INTRODUCTION: The reproductive capacity of mammals is governed by the hypothalamus-pituitary-gonadal (HPG) axis, with gonadotropin-releasing hormone (GnRH) localized on top of it. Neuronal population expressing kisspeptin, neurokinin B (NKB), and dynorphin (KNDy neurons), present in the arcuate nucleus (ARC) of the hypothalamus, are important for regulating GnRH secretion. Both obesity and type 2 diabetes (DM2) are major risk factors for reproductive alterations (e.g., decreased fertility). Because ARC is a site where cross‑talk between metabolism and reproduction occurs, those states may influence KNDy neurons. However, data on the role of metabolic imbalance, gonadectomy, and sex steroid replacement in the regulation of NKB expression are limited, especially in females. AIM(S): The aim of this study was to assess the effects of metabolic disruption (high-fat diet-induced and DM2), ovariectomy, and sex hormone replacement on the number of NKB-immunoreactive (-ir) neurons in the ARC of female rats. METHOD(S): Female rats received a control (C) or high‑fat diet (HFD) for 13 weeks. Streptozotocin injections were performed to induce DM2 in half of the animals from the HFD group. The following groups were obtained: C, HFD, and DM2. Then, animals were divided into three subgroups: ovariectomy (OVX), ovariectomy and estradiol replacement (OVX+E2), and ovariectomy together with estradiol and progesterone replacement (OVX+E2+P4). Metabolic profile was assessed and immunohistochemistry for NKB was performed. RESULTS: There was an effect of operation (p<0.01). In C and DM2, there was a higher number of NKB-ir cells in OVX+E2+P4 vs. OVX. Additionally, in the DM2 group, a higher number of NKB-ir was seen in OVX+E2 vs. OVX. CONCLUSIONS: HFD does not change the response of NKB‑ir neurons to OVX and hormonal replacement. However, in DM2 females, NKB-ir neurons are more sensitive to the OVX+E2 condition. FINANCIAL SUPPORT: Supported by NCN grant 2015/17/B/NZ4/02021.
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