David R. Fischer

Activity and expression of the 20S proteasome are increased in skeletal muscle during sepsis

Recent studies suggest that sepsis stimulates ubiquitin-dependent protein breakdown in skeletal muscle. In this proteolytic pathway, ubiquitinated proteins are recognized, unfolded, and degraded by the multicatalytic 26S protease complex. The 20S proteasome is the catalytic core of the 26S protease complex. The role of the 20S proteasome in the regulation of sepsis-induced muscle proteolysis is not known. We tested the hypothesis that sepsis increases 20S proteasome activity and the expression of mRNA for various subunits of this complex. Proteolytic activity of isolated 20S proteasomes, assessed as activity against fluorogenic peptide substrates, was increased in extensor digitorum longus muscles from septic rats. The proteolytic activity was inhibited by specific proteasome blockers. Northern blot analysis revealed an approximately twofold increase in the relative abundance of mRNA for the 20S α-subunits RC3 and RC9 and the β-subunit RC7. However, Western blot analysis did not show any difference in RC9 protein content between sham-operated and septic rats. The increased activity and expression of the 20S proteasome in muscles from septic rats lend further support for a role of the ubiquitin-proteasome-pathway in the regulation of sepsis-induced muscle proteolysis.

Dantrolene reduces serum TNFα and corticosterone levels and muscle calcium, calpain gene expression, and protein breakdown in septic rats

The effects of dantrolene on serum TNFalpha and corticosterone levels and on muscle calcium, calpain gene expression, and protein breakdown were studied in rats with abdominal sepsis induced by cecal ligation and puncture. Treatment of rats with 10 mg/kg of dantrolene 2 h before and 8 h after induction of sepsis reduced serum TNFalpha and corticosterone, muscle calcium levels, mRNA levels for m- and mu-calpain, and the muscle specific calpain p94, as well as total and myofibrillar protein breakdown rates, determined as release of tyrosine and 3-methylhistidine, respectively, from incubated extensor digitorum longus muscles. The results support the concept that increased calcium concentrations may be an important mechanism of sepsis-induced muscle protein breakdown. The data also indicate that other mechanisms, in addition to reduced muscle calcium concentrations such as decreased levels of TNFalpha and glucocorticoids, may contribute to the anti-catabolic effects of dantrolene during sepsis. The observations are important from a clinical standpoint because they suggest that the catabolic response in skeletal muscle during sepsis may be prevented by treatment with a calcium antagonist.

Decision Modeling to Estimate the Impact of Gastric Bypass Surgery on Life Expectancy for the Treatment of Morbid Obesity

OBJECTIVE To create a decision analytic model to estimate the balance between treatment risks and benefits for patients with morbid obesity. DESIGN Decision analytic Markov state transition model with multiple logistic regression models as inputs. Data from the 2005 National Inpatient Survey were used to calculate in-hospital mortality risk associated with bariatric surgery and then adjusted for 30-day mortality. To calculate excess mortality associated with obesity, we used the 1991-1996 National Health Interview Survey linked to the National Death Index. Bariatric surgery was assumed to influence mortality only through its impact on the excess mortality associated with obesity, and the efficacy of surgery was estimated from a recent large observational trial. INTERVENTION Gastric bypass surgery. Main Outcome Measure Life expectancy. RESULTS Our base case, a 42-year-old woman with a body mass index of 45, gained an additional 2.95 years of life expectancy with bariatric surgery. No surgical treatment was favored in our base case when the 30-day surgical mortality exceeded 9.5% (baseline 30-day mortality, 0.2%) or when the efficacy of bariatric surgery for reducing mortality decreased to 2% or less (baseline efficacy, 53%). CONCLUSIONS The optimal decision for individual patients varies based on the balance of risk between perioperative mortality, excess annual mortality risk associated with increasing body mass index, and the efficacy of surgery; however, for the average morbidly obese patient, gastric bypass improves life expectancy.

Impact of bariatric surgery on life expectancy in severely obese patients with diabetes: A Decision analysis

OBJECTIVE To create a decision analytic model to estimate the balance between treatment risks and benefits for severely obese patients with diabetes. BACKGROUND Bariatric surgery leads to many desirable metabolic changes, but long-term impact of bariatric surgery on life expectancy in patients with diabetes has not yet been quantified. METHODS We developed a Markov state transition model with multiple Cox proportional hazards models and logistic regression models as inputs to compare bariatric surgery versus no surgical treatment for severely obese diabetic patients. The model is informed by data from 3 large cohorts: (1) 159,000 severely obese diabetic patients (4185 had bariatric surgery) from 3 HMO Research Network sites; (2) 23,000 subjects from the Nationwide Inpatient Sample; and (3) 18,000 subjects from the National Health Interview Survey linked to the National Death Index. RESULTS In our main analyses, we found that a 45-year-old woman with diabetes and a body mass index (BMI) of 45 kg/m gained an additional 6.7 years of life expectancy with bariatric surgery (38.4 years with surgery vs 31.7 years without surgery). Sensitivity analyses revealed that the gain in life expectancy decreased with increasing BMI, until a BMI of 62 kg/m is reached, at which point nonsurgical treatment was associated with greater life expectancy. Similar results were seen for both men and women in all age groups. CONCLUSIONS For most severely obese patients with diabetes, bariatric surgery seems to improve life expectancy; however, surgery may reduce life expectancy for the super obese with BMIs over 62 kg/m.

The stress response decreases NF-κB activation in liver of endotoxemic mice

Recent studies suggest that the stress (heat shock) response protects cells and tissues from inflammatory and other noxious insults. The transcription factor nuclear factor-kappa B (NF-&kgr;B), normally sequestered in the cytoplasm by its inhibitory protein I&kgr;B, regulates many genes involved in the inflammatory response to critical illness. Endotoxemia is associated with increased NF-&kgr;B activity in liver but the effect of the stress response on endotoxin-induced NF-&kgr;B activation in the liver is not known. We hypothesized that the stress response inhibits NF-&kgr;B DNA binding activity in liver during endotoxemia. The stress response was induced in mice by hyperthermia (42°C for 3 min) or sodium arsenite (10 mg/kg) and resulted in increased hepatic heat shock protein-72 levels. After induction of the stress response, mice were injected subcutaneously with endotoxin (12.5 mg/kg) or a corresponding volume of sterile saline. NF-&kgr;B DNA binding activity in the nuclear fraction of liver tissue increased and cytoplasmic I&kgr;B-&agr; levels decreased after endotoxin injection, with a maximal effect seen at 60 min. The endotoxin-induced increase in NF-&kgr;B DNA binding activity and decrease in I&kgr;B-&agr; levels were inhibited by prior induction of the stress response. In additional experiments, treatment of mice with sodium arsenite after induction of endotoxemia blunted the increase in NF-&kgr;B activity, indicating a therapeutic potential of sodium arsenite, in addition to its preventive effect. The present results suggest that the protective effects of the stress response in vivo may, at least in part, be due to inhibited NF-&kgr;B activation.

Burn injuries in rats upregulate the gene expression of the ubiquitin-conjugating enzyme E214k in skeletal muscle

Burn injuries are associated with muscle cachexia, which mainly reflects protein breakdown in the ubiquitin-proteasome pathway. Ubiquitination of proteins degraded by this mechanism is regulated by multiple enzymes, including the 14-kd ubiquitin-conjugating enzyme, E2(14k). In this study, burn injuries in rats resulted in increased levels of the 1.2 kilobase E2(14k) transcript in the white, fast-twitch extensor digitorum longus muscle with no changes or only minor changes in the red, slow-twitch soleus muscle, liver, and kidney. The results provide the first evidence that burn injuries upregulate the gene expression of E2(14k) in skeletal muscle and suggest that ubiquitin-proteasome-dependent muscle protein breakdown after thermal injuries may, at least in part, be regulated by E2(14k).

Intraoperative manometry to assess the esophagogastric junction during laparoscopic fundoplication and myotomy.

Surgery for gastroesophageal reflux disease and achalasia is performed to alleviate symptoms by improving esophagogastric junction (EGJ) function. Intraoperative manometry was used to evaluate the pressure-length characteristics of the reconstructed EGJ during laparoscopic Nissen fundoplication and laparoscopic Heller myotomy. Intraoperative manometry was performed in 37 consecutive patients undergoing laparoscopic Nissen fundoplication (n = 22) or laparoscopic Heller myotomy (n = 15). Measurements were taken before surgery, after creation of the pneumoperitoneum, after completion of the myotomy in achalasia, and after creation of the fundoplication. Tracings were analyzed for pressure, length, and the integrated pressure–length relation (area under the curve [AUC]). Statistical comparison was made using paired t tests; intraoperative EGJ measurements did not correlate well with preoperative values for either pressure or length. Laparoscopic Nissen fundoplication significantly increased pressure, length, and AUC of the EGJ compared with prefundoplication values. Laparoscopic Heller myotomy significantly decreased EGJ pressure, length, and AUC. Creation of a Toupet fundoplication after myotomy did not significantly increase pressure, length, and AUC of the EGJ compared with postmyotomy values. Intraoperative manometry identified 2 of 15 achalasia patients (13%) with persistent areas of high pressure after initial myotomy that were corrected by extending the myotomy. Intraoperative manometry identifies mechanical changes created during EGJ surgery and may be a useful adjunct to improve outcomes of laparoscopic Nissen fundoplication and laparoscopic Heller myotomy.

Use of omeprazole in the management of giant duodenal ulcer: Results of a prospective study

BACKGROUND Giant duodenal ulcer (GDU) is generally thought to require surgical intervention. Proton pump inhibitors have beneficial effects in peptic ulcer disease, but their role in GDU disease is unknown. We examined the use of omeprazole in GDU management. METHODS Twenty-eight patients were diagnosed with GDU. One patient required immediate operative intervention. The remaining 27 were placed on omeprazole (40 mg daily). When ulcer healing was documented by endoscopy, the patients were placed on oral histamine-2 receptor antagonist therapy. RESULTS Of the 28 study patients, 20 (71.4%) did not require operative intervention, and 8 (28.6%) required operation for ulcer complications. Of the 15 patients with adherent clot or a visible vessel at initial endoscopy, 7 (46.7%) required operative intervention, as compared with 1 (7.7%) of the 13 patients without a visible vessel or adherent clot. This difference was statistically significant (P < .05). Twenty-three patients underwent antral biopsy and/or enzyme-linked immunosorbent assay for Helicobacter pylori, and 9 (39.1%) had a positive result. CONCLUSIONS Omeprazole is effective in the treatment of GDU disease. An adherent clot or a visible vessel at endoscopy indicates a higher likelihood of complications requiring operation. The relatively low H pylori infection rate, as compared with other peptic ulcer disease, may indicate a different pathophysiology in GDU.

Metabolic Depletion and Failure: Muscle Cachexia During Injury and Sepsis

Severe injury and sepsis are associated with metabolic changes in virtually all organs and tissues and include alterations in carbohydrate, lipid, and protein metabolism.1,2 One of the most prominent metabolic consequences of critical illness is the catabolic response in skeletal muscle. Metabolic depletion and failure in skeletal muscle result in muscle atrophy, weakness, and fatigue, preventing ambulation and delaying recovery in these patients. When respiratory muscles are involved in the catabolic response3, difficulties arise when weaning the patient from the ventilator. In addition, muscle weakness increases the risk for aspiration and pneumonia.

60 – Models of Protein Metabolism

This chapter focuses on models of protein metabolism for muscle and intestine. Methods to measure protein turnover rates in various organs and tissues are important for investigators involved in surgical research because many disease states seen in surgical patients are associated with significant changes in protein synthesis and degradation rates. Many methods used to measure protein synthesis rates are based on the incorporation of radiolabeled amino acids into proteins. When such techniques are used, it is important to understand the concept of precursor specific radioactivity. The specific radioactivity describes the ratio between radiolabeled and unlabeled amino acids and can be expressed as dpm/mole. The amount of radioactivity incorporated into a protein reflects not only the rate of protein synthesis but the specific radioactivity of the precursor amino acid as well.