Specific activation of the integrated stress response uncovers regulation of central carbon metabolism and lipid droplet biogenesis.

The integrated stress response (ISR) enables cells to cope with a variety of insults, but its specific contribution to downstream cellular outputs remains unclear. Using a synthetic tool, we selectively activate the ISR without co-activation of parallel pathways and define the resulting cellular state with multi-omics profiling. We identify time- and dose-dependent gene expression modules, with ATF4 driving only a small but sensitive subgroup that includes amino acid metabolic enzymes. This ATF4 response affects cellular bioenergetics, rerouting carbon utilization towards amino acid production and away from the tricarboxylic acid cycle and fatty acid synthesis. We also find an ATF4-independent reorganization of the lipidome that promotes DGAT-dependent triglyceride synthesis and accumulation of lipid droplets. While DGAT1 is the main driver of lipid droplet biogenesis, DGAT2 plays an essential role in buffering stress and maintaining cell survival. Together, we demonstrate the sufficiency of the ISR in promoting a previously unappreciated metabolic state.

The triglyceride-synthesizing enzyme diacylglycerol acyltransferase 2 modulates the formation of the hepatitis C virus replication organelle.

The replication organelle of hepatitis C virus (HCV), called membranous web, is derived from the endoplasmic reticulum (ER) and mainly comprises double membrane vesicles (DMVs) that concentrate the viral replication complexes. It also tightly associates with lipid droplets (LDs), which are essential for virion morphogenesis. In particular acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1), a rate-limiting enzyme in triglyceride synthesis, promotes early steps of virus assembly. The close proximity between ER membranes, DMVs and LDs therefore permits the efficient coordination of the HCV replication cycle. Here, we demonstrate that exaggerated LD accumulation due to the excessive expression of the DGAT1 isozyme, DGAT2, dramatically impairs the formation of the HCV membranous web. This effect depended on the enzymatic activity and ER association of DGAT2, whereas the mere LD accumulation was not sufficient to hamper HCV RNA replication. Our lipidomics data indicate that both HCV infection and DGAT2 overexpression induced membrane lipid biogenesis and markedly increased phospholipids with long chain polyunsaturated fatty acids, suggesting a dual use of these lipids and their possible competition for LD and DMV biogenesis. On the other hand, overexpression of DGAT2 depleted specific phospholipids, particularly oleyl fatty acyl chain-containing phosphatidylcholines, which, in contrast, are increased in HCV-infected cells and likely essential for viral infection. In conclusion, our results indicate that lipid exchanges occurring during LD biogenesis regulate the composition of intracellular membranes and thereby affect the formation of the HCV replication organelle. The potent antiviral effect observed in our DGAT2 overexpression system unveils lipid flux that may be relevant in the context of steatohepatitis, a hallmark of HCV infection, but also in physiological conditions, locally in specific subdomains of the ER membrane. Thus, LD formation mediated by DGAT1 and DGAT2 might participate in the spatial compartmentalization of HCV replication and assembly factories within the membranous web.

DGAT1 and DGAT2 Inhibitors for Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) Management: Benefits for Their Single or Combined Application.

Inhibiting diacylglycerol acetyltransferase (DGAT1, DGAT2) enzymes (iDGAT1, iDGAT2), involved in triglyceride (TG) synthesis, improves hepatic steatosis in metabolic dysfunction-associated steatotic liver disease (MASLD) patients. However, their potential synergism in disease onset (SLD) and progression (metabolic dysfunction-associated steatohepatitis, fibrosis) has been poorly explored. We investigated iDGAT1 and iDGAT2 efficacy, alone or combined (iDGAT1/2) on fat accumulation and hepatocellular injury in hepatocytes (HepG2) and on fibrogenic processes in hepatic stellate cells (LX2). We further tested whether the addition of MitoQ antioxidant to iDGAT1/2 would enhance their effects. SLD and MASH conditions were reproduced in vitro by supplementing Dulbecco's Modified Eagle's Medium (DMEM) with palmitic/oleic acids (PAOA) alone (SLD-medium), or plus Lipopolisaccaride (LPS), fructose, and glucose (MASH-medium). In SLD-medium, iDGAT1 and iDGAT2 individually, and even more in combination, reduced TG synthesis in HepG2 cells. Markers of hepatocellular damage were slightly decreased after single iDGAT exposure. Conversely, iDGAT1/2 counteracted ER/oxidative stress and inflammation and enhanced mitochondrial Tricarboxylic acid cycle (TCA) and respiration. In HepG2 cells under a MASH-like condition, only iDGAT1/2 effectively ameliorated TG content and oxidative and inflammatory mediators, further improving bioenergetic balance. LX2 cells, challenged with SLD/MASH media, showed less proliferation and slower migration rates in response to iDGAT1/2 drugs. MitoQ combined with iDGAT1/2 improved cell viability and dampened free fatty acid release by stimulating ß-oxidation. Dual DGAT inhibition combined with antioxidants open new perspectives for MASLD management.

Ozenoxacin suppresses sebum production by inhibiting mTORC1 activation in differentiated hamster sebocytes.

Acne vulgaris is a complex condition involving factors that affect the pilosebaceous unit. A primary manifestation of acne pathology is the development of comedones, often linked to the overproduction of sebum resulting from 5α-dihydrotestosterone (5α-DHT) and insulin activity. Ozenoxacin is a topical quinolone that exhibits potent antibacterial activity against Cutibacterium acnes (C. acnes). It is commonly used to treat acne associated with this bacterium; however, its effect on sebum production within the sebaceous glands remains unclear. In this study, the effects of ozenoxacin on sebum production were examined using insulin- and 5α-DHT-differentiated hamster sebocytes. Ozenoxacin showed a dose-dependent inhibition of lipid droplet formation and triacylglycerol (TG) production, which is a major component of sebum. In addition, it suppressed the expression of diacylglycerol acyltransferase 1, stearoyl-CoA desaturase-1, and perilipin-1 mRNA, all important factors involved in sebum synthesis, in a dose-dependent manner. Moreover, ozenoxacin decreased phosphorylated 40S ribosomal protein S6 levels downstream of the mechanistic/mammalian target of rapamycin complex 1 (mTORC1), without altering the phosphorylation of Akt, an upstream regulator of mTORC1, in both insulin- and 5α-DHT-treated hamster sebocytes. Interestingly, nadifloxacin, but not clindamycin, exhibited a similar suppression of sebum production, albeit with lesser potency compared with ozenoxacin. Furthermore, a topical application of a 2% ozenoxacin-containing lotion to the auricle skin of hamsters did not affect the size of the sebaceous glands or epidermal thickness. Notably, it decreased the amount of TG on the skin surface. The results provide novel insights into the sebum-inhibitory properties of ozenoxacin, indicating its potential efficacy in controlling microbial growth and regulating sebum production for acne management.

Diacylglycerol O-acyltransferase 1 inhibitor increases plasma alanine aminotransferase and aspartate aminotransferase activities via a shedding of the intestinal villi and an increase in intestinal permeability in rats.

Diacylglycerol O-acyltransferase 1 (DGAT1) is a key enzyme for fat absorption step in the enterocytes. We previously reported that DGAT1 inhibition increased plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in corn oil-loaded rats via protein kinase C (PKC) activation. In the present study, we investigated the mechanism with respect to the morphology and permeability of the small intestine, focusing on PKC function, and found that shortening of the intestinal villi and a decrease in the number of tdT-mediated dUTP-biotin nick-end labeling-positive cells in the tips of the villi were observed in the jejunum of DGAT1 inhibitor-treated rats loaded with corn oil. These results suggested that the tips of the villi were shed into the intestinal lumen. Next, fluorescein isothiocyanate-dextran, 110 kDa (FD-110) was administered intraduodenally to DGAT1 inhibitor-treated rats loaded with corn oil and we found that plasma FD-110 concentrations increased, indicating that the intestinal permeability to molecules with a molecular weight of approximately 110,000 (e.g., ALT and AST) increased. Taken together, the present results suggested that DGAT1 inhibitor-treatment in combination with corn oil causes ALT and AST to leak from the enterocytes into the blood by shedding the tips of the intestinal villi and increasing intestinal permeability.

Combined structure-based virtual screening and machine learning approach for the identification of potential dual inhibitors of ACC and DGAT2.

Acetyl-coenzyme A carboxylase (ACC) and diacylglycerol acyltransferase 2 (DGAT2) are recognized as potential therapeutic targets for nonalcoholic fatty liver disease (NAFLD). Inhibitors targeting ACC and DGAT2 have exhibited the capacity to reduce hepatic fat in individuals afflicted with NAFLD. However, there are no reports of dual inhibitors targeting ACC and DGAT2 for the treatment of NAFLD. Here, we aimed to identify potential dual inhibitors of ACC and DGAT2 using an integrated in silico approach. Machine learning-based virtual screening of commercial molecule databases yielded 395,729 hits, which were subsequently subjected to molecular docking aimed at both the ACC and DGAT2 binding sites. Based on the docking scores, nine compounds exhibited robust interactions with critical residues of both ACC and DGAT2, displaying favorable drug-like features. Molecular dynamics simulations (MDs) unveiled the substantial impact of these compounds on the conformational dynamics of the proteins. Furthermore, binding free energy assessments highlighted the notable binding affinities of specific compounds (V003-8107, G340-0503, Y200-1700, E999-1199, V003-6429, V025-4981, V006-1474, V025-0499, and V021-8916) to ACC and DGAT2. The compounds proposed in this study, identified using a multifaceted computational strategy, warrant experimental validation as potential dual inhibitors of ACC and DGAT2, with implications for the future development of novel drugs targeting NAFLD.

The role of DGAT1 and DGAT2 in tumor progression via fatty acid metabolism: A comprehensive review.

Fatty acid metabolism is a complex biochemical process, including the production, breakdown and application of fatty acids. Not only is it an important component of lipid metabolism, fatty acid metabolism is also connected to the energy metabolism pathways of cells and plays a vital role in maintaining the energy balance of organisms. Diacylglycerol-O-acyltransferase 1 (DGAT1) and Diacylglycerol-O-acyltransferase 2 (DGAT2) are key components in regulating lipid metabolism, which provide energy for cell proliferation and growth. Recent studies have shown that DGAT1 and DGAT2 influence tumor progression through fatty acid metabolism in cancer. Although DGAT1 and DGAT2 have similar names, they differ significantly in various aspects and play distinct roles in individual tumors. A comparative analysis of the physiological roles of these enzymes and their differential expressions in different types of tumors will enhance our understanding of their unique characteristics. This article summarizes the characteristics of tumor fatty acid metabolism and explains how DGAT1 and DGAT2 specifically promote tumor progression. In addition, this review discusses the potential of lipid-lowering drugs in tumor treatment, providing a new perspective on targeting fatty acid metabolism to inhibit tumor progression in the future, while emphasizing the importance of DGAT1 and DGAT2 as potential targets for tumor treatment.

Maize genotypes with favourable dgat1-2 and fatb alleles possess stable high kernel oil and better fatty acid health and nutritive indices.

Diverse uses of maize oil attracted various stakeholders, including food, feed, and bioenergy, highlighting the increased demand for sustainable production. Here, 48 diverse sub-tropical maize genotypes varying for dgat1-2 and fatb genes governing oil attributes, were evaluated in three diverse locations to assess trends of oil content, fatty acid (FA) profile, the effect of environment on oil attributes, the impact of different gene combinations and determine FA health and nutritional properties. The genotypes revealed wide variation in oil content (OC: 3.4-6.8 %) and FA compositional traits, namely palmitic (PA, 11.3-24.1 %), oleic (OA, 21.5-42.7 %), linoleic (LA, 36.6-61.7 %), and linolenic (ALA, 0.7-2.3 %) acids. Double-mutants with both favourable alleles (dd/ff) exhibited 51.6 % higher oil, 33.2 % higher OA, and 30.2 % reduced PA compared to wild-types (d+d+/f+f+) across locations. These double-mutants had lower saturated FA (12.2 %), and higher unsaturated FA (87.0 %), indicating reduced susceptibility to autooxidation, with lower atherogenicity (0.14), thrombogenicity (0.27) and peroxidisability (48.15), higher cholesterolemic index (7.16), optimum oxidability (5.27) and higher nutritive-value-index (3.35) compared to d+d+/f+f+, making them promising for significant health and nutritional benefits. Locally adapted stable novel double-mutants with high-oil and better FA properties identified here can expedite the maize breeding programs, meeting production demands and addressing long-standing challenges for breeders.

Lazy neutrophils - a lack of DGAT1 reduces the chemotactic activity of mouse neutrophils.

BACKGROUND: Neutrophils are key players in the innate immune system, actively migrating to sites of inflammation in the highly energetic process of chemotaxis. In this study, we focus on the role of acyl-CoA: diacylglycerol acyltransferase 1 (DGAT1), an enzyme that catalyzes the synthesis of triglycerides, the major form of stored energy, in neutrophil chemotaxis. METHODS AND RESULTS: Using a mouse model of psoriasis, we show that DGAT1-deficiency reduces energy-demanding neutrophil infiltration to the site of inflammation, but this inhibition is not caused by decreased glycolysis and reduced ATP production by neutrophils lacking DGAT1. Flow cytometry and immunohistochemistry analysis demonstrate that DGAT1 also does not influence lipid accumulation in lipid droplets during inflammation. Interestingly, as has been shown previously, a lack of DGAT1 leads to an increase in the concentration of retinoic acid, and here, using real-time PCR and publicly-available next-generation RNA sequencing datasets, we show the upregulation of retinoic acid-responsive genes in Dgat1KO neutrophils. Furthermore, supplementation of WT neutrophils with exogenous retinoic acid mimics DGAT1-deficiency in the inhibition of neutrophil chemotaxis in in vitro transwell assay. CONCLUSIONS: These results suggest that impaired skin infiltration by neutrophils in Dgat1KO mice is a result of the inhibitory action of an increased concentration of retinoic acid, rather than impaired lipid metabolism in DGAT1-deficient mice.

The synthesis of triacylglycerol by diacylglycerol acyltransferases (CsDGAT1A and CsDGAT2D) is essential for tolerance of cucumber's resistance to low-temperature stress.

KEY MESSAGE: CsDGAT1A and CsDGAT2D play a positive regulatory role in cucumber's response to low-temperature stress and positively regulate the synthesis of triacylglycerol (TAG). Triacylglycerol (TAG), a highly abundant and significant organic compound in plants, plays crucial roles in plant growth, development, and stress responses. The final acetylation step of TAG synthesis is catalyzed by diacylglycerol acyltransferases (DGATs). However, the involvement of DGATs in cucumber's low-temperature stress response remains unexplored. This study focused on two DGAT genes, CsDGAT1A and CsDGAT2D, investigating their function in enhancing cucumber's low-temperature stress tolerance. Our results revealed that both proteins were the members of the diacylglycerol acyltransferase family and were predominantly localized in the endoplasmic reticulum. Functional analysis demonstrated that transient silencing of CsDGAT1A and CsDGAT2D significantly compromised cucumber's low-temperature stress tolerance, whereas transient overexpression enhanced it. Furthermore, the TAG content quantification indicated that CsDGAT1A and CsDGAT2D promoted TAG accumulation. In conclusion, this study elucidates the lipid metabolism mechanism in cucumber's low-temperature stress response and offers valuable insights for the cultivation of cold-tolerant cucumber plants.

Functional Characterization of the Effects of CsDGAT1 and CsDGAT2 on Fatty Acid Composition in Camelina sativa.

Triacylglycerols (TAGs) are the storage oils of plant seeds, and these lipids provide energy for seed germination and valuable oils for human consumption. Three diacylglycerol acyltransferases (DGAT1, DGAT2, and DGAT3) and phospholipid:diacylglycerol acyltransferases participate in the biosynthesis of TAGs. DGAT1 and DGAT2 participate in the biosynthesis of TAGs through the endoplasmic reticulum (ER) pathway. In this study, we functionally characterized CsDGAT1 and CsDGAT2 from camelina (Camelina sativa). Green fluorescent protein-fused CsDGAT1 and CsDGAT2 localized to the ER when transiently expressed in Nicotiana benthamiana leaves. To generate Csdgat1 and Csdgat2 mutants using the CRISPR/Cas9 system, camelina was transformed with a binary vector carrying Cas9 and the respective guide RNAs targeting CsDGAT1s and CsDGAT2s via the Agrobacterium-mediated floral dip method. The EDD1 lines had missense and nonsense mutations in the CsDGAT1 homoeologs, suggesting that they retained some CsDGAT1 function, and their seeds showed decreased eicosaenoic acid (C20:1) contents and increased C18:3 contents compared to the wild type (WT). The EDD2 lines had a complete knockout of all CsDGAT2 homoeologs and a slightly decreased C18:3 content compared to the WT. In conclusion, CsDGAT1 and CsDGAT2 have a small influence on the seed oil content and have an acyl preference for C20:1 and C18:3, respectively. This finding can be applied to develop oilseed plants containing high omega-3 fatty acids or high oleic acid.

The effects of the feeding duration of propylene glycol on major meat quality parameters and substantial proteins in the muscle of Akkaraman lambs.

In this study, the effects of propylene glycol (PG) on meat quality and molecular pathways related to energy metabolism in longissimus lumborum muscle on lambs were evaluated. Seventy-two lambs were divided into three groups consisting of 60th, 90th, and 120th of slaughter days. The dosage of the PG and slaughter days were the variables used in the study. Eight animals were slaughtered from each group on each day. The meat quality parameters (e.g., pH, protein, fatty acid profile) and IGF-1, IGFBP4, and DGAT1 (i.e., mRNA and protein levels) were evaluated. The pH 45 min post-slaughter was higher in PG groups on 120th day. On the 4th day after slaughter, the b value was the lowest in the PG3, while 7th day after slaughter it was highest in Con and PG3 on 90th day. The total n3 and n6 were lowest and the NV was highest on 120th day. The IGFBP4 was upregulated in the PG groups on all of the slaughter days. The DGAT1 was upregulated in the PG3 on the 90th day. The IGF-1, DGAT1, IGFBP4 protein levels were found to have increased in the PG3 on 90th day. The IGFBP4 was found to have decreased in the PG3 on 120th day. According to the results of the study, the oral administration of the PG at the 3 mL/kg live weight0.75 for at least 120 days may have positive effects on meat quality in lambs through the IGF-1, DGAT1, and IGFBP4 genes and the proteins encoded by these genes.

The Lipid-Metabolism-Associated Anti-Obesity Properties of Rapeseed Diacylglycerol Oil.

To investigate the effects of rapeseed diacylglycerol oil (RDG) intake on lipid accumulation and metabolism in C57BL/6J mice, obese mice were fed a high-fat diet in which 45% of the total energy content came from RDG (RDGM group) or rapeseed triacylglycerol oil (RTGM group). This diet intervention was conducted for 12 weeks following the establishment of the obese mouse model. By the end of the experiment, the serum glucose levels of the mice in the RTGM and RDGM groups were 13.0 ± 1.3 mmol/L and 9.7 ± 1.5 mmol/L, respectively. Meanwhile, the serum triglyceride level in the RDGM group was 26.3% lower than that in the RTGM group. The weight-loss effect in the RDGM group was accompanied by a significant decrease in the white adipose tissue (WAT) index. The RDG intervention did not significantly change the antioxidant and anti-inflammatory properties of the rapeseed oil in vivo. The RDG diet improved the liver lipid metabolism abnormalities induced by a high-fat diet, leading to decreased liver damage index values (AST and ALT). Additionally, compared to that in the RTGM group, the expression of the adipogenic genes PPAR-γ and DGAT decreased in both the liver and intestine by 21.7% and 16.7% and by 38.7% and 47.2%, respectively, in the RDGM group. Further, most lipolytic genes in BAT showed no significant change after the RDG intervention. This implies that RDG regulates lipid metabolism by altering the expression of adipogenic genes in the liver, intestine, and adipose tissue, thereby reducing the accumulation of WAT. Furthermore, the RDG diet enhanced gut flora diversity, increasing the relative levels of unclassified Muribaculaceae and decreasing the levels of Dubosiella and Faecalibaculum in the mouse gut, potentially accelerating lipid metabolism. Thus, a three-month RDG diet intervention in obese mice exhibited benefits in regulating the somatotype, serum obesity-related indices, gut flora structure, and lipid metabolism in the adipose tissue, liver, and intestine.

Effects of bisphenol A on reproduction, oxidative stress, and lipid regulation in the marine rotifer Brachionus plicatilis.

This study reports the effects of bisphenol A (BPA) on the rotifer Brachionus plicatilis, focusing on growth performance, reproductive output, oxidative stress responses, and lipid metabolism genes. High BPA levels disrupted peak daily offspring production and led to oxidative stress and increased superoxide dismutase and catalase activity. The research identified distinctive monoacylglycerol O-acyltransferase (MGAT) and diacylglycerol O-acyltransferase (DGAT) genes in B. plicatilis, B. rotundiformis, and B. koreanus, enhancing understanding of lipid metabolism in these species. BPA exposure significantly altered MGAT and DGAT expression, and feeding status affected these regulatory patterns. When food was unavailable, BPA reduced DGAT2 and MGAT2a expression. However, under feeding conditions, DGAT2 and MGAT1 levels increased, indicating that nutritional status and BPA exposure interact to affect gene expression.

Identification of key genes for triacylglycerol biosynthesis and storage in herbaceous peony (Paeonia lactifolra Pall.) seeds based on full-length transcriptome.

BACKGROUND: The herbaceous peony (Paeonia lactiflora Pall.) is extensively cultivated in China due to its root being used as a traditional Chinese medicine known as 'Radix Paeoniae Alba'. In recent years, it has been discovered that its seeds incorporate abundant unsaturated fatty acids, thereby presenting a potential new oilseed plant. Surprisingly, little is known about the full-length transcriptome sequencing of Paeonia lactiflora, limiting research into its gene function and molecular mechanisms. RESULTS: A total of 484,931 Reads of Inserts (ROI) sequences and 1,455,771 full-Length non-chimeric reads (FLNC) sequences were obtained for CDS prediction, TF analysis, SSR analysis and lncRNA identification. In addition, gene function annotation and gene structure analysis were performed. A total of 4905 transcripts were related to lipid metabolism biosynthesis pathway, belonging to 28 enzymes. We use these data to identify 10 oleosin (OLE) and 5 diacylglycerol acyltransferase (DGAT) gene members after de-redundancy. The analysis of physicochemical properties and secondary structure showed them similarity in gene family respectively. The phylogenetic analysis showed that the distribution of OLE and DGAT family members was roughly the same as that of Arabidopsis. Quantitative real-time polymerase chain reaction (qRT-PCR) analyses revealed expression changes in different seed development stages, and showed a trend of increasing and then decreasing. CONCLUSION: In summary, these results provide new insights into the molecular mechanism of triacylglycerol (TAG) biosynthesis and storage during the seedling stage in Paeonia lactiflora. It provides theoretical references for selecting and breeding oil varieties and understanding the functions of oil storage as well as lipid synthesis related genes in Paeonia lactiflora.

HuR promotes triglyceride synthesis and intestinal fat absorption.

Triacylglyceride (TAG) synthesis in the small intestine determines the absorption of dietary fat, but the underlying mechanisms remain to be further studied. Here, we report that the RNA-binding protein HuR (ELAVL1) promotes TAG synthesis in the small intestine. HuR associates with the 3' UTR of Dgat2 mRNA and intron 1 of Mgat2 pre-mRNA. Association of HuR with Dgat2 3' UTR stabilizes Dgat2 mRNA, while association of HuR with intron 1 of Mgat2 pre-mRNA promotes the processing of Mgat2 pre-mRNA. Intestinal epithelium-specific HuR knockout reduces the expression of DGAT2 and MGAT2, thereby reducing the dietary fat absorption through TAG synthesis and mitigating high-fat-diet (HFD)-induced non-alcoholic fatty liver disease (NAFLD) and obesity. Our findings highlight a critical role of HuR in promoting dietary fat absorption.

Arabidopsis diacylglycerol acyltransferase1 mutants require fatty acid desaturation for normal seed development.

Diacylglycerol acyltransferase1 (DGAT1) is the major enzyme that synthesizes triacylglycerols (TAG) during Arabidopsis seed development. Mutant dgat1 seeds possess low oil content in addition to a high polyunsaturated fatty acid (PUFA) composition. Two genes encoding endoplasmic reticulum localized desaturase enzymes, fatty acid desaturase2 (FAD2) and fatty acid desaturase3 (FAD3), were upregulated in both dgat1-1 and dgat1-2 developing seeds. Crosses between both dgat1 mutant alleles and fad2-1 failed to generate plants homozygous for both dgat1 and fad2. Reciprocal crosses with wild-type plants demonstrated that both male and female dgat1 fad2 gametophytes were viable. Siliques from DGAT1/dgat1-1 fad2-1/fad2-1 and dgat1-1/dgat1-1 FAD2/fad2-1 possessed abnormal looking seeds that were arrested in the torpedo growth stage. Approximately 25% of the seeds exhibited this arrested phenotype, genetically consistent with them possessing the double homozygous dgat1 fad2 genotype. In contrast, double homozygous dgat1-1 fad3-2 mutant plants were viable. Seeds from these plants possessed higher levels of 18:2 while their fatty acid content was lower than dgat1 mutant controls. The results are consistent with a model where in the absence of DGAT1 activity, desaturation of fatty acids by FAD2 becomes essential to provide PUFA substrates for phospholipid:diacylglycerol acyltransferase (PDAT) to synthesize TAG. In a dgat1 fad2 mutant, seed development is aborted because TAG is unable to be synthesized by either DGAT1 or PDAT.

Rab1b facilitates lipid droplet growth by ER-to-lipid droplet targeting of DGAT2.

Lipid droplets (LDs) comprise a triglyceride core surrounded by a lipid monolayer enriched with proteins, many of which function in LD homeostasis. How proteins are targeted to the growing LD is still unclear. Rab1b, a GTPase regulating secretory transport, was recently associated with targeting proteins to LDs in a Drosophila RNAi screen. LD formation was prevented in human hepatoma cells overexpressing dominant-negative Rab1b. We thus hypothesized that Rab1b recruits lipid-synthesizing enzymes, facilitating LD growth. Here, FRET between diacylglycerol acyltransferase 2 (DGAT2) and Rab1b and activity mutants of the latter demonstrated that Rab1b promotes DGAT2 ER to the LD surface redistribution. Last, alterations in LD metabolism and DGAT2 redistribution, consistent with Rab1b activity, were caused by mutations in the Rab1b-GTPase activating protein TBC1D20 in Warburg Micro syndrome (WARBM) model mice fibroblasts. These data contribute to our understanding of the mechanism of Rab1b in LD homeostasis and WARBM, a devastating autosomal-recessive disorder caused by mutations in TBC1D20.

Palmitic Acid Exerts Anti-Tumorigenic Activities by Modulating Cellular Stress and Lipid Droplet Formation in Endometrial Cancer.

Epidemiological and clinical evidence have extensively documented the role of obesity in the development of endometrial cancer. However, the effect of fatty acids on cell growth in endometrial cancer has not been widely studied. Here, we reported that palmitic acid significantly inhibited cell proliferation of endometrial cancer cells and primary cultures of endometrial cancer and reduced tumor growth in a transgenic mouse model of endometrial cancer, in parallel with increased cellular stress and apoptosis and decreased cellular adhesion and invasion. Inhibition of cellular stress by N-acetyl-L-cysteine effectively reversed the effects of palmitic acid on cell proliferation, apoptosis, and invasive capacity in endometrial cancer cells. Palmitic acid increased the intracellular formation of lipid droplets in a time- and dose-dependent manner. Depletion of lipid droplets by blocking DGAT1 and DGAT2 effectively increased the ability of palmitic acid to inhibit cell proliferation and induce cleaved caspase 3 activity. Collectively, this study provides new insight into the effect of palmitic acid on cell proliferation and invasion and the formation of lipid droplets that may have potential clinical relevance in the treatment of obesity-driven endometrial cancer.

DGAT2 Plays a Crucial Role to Control ESRRA-PROX1 Transcriptional Network to Maintain Hepatic Mitochondrial Sustainability.

BACKGRUOUND: Diacylglycerol O-acyltransferase 2 (DGAT2) synthesizes triacylglycerol (TG) from diacylglycerol; therefore, DGAT2 is considered as a therapeutic target for steatosis. However, the consequence of inhibiting DGAT2 is not fully investigated due to side effects including lethality and lipotoxicity. In this article, we observed the role of DGAT2 in hepatocarcinoma. METHODS: The role of DGAT2 is analyzed via loss-of-function assay. DGAT2 knockdown (KD) and inhibitor treatment on HepG2 cell line was analyzed. Cumulative analysis of cell metabolism with bioinformatic data were assessed, and further compared with different cohorts of liver cancer patients and non-alcoholic fatty liver disease (NAFLD) patients to elucidate how DGAT2 is regulating cancer metabolism. RESULTS: Mitochondrial function is suppressed in DGAT2 KD HepG2 cell along with the decreased lipid droplets. In the aspect of the cancer, DGAT2 KD upregulates cell proliferation. Analyzing transcriptome of NAFLD and hepatocellular carcinoma (HCC) patients highlights negatively correlating expression patterns of 73 lipid-associated genes including DGAT2. Cancer patients with the lower DGAT2 expression face lower survival rate. DGAT2 KD cell and patients' transcriptome show downregulation in estrogen- related receptor alpha (ESRRA) via integrated system for motif activity response analysis (ISMARA), with increased dimerization with corepressor prospero homeobox 1 (PROX1). CONCLUSION: DGAT2 sustains the stability of mitochondria in hepatoma via suppressing ESRRA-PROX1 transcriptional network and hinders HCC from shifting towards glycolytic metabolism, which lowers cell proliferation.