Known as the five-flavoured berry - for its salty, sweet, sour, pungent, and bitter properties - Omija (Schisandra chinensis) contains a variety of phenolic compounds that have beneficial effects on health, including antioxidant and anti-inflammatory effects, and it has frequently been used for medicinal purposes in Asia.
Recent studies have demonstrated that omija alone or in combination with grape pomace have favourable effects on obesity and diabetes, and improves energy metabolism by up-regulating the PGC-1α expression in the skeletal muscle during endurance exercise.
This latest study, published in The Journal of Nutritional Biochemistry, by researchers from Kyungpook National University and Pukyong National University in Korea, investigated the biological and molecular mechanisms underlying the anti-obesity effect of omija fruit ethanol extract (OFE) in mice fed a high-fat diet.
“This study sought to clarify the metabolic actions of long-term supplementation with omija fruit ethanol extract (OFE, 500 mg/kg body weight) in HFD-induced obese mice, in particular by focusing on its role in controlling brown-like transformation of WAT and ameliorating obesity-associated hepatic steatosis and insulin resistance,” they wrote.
In the study, mice were fed a high-fat diet with or without OFE for 16 weeks.
OFE samples were prepared by adding 1 L of 50% ethanol to 100 g of dried omija fruit, followed by extraction at 80°C for two hours and cooling.
The researchers found that dietary OFE significantly increased brown adipose tissue (BAT) weight and energy expenditure, while also decreasing white adipose tissue (WAT) weight and adipocyte size.
They believed this was achieved by up-regulating the expression of brown fat-selective genes in WAT
Increasing evidence suggests that BAT plays an important role in whole-body energy metabolism and thus may be a potential therapeutic target for obesity and its related metabolic diseases.
Increased energy expenditure
“In the present study, the enhanced expression of brown fat-specific genes such as PPARα, CIDEA and COX8β, indicators for the browning of WAT, suggested possible conversion of beige adipocytes in WAT.
“Therefore, the increased BAT weight and up-regulated expression of brown fat-specific genes in WAT may be related to the increased energy expenditure and concomitant decreases in WAT weight observed in OFE-fed obese mice,” they wrote.
OFE also improved hepatic steatosis and dyslipidaemia by enhancing hepatic fatty acid oxidation-related enzymes activity and faecal lipid excretion, added the researchers.
“In addition to steatosis, OFE decreased the expression of pro-inflammatory genes in the liver. Moreover, OFE improved glucose tolerance and lowered plasma glucose, insulin, and homeostasis model assessment of insulin resistance,” they wrote.
They concluded: “These findings indicate that OFE may be helpful in improving obesity and related metabolic disorders such as NAFLD, dyslipidaemia, and insulin resistance.”
Source: The Journal of Nutritional Biochemistry
“Omija fruit ethanol extract improves adiposity and related metabolic disturbances in mice fed a high-fat diet”
Authors: Hyo Jin Park, et al.