Résumés au AASLD2017

Résumés présentés

Trois résumés seront présentés au congrès de l'AASLD.

Deux des résumés seront présentés par nos étudiants, Rafael et Mariana, lors du prochain congrès de l' AASLD qui aura lieu à Washington du 20 au 24 octobre 2017. L'autre résumé est une collaboration avec le département d'hépatologie du CHUM qui a été un des centres participant à l'étude de Dr Bajaj (Virginia Commonwealth University, USA).

De plus, Dr Rose offrira une conférence le 19 octobre lors du symposium conjoint de la Chronic Liver Disease Foundation (CLDF) et l' ISHEN.

Publications connexes

Can We Accurately Assess the Spectrum of Hepatic Encephalopathy (HE) Stages? A Multi-Center Initiative using Standardized Simulated Patients.

Jasmohan S. Bajaj, Bradley Reuter, Kara Walter, Scott W. Biggins, Julien Bissonnette, Christopher F. Rose, Jennifer C. Lai, Michael D. Leise, Patrick S. Kamath, Puneeta Tandon, James Wade.

Reliability of HE characterization and evaluation is essential for accurate management and conduct of multi-center trials but a systematic intervention of trainees and non-trainees is lacking. METHODS: US & Canadian GI trainee/non-trainee practitioners were shown standard- ized simulated patient videos during the same sitting. The videos demonstrated cirrhotic pts with HE below stage 2 (normal/covert), and overt stages (2, 3, & 4). Therespondents were asked to identify the HE stage and answer questions about management after each video. RESULTS: 108 respondents (62 trainees, 46 non-trainees) from 7 centers(77 from four 4 US & 31 from 3 Canadian centers) were included. Trainees included 18 1st yr, 16 2 nd yr, 12 3 rd yr, 14 4 th yr fellows & 2 residents. Non-trainees included 41 consultants & 5 mid-level practitioners. HE stages (Table): A higher % of respondents were better at correctly diagnosing stages ≥2 compared to stages <2 (91 vs 64%, p<0.001). HE sub-stages were identified similarly between trainees and non-trainees with a trend towards better “normal” identification in non-trainees(P=0.13).Management: Most respondents would send pts with stages < 2 rather than ≥2 HE for cognitive testing (70 vs 20%, p<0.001). The reverse was seen for ordering ammonia levels, higher in stages ≥2 than stage<2 HE (36 vs 11%, p<0.001). A higher percent of non-trainees tested ammonia levels in stage <2 HE compared to trainees (16 vs 7%, p=0.03). A higher percent of non-trainees than trainees would prescribe low protein diets in stage ≥2 HE(18 vs 8%, p=0.007). Most respondents would treat pts with stages ≥2 with lactulose (58 vs 93%, p<0.001) & rifaximin (14 vs 50%, p<0.001). More trainees would use rifaximin for stages ≥2 than non-trainees (68 vs 30%, p<0.001). CONCLUSION: In this multi-center study, North American GI practitioners demonstrated poor reliability in lower stages but not stages ≥2 HE. There were significant variations in ordering MHE testing, & lactulose/rifaximin and relatively few respondents order ammonia levels or a low-protein diet. Overt HE ≥stage 2 remains a reliable benchmark of diagnosis across training levels but there is a need for more standardized algorithms for HE management.

Obesity exacerbates the neurological impairments associated to hepatic encephalopathy in chronic liver disease.

Rafael Ochoa-Sanchez, Mélanie Tremblay, Christopher F. Rose.

Hepatic encephalopathy (HE) is a neuropsychiatric syndrome, a major complication of chronic liver disease (CLD/cirrhosis). With an increasing prevalence of obesity-induced cirrhosis and evidence linking blood-derived lipids to neurological impairment, we hypothesize that obesity increases the risk, severity and progression of HE. AIM: Development of an animal model of cirrhosis and obesity to investigate the synergistic effect of obesity and CLD on the development of neurological impairment and HE. M&M: Animal model of CLD and HE: 6-week bile-duct ligation (BDL) rats, as well as Sham-operated controls, were used. Inducing obesity: High-fat diet (HFD) was given for 3 weeks before BDL or Sham surgery. Groups: 1. Obese-BDL rats received HFD for 3 weeks pre-BDL and regular diet (RD) for 6 weeks post-BDL; 2. Lean-BDL rats received RD pre- and post-BDL; 3. Lean-Sham rats received RD pre- and post-Sham surgery. Behaviour: Recognition memory, motor coordination and muscular strength were assessed before surgery, as well as 3 and 6 weeks post-surgery using the novel object recognition, rotarod and grip strength tests, respectively. Body-composition (echoMRI): Fat vs. lean mass and free water (ascites) were also monitored. RESULTS: Before the surgery, body weight (BW) and fat mass of rats on HFD (Obese-BDL) were increased in comparison to rats on RD (Lean-BDL and Lean-Sham). 3 weeks after surgery, BW, fat mass, lean mass and free water were increased in Obese-BDL rats vs. Lean-BDL rats. Long-term memory was reduced in Obese-BDL, but not in Lean-BDL, vs. Lean-Sham rats. 6 weeks after surgery, similar to Lean-BDL rats, Obese-BDL rats lost BW, fat and Lean mass, while free water increased vs. Lean-Sham rats. Motor coordination, forelimb strength and long-term memory were impaired in Obese-BDL rats in comparison to Lean-BDL or Lean-Sham rats, whereas hind-limb strength and short-term memory were impaired in both Obese- and Lean-BDL rats, compared to Lean-Sham rats. CONCLUSION: HFD induces obesity features in healthy non-cirrhotic rats. Such effects are maintained in cirrhotic-BDL rats. Obesity also accelerates the accumulation of free water in cirrhotic-BDL rats. Interestingly, some neurological impairments are detected in Obese-BDL but not in Lean-BDL rats (long-term memory), while others are exacerbated (motor coordination, forelimb strength). This new animal model of CLD and obesity suggests a synergistic effect, which accelerates and worsens the disease-associated abnormalities observed in CLD and HE. Thus, obesity-induced cirrhosis in patients may result in more complex neurological manifestations, suggesting more susceptibility to poor neurological performance.

Glutamine synthetase in endothelial cells of the blood-brain barrier: role in protecting the brain from hyperammonemia-induced neurotoxicity?

Mariana Macedo de Oliveira, Mélanie Tremblay, Christopher F. Rose.

The liver plays a major role in regulating ammonia levels in the blood . Therefore, in liver disease, the loss of hepatic function leads to hyperammonemia and consequently hepatic encephalopathy (HE) . Ammonia-lowering strategies remain the mainstay therapeutic strategy for HE . Ammonia, both as an ion (NH4+) and gas (NH3), easily crosses all plasma membranes, including the blood brain barrier (BBB); the interface between the blood and the brain . Glutamine synthetase (GS), an enzyme which in the process of amidating glutamate to glutamine removes ammonia, plays an important compensatory role during liver disease . GS is expressed in liver, muscle and brain (primarily in astrocytes) but has never been thoroughly explored in the BBB . Methods: Using brain primary microvascular endothelial cells (ECs) and isolated cerebral microvessels (CMV) from the frontal cortex of naïve rats, the presence of GS was assessed using rtPCR, western blot (brain used as positive control), immunohistochemistry (co-localized with endothelial cell marker caveolin-1) . GS activity was also assessed . In addition, to understand the effect of liver disease on GS, ECs were exposed to plasma from bile-duct ligated (BDL) rats (model of chronic liver disease) and sham-operated controls, as well as ammonia chloride (1mM) and oxidative stress (10μM of hydrogen peroxide) . Results: Immunohistochemically, GS was detected in ECs and in vessels of brain from naïve rats . Furthermore, ECs expressed GS mRNA, protein and activity . However, expression of GS was lower compared to brain lysate control samples (p<0 .05) . GS expression in CMV showed similar results to brain but GS activity was less (p<0 .05) . When cells were submitted to ammonia, an increase in GS activity was demonstrated (p<0 .05) . However, when exposed to plasma from BDL rats or oxidative stress, GS activity was significantly reduced when compared to controls (p<0 .01) . Conclusion: These results demonstrate for the first time that GS is present in ECs in both in vivo and in vitro . Interestingly, ammonia stimulates GS in endothelial cells, whereas oxidative stress inhibits GS activity . Furthermore, GS activity is decreased in the presence of plasma from cirrhotic rats, possibly due to the presence of systemic oxidative stress in BDL rats. We speculate that a downregulation of GS allows for a faster and easier entry of ammonia into the brain and therefore may increase the risk of HE . We anticipate that upregulating GS in ECs of the BBB could become a new therapeutic target for HE.