-
1.
The role of water coordination in the pH-dependent gating of hAQP10.
Truelsen, SF, Missel, JW, Gotfryd, K, Pedersen, PA, Gourdon, P, Lindorff-Larsen, K, Hélix-Nielsen, C
Biochimica et biophysica acta. Biomembranes. 2022;(1):183809
Abstract
Human aquaporin 10 (hAQP10) is an aquaglyceroporin that assists in maintaining glycerol flux in adipocytes during lipolysis at low pH. Hence, a molecular understanding of the pH-sensitive glycerol conductance may open up for drug development in obesity and metabolically related disorders. Control of hAQP10-mediated glycerol flux has been linked to the cytoplasmic end of the channel, where a unique loop is regulated by the protonation status of histidine 80 (H80). Here, we performed unbiased molecular dynamics simulations of three protonation states of H80 to unravel channel gating. Strikingly, at neutral pH, we identified a water coordination pattern with an inverted orientation of the water molecules in vicinity of the loop. Protonation of H80 results in a more hydrophobic loop conformation, causing loss of water coordination and leaving the pore often dehydrated. Our results indicate that the loss of such water interaction network may be integral for the destabilization of the loop in the closed configuration at low pH. Additionally, a residue unique to hAQP10 (F85) reveals structural importance by flipping into the channel in correlation with loop movements, indicating a loop-stabilizing role in the closed configuration. Taken together, our simulations suggest a unique gating mechanism combining complex interaction networks between water molecules and protein residues at the loop interface. Considering the role of hAQP10 in adipocytes, the detailed molecular insights of pH-regulation presented here will help to understand glycerol pathways in these cells and may assist in drug discovery for better management of human adiposity and obesity.
-
2.
Plasma Metabolomics Profile of "Insulin Sensitive" Male Hypogonadism after Testosterone Replacement Therapy.
Zolla, L, Ceci, M
International journal of molecular sciences. 2022;(3)
Abstract
Male hypogonadism is a disorder characterized by low levels of testosterone, but patients can either show normal insulin (insulin-sensitive (IS)) or over time they can become insulin-resistant (IR). Since the two groups showed different altered metabolisms, testosterone replacement therapy (TRT) could achieve different results. In this paper, we analyzed plasma from 20 IS patients with low testosterone (<8 nmol/L) and HOMAi < 2.5. The samples, pre- and post-treatment with testosterone for 60 days, were analyzed by UHPLC and mass spectrometry. Glycolysis was significantly upregulated, suggesting an improved glucose utilization. Conversely, the pentose phosphate pathway was reduced, while the Krebs cycle was not used. Branched amino acids and carnosine metabolism were positively influenced, while β-oxidation of fatty acids (FFA) was not activated. Cholesterol, HDL, and lipid metabolism did not show any improvements at 60 days but did so later in the experimental period. Finally, both malate and glycerol shuttle were reduced. As a result, both NADH and ATP were significantly lower. Interestingly, a significant production of lactate was observed, which induced the activation of the Cori cycle between the liver and muscles, which became the main source of energy for these patients without involving alanine. Thus, the treatment must be integrated with chemicals which are not restored in order to reactivate energy production.
-
3.
Investigation on the Antibacterial Activity of Electronic Cigarette Liquids (ECLs): A Proof of Concept Study.
Fuochi, V, Caruso, M, Emma, R, Stivala, A, Polosa, R, Distefano, A, Furneri, PM
Current pharmaceutical biotechnology. 2021;(7):983-994
Abstract
BACKGROUND The key ingredients of e-cigarettes liquid are commonly propane-1,2-diol (also called propylene glycol) and propane-1,2,3-triol (vegetal glycerol) and their antimicrobial effects are already established. The nicotine and flavors which are often present in e-liquids can interfere with the growth of some microorganisms. OBJECTIVE The effect of combining these elements in e-liquids is unknown. The aim of the study was to investigate the possible effects of these liquids on bacterial growth in the presence or absence of nicotine and flavors. METHODS Susceptibilities of pathogenic strains (Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli, Enterococcus faecalis and Sarcina lutea) were studied by means of a multidisciplinary approach. Cell viability and antioxidant assays were also evaluated. RESULTS All e-liquids investigated showed antibacterial activity against at least one pathogenic strain. Higher activity was correlated to the presence of flavors and nicotine. DISCUSSION In most cases, the value of minimal bactericidal concentration is equal to the value of minimal inhibitory concentration showing that these substances have a bactericidal effect. This effect was observed in concentrations up to 6.25% v/v. Antioxidant activity was also correlated to the presence of flavors. Over time, the viability assay in human epithelial lung A549 cells showed a dose-dependent inhibition of cell growth. CONCLUSION Our results have shown that flavors considerably enhance the antibacterial activity of propane-1,2-diol and propane-1,2,3-triol. This study provides important evidence that should be taken into consideration in further investigative approaches, to clarify the different sensitivity of the various bacterial species to e-liquids, including the respiratory microbiota, to highlight the possible role of flavors and nicotine.
-
4.
Computing the Structural Dynamics of RVFV L Protein Domain in Aqueous Glycerol Solutions.
Gogovi, GK, Silayi, S, Shehu, A
Biomolecules. 2021;(10)
Abstract
Many biological and biotechnological processes are controlled by protein-protein and protein-solvent interactions. In order to understand, predict, and optimize such processes, it is important to understand how solvents affect protein structure during protein-solvent interactions. In this study, all-atom molecular dynamics are used to investigate the structural dynamics and energetic properties of a C-terminal domain of the Rift Valley Fever Virus L protein solvated in glycerol and aqueous glycerol solutions in different concentrations by molecular weight. The Generalized Amber Force Field is modified by including restrained electrostatic potential atomic charges for the glycerol molecules. The peptide is considered in detail by monitoring properties like the root-mean-squared deviation, root-mean-squared fluctuation, radius of gyration, hydrodynamic radius, end-to-end distance, solvent-accessible surface area, intra-potential energy, and solvent-peptide interaction energies for hundreds of nanoseconds. Secondary structure analysis is also performed to examine the extent of conformational drift for the individual helices and sheets. We predict that the peptide helices and sheets are maintained only when the modeling strategy considers the solvent with lower glycerol concentration. We also find that the solvent-peptide becomes more cohesive with decreasing glycerol concentrations. The density and radial distribution function of glycerol solvent calculated when modeled with the modified atomic charges show a very good agreement with experimental results and other simulations at 298.15K.
-
5.
Culture conditions affect Lactobacillus reuteri DSM 17938 ability to perform glycerol bioconversion into 3-hydroxypropionic acid.
Nguyen, TL, Saulou-Bérion, C, Delettre, J, Béal, C
Journal of bioscience and bioengineering. 2021;(5):501-508
Abstract
The platform molecule 3-hydroxypropionic acid (3-HP) can be produced using Lactobacillus reuteri through a two-step bioprocess that involves a growth phase followed by a bioconversion phase. The bioproduction is performed by resting cells that convert glycerol into 3-HP and 1,3-propanediol in fed-batch mode. This work aimed at studying the effect of the growth conditions of L. reuteri DSM 17938 during the first step, on the glycerol bioconversion into 3-HP during the second step. A Plackett and Burman design was carried out to test, in controlled bioreactors, the effect of 11 growth conditions simultaneously, at fixed bioconversion conditions. The supplementation of the growth medium with vitamin B12 and cysteine displayed a negative effect on the 3-HP bioproduction. The addition of glucose, phytone peptone, Tween 80, 1,2-propanediol and betaine in the growth medium, together with a low temperature and an optimal pH of 6.0 during the growth phase increased the bioconversion duration from 56 h to 89 h at a glycerol feeding rate of 0.5 g·h-1. A validating experiment displayed that the 3-HP titer, 3-HP production yield and 3-HP specific production rate were significantly improved by 25 %, 150 % and 61 %, respectively.
-
6.
Continuous production of monoacylglycerol via glycerolysis of babassu oil by immobilized Burkholderia cepacia lipase in a packed bed reactor.
Vilas Bôas, RN, Lima, R, Silva, MVC, Freitas, L, Aguiar, LG, de Castro, HF
Bioprocess and biosystems engineering. 2021;(10):2205-2215
Abstract
This study investigated the glycerolysis of babassu oil by Burkholderia cepacia lipase immobilized on SiO2-PVA particles in a continuous packed bed reactor. Experiments were conducted in a solvent-free system at 273.15 K either in an inert atmosphere or in the presence of cocoa butter to prevent lipid oxidation. The reactor (15 × 55 mm) was run at a fixed space time of 9.8 h using different molar ratios of babassu oil to glycerol (1:3, 1:6, 1:9, 1:12, and 1:15) to assess the effects of reactant molar ratio on monoacylglycerol productivity and selectivity. Nitrogen atmosphere and cocoa butter were equally effective in inhibiting lipid oxidation, indicating that addition of cocoa butter to glycerolysis reactions may be an interesting cost-reduction strategy. An oil/glycerol molar ratio of 1:9 resulted in the highest productivity (52.3 ± 2.9 mg g-1 h-1) and selectivity (31.5 ± 1.8%). Residence time distribution data were fitted to an axial dispersion model for closed-vessel boundary conditions, giving a mass transfer coefficient (kc) of 3.4229 × 10-6 m s-1. A kinetic model based on elementary steps of the studied reaction was written in Scilab and compared with experimental data, providing standard deviations in the range of 5.5-7.5%.
-
7.
Bacterial cellulose production from biodiesel-derived crude glycerol, magnetic functionalization, and its application as carrier for lipase immobilization.
Dikshit, PK, Kim, BS
International journal of biological macromolecules. 2020;:902-911
Abstract
The present study aims towards the kinetic analysis of bacterial cellulose (BC) production by Gluconobacter xylinus from biodiesel-derived crude glycerol and its application as support for immobilization of lipase. Enhancement in strength of BC membrane and its magnetic functionalization were accomplished by the impregnation of iron oxide nanoparticles into the BC matrix. Fitting of experimental results to various substrate inhibition models revealed a reduction of substrate affinity (KS) and reaction rate (Vmax), and increase in substrate inhibition concentration of G. xylinus cells in presence of crude glycerol, in comparison to the pure form of glycerol. Improvement in mechanical properties of pristine BC and magnetic strength of functionalized BC membrane were confirmed by stress-strain curve and vibrating sample magnetometry analysis, respectively. This magnetic BC membrane provided suitable support for the immobilization of Candida rugosa lipase. The immobilized enzymes exhibited better activity at various temperatures, broader pH-flexibility, thermostability (retention of 48% of its activity after 180 min at 50 °C), and reusability (59% of its activity sustained after five consecutive runs). In comparison to free lipase, the immobilized lipase exhibited improved stability and activity, which could be applicable for industrial scale.
-
8.
Lifestyle-Intervention-Induced Reduction of Abdominal Fat Is Reflected by a Decreased Circulating Glycerol Level and an Increased HDL Diameter.
Beekman, M, Schutte, BAM, Akker, EBVD, Noordam, R, Dibbets-Schneider, P, de Geus-Oei, LF, Deelen, J, Rest, OV, Heemst, DV, Feskens, EJM, et al
Molecular nutrition & food research. 2020;(10):e1900818
-
-
Free full text
-
Abstract
SCOPE Abdominal obesity is one of the main modifiable risk factors of age-related cardiometabolic disease. Cardiometabolic disease risk and its associated high abdominal fat mass, cholesterol, and glucose concentrations can be reduced by a healthier lifestyle. Hence, the aim is to understand the relation between lifestyle-induced changes in body composition, and specifically abdominal fat, and accompanying changes in circulating metabolic biomarkers. METHODS AND RESULTS Data from the Growing Old Together (GOTO) study was used, which is a single arm lifestyle intervention in which 164 older adults (mean age 63 years, BMI 23-35 kg/m2 ) changed their lifestyle during 13 weeks by 12.5% caloric restriction plus 12.5% increase in energy expenditure. It is shown here that levels of circulating metabolic biomarkers, even after adjustment for body mass index, specifically associate with abdominal fat mass. The applied lifestyle intervention mainly reduces abdominal fat mass (-2.6%, SD = 3.0) and this reduction, when adjusted for general weight loss, is highly associated with decreased circulating glycerol concentrations and increased HDL diameter. CONCLUSION The lifestyle-induced reduction of abdominal fat mass is particularly associated, independent of body mass index or general weight loss, with decreased circulating glycerol concentrations and increased HDL diameter.
-
9.
Short-Term Effects of Growth Hormone on Lipolysis, Glucose and Amino Acid Metabolism Assessed in Serum and Microdialysate of Healthy Young Men.
Krebs, A, Baum, A, Doerfer, J, Gempel, K, Wurm, M, Brichta, C, Sass, JO, Winkler, K, Schwab, KO
Experimental and clinical endocrinology & diabetes : official journal, German Society of Endocrinology [and] German Diabetes Association. 2020;(12):819-826
Abstract
OBJECTIVE We investigated direct effects of a therapeutic growth hormone dose on lipolysis, glucose and amino acid metabolism. METHODS This crossover microdialysis trial involved six healthy male volunteers receiving single subcutaneous injections of both growth hormone (0.035 mg/kg) and placebo (0.9% sodium chloride). The investigation comprised three test days with standard diet. The first day served for adaptation, the second and third one for determining study data during 9 night hours with or without growth hormone. Abdominal subcutaneous microdialysate and blood were continuously collected and forwarded to a separate room next door where hourly taken samples were centrifuged and frozen until analysed. RESULTS Growth hormone achieved the peak serum level after 3 h followed by a plateau-like course for the next 6 h. Glycerol in microdialysate started to rise 2 h following growth hormone injection achieving significance compared to placebo after 9 h (P<0.05). Serum glycerol increased 4 h after growth hormone administration achieving significance after 6 h (P<0.05). Glucose and amino acid concentrations showed neither in microdialysate nor in serum significant differences between growth hormone and placebo. Serum values of insulin and C-peptide revealed no significant difference between growth hormone and placebo. SUMMARY AND CONCLUSION As the result of a high single subcutaneous dose of GH, persistent lipolysis can be shown in continuously collected microdialysate and blood, but no indication for gluconeogenesis or protein anabolism.
-
10.
Effects of Empagliflozin Treatment on Glycerol-Derived Hepatic Gluconeogenesis in Adults with Obesity: A Randomized Clinical Trial.
Neeland, IJ, de Albuquerque Rocha, N, Hughes, C, Ayers, CR, Malloy, CR, Jin, ES
Obesity (Silver Spring, Md.). 2020;(7):1254-1262
-
-
Free full text
-
Abstract
OBJECTIVE The aim of this study was to determine the effects of empagliflozin on glycerol-derived hepatic gluconeogenesis in adults with obesity without type 2 diabetes mellitus (T2DM) using oral carbon 13 (13 C)-labeled glycerol. METHODS A randomized, double-blind, placebo-controlled trial was performed in participants with magnetic resonance imaging assessment of body fat and measurement of glycerol-derived 13 C enrichment in plasma glucose by nuclear magnetic resonance spectroscopy following ingestion of [U-13 C3 ]glycerol. Participants were randomized to oral empagliflozin 10 mg once daily or placebo for 3 months. Glycerol-derived 13 C enrichment studies were repeated, and treatment differences in the mean percentage of 13 C glycerol enrichment in glucose were compared using mixed linear models. RESULTS Thirty-five participants completed the study. Empagliflozin increased glycerol-derived 13 C enrichment between baseline and follow-up by 6.5% (P = 0.005), consistent with less glycerol from visceral adipose tissue (VAT). No difference was found with placebo. Glycerol-derived 13 C enrichment was lower in participants with high VAT compared with low VAT by 12.6% (P = 0.04), but there was no heterogeneity of the treatment effect by baseline VAT. Glycerol-derived 13 C enrichment was inversely correlated with VAT but was not correlated with weight loss. CONCLUSIONS VAT is associated with endogenous glycerol-derived hepatic gluconeogenesis, and empagliflozin reduces endogenous glycerol gluconeogenesis in adults with obesity without T2DM. These findings suggest a mechanism by which sodium-glucose cotransporter 2 inhibitors may prevent T2DM in obesity.