High-fat diet activates liver iPLA(2)γ generating eicosanoids that mediate metabolic stress

High-fat (HF) diet–induced obesity precipitates multiple metabolic disorders including insulin resistance, glucose intolerance, oxidative stress, and inflammation, resulting in the initiation of cell death programs. Previously, we demonstrated murine germline knockout of calcium-independent phospholipase A(2)γ (iPLA(2)γ) prevented HF diet–induced weight gain, attenuated insulin resistance, and decreased mitochondrial permeability transition pore (mPTP) opening leading to alterations in bioenergetics. To gain insight into the specific roles of hepatic iPLA(2)γ in mitochondrial function and cell death under metabolic stress, we generated a hepatocyte-specific iPLA(2)γ-knockout (HEPiPLA(2)γKO). Using this model, we compared the effects of an HF diet on wild-type versus HEPiPLA(2)γKO mice in eicosanoid production and mitochondrial bioenergetics. HEPiPLA(2)γKO mice exhibited higher glucose clearance rates than WT controls. Importantly, HF-diet induced the accumulation of 12-hydroxyeicosatetraenoic acid (12-HETE) in WT liver which was decreased in HEPiPLA(2)γKO. Furthermore, HF-feeding markedly increased Ca(2+) sensitivity and resistance to ADP-mediated inhibition of mPTP opening in WT mice. In contrast, ablation of iPLA(2)γ prevented the HF-induced hypersensitivity of mPTP opening to calcium and maintained ADP-mediated resistance to mPTP opening. Respirometry revealed that ADP-stimulated mitochondrial respiration was significantly reduced by exogenous 12-HETE. Finally, HEPiPLA(2)γKO hepatocytes were resistant to calcium ionophore-induced lipoxygenase-mediated lactate dehydrogenase release. Collectively, these results demonstrate that an HF diet increases iPLA(2)γ-mediated hepatic 12-HETE production leading to mitochondrial dysfunction and hepatic cell death.