Altered transcriptional regulation of phosphoenolpyruvate carboxykinase in rats following endotoxin treatment

Prophylactic and Therapeutic Efficacy of Boric Acid on Lipopolysaccharide-Induced Liver and Kidney Inflammation in Rats

In our study, we aimed to examine possible prophylactic (P) or therapeutic (T) effects of boric acid (BA) on lipopolysaccharide (LPS) induced liver and kidney damages. Thirty-two rats were divided into four groups as control, LPS, BAP+LPS, and LPS+BAT. BA was given orally to the rats one hour before the intraperitoneal LPS administration in the BAP+LPS group and one hour after the LPS administration in the LPS+BAT group. Malondialdehyde (MDA), myeloperoxidase (MPO), interleukin-6 (IL-6), IL-10, reduced glutathione (GSH), total oxidant and antioxidant status (TOS and TAS), semaphorin-3A (SEMA3A), cytochrome c (CYCS), and caspase-3 (CASP3) parameters were determined by ELISA method to monitor inflammation, oxidative stress, and apoptosis in the liver and kidney tissues of rats. In addition, alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, creatinine (CREA), C-reactive protein (CRP), gamma glutamyl transferase (GGT), glucose (GLU), sodium (Na), potassium (K), and chlorine (Cl) biochemical parameters were measured in rat serums to monitor liver and kidney functions. Liver and kidney tissues were also examined histopathologically and immunohistochemically. All data were statistically analyzed. Our histological, biochemical, inflammatory, oxidative stress, and apoptotic findings showed that LPS causes serious damage to liver and kidney tissues. Boric acid application brought about significant improvements on the parameters. However, this improvement was seen in the BAP+LPS group, and the results of the LPS+BAT group were insufficient to improve. Our results showed that boric acid administration is effective on severe liver and kidney damage caused by LPS. It has been concluded that prophylactic application is more effective, while therapeutic application is insufficient.

Molecular profiling of sepsis in mice using Fourier Transform Infrared Microspectroscopy

Sepsis is a life threatening condition resulting from a high burden of infection. It is a major health care problem and associated with inflammation, organ dysfunction and significant mortality. However, proper understanding and delineating the changes that occur during this complex condition remains a challenge. A comparative study involving intra-peritoneal injection of BALB/c mice with Salmonella Typhimurium (infection), lipopolysaccharide (endotoxic shock) or thioglycollate (sterile peritonitis) was performed. The changes in organs and sera were profiled using immunological assays and Fourier Transform Infrared (FTIR) micro-spectroscopy. There is a rapid rise in inflammatory cytokines accompanied with lowering of temperature, respiratory rate and glucose amounts in mice injected with S. Typhimurium or lipopolysaccharide. FTIR identifies distinct changes in liver and sera: decrease in glycogen and protein/lipid ratio and increase in DNA and cholesteryl esters. These changes were distinct from the pattern observed in mice treated with thioglycollate and the differences in the data obtained between the three models are discussed. The combination of FTIR spectroscopy and other biomarkers will be valuable in monitoring molecular changes during sepsis.

Impairment of exogenous lactate clearance in experimental hyperdynamic septic shock is not related to total liver hypoperfusion

Introduction

Although the prognostic value of persistent hyperlactatemia in septic shock is unequivocal, its physiological determinants are controversial. Particularly, the role of impaired hepatic clearance has been underestimated and is only considered relevant in patients with liver ischemia or cirrhosis. Our objectives were to establish whether endotoxemia impairs whole body net lactate clearance, and to explore a potential role for total liver hypoperfusion during the early phase of septic shock.

Methods

After anesthesia, 12 sheep were subjected to hemodynamic/perfusion monitoring including hepatic and portal catheterization, and a hepatic ultrasound flow probe. After stabilization (point A), sheep were alternatively assigned to lipopolysaccharide (LPS) (5 mcg/kg bolus followed by 4 mcg/kg/h) or sham for a three-hour study period. After 60 minutes of shock, animals were fluid resuscitated to normalize mean arterial pressure. Repeated series of measurements were performed immediately after fluid resuscitation (point B), and one (point C) and two hours later (point D). Monitoring included systemic and regional hemodynamics, blood gases and lactate measurements, and ex-vivo hepatic mitochondrial respiration at point D. Parallel exogenous lactate and sorbitol clearances were performed at points B and D. Both groups included an intravenous bolus followed by serial blood sampling to draw a curve using the least squares method.

Results

Significant hyperlactatemia was already present in LPS as compared to sham animals at point B (4.7 (3.1 to 6.7) versus 1.8 (1.5 to 3.7) mmol/L), increasing to 10.2 (7.8 to 12.3) mmol/L at point D. A significant increase in portal and hepatic lactate levels in LPS animals was also observed. No within-group difference in hepatic DO₂, VO₂ or O₂ extraction, total hepatic blood flow (point D: 915 (773 to 1,046) versus 655 (593 to 1,175) ml/min), mitochondrial respiration, liver enzymes or sorbitol clearance was found. However, there was a highly significant decrease in lactate clearance in LPS animals (point B: 46 (30 to 180) versus 1,212 (743 to 2,116) ml/min, P <0.01; point D: 113 (65 to 322) versus 944 (363 to 1,235) ml/min, P <0.01).

Conclusions

Endotoxemia induces an early and severe impairment in lactate clearance that is not related to total liver hypoperfusion.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0928-3) contains supplementary material, which is available to authorized users.

Hypothalamic AMPK activation blocks lipopolysaccharide inhibition of glucose production in mice liver

Endotoxic hypoglycaemia has an important role in the survival rates of septic patients. Previous studies have demonstrated that hypothalamic AMP-activated protein kinase (hyp-AMPK) activity is sufficient to modulate glucose homeostasis. However, the role of hyp-AMPK in hypoglycaemia associated with endotoxemia is unknown. The aims of this study were to examine hyp-AMPK dephosphorylation in lipopolysaccharide (LPS)-treated mice and to determine whether pharmacological hyp-AMPK activation could reduce the effects of endotoxemia on blood glucose levels. LPS-treated mice showed reduced food intake, diminished basal glycemia, increased serum TNF-α and IL-1β levels and increased hypothalamic p-TAK and TLR4/MyD88 association. These effects were accompanied by hyp-AMPK/ACC dephosphorylation. LPS-treated mice also showed diminished liver expression of PEPCK/G6Pase, reduction in p-FOXO1, p-AMPK, p-STAT3 and p-JNK level and glucose production. Pharmacological hyp-AMPK activation blocked the effects of LPS on the hyp-AMPK phosphorylation, liver PEPCK expression and glucose production. Furthermore, the effects of LPS were TLR4-dependent because hyp-AMPK phosphorylation, liver PEPCK expression and fasting glycemia were not affected in TLR4-mutant mice. These results suggest that hyp-AMPK activity may be an important pharmacological target to control glucose homeostasis during endotoxemia.

Effects of simvastatin administration on rodents with lipopolysaccharide-induced liver microvascular dysfunction

Endothelial dysfunction drives vascular derangement and organ failure associated with sepsis. However, the consequences of sepsis on liver sinusoidal endothelial function are largely unknown. Statins might improve microvascular dysfunction in sepsis. The present study explores liver vascular abnormalities and the effects of statins in a rat model of endotoxemia. For this purpose, lipopolysaccharide (LPS) or saline was given to: (1) rats treated with placebo; (2) rats treated with simvastatin (25 mg/kg, orally), given at 3 and 23 hours after LPS/saline challenge; (3) rats treated with simvastatin (25 mg/kg/24 h, orally) from 3 days before LPS/saline injection. Livers were isolated and perfused and sinusoidal endothelial function was explored by testing the vasodilation of the liver circulation to increasing concentrations of acetylcholine. The phosphorylated endothelial nitric oxide synthase (PeNOS)/endothelial nitric oxide synthase (eNOS) ratio was measured as a marker of eNOS activation. LPS administration induced an increase in baseline portal perfusion pressure and a decrease in vasodilation to acetylcholine (sinusoidal endothelial dysfunction). This was associated with reduced eNOS phosphorylation and liver inflammation. Simvastatin after LPS challenge did not prevent the increase in baseline portal perfusion pressure, but attenuated the development of sinusoidal endothelial dysfunction. Treatment with simvastatin from 3 days before LPS prevented the increase in baseline perfusion pressure and totally normalized the vasodilating response of the liver vasculature to acetylcholine and reduced liver inflammation. Both protocols of treatment restored a physiologic PeNOS/eNOS ratio.

CONCLUSION

LPS administration induces intrahepatic endothelial dysfunction that might be prevented by simvastatin, suggesting that statins might have potential for liver protection during endotoxemia.

Oral challenge with increasing doses of LPS modulated the patterns of plasma metabolites and minerals in periparturient dairy cows

We showed recently that repeated oral exposure to LPS stimulated humoral immune responses in periparturient dairy cows. Here, metabolic and mineral responses to repeated oral administration of LPS were investigated. Sixteen clinically healthy, pregnant Holstein cows were orally administered 3 ml of saline solution (control) or 3 ml of saline solution containing 3 increasing doses of LPS, at 07:00 h, as follows: (i) 0.01 µg/kg body mass (BM) on d −14 and −10, (ii) 0.05 µg/kg BM on d −7 and −3, and (iii) 0.1 µg/kg BM on d 3 and 7 relative to parturition. Blood samples were measured shortly before, and at 8 different time-points after (up to 6 h), the first challenge of each LPS dosage to evaluate the post-challenge plasma profile, as well as weekly up to 4 wk postpartum. Results showed that oral administration of LPS lowered concentrations of non-esterified fatty acids ( P < 0.01) and β-hydroxy-butyrate ( P < 0.01) in the plasma, particularly after the third LPS challenge. Also, after the third oral LPS challenge, treatment tended to increase plasma glucose. Plasma calcium did not change, but concentrations of insulin ( P < 0.01) and zinc ( P < 0.01) were greater, while that of copper was lower ( P < 0.01) in the plasma of treated cows. This is the first report to indicate a potential role for repeated oral administration of LPS around parturition to modulate the profile of plasma metabolites and minerals postpartum.

Growth and Development Symposium: Impacts of inflammation on cattle growth and carcass merit

Inflammation caused by bovine respiratory disease (BRD) continues to be one of the greatest challenges facing beef cattle producers and feedlot managers. Inflammation decreases DMI, ADG, and G:F in feedlot calves, decreasing growth rate and increasing days on feed, which results in economic losses during the feeding period. During the past decade, marketing of feedlot animals has changed from selling cattle on a live basis to a grid-based marketing system. When cattle are marketed on a live basis, the economic effects of BRD stop at increased health cost and decreased feedlot performance, carcass weight, and death loss. However, when cattle are marketed in a grid-based system, inflammation has the potential to also affect carcass cutability and quality. The effects of inflammation on feedlot cattle in regards to performance are well understood; however, specific effects on cattle growth and ultimately carcass merit are not as well described. Recent studies in feedlot cattle have indicated that the incidence of BRD decreases both HCW and marbling; however, mechanisms are not understood. Research in other species has demonstrated that during the acute phase response, pro-inflammatory cytokines promote skeletal muscle catabolism to supply AA and energy substrates for immune tissues. Further, during this early immune response, the liver changes its metabolic priorities to the production of acute phase proteins for use in host defense. Together these dramatic shifts in systemic metabolism may explain the detrimental effects on performance and carcass traits commonly associated with BRD in feedlot calves. Moreover, recent studies relative to human health have revealed complex multilevel interactions between the metabolic and immune systems, and highlighted inflammation as being a significant contributor to major metabolic diseases. The objective of this paper is to review data to help explain the economical and physiological effects of inflammation on cattle growth and carcass merit.

Glucagon counteracts interleukin-6-dependent gene expression by redundant action of Epac and PKA

Inflammation is the biological response to injurious stimuli. In the initial phase of the inflammatory process, interleukin-6 (IL-6) is the main inducer of acute phase protein expression in the liver. A prolonged acute phase response is characterised by a disturbed glucose homeostasis and elevated levels of IL-6, insulin, and counterregulatory hormones such as glucagon. Several studies deal with the impact of IL-6 on glucagon-dependent gene expression. In contrast, only very little is known about the influence of G-protein-coupled receptors on IL-6 signalling. Therefore, the aim of this study is to elucidate the regulation of IL-6-induced gene expression by glucagon. We could reveal a novel mechanism of negative regulation of IL-6-induced MAP kinase activation by glucagon in primary murine hepatocytes. IL-6-dependent induction of the ERK-dependent target geneTfpi2, coding for a Kunitz-type serine protease inhibitor, was strongly down-regulated by glucagon treatment. Studying the underlying mechanism revealed a redundant action of the signalling molecules exchange protein activated by cyclic AMP (Epac) and protein kinase A. The metabolic hormone glucagon interferes in IL-6-induced gene expression. This observation is indicative for a regulatory role of G-protein-coupled receptors in the IL-6-dependent inflammatory response.

Inflammation inhibits the expression of phosphoenolpyruvate carboxykinase in liver and adipose tissue

Inhibition of adipocyte triglyceride biosynthesis is required for fatty acid mobilization during inflammation. Triglyceride biosynthesis requires glycerol 3-phosphate and phosphoenolpyruvate carboxykinase (PEPCK) plays a key role. We demonstrate that LPS, zymosan, and TNF-α decrease PEPCK in liver and fat. Turpentine decreases PEPCK in liver, but not in fat. The LPS-induced decrease in PEPCK does not occur in TLR4 deficient animals, indicating that this receptor is required. The LPS-induced decrease in hepatic PEPCK does not occur in TNF receptor/IL-1 receptor knockout mice, but occurs in fat, indicating that TNF-α/IL-1 is essential for the decrease in liver but not fat. In 3T3-L1 adipocytes TNF-α, IL-1, IL-6, and IFNγ inhibit PEPCK indicating that there are multiple pathways by which PEPCK is decreased in adipocytes. The binding of PPARγ and RXRα to the PPARγ response element in the PEPCK promoter is markedly decreased in adipose tissue nuclear extracts from LPS treated animals. Lipopolysaccharide and zymosan reduce PPARγ and RXRα expression in fat, suggesting that a decrease in PPARγ and RXRα accounts for the decrease in PEPCK. Thus, there are multiple cytokine pathways by which inflammation inhibits PEPCK expression in adipose tissue which could contribute to the increased mobilization of fatty acids during inflammation.

Failure to achieve euglycemia despite aggressive insulin control signals abnormal physiologic response to trauma

PURPOSE

We hypothesize that a failure to normalize a patient's glucose on an automated euglycemia protocol signals an adverse response after trauma and that this response can identify patients with an increased mortality.

MATERIALS AND METHODS

There were 1246 ventilated, critically ill trauma patients who were placed on an automated euglycemia. All glucose values collected both by laboratory serum measurements and by bedside arterial samples were included in the analysis.

RESULTS

Forty six thousand two hundred eighteen data entries for glucose (mg/dL) were analyzed. Time to normalization, defined as the first value in the goal range of 80 to 110 mg/dL, was different between the 2 groups, survivors correcting significantly faster (396 vs 487 minutes; P = .003). Mortality in patients who normalized (80-110 mg/dL) in the first 6 hours of admission was 13.6% vs 18.3% in patients requiring greater than 6 hours (P = .02). Patients who never normalized also required significantly greater insulin doses despite there being no significant difference in demographic data between the 2 groups.

CONCLUSIONS

A posttraumatic patient's response to tight glycemic control revealed important prognostic information about the patients' physiologic status. Patients who failed to reach euglycemia in the first 6 hours of admission had an increased hospital mortality. The time to normalization is significantly longer in those patients who died. Patients who did not correct rapidly required significantly higher insulin doses, suggesting insulin resistance.

Glyceroneogenesis is inhibited through HIV protease inhibitor-induced inflammation in human subcutaneous but not visceral adipose tissue

Glyceroneogenesis, a metabolic pathway that participates during lipolysis in the recycling of free fatty acids to triglycerides into adipocytes, contributes to the lipid-buffering function of adipose tissue. We investigated whether glyceroneogenesis could be affected by human immunodeficiency virus (HIV) protease inhibitors (PIs) responsible or not for dyslipidemia in HIV-infected patients. We treated explants obtained from subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) depots from lean individuals. We observed that the dyslipidemic PIs nelfinavir, lopinavir and ritonavir, but not the lipid-neutral PI atazanavir, increased lipolysis and decreased glyceroneogenesis, leading to an increased release of fatty acids from SAT but not from VAT. At the same time, dyslipidemic PIs decreased the amount of perilipin and increased interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) secretion in SAT but not in VAT. Parthenolide, an inhibitor of the NFκB pathway, counteracted PI-induced increased inflammation and decreased glyceroneogenesis. IL-6 (100 ng) inhibited the activity of phosphoenolpyruvate carboxykinase, the key enzyme of glyceroneogenesis, in SAT but not in VAT. Our data show that dyslipidemic but not lipid-neutral PIs decreased glyceroneogenesis as a consequence of PI-induced increased inflammation in SAT that could have an affect on adipocytes and/or macrophages. These results add a new link between fat inflammation and increased fatty acids release and suggest a greater sensitivity of SAT than VAT to PI-induced inflammation.

Interplay of the inflammatory and stress systems in a hepatic cell line: interactions between glucocorticoid receptor agonists and interleukin-6

The liver plays an important role in inflammation and stress by producing the acute phase proteins (APPs) required for resolution of inflammation as well as by delivering systemic glucose, through gluconeogenesis, required to fuel the stress response. Disruption of the interplay between interleukin 6 (IL-6) and glucocorticoids (GCs), the peripheral mediators of inflammation and stress, respectively, may lead to side-effects associated with the pharmacological use of GCs. The current study investigated the interplay between IL-6 and GCs in a hepatoma cell line (BWTG3) at protein (protein activity assays, Western blotting, and ELISA) and mRNA (qPCR) levels. Specifically, the action of dexamethasone (Dex), a known antiinflammatory drug and glucocorticoid receptor (GR) agonist, is compared to that of Compound A (CpdA), a selective glucocorticoid receptor agonist (SEGRA). CpdA, like IL-6, but unlike Dex, increases GR binding and decreases the metabolic enzymes, tyrosine aminotransferase, phosphoenolpyruvate carboxykinase, and gamma glutamyltransferase, at protein or mRNA level. Like Dex, both CpdA and IL-6 increase the positive APPs, serum amyloid A and C-reactive protein, and decrease the negative APP, corticosteroid binding globulin. The study shows that the GC, Dex, and IL-6 generally have divergent effects on the GR and metabolic enzymes, while their functions are convergent on the APPs. In contrast to Dex, CpdA has effects convergent to that of IL-6 on the GR, metabolic enzymes, and APPs. Thus these findings suggest that CpdA, like Dex, modulates APPs, leading to effective control of inflammation, while, in contrast to Dex, it is less likely to lead to GC-induced side-effects.

In vivo phosphoenolpyruvate carboxykinase promoter mapping identifies disrupted hormonal synergism as a target of inflammation during sepsis in mice

In mammals, proper maintenance of blood glucose levels within narrow limits is one of the most critical prerequisites for healthy energy homeostasis and body function. Consequently, hyper- and hypoglycemia represent hallmarks of severe metabolic pathologies, including type II diabetes and acute sepsis, respectively. Although the liver plays a crucial role in the control of systemic glucose homeostasis, the molecular mechanisms of aberrant hepatic glucose regulation under metabolic stress conditions remain largely unknown. Here we report the development of a liver-specific adenoviral in vivo system for monitoring promoter activity of the key gluconeogenic enzyme gene phosphoenolpyruvate carboxykinase (PEPCK) in mice. By employing in vivo promoter deletion technology, the glucocorticoid response unit (GRU) and the cyclic adenosine monophosphate (cAMP)-responsive element (CRE) were identified as critical cis-regulatory targets of proinflammatory signaling under septic conditions. In particular, both elements were found to be required for inhibition of PEPCK transcription during sepsis, thereby mediating endotoxic hypoglycemia. Indeed, expression of nuclear receptor cofactor peroxisome proliferator-activator receptor coactivator 1alpha (PGC-1alpha), the molecular mediator of GRU/CRE synergism on the PEPCK promoter, was found to be specifically repressed in septic liver, and restoration of PGC-1alpha in cytokine-exposed hepatocytes blunted the inhibitory effect of proinflammatory signaling on PEPCK gene expression.

CONCLUSION

The dysregulation of hormonal synergism through the repression of PGC-1alpha as identified by in vivo promoter monitoring may provide a molecular rationale for hypoglycemia during sepsis, thereby highlighting the importance of hepatic glucose homeostasis for metabolic dysfunction in these patients.

Control of gluconeogenic genes during intense/prolonged exercise: hormone-independent effect of muscle-derived IL-6 on hepatic tissue and PEPCK mRNA

Prolonged intense exercise is challenging for the liver to maintain plasma glucose levels. Hormonal changes cannot fully account for exercise-induced hepatic glucose production (HGP). Contracting skeletal muscles release interleukin-6 (IL-6), a cytokine able to increase endogenous glucose production during exercise. However, whether this is attributable to a direct effect of IL-6 on liver remains unknown. Here, we studied hepatic glycogen, gluconeogenic genes, and IL-6 signaling in response to one bout of exhaustive running exercise in rats. To determine whether IL-6 can modulate gluconeogenic gene mRNA independently of exercise, we injected resting rats with recombinant IL-6. Exhaustive exercise resulted in a profound decrease in liver glycogen and an increase in gluconeogenic gene mRNA levels, phosphoenolpyruvate-carboxykinase (PEPCK), glucose-6-phosphatase (G6P), and peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha), suggesting a key role for gluconeogenesis in hepatic glucose production. This was associated to an active IL-6 signaling in liver tissue, as shown by signal transducer and activator of transcription and CAAT/enhancer binding protein-beta phosphorylation and IL-6-responsive gene mRNA levels at the end of exercise. Recombinant IL-6 injection resulted in an increase in IL-6-responsive gene mRNA levels in the liver. We found a dose-dependent increase in PEPCK gene mRNA strongly correlated with IL-6-induced gene mRNA levels. No changes in G6P and PGC-1alpha mRNA levels were found. Taken together, our results suggest that, during very demanding exercise, muscle-derived IL-6 could help increase HGP by directly upregulating PEPCK mRNA abundance.

Prehospital endotracheal intubation in patients with severe traumatic brain injury: guidelines versus reality

The international Brain Trauma Foundation guidelines recommend prehospital endotracheal intubation in all patients with traumatic brain injury (TBI) and a Glasgow Coma Scale (GCS)< or =8. Close adherence to these guidelines is associated with improved outcome, but not all severely injured TBI patients receive adequate prehospital airway support. Here we hypothesized that guideline adherence varies when skills are involved that rely on training and expertise, such as endotracheal intubation. We retrospectively studied the medical records of CT-confirmed TBI patients with a GCS< or =8 who were referred to a level 1 trauma centre in Amsterdam (n=127). Records were analyzed for demographic parameters, prehospital treatment modalities, involvement of an emergency medical service (EMS) and respiratory and metabolic parameters upon arrival at the hospital. Patients were mostly male, aged 45+/-21 years with a median injury severity score (ISS) of 26. Of all patients for whom guidelines recommend endotracheal intubation, only 56% were intubated. In 21 out of 106 severe cases an EMS was not called for, suggesting low guideline adherence. Especially those TBI patients treated by paramedics tended to develop higher levels of stress markers like glucose and lactate. We observed a low degree of adherence to intubation guidelines in a Dutch urban area. Main reasons for low adherence were the unavailability of specialized care, scoop and run strategies and absence of a specialist physician in cases where intubation was recommended. The discrepancy between guidelines and reality warrants changing practice to improve guideline compliance and optimize outcome in TBI patients.

Insulin resistance despite tight glucose control is associated with mortality in critically ill surgical patients

BACKGROUND

The hyperglycemic state following trauma and surgery is related partially to insulin resistance (IR). The objective is to determine if critically ill surgical patients vary in their extent of IR and is IR associated with mortality.

METHODS

Prospective observational study in trauma and surgical intensive care units. There were 925 ventilated, critically ill surgical patients who were placed on an automated euglycemia protocol. A mathematic multiplier (M) employed by the protocol was used as a measure of IR. Outcome, phenotypic, laboratory, and treatment variables were analyzed.

RESULTS

54,141 entries for glucose (mg/dl) and M were analyzed. Median glucose was 118mg/dL, with 45% of values between 80-110mg/dL, 81% between 80-150 mg/dL, and 0.2% less than 40 mg/ dL. M varied by 42 fold over the entire population, and by an average of 11-fold among individual patients. The median blood glucose was not different between groups (118 mg/dl for survivors and 118 mg/dl for non-survivors, P = 0.36). The median insulin dose and M were significantly higher in non-survivors (4.1 U/hr versus 3.4 U/hr, P = 0.005; 0.061 versus 0.058, P = 0.02).

CONCLUSIONS

There was a large amount of variation in insulin resistance, as measured by an adapting multiplier, both across the population and within patients. In the setting of tight glucose control measures of glucose control (median blood glucose and percent in range) do not differentiate between patients who lived and died while measures of insulin resistance (median insulin dose and multiplier) do, suggesting that the insulin resistance is a better predictor of outcome.

Mechanisms determining phenotypic heterogeneity of hepatocytes

This review summarizes results of biochemical and immunohistochemical studies indicating the existence of functional heterogeneity of hepatocytes depending on their localization in the hepatic acinus; this determines characteristic features of metabolism of carbohydrates, lipids, and xenobiotics. The physiological significance of hepatocyte heterogeneity is discussed. According to the proposed model of intercellular communication, the metabolic specialization of hepatocytes is determined by secretory activity of hepatic resident macrophages (Kupffer cells) localized mainly in the periportal zone of the liver acinus. Macrophages participate in secretion of a wide spectrum of intercellular mediators (cytokines, prostaglandins, growth factors) and also in metabolism of numerous blood metabolites and biologically active substances (hormones, lipoproteins, etc.). In the sinusoid and in the space of Disse (also known as perisinusoidal space) they form a concentration gradient of regulatory factors and metabolites inducing the phenotypic differences between hepatocytes.

Glycaemic control and perioperative organ protection

The concept of stress hyperglycaemia as an adaptive, beneficial response in critical illness has recently been challenged. Two large prospective randomized controlled trials in the Leuven University Hospital surgical and medical ICUs demonstrated that maintenance of normoglycaemia with intensive insulin therapy substantially prevents morbidity and reduces mortality. Strict normoglycaemia is required to gain most clinical benefit. With this therapy the risk of hypoglycaemia increased, but without inducing obvious clinical sequellae. Other studies have been used to advocate against implementation of intensive insulin therapy by showing lack of benefit or questioning safety. However, these studies are inconclusive on this subject, due to problems of not reaching normal glucose levels clearly separated from the standard glycaemic group or lack of statistical power. Clearly, future studies should be adequately powered and comply with the study protocol in order to confirm the survival and other clinical benefits of intensive insulin therapy.

The control of hepatic glycogen metabolism in an in vitro model of sepsis

Culturing hepatocytes with a combination of LPS, TNF-alpha, IL-1beta and IFN-gamma resulted in an inhibition of glucose output from glycogen and prevented the repletion of glycogen in freshly cultured cells. The reduced glycogen mobilisation correlated with the lower cell glycogen content and reduced rate of glycogen synthesis from [U-(14)C]glucose rather than alterations in either total phosphorylase or phosphorylase a activity. There was no change in the percentage of glycogen exported as glucose nor the production of lactate plus pyruvate indicating that redistribution of the Gluc-6-P cannot explain the failure of the liver to export glucose. Although changes in glycogen mobilisation correlated with NO production, inhibition of NO synthase by inclusion of L-NMMA in the culture medium failed to prevent the inhibition of either glycogen accumulation or mobilisation by the proinflammatory cytokines, precluding the involvement of NO in this response. LPS plus cytokine treatment had no effect on total glycogen synthase activity although the activity ratio was lowered, indicative of increased phosphorylation. The inhibition of glycogen synthesis correlated with a fall in the intracellular concentrations of Gluc-6-P and UDP-glucose and in the absence of measured changes in kinase activity, it is suggested that the fall in Gluc-6-P reduces both substrate supply and glycogen synthase phosphatase activity. The fall in Gluc-6-P coincided with a reduction in total glucokinase and hexokinase activity within the cells, but no significant change in either the translocation of glucokinase or glucose-6-phosphatase activity. This demonstrates direct cytokine effects on glycogen metabolism independent of changes in glucoregulatory hormones.

Intensive insulin therapy in the intensive care unit: update on clinical impact and mechanisms of action

OBJECTIVE

Hyperglycemia is a common feature of the critically ill and has been associated with increased mortality. In this review, we give an overview of studies associating critical illness-induced hyperglycemia with adverse outcome and describe how mortality and morbidity are affected when blood glucose levels are strictly controlled to normoglycemia with intensive insulin therapy.

RESULTS

Maintaining normoglycemia with intensive insulin therapy improves survival rates and reduces morbidity in prolonged critically ill patients in both surgical and medical intensive care units (ICUs), as shown by 2 large randomized controlled studies. Prevention of cellular glucose toxicity by strict glycemic control appears to play a predominant role, but other metabolic and nonmetabolic effects of insulin also seem to contribute to the clinical benefits of this therapy.

CONCLUSION

These data support the generalized implementation of a strict blood glucose control management with intensive insulin therapy in adult surgical as well as medical ICU patients.

Modulation of the glycemic response using insulin attenuates the pulmonary response in an animal trauma model

BACKGROUND

Hyperglycemia has been shown to be an independent prognostic indicator of poor outcome in the traumatized patient. The role of insulin and the prevention of hyperglycemia in the trauma patient have as yet not been fully explored. We hypothesized that the systemic inflammatory response to trauma could be modified by modulating the glycemic response to trauma using insulin.

METHODS

A rodent model of end- organ (lung) injury in trauma was chosen. Two groups underwent bilateral femur fracture and 15% blood loss. The third group was anesthetized only. The treatment group immediately received subcutaneous insulin according to a sliding scale. The control groups received normal saline subcutaneously. The animals were maintained under anesthesia for 4 hours from injury. Blood samples were then taken. Bronchoalveolar lavage was performed for neutrophil content and total protein estimation. The left lower lobe was harvested for wet:dry lung weight ratios as a measure of end-organ tissue edema.

RESULTS

Measures of end-organ injury, wet:dry lung weight ratios, and bronchoalveolar lavage neutrophil content were significantly reduced in the insulin-treated animals compared with in the controls (p < 0.05). Neutrophil respiratory burst activity was increased in insulin-treated animals compared with in controls (p < 0.05).

CONCLUSIONS

Insulin reduces leukocyte lung sequestration and end-organ (lung) edema, indicating an endothelial protective effect in this injured-animal model without attenuating neutrophil function. This work confirms that modifying the glycemic response to trauma using insulin may have a role in reducing adult respiratory distress syndrome rates in injured patients and thereby lead to improved outcomes.

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.

Prognostic value of admission laboratory parameters in traumatic brain injury: results from the IMPACT study

Abnormalities in laboratory parameters are frequent following traumatic brain injury (TBI), but few studies have investigated their predictive value. We aimed to describe and quantify the relation between laboratory parameters that are routinely determined on admission and final outcome following TBI. Individual patient data were available in the IMPACT database from six Phase III randomized controlled trials and one observational study in TBI. We studied glucose (N = 4834), sodium ( N = 5270), pH ( N = 3398), hemoglobin (Hb, N = 3875), platelet count ( N = 1629), and prothrombin time (PT; N = 840) for their associations with outcome at 6 months (Glasgow Outcome Scale [GOS]). We used logistic regression models with linear, quadratic, and restricted cubic spline functions. The strength of the associations was expressed as an unadjusted odds ratio, calculated over the shift in outcome between the 25th and 75th percentiles. Proportional odds methodology was further applied to quantify the strength of the associations across the full range of the GOS. All parameters were consistently associated with outcome in a continuous relationship: glucose and prothrombin time showed a positive linear relation to outcome (i.e., increasing values associated with poorer outcome) and Hb, platelets, and pH an inverse linear relation (i.e., low values associated with poorer outcome). Sodium demonstrated a U-shaped relation to outcome, with low levels being more strongly related to poorer outcome. Effects were strongest for increasing levels of glucose (odds ratio 1.7; 95% CI 1.54-1.83) and decreasing levels of Hb (odds ratio 0.7; CI 0.60-0.78). Higher glucose values were associated with increasing age, but on adjusted analysis, the strength of the association with outcome remained. Whether treatment of abnormal values may improve outcome needs further rigorous study.

Diabetes of injury: novel insights

Critically ill patients usually develop hyperglycemia, a condition referred to as "diabetes of injury." More and more evidence argues against the concept that this is an adaptive beneficial response. Indeed, the development of hyperglycemia seems to be detrimental for the outcome of critically ill patients, because maintenance of normoglycemia with intensive insulin therapy prevents morbidity and reduces mortality of critically ill patients to a large extent. The mechanisms underlying these clinical benefits are being studied further.

Glucose metabolism and insulin therapy

Hyperglycemia is a common feature of the critically ill patient and has been associated with increased mortality. Maintaining normoglycemia with insulin therapy improves survival and reduces morbidity in surgical ICU patients, as shown by a large randomized controlled study. Prevention of glucose toxicity by strict glycemic control but also other metabolic and non-metabolic effects of insulin contribute to these clinical benefits.

Glycemic and nonglycemic effects of insulin: how do they contribute to a better outcome of critical illness?

PURPOSE OF REVIEW

This review gives an overview of the clinical outcome benefits associated with intensive insulin therapy administered to critically ill patients and of the progress in the unraveling of the mechanisms underlying these positive effects.

RECENT FINDINGS

In a large, prospective, randomized, controlled study, strict blood glucose control with intensive insulin therapy strongly reduced mortality and morbidity of surgical intensive care patients. These results were recently confirmed in a more heterogeneous patient population admitted to a mixed medical-surgical intensive care unit. Most of the clinical benefits of intensive insulin therapy appear to be related to prevention of hyperglycemia, which has been demonstrated to adversely affect outcome. Part of the improvement is related to protection of the mitochondrial compartment and innate immunity from glucose toxicity. Also, direct insulin effects contribute to the improved outcome. The beneficial nonglycemic metabolic actions of insulin include a partial correction of the abnormal serum lipid profile and counteraction of the catabolic state evoked by critical illness. The prevention of excessive inflammation and myocardial protection illustrate other nonmetabolic direct anti-inflammatory and anti-apoptotic properties of insulin, although lowering of glucose levels may have played a role in these events as well.

SUMMARY

Substantial progress has been made in the understanding of the mechanisms underlying the improved survival and reduced morbidity with intensive insulin therapy in critical illness. More studies, however, are needed to further elucidate the exact pathways involved and the relative contribution of prevention of glucose toxicity and direct nonglycemic effects of insulin.

Possible pathomechanisms of sudden infant death syndrome: key role of chronic hypoxia, infection/inflammation states, cytokine irregularities, and metabolic trauma in genetically predisposed infants

Chronic hypoxia, viral infections/bacterial toxins, inflammation states, biochemical disorders, and genetic abnormalities are the most likely trigger of sudden infant death syndrome (SIDS). Autopsy studies have shown increased pulmonary density of macrophages and markedly more eosinophils in the lungs accompanied by increased T and B lymphocytes. The elevated levels of immunoglobulins, about 20% more muscle in the pulmonary arteries, increased airway smooth muscle cells, and increased fetal hemoglobin and erythropoietin are evidence of chronic hypoxia before death. Other abnormal findings included mucosal immune stimulation of the tracheal wall, duodenal mucosa, and palatine tonsils, and circulating interferon. Low normal or higher blood levels of cortisol often with petechiae on intrathoracic organs, depleted maternal IgG antibodies to endotoxin core (EndoCAb) and early IgM EndoCAb triggered, partial deletions of the C4 gene, and frequent IL-10-592*A polymorphism in SIDS victims as well as possible hypoxia-induced decreased production of antiinflammatory, antiimmune, and antifibrotic cytokine IL-10, may be responsible for the excessive reactions to otherwise harmless infections. In SIDS infants, during chronic hypoxia and times of infection/inflammation, several proinflammatory cytokines are released in large quantities, sometimes also representing a potential source of tissue damage if their production is not sufficiently well controlled, eg, by pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP). These proinflammatory cytokines down-regulate gene expression of major cytochrome P-450 and/or other enzymes with the specific effects on mRNA levels, protein expression, and enzyme activity, thus affecting metabolism of several endogenous lipophilic substances, such as steroids, lipid-soluble vitamins, prostaglandins, leukotrienes, thromboxanes, and exogenous substances. In SIDS victims, chronic hypoxia, TNF-alpha and other inflammatory cytokines, and arachidonic acid (AA) as well as n-3 polyunsaturated fatty acids (FA), stimulated and/or augmented superoxide generation by polymorphonuclear leukocytes, which contributed to tissue damage. Chronic hypoxia, increased amounts of nonheme iron in the liver and adrenals of these infants, enhanced activity of CYP2C9 regarded as the functional source of reactive oxygen species (ROS) in some endothelial cells, and nicotine accumulation in tissues also intensified production of ROS. These increased quantities of proinflammatory cytokines, ROS, AA, and nitric oxide (NO) also resulted in suppression of many CYP450 and other enzymes, eg, phosphoenolpyruvate carboxykinase (PEPCK), an enzyme important in the metabolism of FA during gluconeogenesis and glyceroneogenesis. PEPCK deficit found in SIDS infants (caused also by vitamin A deficiency) and eventually enhanced by PACAP lipolysis of adipocyte triglycerides resulted in an increased FA level in blood because of their impaired reesterification to triacylglycerol in adipocytes. In turn, the overproduction and release of FA into the blood of SIDS victims could lead to the metabolic syndrome and an early phase of type 2 diabetes. This is probably the reason for the secondary overexpression of the hepatic CYP2C8/9 content and activity reported in SIDS infants, which intensified AA metabolism. Pulmonary edema and petechial hemorrhages often present in SIDS victims may be the result of the vascular leak syndrome caused by IL-2 and IFN-alpha. Chronic hypoxia with the release of proinflammatory mediators IL-1alpha, IL-1beta and IL-6, and overloading of the cardiovascular and respiratory systems due to the narrowing airways and small pulmonary arteries of these children could also contribute to the development of these abnormalities. Moreover, chronic hypoxia of SIDS infants induced also production of hypoxia-inducible factor 1alpha (HIF-1alpha), which stimulated synthesis and release of different growth factors by vascular endothelial cells and intensified subclinical inflammatory reactions in the central nervous system, perhaps potentiated also by PACAP and VIP gene mutations. These processes could lead to the development of brainstem gliosis and disorders in the release of neuromediators important for physiologic sleep regulation. All these changes as well as eventual PACAP abnormalities could result in disturbed homeostatic control of the cardiovascular and respiratory responses of SIDS victims, which, combined with the nicotine effects and metabolic trauma, finally lead to death in these often genetically predisposed children.

Clinical potential of insulin therapy in critically ill patients

Stress of critical illness is often accompanied by hyperglycaemia, whether or not the patient has a history of diabetes mellitus. This has been considered to be part of the adaptive metabolic response to stress. The level of hyperglycaemia in patients with acute myocardial infarction (MI) or stroke upon admission to the hospital has been related to the risk of adverse outcome. However, until recently, there was no evidence of a causal relationship and thus stress-induced hyperglycaemia was only treated with exogenous insulin when it exceeded 12 mmol/L (220 mg/dL). In patients with known diabetes, even higher levels were often tolerated. Recently, new data became available in support of another approach. In this review, we focus on the new evidence and the clinical aspects of managing hyperglycaemia with insulin in critically ill patients, drawing a parallel with diabetes management. Particularly, the 'Diabetes and Insulin-Glucose infusion in Acute Myocardial Infarction (DIGAMI) study' and the 'insulin in intensive care study' have provided novel insights. The DIGAMI study showed that in patients with diabetes, controlling blood glucose levels below 12 mmol/L for 3 months after acute MI improves long-term outcome. In the recent study of predominantly surgical intensive care patients, the majority of whom did not previously have diabetes, it was shown that an even tighter control of blood glucose with exogenous insulin, aiming for normoglycaemia, dramatically improved outcome. Indeed, in this large prospective, randomised, controlled study, 1548 intensive care patients had been randomly allocated to either the conventional approach, with insulin infusion started only when blood glucose levels exceeded 12 mmol/L, or intensive insulin therapy, with insulin infused to maintain blood glucose at a level of 4.5-6.1 mmol/L (80-110 mg/dL). Intensive insulin therapy reduced intensive care mortality by more than 40% and also decreased a number of morbidity factors including acute renal failure, polyneuropathy, ventilator-dependency and septicaemia. Future studies will be needed to further unravel the mechanisms that explain the beneficial effects of this simple and cost-saving intervention. Although available evidence supports implementation of intensive insulin therapy in surgical intensive care, the benefit for other patient populations, such as patients on medical intensive care units or hospitalised patients who do not require intensive care but who do present with stress-induced hyperglycaemia, remains to be investigated.

Gastrointestinal disorders of the critically ill. Shock liver

Shock liver describes a collecting pool of critically ill patients in whom the elevation of liver function tests or overt hepatic dysfunction is apparent. Different grades of shock liver affect about 50% of all intensive-care patients, varying from a mild elevation of serum aminotransferase and bilirubin levels in septic patients to an acute onset of high serum aminotransferases after haemodynamic shock. Abnormalities can subside within days or progressively deteriorate when persistent hepatic microcirculatory failure is present. Although hepatic injury in critically ill patients influences mortality rates it is underdiagnosed. The underlying pathophysiology involves changes in the portal and arterial blood supply as well as in microcirculation. Cross-talk between hepatocytes, Kupffer cells and endothelial cells, leading to an inflammatory response mediated primarily by tumour necrosis factor-alpha (TNF-alpha), is central to shock liver. The liver is a victim of shock inducers, and can also be the orchestrator of the inflammatory response syndrome (IRS). Hepatic injury by TNF-alpha is modulated by the prevalent pro-inflammatory or anti-inflammatory mediator profile elaborated by Kupffer cells. Kupffer cells additionally participate in the clearance of endotoxin, bacteria and inflammatory mediators and are thereby capable of preventing IRS. The hepatocyte undergoes dramatic alterations in synthetic activity, biliary transport, bile flow and glucose metabolism. Although standard determinations of aminotransferases, coagulation studies, glucose, lactate and bilirubin can detect hepatic injury they only partially reflect the cellular mechanisms driving shock liver. The management of shock liver is focused on the prevention of precipitating causes by controlling sepsis, circulation parameters and metabolism in addition to the cautious monitoring of therapeutic measures that can increase hepatic injury, which include intravenous nutrition, mechanical ventilation and catecholamine administration.

Liver in sepsis and systemic inflammatory response syndrome

In patients with sepsis and SIRS, the liver has two opposing roles: a source of inflammatory mediators and a target organ for the effects of the inflammatory mediators. The liver is pivotal in modulating the systemic response to severe infection, because it contains the largest mass of macrophages (Kupffer cells) in the body; these macrophages can clear the endotoxin and bacteria that initiate the systemic inflammatory response. This article summarizes the functional changes that take place in the liver during sepsis and systemic inflammatory response syndrome and discusses the cellular and molecular mechanisms that underlie clinical outcomes.

Regulation of the acid-labile subunit in sustained endotoxemia

The effect of sustained endotoxemia on expression of the acid-labile subunit (ALS) in relation to hepatic markers of altered GH and insulin sensitivity was examined. Juvenile rats were injected with endotoxin twice daily for 48 h, causing reduced food intake and attenuated growth. In pair-fed controls, food restriction caused marked suppression of ALS gene expression and circulating levels within 12 h, and endotoxemia augmented this effect. This acute effect of endotoxin corresponded temporally with transient induction of suppressor of cytokine signaling (SOCS)-3, cytokine-inducible SH2-containing protein (CIS), phosphoenolpyruvate carboxykinase (PEPCK), and insulin-like growth factor-binding protein (IGFBP)-1 and suppression of GH receptor (GHR). During the subsequent 36 h of sustained endotoxin treatment, expression of ALS recovered to, and then rose above, that of their pair-fed controls. This effect was paralleled by other ternary complex components. The inductive effect of sustained endotoxemia relative to pair-fed controls could not be explained by differences in expression of GHR, SOCS-3, or CIS but coincided with normalized PEPCK and IGFBP-1 levels, suggesting better hepatic insulin sensitivity in these animals. These data may indicate that, in sustained endotoxemia, ALS levels are regulated through modulation of hepatic insulin sensitivity.

Accelerated recovery after endotoxic challenge in heat shock-pretreated mice

The inflammatory response induced by bacterial lipopolysaccharide (LPS) has profound metabolic and physiological effects. Thus hepatic glucose production is depressed after LPS administration, which is, at least in part, due to the downregulation of phosphoenolpyruvate carboxykinase (PEPCK) expression. PEPCK is a key regulatory enzyme of the gluconeogenic pathway. Expression of heat shock proteins (hsps) is a well-conserved response to stress correlated with protection from subsequent insults including inflammation. In this study, the expression of PEPCK was observed to be preserved after injection of LPS in heat shock-pretreated mice. Protection of PEPCK expression was limited to the time after heat shock treatment that displayed hsp70. Comparison of the transcription rate and mRNA levels of PEPCK after LPS injection between mice that were heat shock pretreated or not indicated that the preservation of PEPCK expression was not due to initial protection from the LPS challenge. On the contrary, it was mediated by a rapid recovery after the LPS insult at the level of transcription. These observations suggest that the mechanism of heat shock-mediated protection (stress tolerance) after LPS challenge is due to an increase in the capacity of the organism to recover rather than deterrence from the insult.

In vivo and in vitro regulation of sterol 27-hydroxylase in the liver during the acute phase response. potential role of hepatocyte nuclear factor-1

The host response to infection is associated with several alterations in lipid metabolism that promote lipoprotein production. These changes can be reproduced by lipopolysaccharide (LPS) administration. LPS stimulates hepatic cholesterol synthesis and suppresses the conversion of cholesterol to bile acids. LPS down-regulates hepatic cholesterol 7alpha-hydroxylase, the rate-limiting enzyme in the classic pathway of bile acid synthesis. We now demonstrate that LPS markedly decreases the activity of sterol 27-hydroxylase, the rate-limiting enzyme in the alternate pathway of bile acid synthesis, in the liver of Syrian hamsters. Moreover, LPS progressively decreases hepatic sterol 27-hydroxylase mRNA levels by 75% compared with controls over a 24-h treatment period. LPS also decreases oxysterol 7alpha-hydroxylase mRNA levels in mouse liver. In vitro studies in HepG2 cells demonstrate that tumor necrosis factor and interleukin (IL)-1 decrease sterol 27-hydroxylase mRNA levels by 48 and 80%, respectively, whereas IL-6 has no such effect. The IL-1-induced decrease in sterol 27-hydroxylase mRNA expression occurs early, is sustained for 48 h, and requires very low doses. In vivo IL-1 treatment also lowers hepatic sterol 27-hydroxylase mRNA levels in Syrian hamsters. Studies investigating the molecular mechanisms of LPS-induced decrease in sterol 27-hydroxylase show that LPS markedly decreases mRNA and protein levels of hepatocyte nuclear factor-1 (HNF-1), a transcription factor that regulates sterol 27-hydroxylase, in the liver. Moreover, LPS decreases the binding activity of HNF-1 by 70% in nuclear extracts in hamster liver, suggesting that LPS may down-regulate sterol 27-hydroxylase by decreasing the binding of HNF-1 to its promoter. Coupled with our earlier studies on cholesterol 7alpha-hydroxylase, these data indicate that LPS suppresses both the classic and alternate pathways of bile acid synthesis. A decrease in bile acid synthesis in liver would reduce cholesterol catabolism and thereby contribute to the increase in hepatic lipoprotein production that is induced by LPS and cytokines.

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.

A role for the endocrine and pro-inflammatory mediator MIF in the control of insulin secretion during stress

The systemic response to injury or infection is often accompanied by significant alterations in host metabolism and glucose homeostasis. Within the liver, these changes include a decrease in glycogenesis and an increase in gluconeogenesis, and in peripheral tissues, the development of insulin resistance and the increased utilization of glucose by non-insulin-dependent pathways. Depending on the severity and the duration of the response, both hyper- and hypoglycemia can ensue and each can become a clinically important manifestation of the systemic inflammatory response. The protein known as macrophage migration inhibitory factor (MIF) has been identified recently to play a central role in host immunity and to regulate glucocorticoid effects on the immune and inflammatory systems. MIF is released in vivo from activated immune cells as well as by the anterior pituitary gland upon stimulation of the hypothalamic-pituitary-adrenal axis. MIF also has been found to be secreted together with insulin from the pancreatic beta-cells and to act as an autocrine factor to stimulate insulin release. Since circulating MIF levels are elevated during stress or systemic inflammatory processes, this protein may play a central role in the control of insulin secretion during various disease states.

Tumor necrosis factor inhibits the transcriptional rate of glucose-6-phosphatase in vivo and in vitro

Recombinant human tumor necrosis factor-alpha (TNF) injection in mice was associated with a reduced blood glucose level, already manifest 6 hours following cytokine administration. Insulin levels were not affected. Glycogen content was decreased in a dose-dependent and time-response manner. The activity of glucose-6-phosphatase (G6Pase) was already reduced 6 hours after TNF injection and was sustained 12 hours afterward. Phosphoenolpyruvate carboxykinase (PEPCK) activity was not affected initially (6 hours after injection), but a 50% reduction was observed 12 hours following cytokine administration compared with levels in fasting controls. Both liver G6Pase and PEPCK mRNAs were markedly reduced due to an inhibition of the transcriptional rate. A direct inhibitory effect of TNF on G6Pase promoter activity was demonstrated using HuH-7 cells transiently transfected with G6Pase promoter, fused to a reporter gene.

Cytokines (IL-1beta and TNFalpha) in relation to biochemical and immunological effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in rats

Previous studies in different strains of rats and mice have shown that the inhibition of gluconeogenesis as a result of reduced liver phosphoenolpyruvate carboxykinase (PEPCK) activity together with appetite suppression play critical roles in the acute toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Recent immunological studies in rats demonstrated that exposure to low doses of TCDD resulted in an early and enhanced IgG response to immunization with sheep red blood cells (SRBC) and an enhanced delayed-type hypersensitivity (DTH) reaction as well as a positive popliteal lymph node (PLN) response. However, high doses of TCDD suppressed the DTH reaction. This study aimed at examining the involvement of cytokines (IL-1 and TNF) in mediating the above effects. Liver samples from a previous dose-response study on DTH reaction were investigated, in which rats were treated with TCDD (1, 3, 10, 30 and 90 microg/kg) and immunized with an antigen. mRNA levels of IL-1beta were elevated begining at the 1 microg/kg (non-lethal) dosage group with a maximum increase of about 5-fold above controls in the 90 microg/kg (lethal) dosage group. mRNA levels of TNFalpha were also significantly elevated begining at the 30 microg/kg dosage group. These results suggest that at low doses of TCDD, increased IL-1beta could be responsible for immune function stimulation, whereas at high doses of TCDD, greatly elevated TNFalpha and IL-1beta levles may exacerbate or mediate acute toxicity including immune suppression and related biochemical effects. A time course study (60 microg TCDD/kg without immunization) revealed that liver mRNA levels of TNFalpha were significantly elevated starting 24 h, and reaching a maximum 48 h after dosing with TCDD. This change was accompanied by a transient increase of mRNA levels of IL-1beta at day 4 after TCDD dosage. Thus, these data demonstrated that TCDD alone (without immunization) can cause transient increases of mRNA levels of TNFalpha and IL-1beta in liver. Results from these experiments suggest that TCDD-induced cytokine changes may play important roles in various effects of TCDD.

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.

Metabolic consequences of sepsis. Correlation with altered intracellular calcium homeostasis

The availability of adequate substrate for energy homeostasis is a minimal requirement for vital organ function that normally is provided through dietary intake. When dietary sources of nutrients are inadequate, the body relies on alternate sources of energy provided by gluconeogenesis, lipolysis, and ketogenesis. Sepsis is associated with disruption of virtually all these provisional sources of energy substrate (see Fig. 4). In addition, sepsis impairs the function of the glycolytic pathway, the integrity of which is necessary for glucose to be used effectively for energy production. These abnormalities, coupled with disruption of the intracellular energy-producing machinery (e.g., glycolytic and gluconeogenic enzymes, mitochondria) eventually lead to a reduction in intracellular ATP. Furthermore, a reduction in intracellular ATP can undermine virtually all the energy-consuming functions of the cell, including energy substrate formation (e.g., failed gluconeogenesis), antioxidant production, and calcium homeostasis. High levels of intracellular calcium, in turn, are known to activate many potentially destructive enzymatic pathways (e.g., proteases, phospholipases, endonucleases) that further diminish cell function and may result in cell death. In this context, iCa2+ accumulation may play an important role in the progression from early sepsis to MODS, the most common cause of mortality in the ICU.

Trace metal, acute phase and metabolic response to endotoxin in metallothionein-null mice

Accumulation of hepatic zinc via metallothionein (MT) induction during infection/inflammation is postulated to benefit a range of metabolic processes. The metabolic consequences of two doses of endotoxin (LPS) (1 and 5 mg/kg, intraperitoneally) were examined in normal (MT+/+) and MT-null (MT-/-) mice (all results means =/- S.E.M., n=6). At 16 h after 1 mg/kg LPS, hypozincaemia was pronounced in the MT+/+ mice (4.4+/-0.2 microM), concomitant with a 36% increase in hepatic Zn and a > 10-fold increase in hepatic MT. Plasma Zn (16.6+/-0.7 microM) and total hepatic Zn were unchanged in MT -/- mice, confirming the importance of MT in altering plasma and hepatic Zn during inflammation. Plasma iron was lower in LPS-treated MT-/- mice, whereas plasma copper increased to a similar extent in both groups of mice. Plasma fibrinogen more than doubled, and was similar in both groups of mice, which questions the importance of MT in acute-phase protein synthesis. Blood and liver glucose concentrations were not significantly different between groups before or after LPS, whereas blood and liver lactate concentrations were significantly lower (31% and 24% respectively) in MT-/- mice after LPS. At 16 h after 5 mg/kg LPS, plasma Zn was decreased even further in MT+/+ mice (2.6+/-0.3 microM), but remained unchanged in MT-/- mice at concentrations significantly above those in 16-h fasted MT-/- mice (15.8+/-0.5 versus 11.3+/-0.3 microM). Total liver Zn was 17% lower than fasting values in MT-/- mice, in contrast with 32% higher in MT+/+ mice. Synthesis of MT (in MT+/+ mice) and fibrinogen in all mice was not further enhanced by the higher LPS dose. Blood glucose was significantly decreased by 18% in MT+/+ mice and by 38% in MT-/- mice after 5 mg/kg LPS. There was a marked 44% decrease in liver glucose in MT-/- mice; that in MT+/+ mice was unchanged from fasting levels, implying a deficit in hepatic gluconeogenesis in LPS-treated MT-/- mice. In the absence of any indication of major hepatotoxicity, the results of this study indicate that energy production, and not acute-phase protein synthesis, may be most influenced by Zn supply during endotoxaemia, suggesting that MT has a role in maintaining hepatic and blood glucose in this metabolic setting.

Improvement of glucose tolerance with immunomodulators on type 2 diabetic animals

Cytokine-inducers prevent insulin-dependent diabetes mellitus (IDDM) in animal models. We extend this therapy to non-insulin-dependent diabetes mellitus (NIDDM), because it was reported that diabetes of KK-Ay mice, a model for NIDDM, was recovered by allogenic bone-marrow transplantation that also prevented IDDM in animal models. An i.p. or i.v. injection of streptococcal preparation (OK-432) lowered fasting blood glucose (FBG) levels and markedly improved glucose tolerance test (GTT) in KK-Ay mice for more than 32 h regardless of the glucose loading routes (oral, i.v. or i.p.), while an i.v. injection of BCG improved FBG and GTT for more than 4 wks without body weight loss. The improvement of FBG and GTT with OK-432 was brought about in other NIDDM animals, GK rats and Wistar fatty rats. Among various cytokines possibly induced by OK-432 and BCG, IL-1 alpha, TNF alpha and lymphotoxin significantly improved FBG and GTT in KK-Ay mice, whereas IL-2 and IFN gamma did not. There were no differences between the OK-432-treated KK-Ay mice and control in histology of the pancreas, degree of insulin-induced decrease in blood glucose levels, and muscle glycogen synthase activities. As to insulin secretion, there is a tendency that the OK-432-treatment less that 1 week did not affect insulin levels during GTT, whereas the treatment more than 2 weeks increased the insulin levels. Thus, cytokine-inducers improved FBG and glucose tolerance of NIDDM animals probably via cytokines. The results imply a role of the cytokines in glucose tolerance of NIDDM, although precise immune and metabolic mechanisms remain to be elucidated.