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Autophagy Sep 2021Impaired macroautophagy/autophagy has been implicated in experimental and human nonalcoholic steatohepatitis (NASH). However, the mechanism underlying autophagy...
Impaired macroautophagy/autophagy has been implicated in experimental and human nonalcoholic steatohepatitis (NASH). However, the mechanism underlying autophagy dysregulation in NASH is largely unknown. Here, we investigated the role and mechanism of TXNIP/VDUP1 (thioredoxin interacting protein), a key mediator of cellular stress responses, in the pathogenesis of NASH. Hepatic TXNIP expression was upregulated in nonalcoholic fatty liver disease (NAFLD) patients and in methionine choline-deficient (MCD) diet-fed mice, as well as in palmitic acid (PA)-treated hepatocytes. Upregulation of hepatic TXNIP was positively correlated with impaired autophagy, as evidenced by a decreased number of MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3 beta) puncta and increased SQSTM1/p62 (sequestosome 1) expression. Deletion of the gene enhanced hepatic steatosis, inflammation, and fibrosis, accompanied by impaired autophagy and fatty acid oxidation (FAO) in MCD diet-fed mice. Mechanistically, TXNIP directly interacted with and positively regulated p-PRKAA, leading to inactivation of MTOR (mechanistic target of rapamycin kinase) complex 1 (MTORC1) and nuclear translocation of TFEB (transcription factor EB), which in turn promoted autophagy. Inhibition of MTORC1 by rapamycin induced autophagy and increased the expression levels of FAO-related genes and concomitantly attenuated lipid accumulation in PA-treated -knockout (KO) hepatocytes, which was further abolished by silencing of . Rapamycin treatment also attenuated MCD diet-induced steatosis, inflammation, and fibrosis with increased TFEB nuclear translocation and restored FAO in -KO mice. Our findings suggest that elevated TXNIP ameliorates steatohepatitis by interacting with PRKAA and thereby inducing autophagy and FAO. Targeting TXNIP may be a potential therapeutic approach for NASH. ACOX1: acyl-Coenzyme A oxidase 1, palmitoyl; ACSL1: acyl-CoA synthetase long-chain family member 1; ACTA2/α-SMA: actin, alpha 2, smooth muscle, aorta; ACTB: actin beta; ADGRE1/F4/80: adhesion G protein-coupled receptor E1; AMPK: AMP-activated protein kinase; ATG: autophagy-related; BafA1: bafilomycin A1; COL1A1/Col1α1: collagen, type I, alpha 1; CPT1A: carnitine palmitoyltransferase 1a, liver; CQ: chloroquine; DGAT1: diacylglycerol O-acyltransferase 1; DGAT2: diacylglycerol O-acyltransferase 2; ECI2/Peci: enoyl-Coenzyme A isomerase 2; EHHADH: enoyl-Coenzyme A, hydratase/3-hydroxyacyl Coenzyme A dehydrogenase; FAO: fatty acid oxidation; FASN: fatty acid synthase; FFA: free fatty acids; GFP: green fluorescent protein; GK/GYK: glycerol kinase; GOT1/AST: glutamic-oxaloacetic transaminase 1, soluble; GPAM: glycerol-3-phosphate acyltransferase, mitochondrial; GPT/ALT: glutamic pyruvic transaminase, soluble; H&E: hematoxylin and eosin; IL1B/IL-1β: interleukin 1 beta; IL6: interleukin 6; IOD: integral optical density; KO: knockout; Leu: leupeptin; LPIN1: lipin 1; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MCD: methionine choline-deficient; MMP9: matrix metallopeptidase 9; mRNA: messenger RNA; MTORC1: mechanistic target of rapamycin kinase complex 1; NAFLD: nonalcoholic fatty liver diseases; NASH: nonalcoholic steatohepatitis; PA: palmitic acid; PPARA/PPARα: peroxisome proliferator activated receptor alpha; PPARG/PPARγ: peroxisome proliferator activated receptor gamma; qRT-PCR: quantitative real-time PCR; RPS6KB1/p70S6K1: ribosomal protein S6 kinase, polypeptide 1; RPTOR: regulatory associated protein of MTOR complex 1; SCD1: stearoyl-Coenzyme A desaturase 1; SEM: standard error of the mean; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB; TG: triglyceride; TGFB/TGF-β: transforming growth factor, beta; TIMP1: tissue inhibitor of metalloproteinase 1; TNF/TNF-α: tumor necrosis factor; TXNIP/VDUP1: thioredoxin interacting protein; WT: wild-type.
Topics: Animals; Autophagy; Carrier Proteins; Fatty Acids; Humans; Lipid Metabolism; Mice; Non-alcoholic Fatty Liver Disease; Thioredoxins
PubMed: 33190588
DOI: 10.1080/15548627.2020.1834711 -
Water Research Dec 2022Glycerol is abundantly present in wastewater from industries such as biodiesel production facilities. Glycerol is also a potential carbon source for microbes that are...
Glycerol is abundantly present in wastewater from industries such as biodiesel production facilities. Glycerol is also a potential carbon source for microbes that are involved in wastewater nutrient removal processes. The conversion of glycerol in biological phosphorus removal of aerobic granular sludge processes has not been explored to date. The current study describes glycerol utilization by aerobic granular sludge and enhanced biological phosphorus removal (EBPR). Robust granules with good phosphorus removal capabilities were formed in an aerobic granular sludge sequencing batch reactor fed with glycerol. The interaction between the fermentative conversion of glycerol and product uptake by polyphosphate accumulating organisms (PAO) was studied using stoichiometric and microbial community analysis. Metagenomic, metaproteomic and microscopic analysis identified a community dominated by Actinobacteria (Tessaracoccus and Micropruina) and a typical PAO known as Ca. Accumulibacter. Glycerol uptake facilitator (glpF) and glycerol kinase (glpK), two proteins involved in the transport of glycerol into the cellular metabolism, were only observed in the genome of the Actinobacteria. The anaerobic conversion appeared to be a combination of a substrate fermentation and product uptake-type reaction. Initially, glycerol fermentation led mainly to the production of 1,3-propanediol (1,3-PDO) which was not taken up under anaerobic conditions. Despite the aerobic conversion of 1,3-PDO stable granulation was observed. Over time, 1,3-PDO production decreased and complete anaerobic COD uptake was observed. The results demonstrate that glycerol-containing wastewater can effectively be treated by the aerobic granular sludge process and that fermentative and polyphosphate accumulating organisms can form a food chain in glycerol-based EBPR processes.
Topics: Sewage; Glycerol; Wastewater; Phosphorus; Polyphosphates; Bacteria
PubMed: 36395566
DOI: 10.1016/j.watres.2022.119340 -
International Journal of Molecular... Jan 2018The aquaglyceroporin AQP7 is a pore-forming transmembrane protein that facilitates the transport of glycerol across cell membranes. Glycerol is utilized both in... (Review)
Review
The aquaglyceroporin AQP7 is a pore-forming transmembrane protein that facilitates the transport of glycerol across cell membranes. Glycerol is utilized both in carbohydrate and lipid metabolism. It is primarily stored in white adipose tissue as part of the triglyceride molecules. During states with increased lipolysis, such as fasting and diabetes, glycerol is released from adipose tissue and metabolized in other tissues. AQP7 is expressed in adipose tissue where it facilitates the efflux of glycerol, and AQP7 deficiency has been linked to increased glycerol kinase activity and triglyceride accumulation in adipose tissue, leading to obesity and secondary development of insulin resistance. However, AQP7 is also expressed in a wide range of other tissues, including kidney, muscle, pancreatic β-cells and liver, where AQP7 also holds the potential to influence whole body energy metabolism. The aim of the review is to summarize the current knowledge on AQP7 in adipose tissue, as well as AQP7 expressed in other tissues where AQP7 might play a significant role in modulating whole body energy metabolism.
Topics: Animals; Aquaglyceroporins; Energy Metabolism; Humans; Models, Biological; Organ Specificity
PubMed: 29300344
DOI: 10.3390/ijms19010154 -
Bioscience Reports Apr 2023Glycerol kinase (GK; EC 2.7.1.30) facilitates the entry of glycerol into pathways of glucose and triglyceride metabolism and may play a potential role in Type 2 diabetes...
BACKGROUND
Glycerol kinase (GK; EC 2.7.1.30) facilitates the entry of glycerol into pathways of glucose and triglyceride metabolism and may play a potential role in Type 2 diabetes mellitus (T2DM). However, the detailed regulatory mechanisms and structure of the human GK are unknown.
METHODS
The human GK gene was cloned into the pET-24a(+) vector and over-expressed in Escherichia coli BL21 (DE3). Since the protein was expressed as inclusion bodies (IBs), various culture parameters and solubilising agents were used but they did not produce bioactive His-GK; however, co-expression of His-GK with molecular chaperones, specifically pKJE7, achieved expression of bioactive His-GK. The overexpressed bioactive His-GK was purified using coloumn chromatography and characterised using enzyme kinetics.
RESULTS
The overexpressed bioactive His-GK was purified apparently to homogeneity (∼295-fold) and characterised. The native His-GK was a dimer with a monomeric molecular weight of ∼55 kDa. Optimal enzyme activity was observed in TEA buffer (50 mM) at 7.5 pH. K+ (40 mM) and Mg2+ (2.0 mM) emerged as prefered metal ions for His-GK activity with specific activity 0.780 U/mg protein. The purified His-GK obeyed standard Michaelis-Menten kinetics with Km value of 5.022 µM (R2=0.927) for its substrate glycerol; whereas, that for ATP and PEP was 0.767 mM (R2=0.928) and 0.223 mM (R2=0.967), respectively. Other optimal parameters for the substrate and co-factors were also determined.
CONCLUSION
The present study demonstrates that co-expression of molecular chaperones assists with the expression of bioactive human GK for its characterisation.
Topics: Humans; Glycerol Kinase; Diabetes Mellitus, Type 2; Glycerol; Molecular Chaperones; Escherichia coli
PubMed: 37021775
DOI: 10.1042/BSR20222258 -
Frontiers in Plant Science 2021Glycerol-induced resistance to various pathogens has been reported in different plants. Glycerol kinase (GK), a vital rate-limiting enzyme that catalyzes glycerol...
Glycerol-induced resistance to various pathogens has been reported in different plants. Glycerol kinase (GK), a vital rate-limiting enzyme that catalyzes glycerol conversion to glycerol-3-phosphate (G3P), participates in responses to both abiotic and biotic stresses. However, its physiological importance in rice defenses against pathogens remains unclear. In this research, quantification analysis revealed that GK levels were significantly induced in rice leaves infected by pv. strain PXO99. A typical GK-encoding gene was cloned in rice. The transcriptional levels of were significantly induced by salicylic acid, jasmonic acid, and PXO99. Ectopic expression of partially rescued the resistance to in the mutant. In the overexpressing transgenic rice lines (-OE), the content of GK and the transcriptional level of were increased and the resistance to bacterial blight and blast was improved, while reduced expression impaired the resistance in -RNAi lines. The wax contents and expression of the wax synthesis regulatory genes were significantly increased in the overexpression lines but decreased in the -RNAi lines. We then confirmed the interaction partner of OsNHO1 using yeast two-hybrid and bimolecular fluorescence complementation assays. The transcription of the interaction partner-encoding genes and in -RNAi lines was downregulated but upregulated in -OE lines. Thus, we concluded that provided disease resistance by affecting the wax content and modulating the transcription levels of genes.
PubMed: 35126424
DOI: 10.3389/fpls.2021.800625 -
The ISME Journal Jul 2023During oral biofilm development, interspecies interactions drive species distribution and biofilm architecture. To understand what molecular mechanisms determine these...
During oral biofilm development, interspecies interactions drive species distribution and biofilm architecture. To understand what molecular mechanisms determine these interactions, we used information gained from recent biogeographical investigations demonstrating an association of corynebacteria with streptococci. We previously reported that Streptococcus sanguinis and Corynebacterium durum have a close relationship through the production of membrane vesicle and fatty acids leading to S. sanguinis chain elongation and overall increased fitness supporting their commensal state. Here we present the molecular mechanisms of this interspecies interaction. Coculture experiments for transcriptomic analysis identified several differentially expressed genes in S. sanguinis. Due to its connection to fatty acid synthesis, we focused on the glycerol-operon. We further explored the differentially expressed type IV pili genes due to their connection to motility and biofilm adhesion. Gene inactivation of the glycerol kinase glpK had a profound impact on the ability of S. sanguinis to metabolize C. durum secreted glycerol and impaired chain elongation important for their interaction. Investigations on the effect of type IV pili revealed a reduction of S. sanguinis twitching motility in the presence of C. durum, which was caused by a decrease in type IV pili abundance on the surface of S. sanguinis as determined by SEM. In conclusion, we identified that the ability to metabolize C. durum produced glycerol is crucial for the interaction of C. durum and S. sanguinis. Reduced twitching motility could lead to a closer interaction of both species, supporting niche development in the oral cavity and potentially shaping symbiotic health-associated biofilm communities.
Topics: Glycerol; Streptococcus; Streptococcus sanguis; Biofilms; Symbiosis; Streptococcus mutans
PubMed: 37169870
DOI: 10.1038/s41396-023-01426-9 -
The Journal of Clinical Investigation Jan 1978A 70-yr-old mildly diabetic white male was discovered to have an elevated level of serum free glycerol in the range of 75 mg/dl and to excrete about 13 g of free...
A 70-yr-old mildly diabetic white male was discovered to have an elevated level of serum free glycerol in the range of 75 mg/dl and to excrete about 13 g of free glycerol in the urine per 24 h. During a 24-h fast the urine glycerol loss increased to 21.5 g per 24 h. Studies carried out in vitro using leukocytes prepared from the patient's blood which were incubated with [14C]glycerol demonstrated an almost complete absence of glycerol oxidation to 14CO2 and of glycerol phosphorylation, in contrast to control studies with leukocytes collected from normal subjects. Homogenates of the patient's leukocytes contained negligible activity of ATP:glycerol phosphotransferase (glycerokinase EC 2.7.1.30) as measured by a direct spectrophotometric method. Marked hyperglycerolemia has thus far been detected in one brother and in one son of the daughter of this patient. This evidence suggests an x-linked recessive inheritance pattern of the trait. There is a high prevalence of diabetes mellitus in this family.
Topics: Aged; Diabetes Mellitus; Glycerol; Glycerol Kinase; Humans; Leukocytes; Male; Pedigree
PubMed: 618910
DOI: 10.1172/JCI108914 -
Nature Metabolism Feb 2024Cellular senescence affects many physiological and pathological processes and is characterized by durable cell cycle arrest, an inflammatory secretory phenotype and...
Cellular senescence affects many physiological and pathological processes and is characterized by durable cell cycle arrest, an inflammatory secretory phenotype and metabolic reprogramming. Here, by using dynamic transcriptome and metabolome profiling in human fibroblasts with different subtypes of senescence, we show that a homoeostatic switch that results in glycerol-3-phosphate (G3P) and phosphoethanolamine (pEtN) accumulation links lipid metabolism to the senescence gene expression programme. Mechanistically, p53-dependent glycerol kinase activation and post-translational inactivation of phosphate cytidylyltransferase 2, ethanolamine regulate this metabolic switch, which promotes triglyceride accumulation in lipid droplets and induces the senescence gene expression programme. Conversely, G3P phosphatase and ethanolamine-phosphate phospho-lyase-based scavenging of G3P and pEtN acts in a senomorphic way by reducing G3P and pEtN accumulation. Collectively, our study ties G3P and pEtN accumulation to controlling lipid droplet biogenesis and phospholipid flux in senescent cells, providing a potential therapeutic avenue for targeting senescence and related pathophysiology.
Topics: Humans; Lipid Metabolism; Glycerol; Ethanolamines; Phosphates; Glycerophosphates
PubMed: 38409325
DOI: 10.1038/s42255-023-00972-y -
Scientific Reports Mar 2022The fall armyworm (FAW), Spodoptera frugiperda, is native to the tropical and subtropical areas of the American continent and is one of the world's most destructive...
The fall armyworm (FAW), Spodoptera frugiperda, is native to the tropical and subtropical areas of the American continent and is one of the world's most destructive insect pests and invaded Africa and spread to most of Asia in two years. Glycerol is generally used as a cryoprotectant for overwintering insects in cold areas. In many studies, the increase in glycerol as a main rapid cold hardening (RCH) factor and enhancing the supercooling point was revealed at low temperatures. There are two genes, including glycerol-3-phosphate dehydrogenase (GPDH) and glycerol kinase (GK), that were identified as being associated with the glycerol synthesis pathway. In this study, one GPDH and two GK sequences (GK1 and GK2) were extracted from FAW transcriptome analysis. RNA interference (RNAi) specific to GPDH or GK1 and GK2 exhibited a significant down-regulation at the mRNA level as well as a reduction in survival rate when the RNAi-treated of FAW larvae post a RCH treatment. Following a cold period, an increase in glycerol accumulation was detected utilizing high-pressure liquid chromatography and colorimetric analysis of glycerol quantity in RCH treated hemolymph of FAW larvae. This research suggests that GPDH and GK isozymes are linked to the production of a high quantity of glycerol as an RCH factor, and glycerol as main cryoprotectant plays an important role in survival throughout the cold period in this quarantine pest studied.
Topics: Animals; Cryoprotective Agents; Glycerol; Glycerol Kinase; Glycerolphosphate Dehydrogenase; Larva; Moths; Spodoptera
PubMed: 35260770
DOI: 10.1038/s41598-022-08174-4