B2 - Autophagy as a regulator of adipose tissue inflammation and dysfunction: an Immuno-metabolic function of E2F1

We identified E2F1 as a key transcription factor driving increased autophagy gene expression in human adipose tissue (AT) in obesity. Here we hypothesize hat adipose tissue E2F1, a transcription factor that molecularly defines a high-risk obese sub­pheno­type, participates in a bi-directional E2F1-miRNA co-regulatory network, resulting in increased AT autophagy, inflammation and dysfunction. To test this hypothesis, we define the following aims:

Aim 1. To elucidate mechanisms upstream of dysregulated autophagy and inflammation:

i. Transcriptional and post-transcriptional mechanisms for E2F1 up-regulation;

ii. Obesity-related E2F1-miRNA regulatory network alterations, and

iii. Their putative role in regulating AT autophagy, inflammation and dysfunction.

Aim 2. To explore the downstream consequences of elevated adipose E2F1 and autophagy in obesity:

i. Identify pathways linked to increased AT E2F1 in obesity (unbiased approach derived from RNA-Seq of E2F1high Vs E2F1low adipose tissue of similarly obese patients);

ii. Investigate by a novel in vivo model (an inducible, adipocyte-specific Atg7-KO) whether tempering AT autophagy in obesity can relieve inflammation and metabolic-endocrine dysfunction.

Impact: These studies will unravel the role of AT macrophage autophagy, and of an E2F1-miRNA network, in dysregulating AT autophagy, inflammation, and metabolic-endocrine functions in obesity.

Figure 1. Increased human AT E2F1 expression and E2F1 mRNA stability. A. Hierarchical clustering of differentially expressed genes. Differential trans­criptome between E2F1high and E2F1low is presented, divided to clusters of upregulated and downregulated genes. B and C. Selected pathway analyses, using STRING10© protein-interaction database. Shown are predicted and/or experimentally established pathways of ECM-related genes and TNF-related superfamily genes, differentially expressed in our cohort. Line thickness represents confidence level of the interaction.

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Bechor S, Nachmias D, Elia N, Haim Y, Vatarescu M, Leikin-Frenkel A, Gericke M, Tarnovsky T, Las G, Rudich A. Adipose tissue conditioned media support macrophage lipid-droplet biogenesis by interfering with autophagic flux. Biochim Biophys Acta. 2017;1862:1001-12.


Pecht T, Haim Y, Bashan N, Shapiro H, Harman-Boehm I, Kirshtein B, Clement K, Shai I, Rudich A. Circulating blood monocyte subclasses and lipid-laden adipose tissue macrophages in human obesity. PLoS One. 2016;11:e0159350.


Slutsky N, Vatarescu M, Haim Y, Goldstein N, Kirshtein B, Harman-Boehm I, Gepner Y, Shai I, Bashan N, Blüher M, Rudich A. Decreased adiponectin links elevated adipose tissue autophagy with adipocyte endocrine dysfunction in obesity. Int J Obes (Lond). 2016;40:912-20.


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Haim Y, Tarnovscki T, Bashari D, Rudich A. A chromatin immunoprecipitation (ChIP) protocol for use in whole human adipose tissue. Am J Physiol Endocrinol Metab. 2013;305:E1172-7.


Pecht T, Gutman-Tirosh A, Bashan N, Rudich A. Periperal blood leucocyte subclasses as potential biomarkers of adipose tissue inflammation and obesity subphenotypes in humans. Obes Rev. 2014;15:322-37.


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Tirosh A, Golan R, Harman-Boehm I, Henkin Y, Schwarzfuchs D, Rudich A, Kovsan J, Fiedler G, Blüher M, Stumvoll M, Thiery J, Stampfer M, Shai I. Renal function following three distinct weight loss dietary strategies during 2 years of randomized controlled trial. Diabetes Care. 2013;36:2225-32.


Wolak T, Sion-Vardi N, Novack V, Greenberg G, Szendro G, Tarnovscki T, Nov O, Shelef I, Paran E, Rudich A. N-terminal osteopontin, rather than full-length protein or C-terminal fragment, associates with carotid plaque inflammation in hypertensive patients. Am J Hypertension. 2013;26:326-33.


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Shapiro H, Pecht T, Shaco-Levy R, Harman-Boehm I, Kirshtein B, Kuperman Y, Chen A, Blüher M, Shai I, Rudich A. Adipose tissue foam cells are present in human obesity. J Clin Endocrinol Metab. 2013;98:1173-81.


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Blüher M, Rudich A, Klöting N, Golan R,Henkin Y, Rubin E, Schwarzfuchs D, Gepner Y, Stampfer M, Fiedler M, Thiery J, Stumvoll M, Shai I. Two patterns of adipokine and other biomarker dynamics in a long term weight loss intervention. Diabetes Care. 2012;35:342-9.


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Maixner N, Kovsan J, Harman-Boehm I, Blüher M, Bashan N, Rudich A. Adipose tissue autophagy. Obesity Facts. 2012;5:710-21.


Kovsan J, Bluher M, Tarnovscki T, Kloting N, Kirshtein B, Madar L, Shai I, Golan R, Harman-Boehm I, Schon MR, Greenberg AS, Elazar Z, Bashan N, Rudich A. Altered autophagy in human adipose tissues in obesity. J Clin Endocrinol Metab. 2011;96:E268-77.


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Bluher M, Bashan N, Shai I, Harman-Boehm I, Tarnovscki T, Avinaoch E, Stumvoll M, Dietrich A, Kloting N, Rudich A. Activated Ask1-MKK4-p38MAPK/JNK stress signaling pathway in human omental fat tissue may link macrophage infiltration to whole-body Insulin sensitivity. J Clin Endocrinol Metab. 2009;94:2507-15.


Harman-Boehm I, Bluher M, Redel H, Sion-Vardy N, Ovadia S, Avinoach E, Shai I, Kloting N, Stumvoll M, Bashan N, Rudich A. Macrophage infiltration into omental versus subcutaneous fat across different populations: effect of regional adiposity and the comorbidities of obesity.J Clin Endocrinol Metab. 2007;92:2240-7.


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PROJEKT TEAM

Tal Precht, PhD student

info@bl.de

Yulia Haim, PhD student