PEPCK mRNA abundance in 10-day-old rats. Indomethacin attenuated the TNF-alpha-induced glucose dyshomeostasis.

Natural pathogens of laboratory mice, rats, and rabbits and their effects on research

Laboratory mice, rats, and rabbits may harbor a variety of viral, bacterial, parasitic, and fungal agents. Frequently, these organisms cause no overt signs of disease. However, many of the natural pathogens of these laboratory animals may alter host physiology, rendering the host unsuitable for many experimental uses. While the number and prevalence of these pathogens have declined considerably, many still turn up in laboratory animals and represent unwanted variables in research. Investigators using mice, rats, and rabbits in biomedical experimentation should be aware of the profound effects that many of these agents can have on research.

Administration of ATP-MgCl2 following hemorrhage and resuscitation increases hepatic phosphoenolpyruvate carboxykinase and decreases pyruvate kinase activities

Since administration of ATP-MgCl2 following trauma and hemorrhagic shock improves tissue perfusion as well as cell and organ function, the aim of this study was to determine whether this agent has any salutary effects on the hepatic rate-controlling enzymes specific for gluconeogenesis, such as phosphoenolpyruvate carboxykinase (PEPCK), and for glycolysis, such as pyruvate kinase (PK), under such conditions. To study this, rats underwent a 5-cm midline laparotomy (i.e., trauma-induced) and were bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of maximum bleed out volume was returned in the form of Ringer's lactate (RL). The animals were then resuscitated with 3 times the volume of shed blood with RL over 45 min, followed by 2 times RL with ATP-MgCl2 (50 micromol/kg body wt.) or an equivalent volume of normal saline over 95 min. Hepatic PEPCK, PK and glucokinase activities were determined 4 h after the completion of resuscitation. The mRNA levels of PEPCK and PK in the isolated hepatocytes were determined by Northern blot analysis. The results indicate that glucokinase activity was not significantly altered after hemorrhage, irrespective of ATP-MgCl2 treatment. Although the mRNA levels of PEPCK were similar in all groups, PEPCK activity decreased significantly after hemorrhage. ATP-MgCl2 treatment, however, restored PEPCK activity. Hemorrhage resulted in an increase in PK activity and its mRNA. ATP-MgCl2 treatment significantly decreased PK activity and the mRNA. Thus, up-regulation of the gluconeogenic enzyme, PEPCK, and down-regulation of the glycolytic enzyme, PK, by ATP-MgCl2 may be responsible, in part, for the beneficial effects of this agent following trauma-hemorrhage and resuscitation.

Impairment by interleukin 1 beta and tumour necrosis factor alpha of the glucagon-induced increase in phosphoenolpyruvate carboxykinase gene expression and gluconeogenesis in cultured rat hepatocytes

The influence of the inflammatory mediators interleukin 1 beta (IL1 beta) and tumour necrosis factor alpha (TNF alpha) on the glucagon-induced expression of phosphoenolpyruvate carboxykinase (PCK) and on glucose formation via gluconeogenesis was investigated in cultured rat hepatocytes. Gene expression was monitored by determination of mRNA levels and of enzyme activity. Glucose formation was estimated with newly synthesized radioactive glucose derived from a radiolabelled lactate precursor. Glucagon (0.1 or 1 nM) induced PCK mRNA transiently to a maximum 2 h after its application. In the presence of recombinant human (rh) IL1 beta or rhTNF alpha the increase in PCK mRNA levels was totally inhibited at 0.1 nM glucagon, whereas at 1 nM glucagon the maximal increase was inhibited by only 25%. Glucagon (0.1 or 1 nM) induced PCK activity to a maximum after 4 h (4-fold and 6-fold over prestimulatory activity respectively). In the presence of rhIL1 beta or rhTNF alpha the maximal increase was inhibited by approx. 50%. Addition of rhIL1 beta or rhTNF alpha 2 h after glucagon, at the maximal glucagon-induced PCK mRNA levels, accelerated the decay of PCK mRNA. Glucagon (1 or 10 nM) [corrected] increased glucose formation from lactate by 1.3-fold and 1.7-fold respectively over unstimulated rates. In the presence of rhIL1 beta or rhTNF alpha this increase in glucose formation was inhibited by 60-90%. At 0.1 nM, glucagon doubled the intracellular cAMP concentration. This increase was prevented by rhIL1 beta or rhTNF alpha. At 1 nM, glucagon increased cAMP concentrations by 10-fold. In the presence of rhIL1 beta or rhTNF alpha this increase was inhibited by 70%. From the results it is suggested that rhIL1 beta and rhTNF alpha prevented glucagon-stimulated PCK gene expression and gluconeogenesis at least in part by inhibition of the glucagon-stimulated increase in cAMP concentrations.