Characterization of obesity-related diseases and inflammation using single cell immunophenotyping in two different diet-induced obesity models.

Abstract

Obesity is a growing problem worldwide and a major risk factor for many chronic diseases. The accumulation of adipose tissue leads to the release of significant amounts of pro-inflammatory cytokines and adipokines, resulting in a low-grade systemic inflammation. However, the mechanisms behind the development of obesity-related diseases are not fully understood. Therefore, our study aimed to investigate the pathological changes and inflammatory processes at systemic level and in individual organs in two different diet-induced mouse obesity models. Male C57BL6/J mice were fed by high-fat diet (HFD), high-fat/high-fructose diet (HFD + FR) or normal chow for 21 weeks starting at 3 months of age (n = 15 animals/group). Insulin resistance was tested by oral glucose tolerance test. Pathological changes were investigated on hematoxylin-eosin-stained liver and brown adipose tissue sections. The gene expression levels of adipokines and cytokines were analyzed by qPCR in adipose tissues, whereas serum protein concentrations were determined by multiplex immunoassays. Immunophenotyping of isolated blood, bone marrow and spleen cells was performed by single-cell mass cytometry. Weight gain, glucose intolerance and hepatic steatosis were more severe in the HFD + FR group than in the control and HFD groups. This was accompanied by a higher level of systemic inflammation, as indicated by increased expression of pro-inflammatory genes in visceral white adipose tissue and by a higher serum TNFα level. In addition, immunophenotyping revealed the increase of the surface expressions of CD44 and CD69 on various cell types, such as CD8+ and CD4 + T-cells, B-cells and macrophages, in animals with obesity. The combination of HFD with fructose supplementation promotes more properly the symptoms of metabolic syndrome. Therefore, the combined high-fat/high-fructose nutrition can be a more suitable model of the Western diet. However, despite these differences, both models showed immunophenotypic changes that may be associated with increased risk of obesity-related cancer.