Association between Urinary Metabolites Measured via Targeted Metabolomics and Glucose Metabolism in Healthy Adults on Diets Differing in Protein Sources

Background: While a plant-based diet rich in dietary fiber is known to reduce the risk of Type 2 Diabetes (T2D), the effects of consuming more plant protein than animal protein on the development of T2D still require further investigation. Objectives: To investigate the impact of replacing animal protein sources with plant protein sources on urinary metabolites measured by nuclear magnetic resonance (NMR) spectroscopy and insulin resistance in healthy adults, as well as the association between these metabolites and glucose metabolism biomarkers. Methods: Sub-analysis of 12-week randomized controlled trial including 86 participants (78% women, mean age: 47.9, mean BMI: 24.95 ± 3.93) randomly assigned to diets providing 17 energy percent (E%) of protein predominantly (70%) either from animal or plant origin. We analyzed the association between urinary metabolite concentrations from 24-hour urine samples by NMR spectroscopy and glucose metabolism biomarkers (fasting insulin and glucose used to calculate HOMA2 indices), using the non-parametric Spearman’s correlation test, adjusted for False Discovery Rate. Principal Component Analysis was employed to identify potential trends in metabolite profiles associated with glucose metabolism (insulin resistance). Results: Among the metabolites that differed significantly between the groups, 3-hydroxyisobutyrate (r = 0.35), 3-hydroxyisovalerate (r = 0.25), 4-deoxyerythronic acid (r = 0.31), glycolic acid (r = 0.26), trans-aconitate (r = 0.26), and valine (r = 0.26) were significantly positively correlated with HOMA2-IR at 12-wk. Among the metabolites that did not differ significantly between the groups, acetate (r = - 0.29) and uracil (r = - 0.26) showed significant negative correlations HOMA2-IR at 12-wk. Citrate (r = 0.32) and hypoxanthine (r = 0.29) exhibited significant positive correlations with HOMA2-IR at 12 weeks. Conclusions: Relative increase in plant protein sources resulted in alterations in urinary metabolites associated with insulin resistance.