This article describes a rapid UPLC‐MS/MS method to quantitate novel bile acids in biological fluids and the evaluation of their diagnostic potential in Niemann‐Pick C (NPC). Two new compounds, NPCBA1 (3β‐hydroxy,7β‐N‐acetylglucosaminyl‐5‐cholenoic acid) and NPCBA2 (probably 3β,5α,6β‐trihydroxycholanoyl‐glycine), were observed to accumulate preferentially in NPC patients: median plasma concentrations of NPCBA1 and NPCBA2 were 40‐ and 10‐fold higher in patients than in controls. However, NPCBA1 concentrations were normal in some patients because they carried a common mutation inactivating the GlcNAc transferase required for the synthesis of this bile acid. NPCBA2, not containing a GlcNAc moiety, is thus a better NPC biomarker.

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Bile acids, the metabolites of cholesterol, are signaling molecules that play critical role in many physiological functions. They undergo enterohepatic circulation through various transporters expressed in intestine and liver. Human organic anion-transporting polypeptides (OATP) 1B1 and OATP1B3 contribute to hepatic uptake of bile acids such as taurocholic acid. However, the transport properties of individual bile acids are not well understood. Therefore, we selected HEK293 cells overexpressing OATP1B1 and OATP1B3 to evaluate the transport of five major human bile acids (cholic acid, chenodeoxycholic acid, deoxycholic acid, ursodeoxycholic acid, lithocholic acid) together withtheir glycine and taurine conjugates via OATP1B1 and OATP1B3. The bile acids were quantified by liquid chromatography-tandem mass spectrometry. The present study revealed that cholic acid, chenodeoxyxcholic acid, and deoxycholic acid were transported by OATP1B1 and OATP1B3, while ursodeoxycholic acid and lithocholic acid were not significantly transported by OATPs. However, all the conjugated bile acids were taken up rapidly by OATP1B1 and OATP1B3. Kinetic analyses revealed the involvement of saturable OATP1B1- and OATP1B3-mediated transport of bile acids. The apparent Km values for OATP1B1 and OATP1B3 of the conjugated bile acids were similar (0.74–14.7 μM for OATP1B1 and 0.47–15.3 μM for OATP1B3). They exhibited higher affinity than cholic acid (47.1 μM for OATP1B1 and 42.2 μM for OATP1B3). Our results suggest that conjugated bile acids (glycine and taurine) are preferred to unconjugated bile acids as substrates for OATP1B1 and OATP1B3.

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acetylglucosamine; HQC, high quality control; LC/MS/MS, liquid chromatography/tandem mass spectrometry; LQC, low quality control; MQC, middle quality control; NPC, Niemann-Pick disease type C; NPC1, NPC intracellular cholesterol transporter 1; NPC2, NPC intracellular cholesterol transporter 2; Niemann-Pick disease type C; S7B-Δ 5-CA, 3β-sulfooxy-7β-hydroxy-5-cholen-24-oic acid; S7O-Δ 5-CA, 3β-sulfooxy-7-oxo-5-cholen-24-oic acid; SNAG-Δ 5-CA, nonamidated 3βsulfooxy-7β-N-acetylglucosaminyl-5-cholen-24-oic acid; SNAG-Δ 5-CG, glycineamidated 3β-sulfooxy-7β-N-acetylglucosaminyl-5-cholen-24-oic acid; SNAG-Δ 5-CT, taurine-amidated 3β-sulfooxy-7β-N-acetylglucosaminyl-5-cholen-24-oic acid; SRM, selected reaction monitoring; ROC, receiver operating characteristic.

to wild-type DPD. Moreover, the band patterns observed in the immunoblots of blue native gels indicated that DPD dimerization is required for enzymatic activity in DPD.Thus, the detection of rare DPYD variants might facilitate severe adverse effect prediction of 5-FU-based chemotherapy in the Japanese population.

In steatotic livers of mice, hypoxia up-regulates expression of HIF1A, which reduces expression of AQP8 and concentrates biliary lipids via suppression of water secretion from hepatocytes. This promotes cholesterol gallstone formation. Livers from patients with NAFLD and gallstones express higher levels of HIF1A than livers from patients with NAFLD without gallstones.