The hidden linkage between childhood obesity and immune system diseases
The hidden linkage between childhood obesity and immune system diseases
Ata Khosh Lahni,1Sepideh Meidaninikjeh,2,*
1. Department of Clinical Laboratory Sciences, Ardabil Branch, Islamic Azad University, Ardabil, Iran 2. PhD of Microbiology, Department of Microbiology, Faculty of Biological Sciences, Alzahra University, Tehran, Iran
Introduction: Obesity, which is commonly measured by body_ mass_ index (BMI), is recognized as one of the growing medical problems of the 21st century in children. It has nearly tripled between 1975 and 2016 (1). Obesity affects many organs and causes various diseases, including metabolic, cardiovascular and liver diseases. However, one of the most important organs affected by obesity and fat tissue is the immune system. Immune system dysfunction can cause many diseases including autoimmune diseases such as multiple sclerosis (MS), allergies and cancers (2). Therefore, childhood obesity is an important medical issue that requires further studies.
Methods: In this study, articles about childhood obesity and immune system diseases were searched and reviewed from Scopus and web of sciences databases.
Results: The increase in the size and number of fat cells due to weight gain and obesity leads to the secretion of pro-inflammatory molecules, causing chronic inflammation in the body. For instance, macrophages, the most common type of immune cell in adipose tissue, are associated with obesity. In obese individuals, there is a development of M1 macrophage phenotype, which is directly linked to systemic inflammation in the body. Conversely, M2 macrophages play regulatory and homeostatic roles. Additionally, neutrophils, mast cells, and dendritic cells (DC) in adipose tissues contribute to the inflammation process by releasing pro-inflammatory mediators (3). In obesity, the secretion of two pro-inflammatory cytokines interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α) increases. These cytokines contributed to systematic inflammation by inhibition an anti-inflammatory factor called adiponectin in the body. IL-6 is directly related to visceral and peri-abdominal obesity by accelerating cell proliferation, angiogenesis and metastasis. Moreover, TNF-α increases cell proliferation and DNA damage, leading to tumor growth in obese individuals. Studies have found a direct correlation between BMI in children and adolescence and the mortality rate of various adult cancers, such as liver, colon, and kidney (3-5). Furthermore, inflammatory conditions resulting from obesity are significantly associated with autoimmune diseases, including type 1 diabetes (T1D) and MS (6).
Conclusion: Obesity and excess adipose tissue in children and adolescents can have adverse effects on the immune system, leading to systematic inflammation and diseases such as type 1 diabetes, multiple sclerosis and various cancers. Therefore, controlling weight and BMI in children and adolescents can be beneficial for disease prevention.