The effects of lipid-supplemented total parenteral nutrition (TPN) on hepatic and lipoprotein lipase activity in a premature neonatal piglet model
Matthew J Hyde1, Encarnación Amusquivar3, John Laws2, Anne M Corson2, Richard R Geering2, Ian J Lean2, Guy Putet4, Peter F Dodds2, Emilio Herrera3 & Lynne Clarke1
We have previously shown that premature piglets maintained on TPN develop fatty livers, but the underlying mechanisms associated with this response in unknown. The aim of the experiment was to use a piglet model for the premature human neonate on TPN to investigate lipase activity in key tissues.
Piglets were delivered, by Caesarean, two days prematurely. Bilateral jugular catheters were surgically inserted within 6 hours of birth. Six control piglets were fed enterally; six were given TPN supplemented with a lipid emulsion - Intralipid®. Lipoprotein lipase (LPL) activity in the liver, adipose tissue and skeletal muscle was determined by the conversion of 1-14C-triolein to 1-14C-oleic acid. Hepatic lipase (HL) activity in the liver was determined in a similar manner. Plasma concentrations of triacylglyercol (TAG) and non-esterified fatty acids (NEFA) were measured. All in-vivo work was approved by the Home Office.
Compared to enterally-fed piglets, LPL activity was decreased in liver (Enteral: 2994±797; TPN 1220±808) and muscle (Enteral: 409±128; TPN 163±141) in pigs on TPN, but the reverse situation was observed in adipose tissue (Enteral: 1454±869; TPN 3406±872). HL activity was also decreased (P<0.001) in the TPN group (Enteral: 0.835±0.092; TPN 0.252±0.092) and demonstrated a negative correlation with the lipid content of the liver (P<0.01 R2=35.9). Plasma concentrations of TAG and NEFA were similar across the treatments.
In conclusion, it is evident that premature piglets on TPN are able to efficiently remove circulating lipids and these are preferentially taken up by the liver as opposed to adipose tissue. There appears to be a correlation between HL activity and lipid accumulation within the liver. The factors regulating lipase activity during TPN require further study.
MH is funded by a BBSRC studentship. The study was part of Perilip, supported by the EU (QLK1-2001-00138).