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. 2023 Apr 27;24(9):7962. doi: 10.3390/ijms24097962

Figure 3.

Figure 3

Model summarizing how essential oils or fragrant compounds (fragrant components) regulate appetite. Fragrant components regulate appetite via four pathways. (A) Fragrant components directly modulate the activity of NPY/AgRP and POMC/CART neurons in the ARC of the hypothalamus. Decreased NPY/AgRP mRNA expression or increased POMC/CART mRNA expression reduces appetite. (B) Under obesity conditions, leptin resistance develops, and food intake does not decrease despite increased leptin levels. Some essential oils can improve leptin resistance by increasing intracellular signaling pathways and transporting leptin across the BBB to the ARC, eventually decreasing food intake. (C) Fragrant components can excite WAT sympathetic nerves (to stimulate lipolysis), enhance BAT thermogenesis (to increase energy expenditure), and trigger adrenal SNA to induce adrenaline production, eventually decreasing food intake. Fragrant components may also, through the parasympathetic gastric nerve, inhibit gastric motility and gastric secretion to suppress appetite. (D) Essential oils can also regulate food intake through a scent-taste association, forming a memory or perception of a current meal, resulting in an altered amount of food intake at a later meal. Fragrant components, through the olfactory or respiratory systems, can target specific brain regions such as the HPC, hypothalamus, or amygdala to regulate appetite. Signals from the hypothalamus can also be projected onto the corticolimbic system and vice versa. Blue and red arrows represent appetite-downregulating and appetite-upregulating pathways, respectively. Black arrows represent suggested mechanisms from selected papers, and dashed black arrows represent information from other references. AgRP: agouti-related protein; ANS: autonomic nervous system; ARC: arcuate nucleus; BAT: brown adipose tissues; CART: cocaine- and amphetamine-regulated transcript; HPC: hippocampus; NPY: neuropeptide Y; PFC: the prefrontal cortex; POMC: proopiomelanocortin; PSNA: parasympathetic nerve activity; SNA: sympathetic nerve activity; WAT: white adipose tissue.