NEAT1/hsa-miR-372-3p axis participates in rapamycin-induced lipid metabolic disorder

Knockdown of NEAT1 prevents post-stroke lipid droplet agglomeration in microglia by regulating autophagy

BACKGROUND

Lipid droplets (LD), lipid-storing organelles containing neutral lipids like glycerolipids and cholesterol, are increasingly accepted as hallmarks of inflammation. The nuclear paraspeckle assembly transcript 1 (NEAT1), a long non-coding RNA with over 200 nucleotides, exerts an indispensable impact on regulating both LD agglomeration and autophagy in multiple neurological disorders. However, knowledge as to how NEAT1 modulates the formation of LD and associated signaling pathways is limited.

METHODS

In this study, primary microglia were isolated from newborn mice and exposed to oxygen-glucose-deprivation/reoxygenation (OGD/R). To further explore NEAT1-dependent mechanisms, an antisense oligonucleotide (ASO) was adopted to silence NEAT1 under in vitro conditions. Studying NEAT1-dependent interactions with regard to autophagy and LD agglomeration under hypoxic conditions, the inhibitor and activator of autophagy 3-methyladenine (3-MA) and rapamycin (RAPA) were used, respectively. In a preclinical stroke model, mice received intraventricular injections of ASO NEAT1 or control vectors in order to yield NEAT1 knockdown. Analysis of readout parameters included qRT-PCR, immunofluorescence, western blot assays, and behavioral tests.

RESULTS

Microglia exposed to OGD/R displayed a temporal pattern of NEAT1 expression, peaking at four hours of hypoxia followed by six hours of reoxygenation. After effectively silencing NEAT1, LD formation and autophagy-related proteins were significantly repressed in hypoxic microglia. Stimulating autophagy in ASO NEAT1 microglia under OGD/R conditions by means of RAPA reversed the downregulation of LD agglomeration and perilipin 2 (PLIN2) expression. On the contrary, application of 3-MA promoted repression of both LD agglomeration and expression of the LD-associated protein PLIN2. Under in vivo conditions, NEAT1 was significantly increased in mice at 24 h post-stroke. Knockdown of NEAT1 significantly alleviated LD agglomeration and inhibited autophagy, resulting in improved cerebral perfusion, reduced brain injury and increased neurological recovery.

CONCLUSION

NEAT1 is a key player of LD agglomeration and autophagy stimulation, and NEAT1 knockdown provides a promising therapeutic value against stroke.

Early Leishmania infectivity depends on miR-372/373/520d family-mediated reprogramming of polyamines metabolism in THP-1-derived macrophages

Leishmania amazonensis is a protozoan that primarily causes cutaneous leishmaniasis in humans. The parasite relies on the amino acid arginine to survive within macrophages and establish infection, since it is a precursor for producing polyamines. On the other hand, arginine can be metabolized via nitric oxide synthase 2 (NOS2) to produce the microbicidal molecule nitric oxide (NO), although this mechanism does not apply to human macrophages since they lack NOS2 activity. MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression at posttranscriptional levels. Our previous work showed that mmu-miR-294 targets Nos2 favoring Leishmania survival in murine macrophages. Here, we demonstrate that human macrophages upregulate the hsa-miR-372, hsa-miR-373, and hsa-miR-520d, which present the same seed sequence as the murine mmu-miR-294. Inhibition of the miR-372 impaired Leishmania survival in THP-1 macrophages and the effect was further enhanced with combinatorial inhibition of the miR-372/373/520d family, pointing to a cooperative mechanism. However, this reduction in survival is not caused by miRNA-targeting of NOS2, since the seed-binding motif found in mice is not conserved in the human 3'UTR. Instead, we showed the miR-372/373/520d family targeting the macrophage's main arginine transporter SLC7A2/CAT2 during infection. Arginine-related metabolism was markedly altered in response to infection and miRNA inhibition, as measured by Mass Spectrometry-based metabolomics. We found that Leishmania infection upregulates polyamines production in macrophages, as opposed to simultaneous inhibition of miR-372/373/520d, which decreased putrescine and spermine levels compared to the negative control. Overall, our study demonstrates miRNA-dependent modulation of polyamines production, establishing permissive conditions for intracellular parasite survival. Although the effector mechanisms causing host cell immunometabolic adaptations involve various parasite and host-derived signals, our findings suggest that the miR-372/373/520d family may represent a potential target for the development of new therapeutic strategies against cutaneous leishmaniasis.

Mulberry leaves supplementation alters lipid metabolism and promotes fatty acid β oxidation in growing mutton sheep

Mulberry leaves (MLs) are an unconventional feed with fiber and various active ingredients, and are acknowledged as likely to regulate lipid metabolism, while the molecular mechanism remains undefined. Therefore, our objective was to define the role of MLs on the overall lipid metabolism. We conducted a feeding experiment of three groups on growing mutton sheep fed with dried mulberry leaves (DMLs), with fermented mulberry leaves (FMLs), or without MLs (as control). Analyses of transcriptome and widely target lipids demonstrated the addition of MLs triggered big perturbations in genes and metabolites related to glycerolipid, phospholipid, ether lipid, and sphingolipid metabolism. Additionally, the variations of the above lipids in the treatment of MLs possibly facilitate immunity enhancement of growing mutton sheep via the activation of complement and coagulation cascades. Furthermore, treatments with MLs could expedite proceedings of lipid degradation and fatty acid β oxidation in mitochondria, thereby to achieve the effect of lipid reduction. Besides, added DMLs also fuel fatty acid β-oxidation in peroxisomes and own much stronger lipolysis than added FMLs, possibly attributed to high fiber content in DMLs. These findings establish the novel lipid-lowering role and immune protection of MLs, which lays the foundation for the medicinal application of MLs.

Current advancements and future perspectives of long noncoding RNAs in lipid metabolism and signaling

BACKGROUND

The investigation of lncRNAs has provided a novel perspective for elucidating mechanisms underlying diverse physiological and pathological processes. Compelling evidence has revealed an intrinsic link between lncRNAs and lipid metabolism, demonstrating that lncRNAs-induced disruption of lipid metabolism and signaling contribute to the development of multiple cancers and some other diseases, including obesity, fatty liver disease, and cardiovascular disease.

AIMOF REVIEW

The current review summarizes the recent advances in basic research about lipid metabolism and lipid signaling-related lncRNAs. Meanwhile, the potential and challenges of targeting lncRNA for the therapy of cancers and other lipid metabolism-related diseases are also discussed.

KEY SCIENTIFIC CONCEPT OF REVIEW

Compared with the substantial number of lncRNA loci, we still know little about the role of lncRNAs in metabolism. A more comprehensive understanding of the function and mechanism of lncRNAs may provide a new standpoint for the study of lipid metabolism and signaling. Developing lncRNA-based therapeutic approaches is an effective strategy for lipid metabolism-related diseases.

A mixed blessing for liver transplantation patients - Rapamycin

BACKGROUND

Liver transplantation (LT) is an effective treatment option for end-stage liver disease. Mammalian target of rapamycin (mTOR) inhibitors, such as rapamycin, are widely used post LT.

DATA SOURCES

In this review, we focused on the anti-cancer activities and metabolic side effects of rapamycin after LT. The literature available on PubMed for the period of January 1999-September 2022 was reviewed. The key words were rapamycin, sirolimus, liver transplantation, hepatocellular carcinoma, diabetes, and lipid metabolism disorder.

RESULTS

Rapamycin has shown excellent effects and is safer than other immunosuppressive regimens. It has exhibited excellent anti-cancer activity and has the potential in preventing hepatocellular carcinoma (HCC) recurrence post LT. Rapamycin is closely related to two long-term complications after LT, diabetes and lipid metabolism disorders.

CONCLUSIONS

Rapamycin prevents HCC recurrence post LT in some patients, but it also induces metabolic disorders. Reasonable use of rapamycin benefits the liver recipients.

Knockdown of miR-372-3p Inhibits the Development of Diabetic Cardiomyopathy by Accelerating Angiogenesis via Activating the PI3K/AKT/mTOR/HIF-1α Signaling Pathway and Suppressing Oxidative Stress

Background

DCM is the most common and malignant complication of diabetes. It is characterized by myocardial dilatation, hypertrophy, fibrosis, ventricular remodeling, and contractile dysfunction. Although many studies have demonstrated the function of miRNAs in the progression of DCM, but the specific role of miR-372-3p in DCM remains unknown.

Methods

C57/BL6J mice were used to construct mouse models of DCM by intraperitoneal injection of STZ (50 mg/kg/d) for 5 consecutive days. Then the mice were randomly divided into model group (intramyocardial injection of empty lentivirus) and miR-372-3p KD group (intramyocardial injection of miR-372-3p KD lentivirus at 10⁹/mouse). Besides, the control group (injection of 0.9% normal saline) was also set up. LY294002, a PI3K inhibitor, was employed in the current study. Western blotting, immunofluorescence staining, quantitative ultrasound method, Masson's trichrome staining, and bioinformatics analysis were performed.

Results

It was found that miR-372-3p KD significantly improved left ventricular dysfunction and cardiac hypertrophy in DCM mice. Furthermore, it also improved myocardial interstitial fibrosis and remodeling in DCM mice. Immunofluorescence staining and RT-qPCR revealed that miR-372-3p KD might accelerate cardiac remodeling by increasing angiogenesis in DCM mice. Western blotting results revealed that miR-372-3p was an upstream target of the PI3K/AKT-mTOR and HIF-1α signals, as well as NOX2, NOX4, which were responsible for angiogenesis in DCM mice. Besides, the in vitro experiment showed that LY294002 markedly diminished the increased expression levels of p-PI3K, AKT, p-mTOR, p-P70S6K, HIF-1α, NOX2, and NOX4 in the model group and the miR-372-3p KD group, suggesting that PI3K signaling pathway and oxidative stress are involved in miR-372-3p KD-induced angiogenesis in HG-stimulated C166 cells.

Conclusions

MiR-372-3p KD inhibits the development of DCM via activating the PI3K/AKT/mTOR/HIF-1α signaling pathway or suppressing oxidative stress. This offers an applicable biomarker for DCM treatment.

Metabolic Control by DNA Tumor Virus-Encoded Proteins

Viruses co-opt a multitude of host cell metabolic processes in order to meet the energy and substrate requirements for successful viral replication. However, due to their limited coding capacity, viruses must enact most, if not all, of these metabolic changes by influencing the function of available host cell regulatory proteins. Typically, certain viral proteins, some of which can function as viral oncoproteins, interact with these cellular regulatory proteins directly in order to effect changes in downstream metabolic pathways. This review highlights recent research into how four different DNA tumor viruses, namely human adenovirus, human papillomavirus, Epstein-Barr virus and Kaposi's associated-sarcoma herpesvirus, can influence host cell metabolism through their interactions with either MYC, p53 or the pRb/E2F complex. Interestingly, some of these host cell regulators can be activated or inhibited by the same virus, depending on which viral oncoprotein is interacting with the regulatory protein. This review highlights how MYC, p53 and pRb/E2F regulate host cell metabolism, followed by an outline of how each of these DNA tumor viruses control their activities. Understanding how DNA tumor viruses regulate metabolism through viral oncoproteins could assist in the discovery or repurposing of metabolic inhibitors for antiviral therapy or treatment of virus-dependent cancers.