Background: LIGHT (lymphotoxin-like inducible protein that competes with glycoprotein D for herpesvirus entry on T cells) is a member of the tumor necrosis factor (TNF) family, primarily expressed in lymphocytes, which was associated with the induction of pro-inflammatory cytokines and alterations of lipid homeostasis in animal models. We aimed to analyze whether LIGHT has a role in the human obesity-associated inflammatory status.
Methods: The association between circulating LIGHT concentrations and clinical variables was studied in 190 subjects with different degrees of obesity and glucose tolerance. The expression and release of 21 different cytokines, and the expression of genes involved in lipid metabolism were also evaluated after stimulation with LIGHT in cultured human differentiated adipocytes.
Results: Serum LIGHT concentrations positively associated with body mass index (BMI), fat mass, glycated hemoglobin and fasting triglycerides, and negatively with high-density lipoprotein cholesterol. Circulating LIGHT concentrations were significantly increased in morbidly obese subjects and in patients with type 2 diabetes. LIGHT induced the secretion of several cytokines and upregulated the expression and secretion of interleukin-6 (IL-6), IL-8, Growth Regulated Oncogene (GRO) and monocyte chemotactic protein-1 (MCP-1). These observations were concomitant with the activation of nuclear factor (NF)-kappaB signalling in human differentiated adipocytes. LIGHT also upregulated the expression and synthesis of its own receptor (herpesvirus entry mediator (HVEM)) and decreased the expression of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) and fatty acid synthase.
Conclusion: These data suggest that LIGHT may have a role in mediating chronic inflammation and alterations of lipid metabolism in obese subjects.