MiR‐145 Regulates Lipogenesis in Goat Mammary Cells Via Targeting INSIG1 and Epigenetic Regulation of Lipid‐Related Genes

Abstract

MicroRNAs (miRNAs) are noncoding RNA molecules that regulate gene expression at the post-transcriptional level to cause translational repression or degradation of targets. The profiles of miRNAs across stages of lactation in small ruminant species such as dairy goats is unknown. A small RNA library was constructed using tissue samples from mammary gland of Saanen dairy goats harvested at mid-lactation followed by sequencing via Solexa technology. A total of 796 conserved miRNAs, 263 new miRNAs, and 821 pre-miRNAs were uncovered. After comparative analyses of our sequence data with published mammary gland transcriptome data across different stages of lactation, a total of 37 miRNAs (including miR-145) had significant differences in expression over the lactation cycle. Further studies revealed that miR-145 regulates metabolism of fatty acids in goat mammary gland epithelial cells (GMEC). Compared with nonlactating mammary tissue, lactating mammary gland had a marked increase in expression of miR-145. Overexpression of miR-145 increased transcription of genes associated with milk fat synthesis resulting in greater fat droplet formation, triacylglycerol accumulation, and proportion of unsaturated fatty acids. In contrast, silencing of miR-145 impaired fatty acid synthesis. Inhibition of miR-145 increased methylation levels of fatty acid synthase (FASN), stearoyl-CoA desaturase 1 (SCD1), peroxisome proliferator-activated receptor gamma (PPARG), and sterol regulatory element binding transcription factor 1 (SREBF1). Luciferase reporter assays confirmed that insulin induced gene 1 (INSIG1) is a direct target of miR-145. These findings underscore the need for further studies to evaluate the potential for targeting miR-145 for improving beneficial milk components in ruminant milk. J. Cell. Physiol. 232: 1030-1040, 2017. © 2016 Wiley Periodicals, Inc.

Milk’s Role as an Epigenetic Regulator in Health and Disease

“…miRNA-145 is another miRNA epigenetically involved in the regulation of metabolism of fatty acids in goat MECs [126]. Overexpression of miRNA-145 increased the transcription of genes associated with milk fat synthesis resulting in the expansion of the lipid droplet compartment, increase of triacylglycerol accumulation, and upregulation of the proportion of unsaturated fatty acids.…”

“…Overexpression of miRNA-145 increased the transcription of genes associated with milk fat synthesis resulting in the expansion of the lipid droplet compartment, increase of triacylglycerol accumulation, and upregulation of the proportion of unsaturated fatty acids. In contrast, silencing of miRNA-145 impaired fatty acid synthesis [126]. Remarkably, inhibition of miRNA-145 increased methylation levels of FAS , SCD1 , PPARG , and SREBP1 .…”

Comparison of mammary lipid metabolism in dairy cows and goats fed diets supplemented with starch, plant oil, or fish oil

“…These data suggest differential posttranscriptional regulation of FASN among species due to (1) higher translation repression or degradation of mRNA in cows, which affects FASN protein synthesis and mRNA stability (Semenkovich et al, 1993) and may involve microRNA such as miR-145 (Wang et al, 2017) and miR-24 (Wang et al, 2015) that target FASN mRNA; (2) different ubiquitination of lysine or phosphorylation in sites of the protein sequence affecting protein activity (Wakil et al, 1989;Jensen-Urstad and Semenkovich, 2012); or (3) other mechanisms. In addition to the multifunctional enzyme FAS, the biosynthesis of de novo FA requires considerable amounts of reducing equivalents in the form of NADPH.…”

Non-Coding RNA Roles in Ruminant Mammary Gland Development and Lactation

“…In another study, miR-135a was reported to target and regulate prolactin receptor (PRLR) gene in GMEC [92]. Inhibition of the expression of miR-145 in GMEC was shown to increase methylation levels of fatty acid synthase (FASN), stearoyl-CoA desaturase 1 (SCD1), peroxisome proliferator-activated receptor gamma (PPARG) and sterol regulatory element binding transcription factor 1 (SREBF1) [93]. MiR-24 control of triacylglycerol synthesis in goat mammary epithelial cells by target-…”

“…The ability of miR-145 to regulate lipogenesis in GMEC through targeting insulin-induced gene 1 (INSIG1) and epigenetic regulation of lipidrelated genes has been demonstrated [93]. MiR-143 was shown to inhibit proliferation as well as induce apoptosis of GMEC [95].…”