Hepatic fatty acid synthesis and oxidation were studied in rats after low-fat (LF) or high-fat (HF) total parenteral nutrition (TPN) to ascertain the relationship between these metabolic processes and hepatic lipid content. Hepatic total lipid was elevated ≈30% with LF-TPN and ≈125% with HF-TPN compared to mean value of stock-diet fed rats. Five lipogenic enzymes were measured: acetyl CoA carboxylase (ACX), fatty, acid synthetase, glucose-6-phosphate dehydrogenase, malic enzyme and ATP-citrate lyase. Activity of ACX decreased significantly with LF-TPN and HF-TPN, compared to stock-diet feeding. Fatty acid oxidation was assessed by measuring liver levels of carnitine, mitochondrial carnitine palmitoyltransferase (CPT) and palmitate oxidation in vitro. Both CPT activity and palmitate oxidation increased significantly with HF-TPN compared to diet-fed or LF-TPN, whereas liver carnitine content was unaffected by either TPN. Mild fatty liver occurred with LF-TPN despite normal fatty acid oxidation parameters and lack of lipogenic enzyme stimulation. Fatty liver occurred with HF-TPN despite a significant increase in fatty acid oxidation and marked inhibition of ACX activity.
- Carnitine palmitoyltransferase
- Lipogenic enzymes
- Parenteral nutrition
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Nutrition and Dietetics