C. Choisy

In Vivo Bioluminescent Imaging of a New Model of Infectious Complications in Head-Injury Rats

Infectious complications are responsible for 10-25% of mortality in head-injured patients. In the present work we developed a model of infectious complications in head-injury rats using Escherichia coli (E. coli) with a stable copy of the lux operon, and monitored the infection in vivo by optical imaging. Rats were randomized into three groups: AL (healthy rats), HI (head-injury rats), and HI-EC (HI rats+single enteral bolus of E. coli, 1.3×10(9)/rat given 2 days after HI). Infection was evaluated with a camera at 2 and 6 h after E. coli challenge. Blood and organs were sampled to assess biological parameters. HI was associated with body weight loss, muscle atrophy, and plasma amino acid disturbances, in particular glutamine depletion (AL 919±37 versus HI 647±25 and HI-EC 717±20 μmol/L; p<0.05). In the HI-EC rats, the luminescence signal was observed at T+2 (mean [range]: 34,778 cpm [1617-2,918,810]), and was significantly decreased at T+6 (0 cpm [0-847,922]; p<0.05). Bacterial challenge was associated with a specific body weight loss and a decrease in gastrocnemius protein content, in alanine (AL 512±41 versus HI-EC 395±29 μmol/L; p<0.05), and in sulfur plasma amino acids. In conclusion, we propose a controlled model of HI with infectious complications characterized by specific metabolic alterations. Combined with the in vivo monitoring of the infection by bioluminescence, this model offers a valuable tool to evaluate specific strategies for HI patients.

Arginine reduces bacterial invasion in rats with head injury: An in vivo evaluation by bioluminescence*

Objectives:The benefit of arginine in intensive care unit patients with severe sepsis is still controversial. An excessive supply of arginine could lead to an overproduction of nitric oxide and could be responsible for septic shock and multiorgan failure. However, this claim is not supported by any experimental or clinical data. We set out to determine whether an enteral supply of arginine would modulate bacterial invasion in rats with head injury. Methods:Male Sprague-Dawley rats with head injury were randomized into two groups. Group 1 included rats with head injury fed a standard enteral nutrition (Sondalis HP, n = 10) and group 2 included rats with head injury fed the standard enteral nutrition plus arginine (4 g/kg/d, n = 11). Two days after head injury, the rats received a single enteral bolus of luminescent Escherichia coli Xen 14. Bacterial proliferation was evaluated in vivo at time + 2 hrs and time + 6 hrs after E. coli challenge. Four days after head injury, blood was sampled for arginine and fibrinogen assay. Muscles, intestine, spleen, and thymus were removed and weighed. Results:There was no mortality in either group. The luminescence signal was similar in the two groups at time +2 hrs (group 1: 414 [5–823] vs. group 2: 496 [0.1–993] (median value[min-max]; not significant) and was significantly lower at time +6 hrs in group 2 (group 1: 71 [0–142] vs. group 2: 8.5 [0–17]; p = .026). Arginine treatment did not improve any nutritional parameters. Conclusions:Arginine was not responsible for mortality in rats with head injury with infectious complications and reduced the intensity of bacterial invasion.

PP054-SUN: Immunonutrition: Effect of age on Arginine and Related Amino Acids Systemic Bioavailability After Surgical Stress

gastrointestinal disorders. However, inappropriate chronic exposure and/or prescription have been recently associated with a number of adverse events, especially in the elderly. Among known drug-class effects of PPI, hypomagnesaemia has been recently shown by a growing number of case reports and series. However, epidemiological studies addressing this topic, especially in older subjects, are still needed. Methods: We cross-sectionally investigated the relationship between PPI use and magnesium status in a large cohort of community-dwelling older volunteers from the Baltimore Longitudinal Study of Aging (BLSA). 4017 older subjects 65 years or older (1983 women and 2034 men) with complete data on serum magnesium levels and PPI use were evaluated. Subjects were categorized according to PPI use. Linear regression models adjusted for age and sex (Model 1) and for additional confounders including BMI, mineral and magnesium supplements, creatinine, calcium serum levels, TSH, use of diuretics, digitalis, antibiotics, calcineurin inhibitors, presence of chronic disease (type 2 diabetes, cardiovascular diseases, cancer) (Model 2) were used to address the relationship between PPI use and serum magnesium levels. Results: 505 subjects (12.6%) were PPI users. After adjustment for age and sex, PPI users exhibited significantly lower magnesium levels than non-users counterpart (1.99±0.22 vs 2.03±0.20mg/ml, p < 0.001). PPI use was negatively associated with serum magnesium levels independent of multiple confounders ( 0.041±0.009, p < 0.0001). Conclusion: In community-dwelling older subjects the use of PPIs is negatively and independently associated with serum magnesium levels.