The Involvement of the microRNAs miR-466c and miR-340 in the Palmitate-Mediated Dysregulation of Gonadotropin-Releasing Hormone Gene Expression.

Diets high in saturated fatty acids are associated with obesity and infertility. Palmitate, the most prevalent circulating saturated fatty acid, is sensed by hypothalamic neurons, contributing to homeostatic dysregulation. Notably, palmitate elevates the mRNA levels of gonadotropin-releasing hormone (Gnrh) mRNA and its activating transcription factor, GATA binding protein 4 (Gata4). GATA4 is essential for basal Gnrh expression by binding to its enhancer region, with Oct-1 (Oct1) and CEBP-ß (Cebpb) playing regulatory roles. The pre- and post-transcriptional control of Gnrh by palmitate have not been investigated. Given the ability of palmitate to alter microRNAs (miRNAs), we hypothesized that palmitate-mediated dysregulation of Gnrh mRNA involves specific miRNAs. In the mHypoA-GnRH/GFP neurons, palmitate significantly downregulated six miRNAs (miR-125a, miR-181b, miR-340, miR-351, miR-466c and miR-503), and the repression was attenuated by co-treatment with 100 µM of oleate. Subsequent mimic transfections revealed that miR-466c significantly downregulates Gnrh, Gata4, and Chop mRNA and increases Per2, whereas miR-340 upregulates Gnrh, Gata4, Oct1, Cebpb, and Per2 mRNA. Our findings suggest that palmitate may indirectly regulate Gnrh at both the pre- and post-transcriptional levels by altering miR-466c and miR-340, which in turn regulate transcription factor expression levels. In summary, palmitate-mediated dysregulation of Gnrh and, consequently, reproductive function involves parallel transcriptional mechanisms.

The Regulation of Phoenixin: A Fascinating Multidimensional Peptide.

The phoenixin (PNX) peptide is linked to the control of reproduction, food intake, stress, and inflammation. However, little is known about what regulates its gene and protein expression, information that is critical to understand the physiological role of PNX. In this review, we summarize what is known about the transcriptional control of Pnx and its receptor Gpr173. A main function of PNX is as a positive regulator of the hypothalamic-pituitary-gonadal axis, but there is a lack of research on its control by reproductive hormones and peptides. PNX is also associated with food intake, and its expression is linked to feeding status, fatty acids, and glucose. It is influenced by environmental and hormonal-induced stress. The regulation of Pnx in most contexts remains an enigma, in part due to conflicting and negative results. An extensive analysis of the response of the Pnx gene to factors related to reproduction, metabolism, stress, and inflammation is required. Analysis of the Pnx promoter and epigenetic regulation must be considered to understand how this level of control contributes to its pleiotropic effects. PNX is now linked to a broad range of functions, but more research on its gene regulation is required to understand its place in overall physiology and therapeutic potential.

Matrix Stiffness-Regulated Growth of Breast Tumor Spheroids and Their Response to Chemotherapy.

Interactions between tumor cells and the extracellular matrix (ECM) are an important factor contributing to therapy failure in cancer patients. Current in vitro breast cancer spheroid models examining the role of mechanical properties on spheroid response to chemotherapy are limited by the use of two-dimensional cell culture, as well as simultaneous variation in hydrogel matrix stiffness and other properties, e.g., hydrogel composition, pore size, and cell adhesion ligand density. In addition, currently used hydrogel matrices do not replicate the filamentous ECM architecture in a breast tumor microenvironment. Here, we report a collagen-alginate hydrogel with a filamentous architecture and a 20-fold variation in stiffness, achieved independently of other properties, used for the evaluation of estrogen receptor-positive breast cancer spheroid response to doxorubicin. The variation in hydrogel mechanical properties was achieved by altering the degree of cross-linking of alginate molecules. We show that soft hydrogels promote the growth of larger MCF-7 tumor spheroids with a lower fraction of proliferating cells and enhance spheroid resistance to doxorubicin. Notably, the stiffness-dependent chemotherapeutic response of the spheroids was temporally mediated: it became apparent at sufficiently long cell culture times, when the matrix stiffness has influenced the spheroid growth. These findings highlight the significance of decoupling matrix stiffness from other characteristics in studies of chemotherapeutic resistance of tumor spheroids and in development of drug screening platforms.