In-vitro direct measurement of fat (solvent extraction) In the anterior and posterior area of the tongue – a pilot study (preliminary results)

Introduction: There is growing interest on fat accumulation in the tongue, as it is an important contributing factor to Obstructive Sleep Apnea-Hypopnea (OSAH).
Literature showed that tongue fat percentage (Fat %) correlates with BMI, appears to be higher in the posterior part in apneic subjects compared to controls and is strongly associated with male gender.
However, the analysis of medical imaging is scarce, as the images are based on algorithms. The objective of this study is to compare Fat % by an in-vitro direct measurement method (solvent extraction) in the tongue (anterior vs posterior) and adipose tissue controls.
Methods: 32 samples were collected on three fresh human cadavers (mean age = 71 ± 12).
- Tongue (N=28), subgrouped in anterior (N=10) and posterior (N=18) region, separated by foramen caecum and sulcus terminalis.
- Abdominal adipose tissue samples were used to determine the reference.
Fat quantification was performed by automated solvent extraction (Soxhlet method - Petroleum ether 40/60).
Results: The non-parametric Mann-Whitney test (p-value 0,05) showed that Fat % was significantly higher in the posterior area of the tongue compared to anterior (mean 5.5 ± 4.2 %; min-max: [0.1-12.4] vs 12.30 ± 9 %; min-max: [2.4-35.7]; p= 0.0135). Controls (abdominal fat) showed 95.7 ± 3.5 % Fat.
Conclusions: (1) Solvent extraction showed a higher Fat % in the posterior part of the tongue compared to anterior. According to the literature, this could lead to a greater collapsibility of the upper airway in OSAH patients. (2) Raw data from solvent extraction were lower but equal in proportion compared with indirect medical imaging data depicted in the literature. (3) Interindividual variability was important, so more replication is needed to provide reliable data on physiological distribution in the tongue, exacerbated by obesity and OSAH.