Modulation of Leptin and Serotonin by Honey and Its Glycoproteins Against High-Fat Diet-Induced Metabolic and Anxiety Phenotypes.

Background: Obesity-linked anxiety may involve leptin resistance, impairing serotonin (5-hydroxytryptamine; 5-HT) signaling. In addition to drugs, nutraceuticals have been explored for their potential to address this pathophysiology. Herein, natural honey and its glycoproteins were assessed for their roles in modulating the leptin-serotonin axis to alleviate metabolic and anxiety-related disturbances. Methodology: Sixty Wistar rats were allocated to two groups (n = 30 each), one on a normal diet (ND) and the other on a high-fat diet (HFD), for four weeks to induce obesity. Each group was further divided into five sub-groups (n = 6 each) as follows: saline, low honey dose (LHD, 1 g/kg), high honey dose (HHD, 2 g/kg), low protein dose (LPD, 0.25 mg/kg), and high protein dose (HPD, 0.5 mg/kg), while continuing on the ND or HFD. The interventions were administered for four weeks. Body weight and behavioral activities were measured weekly, whereas serum leptin and triglycerides, and brain 5-HT and its primary metabolite, 5-hydroxyindoleacetic acid (5-HIAA), were measured at sacrifice. Statistical analyses were performed using ANOVA, Tukey's post hoc test, and correlation analyses. Results: The HFD induced leptin-driven metabolic dysfunction and serotonergic disruption, exacerbating anxiety-like behavior and locomotor deficits compared with the ND rats (p < 0.05). HHD produced a dual metabolic-neurochemical improvement by reducing hyperleptinemia, elevating 5-HT, and restoring locomotor activity while reducing anxiety-like behavior. In contrast, HPD increased 5-HIAA without altering 5-HT, reflecting an imbalanced serotonin turnover that yielded only partial anxiolytic effects. Overall, HHD partially reversed HFD-induced pathology through leptin-serotonin crosstalk, whereas HPD provided more targeted neurochemical modulation. Conclusions: Natural honey and its glycoproteins attenuate HFD-induced metabolic dysregulation and anxiety-like behavior by counteracting hyperleptinemia and enhancing serotonin synthesis. These findings highlight the potential of diet-personalized, honey-based interventions for metabolic-CNS comorbidities, warranting validation through clinical trials.