Mitochondrial changes synergize with long chain fatty acid derivatives to support Th17 inflammation in diabetes

Obesity-associated Type 2 diabetes (T2D) is driven by chronic inflammation. A combinatorial Th17 cytokine profile characterizes and mathematically predicts T2D in people, but the mechanisms that generate the Th17 profile are not clear. We tested the possibility that anaerobic glycolysis, which fuels inflammatory cytokine production from multiple immune cell types, drives the T2D-associated Th17 profile. We showed that activated PBMCs and purified CD4+T cells from T2D subjects prefer anaerobic glucose metabolism to produce ATP regardless of fuel availability. Unexpectedly, glucose starvation did not abrogate the T2D-predictive Th17 profile. Gene expression array suggested that mitochondrial fatty acid uptake catalyzing protein CPT1a differentiated PBMCs from T2D and ND subjects. CPT1a inhibition by etomoxir strongly down-regulated the Th17 profile, surprisingly independent of CPT1a-mediated fatty acid oxidation (OXPHOS). These data suggest that OXPHOS-independent mitochondrial changes that are also glucose-independent support the Th17 profile in T2D. Analyses from T2D vs ND PBMCs showed a lower CACT:CPT1a protein ratio in T2D, indicating defects in lipid uptake and thus defects in lipid flux. We knocked down CACT protein and overloaded PBMCs from lean subjects with fatty acylcarnitines to mimic lipid uptake defects in T2D. 16C-fatty acylcarnitine, but not 6C- or 10C-derivatives, increased frequency of CD4+IL-17+T cells, and phenocopied the Th17 profile only in CACT knockdown cells. 16C-fatty acylcarnitine alone had no effect. We conclude that excessive long chain fatty acylcarnitine combines with dysfunctional mitochondria to support a T2D-associated Th17 profile largely independent of glycolysis.