Citrus p-Synephrine Improves Energy Homeostasis by Regulating Amino Acid Metabolism in HFD-Induced Mice

Abstract

p-Synephrine is a common alkaloid widely distributed in citrus fruits. However, the effects of p-synephrine on the metabolic profiles of individuals with energy abnormalities are still unclear. In the study, we investigated the effect of p-synephrine on energy homeostasis and metabolic profiles using a high fat diet (HFD)-induced mouse model. We found that p-synephrine inhibited the gain in body weight, liver weight and white adipose tissues weight induced by HFD. p-Synephrine supplementation also reduced levels of serum total cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C) but not to a statistically significant degree. Histological analysis showed that HFD induced excessive lipid accumulation and glycogen loss in the liver and adipocyte enlargement in perirenal fat tissue, while p-synephrine supplementation reversed the changes induced by HFD. Moreover, HFD feeding significantly increased mRNA expression levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) and reduced the mRNA expression level of interleukin-10 (IL-10) compared to the control group, while p-synephrine supplementation significantly reversed these HFD-induced changes. Liver and serum metabolomic analysis showed that p-synephrine supplementation significantly altered small molecule metabolites in liver and serum in HFD mice and that the changes were closely associated with improvement of energy homeostasis. Notably, amino acid metabolism pathways, both in liver and serum samples, were significantly enriched. Our study suggests that p-synephrine improves energy homeostasis probably by regulating amino acid metabolism in HFD mice, which provides a novel insight into the action mechanism of p-synephrine modulating energy homeostasis.

Keywords: HFD; amino acid; citrus; energy homeostasis; metabolome; p-synephrine.

Figure 1

The effect p-synephrine supplementation on HFD-induced mice: (A) changes in body weight during the 8-week intervention period, (B) body weight in the 7th week, (C) body weight in the 8th week, (D) average daily food intake per mouse, (E) liver weight of mice, (F) perirenal fat tissue weight of mice, (G) subcutaneous fat tissue weight of mice, and (H) epididymal fat tissue weight of mice. The results were considered statistically significant when p < 0.05 between groups. * p < 0.05; ** p < 0.01; *** p < 0.001; ns, not significant.

Figure 2

The effect of p-synephrine supplementation on serum lipid levels: (A) serum TC content, (B) TG content, (C) HDL-C content and (D) LDL-C content. The results were considered statistically significant when p < 0.05 between groups. * p < 0.05; ** p < 0.01; *** p < 0.001; ns, not significant.

Figure 3

Morphological observation and histopathological analysis of liver and adipose tissues: (A) representative images of liver tissue; (B) representative images of white adipose tissues and brown fat tissue with epididymal fat, perirenal fat, subcutaneous fat, and brown fat shown in sequence from top to bottom; (C) representative images of H&E staining of liver tissue; (D) representative images of PAS staining of liver tissue; and (E) representative images of H&E staining of subcutaneous fat tissue.

Figure 4

The effect of p-synephrine intervention on the mRNA expression levels of inflammatory cytokines: (A) TNF-α, (B) IL-1β, (C) IL-6, and (D) IL-10. The results were considered statistically significant when p < 0.05 between groups. * p < 0.05; ** p < 0.01; *** p < 0.001; ns, not significant.

Figure 5

Liver metabolome analysis and heatmap of metabolite distribution among different treatment groups.

Figure 6

Liver metabolome analysis and representative results: (A) metabolites with significant inter-group differences and (B) metabolic pathways significantly enriched by differential metabolites.

Figure 7

Representative results from serum metabolome analysis: PCA analysis of datasets (A) under the positive ion model and (B) under the negative ion model; volcano plots from difference analysis (C) between the CON group the and HFD group and (D) between the HFD group and the p-synephrine intervention group; (E) VIP values used to reflect differences among multiple groups; and (F) metabolic pathways significantly enriched by differential metabolites.

Figure 8

Pearson’s correlation analysis revealed relationships between HFD-induced symptoms and differential metabolites in liver and serum. Pentaenoylcarnitine means (5Z,8Z,10E,14Z,17Z)-12-hydroxyicosa-5,8,10,14,17-pentaenoylcarnitine. * p < 0.05; ** p < 0.01.