Coronaviral ORF6 protein mediates inter-organelle contacts and modulates host cell lipid flux for virus production.

Lipid droplets (LDs) form inter-organelle contacts with the endoplasmic reticulum (ER) that promote their biogenesis, while LD contacts with mitochondria enhance ß-oxidation of contained fatty acids. Viruses have been shown to take advantage of lipid droplets to promote viral production, but it remains unclear whether they also modulate the interactions between LDs and other organelles. Here, we showed that coronavirus ORF6 protein targets LDs and is localized to the mitochondria-LD and ER-LD contact sites, where it regulates LD biogenesis and lipolysis. At the molecular level, we find that ORF6 inserts into the LD lipid monolayer via its two amphipathic helices. ORF6 further interacts with ER membrane proteins BAP31 and USE1 to mediate ER-LDs contact formation. Additionally, ORF6 interacts with the SAM complex in the mitochondrial outer membrane to link mitochondria to LDs. In doing so, ORF6 promotes cellular lipolysis and LD biogenesis to reprogram host cell lipid flux and facilitate viral production.

Lipolysis is accompanied by immune microenvironment remodeling in adipose tissue of obesity with different exercise intensity.

OBJECTIVE: Obesity and overweight are risk factors for chronic disease worldwide. The purpose of this study was to compare the transcriptome of exercise-induced fat mobilization in obese people, and to explore the effect of different exercise intensity on the correlation of immune microenvironment remodeling and lipolysis in adipose tissue. MATERIALS AND METHODS: Microarray datasets of adipose tissue before and after exercise were downloaded from the Gene Expression Omnibus. Then, we used gene-enrichment analysis and PPI-network construction to elucidate the function and enrichment pathways of the differentially expressed genes (DEGs) and to identify the central genes. A network of protein-protein interactions was obtained using STRING and visualized with Cytoscape. RESULTS: A total of 929 DEGs were identified between 40 pre-exercise (BX) samples and 65 post-exercise (AX) samples from GSE58559, GSE116801, and GSE43471. Among these DEGs, adipose tissue-expressed genes were duly recognized. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that DEGs were mostly enriched in lipid metabolism. Studies have found that mitogen-activated protein kinase (MAPK) signaling pathway and forkhead box O (FOXO) signaling pathway are up-regulated, while Ribosome, coronavirus disease (COVID-19) and IGF-1 gene are down-regulated. Although we found the up-regulated genes that noted IL-1 among others, and the down-regulated gene was IL-34. The increase of inflammatory factors leads to changes in cellular immune microenvironment, and high-intensity exercise leads to increased expression of inflammatory factors in adipose tissue, leading to inflammatory responses. CONCLUSIONS: Exercise at different intensities leads to the degradation of adipose and is accompanied by changes in the immune microenvironment within adipose tissue. High intensity exercise can cause the imbalance of immune microenvironment of adipose tissue while causing fat degradation. Therefore, moderate intensity and below exercise is the best way for the general population to reduce fat and weight.

Therapeutic strategy targeting host lipolysis limits infection by SARS-CoV-2 and influenza A virus.

The biosynthesis of host lipids and/or lipid droplets (LDs) has been studied extensively as a putative therapeutic target in diverse viral infections. However, directly targeting the LD lipolytic catabolism in virus-infected cells has not been widely investigated. Here, we show the linkage of the LD-associated lipase activation to the breakdown of LDs for the generation of free fatty acids (FFAs) at the late stage of diverse RNA viral infections, which represents a broad-spectrum antiviral target. Dysfunction of membrane transporter systems due to virus-induced cell injury results in intracellular malnutrition at the late stage of infection, thereby making the virus more dependent on the FFAs generated from LD storage for viral morphogenesis and as a source of energy. The replication of SARS-CoV-2 and influenza A virus (IAV), which is suppressed by the treatment with LD-associated lipases inhibitors, is rescued by supplementation with FFAs. The administration of lipase inhibitors, either individually or in a combination with virus-targeting drugs, protects mice from lethal IAV infection and mitigates severe lung lesions in SARS-CoV-2-infected hamsters. Moreover, the lipase inhibitors significantly reduce proinflammatory cytokine levels in the lungs of SARS-CoV-2- and IAV-challenged animals, a cause of a cytokine storm important for the critical infection or mortality of COVID-19 and IAV patients. In conclusion, the results reveal that lipase-mediated intracellular LD lipolysis is commonly exploited to facilitate RNA virus replication and furthermore suggest that pharmacological inhibitors of LD-associated lipases could be used to curb current COVID-19- and future pandemic outbreaks of potentially troublesome RNA virus infection in humans.

Anti-adipogenic and Pro-lipolytic Effects on 3T3-L1 Preadipocytes by CX-4945, an Inhibitor of Casein Kinase 2.

Casein kinase 2 (CK2) is a ubiquitously expressed serine/threonine kinase and is upregulated in human obesity. CX-4945 (Silmitasertib) is a CK2 inhibitor with anti-cancerous and anti-adipogenic activities. However, the anti-adipogenic and pro-lipolytic effects and the mode of action of CX-4945 in (pre)adipocytes remain elusive. Here, we explored the effects of CX-4945 on adipogenesis and lipolysis in differentiating and differentiated 3T3-L1 cells, a murine preadipocyte cell line. CX-4945 at 15 µM strongly reduced lipid droplet (LD) accumulation and triglyceride (TG) content in differentiating 3T3-L1 cells, indicating the drug's anti-adipogenic effect. Mechanistically, CX-4945 reduced the expression levels of CCAAT/enhancer-binding protein-α (C/EBP-α), peroxisome proliferator-activated receptor-γ (PPAR-γ), fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), and perilipin A in differentiating 3T3-L1 cells. Strikingly, CX-4945 further increased the phosphorylation levels of cAMP-activated protein kinase (AMPK) and liver kinase B-1 (LKB-1) while decreasing the intracellular ATP content in differentiating 3T3-L1 cells. In differentiated 3T3-L1 cells, CX-4945 had abilities to stimulate glycerol release and elevate the phosphorylation levels of hormone-sensitive lipase (HSL), pointing to the drug's pro-lipolytic effect. In addition, CX-4945 induced the activation of extracellular signal-regulated kinase-1/2 (ERK-1/2), and PD98059, an inhibitor of ERK-1/2, attenuated the CX4945-induced glycerol release and HSL phosphorylation in differentiated 3T3-L1 cells, indicating the drug's ERK-1/2-dependent lipolysis. In summary, this investigation shows that CX-4945 has strong anti-adipogenic and pro-lipolytic effects on differentiating and differentiated 3T3-L1 cells, mediated by control of the expression and phosphorylation levels of CK2, C/EBP-α, PPAR-γ, FAS, ACC, perilipin A, AMPK, LKB-1, ERK-1/2, and HSL.

Efficacy of a Novel Injection Lipolysis to Induce Targeted Adipocyte Apoptosis: A Randomized, Phase IIa Study of CBL-514 Injection on Abdominal Subcutaneous Fat Reduction.

BACKGROUND: CBL-514 is a novel injectable drug that may be safe and efficacious for localized abdominal subcutaneous fat reduction. OBJECTIVES: The aim of this study was to assess the safety and efficacy of CBL-514 in reducing abdominal subcutaneous fat volume and thickness. METHODS: This Phase IIa, open-label, random allocation study consisted of a 6-week treatment period and follow-up at 4 and 8 weeks following the last treatment. Participants were randomly allocated to receive 1.2 mg/cm2 (180 mg), 1.6 mg/cm2 (240 mg), or 2.0 mg/cm2 (300 mg) of CBL-514 with up to 4 treatments, each comprising 60 injections into the abdominal adipose layer. Changes in abdominal subcutaneous fat were assessed by ultrasound at follow-up visits. Treatment-emergent adverse events were recorded. RESULTS: Higher doses of CBL-514 (unit dose, 2.0 and 1.6 mg/cm2) significantly improved the absolute and percentage reduction in abdominal fat volume (P < 0.00001) and thickness (P < 0.0001) compared with baseline. Although the COVID-19 pandemic halted some participant recruitment and follow-ups, analysis was unaffected, even after sample size limitations. CONCLUSIONS: CBL-514 injection at multiple doses up to 300 mg with a unit dose of 2.0 mg/cm2 is safe, well-tolerated, and reduced abdominal fat volume and thickness by inducing adipocyte apoptosis. Although other procedures exist to treat abdominal fat, they have limitations and may cause complications. At a dose of 2.0 mg/cm2, CBL-514 safely and significantly reduced abdominal fat volume by 24.96%, making it a promising new treatment for routine, nonsurgical abdominal fat reduction in dermatologic clinics.

The lipolytic activity of LipJ, a stress-induced enzyme, is regulated by its C-terminal adenylate cyclase domain.

Aim: The confirmation of lipolytic activity and role of Rv1900c in the Mycobacterium physiology Methods:rv1900c/N-terminus domain (rv1900NT) were cloned in pET28a/Escherichia coli, purified by affinity chromatography and characterized. Results: A zone of clearance on tributyrin-agar and activity with pNP-decanoate confirmed the lipolytic activity of Rv1900c. The Rv1900NT demonstrated higher enzyme specific activity, Vmax and kcat, but Rv1900c was more thermostable. The lipolytic activity of Rv1900c decreased in presence of ATP. Mycobacterium smegmatis expressed rv1900c/rv1900NT-altered colony morphology, growth, cell surface properties and survival under stress conditions. The effect was more prominent with Rv1900NT as compared with Rv1900c. Conclusion: The study confirmed the lipolytic activity of Rv1900c and suggested its regulation by the adenylate cyclase domain and role in the intracellular survival of bacteria.

Lay abstract Tuberculosis (TB) remains the top contagious/infectious killer in the world. It is caused by the bacteria Mycobacterium tuberculosis. The bacteria resides/replicates in the immune cell that normally has to eradicate infectious microorganisms. Though the treatment of TB is available, the emergence of drug-resistant bacteria is of major concern. The treatment of drug-resistant TB has been reported to be more difficult due to lengthy and complex treatment regimens. Therefore, there is an urgent need for new and better drugs to treat TB/drug-resistant TB. For this purpose understanding the role of each protein in the physiology of mycobacteria is required. Lipids play a critical role in the intracellular survival of this pathogen in the host. Our study demonstrated that LipJ supported the intracellular survival of bacteria. Therefore, it could be a potential drug target.