ORIGINAL ARTICLE Decreased adiponectin links elevated adipose tissue autophagy with adipocyte endocrine dysfunction in obesity N Slutsky 1 , M Vatarescu 1 , Y Haim 1 , N Goldstein 1 , B Kirshtein 2 , I Harman-Boehm 2 , Y Gepner 3 , I Shai 3 , N Bashan 1 , M Blüher 4 and A Rudich 1,5 BACKGROUND/OBJECTIVES: Adipose tissue (AT) autophagy gene expression is elevated in human obesity, correlating with increased metabolic risk, but mechanistic links between the two remain unclear. Thus, the objective of this study was to assess whether elevated autophagy may cause AT endocrine dysfunction, emphasizing the putative role of adiponectin in fat–liver endocrine communication. SUBJECTS/METHODS: We utilized a large (N= 186) human AT biobank to assess clinical associations between human visceral AT autophagy genes, adiponectin and leptin, by multivariate models. A broader view of adipocytokines association with elevated autophagy was assessed using adipocytokine array. Finally, to establish causality, ex vivo studies utilizing a murine AT–hepatocyte cell line co-culture system was used. RESULTS: Circulating high-molecular-weight adiponectin and leptin levels were associated with human omental-AT expression of ATG5 mRNA, associations that remained significant (β = - 0.197, P= 0.011; β = 0.267, P o0.001, respectively) in a multivariate model adjusted for age, sex, body mass index and interleukin-6 (IL-6). A similar association was observed with omental-AT LC3A mRNA levels. Bafilomycin-A1 (Baf A) pretreatment of AT explants from high-fat-fed (HFF) mice had no effect on the secretion of some AT-derived endocrine factors, but partially or fully reversed obesity-related changes in secretion of a subset of adipocytokines by 430%, including the obesity-associated upregulation of IL-6, vascular endothelial growth factor, tumor necrosis factor alpha (TNFα) and certain insulin-like growth factor-binding proteins, and the HFF-induced downregulated secretion of IL-10 and adiponectin. Similarly, decreased adiponectin and increased leptin secretion from cultured adipocytes stimulated with TNFα+IL-1β was partially reversed by small interfering RNA-mediated knockdown of ATG7. AT explants from HFF mice co-cultured with Hepa1c hepatoma cells impaired insulin-induced Akt and GSK3 phosphorylation. This effect was significantly reversed by pretreating explants with Baf A, but not if adiponectin was immunodepleted from the conditioned media. CONCLUSIONS: Reduced secretion of adiponectin may link obesity-associated elevated AT autophagy/lysosomal activity with adipose endocrine dysfunction. International Journal of Obesity (2016) 40, 912–920; doi:10.1038/ijo.2016.5 INTRODUCTION Autophagy (‘self-digestion’) is increasingly demonstrated to be up- or downregulated in obesity, but the functional and clinical significance of this dysregulation largely remains elusive, 1 for several reasons. First, autophagy in different tissues seems differentially affected by obesity: it is downregulated in the liver (mouse models), 2,3 but reported to be upregulated in AT of both mice and humans in most, 4–8 though not all, 9,10 studies. Second, in obese mice, diminished liver autophagy functionally contributes to insulin resistance. 3 Conversely, in adipocytes and in adipose tissue (AT), elevated autophagy was suggested to reflect impaired insulin signaling (decreased adipocyte mTOR activity, since mTOR inhibits autophagy), 6 and to strongly associate with whole-body insulin resistance. 4,5 Moreover, obese patients with increased intra-abdominal (visceral) adiposity had higher AT autophagy than patients with similar body mass index, but with the more cardiometabolically benign subcutaneous fat distribution. 5 Thus, AT autophagy is likely upregulated in obesity, associating with higher cardiometabolic risk. As most clinical studies mentioned above rely on cross-sectional analyses, it remains unclear whether elevated AT autophagy is causal for, is the consequence of, or acts to protect against, adipose dysfunction in obesity. In mice, adipocyte-specific genetic deletion of autophagy genes (mainly Atg7 or Atg5) resulted in a ‘browning’ phenotype: 11–13 AT exhibited key features of brown fat, and mice were lean, hyper-metabolic and resistant to obesity. These findings suggest that elevated AT autophagy serves as an obesity-associated process for AT ‘whitening’ (that is, contributing to adipocyte energy storage capacity rather than energy dissipa- tion). Yet, the genetic defect in these knockout animals is developmental, occurring during adipogenesis, 1,2 thereby render- ing the relevance to obesity-related activated autophagy in mature adipocytes questionable. Addressing this major question, human AT explants were incubated with the PI-3 kinase inhibitor 3-methyladenine (3-MA), which inhibits autophagosome 1 Department of Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel; 2 Soroka Academic Medical Center and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel; 3 Department of Epidemiology, Ben-Gurion University of the Negev, Beer-Sheva, Israel; 4 Department of Medicine, University of Leipzig, Leipzig, Germany and 5 National Institute of Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel. Correspondence: Professor A Rudich, Department of Clinical Biochemistry and Pharmacology, and the National Institute of Biotechnology in the Negev, Beer-Sheva 84103, Israel. E-mail: rudich@bgu.ac.il Received 2 July 2015; revised 15 November 2015; accepted 9 December 2015; accepted article preview online 20 January 2016; advance online publication, 16 February 2016 International Journal of Obesity (2016) 40, 912 – 920 © 2016 Macmillan Publishers Limited All rights reserved 0307-0565/16 www.nature.com/ijo