Nutritional hepatic steatosis and mortality after burn injury in rats

Correlation of thermal burn hepatic dysfunction with outcomes

INTRODUCTION

Organ dysfunction and failure increase the morbidity and mortality following major burn. Alteration of liver morphology and function is common following major burns; however, it has not received much attention. In this study we have assessed the impact of thermal burn on liver in relation with mortality.

MATERIAL AND METHODS

55 patients (33 female and 22 males) with TBSA 10-90% and age ranged from 18 to 75 years were included. A bed side serial ultrasonography to assess the volume of liver and liver function tests was done on the 2nd, 9th and 16th day following burn. Baseline demographic and clinical information such as age, gender, burn size and outcome of patient were also collected.

RESULTS -

8 patients died during 2nd week following burn and 47 survived. The mean TBSA for survivors was 37% and for non survivors 80%. Mean liver volume in survivors steadily decreased from 1693.70 cm3 to 1631.31 cm3 over 3 weeks. Mean liver volume in non- survivors steadily increased from 1855.88 cm3 to 2028.50 cm3 over 2 weeks. Liver function test in survivors steadily improved while in non survivors it deteriorated over 2 weeks.

CONCLUSION

There is a correlation between altered liver morphology and function with mortality among severely burnt patients however liver volume did not show statistical significance. A decreasing trend of liver dysfunction parameters and hepatomegaly following burn is associated with good prognosis.

Early Enteral Nutrition for Burn Injury

Significance: Nutrition has been recognized as a critical component of acute burn care and ultimate wound healing. Debate remains over the appropriate timing of enteral nutrition and the benefit of supplemental trace elements, antioxidants, and immunonutrition for critically ill burn patients. Pharmacotherapy to blunt the metabolic response to burn injury plays a critical role in effective nutritional support. Recent Advances: Further evidence is demonstrating long-term benefits from pharmacologic immunomodulation given the prolonged metabolic response to injury that may last for over a year following the initial insult. Critical Issues: The majority of evidence regarding early enteral feeding comes from mixed populations and smaller studies. However, on balance, available evidence favors early feeding. Data regarding immunonutrition does not support the routine use of these products. Limited data regarding use of antioxidants and trace elements support their use. Future Directions: Further evaluation of anti-inflammatory mediators of the immune response, such as statins, will likely play a role in the future. Further data are needed on the dosing and route of micronutrients as well as the utility of immunonutrition. Finally, little is known about nutrition in the obese burn patient making this an important area for investigation.

Long-term persistance of the pathophysiologic response to severe burn injury

Background

Main contributors to adverse outcomes in severely burned pediatric patients are profound and complex metabolic changes in response to the initial injury. It is currently unknown how long these conditions persist beyond the acute phase post-injury. The aim of the present study was to examine the persistence of abnormalities of various clinical parameters commonly utilized to assess the degree hypermetabolic and inflammatory alterations in severely burned children for up to three years post-burn to identify patient specific therapeutic needs and interventions.

Methodology/Principal Findings

Patients: Nine-hundred seventy-seven severely burned pediatric patients with burns over 30% of the total body surface admitted to our institution between 1998 and 2008 were enrolled in this study and compared to a cohort non-burned, non-injured children. Demographics and clinical outcomes, hypermetabolism, body composition, organ function, inflammatory and acute phase responses were determined at admission and subsequent regular intervals for up to 36 months post-burn. Statistical analysis was performed using One-way ANOVA, Student's t-test with Bonferroni correction where appropriate with significance accepted at p<0.05. Resting energy expenditure, body composition, metabolic markers, cardiac and organ function clearly demonstrated that burn caused profound alterations for up to three years post-burn demonstrating marked and prolonged hypermetabolism, p<0.05. Along with increased hypermetabolism, significant elevation of cortisol, catecholamines, cytokines, and acute phase proteins indicate that burn patients are in a hyperinflammatory state for up to three years post-burn p<0.05.

Conclusions

Severe burn injury leads to a much more profound and prolonged hypermetabolic and hyperinflammatory response than previously shown. Given the tremendous adverse events associated with the hypermetabolic and hyperinflamamtory responses, we now identified treatment needs for severely burned patients for a much more prolonged time.

Association between dietary fat content and outcomes in pediatric burn patients

BACKGROUND

The aim of the study was to compare a low fat/high-carbohydrate diet and a high-fat diet on clinical outcomes by a retrospective cohort study.

METHODS

Nine hundred forty-four children with burns ≥ 40% of their total body surface area (TBSA) were divided into two groups: patients receiving Vivonex T.E.N. (low-fat/high-carbohydrate diet; n = 518) and patients receiving milk (high-fat diet; n = 426). Patient demographics, caloric intake, length of hospital stay, and incidence of sepsis, mortality, hepatic steatosis, and organomegaly at autopsy were determined.

RESULTS

Demographics and caloric intake were similar in both groups. Patients receiving Vivonex T.E.N. had shorter (intensive care unit) ICU stays (Vivonex T.E.N.: 31 ± 2 d; milk: 47 ± 2 d; P < 0.01), shorter ICU stay per % TBSA burn (Vivonex T.E.N.: 0.51 ± 0.02 d/%; milk: 0.77 ± 0.03 d/%; P < 0.01), lower incidence of sepsis (Vivonex T.E.N.: 11%; milk: 20%; P < 0.01), and lived significantly longer until death than those receiving milk (Vivonex T.E.N.: 20 ± 3 d; milk: 10 ± 2 d; P < 0.01). There was no difference in overall mortality between the two groups (Vivonex T.E.N.:15% versus milk: 13%; P < 0.9). Autopsies revealed decreased hepatic steatosis and decreased enlargement of kidney and spleen in patients receiving Vivonex T.E.N.

CONCLUSIONS

The period with a low-fat/high-carbohydrate diet was associated with lower LOS, decreased incidence of organomegaly, infection, and hepatic steatosis post-burn compared with the period when a high-fat diet was used. These associations indicate the benefit of high carbohydrate/low fat nutrition; however, the findings in these time periods can also be likely due to the multifactorial effects of advances in burn care. We believe that these results have some relevance because high fat is associated with poorer outcomes compared with low fat.

Hepatocellular damage following burn injury demonstrated by a more sensitive marker: alpha-glutathione S-transferase

Following burn injury, some complex reactions are initiated that are mainly managed by the liver and that can cause injury at the liver. Alpha glutathione S-transferase (alpha-GST) is a sensitive marker that is very sensitive in the monitoring of hepatocellular damage. We tried, in this study, to demonstrate liver injury in burn patients using alpha-GST. Forty-four patients with burn injury treated at the Burn Treatment and Care unit of the Atatürk University Medical School between July 2006 and July 2007 were included in the study. Patient data were collected. Three blood samples were taken from the patients (at admittance [first sample], 120 hours after admittance [second sample], and on the fourteenth day [third sample]) for the analysis of alpha-GST, alanine amino transferase, aspartate amino transferase activities, and albumin and c-reactive protein levels. There was a statistically significant difference between alpha-GST activities of the study group at admission (P<.001), on the fifth day (P<.001), and the 14th day (P<.001) and those of the control group. There was a decrease in alpha-GST activities during the hospitalization period. Alanine amino transferase and aspartate amino transferase activities in all three samples of the study group were not different from each other and from the values obtained from the control group. The albumin levels of the study group were significantly different from those of the control group. The c-reactive protein levels of the study group were different from those of the control group at admission, on the fifth day, and fourteenth day (P<.001, P<.001, and P<.01). Our findings suggest that burn injury causes liver injury, and alpha-GST can be used to demonstrate this.

The hepatic response to thermal injury: is the liver important for postburn outcomes?

Thermal injury produces a profound hypermetabolic and hypercatabolic stress response characterized by increased endogenous glucose production via gluconeogenesis and glycogenolysis, lipolysis, and proteolysis. The liver is the central body organ involved in these metabolic responses. It is suggested that the liver, with its metabolic, inflammatory, immune, and acute phase functions, plays a pivotal role in patient survival and recovery by modulating multiple pathways following thermal injury. Studies have evaluated the role and function of the liver during the postburn response and showed that liver integrity and function are essential for survival, and that hepatic acute phase proteins are strong predictors for postburn survival. This review discusses these studies and delineates the pivotal role of the liver in patients following severe thermal injury.

Combination of recombinant human growth hormone and propranolol decreases hypermetabolism and inflammation in severely burned children

OBJECTIVE

Recombinant human growth hormone (rhGH) is a salutary modulator of posttraumatic metabolic responses. However, rhGH administration is associated with deleterious side effects, such as hyperglycemia, increased free fatty acids, and triglycerides, which limit its use. Administration of beta-blocker attenuates cardiac work and resting energy expenditure after severe thermal injury and improves fat metabolism and insulin sensitivity. Therefore, the combination of rhGH plus propranolol appears ideal. The aim of the present study was to determine whether rhGH plus propranolol improves hypermetabolism and the inflammatory and acute phase response after severe burn without causing adverse side effects.

DESIGN

Prospective randomized control trial.

SETTING

Shriners Hospitals for Children.

PATIENTS

Fifteen pediatric patients with burns > 40% total body surface area, 0.1-16 yrs of age, admitted within 7 days after burn. Fifteen children were matched for burn size, age, gender, inhalation injury, and infection and served as controls.

INTERVENTIONS

Patients in the experimental group received rhGH (0.2 mg/kg/day) and propranolol (to decrease heart rate by 15%) for > or = 15 days.

MEASUREMENTS AND MAIN RESULTS

Outcome measurements included resting energy expenditure, body composition, acute phase proteins, and cytokines. Both cohorts were similar in age, burn size, gender, and accompanying injuries. Percent predicted resting energy expenditure significantly decreased in patients receiving rhGH/propranolol (Delta -5% +/- 8%) compared with controls (Delta +35% +/- 20%) (p < .05). rhGH/propranolol administration significantly decreased serum C-reactive protein, cortisone, aspartate aminotransferase, alanine aminotransferase, free fatty acids, interleukin-6, interleukin-8, and macrophage inflammatory protein-1beta when compared with controls, while growth hormone/propranolol increased serum insulin-like growth factor-I, insulin-like growth factor binding protein-3, growth hormone, prealbumin, and interleukin-7 when compared with placebo (p < .05).

CONCLUSIONS

rhGH in combination with propranolol attenuates hypermetabolism and inflammation without the adverse side effects found with rhGH therapy alone.

Postburn trauma insulin resistance and fat metabolism

Hyperglycemia and insulin resistance have long been recognized in severe burn patients. More recently, it has been observed that controlling hyperglycemia, or alleviating insulin resistance, is associated with improved outcomes. This has led to a renewed interest in the etiology of insulin resistance in this population. The postinjury hyperglycemic response appears to be associated with multiple metabolic abnormalities, such as elevated basal energy expenditure, increased protein catabolism, and, notably, significant alterations in fat metabolism. The synergy of all of the responses is not understood, although many studies have been conducted. In this article we will review the present understanding of the relationship between fat metabolism and insulin resistance posttrauma, and discuss some of the recent discoveries and potential therapeutic measures. We propose that the insulin resistance is likely related to the development of "ectopic" fat stores, i.e., triglyceride (TG) storage in sites such as the liver and muscle cells. Deposition of TG in ectopic sites is due to an increase in free fatty acid delivery secondary to catecholamine-induced lipolysis, in conjunction with decreased beta-oxidation within muscle and decreased hepatic secretion of fats. The resultant increases in intracellular TG or related lipid products may in turn contribute to alterations in insulin signaling.

Changes in liver function and size after a severe thermal injury

Hepatic homeostasis and metabolism are essential for survival in critically ill and severely burned patients. There is evidence that the liver undergoes hypertrophy after burn. However, the extension and the duration of liver enlargement are not known. The aim of the present study was to determine the changes in liver size, weight, and hepatic protein synthesis in a large prospective clinical trial throughout acute hospitalization and up to 12 months after burn. Liver size was measured by means of ultrasound, and liver weight was calculated weekly during short-term hospital stay and at 6, 9, and 12 months after burn. The liver size was then compared with the predicted liver size for each individual. The levels of hepatic proteins and enzymes were determined by using standard laboratory techniques. One hundred two children were included in the study, with 58% +/- 2% total body surface area and 45% +/- 2% third-degree burn. Liver size and weight significantly increased during the first week after burn (mean +/- SEM, 85% +/- 5%), peaked at 2 weeks after burn (mean +/- SEM, 126% +/- 19%), and, at discharge, increased by 89% +/- 10%. At 6, 9, and 12 months, the liver weight increased by 40% to 50% compared with the predicted liver weight. The hepatic protein synthesis was affected up to 9 months after burn. The liver demonstrates a significant enlargement during short-term hospitalization, accompanied with impairment in the hepatic protein synthesis. The treatment to prevent liver enlargement and the improved impaired function may result in a reduction of complications accompanied with liver hypertrophy and failure.

Increased liver weights in severely burned children: comparison of ultrasound and autopsy measurements

Hepatomegaly is a common finding at autopsy in severely burned children surviving less than 6 months. This study validates a reliable ultrasound method which can be used to identify changes in liver size in severely burned children during acute hospitalization. Thirty-eight children, age 0.5-17 years with burns covering over 40% of their total surface area were studied at autopsy. Liver weight was measured at autopsy and compared to predicted liver weight for age and height. Eighteen had liver size measured by ultrasound within 10 days of death while five had ultrasound liver measures after death just prior to autopsy. All burned children who survived 7 days or more (n = 33) had liver weights at autopsy that were greater than predicted for age and height while all 23 livers measured by ultrasound were greater than predicted. Autopsy weights correlated well with weights estimated by ultrasound, R = 0.824. At autopsy, those who survived 7 days or more had enlarged livers ranging from 142 to 406% of their predicted normal age and height. Common histologic findings include large and small-droplet fat deposits, and cholestasis. The degree of these histologic abnormalities correlated with the increase in liver weight, R = 0.652. Ultrasound is a valid, noninvasive method for measuring liver weight changes in severely burned children during acute hospitalization. Ninety-five percent of the severely burned children from this institute had significant hepatomegaly identified at autopsy.

Impact of chronic and acute high-fat feeding on acute experimental pancreatitis complicated by endotoxinaemia

BACKGROUND

Obesity is associated with increased severity in patients with acute pancreatitis (AP). The underlying mechanisms are unknown. Genetically obese rats exhibit decreased survival rate in experimental AP, but the clinical relevance of this model of obesity may be questioned. It is proposed that development of organ failure in AP occurs in two stages: initial priming of leucocytes followed by a second inflammatory attack. The aim was to evaluate the impact of diet-induced obesity on outcome in a 'two-hit' model of AP.

METHODS

Lipopolysaccharide (LPS) was injected i.p. 3 h after retrograde bile duct infusion of sodium taurocholate in rats. Three experiments were done: 1) an LPS dose-response experiment, 2) chronic high-fat feeding (HF) for 16 weeks, and 3) acute HF for 10 days. Control rats received normal chow. Obesity, morphology and survival rate were assessed.

RESULTS

LPS dose-dependently decreased survival rate and increased morphological severity. HF increased weight, intra-abdominal and liver fat. Only acute HF induced hyperlipidaemia. In AP, acute obese rats exhibited less pancreatic inflammation, but total histological severity between groups was not different. In the chronic experiment only obese animals succumbed before 24 h of pancreatitis, but 72-h survival rate was not statistically different in either high-fat experiment.

CONCLUSION

An addition of LPS to AP decreases survival rate and intensifies the peri-pancreatic processes. Despite significant obesity, neither hyperlipidaemia nor increased intra-abdominal or hepatic fat influenced local pancreatic injury or survival negatively. The amount of fat per se seems not to be responsible for the deleterious influence of obesity on acute pancreatitis.

Alteration of hepatic fatty acid metabolism after burn injury in pigs

BACKGROUND

The primary goal of this study was to investigate hepatic fatty acid (FA) metabolism after severe thermal injury.

METHODS

Sixteen pigs were divided into control (n = 8) and burn (n = 8, with 40% full thickness total body surface area burned) groups. Catheters were inserted in the right common carotid artery, portal vein, and hepatic vein for blood sampling. Flow probes were placed around the hepatic artery and portal vein for blood flow measurements. Animals were given pain medication and sedated until the tracer study on day 4 after burn. The pigs were infused for 4 hours with U-13C16-palmitate in order to quantify hepatic FA kinetics and oxidation.

RESULTS

Liver triglyceride (TG) content was elevated from 162 +/- 16 (control) to 297 +/- 28 micromol TG/g dry liver wt. (p < .05). Hepatic FA uptake and oxidation were similar between the 2 groups, as were malonyl-coenzyme A (CoA) levels and activities of acetyl-CoA carboxylase and adenosine monophosphate (AMP)-activated protein kinase. In contrast, incorporation of plasma-free fatty acids into hepatic TG was elevated (p < .05) and very low density lipoprotein TG (VLDL-TG) secretion was decreased from 0.17 +/- 0.02 (control) to 0.03 +/- 0.01 micromol/kg per minute in burned pigs (p < .05).

CONCLUSIONS

The accumulation of hepatic TG in burned animals is due to inhibition of VLDL-TG secretion and to increased synthesis of hepatic TG. Fatty acids are not channeled to TG because of impaired oxidation.

Choline deficiency causes reversible hepatic abnormalities in patients receiving parenteral nutrition: proof of a human choline requirement: a placebo-controlled trial

BACKGROUND

Previous studies have shown that plasma free choline concentrations are significantly decreased in many long-term home total parenteral nutrition (TPN) patients. Furthermore, low choline status has been associated with both hepatic morphologic and hepatic aminotransferase abnormalities. A preliminary pilot study suggested choline-supplemented TPN may be useful in reversal of these hepatic abnormalities.

METHODS

Fifteen patients (10 M, 5 F) who had required TPN for > or =80% of their nutritional needs were randomized to receive their usual TPN (n = 8), or TPN to which 2 g choline chloride had been added (n = 7) for 24 weeks. Baseline demographic data were similar between groups. Patients had CT scans of the liver and spleen, and blood for plasma free and phospholipid-bound choline, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase, gamma glutamyl transferase (GGT), bilirubin, serum lipids, complete blood count (CBC), and chemistry profile obtained at baseline, and weeks 2, 4, 6, 12, 16, 20, 24, and 34. CT scans were analyzed for Hounsfield unit (HU) densities.

RESULTS

There were no significant differences in any measured parameters after 2 weeks. However, at 4 weeks, a significant difference in liver HU between groups was observed (13.3+/-5.0 HU [choline] vs 5.8+/-5.2 HU [placebo], p = .04). This significant trend continued through week 24. Recurrent hepatic steatosis and decreased HU were observed at week 34, 10 weeks after choline supplementation had been discontinued. A significant increase in the liver-spleen differential HU was also observed in the choline group (10.6+/-6.2 HU [choline] vs 1.3+/-3.3 HU [placebo], p = .01). Serum ALT decreased significantly (p = .01 to .05) in the choline group vs placebo at weeks 6,12, 20, and 24. Serum AST was significantly decreased in the choline group by week 24 (p = .02). The serum alkaline phosphatase was significantly reduced in the choline group at weeks 2, 12, 20, 24, and 34 (p = .02 to 0.07). Total bilirubin was normal in these patients and remained unchanged during the study. Serum GGT tended to decrease more in the choline group, but the greater decrease was not statistically significant.

CONCLUSIONS

Choline deficiency is a significant contributor to the development of TPN-associated liver disease. The data suggest choline is a required nutrient for long-term home TPN patients.

Fatty acid content of plasma lipids and erythrocyte phospholipids are altered following burn injury

The objective of this study was to examine compositional and quantitative changes in fatty acids of plasma components and red blood cell phospholipids (PL) immediately following and during recovery from burn injury. Subjects (n = 10) with >10% total body surface area burn had blood drawn at specific timepoints (0 to >50 d) following burn injury. Fatty acid composition of red blood cell PL and plasma PL, cholesteryl esters (CE), and triglycerides was determined using gas-liquid chromatography after separating each fraction from extracted lipids by thin-layer chromatography. Total plasma PL and CE in burn patients were lower than in healthy control subjects with reduced 20:4n-6, n-6, and n-3 fatty acids and higher levels of monounsaturated and saturated fatty acids early after burn. CE levels remained half that of healthy control values up to 50 d post-burn. Red blood cell PL had decreased 20:4n-6 content and profiles similar to that of an essential fatty acid deficiency early after burn. These results suggest an impairment in lipoprotein and polyunsaturated fatty acid metabolism in the early post-burn period. Lower levels of 20:4n-6 and n-3 fatty acids in every plasma fraction suggest increased use of these fatty acids for wound healing and immune function following burn injury. Further work is needed to determine the ability of burn patients to utilize essential fatty acids in order to design nutritional intervention that promotes wound healing and immunological functions consistent with recovery in these patients.