Global sex differences in obesity rates are persistent, suggesting the involvement of sex steroids. In addition, adipose tissue is a metabolic site for steroidogenesis. Here, we compared female reproductive parameters in a rat model of obesity, with the same parameters in its lean control strain, and tested for an association with integrated measures of corticosterone and testosterone. Steroids were extracted and quantified from 17 Otsuka Long Evans Tokushima Fatty (OLETF; an animal model for obesity) and 13 Long Evans Tokushima Otsuka (LETO; the lean control strain) hair samples that were collected after weaning offspring. The obese OLETF mothers had higher hair testosterone levels than the control LETO strain. Overall, testosterone, but not corticosterone, predicted litter sex ratios. Younger mothers with large litters and older mothers with small litters tended to have the highest sex ratios (i.e., male-biased litters). In the lean LETO strain, but not in the obese OLETF, maternal testosterone was positively associated with litter size and number of male pups. Corticosterone did not differ between the two strains and was not associated with testosterone or with reproductive parameters. This study suggests that long-term circulating testosterone is associated with female reproduction in multiple ways. The possible trade-off between litter size and sex ratio may be mediated by testosterone and influenced by body fat and composition, which influence the individual's well-being. Exploring the multiple roles of testosterone in females may also help explain the complex relationship between obesity and reproduction.
Keywords: Corticosterone; Hair-testing; Litter size; Reproduction; Sex ratio; Testosterone.
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