Thyroxine is a potential endogenous antagonist of macrophage migration inhibitory factor (MIF) activity.

Abnormally low plasma concentrations of thyroid hormones during sepsis often occur in the absence of thyroidal illness; however, the mechanisms involved in the "euthyroid sick syndrome" remain poorly understood. Here, we describe a previously unrecognized interaction between the thyroid hormone thyroxine (T(4)) and the proinflammatory cytokine macrophage migration inhibitory factor (MIF), together with its clinical relevance in sepsis. We found that in both patients with severe sepsis, and our rodent model, low plasma T(4) concentrations were inversely correlated with plasma MIF concentrations. The MIF molecule contains a hydrophobic pocket that is important for many of its proinflammatory activities. Binding of L-T(4) (or its hormonally inert isomer D-T(4)) significantly, and dose-dependently, inhibited the catalytic activity of this pocket. Moreover, administration of exogenous D-T(4) significantly improved survival in mice with severe sepsis. To examine the specificity of the MIFT(4) interaction, wild-type and MIF knockout mice were subjected to the carrageenan-air pouch model of inflammation and then treated with D-T(4) or vehicle. D-T(4) significantly inhibited leukocyte infiltration in wild-type mice but not in MIF knockout mice, providing evidence that in vivo T(4) may influence MIF-mediated inflammatory responses via inhibition of its hydrophobic proinflammatory pocket. These findings demonstrate a new physiological role for T(4) as a natural inhibitor of MIF proinflammatory activity. The data may also, in part, explain the low plasma T(4) concentrations in critically ill, euthyroid patients and suggest that targeting the imbalance between MIF and T(4) may be beneficial in improving outcome from sepsis.

Milk fat globule epidermal growth factor 8 attenuates acute lung injury in mice after intestinal ischemia and reperfusion.

RATIONALE: Milk fat globule epidermal growth factor 8 (MFG-E8) is a potent opsonin for the clearance of apoptotic cells and is produced by mononuclear cells of immune competent organs including the spleen and lungs. It attenuates chronic and acute inflammation such as autoimmune glomerulonephritis and bacterial sepsis by enhancing apoptotic cell clearance. Ischemia-reperfusion (I/R) injury of the gut results in severe inflammation, apoptosis, and remote organ damage, including acute lung injury (ALI). OBJECTIVES: To determine whether MFG-E8 attenuates intestinal and pulmonary inflammation after gut I/R. METHODS: Wild-type (WT) and MFG-E8(-/-) mice underwent superior mesenteric artery occlusion for 90 minutes, followed by reperfusion for 4 hours. A group of WT mice was treated with 0.4 microg/20 g recombinant murine MFG-E8 (rmMFG-E8) at the beginning of reperfusion. Four hours after reperfusion, MFG-E8, cytokines, myeloperoxidase activity, apoptosis, and histopathology were assessed. A 24-hour survival study was conducted in rmMFG-E8- and vehicle-treated WT mice. MEASUREMENTS AND MAIN RESULTS: Mesenteric I/R caused severe widespread injury and inflammation of the small intestines and remote organs, including the lungs. MFG-E8 levels decreased in the spleen and lungs by 50 to 60%, suggesting impaired apoptotic cell clearance. Treatment with rmMFG-E8 significantly suppressed inflammation (TNF-alpha, IL-6, IL-1beta, and myeloperoxidase) and injury of the lungs, liver, and kidneys. MFG-E8-deficient mice suffered from greatly increased inflammation and potentiated ALI, whereas treatment with rmMFG-E8 significantly improved the survival in WT mice. CONCLUSIONS: MFG-E8 attenuates inflammation and ALI after gut I/R and may represent a novel therapeutic agent.

Human ghrelin ameliorates organ injury and improves survival after radiation injury combined with severe sepsis.

In the terrorist radiation exposure scenario, radiation victims are likely to suffer from additional injuries such as sepsis. Our previous studies have shown that ghrelin is protective in sepsis. However, it remains unknown whether ghrelin ameliorates sepsis-induced organ injury and mortality after radiation exposure. The purpose of this study is to determine whether human ghrelin attenuates organ injury and improves survival in a rat model of radiation combined injury (RCI) and, if so, the potential mechanism responsible for the benefit. To study this, adult male rats were exposed to 5-Gy whole body irradiation followed by cecal ligation and puncture (CLP, a model of sepsis) 48 h thereafter. Human ghrelin (30 nmol/rat) or vehicle (saline) was infused intravenously via an osmotic minipump immediately after radiation exposure. Blood and tissue samples were collected at 20 h after RCI (68 h after irradiation or 20 h after CLP) for various measurements. To determine the longterm effect of human ghrelin after RCI, the gangrenous cecum was removed at 5 h after CLP and 10-d survival was recorded. In addition, vagotomy or sham vagotomy was performed in sham and RCI animals immediately prior to ghrelin administration, and various measurements were performed at 20 h after RCI. Our results showed that serum levels of ghrelin and its gene expression in the stomach were decreased markedly at 20 h after RCI. Administration of human ghrelin attenuated tissue injury markedly, reduced proinflammatory cytokine levels, decreased tissue myeloperoxidase activity, and improved survival after RCI. Furthermore, elevated plasma levels of norepinephrine (NE) after RCI were reduced significantly by ghrelin. However, vagotomy prevented ghrelin's beneficial effects after RCI. In conclusion, human ghrelin is beneficial in a rat model of RCI. The protective effect of human ghrelin appears to be attributed to re-balancing the dysregulated sympathetic/parasympathetic nervous systems.

Orexigenic hormone ghrelin ameliorates gut barrier dysfunction in sepsis in rats.

OBJECTIVES: We have recently shown that ghrelin, a novel orexigenic hormone, is reduced in sepsis. Ghrelin treatment, mediated through ghrelin receptors in the brain, attenuates sepsis-induced inflammation and mortality. Gut barrier dysfunction is common in sepsis. High-mobility group B1 (HMGB1) increases gut permeability both in vitro and in vivo. However, it remains unknown whether ghrelin has any effects on HMGB1 and gut barrier function in sepsis. We hypothesized that ghrelin decreases HMGB1 release and attenuates sepsis-induced gut barrier dysfunction through central ghrelin receptors. DESIGN: Prospective, controlled, and randomized animal study. SETTING: A research institute laboratory. SUBJECTS: Male adult Sprague-Dawley rats (275-325 g). INTERVENTIONS: Cecal ligation and puncture (CLP) followed by injection/infusion of ghrelin. MEASUREMENTS AND MAIN RESULTS: Five hours after CLP, a bolus intravenous injection of 2 nmol of ghrelin was followed by a continuous infusion of 12 nmol of ghrelin via an osmotic mini-pump for 15 hrs. Twenty hours after CLP, brain ghrelin levels, serum HMGB1 levels, ileal mucosal permeability to fluorescein isothiocyanate dextran, bacterial counts in the mesenteric lymph nodes complex, and gut water content were determined. In additional groups of animals, bilateral trunk vagotomy was performed at 5 hrs after CLP before ghrelin injection. Furthermore, to confirm the role of central ghrelin receptors in ghrelin's effect, ghrelin (1 nmol) was administered through intracerebroventricular injection at 5 hrs after CLP. Our results showed that brain levels of ghrelin decreased by 34% at 20 hrs after CLP. Intravenous administration of ghrelin completely restored brain levels of ghrelin, significantly reduced the elevated HMGB1 levels, and attenuated gut barrier dysfunction. Vagotomy eliminated ghrelin's inhibition of HMGB1 and attenuation of gut barrier dysfunction. Intracerebroventricular injection of ghrelin decreased serum HMGB1 levels and ameliorated gut barrier dysfunction. CONCLUSIONS: Ghrelin reduces serum HMGB1 levels and ameliorates gut barrier dysfunction in sepsis by vagus nerve activation via central ghrelin receptors. Ghrelin can be further developed as a novel agent to protect gut barrier function in sepsis.

Human adrenomedullin combined with human adrenomedullin binding protein-1 is protective in gut ischemia and reperfusion injury in the rat.

Previous studies have demonstrated that co-administration of rat adrenomedullin (AM) and human AM binding protein-1 (AMBP-1) has various beneficial effects following adverse circulatory conditions. In order to reduce rat proteins to elicit possible immune responses in humans, we determined the effect of human AM combined with human AMBP-1 after intestinal ischemia and reperfusion (I/R). Intestinal ischemia was induced in the rat by occluding the superior mesenteric artery for 90 min. At 60 min after the beginning of reperfusion, human AM/AMBP-1 at 3 different dosages was administered intravenously over 30 min. At 240 min after the treatment, blood and tissue samples were harvested and measured for pro-inflammatory cytokines (i.e., TNF-alpha and IL-6), myeloperoxidase activities in the gut and lungs, and cleaved caspase-3 expression in the lungs, as well as serum levels of hepatic enzymes and lactate. In additional groups of animals, a 10-day survival study was conducted. Results showed that administration of human AM/AMBP-1 reduced pro-inflammatory cytokines, attenuated organ injury, and improved the survival rate in a seemingly dose-response fashion. Co-administration of the highest dose of human AM/AMBP-1 in this study had the optimal therapeutic effect in the rat model of intestinal I/R.

Human vasoactive hormone adrenomedullin and its binding protein rescue experimental animals from shock.

We recently discovered that vascular responsiveness to adrenomedullin (AM), a vasoactive hormone, decreases after hemorrhage, which is markedly improved by the addition of its binding protein AMBP-1. One obstacle hampering the development of AM/AMBP-1 as resuscitation agents in trauma victims is the potential immunogenicity of rat proteins in humans. Although less potent than rat AM, human AM has been shown to increase organ perfusion in rats. We therefore hypothesized that administration of human AM/AMBP-1 improves organ function and survival after severe blood loss in rats. To test this, male Sprague-Dawley rats were bled to and maintained at an MAP of 40 mmHg for 90 min. They were then resuscitated with an equal volume of shed blood in the form of Ringer's lactate (i.e., low-volume resuscitation) over 60 min. At 15 min after the beginning of resuscitation, human AM/AMBP-1 (12/40 or 48/160 microg/kg BW) were administered intravenously over 45 min. Various pathophysiological parameters were measured 4h after resuscitation. In additional groups of animals, a 12-day survival study was conducted. Our result showed that tissue injury as evidenced by increased levels of transaminases, lactate, and creatinine, was present at 4h after hemorrhage and resuscitation. Moreover, pro-inflammatory cytokines TNF-alpha and IL-6 were also significantly elevated. Administration of AM/AMBP-1 markedly attenuated tissue injury, reduced cytokine levels, and improved the survival rate from 29% (vehicle) to 62% (low-dose) or 70% (high-dose). However, neither human AM alone nor human AMBP-1 alone prevented the significant increase in ALT, AST, lactate and creatinine at 4h after the completion of hemorrhage and resuscitation. Moreover, the half-life of human AM and human AMBP-1 in rats was 35.8 min and 1.68 h, respectively. Thus, administration of human AM/AMBP-1 may be a useful approach for attenuating organ injury, and reducing mortality after hemorrhagic shock.

High glucose variability increases cerebral infarction in patients with spontaneous subarachnoid hemorrhage.

PURPOSE: High glucose variability is a significant marker for poor outcome in critically ill patients. We evaluated the impact of high glucose variability on cerebral infarction following spontaneous subarachnoid hemorrhage (SAH). MATERIALS AND METHODS: Consecutive adult patients with spontaneous SAH and Hunt Hess score of at least 3 were retrospectively identified. Patients were excluded if their intensive care unit length of stay was less than 24 hours or if there were less than 5 glucose assessments. Glucose values from the first 7 days of intensive care unit admission were assessed. Variability was calculated as the average change in glucose over time for each patient. Classification and regression tree analysis was used to determine high vs low glucose variability, and the incidence of cerebral infarction was compared. Multivariate analysis was used to control for confounding variables. RESULTS: There were 42 patients. Classification and regression tree analysis revealed a change in glucose greater than 9.52 mg/dL/h as the determinant for high variability. The incidence of cerebral infarction was 64% when glucose variability was high vs 20% when it was low (P=.006). Multivariate analysis identified high glucose variability (odds ratio [95% confidence interval]=11.4 [1.9-70.2], P=.008) and female sex (odds ratio [95% confidence interval]=5.2 [1-26.8], P=.047) as independent predictors for cerebral infarction. CONCLUSION: Glucose variability is a significant predictor of cerebral infarction in patients with severe spontaneous SAH.

The effect of a computer-assisted insulin protocol on glycemic control in a surgical intensive care unit.

BACKGROUND: Computer-assisted insulin protocols (CAIPs) contain complex mathematical algorithms to assist with insulin dosing. This study compared the quality of glucose control utilizing a CAIP with a paper-based insulin protocol (PBIP). METHODS: This before-after study identified consecutive patients who received continuous insulin therapy for at least 24 h. Patients were stratified into two groups (PBIP and CAIP). The target blood glucose range for both was 80-110 mg/dL. Hypoglycemia was defined as the percentage of patients with any glucose value <40 mg/dL. Variability was measured by reporting the SD for each patients mean glucose value. RESULTS: There were 192 patients evaluated (PBIP, n = 145; CAIP, n = 47). More glucose readings were within target range using the CAIP protocol (49 ± 14% vs. 40 ± 12%, P < 0.001), but no difference in mean glucose was noted (113 ± 11 mg/dL with CAIP vs. 116 ± 11 mg/dL with PBIP, P = 0.067). The incidence of hypoglycemia was similar between the CAIP and PBIP groups, respectively (2.1% vs. 4.1%, P = 0.518). Glucose variability was lower with the CAIP (25 ± 9 mg/dL vs. 31 ± 11 mg/dL, P = 0.001). The CAIP required more frequent blood glucose assessments (16 ± 2 vs. 12 ± 2 per day, P < 0.001), more insulin dosing adjustments (14 ± 3 vs. 5 ± 2 per day, P < 0.001), and more time per day (84 ± 15 vs. 51 ± 8 min per patient, P < 0.001) compared with the PBIP. CONCLUSIONS: A CAIP will lead to minor improvements in glucose control and decrease glucose variability but will not change the rate of hypoglycemia or response to insulin therapy. These differences could largely be due to more aggressive monitoring and titrations required by a CAIP.