Figure 1.

The cellular transition from lean to obese hypertrophied adipose tissue leads to elevated inflammation and inhibition of adipogenesis. Overnutrition or lack of exercise can lead to hypertrophy growth of adipocytes and eventually obesity. During this process, adipocytes become mature and increase in size. Adipocyte maturation promotes the secretion of FFA and a variety of proinflammatory adipokines (such as leptin, resistin, visfatin) and inhibits the expression of anti-inflammatory adipokine (adiponectin) and antimicrobial peptide CAMP. In addition, increased local levels of WNT and TGFβ inhibit the adipogenic potential of pAds, therefore blocking adipogenesis and adipocyte hyperplasia in obese adipose. Furthermore, the expression of a panel of proinflammatory cytokines and chemokines, including IL-6, CCL2, IL-1β, and TNF-α, are secreted by adipocytes and pAds, and infiltrated macrophages are increased in obese adipose. Together, obesity increases adipose tissue secretome, leading to the development of a chronic low-grade inflammatory state in individuals who are obese. FB, fibroblast; FFA, free fatty acid; pAd, preadipocyte; WAT, white adipose tissue.