Model-guided identification of a therapeutic strategy to reduce hyperammonemia in liver diseases

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• 作者：Ahmed Ghallab¹ ; ² ; ^{ghallab@ifado.de" class="auth_mail" title="E-mail the corresponding author} ; Gé ; raldine Celliè ; re³ ; ^&dagger ; ; Sebastian G. Henkel⁴ ; ^&dagger ; ; Dominik Driesch⁴ ; Stefan Hoehme⁵ ; Ute Hofmann⁶ ; Sebastian Zellmer⁷ ; Patricio Godoy¹ ; Agapios Sachinidis⁸ ; Meinolf Blaszkewicz¹ ; Raymond Reif¹ ; Rosemarie Marchan¹ ; Lars Kuepfer⁹ ; Dieter Hä ; ussinger¹⁰ ; Dirk Drasdo³ ; ⁵ ; ^&Dagger ; ; Rolf Gebhardt⁷ ; ^&Dagger ; ; Jan G. Hengstler¹ ; ^&Dagger ; ; ^{hengstler@ifado.de" class="auth_mail" title="E-mail the corresponding author}
• 关键词：CCl4 ; carbon tetrachloride ; GDH ; glutamate dehydrogenase ; AOA ; aminooxy acetate ; ALT ; alanine transaminase ; AST ; aspartate transaminase ; α-KG ; alpha-ketoglutarate ; PDAC ; 2 ; 6-pyridinedicarboxylic acid
• 刊名：Journal of Hepatology
• 出版年：2016
• 出版时间：April 2016
• 年：2016
• 卷：64
• 期：4
• 页码：860-871
• 全文大小：2298 K

文摘

Recently, spatial-temporal/metabolic mathematical models have been established that allow the simulation of metabolic processes in tissues. We applied these models to decipher ammonia detoxification mechanisms in the liver.

Methods

An integrated metabolic-spatial-temporal model was used to generate hypotheses of ammonia metabolism. Predicted mechanisms were validated using time-resolved analyses of nitrogen metabolism, activity analyses, immunostaining and gene expression after induction of liver damage in mice. Moreover, blood from the portal vein, liver vein and mixed venous blood was analyzed in a time dependent manner.

Results

Modeling revealed an underestimation of ammonia consumption after liver damage when only the currently established mechanisms of ammonia detoxification were simulated. By iterative cycles of modeling and experiments, the reductive amidation of alpha-ketoglutarate (α-KG) via glutamate dehydrogenase (GDH) was identified as the lacking component. GDH is released from damaged hepatocytes into the blood where it consumes ammonia to generate glutamate, thereby providing systemic protection against hyperammonemia. This mechanism was exploited therapeutically in a mouse model of hyperammonemia by injecting GDH together with optimized doses of cofactors. Intravenous injection of GDH (720 U/kg), α-KG (280 mg/kg) and NADPH (180 mg/kg) reduced the elevated blood ammonia concentrations (>200 μM) to levels close to normal within only 15 min.

Conclusion

If successfully translated to patients the GDH-based therapy might provide a less aggressive therapeutic alternative for patients with severe hyperammonemia.