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Cited by 63Cholesterol and Lipid MetabolismProtease and Inhibitor MechanismsLipoproteins and Cardiovascular Health

The DOI matches its Crossref record; 67 of the 67 references it cites were found in a registry or an index; 34 of the 54 sources its claims cite were checked for support.

Membrane type 1 matrix metalloproteinase promotes LDL receptor shedding and accelerates the development of atherosclerosis

Open access
Alabi, Adekunle, Xia, Xiao-Dan, Gu, Hong-Mei, Wang, Faqi, Deng, Shi-Jun, Yang, Nana, Adijiang, Ayinuer, Douglas, Donna N., Kneteman, Norman M., Xue, Yazhuo, Chen, Li, Qin, Shucun, Wang, Guiqing, Zhang, Da-Wei·2021·Nature Communications
DOI 10.1038/s41467-021-22167-3PMC PMC7994674
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Abstract

Plasma low-density lipoprotein (LDL) is primarily cleared by LDL receptor (LDLR). LDLR can be proteolytically cleaved to release its soluble ectodomain (sLDLR) into extracellular milieu. However, the proteinase responsible for LDLR cleavage is unknown. Here we report that membrane type 1-matrix metalloproteinase (MT1-MMP) co-immunoprecipitates and co-localizes with LDLR and promotes LDLR cleavage. Plasma sLDLR and cholesterol levels are reduced while hepatic LDLR is increased in mice lacking hepatic MT1-MMP. Opposite effects are observed when MT1-MMP is overexpressed. MT1-MMP overexpression significantly increases atherosclerotic lesions, while MT1-MMP knockdown significantly reduces cholesteryl ester accumulation in the aortas of apolipoprotein E (apoE) knockout mice. Furthermore, sLDLR is associated with apoB and apoE-containing lipoproteins in mouse and human plasma. Plasma levels of sLDLR are significantly increased in subjects with high plasma LDL cholesterol levels. Thus, we demonstrate that MT1-MMP promotes ectodomain shedding of hepatic LDLR, thereby regulating plasma cholesterol levels and the development of atherosclerosis.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

MT1-MMP binds LDLR and promotes its ectodomain shedding, increasing soluble LDLR and reducing hepatic LDLR, thereby raising plasma cholesterol and accelerating atherosclerosis in mice. Human plasma sLDLR correlates with total and LDL cholesterol, supporting a role for LDLR shedding in cholesterol metabolism.

Key findings

  • MT1-MMP co-immunoprecipitated and co-localized with LDLR and promoted LDLR ectodomain cleavage; MT1-MMP knockdown increased cellular LDLR and reduced sLDLR, while wild-type MT1-MMP overexpression reduced LDLR and increased sLDLR, with no effect of the catalytically dead E240A mutant.
  • Liver-specific MT1-MMP knockout (MT1LKO) increased hepatic LDLR and reduced plasma sLDLR by ~67% and total cholesterol; reintroduction of human MT1-MMP reversed these effects. Conversely, MT1-MMP overexpression in C57BL/6J mice reduced liver LDLR and increased HDL and non-HDL cholesterol.
  • In apoE−/− mice, MT1-MMP overexpression increased aortic sinus lesion area (157.5 ± 21.03 vs. 238.0 ± 21.23 μm² × 10³, p = 0.0228) and plasma total cholesterol (791 vs. 896 mg/dL, p = 0.0283). Hepatic MT1-MMP knockdown in MT1Flox/apoE−/− mice reduced aortic cholesteryl ester accumulation by ~33% (7.046 vs. 4.706 μg per aorta, p = 0.0463) without significantly affecting plasma total cholesterol (p = 0.2578) or lesion size (p = 0.6081).
  • In 148 adult Chinese subjects, plasma sLDLR correlated with total cholesterol (r = 0.41, p = 0.00000028) and LDL-C (r = 0.198, p = 0.0199), and was significantly higher in medium/high cholesterol groups. sLDLR associated with apoB- and apoE-containing lipoproteins; human VLDL contained ~35-fold more sLDLR per μg protein than LDL.

Methods

  • Cell studies used Huh7.5, HepG2, Hepa1c1c7, McArdle, HEK293, and primary human/mouse hepatocytes with siRNA knockdown, plasmid/adenoviral overexpression, wild-type vs. E240A MT1-MMP, immunoblotting, co-immunoprecipitation, confocal microscopy, cell-surface biotinylation, Dil-LDL uptake, qRT-PCR, and sLDLR ELISA.
  • Mouse studies used liver-specific MT1-MMP knockout (MT1LKO via Alb-Cre), AAV/adenovirus-mediated overexpression or knockdown, chow or Western-type diet, apoE−/− and MT1Flox/apoE−/− backgrounds, plasma lipid/FPLC analysis, liver LDLR immunoblotting, and atherosclerosis quantification by aortic sinus lesion area and aortic cholesteryl ester.
  • Human data came from 148 fasting adult Chinese participants; plasma total cholesterol, LDL-C, sLDLR, and PCSK9 were measured, with gel filtration for lipoprotein distribution. Analyses used Student’s t test, one-way ANOVA with Tukey post-hoc test, and Pearson correlation.

Limitations

  • The paper states that other hepatic proteinases might also mediate LDLR shedding, noting ADAM17 can promote LDLR shedding in HepG2 cells to a small extent, and that LDLR shedding in other tissues may contribute to plasma sLDLR in MT1LKO mice; more experiments are needed.
  • The paper notes that apoE−/− mice lack apoE, so remnant lipoproteins cannot be cleared by LDLR, which may explain why MT1-MMP knockdown did not significantly affect plasma cholesterol in apoE−/− mice despite reduced aortic cholesteryl ester.
  • Evident from the text: the human analysis is cross-sectional and cannot establish causality, and the cohort is limited to adult Chinese participants, so generalizability to other populations is uncertain.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1038/s41467-021-22167-3

Cites

67 of 67 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

34 of 54 cited sources checked · 15 supported · 1 flagged · accuracy not yet measured

  • Premisecitation

    MT1-MMP null mice die at 3-4 weeks.

    “Considering that MT1-MMP null mice die at 3–4 weeks17,18”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [17] Zhou, Z. et al. Impaired endochondral ossification and angiogenesis in mice deficient in membrane-type matrix metalloproteinase I. Proc. Natl Acad. Sci. USA 97, 4052–4057 (2000). source
    • cites [18] Holmbeck, K. et al. MT1-MMP-deficient mice develop dwarfism, osteopenia, arthritis, and connective tissue disease due to inadequate collagen turnover. Cell 99, 81–92 (1999). source

      The Results section reports that 33% of MT1-MMP-deficient mice died before weaning, but most died between days 50 and 90. That contradicts the claim that MT1-MMP null mice die at 3–4 weeks. (LLM, conf=0.90)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured
  • Premisecitation

    LDLR and its family members such as VLDLR, apoER, and LRP1 undergo ectodomain shedding to release soluble forms into extracellular fluids such as cerebrospinal fluid and blood.

    “LDLR and its family members such as VLDLR, apoER and LRP1 undergo ectodomain shedding to release their soluble forms into the extracellular milieu such as cerebrospinal fluid and blood12,29,30.”
    Quote in the paperSubstantial claim2 of 3 sources checked
    • cites [12] Fischer, D. G., Tal, N., Novick, D., Barak, S. & Rubinstein, M. An antiviral soluble form of the LDL receptor induced by interferon. Science 262, 250–253 (1993). source
    • cites [29] Chen, Q., Takahashi, Y., Oka, K. & Ma, J. X. Functional differences of very-low-density lipoprotein receptor splice variants in regulating Wnt signaling. Mol. Cell Biol. 36, 2645–2654 (2016). source

      The Results section ('Presence of sVLDLR-N in CM from RPE cells and IPM'; page unavailable) reports that VLDLR undergoes ectodomain shedding. The Discussion (page unavailable) reports soluble VLDLR in mouse and human plasma. The cited paper does not establish the same claim for LDLR, apoER, or LRP1, or report soluble forms in cerebrospinal fluid. (LLM, conf=0.87)

      Experimental — accuracy not yet measured
    • cites [30] Rebeck, G. W., LaDu, M. J., Estus, S., Bu, G. & Weeber, E. J. The generation and function of soluble apoE receptors in the CNS. Mol. Neurodegener. 1, 15 (2006). source
  • Premisecitation

    Two independent studies revealed a mild but significant correlation between serum concentrations of sLDLR and LDL-C in healthy adult Japanese and Canadian white populations.

    “Consistently, two independent studies revealed a mild but significant correlation between serum concentrations of sLDLR and LDL-C in healthy adult Japanese and Canadian white population11,14.”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [11] Shimohiro, H., Taniguchi, S. I., Koda, M., Sakai, C. & Yamada, S. Association between serum soluble low-density lipoprotein receptor levels and metabolic factors in healthy Japanese individuals. J. Clin. Lab Anal. 29, 52–56 (2014). source
    • cites [14] Mayne J., et al. Associations between soluble LDLR and lipoproteins in a Caucasian Cohort and the effect of PCSK9 loss-of-function. J. Clin. Endocrinol. Metab. 103, 3486–3495(2018). source
  • Premisecitation

    Knockdown of ADAM17 has only a marginal effect on ectodomain cleavage of LDLR in HepG2 cells.

    “Knockdown of a disintegrin and metalloproteinase 17 (ADAM17), a metalloproteinase responsible for the shedding of many transmembrane proteins, however, has only a marginal effect on ectodomain cleavage of LDLR in HepG2 cells15.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [15] Strom, T. B., Tveten, K., Laerdahl, J. K. & Leren, T. P. Mutation G805R in the transmembrane domain of the LDL receptor gene causes familial hypercholesterolemia by inducing ectodomain cleavage of the LDL receptor in the endoplasmic reticulum. FEBS Open Bio 4, 321–327 (2014). source

      The Discussion reports that ADAM17 silencing by siRNA caused only a marginal increase in the 120 kDa G805R-LDLR precursor. The cited observation concerns the G805R mutant and a change in precursor abundance, rather than a direct measurement of ectodomain cleavage of LDLR generally in HepG2 cells. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
  • Interpretationcitation

    The reduction in plasma cholesterol in MT1LKO mice is likely caused by enhanced LDLR-mediated clearance of LDL, chylomicron remnants, and apoE-containing HDL particles.

    “This reduction is likely caused by enhanced LDLR-mediated clearance of LDL, chylomicron remnants, as well as apoE-containing HDL particles as reported in PCSK9 knockout mice5,33,39.”
    Quote in the paperSubstantial claim3 of 3 sources checked
    • cites [5] Rashid, S. et al. Decreased plasma cholesterol and hypersensitivity to statins in mice lacking Pcsk9. Proc. Natl Acad. Sci. USA 102, 5374–5379 (2005). source

      The Results and Discussion (pages not available in our copy) report increased hepatic LDLR, faster LDL clearance, and reduced cholesterol in Pcsk9-knockout mice. The Results also note that mouse HDL contains apoE and can bind LDLR, but the paper does not report enhanced clearance of chylomicron remnants. The MT1LKO interpretation is the citing authors’ own inference, not a finding attributed to this source. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [33] Zaid, A. et al. Proprotein convertase subtilisin/kexin type 9 (PCSK9): hepatocyte-specific low-density lipoprotein receptor degradation and critical role in mouse liver regeneration. Hepatology 48, 646–654 (2008). source

      The Cholesterol Analyses section (page unavailable) reports lower plasma LDL and HDL cholesterol in PCSK9-knockout mice, and the Discussion says PCSK9 affects circulating cholesterol through LDLR. The paper does not report clearance of chylomicron remnants or specifically identify the affected HDL as apoE-containing particles. The proposed cause of the reduction in MT1LKO mice is the citing authors’ inference, not a finding tested here. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
    • cites [39] Choi, S. et al. Decreased APOE-containing HDL subfractions and cholesterol efflux capacity of serum in mice lacking Pcsk9. Lipids Health Dis. 12, 112 (2013). source

      The Discussion (page not provided) proposes that increased LDLR promotes clearance of APOE-containing HDL in Pcsk9 knockout mice, supporting that part of the cited comparison. The paper does not report LDLR-mediated clearance of chylomicron remnants or establish this mechanism in MT1LKO mice; its discussion of LDL cholesterol does not establish the full three-particle explanation. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • Rests on an assumption: Hepatic LDLR is critical for the clearance of circulating apoB-100 and apoE-containing lipoproteins.
  • Probably not a substantial claim. 39
  • It may state two separate claims as one. 40
  • The quote only partly states this claim. 5

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    Both loss-of-function and gain-of-function PCSK9 mutations can impair PCSK9 secretion and reduce its plasma levels.

    “However, both loss-of-function and gain-of-function mutations can impair PCSK9 secretion and reduce its plasma levels34–38.”
    Quote in the paperNot a substantial claim2 of 5 sources checked
    • cites [34] Seidah, N. G. New developments in proprotein convertase subtilisin-kexin 9’s biology and clinical implications. Curr. Opin. Lipido. 27, 274–281 (2016). source
    • cites [35] Chorba, J. S., Galvan, A. M. & Shokat, K. M. Stepwise processing analyses of the single-turnover PCSK9 protease reveal its substrate sequence specificity and link clinical genotype to lipid phenotype. J. Biol. Chem. 293, 1875–1886 (2018). source

      The secretion-assay section reports that most PCSK9 mutants affecting secretion reduced it, and the Discussion specifically describes impaired secretion for S127R, a gain-of-function mutant. The paper does not establish that these secretion defects reduce plasma PCSK9 levels; its Discussion instead notes that serum levels fluctuate substantially. (LLM, conf=0.87)

      Experimental — accuracy not yet measured
    • cites [36] Cameron, J. et al. Effect of mutations in the PCSK9 gene on the cell surface LDL receptors. Hum. Mol. Genet 15, 1551–1558 (2006). source

      The ‘Autocatalytic cleavage and secretion of mutant PCSK9’ section reports no detectable secreted PCSK9 for the loss-of-function mutant G106R and reduced maturation of the gain-of-function mutant S127R. It does not establish reduced secretion for S127R or report reduced plasma PCSK9 levels for either mutation class; its measurements were made in transfected HepG2 cells. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
    • cites [37] Ruotolo, A. et al. The novel variant p.Ser465Leu in the PCSK9 gene does not account for the decreased LDLR activity in members of a FH family. Clin. Chem. Lab Med 52, e175–e178 (2014). source
    • cites [38] Kotowski, I. K. et al. A spectrum of PCSK9 alleles contributes to plasma levels of low-density lipoprotein cholesterol. Am. J. Hum. Genet 78, 410–422 (2006). source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    MT1-MMP activates pro-MMP2.

    “MT1-MMP activates pro-MMP217,22.”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [17] Zhou, Z. et al. Impaired endochondral ossification and angiogenesis in mice deficient in membrane-type matrix metalloproteinase I. Proc. Natl Acad. Sci. USA 97, 4052–4057 (2000). source
    • cites [22] Butler, G. S. et al. The TIMP2 membrane type 1 metalloproteinase “receptor” regulates the concentration and efficient activation of progelatinase A. A kinetic study. J. Biol. Chem. 273, 871–880 (1998). source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Serum levels of sLDLR are positively correlated with plasma LDL-C levels.

    “Serum levels of sLDLR are positively correlated with plasma LDL-C levels11,14.”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [11] Shimohiro, H., Taniguchi, S. I., Koda, M., Sakai, C. & Yamada, S. Association between serum soluble low-density lipoprotein receptor levels and metabolic factors in healthy Japanese individuals. J. Clin. Lab Anal. 29, 52–56 (2014). source
    • cites [14] Mayne J., et al. Associations between soluble LDLR and lipoproteins in a Caucasian Cohort and the effect of PCSK9 loss-of-function. J. Clin. Endocrinol. Metab. 103, 3486–3495(2018). source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    MT1-MMP has been reported to cleave transmembrane proteins such as death receptor-6, neuropilin-1, and LRP-1 in breast cancer cells.

    “MT1-MMP has been reported to cleave transmembrane proteins such as death receptor-6, neuropilin-1, and LDLR-related protein 1 (LRP-1) in breast cancer cells20,21.”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [20] Tam, E. M., Morrison, C. J., Wu, Y. I., Stack, M. S. & Overall, C. M. Membrane protease proteomics: Isotope-coded affinity tag MS identification of undescribed MT1-matrix metalloproteinase substrates. Proc. Natl Acad. Sci. USA 101, 6917–6922 (2004). source
    • cites [21] Rozanov, D. V., Hahn-Dantona, E., Strickland, D. K. & Strongin, A. Y. The low density lipoprotein receptor-related protein LRP is regulated by membrane type-1 matrix metalloproteinase (MT1-MMP) proteolysis in malignant cells. J. Biol. Chem. 279, 4260–4268 (2004). source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    Knockout of PCSK9 reduced cholesteryl ester accumulated in the aortas of apoE−/− mice by ~39%, even though the sizes of the entire lesions were not significantly altered.

    “Denis et al. reported that knockout of PCSK9 reduced cholesteryl ester accumulated in the aortas of apoE−/− mice by ~39%, even though the sizes of the entire lesions were not significantly altered28.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [28] Denis, M. et al. Gene inactivation of proprotein convertase subtilisin/kexin type 9 reduces atherosclerosis in mice. Circulation 125, 894–901 (2012). source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    The MT1Flox mice have been successfully used to generate knockout of MT1-MMP in monocytes/macrophages and epidermis.

    “The MT1Flox mice, in which exons 2 and 4 of the MT1-MMP gene (containing prodomain and catalytic domain) are flanked by LoxP sites, have been successfully used to generate knockout of MT1-MMP in monocytes/macrophages and epidermis26,27.”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [26] Klose, A., Zigrino, P. & Mauch, C. Monocyte/macrophage MMP-14 modulates cell infiltration and T-cell attraction in contact dermatitis but not in murine wound healing. Am. J. Pathol. 182, 755–764 (2013). source
    • cites [27] Zigrino, P. et al. Loss of epidermal MMP-14 expression interferes with angiogenesis but not with re-epithelialization. Eur. J. Cell Biol. 91, 748–756 (2012). source

  • Probably not a substantial claim.

    Premisecitation

    Active MMP2 can cleave PCSK9.

    “We have previously reported that active MMP2 can cleave PCSK923.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [23] Wang, X. et al. MMP-2 inhibits PCSK9-induced degradation of the LDL receptor in Hepa1-c1c7 cells. FEBS Lett. 589, 490–496 (2015). source

  • Probably not a substantial claim.

    Premisecitation

    Ectodomain cleavage of LDLR is inhibited by metalloproteinase inhibitors.

    “It has been shown that ectodomain cleavage of LDLR is inhibited by metalloproteinase inhibitors10,15.”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [10] Begg, M. J., Sturrock, E. D. & van der Westhuyzen, D. R. Soluble LDL-R are formed by cell surface cleavage in response to phorbol esters. Eur. J. Biochem 271, 524–533 (2004). source
    • cites [15] Strom, T. B., Tveten, K., Laerdahl, J. K. & Leren, T. P. Mutation G805R in the transmembrane domain of the LDL receptor gene causes familial hypercholesterolemia by inducing ectodomain cleavage of the LDL receptor in the endoplasmic reticulum. FEBS Open Bio 4, 321–327 (2014). source

  • It may state two separate claims as one.

    Premisecitation

    The shed ectodomains of VLDLR and apoER contain the ligand-binding domain and can bind Reelin, functioning as a competitive negative regulator to block Reelin binding to cell surface receptors.

    “The shed ectodomains of VLDLR and apoER contain the ligand-binding domain and can bind to their ligand, Reelin, functioning as a competitive negative regulator to block binding of Reelin to the cell surface receptors29,30,40.”
    Quote in the paperNot a substantial claim3 of 3 sources checked
    • cites [29] Chen, Q., Takahashi, Y., Oka, K. & Ma, J. X. Functional differences of very-low-density lipoprotein receptor splice variants in regulating Wnt signaling. Mol. Cell Biol. 36, 2645–2654 (2016). source

      The Results section (page unavailable) confirms shedding of the VLDLR ectodomain, and the Introduction (page unavailable) says that VLDLR binds Reelin. Neither passage establishes that the shed ectodomain binds Reelin or competitively blocks its binding to cell-surface receptors; the paper also does not establish those claims for apoER. Its demonstrated inhibitory effect concerns Wnt signaling instead. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • cites [30] Rebeck, G. W., LaDu, M. J., Estus, S., Bu, G. & Weeber, E. J. The generation and function of soluble apoE receptors in the CNS. Mol. Neurodegener. 1, 15 (2006). source

      The “Functions of soluble apoE receptors” section (page not supplied) says soluble ApoER2 contains a ligand-binding domain and blocks Reelin binding to cell-surface ApoER2 and VLDLR. The “Soluble ApoER2 and VLDLR” section says VLDLR also releases a soluble receptor, but our copy does not establish that soluble VLDLR binds Reelin or blocks its binding. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • cites [40] Koch, S. et al. A secreted soluble form of ApoE receptor 2 acts as a dominant-negative receptor and inhibits Reelin signaling. EMBO J. 21, 5996–6004 (2002). source

      The Results and Discussion (page numbers unavailable) show that a secreted ApoER2 fragment contains the ligand-binding domain, binds Reelin, and inhibits its binding to both ApoER2 and VLDLR. The Discussion also describes it as blocking Reelin’s interaction with receptors on neurons. The paper does not show that a shed VLDLR ectodomain itself acts as a competitive inhibitor. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    MT1-MMP efficiently mediated LRP1 shedding in fibroblastoid type but not the epithelioid variant of HT1080 cells.

    “It has been reported that MT1-MMP efficiently mediated LRP1 shedding in fibroblastoid type but not the epithelioid variant of HT1080 cells21.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [21] Rozanov, D. V., Hahn-Dantona, E., Strickland, D. K. & Strongin, A. Y. The low density lipoprotein receptor-related protein LRP is regulated by membrane type-1 matrix metalloproteinase (MT1-MMP) proteolysis in malignant cells. J. Biol. Chem. 279, 4260–4268 (2004). source

      The Results report MT1-MMP-mediated LRP cleavage in HT1080 cells, and the Discussion says stimulation of MT1-MMP enhanced the release of LRP material. Neither passage distinguishes fibroblastoid from epithelioid HT1080 variants or supports the claim that shedding occurs in one but not the other. No page numbers are available in our copy. (LLM, conf=0.87)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Mouse HDL is more enriched in apoE compared to human HDL.

    “This might be caused by the fact that mouse HDL is more enriched in apoE compared to human HDL41.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [41] Shapiro, M. D., Tavori, H. & Fazio, S. PCSK9: from basic science discoveries to clinical trials. Circ. Res. 122, 1420–1438 (2018). source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    MT1-MMP plays an essential role in tissue remodelling by cleaving extracellular matrix components and many non-extracellular matrix substrates.

    “MT1-MMP plays an essential role in tissue remodelling by cleaving extracellular matrix components and many non-extracellular matrix substrates16,20,21,43.”
    Quote in the paperNot a substantial claim3 of 4 sources checked
    • cites [16] Itoh, Y. Membrane-type matrix metalloproteinases: their functions and regulations. Matrix Biol. 44-46, 207–223 (2015). source
    • cites [20] Tam, E. M., Morrison, C. J., Wu, Y. I., Stack, M. S. & Overall, C. M. Membrane protease proteomics: Isotope-coded affinity tag MS identification of undescribed MT1-matrix metalloproteinase substrates. Proc. Natl Acad. Sci. USA 101, 6917–6922 (2004). source
    • cites [21] Rozanov, D. V., Hahn-Dantona, E., Strickland, D. K. & Strongin, A. Y. The low density lipoprotein receptor-related protein LRP is regulated by membrane type-1 matrix metalloproteinase (MT1-MMP) proteolysis in malignant cells. J. Biol. Chem. 279, 4260–4268 (2004). source
    • cites [43] Jin, G. et al. MT1-MMP cleaves Dll1 to negatively regulate Notch signalling to maintain normal B-cell development. EMBO J. 30, 2281–2293 (2011). source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    MT1-MMP is highly expressed in various types of cancer cells and promotes cancer metastasis and angiogenesis.

    “It is well documented that MT1-MMP is highly expressed in various types of cancer cells and promotes cancer metastasis and angiogenesis16,44,47–50.”
    Quote in the paperNot a substantial claim5 of 6 sources checked
    • cites [16] Itoh, Y. Membrane-type matrix metalloproteinases: their functions and regulations. Matrix Biol. 44-46, 207–223 (2015). source

      The MT1-MMP section identifies the enzyme as involved in cancer-cell invasion, metastasis, and angiogenesis, and says it was discovered in invasive cancer cells. The Gene and protein expression section describes MT1-MMP upregulation in particular cells under particular conditions, but does not establish that it is highly expressed across various types of cancer cells. Page numbers are unavailable in our copy. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • cites [44] Amar, S., Smith, L. & Fields, G. B. Matrix metalloproteinase collagenolysis in health and disease. Biochim Biophys. Acta 1864, 1940–1951 (2017). source

      Section 5, “The role of collagen catabolism in disease” (page unavailable), says MT1-MMP appears to play a significant role in tumor metastasis and that its collagenolysis has been correlated with metastasis in vivo. It does not establish that MT1-MMP is highly expressed across various cancer-cell types or that it promotes angiogenesis; its discussion of endothelial-cell migration does not establish the latter claim. (LLM, conf=0.87)

      Experimental — accuracy not yet measured
    • cites [47] Cui G., Cai F., Ding Z., Gao L. MMP14 predicts a poor prognosis in patients with colorectal cancer. Hum Pathol. 83, 36–42 (2018). source
    • cites [48] Naseh, G., Mohammadifard, M. & Mohammadifard, M. Upregulation of cyclin-dependent kinase 7 and matrix metalloproteinase-14 expression contribute to metastatic properties of gastric cancer. IUBMB Life 68, 799–805 (2016). source

      The Discussion reports MMP14 overexpression in several cancers and links it to metastasis. The Introduction says MMP14 has been suggested to facilitate angiogenesis and cancer-cell dissemination, while the Discussion says it may promote angiogenesis. These passages support the general association but are more tentative than the claim that MT1-MMP promotes both outcomes as an established fact. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
    • cites [49] Pekkonen P., et al. Lymphatic endothelium stimulates melanoma metastasis and invasion via MMP14-dependent Notch3 and beta1-integrin activation. Elife 7, e32490 (2018). source

      The Results section reports that MMP14 (MT1-MMP) is frequently induced in invasive melanoma and that high expression correlates with melanoma progression and metastasis. The Discussion links MMP14 to invasive behavior but cautions that high MMP14 alone was not sufficient for distant metastasis. The paper does not establish high expression across various cancer types or show that MMP14 promotes angiogenesis; the angiogenesis passages concern other mechanisms or an assay adapted for this study. Page numbers are unavailable in our copy. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
    • cites [50] Swayampakula, M. et al. The interactome of metabolic enzyme carbonic anhydrase IX reveals novel roles in tumor cell migration and invadopodia/MMP14-mediated invasion. Oncogene 36, 6244–6261 (2017). source

      The Discussion links MMP14 (MT1-MMP) expression to cancer progression and metastasis and reports significant expression in subsets of triple-negative breast tumors. It does not establish high expression across various cancer-cell types or say that MT1-MMP promotes angiogenesis; a search for MMP14 and angiogenesis found no supporting passage. (LLM, conf=0.85)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    MT1-MMP has been shown to shed LRP1 in breast carcinoma MCF7 cells, vascular smooth muscle cells, and cartilage.

    “Recently, MT1-MMP has been shown to shed LRP1 in breast carcinoma MCF7 cells as well as in vascular smooth muscle cells and in cartilage21,45,46.”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites [21] Rozanov, D. V., Hahn-Dantona, E., Strickland, D. K. & Strongin, A. Y. The low density lipoprotein receptor-related protein LRP is regulated by membrane type-1 matrix metalloproteinase (MT1-MMP) proteolysis in malignant cells. J. Biol. Chem. 279, 4260–4268 (2004). source
    • cites [45] Lehti, K., Rose, N. F., Valavaara, S., Weiss, S. J. & Keski-Oja, J. MT1-MMP promotes vascular smooth muscle dedifferentiation through LRP1 processing. J. Cell Sci. 122, 126–135 (2009). source
    • cites [46] Kishimoto, N., Iga, N., Yamamoto, K., Takamune, N. & Misumi, S. Virion-incorporated alpha-enolase suppresses the early stage of HIV-1 reverse transcription. Biochem Biophys. Res Commun. 484, 278–284 (2017). source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    Overexpression of PCSK9 enhances the development of atherosclerosis and knockout of PCSK9 reduces the levels of aortic cholesterol in apoE−/− mice.

    “It has been reported that overexpression of PCSK9 enhances the development of atherosclerosis and knockout of PCSK9 reduces the levels of aortic cholesterol in apoE−/− mice 28.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [28] Denis, M. et al. Gene inactivation of proprotein convertase subtilisin/kexin type 9 reduces atherosclerosis in mice. Circulation 125, 894–901 (2012). source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Knockout of PCSK9 in mice dramatically reduces plasma levels of LDL and HDL due to enhanced LDLR-mediated clearance of LDL and apoE-HDL.

    “For example, knockout of PCSK9 in mice dramatically reduces plasma levels of LDL and HDL due to enhanced LDLR-mediated clearance of LDL and apoE-HDL5,39.”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [5] Rashid, S. et al. Decreased plasma cholesterol and hypersensitivity to statins in mice lacking Pcsk9. Proc. Natl Acad. Sci. USA 102, 5374–5379 (2005). source

      The Results report nearly undetectable LDL cholesterol and an approximately 30% reduction in HDL cholesterol in Pcsk9-knockout mice. They also show increased hepatic LDLR and explain that apoE-containing mouse HDL can bind LDLRs. The paper directly measures faster LDL clearance, but does not directly measure enhanced clearance of apoE-HDL; that part of the proposed mechanism is an inference. (LLM, conf=0.83)

      Experimental — accuracy not yet measured
    • cites [39] Choi, S. et al. Decreased APOE-containing HDL subfractions and cholesterol efflux capacity of serum in mice lacking Pcsk9. Lipids Health Dis. 12, 112 (2013). source

      The Conclusions state that PCSK9 regulates LDL and HDL levels through LDLR in mice, and the Results report lower HDL cholesterol in Pcsk9 knockout mice. But the Discussion presents faster LDLR-mediated clearance of APOE-containing HDL as a hypothesis, not an established sole cause; it also reports an LDLR-independent effect. HDL reductions varied by sex and diet, so “dramatically” does not describe every group studied. (LLM, conf=0.87)

      Experimental — accuracy not yet measured

  • It may state two separate claims as one. The quote only partly states this claim.

    Findingown data

    Overexpression of wild-type MT1-MMP, but not the catalytically inactive E240A mutant, reduces LDLR protein levels in cultured hepatocytes.

    “MT1-MMP reduced cellular LDLR levels in a dose-dependent manner (Fig. 1d).”
    • Also stated in: § MT1-MMP promotes ectodomain cleavage of LDLR · plain
      “overexpression of the wild-type MT1-MMP but not MT1-E240A markedly reduced LDLR levels in HepG2, Huh7.5, Hepa1c1c7 and rat hepatoma-derived McArdle cells”
    • Also stated in: § MT1-MMP promotes ectodomain cleavage of LDLR · plain
      “LDLR protein levels were markedly increased in MT1-MMP knockdown cells (Fig. 3g) but reduced in MT1-MMP-overexpressing cells (Fig. 3h).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    In adult Chinese, plasma sLDLR levels were positively correlated with plasma LDL cholesterol levels, but to a lesser extent than with total cholesterol.

    “Plasma LDL-C levels were also significantly correlated to sLDLR levels (Supplementary Fig. 5c, r = 0.198, p = 0.0199), but to a lesser extent than plasma total cholesterol levels.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    Liver TG and total cholesterol levels are not significantly affected by hepatic MT1-MMP deficiency.

    “the lack of MT1-MMP in hepatocytes did not significantly affect the levels of liver TG or total cholesterol (Supplementary Fig. 3f, g).”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    MT1-MMP knockdown in primary human hepatocytes reduces MT1-MMP mRNA but not LDLR mRNA.

    “MT1-MMP siRNA reduced mRNA levels of MT1-MMP but not that of LDLR.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    Overexpression of MT1-MMP reduced LDLR in cultured cells and mouse liver and increased sLDLR in culture medium and mouse plasma, but had no effect on PCSK9 expression.

    “(3) overexpression of MT1-MMP reduced LDLR in cultured cells and mouse liver and increased sLDLR in culture medium and mouse plasma, but had no effect on PCSK9 expression”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    In mouse plasma, there was a shoulder of sLDLR at fraction 15 partially overlapping HDL and an additional small peak in VLDL fractions 8-10.

    “There was a shoulder at fraction 15 that was partially overlapped with HDL. An additional small peak of sLDLR was present in the VLDL fractions 8–10.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    In the adult Chinese cohort, plasma PCSK9 did not significantly associate with plasma LDL cholesterol in the whole group or in women, but did exhibit a positive correlation with plasma LDL cholesterol in men.

    “As shown in Supplementary Fig. 5d, e, plasma levels of PCSK9 did not significantly associate with plasma LDL cholesterol in the whole group or women but did exhibit a positive correlation with plasma LDL cholesterol levels in men (r = 0.2255, p = 0.0303; Supplementary Fig. 5f).”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    On a Western-type diet, hepatic MT1-MMP knockout reduces plasma non-HDL cholesterol levels.

    “hepatic knockout of MT1-MMP significantly and markedly reduced plasma levels of non-HDL and HDL cholesterol (Supplementary Fig. 5g, h).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Findingown data

    Plasma TG levels are comparable in MT1LKO and MT1Flox mice.

    “plasma TG levels were comparable in MT1LKO and MT1Flox mice (Supplementary Fig. 3e).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Findingown data

    Plasma levels of sLDLR were comparable among men, women, and undisclosed gender groups in the recruited adult Chinese cohort.

    “The levels of sLDLR were comparable among the men, women and undisclosed group (Supplementary Fig. 5a).”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    MT1-MMP regulates LDLR expression and LDL uptake in cultured hepatocytes.

    “Together, these findings demonstrate that MT1-MMP regulates LDLR expression and LDL uptake in cultured hepatocytes.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    Knockout of hepatic MT1-MMP in mice increased LDLR in the liver and reduced plasma levels of sLDLR.

    “(2) knockout of hepatic MT1-MMP in mice increased LDLR in the liver and reduced plasma levels of sLDLR”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    In adult Chinese, sLDLR levels were significantly higher in the medium/borderline-high and high plasma cholesterol groups than in the normal group, with no significant difference between medium and high groups.

    “The levels of sLDLR in the medium and high groups were significantly higher than that in the normal group, while there was no significant difference between the medium and high group (Fig. 6i).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Findingown data

    There was no significant correlation between plasma sLDLR levels and age in the adult Chinese cohort.

    “There was no significant correlation between plasma levels of sLDLR and ages (Supplementary Fig. 5b, r = 0.047, p = 0.5925).”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    Knockout of hepatic MT1-MMP in mice markedly reduced plasma sLDLR levels by ~67% and significantly increased liver LDLR levels.

    “We noticed that knockout of hepatic MT1-MMP in mice markedly reduced the levels of plasma sLDLR by ~67% and significantly increased liver LDLR levels (Fig. 4d, e).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    Leupeptin and pepstatin have no effect on LDLR levels.

    “Leupeptin (an inhibitor of serine and cysteine proteases) and pepstatin (an inhibitor of aspartyl proteases), however, had no effect on LDLR levels (Supplementary Fig. 1e).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one. The quote only partly states this claim.

    Findingown data

    MT1-MMP co-immunoprecipitates and co-localizes with LDLR in cultured hepatocytes.

    “membrane type 1-matrix metalloproteinase (MT1-MMP) co-immunoprecipitates and co-localizes with LDLR”
    • Also stated in: § MT1-MMP promotes ectodomain cleavage of LDLR · hedged
      “Together, these findings indicate that MT1-MMP associates with LDLR.”
    • Also stated in: § MT1-MMP promotes ectodomain cleavage of LDLR · hedged
      “a majority of endogenous MT1-MMP (green) and LDLR (red) could be detected on the cell periphery and co-localized in Huh7.5 cells”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. The quote only partly states this claim.

    Findingown data

    On a Western-type diet, hepatic MT1-MMP knockout reduces plasma HDL cholesterol levels.

    “hepatic knockout of MT1-MMP significantly and markedly reduced plasma levels of non-HDL and HDL cholesterol (Supplementary Fig. 5g, h).”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    MT1-MMP interacted with LDLR and knockdown of MT1-MMP expression in different cell types including human primary hepatocytes increased cellular LDLR levels but decreased sLDLR levels in culture medium.

    “In the present study, we found that (1) MT1-MMP interacted with LDLR and knockdown of MT1-MMP expression in different cell types including human primary hepatocytes increased cellular LDLR levels, but decreased sLDLR levels in culture medium”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingreasoning

    MT1LKO mice, especially on the Western-type diet, exhibited an increase in liver LDLR levels and a significant reduction in plasma levels of total cholesterol, HDL, and non-HDL cholesterol.

    “Furthermore, MT1LKO mice, especially on the Western-type diet exhibited an increase in liver LDLR levels and a significant reduction in plasma levels of total cholesterol, HDL and non-HDL cholesterol.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Study design and conductown data

    The two MT1-MMP siRNAs efficiently reduce MT1-MMP but not MT2-MMP levels.

    “The two MT1-MMP siRNAs that targeted different regions in the MT1-MMP mRNA efficiently reduced the levels of MT1-MMP but not MT2-MMP (the closest family member to MT1-MMP) (Fig. 1a).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Interpretationown data

    MT1-MMP regulates hepatic LDLR and plasma cholesterol levels in mice.

    “Thus, MT1-MMP regulates hepatic LDLR and plasma cholesterol levels in mice.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Plasma LDL-C catabolism is mainly mediated via hepatic LDLR.

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Study design and conductown data

    Body weight and plasma ALT activities are comparable in MT1LKO and MT1Flox mice.

    “Body weight and plasma ALT activities were also comparable in MT1LKO and MT1Flox mice (Supplementary Fig. 2e, f).”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Interpretationown data

    Plasma levels of cholesterol, but not PCSK9, are positively correlated with sLDLR levels.

    “Together, these findings indicate that plasma levels of cholesterol but not PCSK9 are positively correlated to sLDLR levels.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Study design and conductown data

    On a Western-type diet, MT1LKO mice show similar body weight gain, H&E staining of liver sections, plasma ALT activities, and plasma active MMP2 as MT1Flox mice.

    “MT1LKO mice showed similar body weight gain (Supplementary Fig. 4d), H&E staining of liver sections (Supplementary Fig. 4e), plasma ALT activities (Supplementary Fig. 4f) and plasma levels of active MMP2 (Supplementary Fig. 4g, h) as MT1Flox mice.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Plasma levels of sLDLR were positively associated with non-HDL-C and small LDL numbers in FH children.

    “Recently, Girona et al reported that plasma levels of sLDLR were positively associated with non-HDL-C and small LDL numbers in FH children31.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [31] Girona, J. et al. Plasma inducible degrader of the LDLR, soluble low-density lipoprotein receptor, and proprotein convertase subtilisin/kexin type 9 levels as potential biomarkers of familial hypercholesterolemia in children. J. Clin. Lipido. 12, 211–218 (2018). source

  • It may state two separate claims as one.

    Study design and conductown data

    MT1LKO mice are active, fertile and indistinguishable from floxed littermates.

    “MT1LKO mice were active, fertile and indistinguishable from floxed littermates (Supplementary Fig. 2d).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Interpretationown data

    MT1-MMP promotes ectodomain shedding of hepatic LDLR, thereby regulating plasma cholesterol levels and the development of atherosclerosis.

    “Thus, we demonstrate that MT1-MMP promotes ectodomain shedding of hepatic LDLR, thereby regulating plasma cholesterol levels and the development of atherosclerosis.”
    • Also stated in: § Introduction · boosted
      “Taken together, these findings demonstrate that hepatic LDLR ectodomain is shed by MT1-MMP and that MT1-MMP regulates plasma LDL-C metabolism and the development of atherosclerosis.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Plasma LDL-C catabolism is mainly mediated via hepatic LDLR.

  • It may state two separate claims as one.

    Study design and conductown data

    MT1-MMP siRNAs efficiently reduce mRNA levels of MT1-MMP but not MT2-MMP, LDLR, SREBP-2, PCSK9, or IDOL.

    “qRT-PCR data showed that both MT1-MMP siRNAs efficiently reduced mRNA levels of MT1-MMP but not that of MT2-MMP, LDLR, SREBP-2, PCSK9, or IDOL (Fig. 2b)”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    ADAM17 can promote LDLR shedding in HepG2 cells to a small extent.

    “For example, it has been reported that ADAM17 can promote LDLR shedding in HepG2 cells to a small extent15.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [15] Strom, T. B., Tveten, K., Laerdahl, J. K. & Leren, T. P. Mutation G805R in the transmembrane domain of the LDL receptor gene causes familial hypercholesterolemia by inducing ectodomain cleavage of the LDL receptor in the endoplasmic reticulum. FEBS Open Bio 4, 321–327 (2014). source

      Checked before — its earlier verdict is held back until a new check runs.

  • It may state two separate claims as one.

    Interpretationown data

    The main form of sLDLR likely consists of the entire ligand-binding domain of LDLR and may retain the ability to bind LDLR ligands.

    “The molecular mass of the main form of sLDLR detected in our study was around 100 kDa that should consist of the entire ligand-binding domain of the receptor, indicating that sLDLR might retain the ability to bind LDLR ligands.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Study design and conductown data

    MT1LKO mice do not display a significant collagen difference in liver sections or plasma active MMP2.

    “MT1LKO mice, however, did not display a significant collagen difference in Mason’s trichrome staining of liver sections (Supplementary Fig. 3a) and plasma active MMP2 (Supplementary Fig. 3b).”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Interpretationown data

    MT1-MMP promotes ectodomain shedding of LDLR and accelerates the development of atherosclerosis.

    “Together, these findings indicate that MT1-MMP promotes ectodomain shedding of LDLR and accelerates the development of atherosclerosis.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Hepatic LDLR is critical for the clearance of circulating apoB-100 and apoE-containing lipoproteins.

  • Probably not a substantial claim.

    Premisenone given

    The exact role of MT1-MMP in LDLR shedding is unclear.

    “The exact role of MT1-MMP in LDLR shedding, however, is unclear.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    Knockout of PCSK9 in apoE−/− mice did not significantly affect plasma cholesterol levels or atherosclerotic plaque sizes despite increased hepatic LDLR levels.

    “This was similar to a phenotype reported in the study of PCSK9 that knockout of PCSK9 in apoE−/− mice did not significantly affect plasma cholesterol levels or atherosclerotic plaque sizes despite of increased hepatic LDLR levels28.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [28] Denis, M. et al. Gene inactivation of proprotein convertase subtilisin/kexin type 9 reduces atherosclerosis in mice. Circulation 125, 894–901 (2012). source

      Checked before — its earlier verdict is held back until a new check runs.

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Study design and conductnone given

    Each qRT-PCR sample was processed in triplicate and relative gene expression was normalized to GAPDH, which had similar amplification efficiency to the target genes.

    “Each sample was processed in triplicate, and the average cycle threshold was calculated. Relative gene expression was normalized to the glyceraldehyde-3-phosphate dehydrogenase gene (GAPDH) that had a similar amplification efficiency as that of the target genes.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Study design and conductnone given

    The presence of the desired mutation and the integrity of each construct were verified by DNA sequencing.

    “The presence of the desired mutation and the integrity of each construct were verified by DNA sequencing.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one. The quote only partly states this claim.

    Study design and conductown data

    In the overexpression experiment, 8-10-week-old male apoE−/− mice were randomly divided into two groups (11-13 mice per group).

    “The mice were randomly divided into two groups (11-13 mice per group) and injected with AAV-Empty (the control group) or AAV-MT1-MMP (1.0 × 1011 gc per mouse).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim.

    Study design and conductnone given

    In the knockdown experiment, male apoE−/−/MT1Flox mice (8-10 weeks old) were randomly divided into two groups (11 mice per group).

    “Male apoE−/−/MT1Flox mice (8–10 weeks old) were randomly divided into two groups (11 mice per group) and injected with AAV-GFP (the control group) or AAV-TBG-Cre (1.0x1011 gc per mouse).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    Plasma sample from Ldlr−/− mice was used as a negative control for mouse plasma samples.

    “Plasma sample from Ldlr−/− mice was used as a negative control for mouse plasma samples.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    Same amount of whole-cell lysate was subjected to immunoblotting.

    “Same amount of whole-cell lysate was subjected to immunoblotting.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Inhibition of PCSK9 in humans markedly reduces plasma levels of LDL but not HDL cholesterol.

    “On the other hand, inhibition of PCSK9 in human markedly reduces plasma levels of LDL but not HDL cholesterol42.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [42] Sabatine, M. S. PCSK9 inhibitors: clinical evidence and implementation. Nat. Rev. Cardiol. 16, 155–165 (2019). source

  • Probably not a substantial claim.

    Study design and conductnone given

    LDL uptake was calculated by normalization of the fluorescence units to the amount of total proteins in the same well.

    “LDL uptake was calculated by normalization of the fluorescence units to the amount of total proteins in the same well.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Premisecitation

    MT1-MMP is expressed in human atherosclerotic plaques and promotes plaque rupture by enhancing degradation of collagens.

    “In addition, MT1-MMP is expressed in human atherosclerotic plaques and promotes plaque rupture by enhancing degradation of collagens51.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [51] Johnson, J. L., Sala-Newby, G. B., Ismail, Y., Aguilera, C. M. & Newby, A. C. Low tissue inhibitor of metalloproteinases 3 and high matrix metalloproteinase 14 levels defines a subpopulation of highly invasive foam-cell macrophages. Arterioscler Thromb. Vasc. Biol. 28, 1647–1653 (2008). source

      Checked before — its earlier verdict is held back until a new check runs.

  • Probably not a substantial claim.

    Study design and conductnone given

    Equal amount of total proteins was analyzed by immunoblotting.

    “Equal amount of total proteins was analyzed by immunoblotting.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Study design and conductown data

    The integrity of the cDNA of MT1-MMP and cre was verified by DNA sequencing.

    “The integrity of the cDNA of MT1-MMP and cre was verified by DNA sequencing.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductnone given

    All experiments except for where indicated were repeated at least three times.

    “All experiments except for where indicated were repeated at least three times.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Study design and conductown data

    All data met normal distribution criteria and variance between groups analysed by F-test showed no significant difference (p > 0.05).

    “All data met normal distribution criteria and variance between groups that was analysed by F-test showed no significant difference (p > 0.05).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim.

    Study design and conductnone given

    Specific levels were calculated by subtraction of counts of plasma samples of Ldlr−/− mice from that of MT1LKO and MT1Flox mice.

    “Specific levels were calculated by subtraction of counts of plasma samples of Ldlr−/− mice from that of MT1LKO and MT1Flox mice.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Study design and conductnone given

    All animal procedures were approved by the University of Alberta's Animal Care and Use Committee (protocol number AUP00000456) and conducted in accordance with Canadian Council on Animal Care guidelines.

    “All animal procedures were approved by the University of Alberta’s Animal Care and Use Committee (protocol number AUP00000456) and were conducted in accordance with guidelines of the Canadian Council on Animal Care.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim.

    Study design and conductown data

    Specific binding was determined by subtracting nonspecific binding, measured in the presence of excess unlabeled LDL, from total binding.

    “The results obtained in the presence of excess unlabeled LDL revealed the nonspecific binding. Specific binding was calculated by subtraction of nonspecific binding from the total counts measured in the absence of unlabeled LDL.”
    Quote in the paperSubstantial claim
67 of 67

  • The paper relies on this without support.

    Plasma LDL-C catabolism is mainly mediated via hepatic LDLR.

    “the catabolism of plasma LDL-C is mainly mediated via hepatic LDLR”

  • The authors state this as an assumption.

    The proteinase responsible for LDLR ectodomain shedding was unknown.

    “The proteinase responsible for LDLR ectodomain shedding, however, remains unknown.”

  • The paper relies on this without support.

    Hepatic LDLR is critical for the clearance of circulating apoB-100 and apoE-containing lipoproteins.

    “Hepatic LDLR is critical for the clearance of circulating apoB-100 and apoE-containing lipoproteins.”

  • The paper relies on this without support.

    The majority of plasma cholesterol in apoE−/− mice is remnant cholesterol.

    “It is of note that majority of plasma cholesterol in apoE−/− mice is remnant cholesterol.”

  • The paper relies on this without support.

    apoE−/− mice do not express apoE, the ligand of LDLR.

    “apoE−/− mice do not express apoE, the ligand of LDLR.”
5 of 5

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Extracellular cleavage of the LDLR catalysed by MT1-MMP releases almost the entire ectodomain intact into the extracellular space as a soluble form of the receptor (sLDLR).

    “The extracellular cleavage of the LDLR catalysed by MT1-MMP releases almost the entire ectodomain intact into the extracellular space as a soluble form of the receptor (sLDLR) (Figure 1H).”

    From Post-translational regulation of the low-density lipoprotein receptor provides new targets for cholesterol regulation (2024) · cites this paper as [58]

    The Results section (‘MT1-MMP promotes ectodomain cleavage of LDLR’; page unavailable) reports that MT1-MMP increases a cleaved LDLR ectodomain and sLDLR in culture medium. It identifies a roughly 100–120 kDa fragment, but does not establish that almost the entire ectodomain is released intact. (LLM, conf=0.82)

    Experimental — accuracy not yet measured

  • sLDLR retains the complete ligand binding domain.

    “The sLDLR retains the complete ligand binding domain and is still able to bind lipoprotein particles, potentially preventing their binding to the intact cell surface form of the receptor [58].”

    From Post-translational regulation of the low-density lipoprotein receptor provides new targets for cholesterol regulation (2024) · cites this paper as [58]

    In Results (‘sLDLR and plasma lipoproteins’), the authors say the main form of sLDLR ‘should consist of’ the entire ligand-binding domain. That supports the proposed structure, but the citing claim states it as established for sLDLR generally, rather than as an inference about its main detected form. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • sLDLR potentially prevents lipoprotein binding to the intact cell surface form of the receptor.

    “The sLDLR retains the complete ligand binding domain and is still able to bind lipoprotein particles, potentially preventing their binding to the intact cell surface form of the receptor [58].”

    From Post-translational regulation of the low-density lipoprotein receptor provides new targets for cholesterol regulation (2024) · cites this paper as [58]

    The Results section (‘sLDLR and plasma lipoproteins’; page unavailable) says sLDLR likely retains the entire ligand-binding domain and reports evidence that it associates with lipoproteins. The Discussion raises whether sLDLR-bound LDL is taken up by cell-surface LDLR as efficiently as unbound LDL, but does not establish that sLDLR prevents lipoproteins from binding that receptor. (LLM, conf=0.85)

    Experimental — accuracy not yet measured

  • Silencing of MT1-MMP in human HepG2 hepatoma cells and mouse hepatocytes increased total and cell surface LDLR, accompanied by a concomitant increase in LDL uptake.

    “Silencing of MT1-MMP in human HepG2 hepatoma cells and mouse hepatocytes increased total and cell surface LDLR, which was accompanied by a concomitant increase in LDL uptake [99].”

    From The low-density lipoprotein receptor: Emerging post-transcriptional regulatory mechanisms (2025) · cites this paper as [99]

    In Results, ‘MT1-MMP regulates LDLR expression’ (page not provided), silencing MT1-MMP increased LDLR levels in HepG2 cells, with similar results in the mouse hepatocyte line Hepa1c1c7. Increased cell-surface LDLR and LDL uptake were demonstrated in Huh7.5 cells, not in the HepG2 and mouse cells named in the claim. (LLM, conf=0.90)

    Experimental — accuracy not yet measured

  • The shed sLDLR retains its ability to bind LDL, effectively competing with the LDLR for clearance of the particle.

    “Intriguingly, the shed sLDLR retains its ability to bind LDL, effectively competing with the LDLR for clearance of the particle.”

    From The low-density lipoprotein receptor: Emerging post-transcriptional regulatory mechanisms (2025) · cites this paper as [99]

    The Results section (‘sLDLR and plasma lipoproteins’; page not provided) reports that sLDLR associates with LDL and other apoB- and apoE-containing lipoproteins, supporting its ability to bind LDL. The Discussion (page not provided) treats whether sLDLR-bound LDL is taken up as efficiently by cell-surface LDLR as an open question; it does not establish that sLDLR competes with LDLR for LDL clearance. (LLM, conf=0.89)

    Experimental — accuracy not yet measured

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Knockdown control-group size differs between Methods and Fig. 6

    Minor

    The atherosclerosis Methods say the knockdown mice were divided into two groups of 11, but the Fig. 6 caption reports 13 mice in the GFP control group.

  • Supplementary Fig. 5g-h is assigned incompatible results

    Minor

    The text cites Supplementary Fig. 5g-h for reduced plasma cholesterol in knockout mice, but later identifies those panels as analyses of PCSK9 and sLDLR in human subjects.

2 of 2

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Metadata

Authors
Alabi, A., Xia, X.-D., Gu, H.-M., Wang, F., Deng, S.-J., Yang, N., Adijiang, A., Douglas, D. N., Kneteman, N. M., Xue, Y., Chen, L., Qin, S., Wang, G., & Zhang, D.-W.
Affiliations
  • University of Alberta (CA)
  • Weifang Medical University (CN)
  • Shandong First Medical University (CN)
  • Guangzhou Medical University (CN)
ORCID
Venue
Nature Communications
Publisher
Springer Science and Business Media LLC
Published
2021-03-25
Volume
12
Issue
1
Pages
1889-1889
ISSN
2041-1723 (ISSN-L)
DOI
10.1038/s41467-021-22167-3
PMC
PMC7994674
OpenAlex
W3138042389
Semantic Scholar
e5caa74fd9848f2a7f1fc51f038ad7965e85d886
Cited by
63
References
67
Citations by year
2026: 8 · 2025: 10 · 2024: 17 · 2023: 13 · 2022: 10 · 2021: 4
FWCI
4.44
Type
journal article
Language
en
Open access
Licence
Locations
  • Nature Communications (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • RePEc: Research Papers in Economics (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
  • Heart and Stroke Foundation of Canada (G-16-00012559)
  • Gouvernement du Canada | Canadian Institutes of Health Research (CIHR PS 155994)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Biochemistry › Cholesterol and Lipid Metabolism
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cancer Research › Protease and Inhibitor Mechanisms
  • Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Lipoproteins and Cardiovascular Health
Keywords
MT1-MMP, LDL receptor, ectodomain shedding, atherosclerosis, serum cholesterol, LDL clearance, hepatic LDL receptor, ApoE-deficient mice, apolipoprotein B, cholesteryl ester accumulation, serum lipoproteins
MeSH terms
Dependovirus, Animals, Apolipoproteins E, Cholesterol Esters, Female, Humans, Lipoproteins, LDL, Male, Mice, Inbred C57BL, Receptors, LDL, Mice, Knockout, Cell Line, Tumor, Atherosclerosis, Mice, Apolipoprotein B-100, Matrix Metalloproteinase 14, Hep G2 Cells, HEK293 Cells

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

A language model drew the claims from the paper on 2026-11-08, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).

A second model labelled each claim on 2026-11-08 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).

Cited sources are checked with a language model’s help (gpt-6-sol).

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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