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Department of Surgery, Friedrich Alexander University of Erlangen (M.G.J., D.K.), Erlangen, Germany; Department of Surgery, University of Regensburg (U.B.), Regensburg, Germany; and Institute of Veterinary Biochemistry, Free University Berlin (R.E.), Berlin, Germany
Address all correspondence and requests for reprints to: Dr. Marc G. Jeschke, Shriners Hospital for Children, Galveston Burns Unit, 815 Market Street, Galveston, Texas 77550. E-mail: mcjeschke{at}hotmail.com.
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Abstract |
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. Insulin administration further decreased high mobility group 1 protein in the serum compared with controls. In addition, insulin increased antiinflammatory cytokine expression in the liver; serum levels of IL-2, IL-4, and IL-10; and hepatic suppressor of cytokine signaling-3 mRNA expression. Insulin modulates the inflammatory response by decreasing the proinflammatory and increasing the antiinflammatory cascade. Because glucose and electrolyte levels did not differ between insulin-treated patients and controls, we hypothesize that the effects are direct antiinflammatory mechanisms of insulin, rather than indirect, through modulation of glucose or electrolyte metabolism. |
Introduction |
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The pathophysiological cascade is mediated by proinflammatory cytokines, such as IL-1ß, IL-6, macrophage inhibitory factor (MIF), or TNF, that are potentially detrimental (3, 4, 5). Proinflammatory mediators are balanced by antiinflammatory cytokines, such as IL-2, IL-4, or IL-10 (6, 7). Recently, it was shown that the expression and synthesis of pro- and antiinflammatory cytokines are controlled by several pro- and antiinflammatory signal transcription factors. Signal transducer and activator of transcription (STAT-3 and -5) and CCCAT-enhancer binding protein-ß (C/EBP-ß) belong to the proinflammatory signal transcription factors (8, 9, 10). Suppressors of cytokine signaling (SOCS-1, -2, and -3) belong to the group of signal transcription factors that suppresses proinflammatory cytokine expression (11, 12, 13). RANTES (regulated on activation, normally T cell expressed and secreted) exerts an indifferent role during the inflammatory cascade (13). Recently, the group of Tracey et al. (14) showed that high mobility group 1 protein (HMG-1) is a late mediator of lethality during a septic state and possibly involved in the clinical outcome of septic patients.
The magnitude and duration of the systemic inflammatory response syndrome determines the development and degree of tissue damage, multiorgan failure, or even death (14, 15). Despite recent advances in the understanding of the molecular cascade of the systemic inflammatory response syndrome the lack of an effective treatment still remains a clinical problem. Intensive insulin therapy was shown to decrease mortality in critically ill patients (16). Insulin given at doses to maintain blood glucose less than 110 mg/dl prevented the incidence of multiorgan failure and thus improved clinical outcome and rehabilitation of mainly patients undergoing thoracic surgery (16). Insulin administration furthermore decreased the incidence of sepsis and septic events in these patients (16). The mechanisms by which insulin improves survival in critically ill patients are not known. Insulin was shown to alter inflammatory mediators and improve liver morphology and function after a thermal injury (17, 18). However, hepatic signaling and cytokine synthesis are different during the aftermath of a burn and endotoxemia (19). Therefore, the aim of the present study was to determine whether insulin administration modulates the systemic inflammatory response during endotoxemia.
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Materials and Methods |
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Twelve rats received no injury, no treatment, no anesthesia, and no analgesia. Rats received the same chow and were pair-fed to the treatment animals. Animals were killed at the same time points as treated animals 1, 2, 5, and 7 d. These rats served as nonendotoxemic, untreated, time-matched sham rats to establish baseline levels in the present study.
LPS at a dose of 3 mg/kg body weight was chosen, because this represents half of the 50% lethal dose for LPS, but induces a severe endotoxemic reaction. The insulin used was protamine-insulin (Berlininsulin H, Berlin-Chemie AG, Berlin, Germany), a form of insulin that is released over a 24-h period. The dose of 5 IU/kg body weight was determined in a dose-response study measuring the effect of various insulin doses on IL-1ß and TNF (data not shown).
Nutrition
Rats were fed a standard rat diet composed as follows: 64% carbohydrates, 5% fat, and 14% protein (Teklad 2014, Harlan, Indianapolis, IN). The average food intake was 26 ± 3 g/d. Both groups of rats were pair-fed according to caloric intake. The feeding protocol was as follows: 25 calories on the day of endotoxemia, 51 calories on the first day, 76 calories on the second day, and 101 calories from the third day on. It was ensured that the nutritional intake was the same in all groups.
Serum glucose and electrolytes
Serum glucose and electrolytes levels were determined by standard laboratory techniques (Boehringer, Ingelheim, Germany).
Hepatic signal transcription factor mRNA and cytokine mRNA expression
Total RNA was prepared from rat liver samples according to the method described by Chomczynski and Sacchi (19, 20) using TRIzol reagent (Life Technologies, Gaithersburg, MD), and analysis was performed as previously published. Total RNA was quantified spectroscopically (OD 260 nm) or fluorometrically using Pico Green dye and equilibrated to an absolute quantity of 0.5 µg/µl. Subsequently, RT-PCR was performed. Total liver RNA (0.5 µg) was introduced to synthesize cDNA in a 60-µl reaction mixture using 2.5 µM random hexamers (Amersham Pharmacia Biotech, Freiburg, Germany) and Superscript II reverse transcriptase (Life Technologies, Inc.). The following primers were used to amplify specific rat transcripts for: 18S rRNA (QuantumRNA, Ambion, Inc., Austin, TX; 488 bp): forward, 5'-TCAAGAACGAAAGTCGGAGG-3'; reverse, 5'-GGACATCTAAGGGCATCACA-3'; C/EBP-ß (according to EMBL accession no. M84011; 190 bp): forward, 5'-GAGCGACGAGTACAAGA-3'; reverse, 5'-CTGCTTGAACAAGTTCCG-3'; RANTES (according to EMBL accession no. U06436; 178 bp): forward, 5'-TGCCTCCCCATATGGCTC-3'; reverse, 5'-AACCCACTTCTTCTCTGGGTTG-3'; STAT-3 (according to EMBL accession no. X91810; 436 bp): forward, 5'-TGGACCAGATGCGGAGAAG; reverse 5'-AATTTGACCAGCAACCTGAC; STAT-5 (according to EMBL accession no. X91988; 317 bp): forward, 5'-TCATCATCGAGAAGCAGCC-3'; reverse, 5'-TTCCGTCACAGACTCTGCAC-3'; SOCS-3 (according to EMBL accession no. AJ249240; 300 bp): forward, 5'-AAGACCTTCAGCTCCAAGAGC-3'; reverse, 5'-CTTGAGTACACAGTCAAAGCGG-3'; IL-1 (305 bp): forward, 5'-CTTCCTTGTGCAAGTGTCTGAAGC-3'; reverse, 5'-AAGAAGGTCCTTG GGTCCTCATCC-3'; IL-6 (559 bp): forward, 5'-AGCCCACCAGGAACGAAAGTC-3'; reverse, 5'-TGGAAGTTGGGGTA GGAAGGA-3'; TNF (209 bp): forward, 5'-TGCCTCAGCCTCTTCTCATT-3'; reverse, 5'-GCTTGGTGGTTTG CTACGAC-3'; MIF (470 bp): forward, 5'-CGGCCGTCGTTCGCAGTCTC-3'; reverse, 5'-CCGGAAGGTGGCC ATCATTACG-3'; IL-2 (190 bp): forward, 5'-CAGCGTGTGTTGGATTTGAC-3'; reverse, 5'-TGATGCTTTGACA GATGGCTA-3'; IL-10 (417 bp): forward, 5'-GAACCACCCGGCGTCTAC-3'; reverse, 5'-AGGGATGAGGG CAAGTGAAA-3'; interferon-
(IFN-; 292 bp): forward, 5'-GGCAAAAGGACGGTAACACGA-3'; reverse, 5'-CGACTCCTTTTCC GCTTCCTT-3'.
The predicted size of each RT-PCR product is given in parentheses. Each PCR was initially performed in a thermal cycler (Biometra, Gottingen, Germany) as previously described using standardized amplification programs. Five microliters of each reaction were subsequently subjected to agarose gel electrophoresis, followed by ethidium bromide staining. Absolute transcript concentrations were quantified introducing external cDNA standards by use of a real-time PCR cycler (Light Cycler, Roche Diagnostics, Mannheim, Germany). Each gene-specific standard was prepared using the corresponding gel-purified amplicon, followed by a spectroscopic nucleic acid concentration determination. After serial dilutions of resulting DNA standards, final sensitivity levels between 0.1 pg and 1 ng specific transcript/sample were performed during real-time PCR as follows. Using 1 µl of each cDNA, the Master SYBR Green protocol was performed (Roche Diagnostics) in a 10-µl sample volume in glass capillaries using the following experimental conditions: 1) 10-min preincubation at 95 C; 2) amplification at 95 C for 5 sec, 55 C for 10 sec with fluorescence detection, and 72 C for 18 sec for 45 cycles; and 3) melting curve: 94 C for 10 sec, 50 C for 60 sec, then 0.1 C/sec up to 90 C under continuous fluorescence detection. Confirmation of each amplicon identity was obtained through melting curve analysis as well as by sequencing of resulting RT-PCR products (TOBLAP, Munich, Germany). Sequence analysis of each PCR product confirmed 100% homology to the published rat sequences. As negative controls, water instead of RNA was used.
Hepatic and serum cytokine protein concentrations
Hepatic and serum proinflammatory cytokines IL-1ß, IL-6, MIF, and TNF, and antiinflammatory cytokines IL-2, IL-4, and IL-10 were determined by ELISA (R&D Systems, Inc., Minneapolis, MN). Serum was used either pure or diluted, and measurements were performed according to kit guidelines. Liver was completely homogenized in a lysis buffer (HEPES, sucrose, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, dithiothreitol, phenylmethylsulfonylfluoride, leupeptin, EDTA, and pepstatin) in a ratio of 1:6. The exact concentration was 100 mM HEPES, 10% sucrose, and 0.1% 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate. On 10 ml of this solution, one tablet of Complete Mini was added and stored on ice. After homogenization, samples were centrifuged at 4 C at 14,000 rpm for 10 min. The clean supernatant was then used to determine cytokine protein concentration.
Serum HMG-1 was determined by pooling the sample according to time points and treatment groups. Samples were then analyzed by Western blotting (SDS-PAGE gel) as previously described (3). Briefly, serum samples were ultrafiltered with Centricon 100 (Millipore Corp., Bedford, MA). The elute was fractionated by SDS-PAGE, transferred to a polyvinylidene difluoride immunoblot membrane (Bio-Rad Laboratories, Hercules, CA), and probed with either specific HMG-1 antiserum (Dr. K. J. Tracey, North Shore, Manhasset, Long Island, NY; 1:250 dilution) or purified IgG from anti-HMG-1 antiserum (Dr. K. J. Tracey; 5 µl/ml) for Western blot analysis. Polyclonal anti-HMG-1 IgG was purified using protein A-agarose according to the manufacturer’s instruction (Pierce Chemical Co., Rockford, IL). Western blots were scanned with a silver image scanner (Silverscanner II, Lacie Ltd., Beaverton, OR), and the relative band intensity was quantified using NIH IMAGR 1.59 software. The levels of HMG-1 were determined by reference to standard curves generated with purified HMG-1. The determination of HMG-1 was performed at Dr. Tracey’s laboratory.
Ethics and statistics
These studies were reviewed and approved by the animal care and use committee, assuring that all animal received humane care. Statistical comparisons were made by ANOVA and t test with Bonferroni’s correction. Data are expressed as the mean ± SD or the mean ± SEM where appropriate. Significance was accepted at P < 0.05.
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Results |
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). Furthermore, there were no significant differences in serum sodium, potassium, calcium, and phosphate levels between endotoxemia and insulin 1, 2, 5, and 7 d after the induction of endotoxemia (Table 1).
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). Endotoxemia caused a 10- to 15-fold increase in hepatic STAT-3 mRNA expression compared with normal animals. Insulin-treated animals demonstrated significantly decreased hepatic STAT-3 mRNA levels, which were in the normal range 2 d after the induction of endotoxemia. Insulin decreased significantly hepatic STAT-3 mRNA expression 1, 2, and 5 d after LPS administration compared with endotoxemia (P < 0.05; Fig. 1B). Similar to STAT-3, insulin decreased hepatic STAT-5 mRNA levels. Insulin administration significantly decreased hepatic STAT-5 mRNA on d 1, 2, and 5 after LPS administration compared with that in endotoxemic animals (P < 0.05; Fig. 1C).
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). Hepatic SOCS-3 mRNA levels were increased after LPS injection in the endotoxemia and insulin group compared with normal levels (Fig. 1E). Insulin treatment significantly increased hepatic SOCS-3 mRNA expression 5 and 7 d after LPS treatment compared with endotoxemia (P < 0.05; Fig. 1E).
Hepatic cytokine mRNA expression
Endotoxemia caused an increase in hepatic IL-1ß mRNA expression in the LPS and the LPS plus insulin group. Insulin administration, however, significantly decreased hepatic IL-1ß mRNA 1 and 2 d after LPS injection compared with endotoxemic rats receiving no insulin (P < 0.05; Fig. 2A). Hepatic IL-6 mRNA expression increased after LPS injection compared with normal values. Insulin treatment decreased the hepatic IL-6 mRNA concentration on d 2 and 7 after LPS injection compared with endotoxemia (P < 0.05; Fig. 2B). Insulin administration increased hepatic IL-10 mRNA expression on d 1 after LPS injection compared with controls (P < 0.05; Fig. 2C). LPS caused an increase in hepatic TNF mRNA throughout the entire study period (d 1: LPS, 0.05 ± 0.004; LPS plus insulin, 0.06 ± 0.011; normal, 0.001 ± 0.0008; d 2: LPS, 0.027 ± 0.003; LPS plus insulin, 0.024 ± 0.002; normal, 0.002 ± 0.0003; d 5: LPS, 0.016 ± 0.003; LPS plus insulin, 0.014 ± 0.003; normal, 0.006 ± 0.003; d 7: LPS, 0.02 ± 0.0032; LPS plus insulin, 0.024 ± 0.0035; normal, 0.008 ± 0.004). There were no significant differences between endotoxemia and insulin for hepatic mRNA expression of TNF. Hepatic MIF mRNA was increased with LPS administration (d 1: LPS, 0.023 ± 0.0021; LPS plus insulin, 0.025 ± 0.0025; normal, 0.0062 ± 0.0003; d 2: LPS, 0.025 ± 0.0055; LPS plus insulin, 0.034 ± 0.004; normal, 0.0068 ± 0.0003; d 5: LPS, 0.038 ± 0.0049; LPS plus insulin, 0.033 ± 0.006; normal, 0.0066 ± 0.0003; d 7: LPS, 0.04 ± 0.0091; LPS plus insulin, 0.044 ± 0.006; normal, 0.0067 ± 0.004). There were no significant differences between endotoxemia and insulin for hepatic mRNA expression of MIF. Hepatic IFN- mRNA decreased with LPS administration (d 1: LPS, 0.017 ± 0.003; LPS plus insulin, 0.012 ± 0.003; normal, 0.07 ± 0.02; d 2: LPS, 0.022 ± 0.006; LPS plus insulin, 0.017 ± 0.003; normal, 0.09 ± 0.04; d 5: LPS, 0.022 ± 0.008; LPS plus insulin, 0.015 ± 0.002; normal, 0.10 ± 0.05; d 7: LPS, 0.024 ± 0.0054; LPS plus insulin, 0.019 ± 0.0021; normal, 0.09 ± 0.04). There were no significant differences between endotoxemia and insulin for hepatic mRNA expression of IFN-. Hepatic IL-2 mRNA decreased in the LPS and LPS plus insulin group. IL-2 mRNA was almost 10-fold decreased compared with normal IL-2 throughout the entire study period. There were no significant differences between LPS vs. LPS plus insulin.
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). The hepatic TNF protein concentration demonstrated a different pattern. TNF increased over the study period and reached its maximum in the endotoxemia and insulin group 7 d after LPS application. Insulin decreased hepatic TNF expression on d 1 after LPS application compared with endotoxemia (P < 0.05; Fig. 3B). Endotoxemia increased the hepatic IL-6 protein concentration immediately after LPS injection. Insulin decreased hepatic IL-6 protein on d 1 and 2 after LPS injection compared with endotoxemia (P < 0.05; Fig. 3C). The hepatic MIF concentration was increased after LPS administration. Insulin decreased hepatic MIF expression 2 d after LPS administration compared with endotoxemia (P < 0.05; d 2: LPS, 294 ± 8 pg/ml homogenate; LPS plus insulin, 200 ± 10 pg/ml homogenate). There were no significant differences between LPS and LPS plus insulin at other time points.
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). The hepatic IL-4 protein concentration was decreased after LPS application until 5 d after the injection. Insulin significantly increased the hepatic IL-4 concentration 7 d after LPS application (P < 0.05; Fig. 3E). The hepatic IL-2 protein concentration was decreased in both LPS and LPS plus insulin groups during the first 5 d after LPS administration, but returned to normal levels on d 7 after LPS. There was no significant difference in the hepatic IL-2 protein concentration between LPS and LPS plus insulin groups.
Serum cytokine concentration
Serum IL-1ß concentrations increased during the first day after induction of endotoxemia. Levels demonstrated a rapid decrease and reached the normal range 7 d after LPS induction. Insulin significantly decreased the serum IL-1ß concentration on d 1, 2, and 5 after LPS injection compared with levels in endotoxemic animals receiving saline (P < 0.05; Fig. 4A). LPS injection caused an increase in the serum TNF concentration on d 1–7. Insulin attenuated the increase in serum TNF on d 1, 2, 5, and 7 and significantly decreased serum TNF compared with levels in endotoxemic rats (P < 0.05; Fig. 4B). In addition, insulin significantly decreased serum IL-6 concentrations on d 1, 2, and 7 after LPS compared with control levels, which were almost 300 times elevated above normal levels (P < 0.05; Fig. 4C). The concentration of MIF was elevated immediately after LPS injection. Insulin significantly decreased serum MIF 2 and 7 d after endotoxemia (P < 0.05; Fig. 4D).
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). There was no significant difference between insulin and endotoxemia in serum levels of IL-2 and IL-4. Insulin increased dose- and time-dependent antiinflammatory cytokines and decreased proinflammatory cytokines. Thus, ratios of proinflammatory to antiinflammatory cytokines, which are predictors for organ function and systemic homoeostasis, significantly improved toward normal in the insulin treatment group.
The serum HMG-1 protein concentration was increased after LPS injection. On d 1 after LPS administration, HMG-1 levels were higher in endotoxemic rats receiving insulin, but beginning on d 2, serum HMG-1 was 2- to 3-fold lower in the insulin-treated group compared with the endotoxemic group receiving saline (Fig. 5).
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Discussion |
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Insulin decreased the proinflammatory mediators IL-1, IL-6, and TNF as well as MIF. At the same time, insulin significantly increased the antiinflammatory cytokines IL-2, IL-4, and IL-10. IL-4 was only determined as a protein and not as hepatic mRNA, because the IL-4 primer to quantify mRNA did not result in valid and reproducible data. Clinical studies demonstrated that nonsurvivors with pancreatitis had increased IL-6 to IL-10 ratios compared with survivors (26). Our group found that ratios of proinflammatory to antiinflammatory cytokines correlate with organ function and can be used as predictors for mortality in pediatric severe burn patients (27). Hence, by decreasing proinflammatory and increasing antiinflammatory cytokines insulin equilibrates the balance between pro- and antiinflammatory cytokines and may improve organ function and mortality after trauma.
Insulin decreased serum IL-1, TNF, IL-6, and MIF and increased IL-10 and IL-4. In the liver we found that insulin decreased IL-1, TNF, and IL-6 and increased IL-10 and IL-4 at the protein level. However, insulin affects only hepatic mRNA expression of IL-1, IL-6, and IL-10. Thus, it appears that for these cytokines (IL-1, IL-6, and IL-10), insulin acts at a pretranscriptional level and through intracellular signal transcription factors. Because for hepatic TNF, only the protein concentration was affected, not mRNA expression, it seems likely that either insulin modulates TNF at a posttranscriptional level, or insulin affects cytokine synthesis and release in other organs, which lead to a decreased concentration in the circulation and subsequently in the liver. We did not determine the cytokine concentration in other organs; therefore, we cannot answer this question.
HMG-1 was named for its rapid migration properties on electrophoretic gels (3). HMG-1 is a member of the nonhistone chromatin-associated proteins (3). Intracellular HMG-1 has been studied for its function in binding DNA and stabilizing nucleosome formation; extracellular HMG-1 was recently shown to be a late mediator of delayed endotoxin lethality (3, 14). During lethal endotoxemia in mice, serum HMG-1 increased 16–36 h after LPS administration. Lethality could be improved by administering anti-HMG-1 antibodies (3, 14). In critically ill patients, HMG-1 levels were increased, but even moreso in nonsurvivors (14). Furthermore, in animal studies it was shown that attenuating HMG-1 levels, e.g. with the administration of acetylcholine, improved survival (28). In the present study we showed that insulin decreased extracellular serum HMG-1 levels in endotoxemic rats starting from d 2, and therefore, decreased HMG-1 levels indicate possible improved outcome with the administration of insulin.
To determine whether insulin exerts its effects on cytokines through changes in blood glucose or directly by modulating signal transcription factors, we measured hepatic signal transcription factor mRNA expression. We found that insulin alters the intracellular signal cascade in the liver. Insulin decreased the proinflammatory signal transcription factors STAT-3, STAT-5, and C/EBP-ß. An up-regulation of these transcription factors has been associated with impaired organ function and protein synthesis, such as albumin (8, 9, 10). Therefore, it appears that insulin improves organ function and protein synthesis during the hypermetabolic response through these signal transcription factors. In addition to proinflammatory transcription factors, we determined factors that were identified to either suppress cytokine signaling (SOCS) or regulate T cell function (RANTES). Members of the SOCS family of proteins play key roles in the negative regulation of cytokine signal transduction by acting in a negative feedback loop and inhibiting the cytokine-activated Janus kinase (JAK)/STAT signaling pathway to modulate cellular responses (29). Direct interaction of SOCS Src homology 2 domains with the JAKs or cytokine receptors allows their recruitment to the signaling complex, where they inhibit JAK catalytic activity or block access of the STATs to receptor binding sites (29). Because we have shown that insulin decreased STAT-5 and increased SOCS-3, major players during the aftermath of a thermal injury (11), it remains to be defined whether insulin decreases cytokines, STAT-3, STAT-5, and C/EBP-ß in a direct fashion or indirectly through SOCS-3.
RANTES is a member of a large supergene family of proinflammatory cytokines called CC chemokines that appear to play a fundamental role in inflammatory processes. Although the expression of RANTES was first thought to be limited to activated T cells, recent data have shown that it is produced by a variety of tissue types in response to specific stimuli. Deletion analysis of the promoter region indicates that different transcriptional mechanisms control the expression of RANTES in the various tissues studied. After trauma, the immune system plays a crucial role in survival and clinical outcome (13). Growth factors such as GH can affect T helper type 1 and 2 cells by restoring the T helper type 1 response and can improve the immune system after thermal injury (29). We did not define the function of the immune system in the present study; however, it appears that insulin may have some beneficial effects by modulating the T cell response because insulin significantly increased hepatic RANTES mRNA expression 7 d after endotoxemia.
It was very surprising that insulin at the dose administered in the present study did not alter glucose levels. In previous experiments we used the same insulin dosage, and we found that insulin significantly decreased blood glucose levels (17). This leads us to hypothesize that glucose metabolism must be different during sepsis and during the hypermetabolism after burn injury, or the dose of insulin chosen in this study was not sufficient to significantly reduce insulin resistance during endotoxemia. It was also surprising that glucose levels were decreased in the LPS and LPS plus insulin groups on the first day after the induction of endotoxemia and were not increased. It has to be mentioned that we measured glucose at large time intervals that may have missed slight and temporal changes occurring during the early period after LPS and insulin administration. In contrast, during the stress response, insulin levels are usually normal or decreased despite the peripheral insulin resistance (30, 31). Changes in whole body glucose uptake and glucose oxidation in sepsis are complex and dependent on the severity of illness and the stage of the disease. Whole body glucose uptake and glucose oxidation are increased during the early stages of endotoxemia and sepsis (32, 33). This results from a cytokine-induced increase in noninsulin-mediated glucose uptake by tissue that encompass high concentrations of mononuclear phagocytes, including liver, lung, spleen, and ileum (34, 35). This could explain why in our study glucose levels were decreased at an early time point. During the endotoxemic and septic phases, the insulin resistance increases with a decrease in glucose utilization oxidation leading to hyperglycemia.
Stress-related hyperglycemia and insulin resistance are almost universal findings in patients with sepsis (36). The pathophysiological causes of this response are probably proinflammatory mediators and stress-related hormones (36). Hyperglycemia is per se proinflammatory; however, it also appears in accord with the results presented in this study showing that insulin exerts antiinflammatory properties (37). We demonstrated that insulin attenuated the inflammatory response by decreasing proinflammatory and increasing antiinflammatory cytokines, thus restoring systemic homeostasis. Based on our data we hypothesize that the antiinflammatory effect of insulin is probably due to modulation of cellular signal transcription factors rather than through changes in blood glucose and metabolism. We suggest that insulin may represent an important and safe therapeutic option in the treatment of critically ill patients.
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Acknowledgments |
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Footnotes |
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, interferon-; JAK, Janus kinase; LPS, lipopolysaccharides; MIF, macrophage inhibitory factor; RANTES, regulated on activation, normal T cell expressed and secreted; SOCS, suppressor of cytokine signaling; STAT, signal transducer and activator of transcription. Received May 10, 2004.
Accepted for publication June 2, 2004.
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, C/EBPß, and C/EBP
to thermal injury. Surgery 119:674–683[CrossRef][Medline]
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