Dysregulated monocyte compartment in human obesity

Abstract Background Monocytes can be divided in classical monocytes (CM), intermediate monocytes (IM) and non-classical monocytes (NCM). CD56+ monocytes are part of the classical monocytes. Aim of the study was to assess the occurrence of the different monocyte subpopulations in human obesity. Methods 110 age-matched subjects were included in the study and classified according to the definition of the World Health Organization into lean (n=27), overweight (n=23) and obese (n=60). Monocyte subpopulations were analyzed by flow cytometry (antibody staining of CD14, CD16, CD56). Results Obese subject showed a higher BMI, fat mass, and waist circumference, deterioration of metabolic parameters, and the absolute amount of leukocytes and monocytes were increased. The calculated absolute numbers of CM, IM and CD56+ monocytes were significantly increased in obese subjects compared to lean and overweight. In contrast, the absolute numbers of NCM were equal between lean, overweight and obese subjects. Strong associations between the absolute numbers of CM, IM and CD56+ monocytes with the BMI, fat mass, and waist circumference were detectable in the whole cohort. Triglyceride, HDL-c values and HbA1c were also strongly correlated with numbers of CM, IM and CD56+ monocytes. Obese subjects with impaired glucose tolerance had increased numbers of CD56+ monocytes in comparison to obese subsects with normal glucose tolerance. Stratification of obese subjects in subjects with and without type 2 diabetes mellitus showed no difference in absolute numbers of CM but significant increased numbers of IM and NCM. Conclusion The amount of CM, IM and CD56+ monocytes are expanded in the blood of obesity subjects and contribute to monocytosis in obesity.