Expansion of adipose tissue mass by hypertrophy and hyperplasia is the hallmark of obesity. An automated cDNA screen was established to identify secreted human proteins with an inhibitory effect on adipocyte differentiation and, thereby, a potential inhibitory effect on adipose tissue growth. A member of the TNF superfamily, TNF-like weak inducer of apoptosis (TWEAK; TNF superfamily 12) was identified by means of high-throughput screening with the lipophilic dye Nile Red as an inhibitor of murine adipocyte differentiation and, subsequently, also of human adipocyte differentiation. TWEAK inhibited lipid deposition in a dose-dependent manner without causing cytotoxic effects. This inhibitory action was mimicked by an agonistic antibody of the TWEAK receptor. The TWEAK receptor (fibroblast growth factor inducible 14; CD266) was expressed on human primary preadipocytes and mature adipocytes. Knockdown of TWEAK receptor by short-hairpin RNA abolished the inhibitory effect of TWEAK on cell differentiation, demonstrating that the effects of TWEAK are mediated by its specific receptor. Inhibition of differentiation was the result of interference at an early step of transcriptional activation as assessed by decreased peroxisome proliferator-activated receptor-gamma, CCAAT enhancer-binding protein alpha (C/EBPalpha), and CCAAT enhancer-binding protein beta (C/EBPbeta) mRNA expression. In contrast to TNFalpha, basal and insulin-stimulated glucose uptake and lipolysis of terminally differentiated mature adipocytes and secretion of proinflammatory cytokines were not altered in the presence of TWEAK, and nuclear factor kappa B activity was only weakly induced. We conclude from our findings that TWEAK and the corresponding agonistic antibody have the potential to prevent adipose tissue growth without adversely influencing central metabolic pathways or proinflammatory cytokine secretion in adipose tissue.

Objective: The member of the tumor necrosis factor family LIGHT (lymphotoxin-like inducible protein that competes with glycoprotein D for herpesvirus entry on T cells; TNFSF14 (tumor necrosis factor super family protein 14) is primarily expressed in lymphocytes, in which it induces the expression of pro-inflammatory cytokines and alterations of lipid homeostasis. Recently, the protein was shown to be upregulated in obesity and to induce cytokine secretion from adipocytes. Research Methods and Procedures: Using an automated complementary DNA (cDNA) screen, LIGHT was identified to inhibit adipose differentiation. As cellular models for adipogenesis mouse 3T3-L1, human SGBS (Simpson-Golabi-Behmel syndrome) and primary human preadipocytes differentiated in vitro were used as well as primary human adipocytes to study adipocyte functions. Analysis of lipid deposition by Oil Red O staining, mRNA expression by quantitative reverse transcriptase-PCR, nuclear factor (NF)-kB activation as well as protein secretion by enzyme linked immunosorbent assay and Luminex technology was performed. Results: LIGHT was found to inhibit lipid accumulation in the three models of preadipocytes in a dose-dependent manner without cytotoxic effects. This inhibition of differentiation was probably because of interference at early steps of adipogenesis, as early exposure during differentiation showed the strongest effect, as assessed by decreased peroxisome proliferator-activated receptor-g (PPARg) and CCAAT/enhancer-binding protein-a (C/EBPa) mRNA expression. In contrast to TNFa, basal and insulinstimulated glucose uptake and lipolysis of terminally differentiated mature adipocytes were not altered in the presence of LIGHT. At a concentration sufficient to inhibit differentiation, secretion of proinflammatory cytokines was not significantly induced and NF-kB activity was only modestly induced compared with TNFa. Conclusion: LIGHT is a novel inhibitor of human adipocyte differentiation without adversely influencing central metabolic pathways in adipocytes.

when using infliximab, special awareness of potential risks is necessary in patients with chronic infections or in a state of immunodeficiency.