Final Report Summary - IEMTX (Therapies for inborn errors of metabolism)
The overall goal of this proposal was to develop new therapies for inborn errors of metabolism (IEMs). Although individually rare, IEMs cumulatively represent a significant medical burden, particularly in children. Expanded newborn screening by tandem mass spectrometry provides the unprecedented opportunity to screen for several IEMs on one single blood sample and allows early detection and treatment. However, current treatment options are limited, and the outcomes remain poor in many cases. Lactic acidosis and hyperammonemia are among the most common alterations observed in IEMs and we generated preclinical data supporting the efficacy of novel treatments for both these conditions. Besides IEMs, lactic acidosis and hyperammonemia can also occur in non-genetic disorders and the drugs we developed for these two life-threatening conditions can also be used in acquired disorders.
We showed that phenylbutyrate prevents inactivation by phosphorylation of pyruvate dehydrogenase complex (PDHC) and is effective for treatment of congenital PDHC deficiency and secondary forms of lactic acidosis. Results of these studies have led to a clinical trial that is currently ongoing.
While enhancement of PDHC is effective for therapy of lactic acidosis, we found that inhibiting PDHC has potential for therapy of acute liver failure, independently of its etiology. The development of this therapy was based on our discovery that PDHC and lactic dehydrogenase translocate to the nucleus resulting in detrimental gene expression during acute liver failure. A single small molecule that was found to inhibit both enzymes was effective in reducing liver damage and improving survival in mice with acute liver failure. Therefore, the results of this study might pave the way towards the first non-symptomatic drug treatment for acute liver failure.
We found that hepatic autophagy is an important mechanism for ammonia detoxification because it supports urea synthesis by providing critical intermediates of the cycle, and we generated preclinical data showing that autophagy enhancement has potential for therapy of both primary and secondary causes of hyperammonemia. Hepatic autophagy was found to be triggered by hyperammonemia through an α-ketoglutarate-dependent inhibition of mTOR. While deficiency of autophagy impaired ammonia detoxification, autophagy enhancement by rapamycin and Tat-Beclin-1 increased ureagenesis and protected against hyperammonemia in a variety of acute and chronic hyperammonemia animal models, including acute liver failure and ornithine transcarbamylase deficiency, the most frequent inherited urea-cycle disorder.
Finally, we generated two novel tools that can be used for future investigation in IEMs and metabolic diseases in general: a computational tool for metabolic pathway analysis and a rapid and efficient tool to generate human iPSC that can be converted in disease-relevant cells. In silico modeling of liver metabolism was found to recapitulate known metabolic disturbances as well as previously unrecognized alterations which were confirmed in disease models and in patients. A novel system based on high cloning capacity, non-integrating helper-dependent adenoviral (HDAd) vector expressing the appropriate combination of reprogramming transcription factors was found to be effective in generating iPSC rapidly and at low costs.
In summary, the results of the proposed study have provided novel and effective treatments for inborn errors of metabolism and tools to investigate the pathogenesis and treatments of inborn errors of metabolism.
We showed that phenylbutyrate prevents inactivation by phosphorylation of pyruvate dehydrogenase complex (PDHC) and is effective for treatment of congenital PDHC deficiency and secondary forms of lactic acidosis. Results of these studies have led to a clinical trial that is currently ongoing.
While enhancement of PDHC is effective for therapy of lactic acidosis, we found that inhibiting PDHC has potential for therapy of acute liver failure, independently of its etiology. The development of this therapy was based on our discovery that PDHC and lactic dehydrogenase translocate to the nucleus resulting in detrimental gene expression during acute liver failure. A single small molecule that was found to inhibit both enzymes was effective in reducing liver damage and improving survival in mice with acute liver failure. Therefore, the results of this study might pave the way towards the first non-symptomatic drug treatment for acute liver failure.
We found that hepatic autophagy is an important mechanism for ammonia detoxification because it supports urea synthesis by providing critical intermediates of the cycle, and we generated preclinical data showing that autophagy enhancement has potential for therapy of both primary and secondary causes of hyperammonemia. Hepatic autophagy was found to be triggered by hyperammonemia through an α-ketoglutarate-dependent inhibition of mTOR. While deficiency of autophagy impaired ammonia detoxification, autophagy enhancement by rapamycin and Tat-Beclin-1 increased ureagenesis and protected against hyperammonemia in a variety of acute and chronic hyperammonemia animal models, including acute liver failure and ornithine transcarbamylase deficiency, the most frequent inherited urea-cycle disorder.
Finally, we generated two novel tools that can be used for future investigation in IEMs and metabolic diseases in general: a computational tool for metabolic pathway analysis and a rapid and efficient tool to generate human iPSC that can be converted in disease-relevant cells. In silico modeling of liver metabolism was found to recapitulate known metabolic disturbances as well as previously unrecognized alterations which were confirmed in disease models and in patients. A novel system based on high cloning capacity, non-integrating helper-dependent adenoviral (HDAd) vector expressing the appropriate combination of reprogramming transcription factors was found to be effective in generating iPSC rapidly and at low costs.
In summary, the results of the proposed study have provided novel and effective treatments for inborn errors of metabolism and tools to investigate the pathogenesis and treatments of inborn errors of metabolism.