Résultats au CASL 2016

Fellowship for Rafael

Deux résumés ont été acceptés par la Canadian Association for Study of the Liver Meeting.

Nos résultats seront présentés au CASL, qui aura lieu à Montréal, les 26 au 29 février. Les deux résumés seront présentés oralement par Cristina Bosoi et Marc-André Clément.

Publications connexes

Oral

Ornithine phenylacetate attenuates loss of muscle mass and improves hepatic encephalopathy in bile-duct ligated rats.

Cristina R. Bosoi, Mariana Oliveira, Marc-André Clément, Mélanie Tremblay, Gabrie Ten Have, Nicholaas Deutz, Christopher F. Rose.

Background: Chronic liver disease (CLD) induces numerous complications including muscle mass loss and hepatic encephalopathy (HE) which negatively impact the clinical outcome. Furthermore, muscle mass wasting and HE have been shown to lead to poor prognosis following liver transplantation. Hyperammonemia is considered the central component in the pathogenesis of HE, however recent studies have suggested ammonia to be toxic to other organs besides the brain, such as the muscle. Aims: The aim of this study was to investigate the effect of ammonia on muscle mass in rats treated with an oral formulation of ornithine phenylacetate (OP; OCR-002). Methods: Bile-duct ligated (BDL) rats were divided into 4 experimental groups; 1) Sham; 2) BDL; 3) Sham + OP; 4) BDL + OP. OP was administered orally by gavage (1g/kg) daily for 5 weeks starting 1 week after surgery. Two days before sacrifice, locomotor activity (day/night) was assessed in infrared beam cages for 24 h. The day of the sacrifice, body weight, fat and lean mass (EchoMRI) were measured, followed by i.p. injection of a stable isotopes tracers cocktail (Phe/Gly) in order to asses fractional synthesis of protein (FSR). At sacrifice, samples were collected to measure blood ammonia (commercial kit), cerebral edema (specific gravity method) and muscle FSR. Results : At 6-weeks, BDL rats demonstrated a 4-fold increase in blood ammonia vs Sham-operated controls. This increase was reduced by 40% in OP-treated BDL rats. Body weight decreased in BDL rats compared to sham-operated controls (360.2g±13.6 vs 476.8g±10.4; p<0.001) and significantly increased following OP-treatment (429.6g±117.9; p<0.001 vs BDL). This was due to a higher gain of lean mass in OP-treated BDL rats compared to BDL rats (303.1g±10.7 in BDL+OP vs 264.4g±10.5 in BDL, p<0.01). This was accompanied by increased muscle FSR in OP-treated BDL rats. Fat mass remained unchanged between treated and untreated BDL groups. OP treatment also normalized brain water content in BDL rats. Locomotor activity in BDL rats was reduced compared with sham-operated controls but no significant change was found between BDL+OP and SHAM+OP. Conclusions: This is the first study demonstrating the efficient ammonia-lowering effect of an oral formulation of OP. Moreover, OP long-term treatment is a safe, non-antibiotic alternative with protective effects on the development of cirrhosis complications such as HE and muscle mass loss in rats with CLD. Whether the effect of OP on muscle mass loss attenuation is a result of lowering blood ammonia or directly improves muscle metabolism remains to be established.

Oral

Minimal hepatic encephalopathy renders the brain susceptible to hypotension-induced neuronal cell loss in BDL rats.

Marc-André Clément, Cristina Bosoi, Mélanie Tremblay, Chantal Bémeur, Christopher F. Rose.

Background: Hepatic encephalopathy (HE) is a major neuropsychiatric complication caused by liver disease characterized by cognitive and motor dysfunction. Historically, HE has always been considered to be a reversible metabolic disorder and has therefore been expected to completely resolve following liver transplantation (LT). However, persisting neurological complications remain a common problem affecting as many as 47% of LT recipients. LT is a major surgical procedure accompanied by intraoperative stress, including blood loss and hypotension. Aim : We hypothesize, in the setting of minimal HE (MHE), the compromised brain becomes susceptible to hypotensive insults, resulting in cell injury and death. Methods: Six-week bile-duct ligated (BDL) rats with MHE and respective controls (SHAM) were used. Blood is withdrawn from the femoral artery (inducing hypovolemia) until a mean arterial pressure of 30, 60 and 90 mmHg (hypotension) and maintained for 120 minutes. Cerebral blood flow (BCF) was assessed by injecting fluorescent microspheres through the brachial artery. Upon sacrifice, brains were extracted for apoptotic analysis (western blot) and neuronal cell count (immunohistochemistry). In a separate group, BDL rats were treated for MHE with ornithine phenylacetate (OP; OCR-002), administered orally (1g/kg) for 3 weeks. Results: Both BDL rats and SHAM-operated controls without hypotension did not display any cell injury or neuronal loss. However, BDL rats following hypotension (30 and 60mmHg) demonstrated a significant decrease in neuronal cell count in the frontal cortex (using NeuN+DAPI and Cresyl Violet) compared to hypotensive SHAM-operated controls. In addition, neuronal loss was associated with an increased in cleaved caspase-3, suggesting apoptotic cell death. CBF decreased in BDL rats compared to SHAM and correlated with degree of hypotension insult. BDL rats treated with OP resulted in a decrease in blood ammonia and improvement in behaviour and did not lead to neuronal cell death following hypotension. Discussion: These findings strongly suggest that cirrhotic patients with MHE are more susceptible to hypotension-induced neuronal cell loss. Moreover, these results suggest a patient with HE (even MHE), with a “frail brain”, will fare worse during liver transplantation and consequently result in poor neurological outcome. Combination of MHE and hypotension may account for the persisting neurological complications observed in a number of cirrhotic patients following LT. Therefore, MHE, should not to be ignored and merits to be treated in order to reduce the risk of neurological complications occurring post-LT.

Oral

Cirrhotic patients with sarcopenia and sarcopenic obesity have an increased risk of hyperammonemia and hepatic encephalopathy.

Aldo Montano-Loza, Andres Duarte-Rojo, Rahima Bhanji, Christopher F. Rose.

Background: Muscle mass functions as an alternative site of ammonia detoxification in patients with cirrhosis.Aims: In this study we aimed to investigate if sarcopenia, myosteatosis, and obesity are associated with hyperammonemia and hepatic encephalopathy (HE) in patients with cirrhosis. Methods: A total of 204 cirrhotic patients were studied. Muscularity assessment was analyzed using CT scans at the level of the 3rd lumbar vertebral body. Sarcopenia was defined using the skeletal muscle index and myosteatosis according to the muscle attenuation index. Overweight-obesity was defined as a body mass index ≥25 kg/m2. Sarcopenic-obesity was defined as concomitant sarcopenia and overweight-obesity. HE was evaluated clinically (West -Heaven criteria) and defined as absent in patients not using specific treatment (i.e. lactulose, rifaximin) and with no prior episodes of HE in the preceding year. Ammonia blood levels were also performed (nl. 0-35 μmol/L) at the time of the muscularity assessment. Results: Mean age was 56±1 years and 141 were males (69%). Sarcopenia was noted in 96 patients (47%), 137 had myosteatosis (67%), 136 were overweight-obese (67%), and 53 (28%) had sarcopenic-obesity. Patients with sarcopenia (87±6 vs. 61±4 μmol/L, P<0.001), and sarcopenic-obesity (95±9 vs. 40±3 μmol/L, P<0.001) had higher levels of ammonia (Figure 1). Levels of ammonia were not different among patients with myosteatosis (77±5 vs. 67±5 μmol/L, P=0.2), and overweight-obesity (76±5 vs. 67±5 μmol/L, P=0.2). Patients with sarcopenia (84 vs. 63%, P=0.001) and sarcopenic-obesity (93 vs. 65%, P<0.001) had higher frequency of hyperammonemia. Patients with myosteatosis had a trend (P=0.06), and overweight-obesity was not associated with hyperammonemia (P=0.1). Lastly, patients with sarcopenia (42 vs. 26%, P<0.001), and sarcopenic obesity (47 vs. 30%, P<0.001) had higher frequency of HE. Sarcopenia and sarcopenic-obesity increased the risk of hyperammonemia (OR 3.2, P=0.001, and OR 7.0, P<0.001). Also, sarcopenia increased the risk of HE (OR 2.0, P<0.001, and OR 2.1, P<0.001). Conclusions: Cirrhotic patients with sarcopenia and sarcopenic-obesity have higher ammonia levels and risk for HE. Muscle mass plays a protective role for hyperammonemia and therapeutic strategies to avoid muscle depletion might decrease the risk of HE in cirrhosis. Funding Agencies:This study has been funded with a Clinical Research Award from the American College of Gastroenterology Institute 2011