Role of adipose tissue inflammation in fat pad loss induced by fasting in lean and mildly obese mice.

Inflammation induced by obesity contributes to insulin resistance and atherosclerosis. Indeed, high levels of proinflammatory cytokines trigger chronic low-grade inflammation and promote detrimental metabolic effects in the adipose tissue. On the other hand, inflammation seems to control fat pad expansion and to have important functions on lipolysis and glucose metabolism. Thus, it is possible that inflammation may also drive fat pad loss, as seen during long-fast periods. Herein, we have used fasting as a strategy to induce weight loss and evaluate the possible role of inflammation on adipose tissue remodeling. Male BALB-c mice were fed with chow diet (lean mice) or with high-carbohydrate refined diet (mildly obese mice) for 8 weeks. After that, animals were subjected to 24 h of fasting. There was a 63% reduction of adiposity in lean mice following fasting. Furthermore, the adipose tissue was enriched of immune cells and had a higher content of IL-6, TNF-alpha, IL-10, TGF-ß and CXCL-1. Interestingly, mildly obese mice, subjected to the same 24-h fasting period, lost only 33% of their adiposity. Following fasting, these mice did not show any increment in leukocyte recruitment and cytokine levels, as did lean mice. Our findings indicate that inflammation participates in fat mass loss induced by fasting. Although the chronic low-grade inflammation seen in obesity is associated with metabolic diseases, a lower inflammatory response triggered by fasting in mildly obese mice impairs fat pad mobilization.