Obesity is accompanied by and accelerated with chronic
inflammation in adipose tissue, especially visceral adipose tissue (VAT). This low-level
inflammation predisposes the host to the development of
metabolic disease, most notably
type 2 diabetes. We have focused on the capacity of
glycolipid-reactive, CD1d-restricted natural killer T (NKT) cells to modulate
obesity and its associated metabolic sequelae. We previously reported that CD1d knockout (KO) mice are partially protected against the development of
obesity-associated
insulin resistance, and these findings were recapitulated in mice with an adipocyte-specific CD1d deficiency, suggesting that NKT cell-adipocyte interactions play a critical role in exacerbating disease. However, many other CD1d-expressing cells contribute to the in vivo responses of NKT cells to
lipid antigens. In the present study, we examined the role of CD1d expression by macrophages (Mϕ) in the development of
obesity-associated metabolic
inflammation using LysMcre-cd1d1f/f mice where the CD1d1 gene is disrupted in a Mϕ-specific manner. Unexpectedly, these animals contained a higher frequency of T-bet+ CD4+ T cells in VAT with increased production of Th1
cytokines that aggravated VAT
inflammation. Mϕ from mutant mice displayed increased production of
IL-12p40, suggesting M1 polarization. These findings indicate that interactions of CD1d on Mϕ with NKT cells play a beneficial role in
obesity-associated VAT
inflammation and
insulin resistance with a sharp contrast to an aggravating role of CD1d in another type of antigen-presenting cell, dendritic cells.