Agrimol B suppresses adipogenesis through modulation of SIRT1-PPAR gamma signal pathway

TFEB activator Tanshinone IIA and derivatives derived from Salvia miltiorrhiza Bge. attenuate hepatic steatosis and insulin resistance

ETHNOPHARMACOLOGICAL RELEVANCE

Salvia miltiorrhiza Bge. (SMB) is an herbal medicine extensively used for improving metabolic disorders, including Nonalcoholic fatty liver disease (NAFLD). However, the potential material basis and working mechanism still remained to be elucidated.

AIM OF THE STUDY

To find potential ingredients for therapy of NAFLD by high content screening and further verify the efficacy on restoring hepatic steatosis and insulin resistance, and clarify the potential working mechanism.

MATERIALS AND METHODS

The mouse transcription factor EB (Tfeb) in preadipocytes was knocked out by CRISPR-Cas9 gene editing. High content screening of TFEB nuclear translocation was performed to identify TFEB activators. The effect of candidate compounds on reducing lipid accumulation was evaluated using Caenorhabditis elegans (C. elegans). Then the role of Salvia miltiorrhiza extract (SMB) containing Tanshinone IIA and the derivatives were further investigated on high-fat diet (HFD) fed mice. RNA-seq was performed to explore potential molecular mechanism of SMB. Finally, the gut microbiota diversity was evaluated using 16S rRNA sequencing to investigate the protective role of SMB on regulating gut microbiota homeostasis.

RESULTS

Knockout of Tfeb led to excessive lipid accumulation in adipocytes while expression of TFEB homolog HLH-30 in C. elegans (MAH240) attenuated lipid deposition. Screening of TFEB activators identified multiple candidates from Salvia miltiorrhiza, all of them markedly induced lysosome biogenesis in HepG2 cells. One of the candidate compounds Tanshinone IIA significantly decreased lipid droplet deposition in HFD fed C. elegans. Administration of SMB on C57BL/6J mice via gastric irrigation at the dose of 15 g/kg/d markedly alleviated hepatic steatosis, restored serum lipid profile, and glucose tolerance. RNA-seq showed that gene expression profile was altered and the genes related to lipid metabolism were restored. The disordered microbiome was remodeled by SMB, Firmicutes and Actinobacteriotawere notably reduced, Bacteroidota and Verrucomicrobiota were significantly increased.

CONCLUSION

Taken together, the observations presented here help address the question concerning what were the main active ingredients in SMB for alleviating NAFLD, and established that targeting TFEB was key molecular basis for the efficacy of SMB.

Targeted degradation of NDUFS1 by agrimol B promotes mitochondrial ROS accumulation and cytotoxic autophagy arrest in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a global public health problem with increased morbidity and mortality. Agrimol B, a natural polyphenol, has been proved to be a potential anticancer drug. Our recent report showed a favorable anticancer effect of agrimol B in HCC, however, the mechanism of action remains unclear. Here, we found agrimol B inhibits the growth and proliferation of HCC cells in vitro as well as in an HCC patient-derived xenograft (PDX) model. Notably, agrimol B drives autophagy initiation and blocks autophagosome-lysosome fusion, resulting in autophagosome accumulation and autophagy arrest in HCC cells. Mechanistically, agrimol B downregulates the protein level of NADH:ubiquinone oxidoreductase core subunit S1 (NDUFS1) through caspase 3-mediated degradation, leading to mitochondrial reactive oxygen species (mROS) accumulation and autophagy arrest. NDUFS1 overexpression partially restores mROS overproduction, autophagosome accumulation, and growth inhibition induced by agrimol B, suggesting a cytotoxic role of agrimol B-induced autophagy arrest in HCC cells. Notably, agrimol B significantly enhances the sensitivity of HCC cells to sorafenib in vitro and in vivo. In conclusion, our study uncovers the anticancer mechanism of agrimol B in HCC involving the regulation of oxidative stress and autophagy, and suggests agrimol B as a potential therapeutic drug for HCC treatment.

Activating the iNOS regulatory pathway by arginine deprivation targets energy metabolism to induce autophagy-dependent apoptosis against spinal echinococcosis

Spinal echinococcosis is one of the most overlooked zoonotic parasitic diseases worldwide. There is currently no safe and effective treatment to eradicate it, and research based on the physiological-metabolic signature of the disease is lacking. Herein, we repurposed agrimol B as a potent anti-hydatid compound and validated its pharmacological mechanism based on arginine uptake as a target through multi-omics sequencing. This herbal component suppressed energy metabolism and activated ROS aggregation by inducing mitochondrial membrane potential depolarization, which subsequently triggered autophagy-dependent apoptosis leading to parasite death. Moreover, we discovered that arginine deprivation induced metabolic changes led to a shift from ornithine to nitrogen oxide synthesis, thus boosting the iNOS enzyme-regulated dominant metabolic pathway. The excess NO targeted the mitochondrial respiratory chain complex IV to disrupt energy metabolic homeostasis and induced a downstream pathological waterfall effect to kill the hydatid. A novel metabolic regulatory mechanism targeting mitochondrial damage for arginine starvation therapy was discovered. Finally, arginine depletion was found to be superior to the anti-spinal echinococcosis effect of albendazole and accompanied by the potential for disc protection. This study unveils the role of arginine in the physiological metabolism of Echinococcus granulosus and reveals the value of targeting arginine metabolism as a potential therapy. In addition, agrimol B is proposed as a promising therapeutic strategy for spinal echinococcosis to block arginine uptake and break this parasite's metabolic balance.

Enhanced detection of ligand-PPARγ binding based on surface plasmon resonance through complexation with SRC1- or NCOR2-related polypeptide

A previous study reported the use of a biosensing technique based on surface plasmon resonance (SPR) for the ligand binding detection of peroxisome proliferator activator receptor gamma (PPARγ). This detection was designed based on the structural properties of PPARγ. Because of cross-linked protein inactivation and the low molecular weight of conventional ligands, direct ligand binding detection based on SPR has low stability and repeatability. In this study, we report an indirect response methodology based on SPR technology in which anti-His CM5 chip binds fresh PPARγ every cycle, resulting in more stable detection. We developed a remarkable improvement in ligand-protein binding detectability in vitro by introducing two coregulator-related polypeptides into this system. In parallel, a systematic indirect response methodology can reflect the interaction relationship between ligands and proteins to some extent by detecting the changes in SA-SRC1 and GST-NCOR2 binding to PPARγ. Rosiglitazone, a PPARγ agonist with strong affinity, is a potent insulin-sensitizing agent. Some ligands may be competitively exerted at the same sites of PPARγ (binding rosiglitazone). We demonstrated using indirect response methodology that selective PPARγ modulator (SPPARM) candidates of PPARγ can be found by competing for the binding of the rosiglitazone site on PPARγ, although they may have no effect on polypeptides and PPARγ binding.

Agrimol B alleviates cisplatin-induced acute kidney injury by activating the Sirt1/Nrf2 signaling pathway in mice

Cisplatin (CDDP) is a widely used chemotherapeutic agent that has remarkable antineoplastic effects. However, CDDP can cause severe acute kidney injury (AKI), which limits its clinical application. Agrimol B is the main active ingredient found in Agrimonia pilosa Ledeb and has a variety of pharmacological activities. The effect of agrimol B on CDDP-induced renal toxicity has not been determined. To investigate whether agrimol B has a protective effect against CDDP-induced AKI, we first identify Sirtuin 1 (Sirt1) as a critical target protein of agrimol B in regulating AKI through network pharmacology analysis. Subsequently, the AKI mouse model is induced by administering a single dose of CDDP via intraperitoneal injection. By detecting the serum urea nitrogen and creatinine levels, as well as the histopathological changes, we confirm that agrimol B effectively reduces CDDP-induced AKI. In addition, treatment with agrimol B counteracts the increase in renal malondialdehyde level and the decrease in superoxide dismutase (SOD), catalase and glutathione levels induced by CDDP. Moreover, western blot results reveal that agrimol B upregulates the expressions of Sirt1, SOD2, nuclear factor erythroid2-related factor 2, and downstream molecules, including heme oxygenase 1 and NAD(P)H quinone dehydrogenase 1. However, administration of the Sirt1 inhibitor EX527 abolishes the effects of agrimol B. Finally, we establish a tumor-bearing mouse model and find that agrimol B has a synergistic antitumor effect with CDDP. Overall, agrimol B attenuates CDDP-induced AKI by activating the Sirt1/Nrf2 signaling pathway to counteract oxidative stress, suggesting that this compound is a potential therapeutic agent for the treatment of CDDP-induced AKI.

Epigenomics Analysis of the Suppression Role of SIRT1 via H3K9 Deacetylation in Preadipocyte Differentiation

Sirtuin 1 (SIRT1) overexpression significantly inhibits lipid deposition during yak intramuscular preadipocyte (YIMA) differentiation; however, the regulatory mechanism remains unknown. We elucidated the role of SIRT1 in YIMA differentiation using lentivirus-mediated downregulation technology and conducted mRNA-seq and ChIP-seq assays using H3K9ac antibodies after SIRT1 overexpression in order to reveal SIRT1 targets during YIMA adipogenesis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed in order to identify the functional annotation of common genes. In addition, a potential target of SIRT1 was selected to verify its effects on the differentiation and proliferation of YIMAs. SIRT1 interfered with lipid deposition and promoted YIMA differentiation. In total, 143,518 specific peaks were identified after SIRT1 overexpression, where genes associated with downregulation peaks were enriched in transcription, gene expression, lipid-related processes, and classical lipid-related pathways. The H3K9ac signal in the whole genome promoter region (2 kb upstream and downstream of the transcription start site (TSS)) was weakened, and the peaks were distributed across all gene functional regions. Genes that lost signals in their TSS region or gene body region were enriched in both biological processes and pathways associated with lipogenesis. The ChIP-seq results revealed 714 common differential genes in mRNA-seq, which were enriched in "MAPK signaling", "lipid and atherosclerosis", "mTOR signaling", and "FoxO signaling" pathways. A total of 445 genes were downregulated in both their H3K9ac signals and mRNA expression, and one of their most significantly enriched pathways was FoxO signaling. Nine genes (FBP2, FPGT, HSD17B11, KCNJ15, MAP3K20, SLC5A3, TRIM23, ZCCHC10, and ZMYM1) lost the H3K9ac signal in their TSS regions and had low mRNA expression, and three genes (KCNJ15, TGM3, and TRIM54) had low expression but lost their H3K9ac signal in the gene body region. The interference of TRIM23 significantly inhibited fat deposition during preadipocyte differentiation and promoted cell proliferation by increasing S-phase cell numbers. The present study provides new insights into the molecular mechanism of intramuscular fat content deposition and the epigenetic role of SIRT1 in adipocyte differentiation.

Agrimonia pilosa: A Phytochemical and Pharmacological Review

Agrimonia pilosa Ledeb., which belongs to Agrimonia and Rosaceae, is used in traditional Chinese medicine. It exhibits excellent medicinal properties and has been used to treat various diseases, such as tumors, trichomoniasis, vaginitis, diarrhea, and dysentery. Phytochemical studies have revealed that Agrimonia has over 100 secondary metabolites that can be categorized into six classes, i.e., flavonoids, isocoumarins, triterpenes, phloroglucinol derivatives, tannins, and organic acids. This review summarizes recently published literature on the chemical structures of 90 bioactive compounds that have been identified in A. pilosa and examines their pharmacological properties, including their antitumor, anti-inflammatory, antioxidant, antibacterial, and antidiabetic properties, as well as the potential development of parasitic resistance to these chemicals. This review highlights existing knowledge gap and serves as a basis for developing novel preparations of A. pilosa with medicinal value.

Correlation Effects in Trimeric Acylphloroglucinols

Trimeric acylphloroglucinols (T-ACPLs) are a subclass of the large class of acylphloroglucinols—derivatives of 1,3,5-trihydroxybenzene containing an R–C=O group. T-ACPL molecules contain three acylphloroglucinol moieties linked by methylene bridges. Many of them are present in natural sources and exhibit biological activities, often better than the corresponding activities of monomeric acylphloroglucinols. All the stable conformers of T-ACPLs contain seven intramolecular hydrogen bonds, which constitute the dominant stabilising factors. A total of 38 different T-ACPLs, including both naturally occurring and model molecules, have been calculated at the HF and DFT/B3LYP levels. The DFT/B3LYP calculations were carried out both without and with Grimme’s dispersion correction, to highlight the dispersion (and, therefore, also electron correlation) effects for these molecules. The roles of dispersion are evaluated considering the effects of Grimme’s correction on the estimation of the conformers’ energies, the description of the characteristics of the individual hydrogen bonds, the conformers’ geometries and other molecular properties. Overall, the results offer a comprehensive overview of the conformational preferences of T-ACPL molecules, their intramolecular hydrogen bond patterns, and the correlation effects on their properties.

Adipose and non-adipose perspectives of plant derived natural compounds for mitigation of obesity

ETHNOPHARMACOLOGICAL RELEVANCE

Phyto-preparations and phyto-compounds, by their natural origin, easy availability, cost-effectiveness, and fruitful traditional uses based on accumulated experiences, have been extensively explored to mitigate the global burden of obesity.

AIM OF THIS REVIEW

The review aimed to analyse and critically summarize the prospect of future anti-obesity drug leads from the extant array of phytochemicals for mitigation of obesity, using adipose related targets (adipocyte formation, lipid metabolism, and thermogenesis) and non-adipose targets (hepatic lipid metabolism, appetite, satiety, and pancreatic lipase activity). Phytochemicals as inhibitors of adipocyte differentiation, modulators of lipid metabolism, and thermogenic activators of adipocytes are specifically discussed with their non-adipose anti-obesogenic targets.

MATERIALS AND METHODS

PubMed, Google Scholar, Scopus, and SciFinder were accessed to collect data on traditional medicinal plants, compounds derived from plants, their reported anti-obesity mechanisms, and therapeutic targets. The taxonomically accepted name of each plant in this review has been vetted from "The Plant List" (www.theplantlist.org) or MPNS (http://mpns.kew.org).

RESULTS

Available knowledge of a large number of phytochemicals, across a range of adipose and non-adipose targets, has been critically analysed and delineated by graphical and tabular depictions, towards mitigation of obesity. Neuro-endocrinal modulation in non-adipose targets brought into sharp dual focus, both non-adipose and adipose targets as the future of anti-obesity research. Numerous phytochemicals (Berberine, Xanthohumol, Ursolic acid, Guggulsterone, Tannic acid, etc.) have been found to be effectively reducing weight through lowered adipocyte formation, increased lipolysis, decreased lipogenesis, and enhanced thermogenesis. They have been affirmed as potential anti-obesity drugs of future because of their effectiveness yet having no threat to adipose or systemic insulin sensitivity.

CONCLUSION

Due to high molecular diversity and a greater ratio of benefit to risk, plant derived compounds hold high therapeutic potential to tackle obesity and associated risks. This review has been able to generate fresh perspectives on the anti-diabetic/anti-hyperglycemic/anti-obesity effect of phytochemicals. It has also brought into the focus that many phytochemicals demonstrating in vitro anti-obesogenic effects are yet to undergo in vivo investigation which could lead to potential phyto-molecules for dedicated anti-obesity action.

Identification and functional prediction of long noncoding RNAs related to intramuscular fat content in Laiwu pigs

Objective

Intramuscular fat (IMF) is a critical economic indicator of pork quality. Studies on IMF among different pig breeds have been performed via high-throughput sequencing, but comparisons within the same pig breed remain unreported.

Methods

This study was performed to explore the gene profile and identify candidate long noncoding RNA (lncRNAs) and mRNAs associated with IMF deposition among Laiwu pigs with different IMF contents. Based on the longissimus dorsi muscle IMF content, eight pigs from the same breed and management were selected and divided into two groups: a high IMF (>12%, H) and low IMF group (<5%, L). Whole-transcriptome sequencing was performed to explore the differentially expressed (DE) genes between these two groups.

Results

The IMF content varied greatly among Laiwu pig individuals (2.17% to 13.93%). Seventeen DE lncRNAs (11 upregulated and 6 downregulated) and 180 mRNAs (112 upregulated and 68 downregulated) were found. Gene Ontology analysis indicated that the following biological processes played an important role in IMF deposition: fatty acid and lipid biosynthetic processes; the extracellular signal-regulated kinase cascade; and white fat cell differentiation. In addition, the peroxisome proliferator-activated receptor, phosphatidylinositol-3-kinase-protein kinase B, and mammalian target of rapamycin pathways were enriched in the pathway analysis. Intersection analysis of the target genes of DE lncRNAs and mRNAs revealed seven candidate genes associated with IMF accumulation. Five DE lncRNAs and 20 DE mRNAs based on the pig quantitative trait locus database were identified and shown to be related to fat deposition. The expression of five DE lncRNAs and mRNAs was verified by quantitative real time polymerase chain reaction (qRT-PCR). The results of qRT-PCR and RNA-sequencing were consistent.

Conclusion

These results demonstrated that the different IMF contents among pig individuals may be due to the DE lncRNAs and mRNAs associated with lipid droplets and fat deposition.

Prospective Role of Polyphenolic Compounds in the Treatment of Neurodegenerative Diseases

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Aging is an important stage of the human life cycle and the primary risk factor for neurodegenerative diseases (ND). The aging process contributes to modifications in cells, which may lead to a lack of nutrient signaling, disrupted cellular activity, increased oxidative pressure, cell homeostasis depletion, genomic instability, misfolded protein aggregation, impaired cellular protection, and telomere reduction. The neuropathologies found in Alzheimer's disease (AD) and Parkinson's disease (PD) are internally and extrinsically compound environmental stressors which may be partially alleviated by using different phytochemicals. The new therapies for ND are restricted as they are primarily targeted at final disease progression, including behavioral shifts, neurological disorders, proteinopathies, and neuronal failure. This review presents the role of phytochemicals-related polyphenolic compounds as an accompanying therapy model to avoid neuropathologies linked to AD, PD and to simultaneously enhance two stochastic stressors, namely inflammation and oxidative stress, promoting their disease pathologies. Therefore, this approach represents a prophylactic way to target risk factors that rely on their action against ND that does not occur through current pharmacological agents over the life of a person.

Holistic approach to microwave-reflux extraction and thermo-analytical fingerprints of under-utilized Artocarpus heterophyllus seed wastes

The increase in wastes generated from jackfruit seeds has been largely under-utilized in Malaysia. Due to the high nutritional and medicinal content embedded in the cellulosic structure of jackfruit wastes, a need then arises for their physicochemical elucidations. In this study, the extraction of Artocarpus heterophyllus seed was carefully investigated using Taguchi orthogonal optimization design. Complete functional group characteristics and chemical profile of the A. heterophyllus seed extracts were obtained using different physicochemical characterization. The optimal conditions of the microwave extraction parameters were determined at 5 min of irradiation time, 450 W of power and 50 °C of temperature. Under this condition, the optimal yield of 17.34 (mg/g) % was achieved at an SNR ratio of 24.78. The mass spectrometry analysis tentatively identified a total of 90 and 148 secondary metabolites at positive and negative ESI modes, respectively. The chemical profile obtained provided a baseline reference for further investigation on the food and medicinal bioactive from Artocarpus heterophyllus seed oleoresins. The FT-infrared emission spectrum shows the presence of some specific carbohydrates and amide protein functional groups directly linked to C–O (1008 cm⁻¹) the carbonyl (C=O) groups, respectively. Moreover, the morphological characteristics of the jackfruit raw and crude extracts conspicuously revealed large-sized globules which suggest the carbohydrates and protein contents. The result of this study indicates that the use of microwave extraction technology produced high-quality extracts with lower degradation of the thermal labile constituents. This will assist in determining the suitable conditions necessary for the total recovery of medicinal and nutritional constituents and conversion of agricultural waste products into useful products.

Ultrastructure changes induced by the phloroglucinol derivative agrimol G isolated from Leucosidea sericea in Haemonchus contortus

Plant extracts used for the treatment of helminth infections in sheep are an alternative to chemical anthelmintic drugs. Previous studies have reported the anthelmintic activity of acetone leaf extracts of Leucosidea sericea. For this study, we evaluate the ultrastructure changes induced by the acetone leaf extract of L. sericea and the component agrimol G (AG) that was isolated for the first time on adult haemonchus parasites. Adult haemonchus parasites harvested from sheep were incubated with the plant extract and AG for 3 h and evaluated by both scanning and transmission electron microscopy in comparison and in combination with albendazole or ivermectin. In all cases the method of evaluation shows ultrastructural changes, with albendazole inducing mitochondrial damage and ivermectin inducing muscle degeneration, both as previously described. Incubation with the plant extract and AG resulted in the formation of numerous non-membrane bound multi-vesicular like bodies and evenly spread disruptions/erosion in the epicuticle. Combining AG with ivermectin or albendazole resulted in an absence of effect of AG. Based on the structural changes induced by AG, together with the absence of an effect in combination with ivermectin and albendazole would suggest a disrupted microtubular network. The latter does however require biochemical confirmation.

Dietary Polyphenols: A Multifactorial Strategy to Target Alzheimer's Disease

Ageing is an inevitable fundamental process for people and is their greatest risk factor for neurodegenerative disease. The ageing processes bring changes in cells that can drive the organisms to experience loss of nutrient sensing, disrupted cellular functions, increased oxidative stress, loss of cellular homeostasis, genomic instability, accumulation of misfolded protein, impaired cellular defenses and telomere shortening. Perturbation of these vital cellular processes in neuronal cells can lead to life threatening neurological disorders like Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, Lewy body dementia, etc. Alzheimer's Disease is the most frequent cause of deaths in the elderly population. Various therapeutic molecules have been designed to overcome the social, economic and health care burden caused by Alzheimer's Disease. Almost all the chemical compounds in clinical practice have been found to treat symptoms only limiting them to palliative care. The reason behind such imperfect drugs may result from the inefficiencies of the current drugs to target the cause of the disease. Here, we review the potential role of antioxidant polyphenolic compounds that could possibly be the most effective preventative strategy against Alzheimer's Disease.

Agrimonia procera Wallr. Extract Increases Stress Resistance and Prolongs Life Span in Caenorhabditis elegans via Transcription Factor DAF-16 (FoxO Orthologue)

Agrimonia procera is a pharmacologically interesting plant which is proposed to protect against various diseases due to its high amount of phytochemicals, e.g., polyphenols. However, in spite of the amount of postulated health benefits, studies concerning the mechanistic effects of Agrimonia procera are limited. Using the nematode Caenorhabditis elegans, we were able to show that an ethanol extract of Agrimonia procera herba (eAE) mediates strong antioxidative effects in the nematode: Beside a strong radical-scavenging activity, eAE reduces accumulation of reactive oxygen species (ROS) accumulation and protects against paraquat-induced oxidative stress. The extract does not protect against amyloid-β-mediated toxicity, but efficiently increases the life span (up to 12.7%), as well as the resistance to thermal stress (prolongation of survival up to 22%), of this model organism. Using nematodes deficient in the forkhead box O (FoxO)-orthologue DAF-16, we were able to demonstrate that beneficial effects of eAE on stress resistance and life span were mediated via this transcription factor. We showed antioxidative, stress-reducing, and life-prolonging effects of eAE in vivo and were able to demonstrate a molecular mechanism of this extract. These results may be important for identifying further molecular targets of eAE in humans.

Deoxyschizandrin Loaded Liposomes on the Suppression Lipid Accumulation in 3T3-L1 Adipocytes

Deoxyschizandrin (DS) is a bioactive benzocyclooctadiene lignan found in the fruit of Schisandra chinensis. However, poor bioavailability and non-specificity of DS frequently caused low therapeutic efficacy. In the present study, DS-liposome (DS-lipo) was implemented to enhance the hepatic targeting and inhibition effects on adipocyte differentiation in 3T3-L1 cells. The formulations enabled encapsulation of as much as 24.14% DS. The DS-lipo prepared was about 73.08 nm, as measured by laser light scattering (LLS) morphology. In the visual field of a scanning electron microscope (SEM), the liposomes were spherical with similar size and uniform dispersion. Fluorescence live imaging study exhibited hepatic targeting of liposomes in vivo. Furthermore, High-Content Analysis (HCS) imaging microassay analyses revealed DS-lipo and DS reduced cytoplasmic lipid droplet in 3T3-L1 adipocytes, with the IC₅₀ value of 8.68 μM and 31.08 μM, respectively. The lipid droplet accumulation inhibition rate of 10 μM DS-lipo was above 90%, which was even superior to the effect of 30 μM DS solution. The current findings suggest that DS-lipo was a therapeutic strategy for alleviating lipid-associated diseases and nonalcoholic fatty liver disease (NAFLD).

Metabolic Circuit Involving Free Fatty Acids, microRNA 122, and Triglyceride Synthesis in Liver and Muscle Tissues

BACKGROUND & AIMS

Effective treatments are needed for hepatic steatosis characterized by accumulation of triglycerides in hepatocytes, which leads to hepatocellular carcinoma. MicroRNA 122 (MIR122) is expressed only in the liver, where it regulates lipid metabolism. We investigated the mechanism by which free fatty acids (FFAs) regulate MIR122 expression and the effect of MIR122 on triglyceride synthesis.

METHODS

We analyzed MIR122 promoter activity and validated its target mRNAs by transfection of Luciferase reporter plasmids into Huh7, BNL-1ME, and HEK293 cultured cell lines. We measured levels of microRNAs and mRNAs by quantitative real-time PCR analysis of RNA extracted from plasma, liver, muscle, and adipose tissues of C57BL/6 mice given the FFA-inducer CL316243. MIR122 was inhibited using an inhibitor of MIR122. Metabolic profiles of mice were determined using metabolic chambers and by histologic analyses of liver tissues. We performed RNA sequence analyses to identify metabolic pathways involving MIR122.

RESULTS

We validated human Agpat1 and Dgat1 mRNAs, involved in triglyceride synthesis, as targets of MIR122. FFAs increased MIR122 expression in livers of mice by activating the retinoic acid-related orphan receptor alpha, and induced secretion of MIR122 from liver to blood. Circulating MIR122 entered muscle and adipose tissues of mice, reducing mRNA levels of genes involved in triglyceride synthesis. Mice injected with an inhibitor of MIR122 and then given CL316243, accumulated triglycerides in liver and muscle tissues, and had reduced rates of β-oxidation. There was a positive correlation between level of FFAs and level of MIR122 in plasma samples from 6 healthy individuals, collected before and during fasting.

CONCLUSIONS

In biochemical and histologic studies of plasma, liver, muscle, and adipose tissues from mice, we found that FFAs increase hepatic expression and secretion of MIR122, which regulates energy storage vs expenditure in liver and peripheral tissues. Strategies to reduce triglyceride levels, by increasing MIR122, might be developed for treatment of metabolic syndrome.

SFRP5 is a target gene transcriptionally regulated by PPARγ in 3T3-L1 adipocytes

Secreted frizzled-related protein 5 (SFRP5) is a newly identified adipokine. SFRP5 expression increases during the differentiation and maturation of adipocytes, but the factors regulating SFRP5 expression during this process remain unclear. This study showed that peroxisome proliferator-activated receptor γ (PPARγ) adenovirus transfection could enhance the SFRP5 expression of 3T3-L1 adipocytes. Three potential binding sites of PPARγ in the SFRP5 promoter domain were found by bioinformatics analysis. Luciferase reporter gene assay demonstrated that PPARγ regulated the activity of the SFRP5 promoter through cis-acting elements at -2,284--1,500bp. Further experiments verified that PPARγ could specifically bind to the SFRP5 promoter at -2,284--2,263bp using chromatin immunoprecipitation and electrophoretic mobility shift assay. These results suggest that SFRP5 be a target gene of PPARγ, and its expression may be under the transcriptional regulation of PPARγ.

Resveratrol induces apoptosis and inhibits adipogenesis by stimulating the SIRT1-AMPKα-FOXO1 signalling pathway in bovine intramuscular adipocytes

Sirtuin type 1 (SIRTl) and AMP-activated protein kinase (AMPK) play important roles in regulating energy metabolism, cell proliferation and differentiation, ageing, apoptosis, and metabolism. The effect of 100, 200, and 400 μm Resveratrol (RES), an activator of SIRT1, on apoptosis of bovine intramuscular adipocytes was investigated by nuclear staining, flow cytometry, quantitative real-time polymerase chain reaction, and western blotting. Results show that RES inhibited adipogenesis, decreased cell viability, and increased apoptotic rates in a dose-dependent way. RES up-regulated SIRT1, AMPKα, forkhead box O1 (FOXO1), hormone-sensitive lipase (HSL), lipoprotein lipase (LPL), caspase-3, and Bax; and down-regulated peroxisome proliferator-activated receptor-gamma (PPARγ), fatty acid synthase (FAS), and Bcl-2, at both mRNA and protein level. The effect of RES was abolished by addition of sirtinol (an inhibitor of SIRT1). This is the first study demonstrating a role for AMPK-SIRT1-FOXO1 signalling pathway in regulating apoptosis in bovine intramuscular adipocytes. Our findings provide important information on the mechanism by which RES controls deposition of cattle intramuscular fat via adipocyte apoptosis.

Melatonin and the pathologies of weakened or dysregulated circadian oscillators

Dynamic aspects of melatonin's actions merit increasing future attention. This concerns particularly entirely different effects in senescent, weakened oscillators and in dysregulated oscillators of cancer cells that may be epigenetically blocked. This is especially obvious in the case of sirtuin 1, which is upregulated by melatonin in aged tissues, but strongly downregulated in several cancer cells. These findings are not at all controversial, but are explained on the basis of divergent changes in weakened and dysregulated oscillators. Similar findings can be expected to occur in other accessory oscillator components that are modulated by melatonin, among them several transcription factors and metabolic sensors. Another cause of opposite effects concerns differences between nocturnally active laboratory rodents and the diurnally active human. This should be more thoroughly considered in the field of metabolic syndrome and related pathologies, especially with regard to type 2 diabetes and other aspects of insulin resistance. Melatonin was reported to impair glucose tolerance in humans, especially in carriers of the risk allele of the MT₂ receptor gene, MTNR1B, that contains the SNP rs10830963. These findings contrast with numerous reports on improvements of glucose tolerance in preclinical studies. However, the relationship between melatonin and insulin may be more complex, as indicated by loss-of-function mutants of the MT₂ receptor that are also prodiabetic, by the age-dependent time course of risk allele overexpression, by progressive reduction in circadian amplitudes and melatonin secretion, which are aggravated in diabetes. By supporting high-amplitude rhythms, melatonin may be beneficial in preventing or delaying diabetes.

Autophagy regulates turnover of lipid droplets via ROS-dependent Rab25 activation in hepatic stellate cell

Activation of hepatic stellate cells (HSCs) is a pivotal event in liver fibrosis, characterized by dramatic disappearance of lipid droplets (LDs). Although LD disappearance has long been considered one of the hallmarks of HSC activation, the underlying molecular mechanisms are largely unknown. In this study, we sought to investigate the role of autophagy in the process of LD disappearance, and to further examine the underlying mechanisms in this molecular context. We found that LD disappearance during HSC activation was associated with a coordinate increase in autophagy. Inhibition or depletion of autophagy by Atg5 siRNA impaired LD disappearance of quiescent HSCs, and also restored lipocyte phenotype of activated HSCs. In contrast, induction of autophagy by Atg5 plasmid accelerated LD loss of quiescent HSCs. Importantly, our study also identified a crucial role for reactive oxygen species (ROS) in the facilitation of autophagy activation. Antioxidants, such as glutathione and N-acetyl cysteine, significantly abrogated ROS production, and in turn, prevented autophagosome generation and autophagic flux during HSC activation. Besides, we found that HSC activation triggered Rab25 overexpression, and promoted the combination of Rab25 and PI3KCIII, which direct autophagy to recognize, wrap and degrade LDs. Down-regulation of Rab25 activity, using Rab25 siRNA, blocked the target recognition of autophagy on LDs, and inhibited LD disappearance of quiescent HSCs. Moreover, the scavenging of excessive ROS could disrupt the interaction between autophagy and Rab25, and increase intracellular lipid content. Overall, these results provide novel implications to reveal the molecular mechanism of LD disappearance during HSC activation, and also identify ROS-Rab25-dependent autophagy as a potential target for the treatment of liver fibrosis.

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Autophagosome generation and autophagic flux are increased during HSC activation.

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The inhibition of autophagy blocks LD disappearance of quiescent HSCs.

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The induction of autophagy accelerates LD disappearance of quiescent HSCs.

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Rab25 activation is required for autophagy to degrade LDs during HSC activation.

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Mitochondrial H₂O₂ production triggers autophagy activation during HSC activation.