Omega-3 polyunsaturated fatty acids modify glucose metabolism in THP-1 monocytes
Chronic inflammation is a driving factor in diseases like obesity and type 2 diabetes. Enhanced glucose metabolism, including via oxidative phosphorylation, may contribute to heightened immune activation. A recent clinical trial showed that supplementation with the n-3 fatty acid -linolenic acid (ALA) reduced oxidative phosphorylation rates in human monocytes. However, the mechanism remains unknown. Therefore, our objective was to explore the direct effects of ALA and docosahexaenoic acid (DHA) on glucose metabolism in a cell culture model and to explore the molecular mechanism. THP-1 monocytes were treated for 48h with 10-40 M of ALA or DHA and compared with vehicle and oleic acid controls. The Seahorse XFe24 system was used to approximate catabolic rates in the presence of glucose, including glycolysis and oxidative phosphorylation. The latter was validated by respirometry using an Oroboros O2k Oxygraph. Both ALA and DHA treatments reduced oxidative phosphorylation and increased glycolytic rates relative to control conditions. We identified pyruvate dehydrogenase kinase 4 (PDK4), an enzyme that inhibits the conversion of pyruvate to acetyl-CoA, as a possible mechanistic candidate. This gene was significantly upregulated by ALA and, to a greater extent, by DHA. Using fluorescent indicators, we also found that DHA increased reactive oxygen species while ALA had no effect. Our data suggest that ALA and DHA trigger a re-wiring of bioenergetic pathways in monocytes, possibly via the upregulation of PKD4. Given the close relationship between cell metabolism and immune cell activation, this may represent a novel mechanism by which n-3 fatty acids modulate immune function and inflammation.