Glycerol is a biomarker of lipolysis, the physiological process by which triglycerides stored in adipose tissue are mobilized to release fatty acids and glycerol, thereby supplying energy to the body. Its blood concentration rises in various pathological conditions — metabolic diseases, cardiovascular diseases, cancer cachexia — but also in response to energy stress such as physical exercise. Its measurement is therefore of interest in many health-related contexts. Current quantification methods, however, remain costly and time-consuming, and require plasma to be extracted from blood before glycerol content can be determined, all steps liable to introduce bias.
To address these limitations, the authors describe DietSee, a portable point-of-care measurement device based on a strip-format biosensor. It enables glycerol to be quantified directly from whole blood within six seconds, using a single drop collected from the fingertip. The sensor's performance was first evaluated on buffer solutions and on human and murine plasma samples spiked with glycerol, in comparison with the reference colorimetric method. The measurements obtained with DietSee showed strong correlation with this method and a linear response across a wide concentration range (40 to 750 μM), representative of physiological values. In human blood, validation covered a hematocrit range of 30 to 55%, with high correlation to reference measurements (R² = 0.97).
The selectivity assessment involved fourteen exogenous substances (drugs, vitamins) and seven endogenous substances: none produced notable interference at the concentrations tested, with the sole exception of ascorbic acid above 42.6 μM. Storage stability proved high, exceeding two years for strips kept dry at 4 °C. Finally, the authors tested the device in three biological settings requiring real-time monitoring of lipolysis. In mice deficient in hormone-sensitive lipase (Hsl), measured blood glycerol was 50% lower than in control animals; after injection of a beta-3 agonist stimulating lipolysis, glycerol in control mice doubled within ten minutes, whereas it increased only marginally in deficient mice. In eighteen lean, healthy men, glycerol rose significantly after endurance or interval-sprint exercise, with endurance producing the most pronounced increase. A trial comparing two dietary regimens during running further revealed a metabolic difference between subjects.
In conclusion, this glycerometer constitutes a sensitive, selective, and rapid tool, suitable for both humans and mice, allowing an individual's metabolic status to be characterized from a single drop of blood. Its versatility opens applications both in health and in research on lipolysis and metabolic disorders.