Detection and quantification of d-glucuronic acid in human bile using ¹H NMR spectroscopy: Relevance to the diagnosis of pancreatic cancer

Objective: There are no specific biomarkers available for the definitive diagnosis of pancreatic cancer. Analysis of d-glucuronic acid (GlcUA) in bile could be valuable in this regard. Materials and methods: Bile samples obtained from patients with pancreatic cancer (n = 4), chronic pancreatitis (n = 3) and control patients with biliary obstruction (n = 10) were analyzed by ¹H NMR spectroscopy. GlcUA was quantified from the peak area of the α-¹CH signal (at 5.24 ppm) obtained by deconvolution. Results: GlcUA was detected in human bile by one-dimensional ¹H NMR and two-dimensional ¹H-¹H COSY and TOCSY experiments. Quantification of GlcUA was achieved by measuring the peak area of the α-¹CH signal using CPMG experiment, and the quantities of GlcUA were calibrated to account for the attenuation due to T ₂ relaxation. GlcUA was observed at elevated levels in bile samples obtained from pancreatic cancer patients, whereas it was either absent or found in negligible amounts in control and chronic pancreatitis patients. The reason for the presence of elevated levels of GlcUA could be the hydrolysis of biliary bilirubin diglucuronide by β-glucuronidase, released excessively from pancreatic tissue during the course of malignancy. Conclusion: Analysis of d-glucuronic acid in bile could be valuable in the detection of pancreatic cancer, and detecting GlcUA by in vivo ¹H MRS has the potential to help in the non-invasive diagnosis of pancreatic cancer. Given that only four cancer patients have been studied so far, the new biomarker is regarded as a preliminary finding, but one that warrants further investigation.