Biology subjects

Theusch, E.

Publications and source records attributed to Theusch, E..

6 recordsLinked to original sources

bioRxiv2025

MIR192 Upregulates GLP-1 Receptor and Improves Statin-Induced Impairment of Insulin Secretion

Statins are a commonly prescribed cholesterol lowering drug class that can increase the risk of new-onset diabetes (NOD). To investigate the molecular mechanisms underlying this effect, we generated human induced pluripotent stem cells (iPSCs) from individuals identified from electronic health records of Kaiser Permanente of Northern California who were susceptible to developing NOD after statin initiation or controls who maintained stable fasting glucose on statin treatment. RNA-seq analysis of iPSCs incubated with atorvastatin, simvastatin or mock buffer for 24 hours identified the long non-coding RNA MIR194-2HG as a top candidate gene. Statin-induced increases in its expression were observed in NOD resistant controls, while statin-induced reductions occurred in NOD susceptible cases. MIR194-2HG encompasses two microRNA genes: MIR192 and MIR194-2. The mature microRNA miR-192-5p, derived from the 5 arm of MIR192, was predicted to bind the 3UTR of the glucagon like peptide 1 (GLP-1) receptor (GLP1R) transcript. Transfection of a rat insulinoma cell line INS-1 with a miR-192-5p mimic increased Glp1r transcript (1.41-fold) and protein (1.51-fold) levels compared to a scrambled control. Using a luciferase reporter containing the human GLP1R 3UTR, miR-192-5p overexpression similarly increased luciferase signal (1.44-fold). The miR-192-5p mimic enhanced glucose stimulated insulin secretion (GSIS) in response to GLP1R agonists (1.64-1.81-fold) and rescued simvastatin-induced GSIS impairment in INS-1 cells. Wild-type mice treated with miR-192 AAV8 had improved glucose sensitivity. Islets isolated from these mice exhibited enhanced GLP-1 potentiated GSIS during perifusion ex vivo. These effects were absent in the DIRKO (Glp1r/Gipr double knockout) mouse islets, consistent with the idea that miR-192 promotes GLP-1 mediated GSIS through GLP1R. These findings implicate MIR192 in statin-induced impairment of GSIS by modulating GLP1R, potentially contributing to the susceptibility to NOD in statin users.

cell biology↗

bioRxiv2025

Predicting Metabolic Dysfunction Associated Steatotic Liver Disease Risk Using Patient-Derived Induced Pluripotent Stem Cells

Background and AimsMetabolic Dysfunction Associated Steatotic Liver Disease (MASLD) is reversible at early stages, making early identification of high-risk individuals clinically valuable. Previously, we demonstrated that patient-derived induced pluripotent stem cells (iPSCs) harboring MASLD DNA risk variants exhibit greater oleate-induced intracellular lipid accumulation than those without these variants. This study aimed to develop an iPSC-based MASLD risk predictor using functional lipid accumulation assessments. MethodsWe quantified oleate-induced intracellular lipid accumulation in iPSCs derived from three cohorts of diverse ancestry: 1) CIRM cohort (20 biopsy-confirmed MASH cases, 2 biopsy-confirmed MASLD cases, 17 controls), 2) POST cohort (18 MASLD cases, 17 controls), and 3) UCSF cohort (4 biopsy-confirmed MASH cases, 8 controls). Lipid accumulation levels in the CIRM cohort were used to define an iPSC-based MASLD risk score, which was used to predict case/control status in the POST and UCSF cohorts. ResultsIn all three cohorts, lipid accumulation was higher in MASLD/MASH cases vs. controls (CIRM cases vs. controls 3.32 {+/-} 0.25 vs. 2.70 {+/-} 0.19 -fold change, p=0.06; POST cases vs. controls 3.63 {+/-} 0.33 vs. 2.70 {+/-} 0.31, p=0.05; and UCSF cases vs. controls 4.39{+/-}0.46 vs. 2.03{+/-}0.20, p=0.0002). The iPSC-based MASLD risk score achieved a sensitivity of 44% and specificity of 75% in the POST cohort and 75% and 100%, respectively, in the UCSF cohort. Differences in cohort disease severity and cardiometabolic profiles may explain performance variability. ConclusionWhile validation in larger cohorts is needed, these findings suggest that oleate-induced intracellular lipid accumulation in subject-derived iPSCs is predictive of MASH development. Additional cellular phenotypes and donor information should be explored to improve predictive accuracy to inform MASLD surveillance and prevention strategies.

cell biology↗

bioRxiv2024

Loss of TMEM55B modulates lipid metabolism through dysregulated lipophagy and mitochondrial function

Lipophagy is a form of selective autophagy that targets the lipid droplets for lysosomal decay and has been implicated in the onset and progression of metabolic dysfunction-associated steatotic liver disease (MASLD). Factors that augment lipophagy have been identified as targets for MASLD therapeutic development. TMEM55B is a key regulator of lysosomal positioning which is critical for the lysosome fusion with the autophagosome, but less studied. Here, we demonstrate that inhibition of TMEM55B in murine models accelerates MASLD onset and progression. In cellular models, TMEM55B deficiency enhances lipophagy, leading to increased fatty acid release from lysosomes to mitochondria but simultaneously impairs mitophagy, causing an accumulation of dysfunctional mitochondria. This imbalance leads to increased lipid accumulation and oxidative stress, worsening MASLD. These findings underscore the importance of lysosomal positioning in lipid metabolism and suggest that augmenting lipophagy may exacerbate disease in the context of mitochondrial dysfunction.

cell biology↗

bioRxiv2024

TOMM40 regulates hepatocellular and plasma lipid metabolism via an LXR-dependent pathway

The gene encoding TOMM40 (Transporter of Outer Mitochondrial Membrane 40) is adjacent to that encoding APOE, which has a central role in lipid and lipoprotein metabolism. Human genetic variants near APOE and TOMM40 are strongly associated with plasma lipid levels, but a specific role for TOMM40 in lipid metabolism has not been established. Investigating this, we show that suppression of TOMM40 in human hepatoma cells upregulates expression of APOE and LDLR in part via activation of LXRB (NR1H2) by oxysterols, with consequent increased uptake of VLDL and LDL. This is in part due to disruption of mitochondria-endoplasmic reticulum contact sites, with resulting accrual of reactive oxygen species and non-enzymatically derived oxysterols. With TOMM40 knockdown, cellular triglyceride and lipid droplet content are increased, effects attributable in part to receptor-mediated VLDL uptake, since lipid staining is significantly reduced by concomitant suppression of either LDLR or APOE. In contrast, cellular cholesterol content is reduced due to LXRB-mediated upregulation of the ABCA1 transporter as well as increased production and secretion of oxysterol-derived cholic acid. Consistent with the findings in hepatoma cells, in vivo knockdown of TOMM40 in mice results in significant reductions of plasma triglyceride and cholesterol concentrations, reduced hepatic cholesterol and increased triglyceride content, and accumulation of lipid droplets leading to development of steatosis. These findings demonstrate a role for TOMM40 in regulating hepatic lipid and plasma lipoprotein levels and identify mechanisms linking mitochondrial function with lipid metabolism. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=132 SRC="FIGDIR/small/600910v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@17b0c8forg.highwire.dtl.DTLVardef@17599aaorg.highwire.dtl.DTLVardef@1bb6ab2org.highwire.dtl.DTLVardef@15a035f_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2023

TOMM40 and TOMM22 of the Translocase Outer Mitochondrial Membrane Complex rescue statin-impaired mitochondrial dynamics, morphology, and mitophagy in skeletal myotubes

BackgroundStatins are the drugs most commonly used for lowering plasma low-density lipoprotein (LDL) cholesterol levels and reducing cardiovascular disease risk. Although generally well tolerated, statins can induce myopathy, a major cause of non-adherence to treatment. Impaired mitochondrial function has been implicated as a cause of statin-induced myopathy, but the underlying mechanism remains unclear. We have shown that simvastatin downregulates transcription of TOMM40 and TOMM22, genes that encode major subunits of the translocase of outer mitochondrial membrane (TOM) complex which is responsible for importing nuclear-encoded proteins and maintaining mitochondrial function. We therefore investigated the role of TOMM40 and TOMM22 in mediating statin effects on mitochondrial function, dynamics, and mitophagy. MethodsCellular and biochemical assays and transmission electron microscopy were used to investigate effects of simvastatin and TOMM40 and TOMM22 expression on measures of mitochondrial function and dynamics in C2C12 and primary human skeletal cell myotubes. ResultsKnockdown of TOMM40 and TOMM22 in skeletal cell myotubes impaired mitochondrial oxidative function, increased production of mitochondrial superoxide, reduced mitochondrial cholesterol and CoQ levels, disrupted mitochondrial dynamics and morphology, and increased mitophagy, with similar effects resulting from simvastatin treatment. Overexpression of TOMM40 and TOMM22 in simvastatin-treated muscle cells rescued statin effects on mitochondrial dynamics, but not on mitochondrial function or cholesterol and CoQ levels. Moreover, overexpression of these genes resulted in an increase in number and density of cellular mitochondria. ConclusionThese results confirm that TOMM40 and TOMM22 are central in regulating mitochondrial homeostasis and demonstrate that downregulation of these genes by statin treatment mediates disruption of mitochondrial dynamics, morphology, and mitophagy, effects that may contribute to statin-induced myopathy. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=102 SRC="FIGDIR/small/546411v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@1845842org.highwire.dtl.DTLVardef@1be8a26org.highwire.dtl.DTLVardef@5fd618org.highwire.dtl.DTLVardef@1e0f523_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2023

Participant-derived cell line transcriptomic analyses and mouse studies reveal a role for ZNF335 in plasma cholesterol statin response

BackgroundStatins lower circulating low-density lipoprotein cholesterol (LDLC) levels and reduce cardiovascular disease risk. Though highly efficacious in general, there is considerable inter-individual variation in statin efficacy that remains largely unexplained. MethodsTo identify novel genes that may modulate statin-induced LDLC lowering, we used RNA-sequencing data from 426 control- and 2 M simvastatin-treated lymphoblastoid cell lines (LCLs) derived from European and African American ancestry participants of the Cholesterol and Pharmacogenetics (CAP) 40 mg/day 6-week simvastatin clinical trial (ClinicalTrials.gov Identifier: NCT00451828). We correlated statin-induced changes in LCL gene expression with plasma LDLC statin response in the corresponding CAP participants. For the most correlated gene identified (ZNF335), we followed up in vivo by comparing plasma cholesterol levels, lipoprotein profiles, and lipid statin response between wild-type mice and carriers of a hypomorphic (partial loss of function) missense mutation in Zfp335 (the mouse homolog of ZNF335). ResultsThe statin-induced expression changes of 147 human LCL genes were significantly correlated to the plasma LDLC statin responses of the corresponding CAP participants in vivo (FDR=5%). The two genes with the strongest correlations were zinc finger protein 335 (ZNF335 aka NIF-1, rho=0.237, FDR-adj p=0.0085) and CCR4-NOT transcription complex subunit 3 (CNOT3, rho=0.233, FDR-adj p=0.0085). Chow-fed mice carrying a hypomorphic missense (R1092W; aka bloto) mutation in Zfp335 had significantly lower non-HDL cholesterol levels than wild type C57BL/6J mice in a sex combined model (p=0.04). Furthermore, male (but not female) mice carrying the Zfp335R1092W allele had significantly lower total and HDL cholesterol levels than wild-type mice. In a separate experiment, wild-type mice fed a control diet for 4 weeks and a matched simvastatin diet for an additional 4 weeks had significant statin-induced reductions in non-HDLC (-43{+/-}18% and -23{+/-}19% for males and females, respectively). Wild-type male (but not female) mice experienced significant reductions in plasma LDL particle concentrations, while male mice carrying Zfp335R1092W allele(s) exhibited a significantly blunted LDL statin response. ConclusionsOur in vitro and in vivo studies identified ZNF335 as a novel modulator of plasma cholesterol levels and statin response, suggesting that variation in ZNF335 activity could contribute to inter-individual differences in statin clinical efficacy.

genomics↗