Gene Expression Profiling in Liver of Mice Fed a High-Fat Diet Supplemented With Watermelon Flesh, Arginine, or Citrulline Shows Similar Pattern Changes

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Abstract Objectives Watermelon is a nutrient-dense fruit known to contain high levels or arginine and citrulline; these two compounds may influence the nitric oxide pathway, vasodilation, and thus be hypotensive. We tested the hypothesis that when C57BL/6J male mice fed a high-fat diet (HF) had additions to the HF diet of either watermelon flesh (WF), arginine (ARG) or citrulline (CIT), changes in gene expression patterns would occur vs. those seen in HF. Further, we hypothesize that patterns of expression seen in WF, ARG, and CIT groups would be somewhat similar based on increased dietary levels of ARG and CIT in all three groups. Methods Following prior work (Becraft et al.; 2018, Egea et al. 2020), groups of mice were provided either a low-fat diet (LF, 10% kcal fat), high-fat diet (HF, 45% kcal fat), HF plus Watermelon Flesh (WF), HF plus 1% (w/w) arginine (ARG) or 1% (w/w citrulline (CIT) for 10 weeks. Watermelon flesh was provided at 10% of total energy. After ten weeks, animals were euthanized, and liver total RNA was isolated using Trizol. Total RNA was then used for gene expression analysis (N = 4 per group) using Clariom S microarrays and TAC analysis software (ThermoFisher). Results Mice fed WF, ARG, and CIT had several shared canonical pathways of gene expression, including eicosanoid metabolism via cytochrome P450 monooxygenases and exercise-induced circadian rhythm (All P < 0.05). Intake of WF and ARG significantly up-regulated both Cyp2c9 and Cyp2c38 mRNA levels (P < 0.05). The Bst2 gene was significantly down-regulated in all three groups compared to HF mice (P < 0.05). The Cyp2b9 gene was upregulated ∼10.7 fold in WF, and > 1000-fold in ARG mice (P < 0.05). Conclusions We demonstrated that when added to a HF diet, WF, ARG, and CIT all produced a change in hepatic gene expression in male mice. Possibly due to the close relationship of ARG and CIT metabolism, and high content of ARG and CIT in WF, expression patterns observed in all three groups demonstrated a high degree of similarity. Several genes, including Cyp2c9, Cyp2c38, and Elvol5 were up-regulated; these genes may be involved in modifying steroids and arachidonic acid and other long-chain fatty acids. Funding Sources National Watermelon Promotion Board.