Expression of CD25 in Individuals with Obesity with or Without Insulin Resistance after Following a North American Diet

Obesity and insulin resistance (IR) are associated with systemic inflammation, lower immune function, and a higher risk of infection. We previously reported that individuals with obesity and type 2 diabetes have an impaired T cell response (i.e., lower IL-2 production, a marker of proliferation) upon T cell stimulation despite having more activated T cells compared to normoglycemic (NG) individuals with obesity. It remains unclear if the immune dysfunction is caused by adiposity, hyperglycemia and/or dietary patterns. The aim of this study was to investigate the effect of consuming an isocaloric North American-type diet on the IL-2 receptor (CD25) expression and cardiometabolic risk factors in lean, obese-NG, and obese-IR individuals. This is a three parallel-arm trial in controlled feeding conditions being conducted at the Human Nutrition Research Unit, at the University of Alberta. Three groups of adults: Lean-NG (n = 7), Obese-NG (n = 8), and Obese-IR (n = 9) consumed an isocaloric standardized diet containing 35% fat, 48% carbohydrate, and 17% protein for 4 weeks. All meals were provided to participants. Blood samples were collected in the fasting state before and after the intervention and cardiometabolic risk factors were measured. Peripheral blood mononuclear cells (PBMCs) were isolated and the proportion of total immune cells expressing CD25 was determined by flow cytometry. At baseline and post-intervention, Obese-IR had higher levels of glucose, insulin, and HOMA-IR and lower levels of HDL-C compared to both Lean-NG and Obese-NG groups (P < 0.05). At baseline, the proportion of PBMCs expressing CD25 tended to be lower in the Lean-NG (17.6 ± 2.7) compared to both Obese-NG (23.3 ± 4.8) and Obese-IR (23.2 ± 4.8) (P = 0.08). Post-intervention, the expression of CD25 was reduced in Lean-NG and Obese-IR groups (P < 0.01) but similar trends were still observed among all groups (P = 0.07). Our preliminary data suggest that obesity, independent of IR, is associated with greater activation of immune cells and consuming a North American-type diet lowers the expression of the IL-2 receptor in individuals with and without obesity. Therefore, both excess adiposity and dietary pattern appear to modulate the function of immune cells in obesity. Canadian Institutes of Health Research.