28 This makes it extremely Endocrinology antagonist difficult to delineate which shedding events are involved in obesity-associated pathologies. Because the biological significance of TNFR1 shedding in NAFLD and insulin resistance was unclear, we aimed to unravel the extent

to which it controls the initiation of NAFLD and the progression towards NASH, as well as its role in the development of insulin resistance. We used knockin mutant mice expressing nonsheddable TNFR1s (p55Δns mice), which have been shown to exhibit persistent expression of the receptor at the cell surface. This dominant mutation leads to a spontaneous inflammatory response resulting in enhanced antibacterial host defenses, increased susceptibility to endotoxic shock, exacerbated TNF-dependent arthritis, and in a mild form of chronic hepatitis.29 Using this gain-of-function approach, we demonstrated PI3K Inhibitor Library ic50 that the inability of TNFR1 shedding did not result in obesity, insulin resistance, or hepatic steatosis in mice. However, p55Δns mice showed a rapid progression towards NASH. Our data therefore suggest that activation of TNFR1 ectodomain shedding does not safeguard against the development

of hepatic steatosis, obesity, or insulin resistance, although it is pivotal in attenuating the progression towards NASH. ADAM17, ADAM metallopeptidase domain17; ALT, alanine aminotransferase, AST, aspartate transaminase; Bfl1, BCL2-related protein A1; Cd11b, integrin, alpha M (Mac 1); Cd68, cluster of differentiation 68; Ciap, cellular inhibitors of

apoptosis; Col1a1, collagen type 1 alpha 1; HFD, high-fat diet; Il1β, interleukin-1β; Il6, interleukin-6; LDLR, low density lipoprotein receptor; MCD-diet, methionine choline-deficient diet; Mcp1, monocyte chemotactic Dichloromethane dehalogenase protein-1; NAFLD, nonalcoholic fatty liver disease; NASH, nonalcoholic steatohepatitis; Mmp9, matrix metallopeptidase; NF-κB, nuclear factor kappa B; OGTT, oral glucose tolerance test; p55ΔNS/+, TNFR1 nonsheddable heterozygous mice; p55ΔNS/ΔNS, TNFR1 nonsheddable homozygous mice; PBS, phosphate-buffered saline; Ppia, peptidylprolyl isomerase A (cyclophilin A); RT-PCR, real-time polymerase chain reaction; TACE, TNFα converting enzyme; TG, triglycerides; Timp1, tissue inhibitor of metalloproteinase 1; TNF, tumor necrosis factor; TNFR1, TNF receptor 1; TNFR1ns, TNFR1 nonsheddable; Traf1, TNFR-associated factor 1; wildtype mice, p55+/+. Mice containing the TNFR1 nonsheddable mutation heterozygously and homozygously (referred to as p55Δns/+ and p55Δns/Δns mice, respectively) and their wildtype littermates (p55+/+)29 in a C57Bl/6 background were purchased from the European Mouse Mutant Archive (EMMA, Monterotondo Scalo, Italy) and crossed into a C57Bl/6 background for at least 10 generations.