Leptin and Inflammation

Abstract

The past few years of research on leptin have provided important information on the link between metabolism and immune homeostasis. Adipocytes influence not only the endocrine system but also the immune response through several cytokine-like mediators known as adipokines, which include leptin. It is widely accepted that leptin can directly link nutritional status and pro-inflammatory T helper 1 immune responses, and that a decrease of leptin plasma concentration during food deprivation can lead to an impaired immune function. Additionally, several studies have implicated leptin in the pathogenesis of chronic inflammation, and the elevated circulating leptin levels in obesity appear to contribute to the low-grade inflammatory background which makes obese individuals more susceptible to increased risk of developing cardiovascular diseases, type II diabetes, or degenerative disease including autoimmunity and cancer. Conversely, reduced levels of leptin such as those found in malnourished individuals have been linked to increased risk of infection and reduced cell-mediated immune responses. We discuss here the functional influences of leptin in the physiopathology of inflammation, and the effects of leptin in the modulation of such responses.

Conflict of interest statement

Disclosure

The authors declare no conflict of interests.

Figures

Figure 1

Leptin is at the interface between metabolism and inflammatory responses. Leptin production by the adipose tissue facilitates the secretion of proinflammatory cytokines such as TNF, IL-1 and IL-6, which in turn promote the release of leptin from adipocytes. More leptin is available when the body fat mass is large, such as in obesity. Excess of leptin promotes inflammation and and the expansion of effector T cells (Teff) but it constrains the proliferation of regulatory T cells (Tregs), whereas reduced leptin levels facilitate the activity of the Tregs but associate with reduced number of Teff.

Figure 2

Schematic representation of the dichotomous association between leptin levels and pathological conditions.

Figure 3

A healthy immune status associates with balanced serum leptin levels.