Eriodictyol regulates white adipose tissue browning and hepatic lipid metabolism in high fat diet-induced obesity mice via activating AMPK/SIRT1 pathway

Abstract

Ethnopharmacological relevance: Blossom of Citrus aurantium L. var. amara Engl. (CAVA) has been popularly consumed as folk medicine and dietary supplement owing to its various beneficial effects and especially anti-obesity potential. Our previous study predicted that eriodictyol was probably one of the key active compounds of the total flavonoids from blossom of CAVA. However, effects of eriodictyol in anti-obesity were still elusive.

Aim of the study: This study was performed to explore the precise role of eriodictyol in white adipose tissue (WAT) browning and hepatic lipid metabolism, and simultaneously, to verify the impact of eriodictyol on the total flavonoids of CAVA in losing weight.

Materials and methods: The pancreas lipase assay was conducted and oleic acid-induced HepG2 cells were established to preliminarily detect the lipid-lowering potential of eriodictyol. Then, high fat diet-induced obesity (DIO) mouse model was established for in vivo studies. The biochemical indicators of mice were tested by commercial kits. The histopathological changes of WAT and liver in mice were tested by H&E staining, Oil Red O staining and Sirius Red staining. Immunohistochemical, Western blot assay, as well as RT-qPCR analysis were further performed. Additionally, molecular docking assay was used to simulate the binding of eriodictyol with potential target proteins.

Results: In vitro studies showed that eriodictyol intervention potently inhibited pancreatic lipase activity and reversed hepatic steatosis in oleic acid-induced HepG2 cells. Consistently, long-term medication of eriodictyol also effectively prevented obesity and improved lipid and glucose metabolism in diet-induced obesity mice. Obesity-induced histopathological changes in iWAT, eWAT and BAT, and abnormal expression levels of IL-10, IL-6 and TNF-α in iWAT of DIO mice were also significantly reversed by eriodictyol treatment. Eriodictyol administration significantly and potently promoted browning of iWAT by increasing expression levels of thermogenic marker protein of UCP1, as well as brown adipocyte-specific genes of PGC-1α, SIRT1 and AMPKα1. Further assays revealed that eriodictyol enhanced mitochondrial function, as shown by an increase in compound IV activity and the expression of tricarboxylic acid cycle-related genes. Besides, eriodictyol addition markedly reversed hepatic damages and hepatic inflammation, and enhanced hepatic lipid metabolism in DIO mice, as evidenced by its regulation on p-ACC, CPT1-α, UCP1, PPARα, PGC-1α, SIRT1 and p-AMPKα expression. Molecular docking results further validated that AMPK/SIRT1 pathway was probably the underlying mechanisms by which eriodictyol acted.

Conclusion: Eriodictyol exhibited significant anti-obesity effect, which was comparable to that of the total flavonoids from blossom of CAVA. These findings furnished theoretical basis for the application of eriodictyol in weight loss.

Keywords: Eriodictyol; Hepatic lipid metabolism; Obesity; White adipose tissue browning.