Transcriptomic analysis of hepatic responses to testosterone deficiency in miniature pigs fed a high-cholesterol diet

Abstract

BackgroundRecent studies have indicated that low serum testosterone levels are associated with increased risk of developing hepatic steatosis; however, the mechanisms mediating this phenomenon have not been fully elucidated. To gain insight into the role of testosterone in modulating hepatic steatosis, we investigated the effects of testosterone on the development of hepatic steatosis in pigs fed a high-fat and high-cholesterol (HFC) diet and profiled hepatic gene expression by RNA-Seq in HFC-fed intact male pigs (IM), castrated male pigs (CM), and castrated male pigs with testosterone replacement (CMT).ResultsSerum testosterone levels were significantly decreased in CM pigs, and testosterone replacement attenuated castration-induced testosterone deficiency. CM pigs showed increased liver injury accompanied by increased hepatocellular steatosis, inflammation, and elevated serum alanine aminotransferase levels compared with IM pigs. Moreover, serum levels of total cholesterol, low-density lipoprotein cholesterol, and triglycerides were markedly increased in CM pigs. Testosterone replacement decreased serum and hepatic lipid levels and improved liver injury in CM pigs. Compared to IM and CMT pigs, CM pigs had lower serum levels of superoxide dismutase but higher levels of malondialdehyde. Gene expression analysis revealed that upregulated genes in the livers of CM pigs were mainly enriched for genes mediating immune and inflammatory responses, oxidative stress, and apoptosis. Surprisingly, the downregulated genes mainly included those that regulate metabolism-related processes, including fatty acid oxidation, steroid biosynthesis, cholesterol and bile acid metabolism, and glucose metabolism. KEGG analysis showed that metabolic pathways, fatty acid degradation, pyruvate metabolism, the tricarboxylic acid cycle, and the nuclear factor-kappaB signaling pathway were the major pathways altered in CM pigs.ConclusionsThis study demonstrated that testosterone deficiency aggravated hypercholesterolemia and hepatic steatosis in pigs fed an HFC diet and that these effects could be reversed by testosterone replacement therapy. Impaired metabolic processes, enhanced immune and inflammatory responses, oxidative stress, and apoptosis may contribute to the increased hepatic steatosis induced by testosterone deficiency and an HFC diet. These results deepened our understanding of the molecular mechanisms of testosterone deficiency-induced hepatic steatosis and provided a foundation for future investigations.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1283-0) contains supplementary material, which is available to authorized users.

Testosterone Deficiency Induces Changes of the Transcriptomes of Visceral Adipose Tissue in Miniature Pigs Fed a High-Fat and High-Cholesterol Diet

“…In the previous study, APOE, APOC3, and APOA5 were shown to be positively associated with plasma triglyceride levels [31,32], which indicated VAT accumulation. Accordingly, our previous results found the levels of serum triglyceride were highly significant increased under testosterone deficiency in pigs fed a HFC diet [18]. Thus, our data suggested that these enhanced lipoproteins might contribute to VAT changes caused by testosterone deficiency under HFC feeding.…”

“…Therefore, by using pig model, our previous study discovered that castration-induced testosterone deficiency resulted in significant changes of miRNAs in subcutaneous adipose tissue, which were associated with fatty acid metabolism by acting on their target genes [17]. Moreover, we also found that testosterone deficiency caused severe hypercholesterolemia and hepatic steatosis in pigs fed a HFC diet and could be reversed by testosterone replacement therapy [18,19]. However, thus far, little is known about the underlying mechanisms of changes in VAT induced by testosterone deficiency under HFC diet, particularly in alterations of gene expression and regulation in VAT caused by testosterone changes.…”

Genome-Wide Analysis and Functional Characterization of the Polyadenylation Site in Pigs Using RNAseq Data

“…(6) Liver tissues were collected from the following three groups: high fat diet-fed intact male pigs, castrated male pigs, and castrated male pigs with testosterone replacement, from which total RNA was extracted and sequenced in 100-bp paired-end reads (SRP049250)44.…”

Cutaneous transcriptome analysis in NIH hairless mice

“…Transcriptome sequencing is used to study transcripts of particular tissues or organs of a species in a particular state and is superior to microarrays in terms of information volume and accuracy [ 12 ]. By constructing a transcriptome library, we can obtain information about transcripts and alternative splicing and can determine the differential expression patterns of specific genes [ 13 – 16 ].…”