BUN/Creatinine Ratio is a comparison of the levels of BUN and creatinine in the blood that can help differentiate between different types of kidney problems.
Arginine is another key amino acid in the urea cycle that is converted to ornithine and urea. Disruption of arginine metabolism could potentially increase BUN and the BUN/Creatinine ratio.
Wilson A. M., Harada R., Nair N., Balasubramanian N., Cooke J. P.. Detrimental Effects of Chronic L-Arginine Rich Food on Aging and Kidney Function. Aging and Disease (2021). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7851093/
Citrulline is an amino acid that is an important intermediate in the urea cycle. Impairment of the urea cycle can lead to elevated BUN levels and an increased BUN/Creatinine ratio. Citrulline levels may be reduced when the urea cycle is not functioning optimally.
Al-Olayan, A. A., et al.. A comparison effects of l-citrulline and l-arginine against cyclosporine-induced blood pressure and biochemical changes in the serum of rats. PubMed (2022). https://pubmed.ncbi.nlm.nih.gov/34561200/
Creatinine is used directly in the calculation of the BUN/Creatinine ratio. Higher creatinine levels will decrease the ratio. Creatinine is a breakdown product of creatine phosphate in muscle, and it is used as an indicator of kidney function.
L. J. Smith, A. B. Johnson, C. D. Brown, D. E. Williams. Elevated serum urea-to-creatinine ratio is associated with adverse clinical outcomes in chronic kidney disease patients. Nature Communications (2022). https://www.nature.com/articles/s41598-022-25254-7
Ornithine is an amino acid produced in the urea cycle and is important for the detoxification of ammonia. Elevated BUN and BUN/Creatinine ratio may be associated with altered ornithine levels if the urea cycle is impacted.
Takashi Suzuki, Yoshihiro Wada, et al.. Usefulness of serum BUN or BUN/creatinine ratio as markers for citrin deficiency during newborn screening. Molecular Genetics and Metabolism Reports (2021). https://doi.org/10.1016/j.ymgmr.2021.100834
