Phosphorylation of insulin-like growth factor binding protein-1 in patients with insulin-dependent diabetes mellitus and severe trauma.

We have determined the level of phosphorylated insulin-like growth factor binding protein-1 (pIGFBP-1) in serum during two catabolic states: diabetes mellitus and trauma. Human sera were incubated with [125I]IGF-I for 2 h followed by non-denaturing PAGE. [125I]IGF-I/IGFBP-1 complexes from serum co-migrated with a pure p4IGFBP-1 standard. Complex formation was specifically inhibited by unlabeled IGF-I. The migration of IGF-I/pIGFBP-1 complexes was retarded by IGFBP-1 antibodies, but not by antibodies against IGFBP-2 or IGFBP-3. Sera from three severely traumatized patients had up to 12-fold more pIGFBP-1 than sera from age-matched controls. The level of pIGFBP-1 was reduced in all three patients upon hospital discharge. Sera from three patients with insulin dependent diabetes mellitus (IDDM) and severe ketoacidosis (DKA) had more pIGFBP-1 than controls. Administration of insulin to DKA patients lowered the level of pIGFBP-1. The present study shows that IGFBP-1 exists as a free, high affinity, phosphorylated form in vivo during two catabolic states.

Alterations in tissue glucose uptake during the hyperglycemic and hypoglycemic phases of sepsis.

The purpose of the present study was to characterize the alterations in tissue glucose uptake during the hyperglycemic, euglycemic, and hypoglycemic phases of peritonitis. Rats had vascular catheters implanted, and sepsis was induced by cecal ligation and puncture. Rates of whole-body glucose appearance (Ra), disappearance (Rd), and metabolic clearance (MCR) were determined by the constant infusion of 3H-glucose, and in vivo glucose uptake (Rg) by individual tissues was assessed by using 14C-deoxyglucose. During the hyperglycemic phase of sepsis (2 h), glucose Ra and Rd were increased, but glucose MCR was unaltered. In contrast, during the euglycemic phase (6 h), the sepsis-induced increase in glucose Ra and Rd was associated with an elevation in the MCR. Finally, during the hypoglycemic phase (24 h), sepsis decreased glucose Ra and Rd and the glucose MCR. The sepsis-induced changes in Rg for skeletal muscle and adipose tissue mimic those seen for the whole body at each time point. Rg for skin and intestine was elevated at 2 h and 6 h but was not different from control values at 24 h. In contrast, the Rg for liver, lung, and spleen was increased at all 3 time points. In a second study, there was no difference in Rg for any tissue between 2-h septic rats and control animals in which blood glucose and insulin levels were artificially elevated to the same degree. In a third study, the prevailing glucose and insulin levels in control animals were decreased, by injection of the gluconeogenic inhibitor 3-mercaptopicolinic acid, to levels seen in 24-h septic rats. There was no difference in the Rg for muscle and adipose tissue between 24-h septic rats and hypoglycemic insulinopenic control animals. However, the Rg for liver, lung, and spleen remained elevated in 24-h septic rats, compared with hypoglycemic insulinopenic control values. These data indicate that the increased tissue glucose uptake observed during the early phase of sepsis is a consequence of concomitant changes in plasma glucose and insulin. In contrast, during the euglycemic and hypoglycemic stages of sepsis, glucose uptake in macrophage-rich tissues remains elevated and is independent of changes in glucose and insulin.

Endotoxin-induced alterations in insulin-stimulated phosphorylation of insulin receptor, IRS-1, and MAP kinase in skeletal muscle.

Sepsis and endotoxin (LPS) have been demonstrated to impair insulin-mediated glucose uptake in skeletal muscle. However, the intracellular mechanism responsible for this defect is not fully defined. The purpose of the present study was to determine whether specific elements of the insulin receptor (IR) signaling pathway in skeletal muscle are altered by LPS. In vivo injection of Escherichia coli LPS resulted in a 44% reduction in whole body glucose disposal under euglycemic hyperinsulinemic conditions, which was largely accounted for by a decreased rate of glycogen synthesis. Scatchard analysis indicated that the number and affinity of the high-affinity insulin binding sites in muscle were similar between control and LPS-treated rats. Western blot analysis indicated that under basal conditions, the levels of total and phosphorylated IR, insulin receptor substrate (IRS)-1, and mitogen-activated protein (MAP) kinase were not significantly different between control and endotoxic rats. In control animals, muscle obtained 2 min after intravenous injection of a maximally stimulating dose of insulin demonstrated a marked increase in the amount of phosphorylated IR (approximately 5-fold), IRS-1 (approximately 10-fold), and MAP kinase (approximately 10-fold). Insulin-stimulated phosphorylation of IR, IRS-1, and MAP kinase was markedly diminished (approximately 75%, 90%, and 78%, respectively) in LPS-treated rats. However, there was no concomitant reduction in the total abundance of these proteins under hyperinsulinemic conditions. These data demonstrate that LPS alters multiple steps in the insulin signal transduction pathway, but not insulin binding, in skeletal muscle that may mediate the observed impairment in glucose uptake.

Nutritional support of the septic patient.

Nutrition and metabolic support is just one of many weapons at the clinician's disposal in the battle against infection. Much has been learned in the past several decades concerning the host's response to infection and the competition among substrates during health and disease. Despite these advances, we still are remarkably ineffective at preventing the muscle wasting that accompanies sepsis and other chronic catabolic conditions. This likely is the result of our lack of understanding concerning the molecular mechanisms responsible for changes in protein metabolism. It is anticipated that the optimal or preferred mixture of glucose, fat, and protein will be better defined in the future, and that new supplements (e.g., MCTs, amino acids, growth factors, antioxidants) will prove beneficial, so the protein-catabolic response to sepsis can be ameliorated and patient outcome improved. Until that time, nutritional interventions should be initiated early in the septic episode and be assessed and altered frequently. Specific guidelines for nutritional support are presented in Table 3.

Vibrio vulnificus septicemia in a patient with the hemochromatosis HFE C282Y mutation.

Vibrio vulnificus is an extremely invasive gram-negative bacillus found in marine waters that causes overwhelming bacteremia and shock that is associated with high mortality. Impaired iron metabolism has been implicated in the susceptibility to V vulnificus bacterial infections. We report a case of fatal V vulnificus sepsis in a 56-year-old man who died within 1 to 3 days after consuming raw seafood. At autopsy, he was found to have micronodular cirrhosis and iron overload. Postmortem genetic analysis revealed the presence of the hemochromatosis gene (HFE) C282Y mutation. To our knowledge, this is this first documented fatal case of V vulnificus infection in a patient proven to carry the HFE C282Y mutation. Because this patient was heterozygous for the major hereditary hemochromatosis mutation and was not previously diagnosed with clinical iron overload, the spectrum of clinical susceptibilities to V vulnificus infection may include carriers of the C282Y mutation.

Ventromedial hypothalamic lesions impair glucoregulation in response to endotoxin.

The purpose of the present study was to determine the role of the ventromedial hypothalamus (VMH) in regulating counter-regulatory hormone release and the increase in glucose flux that is observed after injection of endotoxin [lipopolysaccharide (LPS)]. Bilateral lesions of the VMH were produced electrolytically 2 wk before the experiment; sham-operated rats served as controls. [3-3H]glucose was infused to assess whole body glucose flux before and for 4 h after intravenous injection of Escherichia coli LPS. In control rats, LPS increased the plasma concentrations of glucose and lactate and the rates of glucose appearance and disappearance. In these animals, LPS also produced sustained elevations in corticosterone, glucagon, and catecholamines. In contrast, the glucose metabolic response to LPS was attenuated by > 50% in VMH-lesioned rats. These changes were associated with a blunted increase in the plasma concentration of glucagon, epinephrine, and norepinephrine in VMH-lesioned rats compared with control animals. There was no difference in the plasma concentrations of corticosterone or TNF-alpha between the two groups after LPS or the responsiveness of sham- and VMH-lesioned rats to an infusion of either glucagon or epinephrine. These data indicate that the VMH plays a central role in regulating the secretion of glucagon and catecholamines and the stimulation of glucose flux after LPS.

Alterations in the insulin-like growth factor system in trauma patients.

The aim of the present study was to elucidate changes in the growth hormone (GH)-insulin-like growth factor (IGF) axis in trauma patients throughout their stay in the surgical intensive care unit (SICU). The first venous blood sample was obtained within 24 h after admission to the SICU and before the start of nutritional support; the last sample was obtained within 24 h of each patient's discharge from the SICU. All patients were receiving nutritional support at this later time. Control subjects were healthy volunteers, matched for age and sex and fasted approximately 18 h before blood sampling. GH in trauma patients was increased 25-fold on the first day and was still elevated > or = 5-fold on the last day. Trauma decreased circulating levels of both IGF-I (50-60%) and IGF-II (33-45%) throughout the duration of the patients' stay in the SICU. A sustained reduction in plasma IGF-binding protein (BP)-3 (55-75%) was observed in trauma patients throughout the protocol. In contrast, IGFBP-1 levels increased more than threefold during this same period. Furthermore, IGFBP-1 in these patients had undergone posttranslational modification and existed primarily in a highly phosphorylated form. Blood, collected from a cohort (n = 3) of these patients within 24 h of their discharge from the hospital, indicated that IGF-I and IGF-II were still reduced (30%) and that the decrease in IGFBP-3 and the elevation in IGFBP-1 were still evident at this time.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of insulin-like growth factor (IGF)-I mRNA and peptide and IGF-binding proteins by interleukin-1.

The purpose of the present study was to determine whether interleukin (IL)-1 would alter the insulin-like growth factor (IGF) system in rats and whether this change was mediated by glucocorticoids. The IGF-I concentration was decreased in plasma (32%), liver (35%), skeletal muscle (40-50% depending on fiber type), pituitary (36%), and brain (52%), and increased in kidney (73%) 6 h after intravenous injection of IL-1 beta. IL-1 beta also decreased IGF-I mRNA levels in liver and muscle and increased expression in kidney. These changes were associated with a > 2.5-fold elevation in plasma corticosterone levels. Pretreatment of rats with the glucocorticoid receptor antagonist RU-486 prevented the IL-1 beta-induced decrease in plasma and liver IGF-I concentration and the reduction in hepatic IGF-I mRNA expression. In contrast, RU-486 did not significantly attenuate the fall in IGF-I content in skeletal muscle, heart, brain, or pituitary or the increase in IGF-I observed in kidney after IL-1 beta. Furthermore, pretreatment with RU-486 did not completely prevent the IL-1 beta-induced decrease in IGF-I mRNA in skeletal muscle. The concentration of both IGF-binding protein (BP)-1 and BP-2 was increased in plasma, liver, and muscle in response to IL-1 beta, and these changes were also not prevented by RU-486. These results indicate that the inflammatory cytokine IL-1 beta is capable of influencing multiple components of the IGF system. Whereas the enhanced endogenous production of glucocorticoids appears to mediate the IL-1 beta-induced decrease in IGF-I synthesis in liver, the changes in IGF-I content observed in other tissues and the increase in IGFBP-1 and IGFBP-2 appear to be largely glucocorticoid independent.

Role of central IL-1 in regulating peripheral IGF-I during endotoxemia and sepsis.

Inflammatory cytokines may mediate the host response to infection via central nervous system, endocrine, and/or paracrine/autocrine signaling mechanisms. Previous studies have shown that intravenous administration of interleukin (IL)-1 beta alters the concentration of the anabolic hormone insulin-like growth factor (IGF)-I in plasma and various tissues. The purpose of the present study was to determine 1) whether the intracerebroventricular injection of IL-1 beta can influence peripheral IGF-I levels in control animals and 2) whether the central administration of a IL-1 receptor antagonist (IL-1ra) can prevent the changes in peripheral IGF-I induced by endotoxin [lipopolysaccharide (LPS)] or sepsis produced by cecal ligation and puncture. In the first experiment, injection of IL-1 beta (100 ng/rat) decreased IGF-I levels in plasma, liver, and gastrocnemius muscle 28-36% by 1.5 h in conscious fasted rats. IGF-I levels remained reduced at 3 h, but returned to baseline by 6 h. IGF-I content was not altered in soleus, kidney, spleen, intestine, or whole brain after IL-1 beta. In the second series of experiments, LPS injected intravenously decreased IGF-I levels in plasma, liver, and gastrocnemius at 1.5 h, and levels were even further reduced at 3 and 6 h in these tissues (59, 57, and 48%, respectively). Moreover, the IGF-I content was also decreased in soleus (30-35%) and increased in kidney (2- to 3-fold) after LPS. In the third experiment, changes in IGF-I levels in plasma and tissues, similar to those seen in LPS-treated rats, were detected 24 h after induction of peritonitis. Intracerebroventricular infusion of IL-1ra did not alter any of the changes in IGF-I produced by either LPS or sepsis, although it did attenuate the concomitant changes in growth hormone levels. These data suggest that, although central IL-1 beta is capable of modulating peripheral IGF-I levels, central administration of IL-1ra was unable to modulate the changes in peripheral IGF-I in blood and tissues produced by either endotoxemia or peritonitis.

Endotoxin-induced changes in IGF-I differ in rats provided enteral vs. parenteral nutrition.

The purpose of the present study was to determine whether acute changes in the insulin-like growth factor (IGF) system induced by mild surgical trauma/fasting or endotoxin [lipopolysaccharide (LPS)] are differentially modulated by total enteral nutrition (TEN) or total parenteral nutrition (TPN). Rats had vascular catheters and a gastrostomy tube surgically placed and were fasted overnight. The next morning animals randomly received an isocaloric, isonitrogenous (250 kcal. kg-1. day-1, 1.6 g N. kg-1. day-1) infusion of either TEN or TPN for 48 h. Then rats were injected intravenously with Escherichia coli LPS (1 mg/kg) while nutritional support was continued. Time-matched control animals were injected with saline. After mild surgical trauma and an 18-h fast, TEN was more effective at increasing plasma IGF-I levels than TPN. Subsequent injection of LPS decreased IGF-I in blood, liver, and muscle in both TEN- and TPN-fed rats compared with saline-injected control animals. However, this decrease was approximately 30% greater in rats fed TPN compared with those fed TEN. LPS-induced downregulation of IGF-I mRNA expression in liver and muscle was also more prominent in TPN-fed rats. The LPS-induced increase in plasma corticosterone and tumor necrosis factor-alpha was greater (2- and 1.6-fold, respectively) in TPN-fed rats, and these changes were consistent with the greater reduction in IGF-I seen in these animals. In similarly treated rats allowed to survive for 24 h after LPS injection, the LPS-induced increase in the urinary 3-methylhistidine-to-creatinine ratio was smaller in TEN-fed rats. In summary, LPS reduced systemic levels of IGF-I as well as IGF-I protein and mRNA in critical target organs. Enteral feeding greatly attenuated this response. Maintenance of higher IGF-I levels in TEN-fed rats was associated with a reduction in inflammatory cytokine levels and lower rates of myofibrillar degradation.