Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids

BackgroundElevated postprandial hypertriglyceridemia (PP-HTG) is a significant risk factor for development of cardiovascular diseases, however, the mechanisms underlying its exaggerated rise remains poorly understood. MicroRNAs (miRs) are known to be implicated in the regulation of lipid metabolism, thus identifying them as potential key players. We presently investigated whether miRs may control postprandial triglyceride (PP-TG) response. MethodsPostprandial changes in circulating miR expression as a function of the degree of postprandial TG response were evaluated in non-dyslipidemic healthy subjects (n=32). The impact of miR-100-5p on hepatic gene expression was evaluated in differentiated Caco2 and HepG2 cells by analysis of hepatic transcriptome (RNAseq), western blot and ELISA. In vivo studies were conducted in C57BL/6J mice overexpressing mimic miR-100-5p. ResultsPostprandial variation in circ-miR-100-5p levels inversely correlate with PP-TG response. Cir-miR-100-5p was preferentially associated with TGRL particles of intestinal origin in subjects exhibited a low PP TG response. Differential analysis of transcriptome from HepG2 cells transfected by either mimic miR-100-5p or scrambled mimic miR as control allowed us to identify PCSK9 as a down-regulated gene. Overexpression of miR-100-5p in HepG2 cells significantly decreased PCSK9 mRNA levels by 52% (p<0.0001), cellular protein content by 28 % (p<0.0001) as well as PCSK9 secretion by 39% (p<0.0001). In vivo systemic delivery of mimic miR-100-5p induced a two-fold reduction (p<0.0001) on PP-TG in mice, such effect being abolished by blocking the circulating form of PCSK9 with alirocumab. Finally, we revealed a significant inverse relationship between circulating miR-100-5p expression levels and both PCSK9 levels and the magnitude of postprandial hypertriglyceridemia. ConclusionTaken together, our observations reveal that miR-100-5p regulates postprandial hypertriglyceridemia by targeting PCSK9, thus enhancing hepatic triglyceride-rich lipoproteins (TGRL) uptake. Our findings allow us to propose circ-miR-100-5p as a potential biomarker for early identification of subjects at high cardiovascular risk, prior to appearance of classical clinical features of metabolic disorders. Postprandial clinical study, HDL-PP (NCT03109067) Lay summaryThis study examined whether miRs may control postprandial triglyceride response Key findingsOur data reveal that miR-100-5p regulates postprandial hypertriglyceridemia by targeting PCSK9 Our observations allow us to propose miR-100-5p as a potential biomarker for early identification of subjects at high cardiovascular risk

BackgroundMetabolic dysfunction-associated steatotic liver disease (MASLD) is challenging to study in vivo in humans and in vitro models are limited. Although primary human hepatocytes (PHHs) are considered the gold-standard, immortalized hepatic cell lines are utilised due to scalability. This study compared the metabolic responses of PHHs with our Huh7-based model cultured in physiologically-relevant fatty acid (FA) mixtures. MethodsPHH and Huh7 cells were treated with 2% human serum, sugars and FAs enriched in either unsaturated (OPLA) or saturated (POLA) FAs for 4 or 7 days, respectively. Stable isotope tracers investigated basal metabolic changes in response to treatment. Cell viability, media biochemistry, intracellular metabolism, lipid droplet morphology and gene expression were quantified. ResultsHuh7 cells had greater viability than PHHs, while NEFA uptake and triglyceride secretion were similar. OPLA and POLA increased large lipid droplets in Huh7 cells, whereas only OPLA produced comparable effects in PHHs. Despite higher baseline TG in PHHs, both models showed similar lipid composition, de novo lipogenic responses, and glycogen levels. Compared to Huh7 cells, PHHs exhibited higher 3-hydroxybutyrate, lower lactate, reduced glucose uptake, and donor-dependent transcriptomic variability. ConclusionsHuh7 cells are metabolically adaptable and when cultured in physiologically-relevant media, produce metabolic readouts similar PHH cells.

Metabolic dysfunction-associated steatohepatitis (MASH) is associated with increased expression of peroxisome proliferator-activated receptor gamma (PPAR{gamma}, Pparg) and reduced expression of genes involved in methionine metabolism in the liver. The nuclear receptor PPAR{gamma} is activated by fatty acids, and the knockout of Pparg in hepatocytes (Pparg{Delta}Hep) reduced the negative effects of MASH on methionine metabolism. Here, we sought to determine whether hepatocyte Pparg is required for the transcriptional regulation of genes involved in hepatic methionine metabolism in conditions with altered fatty acid flux to the liver: fasting, refeeding, and high-fat diet (HFD)-induced obesity/steatosis. Fasting induced liver steatosis and increased the expression of key genes involved in the methionine metabolism in the liver, while 6h-refeeding reversed these effects and reduced the expression of phosphatidylethanolamine N-methyltransferase (Pemt) and cystathionine beta synthase (Cbs). Overall, fasting and refeeding did not alter hepatocyte Pparg expression nor Pparg{Delta}Hep affected fasting and refeeding-mediated regulation of methionine metabolism gene expression. Diet-induced steatosis reduced hepatic Pemt expression in control (Pparg-intact) mice, and the thiazolidinedione (TZD)-mediated activation of PPAR{gamma} in diet-induced obese control (Pparg-intact) mice reduced the expression of betaine homocysteine S-methyltransferase (Bhmt) and Cbs. However, diet-induced steatosis increased hepatocyte Pparg expression, and Pparg{Delta}Hep blocked the negative effects of HFD and TZD on hepatic methionine metabolism. The PPAR{gamma}-dependent reduction of hepatic Bhmt and Cbs expression was confirmed in mouse primary hepatocytes. Taken together, hepatocyte Pparg may serve as a negative regulator of hepatic methionine metabolism in diet-induced obese mice and these actions could contribute to promoting the onset of MASH.

ObjectiveGlucokinase Regulatory Protein (GKRP) controls the activity of Glucokinase (GCK) to regulate liver glucose uptake and storage. Coding variants in GCKR, the gene encoding GKRP, strongly associate with fatty liver disease, hypertriglyceridemia, and hypercholesterolemia. Here, we sought to investigate the mechanisms by which a common GKRP variant affects hepatic lipid and cholesterol metabolism. MethodsWe developed mouse models to examine how the human GKRP P446L variant influences liver and systemic metabolism. Endogenous Gckr expression was ablated in adult mouse hepatocytes, together with re-expression of either human GKRP P446L or the reference GKRP protein. We assessed body weight, adiposity, systemic glucose homeostasis, and hepatic metabolites in mice expressing reference GKRP or GKRP P446L under multiple metabolic conditions. To determine whether the effects of GKRP P446L may result from reduced GCK activity, we analyzed mice with liver-specific deletion of Gck. ResultsHepatic expression of GKRP P446L resulted in reduced GKRP and GCK protein levels and elevated serum cholesterol. Hepatic deletion of Gck in mice recapitulated several effects of GKRP P446L, including increased hepatic cholesterol and triglyceride content. The elevated cholesterol was associated with increased cholesterogenic gene expression and cholesterol synthesis. Hepatic expression of an alternative hexokinase (HKII) normalized the effects of GCK-deficiency, suggesting that impaired glucose phosphorylation underlies the phenotype. ConclusionsThe GKRP P446L variant reduced GKRP protein abundance, and diminished GCK activity while increasing cholesterol levels. Loss of GCK elevated cholesterol and hepatic triglyceride levels. Collectively, these findings demonstrate that GCK suppresses hepatic cholesterol synthesis and lipid accumulation, suggesting that reduced GCK activity underlies the metabolic abnormalities associated with the GKRP P446L variant. HighlightsO_LIThe GKRP P446L variant reduces GKRP protein abundance and diminishes GCK activity. C_LIO_LIExpression of GKRP P446L in mouse hepatocytes increases serum cholesterol levels. C_LIO_LIHepatic GCK activity suppresses cholesterogenic gene expression and cholesterol synthesis. C_LI

The secretion of glucagon from the pancreatic alpha () cell within the islets of Langerhans is physiologically regulated by nutrients (glucose, amino acids, fatty acids), neurotransmitters, and paracrine hormones. Insulin and somatostatin form an intra-islet paracrine network to control glucagon secretion through direct inhibitory effects on cell secretory granule exocytosis. In a potential new cellular pathway for the regulation of glucagon secretion, we have previously identified the neuronal trafficking protein Stathmin-2 (Stmn2) as a negative regulator of glucagon trafficking and secretion by directing glucagon to degradative lysosomes. In this study, we examined if insulin and somatostatin direct glucagon to lysosomes in a Stmn2-dependent manner as part of their paracrine mechanisms. Using the TC1-6 glucagon-secreting cell line and confocal microscopy of both fixed and live cells, we show that insulin and somatostatin direct glucagon, glucagon+LAMP1+ vesicles, and LAMP1-RFP to the intracellular region, away from sites of exocytosis. As visualized in live cells, insulin treatment resulted in the rapid retrograde transport of lysosomes from the cell periphery, and this effect was lost under siRNA-mediated silencing of Stmn2. Somatostatin appeared to enhance the intracellular retention of lysosomes, also in a Stmn2-dependent manner. We determined a possible mechanism for Stmn2 in the regulation of lysosome transport in TC1-6 cells through the Arf-like small GTPase Arl8, indicating that Stmn2 may function in lysosomal positioning along microtubules. We propose that Stmn2-mediated lysosomal transport may be a potential new pathway, in addition to inhibition of secretory granule exocytosis, through which insulin and somatostatin regulate glucagon secretion.

The liver is widely considered to be one of the most conserved organs amongst vertebrates, with it being involved in blood detoxification, bile production and the metabolism of xenobiotic compounds. Liver organoids have previously been derived from several species and used as models of drug metabolism, toxicity, and fundamental tissue biology. To date, however, these models have not been developed from ruminant species, specifically cattle and sheep. Here we present the first report of the development and comprehensive characterisation of bovine and ovine liver organoids derived from primary liver tissue. When initially established, organoids from both species were comprised of KRT19- and KRT18-positive cholangiocytes. The capacity for organoids to differentiate into hepatocyte-enriched cultures was evaluated and it was noted that there was an increase in hepatocyte markers in bovine cultures. A comparative analysis of the liver tissue and organoids of both species revealed species-specific differences in gene expression, which were conserved within organoid cultures. Most notably, bovine liver tissue and organoids had enriched expression of genes associated with fatty acid uptake and storage whereas ovine samples had higher expression of genes associated with fatty acid conversion, highlighting fundamental differences between these two ruminant species. Differences in expression of cytochrome P450 family genes were identified alongside those associated with an inflammatory response specifically in bovine samples, whereas ovine samples had higher expression of genes associated with a protective immune response. Despite this, transcriptomic analysis of organoids from both species, cultured in both growth and differentiation media, revealed preserved expression of genes associated with key liver functions, including gluconeogenesis and xenobiotic metabolism. Transcripts associated with the flavin-containing monooxygenases (FMO) family were expressed in both organoid growth media and organoid development media (OGM and ODM respectively), and both species could metabolise triclabendazole into its primary metabolite triclabendazole sulfoxide, therefore validating the potential of the organoids to be applied as in vitro models of metabolism and/or toxicity. Overall, this study provides novel insights into differences in liver composition and function between ruminant species, as well as providing novel experimental models of the liver for both cattle and sheep.

The ubiquitin conjugating enzyme UBE2J1/Ubc6e localizes to the endoplasmic reticulum where it mediates the ubiquitination and proteasomal degradation of terminally misfolded proteins. Although the protein is known to undergo phosphorylation at serine S184, we have considered modification at an additional site and used a bespoke anti-phospho antibody to confirm phosphorylation also at serine residue S266. Despite the well-described role of UBE2J1 in ER associated degradation (ERAD), we found no evidence for regulation at S266 during Unfolded Protein Response (UPR) induction by thapsigargin. Instead, our studies suggest that phosphorylation occurs independently at the S184 and S266 sites, with mutation at one site failing to disrupt basal phosphorylation at the second. We identified several contexts in which these two phosphorylations were differentially regulated. For example, ER localization, which is important for phosphorylation at S184, was not required for modification at S266, and sensitivity to proteasome inhibitors, which is regarded as a distinguishing feature of the S184 phospho-variant, was unaltered by the S266A mutation. Regarding regulation at S266 on the other hand, we found that pharmacological activation of protein kinase A resulted in rapid phosphorylation, with differential use of phospho-specific antibodies confirming that phosphorylation at S184 was unchanged by this treatment. Hormonal stimulation by glucagon resulted in a similar pattern of UBE2J1 phosphorylation, which occurred exclusively at S266 and could be inhibited by H89. The differential regulation demonstrated in these studies extends our understanding of the UBE2J1 enzyme, and may indicate a role in the integration of energy metabolism with environmental stress conditions.

Mast cells (MCs) are myeloid cells of the innate immune system. As a first line of defence they fulfill effector functions and immune modulatory properties. Upon activation they release pro-inflammatory mediators such as cytokines and proteases. It has been suggested that MCs may contribute to the development of liver fibrosis. However, investigating hepatic MC biology in mice is challenging due to low MC numbers and a lack of suitable detection techniques relying on MC proteins and their modifications. Here, we evaluated whether the expression strength of MC markers correlates with the degree of liver fibrosis in mice and aimed to determine the frequency and localization of hepatic MCs. We applied both a toxic (DEN/CCl4 treatment) and a genetic (Mdr2-/- mice) liver fibrosis model in C57BL/6 mice and found a significant correlation between fibrosis grade and the expression of several established mast cell markers. This correlation was further supported in patients with fibrosis and hepatocellular carcinoma (HCC) using publicly available transcriptomics datasets. We used FACS to purify and isolate MCs from fibrotic mouse livers and verified MC signatures by qPCR analysis of MC-specific gene expression. Hepatic MCs were predominantly negative for Mast-Cell-Protease 5 (Mcpt5) and occurred at a low frequency (approximately 1-2% of leukocytes). Using Molecular CartographyTM of fibrotic liver sections, we determined the spatial localization, expression signature, abundance (approximately 2 cells/mm2) and cellular environment of murine hepatic MCs. In summary, we demonstrated the existence of MCs in murine fibrotic livers and defined an MC expression signature that correlates with the strength of liver fibrosis. These findings will help to study MC biology in murine models of liver disease more effectively in the future.

Harbour porpoises (Phocoena phocoena) in the North and Baltic Seas are increasingly impacted by anthropogenic pressures, including underwater noise, fisheries and pollution. These pressures correlate with declining population health, particularly affecting the respiratory system. Growing pathological lesions, partly resulting from high prevalence of parasitic infestations and subsequent diseases, can impair tissue function and oxygen supply to distant end-organs. In this study, we applied an integrative MultiOmics approach (proteomics, metabolomics, lipidomics) to analyse the lungs and muscles of 12 wild harbour porpoises with compromised respiratory health. Our aim was to identify dysregulated biological pathways across omics layers to advance insights into adaptive physiological responses and to define disease-associated molecular signatures that could assist health assessments. Our analysis revealed pronounced immune system and antioxidative responses in the lungs and muscles, indicated by enhanced immunoglobulins, plasmalogens and glutathione-related proteins. In the lungs, high cardiolipin levels and reduced collagen suggest impaired tissue structure and function, while tissue maintenance processes were elevated in the muscle. Both tissues exhibited metabolic alterations suggestive of energetic imbalance, including increased purine metabolism in the lung and decreased lipid metabolism in the muscle. Several dysregulated molecules were shared across tissues, pointing to pathophysiological effects. The proposed disease-associated molecular signatures included the protein SLC25A4, the metabolite O-phosphoethanolamine and the lipid TG O-16:0_16:0_20:4 for the lung, and the protein SPEG, the metabolite pipecolic acid, and the lipid BMP 18:1_22:6 in the muscle. Our findings elucidate the complexity of molecular mechanisms linking anthropogenic and environmental stressors with vulnerability and resilience in a marine sentinel species. Furthermore, this study highlights the potential of integrative omics to define disease-related marker panels, thereby supporting ongoing and future health monitoring and conservation efforts.

Metabolic syndrome (MetS), characterized by abdominal obesity, insulin resistance, dyslipidemia, and hypertension, affects a substantial proportion of the global population and increases the risk for cardiovascular disease, diabetes, and metabolic dysfunction-associated steatotic liver disease (MASLD). Despite its prevalence, there are currently no effective pharmacological therapies targeting MetS, highlighting the need to identify novel etiological mechanisms, particularly within the gastrointestinal (GI) tract. Using a mouse model of MetS and healthy lean controls, we assessed the colonic microenvironment through metabolomic, transcriptomic, and microbiome analyses. Colonic organoids were cultured to further explore epithelial alterations. Additionally, human MetS fecal metabolomics data were cross-compared with the mouse model to validate translational relevance. MetS mice exhibited upregulation of colonic anabolic pathways, including glycolysis, the pentose phosphate pathway, and the tryptophan/kynurenine pathway, without evidence of intestinal inflammation. Microbiome analysis revealed an increased abundance of the genus Lactobacillus in MS NASH mice. Colonic organoids from MetS mice showed altered goblet cell differentiation. Comparative analysis with human MetS fecal metabolomics demonstrated similar dysregulated pathways, underscoring the translational relevance of these findings. Our study reveals significant metabolic and microbial alterations in the colon of MS NASH mice, implicating a dysfunctional GI tract as a potential etiological factor in MetS. These findings highlight specific metabolic pathways and microbial signatures that could serve as future therapeutic targets for MetS. NEW & NOTEWORTHYThis study identifies the colon as a metabolically active tissue affected in metabolic syndrome. Despite the absence of intestinal inflammation, MS NASH mice displayed altered colonic metabolism and microbiota composition, with conserved metabolite changes matching those seen in humans with metabolic syndrome. These findings highlight colonic metabolic dysfunction as a potential driver of gut dysbiosis and disease progression in metabolic syndrome and MASLD. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=134 SRC="FIGDIR/small/716131v1_ufig1.gif" ALT="Figure 1"> View larger version (77K): org.highwire.dtl.DTLVardef@1b7c685org.highwire.dtl.DTLVardef@4a832aorg.highwire.dtl.DTLVardef@1e95c66org.highwire.dtl.DTLVardef@1b14209_HPS_FORMAT_FIGEXP M_FIG C_FIG

BackgroundThis study was designed to investigate the relationship between visceral fat metabolic score (METS-VF), lipid accumulation product (LAP), visceral adiposity index (VAI) and thyroid function. MethodsUtilizing data from the National Health and Nutrition Examination Survey (NHANES) 2007-2012, participants were excluded if they lacked data on METS-VF, LAP, VAI or thyroid function, or were under 18 years of age. Multiple linear regression, smooth curve fitting, and subgroup analyses were performed to determine the independent relationship between lipid accumulation and thyroid function. ResultsAfter full covariate adjustment, all three visceral adiposity indices showed significant positive associations with FT3 (LAP: {beta}=0.028, VAI: {beta}=0.024, METS-VF: {beta}=0.026; all P<0.001), FT3/FT4 ratio, TT3, TT4, and TgAb. LAP and VAI demonstrated inverse associations with FT4 ({beta}=-0.218 and -0.183, respectively; both P<0.001), while VAI and METS-VF were positively associated with TSH ({beta}=0.149, P=0.041; {beta}=0.167, P=0.025). Quartile analyses confirmed dose-dependent relationships, with Q4 participants showing elevated FT3, FT3/FT4, TT3, TT4, and reduced FT4 compared to Q1. RCS analyses revealed distinct non-linear patterns: LAP exhibited non-linearity with FT3, TSH, TT3, and TT4 (all P-nonlinear<0.05) but linear inverse associations with FT4. VAI displayed reverse L-shaped curves for FT3, TSH, and TT3 with plateaus at higher levels, while TT4 showed an inverted U-shape. METS-VF demonstrated non-linear increases for FT3 and TT3, linear associations with TSH and TT4, and an inverted U-curve for FT4. Stratified analyses identified age, race, and smoking as consistent modifiers of FT3/FT4 associations across all indices (interaction P<0.05), with stronger effects in younger/older adults, males, White participants, and high-income groups. TT3 and TT4 modification patterns varied by index. Thyroid autoantibodies showed minimal associations across all indices. ConclusionVisceral lipid accumulation is closely associated with thyroid dysfunction, and this association exhibits significant non-linear characteristics, which are modulated by factors such as age, race, and lifestyle habits. These findings provide new perspectives for the early identification and intervention of obesity-related thyroid dysfunction.

PurposeHyperosmolar stress (HOS) is a major contributor to corneal epithelial cell damage in dry eye disease. We have previously shown that HOS damages mitochondria and impairs cell metabolism in corneal epithelial cells. Small extracellular vesicles (sEVs) are cell-derived lipid envelopes that are present in all body fluids, including tears. Prior studies suggest that sEV release and composition may be linked with changes in cell metabolism. In this study, we tested the effects of HOS on sEV release and composition, and found that sEV cargo may reflect early, underlying changes in dry eye disease. MethodsTelomerase-immortalized human corneal epithelial (hTCEpi) cells were treated with 450 mOsm NaCl for five days to induce chronic HOS. sEVs were isolated using differential centrifugation followed by iodixanol density gradient flotation. Particle number was determined using Nanoparticle Tracking Analysis (NTA). Mass spectrometry was used to assess the sEV proteome, and selected proteins were validated by immunoblot. Proteome pathways were analyzed using KEGG and CORUM. ResultsPathway analysis revealed an increase in metabolic proteins and proteasome components in sEV cargo released from hTCEpi cells exposed to HOS. These proteins were increased more than fourfold in HOS-sEVs. Examination of proteins involved in the endosomal pathway and NTA further confirmed an increase in HOS-sEV release. ConclusionOur findings suggest a potential mechanism whereby corneal epithelial cells exposed to HOS retain proteins involved in maintaining tissue integrity, while simultaneously releasing unneeded proteins involved in cell metabolism. The presence of metabolic proteins in sEVs may serve as early indicators of dry eye disease.

Autophagy is a catabolic process used for the degradation of organelles and proteins. Macroautophagy involves the formation of autophagosomes and subsequent fusion with lysosomes to mediate cargo degradation. It also functions as a cellular defence mechanism, known as xenophagy, during infection. Previous studies show that different viruses manipulate the autophagy pathway of the host cell to assure successful replication and/or virion assembly. Vaccinia virus (VACV), the prototypic poxvirus, replicates exclusively in the cytoplasm of host cells. It is known that VACV infection causes LC3 lipidation and prevents autophagosome formation, yet the double membrane vesicles formed during autophagy do not serve as the source of the mature VACV membrane. To date the viral protein(s) causing increased LC3 lipidation have not been identified. Here we developed an image-based screening approach based on LC3 granularity to identify candidate VACV genes affecting its lipidation. We identify several candidate viral membrane proteins as effectors of LC3 lipidation, suggesting that the interplay between VACV and autophagy is more directed than previously thought.

Bisphenol A (BPA) and Bisphenol S (BPS) exposure disrupt ovarian function and granulosa cell (GC) steroidogenesis. Extracellular vesicles (EVs) and their miRNA cargo, as mediators of cellular response to environmental stimuli, might be involved in fertility and folliculogenesis. This study explored modulation of microRNA expression after 48h BPA or BPS exposure (10 {micro}M) in ovine primary GC and EVs from corresponding conditioned medium (CM EVs). Small RNA sequencing of control (0h) and 48h treated GC, CM EVs as well as follicular fluid EVs allowed identification of 533 ovine miRNAs, including 129 new sequences. BPA did not alter miRNA expression in GC, while BPS decreased cellular oar-24b miR. In contrast, BPA modified expression of 4 miRNAs in CM-EVs, including 3 new sequences, and two miRNAs were modified by BPS. Both compounds reduced expression of sequence homologous to miR-1306. Further studies are required to decipher their roles in bisphenol toxicity in GC.

SGLT2 inhibitor (SGLT2i)-induced diabetic hyperketonemia is a life-threatening acute complication of diabetes. While Celastrol has been reported to exert beneficial effects on obesity; its potential role in ketogenesis remains unclear. In this study, Celastrol administration significantly attenuates the fasting-induced elevation of blood {beta}-hydroxybutyrate. Moreover, a 7-day course of Celastrol (1 mg/kg/day) leads to reductions in body weight and fat mass. Mechanistically, Celastrol specifically downregulates HMGCS2 expression and suppressess hepatic ketogenesis through inhibiting PPAR expression in the short term ([&le;] 2 days). However, after prolonged treatment for 7 days, Celastrol modulates both PPARand serum free fatty acids (FFAs) levels. Furthermore, anti-ketogenic effect of Celastrol is abolished in Ppar{square} /{square} mice. Importantly, Celastrol effectively ameliorates SGLT2i-induced hyperketonemia. In summary, Celastrol curbs hepatic ketone overproduction in a PPAR-dependent manner, indicating its protective potential against SGLT2i-induced hyperketonemia.

The use of decellularized diseased livers in regenerative medicine is a promising approach for eliminating organ shortages. Bioengineering studies have shown that ECM can impact cell physiology, inducing cell activation, function, and ECM deposition, which suggests that the ECM has a "memory" that is involved in the outcome after recellularization. However, the effect of diseased ECM memory on new cells in vitro and in vivo has not been thoroughly investigated. Since it has been increasingly recognized that liver ECM changes due to different factors, it is comprehensively that diseased ECM obtained from discarded organs will ensure a distinct environment and impact cell survival and physiology. Thus, we aimed at investigating the impact of the memory of diseased ECM obtained from metabolic dysfunction-associated steatohepatitis (MASH)-derived organs on steatohepatitis establishment. To address this aim, we explored decellularized ECM obtained from rats and humans with MASH in different contexts. First, MASH ECM was characterized and then submitted to transplantation to investigate whether a MASH-derived ECM could be used as a scaffold for transplantation and to promote steatohepatitis features in control animals. Histological analysis revealed that the MASH-ECM was completely recellularized after transplantation in both control and MASH recipient rats. However, steatosis and fibrosis were observed in MASH ECM after transplantation in both groups. Molecular analysis showed that MASH ECM stimulates de novo lipogenesis and fibrosis 30 days after transplantation. Untargeted metabolomic analysis revealed that cells grown on MASH ECM had a similar metabolic profile, even when transplanted into healthy or MASH recipient rats. In addition, we observed that MASH ECM promoted impaired lipid oxidation and mitochondrial dysfunction when transplanted into healthy recipients. Altered lipid turnover and inflammatory signaling were observed in MASH ECM transplanted in MASH recipients. In vitro analysis revealed that MASH ECM induced lipid accumulation in HepG2 cells after 10 days of culture. Calcium signalling experiments obtained from HepG2 cells cultured in MASH ECM showed a lower response to ATP, a reduced calcium signalling amplitude, and a distinct response profile than that observed in healthy ECM. On the other hand, a diseased human-derived ECM could still provide an environment that allows cell development. Taken together, our data showed that MASH ECM impacts cell metabolism, promoting steatohepatitis maintenance. In conclusion, our data confirm that diseased ECM memory can impact cell physiology contributing to disease progression.

Cholesterol is a key component of cellular membranes, regulating membrane organization, fluidity, and signaling. However, cholesterol analysis remains technically challenging, as no single method currently allows both accurate quantification and spatially resolved visualization. Biochemical assays provide accurate quantification but lack spatial resolution, whereas imaging strategies can perturb membrane organization or cholesterol accessibility. Here, we describe optimized protocols using fluorescent D4 probes derived from the cholesterol-binding domain of perfringolysin O (D4-mCherry and D4-GFP) to detect, visualize, and quantify cholesterol in biological samples. We detail procedures for probe production, purification, and application, and establish conditions that ensure robust and reproducible labeling of membrane-accessible cholesterol. By combining fluorescence-based imaging with quantitative analysis, this approach enables the assessment of cholesterol distribution while preserving its native membrane environment. The proposed methodology provides a versatile and reliable framework for studying cholesterol in a wide range of experimental systems.

BackgroundCarnitine plays an obligatory role in energetics owing to its role in the translocation of long-chain fatty acids into the mitochondrion for oxidation. Here, we determined the metabolic and behavioral consequences of systemic carnitine deficiency (SCD) in mice. MethodsFemale C57BL/6J mice were randomized to receive normal drinking water (control, n = 8) or drinking water supplemented with mildronate 4g.L-1 (mildronate, n = 8) for 21 days. Body composition was assessed at baseline and post treatment. Metabolic and behavioral phenotyping was performed continuously over 72 hours following 14 days of control or mildronate treatment. Stable isotope were used to assess whole-body substrate oxidation. Carnitine subfractions were quantified in skeletal muscle and liver, as was mitochondrial respiratory function. Liver and muscle samples also underwent proteomic analysis. ResultsMildronate treatment depleted total carnitine in muscle and liver by [~]97% (P < 0.001) and [~]90% (P < 0.001), respectively. Carnitine depletion was accompanied by lower total energy expenditure (P = 0.01), attributable to lower voluntary wheel running (P = 0.01). Oxidation rates of palmitate (P < 0.01) but not octanoate were lower whereas rates of glucose oxidation were greater in carnitine depleted mice (P < 0.01). Mitochondrial respiratory capacity was unaltered by carnitine deficiency. Carnitine deficiency remodeled muscle and liver proteomes to support lipid oxidation and energy production. SummaryIn mice, carnitine deficiency is characterized by decreased long-chain fatty acid oxidation despite preserved mitochondrial respiratory capacity. Carnitine deficiency resulted in lower voluntary exercise and a concomitant reduction in energy expenditure.

Background & AimsMetabolic disorders such as dyslipidemia, metabolic dysfunction-associated steatotic liver disease (MASLD), and diabetes are promoted by chronic pro-inflammatory and pro-oxidative states. Paraoxonase 1 (PON1), a liver-derived HDL-associated enzyme, plays an important antioxidant role by hydrolyzing oxidized lipids and protecting against oxidative stress- induced damage. Genetic variation in PON1, particularly in promoter and coding regions, modulates enzyme expression and activity, thereby influencing susceptibility to metabolic and cardiovascular diseases. This study investigated the genetic determinants of serum paraoxonase (PONase) activity and their relationship with dysmetabolic phenotypes. MethodsA genome-wide association study was conducted in 922 Portuguese individuals from the PREVADIAB2 cohort. Genetic variants and haplotypes related to PONase activity were analyzed, and associations with dysglycemia and liver fibrosis were evaluated in individuals aged over 55 years. ResultsWe identified two key PON1 variants as determinants of PONase activity: rs2057681 (in strong linkage disequilibrium with the non-synonymous Q192R variant) and rs854572 (located in the promoter region). Analysis of rs854572-rs2057681 haplotypes revealed that specific combinations differentially modulate PONase activity and confer risk or protection for dysglycemia and liver fibrosis, depending on the rs2057681 genotype context. Notably, although PONase activity was strongly associated with PON1 variants, it did not directly correlate with dysmetabolic phenotypes, suggesting that genetic context and haplotype structure, rather than enzyme activity alone, shape disease susceptibility. ConclusionsThese findings highlight the complex genetic architecture of PON1 and its role in metabolic disease risk, supporting the use of PON1 genetic information to uncover predisposition to dysmetabolic conditions. Our results provide insights into the interplay between PON1 genetics, enzyme function, and dysmetabolism, with implications for risk stratification in metabolic liver disease. Lay SummaryPON1 is a liver-derived gene that encodes an enzyme involved in protection against oxidative stress, a key contributor to metabolic liver disease and diabetes. In this study, we found that specific combinations of PON1 genetic variants are associated with abnormalities in blood glucose regulation and with markers of liver fibrosis. These associations were dependent on genetic configuration rather than enzyme activity alone, suggesting that PON1 genetic information may help identify individuals at higher risk of metabolic liver disease.

AimsThe Mediterranean diet is associated with reduced cardiometabolic risk, yet its physiological effects during pregnancy and its impact on placental metabolism remain incompletely understood. This study aimed to determine whether maternal adherence to a Mediterranean diet during pregnancy influences placental lipid metabolism and signalling pathways involved in nutrient handling, tissue remodelling, and inflammation, and to assess their relationship with pregnancy outcomes. MethodsPlacental samples and clinical outcome data were analysed from pregnant women participating in an unblinded randomized clinical trial of a Mediterranean diet intervention. Placental lipid composition was quantified and the expression of genes and signalling pathways involved in lipid metabolism, nutrient transport, inflammation, and tissue remodelling was evaluated. ResultsMaternal adherence to a Mediterranean diet during pregnancy was associated with significant alterations in placental lipid composition, including reduced C18:0 and C24:0 and increased C18:1n9c, C20:3n6, and C22:0, with lower total short-chain fatty acids and higher monounsaturated fatty acids. Placental expression of lipid metabolism regulators ALOX15 and PPAR{gamma} was reduced, alongside downregulation of AKT and p38 MAPK signalling pathways. Placentas from mothers adhering to the Mediterranean diet also showed lower expression of amino acid and glucose transporters SLC3A2 and SLC2A1, as well as altered inflammatory and extracellular matrix remodelling markers, including decreased SOCS3 and GHR and increased PAI1 and MMP3. ConclusionsMaternal adherence to a Mediterranean diet during pregnancy modifies placental lipid composition and regulates pathways involved in lipid handling, nutrient transport, inflammation, and tissue remodelling, providing insight into mechanisms linking maternal diet with placental metabolic function.