LaRusso, N. F.

Background: Patients with primary sclerosing cholangitis (PSC) are at risk for developing gallbladder neoplasia (GBN) and biliary neoplasia, including cholangiocarcinoma (CCA), because of chronic inflammation and an underlying field effect. However, the risk of CCA after GBN detection in those with PSC remains poorly understood. We aimed to determine if the incidence of CCA is higher in those with GBN. Methods: We conducted a retrospective review of adult patients with large-duct PSC seen at Mayo Clinic between January 1, 1995, and December 31, 2019. Incidence rates for CCA development were calculated. Cox regression analyses were performed to determine features associated with CCA development beginning at the time of PSC diagnosis. Results: Our study included 1,829 patients with PSC. CCA and GBN developed in 334 (18.26%) and 71 individuals (3.88%), respectively. Among those with GBN, 14 (19.72%) developed CCA. The annual incidence of CCA was nearly twofold higher in patients with GBN (4.34% versus 2.21%). GBN was associated with CCA in an unadjusted analysis (hazard ratio 2.14 [95% CI 1.16–3.94]). When adjusting for other predictors of CCA, an association between GBN and CCA may remain. Conclusions: While few patients with PSC develop GBN, this subgroup is more likely to develop CCA. Consequently, once GBN is detected, clinicians should consider more intensive screening for CCA.

While previous work has demonstrated that monosaccharides can be absorbed from bile, studies of sugar transport by the biliary, epithelia (i.e., cholangiocytes) are lacking. Using a novel model of polarized rat cholangiocytes in primary culture, designated normal rat cholangiocytes (NRC), we examined directly the uptake and transcellular transport of a nonmetabolizable monosaccharide, methyl alpha-D-glucopyranoside (AMG). When the apical or basolateral domain of cholangiocytes was exposed to radiolabeled AMG or sucrose (control), only apical absorption of AMG was evident. This apical uptake was time dependent, saturable, and significantly inhibited (> or = 90%) by removal of Na+ or in the presence of phlorizin (0.1 mM), a competitive inhibitor of the Na(+)-glucose cotransporter. The transcellular flux of AMG was also polar (i.e., apical to basolateral). Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed the presence of the transcript for the specific Na(+)-glucose cotransporter SGLT1 in NRC and in freshly isolated cholangiocytes but not in purified hepatocytes; in contrast, the transcript for SGLT2 was absent in all liver samples. In situ RT-PCR on frozen sections of normal rat liver showed that SGLT1 was expressed exclusively in cholangiocytes. Immunoblot analysis using a specific polyclonal antibody for the facilitative glucose transporter GLUT1 demonstrated it to be present in vesicles derived from NRC enriched in basolateral plasma membrane domains. Our data are consistent with the concept that SGLT1 is present on the apical domain of biliary epithelia and, in conjunction with GLUT1 on the basolateral domain, accounts for glucose absorption from bile.