Short-time fasting affects metabolic markers without impact on follicle and oocyte development in rabbit model
Our goal was to elucidate whether acute energy restriction has any influence on ovarian reproductive processes and the relationship with some metabolic markers in the rabbit model. A total of 22 nulliparous rabbits were randomly distributed in 2 groups: control group fed ad libitum (C; n=12) and 72-h fasted group (F; n=10). Before and after the deprivation period, body weight (BW), estimated body composition, serum triglycerides (TG), nonesterified fatty acids (NEFA), and leptin concentrations were measured. After fasting, ovaries were retrieved: one was used to study oocyte in vitro nuclear and cytoplasmic maturation (in terms of granule cortical migration; Arias-Alvarez et al. 2010 Theriogenology 73, 26-35) and the other one was processed histologically to assess follicle categorization and atresia rate by TUNEL and by immunolocalization of procaspase-3 (PC3). Statistical analysis was carried out by MIXED and CATMOD procedures of SAS program. The BW of control rabbits increased at the end of the experiment (3.96±0.06 v. 4.03±0.09kg; P<0.05), but the fasted group showed similar weight compared with 72h before and the C group (3.97±0.09kg). No differences were observed on estimated body composition between C and F animals (61.0±0.52% water, 2.96±0.02% ash, 18.6±0.51% lipids, 18.4±0.05% protein, and 1206±21.6 kJ/100g of energy). The TG was similar between groups (74.4±9.9 v. 49.3±10.4mgdL(-1)), whereas NEFA concentrations were significantly higher in the F group than before fasting (0.29±0.04mmolL(-1) v. 0.17±0.03mmolL(-1); P<0.05) and than in the control group (0.09±0.04mmolL(-1); P<0.05). In opposition, leptin concentrations were lower in the F group than before fasting (2.2±0.6 v. 5.1±0.4; P<0.05) and than in C rabbits after fasting (4.6±0.5ngmL(-1); P<0.05). No differences were found in the number of primordial (192.0±52.9 v. 276.0±88.6), primary (36.7±6.6 v. 45.5±7.8), secondary (37.1±7.5 v. 54.1±14.6), and antral follicles (21.9±2.1 v. 22.3±2.2) between the C and F group. The rates of healthy (53.2±4.3 v. 57.4±5.0), early atretic measured as <50% of apoptotic cells (15.4±2.2 v. 17.2±2.6), and late follicles measured as >50% of apoptotic cells (31.4±3.6 v. 25.4±4.2) did not differ between groups. Cytoplasm staining of PC3 was observed in stroma, follicles of all sizes, and corpora lutea of both groups. Atretic follicles did not exhibit immunoreactivity to PC3. No significant differences were observed in nuclear maturation and migrated cortical granule rates (63.6 v. 53.7% and 12.0 v. 4.7%, respectively). In conclusion, acute fasting affects BW and some metabolic markers (NEFA and leptin), but follicle and oocyte development is not impaired in our rabbit model.
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