ETHNOPHARMACOLOGICAL RELEVANCE: Citrus aurantium L. var. amara Engl. is a folk medicine and dietary supplement popularly used in alleviating indigestion due to food retention and obesity. p-Synephrine, a principal proto-alkaloid in Citrus aurantium L. var. amara Engl., is extensively utilized due to its numerous benefits, particularly its potential to ameliorate obesity. Previous studies of our research demonstrated that p-synephrine had the potential to alleviate insulin resistance (IR) and liver lipid accumulation caused by high-fat diet (HFD), as well as enlargement of cells in adipose tissue. However, the effects of p-synephrine in ameliorating non-alcoholic fatty liver disease (NAFLD) were still unclear.
AIM OF STUDY: To explore the effects of p-synephrine on HFD-induced NAFLD and its mechanisms.
METHODS: NAFLD mice were developed by HFD feeding and treated with p-synephrine once a day for 21 weeks. The protective effects of p-synephrine against NAFLD and its mechanisms were evaluated by OGTT, ITT, biochemical index measurements, H&E, immunofluorescence, Sirius red staining, oil red O staining, immunohistochemistry, RT-qPCR, Western blot, network pharmacology, and molecular docking assays.
RESULTS: The results of network pharmacology suggested that AMPK-α1 might be the core target, and AMPK and insulin signaling pathways might be the key regulatory pathways of p-synephrine to alleviate NAFLD. Molecular docking confirmed AMPK-α1 as a probable direct molecular target. p-Synephrine significantly reduced HFD-induced weight gain of the body, liver, and iWAT. It improved glucose tolerance, insulin tolerance and lipid metabolism disorders caused by HFD. Serum levels of NO, TNF-α, and IL-6 in NAFLD mice were suppressed. AST, ALT, and HYP levels in serum and liver were inhibited. Morphological observation showed p-synephrine alleviated hepatic steatosis and fibrosis. p-Synephrine administration also significantly inhibited hepatic de novo lipogenesis (DNL), as evidenced by its regulation of non-esterified fatty acid (NEFA) and TG contents, as well as SREBP-1c, FASN, and ACC1 mRNA expression levels. p-Synephrine also reversed HFD-induced histopathological changes in iWAT, promoted iWAT browning by increasing UCP1 and PGC-1α expression. Simultaneously, p-synephrine intervention markedly increased phosphorylation levels of IRS-1, PI3K, and Akt, and protein expression of GLUT-4 in iWAT and liver. Expression of TNF-α, IL-6, and IL-1β and NF-κB activation in iWAT and liver were attenuated through the treatment of p-synephrine. Further assays showed that p-synephrine intervention potently regulated AMPK pathway in iWAT and liver of mice.
CONCLUSION: This investigation proposed that p-synephrine had the potential to ameliorate HFD-induced NAFLD by regulating liver-adipose axis through AMPK/NF-κB pathway.
