The Effect of Endurance Training and Dill Seed Extract on Insulin Sensitivity and Nicotinamide N-methyltransferase Levels in the Liver and Adipose Tissue of Obese Rats

Background: Evidence suggests that exercise training and dill extract can influence obesity and related metabolic conditions, such as type 2 diabetes. Objectives: This study aimed to investigate the effects of endurance training (ET) and dill seed extract (DSE) on insulin sensitivity and nicotinamide N-methyltransferase (NNMT) levels in the liver and adipose tissue of obese rats. Methods: Forty male Wistar rats were divided into a high-fat diet [HFD (n = 32)] group and a standard diet [normal control (NC ) n = 8] group. After inducing obesity in the HFD group over 8 weeks, the rats were further divided into four groups: Obese control (OC), DSE, ET, and ET+DSE. Endurance training was performed at 70 - 80% VO₂max, and DSE was administered at a dose of 300 mg/kg body weight (five and three times per week, respectively) for 10 weeks. Plasma and tissue samples were collected after the intervention. The NNMT levels were measured using ELISA, and insulin sensitivity was assessed using the QUICKI Index. Data were analyzed using repeated measures analysis of variance, one-way analysis of variance (ANOVA), Tukey's post hoc test, Kruskal-Wallis test, and Mann-Whitney U test, with a significance level of P < 0.05. Results: After 10 weeks of intervention, blood glucose levels were significantly lower in the DSE (10.63%, P = 0.001), ET (15.89%, P = 0.001), ET + DSE (22.09%, P = 0.001), and NC (25.30%, P = 0.001) groups compared to the OC group. Similarly, insulin levels were significantly reduced in the DSE (57.30%, P = 0.01), ET (48.07%, P = 0.02), ET+DSE (63.88%, P = 0.002), and NC (59.00%, P = 0.007) groups compared to the OC group. The QUICKI Index was significantly higher in the DSE (11.87%, P = 0.003), ET (10.66%, P = 0.01), ET + DSE (16.82%, P = 0.001), and NC (15.18%, P = 0.001) groups compared to the OC group. However, no significant differences were observed in NNMT levels in the liver and adipose tissue or in liver triglyceride (TG) levels between the groups (P ≥ 0.05). Conclusions: Endurance training and DSE improved insulin sensitivity in obese rats but did not affect NNMT levels in the liver and adipose tissue. This lack of effect on NNMT levels may be due to the HFD's inability to influence this enzyme.