Showing papers by "Shriners Hospitals for Children - Galveston published in 2004"

Amino acid ingestion improves muscle protein synthesis in the young and elderly

Abstract: We recently demonstrated that muscle protein synthesis was stimulated to a similar extent in young and elderly subjects during a 3-h amino acid infusion. We sought to determine if a more practical ...

CCL17 and IL-10 as Effectors That Enable Alternatively Activated Macrophages to Inhibit the Generation of Classically Activated Macrophages

Abstract: Classically activated macrophages (CAMφ) have been described as a major effector cell on the host’s innate immunities. However, CAMφ are not generated in immunocompromised hosts whose alternatively activated macrophages (AAMφ) predominate. In this study, the mechanism by which AAMφ suppress the ability of resident macrophages (RMφ) to generate CAMφ was investigated. AAMφ were isolated from peritoneal exudates of mice 2 days after third-degree thermal injuries affecting 15% total body surface area. CAMφ were generated from RMφ (peritoneal Mφ from normal mice) through stimulation with CpG DNA, a typical CAMφ inducer. RMφ did not polarize to CAMφ when they were cultured with AAMφ in a dual-chamber Transwell even when supplemented with CpG DNA. In addition, RMφ stimulated with CpG DNA did not convert to CAMφ when they were cultured with the culture fluids of AAMφ (AAMφ Culture-Sup). AAMφ Culture-Sup contained IL-6, IL-10, CCL17, PGE2, and TGF-β. Among these, CCL17 and IL-10 inhibited CAMφ generation. The ability of AAMφ Culture-Sup to inhibit CAMφ generation was eliminated when the Culture-Sup was treated with a mixture of mAbs directed against CCL17 and IL-10. These results indicate that CCL17 and IL-10 released from AAMφ inhibit CAMφ generation from RMφ stimulated with CpG DNA.

Effect of an amino acid, protein, and carbohydrate mixture on net muscle protein balance after resistance exercise

Abstract: This study tests the hypotheses that (a) a mixture of whey protein, amino acids (AA), and carbohydrates (CHO) stimulates net muscle protein synthesis to a greater extent than isoenergetic CHO alone after resistance exercise; and (b) that the stimulatory effect of a protein, AA, and CHO mixture will last beyond the 1st hour after intake. Eight subjects participated in 2 trials. In one (PAAC), they ingested 77.4 g CHO, 17.5 g whey protein, and 4.9 g AA 1 hr after resistance exercise. In the other (CON), 100 g CHO was ingested instead. They received a primed constant infusion of L-[2H5]-phenylalanine, and samples from femoral artery and vein, and biopsies from vastus lateralis were obtained. The area under the curve for net uptake of phenylalanine into muscle above pre-drink value was 128+/- 42 mg x leg(- 1) (PAAC) versus 32+/- 10 mg x leg (-1) (CON) for the 3 hr after the drink (p =.04). The net protein balance response to the mixture consisted of two components, one rapid immediate response, and a smaller delayed response about 90 min after drink, whereas in CON only a small delayed response was seen. We conclude that after resistance exercise, a mixture of whey protein, AA, and CHO stimulated muscle protein synthesis to a greater extent than isoenergetic CHO alone. Further, compared to previously reported findings, the addition of protein to an AA+ CHO mixture seems to extend the anabolic effect.

Potential Ergogenic Effects of Arginine and Creatine Supplementation

Abstract: The rationale for the use of nutritional supplements to enhance exercise capacity is based on the assumption that they will confer an ergogenic effect above and beyond that afforded by regular food ingestion alone. The proposed or advertised ergogenic effect of many supplements is based on a presumptive metabolic pathway and may not necessarily translate to quantifiable changes in a variable as broadly defined as exercise performance. L-arginine is a conditionally essential amino acid that has received considerable attention due to potential effects on growth hormone secretion and nitric oxide production. In some clinical circumstances (e.g., burn injury, sepsis) in which the demand for arginine cannot be fully met by de novo synthesis and normal dietary intake, exogenous arginine has been shown to facilitate the maintenance of lean body mass and functional capacity. However, the evidence that supplemental arginine may also confer an ergogenic effect in normal healthy individuals is less compelling. In contrast to arginine, numerous studies have reported that supplementation with the arginine metabolite creatine facilitates an increase in anaerobic work capacity and muscle mass when accompanied by resistance training programs in both normal and patient populations. Whereas improvement in the rate of phosphocreatine resynthesis is largely responsible for improvements in acute work capacity, the direct effect of creatine supplementation on skeletal muscle protein synthesis is less clear. The purpose of this review is to summarize the role of arginine and its metabolite creatine in the context of a nutrition supplement for use in conjunction with an exercise stimulus in both healthy and patient populations.

Gene expression profiles from hypertrophic scar fibroblasts before and after IL-6 stimulation.

Abstract: The structural rearrangement of collagen fibres in hypertrophic scar causes abnormal contracture, low tensile strength, and raised scars, which cause functional impairment and disfigurement. It is hypothesized that changes in the genes of cytokines, extracellular matrix proteins, and proteins regulating programmed cell death are related to hypertrophic scar formation. To test this hypothesis, fibroblasts were cultured from hypertrophic scars and their response to interleukin-6 (IL-6) stimulation was studied by defining their gene expression profiles. Affymetrix gene chip analysis was used to identify up- or down-regulation in the 12 625 genes present in the affymetrix array. RT-PCR and ELISA assays were used to validate microarray expression profiles further. Comparison of gene profiles showed an increase of 12 genes in hypertrophic scar fibroblasts compared with normal skin fibroblasts, while the expression of 14 genes decreased. Thirty-three genes were affected by IL-6 treatment in the hypertrophic scar fibroblasts, while 57 genes were affected in normal skin fibroblasts. Messenger RNA to beta-actin ratios for matrix metalloproteinase-1 (MMP-1) and MMP-3 were increased with IL-6 in normal skin fibroblasts from 2.43 +/- 0.06 to 5.50 +/- 0.45 and from 0.75 +/- 0.09 to 1.98 +/- 0.01, respectively. No change in these matrix metalloproteinases could be shown with IL-6 stimulation in hypertrophic scar fibroblasts. Secreted protein levels of pro-MMP-1 and MMP-3 were elevated in the supernatants from normal skin fibroblasts from 2.00 +/- 0.09 and 1.72 +/- 0.10 ng/ml to 4.60 +/- 0.12 and 3.41 +/- 0.20 ng/ml, respectively, after treatment with IL-6 (p < 0.05). No changes were observed in hypertrophic scar fibroblasts treated with IL-6. Values are means +/- SEM. The absence of any up-regulation of MMP-1 and MMP-3 in hypertrophic scar fibroblasts, in response to IL-6, suggests that suppression of matrix metalloproteinases may play a role in the excessive accumulation of collagen formed in hypertrophic scars. While the pathogenesis of abnormal hypertrophic scars remains poorly understood, the use of gene expression arrays may prove helpful in identifying the mechanisms responsible for this type of abnormal scar formation and in formulating an effective therapeutic protocol.

Review of evidenced-based practice for the prevention of pressure sores in burn patients.

Abstract: Pressure ulcers represent a complex clinical problem, with a reported incidence of 2.7% to 29.5% in hospitalized patients and an etiology that is multifactorial. The prevention of pressure sores in the burn patient population is clearly an area of practice in need of guidelines for care. A multidisciplinary group of advanced burn care professionals have compiled, critiqued, and summarized herein the current evidence of practice in nursing, nutrition, and rehabilitation as it pertains to the prevention of pressure sores after burn injuries. A broad overview of risk factors and assessment scales is described, and current intervention practices and recommendations for care are provided based, whenever possible, on research findings. In addition, research questions are generated in an attempt to move the specialty of burns toward the formal investigation of pressure sores with the ultimate goal being the development of evidence-based practice guidelines.

Gamma Interferon Does Not Enhance Clearance of Pseudomonas aeruginosa but Does Amplify a Proinflammatory Response in a Murine Model of Postseptic Immunosuppression

Abstract: Patients that have suffered a major injury may sustain a period of immunocompromise and altered Th1/Th2 cytokine balance that can predispose them to opportunistic infections. Pseudomonas aeruginosa is frequently a causative organism for nosocomial infections in critically ill patients and is associated with high mortality. We previously mimicked this clinical scenario by challenging mice with P. aeruginosa 5 days after a cecal ligation and puncture (CLP) procedure. Mice that were subjected to CLP had reduced ability to clear bacteria, significantly lower gamma interferon (IFN-gamma) concentrations in plasma, and significantly elevated levels of interleukin 10 (IL-10) in plasma in response to the Pseudomonas challenge compared to uninjured control mice. We investigated the significance of the alteration in IFN-gamma by administering recombinant IFN-gamma to post-CLP mice at the time of Pseudomonas challenge and by challenging IFN-gamma knockout (IFN-gamma KO) mice with Pseudomonas. Administration of IFN-gamma to post-CLP mice attenuated IL-10 secretion and enhanced IL-12 secretion but did not improve bacterial clearance or survival after Pseudomonas challenge. Furthermore, IFN-gamma KO mice had significantly higher plasma IL-10 concentrations but did not exhibit impaired bacterial clearance or increased mortality following Pseudomonas challenge. These data indicate that systemic administration of IFN-gamma effectively reverses alterations in immune function that are commonly associated with immunosuppression in critically injured mice but does not improve bacterial clearance or survival following Pseudomonas challenge. Further, endogenous IFN-gamma does not appear to contribute significantly to early clearance of Pseudomonas bacteremia, nor does it affect the mortality rate after a lethal Pseudomonas challenge.

Leucine Supplementation Has an Anabolic Effect on Proteins in Rabbit Skin Wound and Muscle

Abstract: We investigated the effect of leucine supplementation on protein metabolism in skin wounds and muscle in anesthetized rabbits. l-[ring-(13)C(6)]phenylalanine was infused on d 7 after the ear was scalded, and the scalded ear and uninjured hindlimb were used as arteriovenous units to reflect protein kinetics in skin wounds and muscle. In comparison with a commercially available amino acid solution (10% Travasol), isonitrogenous [1638 micromol/(kg . h)] infusion of the amino acid solution with supplemental leucine to account for 35% of total nitrogen increased the net phenylalanine balance (P < 0.05) in the skin wound and muscle from -6.7 +/- 6.1 to 0.9 +/- 1.4 and from -4.4 +/- 2.4 to -1.0 +/- 0.4 micromol/(100 g . h), respectively. Infusion of leucine alone did not significantly improve the net phenylalanine balance in either skin wounds [-4.0 +/- 4.6 micromol/(100 g . h)] or muscle [-2.7 +/- 0.7 micromol/(100 g . h)]. We conclude that leucine supplementation had an anabolic effect on proteins in skin wounds and muscle, provided that adequate additional amino acids were also available.

CCL2, a product of mice early after systemic inflammatory response syndrome (SIRS), induces alternatively activated macrophages capable of impairing antibacterial resistance of SIRS mice

Abstract: Infection associated with systemic inflammatory response syndrome (SIRS) is a major cause of morbidity and mortality in patients with major surgery, polytrauma, and severe burn injury. In previous studies, mice with severe pancreatitis (a mouse model of SIRS, SIRS mice) have been shown to be greatly susceptible to various infections. In the present study, a mechanism involved in the impaired resistance of SIRS mice to infectious complications was investigated. Sera from SIRS mice impaired the resistance of normal mice to infectious complications induced by cecal ligation and puncture (CLP). CC chemokine ligand 2 (CCL2) was detected in sera of SIRS mice. Resident macrophages (RMphi) cultured with SIRS mouse sera converted to alternatively activated macrophages (AAMphi), which were also demonstrated in mice treated with recombinant murine CCL2. However, AAMphi were not demonstrated in mice injected with SIRS mouse sera and anti-CCL2 monoclonal antibody (mAb) in combination. Furthermore, normal mice that received SIRS mouse sera and anti-CCL2 mAb resisted CLP-induced infectious complications. These results indicate that the resistance of SIRS mice to infectious complications is impaired by AAMphi generated from RMphi in response to SIRS-associated CCL2 production.

Insulin-Like Growth Factor I Increases Rat Peptide YY Promoter Activity through Sp1 Binding Sites

Abstract: Studies in rodents demonstrate that the mitogen, IGF-I, stimulates intestinal peptide YY (PYY) expression. To investigate whether the stimulatory influence of IGF-I is exerted at the level of gene transcription, rat PYY 5′-upstream sequences (−2800/+37 bp, −770/+37 bp, −127/+37 bp) fused to the firefly luciferase (luc) reporter gene were transfected into rat pheochromocytoma cells (PC12) and luc activity measured after IGF-I treatment. IGF-I increased transcriptional activity of all constructs similarly; the PYY (−127/+37 bp)-luc construct was used in subsequent experiments. IGF-I increased PYY (−127/+37 bp)-luc activity in a time- and dose-dependent fashion. Sequence analysis detected five putative Sp1 binding sites in the −127/+37-bp sequence. EMSA and supershift experiments using two oligonucleotide fragments of the −127/+37 region showed that Sp1 and Sp3 proteins bound to putative Sp1 sites. Overexpression of Sp1 greatly increased PYY (−127/+37 bp)-luc activity and site-directed mutagenesis of putativ...

Effect of IL-12 and soluble IL-4 receptor on the herpesvirus infection in human SCID chimeras whose Th2 cells predominate.

Abstract: Th2 cytokines, commonly detected in burn patients, have been shown as inhibitors for the generation of Th1 cells that are essential for the host's resistance against herpes simplex virus type 1 (HSV-1) infection. In this study, the possibility of immunological treatment through the regulation of Th1/Th2 responses was examined in two kinds of human severe combined immunodeficiency (SCID) chimera models reflecting human immune functions. SCID mice injected with a mixture of PBMC from a healthy donor and Th2 cells experimentally generated from the same healthy PBMC (Th2 SCID chimeras) were more susceptible to HSV-1 infection when compared with SCID mice injected with healthy donor PBMC (healthy SCID chimeras). When Th2 SCID chimeras were individually treated with human IL-12 (hIL-12) or human soluble IL-4 receptor (hsIL-4R), hIFN- was not produced in their sera after antihuman CD3 mAb stimulation. However, hIFN- production in sera of Th2 SCID chimeras treated with the combination therapy of hIL-12 and hsIL-4R was recovered at levels observed in healthy SCID chimeras. When Th2 SCID chimeras infected with HSV-1 were treated with saline, hIL-12, hsIL-4R or a combination of hIL-12 and hsIL-4R, 13%, 13%, 25% or 100% of them survived, respectively. Also, Th1 responses (hIFN- production) were demonstrated in Th2 SCID chimeras that became resistant against HSV-1 infection after the combination treatment. These results suggest that individuals whose Th2 cells predominated may be immunologically controlled by the combination treatment between a Th1 response inducer and a Th2 response inhibitor.