P: 37 Probiotics Combined With Rifaximin for the Treatment of Chronic Hepatic Encephalopathy: A Longitudinal In Vivo 1H-MRS Study of Brain Metabolism Using BDL Rats
Authors: Flatt Emmanuelle , Braissant Olivier , Mitrea Stefanita , Sessa Dario , Mastromarino Paola , Gruetter Rolf , McLin Valérie A. , Cudalbu Cristina 
Published: September 2019

BACKGROUND:
Chronic hepatic encephalopathy (HE) is a severe complication of chronic liver disease (CLD), and finding the right treatment to reduce HE episodes before liver transplant remains a challenge. Both rifaximin (non-absorbable antibiotic) and probiotics are currently used to reduce HE symptoms, but their precise effect on brain metabolites has never been studied. Our aims were: 1) to assess in vivo and longitudinally the effect of the combination of probiotics and rifaximin on bile duct ligated (BDL) rats in different brain regions; and 2) to compare these results with both non-treated (n = 17) and rifaximin-only treated rats (n = 12).1,2

METHODS:
In vivo 1H-MRS at 9.4 Tesla combined with biochemical tests (plasma NH4+, bilirubin) and microbiota analysis were performed on adult Wistar rats (n = 9) before BDL3,4 (week 0) and at weeks 2, 4, 6 and 8 after surgery. Evolution of metabolites was studied using the SPECIAL sequence (TE = 2.8 ms) in the hippocampus (2 × 2.8 × 2 mm3) and cerebellum (2.5 × 2.5 × 2.5 mm3). Metabolite concentrations were estimated using LCModel and water as internal reference. Probiotics administration (VIVOMIXX®, 60 billion bacteria/kg of rat) started two weeks before BDL-surgery until the end of the study. Rifaximin (15.7 mg/kg/day = 'human-dose') was administered twice daily starting two weeks after BDL-surgery.

RESULTS:
All rats displayed the characteristic rise in plasma bilirubin, regardless of treatment group, as well as a similar ammonium increase (Figure 1a). The characteristic pattern of chronic HE was observed (Figure 1e): a gradual increase of brain glutamine followed by a gradual decrease in the other brain osmolytes (myo-inositol, taurine, total choline) and a later decrease of glutamate and creatine. The combination of probiotics and rifaximin improved some of the neuro-metabolic changes associated with CLD at early stages of HE (week 4) in the cerebellum: the 'probiotics + rifaximin' group showed a lower rise of brain glutamine (+33% vs +66%, Figure 1c) and a smaller decrease of creatine (−4% vs −14%). In the hippocampus, rats receiving both probiotics and rifaximin exhibited a smaller increase in brain glutamine even at week 8 after BDL compared to non-treated rats (+99% vs +136%, Figure 1d) and a smaller decrease in brain myo-inositol and glutamate (−20% vs −30% and −7% vs −13%, respectively). Also, bifidobacteria concentration was slightly higher in the 'probiotics+rifaximin' group at week 8 (Figure 1b). Finally, the administration of rifaximin associated with this probiotic showed more beneficial effects than rifaximin only, and both could be used to maintain a balanced microbiota and may provide opportunities for reducing the spread of antibiotic resistances.

CONCLUSIONS:
To conclude, some promising changes were induced in the neurometabolic profile of BDL-rats who were treated with this specific probiotic and rifaximin (glutamine, myo-inositol, creatine and glutamate).