Elongation factor 1A1 regulates metabolic substrate preference in mammalian cells.

Eukaryotic elongation factor 1A1 (EEF1A1) is canonically involved in protein synthesis but also has noncanonical functions in diverse cellular processes. Previously, we identified EEF1A1 as a mediator of lipotoxicity and demonstrated that chemical inhibition of EEF1A1 activity reduced mouse liver lipid accumulation. These findings suggested a link between EEF1A1 and metabolism. Therefore, we investigated its role in regulating metabolic substrate preference. EEF1A1-deficient Chinese hamster ovary (2E2) cells displayed reduced media lactate accumulation. These effects were also observed with EEF1A1 knockdown in human hepatocyte-like HepG2 cells and in WT Chinese hamster ovary and HepG2 cells treated with selective EEF1A inhibitors, didemnin B, or plitidepsin. Extracellular flux analyses revealed decreased glycolytic ATP production and increased mitochondrial-to-glycolytic ATP production ratio in 2E2 cells, suggesting a more oxidative metabolic phenotype. Correspondingly, fatty acid oxidation was increased in 2E2 cells. Both 2E2 cells and HepG2 cells treated with didemnin B exhibited increased neutral lipid content, which may be required to support elevated oxidative metabolism. RNA-seq revealed a >90-fold downregulation of a rate-limiting glycolytic enzyme, hexokinase 2, which we confirmed through immunoblotting and enzyme activity assays. Pathway enrichment analysis identified downregulations in TNFA signaling via NFKB and MYC targets. Correspondingly, nuclear abundances of RELB and MYC were reduced in 2E2 cells. Thus, EEF1A1 deficiency may perturb glycolysis by limiting NFKB- and MYC-mediated gene expression, leading to decreased hexokinase expression and activity. This is the first evidence of a role for a translation elongation factor, EEF1A1, in regulating metabolic substrate utilization in mammalian cells.

Elongation factor 1A1 inhibition elicits changes in lipid droplet size, the bulk transcriptome, and cell type-associated gene expression in MASLD mouse liver.

Eukaryotic elongation factor 1A1 (EEF1A1), originally identified for its role in protein synthesis, has additional functions in diverse cellular processes. Of note, we previously discovered a role for EEF1A1 in hepatocyte lipotoxicity. We also demonstrated that a two-week intervention with the EEF1A1 inhibitor didemnin B (DB) (50 µg/kg) decreased liver steatosis in a mouse model of obesity and metabolic dysfunction-associated steatotic liver disease (MASLD) (129S6/SvEvTac mice fed western diet (42% fat) for 26 weeks). Here, we further characterized hepatic changes occurring in these mice by assessing lipid droplet (LD) size, bulk differential expression, and cell type-associated alterations in gene expression. Consistent with the previously demonstrated decrease in hepatic steatosis, we observed decreased median LD size in response to DB. Bulk RNA-seq followed by gene set enrichment analysis revealed alterations in pathways related to energy metabolism and proteostasis in DB-treated mouse livers. Deconvolution of bulk data identified decreased cell-type association scores for cholangiocytes, mononuclear phagocytes, and mesenchymal cells in response to DB. Overrepresentation analyses of bulk data using cell type marker gene sets further identified hepatocytes and cholangiocytes as the primary contributors to bulk differential expression in response to DB. Thus, we show that chemical inhibition of EEF1A1 decreases hepatic LD size and decreases gene expression signatures associated with several liver cell types implicated in MASLD progression. Furthermore, changes in hepatic gene expression were primarily attributable to hepatocytes and cholangiocytes. This work demonstrates that EEF1A1 inhibition may be a viable strategy to target aspects of liver biology implicated in MASLD progression.

The marine compound and elongation factor 1A1 inhibitor, didemnin B, provides benefit in western diet-induced non-alcoholic fatty liver disease.

Inhibition of eukaryotic elongation factor 1A1 (EEF1A1) with the marine compound didemnin B decreases lipotoxic HepG2 cell death in vitro and improves early stage non-alcoholic fatty liver disease (NAFLD) in young genetically obese mice. However, the effects of didemnin B on NAFLD in a model of long-term diet-induced obesity are not known. We investigated the effects of didemnin B on NAFLD severity and metabolic parameters in western diet-induced obese mice, and on the cell types that contribute to liver inflammation and fibrosis in vitro. Male 129S6 mice were fed either standard chow or western diet for 26 weeks, followed by intervention with didemnin B (50 µg/kg) or vehicle by intraperitoneal (i.p.) injection once every 3 days for 14 days. Didemnin B decreased liver and plasma triglycerides, improved oral glucose tolerance, and decreased NAFLD severity. Moreover, didemnin B moderately increased hepatic expression of genes involved in ER stress response (Perk, Chop), and fatty acid oxidation (Fgf21, Cpt1a). In vitro, didemnin B decreased THP-1 monocyte proliferation, disrupted THP-1 monocyte-macrophage differentiation, decreased THP-1 macrophage IL-1ß secretion, and decreased hepatic stellate cell (HSteC) proliferation and collagen secretion under both basal and lipotoxic (high fatty acid) conditions. Thus, didemnin B improves hepatic steatosis, glucose tolerance, and blood lipids in obesity, in association with moderate, possibly hormetic, upregulation of pathways involved in cell stress response and energy balance in the liver. Furthermore, it decreases the activity of the cell types implicated in liver inflammation and fibrosis in vitro. These findings highlight the therapeutic potential of partial protein synthesis inhibition in the treatment of NAFLD.

Two-Week Isocaloric Time-Restricted Feeding Decreases Liver Inflammation without Significant Weight Loss in Obese Mice with Non-Alcoholic Fatty Liver Disease.

Prolonged, isocaloric, time-restricted feeding (TRF) protocols can promote weight loss, improve metabolic dysregulation, and mitigate non-alcoholic fatty liver disease (NAFLD). In addition, 3-day, severe caloric restriction can improve liver metabolism and glucose homeostasis prior to significant weight loss. Thus, we hypothesized that short-term, isocaloric TRF would improve NAFLD and characteristics of metabolic syndrome in diet-induced obese male mice. After 26 weeks of ad libitum access to western diet, mice either continued feeding ad libitum or were provided with access to the same quantity of western diet for 8 h daily, over the course of two weeks. Remarkably, this short-term TRF protocol modestly decreased liver tissue inflammation in the absence of changes in body weight or epidydimal fat mass. There were no changes in hepatic lipid accumulation or other characteristics of NAFLD. We observed no changes in liver lipid metabolism-related gene expression, despite increased plasma free fatty acids and decreased plasma triglycerides in the TRF group. However, liver Grp78 and Txnip expression were decreased with TRF suggesting hepatic endoplasmic reticulum (ER) stress and activation of inflammatory pathways may have been diminished. We conclude that two-week, isocaloric TRF can potentially decrease liver inflammation, without significant weight loss or reductions in hepatic steatosis, in obese mice with NAFLD.

Non-parenchymal hepatic cell lipotoxicity and the coordinated progression of non-alcoholic fatty liver disease and atherosclerosis.

PURPOSE OF REVIEW: Non-alcoholic fatty liver disease (NAFLD) appears to be independently associated with the development of atherosclerosis. The biological mechanisms underlying this association are complex, and likely involve liver-resident cell types other than hepatocytes. Thus, we review recent evidence that non-parenchymal hepatic cell responses to lipid excess contribute to the pathogenesis of both NAFLD and atherosclerosis. RECENT FINDINGS: Significant independent associations between NAFLD and atherosclerosis have been identified through cross-sectional studies and meta-analyses. Mechanistic studies in cell cultures and in rodent models suggest that liver-resident macrophages, activated hepatic stellate cells (HSC) and liver sinusoidal endothelial cells (LSEC) mount lipotoxic responses under NAFLD conditions which can contribute to the progression of both NAFLD and atherosclerosis. SUMMARY: Non-parenchymal hepatic cell types exhibit some similarity in their responses to lipid excess, and in their pathogenic mechanisms, which likely contribute to the coordinated progression of NAFLD and atherosclerosis. In response to lipotoxic conditions, macrophages, Kupffer cells and HSC initiate robust inflammatory responses, whereas LSEC generate excess reactive oxygen species (ROS). The extent to which inflammatory cytokines and ROS produced by non-parenchymal cells contribute to the progression of both NAFLD and atherosclerosis warrants further investigation.

Cell Membrane-Derived Nanoparticles as Biomimetic Nanotherapeutics to Alleviate Fatty Liver Disease.

The prevalence of metabolic dysfunction associated-steatotic liver disease (MASLD) (formerly known as nonalcoholic fatty liver disease; NAFLD) is estimated at around 32% of the world's population, resulting in a major healthcare concern in recent times. Current pharmaceutical methods lack efficacy for the treatment of the disease because of suboptimal pharmacokinetic parameters including poor bioavailability, short half-life, and premature clearance. Designing an efficient drug delivery system that provides a protective environment is critical for addressing these challenges. Such a system should aim to enhance the cellular uptake of drugs, improve their bioavailability, and reduce the chances of rapid clearance. Here, we developed nanoengineered natural cell membrane-derived nanoparticles (CMNs) incorporated with a model drug, rosuvastatin, in the bilayer assembly of CMNs to reduce the accumulation of lipids in hepatocytes, a hallmark of MASLD. We used a cell extrusion technique to develop self-assembled CMNs with precise size control compared to the cell shearing method. Interestingly, the prepared CMNs were found to be nonphagocytic, representing around 1.13% of phosphatidylserine receptors on healthy cells, which allows the possibility of their use as stealth nanoparticles for drug delivery. Furthermore, CMNs exhibit higher drug-loading efficiency, excellent cytocompatibility, and enhanced cellular internalization capabilities. Moreover, we show that the delivery of rosuvastatin-loaded CMNs in the in vitro MASLD model efficiently reduced hepatocyte lipid accumulation, including total cholesterol (26.8 ± 3.1%) and triglycerides (11.8 ± 0.8%), compared to the negative control. Taken together, the nanoengineered biomimetic CMNs enhance the drug's bioactivity in hepatic cells, establishing a foundation for further investigation of this drug delivery system in treating MASLD.

Vitamin D intervention does not improve vascular regeneration in diet-induced obese male mice with peripheral ischemia.

Vitamin D appears to either promote or inhibit neovascularization in a disease context-dependent manner. The effects of vitamin D, alone or in combination with niacin, on endothelial cell (EC) angiogenic function and on revascularization in obese animals with peripheral ischemia are unknown. Here, we report that supplementation of high palmitate medium with vitamin D, niacin or both vitamins increased EC tube formation, which relies primarily on cell migration, and also maintained tube stability over time. Transcriptomic analyses revealed that both vitamins increased stress response and anti-inflammatory gene expression. However, vitamin D decreased cell cycle gene expression and inhibited proliferation, while niacin induced stable expression of miR-126-3p and -5p and maintained cell proliferation in high palmitate. To assess vascular regeneration, diet-induced obese mice received vitamin D, niacin or both vitamins following hind limb ischemic injury. Niacin, but not vitamin D or combined treatment, improved recovery of hind limb use. Histology of tibialis anterior sections revealed no improvements in revascularization, regeneration, inflammation or fibrosis with vitamin D or combined treatment. In summary, although both vitamin D and niacin increased angiogenic function of EC cultures in high fat, only niacin improved recovery of hind limb use following ischemic injury in obese mice. It is possible that inhibition of cell proliferation by vitamin D in high-fat conditions limits vascular regeneration and recovery from peripheral ischemia in obesity.