Differential expression of microRNAs in luteinising hormone-treated mouse TM3 Leydig cells

microRNA-378b regulates ethanol-induced hepatic steatosis by targeting CaMKK2 to mediate lipid metabolism

Alcoholic liver disease (ALD) has seriously harmed the health of people worldwide, but its underlying mechanisms remain unclear. This study aims to clarify the biological function of microRNA-378b (miR-378b) in ethanol (EtOH)-induced hepatic lipid accumulation. Here, we report miR-378b is over-expressed in EtOH-induced cells and EtOH-fed mice and finally accelerates lipid accumulation. MiR-378b directly targets Ca2+/calmodulin-dependent protein kinase kinase 2 (CaMKK2), a kinase of AMP-activated protein kinase (AMPK), and mediates the protein level of CaMKK2. Over-expression of miR-378b exacerbated the lipid accumulation induced by EtOH and inhibited CaMKK2 and the AMPK cascade while inhibition of miR-378b ameliorated lipid metabolism dysfunction in vivo and in vitro. In brief, our results show that miR-378b plays an important role in the regulation of lipid metabolism by directly targeting CaMKK2.

Cyclin-dependent kinase inhibitor 1B acts as a novel molecule to mediate testosterone synthesis and secretion in mouse Leydig cells by luteinizing hormone (LH) signaling pathway

Cyclin-dependent kinase inhibitor 1B (Cdkn1b, p27) plays important regulatory roles in many cellular processes. p27 is highly expressed in the mouse testis, but its roles and underlying mechanisms for testosterone synthesis and secretion remain not well understood. In the current study, we found that p27 located in Leydig cells and Sertoli cells of adult mouse testis. To explore the function of p27 in Leydig cells, p27 inhibitor and activator were injected into the adult mice, primary Leydig cells and TM3 cells. Our in vivo and in vitro results showed that change in the expression of p27 significantly alters the testosterone in both globe serum and culture medium. Meanwhile, the steroidogenesis-related gene expression was significantly regulated too. Moreover, our in vitro study showed that luteinizing hormone (LH) significantly increased p27 mRNA levels. Furthermore, our results proved that altering the mRNA expression of p27 leads to the synchronized changes of Lhcgr, Star, Cyp11a1, Hsd3b6, Cyp11a1, and Hsd17b3. Alterations of p27 also result in synchronously changes of RAF1 and ERK1/2 phosphorylation. These findings indicate that p27 plays vital roles in LH-induced testosterone production, providing a novel mechanism that p27 acts as an upstream molecule to elevate ERK1/2 phosphorylation to promote the expression of StAR and other cholesterol-metabolizing enzymes.

Analysis of the miRNA Expression Profiles in the Zearalenone-Exposed TM3 Leydig Cell Line

Zearalenone (ZEN), an important environmental pollutant, can cause serious harm to human and animal health. The aim of our study was to examine the effect of zearalenone (ZEN) on miRNA expression profiles in the mouse Leydig cell line (TM3 Leydig cell line) by miRNA sequencing. The effect of ZEN on the viability of TM3 Leydig cells was verified by Cell Counting Kit-8 (CCK-8). MiRNA sequencing was performed 24 h after the exposure of TM3 Leydig cells with 50 μmol/L of ZEN. Bioinformatics predicted the miRNA target genes, performed Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, and conducted miRNA-gene-pathway mapping to show the relationship between miRNA, the target gene, and the signalling pathway. The expression levels of miRNA and the miRNA target genes associated with ZEN toxicology were verified by quantitative real-time polymerase chain reaction. The miRNA sequencing revealed a significant change (p < 0.05) in the 197 miRNAs in the ZEN-treated and control groups, among which 86 were up-regulated and 111 were down-regulated. GO analysis of the target genes of these miRNAs indicated various biological functions. KEGG analysis showed that the predicted miRNA target genes were involved in signalling pathways, such as cancer, apoptosis, and oxidation, namely, the Ras signalling pathway, Rap1 signalling pathway, PI3K-AKT signalling pathway, Foxo signalling pathway, and AMPK signalling pathway. These results suggest that ZEN, as an estrogen-like toxin, is regulated by microRNAs. Our results can help to examine the toxicological effects of ZEN-regulated miRNAs on germ cells.

Current knowledge on the acute regulation of steroidogenesis

How rapid induction of steroid hormone biosynthesis occurs in response to trophic hormone stimulation of steroidogenic cells has been a subject of intensive investigation for approximately six decades. A key observation made very early was that acute regulation of steroid biosynthesis required swift and timely synthesis of a new protein whose role appeared to be involved in the delivery of the substrate for all steroid hormones, cholesterol, from the outer to the inner mitochondrial membrane where the process of steroidogenesis begins. It was quickly learned that this transfer of cholesterol to the inner mitochondrial membrane was the regulated and rate-limiting step in steroidogenesis. Following this observation, the quest for this putative regulator protein(s) began in earnest in the late 1950s. This review provides a history of this quest, the candidate proteins that arose over the years and facts surrounding their rise or decline. Only two have persisted-translocator protein (TSPO) and the steroidogenic acute regulatory protein (StAR). We present a detailed summary of the work that has been published for each of these two proteins, the specific data that has appeared in support of their role in cholesterol transport and steroidogenesis, and the ensuing observations that have arisen in recent years that have refuted the role of TSPO in this process. We believe that the only viable candidate that has been shown to be indispensable is the StAR protein. Lastly, we provide our view on what may be the most important questions concerning the acute regulation of steroidogenesis that need to be asked in future.