Effect of an Anti-Oxidant Treatment on Resistin Serum Levels.A Randomized Study

INTRODUCTION

Background

Resistin, a recently described adipokine, belonging to the cysteine-rich secretory protein family, was originally described as an adipocyte-derived polypeptide, that provides the link between obesity and insulin resistance in mice1-2. However, resistin is expressed at very low concentrations in human adipose cells, whereas at high levels in mononuclear leukocytes, macrophages, spleen, bone marrow cells. The striking differences in the genomic organization and cellular source of resistin in rodents make the biological effects found in the mouse not readily transferable to humans3-5. Accordingly, an increasing number of reports raised doubts regarding the possibility of an important relationship between human resistin and various metabolic disturbances, characteristic of obesity and type 2 diabetes4-5. Resistin was originally found to be related to proteins induced during lung inflammation6, and the high expression levels of resistin in leukocytes, the associations between this protein and inflammatory markers, the property to stimulate in vivo inflammatory cytokines suggest the possibility that resistin may be involved in the inflammation process6.

Data supporting the participation of resistin in oxidative processes have been sporadically published. A significant interaction among a single nucleotide polymorphism in the promoter of the human resistin gene and a marker of oxidative stress (NAD(P)H:quinone oxidoreductase I) has been found7. Retinoic acid, the acid form of vitamin A, inhibited the expression of resistin in mice and reduced the higher resistin levels of ten males affected by psoriasis8. Resistin serum levels were inversely associated with nitrotyrosine (NT), a product of free radical activity9.

A pilot-analysis performed in five healthy volunteers showed that oral administration of vitamin C for 15 days determined a slight reduction in resistin serum levels.