Time-dependent alterations in mRNA, protein and microRNA during in vitro adipogenesis

Long noncoding RNA AI504432 upregulates FASN expression by sponging miR-1a-3p to promote lipogenesis in senescent adipocytes

Aging affects lipid metabolism and can cause obesity as it is closely related to the disorder of many lipogenic regulatory factors. LncRNAs have been recognized as pivotal regulators across diverse biological processes, but their effects on lipogenesis in aging remain to be further studied. In this work, using RNA sequencing (RNA-Seq), we found that the expression of lncRNA AI504432 was significantly upregulated in the eWAT (epididymal white adipose tissue) of aging mice, and the knockdown of AI504432 notably reduced the expression of several adipogenic genes (e.g., Cebp/α, Srebp-1c, Fasn, Acaca, and Scd1) in senescent adipocytes. The bioinformatics investigation revealed that AI504432 possessed a binding site for miR-1a-3p, and the discovery was verified by the luciferase reporter assay. The expression of Fasn was increased upon the inhibition of miR-1a-3p but restored upon the simultaneous silencing of AI504432. Taken together, our results suggested that AI504432 controlled lipogenesis through the miR-1a-3p/Fasn signaling pathway. The findings may inspire new therapeutic approaches to target imbalanced lipid homeostasis due to aging.

Expression Profiling of Adipogenic and Anti-Adipogenic MicroRNA Sequences following Methylmercury Exposure in Caenorhabditis elegans

MicroRNA (miRNA) are important regulators of gene expression that respond not only to developmental and pathological cues, but also to environmental stimuli. Dyslipidemia is a hallmark of metabolic conditions and has been shown to significantly affect the expression of circulating miRNA sequences. Recently, our lab has shown that the environmental toxicant methylmercury (MeHg) causes dyslipidemia in the Caenorhabditis elegans model organism. While 10 and 20 μM MeHg increases the expression of adipogenic transcription factors and lipid-binding proteins in worms, there is limited information on how the toxicant affects the miRNA regulators of these genes. We hypothesized that MeHg would increase the expression of adipogenic miRNA sequences and/or decrease the expression of anti-adipogenic miRNA sequences. We further hypothesized that the target mRNA sequences for the miRNAs affected by MeHg would be consequently altered. We selected three potentially adipogenic (mir-34, mir-124, and mir-355) and three potentially anti-adipogenic (mir-240, mir-786, and let-7) miRNA sequences homologous to known human miRNA sequences altered in obesity, and quantified their levels 24 h and 48 h post MeHg treatment. At 24 h post exposure, MeHg significantly increased expression of both the adipogenic and anti-adipogenic miRNA sequences 1.5-3x above untreated control. By 48 h post exposure, only the adipogenic miRNA sequences were elevated, while the anti-adipogenic miRNA sequences were decreased by 50% compared to untreated control. These data suggest that there are developmental changes in miRNA expression over time following MeHg exposure. We next selected one target mRNA sequence for each miRNA sequence based on miRNA-mRNA relationships observed in humans. MeHg altered the gene expression of all the target genes assayed. Except for mir-34, all the tested miRNA-mRNA sequences showed a conserved relationship between nematode and humans. To determine whether the selected miRNA sequences were involved in lipid accumulation in response to MeHg, lipid storage was investigated in transgenic worm strains that lacked the specific miRNA strains. Of the six strains investigated, only the mir-124 and let-7 mutant worms had lipid storage levels that were statistically different from wild type, suggesting that these two sequences can be potential mediators of MeHg-induced lipid dysregulation.

The cross-talk between adipokines and miRNAs in health and obesity-mediated diseases

BACKGROUND

Multiple studies have revealed a direct correlation between obesity and the development of multiple comorbidities, including metabolic diseases, cardiovascular disorders, chronic inflammatory disease, and cancers. However, the molecular mechanism underlying the link between obesity and the progression of these diseases is not completely understood. Adipokines are factors that are secreted by adipocytes and play a key role in whole body homeostasis. Collaboratively, miRNAs are suggested to have key functions in the development of obesity and obesity-related disorders. Based on recently emerging evidence, obesity leads to the dysregulation of both adipokines and obesity-related miRNAs. In the present study, we described the correlations between obesity and its related diseases that are mediated by the mutual regulatory effects of adipokines and miRNAs.

METHODS

We reviewed current knowledge of the modulatory effects of adipokines on miRNAs activity and their relevant functions in pathological conditions and vice versa.

RESULTS

Our research reveals the ability of adipokines and miRNAs to control the expression and activity of the other class of molecules, and their effects on obesity-related diseases.

CONCLUSIONS

This study may help researchers develop a roadmap for future investigations and provide opportunities to develop new therapeutic and diagnostic methods for treating obesity-related diseases.

Betulinic acid lowers lipid accumulation in adipocytes through enhanced NCoA1-PPARγ interaction

BACKGROUND

Investigation for a naturally occurring anti-obesity drug has become the need of society all over the world. Betulinic acid (BA) is a lupane-type pentacyclic triterpene and is sourced from various organisms. This high potential biologically active molecule is reported to have anti-obesity effect. In this study, we report the molecular mechanism of action of BA that underlies anti-obesity activity and also an improved method of its isolation common teak tree.

METHODS

Mouse pre-adipocyte cells were used to develop hyperlipidemic conditions in vitro. Change in expression of genes associated to adipogenesis was checked using quantitative real-time PCR (qPCR). Co-factor specificity of PPAR gamma was analyzed through immune precipitation and immunoblot.

RESULTS

Betulinic acid was found to be effective in reducing the lipid content in 3T3L1 cells. Level of PPAR gamma and LXR alpha was reduced in connection to reduced adipogenesis. Change in steroid responsive co-activators (SRCs) during BA treatment proved that the compound can impart profound change in co-factor selectivity, which is crucial in determining the activity profile of PPAR gamma. BA treatment enhanced the SRC-1 interaction with PPAR gamma while reducing the levels of SRC-3.

CONCLUSION

Present study has proved that betulinic acid, a promising candidate in anti-obesity drug development, has potential in regulating the activity of PPAR gamma through co-factor modulation.

Changes in morphology and miRNAs expression in small intestines of Shaoxing ducks in response to high temperature

During summer days the extreme heat may cause damage to the integrity of animal intestinal barrier. Little information is available concerning morphological changes in the duck intestines in response to high temperature. And the molecular mechanisms underlying the pathogenesis of high temperature-induced intestinal injury remain undefined. MicroRNAs (miRNAs) are known to play key roles in post-transcriptional regulation of gene expression that influences various biological processes. The purpose of this study was to explore the changes in morphology and miRNA expression profiles of the three intestinal segments (duodenum, jejunum and ileum) of ducks in response to high temperature. Sixty female Shaoxing ducks (Anas platyrhynchos), 60 days old, were allocated in two groups, including control ducks kept at 25 °C, and ducks subjected to high ambient temperatures of 30-40 °C for 15 successive days, which mimicked the diurnal temperature variations experienced in hot seasons. Three ducks from each group were executed at the end of feeding experiment, and the samples of three intestinal segments were collected for morphological examination and Illumina deep sequencing analyses. Histopathological examination of the intestinal mucous membrane was performed with HE staining method. The results demonstrated that varying degrees of damage to each intestinal segment were found in heat-treated ducks, and there were more severe injuries in duodenum and jejunum than those in ileum. Illumina high-throughput sequencing and bioinformatic methods were employed in this study to identify the miRNA expression profile of three different intestinal tissues in control and heat-treated ducks. A total of 75,981,636, 88,345,563 and 100,179,422 raw reads were obtained from duodenum, jejunum and ileum, respectively, from which 74,797,633 clean reads in duodenal libraries, 86,406,445 clean reads in jejunal libraries, and 98,518,858 lean reads in ileal libraries were derived after quality control, respectively. And a total of 276 known and 182 novel miRNAs were identified in the three intestinal segments of ducks under control and heat-treated conditions. By comparing the same tissues in different conditions, 16, 18 and 15 miRNAs were found to be significantly differentially expressed between control and heat-treated ducks in duodenum, jejunum and ileum, respectively, of which 1 miRNA was expressed in both the duodenum and jejunum, 2 miRNAs were expressed in both the duodenum and ileum, and 3 miRNAs were found to be expressed in both the jejunum and ileum. In addition, two differentially expressed miRNAs in each comparison were randomly selected and validated by quantitative qRT-PCR. Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated that the differentially expressed miRNAs may be involved in the high temperature-induced intestinal injury in ducks. Our work provides the comprehensive miRNA expression profiles of small intestines in the normal and heat-treated ducks. These findings suggest the involvement of specific molecular mechanisms of post-transcriptional regulation to explain the high temperature-induced changes in the duck small intestine.

Protein engineering: Regulatory perspectives of stearoyl CoA desaturase

Stearoyl Co A desaturase (SCD) is a rate-limiting lipogenic enzyme that plays an integral role in catalyzing the synthesis of monounsaturated fatty acids, chiefly oleate and palmitoleate. Both contribute a major part of the biological membrane. Numerous SCD isoforms exist in mouse and humans, i.e., SCD-1 to SCD-4 and SCD-1 and SCD-5, respectively. From the biological viewpoint, hyperexpression of SCD1 cause many metabolic disorders including obesity, insulin resistance, hypertension, and hypertriglyceridemia, etc. Herein, an effort has been made to highlight the value of protein engineering in controlling the SCD-1 expression with the involvement of different inhibitors as therapeutic agents. The first part of the review describes Stearoyl CoA desaturase index and different SCD isoforms. Various regulatory aspects of SCD are reviewed in four subsections, i.e., (1) hormonal regulation, (2) regulation by dietary carbohydrates, (3) regulation by green tea, and (4) regulation via polyunsaturated fatty acids (PUFAs). Moreover, the regulation of Stearoyl CoA desaturase expression in the metabolism of fats and carbohydrates is discussed. The third part mainly focuses on natural and synthetic inhibitors. Towards the end, information is also given on potential future considerations of SCD-1 inhibitors as metabolic syndrome therapeutics, yet additional work is required.