Hongzeng Li,Wen Yuan,Yuxin Tian,Feiyue Tian,Yunfei Wang,Xiangrong Sun,Yanling Gong
Eugenol, an active ingredient of many medicinal aromatic plants, has been proved to have the hypolipidemic effect, but its potential mechanism of action is still unknown. This study aimed to investigate whether eugenol regulates liver lipid accumulation in high-fat diet (HFD) induced nonalcoholic fatty liver disease (NAFLD) rats via the gut-brain-liver axis involving glucagon-like peptide-1 (GLP-1). Hepatic vagotomy was performed in NAFLD rats to determine the role of eugenol in regulating hepatic lipid accumulation via vagus nerve. The results showed that after eight weeks of eugenol administration in NAFLD rats, serum total cholesterol (TC), triglyceride (TG) and hepatic TG decreased. However, eugenol showed no significant effect on the increased food intakes and weight gain caused by the HFD. Eugenol promoted the secretion of GLP-1 into the blood, increased GLP-1 receptor (GLP-1R) expression in the duodenum , liver, arcuate nucleus (ARC) and paraventricular nucleus (PVN), increased c-fos expression in the nucleus tractus solitarii (NTS), and promoted ZO-1 and occludin expression in duodenum. Furthermore, steatosis and lipid accumulation were significantly alleviated. Hepatic vagotomy partially attenuated the improvement of eugenol in hepatic lipid accumulation in NAFLD rats. In conclusion, eugenol regulates hepatic lipid metabolism via a gut-brain-liver axis involving in GLP-1, providing a new strategy for the treatment of NAFLD.
Liu Xin,Jin Yongzeng,Cheng Xinyi,Song Qinghua,Wang Yanan,He Ling,Chen Tong
Rationale The plasma ceramide levels in Alzheimer’s disease (AD) patients are found abnormally elevated, which is related to cognitive decline. Objectives This research was aimed to investigate the mechanisms of aberrant elevated ceramides in the pathogenesis of AD. Results The ICR mice intracerebroventricularly injected with Aβ 1-42 and APP/PS1 transgenic mice were employed as AD mice. The cognitive deficiency, impaired episodic and spatial memory were observed without altered spontaneous ability. The serum levels of p-tau and ceramide were evidently elevated. The modified expressions and activities of glycogen synthase kinase-3β (GSK-3β) and protein phosphatase 2A (PP2A) influenced the serum content of p-tau. The levels of ceramide synthesis-related genes including sptlc1, sptlc2, cers2, and cers6 in the liver of AD mice were increased, while the ceramide degradation-related gene asah2 did not significantly change. The regulations of these genes were conducted by activated nuclear factor kappa-B (NF-κB) signaling. NF-κB, promoted by free fatty acid (FFA), also increased the hepatic concentrations of proinflammatory cytokines. The FFA amount was modulated by fatty acid synthesis-related genes acc1 and srebp-1c. Besides, the decreased levels of pre-proopiomelanocortin (pomc) mRNA and increased agouti-related protein (agrp) mRNA were found in the hypothalamus without significant alteration of melanocortin receptor 4 (MC4R) mRNA. The bioinformatic analyses proved the results using GEO datasets and AlzData. Conclusions Ceramide was positively related to the increased p-tau and impaired cognitive function. The increased generation of ceramide and endoplasmic reticulum stress in the hypothalamus was positively related to fatty acid synthesis and NF-κB signaling via brain–liver axis.
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