Intramuscular fat assessment in relation to sleep apnea: a new approach of direct measurement of lipidic deposit in human tissue with soxhlet method

ntroduction: Solvent extraction is an in-vitro direct method to assess fat percentage on muscle samples and is a well-known reference method in food analysis. This application will be tested for its reliability in order to be used for later comparison with medical imaging and create, in a second phase, a non-invasive easy-to-use technique for tongue fat quantification in sleep apnea. Methods: Muscular fat quantification by automated solvent extraction (with Petroleum ether 40/60) was performed on 12 pork samples and 64 samples collected on three fresh human cadavers (71±12y). Preparation of all samples was standardised according to the Association of Official Agricultural Chemists. Reliability of the measure, drying time of extraction product, and influence of freezing storage were studied. Results: The Wilcoxon matched-pairs signed rank test (p-value 0,05) between 32 pairs of prepared samples showed an excellent repeatability of the measure (mean 16.26±22.58 % vs 16.66±22.78 %; p=0,557). Ideal drying time after analysis was >55 min. and no significant difference was found between freshly analysed prepared pork samples and same samples after 3 weeks of -25°C storage in an airtight container (p=0,437). Conclusions: Our results indicate that automated soxhlet method is a reliable technique to assess Fat % in human tissue. Therefore, it can be applied as a reference for comparison / correlations with medical imaging quantifying lingual fat in patients suffering from obstructive sleep apnea.