A. Munoz Abraham1,3, A. Price2, K. Blomenkamp2, C. Manithody2, H. Osei1,3, P. Rajalakshmi2, V. Kakrala2, C. Denton2,3, J. Krebs2, J. Friend2, W. Phillips2, M. Westrich2, J. Greenspon1,3, G. A. Villalona1,3, A. Jain2,3 1Saint Louis University School Of Medicine,Pediatric Surgery,St. Louis, MO, USA 2Saint Louis University School Of Medicine,Pediatrics,St. Louis, MO, USA 3Cardinal Glennon Children’s Hospital,St. Louis, MO, USA
Background:
Total Parenteral Nutrition (TPN) provides all nutritional needs intravenously. It remains an essential lifesaving therapy, however despite widespread use; enthusiasm is tempered due to significant side effects and a lack of understanding into mechanisms leading to TPN injury. Using a novel ambulatory TPN piglet surgical model, developed in our lab to recapitulate long term human TPN delivery we tested our hypothesis that an altered luminal signaling is a major driver for TPN injury.
Methods:
30 animals were randomly allocated to receive TPN (n=22) or enteral nutrition (EN, n=8) for approximately 3 weeks. A subgroup of TPN animals (n=14) underwent bowel resection. Gut, liver and serum were collected. Samples underwent histology, serum biochemistry, ELISA and western blot assays. Pair wise t-test for normally distributed data otherwise pairwise Mann Whitney U test were conducted. All tests were 2 tailed using a significance level of 0.05.
Results:
We successfully placed surgical catheters and achieved bowel resection in animals. TPN resulted in cholestatic liver injury with significant bilirubin elevation and hepatomegaly, p=0.046. Stellate interlobular fibrosis was noted with TPN. TPN caused an increase in hepatic inflammation noted on CD3 immunohistochemistry (p=0.005). Interestingly, no significant differences in serum ALT were noted. TPN resulted in marked gut atrophy and reduction in muscularis mucosa compared to EN animals demonstrated grossly and histologically. The mean, (±SE) for gut density (g/cm) and villous / crypt (V/C) ratio was 6.34±1.67, 2.67±0.18 for EN vs 2.96±0.34, 2.06±0.16 for TPN (p=0.002, p=0.03 respectively). While the key luminal signaling regulators, gut FXR, TGR5, EGF and MAPKinase were significantly downregulated with TPN (p<0.05), CyP7A1 was several folds higher in TPN animals (p<0.05). Additionally, gut resection (SBS animals) impaired improvement in cholestasis or hepatic fibrosis despite luminal agonists (CDCA) secondary to impaired gut-systemic signaling. As expected, in SBS activation of gut FXR and apical sodium dependent BA transporter was noted with CDCA vs TPN (qPCR p=0.02, p=0.04; respectively). CDCA, however preserved gut mass (gm/cm, p=0.04) demonstrated grossly and histologically.
Conclusion:
Our study reports novel finding of an increased CD3 staining, interlobular stellate hepatic fibrosis and muscularis mucosa reduction associated with TPN therapy. We also noted significant alteration is key hepatobiliary receptors driving luminal signaling and its impairment with gut resection, despite preservation of gut growth with luminal FXR activators. Our study using a novel surgical piglet model presents a paradigm shift to our understanding of TPN injury, as secondary to altered luminal-systemic cross talk.