Inhibitory Effect of Olive Leaf Extract on Obesity in High-fat Diet-induced Mice

Abstract

Background/aim: The rapid increase in the number of people who are overweight or obese, which increases the risk of diseases and health problems, is becoming an important issue. Herein, we investigated whether olive leaf extract (OLE) has potent anti-obesity effects in high-fat induced mouse models.

Materials and methods: C57BL/6 mice were randomized into normal control, high-fat diet (HFD), HFD with OLE, and HFD with garcinia groups and administered experimental diets for 12 weeks. Body weight and food intake were measured once per week and obesity-related biomarkers were evaluated in the serum and adipose tissue.

Results: OLE significantly suppressed weight gain, food efficiency ratio, visceral fat accumulation, and serum lipid composition in HFD-induced mice. Furthermore, the expression of adipogenesis- and thermogenesis-related molecules was decreased in the OLE-treated group.

Conclusion: OLE prevents obesity development by regulating the expression of molecules involved in adipogenesis and thermogenesis.

Keywords: Obesity; adipogenesis; fat; olive leaf extract; thermogenesis.

Figure 1. Effects of olive leaf extract on body weight gain, food intake, and food efficiency ratio (FER) of mice fed high-fat diet (HFD). (A) Experimental groups. (B) Body weight change over a 12-week period. (C-E) Body weight gain, food intake, and FER at 12 weeks. Results are presented as the mean±SEM (n=9) (*p<0.05, **p<0.01, N.S.: Not significant, FER=body weight gain for experimental period/food intake for experimental period).

Figure 2. Effect of olive leaf extract on adipose tissue in HFD-induced mice. (A) Fatty weight of epididymal, perirenal, retroperitoneal, mesenteric, and total weight in each experimental group. (B) Histological analysis of the epididymal adipose tissue from each group was conducted to quantify the size of adipocytes. Results are presented as the mean±SEM (n=9) (*p<0.05, **p<0.01, N.S.: Not significant).

Figure 3. Effects of olive leaf extract on the levels of serum biochemicals and cytokines in obese mice fed high-fat diet. (A) Serum levels of triglycerides, free fatty acid, glucose, total cholesterol, HDL-cholesterol, LDL+VLDL-cholesterol were measured. (B) Leptin and adiponectin levels were analyzed by ELISA. Results are presented as the mean±SEM (n=9) (*p<0.05, **p<0.01, N.S.: Not significant).

Figure 4. RT-PCR analysis of gene expression in the epididymal adipose tissue. The expression levels of adipogenesis-related (PPAR, C/EBP) and thermogenesis-related (PGC-1, UPC-1) mRNAs were evaluated by RT-PCR and normalized to that of GAPDH. Results are presented as the mean±SEM (n=9) (*p<0.05, **p<0.01, N.S.: Not significant).