Evaluation of a piglet model for Parenteral Nutrition-associated Cholestasis (PNAC)

Total parenteral nutrition (TPN) is associated with the development of parenteral nutrition-associated liver disease (PNALD) in infants. Parenteral Nutrition-associated Cholestasis (PNAC) is one of the most common metabolic problems associated with TPN. PNAC can be a life threatening complication of TPN in newborn children, and might ultimately results in the need for a liver transplantation. Incidence of PNALD in infants who receive TPN for at least 2 month can be at 50%. Risk factors appear to be multifactorial including immature hepatic function or lack of enteral feeding, and not fully elucidated. Therefore we aimed to establish a piglet model to evaluate the development and progress of PNALD/PNAC, analyze the molecular mechanisms and compare the findings to human PNALD.

It has been shown previously that piglets at birth correspond to preterm infants regarding the developmental stage of their gastrointestinal tract and therefore we choose 3 day old piglets and divided them into two groups. The TPN group (TPN) underwent general surgery to place a central catheter in the external jugular vein followed by application of parenteral nutrition solution (liquid and lipid phase) adjusted to body weight and nutritional needs for 21 d. The control group (K) received formula for infant piglets orally for the same time period. Blood samples were taken during the experiment and on the final day to analyze liver enzymes (ALT, AST, GGT) and functional liver parameters (bilirubin, cholesterol, albumin, triglycerides). Tissue samples of liver, gallbladder, intestine, pancreas, spleen, lung, brain, muscle and fat were either snap frozen in liquid nitrogen or fixed in paraformaldehyde for histochemical analysis. Haematoxylin eosin staining was performed to evaluate cellular structure as well as sirius red staining for elastic or collagenous fibres. Grade of steatosis was determined by oil red O staining. Expression of specific mRNAs of inflammation (TNF-alpha, MCP1, IL 1β), fibrosis (TGFβ, ACTA2, COLα1, TIMP 1) and fat metabolism were quantified by qRT-PCR. Furthermore a score for cholestasis based on bile acid serum levels and histochemical as well as electron microscopy examination was established to evaluate degree and progress of PNAC.