Intermittent Parenteral Nutrition Reduces Peroxisomal Lipid Oxidation Pathway Transcripts Compared to Continuous Isocaloric Infusion

Introduction: Total parenteral nutrition (TPN) is a lifesaving therapy for patients unable to use enteral nutrition. However, continuous TPN administration can lead to hepatic dysfunction. Introducing a cyclic infusion schedule, with a 6–8-hour cessation period each day, has been shown to improve circulating markers of hepatic function in human patients. Despite these clinical benefits, the underlying metabolic mechanisms remain largely unexplored. This study aimed to model TPN-induced hepatic dysfunction in mice and use untargeted transcriptomic analysis to investigate how cyclic infusions improve outcomes. Methods: 12 male C57B/6 mice aged 9-11 weeks were randomly assigned to 3 groups: chow control (n=4), continuous-rate infusion (CR, n=4), and sinusoidal-rate infusion (SR, n=4). For infused animals, the jugular vein was cannulated with a 0.12 mm diameter silicon catheter attached to TPN syringes on a programmable pump. Mice were infused with 7.8 mL/d of a TPN formula (21.5% dextrose, 5.6% amino acids, 2% Intralipid-20) at a continuous rate (Continuous) or sinusoidal variable-rate (Intermittent) rate for 5 days, after which animals were humanely euthanized and tissues were weighed, processed, and snap frozen. Total mRNA was isolated and purified from hepatic tissues before short-read bulk mRNA sequencing on an Illumina Novaseq platform. Differentially expressed genes (DEGs) were mapped to the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) databases for pathway analysis. Paraffin-embedded hepatic tissues were stained with PMP70 antibodies (Abcam #AB3421) and signal quantified with ImageJ software. Results: A total of 492 DEGs (|LFC| > 0.5, p < 0.05) were identified between the continuous and intermittent groups. GO and KEGG analyses revealed acyl-CoA metabolic process (GO: 0006637), oxidoreductase activity (GO:0016614, GO:0016616), peroxisome (GO:0005777), fatty acid degradation (mmu00071), biosynthesis of unsaturated fatty acids (mmu01040), were upregulated in CR. After applying Benjamini-Hochberg’s false detection rate to adjust for multiple comparisons, differences in 4 genes remained statistically significant (i.e., q < 0.05). Many of these genes, including Acaa1b (LFC = 0.87, p < 0.001, q = 0.03), Ald3a2 (LFC = 0.79, p < 0.001, q = 0.05), ACOT3 (LFC = 0.90, p = 0.002), ACOT4 (LFC = 0.64, p < 0.001, q = 0.04), CD36 (LFC = 0.77, p = 0.001), and Cyp4a15 (LFC = 1.02, p = 0.02), are involved in lipid processing and some specifically in peroxisomal lipid oxidation. Immunofluorescent staining of the peroxisome marker PMP70 in hepatic tissues was elevated in the Continuous group (mean = 11.31 ± 0.93%), compared to control (mean = 8.53 ± 0.97%), but not in the Intermittent group (mean = 8.54 ± 1.42%). Discussion: Untargeted transcriptomic analyses revealed that an intermittent infusion paradigm, in contrast to continuous infusion, protected hepatic tissue against elevated expression of genes involved in peroxisomal lipid oxidation. Aligning with the transcriptomic findings, immunofluorescent staining confirmed the peroxisome marker PMP70 was elevated only under continuous infusion. Peroxisomal lipid oxidation, a PPAR-inducible process, typically accounts for less than 15% of lipid total lipid oxidation. However, increased intracellular fatty acid levels can upregulate peroxisomal oxidation, leading to elevated oxidative stress within cells. Reactive oxygen species are key mediators in immune activation that drive liver disease progression in TPN. These data identify a critical pathway by which cyclic infusions mitigate TPN-induced hepatic dysfunction, offering valuable insights for optimizing this lifesaving nutrition therapy. NIH U01CA272541; R01DK113788; T32DK007665 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.