Free access to lard, sucrose, and chow results in expansion of rat periuterine adipose tissue.

Purpose: Adipose tissue expansion, a common feature of obesity, is associated with metabolic dysfunction, endocrine dysregulation, and adipokine imbalance. Adipocyte hypertrophy and hyperplasia contribute to adipose tissue expansion in a depot-specific manner. Our objective was to determine whether a high-fat, high-carbohydrate diet induces expansion of periuterine adipose tissue (PUT: adipose tissue surrounding the uterus). We hypothesized that free access to lard, sucrose, and chow results in hypertrophy and hyperplasia of adipocytes from rat PUT. Methods: Sixteen Sprague-Dawley female rats were divided into 2 weight-matched groups (n=8 rats/group) after 5 days of baseline measurements of food intake and body weight. One group was offered free access to chow, 30% sucrose solution, and lard (choice group) and the other group remained on chow (chow group) for 3 weeks. Energy intake and body weight were recorded daily. After euthanization, PUT was collected, weighed, and fixed in 4% paraformaldehyde. Samples were embedded in paraffin, sliced into 5 μm sections, and stained with hematoxylin and eosin. To determine hypertrophy, hyperplasia, and cell morphology, we used NIS Elements software to measure cross-sectional area/cell, number of cells/unit area, and adipocyte size distribution, respectively. Results: Total energy intake was greater in choice rats than chow rats (1590 ± 40.60 kcal/21 days vs. 1036 ± 19.00 kcal/21 days, p2/cell vs. 492.0 ± 27.76 μm2/cell, p=0.0001). The number of cells/unit area was smaller in PUT from choice rats compared to chow rats (13.9 x 10-5 ± 0.880 x 10-5 cells/μm2 vs. 20.4 x 10-5 ±0.910 x 10-5 cells/μm2, p=0.0001). PUT from choice rats had large adipocytes in greater frequency compared to PUT from chow rats. Conclusion: Obesity induced by free access to chow, lard, and sucrose resulted in hyperplasia and hypertrophy of adipocytes, and in cell size distribution changes in PUT of female rats of breeding age. Future studies will investigate if obesity-induced PUT expansion influences reproductive capacity and gestational outcomes.