Growth differentiation factor‐15 is associated with age‐related monocyte dysfunction

OBJECTIVE: Age‐associated decreases in immune functions are precipitated by a variety of mechanisms and affect nearly every immune cell subset. In myeloid cells, aging reduces numbers of phagocytes and impairs their functional abilities, including antigen presentation, phagocytosis, and bacterial clearance. Recently, we described an aging effect on several functions in monocytes, including impaired mitochondrial function and reduced inflammatory cytokine gene expression during stimulation with lipopolysaccharide. We hypothesized that circulating factors altered by the aging process underly these changes. Growth differentiation factor‐15 (GDF‐15) is a distant member of the transforming growth factor‐β superfamily that has known anti‐inflammatory effects in macrophages and has been shown to be highly differentially expressed during aging. METHODS: We used biobanked plasma samples to assay circulating GDF‐15 levels in subjects from our previous studies and examined correlations between GDF‐15 and monocyte function. RESULTS: Monocyte interleukin‐6 production due to lipopolysaccharide stimulation was negatively correlated to plasma GDF‐15. Additionally, GDF‐15 was positively correlated to circulating CD16 + monocyte proportions and negatively correlated to monocyte mitochondrial respiratory capacity. CONCLUSIONS: These results suggest that GDF‐15 is a potential circulating factor affecting a variety of monocyte functions and promoting monocyte immunosenescence and thus may be an attractive candidate for therapeutic intervention to ameliorate this.