Development of a ¹³C-glycocholic acid blood test to assess bacterial metabolic activity of the small intestine in canines

The objectives of this study were to establish optimal doses of ¹³C-glycocolic acid (GCA) for use in a GCA blood test as a marker for canine small intestinal bacterial metabolic activity. Four doses of GCA were administered orally to 8 healthy dogs. Blood samples were collected at various time points up to 480 min. The percent dose/min of ¹³C administered as GCA (PCD) and cumulative PCD (CUMPCD) were determined by fractional mass spectrometry. No dog showed any clinically obvious side effects. Doses of 1 and 2 mg/kg of bodyweight (BW) led to a significant increase in PCD and CUMPCD (P < 0.001). The mean CUMPCD was significantly higher for the 1 mg/kg BW dose compared with the 2 and 4 mg/kg BW doses (P < 0.05). Administration of 1 mg/kg BW of ¹³C-glycocholic acid led to an increase in CUMPCD over baseline in gas extracted from blood samples and appears to be the best parameter to evaluate for future clinical studies.