Effect of Diet-Induced Obesity and Endurance Training- Induced weight Reduction on Plasma Leptin in C57BL/6 Mice

The aim of this study was evaluating the effect of highfat iet-induced obesity and weight reduction due to endurance training with two different intensities on plasma leptin in C57BL/6 mice. Thirty C57BL/6 mice (3-4 weeks; 10-15 g) were recruited in this study. Twenty four mice consumed a high-fat diet (60% fat) and 6 mice nourished a standard diet (35% fat) for 12 weeks. 6 obese mice (group: OB) and 6 nonobese mice (group: NB) were killed for basal measurements. After obesity period, 12 mice were trained 5 sessions per week for 12 weeks on a rodent treadmill with high (group: HI) and/or low intensity (group: LI). Each session, the LI group ran at a speed of 15 m/min and 5% incline (~50% VO2max) for 60 min and the HI group at a speed of 22 m/min and 5% incline (~75% VO2max) for 41 min. 6 other obese mice (group: OC) were kept in the cages as the control group till the end of training.Body weight was measured and recorded weekly. Plasma leptin was measured using a specific kit by ELISA method. From 5th week on, mean weight in the groups which had a high-fat diet (OB, OC, HI & LI) showed a significant increase compared to the NB group (p<0.05). In training groups, weight reduction started from 6th week compared to the OC group and at 8th week it was significant (p<0.05). The rate of weight reduction was significantly higher in the HI group than the LI group in 11th and 12th weeks (p<0.05). Plasma leptin concentrations increased 24% in OB compared to the NB group (p<0.05). Plasma leptin concentrations in OC were slightly lower than the NB group, but it declines 27% compared to the OB group (p<0.05). Relative leptin value per gram body weight in OC, HI and LI groups was similar and lower than the two other groups. Blood leptin concentration, although, is closely related to obesity indexes such as BMI, body fat percentage and body fat mass in human and animals, and apparently weight reduction can lead to leptin concentration decrease; however, these results suggest that high-fat diet independent to weight reduction, also, plays a role in hyperleptinemia.