Recent findings point towards an important role of local macrophage proliferation also in obesity-induced adipose tissue inflammation that underlies insulin resistance and type 2 diabetes. Osteopontin (OPN) is an inflammatory cytokine highly upregulated in adipose tissue (AT) of obese and has repeatedly been shown to be functionally involved in adipose-tissue inflammation and metabolic sequelae. In the present work, we aimed at unveiling both the role of OPN in human monocyte and macrophage proliferation as well as the impact of OPN deficiency on local macrophage proliferation in a mouse model for diet-induced obesity. The impact of recombinant OPN on viability, apoptosis, and proliferation was analyzed in human peripheral blood monocytes and derived macrophages. Wild type (WT) and OPN knockout mice (SPP1KO) were compared with respect to in vivo adipose tissue macrophage and in vitro bone marrow-derived macrophage (BMDM) proliferation. OPN not only enhanced survival and decreased apoptosis of human monocytes but also induced proliferation similar to macrophage colony stimulating factor (M-CSF). Even in fully differentiated monocyte-derived macrophages, OPN induced a proliferative response. Moreover, proliferation of adipose tissue macrophages in obese mice was detectable in WT but virtually absent in SPP1KO. In BMDM, OPN also induced proliferation while OPN as well as M-CSF-induced proliferation was similar in WT and SPP1KO. These data confirm that monocytes and macrophages not only are responsive to OPN and migrate to sites of inflammation but also they survive and proliferate more in the presence of OPN, a mechanism also strongly confirmed in vivo. Therefore, secreted OPN appears to be an essential player in AT inflammation, not only by driving monocyte chemotaxis and macrophage differentiation but also by facilitating local proliferation of macrophages.

Obesity and type 2 diabetes mellitus have reached an epidemic level, thus novel treatment concepts need to be identified. Myostatin, a myokine known for restraining skeletal muscle growth, has been associated with the development of insulin resistance and type 2 diabetes mellitus. Yet, little is known about the regulation of myostatin in human obesity and insulin resistance. We aimed to investigate the regulation of myostatin in obesity and uncover potential associations between myostatin, metabolic markers and insulin resistance/sensitivity indices. Circulating active myostatin concentration was measured in the serum of twenty-eight severely obese non-diabetic patients compared to a sex and age matched lean and overweight control group (n=22). Insulin resistance/sensitivity was assessed in the obese group. Skeletal muscle and adipose tissue specimens from the obese group were collected during elective bariatric surgery. Adipose tissue samples from lean and overweight subjects were collected during elective abdominal surgery. Myostatin concentration was increased in obese compared to lean individuals, while myostatin adipose tissue expression did not differ. Muscle myostatin gene expression strongly correlated with expression of metabolic genes such as IRS1, PGC1α, SREBF1. Circulating myostatin concentration correlated positively with insulin resistance indices and negatively with insulin sensitivity indices. The best correlation was obtained for the oral glucose insulin sensitivity index. Our results point to an interesting correlation between myostatin and insulin resistance/sensitivity in humans, and emphasize its need for further evaluation as a pharmacological target in the prevention and treatment of obesity-associated metabolic complications. ^* Equal contributors

The EPHA2 tyrosine kinase receptor is implicated in tumor progression and targeted therapies resistance. We evaluated EPHA2 as a potential resistance marker to the antiepidermal growth factor receptor (EGFR) monoclonal antibody cetuximab in colorectal cancer. We studied activation of EPHA2 in a panel of human colorectal cancer cell lines sensitive or resistant to anti-EGFR drugs. The in vitro and in vivo effects of ALW-II-41-27 (an EPHA2 inhibitor) and/or cetuximab treatment were tested. Formalin-fixed paraffin-embedded tumor specimens from 82 RAS wild-type (WT) metastatic colorectal cancer patients treated with FOLFIRI + cetuximab as first-line therapy in the CAPRI-GOIM trial were assessed for EPHA2 expression by immunohistochemistry and correlated with treatment efficacy. EPHA2 was differentially activated in colorectal cancer cell lines. Combined treatment with ALW-II-41-27 plus cetuximab reverted primary and acquired resistance to cetuximab, causing cell growth inhibition, inducing apoptosis and cell-cycle G1–G2 arrest. In tumor xenograft models, upon progression to cetuximab, ALW-II-41-27 addition significantly inhibited tumor growth. EPHA2 protein expression was detected in 55 of 82 tumor samples, frequently expressed in less-differentiated and left-sided tumors. High levels of EPHA2 significantly correlated with worse progression-free survival [8.6 months; confidence interval (CI) 95%, 6.4–10.8; vs. 12.3 months; CI 95%, 10.4–14.2; P = 0.03] and with increased progression rate (29% vs. 9%, P = 0.02). A specific EPHA2 inhibitor reverts in vitro and in vivo primary and acquired resistance to anti-EGFR therapy. EPHA2 levels are significantly associated with worse outcome in patients treated with FOLFIRI + cetuximab. These results highlight EPHA2 as a potential therapeutic target in metastatic colorectal cancer.

The metabolic syndrome is becoming increasingly prevalent in the general population that is at simultaneous risk for both type 2 diabetes and cardiovascular disease. The critical pathogenic mechanisms underlying these diseases are obesity-driven insulin resistance and atherosclerosis, respectively. To obtain a better understanding of molecular mechanisms involved in pathogenesis of the metabolic syndrome as a basis for future treatment strategies, studies considering both inherent risks, namely metabolic and cardiovascular, are needed. Hence, the aim of this study was to identify pathways commonly dysregulated in obese adipose tissue and atherosclerotic plaques. We carried out a gene set enrichment analysis utilizing data from two microarray experiments with obese white adipose tissue and atherosclerotic aortae as well as respective controls using a combined insulin resistance-atherosclerosis mouse model. We identified 22 dysregulated pathways common to both tissues with p values below 0.05, and selected inflammatory response and oxidative phosphorylation pathways from the Hallmark gene set to conduct a deeper evaluation at the single gene level. This analysis provided evidence of a vast overlap in gene expression alterations in obese adipose tissue and atherosclerosis with Il7r, C3ar1, Tlr1, Rgs1 and Semad4d being the highest ranked genes for the inflammatory response pathway and Maob, Bckdha, Aldh6a1, Echs1 and Cox8a for the oxidative phosphorylation pathway. In conclusion, this study provides extensive evidence for common pathogenic pathways underlying obesity-driven insulin resistance and atherogenesis which could provide a basis for the development of novel strategies to simultaneously prevent type 2 diabetes and cardiovascular disease in patients with metabolic syndrome.

Objective: Macrophages are the main drivers of obesity‐induced adipose tissue (AT) inflammation that causes insulin resistance. Macrophages polarize toward different inflammatory (M1) or protective (M2) phenotypes. Osteopontin (OPN) is an inflammatory cytokine highly expressed in AT in obesity and known to be involved in chronic inflammatory processes. It was hypothesized that OPN polarizes macrophages into a proinflammatory phenotype.Methods: AT macrophages (ATMs) of OPN‐deficient (Spp1^−/−) and wild‐type C57BL/6 (WT) mice with obesity and bone marrow‐derived macrophages (BMDMs) of Spp1^−/− and WT mice as well as human monocyte‐derived macrophages (MDMs) polarized in the presence of OPN were investigated.Results: While ATM infiltration was lower in Spp1^−/− upon high‐fat diet, Spp1^−/− ATMs expressed more M1 and less M2 markers but less tumor necrosis factor‐α compared with WT. There was no effect of OPN deficiency on BMDM polarization. In human MDMs, the presence of OPN during polarization ambiguously altered M1/M2‐related marker expression and diminished LPS‐induced inflammatory cytokine production. Strikingly, phagocytic activity was elevated by the presence of OPN during polarization in both human MDMs and murine BMDMs.Conclusions: In contradiction to our hypothesis, data indicated that OPN does not induce inflammatory macrophages but was a signal to induce phagocytosis, which may be required due to increased adipocyte death in obesity.