Reversing Hyperammonemia in Neuroendocrine Tumors

Hepatic Encephalopathy Without Hyperammonemia in the Setting of Liver Metastases by a Pancreatic Neuroendocrine Tumor

Hepatic encephalopathy (HE) is a neurological impairment that typically occurs in patients with liver dysfunction or portosystemic shunting. Diagnosing HE can be challenging since it requires a process of exclusion. Ammonia is considered a major contributor to HE, though ruling out HE solely based on ammonia levels has the potential for misdiagnosis.  Malignancy infiltration is uncommon as an etiology of HE, although there are reported cases of HE patients with pancreatic neuroendocrine tumors (PNETs) diagnosed by the presence of hyperammonemia. We report a case of a disoriented patient with a PNET and diffuse metastases to the liver who presented without hyperammonemia. After excluding possible etiologies of altered mental status, we diagnosed the patient with HE and started on lactulose, which improved his condition. PNET patients can experience HE without hyperammonemia, and a thorough evaluation to rule out other etiologies is necessary for the diagnosis.

Hyperammonemic Encephalopathy in a Patient with Pancreatic Neuroendocrine Tumor and Portosystemic Shunt

Hyperammonemia can lead to encephalopathy and may be accompanied by a diagnostic dilemma. Imaging as well as biochemical analyses are the cornerstone for identifying possible underlying causes such as severe liver disease or urea cycle defect. We report a case of a patient that presented with neurological deficits based on hyperammonemia in the presence of a large pancreatic neuroendocrine tumor (PNET) and portosystemic shunts in the liver. Prior cases are rather scarce, and the exact mechanism is not fully understood. The case illustrates the added value of a multimodality imaging approach in patients presenting with hyperammonemia-induced encephalopathy.

Marked improvement in hyperammonaemic encephalopathy from multimodal treatment of metastatic neuroendocrine tumour

Gastroenteropancreatic neuroendocrine tumours (GEPNETs) are a heterogenous group of tumours which are rising in incidence. Morbidity and mortality related to these tumours is dependent on the location of metastatic spread. Hyperammonaemia and subsequent encephalopathy has previously been described in GEPNET and is typically associated with a poor prognosis. We describe a case of a 55-year-old woman with hyperammonaemic encephalopathy and a new diagnosis of GEPNET. Given the poor prognosis and the outcomes in this patient group we feel this case highlights the benefit of a multimodality treatment approach including peptide receptor radionucleotide therapy and transarterial chemoembolisation.

Supportive therapy in gastroenteropancreatic neuroendocrine tumors: Often forgotten but important

Neuroendocrine tumors (NETs) are a group of rare and heterogeneous malignancies that can develop in various organs. A significant number of gastroenteropancreatic neuroendocrine tumours (GEP-NETs) is functionally active and presents with symptoms related to the secretion of biologically active substances, leading to the development of distinct clinical syndromes. There are various therapeutic approaches for GEP-NETs, including curative surgery, palliative surgery, local-ablative and loco-regional therapies as well as systemic therapeutic options including peptide receptor radionuclide therapy, cytotoxic therapy, and molecularly targeted therapies. Specific supportive therapy of patients with NETs includes management or prevention of hormone-related clinical syndromes and paraneoplastic states. Supportive therapy plays a key role in NET treatment. Supportive therapy includes debulking surgery and interventional radiologic techniques to reduce tumour bulk or load, as well as systemic medical treatment options to manage or prevent hypersecretion syndromes and treatment-related side effects. Supportive therapies are a type of of comprehensive treatment addressing the patient as a whole person throughout the process of NET treatment. Therefore, supportive therapy also encompasses psychosocial support, expert nursing, nutritional support and management of cancer related pain.

Ammonia Induces Autophagy through Dopamine Receptor D3 and MTOR

Hyperammonemia is frequently seen in tumor microenvironments as well as in liver diseases where it can lead to severe brain damage or death. Ammonia induces autophagy, a mechanism that tumor cells may use to protect themselves from external stresses. However, how cells sense ammonia has been unclear. Here we show that culture medium alone containing Glutamine can generate milimolar of ammonia at 37 degrees in the absence of cells. In addition, we reveal that ammonia acts through the G protein-coupled receptor DRD3 (Dopamine receptor D3) to induce autophagy. At the same time, ammonia induces DRD3 degradation, which involves PIK3C3/VPS34-dependent pathways. Ammonia inhibits MTOR (mechanistic target of Rapamycin) activity and localization in cells, which is mediated by DRD3. Therefore, ammonia has dual roles in autophagy: one to induce autophagy through DRD3 and MTOR, the other to increase autophagosomal pH to inhibit autophagic flux. Our study not only adds a new sensing and output pathway for DRD3 that bridges ammonia sensing and autophagy induction, but also provides potential mechanisms for the clinical consequences of hyperammonemia in brain damage, neurodegenerative diseases and tumors.