Constitutive activation mechanism of a class C GPCR

Class C G-protein-coupled receptors (GPCRs) are activated through binding of agonists to the large extracellular domain (ECD) followed by rearrangement of the transmembrane domains (TMDs). GPR156, a class C orphan GPCR, is unique because it lacks an ECD and exhibits constitutive activity. Impaired GPR156-Gi signaling contributes to loss of hearing. Here we present the cryo-electron microscopy structures of human GPR156 in the Go-free and Go-coupled states. We found that an endogenous phospholipid molecule is located within each TMD of the GPR156 dimer. Asymmetric binding of Gα to the phospholipid-bound GPR156 dimer restructures the first and second intracellular loops and the carboxy-terminal part of the elongated transmembrane 7 (TM7) without altering dimer conformation. Our findings reveal that GPR156 is a transducer for phospholipid signaling. Constant binding of abundant phospholipid molecules and the G-protein-induced reshaping of the cytoplasmic face provide a basis for the constitutive activation of GPR156.

Vutiglabridin exerts anti-ageing effects in aged mice through alleviating age-related metabolic dysfunctions

BACKGROUND

Ageing alters the ECM, leading to mitochondrial dysfunction and oxidative stress, which triggers an inflammatory response that exacerbates with age. Age-related changes impact satellite cells, affecting muscle regeneration, and the balance of proteins. Furthermore, ageing causes a decline in NAD+ levels, and alterations in fat metabolism that impact our health. These various metabolic issues become intricately intertwined with ageing, leading to a variety of individual-level diseases and profoundly affecting individuals' healthspan. Therefore, we hypothesize that vutiglabridin capable of alleviating these metabolic abnormalities will be able to ameliorate many of the problems associated with ageing.

METHOD

The efficacy of vutiglabridin, which alleviates metabolic issues by enhancing mitochondrial function, was assessed in aged mice treated with vutiglabridin and compared to untreated elderly mice. On young mice, vutiglabridin-treated aged mice, and non-treated aged mice, the Senescence-associated beta-galactosidase staining and q-PCR for ageing marker genes were carried out. Bulk RNA-seq was carried out on GA muscle, eWAT, and liver from each group of mice to compare differences in gene expression in various gene pathways. Blood from each group of mice was used to compare and analyze the ageing lipid profile.

RESULTS

SA-β-gal staining of eWAT, liver, kidney, and spleen of ageing mice showed that vutiglabridin had anti-ageing effects compared to the control group, and q-PCR of ageing marker genes including Cdkn1a and Cdkn2a in each tissue showed that vutiglabridin reduced the ageing process. In aged mice treated with vutiglabridin, GA muscle showed improved homeostasis compared to controls, eWAT showed restored insulin sensitivity and prevented FALC-induced inflammation, and liver showed reduced inflammation levels due to prevented TLO formation, improved mitochondrial complex I assembly, resulting in reduced ROS formation. Furthermore, blood lipid analysis revealed that ageing-related lipid profile was relieved in ageing mice treated with vutiglabridin versus the control group.

CONCLUSION

Vutiglabridin slows metabolic ageing mechanisms such as decreased insulin sensitivity, increased inflammation, and altered NAD+ metabolism in adipose tissue in mice experiments, while also retaining muscle homeostasis, which is deteriorated with age. It also improves the lipid profile in the blood and restores mitochondrial function in the liver to reduce ROS generation.

Evaluation of Meibum Lipid Composition According to Tear Interferometric Patterns: RRH: Meibum Composition According to Interferometric Patterns

PURPOSE

To determine the relationship between tear film interferometric patterns and properties of lipid, including rheological properties.

DESIGN

Prospective, cross-sectional laboratory investigation.

METHOD

This study included 105 subjects (94 dry eye patients and 11 normal participants). The subjects were divided into 3 categories (group 1, normal; group 2, thin; and group 3, irregular) according to interferometric patterns. According to tear interferometric patterns, ultra-performance liquid chromatography (LC) quadrupole-linear ion trap/mass spectrometry (MS)-based analysis was used to investigate lipid profiling of meibum. Rheological properties were examined by using a Langmuir-Blodgett trough with saline solution.

RESULTS

Normal subjects showed Pearl-like patterns, and dry eye patients showed either irregular or thin patterns. Group 2 tended to be the evaporative type, and group 3 tended to be the aqueous-deficient type. Lipid profiling using LC-MS identified 280 lipid species of 25 lipid classes. In the meibum of the patient groups, the content of cholesteryl esters and nonpolar lipids was lower than that in the normal group. However, the content of polar lipids such as sphingolipids and phospholipids in the patient groups was higher than that in the normal group. Rheological properties showed that the lift-off areas were comparable among the 3 groups and the surface tension was the highest in group 1, followed by group 3 and group 2.

CONCLUSIONS

The findings of this study suggest that tear interferometric patterns are associated with lipid profiling of meibum and its rheological properties. These results may contribute toward the development of new treatment modalities.

Lipidomic changes in mouse oocytes vitrified in PEG 8000-supplemented vitrification solutions

Cryopreserved oocytes are inevitably exposed to cold stress, which negatively affects the cellular aspects of the oocytes. Lipidomic analysis of the oocytes reveals quantitative changes in lipid classes under conditions of cold stress, leading to potential freezing-vulnerability. We had previously shown that specific phospholipids are significantly downregulated in vitrified-warmed mouse oocytes compared to those in fresh oocytes. In this study, we examined whether supplementation of polyethylene glycol 8000 (PEG 8000) during vitrification influences the lipidome of the oocytes. We used liquid chromatography with tandem mass spectrometry (LC-MS/MS) to study the alteration in the lipidome in three groups of mouse oocytes: fresh, vitrified-warmed, and vitrified with PEG 8000-warmed during vitrification. In these groups, we targeted to analyze 21 lipid classes. We profiled 132 lipid species in the oocytes and statistical analyses revealed lipid classes that were up- or downregulated in these groups. Overall, our data revealed that several classes of lipids were affected during vitrification, and that oocytes vitrified with PEG 8000 to some extent alleviated the levels of changes in phospholipid and sphingolipid contents during vitrification. These results suggest that phospholipids and sphingolipids are influenced by PEG 8000 during vitrification and that PEG 8000 can be considered as a potential candidate for preserving membrane integrity during oocyte cryopreservation.

The impact of phenanthrene on membrane phospholipids and its biodegradation by Sphingopyxis soli

The direct interactions of bacterial membranes and polycyclic aromatic hydrocarbons (PAHs) strongly influence the biological processes, such as metabolic activity and uptake of substrates due to changes in membrane lipids. However, the elucidation of adaptation mechanisms as well as membrane phospholipid alterations in the presence of phenanthrene (PHE) from α-proteobacteria has not been fully explored. This study was conducted to define the degradation efficiency of PHE by Sphingopyxis soli strain KIT-001 in a newly isolated from Jeonju river sediments and to characterize lipid profiles in the presence of PHE in comparison to cells grown on glucose using quantitative lipidomic analysis. This strain was able to respectively utilize 1-hydroxy-2-naphthoic acid and salicylic acid as sole carbon source and approximately 90% of PHE (50 mg/L) was rapidly degraded via naphthalene route within 1 day incubation. In the cells grown on PHE, strain KIT-001 appeared to dynamically change profiles of metabolite and lipid in comparison to cells grown on glucose. The levels of primary metabolites, phosphatidylethanolamines (PE), and phosphatidic acids (PA) were significantly decreased, whereas the levels of phosphatidylcholines (PC) and phosphatidylglycerols (PG) were significantly increased. The adaptation mechanism of Sphingopyxis sp. regarded mainly the accumulation of bilayer forming lipids and anionic lipids to adapt more quickly under restricted nutrition and toxicity condition. Hence, these findings are conceivable that strain KIT-001 has a good adaptive ability and biodegradation for PHE through the alteration of phospholipids, and will be helpful for applications for effective bioremediation of PAHs-contaminated sites.

Serum lipidomic analysis for the discovery of biomarkers for major depressive disorder in drug-free patients

Lipidomic analysis can be used to efficiently identify hundreds of lipid molecular species in biological materials and has been recently established as an important tool for biomarker discovery in various neuropsychiatric disorders including major depressive disorder (MDD). In this study, quantitative targeted serum lipidomic profiling was performed on female subjects using liquid chromatography-mass spectrometry. Global lipid profiling of pooled serum samples from 10 patients currently with MDD (cMDD), 10 patients with remitted MDD (rMDD), and 10 healthy controls revealed 37 differentially regulated lipids (DRLs). DRLs were further verified using multiple-reaction monitoring (MRM) in each of the 25 samples from the three groups of independent cohorts. Using multivariate analysis and MRM data we identified serum biomarker panels of discriminatory lipids that differentiated between pairs of groups: lysophosphatidic acid (LPA)(16:1), triglycerides (TG)(44:0), and TG(54:8) distinguished cMDD from controls with 76% accuracy; lysophosphatidylcholines(16:1), TG(44:0), TG(46:0), and TG(50:1) distinguished between cMDD and rMDD at 65% accuracy; and LPA(16:1), TG(52:6), TG(54:8), and TG(58:10) distinguished between rMDD and controls with 60% accuracy. Our lipidomic analysis identified peripheral lipid signatures of MDD, which thereby provides providing important biomarker candidates for MDD.

Comparative lipidomic profiling of the human commensal bacterium Propionibacterium acnes and its extracellular vesicles

Propionibacterium acnes is a lipophilic commensal bacterium mainly found on the skin and in the gastrointestinal tract. Pathophysiological effects of P. acnes have recently been reported not only in acne progression but in various diseases. As an emerging mode of bacterial communication, extracellular vesicles (EVs) have been demonstrated to conduct critical pathophysiological functions. To provide information on P. acnes lipid composition for the first time, we conducted a comparative lipidomic analysis of P. acnes and P. acnes EVs and identified 214 lipids with high confidence using triplicated liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) analyses. P. acnes EVs contained substantially more PCs, DGs, PAs, PEs, LPAs, LPCs, and MGs than P. acnes, and contained fewer PSs, SO1Ps, SA1Ps, LPGs, LPIs, and LPSs. Distinctively, P. acnes EVs possessed a markedly reduced amount of TG. These findings will provide useful clues for understanding the biological and pathophysiological mechanisms of P. acnes and for clinical applications such as vaccine development, diagnostics and therapeutics.

Identification of absorbed constituents and evaluation of the pharmacokinetics of main compounds after oral administration of yindanxinnaotong by UPLC-Q-TOF-MS and UPLC-QqQ-MS

Yindanxinnaotong capsule (YDXNT), a traditional Chinese formula, has been used to treat cardio-cerebrovascular diseases for several decades. Previous research has focused on evaluating the pharmacological properties and main compounds of YDXNT in vitro and in vivo. However, the multiple bioactive compounds in vivo remain poorly understood. In the present research, an integrative strategy using UPLC-Q-TOF-MS combined with UPLC-QqQ-MS was employed to detect the absorbed constituents and investigate the pharmacokinetics of main compounds in the plasma after oral administration of YDXNT. UPLC-Q-TOF-MS was developed to detect the absorbed constituents and their metabolites in the plasma after oral administration in rats. A total of 52 constituents, including 44 prototype compounds and 8 metabolites, were identified or tentatively characterized. Then, nine main compounds (quercetin, isorhamnetin, kaempferol, ginkgolide A, ginkgolide B, ginkgolide C, bilobalide, tanshinone IIA, and salvianolic acid B) were chosen to further investigate the pharmacokinetic behavior of YDXNT using UPLC-QqQ-MS. The concentration of nine main constituents were in the range of 27.85–76.54 ng mL⁻¹. This research provides a systematic approach for rapid qualitative analysis of absorbed constituents and for evaluating the pharmacokinetics of the main ingredients of YDXNT following its oral administration. More importantly, this work provides key information on the identification of bioactive compounds and the clarification of their action mechanisms, as well as on the pharmacological actions of YDXNT.

Yindanxinnaotong capsule (YDXNT), a traditional Chinese formula, has been used to treat cardio-cerebrovascular diseases for several decades.