Role of MCP-1 on Inflammatory Processes and Metabolic Dysfunction Following High-Fat Feedings in the FVB/N Strain

BACKGROUND: MCP-1 is known to be an important chemokine for macrophage recruitment. Thus, targeting MCP-1 may prevent the perturbations associated with macrophage-induced inflammation in adipose tissue. However, inconsistencies in the available animal literature have questioned the role of this chemokine in this process. The purpose of this study was to examine the role of MCP-1 on obesity-related pathologies. METHODS: Wild-type (WT) and MCP-1 deficient mice on an FVB/N background were assigned to either low-fat-diet (LFD) or high-fat-diet (HFD) treatment for a period of 16 weeks. Body weight and body composition were measured weekly and monthly, respectively. Fasting blood glucose and insulin, and glucose tolerance were measured at 16 weeks. Macrophages, T cell markers, inflammatory mediators, and markers of fibrosis were examined in the adipose tissue at sacrifice. RESULTS: As expected, HFD increased adiposity (body weight, fat mass, fat percent, and adipocyte size), metabolic dysfunction (impaired glucose metabolism and insulin resistance) macrophage number (CD11b(+)F480(+) cells, and gene expression of EMR1 and CD11c), T cell markers (gene expression of CD4 and CD8), inflammatory mediators (pNFκB and pJNK, and mRNA expression of MCP-1, CCL5, CXCL14, TNF-α, and IL-6), and fibrosis (expression of IL-10, IL-13, TGF-β, and MMP2) (P<0.05). However, contrary to our hypothesis, MCP-1 deficiency exacerbated many of these responses resulting in a further increase in adiposity (body weight, fat mass, fat percent and adipocyte size), metabolic dysregulation, macrophage markers (EMR1), inflammatory cell infiltration, and fibrosis (formation of type I and III collagens, mRNA expression of IL-10 and MMP2) (P<0.05). CONCLUSIONS: These data suggest that MCP-1 may be a necessary component of the inflammatory response required for adipose tissue protection, remodeling, and healthy expansion in the FVB/N strain in response to HFD feedings.