Sojeong Park

Previous studies have demonstrated that phloretic acid (PA), a phenolic compound, exerts beneficial effects on inflammation, oxidative stress, and aging. However, its effects on obesity and associated metabolic abnormalities, including dyslipidemia and metabolic dysfunction-associated steatotic liver disease (MASLD), remain unclear. To evaluate the effects of PA on these obesity-related metabolic alterations and explore the underlying mechanisms, male C57BL/6J mice were divided into three groups and fed for 10 weeks with a low-fat diet (10 kcal% fat), a high-fat diet (HFD, 60 kcal% fat), or an HFD containing 0.02% (w/w) PA. PA-supplemented mice showed no significant weight loss and fat loss. However, PA supplementation significantly reduced circulating levels of free fatty acid, triglyceride, and non-high-density lipoprotein cholesterol (HDL-C) while increasing HDL-C levels in HFD-fed mice. It also reduced hepatic lipid deposition and alleviated hepatocellular injury. These effects were accompanied by the coordinated modulation of hepatic lipid metabolism, including reduced lipogenesis and cholesterol esterification, enhanced fatty acid oxidation, and increased bile acid synthesis and excretion. Furthermore, PA attenuated hepatic oxidative stress and suppressed systemic and hepatic inflammation. These observations suggest that PA may counteract HFD-induced MASLD by modulating hepatic lipid metabolism, and that its anti-inflammatory and antioxidant effects may also contribute to these metabolic improvements.

Type 2 diabetes is characterized by insulin resistance, which contributes to dysregulated glucose and lipid metabolism and is associated with chronic inflammation. While previous studies have examined the effects of myricitrin in streptozotocin-induced diabetic models, its impact on the db/db mouse, a model that better reflects insulin resistance-associated metabolic disturbances, remains unclear. In this study, mice were divided into three groups (db/+, db/db, and db/db + 0.02% myricitrin) and were fed their respective diets for five weeks. Myricitrin supplementation reduced fat mass, adipocyte size, and plasma leptin levels, which were elevated in db/db mice. Although myricitrin did not affect fasting blood glucose levels, it lowered plasma insulin, hemoglobin A1c, postprandial glucose levels, and the homeostasis model assessment of insulin resistance, suggesting improvements in insulin sensitivity and glucose homeostasis. Enhanced pancreatic insulin expression, along with reduced hepatic gluconeogenic enzyme activities and mRNA expression, contributed to the improved glucose homeostasis observed in myricitrin-supplemented mice. Additionally, myricitrin reduced hepatic triglyceride levels and lipid droplet accumulation by inhibiting hepatic fatty acid synthase activity. It also decreased plasma inflammatory marker levels and their mRNA expression in adipose tissue. These findings suggest that myricitrin may be a promising therapeutic candidate for type 2 diabetes.

Background/Objectives: This research investigated the effects of myricitrin on hypercholesterolemia and non-alcoholic fatty liver disease (NAFLD) in mice given a high-cholesterol diet (HCD). Methods: C57BL/6J mice were maintained for 20 weeks on an HCD with or without myricitrin. Results: Myricitrin had no impact on the food consumption, body weight, or plasma triglyceride concentrations. However, myricitrin-supplemented mice had lower plasma total cholesterol (TC) concentrations and LDL + VLDL-cholesterol/TC proportion, and higher HDL-cholesterol/TC proportion than control mice, which resulted in a markedly decreased atherogenic index. Moreover, the levels of plasma C-reactive protein, oxidized LDL, lipoprotein(a), and plasminogen activator inhibitor-1, which are indicators for cardiovascular disease (CVD), were reduced, while levels of plasma paraoxonase, a cardioprotective enzyme, were greater in myricitrin-supplemented mice than in control mice. Myricitrin also meaningfully reduced liver weight and hepatic cholesterol content, and slightly alleviated fatty liver and fibrosis caused by an HCD. The plasma and hepatic cholesterol-lowering effects of myricitrin were partly associated with decreased activities of hepatic 3-hydroxy-3-methylglutaryl-CoA reductase and acyl-CoA:cholesterol acyltransferase, which are involved in cholesterol synthesis and esterification, respectively, as well as mRNA expression. Myricitrin also altered other hepatic genes implicated in cholesterol homeostasis, including the downregulation of SREBP2 and ABCA1 mRNA expression and the upregulation of LDLR mRNA expression. Moreover, myricitrin decreased TBARS levels in the liver and erythrocytes by activating antioxidant enzymes (SOD and catalase). Conclusions: These results indicate that dietary myricitrin may offer therapeutic benefits for HCD-caused hypercholesterolemia and NAFLD, and may help reduce CVD risk.