Exploring Metabolic Mechanisms of Obesity in Older Adults: The Bushehr Elderly Health Study

Background: Obesity in older adults is not only associated with fat accumulation but also disrupts metabolic homeostasis and induces low-grade chronic inflammation. Evidence suggests that B vitamins, influence obesity pathophysiology by regulating immunometabolic pathways such as the tryptophan–kynurenine pathway. This study aimed to evaluate associations between tryptophan–kynurenine pathway metabolites and obesity status in older adults. Methods: In this cross-sectional analysis, 396 participants aged ≥60 years were randomly selected from phase II of the Bushehr Elderly Health (BEH) study. Demographic and clinical data were collected and fasting plasma samples were analyzed by GC MS/MS and LC MS/MS. Participants were classified by BMI into normal weight and obese groups. Group comparisons used appropriate statistical tests and logistic regression models were fitted crude and adjusted for age, sex, and diabetes. Results: Obese participants were younger and had higher systolic and diastolic blood pressure, ALT, GGT, and triglycerides. Several tryptophan pathway metabolites were elevated in obesity; notably kynurenine, kynurenic acid, xanthurenic acid, and quinolinic acid. In adjusted models higher kynurenine (AOR= 1.3, P= 0.024), kynurenic acid (AOR= 1.9, P= 0.001), xanthurenic acid (AOR= 1.3, P= 0.024), and quinolinic acid (AOR= 1.3, P= 0.039) were associated with increased odds of obesity. Conclusion: The metabolic profile observed is consistent with activation of the kynurenine pathway in the context of chronic low grade inflammation and B vitamins status in elderly obesity. Kynurenine pathway activation is associated with obesity in older adults; however, causality cannot be inferred due to the cross-sectional design, but this immunometabolic signature may represent a potential target for future longitudinal studies and micronutrient-focused interventional trials.