[41, 42] Next, screening studies by Sveger and Eriksson documented that 15%-20% of infants with α-1-AT deficiency (PiZZ) present with neonatal cholestasis.[43] In Cincinnati we were greatly aided by our colleague Kevin Bove, a pediatric pathologist, who developed an interest and expertise in interpretation of biopsy findings from children with a variety of hepatobiliary disorders.[9, 44] It became clear that if we were to study

diseases such as neonatal cholestasis we needed to understand the normal physiologic events occurring at this stage of liver development. A series of adaptations must occur during transition of the infant to extrauterine life; specifically, the liver of a newborn must conform to the unique metabolic demands that result from discontinuation of the bidirectional exchange of nutrients through the placenta and the biotransformation mechanisms shared with the mother.[31] These BYL719 clinical trial maturational changes as the transition is made from an intrauterine existence to independent life occur predominantly through enzyme induction triggered by substrate and hormonal input. The efficiency with which these anatomic and physiologic adaptations

are established determines the ability of the newborn to cope with a new environment.[31, 45, 46] Historically, there are dramatic examples of inefficiency of hepatic metabolic and excretory function in early life, most notably “physiologic jaundice” (unconjugated hyperbilirubinemia characteristic of the newborn). We therefore were not surprised to discover an analogous phase, which we termed “physiologic cholestasis.” this website We documented that in newborns there is a cholestatic phase of liver development, manifest by delayed hepatic clearance of endogenous and exogenous compounds.[45-47] The morphological and functional differences that characterize the

neonatal versus the mature liver are responsible not only for a decrease in bile flow but also the production of abnormal bile acids. This renders the developing liver uniquely vulnerable to exogenous insults such as E. coli sepsis with endotoxemia, the intravenous administration of amino acids during total parenteral nutritional support, and hypoxia/hypoperfusion.[44, 48, 49] Good fortune once again intervened—my first fellow in Pediatric Gastroenterology Florfenicol at CCHMC was Fred Suchy, who enthusiastically joined me for studies further delineating normal and abnormal hepatobiliary function in neonates. We were able to document that multiple steps in the enterohepatic circulation were reduced in early life, evidenced by elevated serum bile acid levels, reduced intraluminal bile acid concentrations, and reduced hepatocellular transport (uptake and excretion) of bile acids. Another striking feature of “physiologic cholestasis” was the presence of a large proportion of “atypical” bile acids (yet typical for the developmental phase) that are not found in adult human bile.