Firstly, we generated different experimental models of obesity-induced hypogonadism in male and female rats, including (i) rats bred in small litters (SL) and subjected to high fat diet (HFD) after weaning (SL/HFD), (ii) rats subjected to gonadectomy (GNX), (iii) rats subjected to a combination of the above manipulations (SL/HFD/GNX), and (iv) rats subjected to a protocol of neonatal androgenization with testosterone propionate (TP) or a combination of such protocol with nutritional manipulation (SL/HFD/TP), in the specific case of females. After the generation of those pre-clinical models, we evaluated the instauration and progression of obesity-induced hypogonadism as well as its metabolic co-morbidities in those animal models. Our results suggest that early overweight induced by nutritional manipulations not only evoke alterations in the activity of gonadotropic axis at early ages but also impaired metabolic and reproductive function later in life. Yet, the latter seems to be more pronounced in SL/HFD male rats.
Secondly, we measured (i) the circulating levels of the adipose hormone leptin and the pancreatic hormone insulin, as endocrine targets, and (ii) the hypothalamic content of the histone deacetylase Sirtuin 1 (SIRT1) and a specific microRNA (miRNA), as epigenetic markers, in SL/HFD animal models. Interestingly, our hormonal analyses suggest that early alterations in leptin and insulin serum levels might serve as potential endocrine markers for obesity-induced hypogonadism and/or altered reproductive function in male and female rats, respectively. Furthermore, our expression studies of the above epigenetic regulatory elements revealed that alterations in the hypothalamic expression of SIRT1 might contribute to the altered reproductive function observed in SL/HFD female rats, while changes in the hypothalamic expression of a specific miRNA may underlie the phenotype of obesity-induced hypogonadism observed in SL/HFD male rats.
Thirdly, we evaluated the specific impact of the above alterations on the hypothalamic KNDy neurons, epitomized by Kiss1, and its contribution to the phenotype of impaired reproductive function and obesity-induced hypogonadism in SL/HFD female and male rats, respectively. Our data show that SIRT1 alters the activity of KNDy neurons by an epigenetic regulatory mechanism that affects Kiss1 expression in SL/HFD female rats with altered reproductive function. Moreover, we found that a specific miRNA regulates Kiss1 expression in SL/HFD male rats with obesity-induced hypogonadism and that the central manipulation of this miRNA ameliorates such phenotype and its metabolic co-morbidities.
Finally, it is worth to mention that exploitation and dissemination of the results have taken place as planned in the original proposal. All results derived from this project were shared with the scientific community through (i) multidisciplinary seminars and weekly meetings organized by the host group (Tena-Sempere's lab); (ii) International scientific conferences (e.g. Endocrine Society Annual Meeting and International Congress of Neuroendocrinology); and (iii) scientific publications in reputed peer-review journals. Indeed, part of the results of this project has been published in the journal Nature Communications. In addition, the fellow have actively participated in different outreach activities, including 1 seminar with school students (IMIBIC, Cordoba, 2016), (ii) 1 seminar with members of "Asociación Cultural Capella Cordubensis" (IMIBIC, Cordoba, 2017), and (iii) 3 exhibitions: 2 European Researcher's Night (Cordoba, 2017 and 2018) and “Paseo por la Ciencia” (Cordoba, 2017).
