Total urinary polyphenol excretion: a biomarker of an anti-inflammatory diet and metabolic syndrome status

Unlocking the power of polyphenols: A promising biomarker of improved metabolic health and anti-inflammatory diet in adolescents

BACKGROUND

Metabolic syndrome (MetS) in adolescence is a risk factor for future cardiovascular disease. The chronic inflammation associated with MetS can be attenuated by the anti-inflammatory effect of polyphenols. We aimed to evaluate total urinary polyphenols as a biomarker of anti-inflammatory diets and their effect on MetS in adolescents.

METHODS

In this retrospective analysis of a longitudinal cohort study, the relationship between total polyphenol excretion (TPE) in urine, the inflammatory potential of the diet measured through the Children's Dietary Inflammatory Index (C-DII), and the presence of metabolic syndrome was evaluated. The study population consisted of adolescents enrolled in the SI! Program for Secondary Schools trial, who had completed all the study forms and provided urine samples at baseline and at the two-year follow-up. Multivariate linear regression and multinominal logistic regression models were generated to evaluate the relationship of changes in TPE with changes in the C-DII score and changes in MetS status, respectively. An analysis of the ROC curve was performed to assess the potential of TPE as a biomarker of an anti-inflammatory diet.

RESULTS

This study included 662 adolescents, 51.2% were males, and 48.8% were females, with a mean age of 12 (0.38) years at baseline. The relationship between changes in TPE and changes in the C-DII score was stratified by sex with a p-value <0.001 for the interaction. TPE and C-DII were inversely associated in males (-0.13 mg GAE/g creatinine [-0.26; -0.01] per 1-SD increase, p-value = 0.037). In addition, an increase in changes in TPE levels were associated with a reversal in MetS status in all adolescents (1.30 [1.27; 1.34] per 1-SD increase, p-value<0.001). The ROC curve showed that urinary TPE levels can predict dietary inflammatory potential with an AUC = 0.793 (0.725; 0.863) in males.

CONCLUSION

Polyphenols excreted in urine are a potential biomarker of anti-inflammatory diets in males and are associated with a reversal of MetS status in adolescents.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, Identifier: NCT03504059, https://clinicaltrials.gov/study/NCT03504059.

Total (poly)phenol analysis by the Folin-Ciocalteu assay as an anti-inflammatory biomarker in biological samples

The Folin-Ciocalteu method is a well-established and widely used assay for measuring total (poly)phenol content in food/plant products. In recent years, there has been growing interest in applying this method to human samples due to its simplicity and efficacy. However, biological matrices such as blood and urine contain several interference substances that must be eliminated beforehand. This mini-review summarizes the current state of knowledge regarding the use of the Folin-Ciocalteu assay to measure total phenolic content in human urine and blood samples, as well as the preceding cleaning methods to remove interferences. Higher total (poly)phenol levels measured by the Folin-Ciocalteu method have been associated with a decrease in mortality and several risk variables. We focus on the application of this sustainable assay as a biomarker of poly(phenol) intake and its potential use as an anti-inflammatory biomarker in clinical laboratories. The Folin-Ciocalteu method, with a clean-up extraction step, is a reliable tool for determining total (poly)phenol consumption. Here, we also recommend using the Folin-Ciocalteu assay as means to measure anti-inflammatory activity.