Abscisic Acid as a Marker of Metabolic Imbalance: Serum Levels from Diabetic and Smoking Subjects

Background: Abscisic acid (ABA), a phytohormone widely distributed in nature, has recently emerged as an endogenous regulator of glucose homeostasis in humans. Specifically, scientific studies have demonstrated that exogenous ABA supplementation improves glycemic control and reduces insulin requirements, with significant advantages in prediabetic subjects. Beyond its metabolic role, growing evidence suggests that ABA is also involved in immune responses, including those associated with pulmonary diseases. Despite these promising results, the evaluation of plasma ABA levels remains largely unexplored in clinical practice. Methods: This study aimed to evaluate whether plasma ABA concentrations differ among healthy individuals, patients with type 2 diabetes, and smokers, in order to clarify the role of ABA as a potential biomarker of both metabolic imbalance and smoking-related inflammatory stress. Results: Our findings show that ABA levels were significantly higher in healthy subjects (10.9 ± 3.8 ng/mL) compared to diabetic patients (6.8 ± 4.2 ng/mL, p < 0.01 vs. healthy subjects), with the lowest levels observed in smokers (3.5 ± 2.5 ng/mL, p < 0.0001 vs. healthy subjects and p < 0.0001 vs. diabetic patients). Moreover, a significant correlation was observed between ABA plasma concentration and number of cigarettes smoked (R2 = −0.6776, p = 0.0001). Conclusions: Overall, these results highlight the relevance of measuring ABA plasma levels in both metabolic and inflammatory conditions, confirming its role as a biomarker for identifying individuals who can benefit from exogenous supplementation.