Fatty Acid Uptake Unexpectedly Supports a Th17 cytokine signature in Type 2 Diabetes (T2D) Inflammation

Abstract

Abstract Metabolism controls T cell function, but the role of cellular metabolism in regulating our published T2D-associated Th17 cytokine signature is untested. Published work showed Th17 function requires fatty acid (FA) uptake, and suggested Th17s burn fat to support inflammation. We thus hypothesized that chronic exposure of immune cells to FAs, which occurs in T2D patients, drives Th17 inflammation. We used extracellular flux (XF) and cytokine analyses to show that CD3/CD28-stimulated PBMCs from BMI-matched T2D vs. non-T2D subjects were more glycolytic despite overall equal mitochondrial respiration. Consistent with this difference, T cell stimulation in glucose-free media followed by partial least squares analysis of cytokines showed glucose impacted cytokine profiles from T2D and non-T2D cells differently. To challenge the resulting prediction that PBMCs (predominantly T cells) from the two groups used different mechanisms to fuel cytokine responses, we performed XF analysis in the presence of FA +/− glucose. Non-T2D cells utilized FA as a fuel source, but T2D cells were dependent on glucose, despite data showing diabetic vs. non-T2D PBMCs store more lipid in response to elevated exogenous FA. Etomoxir, an inhibitor of FA transport into the mitochondria, caused non-T2D cells to increase glycolysis, but had no effect on T2D cells. These data confirmed that T2D cells exclusively burn glucose, not FA, to generate energy, and that T2D cells cannot be forced to use FA as a fuel. Finally, blockade of FA transport into the mitochondria revealed that FAs were associated with Th17 cytokine production. Together, our results support the unexpected conclusion that FA uptake is uncoupled from FA oxidation to drive the Th17 inflammation in T2D.