EPS mid-career prize 2018: Inference within episodic memory reflects pattern completion.

Recollection of episodic memories is a process of reconstruction where coherent events are inferred from subsets of remembered associations. Here, we investigated the formation of multielement events from sequential presentation of overlapping pairs of elements (people, places, and objects/animals), interleaved with pairs from other events. Retrievals of paired associations from a fully observed event (e.g., AB, BC, AC) were statistically dependent, indicating a process of pattern completion, but retrievals from a partially observed event (e.g., AB, BC, CD) were not. However, inference for unseen "indirect" associations (i.e., AC, BD or AD) from a partially observed event showed strong dependency with each other and with linking direct associations from that event. In addition, inference of indirect associations correlated with the product of performance on the linking direct associations across events (e.g., AC with ABxBC) but not on the non-linking association (e.g., AC with CD). These results were seen across three experiments, with greater differences in dependency between indirect and direct associations when they were separately tested, but similar results following single and repeated presentations of the direct associations. The results could be accounted for by a simple auto-associative network model of hippocampal memory function. Our findings suggest that pattern completion supports recollection of fully observed multielement events and the inference of indirect associations in partly observed multielement events, mediated via the directly observed linking associations (although the direct associations themselves were retrieved independently). Together with previous work, our results suggest that associative inference plays a key role in reconstructive episodic memory and does so through hippocampal pattern completion.

Therapeutic Targeting of Myeloperoxidase Attenuates NASH in Mice.

Myeloperoxidase (MPO) activity has been associated with the metabolic syndrome, cardiovascular and liver disease. Here, we evaluate the therapeutic potential of MPO inhibition on nonalcoholic steatohepatitis (NASH) and NASH-induced fibrosis, the main determinant of outcomes. MPO plasma levels were elevated in patients with nonalcoholic fatty liver disease (NAFLD) compared with healthy controls. In a second cohort, hepatic MPO messenger RNA expression correlated with higher body mass index and hemoglobin A1c, both being risk factors for NAFLD. We could establish by immunohistochemistry that MPO-positive cells were recruited to the liver in various mouse models of fibrogenic liver injury, including bile duct ligation, carbon tetrachloride (CCl4) treatment, spontaneous liver fibrogenesis in multidrug resistance 2 knockout (MDR2 KO) mice, and NASH-inducing diet. Comparison of MPO-deficient mice and their wild-type littermates exposed to a high-caloric diet revealed that MPO deficiency protects against NASH-related liver injury and fibrosis. In line with this, hepatic gene expression analysis demonstrated a MPO-dependent activation of pathways relevant for wound healing, inflammation, and cell death in NASH. MPO deficiency did not affect NAFLD-independent liver injury and fibrosis in MDR2 KO or CCl4-treated mice. Finally, we treated wild-type mice exposed to NASH-inducing diet with an oral MPO inhibitor. Pharmacological MPO inhibition not only reduced markers of MPO-mediated liver damage, serum alanine aminotransferase levels, and hepatic steatosis, but also significantly decreased NASH-induced liver fibrosis. MPO inhibitor treatment, but not MPO deficiency, significantly altered gut microbiota including a significant expansion of Akkermansia muciniphila. Conclusions: MPO specifically promotes NASH-induced liver fibrosis. Pharmacological MPO inhibition attenuates NASH progression and NASH-induced liver fibrosis in mice and is associated with beneficial changes of intestinal microbiota.

Ascites control by TIPS is more successful in patients with a lower paracentesis frequency and is associated with improved survival.

BACKGROUND & AIMS: Refractory ascites is the main reason for the implantation of a transjugular intrahepatic portosystemic shunt (TIPS) in liver cirrhosis, but ascites control by TIPS fails in a relevant proportion of cases. Here, we investigated whether routine parameters pre-TIPS can predict persistent ascites after TIPS implantation and whether persistent ascites predicts long-term clinical outcome. METHODS: A detailed retrospective analysis of 128 patients receiving expanded polytetrafluoroethylene-covered stents for the treatment of refractory ascites was performed. Persistent ascites post-TIPS was defined as the prolonged need for paracentesis >3 months after TIPS. The influence of demographics, laboratory results, pre-TIPS heart and liver ultrasound results, and invasive hemodynamic parameters on persistent ascites was evaluated by univariable and multivariable logistic regression. Predictors of the composite endpoint liver transplantation/death were analyzed using a multivariable Cox regression. RESULTS: Ascites control post-TIPS was achieved in 95/128 patients (74%), whereas ascites remained persistent in 33/128 cases (26%). On multivariable analysis, a lower paracentesis frequency pre-TIPS (odds ratio 1.672; 95% CI 1.253-2.355) and lower baseline creatinine levels (odds ratio 2.640; CI 1.201-6.607) were associated with ascites control. Patients with persistent ascites post-TIPS had and impaired transplant-free survival (median 10.0 vs. 25.8 months), for which persistent ascites was the only independent predictor (hazard ratio 5.654; CI 3.019-10.59). CONCLUSION: TIPS-placement in patients with lower paracentesis frequency and creatinine levels is associated with superior ascites control. Thus, TIPS implantation should be considered in moderate decompensation and not as a last resort. Persistent ascites post-TIPS seems to be the only predictor of liver transplantation and death. LAY SUMMARY: The insertion of a transjugular intrahepatic portosystemic shunt (TIPS) in patients with refractory ascites should be considered in patients with moderate decompensation and not as a last resort, as lower paracentesis frequency and creatinine levels pre-TIPS are associated with superior ascites control. In turn, failure to control ascites seems to be the only predictor of liver transplantation and death.

TIMP-1 is upregulated, but not essential in hepatic fibrogenesis and carcinogenesis in mice.

Tissue inhibitor of metalloproteinases-1 (TIMP-1) is upregulated during hepatic fibrogenesis and considered to promote fibrosis in the injured liver by inhibition of matrix metalloproteases (MMP) and degradation of extracellular matrix. Moreover, TIMP-1 displays anti-apoptotic properties, in patients with hepatocellular carcinoma (HCC) TIMP-1 serum levels are elevated and high TIMP-1 expression levels in HCC are associated with a poor prognosis. Therefore, TIMP-1 could functionally link fibrogenesis and carcinogenesis in the liver. The aim of our study was to characterize the role of TIMP-1 in hepatic fibrogenesis and carcinogenesis. Experimental hepatic fibrogenesis as well as diethylnitrosamine (DEN) -induced hepatocarcinogenesis were studied in TIMP-1-deficient mice and wild type littermates. Hepatic TIMP-1 expression was upregulated following induction of liver fibrosis by bile duct ligation (BDL) or by carbon tetrachloride (CCl4). Unexpectedly, in comparison to wild type littermates, TIMP-1-deficient mice were not protected from liver fibrosis induced by BDL or CCl4. TIMP-1 expression was significantly higher in HCC nodules than in surrounding liver tissue. However, experimental hepatic carcinogenesis was similar in TIMP-1-deficient mice and wild type littermates following DEN-treatment or combined treatment with DEN and CCl4. Therefore we concluded that TIMP-1 is not essential for hepatic fibrogenesis and carcinogenesis in mice.