Journal of Lipid Research最新文献

Matrix metalloproteinase-12 (MMP12) is a proinflammatory macrophage-secreted protein with immunomodulatory functions that affects neutrophil infiltration, cytokine release, macrophage recruitment, and proliferation. We have previously demonstrated that the genetic deletion of MMP12 in a cardiometabolic mouse model ameliorates obesity-induced low-grade inflammation, white adipose tissue dysfunction, and atherosclerosis. Based on the various beneficial metabolic effects of MMP-12 deletion, we hypothesized that loss of MMP-12 also positively affects whole-body energy metabolism and/or brown adipose tissue (BAT) function in a cardiometabolic mouse model. To investigate the effects of MMP12 deletion on whole-body energy metabolism and/or BAT function, we used low-density lipoprotein receptor (Ldlr)/Mmp12 double knockout (DKO) fed a high-fat, sucrose- and cholesterol-enriched diet. DKO mice housed at 22°C showed increased energy expenditure and decreased BAT size and triglyceride (TG) content. Untargeted proteomic analyses revealed the upregulation of proteins and pathways related to mitochondrial function, glucose metabolism, and fatty acid oxidation in the BAT of DKO mice, whereas the abundance of proteins and pathways associated with inflammation was reduced. In addition, DKO mice exhibited reduced macrophage infiltration in BAT, with the infiltrating macrophages showing lower expression of lipid-associated marker genes. Loss of MMP12 was associated with reduced compactness and sphericity of the mitochondria in the BAT. Following an acute cold exposure, DKO mice had decreased circulating lipid concentrations, especially very low-density lipoprotein-TG and LDL-cholesterol, and increased expression of thermogenic genes. We conclude that MMP12 may play a detrimental role in whole-body energy homeostasis and thermogenesis, as it triggers macrophage infiltration, inflammation, and mitochondrial dysfunction in BAT.

Hepatocellular carcinoma (HCC) has a higher incidence in males and is a leading cause of cancer-related deaths, which lacks effective therapies and surveillance markers. Using a murine model of bile acid excess (farnesoid X receptor and small heterodimer partner double knockout, DKO), which phenocopies many aspects of HCC, including sex differences, we investigated the links between sex, bile acid metabolism, and microbial composition. Unexpectedly, the increase in the ratios of carcinogenic deoxycholic acid (DCA) was similar between DKO males with HCC and cancer-resistant DKO females. However, both taurine-conjugated and free cholic acid (CA) sharply increased in the serum of DKO males, with free-CA comprising 65% of the bile acid pool, whereas DKO female serum was mostly comprised of conjugated bile acids. Unlike such sex differences in DKO serum composition, conjugated bile acids were predominant in the hepatic BA pool irrespective of the sex or genotype, as expected. Fecal and cecal microbiota-many of which harbor bile acid transformation/deconjugation capacity-were altered in DKO mice in a sex-specific manner. Untargeted fecal metabolite analysis showed differences in bile acids, phospholipids, and oxidized fatty acids between the genotypes, with DKO females excreting more sulphated and oxidized CA than tumor-bearing DKO males. Further analysis revealed a direct correlation between unconjugated CA levels with the abundance of the microbial genus Faecalibaculum in the DKO HCC model. These findings suggest distinct sex-specific changes in cecal and fecal microbiota, and BA composition may be leveraged in combination as a potential tool for HCC surveillance.

The high-density lipoprotein (HDL) is the most heterogeneous and protein-rich lipoprotein, and its complex proteome has been correlated with many distinct properties. However, the lack of a standardized approach for HDL isolation, combined with the fact that different methods capture overlapping, but distinct HDL subspecies make the establishment of a composition-function relationship a challenge. Key factors influencing HDL proteomic profile are the isolation methodology and the technical variability associated with it. Importantly, interlaboratory technical variability associated with HDL isolation methodologies and how it affects the HDL proteome has never been determined. Here, we used two common methods to isolate HDL particles, ultracentrifugation (UC) and immunoaffinity chromatography against APOA1 (IAC), and performed a thorough evaluation of intralaboratory repeatability as well as intra- and interlaboratory reproducibility of these isolation methods, assessing their influence on HDL-associated proteins composition and abundance. Our results demonstrate that methodological variability has a greater impact on the HDL proteome than interlaboratory differences, with almost 60% of the variance in the data explained by the method of isolation. Importantly, the top 15 HDL proteins account for > 90% of the protein mass in HDL, regardless of the isolation method, and the variability in protein quantification is inversely associated with protein abundance. A joint analysis combining interlaboratory reproducibility of top 15 HDL proteins in multiple days shows 11 and 10 proteins with CV < 25% for UC and IAC, respectively. In summary, our findings demonstrate that standardized isolation methods can achieve acceptable reproducibility within and across laboratories, but they may capture distinct HDL particles.

Metabolic dysfunction-associated steatotic liver disease (MASLD) has become highly prevalent worldwide, largely as a consequence of the global obesity epidemic. This research endeavors to elucidate the role and molecular mechanisms of hepatic glycogen synthase (GS) in MASLD progression. Published transcriptomic data reveal a downward trend in GYS2 gene expression in patients with obesity, MASLD, and metabolic dysfunction-associated steatohepatitis. In mouse models of MASLD, GYS2 gene or protein expression was downregulated, consistent with the human data. Here, GS-deficient mice fed with a normal diet displayed hepatic lipid accumulation and liver injury, whereas hepatic steatosis progression and inflammation were aggravated in mice fed with a high-fat diet. Loss of hepatic GS stimulated fatty acid de novo synthesis through carbohydrate-response element-binding protein and AKT-mTOR1-sterol regulatory element-binding protein 1 axis pathways. In GS-deficient mice, lipid accumulation in the hepatocytes significantly decreased when carbohydrate-response element-binding protein and sterol regulatory element-binding protein 1 levels were suppressed to levels comparable to those of cytotoxic T lymphocyte hepatocytes. Forced expression of hepatic GS by adeno-associated virus in db/db mice ameliorated lipid accumulation in male mice. Our findings provide proof of concept whereby targeting glycogen metabolism in hepatocytes may offer potential therapeutic avenues to treat MASLD.

Mutations in microtubule-associated protein Tau (MAPT), the gene that codes for the protein Tau, cause frontotemporal lobar degeneration (FTLD) with phenotypes ranging from behavioral changes to cognitive impairment and parkinsonism. Recently, lipid changes have been heavily implicated in synucleinopathies and secondary tauopathies such as Alzheimer's disease. Whether mutations in MAPT or accumulation of hyperphosphorylated Tau (pTau) can contribute to lipid changes in primary tauopathies is unknown. Here, we examine the effect of the FTLD-associated mutation MAPT P301S on brain lipid metabolism in a Tau transgenic mouse model. We find that the MAPT P301S mutation drives increased levels of diglycerides and hexosylceramides and lactosylceramides while reducing triglycerides, specifically those triglyceride species containing monounsaturated fatty acids, but does not affect cholesterol metabolism prior to pTau accumulation. Strikingly, with increasing accumulation of pTau, neutral lipids such as cholesteryl esters and triglycerides start to accumulate in the brain of mutant mice, as also reported in the Alzheimer's disease and FTLD brain. Furthermore, with increasing buildup of pTau, we observe decreased cholesterol synthesis and turnover to 24S-hydroxycholesterol. Overall our data indicates that the MAPT P301S mutation and accumulation of pTau are associated with distinct brain lipidomes in vivo.

A significant number of inherited neurodegenerative metabolic diseases (NMDs) arise from altered lipid metabolism, including impaired degradation of sphingolipids and dysfunction in organelle-related machineries involved in lipid processing and trafficking. These lipid dysregulations profoundly impact cellular membranes, signaling pathways, and myelin integrity, contributing to the complex and multisystemic clinical phenotypes characteristic of NMD, which often complicate diagnosis and delay treatment initiation. Here, we present a high-throughput, multiplex LC-MS/MS method for the analysis of an extended panel of NMD biomarkers in plasma and dried blood spots. One-step sample extraction and targeted LC-MS/MS acquisitions in positive and negative ionization allowed the simultaneous measurement of 13 diagnostic biomarkers associated with GM1 and GM2 gangliosidosis, Fabry, Gaucher, and Krabbe diseases, acid sphingomyelinase deficiency, Niemann-Pick disease type C, X-linked adrenoleukodystrophy, peroxisomal biogenesis disorders (Zellweger syndrome), metachromatic leukodystrophy, and mental retardation, enteropathy, deafness, neuropathy, ichthyosis, keratoderma (MEDNIK)/MEDNIK-like syndromes, a disorder of cellular trafficking. The method was analytically and clinically validated, confirming the diagnosis of all targeted NMDs in samples from 89 patients. Additionally, the method allowed the differentiation of X-linked adrenoleukodystrophy from peroxisomal biogenesis disorder and revealed the elevation of C18- and C16-sulfatides in Krabbe disease and MEDNIK syndrome, respectively. This multiplex assay enhances diagnostic efficiency and expands the discovery of novel biomarkers, enabling the quantification of diagnostic markers for a wide range of NMDs. The method is suitable for diagnosis of NMD, as a first- or second-tier test in neonatal screening, as confirmatory testing of variant of unknown significance in genetic panels and for longitudinal monitoring in treatable diseases.

The occurrence of abnormal total cholesterol (TC) can gradually and persistently induce brain damage. Early-onset TC abnormality indicates the accumulation of risks. However, evidence about the impact of early-life TC abnormality on brain morphology remains unclear. This study aimed to investigate the effect of early-onset TC abnormality on brain macrostructure and microstructure. Based on the 16-year follow-up clinical data of participants in the Kailuan study, the involved participants were categorized into three groups: normal TC, early-onset TC abnormality (before 45 years old), and late-onset TC abnormality (after 45 years old). Multimodal neuroimaging data were obtained to evaluate the brain volume and white matter integrity at the voxel-wise level. A generalized linear model was employed to evaluate the association between TC abnormalities and neuroimaging features. Among the 590 involved participants, early-onset TC abnormality was associated with smaller gray matter volume (β = -0.480; 95% CI = -0.914, -0.047), predominantly in the frontal lobe, anterior cingulate gyrus, paracingulate gyrus, specifically in the hippocampus (β = -0.008; 95% CI = -0.013, -0.003). A negative association between early-onset TC abnormality and abnormal fractional anisotropy and mean diffusivity in the fornix. Relative volume reduction of the frontal lobe and arcuate fasciculus injury were observed at the voxel level in late-onset TC abnormality participants. The Montreal Cognitive Assessment score was significantly associated with an increased gray matter volume and an increased white matter fractional anisotropy in participants with early-onset TC abnormality. Moreover, the Montreal Cognitive Assessment score was associated with microstructural integrity in the late-onset group. Early-onset TC abnormality was associated with multiple-region gray matter atrophy and decreased microstructural integrity. Our findings highlight the importance of early-life TC control to decrease the injury of brain morphology and maintain brain health.

Mass spectrometry (MS) imaging using stable isotope-labeled fatty acids provides a groundbreaking approach to precisely localizing exogenous fatty acids and their metabolites in vivo. However, challenges persist, particularly with fatty acids labeled with fixed isotopic numbers, which can lead to spectral interferences and limit the number of metabolites that can be detected. In this study, we employed a bisallylic deuteration method to synthesize dihomo-γ-linolenic acid (DGLA) isotopes with m/z values ranging from +4 to +8 Da relative to endogenous DGLA, which allowed us to meticulously dissect DGLA metabolism in mice using LC-QTof-MS and MS imaging. Our strategy enabled the clear selection of m/z values for phospholipids enriched with deuterated DGLA (D-DGLA) and deuterated ARA (D-ARA) derived from D-DGLA, all while maintaining low background noise. This precision facilitated the successful visualization of D-DGLA and D-ARA-containing phospholipids in lung tissue, revealing their distinct localization compared to endogenous phospholipids. Our findings highlight bisallylic deuteration as a powerful tool for elucidating the in vivo dynamics of exogenous polyunsaturated fatty acids (PUFAs) through MS imaging techniques.

X-linked adrenoleukodystrophy (X-ALD) is a congenital metabolic disorder characterized mainly by inflammatory demyelination and adrenal insufficiency. Newborn screening using hexacosanoyl lysophosphatidylcholine (C26:0-LPC) in dried blood spots as a diagnostic marker can successfully identify potential patients with X-ALD and prevent disease onset. C26:0-LPC accumulates in patients with X-ALD, although the machinery synthesizing it has remained unclear. In this study, we focused on phosphatidylcholine (PC) with C26:0 moiety as a precursor of C26:0-LPC. We identified that lysophospholipid (LPL) acyltransferase 10 (LPLAT10)/LPCAT4/LPEAT2/AGPAT7 (1-acylglycerol-3-phosphate O-acyltransferase 7) is the responsible LPL acyltransferase that produces PC with C26:0 moiety by transferring C26:0-CoA into 2-acyl-LPC. We also found that LPLAT10 deficiency decreased the amount of C26:0-LPC in fibroblasts from X-ALD patients. Mechanistically, LPLAT10 introduced saturated fatty acid-CoA of various chain lengths as substrates into the sn-1 position of LPC but did not transfer C26:0-CoA to other LPL classes, such as lysophosphatidylethanolamine. Structural analysis revealed that a trimethylamine group of PC was placed between two tryptophan residues (W242 and W244), forming a W-X-W motif, possibly through cation-π interaction. Finally, it was shown that exogenously administered C26:0 FFA-d₄ was preferentially incorporated into sphingolipids in the absence of LPLAT10. These results suggest that C26:0-LPC is produced through acyl-chain remodeling of PC catalyzed by LPLAT10 and accumulates in the plasma from X-ALD patients.