OR10-04 Olfactory Odour Stimulation Improves Glucose And Lipid Metabolism In Obese Humans
Authors: Matiashova Lolita , Hoogkamer Anouk , Komai Alexander , Kunz Chery , Popovic Milica , Spaar Yanick , Minder Judith , Zehnder Elias , Welge-Lüssen Lemcke Antje , Timper Katharina 
Published: October 2023

Abstract
Disclosure: L. Matiashova: None. A. Hoogkamer: None. A. Komai: None. C. Kunz: None. M. Popovic: None. Y. Spaar: None. J. Minder: None. E. Zehnder: None. A. Welge-Lüssen Lemcke: None. K. Timper: None.
Introduction: Obesity represents a growing global socioeconomic health burden. Recent studies in mice highlight an important role of the olfactory system in metabolic homeostasis and obesity development. Several animal studies indicate a potential therapeutic role of olfactory stimulation with D-Limonene, a natural flavour and main component citrus fruit peel oil, in metabolism control. Thereby, olfactory stimulation with D-Limonene acutely improved glucose and lipid metabolism, and upon repetitive exposure, reduced food intake and body weight, while olfactory stimulation with the scent of lavender oil had opposite effects. The aim of this study was to investigate the metabolic effects of olfactory stimulation with D-Limonene in obese humans. Methods: Single-centre, randomized cross-over study with n= 38 participants of both genders, age 18-60 years, with a body mass index (BMI) ≥ 35 kg/m2. Participants without co-morbidities and normosmia, as defined by “Sniffin’ Sticks Test” and threshold, discrimination and identification (TDI) score, were included. In the acute study part, 10 h overnight-fasted participants were exposed to the scent of D-Limonene, lavender oil, or placebo (propylene glycol; all Sigma Aldrich) for 15 min via a nasal clip in a randomized order followed by a high-calorie, carbohydrate-rich mixed meal test. Hunger and appetite ratings were assessed using visual analogue scale (VAS) questionnaires. There was a wash-out period of 1 week in between the study days. In the chronic study part, participants were exposed to scent of D-Limonene or placebo for 15 min before breakfast and dinner for 6 weeks in a cross-over fashion with a wash-out period of 2 weeks in between the different treatment periods and body weight as well as metabolic blood parameters were assessed. Result 25 women and 13 men with a median age of 37.5 [28.0: 48.0] years and a median BMI of 38.2 [36.2: 42.8] kg/m2 and normosmia as reflected by a TDI score of 35.5 (33.3-36.8) were enrolled. Acute olfactory stimulation with D-Limonene reduced hunger feeling from preprandial VAS 2.72 ± 2.69 to postprandial VAS 1.95 ± 2.45 (p=0.049*), while no change was observed upon olfactory lavender oil or placebo stimulation. In the chronic phase, Hb1Ac levels increased during 6 weeks of placebo treatment by 0.20 [-0.10:0.20] % (p=0.001**), which was not observed upon D-Limonene treatment (0.00 [-0.20: 0.10] (p=0.980). In addition, fasting triglyceride plasma levels were significantly reduced after 6-week olfactory stimulation with D-Limonene by -0.10 [-0.43: 0.03] mmol/l (p=0.004*), while no change was detected upon placebo treatment (0.00 [-0.21: 0.11] mmol/l (p=0.688)). Conclusion: Overall, our study revealed beneficial effects of olfactory D-Limonene stimulation on hunger feeling upon acute exposure as well as on systemic glucose and lipid metabolism upon repetitive, chronic exposure in subjects with obesity.
Presentation: Friday, June 16, 2023