Obesity and Inflammation: Evidence for an Elementary Lesion

Abstract

In obesity, an inflammatory process of the adipose tissue has been hypothesized; however, direct evidence for a tissue lesion is still lacking. Macrophage infiltration in the adipose tissue of obese individuals seems to be proven, but other alterations of the tissue have not been demonstrated. Moreover, in humans it has not been clarified whether inflammation is an early characteristic of obesity, because no data from obese children are available. In the present study, we assessed the inflammatory involvement of the adipose tissue and identified the elementary "inflammatory" lesion in a group of obese children. The study of children gives us the chance to investigate adipose tissue during early phases of obesity. In all the obese subjects, ultramicroscopic analysis of the adipose tissue demonstrated inflammatory involvement, and the extent of the lesions seemed to depend on the SD score of body mass index. The elementary lesion is a microgranuloma, with fragments of adipocytes, that evolves to fibrosis. Macrophages (and less frequently, lymphocytes or granulocytes) were found in perivascular positions. The lesions were not found in nonobese children. Our study proved that an "inflammatory" process exists in the adipose tissue of obese children, confirming previous findings in animals and obese adults and demonstrating that it is an early alteration in humans. However, the accumulation of macrophages was just one of the components of the inflammatory lesion, which also involved adipocyte degeneration, fibrosis, and, to a lesser extent, granulocyte/lymphocyte accumulation. The finding of fragments of adipocytes in the elementary lesion suggests that, at the beginning of the process, adipocytes may degenerate and that the materials generated by this process can recruit macrophages and other leukocytes. These preliminary results suggest that additional studies should be designed to clarify the cause of adipocyte fragility in obese children.

Metabolic risk-factor clustering estimation in children: to draw a line across pediatric metabolic syndrome

“…Moreover, the existence of an inflammatory process in childhood obesity has been recently confirmed. 82 In addition, a chronic liver damage, such as non-alcoholic steatohepatitis (NASH), could be taken into account for a complete individual risk estimation, based on the high NASH frequency in the pediatric obese population and on possible multiple interrelationships between NASH and MS risk factors. 83,84 Lifestyle and environmental variables seem to correlate with risk of developing the MS (for example, passive and active tobacco smoke exposure, physical inactivity and alcohol consumption), and could potentially be investigated when a risk assessment for the MS has to be carried out in a child.…”

CCL2 level is elevated with metabolic syndrome and CXCL10 level is correlated with visceral fat area in obese children

“…tions of adipose tissue by macrophages; notably, the latter phenomenon has been observed in childhood [5]. Enlarged adipocytes in obesity affect the expression or secretion levels of inflammatory cytokines, called adipocytokines, which contribute to the development of obesity-related metabolic derangements and atherosclerosis [6].…”

Excessive body weight is associated with additional loss of quality of life in children with asthma

“…2 Moreover, it was recently hypothesized that the elementary lesion of obesity might be inflammatory in origin, making a link with asthma as an inflammatory condition more plausible. 3 Furthermore, the decreased activity level associated with poorly controlled asthma may predispose a child to gain excessive body weight. Although a considerable number of studies using different designs indicate that excessive body weight might increase the risk of asthma development, the topic remains controversial because of potential methodologic limitations including definitions of asthma, different anthropometric measures, directionality of causality, and residual confounding in many of these studies.…”