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Dysregulation of macrophage PEPD in obesity determines adipose tissue fibro-inflammation and insulin resistance

Abstract

Resulting from impaired collagen turnover, fibrosis is a hallmark of adipose tissue (AT) dysfunction and obesity-associated insulin resistance (IR). Prolidase, also known as peptidase D (PEPD), plays a vital role in collagen turnover by degrading proline-containing dipeptides but its specific functional relevance in AT is unknown. Here we show that in human and mouse obesity, PEPD expression and activity decrease in AT, and PEPD is released into the systemic circulation, which promotes fibrosis and AT IR. Loss of the enzymatic function of PEPD by genetic ablation or pharmacological inhibition causes AT fibrosis in mice. In addition to its intracellular enzymatic role, secreted extracellular PEPD protein enhances macrophage and adipocyte fibro-inflammatory responses via EGFR signalling, thereby promoting AT fibrosis and IR. We further show that decreased prolidase activity is coupled with increased systemic levels of PEPD that act as a pathogenic trigger of AT fibrosis and IR. Thus, PEPD produced by macrophages might serve as a biomarker of AT fibro-inflammation and could represent a therapeutic target for AT fibrosis and obesity-associated IR and type 2 diabetes.

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Fig. 1: Obesity reduces adipose tissue PEPD activity and promotes PEPD release associated with fibrosis and insulin resistance.
The alternative text for this image may have been generated using AI.
Fig. 2: Pharmacological inhibition of PEPD promotes adipose tissue fibro-inflammation and insulin resistance in lean mice.
The alternative text for this image may have been generated using AI.
Fig. 3: Pepd silencing exacerbates adipose tissue fibro-inflammation and metabolic dysfunctions in diet-induced obese mice.
The alternative text for this image may have been generated using AI.
Fig. 4: ‘Fibro-inflammatory’ and ‘adipose tissue dysfunction’-related pathways are enriched in the gonadal white adipose tissue from Pepd HET mice.
The alternative text for this image may have been generated using AI.
Fig. 5: Haematopoietic-specific Pepd silencing reduced adipose tissue fibro-inflammation and improved insulin sensitivity in obese mice.
The alternative text for this image may have been generated using AI.
Fig. 6: Purified PEPD protein induces fibro-inflammation and adipose tissue insulin resistance.
The alternative text for this image may have been generated using AI.
Fig. 7: High PEPD serum levels are associated with adipose tissue insulin resistance and drives the differences between the pharmacological and genetic animal models of PEPD downregulation.
The alternative text for this image may have been generated using AI.

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Data availability

DEGs and pathways from the RNA-seq analysis are available in Supplementary Tables 1–10. The RNA-seq dataset is deposited in the Gene Expression Omnibus under accession number GSE198358. Source data are provided with this paper. All other raw data are available upon request.

Code availability

Code is available at https://github.com/bpucker/RNA-Seq_analysis/. An archived version is available at https://zenodo.org/record/6192463/.

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Acknowledgements

This work was funded by a Wellcome Trust strategic award (100574/Z/12/Z), MRC MDU (MC_UU_12012/2), H2020 EPoS (Elucidating Pathways of Steatohepatitis grant agreement 634413) and the British Heart Foundation (RG/18/7/33636). The Disease Model Core, Biochemistry Assay Lab, the Histology Core and the Genomics and Transcriptomics Core are funded by MRC_MC_UU_12012/5 and a Wellcome Trust Strategic Award (208363/Z/17/Z). We thank the Wellcome Trust Sanger Institute Mouse Genetics Project (Sanger MGP) and its funders for providing the mutant mouse line (Pepdtm1a(KOMP)Wtsi). We thank the Disease Model Core from the Wellcome-MRC Institute of Metabolic Science and A. Lukasik for their technical assistance in animal work. All animal work was carried out in the Disease Model Core (MRC Metabolic Diseases Unit (MRC_MC_UU_12012/5); Wellcome Trust Strategic Award (100574/Z/12/Z)). We also thank Genomics and Transcriptomics core, the Histology core and G. Strachan from the Imaging core for their technical assistance. All serum biochemistry was conducted by the Biochemistry Assay Laboratory (MRC Metabolic Diseases Unit (MRC_MC_UU_12012/5)). Clinical studies in France were supported by ‘Contrat de Recherche Clinic’ (CRC APHP, Fibrota to J.A.-W. and K.C.), by the National Agency of Research (ANR-Captor to C.R. and K.C.) and by EFSD (to K.C.). H2020 EPoS funded K.C. (Elucidating Pathways of Steatohepatitis grant agreement 634413). A.R.D., Y.H.L., M.D. and M.C. were funded by MRC MDU (MRC_MC_UU_00014/5). M.D. also receives funding from the National Institute for Health Research (Cambridge Biomedical Research Centre at the Cambridge University Hospitals NHS Foundation Trust). D.C. was supported by MRC MDU (MRC_MC_UU_12012/4). S.C. was supported by the ERC Senior Investigator award (669879). We also thank all the patients and their physicians, L. Genser for the surgical procedures, C. Poitou for patient recruitment and F. Marcheli for data management. R. J. F. Loos is supported by a grant from the National Institutes of Health (NIH R01DK107786). M.d.H. is a fellow of the Swedish Heart-Lung Foundation (20170872), is a Kjell and Märta Beijer Foundation researcher and is supported by project grants from the Swedish Heart-Lung Foundation (20140543, 20170678 and 20180706) and the Swedish Research Council (2015-03657 and 2019-01417). We also acknowledge the FATBANK platform promoted by the CIBEROBN and the IDIBGI Biobank (Biobanc IDIBGI, B.0000872), integrated into the Spanish National Biobanks Network, for their collaboration and coordination. The funders had no role in study design, data collection and interpretation, or submitting the work for publication. The authors’ views are their own and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care.

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Authors and Affiliations

Authors

Contributions

V.P. developed the hypothesis, designed the experiments, performed the experimental work, collected and analysed the data, coordinated and directed the project, created the images and wrote the manuscript. S.R.C. designed and conducted part of the experimental work and edited the manuscript. C.R. and J.-M.M.-N. performed and analysed human experiments. S.V. performed the BMT in mice and the GC–MS for the detection of imidopeptides. H.S., G.B., M.C.V.-B., A.R.D., M.D., M.C., S.C., S. Mora, M.M.M., A.E., S. Mukhopadhyay and M.d.H. conducted experiments. J.A.-W. and K.C. supervised enrolment and clinical phenotyping of obese participants. H.S., B.P. and D.C. performed bioinformatics analysis. D.C. also edited the manuscript. G.D., R.L., J.M.F. and K.C. provided access to human data and discussed the manuscript. A.V.P. developed the hypothesis, coordinated and directed the project, wrote the manuscript, is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. All authors critically reviewed and edited the manuscript.

Corresponding authors

Correspondence to V. Pellegrinelli or A. Vidal-Puig.

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Nature Metabolism thanks Kai Sun, Anthony Ferrante and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Christoph Schmitt, in collaboration with the Nature Metabolism team.

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Extended data

Extended Data Fig. 1 Obesity reduces AT PEPD activity and promotes PEPD release in association with AT fibrosis and insulin resistance.

a, Age, BMI, glycaemic and lipidic status in the different human cohorts. b, PEPD serum/ScW levels, BMI and metabolic parameters in obese subjects from cohort cohort 2e (n = 9) with low vs. high VsW PEPD levels. c, PEPD activity/ecplants levels, BMI, blood chemistry parameters and liver Actitest score in obese subjects (cohort 2e,f) with high (>2.065 nmol pro/mg prot/min) vs. low (<2.065 nmol pro/mg prot/min) PEPD peptidase activity in VsW. d, Area under the receiver operating curve (AUC) values (95% CI) for VsW and ScW PEPD peptidase activity (PA) to discriminate subjects with type 2 diabetes (cohort 2e,f).e, Pearson correlation between PEPD serum levels and, ScW and VsW ECM remodelling markers and metabolic parameters in obese subjects from cohort 2b (n = 14 biologically independent samples). f, g, Pepd mRNA relative expression (f), and PEPD prolidase activity (g) in ScW, GnW and liver from C57Bl/6 mice in chow (n = 6) and 58% HFD (n = 8, 20 weeks) conditions.* compared to chow diet. h, ELISA analysis of PEPD protein in serum from C57/Bl6 mice fed chow (n = 6) or 20 weeks 58% HFD (n = 8). I-k. ScW prolidase activity (i), PEPD serum level (j) and ScW peri-ad collagen in C57Bl/6 mice fed 2, 8, 16 or 28 weeks (n = 8/group) with chow diet (ch) of HFD 45% (HF). l, Prolidase activity in the serum of C57Bl6 mice fed chow (2, 28 weeks) or HFD 58% (28 weeks). m, Pearson correlation matrix between ScW and GnW ECM remodelling markers and metabolic parameters in chow and HFD conditions (n = 22). Data presented as mean values +/− SEM. Data was analysed using a two-tailed Student’s t-test (b, c, h) or a 2-way ANOVA followed by a Sidak post-hoc multiple comparisons test (f, g, i-k).

Extended Data Fig. 2 PEPD pharmacological inhibition promotes AT fibro-inflammation independently from obesity.

a-d. ALAT and ASAT serum levels (a), body weight (b), and fat mass % (c), and tissue weight (d) in mice treated 10 weeks or not (control) with CBZ-Pro (n = 8 biologically independent animals per group). e, f. Fasting insulin and FFA blood levels from CBZ-Pro-treated mice compared to control mice (n = 8 biologically independent animals per group) fed chow and HFD 58% for 16 weeks. g. Fasting insulin blood level before and 30 min after glucose injection (2 g/kg) in CBZ-Pro-treated mice compared to controls (n = 8 biologically independent animals per group). h,i. Representative images of blots and quantification of total and basal phosphorylated (Ser473) AKT in GnW (h) and gastrocnemius muscle (i) of CBZ-Pro- treated mice compared to controls (n = 8 biologically independent animals per group). j. Heat map representing the four factors extracted through exploratory factor analysis. The columns report the factors loadings of the observed variables. k. Representative images of red Sirius staining in ScW and GnW of control and CBZ-Pro treated mice (n = 8 biologically independent animals per group) fed HFD 58%, and corresponding quantification of peri-adipocyte collagen content (peri-AD) represented in % Area (excluding perivascular staining). l, m. Blood glucose levels up to 120 min. after an intraperitoneal injection of glucose (2 g/kg) in a glucose tolerance test (l) or insulin (0.75 IU/kg) in an insulin tolerance test (m) in control and CBZ-Pro treated mice (n = 8 biologically independent animals per group) fed HFD 58%. Respective AUC are represented. Data is presented as mean values +/− SEM. Data was analysed using a two-tailed Student’s t-test (a-d, h, i l, m) or a 2-way ANOVA followed by a Turkey (e-g) or Sidak (k-m) post-hoc multiple comparisons test.

Source data

Extended Data Fig. 3 Pepd silencing promotes AT fibrosis but does not affect metabolic parameters in chow fed mice.

a. Pepd RNA relative expression in ScW, GnW, liver and gastrocnemius (SKM) from pepd WT (n = 6), HET (n = 8) and KO mice (n = 5). b. Level of amino acids related to proline metabolism in the serum or GnW explant medium from pepd WT (n = 6), HET (n = 8) and KO mice (n = 5). c-f, h, k. Body length (c), body weight (d), fat mass % (e), tissue weight (f), fed glucose, fasting glucose and FFA (blood levels h), and fasting insulin blood level (k) in pepd WT (n = 6), HET (n = 8) and KO (n = 5) mice fed chow diet. g. Pearson correlations matrix between ScW and GnW ECM remodelling markers, PEPD serum levels and metabolic parameters in pepd mice fed chow (n = 19 biologically independent samples). i, j. Blood glucose levels up to 120 minutes after an intraperitoneal injection of glucose (2 g/kg) in a glucose tolerance test (i, IP-GTT) or insulin (0.75 IU/kg) in an insulin tolerance test (j, IP-ITT), and respective AUC adjusted to basal, in pepd WT (n = 6), HET (n = 8) and KO (n = 5)mice fed chow diet. l-n. Representative images of blots and quantification of total and phosphorylated (Ser473) AKT in GnW (l), liver (m) and gastrocnemius (n) of pepd WT (n = 6-11), HET (n = 6-12) and KO n = 6-8) mice fed chow diet after i.p injection of saline or insulin. 2way ANOVA with Dunnett’s (a) or Sidak’s (I, k, l-n) post-hoc multiple comparisons test; G, genotype; X, interaction. Data is presented as mean values +/− SEM. Data was analysed using a One way ANOVA followed by a Dunnett (b-f, h, k) or Sidak (i, j, l-n) post-hoc multiple comparisons test.

Source data

Extended Data Fig. 4 Pepd silencing exacerbates metabolic disturbances in HFD 58%-fed mice.

Body weight curves and fat mass % curves of pepd WT, HET and KO mice after 20 weeks HFD 45% (n = 8, 11, 9 biologically independent animals per group, respectively) and HFD 58% (n = 8, 11, 8 biologically independent animals per group, respectively). b, c. Blood glucose levels up to 120 min. after an intraperitoneal injection of glucose in a glucose tolerance test (b) or insulin (0.75 IU/kg) in an insulin tolerance test (c) with the representative AUC in pepd WT (n = 9), HET (n-11) and KO (n = 9) mice fed HFD 45%. d. Fasting glucose, insulin and FFA blood levels in pepd WT (n = 8), HET (n = 11) and KO (n = 8) mice fed HFD 45%. e. Representative images of red Sirius staining in ScW and GnW from C57Bl/6 mice fed chow (n = 6), 45%HFD (n = 8) and HFD 58% (n = 8, 20 weeks) conditions and quantification of peri-adipocyte collagen content (peri-AD) represented in % Area (excluding perivascular staining).f. Heat map of gene expression in GnW from C57Bl/6 mice fed 20 weeks with chow (n = 6), 45%HFD (n = 8) and HFD 58% (n = 8). Results are expressed as fold change over chow diet. g. Representative images of blots and quantification of total and basal phosphorylated (Ser473) AKT in gastrocnemius muscle of pepd WT, HET and KO mice fed chow (n = 5, 6, 5 biologically independent animals per group, respectively), and HFD 58% conditions (n = 5, 5, 7 biologically independent animals per group, respectively). h. Heat map of gene expression of fibro-inflammatory and functional markers in gastrocnemius of pepd WT, HET and KO mice fed chow (n = 6, 7, 6 biologically independent animals per group, respectively), and HFD 58% conditions (n = 8, 7, 8 biologically independent animals per group, respectively). i. Heat map of gene expression in GnW from pepd WT, HET and KO fed HFD 45% (n = 6, 10, 9 biologically independent animals per group, respectively) and HFD 58% (n = 8, 9, 9 biologically independent animals per group, respectively) expressed as fold change variation over chow diet; *p < 0.05 compared to chow, #p < 0.05 compared to WT. j, k. Pathway enrichment analysis of the DEGs in GnW (i) and liver (j) from pepd KO mice (n = 9) compared to WT mice (n = 8) fed HFD 45%, using different data bases (KEGG, Reactome, Biocarta, NABA and PID). The heat maps indicate the level of significant changes (false discovery rate-adjusted p-value). Data is presented as mean values +/− SEM. Data was analysed using a 2-way ANOVA followed by a Turkey post-hoc multiple comparisons test; G, genotype; X, interaction (a-c, i), or a one way ANOVA followed by a Sidak (b, c, e) or Dunnett (d, g, h) post-hoc multiple comparisons test. A two-tailed Student’s t-test was also used to analyse the data (f).

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Extended Data Fig. 5 Pepd silencing in hematopoietic cells prevent obesity and associated metabolic disturbances.

a. Prolidase activity in BMDMs during differentiation (n = 4 biologically independent samples). b. Pepd mRNA relative expression in adipocytes (AD), Mɸ (CD11b positive cells) and negative stroma-vascular fraction (SVF) isolated from GnW of WT (n = 6) and LepOb/Ob mice (n = 9). *compared to AD WT, # compared to Mφ WT. c. Abundance of PEPD measured by mass spectrometry in unstimulated human iPS-derived Mɸ differentiated from FPS10C iPS line. Relative abundance of PEPD in comparison of other detected protein in the same sample is plotted in the graph- where actin and cyclin are representing examples of high and low abundant proteins respectively. d, e. Pepd mRNA expression (d) or PEPD ELISA in culture media from BMDMs treated or not (M0) 6 h (d) or 24 (e) with LPS, dexamethasone (GC) or IL4 (n = 4 biologically independent samples). BMDMs were treated with LPS for 1,6 or 24 h: f, g. PEPD level in culture media (f) and prolidase activity in BMDMs (g). h. Prolidase activity in culture media from BMDMs treated without (control) or with LPS (100 ng/ml, 24 h) (n = 4 biologically independent samples). I, j. Blood glucose levels up to 120 min. after an intraperitoneal injection of glucose (2 g/kg) in a glucose tolerance test (i) or insulin (0.75 IU/kg) in an insulin tolerance test (j) in BMT WT (n = 8) and KO mice (n = 6) fed chow. Respective AUC are represented. k-n. Fasting glucose (k), fasting insulin (l), fasting FFA (m) and fed glucose (n) blood levels in BMT-WT (n = 8) mice compared to BMTKO mice (n = 6) fed chow and HFD 58% (20 weeks).. o, p. Tissue weight (o) and Fat mass % (p) in BMT + / + (n = 8) and −/− (n = 6) mice fed chow and HFD 58% for 20 weeks. q. Body weight curve in BMT-WT (n = 8) mice compared to BMTKO mice (n = 6) mice between 0 and 20 weeks HFD 58%. r. Representative images of red Sirius staining ScW and GnW from BMT-WT (n = 8) mice compared to BMTKO mice (n = 6) fed HFD 58% and quantification of peri-AD collagen represented as %. s. Representative images of blots and quantification of total and basal phosphorylated (Ser473) AKT in GnW of of BMT WT and KO mice fed HFD 58% (n = 6/group). Data is presented as mean values +/− SEM. Data was analysed using a One way ANOVA followed by a Dunnett (a, f, g) or Tuckey (d, e) post-hoc multiple comparisons test, or using a 2-way ANOVA followed by a Tukey (b, k—p, r) or Sidak (I, j, q) post-hoc multiple comparisons test; G, genotype; X, interaction. A two-tailed Student’s t-test was also used to analyse the data (h-j, s).

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Extended Data Fig. 6 Purified PEPD protein promotes fibro-inflammation in macrophages through EGFR signaling.

a. Cox2 mRNA relative expression in BMDMs treated or not (control) 4 h with purified PEPD protein active or denaturated (denat PEPD) (n = 3 biologically independent samples).b. Dose response effect of 4 h treatment with purified PEPD protein on cox2 mRNA relative expression in BMDMs (n = 4 biologically independent samples). c. % of cytotoxicity in BMDMs after 4 h treatment with purified PEPD protein (n = 4 biologically independent samples). d. Representative images of blots of total and phosphorylated (Ser 536) NFkB protein and beta-tubulin in BMDMs (n = 4 biologically independent samples) treated with purified PEPD protein (0, 10, 60 min or 24 h, 250 nM). e, f. Tyrosine-kinase receptor phospho-Array of multiple analytes (e) and quantification (f) of phosphorylation levels in cell extract from BMDMs treated without (control) or with purified PEPD protein (10 min, 250 nM). Data from one experiment of a pool of 4 independent macrophage preparations. g. Cox2 mRNA relative expression in BMDMs (n = 4 biologically independent samples) pre-treated (Erlo) or not (PBS) with Erlotinib 5 µM, prior 24 h treatment with (PEPD) or without (control) purified PEPD protein. * compared to control PBS, # compared to PEPD PBS. h-j. mRNA expression of Egfr (h), Cox2 (i) and Il1β (j) in RAW macrophages transfected with Si-EGFR or its negative control (Si-NEG) prior treatment with (PEPD) or without (control) purified PEPD protein (250 nM,24 h). k. Tissue and cell distribution of egfr expression from Tabula muris DataBase; l, m. Heat map of Cox2 mRNA expression (l) and prolidase activity (m) in different tissues from C57Bl/6 mice injected with saline or purified PEPD (n = 11 biologically independent animals per group). n-p. Fat mass (n), fasting glucose (o), free fatty acids (FFA, p) and insulin levels (p), and fed glucose level (p) in PEPD-injected mice compared to controls (n = 11 biologically independent animals per group). q, r. Blood glucose levels up to 120 minutes after an intraperitoneal injection of glucose (2 g/kg) in a glucose tolerance test (q, IP-GTT) or insulin (0.75 IU/kg) in an insulin tolerance test (r, IP-ITT) in PEPD-injected mice compared to controls (n = 11 biologically independent animals per group). Data is presented as mean values +/− SEM. Data was analysed using a One-way ANOVA followed by a Dunnett (b, c) or Tuckey (a) post-hoc multiple comparisons test, or using a 2-way ANOVA followed by a Tukey (g, I, j) or Sidak (l-n, q, r) post-hoc multiple comparisons test. A two-tailed Student’s t-test was also used to analyse the data (h, o, p).

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Extended Data Fig. 7 Purified PEPD protein promotes fibro-inflammation in pre-adipocytes and stellate cells through EGFR signaling.

a. Representative images of confocal analysis of anti-Collagen type I (in red,) and Bodipy staining (lipid accumulation in green) (i) and corresponding quantifications of collagen I staining (j) in 3T3-L1 adipocytes (n = 4 biologically independent samples) pre-treated (Erlo) or not (PBS) with Erlotinib (5 µM) prior treatment with (PEPD) or without (control) purified PEPD protein (250 nM) during the first 5 days of adipogenic differentiation. * compared to control PBS, # compared to PEPD PBS. X, interaction. b. Il-6 level in culture media of mature adipocytes isolated from ScW of C57Bl/6 mice treated or not (control) with purified PEPD protein (250 nM, 24 h, n = 6 biologically independent animals per group). c. Representative images of confocal analysis of anti-Collagen type IV (in green,) and Actin staining (in red) and corresponding quantifications of collagen IV staining in stellate cells (n = 3 biologically independent samples) pre-treated (Erlo) or not (PBS) with Erlotinib (5 µM) prior treatment with (PEPD) or without (control) purified PEPD protein (250 nM). d. Gene expression profile in stellate cells (n = 4) pre-treated (Erlo) or not (PBS) with Erlotinib (5 µM) prior treatment with (PEPD) or without (control) purified PEPD protein (250 nM). e. AST serum level in PEPD-injected mice compared to controls (n = 11/group). f. Representative images of H&E and Sirius staining in the liver from PEPD-injected mice compaired to control (n = 11 biologically independent animals per group, a), and quantification of lipid droplet (steatosis) and collagen contents (fibrosis). g. Liver gene expression profile in PEPD-injected mice compared to controls (n = 11 biologically independent animals per group). h. Representative images of red Sirius staining in gastrocnemius from PEPD-injected mice compaired to control (n = 11 biologically independent animals per group), and quantification of collagen content (fibrosis). i. Gastrocnemius gene expression profile in PEPD-injected mice compared to controls (n = 11 biologically independent animals per group). j. Gene expression profile in muscle fibroblasts pre-treated (Erlo) or not (PBS) with Erlotinib (5 µM) prior treatment with (PEPD) or without (control) purified PEPD protein (250 nM, 5 days). k. Representative images of confocal analysis of anti-Collagen type I (in green,) and αSMA staining (in red), and corresponding quantifications of collagen I and αSMA stainings in muscle fibroblasts (n = 4 biologically independent samples) pre-treated (Erlo) or not (PBS) with Erlotinib (5 µM) prior treatment with (PEPD) or without (control) purified PEPD protein (250 nM, 5 days). Data is presented as mean values +/− SEM. Data was analysed using a 2-way ANOVA followed by aTukey post-hoc multiple comparisons test (a, c, d, j, k), or using a two-tailed Student’s t-test (b, e-i).

Extended Data Fig. 8 High PEPD serum levels is associated with AT insulin resistance and drives the differences between the pharmacologic and genetic animal models of PEPD down-regulation.

a. Heat map representing the four factors extracted through EFA performed among mice fed chow. The columns report the factors loadings of the observed variables. b, c. Pearson correlation matrix between ScW and GnW ECM remodelling markers, PEPD serum levels and metabolic parameters in the mice from the four models (PEPD, CBZ-Pro, BMT and PEPD-injection) fed chow (b) or chow+HFD (c). Metabolic/fibro-inflammatory parameters from the four animal models (that is CBZ-Pro, PEPD, BMT and PEPD-injection) were plotted according to factor 1 and 3.

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Pellegrinelli, V., Rodriguez-Cuenca, S., Rouault, C. et al. Dysregulation of macrophage PEPD in obesity determines adipose tissue fibro-inflammation and insulin resistance. Nat Metab 4, 476–494 (2022). https://doi.org/10.1038/s42255-022-00561-5

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