Carnosic Acid as the Major Bioactive Component in Rosemary Extract Ameliorates High‐fat Diet‐induced Obesity and Metabolic Syndrome in Mice

Abstract

Rosemary has been used as a natural alternative to synthetic antioxidants in Europe and the United States. In this study, we investigated the preventive effects of carnosic acid (CA) enriched rosemary extract on high‐fat diet‐induced obesity and metabolic syndrome in mice. The mice were given a low‐fat (LF) diet, a high‐fat (HF) diet or a high‐fat diet supplemented with 0.14% (w/w, RE#1L), or 0.28% (w/w, RE#1H) rosemary extract with 80% CA, 0.5% (w/w, RE#2) rosemary extract with 45% CA for a period of 16 weeks. RE#1H and RE#2 diets have the same level of CA. The dietary RE supplementation significantly and dose‐dependently reduced body weight gain, percent of fat, plasma ALT, AST, cholesterol, glucose, and insulin levels and liver weight, liver triglyceride and free fatty acid levels. RE administration also decreased the plasma and liver malondialdehyde, advanced glycation end products (AGEs) levels and the liver expression of receptor for AGEs (RAGE). Histological analyses of liver samples showed decreased lipid accumulation in hepatocytes in mice administrated with RE compared with HF diet fed mice. Meanwhile, RE administration enhanced fecal lipid excretion and increased the liver GSH/GSSG ratio. In conclusion, the present study demonstrated that long‐term dietary CA‐enriched rosemary administration could effectively and dose‐dependently attenuate the development of obesity, metabolic syndrome, and fatty liver in HF diet‐induced obese mice. These beneficial effects may be mediated by decreased lipid absorption, improved lipid, glucose and insulin metabolism, decreased inflammation and oxidative stress.