5HTOL/5HIAA ratio as a biomarker of the alcohol hangover

Introduction: The alcohol hangover being themost commonly experienced side-effect of excessive alcohol consumption and the demand for an effective hangover cure requires the identification of sensitive and reliable biomarkers. Previous research has shown a shift in the ratio of two serotonin metabolites, 5-hydroxytryptophol (5-HTOL) and 5-hydroxyindol-3-ylacetic acid (5-HIAA), after recent alcohol consumption. As bothmetabolites are still present in urine even after ethanol has been cleared fromthe body, these are thought to be potential indicators of the alcohol hangover. Methods: On a hangover day and alcohol-free control day, urine samples were collected at 09.30 am. Urine samples of N = 36 participants (18 hangover and 18 hangover resistant) were analyzed on the concentration of 5-HTOL and 5-HIAA. Urine samples were analyzed by performing a gradient HPLC Fluorescent detectionmethod, using an acetonitrile buffer (pH = 5.5) and HIPA as internal standard. Each sample was treated with beta-glucuronidase and extracted with diethyl ether to optimize yield. Results: The urinary concentration of both 5-HIAA and 5-HTOL were significantly higher on the post-alcohol day, compared to control levels (p = 0.000). The 5-HTOL:5-HIAA ratio was also found to be significantly higher in the post-alcohol condition (p = 0.000). In the whole population, the urinary concentrations of 5-HTOL on the post-alcohol day did not significantly correlate with the total hangover score or the 1-item hangover score, nor did the ratio of 5-HTOL:5-HIAA. Only the urinary concentration of 5-HIAA on post-alcohol day was shown to significantly correlate with the total hangover score (p = 0.047; r = 0.333).When analyzing the data for the subset of hangover sensitive drinkers only, none of the correlations were statistically significant. Conclusion: The results of this study confirm that the ratio of 5-HTOL:5-HIAA is a reliable biomarker of recent heavy alcohol consumption. However, the 5-HTOL:5-HIAA ratio is not associated with the severity of the alcohol hangover, or its individual symptoms.