Moderate intensity continuous and interval training affect visceral fat and insulin resistance model in female rat exposed high calorie diet

Chronic high-calorie diet (HCD) combined with physical inactivity promotes obesity and insulin resistance (IR). This study aimed to analyse the comparable effect of moderate-intensity continuous training (MICT) and moderate-intensity interval training (MIIT) on visceral fat weight and IR in subjects exposed to HCD. This randomised post-test research used only a control group design with female rats (Wistar norvegicus), 8 weeks old and 100-200 g of bodyweight. They were randomly divided into four groups: standard diet group (C), HCD group (C1), HCD combined with MICT group (C2) and HCD combined with MIIT group (C3). Each group consisted of six rats. HCD consisted of ad libitum standard diet plus dextrose solution by oral gavage for 4 weeks. The MICT was conducted by swimming plus 6% load of body weight for 10 min in the first week, for 20 min in the second week and 30 min in the third and fourth week. The MIIT was conducted by swimming in a ratio between swimming and rest time at 2:1 plus 6% load of BW, performed 5×/week for 4 weeks, and increased progressively. The mean body weight pre-intervention was 152.79±13.280 g and 150.12±9.195 g post-intervention (P=0.115). The mean fasting blood glucose pre-intervention was 79±8.668 mg/dl, and post-intervention 86.29±12.142 mg/dl (P=0.142). The mean visceral fat weight between C (1.94±0.66 g), C1 (1.45±0.47 g), C2 (1.41±0.44 g), and C3 (1.22±0.59 g) was not significant (P=0.179). The mean triglyceride level for C (173.33±30.30 mg/dl), C1 (157.16±47.32 mg/dl), C2 (112.83±25.49 mg/dl), and C3 (80.33±23.47 mg/dl) was significant (P=0.000). The mean IR model for C (4.796±0.070), C1 (4.728±0.125), C2 (4.620±0.123), C3 (4.360±0.143) was significant (P=0.000). In conclusion, both MICT and MIIT have an effect to improve IR and TG. The MIIT was more effective to improve IR compared to MICT in the female rats exposed to an HCD.

Increased locomotor activity in estrogen-treated ovariectomized rats is associated with nucleus accumbens dopamine and is not reduced by dietary sodium deprivation

Estrogens are well known to increase locomotor activity in laboratory rodents; however, the underlying mechanism remains unclear. We used voluntary wheel running by female rats as an index of locomotor behavior to investigate this issue. We first determined whether the estrogen-induced increase in locomotion was susceptible to inhibition by a physiological challenge, and next whether it was associated with dopaminergic activation in the central reward area, nucleus accumbens. Ovariectomized rats were given estradiol or the oil vehicle and housed in cages with or without running wheels. All rats were given regular rodent chow for 1 week, a sodium-deficient diet for the next week, and then were returned to a regular diet for another week. At the end of the last week, all rats were killed, brains were extracted and dopamine levels in the nucleus accumbens were measured. As expected, estradiol treatment increased distance run. Surprisingly, dietary sodium deprivation further increased running, but this appeared to be related to experience with wheel running, rather than to sodium deprivation, per se. Dopamine was greater in the nucleus accumbens of estradiol-treated rats that ran compared to all other groups. Thus, the estrogen-induced increase in locomotion is a robust phenomenon that is not inhibited by a body sodium challenge and is associated with elevated levels of dopamine in reward pathways. These findings raise the possibility that the estrogen-induced increase in locomotor activity, which occurs during a hormonal milieu conducive to reproduction, may reflect mate-seeking behavior and, thereby, maximize reproductive success.

Estrogen and voluntary exercise interact to attenuate stress-induced corticosterone release but not anxiety-like behaviors in female rats

The beneficial effects of physical exercise to reduce anxiety and depression and to alleviate stress are increasingly supported in research studies. The role of ovarian hormones in interactions between exercise and anxiety/stress has important implications for women's health, given that women are at increased risk of developing anxiety-related disorders, particularly during and after the menopausal transition. In these experiments, we tested the hypothesis that estrogen enhances the positive impact of exercise on stress responses by investigating the combined effects of exercise and estrogen on anxiety-like behaviors and stress hormone levels in female rats after an acute stressor. Ovariectomized female rats with or without estrogen were given access to running wheels for one or three days of voluntary running immediately after or two days prior to being subjected to restraint stress. We found that voluntary running was not effective at reducing anxiety-like behaviors, whether or not rats were subjected to restraint stress. In contrast, stress-induced elevations of stress hormone levels were attenuated by exercise experience in estrogen-treated rats, but were increased in rats without estrogen. These results suggest that voluntary exercise may be more effective at reducing stress hormone levels if estrogen is present. Additionally, exercise experience, or the distance run, may be important in reducing stress.