Abstract:
Obesity in women of reproductive age has been a global health challenge that is rapidly increasing.
Ethical considerations make it difficult to study obesity in human females. However, obesity can be
induced and studied in laboratory animal models. This study aimed at investigating the effect of
obesity on selected reproductive parameters in female Sprague Dawley rat model. Obesity was
induced through a High Energy Diet (HED) after which frequency of occurrence and lengths of
estrous cycles stages, mating success, gestation length, litter size, litter weight, estradiol and cortisol
hormone levels were analyzed. Thirty, three-month-old sexually mature female Sprague Dawley
rats were fed either on HED (n=15) or a control diet (n=15) for seven weeks. After seven weeks of
feed induced obesity, 12 obese rats and 12 controls were evaluated for estrous cycles lengths and
frequency of occurrence through vaginal smears after which 6 rats from the obese group and 6 from
the controls were euthanized using isoflurane and blood collected via cardiac puncture for estradiol
17b and cortisol hormone analyses by ELISA method. Twelve rats (12) (6 obese and 6 controls)
were mated by introduction of male Sprague Dawley rats into the female cages. Mating success was
assessed through vaginal smears. First day of spermatozoa presence in the vagina indicated mating
success and marked day zero of gestation. HED and control diets were maintained throughout the
duration of the experiments. Obese rats had disrupted and extended estrous cycles, elevated serum
cortisol (5.12±1.45) and estradiol (214±17.28) levels. There was an inverse correlation between the
concentrations of cortisol and estradiol in blood sera of obese rats:-r =0.64.There was a mating
success of 66.7%.Single tailed Student t-test analysis indicated that there was no significant
difference in metestrus stage (t=1.44,p=0.14), gestation period (t= -0.76,P= 0.48), litter size (t =
0.28,P= 0.80) and litter weight(t = 0.30,P = 0.78) between the experimental and control rats.
However, there were significant differences in the frequencies of occurrence of proestrus (t=-2.66,
P=.02) estrus (t=5.13, P=.00) and diestrus (t=-2.45, P=.02) stages as well as serum levels of
cortisol (-2.87, P=.04) and estradiol 17b (t=5.37, P=.00). Obesity leads to an inverse relationship
between estradiol and cortisol resulting to disruption in the rat‟s estrous cycles. Findings form a
basis for the formulation of further controlled field trials that will lead to similar research in human
females.
