The Pathogenesis of Obesity-Associated Adipose Tissue Inflammation

Obesity is characterized by a state of chronic, low-grade inflammation. However, excessive fatty acid release may worsen adipose tissue inflammation and contributes to insulin resistance. In this case, several novel and highly active molecules are released abundantly by adipocytes like leptin, resistin, adiponectin or visfatin, as well as some more classical cytokines. Most likely cytokines that are released by inflammatory cells infiltrating obese adipose tissue are such as tumor necrosis factor-alpha (TNF-alpha), interleukin 6 (IL-6), monocyte chemoattractant protein 1 (MCP-1) (CCL-2) and IL-1. All of those molecules may act on immune cells leading to local and generalized inflammation. In this process, toll-like receptor 4 (TLR4)/phosphatidylinositol-3'-kinase (PI3K)/Protein kinase B (Akt) signaling pathway, the unfolded protein response (UPR) due to endoplasmic reticulum (ER) stress through hyperactivation of c-Jun N-terminal Kinase (JNK) -Activator Protein 1 (AP1) and inhibitor of nuclear factor kappa-B kinase beta (IKKbeta)-nuclear factor kappa B (NF-kappaB) pathways play an important role, and may also affect vascular endothelial function by modulating vascular nitric oxide and superoxide release. Additionally, systemic oxidative stress, macrophage recruitment, increase in the expression of NOD-like receptor (NLR) family protein (NLRP3) inflammasone and adipocyte death are predominant determinants in the pathogenesis of obesity-associated adipose tissue inflammation. In this chapter potential involvement of these factors that contribute to the adverse effects of obesity are reviewed.