Type 2 Diabetes (T2DM) is characterized by hyperglycemia, dyslipidemia and increased inflammation. Previously, we showed that high glucose (HG) induces Toll-like receptor (TLR) expression, activity, and inflammation via NF-κB followed by cytokine release in vitro and in vivo. Here, we determined how HG induced inflammation is affected by free fatty acid (FFA) in human monocytes. THP-1 monocytic cells, CD14+ human monocytes, and transiently transfected HEK293 cells were exposed to various FFAs (0-500μM) and glucose (5-20mM) for evaluation of TLR2, TLR4, NF-κB, IL-1β, MCP-1, and superoxide release. In THP-1 cells, palmitate increased cellular TLR2, TLR4 expression; generated reactive oxygen species (ROS); increased NF-κB activity; IL-1β, and MCP-1 release in a dose and time dependent manner. Similar data were observed with stearate and mixture of FFA, but not with oleate. Conversely, NADPH oxidase inhibitor treatment repressed glucose and palmitate stimulated ROS generation and NF-κB activity and decreased IL-1β and MCP-1 expression. Silencing TLR2, TLR4, and p47phox using siRNAs markedly reduced superoxide release and NF-κB activity with concomitant decrease in IL-1β and MCP-1 secretion in stimulated THP-1 cells by both high glucose and palmitate. Moreover, data from transient transfection experiments suggest that TLR6 is required for TLR2 and MD2 for TLR4 to augment inflammation in FFA and glucose exposed cells. These findings were confirmed using human monocytes. We conclude that FFA exacerbates HG induced TLR expression and activity in monocytic cells with excess superoxide release, enhanced NF-κB activity, and induce proinflammatory factors release.
- Copyright © 2010, American Journal of Physiology - Endocrinology and Metabolism