Unraveling the impact of hyperleptinemia on female reproduction: Insights from transgenic pig model

Abstract

Background Infertility is a growing global health concern affecting millions of couples worldwide. Among several factors, an extreme body weight adversely affects reproductive functions. Leptin is a well-known adipokine that serves as an endocrine signal between adiposity and fertility. However, the exact mechanisms underlying the effects of high leptin on female reproduction remain unclear. Methods Transgenic pig overexpressing leptin (♀) were produced by back cross and screened for leptin overexpression, and the growth curve, fat deposition, reproductive performance, apoptosis, serum hormones and cholesterol production, RNA sequencing, and single nucleus RNA sequencing of the leptin-overexpressed pigs and control group were evaluated. Results Transgenic pig overexpressing leptin (♀) were obtained, which exhibited significantly reduced body weight, body size, and back fat thickness. These pigs manifested late onset of puberty (327 vs 150 days), irregular estrous behavior characterized by increased inter-estrous interval (28.1vs 21.3 days), and more numbers of mating until pregnancy (at least 3 times). This reproductive impairment in leptin pigs was related to hormonal imbalances characterized by increased levels of FSH, LH, prolactin, E2, P4, and TSH, altered steroidogenesis such as increased levels of serum CE along with steroidogenic markers (STAR, CYP19A), and ovarian dysfunctions manifested by neutrophilic infiltration and low expression of caspase-3 positive cells on leptin pigs ovary. Meanwhile, bulk RNA sequencing of the ovaries also revealed neutrophilic infiltration followed by upregulation of inflammation-related genes. Further, leptin overexpression triggered immune response, suppressed follicle development and luteinization, imposing metabolism dysfunction and hormone imbalance in the ovary by single-nucleus RNA sequencing (snRNA-seq). Conclusion Low body weight in leptin overexpression pigs adversely affects reproductive performance, causing delayed puberty, irregular estrous cycles, and reduced breeding efficiency. This is linked to metabolic imbalances, increased immune response, and altered ovarian functions. This study provided a theoretical basis for the complex mechanisms underlying leptin, and infertility by employing leptin-overexpressed female pigs.