Effects of Essential Oil Inhalation on the Enhancement of Plasma and Liver Lipid Metabolism in Mice

Abstract

The purpose of this study was to determine the effects of essential oil inhalation on body weight, blood lipid profile, and liver and adipose tissue in mice. Middle-aged male mice (C57BL/6J) were exposed to Lavandula angustifolia (LO) and Citrus aurantium (CAO) essential oils for 7 weeks and compared to mice that did not receive essential oil inhalation treatment. Liver, white adipose tissue, and brown adipose tissue were sampled, kept at -80 °C. Although essential oil inhalation increased feed intake and body weight compared to control group, the amount of weight gain per feed intake was lower in the C. aurantium essential oil group. Moreover, relative weight of fat to body weight, liver fat amount, and blood cholesterol was lower, and triglyceride levels were significantly reduced. Reverse transcription polymerase chain reaction (RT-PCR) expression profiling of genes related to lipid metabolism confirmed changes in the regulation of thermogenesis-related gene Ucp1 and the cholesterol synthesis-related genes Hmgcs1 and Hmgcr. The inhalation of C. aurantium essential oil did not reduce the feed intake in mice; however, its effectiveness in suppressing the increases in body weight and fat mass was demonstrated.

Keywords: Citrus aurantium; Lavandula angustifolia gene expression; anti-obesity; aromatherapy; essential oil inhalation; lipid metabolism.

Figure 1

Total food intake (g), body weight gain (g), and relative white adipocyte tissue (WAT) mass (%) (A) of mice (C57BL/6J) inhaling essential oils for 7 weeks. Body weight gain (g) and percentage gain (%) (B) of mice after 7 weeks of inhalation of essential oils compared to body weight at the start of the experiment. White adipocyte weight (g) and relative WAT mass (%) (C,D) of mice after inhalation of essential oils for 7 weeks. DW (distilled water), LO (Lavandula angustifolia), and CAO (Citrus aurantium) are shown as results for groups of 10 mice (n = 10). Error bars represent SE (mean ± standard error). Significant: ** p < 0.01 vs. DW; significant trend: † 0.05 ≤ p < 0.1 vs DW; Tukey method (n = 10).

Figure 2

Testing the effect of essential oil inhalation on hepatic lipid accumulation in mice (C57BL/6J). Liver sections from the DW (distilled water), LO (Lavandula angustifolia), and CAO (Citrus aurantium) groups were stained with Oil Red O. (A) 100× magnification, scale bar 100 µm, and 1000× magnification, scale bar 50 µm. Quantification of Oil Red O staining was performed using imageJ (B). Error bars represent SE (mean ± standard error). ** p < 0.01 vs. DW, Tukey method (n = 5).

Figure 3

The blood lipid profile of mice (C57BL/6J) inhaling essential oil for 7 weeks. Values of total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, free fatty acids and phospholipids in blood absorbing DW (distilled water), LO (Lavandula angustifolia), and CAO (Citrus aurantium) for 7 weeks. Error bars represent SE (mean ± standard error). ** p < 0.01; * p < 0.05 vs. DW; Tukey method (n = 10).

Figure 4

Effect of 7 weeks of essential oil inhalation on gene expression in the mice (C57BL/6J) liver, WAT (white adipose tissue), and BAT (brown adipose tissue). Band intensities of RT-PCR products after electrophoresis were corrected for GAPDH and are displayed graphically. Error bars represent SE (mean ± standard error). ** p < 0.01; * p < 0.05 vs. DW (distilled water); Tukey method (mouse tissue—n = 10; PCR technical replicate—n = 3).

Figure 5

Gene expression changes in mouse (C57BL/6J) liver and WAT (white adipose tissue) after 7 weeks of CAO (C. aurantium) inhalation (A); Apob/Apoa1 gene expression ratio in WAT after 7 weeks of essential oil inhalation (B); Error bars represent SE (mean ± standard error). Tukey method (mouse tissue n = 10, PCR technical replicate n = 3). VLDL: very low density lipoprotein; TC: total cholesterol; TG: triglyceride; FFA: free fatty acids. ** p < 0.01. Increased expression is indicated by red arrows and decreased expression by blue arrows.

Figure 6

The study experimental design and essential oil exposure methodology for this research.