Glutathione-dependent enzyme activities of peripheral blood mononuclear cells decrease during the winter season compared with the summer in normal-weight and severely obese adolescents

Oxidative stress-related inflammation is known to play a vital role in obesity-associated cardiovascular disease, contributing to the early stages of the pathology as well as during its development. Therefore, it is of great interest to understand how obesity-induced stress modulates antioxidant enzyme activity during puberty. To this end, 27 severely obese adolescents (body mass index > 30, z-score > 3.7) were recruited from a paediatric weight management centre. Eighteen were recruited during the summer and nine in the winter. All underwent a 4-month weight loss programme consisting in diet and physical activity. Twenty normal-weight age-matched adolescents were recruited from the same geographical area to serve as controls. Blood samples were extracted, and antioxidant enzyme activities were determined in peripheral blood mononuclear cells (PBMCs) and erythrocytes. The enzymes studied included catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase. Severely obese adolescents presented lower PBMC-glutathione reductase activity than their corresponding normal-weight counterparts. In addition, glutathione-dependent activities tended to be lower in both groups during the winter compared with summer. These changes coincided with differences in circulating vitamin D levels. Results may suggest that season-dependent factors such as vitamin D could affect glutathione-dependent activities in severely obese as well as in normal-weight adolescents.