Urine-based Detection of Congenital Portosystemic Shunt in C57BL/6 Mice

Abstract

Sporadic occurrence of congenital portosystemic shunt (PSS) at a rate of ∼1 out of 10 among C57BL/6 mice, which are widely used in biomedical research, results in aberrancies in serologic, metabolic, and physiologic parameters. Therefore, mice with PSS should be identified as outliers in research. Accordingly, we sought methods to, reliably and efficiently, identify PSS mice. Serum total bile acids ≥ 40 µM is a bona fide biomarker of PSS in mice but utility of this biomarker is limited by its cost and invasiveness, particularly if large numbers of mice are to be screened. This led us to investigate if assay of urine might serve as a simple, inexpensive, non-invasive means of PSS diagnosis. Metabolome profiling uncovered that Krebs cycle intermediates, i.e., citrate, α-ketoglutarate, and fumarate, were strikingly and distinctly elevated in the urine of PSS mice. We leveraged the iron-chelating and pH-lowering properties of such metabolites as the basis for three urine-based PSS screening tests: urinary iron-chelation assay, pH strip test, and phenol red assay. Our findings demonstrate the feasibility of using these colorimetric assays, whereby their readout can be assessed by direct observation, to diagnose PSS in an inexpensive, rapid, and non-invasive manner. Application of our urinary PSS screening protocols can aid biomedical research by enabling stratification of PSS mice, which, at present, likely confound numerous ongoing studies.

Digestive dynamics: Unveiling interplay between the gut microbiota and the liver in macronutrient metabolism and hepatic metabolic health

“…It may be congenital, or surgically created to alleviate portal hypertension in cirrhotic patients. Intriguingly, some liver cirrhosis patients develop spontaneous PSS and exhibit hyperammonemia and HE (Jayakumar & Norenberg, 2018 ; Lv et al., 2022 ; Yeoh et al., 2022 , 2023 ). Since the liver is bypassed in the presence of PSS, it is interesting to speculate unprocessed diet and gut microbe‐derived metabolites in the circulation.…”

“…Mice with congenital PSS are highly susceptible to cholestatic liver cancer when fed diets containing inulin, a plant‐derived fermentable fiber. Further, mice deficient in AhR have 100% incidence of PSS (Yeoh et al., 2023 ). Thus, PSS underscores the importance of connectivity between gut, gut microbiota, and liver.…”