Triacylglycerol Accumulation Research Articles

Abstract P3073: Altered Mitochondrial Mg 2+ Homeostasis In Liver Links Lipid Metabolism, Inflammation And Atherogenesis

Although evidences show the role of Mg 2+ in lipid metabolism and atherosclerosis, the molecular mechanism by which loss of Mg 2+ homeostasis promotes cardiovascular disease (CVD) is not known. Mg 2+ homeostasis is regulated by mitochondria and Mrs2 is the only known molecular machinery associated with mitochondrial Mg 2+ influx. To begin elucidating the importance of Mg 2+ homeostasis in lipid metabolism and CVD we made liver-specific Mrs2 KO mouse (Mrs2 Δhep ). Liver being the central hub of lipid metabolism, we asked whether loss of Mrs2 alters lipid metabolism and lipoprotein profile. Our results show increased accumulation of hepatic triacylglycerol (TG) and cholesterol in Mrs2 Δhep . Consistent with increased TG/cholesterol, plasma cholesterol and oxidized low density lipoprotein (ox-LDL) levels significantly differed between control and KO. Because ox-LDL contribute to atherosclerosis, we hypothesized altered hepatic lipid metabolism to induce inflammation, immune imbalance and accelerate lesions through modified atherogenic lipoprotein and cytokine profile. Quantification of plasma cytokines and chemokines were performed using the proteome profiler. Because T cells are critical drivers and modifiers of atherosclerosis, we quantified the lymphocyte and monocyte subsets by flow cytometry. Because T regulatory cells have anti-antherogenic roles, we studied the effect of ox-LDL on Tregs. Our results show increased and decreased levels of inflammatory and anti-inflammatory cytokines respectively in Mrs2 Δhep . In Mrs2 Δhep stimulation with ox-LDL showed an increased antigen specific proliferation of T-cells. We also observed increased and decreased population of Th17 and Tregs respectively. The decrease in Tregs population was attributed to increased apoptosis. In conclusion our observation suggests that high levels of ox-LDL in Mrs2 Δhep to induce inflammation and inflammatory cell expansion accompanied by apoptosis in Tregs. Our results conclude dysregulated Mg 2+ homeostasis to alter lipid metabolism and atherogenesis by inducing inflammation and compromised Tregs population. Our study will be the first of its kind to establish a triangular molecular link between Mg 2+ homeostasis, lipid metabolism, and atherogenesis.

An increase in the membrane lipids recycling by PDAT overexpression stimulates the accumulation of triacylglycerol in Nannochloropsis gaditana

Oleaginous microalgae represent potential feedstocks for the sustainable production of lipids thanks to their ability to accumulate triacylglycerols (TAGs). TAG accumulation in several algal species is strongly induced under specific conditions such as nutrient deprivation and high light which, however, also negatively impact growth. Genetic modification of lipogenic pathways can potentially enhance TAG accumulation without negatively affecting growth, avoiding the trade-off between biomass and lipid productivity.In this study, the phospholipid: diacylglycerol acyltransferase (PDAT), an enzyme involved in membrane lipid recycling, was overexpressed in the seawater alga Nannochloropsis gaditana. PDAT overexpression induced increased TAG content in actively growing algae cultures while no effects were observed in conditions naturally stimulating strong lipid accumulation such as high light and nitrogen starvation. The increase of TAG content was confirmed also in a strain cultivated in industrially relevant conditions even though PDAT overexpression, if too strong, the gene overexpression becomes detrimental for growth in the longer term. Results overall suggest that genetic modulation of the PDAT gene represents a promising strategy to increase microalgae lipid content by minimizing negative effects on biomass productivity.

White wine grape pomace as a suitable carbon source for lipid and carotenoid production by fructophilic Rhodorotula babjevae.

We aim to explore the non-structural sugars from white wine grape pomace (WWGP) as the input carbon source for the co-production of multiple high-value products by the non-fastidious yeast Rhodotorula babjevae to create a sustainable and economically appealing process. Water extraction of unfermented, soluble sugars from WWGP yielded extracts with similar amounts of glucose and fructose, which were used to prepare a growth medium. Rhodorotula babjevae multiplied as fast on WWGP-based medium as on a reference medium but achieved higher cell dry weight (CDW) and lower intracellular triacylglycerol accumulation (22.5% vs. 28.6%) in WWGP-based medium. In addition, R. babjevae produced mannitol and arabitol and carotenoids and secreted polyol esters of fatty acids, a rare type of glycolipid as confirmed by Fourier transform-infrared, nuclear magnetic resonance and high-performance liquid chromatography analyses. Remarkably, R. babjevae consumed simultaneously both fructose and glucose when on WWGP-based medium and left glucose practically untouched in the reference medium, evidencing a fructophilic character. Rhodorotula babjevae, a metabolic versatile yeast, proliferated on a minimally processed extract and successfully converted glucose and fructose into high-value products. Different chemicals with market potential can be produced through the valorization of abundant waste feedstocks generated by the wine industry to which R. babjevae can contribute.

Effect of deep-fried oil consumption on lipid profile in rats

BackgroundDeep-frying is a common practice in food preparation. High temperature deep-frying can alter the physicochemical properties of food ingredients, which may, in turn, affect the lipid profile of consumers. Changes in lipid profile are known to be associated with various diseases, such as cancer, diabetes and cardiovascular diseases (CVDs). However, the effect of oils present in deep-fried foods on the lipid profile of consumers is not well studied. MethodsThe bodyweight of wistar strain rats was determined at the beginning and end of the experimental period. Serum was collected from rats fed on an ad libitum diet of either deep-fried oil or fresh oil. Lipid profile, blood glucose, and insulin level were measured by an enzymatic method. ResultsWe found that rats fed deep-fried oil had increased weight (17% in male, 25% in female, 23% on average). Deep-fried oil fed rats had increased triacylglycerol (TAG) accumulation (28% in male, 58% in female and 40% on average) total cholesterol (TC) level (42% in male, 35% in female, 38% on average) and low density lipoprotein (LDL) level (16% in male, 68% in female, 40% on average). Deep-fried oil consumption decreased high density lipoprotein (HDL) level (19% in male, 37% in female, 21% on average), but the effect is statistically insignificant in males. ConclusionsThe increase in TAG, TC, and LDL-cholesterol are indicators of risk of CVDs. We therefore conclude that the consumption of deep-fried oil containing diet affect the lipid profile which might increase the risk of CVDs. Hence, we strongly recommend reducing the consumption of deep-fried oils in the human diet.

Genome-wide association analysis and transcriptome reveal novel loci and a candidate regulatory gene of fatty acid biosynthesis in sesame (Sesamum indicum L.)

The regulatory mechanisms of fatty acid (FA) biosynthesis and triacylglycerols (TAGs) assembly remain largely misunderstood in sesame. Gas chromatography was used to analyze the natural variation in FA compositions and oil content (OC) in 400 sesame accessions grown in three different environments. The phenotypic data was associated with the newly released SNP data from whole-genome resequencing, and 43 significant loci for FA and OC were identified. Comparative transcriptomics analysis of high-OC and low-OC materials was performed, and 515 differentially expressed genes (DEGs) were identified across three seed developmental stages. By integrating the genome-wide association study (GWAS) and DEGs analysis, twenty candidate genes were identified, of which SiTPS1 (trehalose-6-phosphate synthase 1) has emerged as a key regulatory gene of FAs and TAGs metabolism in sesame. Overexpression of SiTPS1 in transgenic Arabidopsis influenced FA composition and significantly increased OC. Our study provides resources for the markers-based improvement of OC and quality in sesame and other crops.

Overexpression of DGAT2 Stimulates Lipid Droplet Formation and Triacylglycerol Accumulation in Bovine Satellite Cells.

Simple SummaryTriacylglycerols are the major component of intramuscular fat, and the final step in their biosynthesis is catalyzed by DGAT2. Bovine skeletal muscle satellite cells were infected with the overexpression adenovirus Ad-DGAT2 and interfering adenovirus sh-DGAT2. The results showed that overexpression of DGAT2 upregulated the expression of genes involved in lipid accumulation and adipogenesis and increased cellular triacylglycerol content. The differentially expressed genes were mainly enriched in the PPAR signaling, glycerolipid metabolism, fatty acid biosynthesis, and AMPK signaling pathways. These results highlight the important regulatory role of DGAT2 during adipogenic transdifferentiation of BSCs and the complexity of intramuscular adipogenesis, as well as providing a theoretical basis for producing high marbling content beef.Intramuscular fat (IMF) is closely related to the tenderness, juiciness, and flavor of beef, and is an important indicator for beef quality assessment internationally. The main components of skeletal intramuscular fat (IMF) are phospholipids and triacylglycerols (TAG), and the final step of TAG biosynthesis is catalyzed by diacylglycerol acyltransferase 2 (DGAT2). To explore the effect of DGAT2 on the differentiation of bovine muscle satellite cells (BSCs) and its role in the signaling pathway related to lipid metabolism, the adenovirus overexpression and interference vector of the DGAT2 gene was constructed in this study, and the overexpression adenovirus Ad-DGAT2 and interfering adenovirus sh-DGAT2 were used to infect BSCs. Overexpression of DGAT2 resulted in a significant increase in the contents of TAG and ADP, and the mRNA and protein expression levels of PPARγ, C/EBPα, and SREBF1 (p < 0.05). Interfering with the expression of DGAT2 reduced the intracellular TAG content and lipid droplet accumulation. Furthermore, the mRNA and protein expression levels of PPARγ, C/EBPα, and SREBF1 (p < 0.05) were significantly downregulated. Transcriptome sequencing showed that a total of 598 differentially expressed genes (DEGs) were screened in BSCs infected with Ad-DGAT2, and these DEGs included 292 upregulated genes and 306 downregulated genes. A total of 49 DEGs were screened in BSCs infected with sh-DGAT2, and these DEGs included 25 upregulated and 24 downregulated genes. KEGG enrichment analysis showed that the DEGs, after overexpression of DGAT2, were mainly enriched in the PPAR signaling pathway, and the fat digestion and absorption, glycerophospholipid metabolism, fatty acid biosynthesis, and AMPK signaling pathways. The DEGs obtained after interfering with DGAT2 were mainly enriched in the metabolic pathways, such as the PPAR signaling pathway and PI3K/AKT signaling pathway. In summary, our study demonstrated that the lipid droplet formation, TAG accumulation, and adipogenic gene expression in BSCs overexpressing DGAT2 were higher than those in the control cells. These results highlight the important role of DGAT2 in regulating BSCs during adipogenic transdifferentiation and underscore the complexity of intramuscular adipogenesis.

PPAR gamma2: The main isoform of PPARγ that positively regulates the expression of the chicken Plin1 gene

Perilipin1 (PLIN1) is a major phosphorylated protein that specifically coats the surface of neutral lipid droplets (LDs) in adipocytes and plays a crucial role in regulating the accumulation and hydrolysis of triacylglycerol (TG). Mammalian studies have shown that Plin1 gene transcription is mainly regulated by peroxisome proliferator-activated receptor-gamma (PPARγ), the master regulator of adipogenesis. However, the regulatory mechanism of the chicken Plin1 (cPlin1) gene is poorly understood. The present study aimed to investigate whether Plin1 is regulated by PPARγ in chickens and identify its exact molecular mechanism. Reporter gene and expression assays showed that PPARγ2, but not PPARγ1, activated (P<0.01) the cPlin1 gene promoter. An electrophoretic mobility shift assay and mutational analysis revealed that PPARγ2 bound to a special site in the cPlin1 gene promoter to enhance its expression. In summary, our results show that PPARγ promotes the expression of the cPlin1 gene and that PPARγ2 is the main regulatory isoform.

Homologous Overexpression of Diacylglycerol Acyltransferase in Oleaginous Fungus Mucor circinelloides WJ11 Enhances Lipid Accumulation under Static Solid Cultivation.

Diacylglycerol acyltransferase (DGAT) catalyzes the binding of acyl-CoA to diacylglycerol to form triacylglycerol (TAG). Previous studies strongly indicate that DGAT2, rather than DGAT1, is crucial for TAG accumulation in the oleaginous fungus Mucor circinelloides. To increase the lipid content of M. circinelloides WJ11, McDGAT2 was overexpressed by homologous recombination; compared to the control strain Mc2075, transformants McDGAT2d showed a significant increase in biomass for both spores and mycelia (from 87.7 to 101.2 mg/g in spores and from 75.6 to 93.1 mg/g in mycelia). McDGAT2 overexpression under static solid fermentation gave a greater boost to lipid accumulation in mycelia than in spores. Total fatty acid content in mycelia increased by 68.0% (from 13.6 to 22.8%) and in spores by 26.3% (from 10.6 to 13.4%). However, under submerged fermentation, the lipid content of McDGAT2d was the same as the control, while biomass was slightly reduced. Transcriptomics showed that NADPH was derived mainly from the pentose phosphate pathway, acetyl-CoA was from multiple pathways, and leucine metabolism played an important role in substrate supply for fatty acid biosynthesis. Static solid fermentation may be the more suitable fermentation method for microbial oil production by filamentous fungi due to its lower fermentation costs.

The Catalytic Domain of Neuropathy Target Esterase Influences Lipid Droplet Biogenesis and Lipid Metabolism in Human Neuroblastoma Cells.

As an endoplasmic reticulum (ER)-anchored phospholipase, neuropathy target esterase (NTE) catalyzes the deacylation of lysophosphatidylcholine (LPC) and phosphatidylcholine (PC). The catalytic domain of NTE (NEST) exhibits comparable activity to NTE and binds to lipid droplets (LD). In the current study, the nucleotide monophosphate (cNMP)-binding domains (CBDs) were firstly demonstrated not to be essential for the ER-targeting of NTE, but to be involved in the normal ER distribution and localization to LD. NEST was associated with LD surface and influenced LD formation in human neuroblastoma cells. Overexpression of NEST enhances triacylglycerol (TG) accumulation upon oleic acid loading. Quantitative targeted lipidomic analysis shows that overexpression of NEST does not alter diacylglycerol levels but reduces free fatty acids content. NEST not only lowered levels of LPC and acyl-LPC, but not PC or alkyl-PC, but also widely altered levels of other lipid metabolites. Qualitative PCR indicates that the increase in levels of TG is due to the expression of diacylglycerol acyltransferase 1 gene by NEST overexpression. Thus, NTE may broadly regulate lipid metabolism to play roles in LD biogenesis in cells.

Early biochemical observations point to nutritional strategies to manage non-alcoholic fatty liver disease

Abstract Non-alcoholic fatty liver disease (NAFLD) is the most prevalent liver disease globally. The first stage of NAFLD is steatosis, the accumulation of triacylglycerols within hepatocytes. Inflammation and oxidative stress both contribute to progression to more severe disease. In 2004 Clinical Science published two papers reporting on fatty acids and oxidative stress markers in the livers of patients with NAFLD; both these papers are highly cited. One paper reported an altered pattern of fatty acids within the livers of patients with NAFLD; there was a lower contribution of polyunsaturated fatty acids (PUFAs) including both n - 6 and n - 3 PUFAs and an altered balance between n - 6 and n - 3 PUFAs in favour of the former. Ratios of precursor PUFAs to their long chain more unsaturated derivatives were altered in NAFLD and were interpreted to indicate a reduced activity of the pathway of synthesis of long chain highly unsaturated PUFAs. The authors interpreted their findings to indicate that a low hepatic content of n - 3 PUFAs has a causal role in NAFLD. The second paper reported lower hepatic antioxidant defences and increased markers of oxidative stress in NAFLD, consistent with a role for oxidative stress in the disease. Many studies have now explored the effect of supplemental n - 3 PUFAs or antioxidants, including vitamin E, in patients with NAFLD with some benefits being reported. There remains much interest in n - 3 PUFAs and antioxidants as preventive and therapeutic strategies in NAFLD and therefore it seems likely that citation of the two papers from 2004 will be sustained.

Omega-3 fatty acids and metabolic partitioning of fatty acids within the liver in the context of nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) is now the most prevalent form of liver disease globally, affecting about 25% of the world's adult population. It is more common in those living with obesity, where it may affect as many as 80% of individuals. The aim of this article is to describe recent human studies evaluating the influence of omega-3 fatty acids on de novo lipogenesis (DNL) and hepatic fatty acid partitioning between incorporation into triacylglycerols (TAGs) and β-oxidation, to discuss the relevance of these effects in the context of NAFLD, and to provide an overview of the mechanisms that might be involved. The omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) decrease hepatic DNL and partition fatty acids away from TAG synthesis and toward β-oxidation. EPA and DHA affect multiple hepatic transcription factors resulting in down-regulation of the DNL pathway and upregulation of β-oxidation. The net result is decreased accumulation of hepatic TAG and lowering of circulating TAG concentrations. Human trials demonstrate that EPA and DHA can decrease liver fat in patients with NAFLD. Increased intake of EPA and DHA may reduce the likelihood of hepatic TAG accumulation and could be used to reduce liver fat in patients with NAFLD.

The synergistic effects of gamma-aminobutyric acid and salinity during the enhancement of microalgal lipid production in photobioreactors

In the present work, combined application of gamma-aminobutyric acid (GABA) and salinity was used to stimulate biolipid production in the microalga Ankistrodesmus sp. EHY in a vertical tubular photobioreactor. Under 2.5 g L−1 NaCl combined with 50 μM GABA, the strain showed 1.36- and 1.27-fold increases in lipid content (59.42%) and lipid productivity (235.13 mg L−1 d−1), respectively, compared with the control. Wide-ranging analyses of the energy yield, biodiesel quality, cellular ultrastructure, signalling molecules, and lipogenesis genes were conducted to elucidate the role of GABA plus salinity on algal lipid accumulation. By using GABA and salinity treatments, the triacylglycerol (TAG) content and energy yield were increased, whereas the carbohydrate yield was decreased. The biodiesel quality of the algal biomass-derived lipids met the approved standards. The combinational strategy also increased the levels of endogenous reactive oxidative species (ROS), Ca2+, an autophagy-related protein (ATG8), glutathione (GSH) and proline, which might be associated with the increase in lipid synthesis and salt stress tolerance. Moreover, transcriptomic and metabolomic data indicated that the expression levels of TAG assembly, antioxidative system and autophagy-related genes, and the metabolite levels of the TCA cycle, GABA shunt and several stress hormones were consistent with the enhancements in lipid accumulation and stress tolerance. In the presence of GABA and salinity, exogenous proline (50 μM) and salicylic acid (SA; 12.5 mg L−1) further increased the lipid productivity to 280.48 mg L−1 d−1 and 263.58 mg L−1 d−1, respectively. Overall, the results demonstrate the significance, mechanism and applicability of using exogenous GABA combined with salinity to effectively stimulate bioenergy production by microalgae.

Novel insight into the resilient drivers of bioaccumulation perchlorate on lipid nutrients alterations in goat milk by spatial multi-omics

The migration of perchlorate into dairy products through water or detergent is becoming increasingly serious. Spatiotemporal profiles of lipid nutrients associated with perchlorate response were investigated by spatial multi-omics of goat milk. In response to perchlorate accumulation, lipoprotein lipase activity was inhibited in glycerolipid metabolism, thereby resulting in the excessive accretion of triglycerides. Goat milk was selected as the test matrix and conducted to simulate the biological cumulation of perchlorate and evaluate effects of different dietary perchlorate levels (0.0–2.0 mg/kg) on nutritional quality of goat milk. Perchlorate altered phospholipase A2 expression level, affected glycerophospholipid metabolism thus triggered significant changes in phosphatidylcholine (23.35–31.88 μg/mL). Excess triacylglycerol accumulation (3259–6032 μg/mL) caused by perchlorate was due to the inhibition of glycerolipid metabolism mediated by lipoprotein lipase. The study indicated that dietary perchlorate exposure resulted in the decline of nutritional quality in goat milk, which indirectly posed a serious threat to the health of consumers.

Ferulic Acid Prevents Nonalcoholic Fatty Liver Disease by Promoting Fatty Acid Oxidation and Energy Expenditure in C57BL/6 Mice Fed a High-Fat Diet.

There is a consensus that ferulic acid (FA), the most prominent phenolic acid in whole grains, displays a protective effect in non-alcoholic fatty liver disease (NAFLD), though its underlying mechanism not fully elucidated. This study aimed to investigate the protective effect of FA on high-fat diet (HFD)-induced NAFLD in mice and its potential mechanism. C57BL/6 mice were divided into the control diet (CON) group, the HFD group, and the treatment (HFD+FA) group, fed with an HFD and FA (100 mg/kg/day) by oral gavage for 12 weeks. Hematoxylin and eosin (H&E) staining and Oil Red O staining were used to evaluate liver tissue pathological changes and lipid accumulation respectively. It was demonstrated that FA supplementation prevented HFD-induced NAFLD, which was evidenced by the decreased accumulation of lipid and hepatic steatosis in the HFD+FA group. Specifically, FA supplementation decreased hepatic triacylglycerol (TG) content by 33.5% (p < 0.01). Metabolic cage studies reveal that FA-treated mice have elevated energy expenditure by 11.5% during dark phases. Mechanistically, FA treatment increases the expression of rate-limiting enzymes of fatty acid oxidation and ketone body biosynthesis CPT1A, ACOX1 and HMGCS2, which are the peroxisome proliferator-activated receptors α (PPARα) targets in liver. In conclusion, FA could effectively prevent HFD-induced NAFLD possibly by activating PPARα to increase energy expenditure and decrease the accumulation of triacylglycerol in the liver.

Deciphering the function and evolution of the target of rapamycin signaling pathway in microalgae.

Microalgae constitute a highly diverse group of photosynthetic microorganisms that are widely distributed on Earth. The rich diversity of microalgae arose from endosymbiotic events that took place early in the evolution of eukaryotes and gave rise to multiple lineages including green algae, the ancestors of land plants. In addition to their fundamental role as the primary source of marine and freshwater food chains, microalgae are essential producers of oxygen on the planet and a major biotechnological target for sustainable biofuel production and CO2 mitigation. Microalgae integrate light and nutrient signals to regulate cell growth. Recent studies identified the target of rapamycin (TOR) kinase as a central regulator of cell growth and a nutrient sensor in microalgae. TOR promotes protein synthesis and regulates processes that are induced under nutrient stress such as autophagy and the accumulation of triacylglycerol and starch. A detailed analysis of representative genomes from the entire microalgal lineage revealed that the highly conserved central components of the TOR pathway are likely to have been present in the last eukaryotic common ancestor, and the loss of specific TOR signaling elements at an early stage in the evolution of microalgae. Here we examine the evolutionary conservation of TOR signaling components in diverse microalgae and discuss recent progress of this signaling pathway in these organisms.

Comparative transcriptome analysis on candidate genes involved in lipid biosynthesis of developing kernels for three walnut cultivars in Xinjiang

Walnut (Juglans regia L.) is a good source of lipids and polyunsaturated fatty acids (PUFAs). In order to explore the biosynthesis molecular mechanism of oil accumulation and fatty acid (FA) synthesis in walnut, the samples at different development periods of three walnut cultivars, ‘Zhipi’ (ZP), ‘Xinwu 417’ (W417) and ‘Xinwen 81’ (W81) were collected for transcriptomic analysis. The analysis of oil accumulation and FA profiles showed that the oil content in mature walnut kernel was nearly 70 %, and over 90 % of FAs were PUFAs. We identified 126 candidate genes including 64 genes for FA de novo synthesis, 45 genes for triacylglycerol assembly, and 17 genes for oil bodies involved in lipid biosynthesis by RNA-sequencing. Ten key enzymes including ACCase, LACS6, LACS8, SAD, FAD2, FAD3, LPAAT1, DGAT2, PDAT2, and PLC encoded by 19 genes were highly associated with lipid biosynthesis. Quantitative PCR analysis further validated 9 important genes, and the results were well consistent with our transcriptomic data. Finally, 5 important transcription factors including WRI1, ABI3, FUS3, PKL and VAL1 were identified, and their main regulatory genes might contain ACCase, KASⅡ, LACS, FAD3 and LPAAT which were determined through correlation analysis of expression levels for 27 walnut samples. These findings will provide a comprehensive understanding and valuable information on the genetic engineering and molecular breeding in walnut.

Inadequate Hepatic Biotransformation of Choline to Phospholipids Contributes to Lipid Disorders in Early Lactation of Contemporary Holstein Cows

ObjectivesContemporary Holsteins (CH) producing more milk than unselected Holsteins (UH), but they are also more susceptible to lipid disorders, especially hepatic steatosis in early lactation. The objective of this study is to investigate the metabolic events underlying the susceptibility of genetically selected cows to lipid disorders.MethodsSerum and liver samples from periparturient CH and UH cows (n = 12/genotype) were examined by biochemical, metabolomics, and transcriptomic analyses. Serum samples were collected weekly from −5 to + 10 weeks of lactation, and the liver samples were collected on day −14, +3, +14, and + 42 of lactation. Data were analyzed by two-way ANOVA with genotype and time as two factors.ResultsThe postpartum increases of blood serum non-esterified fatty acids (NEFAs) was greater in CH cow. Serum triacylglycerols (TAGs) concentration remained comparable to those of the UH cows but the postpartum accumulation of hepatic TAG was greater in CH than in UH cows. This imbalanced lipidome in CH cows was further reflected by a greater decrease of hepatic phosphatidylcholines (PCs), which are responsible for packaging TAGs into the very-low-density lipoproteins (VLDLs). Hepatic choline content did not differ between UH and CH cows, but less phosphocholine and glycerophosphocholine were present in the liver of CH cows. Transcriptomic analysis indicated that, in the CH cows, the expression of CPT and CEPT genes in the CDP-choline pathway, the major PC biosynthesis pathway, were decreased, while the expression of BHMT and PEMT genes in the minor PC biosynthesis pathway, were increased in early lactation.ConclusionsInadequate hepatic biotransformation of choline to phospholipids contributes to PC deficiency and hepatic steatosis in the CH cow. Efforts to elevate PC synthesis could enhance hepatic VLDL export, reduce hepatic steatosis, and improve metabolic health of high-producing dairy cows in early lactation.Funding SourcesUSDA grant.

Nicotinamide Riboside Supplementation to Suckling Male Mice Improves Lipid and Energy Metabolism in Skeletal Muscle and Liver in Adulthood.

Nicotinamide riboside, an NAD+ precursor, has been attracting a lot of attention in recent years due to its potential benefits against multiple metabolic complications and age-related disorders related to NAD+ decline in tissues. The metabolic programming activity of NR supplementation in early-life stages is much less known. Here, we studied the long-term programming effects of mild NR supplementation during the suckling period on lipid and oxidative metabolism in skeletal muscle and liver tissues using an animal model. Suckling male mice received a daily oral dose of NR or vehicle (water) from day 2 to 20 of age, were weaned at day 21 onto a chow diet, and at day 90 were distributed to either a high-fat diet (HFD) or a normal-fat diet for 10 weeks. Compared to controls, NR-treated mice were protected against HFD-induced triacylglycerol accumulation in skeletal muscle and displayed lower triacylglycerol levels and steatosis degree in the liver and distinct capacities for fat oxidation and decreased lipogenesis in both tissues, paralleling signs of enhanced sirtuin 1 and AMP-dependent protein kinase signaling. These pre-clinical findings suggest that mild NR supplementation in early postnatal life beneficially impacts lipid and energy metabolism in skeletal muscle and liver in adulthood, serving as a potential preventive strategy against obesity-related disorders characterized by ectopic lipid accumulation.

Functional Characterization of Soybean Diacylglycerol Acyltransferase 3 in Yeast and Soybean.

Diacylglycerol acyltransferases (DGAT) function as the key rate-limiting enzymes in de novo biosynthesis of triacylglycerol (TAG) by transferring an acyl group from acyl-CoA to sn-3 of diacylglycerol (DAG) to form TAG. Here, two members of the type 3 DGAT gene family, GmDGAT3-1 and GmDGAT3-2, were identified from the soybean (Glycine max) genome. Both of them were predicted to encode soluble cytosolic proteins containing the typical thioredoxin-like ferredoxin domain. Quantitative PCR analysis revealed that GmDGAT3-2 expression was much higher than GmDGAT3-1's in various soybean tissues such as leaves, flowers, and seeds. Functional complementation assay using TAG-deficient yeast (Saccharomyces cerevisiae) mutant H1246 demonstrated that GmDGAT3-2 fully restored TAG biosynthesis in the yeast and preferentially incorporated monounsaturated fatty acids (MUFAs), especially oleic acid (C18:1) into TAGs. This substrate specificity was further verified by fatty-acid feeding assays and in vitro enzyme activity characterization. Notably, transgenic tobacco (Nicotiana benthamiana) data showed that heterogeneous expression of GmDGAT3-2 resulted in a significant increase in seed oil and C18:1 levels but little change in contents of protein and starch compared to the EV-transformed tobacco plants. Taken together, GmDGAT3-2 displayed a strong enzymatic activity to catalyze TAG assembly with high substrate specificity for MUFAs, particularly C18:1, playing an important role in the cytosolic pathway of TAG synthesis in soybean. The present findings provide a scientific reference for improving oil yield and FA composition in soybean through gene modification, further expanding our knowledge of TAG biosynthesis and its regulatory mechanism in oilseeds.

Regulated IRE1α-dependent decay (RIDD)-mediated reprograming of lipid metabolism in cancer.

IRE1α is constitutively active in several cancers and can contribute to cancer progression. Activated IRE1α cleaves XBP1 mRNA, a key step in production of the transcription factor XBP1s. In addition, IRE1α cleaves select mRNAs through regulated IRE1α-dependent decay (RIDD). Accumulating evidence implicates IRE1α in the regulation of lipid metabolism. However, the roles of XBP1s and RIDD in this process remain ill-defined. In this study, transcriptome and lipidome profiling of triple negative breast cancer cells subjected to pharmacological inhibition of IRE1α reveals changes in lipid metabolism genes associated with accumulation of triacylglycerols (TAGs). We identify DGAT2 mRNA, encoding the rate-limiting enzyme in TAG biosynthesis, as a RIDD target. Inhibition of IRE1α, leads to DGAT2-dependent accumulation of TAGs in lipid droplets and sensitizes cells to nutritional stress, which is rescued by treatment with the DGAT2 inhibitor PF-06424439. Our results highlight the importance of IRE1α RIDD activity in reprograming cellular lipid metabolism.