281 Increased Leptin Levels in Children with Infections

Abstract

Leptin is an adipocyte-derived hormone/cytokine that links nutritional status with neuroendocrine and immune functions. As a hormone, leptin regulates food intake and basal metabolism, and is sexually dimorphic that is, its serum concentration is higher in females than in males with a similar body fat mass. As a cytokine, leptin can affect thymic homeostasis and the secretion of acute-phase reactants such as interleukin-1 and tumour-necrosis factor. Similar to other pro-inflammatory cytokines, leptin promotes Thelper1 (TH1)-cell differentiation and can modulate the onset and progression of autoimmune responses in several animal models. Many studies in animals have demonstrated that leptin levels increase acutely during infection and inflammation. We studied the leptin response to infections in 27 children with bacterial infections mainly respiratory and urinary tract. Serum Amyloid A protein (SAA) and C-reactive protein (CRP) in serum were measured by particle-enhanced immunonephelometric assays (BNProSpec Dade Behring), procalcitonin (PCT) levels were determined by chemiluminescence (Brahms), while leptin levels were measured by an enzymatically amplified two-step sandwich-type immunoassay (DSL). The main results of the study are summarized in the table:

Table 1

Leptin levels increased in all patients independently of their BMI, at diagnosis of the infection and returned to normal levels after treatment. This is an indication of normal expression of leptin genes and leptin receptor and this suggests that leptin is also an inflammatory marker. Similar results have been described in patients with sepsis, whereas the non-increase of leptin levels was associated with increased mortality. The secretion of leptin in the first hours of inflammation in children is stimulated by the endotoxins of bacteria as it has been shown in animal models. Leptin seems to play an important role being part of the cytokine network and modulating the inflammatory-immune response and the host defense mechanisms.

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