Arginine

證據等級: L5

預測適應症: 10 個

Arginine: From Hyperammonemia / Urea Cycle Support to Gastroparesis

One-Sentence Summary

Arginine (L-Arginine) is a semi-essential amino acid with established clinical use in hyperammonemia management and urea cycle disorders, and is the sole endogenous precursor of nitric oxide (NO) via nitric oxide synthase (NOS). The TxGNN model predicts it may be effective for Gastroparesis, with mechanistic support from 10 preclinical publications demonstrating that arginine depletion directly causes gastroparesis through disruption of nitrergic pyloric sphincter relaxation. Current evidence is entirely preclinical (L4); no human clinical trials specifically investigating L-arginine for gastroparesis have been identified.

Quick Overview

Item	Content
Original Indication	No approved indication registered in Singapore (commonly used for hyperammonemia / urea cycle disorders and growth hormone stimulation testing)
Predicted New Indication	Gastroparesis
TxGNN Prediction Score	99.42%
Evidence Level	L4 (animal/preclinical mechanistic studies)
Singapore Market Status	✗ Not Marketed
Number of Registrations	0
Recommended Decision	Hold — Pursue as Research Question

Why is This Prediction Reasonable?

L-Arginine is the sole endogenous substrate for nitric oxide synthase (NOS), the enzyme that converts arginine into nitric oxide (NO) and citrulline. In the gastrointestinal tract, NO is the primary inhibitory neurotransmitter of the enteric nitrergic system, mediating smooth muscle relaxation — particularly at the pyloric sphincter. Gastroparesis is characterised by delayed gastric emptying, a condition in which impaired pyloric relaxation (due to loss of nitrergic signalling) plays a central pathophysiological role.

The mechanistic link has been experimentally confirmed at the molecular level. PMID 25057793 (Endocrinology, 2014) directly demonstrated that oral dexamethasone administration in mice caused gastric enlargement from gastroparesis specifically through depletion of L-arginine via glucocorticoid receptor transactivation — an effect entirely abolished in GR(dim) mutant mice lacking transactivation capacity. This positions arginine deficiency not merely as a correlate, but as a causal driver of gastroparesis. Complementarily, PMID 35380456 (Am J Physiol Gastrointest Liver Physiol, 2022) showed that impaired nitrergic relaxation of the pyloric sphincter — due to reduced neuronal NOS (nNOS) expression — directly produces gastroparesis in a Parkinson's disease rat model.

Taken together, the biological rationale for L-arginine supplementation in gastroparesis is mechanistically coherent: restoring arginine bioavailability could replenish NO synthesis in the enteric nervous system, facilitating pyloric relaxation and normalising gastric emptying. However, this pathway has not yet been validated in human subjects, and the translation from animal models to clinical practice requires formal investigation.

Clinical Trial Evidence

No clinical trials specifically investigating L-arginine for gastroparesis were identified. The only trial returned by the database search is a mismatch:

Trial Number	Phase	Status	Enrollment	Key Findings
NCT01702051	N/A	Unknown	150	Observational study of autologous pancreatic islet cell transplantation after pancreatectomy for glycaemic control — no relevance to arginine treatment for gastroparesis; classified as a search mismatch

Currently no clinical trials directly studying L-arginine supplementation for gastroparesis are registered.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
25057793	2014	Animal (mouse)	Endocrinology	Most relevant. Glucocorticoids cause gastroparesis in mice by depleting L-arginine; effect abolished in GR(dim) mutant mice — direct causal evidence linking arginine depletion to gastroparesis
35380456	2022	Animal (rat)	Am J Physiol Gastrointest Liver Physiol	Impaired nitrergic (nNOS-dependent) relaxation of pyloric sphincter in 6-OHDA Parkinson's disease rat model produces gastroparesis; quantifies nNOS reduction
23639814	2013	Animal (mouse)	Am J Physiol Gastrointest Liver Physiol	Tetrahydrobiopterin (BH4) deficiency — an essential NOS cofactor — induces gastroparesis in newborn mice, further supporting the NO pathway
18312542	2008	Animal (rat)	Neurogastroenterol Motil	Decreased nNOS expression in jejunum of diabetic BB-rats; establishes nitrergic dysfunction as a key mechanism in diabetic gastroparesis
19023028	2009	Animal (dog)	Am J Physiol Gastrointest Liver Physiol	Synchronized gastric electrical stimulation restores vagotomy-impaired gastric accommodation via the nitrergic pathway in dogs
31984783	2020	Animal (rat)	Am J Physiol Gastrointest Liver Physiol	Sacral nerve stimulation increases gastric accommodation in rats through a spinal afferent / vagal efferent / nitrergic mechanism
21193530	2011	Animal	Am J Physiol Gastrointest Liver Physiol	Hyperglycemia inhibits gastric motility via nodose ganglia K(ATP) channels; relevant to the diabetic gastroparesis context
18322959	2008	Animal	World J Gastroenterol	Ghrelin and GHRP-6 improve gastric motor function in diabetic mice with gastroparesis; identifies prokinetic targets in the same disease model
8194696	1994	Animal (rat)	Gastroenterology	Food protein-induced anaphylaxis produces delayed gastric emptying in sensitised rats; mediators of gastroparesis explored
33867519	2021	Case Report	Am J Case Reports	MELAS patient (mitochondrial disorder) with gastroparesis; lifestyle normalisation of lactate — indirect metabolic/mitochondrial connection to NO biology

Singapore Market Information

Arginine (DB00125) is currently not registered with the Health Sciences Authority (HSA) of Singapore. There are no product licences on record, and the drug has no approved marketed formulations in Singapore.

Safety Considerations

Please refer to the package insert for safety information.

Note on data gaps: TFDA package insert warnings, contraindications, and formal drug-drug interaction data were not available at the time of this assessment. No drug interactions were identified in the DDI database query. These gaps should be remediated before advancing to clinical feasibility evaluation.

Conclusion and Next Steps

Decision: Hold — Pursue as Research Question

Rationale: The mechanistic case for L-arginine in gastroparesis is biologically well-grounded — arginine is the direct rate-limiting substrate for the nitrergic pathway that controls pyloric sphincter relaxation, and animal studies directly demonstrate that arginine depletion causes gastroparesis. However, all supporting evidence remains at the preclinical level (L4), no human proof-of-concept data exist, and arginine is not registered in Singapore, requiring a full regulatory pathway.

To proceed, the following is needed:

Proof-of-concept human study: Pilot trial of L-arginine supplementation in patients with documented nitrergic-deficient gastroparesis (e.g., diabetic or post-viral gastroparesis with confirmed reduced nNOS expression on gastric biopsy)
Dose optimisation: Pharmacokinetic/pharmacodynamic studies to establish the dose required to meaningfully raise enteric NO bioavailability without systemic cardiovascular effects (blood pressure reduction)
Biomarker strategy: Define measurable endpoints — gastric emptying scintigraphy, breath test, or wireless motility capsule — as primary outcomes for future trials
MOA documentation: Retrieve complete DrugBank mechanism-of-action data to formally characterise arginine's pharmacological profile
Safety review: Assess arginine's safety in target populations (diabetic patients, elderly) including risk of hypotension, hyperkalemia, and interactions with antihypertensives or insulin
Regulatory pathway: Consult HSA on requirements for registering arginine as a pharmaceutical product in Singapore (distinct from its status as a nutritional supplement)
Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.