Transcriptomic and proteomic analysis of liver and muscle alterations caused by surgical stress in rats

Tight Glycemic Control With Insulin Does Not Affect Skeletal Muscle Degradation During the Early Postoperative Period Following Pediatric Cardiac Surgery

OBJECTIVE

Critical illness is associated with significant catabolism, and persistent protein loss correlates with increased morbidity and mortality. Insulin is a potent anticatabolic hormone; high-dose insulin decreases skeletal muscle protein breakdown in critically ill pediatric surgical patients. However, insulin's effect on protein catabolism when given at clinically utilized doses has not been studied. The objective was to evaluate the effect of postoperative tight glycemic control and clinically dosed insulin on skeletal muscle degradation in children after cardiac surgery with cardiopulmonary bypass.

DESIGN

Secondary analysis of a two-center, prospective randomized trial comparing tight glycemic control with standard care. Randomization was stratified by study center.

PATIENTS

Children 0-36 months who were admitted to the ICU after cardiac surgery requiring cardiopulmonary bypass.

INTERVENTIONS

In the tight glycemic control arm, insulin was titrated to maintain blood glucose between 80 and 110 mg/dL. Patients in the control arm received standard care. Skeletal muscle breakdown was quantified by a ratio of urinary 3-methylhistidine to urinary creatinine.

MEASUREMENTS AND MAIN RESULTS

A total of 561 patients were included: 281 in the tight glycemic control arm and 280 receiving standard care. There was no difference in 3-methylhistidine to creatinine between groups (tight glycemic control, 249 ± 127 vs standard care, 253 ± 112, mean ± SD in μmol/g; p = 0.72). In analyses restricted to the patients in tight glycemic control arm, higher 3-methylhistidine to creatinine correlated with younger age, as well as lower weight, weight-for-age z score, length, and body surface area (p < 0.005 for each) and lower postoperative day 3 serum creatinine (r = -0.17; p = 0.02). Sex, prealbumin, and albumin were not associated with 3-methylhistidine to creatinine. During urine collection, 245 patients (87%) received insulin. However, any insulin exposure did not impact 3-methylhistidine to creatinine (t test, p = 0.45), and there was no dose-dependent effect of insulin on 3-methylhistidine to creatinine (r = -0.03; p = 0.60).

CONCLUSION

Although high-dose insulin has an anabolic effect in experimental conditions, at doses necessary to achieve normoglycemia, insulin appears to have no discernible impact on skeletal muscle degradation in critically ill pediatric cardiac surgical patients.

A note on protein expression changes in chicken breast muscle in response to time in transit before slaughtering

Aims of the research were to devise a proteome map of the chicken Pectoralis superficialis muscle, as resolved by two-dimensional gel electrophoresis, and to characterize protein expression changes in the soluble protein fraction in commercial conditions due to age and to time in transit before slaughtering. Broilers were reared under commercial conditions until they reached a mean 1.8 kg and 36 d, or 2.6 kg and 46 d of age. Transport to the slaughterhouse took 90 or 220 minutes. Transport-induced stress was assessed from blood metabolites and leukocyte cell counts, revealing significant changes in albumin, glucose and triglyceride concentrations, in heterophils and leukocyte counts for chickens in transit for longer, and in glucose depending mainly on age. The sarcoplasmic protein fractions were extracted from a total of 39 breast muscle samples, collected 15 min post mortem, for analysis by two-dimensional electrophoresis.

Image and statistical analyses enabled us to study the qualitative and quantitative differences between the samples. Twelve up- or down-regulated protein spots were detected (P < 0.05): 8 related to the age effect, 2 to time in transit, and 2 to the interaction between the two. Age and time in transit influenced the avian proteome regulating the biological processes linked to the cellular housekeeping functions, related mainly to metabolism, cell division and control of apoptosis. Principal component analysis clustering was used to assess differences between birds. Age difference discriminated between the chickens analyzed better than time in transit, which seemed to have less general impact on the proteome fraction considered here.

Isolating and identifying the proteins whose expression changes in response to transport duration and age shed some light on the biological mechanisms underlying growth and stress-related metabolism in chickens. Our results, combined with a further characterization of the chicken proteome associated with commercial chicken slaughtering management, will hopefully inspire alternative strategies and policies, and action to reduce the impact of stress related to time in transit.

Dietary tools to modulate glycogen storage in gilthead seabream muscle: glycerol supplementation

The quality and shelf life of fish meat products depend on the skeletal muscle's energetic state at slaughter, as meat decomposition processes can be exacerbated by energy depletion. In this study, we tested dietary glycerol as a way of replenishing muscle glycogen reserves of farmed gilthead seabream. Two diets were tested in duplicate (n = 42/tank). Results show 5% inclusion of crude glycerol in gilthead seabream diets induces increased muscle glycogen, ATP levels and firmness, with no deleterious effects in terms of growth, proximate composition, fatty acid profile, oxidative state, and organoleptic properties (aroma and color). Proteomic analysis showed a low impact of glycerol-supplementation on muscle metabolism, with most changes probably reflecting increased stress coping capacity in glycerol-fed fish. This suggests inclusion of crude glycerol in gilthead seabream diets (particularly in the finishing phase) seems like a viable strategy to increase glycogen deposition in muscle without negatively impacting fish welfare and quality.

Hindlimb Muscle Atrophy Occurs From Short-Term Undernutrition in Rats

The purpose of this study was to examine the effect of short-term (7 days) undernutrition on Type I (soleus) and Type II (plantaris, gastrocnemius) muscles in rats. Male Sprague-Dawley rats ( N = 20) were randomly assigned to one of two groups: a control group ( n = 10) in which animals were allowed to have water and pellets ad libitum and an undernourished group ( n = 10) in which animals were allowed to have 37% of the total food intake of the control group and water ad libitum. Body weight and food intake were measured daily. After 7 days, rats were anesthetized and the soleus, plantaris, and gastrocnemius muscles and liver were dissected. Body weight, liver weight, muscle weight, Types I and II fiber cross-sectional area, and myofibrillar protein content were determined. After 7 days of undernutrition, the undernourished group showed significant decreases ( p < .05) compared to the control group in body weight, liver weight, muscle weight of soleus, plantaris, and gastrocnemius muscles, and cross-sectional areas of Types I and II fiber of the plantaris and gastrocnemius muscles.

Decreased expression of hepatic signaling phosphoproteins after laparoscopic and hand-assisted surgery in a porcine model

OBJECTIVE

Minimally-invasive surgery (MIS) is associated with a decreased activation of both systemic and peritoneal immunity compared with the open technique. However, hepatic response to laparoscopic (LAP) and hand-assisted laparoscopic (HAL) surgery has not been defined well. We postulated that both LAP and HAL approaches are associated with a diminished activation of hepatic inflammatory signaling pathways compared with the traditional open surgery.

MATERIALS AND METHODS

Eighteen pigs underwent a transabdominal nephrectomy via Open, HAL, or LAP approach. Liver samples were obtained 24 h postoperatively and spot frozen. Frozen tissue samples were then homogenized and the nuclear pellets were separated and stored. Nuclear extracts were analyzed for activation of three nuclear signaling phosphoproteins: nuclear factor-kappaB (NFκB)-p65, heat-shock protein 27 (HSP27), and p38 mitogen-activated protein kinases (p38MAPK) using a standard Bioplex technique. Statistical comparison was performed using ANOVA and Student's t-test.

RESULTS

The average expression of HSP27 was significantly higher in the Open versus either the LAP or the HAL groups (P = 0.028 and P = 0.039). The average expression of NFκB-p65 was significantly higher in the Open versus either the LAP or the HAL groups (P = 0.032 and P = 0.049). The average expression of p38MAPK was significantly higher in the Open versus either the LAP or the HAL groups (P = 0.007 and P = 0.036). There was no significant difference in the expressions of HSP27 and NFκB-p65 between LAP and HAL groups (P = 0.38 and P = 0.20), however, detection of p38MAPK generated statistical difference between these two groups (P = 0.018).

CONCLUSION

Hand-assisted laparoscopic surgery has been widely accepted as an effective alternative to traditional laparoscopic procedures. We demonstrated that both laparoscopic and hand-assisted approaches resulted in blunted hepatic stress manifested by diminished expression of hepatic HSP27, NFκB, and p38-MAPK. In addition, the hand-assisted approach was equal to the laparoscopic approach in two of the three phosphoproteins studied. It appears that the use of hand-assisted techniques did not abrogate immunologic benefits of pure laparoscopy. Overall, in addition to the clinical benefits of minimal access, both hand-assisted and pure laparoscopic techniques may also confer an immunologic advantage over laparotomy.

Comparative proteomic profile of rat sciatic nerve and gastrocnemius muscle tissues in ageing by 2-D DIGE

Ageing induces a progressive morphological change and functional decline in muscles and in nerves. Light and electron microscopy, 2-D DIGE and MS, were applied to profile the qualitative and quantitative differences in the proteome and morphology of rat gastrocnemius muscle and sciatic nerve, in healthy 22-month-old rats. At muscle level, morphological changes are associated to fibre atrophy accompanied by myofibrillar loss and degeneration, disappearance of sarcomeres and sarcoplasmic reticulum dilatation, internal migration of nuclei, longitudinal fibre splitting, increment of subsarcolemmal mitochondria aggregates and increment of lipofuscin granules. Sciatic nerve shows myelin abnormalities like enfoldings, invaginations, onion bulbs, breakdowns and side axonal atrophy. Proteomic analysis identified changes correlated to morphological abnormalities in metabolic, contractile and cytoskeletal proteins, deregulation of iron homeostasis, change of Ca(2+) balance and stress response proteins, accompanied by a deregulation of myelin membrane adhesion protein and proteins regulating the neuronal caliber. By comparing proteomic results from the two tissues, 16 protein isoforms showed the same up and down regulation trend suggesting that there are changes implying a general process which may act as a signal event of degeneration. Only beta enolase and tropomyosin 1alpha were differentially expressed in the tissues.

Molecular and cellular events in alcohol-induced muscle disease

Alcohol consumption induces a dose-dependent noxious effect on skeletal muscle, leading to progressive functional and structural damage of myocytes, with concomitant reductions in lean body mass. Nearly half of high-dose chronic alcohol consumers develop alcoholic skeletal myopathy. The pathogenic mechanisms that lie between alcohol intake and loss of muscle tissue involve multiple pathways, making the elucidation of the disease somewhat difficult. This review discusses the recent advances in basic and clinical research on the molecular and cellular events involved in the development of alcohol-induced muscle disease. The main areas of recent research interest on this field are as follows: (i) molecular mechanisms in alcohol exposed muscle in the rat model; (ii) gene expression changes in alcohol exposed muscle; (iii) the role of trace elements and oxidative stress in alcoholic myopathy; and (iv) the role of apoptosis and preapoptotic pathways in alcoholic myopathy. These aforementioned areas are crucial in understanding the pathogenesis of this disease. For example, there is overwhelming evidence that both chronic alcohol ingestion and acute alcohol intoxication impair the rate of protein synthesis of myofibrillar proteins, in particular, under both postabsorptive and postprandial conditions. Perturbations in gene expression are contributory factors to the development of alcoholic myopathy, as ethanol-induced alterations are detected in over 400 genes and the protein profile (i.e., the proteome) of muscle is also affected. There is supportive evidence that oxidative damage is involved in the pathogenesis of alcoholic myopathy. Increased lipid peroxidation is related to muscle fibre atrophy, and reduced serum levels of some antioxidants may be related to loss of muscle mass and muscle strength. Finally, ethanol induces skeletal muscle apoptosis and increases both pro- and antiapoptotic regulatory mechanisms.

Iron load and redox stress in skeletal muscle of aged rats

Loss of skeletal muscle mass (sarcopenia) is a major contributor to disability in old age. We used two-dimensional gel electrophoresis and mass spectrometry to screen for changes in proteins, and cDNA profiling to assess transcriptional regulations in the gastrocnemius muscle of adult (4 months) and aged (30 months) male Sprague-Dawley rats. Thirty-five proteins were differentially expressed in aged muscle. Proteins and mRNA transcripts involved in redox homeostasis and iron load were increased, representing novel components that were previously not associated with sarcopenia. Tissue iron levels were elevated in senescence, paralleling an increase in transferrin. Proteins involved in redox homeostasis showed a complex pattern of changes with increased SOD1 and decreased SOD2. These results suggest that an elevated iron load is a significant component of sarcopenia with the potential to be exploited clinically, and that mitochondria of aged striated muscle may be more vulnerable to radicals produced in cell respiration.

Proteome profile of cytosolic component of zebrafish liver generated by LC-ESI MS/MS combined with trypsin digestion and microwave-assisted acid hydrolysis

The zebrafish genome has recently been sequenced and annotated allowing for high-throughput proteomic analysis. Here, we report for the first time a proteomic subset of zebrafish liver, an important organ for metabolizing toxins. Using a newly developed analytical procedure, we have identified 1204 proteins from the cytosolic component of a zebrafish liver tissue sample. Our methods involve cell-compartment fractionation of liver tissue samples, four levels of protein digestion, and off-line two-dimensional liquid chromatography (2-D LC) separations of resultant peptides. Proteins are identified using an electrospray ionization quadrupole time-of-flight tandem mass spectrometer (ESI-QTOF MS/MS), which provides high-resolution and high-accuracy mass measurement of peptide ions and their fragment ions. We demonstrate that greater proteome coverage can be achieved by combining the results obtained from four methods of protein digestion: three tryptic digests (one in buffer, one in methanol, and another in SDS), and a microwave-assisted acid hydrolysate of the protein extracts. Identified proteins--which included several groups of established protein biomarkers--were functionally classified. We discuss the functions and implications of these biomarkers within the context of zebrafish toxicology.

Nutritional modulation of protein metabolism after gastrointestinal surgery

BACKGROUND

The metabolic response to surgery includes alterations in protein metabolism, resulting in a net loss of proteins. Protein hypercatabolism is considered an unavoidable consequence of injury, and an important source of morbidity and mortality. Our purpose was to determine the effect of nutrition on protein metabolism following gastrointestinal surgery, and to elucidate whether postoperative protein loss can be prevented with adequate nutritional support.

METHODS

Patients who had undergone gastrointestinal surgery were given four different parenteral nutritions with increasing glucose, lipid and amino acid content during the 7 days following surgery. Nitrogen balance, protein synthesis and protein breakdown were determined using in vivo stable isotope labelling. Other metabolites (3-methylhistidine, creatinine, urea, cortisol, glucose, insulin, amino acids and C-reactive protein) were measured.

RESULTS

A nutrition-dependent alteration of protein metabolism was found in response to surgical injury. Nutrition modified nitrogen balance, whole-body protein breakdown and, to a lesser extent, whole-body protein synthesis and muscle protein breakdown. The low-energy parenteral nutrition without amino acids produced a negative nitrogen balance (postoperative day 7=-0.381 g protein kg(-1)day(-1)) and important alterations in postoperative protein metabolism that did not normalize during the study period (day 7 protein synthesis=239% and protein breakdown 217% vs preoperative). Patients receiving the two low energy parenteral nutritions containing amino acids had a less negative nitrogen balance (day 7=-0.011 and -0.133 g protein kg(-1)day(-1)) and a transient increase in protein metabolism. The complete parenteral nutrition maintained, during all studied days, protein metabolism parameters within the preoperative reference range (synthesis day 2=92%, day 4=110% day 7=79%; breakdown day 2=85%, day 4=80%, day 7=76% vs preoperative) and a positive nitrogen balance (day 2=+0.0387, day 4=+0.578 and day 7=+0.227 g protein kg(-1)day(-1)).

CONCLUSION

Complete nutritional support can prevent protein loss after gastrointestinal surgery and maintain protein metabolism without alterations.

Unravelling the role of the ToxR-like transcriptional regulator WmpR in the marine antifouling bacterium Pseudoalteromonas tunicata

The dark-green-pigmented marine bacterium Pseudoalteromonas tunicata produces several target-specific compounds that act against a range of common fouling organisms, including bacteria, fungi, protozoa, invertebrate larvae and algal spores. The ToxR-like regulator WmpR has previously been shown to regulate expression of bioactive compounds, type IV pili and biofilm formation phenotypes which all appear at the onset of stationary phase. In this study a comparison of survival under starvation or stress between the wild-type P. tunicata strain and a wmpR mutant (D2W2) does not suggest a role for WmpR in regulating starvation- and stress-resistant phenotypes such as those that may be required in stationary phase. Both proteomic [2-dimensional PAGE (2D-PAGE)] and transcriptomic (RNA arbitrarily primed PCR) studies were used to discover members of the WmpR regulon. 2D-PAGE identified 11 proteins that were differentially expressed by WmpR. Peptide sequence data were obtained for six of these proteins and identified using the draft P. tunicata genome as being involved in protein synthesis, amino acid transamination and ubiquinone biosynthesis, as well as hypothetical proteins. The transcriptomic analysis identified three genes significantly up-regulated by WmpR, including a TonB-dependent outer-membrane protein, a non-ribosomal peptide synthetase and a hypothetical protein. Under iron-limitation the wild-type showed greater survival than D2W2, indicating the importance of WmpR under these conditions. Results from these studies show that WmpR controls the expression of genes encoding proteins involved in iron acquisition and uptake, amino acid metabolism and ubiquinone biosynthesis in addition to a number of proteins with as yet unknown functions.

Genomic analysis of the impact of fescue toxicosis on hepatic function1

Fescue toxicosis is caused by consumption of toxins produced by an endophytic fungus, Neotyphodium coenophialum, in tall fescue [Lolium arundinaceum (Schreb.) Darbysh]. Microarray analysis was used to identify shifts in genetic expression associated with the affected physiological processes to identify potential targets for future pharmacological/toxicological intervention. Male rats (n = 24) were implanted with temperature transmitters, which measure core temperature every 5 min. After an 8-d recovery, the rats were fed an endophyte-free diet for 5 d. During the following 5-d treatment period, rats were fed either an endophyte-free or an endophyte-infected (91.5 microg of ergovaline.kg of BW(-1).d(-1)) diet. At the end of treatment, rats were euthanized and a sample of the liver was obtained. Feed conversion efficiency was calculated for both treatment groups. Serum prolactin concentrations were measured using ELISA. Liver tissue RNA was reverse transcribed and hybridized to an oligonucleotide microarray chip. Microarray data were analyzed using a 2-step ANOVA model and validated by quantitative real-time PCR. Significant reductions in mean core temperature, feed intake, feed conversion efficiency, BW, liver weight per unit of BW, and serum prolactin concentrations were observed in endophyte-infected rats. There was downregulation (P < 0.05) of various genes associated with energy metabolism, growth and development, and antioxidant protection, as well as an upregulation of genes associated with gluconeogenesis, detoxification, and biotransformation. This study demonstrated that even short-term exposure of rats to tall fescue endophytic toxins under thermoneutral conditions can result in physiological responses associated with altered gene expression within the liver.

New Paradigms in Cardiovascular Medicine

Considerable progress has been made in understanding the pathophysiology of perioperative stress responses and their impact on the cardiovascular system; however, researchers are just beginning to unravel genetic and molecular determinants that predispose to increased risk for postoperative cardiovascular adverse events. A new field, coined perioperative genomics, aims to apply functional genomic approaches to uncover the biological reasons why similar patients can have dramatically different clinical outcomes after surgery. For the perioperative physician, such findings may soon translate into prospective risk assessment incorporating genomic profiling of markers important in inflammatory, thrombotic, vascular, and neurologic responses to perioperative stress, with implications ranging from individualized additional pre-operative testing and physiological optimization, to perioperative decision-making, choice of monitoring strategies, and critical care resource utilization. We review current knowledge regarding genomic technologies in perioperative cardiovascular disease characterization and outcome prediction, as well as discuss future trends/challenges for translating integrated "omic" information into daily clinical management of the surgical patient.