Identification of circulating monocytes with a metabolic phenotype.
Peripheral blood was obtained from healthy individuals to analyse metabolic markers in circulating monocytes. Cell staining was performed as described in materials and methods. Cells were analysed by multi-parametric flow cytometry. We used ABCA1, CD36 and PLIN2 to define the metabolic population (Fig 1A). Interestingly, with this strategy, we proved by the first time the presence in bloodstream of monocytes with metabolic phenotype (MoMe). We could identify two populations according to the ABCA1 and CD36 expression (3.4%, 1.93%-9%, median and IQR) or ABCA1, CD36 and PLIN2 expression (2.05%, 0.95%-4.17%, median and IQR respectively) (Fig 1B). Since a common marker for the study of monocytes is CD14, we decided to evaluate this molecule expression in metabolic monocytes (Fig 1C), we found that in each subject, there are metabolic monocytes with different CD14 expression levels. We found a range from a small population that does not express this marker (6.83%, 3.33%-14.08%median and IQR), to CD14 positive metabolic monocytes with dim (31.05%, 20.48%-40.78%, median and IQR) and high expression, but the most predominant fraction was the one with high expression of CD14 (p<0.0001, 58.75%, 43.13%-75.33%, median and IQR).