Lower levels of leptin are associated with severity parameters in visceral leishmaniasis patients

Abstract

Visceral leishmaniasis (VL) is the most severe clinical form of leishmaniasis, and if untreated may be fatal. It affects important organs of the immune system and is characterized by a specific immunosuppression, along with intense cellular activation and cytokine storm. Moreover, VL is now recognized as a systemic inflammatory response syndrome (SIRS), in which multiple cytokines and other pro-inflammatory molecules are released. The action of these inflammatory mediators may be considered risk factors for poor prognosis and death. Leptin, a hormone derived from adipose tissue, has been described with several immunoregulatory functions in vitro and in vivo Leishmania infection models, particularly for enhancing the macrophage microbicidal mechanisms. Considering that evaluation of immunologic parameters that may be associated with this clinical scenario may help to decrease VL lethality, we evaluated whether leptin is associated with VL pathogenesis. Thirty-one patients were recruited in the active phase of VL, of which 22 were followed up until one month after therapy (1mpt). Except for creatinine levels, all clinical parameters were altered in active VL patients, especially leucocyte counts and albumin and hemoglobin levels. Also, elevated levels of lipopolysaccharide (LPS), immunoglobulins (Ig)G1 and G3 anti-Leishmania and interleukins (IL)-6 and -10 were higher than in healthy individuals. In contrast, active VL patients presented diminished serum leptin levels and positive correlation with leukocytes counts and hemoglobin and albumin levels. After 1mpt, VL patients showed a significant increase in leptin levels, reaching values similar to healthy volunteers. As expected, only LPS levels remained elevated after 1mpt. These findings suggest that leptin levels are affected in Leishmania infection and the correlation with important parameters associated with the prognosis of VL points to the involvement of this molecule in VL immunopathogenesis. Additional studies are needed to evaluate the possibility of leptin as a prognostic marker of VL.

Fig 1. Plasma LPS levels in visceral leishmaniasis (VL) patients during clinical follow up.

(A) LPS levels were analyzed in the active phase and one-month post-treatment (1 mpt) in VL patients and in healthy volunteers. (B) The insert shows the LPS levels from the same patients prospectively evaluated in two different time points (n = 22). Each symbol represents one patient. The horizontal bar represents the median values. Asterisks denote a statistically significant difference between groups, *p<0.05; **p<0.01.

Fig 2. Titers of the anti-Leishmania (L.) infantum immunoglobulin G1 (IgG1) and IgG3 in visceral leishmaniasis (VL) patients during clinical follow up.

(A and C) IgG1 and IgG3 levels of VL patients in the active phase, after one-month post-treatment (1 mpt) and in healthy volunteers. (B and D) The insert shows the IgG1 and IgG3 levels from the same patients prospectively evaluated in two different time points (n = 22). Each symbol represents one patient. The horizontal bar represents the median values. Asterisks denote a statistically significant difference between groups, *p<0.05; ***p<0.0001.

Fig 3. Plasma IL-6 and IL-10 levels in visceral leishmaniasis (VL) patients during clinical follow up.

(A) IL-6 and (C) IL-10 levels were analyzed in the active phase and one-month post-treatment (1 mpt) in VL patients and in healthy volunteers. (B and D) The insert shows the IL-6 and IL-10 levels from the same patients prospectively evaluated in two different time points (n = 22). Each symbol represents one patient. The horizontal bar represents the median values. Asterisks denote a statistically significant difference between groups, *p<0.05; **p<0.01.

Fig 4. Levels of plasma leptin in patients with visceral leishmaniasis during clinical follow up (VL).

(A) Leptin levels of VL patients in the active phase (n = 31), after one-month post-treatment (1 mpt, n = 22) and in healthy volunteers. (B) The insert shows the same patients prospectively evaluated in two different time points (n = 22). Each symbol represents one patient. The horizontal bar represents the median values. Asterisks denote a statistically significant difference between groups, *p<0.05; **p<0.01.

Fig 5. Correlations between laboratorial biomarkers of severity and leptin and cytokine levels in visceral leishmaniasis (VL) patients during active phase.

Positive correlations between the leptin levels and (A) leukocytes, (B) hemoglobin and (C) albumin levels of the VL patients in the active phase of disease. Negative correlations between IL-10 and IL-6 levels and albumin and neutrophils levels (D and E, respectively). Each symbol represents one patient in the active phase of VL. Spearman correlation. p<0.05, p<0.01, p<0.005.